Epitaxial oxide materials, structures, and devices

Abstract

The present invention provides a semiconductor structure having an oxide epitaxial layer with a large bandgap energy, and a method for forming such a structure. [Solution] The semiconductor structure is (Al x Ga 1-x ) y O z The semiconductor structure includes an epitaxial oxide material such as (wherein 0≦x≦1, 1≦y≦3, and 2≦z≦4). The semiconductor structure may include one or more superlattices containing the epitaxial oxide material. The semiconductor structure may include one or more doped superlattices including a host layer and an impurity layer, the host layer containing the epitaxial oxide material. The semiconductor structure may include one or more gradient layers or regions containing the epitaxial oxide material. The semiconductor structure may be part of a semiconductor device such as an optoelectronic device, light-emitting diode, laser diode, photodetector, solar cell, high-power diode, high-power transistor, transducer, or high-electron-mobility transistor.

Description

[Technical Field]

[0001] Related applications This application is related to U.S. Patent Application No. 16 / 990,349, titled "Metal Oxide Semiconductor-Based Light Emitting Device," filed on August 11, 2020; International Application No. __[[Agent Reference Number SILUP025WO]]__, titled "Ultrawide Bandgap Semiconductor Devices Including Magnesium Germanium Oxides," filed on the same day; and "Epitaxial Oxide Materials, Structures and In relation to the international application number __[[Agent reference number SILUP029WO]]__ titled “Devices”, all of these are incorporated herein by reference for all purposes.

[0002] The following publications are referenced in this application, and their contents are incorporated herein by reference in their entirety. U.S. Patent No. 9,412,911, entitled "OPTICAL TUNING OF LIGHT EMITTING SEMICONDUCTOR JUNCTIONS," was issued on 9 August 2016 and assigned to the applicant of this application. ·“ADVANCED ELECTRONIC DEVICE STRUCTURES” U.S. Patent No. 9,691,938, titled “USING SEMICONDUCTOR STRUCTURES AND SUPERLATTICES,” was issued on 27 June 2017 and assigned to the applicant of the present application. U.S. Patent No. 10,475,956, entitled "OPTOELECTRONIC DEVICE," was issued on November 12, 2019, and assigned to the applicant of this application.

[0003] The contents of each of the above publications are explicitly incorporated in their entirety by reference. [Background technology]

[0004] Electronic and optoelectronic devices such as diodes, transistors, photodetectors, LEDs, and lasers utilize epitaxial semiconductor structures to control the transport of free carriers, detect light, or generate light. Wide-bandgap semiconductor materials, such as those with a bandgap greater than approximately 4 eV, are useful in several applications, including high-power devices and optoelectronic devices that detect or emit ultraviolet (UV) wavelength light.

[0005] For example, UV-emitting devices (UVLEDs) have many applications in medical, medical diagnostics, water purification, food processing, sterilization, sterile packaging, and deep submicron lithography. New applications in biosensing, communications, the pharmaceutical process industry, and materials manufacturing are also made possible by providing ultrashort wavelength light sources in compact, lightweight packages with high electrical conversion efficiency, such as UVLEDs. The electro-optical conversion of electrical energy to individual light wavelengths with very high efficiency has generally been achieved using semiconductors with the necessary properties to achieve spatial recombination of electron and hole charge carriers and emit light of the required wavelengths. When UV light is required, UVLEDs have been developed almost exclusively using gallium-indium-aluminum-nitride (GaInAlN) compositions that form a wurtzite-type crystal structure.

[0006] In another example, high-power RF switches are used in transceivers of wireless communication systems to separate transmit and receive signals. Such RF switches are composed of transistors. The requirement for a switch is that it can handle high voltages without damage. Typical RF switches use transistor devices employing low-bandgap semiconductors (e.g., Si or GaAs) with relatively low breakdown voltages (e.g., less than about 3V), and therefore many transistor devices are connected in series to withstand the required voltage. To reduce the number of transistor devices connected in series and improve the maximum voltage limit of the RF switch, semiconductors with wider bandgaps and higher breakdown voltages (e.g., GaN) are used. [Overview of the Initiative] [Means for solving the problem]

[0007] In some embodiments, the semiconductor structure includes an epitaxial oxide material. In some embodiments, the semiconductor structure includes one or more superlattices including an epitaxial oxide material. In some embodiments, the semiconductor structure includes one or more doped superlattices including a host layer and an impurity layer, the host layer including an epitaxial oxide material. In some embodiments, the semiconductor structure includes one or more gradient layers or regions including an epitaxial oxide material. In some embodiments, the semiconductor structure includes one or more chirp layers including an epitaxial oxide material. In some embodiments, the semiconductor structure includes one or more chirp layers including an epitaxial oxide material, the chirp layers are adjacent to a metal layer. In some embodiments, the semiconductor structure is (Al x Ga 1-x ) y O z The space group includes such that x is 0-1, y is 1-3, and z is 2-4, for example, R3c (i.e., α), pna21 (i.e., κ), C2m (i.e., β), Fd3m (i.e., γ), and / or Ia3 (i.e., δ).

[0008] The semiconductor structures described herein may be part of semiconductor devices such as optoelectronic devices having emission or detection wavelengths including ultraviolet and deep ultraviolet, light-emitting diodes, laser diodes, photodetectors, solar cells, high-power diodes, high-power transistors, transducers, or high-electron-mobility transistors.

[0009] Embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. [Brief explanation of the drawing]

[0010] [Figure 1] This is a process flow diagram for constructing a metal oxide semiconductor-based LED according to an exemplary embodiment of the present disclosure. [Figure 2] A and B schematically illustrate two classes of LED devices based on vertical and waveguide light confinement and emission, arranged on a substrate, according to exemplary embodiments of the present disclosure. [Figure 3A] This is a schematic diagram of different LED device configurations according to exemplary embodiments of the present disclosure, including multiple regions. [Figure 3B] This is a schematic diagram of different LED device configurations according to exemplary embodiments of the present disclosure, including multiple regions. [Figure 3C] This is a schematic diagram of different LED device configurations according to exemplary embodiments of the present disclosure, including multiple regions. [Figure 3D] This is a schematic diagram of different LED device configurations according to exemplary embodiments of the present disclosure, including multiple regions. [Figure 3E] This is a schematic diagram of different LED device configurations according to exemplary embodiments of the present disclosure, including multiple regions. [Figure 4] The following schematic diagram illustrates the injection of oppositely charged carriers from a physically separated region into a recombination region according to an exemplary embodiment of the present disclosure. [Figure 5] The possible light emission directions from the light-emitting region of an exemplary embodiment of the present disclosure are shown. [Figure 6]An exemplary embodiment of this disclosure shows an opening through an opaque region that enables light emission from an LED. [Figure 7] The exemplary selection criteria for constructing a metal oxide semiconductor structure according to the exemplary embodiments of this disclosure are shown. [Figure 8] This is an exemplary process flow diagram for selecting and epitaxially depositing a metal oxide structure according to exemplary embodiments of the present disclosure. [Figure 9] This is a summary of the technically relevant semiconductor band gaps as a function of electron affinity, showing the relative band lineup. [Figure 10] This is an exemplary schematic process flow for depositing multiple layers that form multiple regions including LEDs, according to exemplary embodiments of the present disclosure. [Figure 11] This is a ternary alloy optical bandgap adjustment curve for a gallium oxide-based metal oxide semiconductor ternary composition according to an exemplary embodiment of the present disclosure. [Figure 12] This is a ternary alloy optical bandgap adjustment curve for an aluminum oxide-based metal oxide semiconductor ternary composition according to an exemplary embodiment of the present disclosure. [Figure 13A] This is an exemplary embodiment of the present disclosure that represents the electron energy versus crystal momentum of a metal oxide-based optoelectronic semiconductor exhibiting a direct band gap. [Figure 13B] This is an exemplary embodiment of the present disclosure showing an indirect bandgap and an electronic energy versus crystal momentum representation of a metal oxide-based optoelectronic semiconductor. [Figure 13C] This is an exemplary embodiment of the present disclosure, representing the electron energy versus crystal momentum that exhibits photo-emitting and absorption transitions allowed at k=0 with respect to the axis of symmetry of the Ga2O3 monoclinic crystal. [Figure 13D] This is an exemplary embodiment of the present disclosure, representing the electron energy versus crystal momentum that exhibits photo-emitting and absorption transitions allowed at k=0 with respect to the axis of symmetry of the Ga2O3 monoclinic crystal. [Figure 13E]This is an exemplary embodiment of the present disclosure, representing the electron energy versus crystal momentum that exhibits photo-emitting and absorption transitions allowed at k=0 with respect to the axis of symmetry of the Ga2O3 monoclinic crystal. [Figure 14] A and B show sequential deposition of multiple heterogeneous metal oxide semiconductor layers having different crystal symmetries for embedding light-emitting regions, according to exemplary embodiments of the present disclosure. [Figure 15] This is a schematic diagram of an atomic deposition tool for creating multilayer metal oxide semiconductor films containing multiple material compositions, according to exemplary embodiments of the present disclosure. [Figure 16] This figure illustrates the sequential deposition of layers and regions having similar crystal symmetry types that match the substrate, according to exemplary embodiments of the present disclosure. [Figure 17] An exemplary embodiment of the present disclosure shows the sequential deposition of regions having different crystal symmetries with respect to a first surface of a substrate, thereby demonstrating surface modification of the substrate. [Figure 18] An exemplary embodiment of the present disclosure shows a buffer layer deposited with the same crystal symmetry as the underlying substrate to enable subsequent heterosymmetric deposition of the oxide material. [Figure 19] An exemplary embodiment of the present disclosure shows a structure comprising multiple heterosymmetric regions sequentially deposited as a function of the growth direction. [Figure 20A] An exemplary embodiment of this disclosure shows a crystal symmetry transition region linking two deposited crystal symmetries. [Figure 20B] The exemplary embodiments of this disclosure show the change in specific crystal surface energy as a function of crystal surface orientation in the case of corundum sapphire and monoclinic Gallia single-crystal oxide materials. [Figure 21] Figures A to C schematically illustrate the changes in the electronic energy configuration or band structure of a metal oxide semiconductor under the influence of biaxial strain applied to a crystal unit cell, according to exemplary embodiments of the present disclosure. [Figure 22] Figures A and B schematically illustrate the change in the band structure of a metal oxide semiconductor under the influence of uniaxial strain applied to a crystal unit cell, according to exemplary embodiments of the present disclosure. [Figure 23] Figures A to C show the effect of exemplary embodiments of this disclosure on the band structure of monoclinic gallium oxide as a function of uniaxial strain applied to a crystal unit cell. [Figure 24] A and B represent the Ek electron configurations of two different binary metal oxides according to exemplary embodiments of the present disclosure, one having a wide direct bandgap material and the other having a narrow indirect bandgap material. [Figure 25] Figures A-C illustrate the effect of valence band mixing of two binary dissimilar metal oxide materials that together form a ternary metal oxide alloy, according to exemplary embodiments of the present disclosure. [Figure 26] The exemplary embodiments of this disclosure schematically show a portion of the energy versus crystal momentum of controlled valence bands supplied from two bulk metal oxide semiconductor materials up to the first Brillouin zone. [Figure 27A] This invention demonstrates the effect of a one-dimensional superlattice (SL) on an Ek configuration for a layered structure having a superlattice period equal to approximately twice the bulk lattice constant of the host metal oxide semiconductor, and shows the creation of a superlattice Brillouin zone that opens an artificial band gap at the zone center, according to exemplary embodiments of this disclosure. [Figure 27B] This invention demonstrates the effect of a one-dimensional superlattice (SL) on an Ek configuration for a layered structure having a superlattice period equal to approximately twice the bulk lattice constant of the host metal oxide semiconductor, and shows the creation of a superlattice Brillouin zone that opens an artificial band gap at the zone center, according to exemplary embodiments of this disclosure. [Figure 27C] The digital alloy represents a two-layer binary superlattice containing multiple thin epitaxial layers of Al2O3 and Ga2O3 that repeat with a fixed unit cell period, simulating an equivalent ternary AlxGa1-xO3 bulk alloy depending on the constituent layer thickness ratio of the superlattice period, according to exemplary embodiments of the present disclosure. [Figure 27D]The digital alloy represents another two-layer binary superlattice containing multiple thin epitaxial layers of NiO and Ga2O3 that repeat with a fixed unit cell period, simulating an equivalent ternary (NiO)x(Ga2O3)1-x bulk alloy depending on the constituent layer thickness ratio of the superlattice period, according to exemplary embodiments of the present disclosure. [Figure 27E] The present invention exhibits yet another ternary material binary superlattice containing multiple thin epitaxial layers of MgO and NiO that repeat with a fixed unit cell period, and the digital alloy simulates an equivalent ternary bulk alloy (NiO)x(MgO)1-x depending on the constituent layer thickness ratio of the superlattice period, and the binary metal oxides used in the repeating units are each selected so that their thickness varies between 1 and 10 unit cells, thereby constituting the unit cells of SL according to the exemplary embodiments of this disclosure. [Figure 27F] Further possible quaternary binary superlattices are shown, including multiple thin epitaxial layers of MgO, NiO, and Ga2O3 that repeat with a fixed unit cell period, and the digital alloy simulates an equivalent quaternary bulk alloy (NiO)x(Ga2O3)y(MgO)z, depending on the constituent layer thickness ratio of the superlattice period, including the SL unit cell according to the exemplary embodiment of this disclosure, where each of the binary metal oxides used in the repeating units is selected such that their respective thicknesses vary from 1 to 10 unit cells. [Figure 28] A chart of ternary metal oxide combinations that may be employed in the formation of optoelectronic devices according to various exemplary embodiments of this disclosure is shown. [Figure 29] This is an exemplary design flowchart for tuning and building optoelectronic functions in an LED region according to exemplary embodiments of the present disclosure. [Figure 30] The heterojunction band lineup of binary Al2O3, ternary alloy (Al,Ga)O3, and binary Ga2O3 semiconductor oxides according to exemplary embodiments of this disclosure is shown. [Figure 31] This exhibits a three-dimensional crystalline unit cell of a corundum-symmetric crystal structure (alpha phase) Al2O3 used to calculate the Ek band structure according to an exemplary embodiment of the present disclosure. [Figure 32] A and B show the calculated energy-momentum configuration of alpha-Al2O3 near the center of the Brillouin zone according to exemplary embodiments of the present disclosure. [Figure 33] This disclosure shows a three-dimensional crystal unit cell of a monoclinic symmetric crystal structure Al2O3 used to calculate the Ek band structure according to an exemplary embodiment of this disclosure. [Figure 34] A and B show the calculated energy-momentum configuration of theta Al2O3 near the center of the Brillouin zone according to exemplary embodiments of the present disclosure. [Figure 35] This exhibits a three-dimensional crystal unit cell of a corundum symmetric crystal structure (alpha phase) Ga2O3 used to calculate the Ek band structure according to an exemplary embodiment of the present disclosure. [Figure 36] A and B show the calculated energy-momentum configuration of corundum alpha Ga2O3 near the center of the Brillouin zone according to exemplary embodiments of the present disclosure. [Figure 37] This exhibits a three-dimensional crystal unit cell of monoclinic symmetric crystal structure (beta phase) Ga2O3 used to calculate the Ek band structure according to an exemplary embodiment of the present disclosure. [Figure 38] A and B show the calculated energy-momentum configuration of betaGa2O3 near the center of the Brillouin zone according to exemplary embodiments of the present disclosure. [Figure 39] An exemplary embodiment of the present disclosure shows a three-dimensional crystal unit cell of the orthorhombic crystal structure of a bulk ternary alloy of (Al,Ga)O3 used to calculate the Ek band structure. [Figure 40] The calculated energy-momentum configuration of (Al,Ga)O3 near the center of the Brillouin zone, showing the direct band gap, is shown according to exemplary embodiments of the present disclosure. [Figure 41] This is a process flow diagram for forming an optoelectronic semiconductor device according to exemplary embodiments of the present disclosure. [Figure 42]This shows a cross-sectional portion of the (Al,Ga)O33 original structure formed by sequentially depositing Al-O-Ga-O-…-O-Al epitaxial layers along the growth direction, according to an exemplary embodiment of the present disclosure. [Figure 43A] Table I shows the selection of substrate crystals for depositing metal oxide structures in various exemplary embodiments of this disclosure. [Figure 43B] Table II shows the unit cell parameters for the selection of metal oxides in various exemplary embodiments of this disclosure, illustrating the lattice constant mismatch between Al2O3 and Ga2O3. [Figure 44A] The calculated formation energies of aluminum-gallium-oxide ternary alloys as functions of composition and crystal symmetry are shown according to exemplary embodiments of the present disclosure. [Figure 44B] The following shows experimental high-resolution X-ray diffraction (HRXRD) of two different compositional examples of high-quality single-crystal ternary (AlxGa1-x)2O3 epitaxially deposited on a bulk (010)-oriented Ga2O3 substrate, according to exemplary embodiments of the present disclosure. [Figure 44C] The experimental HRXRD and X-ray micro-angle incident reflection (GIXR) of an exemplary superlattice comprising two layers of repeating unit cells selected from elastically strained [(AlxGa1-x)2O3 / Ga2O3] on a β-Ga2O3(010) oriented substrate are shown according to exemplary embodiments of the present disclosure. [Figure 44D] Exemplary embodiments of this disclosure show two exemplary experimental HRXRD and GIXR layers of different compositions of high-quality single-crystal ternary (AlxGa1-x)2O3 layers epitaxially deposited on a bulk (001)-oriented Ga2O3 substrate. [Figure 44E] Exemplary embodiments of this disclosure show experimental HRXRD and GIXR of superlattices comprising two layers of repeating unit cells selected from elastically strained [(AlxGa1-x)2O3 / Ga2O3] on a β-Ga2O3(001) oriented substrate. [Figure 44F] The experimental HRXRD and GIXR of an elastically strained cubic symmetric binary nickel oxide (NiO) epitaxial layer on a monoclinic symmetric β-Ga2O3(001) oriented substrate are shown according to exemplary embodiments of the present disclosure. [Figure 44G] The experimental HRXRD and GIXR of an elastically strained monoclinic Ga2O3(100) oriented epitaxial layer on a cubic crystal symmetric MgO(100) oriented substrate are shown according to exemplary embodiments of the present disclosure. [Figure 44H] Exemplary embodiments of this disclosure demonstrate experimental HRXRD and GIXR of superlattices comprising two layers of repeating unit cells selected from elastically strained [(AlxEr1-x)2O3 / Al2O3] on a corundum crystal-symmetric α-Al2O3(001) oriented substrate. [Figure 44I] An exemplary embodiment of this disclosure shows the strain-free energy-crystal momentum (Ek) dispersion near the center of the Brillouin zone for ternary aluminum-erbium oxide (AlxEr1-x)2O3 exhibiting a direct band gap at Γ(k=0). [Figure 44J] Exemplary embodiments of this disclosure show experimental HRXRD and GIXR of superlattices consisting of two-layer unit cells of monoclinic crystal symmetric Ga2O3(100) oriented films bonded to a cubic (spinel) crystal symmetric ternary composition of magnesium gallium oxide, MgxGa2(1-x)O3-2x, with SL epitaxially deposited on a monoclinic Ga2O3(010) oriented substrate. [Figure 44K] An exemplary embodiment of the present disclosure shows the strain-free energy-crystal momentum (Ek) dispersion near the center of the Brillouin zone for ternary magnesium-gallium oxide MgxGa2(1-x)O3-2x exhibiting a direct band gap at Γ(k=0). [Figure 44L] The experimental HRXRD and GIXR of an elastically strained orthorhombic Ga2O3 epitaxial layer on a cubic crystalline magnesium-aluminum-oxide MgAl2O4(100) oriented substrate are shown according to exemplary embodiments of the present disclosure. [Figure 44M] An exemplary embodiment of the present disclosure shows an experimental HRXRD of an elastically strained ternary zinc-gallium-oxide (ZnGa2O4) epitaxial layer deposited on a wurtzite-type zinc oxide (ZnO) layer on a monoclinic crystalline symmetric gallium oxide (-2O1) oriented substrate. [Figure 44N]An exemplary embodiment of the present disclosure shows the strain-free energy-crystal momentum (Ek) dispersion near the center of the Brillouin zone for ternary cubic zinc-gallium oxide ZnxGa2(1-x)O3-2x(x=0.5) exhibiting an indirect band gap at Γ(k=0). [Figure 44O] An exemplary embodiment of the present disclosure shows an epitaxial layer stack deposited along the growth direction in the case of an orthorhombic Ga2O3 crystal symmetry film using an intermediate layer and a prepared substrate surface. [Figure 44P] Exemplary embodiments of this disclosure show experimental HRXRDs of two distinctly different crystalline binary Ga2O3 compositions deposited on a rhomboid sapphire α-Al2O3(0001) oriented substrate controlled by growth conditions. [Figure 44Q] This figure shows the strain-free energy-crystal momentum (Ek) dispersion near the center of the Brillouin zone for a binary orthorhombic gallium oxide exhibiting a direct band gap at Γ(k=0), according to an exemplary embodiment of the present disclosure. [Figure 44R] Exemplary embodiments of this disclosure show two exemplary experimental HRXRD and GIXR of different compositions of high-quality single-crystal corundum symmetric ternary (AlxGa1-x)2O3 epitaxially deposited on bulk (1-100) oriented corundum crystalline symmetric Al2O3 substrates. [Figure 44S] An exemplary embodiment of the present disclosure shows an experimental HRXRD of a monoclinic top active Ga2O3 epitaxial layer deposited on a ternary erbium-gallium oxide (ErxGa1-x)2O3 transition layer deposited on a single-crystal silicon (111) oriented substrate. [Figure 44T] Exemplary embodiments of this disclosure show experimental HRXRD and GIXR of exemplary high-quality single-crystal corundum-symmetric binary Ga2O3 epitaxially deposited on a bulk (11-20) oriented corundum crystal-symmetric Al2O3 substrate, demonstrating that two thicknesses of Ga2O3 are pseudomorphically strained relative to the underlying Al2O3 substrate (i.e., elastic deformation of the bulk Ga2O3 unit cell). [Figure 44U]The present disclosure presents exemplary embodiments of experimental HRXRD and GIXR of an exemplary high-quality single-crystal corundum-symmetric superlattice [Al2O3 / Ga2O3], which includes two layers of binary pseudomorphic Ga2O3 and Al2O3 epitaxially deposited on a bulk (11-20) oriented corundum-symmetric Al2O3 substrate, demonstrating the unique properties of corundum crystal symmetry. [Figure 44V] The following are experimental transmission electron microscope images (TEM) of a high-quality single-crystal superlattice made of SL[Al2O3 / Ga2O3] deposited on a corundum Al2O3 substrate exhibiting a low dislocation defect density, according to an exemplary embodiment of the present disclosure. [Figure 44W] An exemplary embodiment of the present disclosure shows an experimental HRXRD of a corundum crystal symmetric top active (AlxGa1-x)2O3 epitaxial layer deposited on a single corundum Al2O3(1-102) oriented substrate. [Figure 44X] The exemplary embodiments of this disclosure demonstrate experimental HRXRD and GIXR of exemplary high-quality single-crystal corundum-symmetric superlattices containing two layers of ternary pseudomorphic (AlxGa1-x)2O3 and Al2O3 epitaxially deposited on a bulk (1-102)-oriented corundum crystal-symmetric Al2O3 substrate, where the superlattices [Al2O3 / (AlxGa1-x)2O3] demonstrate the unique properties of corundum crystal symmetry. [Figure 44Y] This exhibits experimental wide-angle HRXRD of a cubic crystal symmetric top-level activated magnesium oxide (MgO) epitaxial layer deposited on a single-crystal cubic (spinel) magnesium-aluminum-oxide (MgAl2O4(100)) oriented substrate, according to exemplary embodiments of the present disclosure. [Figure 44Z] An exemplary embodiment of this disclosure shows the strain-free energy-crystal momentum (Ek) dispersion near the center of the Brillouin zone for the ternary magnesium-aluminum oxide MgxAl2(1-x)O3-2x(x=0.5) exhibiting a direct band gap at Γ(k=0). [Figure 45]The structure of the epitaxial region of a metal oxide UV LED comprising a pin heterojunction diode and multiple quantum wells for adjusting the luminescence energy, according to exemplary embodiments of the present disclosure, is schematically shown. [Figure 46] Figure 45 is an energy band diagram of the epitaxial metal oxide UV LED structure against the growth direction, where the k=0 representation of the band structure is plotted according to the exemplary embodiments of this disclosure. [Figure 47] An exemplary embodiment of the present disclosure shows a spatial carrier confinement structure in an MQW region of Figure 46, in which the MQW region has a narrow-bandgap material containing Ga2O3, and has quantized electron and hole wave functions that spatially recombine within the MQW region to generate predetermined emitted photon energies determined by the quantized states in the conduction band and valence band, respectively. [Figure 48] Figure 47 shows a computational optical absorption spectrum for the device structure according to an exemplary embodiment of the present disclosure, where the lowest energy electron-hole recombination is determined by the quantization energy level in the MQW, resulting in sharp, discrete absorption / emission energies. [Figure 49] This is the energy band diagram versus growth direction of an epitaxial metal oxide UV LED structure having a narrow bandgap material in which the MQW region contains (Al0.05Ga0.95)2O3, according to an exemplary embodiment of the present disclosure. [Figure 50] Figure 49 shows a computational optical absorption spectrum for the device structure according to an exemplary embodiment of the present disclosure, where the lowest energy electron-hole recombination is determined by the quantization energy level in the MQW, resulting in sharp, discrete absorption / emission energies. [Figure 51] This is an energy band diagram versus growth direction of an epitaxial metal oxide UV LED structure having a narrow bandgap material in which the MQW region contains (Al0.1Ga0.9)2O3, according to an exemplary embodiment of the present disclosure. [Figure 52]Figure 49 shows a computational optical absorption spectrum for the device structure according to an exemplary embodiment of the present disclosure, where the lowest energy electron-hole recombination is determined by the quantization energy level in the MQW, resulting in sharp, discrete absorption / emission energies. [Figure 53] This is an energy band diagram versus growth direction of an epitaxial metal oxide UV LED structure having a narrow bandgap material in which the MQW region contains (Al0.2Ga0.8)2O3, according to an exemplary embodiment of the present disclosure. [Figure 54] Figure 53 shows a computational optical absorption spectrum for the device structure according to an exemplary embodiment of the present disclosure, where the lowest energy electron-hole recombination is determined by the quantization energy level in the MQW, resulting in sharp, discrete absorption / emission energies. [Figure 55] The work function energies of pure metals are plotted, and the metal species are sorted from highest to lowest work function for application to p-type and n-type ohmic contacts to metal oxides, according to the exemplary embodiments of this disclosure. [Figure 56] This is a reciprocal lattice map biaxial X-ray diffraction pattern of pseudomorphic ternary (Al0.5Ga0.5)2O3 on an A-plane Al2O3 substrate according to an exemplary embodiment of the present disclosure. [Figure 57] This is a biaxial X-ray diffraction pattern of a pseudomorphic 10-period SL[Al2O3 / Ga2O3] on an A-plane Al2O3 substrate, exhibiting in-plane lattice matching throughout the entire structure, according to an exemplary embodiment of the present disclosure. [Figure 58] A and B show the optical mode structure and threshold gain of a slab of a metal oxide semiconductor material according to exemplary embodiments of the present disclosure. [Figure 59] A and B show the optical mode structure and threshold gain of a slab of a metal oxide semiconductor material according to another exemplary embodiment of the present disclosure. [Figure 60] An exemplary embodiment of the present disclosure shows an optical cavity formed using an optical gain medium embedded between two optical reflectors. [Figure 61]An exemplary embodiment of the present disclosure shows an optical cavity formed using an optical gain medium embedded between two optical reflectors, demonstrating that two optical wavelengths can be supported by the gain medium and the cavity length. [Figure 62] An exemplary embodiment of the present disclosure shows an optical cavity formed using a finite-thickness optical gain medium embedded between two optical reflectors and positioned at the peak electric field intensity of the fundamental wavelength mode, demonstrating that only one optical wavelength can be supported by the gain medium and the cavity length. [Figure 63] An exemplary embodiment of the present disclosure shows an optical cavity formed using two finite-thickness optical gain media embedded between two optical reflectors and positioned at the peak electric field intensity of a shorter wavelength mode, demonstrating that only one optical wavelength can be supported by the gain media and cavity length. [Figure 64] A and B illustrate a single quantum well structure comprising a metal oxide ternary material having quantized electronic and hole states, according to exemplary embodiments of the present disclosure, showing two different quantum well thicknesses. [Figure 65] Figures A and B show a single quantum well structure comprising a metal oxide ternary material having quantized electron and hole states, according to an exemplary embodiment of the present disclosure, illustrating two different quantum well thicknesses. [Figure 66] Figures 64A, 64B, 65A, and 65B show the spontaneous emission spectra from the quantum well structures disclosed. [Figure 67] A and B show the spatial energy band structure and associated energy-crystal momentum band structure of a metal oxide quantum well according to exemplary embodiments of the present disclosure. [Figure 68] Figures A and B show the population inversion distribution mechanism of electrons and holes in the quantum well band structure, and the resulting gain spectrum of the quantum well. [Figure 69] A and B show the energy states of electrons and holes in the packed conduction band and valence band in the energy momentum space for direct and pseudo-direct bandgap metal oxide structures according to exemplary embodiments of the present disclosure. [Figure 70] A and B illustrate an exemplary embodiment of the present disclosure of an impact ionization process of metal oxide implanted hot electrons resulting in pair formation. [Figure 71] A and B illustrate an impact ionization process of metal oxide implanted hot electrons resulting in pair formation, according to another exemplary embodiment of the present disclosure. [Figure 72] A and B illustrate the effect of an electric field applied to a metal oxide to generate a plurality of impulse ionization events, according to another exemplary embodiment of the present disclosure. [Figure 73] An exemplary embodiment of the present disclosure shows a vertical ultraviolet laser structure in which the reflector forms part of the cavity and electrical circuit. [Figure 74] An exemplary embodiment of the present disclosure shows a vertical ultraviolet laser structure in which the reflector forming the optical cavity is isolated from the electrical circuit. [Figure 75] An exemplary embodiment of the present disclosure shows a waveguide-type ultraviolet laser structure in which the reflector forming the optical cavity is isolated from the electrical circuit, and the optical gain medium embedded in the lateral cavity can have a length optimized for low threshold gain. [Figure 76A-1] A table showing the minimum bandgap energy and lattice parameters obtained by DFT calculations for several examples of epitaxial oxide materials is presented. [Figure 76A-2] A table showing the minimum bandgap energy and lattice parameters obtained by DFT calculations for several examples of epitaxial oxide materials is presented. [Figure 76B] The charts showing the minimum bandgap energy and lattice parameters obtained by DFT calculations for several examples of epitaxial oxide materials are presented. [Figure 76C] The charts showing the minimum bandgap energy and lattice parameters obtained by DFT calculations for several examples of epitaxial oxide materials are presented. [Figure 76D]The charts showing the minimum bandgap energy and lattice parameters obtained by DFT calculations for several examples of epitaxial oxide materials are presented. [Figure 77] The following charts show the band gap (minimum band gap energy (eV)) of epitaxial oxide materials obtained from several DFT calculations, and, in some cases, the crystal symmetry versus the lattice constant of the epitaxial oxide material. [Figure 78] A schematic example illustrating how epitaxial oxide materials with monoclinic unit cells can be adapted to epitaxial oxide materials with cubic unit cells is provided. [Figure 79] The following charts show the band gap (minimum band gap energy (eV)) of epitaxial oxide materials obtained from several DFT calculations, and, in some cases, the crystal symmetry versus the lattice constant of the epitaxial oxide material. [Figure 80] The charts of band gap (minimum band gap energy (eV)) versus lattice constants for several epitaxial oxide materials obtained by DFT calculations are shown, where all epitaxial oxide materials have cubic crystal symmetry with either an Fd3m or Fm3m space group. [Figure 81] The atomic structure of κ-Ga2O3 (i.e., Ga2O3 with the Pna21 space group) obtained by DFT calculation is shown. [Figure 82A] The band structure of κ-(AlxGa1-x)2O3 obtained by DFT calculation is shown, where x=0 in the equation. [Figure 82B] The band structure of κ-(AlxGa1-x)2O3 obtained by DFT calculation is shown, where x = 0.5 in the equation. [Figure 82C] The band structure of κ-(AlxGa1-x)2O3 obtained by DFT calculation is shown, where x=1 in the equation. [Figure 82D] The minimum band gap energy of κ-(AlxGa1-x)2O3 obtained by DFT calculation is shown, where x = 1, 0.5, and 0, indicating band bending due to the polarity of the material. [Figure 83]The band structure of Li-doped κ-Ga2O3, obtained by DFT calculations, is shown. In this structure, one Ga atom is replaced by a Li atom within each unit cell. [Figure 84] This chart summarizes the results from DFT calculations of the band structure of κ-Ga2O3 doped with different dopants. [Figure 85] Several DFT calculations have shown epitaxial oxide materials with lattice constants ranging from approximately 4.8 angstroms to approximately 5.3 angstroms, which can serve as substrates for α- and κ-AlxGa1-xOy such as LiAlO2 and Li2GeO3, and / or form heterostructures with them. [Figure 86] Several additional DFT calculations have shown epitaxial oxide materials with lattice constants ranging from approximately 4.8 angstroms to approximately 5.3 angstroms, which include α-SiO2, Al(111) 2x3 (i.e., the six atoms of Al(111) forming the 2x3 subarray have an acceptable lattice mismatch with one unit cell of κ-AlxGa1-xOy), and AlN(100) 1x4, which can serve as substrates for α- and κ-AlxGa1-xOy and / or form heterostructures with them. [Figure 87A] The atomic structure of κ-Ga2O3 on the surface of several compatible substrates is shown. [Figure 87B] The atomic structure of κ-Ga2O3 on the surface of several compatible substrates is shown. [Figure 87C] The atomic structure of κ-Ga2O3 on the surface of several compatible substrates is shown. [Figure 87D] The atomic structure of κ-Ga2O3 on the surface of several compatible substrates is shown. [Figure 87E] The atomic structure of κ-Ga2O3 on the surface of several compatible substrates is shown. [Figure 88] A flowchart illustrating an exemplary method for forming a semiconductor structure containing κ-AlxGa1-xOy is shown. [Figure 89A]This is a plot of the XRD intensity versus angle (in the Ω-2θ scan) of the experimental structure. [Figure 89B] This is a plot of the XRD intensity versus angle (in the Ω-2θ scan) of the experimental structure. [Figure 89C] This is a plot of the XRD intensity versus angle (in the Ω-2θ scan) of the experimental structure. [Figure 90A] An example of semiconductor structure 6201 containing an epitaxial oxide material in a layer or region is shown. [Figure 90B] An example of semiconductor structure 6202 containing an epitaxial oxide material in a layer or region is shown. [Figure 90C] An example of semiconductor structure 6203 containing an epitaxial oxide material in a layer or region is shown. [Figure 90D] An example of semiconductor structure 6204 containing an epitaxial oxide material in a layer or region is shown. [Figure 90E] An example of semiconductor structure 6205 containing an epitaxial oxide material in a layer or region is shown. [Figure 90F] An example of semiconductor structure 6206 containing an epitaxial oxide material in a layer or region is shown. [Figure 90G] An example of semiconductor structure 6207 containing an epitaxial oxide material in a layer or region is shown. [Figure 90H] An example of semiconductor structure 6208 containing an epitaxial oxide material in a layer or region is shown. [Figure 90I] An example of semiconductor structure 6209 containing an epitaxial oxide material in a layer or region is shown. [Figure 90J] An example of semiconductor structure 6201b containing an epitaxial oxide material in a layer or region is shown. [Figure 90K] An example of semiconductor structure 6202b containing an epitaxial oxide material in a layer or region is shown. [Figure 90L] An example of semiconductor structure 6203b containing an epitaxial oxide material in a layer or region is shown. [Figure 91A] This is a schematic diagram of an example of a semiconductor structure containing an epitaxial oxide layer on a suitable substrate. [Figure 91B] For an example of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials, the electron energy (y-axis) versus growth direction (x-axis) is shown. [Figure 91C] For an example of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials, the electron energy (y-axis) versus growth direction (x-axis) is shown. [Figure 91D] For an example of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials, the electron energy (y-axis) versus growth direction (x-axis) is shown. [Figure 91E] For an example of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials, the electron energy (y-axis) versus growth direction (x-axis) is shown. [Figure 91F] For an example of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials, the electron energy (y-axis) versus growth direction (x-axis) is shown. [Figure 91G] For an example of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials, the electron energy (y-axis) versus growth direction (x-axis) is shown. [Figure 91H] For an example of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials, the electron energy (y-axis) versus growth direction (x-axis) is shown. [Figure 91I] For an example of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials, the electron energy (y-axis) versus growth direction (x-axis) is shown. [Figure 92A] Examples of energy versus growth direction (distance, z) and wave functions for electrons and holes confined in each of different digital alloys are shown. [Figure 92B] Examples of energy versus growth direction (distance, z) and wave functions for electrons and holes confined in each of different digital alloys are shown. [Figure 92C]Examples of energy versus growth direction (distance, z) and wave functions for electrons and holes confined in each of different digital alloys are shown. [Figure 93] Figures 92A to 92C show plots of the effective band gap versus average composition (x) for the digital alloys. [Figure 94A] This shows the complete Ek-band structure of the epitaxial oxide material, which can be derived from the atomic structure of the crystal. [Figure 94B] This shows a simplified band structure representing the minimum band gap of the material, where the x-axis is space (z) rather than the wave vector (as in the Ek diagram). [Figure 95] This shows an example of a simplified band structure for a pin device containing an epitaxial oxide layer. [Figure 96] This shows a simplified band structure of a heterojunction pin device containing an epitaxial oxide layer. [Figure 97] This shows a simplified band structure of a multiple heterojunction PIN device containing an epitaxial oxide layer. [Figure 98A] This presents another example of a pin structure with multiple quantum wells, where the barrier layer of the multiple quantum well structure in the i-region has a band gap larger than the band gaps of the n- and p-layers. [Figure 98B] Figure 98A shows a single quantum well in the multiple quantum well structure. [Figure 99] Another example of a PIN structure with multiple quantum wells in the n, i, and p layers is shown. [Figure 100] Similar to the structure in Figure 99, another example of a PIN structure with multiple quantum wells in the n, i, and p layers is shown. [Figure 101A] An example of a semiconductor structure containing an (AlxGa1-x)2O3 layer is shown, where 0≦x≦1 in each layer. [Figure 101B] Figure 101A shows the structure in which the layers have been etched so that contacts can be formed on any layer of the semiconductor structure using "contact region #2", "contact region #3", and "contact region #4". [Figure 101C] Figure 101B shows the structure, which includes an additional "contact region #5" that contacts the back surface (opposite side of the epitaxial oxide layer) of the substrate ("SUB"). [Figure 102A] Figures 28, 76A-1, 76A-2, and 76B show simplified Ek diagrams of the Brillouin zone center of epitaxial oxide materials, illustrating the impact ionization process. [Figure 102B] Figures 28, 76A-1, 76A-2, and 76B show simplified Ek diagrams of the Brillouin zone center of epitaxial oxide materials, illustrating the impact ionization process. [Figure 103A] The graph shows the energy versus bandgap plots for epitaxial oxide materials (including the conductive band edge Ec and valence band edge Ev), with the dotted line indicating the approximate threshold energy required for hot electrons to generate excess electron-hole pairs through the impulse ionization process. [Figure 103B] An example of a hot electron in α-Ga2O3 with a band gap of approximately 5 eV is shown. [Figure 104A] A schematic diagram of an epitaxial oxide material having two planar contact layers (e.g., a metal or highly doped semiconductor contact material and a metal contact) coupled to an applied voltage Va is shown. [Figure 104B] The band diagram of the structure shown in Figure 104A is shown along the growth direction ("z") of the epitaxial oxide material. [Figure 104C] The band diagram of the structure shown in Figure 104A is shown along the growth direction ("z") of the epitaxial oxide material. [Figure 105] A schematic diagram of an example of an electroluminescent device including a high work function metal, an ultrawide bandgap layer, a wide bandgap epitaxial oxide layer, and a second metal contact is shown. [Figure 106]Figures A and B show schematic diagrams of an example of an electroluminescent device that is a pin diode, comprising a p-type semiconductor layer, a non-doped (NID) epitaxial oxide layer, an impulse ionization region (IIR), and an n-type semiconductor layer. [Figure 107] This shows the minimum band gap energy versus sublattice constant for monoclinic β(AlxGa1-x)2O3. [Figure 108] This shows the minimum band gap energy versus the sublattice constant "a" for hexagonal α(AlxGa1-x)2O3. [Figure 109] Examples of several embodiments that form the R3c(AlxGa1-x)2O3 epitaxial structure are shown. [Figure 110] This example demonstrates the implementation of stepwise incremental adjustment of the effective alloy composition in each SL region along the growth direction of the chirp layer. [Figure 111] (110) An experimental XRD plot of a step-gradient SL (SGSL) structure (forming a chirp layer) using a digital alloy containing a bilayer of αGa2O3 and αAl2O3 deposited on oriented sapphire (zero miscut) is shown. [Figure 112] Another example of a step-graded SL that can be used to form a pseudo-substrate with an in-plane lattice constant tuned for a subsequent high-quality, tightly lattice-matched active layer such as "bulk" (meaning a single layer, not SL) α(Alx5Ga1-x5)2O3. [Figure 113] This example shows a high-complexity digital alloy grading interleaved with a wide bandgap spacer, in this case an αAl2O3 interposer layer. [Figure 114A] Figure 113 shows plots of high-resolution Bragg XRD (upper plot) and micro-angle incident X-ray reflection (XRR) (lower plot) of a chirp SL with the interposer described. [Figure 114B] Figure 113 shows plots of high-resolution Bragg XRD (upper plot) and micro-angle incident X-ray reflection (XRR) (lower plot) of a chirp SL with the interposer described. [Figure 115A]Figures 112 and 113 show electron band diagrams as a function of the growth direction of the chirp layer structure. [Figure 115B] Figures 112 and 113 show electron band diagrams as a function of the growth direction of the chirp layer structure. [Figure 115C] For the chirp layer structure shown in Figures 112 and 113, the lowest energy quantization energy wavefunction confined within the αGa2O3 layer of the chirp layer is shown. [Figure 115D] Figures 115A to 115C show the wavelength spectra of the oscillator intensity of the electric dipole transition between the conduction band and valence band of the chirp layer, as modeled. [Figure 116A] This figure shows cross-sectional views of semiconductor structures (or stacks) for optoelectronic devices according to several embodiments of the present semiconductor structure having one or more superlattices containing epitaxial oxide materials. [Figure 116B] This figure shows cross-sectional views of semiconductor structures (or stacks) for optoelectronic devices according to several embodiments. [Figure 116C] This figure shows cross-sectional views of semiconductor structures (or stacks) for optoelectronic devices according to several embodiments. [Figure 117] This figure shows a cross-sectional view of a semiconductor structure (or stack) for an optoelectronic device according to one embodiment of the present semiconductor structure having one or more superlattices containing epitaxial oxide materials. [Figure 118] This figure shows a cross-sectional view of an optoelectronic device according to one embodiment of the semiconductor structure having one or more superlattices containing epitaxial oxide materials. [Figure 119] This figure shows a cross-sectional view of an optoelectronic device according to one embodiment of the semiconductor structure having one or more superlattices containing epitaxial oxide materials. [Figure 120] This figure shows a cross-sectional view of an optoelectronic device according to one embodiment of the semiconductor structure having one or more superlattices containing epitaxial oxide materials. [Figure 121]This figure shows a cross-sectional view of an optoelectronic device according to one embodiment of the semiconductor structure having one or more superlattices containing epitaxial oxide materials. [Figure 122] This figure shows a perspective view of an optoelectronic device according to one embodiment of the semiconductor structure having one or more superlattices containing epitaxial oxide materials. [Figure 123] This figure shows a cross-sectional view of an optoelectronic device according to one embodiment of the semiconductor structure having one or more superlattices containing epitaxial oxide materials. [Figure 124] A schematic example of interatomic forces (or stresses) present within a structure containing two unit cells is shown. [Figure 125] This specification outlines the effect of an embedded depletion field having potential energy along a distance parallel to the growth direction in a semiconductor structure having one or more superlattices containing the epitaxial oxide materials described herein. [Figure 126] This is a cross-sectional view of a structure including a semiconductor layer and a doped superlattice according to one embodiment. [Figure 127] This is a flowchart illustrating an example of a method for fabricating the doped superlattice described herein via a film formation process. [Figure 128] Figure 127 shows an example of a shutter sequence in the film formation process. [Figure 129] This is a cross-sectional view of an electronic device according to several embodiments. [Figure 130] Figure 129 is a cross-sectional view of an example of an LED device based on the structure of the electronic device shown. [Figure 131] Figures 129 and 130 show a cross-sectional view illustrating an example of an LED device based on the electronic and LED devices shown. [Figure 132] Figure 131 is a cross-sectional view of an example of an LED device based on the LED device shown. [Figure 133] This is a cross-sectional view showing an example of an LED device. [Figure 134]This shows a metal-polar "p-UP" LED structure for metal-polar epitaxial oxide film growth with respect to the growth axis (also called the growth direction "z"). [Figure 135] This shows an oxygen-polar "p-DOWN" LED structure for growing oxygen-polarized epitaxial oxide films relative to the growth axis. [Figure 136] Several embodiments of semiconductor structures (or stacks) for generating the electrical and optical components of a pn diode are shown. [Figure 137] Several embodiments of semiconductor structures (or stacks) for generating the electrical and optical components of a pin diode are shown. [Figure 138] This shows a further gradient pattern growth sequence in a gradient region with a chirp bilayer period and a constant xave superlattice structure. [Figure 139] A schematic flow diagram is shown for forming a semiconductor structure having gradient layers or gradient regions. [Figure 140A] This shows an epitaxial oxide semiconductor structure having an epitaxial oxide layer containing a wide-bandgap semiconductor and an adjacent epitaxial oxide layer containing a narrow-bandgap semiconductor. [Figure 140B] This shows a semiconductor structure having an epitaxial oxide layer containing a wide-bandgap semiconductor, an epitaxial oxide layer containing a narrow-bandgap semiconductor, and an epitaxial oxide chirp layer between the narrow-bandgap epitaxial oxide layer and the wide-bandgap epitaxial oxide layer. [Figure 140C] The diagram shows electrons moving from left to right within the structure. [Figure 140D] The diagram shows electrons moving from left to right within the structure (including the epitaxial oxide chirp layer). [Figure 141A] This is a schematic diagram of an example of a semiconductor structure including an epitaxial oxide semiconductor-metal junction according to several embodiments, wherein the epitaxial oxide semiconductor material is piezoelectric, and the composition or strain is steeply graded within the contact layer adjacent to the interface with the metal contact. [Figure 141B] This is a schematic diagram of an example of a semiconductor structure including a metal contact, an epitaxial oxide material of a specific composition, and an epitaxial oxide semiconductor-metal junction including a contact layer. [Figure 142] This shows a simplified schematic side view of the LED structure including the mesa structure, and an enlarged view of the sublayer thickness of the ohmic chirp layer (or chirp layer). [Figure 143] A and B illustrate examples of optimizing light extraction by selecting metal contact materials and emitter positions in LEDs or lasers. [Figure 144A] An example of a semiconductor structure having a distributed Bragg reflector (DBR) as part of the doped layer within the diode structure is shown. [Figure 144B] An example of a semiconductor structure having a distributed Bragg reflector (DBR) as part of the doped layer within the diode structure is shown. [Modes for carrying out the invention]

[0011] Disclosed herein are embodiments of optoelectronic semiconductor light-emitting devices that can be configured to emit light having wavelengths in the range of about 150 nm to about 280 nm. The device includes a metal oxide substrate having at least one epitaxial semiconductor metal oxide layer disposed thereon. The substrates include Al2O3, Ga2O3, MgO, LiF, MgAl2O4, MgGa2O4, LiGaO2, LiAlO2, (Al x Ga 1-x ) may include 2O3, MgF2, LaAlO3, TiO2, or quartz. In certain embodiments, one or more of the at least one semiconductor layers include at least one of Al2O3 and Ga2O3.

[0012] In a first aspect, the disclosure provides an optoelectronic semiconductor light-emitting device configured to emit light having wavelengths in the range of about 150 nm to about 280 nm, the device comprising a substrate having at least one epitaxial semiconductor layer disposed thereon, each of the one or more epitaxial semiconductor layers comprising a metal oxide.

[0013] In another form, each metal oxide of the one or more semiconductor layers is Al2O3, Ga2O 3、 MgO, NiO, Li2O, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, IrO2, and is selected from the group consisting of any combination of the foregoing metal oxides.

[0014] In another form, at least one of the one or more semiconductor layers is a single crystal.

[0015] In another form, at least one of the one or more semiconductor layers has a rhombohedral, hexagonal, or monoclinic crystal symmetry.

[0016] In another form, at least one of the one or more semiconductor layers is composed of a binary metal oxide, and the metal oxide is selected from Al2O3 and Ga2O3.

[0017] In another form, at least one of the one or more semiconductor layers is composed of a ternary metal oxide composition, and the ternary metal oxide composition includes at least one of Al2O3 and Ga2O3, and optionally, a metal oxide selected from MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2.

[0018] In another form, at least one of the one or more semiconductor layers is (Al x Ga 1-x )2O3 ternary metal oxide composition, where 0 < x < 1.

[0019] In another form, at least one of the one or more semiconductor layers includes a uniaxially deformed unit cell.

[0020] In another form, at least one of the one or more semiconductor layers includes a biaxially deformed unit cell.

[0021] In another form, at least one of the one or more semiconductor layers includes a unit cell that is triaxially deformed.

[0022] In another form, at least one of the one or more semiconductor layers is composed of a quaternary metal oxide composition, and the quaternary metal oxide composition includes either (i) a metal oxide selected from Ga2O3, Al2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, IrO2, or (ii) a metal oxide selected from Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2.

[0023] In another form, at least one of the one or more semiconductor layers is a quaternary metal oxide composition (Ni x Mg 1-x ) y Ga 2(1-y) O 3-2y and is composed of, where 0 < x < 1 and 0 < y < 1.

[0024] In another form, the surface of the substrate is configured to enable lattice matching of the crystal symmetry of at least one semiconductor layer.

[0025] In another form, the substrate is a single crystal substrate.

[0026] In another form, the substrate is selected from Al2O3, Ga2O3, MgO, LiF, MgAl2O4, MgGa2O4, LiGaO2, LiAlO2, MgF2, LaAlO3, TiO2, and quartz.

[0027] In another form, the surface of the substrate has matching of crystal symmetry and in-plane lattice constants to enable homoepitaxy or heteroepitaxy of at least one semiconductor layer.

[0028] In another form, one or more of the at least one semiconductor layer is of the direct bandgap type.

[0029] In a second aspect, the disclosure provides an optoelectronic semiconductor device for generating light of a predetermined wavelength, comprising a substrate and one or more epitaxial metal oxide layers supported by the substrate, each comprising a light-emitting region having a light-emitting region band structure configured to generate light of a predetermined wavelength.

[0030] In another embodiment, constructing an emission region band structure for generating light of a predetermined wavelength involves selecting one or more epitaxial metal oxide layers such that they have an emission region bandgap energy capable of generating light of a predetermined wavelength.

[0031] In another form, selecting one or more epitaxial metal oxide layers to have an emission region bandgap energy capable of generating light of a predetermined wavelength is a method in which a metal species (A) and oxygen (O) are bonded in a relative ratio of x and y. x O y This involves forming one or more epitaxial metal oxide layers containing a binary metal oxide in the form of [a specific type of metal oxide].

[0032] In another form, the binary metal oxide is Al2O3.

[0033] In another form, the binary metal oxide is Ga2O3.

[0034] In another form, the binary metal oxide is selected from the group consisting of MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2.

[0035] In another embodiment, selecting one or more epitaxial metal oxide layers to have an emission region bandgap energy capable of generating light of a predetermined wavelength includes forming one or more epitaxial metal oxide layers of a ternary metal oxide.

[0036] In another form, a ternary metal oxide contains metal species (A) and (B) bonded with oxygen (O) in relative ratios x, y, and n, A x By O n is a ternary metal oxide bulk alloy in the form of

[0037] In another form, the relative ratio of metal species B to metal species A ranges from a minority relative ratio to a majority relative ratio.

[0038] In another form, the ternary metal oxide is A x B 1-x O n in the form of, where 0 < x < 1.0.

[0039] In another form, metal species A is Al and metal species B is selected from the group consisting of Zn, Mg, Ga, Ni, rare earths, Ir, Bi, and Li.

[0040] In another form, metal species A is Ga and metal species B is selected from the group consisting of Zn, Mg, Ni, Al, rare earths, Ir, Bi, and Li.

[0041] In another form, the ternary metal oxide is (Al x Ga 1-x )2O3 in the form of, where 0 < x < 1. In other forms, x is about 0.1, or about 0.3, or about 0.5.

[0042] In another form, the ternary metal oxide is formed by continuous deposition of unit cells formed along the unit cell direction and includes an alternating arrangement layer of metal species A and metal species B having an intermediate O layer to form a ternary metal oxide regular alloy structure that forms a metal oxide regular alloy in the form of A - O - B - O - A - O - B - etc.

[0043] In another form, metal species A is Al, metal species B is Ga, and the ternary metal oxide regular alloy is in the form of Al - O - Ga - O - Al - etc.

[0044] In another form, the ternary metal oxide is in the form of a host binary metal oxide crystal having a crystal modifying species.

[0045] In another configuration, the host binary metal oxide crystal is selected from the group consisting of Ga2O3, Al2O3, MgO, NiO, ZnO, Bi2O3, r-GeO2, Ir2O3, RE2O3, and Li2O, and the crystal modifier species is selected from the group consisting of Ga, Al, Mg, Ni, Zn, Bi, Ge, Ir, RE, and Li.

[0046] In another embodiment, selecting one or more epitaxial metal oxide layers to have an emission region bandgap energy capable of generating light of a predetermined wavelength includes forming the one or more epitaxial metal oxide layers as a superlattice comprising two or more layers of metal oxide that form unit cells and are repeated along the growth direction with a fixed unit cell period.

[0047] In another form, the superlattice is a bilayer superlattice containing repeating layers of two different metal oxides.

[0048] In another form, the two different metal oxides include a first binary metal oxide and a second binary metal oxide.

[0049] In another form, the first binary metal oxide is Al2O3 and the second binary metal oxide is Ga2O3.

[0050] In another form, the first binary metal oxide is NiO, and the second binary metal oxide is Ga2O3.

[0051] In another form, the first binary metal oxide is MgO and the second binary metal oxide is NiO.

[0052] In another form, the first binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2, and the second binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2, excluding the first selected binary metal oxide.

[0053] In another form, the two different metal oxides include binary metal oxides and ternary metal oxides.

[0054] In another form, the binary metal oxide is Ga2O3, and the ternary metal oxide is (Al x Ga 1-x )2O3, and in the formula 0 <x<1.0である。

[0055] In another form, the binary metal oxide is Ga2O3, and the ternary metal oxide is Al x Ga 1-x O3, and in the formula 0 <x<1.0である。

[0056] In another form, the binary metal oxide is Ga2O3, and the ternary metal oxide is Mg x Ga 2(1-x) O 3-2x And in the formula 0 <x<1.0である。

[0057] In another form, the binary metal oxide is Al2O3, and the ternary metal oxide is (Al x Ga 1-x )2O3, and in the formula 0 <x<1.0である。

[0058] In another form, the binary metal oxide is Al2O3, and the ternary metal oxide is Al x Ga 1-x O3, and in the formula 0 <x<1.0である。

[0059] In another form, the binary metal oxide is Al2O3, and the ternary metal oxide is (Al x Er1-x ) is 2O3.

[0060] In another form, ternary metal oxides are (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al 2x Mg 1-x )O 2x+1 , (Ga 2x Mg 1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge 1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE 1-x )O3, (Al x RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 and (Ga 2x Li 2(1-x) )O 2x+1 Selected from the group consisting of, where 0 <x<1.0である。

[0061] In another form, the binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2.

[0062] In another form, the two different metal oxides include a first ternary metal oxide and a second ternary metal oxide.

[0063] In another form, the first ternary metal oxide is Al x Ga 1-x O, and the second ternary metal oxide is (Al x Ga 1-x )2O3 or Al y Ga 1-y O3, where 0 < x < 1 and 0 < y < 1.

[0064] In another form, the first ternary metal oxide is (Al x Ga 1-x )O3, and the second ternary metal oxide is (Al y Ga 1-y )O3, where 0 < x < 1 and 0 < y < 1.

[0065] In another form, the first ternary metal oxide is (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al 2x Mg 1-x )O 2x+1 , (Ga 2x Mg 1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge 1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE1-x )O3, (Al x RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 and (Ga 2x Li 2(1-x) )O 2x+1 A second ternary metal oxide is selected from the group consisting of the first selected ternary metal oxide, (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al 2x Mg 1-x )O 2x+1 , (Ga 2x Mg 1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge 1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE 1-x )O3, (Al x RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 , and (Ga 2x Li 2(1-x) )O 2x+1 Selected from the group consisting of, where 0 <x<1.0である .

[0066] In another form, the superlattice is a three-layer superlattice containing repeating layers of three different metal oxides.

[0067] In another form, the three different metal oxides include a first binary metal oxide, a second binary metal oxide, and a third binary metal oxide.

[0068] In another form, the first binary metal oxide is MgO, the second binary metal oxide is NiO, and the third binary metal oxide is Ga2O3.

[0069] In another form, the first binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2; the second binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2, excluding the first selected binary metal oxide; and the third binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2, excluding the first and second selected binary metal oxides.

[0070] In another form, the three different metal oxides include a first binary metal oxide, a second binary metal oxide, and a ternary metal oxide.

[0071] In another form, the first binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3 and IrO2, the second binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3 and IrO2 (where the first selected binary metal oxide is absent), and the ternary metal oxide is (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al 2xMg 1-x )O 2x+1 , (Ga 2x Mg 1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge 1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE 1-x )O3, (Al x RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 and (Ga 2x Li 2(1-x) )O 2x+1 Selected from the group consisting of, where 0 <x<1である。

[0072] In another form, the three different metal oxides include a binary metal oxide, a first ternary metal oxide, and a second ternary metal oxide.

[0073] In another form, the binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3 and IrO2, and the first ternary metal oxide is (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al 2x Mg 1-x )O 2x+1 , (Ga 2x Mg1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge 1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE 1-x )O3, (Al x RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 and (Ga 2x Li 2(1-x) )O2 x+1 A second ternary metal oxide is selected from the group consisting of the first selected ternary metal oxide, (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al 2x Mg 1-x )O 2x+1 , (Ga 2x Mg 1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE 1-x )O3, (Al x RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 and (Ga 2x Li 2(1-x) )O 2x+1 Selected from the group consisting of, where 0 <x<1である。

[0074] In another form, the three different metal oxides include a first ternary metal oxide, a second ternary metal oxide, and a third ternary metal oxide.

[0075] In another form, the first ternary metal oxide is (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al 2x Mg 1-x )O 2x+1 , (Ga 2x Mg 1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge 1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE 1-x )O3, (Alx RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 and (Ga 2x Li 2(1-x) )O 2x+1 A second ternary metal oxide is selected from the group consisting of the first selected ternary metal oxide, (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al 2x Mg 1-x )O 2x+1 , (Ga 2x Mg 1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x .Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge 1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE 1-x )O3, (Al x RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 and (Ga 2x Li 2(1-x) )O 2x+1 A third ternary metal oxide is selected from the group consisting of (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al2x Mg 1-x )O 2x+1 , (Ga 2x Mg 1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge 1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE 1-x )O3, (Al x RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 and (Ga 2x Li 2(1-x) )O 2x+1 Selected from the group consisting of, where 0 <x<1である。

[0076] In another form, the superlattice is a four-layer superlattice containing repeating layers of at least three different metal oxides.

[0077] In another form, the superlattice is a four-layer superlattice containing repeating layers of three different metal oxides, where selected metal oxide layers of three different metal oxides are repeated in the four-layer superlattice.

[0078] In another form, the three different metal oxides include a first binary metal oxide, a second binary metal oxide, and a third binary metal oxide.

[0079] In another configuration, the first binary metal oxide is MgO, the second binary metal oxide is NiO, and the third binary metal oxide is Ga2O3, which forms a four-layer superlattice containing MgO-Ga2O3-NiO-Ga2O3 layers.

[0080] In another form, three different metal oxides are Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, IrO2, (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al 2x Mg 1-x )O 2x+1 , (Ga 2x Mg 1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge 1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE 1-x )O3, (Al x RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 and (Ga 2x Li 2(1-x) )O 2x+1 Selected from the group consisting of, where 0 <x<1.0である。

[0081] In another form, the superlattice is a four-layer superlattice containing repeating layers of four different metal oxides.

[0082] In another form, four different metal oxides are Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, IrO2, (Ga 2x Ni 1-x )O 2x+1 , (Al 2x Ni 1-x )O 2x+1 , (Al 2x Mg 1-x )O 2x+1 , (Ga 2x Mg 1-x )O 2x+1 , (Al 2x Zn 1-x )O 2x+1 , (Ga 2x Zn 1-x )O 2x+1 , (Ga x Bi 1-x )2O3, (Al x Bi 1-x )2O3, (Al 2x Ge 1-x )O 2+x , (Ga 2x Ge 1-x )O 2+x , (Al x Ir 1-x )2O3, (Ga x Ir 1-x )2O3, (Ga x RE 1-x )O3, (Al x RE 1-x )O3, (Al 2x Li 2(1-x) )O 2x+1 and (Ga 2x Li 2(1-x) )O 2x+1 Selected from the group consisting of, where 0 <x<1.0である。

[0083] In another form, each individual layer of two or more metal oxide layers forming a superlattice unit cell has a thickness that is less than or approximately equal to the electron de Broglie wavelength in each individual layer.

[0084] In another embodiment, constructing an emission region band structure for generating light of a predetermined wavelength involves modifying the initial emission region band structure of one or more epitaxial metal oxide layers when forming an optoelectronic device.

[0085] In another embodiment, modifying the initial luminescence region band structure of one or more epitaxial metal oxide layers when forming an optoelectronic device involves introducing a predetermined strain into one or more epitaxial metal oxide layers during the epitaxial deposition of the one or more epitaxial metal oxide layers.

[0086] In another configuration, a predetermined strain is introduced to modify the initial emission region band structure from an indirect band gap to a direct band gap.

[0087] In another configuration, a predetermined strain is introduced to modify the initial band gap energy of the initial emission region band structure.

[0088] In another configuration, a predetermined strain is introduced to modify the initial valence electron band structure of the initial emission region band structure.

[0089] In another form, modifying the initial valence band structure involves increasing or decreasing the selected valence band relative to the Fermi energy level of the emission region.

[0090] In another form, modifying the initial valence band structure includes modifying the shape of the valence band structure to modify the localization characteristics of holes formed in the light-emitting region.

[0091] In another embodiment, introducing a predetermined strain into one or more epitaxial metal oxide layers involves selecting strained metal oxide layers having a composition and crystal symmetry that, when epitaxially formed on a substrate having a substrate composition and crystal symmetry, introduce a predetermined strain into the strained metal oxide layer.

[0092] In another form, the given strain is a biaxial strain.

[0093] In another form, the underlying layer is a metal oxide having a first crystal symmetry type, and the strained metal oxide layer also has a first crystal symmetry type, but has different lattice constants in order to introduce biaxial strain into the strained metal oxide layer.

[0094] In another configuration, the underlying metal oxide layer is Ga2O3, the strained metal oxide layer is Al2O3, and biaxial compression is introduced into the Al2O3 layer.

[0095] The underlying metal oxide layer is Al2O3, the strained metal oxide layer is Ga2O3, and biaxial tension is introduced into the Ga2O3 layer.

[0096] In another form, the given strain is a uniaxial strain.

[0097] In another form, the underlying layer has a first crystal symmetry type with asymmetric unit cells.

[0098] In another form, the strained metal oxide layer is monoclinic Ga2O3, Al x Ga 1-x It is either O or Al2O3, and in the formula x < 0 < 1.

[0099] In another form, the underlying layer and the strained layer form a superlattice layer.

[0100] In another embodiment, modifying the initial luminescence region band structure of one or more epitaxial metal oxide layers when forming an optoelectronic device involves introducing a predetermined strain into one or more epitaxial metal oxide layers after the epitaxial deposition of the one or more epitaxial metal oxide layers.

[0101] In another embodiment, the optoelectronic device comprises a first conductivity region having one or more epitaxial metal oxide layers having a first conductivity region band structure configured to work in conjunction with an emitting region to generate light of a predetermined wavelength.

[0102] In another embodiment, configuring a first conductivity region band structure to work in combination with an emission region to produce light of a predetermined wavelength includes selecting a first conductivity region energy band gap that is larger than the emission region energy band gap.

[0103] In another embodiment, configuring a first conductivity type region band structure to operate in combination with an emission region to produce light of a predetermined wavelength includes selecting the first conductivity type region to have an indirect band gap.

[0104] In another embodiment, forming a first conductive region band structure involves selecting a suitable metal oxide material or multiple materials in accordance with the principles and techniques considered in this disclosure relating to the light-emitting region, forming a superlattice in accordance with the principles and techniques considered in this disclosure relating to the light-emitting region, and / or in accordance with the principles and techniques considered in this disclosure relating to the light-emitting region. This includes one or more of the following: modifying the band structure of a first conductivity type region by applying strain.

[0105] In another configuration, the first conductivity type region is an n-type region.

[0106] In another embodiment, the optoelectronic device comprises a second conductivity region including one or more epitaxial metal oxide layers having a second conductivity region band structure configured to operate in combination with an emitting region and a first conductivity region to generate light of a predetermined wavelength.

[0107] In another embodiment, configuring a second conductivity region band structure to work in conjunction with an emission region to produce light of a predetermined wavelength involves selecting a second conductivity region energy band gap that is larger than the emission region energy band gap.

[0108] In another embodiment, configuring a second conductivity type region band structure to operate in combination with an emission region to produce light of a predetermined wavelength includes selecting the second conductivity type region to have an indirect band gap.

[0109] In another embodiment, constructing a second conductivity-type region band structure includes one or more of the following: selecting a suitable metal oxide material or a set of materials in accordance with the principles and techniques considered in this disclosure relating to the light-emitting region; forming a superlattice in accordance with the principles and techniques considered in this disclosure relating to the light-emitting region; and / or modifying the first conductivity-type region band structure by applying strain in accordance with the principles and techniques considered in this disclosure relating to the light-emitting region.

[0110] In another configuration, the second conductivity type region is a p-type region.

[0111] In another form, the substrate is formed from a metal oxide.

[0112] In other forms, metal oxides are Al2O3, Ga2O3, MgO, LiF, MgAl2O4, MgGa2O4, LiGaO2, LiAlO2, (Al x Ga 1-x ) Selected from the group consisting of 2O3, LaAlO3, TiO2, and quartz.

[0113] In another form, the substrate is formed from a metal fluoride.

[0114] In other forms, metal fluorides are MgF2 or LiF.

[0115] In another form, the given wavelength is in the wavelength range of 150 nm to 700 nm.

[0116] In another form, the given wavelength is in the wavelength range of 150 nm to 280 nm.

[0117] In a third aspect, the disclosure provides a method for forming an optoelectronic semiconductor device configured to emit light having wavelengths in the range of about 150 nm to about 280 nm, the method comprising: providing a metal oxide substrate having an epitaxial growth surface; oxidizing the epitaxial growth surface to form an activated epitaxial growth surface; and exposing the activated epitaxial growth surface to one or more atomic beams each containing high-purity metal atoms and one or more atomic beams each containing oxygen atoms, under conditions for depositing two or more epitaxial metal oxide films.

[0118] In another form, the metal oxide substrate includes an Al or Ga metal oxide substrate.

[0119] In another form, one or more atomic beams, each containing high-purity metal atoms, are used to produce Al, Ga 、 Mg, Ni, Li, Zn, Si, Ge, Er, Y, La, Pr, Gd, Pd, Bi, Ir 、 and includes any one or more metals selected from the group consisting of any combination of the aforementioned metals.

[0120] In another form, one or more atomic beams, each containing high-purity metal atoms, contain any one or more metals selected from the group consisting of Al and Ga, and the epitaxial metal oxide film is (Al x Ga 1-x The formula contains 2O3, and 0 ≤ x ≤ 1.

[0121] In another embodiment, the conditions for depositing two or more epitaxial metal oxide films include exposing an activated epitaxial growth surface to an atomic beam containing high-purity metal atoms and an atomic beam containing oxygen atoms, with an oxygen:total metal flux ratio > 1.

[0122] In another embodiment, at least one of two or more epitaxial metal oxide films provides a first conductivity type region comprising one or more epitaxial metal oxide layers, and at least another film of the two or more epitaxial metal oxide films provides a second conductivity type region comprising one or more epitaxial metal oxide layers.

[0123] In another form, two or more epitaxial (Al x Ga 1-x ) At least one of the 2O3 membranes is one or more epitaxial (Al x Ga 1-x ) Provides a first conductive region including a 2O3 layer, and two or more epitaxial (Al x Ga 1-x ) At least one other of the 2O3 membranes is one or more epitaxial (Al x Ga 1-x ) Provides a second conductive region including a 2O3 layer.

[0124] In another configuration, the substrate is placed in an ultra-high vacuum chamber (5 × 10) before the oxidation step. -10 It is treated by high-temperature (>800°C) desorption within a Torr (less than 35°C) to form an atomically flat epitaxial growth surface.

[0125] In another form, the method further includes monitoring the surface in real time to evaluate the quality of the atomic surface.

[0126] In another configuration, the surface is monitored in real time by reflected high-energy electron diffraction (RHEED).

[0127] In another form, oxidizing an epitaxial growth surface involves exposing the epitaxial growth surface to an oxygen source under conditions that oxidize the epitaxial growth surface.

[0128] In another configuration, the oxygen source is selected from one or more of the group consisting of oxygen plasma, ozone, and nitrous oxide.

[0129] In another configuration, the oxygen source is radio-frequency inductively coupled plasma (RF-ICP).

[0130] In another form, the method further includes monitoring the surface in real time to assess the oxygen density of the surface.

[0131] In another configuration, the surface is monitored in real time by RHEED.

[0132] In another embodiment, atomic beams containing high-purity Al atoms and / or high-purity Ga atoms are each radiated by a filament and delivered by an ejection cell containing an inert ceramic crucible, which is controlled by feedback sensing that monitors the metal melting temperature within the crucible. ru.

[0133] In another form, high-purity elemental metals with a purity of 6N to 7N or higher are used.

[0134] In another embodiment, the method further includes measuring the beam fluxes of Al and / or Ga and oxygen atomic beams to determine the relative flux ratio, and then exposing the activated epitaxial growth surface to the atomic beams at the determined relative flux ratio.

[0135] In another embodiment, the method further includes rotating the substrate as the activated epitaxial growth surface is exposed to the atomic beam to accumulate a uniform amount of atomic beam intersecting the substrate surface for a given deposition time.

[0136] In another embodiment, the method further includes heating the substrate when the activated epitaxial growth surface is exposed to an atomic beam.

[0137] In another configuration, the substrate is radiatively heated from behind using a blackbody emissivity that matches the absorption below the band gap of the metal oxide substrate.

[0138] In another form, the activated epitaxial growth surface is approximately 1 × 10⁻⁶ -6 Torr ~ approximately 1 × 10 -5 Exposed to an atomic beam in a Torr vacuum.

[0139] In another form, the atomic beam flux of Al and Ga on the substrate surface is approximately 1 × 10⁻⁶. -8 Torr ~ approximately 1 × 10 -6 It's Torr.

[0140] In another configuration, the oxygen atom beam flux on the substrate surface is approximately 1 × 10⁻⁶. -7 From Torr, approximately 1 × 10 -5 It's Torr.

[0141] In another form, the Al or Ga metal oxide substrate is A-plane sapphire.

[0142] In another form, the Al or Ga metal oxide substrate is monoclinic Ga2O3.

[0143] In another form, two or more epitaxial (Al x Ga 1-x The 2O3 film contains corundum-type AlGaO3.

[0144] In another form, two or more epitaxial (Al x Ga 1-x For each of the 2O3 membranes, x ≤ 0.5.

[0145] In a fourth aspect, the disclosure provides a method for forming a multilayer semiconductor device, comprising: forming a first layer having a first crystal symmetry and a first composition; and depositing a metal oxide layer having a second crystal symmetry and a second composition on the first layer in a non-equilibrium environment, wherein the deposition of the second layer on the first layer includes initial matching the second crystal symmetry to the first crystal symmetry.

[0146] In another embodiment, initial matching of the second crystal symmetry type to the first crystal symmetry type includes matching the first lattice configuration of the first crystal symmetry type with the second lattice configuration of the second crystal symmetry type at the horizontal plane growth interface.

[0147] In another embodiment, matching the first and second crystal symmetries involves substantially matching the end-face lattice constants of the first and second lattice configurations.

[0148] In another configuration, the first layer is corundum Al2O3 (sapphire), and the metal oxide layer is corundum Ga2O3.

[0149] In another configuration, the first layer is monoclinic Al2O3, and the metal oxide layer is monoclinic Ga2O3.

[0150] In another configuration, the first layer is R-face corundum Al2O3 (sapphire) prepared under O-rich growth conditions, and the metal oxide layer is corundum AlGaO3 selectively grown at low temperatures (<550°C).

[0151] In another configuration, the first layer is M-plane corundum Al2O3 (sapphire), and the metal oxide layer is corundum AlGaO3.

[0152] In another configuration, the first layer is A-plane corundum Al2O3 (sapphire), and the metal oxide layer is corundum AlGaO3.

[0153] In another configuration, the first layer is corundum Ga2O3, and the metal oxide layer is corundum Al2O3 (sapphire).

[0154] In another configuration, the first layer is monoclinic Ga2O3, and the metal oxide layer is monoclinic Al2O3 (sapphire).

[0155] In another configuration, the first layer is (-201) oriented monoclinic Ga2O3, and the metal oxide layer is (-201) oriented monoclinic AlGaO3.

[0156] In another configuration, the first layer is (010) oriented monoclinic Ga2O3, and the metal oxide layer is (010) oriented monoclinic AlGaO3.

[0157] In another configuration, the first layer is (001) oriented monoclinic Ga2O3, and the metal oxide layer is (001) oriented monoclinic AlGaO3.

[0158] In another embodiment, the first and second crystal symmetries are different, and aligning the first and second lattice arrangements involves reorienting the metal oxide layer to substantially align the in-plane atomic arrangement at the horizontal plane growth interface.

[0159] In another configuration, the first layer is C-face corundum Al2O3 (sapphire), and the metal oxide layer is one of monoclinic, triclinic, or hexagonal AlGaO3.

[0160] In another form, C-plane corundum Al2O3 (sapphire) is prepared under O-rich growth conditions to selectively grow hexagonal AlGaO3 at lower growth temperatures (<650°C).

[0161] In another approach, C-plane corundum Al2O3 (sapphire) is prepared under oxygen-rich growth conditions, and monoclinic AlGaO3 is selectively grown at a higher growth temperature (>650°C) with the Al% limited to approximately 45-50%.

[0162] In another configuration, R-plane corundum Al2O3 (sapphire) is prepared under oxygen-rich growth conditions, and monoclinic AlGaO3 is selectively grown at a growth temperature (>700°C) with an Al% content of <50%.

[0163] In another form, the first layer is A-plane corundum Al2O3 (sapphire), and metal oxide The material layer is (110) oriented monoclinic Ga2O3.

[0164] In another configuration, the first layer is (110) oriented monoclinic Ga2O3, and the metal oxide layer is corundum AlGaO3.

[0165] In another configuration, the first layer is (010) oriented monoclinic Ga2O3, and the metal oxide layer is (111) oriented cubic MgGa2O4.

[0166] In another configuration, the first layer is (100)-oriented cubic MgO, and the metal oxide layer is (100)-oriented monoclinic AlGaO3.

[0167] The first layer is (100) oriented cubic NiO, and the metal oxide layer is (100) oriented monoclinic AlGaO3.

[0168] In another embodiment, initial matching the second crystal symmetry to the first crystal symmetry involves depositing a buffer layer between the first layer and the metal oxide layer in a non-equilibrium environment, wherein the crystal symmetry of the buffer layer is the same as that of the first crystal symmetry, providing an atomically planar layer for seeding the metal oxide layer having the second crystal symmetry.

[0169] In another configuration, the buffer layer includes an O-terminated template for seeding the metal oxide layer.

[0170] In another configuration, the buffer layer includes a metal-terminated template for seeding the metal oxide layer.

[0171] In another embodiment, the first and second crystal symmetries are selected from the group consisting of cubic, hexagonal, orthorhombic, trigonal, rhombic, and monoclinic crystals.

[0172] In another embodiment, the first crystal symmetry and first composition of the first layer, and the second crystal symmetry and second composition of the second layer are selected to introduce a predetermined strain into the second layer.

[0173] In another form, the first layer is a metal oxide layer.

[0174] In another configuration, the first and second layers form a superlattice by creating repeating unit cells with a fixed unit cell period.

[0175] In another embodiment, the first and second layers are configured to have substantially equal but opposite strains in order to facilitate the formation of a defect-free superlattice.

[0176] In another embodiment, the method involves depositing an additional metal oxide layer having a third crystal symmetry and a third composition on a metal oxide layer in a non-equilibrium environment.

[0177] In another form, the third crystal form is selected from the group consisting of cubic, hexagonal, orthorhombic, trigonal, rhombic, and monoclinic crystals.

[0178] In another form, a multilayer semiconductor device is an optoelectronic semiconductor device that generates light of a predetermined wavelength.

[0179] In another form, the given wavelength is in the wavelength range of 150 nm to 700 nm.

[0180] In another form, the given wavelength is in the wavelength range of 150 nm to 280 nm.

[0181] In a fifth aspect, the Disclosure provides a method for forming an optoelectronic semiconductor device that generates light of a predetermined wavelength, the method comprising introducing a substrate; depositing a first conductivity type region comprising one or more epitaxial layers of metal oxide in a non-equilibrium environment; depositing an emission region comprising one or more epitaxial layers of metal oxide and comprising an emission region band structure configured to generate light of a predetermined wavelength in a non-equilibrium environment; and depositing a second conductivity type region comprising one or more epitaxial layers of metal oxide in a non-equilibrium environment.

[0182] In another embodiment, the given wavelength is in the wavelength range of approximately 150 nm to approximately 700 nm. In yet another embodiment, the given wavelength is in the wavelength range of approximately 150 nm to approximately 425 nm. In one example, bismuth oxide can be used to produce wavelengths up to approximately 425 nm.

[0183] In another form, the specified wavelength is in the wavelength range of approximately 150 nm to approximately 280 nm.

[0184] In yet another form, luminescence efficiency is controlled by the selection of the crystal symmetry type of the luminescent region. The optical selection rules for electric dipole emission are governed by the symmetry of the states of the conduction band and valence band, and the crystal symmetry type. A luminescent region having a crystal structure with point group symmetry can have either inverted centrosymmetry or non-inverted symmetry properties. The favorable selection of crystal symmetry to promote electric dipole or magnetic dipole optical transitions is asserted herein for applications to luminescent regions. Conversely, the favorable selection of crystal symmetry to suppress electric dipole or magnetic dipole optical transitions is also possible to promote optically non-absorbent regions of the device.

[0185] In summary, Figure 1 is a process flow diagram for constructing an optoelectronic semiconductor optoelectronic device according to an exemplary embodiment. In one example, the optoelectronic semiconductor device is a UV LED, and in a further example, the UV LED is configured to produce a predetermined wavelength in the wavelength range of approximately 150 nm to approximately 280 nm. In this example, the construction process first includes (i) selecting a desired operating wavelength (e.g., a UVC wavelength or a lower wavelength) in step 10, and (ii) selecting the optical configuration of the device (e.g., a perpendicular light-emitting device 70 in which the optical output vector or direction is substantially perpendicular to the plane of the epitaxial layer, or a waveguide device 75 in which the optical output vector is substantially parallel to the plane of the epitaxial layer) in step 60. The light emission properties of the device are partially implemented by the selection of semiconductor material 20 and optical material 30.

[0186] Taking UV LEDs as an example, an optoelectronic semiconductor device constructed according to the process shown in Figure 1 includes an emissive region based on a selected emissive region material 35, where photons are generated by the favorable spatial recombination of electrons in the conduction band and holes in the valence band. In one example, the emissive region includes one or more metal oxide layers.

[0187] The light-emitting region may have a direct bandgap band structure configuration. This may be an intrinsic property of the selected material(s) or can be tuned using one or more of the techniques of this disclosure. The photorecombination or light-emitting region may be clad by an electron and hole reservoir containing n-type and p-type conductive regions. The n-type and p-type conductive regions are selected from an electron and hole injection material 45 that may have a larger bandgap than the light-emitting region material 35 or may contain an indirect bandgap structure that limits light absorption at the operating wavelength. In one example, the n-type and p-type conductive regions are formed from one or more metal oxide layers.

[0188] Doping with impurities in Ga2O3 and low Al% AlGaO3 affects both n-type and p-type materials. This is possible for both types of doping. n-type doping is particularly preferred for Ga2O3 and AlGaO3, while p-type doping is more difficult but possible. Suitable impurities for n-type doping are Si, Ge, Sn, and rare earth elements (e.g., erbium (Er) and gadolinium (Gd)). The use of Ge flux for co-deposition doping control is particularly suitable. In p-type co-doping with group III metals, the Ga site is magnesium (Mg 2+ ), zinc (Zn 2+ ) and atomic nitrogen (N relative to the O site) 3- It can be substituted via substitution. Further improvements can be made using iridium (Ir), bismuth (Bi), nickel (Ni), and palladium (Pd).

[0189] Digital alloys using NiO, Bi2O3, Ir2O3, and PdO can also be used in some embodiments to advantageously support p-type formation in Ga2O3-based materials. While p-type doping of AlGaO3 is possible, cubic crystal symmetric metal oxides (e.g., Li-doped NiO or Ni-vacant NiO) are also possible. x>1 Alternative doping strategies using wurtzite p-type Mg:GaN are also possible.

[0190] Another opportunity is the ability to form a hexagonal symmetric, highly polar form and epsilon phase Ga2O3 directly integrated into AlGaO3, thereby inducing polarization pairing according to the principles and techniques described and referenced in U.S. Patent No. 9,691,938. An optical material 30 is also required to confine light within the device as a differential change in refractive index. For far-ultraviolet or vacuum ultraviolet light, the selection of optically transparent materials ranges from MgO to metallic fluorides such as MgF2 and LiF. According to this disclosure, single-crystal LiF and MgO substrates are found to be advantageous for the realization of UV LEDs.

[0191] The electrical material 50 forming the contact area to the electron and hole injector region is selected from metals with low and high work functions, respectively. In one example, the metal ohmic contact is formed in situ directly on the final metal oxide surface, resulting in a reduction of any intermediate-level traps / defects that occur at the semiconductor oxide-metal interface. The device is then constructed in step 80.

[0192] Figures 2A and 2B schematically show a vertical emission device 110 and a waveguide emission device 140 according to exemplary embodiments. Device 110 has a substrate 105 and a light-emitting structure 135. Similarly, device 140 has a substrate 155 and a light-emitting structure 145. Light 125 and 130 from device 110, and light 150 from device 140, are generated from a photo-generating region 120, propagate from region 120 through the device, and are confined by an optical escape cone defined by the difference in refractive index at the semiconductor-air interface. Because metal oxide semiconductors have a very large bandgap energy, their refractive index is significantly lower compared to III-N materials. Therefore, using metal oxide materials provides an improved optical escape cone and thus higher optical output coupling efficiency compared to conventional light-emitting devices. Waveguide devices operating in single-mode and multi-mode are also possible.

[0193] Broadband stripe waveguides can also utilize elemental metals Al or Mg to directly form ultraviolet plasmon guides at the semiconductor-metal interface. This is an efficient method for forming waveguide structures. Ek-band structures for Al, Mg, and Ni will be discussed later. Once the desired material selection is available, the process for constructing semiconductor optoelectronic devices may occur in step 80 (see Figure 1).

[0194] Figure 3A shows a functional region of the epitaxial structure of an optoelectronic semiconductor device 160 for generating light of a predetermined wavelength, according to an exemplary embodiment.

[0195] The substrate 170 is provided with a surface featuring favorable crystal symmetry and matching in-plane lattice constants, This allows for homoepitaxy or heteroepitaxy of the first conductivity region 175 having a subsequent non-absorbent spacer region 180, an emitting region 185, an optional second spacer region 190, and a second conductivity region 195. In one example, the in-plane lattice constant and lattice shape / arrangement are matched to modify (i.e., reduce) lattice defects. Electrical excitations are provided by a source 200 connected to electron injection and hole injection regions of the first conductivity region 175 and the second conductivity region 195. Ohmic metal contacts and low-bandgap or semimetallic zero-bandgap oxide semiconductors are shown in another exemplary embodiment as regions 196, 197, and 198 in Figure 3B.

[0196] The first and second conductivity regions 175 and 195 are, in one example, formed using a metal oxide having a wide bandgap and are electrically contacted using the ohmic contact regions 197, 198 and 196 described herein. In the case of an insulating type substrate 170, the electrical contact configuration is achieved through the ohmic contact region 198 and the first conductivity region 175 for one conductivity type (i.e., electrons or holes), and using the ohmic contact region 196 and the second conductivity region 195 for the other. The ohmic contact region 198 may optionally be created on an exposed portion of the first conductivity region 175. The insulating substrate 170 may also be transparent or opaque with respect to the operating wavelength; in the case of a transparent substrate, the lower ohmic contact region 197 may be used as an optical reflector as part of an optical resonator in another embodiment.

[0197] In the case of a vertically conductive device, the substrate 170 is conductive and may be either transparent or opaque with respect to the operating wavelength. Electrical or ohmic contact areas 197 and 198 are arranged to favorably enable both electrical connections and optical propagation within the device.

[0198] Figure 3C schematically shows further possible electrical arrangements of electrical contact regions 196 and 198, with mesa-etched portions for exposing low-conductivity regions 175 and 198. The ohmic contact region 196 may be further patterned to expose a portion of the device for photoextraction.

[0199] Figure 3D shows yet another electrical configuration in which an insulating substrate 170 is used such that a first conductive region 175 is exposed and an electrical contact is formed on the partially exposed portion of the first conductive region 175. For conductive and transparent substrate contacts, an ohmic contact region 198 is not required, and a spatially arranged electrical contact region 197 is used.

[0200] Figure 3E further illustrates possible arrangements of optical apertures 199 partially or completely etched into an optically opaque substrate 170 for optical coupling of light generated from the light-emitting region 185. Optical apertures can also be utilized using the earlier embodiments shown in Figures 3A to 3D.

[0201] Figure 4 schematically illustrates the operation of the optoelectronic semiconductor device 160, and the exemplary configuration includes an electron injection region 180 and a hole injection region 190 with an electrical bias 200, which transport mobile electrons 230 and holes 225 and direct them to a recombination region 220. The resulting electron-hole recombination forms a spatial emission region 185.

[0202] A very large energy band gap (E G ) metal oxide semiconductor (E G Electrons with >4eV may exhibit low-mobility hole-type carriers and may even be highly localized spatially, thus limiting the spatial range of hole injection. Subsequently, the regions adjacent to the hole injection region 190 and the recombination region 220 may be favorable for the recombination process. Furthermore, the hole injection region 190 itself may be a preferred region for injecting electrons such that the recombination region 220 is located within a portion of the hole injection region 190.

[0203] Referring to Figure 5, selective spatial recombination of electrons and holes generates light or emission within the device 160, producing high-energy photons 240, 245, and 250 of predetermined wavelengths determined by the band structure configuration of the metal oxide layer that forms the emission region 185, as will be described later. Both electrons and holes instantly annihilate, generating photons that are characteristic of the band structure of the selected metal oxide.

[0204] Light generated within the light-emitting region 185 can propagate within the device according to the crystal symmetry of the metal oxide host region. The crystal symmetry group of the host metal oxide semiconductor has distinct energy and crystal momentum dispersions known as Ek configurations that characterize the band structures of various regions, including the light-emitting region 185. Non-trivial Ek dispersions are essentially determined by the physical atomic arrangement that underlies the distinct crystal symmetry of the host medium. In general, the possible polarization, emission energy, and intensity of the light-emitting oscillator are directly related to the valence band dispersion of the host crystal. According to this disclosure, embodiments favorably configure a band structure, including the valence band dispersion of a selected metal oxide semiconductor, for application to optoelectronic semiconductor devices, such as UV LEDs, in one example.

[0205] The vertically generated light 240 and 245 must satisfy optical selection rules for the underlying band structure. Similarly, there are optical selection rules for the generation of transverse light 250. These optical selection rules can be achieved for each region within the UV LED by favorable arrangement of crystal symmetry and the physical spatial orientation of the crystal. Favorable orientation of the constituent metal oxide crystal as a function of the growth direction is beneficial for the optimal operation of the UV LED of this disclosure. Furthermore, the selection of optical properties 30 in the process flow diagram shown in Figure 1, such as the refractive index, which forms the waveguide device, is shown for light confinement and low loss.

[0206] Figure 6 further illustrates another embodiment, for completeness, which includes an optical aperture 260 located within the optoelectronic semiconductor device 160, enabling the use of a material 195 opaque to the operating wavelength and providing optical output coupling from the light-emitting region 185.

[0207] Figure 7 outlines selection criteria 270 for one or more metal oxide crystal compositions according to exemplary embodiments. First, a semiconductor material 275 is selected. The semiconductor material 275 may include a metal oxide semiconductor 280 which may be one or more of binary oxides, ternary oxides, or quaternary oxides. The recombination region 220 (see, for example, Figure 5) that forms the light-emitting region 185 of the optoelectronic semiconductor device 160 is selected to exhibit efficient electron-hole recombination, while the conductive region is selected for its ability to provide a source of electrons and holes. Metal oxide semiconductors can also be selectively produced from multiple possible crystal symmetries, even if the constituent metal species are the same. A containing one metal species x O y A binary metal oxide of this form may be used, in which the metal species (A) bonds with oxygen (O) in a relative ratio of x to y. Even if the relative ratio of x to y is the same, multiple crystal structure configurations with significantly different crystal symmetry groups are possible.

[0208] As will be explained below, compositions Ga2O3 and Al2O3 exhibit several advantageous and distinct crystal symmetries (e.g., monoclinic, rhombohedral, triclinic, and hexagonal), but attention should be paid to their usefulness in incorporating them to construct UV LEDs. Other advantageous metal oxide compositions such as MgO and NiO show little variation in the achievable crystal structure, i.e., cubic.

[0209] The addition of a favorable second heterologous metal species (B) enhances the binary metal oxide crystal structure of the host, A x B y O nIt is also possible to produce ternary metal oxides in this form. The ternary metal oxides range from dilute additions of type B to the majority relative proportions. As described below, ternary metal oxides advantageously form bandgap emission structures directly in various embodiments. It can be used in quaternary composition A x B y C z O n Further materials can be designed that contain three different cation atoms bonded to oxygen, forming a structure.

[0210] In general, while it is theoretically possible to form complex oxide materials by incorporating more (>4) dissimilar metal atoms, it is rare to produce high crystalline quality with a very clear crystal symmetry structure. Such composite oxides are generally polycrystalline or amorphous and therefore lack optimal utility for applications in optoelectronic devices. As will become apparent, this disclosure seeks substantially single-crystal, low-defect-density configurations for forming UV LED epitaxial forming devices by utilizing band structure in various examples. Some embodiments include achieving the desired Ek configuration by adding another different metal species.

[0211] The selection of a desired bandgap structure for each of the UVLED regions of the optoelectronic semiconductor device 160 may include the integration of different crystal symmetries. For example, monoclinic and cubic crystal symmetry host regions, including a portion of the UVLED, can be utilized. The epitaxial formation relationship then requires attention to the formation of low-defect layers. The type of layer formation step is then classified as homosymmetric and heterosymmetric formation 285. To achieve the goal of providing a material that forms an epitaxial layer structure, band structure modifiers 290 such as digital alloys, biaxial strain, uniaxial strain, and superlattice formation can be utilized.

[0212] Next, the epitaxy process 295 is defined by the type and sequence of material compositions required for deposition. This disclosure describes novel processes and compositions for achieving this objective.

[0213] Figure 8 shows the formation steps of the epitaxy process 300. In step 310, a film-forming substrate for supporting the light-emitting region is selected to have the properties of the desired crystal symmetry type, as well as optical and electrical properties. In one example, the substrate is selected to be optically transparent to the operating wavelength and to have a crystal symmetry that matches the required epitaxial crystal symmetry type. Equivalent crystal symmetries can be used for both the substrate and the epitaxial film(s), but there are also optimizations 315 to match the in-plane atomic arrangement, such as favorable co-incidence of in-plane shapes of each crystal plane from different crystal symmetries or in-plane lattice constants.

[0214] The substrate surface has a distinct two-dimensional crystalline arrangement of terminating surface atoms. In a vacuum, this discontinuity of distinct crystalline structure in the prepared surface results in minimization of the surface energy of the dangling bonds of the terminating atoms. For example, in one embodiment, a metal oxide surface can be prepared as an oxygen-terminated surface, or in another embodiment, as a metal-terminated surface. Metal oxide semiconductors can have complex crystalline symmetries, and terminating pure species may require care. For example, both Ga2O3 and Al2O3 can be O-terminated by high-temperature annealing in a vacuum followed by sustained exposure to atomic or molecular oxygen at high temperatures.

[0215] The crystal surface orientation 320 of the substrate can also be selected to achieve selective film formation crystal symmetry of epitaxial metal oxides. For example, A-face sapphire can be used to favorably select (110)-oriented alpha-phase-forming high-quality epitaxial Ga2O3, AlGaO3, and Al2O3, while C-face sapphire can produce hexagonal and monoclinic Ga2O3 and AlGaO3 films. Ga2O3-oriented surfaces can also be selectively used for film formation selection of AlGaO3 crystal symmetry.

[0216] Next, the growth conditions 325 are optimized for the relative ratio of elemental metals and activated oxygen necessary to achieve the desired material properties. The growth temperature is also determined in the determination of possible crystal structure symmetries. This plays a crucial role. A wise selection of the substrate surface energy through appropriate crystal surface orientation also determines the temperature process window of the epitaxial process in which the epitaxial structure 330 is deposited.

[0217] A database of material selections 350 for applications in UV LED-based optoelectronic devices is disclosed in Figure 9. Metal oxide materials 380 are plotted as a function of their electron affinity energy 375 relative to vacuum. Arranged from left to right, semiconductor materials have increasing optical band gaps, thus increasing their usefulness in short-wavelength UV LEDs. Using lithium fluoride (LiF) as an example in this graph, LiF has a band gap 370 (represented as boxes for each material), which is the energy difference in electron volts between the minimum value 360 ​​of the conduction band and the maximum value 365 of the valence band. The absolute energy positions represented by the minimum value 360 ​​of the conduction band and the maximum value 365 of the valence band are plotted against vacuum energy. Narrow-bandgap materials such as rare-earth nitrides (RE-N), germanium (Ge), palladium oxide (PdO), and silicon (Si) do not provide suitable host properties for the light-emitting region, but can be advantageously used for forming electrical contacts. The inherent electron affinity of a given material can be used to form ohmic contacts and metal-insulator-semiconductor junctions as needed.

[0218] The preferred material combination for use as a substrate is bismuth oxide (Bi2O3), nickel oxide (NiO), and germanium oxide (GeO2O3). x~2These include gallium oxide (Ga2O3), lithium oxide (Li2O), magnesium oxide (MgO), aluminum oxide (Al2O3), single-crystal quartz SiO2, and finally lithium fluoride 355 (LiF). Specifically, Al2O3 (sapphire), Ga2O3, MgO, and LiF are available as large, high-quality single-crystal substrates and, in some embodiments, can be used as substrates for UV LED type optoelectronic devices. Additional embodiments of substrates for UV LED applications also include single-crystal cubic symmetric magnesium aluminate (MgAl2O4) and magnesium gallate (MgGa2O4). In some embodiments, ternary forms of AlGaO3 can be prepared as monoclinic (high Ga%) and corundum (high Al%) crystal symmetric bulk substrates using large-area formation methods such as Czochralski (CZ) and edge-fed growth (EFG).

[0219] Considering Ga2O3 and Al2O3 as host metal oxide semiconductors, in some embodiments, alloying and / or doping via elements selected from database 350 is advantageous for film formation properties.

[0220] Therefore, elements selected from silicon (Si), germanium (Ge), Er (erbium), Gd (gadolinium), Pd (palladium), Bi (bismuth), Ir (iridium), Zn (zinc), Ni (nickel), Li (lithium), and magnesium (Mg) are desirable crystal modifiers for forming ternary crystal structures or for forming dilute additives to Al2O3, AlGaO3, or Ga2O3 host crystals (see semiconductor 280 in Figure 7).

[0221] Further embodiments include selection from the group of crystal modifiers selected from the group consisting of Bi, Ir, Ni, Mg, and Li.

[0222] In applications to host crystals Al2O3, AlGaO3, or Ga2O3, possible multivalent states using Bi and Ir can be added to enable p-type impurity doping. Addition of Ni and Mg cations also enables substitutional doping of p-type impurities at Ga or Al crystal sites. In one embodiment, lithium may be used as a crystal modifier that can increase the band gap and modify the crystal symmetry as much as possible, ultimately This can be used for orthorhombic lithium gallate (LiGaO2) and tetragonal aluminum gallate (LiAlO2). For n-type doping, Si and Ge may be used as impurity dopants, with Ge providing an improved growth process for film formation.

[0223] Other materials are also possible, but database 350 offers properties that are advantageous for application to UV LEDs.

[0224] Figure 10 shows a sequential epitaxial layer formation process flow 400 used to epitaxially integrate material regions defined within an optoelectronic semiconductor device 160 according to an exemplary embodiment.

[0225] The substrate 405 is prepared using a surface 410 configured to receive a first conductive crystal structure layer(s) 415 which may contain multiple epitaxial layers. Next, a first spacer region composition layer(s) 420 which may contain multiple epitaxial layers is formed on layer 415. Then, an emitting region 425 is formed on layer 420, and region 425 may contain multiple epitaxial layers. Next, a second spacer region 430 which may contain multiple epitaxial layers is deposited on region 425. Then, a second conductive cap region 435 which may contain multiple epitaxial layers completes the majority of the UV LED epitaxial structure. To complete the optoelectronic semiconductor device, other layers may be added, such as an ohmic metal layer and passive optical layers such as light-confining or anti-reflective layers.

[0226] Referring to Figure 11, possible selections of the ternary metal oxide semiconductor 450 are shown for the case of gallium oxide-based (GaOx-based) composition 485. Ternary oxide alloy A x B 1-x The optical band gap 480 for various values ​​of x in O is graphed. As previously mentioned, metal oxides can exhibit several stable forms of more complex crystal symmetry structures by the addition of other species that form ternaries. However, exemplary general trends can be found by favorably incorporating or alloying aluminum, group II cations {Mg, Ni, Zn}, iridium, erbium, gadolinium atoms, and lithium atoms into Ga oxides. Ni and Ir typically form deep d-bands, but useful optical structures can be formed at high Ga%. Ir can have multiple valence states, and in some embodiments, the Ir2O3 form is utilized.

[0227] X = one of {Ir, Ni, Zn, Bi} is Ga x X 1-x When O is alloyed, the available optical band gap decreases (see curves labeled 451, 452, 453, and 454). Conversely, when one of Y={Al, Mg, Li, RE} is alloyed, ternary Ga x Y 1-x The available band gap for O increases (see curves 456, 457, 458, and 459).

[0228] Therefore, Figure 11 can be understood as an application for forming light-emitting and conductive regions according to this disclosure.

[0229] Similarly, Figure 12 discloses possible selections of ternary metal oxide semiconductors 490 for aluminum oxide-based (AlOx-based) compositions 485 with respect to the optical band gap 480. Examining the curves, one of X = {Ir, Ni, Zn, Mg, Bi, Ga, RE, Li} is Al x X 1-xWhen alloyed with O, it is observed that the available optical band gap decreases. The Y={Ni, Mg, Zn} group forms a spinel crystal structure, but all are ternary Al x Y 1-x This reduces the available band gap of O (see curves 491, 492, 493, 494, 495, 496, 500, 501). Figure 12 shows rhombohedral crystal pairs. The energy gap of 502 for alpha-phase aluminum oxide (Al2O3) is also shown.

[0230] Therefore, Figure 12 can be understood in terms of applications to the formation of luminescent and conductive regions according to this disclosure. Figure 28 shows Chart 2800 of potential ternary oxide combinations (0 ≤ x ≤ 1) that can be employed according to this disclosure. Chart 2800 shows the crystal growth modifier at the bottom of the left column and the host crystal across the top of the chart.

[0231] Figures 13A and 13B show the direct band gap (Figure 13A) and indirect band gap (Figure 13B) of possible metal oxide-based semiconductors, illustrating concepts related to the formation of optoelectronic devices according to this disclosure. Researchers in the fields of quantum mechanics and crystal structure design know that symmetry directly determines the electronic or band structure of a single crystal structure.

[0232] Generally, when applied to luminescent crystal structures, two classes of electron band structures exist, as shown in Figures 13A and 13B. The fundamental process utilized in the optoelectronic devices of this disclosure is the physical recombination of (large amounts of) electron and hole particle-like charge carriers, which is the manifestation of allowable energy and crystal momentum. The recombination process can be generated by conserving the crystal momentum of the incident carriers from the initial state to the final state.

[0233] The final state is achieved when electrons and holes annihilate each other, forming a massless photon (i.e., the momentum k of the massless photon in the final state). γ ga kγ The case of (=0) requires a special Ek band structure as shown in Figure 13A. Metal oxide semiconductor structures with pure crystal symmetry can be calculated using various computational techniques. One such method is density function theory, which, using the first principle, can construct an atomic structure including distinct pseudopotentials associated with each constituent atom containing the structure. The band structure resulting from the crystal symmetry and spatial geometry can be calculated using an iterative calculation scheme of ab initio total energy calculations with a plane wave basis.

[0234] Figure 13A shows the reciprocal space energy versus crystal momentum or band structure of the crystal structure. The momentum vector of the crystal k =

number

number

number

[0235] The dispersions 525 and 535 represent the electron energy in electron volts (530 in the increasing direction, 585 in the decreasing direction) and the crystal momentum in reciprocal space units (positive K representing different crystal wave vectors from the Brillouin zone center). BZ 545 and negative K BZThe band structure is plotted with respect to 540). The band structure 520 is shown at the highest point of symmetry in the crystal, labeled as the Γ point representing the band structure at k=0. The band gap is defined by the energy difference between the minimum and maximum values ​​of 525 and 535, respectively. Electrons propagating through the crystal minimize their energy and relax to the minimum value of the conduction band 565. Similarly, holes relax to the lowest energy state 580.

[0236] If 565 and 580 are simultaneously located at k=0, then a direct recombination process can occur in which the electron and hole annihilate each other, producing a new massless photon 570 with an energy approximately equal to the bandgap energy 560. That is, the electron and hole at k=0 can recombine and recombine and conserve the crystal moment to produce a massless particle called a “direct” bandgap material. As disclosed, this situation is actually rare, and only a small subset of all crystal-symmetric semiconductors exhibit this favorable configuration.

[0237] Referring to the crystal structure 590 in Figure 13B, if the primary bands 525 and 620 of the band structure do not have a minimum value of 565 and a maximum value of 610, respectively, at k=0, this is called an "indirect" configuration. The minimum band gap energy 600 is still defined as the energy difference between the minimum value of the conductive band and the maximum value of the valence band occurring with the same wave vector, and is known as the indirect band gap energy 600. The luminescence process is clearly undesirable because crystal momentum cannot be conserved in recombination events, and secondary particles such as crystal vibrational quantum phonons are required to conserve crystal momentum. In metal oxides, the longitudinal optical phonon energy is proportional to the band gap and is very large compared to the energy seen in GaAs, Si, etc.

[0238] Therefore, it is difficult to use indirect Ek configurations for the purpose of luminescence. This disclosure describes methods for manipulating the otherwise indirect band gap of a particular crystal symmetry structure to convert or modify the zone-center k=0 properties of the band structure into direct band-gap dispersions suitable for luminescence. These methods are disclosed herein for application to the fabrication of optoelectronic devices, specifically UV LEDs.

[0239] Even when a direct bandgap configuration exists, the design choice faces the specific crystal symmetry of a given metal oxide, which has electric dipole selection rules governed by symmetry characteristic groups assigned to each energy band. In the case of Ga2O3 and Al2O3, optical absorption is controlled between the lowest conductivity band and the three uppermost valence bands.

[0240] Figures 13C to 13E show the emission and absorption transitions at k=0 with respect to the monoclinic symmetry of Ga2O3. Figures 13C to 13E each show the three valence bands E vi (k)621, 622, and 623 are shown. In Figure 13C, the optically permissible electric dipole transition is shown to be permissible for electron 566 and hole 624 with respect to the optical deflection vectors in the a-axis and c-axis of the monoclinic unit cell. With respect to reciprocal space Ek, this corresponds to the wave vector 627 of the Γ-Y ​​branch. Similarly, the electric dipole transition between electron 566 and hole 625 in Figure 13D is permissible for the deflection along the c-axis 628 of the crystal unit cell. Furthermore, the higher energy transition between electron 566 and hole 626 in Figure 13E is permissible for the optical deflection field along the b-axis 629 of the unit cell, corresponding to the Ek(Γ-X) branch.

[0241] Clearly, the magnitudes of energy transitions 630, 631, and 632 in Figures 13C, 13D, and 13E increase only at the lowest energy transitions favorable for luminescence. However, the Fermi energy level (E F ) is the lowest valence band 621, which is E F Higher, 622 is E FIf configured to be lower, emission can occur at energy 631. These selection rules are particularly useful when designing waveguide devices with optical polarization that depends on specific TE, TM, and TEM operating modes.

[0242] Referring to the above description relating to the band structure, and hereby referring to Figures 14A and 14B, these figures illustrate how these complex elements can be incorporated into the device structure 160. Each functional region of the UV LED has a specific Ek dispersion, having both indirect and direct materials, which may result from dramatically different crystal symmetries. This, in turn, allows for the advantageous embedding of the light-emitting regions within the device.

[0243] Figures 14A and 14B show representations of composite Ek materials by a single block 633 defined by layer thicknesses 655, 660, and 665, and fundamental bandgap energies 640, 645, and 650, respectively. The relative alignment of the conductive band edge and the valence band edge is shown in block 633. Figure 14B shows the electron energy 670 versus the spatial growth direction 635 for three distinct materials having bandgap energies 640, 645, and 650. For example, a first region with a final surface lattice constant geometry that can provide mechanical-elastic deformation of subsequent crystals 645 is possible, which is deposited along the growth direction 635 using an indirect crystal. For example, this can occur when growing AlGaO3 directly on Ga2O3.

[0244] Epitaxial manufacturing method

[0245] Non-equilibrium growth techniques are known in the prior art and are called atomic and molecular beam epitaxy, chemical vapor phase epitaxy, or physical vapor phase epitaxy. Atomic and molecular beam epitaxy utilizes atomic beams of components directed at spatially separated growth surfaces, as shown in Figure 15. Molecular beams are also used, but according to this disclosure, only combinations of molecular and atomic beams are available.

[0246] One guideline is to use a pure component source that can be multiplexed on the growth surface through favorable condensation and kinematically favorable growth conditions in order to physically construct crystalline atomic layers layer by layer. While the grown crystal can substantially self-assemble, the control of this method also allows for intervention at the atomic level, enabling the deposition of epitaxial layers of a single type and atomic thickness. Unlike equilibrium growth techniques that depend on the thermodynamic chemical potential of bulk crystal formation, this technique allows for the deposition of very thin atomic layers with growth parameters far removed from the equilibrium growth temperature of bulk crystals.

[0247] For example, Al2O3 films are formed at film formation temperatures in the range of 300-800°C, but conventional bulk equilibrium growth of Al2O3 (sapphire) is produced at temperatures far exceeding 1500°C and requires a molten reservoir containing Al and O liquids that can be configured to position solid seed crystals very close to the molten surface. Careful positioning of the seed crystal orientation ensures that it is placed in contact with the molten material, forming recrystallized portions in the vicinity of the molten material. When the seed and partially solidified recrystallized portions are pulled away from the molten material, a continuous crystalline boule is formed.

[0248] Such equilibrium growth methods for metal oxides limit the possible combinations of metals and the complexity of discontinuous regions that can lead to the formation of heteroepitaxial structures. The non-equilibrium growth techniques according to this disclosure can operate with growth parameters far from the melting point of the target metal oxide and can even modulate the atomic species present in a single atomic layer of the crystal unit cell along a pre-selected growth direction. Such non-equilibrium growth methods are not bound by the equilibrium phase diagram. They are not bundled. For example, this method utilizes an evaporation source material that includes a beam that strikes the growth surface in an ultra-high purity and substantially neutral charge state. Charged ions may be generated, but these should be kept to a minimum as much as possible.

[0249] In the case of metal oxide growth, the relative ratios of the component source beams can be altered in known ways. For example, oxygen-rich and metal-rich growth conditions can be achieved by controlling the relative beam flux measured at the growth surface. Almost all metal oxides grow optimally under oxygen-rich growth conditions, similar to the arsenic-rich growth of gallium arsenide (GaAs), but some materials are different. For example, GaN and AlN require metal-rich growth conditions with a very narrow growth window, which is one of the biggest limitations on mass production.

[0250] Metal oxides prefer oxygen-rich growth within a broad growth window, but there is an opportunity to intervene and create intentionally metal-deficient growth conditions. For example, both Ga2O3 and NiO prefer cation vacancies for the generation of active-hole conductive types. Physical cation vacancies can generate electron-carrier type holes and therefore prefer p-type conductivity.

[0251] Referring here to Figure 41, a process flow diagram 4100 of the method for forming an optoelectronic semiconductor device according to the present disclosure is shown as an overview. In one example, the optoelectronic semiconductor device is configured to emit light at wavelengths of approximately 150 nm to approximately 280 nm.

[0252] In step 4110, a metal oxide substrate having an epitaxial growth surface is provided. In step 4120, the epitaxial growth surface is oxidized to form an activated epitaxial growth surface. In step 4130, the activated epitaxial growth surface is exposed to one or more atomic beams containing high-purity metal atoms and one or more atomic beams containing oxygen atoms, under conditions for depositing two or more epitaxial metal oxide films or layers.

[0253] Referring again to Figure 15, one example shows an epitaxial deposition system 680 for providing atomic and molecular beam epitaxy according to method 4100, as referenced in Figure 41.

[0254] In one example, the substrate 685 is rotated about axis AX and radiatively heated by a heater 684 having an emissivity designed to match the absorption of the metal oxide substrate. The high vacuum chamber 682 has several element sources 688, 689, 690, 691, 692 that can produce atoms or molecular species as beams of pure atomic components. A plasma source or gas source 693 and a gas feed 694, which is a connection to the gas source 693, are also shown.

[0255] For example, sources 689-692 may include ejection-type sources of liquid Ga and Al and Ge or precursor-based gases. Active oxygen sources 687 and 688 may be supplied via plasma-excited molecular oxygen (forming atomic O and O2*), ozone (O3), nitrous oxide (N2O), etc. In some embodiments, plasma-excited oxygen is used as a controllable source of atomic oxygen. Multiple gases can be injected via sources 695, 696, and 697 to provide mixtures of different species for growth. For example, atomic nitrogen and excited molecular nitrogen make it possible to purify n-type, p-type, and semi-insulating conductive films on Ga oxide-based materials. A vacuum pump 681 maintains the vacuum, and a mechanical shutter intersecting the atomic beam 686 modulates the respective beam fluxes, providing a line of sight to the substrate deposition surface.

[0256] This deposition method has proven particularly useful in enabling the flexibility to incorporate elemental species into Ga oxide-based and Al oxide-based materials.

[0257] Figure 16 shows an embodiment of an epitaxial process 700 for constructing a UV LED as a function of the growth direction 705. A homosymmetric layer 735 can be formed using a native substrate 710. The substrate 710 and the crystalline epitaxy layer 735 are homosymmetric and are labeled as type 1 herein. For example, corundum-type sapphire substrates can be used to deposit corundum crystal symmetric layers 715, 720, 725, and 730. Yet another example is using monoclinic substrate crystal symmetry to form monoclinic crystal symmetric layers 715-730. This is readily possible using native substrates for growing target materials disclosed herein (see, for example, Table I in Figure 43A). Of particular interest is the growth of epitaxial layers such as corundum AlGaO3 having multiple compositions for layers 715-730. Alternatively, a monoclinic Ga2O3 substrate 710 can be used to form multiple monoclinic AlGaO3 compositions for layers 715-730.

[0258] Referring here to Figure 17, a further epitaxial process 740 is illustrated, using a substrate 710 having a crystal symmetry that is essentially heterosymmetric with respect to the crystal type of the target epitaxial metal oxide layers 745, 750, 755, and 760. That is, the substrate 710 is of crystal symmetry type 1, which is heterosymmetric with respect to the crystal structure epitaxy 765 consisting of layers 745, 750, 755, and 760, all of which are of type 2.

[0259] For example, a C-plane corundum sapphire substrate can be used to deposit at least one of monoclinic, triclinic, or hexagonal AlGaO3 structures. Another example is the epitaxial deposition of a corundum AlGaO3 structure using a (110)-oriented monoclinic Ga2O3 substrate. Yet another example is the epitaxial deposition of a (100)-oriented monoclinic AlGaO3 film using a MgO(100)-oriented cubic symmetric substrate.

[0260] Process 740 can also be used to produce a corundum Ga2O3 modified surface 742 by selectively diffusing Ga atoms into the surface structure provided by the Al2O3 substrate. This can be done by increasing the growth temperature of the substrate 710, exposing the Al2O3 surface to excess Ga and simultaneously providing an O atom mixture. Under Ga-rich conditions and high temperatures, Ga adsorbed atoms selectively adhere to O sites, forming volatile suboxide Ga2O, and the excess Ga further diffuses the Ga adsorbed atoms onto the Al2O3 surface. Under suitable conditions, a corundum Ga2O3 surface structure can be obtained, resulting in monoclinic AlGaO3 crystal symmetry, enabling a Ga-rich AlGaO3 corundum structure or lattice matching of thicker layers.

[0261] Figure 18 illustrates yet another embodiment of process 770 in which a buffer layer 775 is deposited on a substrate 710, the buffer layer 775 having the same crystal symmetry type (Type 1) as the substrate 710, thereby allowing atomically planar layers to seed alternative crystal symmetry types for layers 780, 785, 790 (Types 2, 3…N). For example, a monoclinic buffer 775 is deposited on a monoclinic bulk Ga2O3 substrate 710. Next, cubic MgO and NiO layers 780-790 are formed. In this figure, a heterosymmetric crystal structure epitaxy with a homosymmetric buffer layer is labeled as structure 800.

[0262] Figure 19 further illustrates a further embodiment of process 805 showing sequential changes along the growth direction 705 for multiple crystal symmetries. For example, a corundum Al2O3 substrate 710 (Type 1) generates an O-terminated template 810, which then seeds a Type 2 crystal symmetry corundum AlGaO3 layer 815. Subsequently, a Type 3 crystal symmetry hexagonal AlGaO3 layer 820 can be formed, and then a cubic crystal symmetry type (Type N), such as a MgO or NiO layer 830, can be formed. Layers 815, 820, 825, and 830 are shown in this figure. The tetrasymmetric crystal structure is collectively labeled as epitaxy 835. Such crystal growth is possible using very different crystal symmetry layers, where co-incident shapes of in-plane lattices can occur. Although rare, this is the case with (100) oriented cubic Mg x Ni 1-x This has been found to be possible in this disclosure using O(0≦x≦1) and monoclinic AlGaO3 compositions. This procedure can then be repeated along the growth direction.

[0263] Another embodiment is shown in Figure 20A, in which a type 1 crystal symmetry substrate 710 has a prepared surface (template 810) that seeds a first crystal symmetry type 815 (type 2), which can then be designed to transition to another symmetry type 845 (transition type 2-3) over a given layer thickness. An optional layer 850 can then be grown with yet another crystal symmetry type (type N). For example, a C-plane sapphire substrate 710 forms a corundum Ga2O3 layer 815, which is then relaxed to a hexagonal or monoclinic crystal symmetry type. Further growth of layer 850 can then be used to form a high-quality relaxed layer with high crystal structure quality. Layers 815, 845, and 850 are collectively labeled as heterosymmetric crystal structure epitaxy 855 in this figure.

[0264] Referring here to Figure 20B, Chart 860 shows the variation of a specific crystal surface energy 865 as a function of crystal surface orientation 870 for corundum-sapphire 880 and monoclinic Gallia single-crystal oxide material 875. According to this disclosure, it has been found that AlGaO3 crystal symmetry can be selectively formed using the crystal surface energies of technically relevant corundum Al2O3 880 and monoclinic substrates.

[0265] For example, the C-face of sapphire can be prepared under oxygen-rich growth conditions to selectively grow hexagonal AlGaO3 at lower growth temperatures (<650°C) and monoclinic AlGaO3 at higher temperatures (>650°C). Monoclinic AlGaO3 is limited to about 45-50% Al% due to monoclinic crystal symmetry with about 50% tetrahedral coordination bonds (TCBs) and 50% octahedral coordination bonds (OCBs). Ga can correspond to both TCBs and OCBs, but Al preferentially seeks OCB sites. R-face sapphires can correspond to corundum AlGaO3 compositions with Al% in the range of 0-100% grown at low temperatures below about 550°C under oxygen-rich conditions, and monoclinic AlGaO3 with Al <50% grown at high temperatures >700°C.

[0266] Remarkably, M-face sapphires can be grown only with corundum AlGaO3 compositions of Al%=0~100%, providing an atomically flat surface and an even more stable surface.

[0267] Even more surprising is the discovery of A-plane sapphire surfaces for corundum AlGaO3 compositions with extremely low defect densities and for AlGaO3 capable of superlattices (see explanation below). This result is essentially due to the fact that both corundum Ga2O3 and corundum Al2O3 share an exclusive crystal symmetry structure formed by OCB. This translates into very stable growth conditions within a growth temperature window ranging from room temperature to 800°C. This clearly demonstrates the need for attention to crystal symmetry design, which can generate novel structural forms applicable to LEDs such as UV LEDs.

[0268] Similarly, native monoclinic Ga2O3 substrates with (-201) oriented surfaces can only accommodate monoclinic AlGaO3 compositions. The Al% of (-201) oriented films is significantly lower due to the TCB presented by the growing crystal surface. While this does not favor a large Al percentage, it can be used to form very shallow MQWs of AlGaO3 / Ga2O3.

[0269] Surprisingly, the (010) and (001) oriented surfaces of monoclinic Ga2O3 can correspond to monoclinic AlGaO3 structures of very high crystal quality. The main limitation is the accumulation of biaxial strain. Careful strain control in this disclosure using AlGaO3 / Ga2O3 superlattices allowed us to find a limit of Al% < 40%, enabling us to achieve higher quality films using (001) oriented Ga2O3 substrates. Furthermore, a further example of (010) oriented monoclinic Ga2O3 substrates is the extremely high-quality lattice matching of MgGa2O4(111) oriented films with a cubic crystal symmetry structure.

[0270] Similarly, the crystal symmetry of MgAl2O4 is compatible with the corundum AlGaO3 composition. It has also been experimentally found in accordance with this disclosure that (100)-oriented Ga2O3 provides nearly perfect matching lattice alignment for cubic MgO(100) and NiO(100) films. Even more surprising is the usefulness of (110)-oriented monoclinic Ga2O3 substrates for the epitaxial growth of corundum AlGaO3.

[0271] These unique properties, for example, through the selective use of crystal surface orientation, provide selective utility for Al2O3 and Ga2O3 crystal symmetric substrates, offering many advantages in the manufacture of LEDs, specifically UV LEDs.

[0272] In some embodiments, conventional bulk crystal growth techniques can be employed to form corundum-AlGaO3 compositional bulk substrates having corundum and monoclinic crystal symmetry. These ternary AlGaO3 substrates are also expected to have value for application in UV LED devices.

[0273] Band structure modifier

[0274] The optimization of the AlGaO3 band structure can be achieved by paying attention to structural deformations of a given crystal symmetry. In solid-state, specifically semiconductor-based, electro-optically driven ultraviolet light-emitting devices, the valence band structure (VBS) is crucial. Typically, it is the VBSE-k dispersion that determines the efficiency of light emission generation through direct electron-hole recombination. Therefore, attention is focused on valence band tuning options to achieve one exemplary UVLED operation.

[0275] Band structure formation due to biaxial strain

[0276] In some embodiments, selective epitaxial deposition of AlGaO3 crystal structures can be formed under elastic structural deformation by using compositional control or by using a surface crystal geometry arrangement that allows for epitaxial registration of the AlGaO3 film while still maintaining the elastic deformation of the AlGaO3 unit cells.

[0277] For example, Figures 21A–21C show the change in Ek band structure near the center of the Brillouin zone (k=0), which is favorable for eh recombination to generate bandgap energy photons under the influence of biaxial strain applied to the crystal unit cell. The band structures of both corundum and monoclinic Al2O3 are direct. The deposition of Al2O3, Ga2O3, or AlGaO3 thin films on suitable surfaces that can elastically strain the in-plane lattice constant of the film can be achieved and designed according to this disclosure.

[0278] The lattice constant mismatch between Al2O3 and Ga2O3 is shown in Table II of Figure 43B. Ternary alloys can be roughly interpolated between two endpoints of the same crystal symmetry type. In general, Al2O3 films deposited on a Ga2O3 substrate that preserves crystal orientation form an Al2O3 film with biaxial tension, while Ga2O3 films deposited on an Al2O3 substrate with the same orientation have a compressed crystal orientation.

[0279] Monoclinic and corundum crystals have non-trivial geometric structures with relatively complex strain tensors compared to conventional cubic, sphalerite, and even wurtzite crystals. General trends observed for Ek dispersion near the BZ center are shown in Figures 21A and 21B. For example, Figure 890 in Figure 21A describes a c-plane corundum crystal unit cell 894 with unstrained (σ=0) Ek dispersion, comprising a conductive band 891 and a valence band 892 separated by a band gap 893. Biaxial compression of unit cell 899 in Figure 895 in Figure 21B alters the dispersion by hydrostatically lifting the conductive band, for example, the conductive band 896, and distorting the Ek curvature of the valence band 897. The compressive strain (σ<0) band gap 898 generally increases as follows:

number

[0280] Conversely, as shown in Figure 900 of Figure 21C, the biaxial tension applied to the unit cell 904 is the band gap 903

number

[0281] Band structure formation due to uniaxial strain

[0282] Of particular interest is the possibility of favorably modifying the valence band structure using uniaxial strain, as shown in Figures 22A and 22B, where the reference numerals in Figure 22A correspond to those in Figure 21A. For example, in-plane uniaxial deformation of unit cell 894 along substantially one crystal direction, as shown in unit cell 909, deforms the valence band 907 asymmetrically, as shown in Figure 905, which also shows the conductive band 906 and band gap 908.

[0283] In the case of monoclinic and corundum crystal symmetric films, similar behavior occurs, and Al2O3 / Ga2O3 and Al2O3 are formed on Al2O3 and Ga2O3 substrates. x Ga 1-x O3 / Ga2O3 and Al x Ga 1-x This can be represented by an elastically distorted superlattice structure containing O3 / Al2O3. Such structures were grown in connection with this disclosure, and the critical layer thickness (CLT) was found to depend on the surface orientation of the substrate and range from 1–2 nm to about 50 nm for binary Ga2O3 on sapphire. Monoclinic Al x Ga 1-x O 3x If x < 10%, CLT can exceed 100 nm on Ga2O3.

[0284] Uniaxial strain can be achieved by growth on a crystal-symmetric surface having a surface shape with asymmetric surface unit cells. This can be achieved in both corundum and monoclinic crystals under various surface orientations, as shown in Figure 20B, but is also possible in other surface orientations and crystals, such as MgO(100), MgAl2O4(100), 4H-SiC(0001), ZnO(111), Er2O3(222), and AlN(0002).

[0285] Figure 22B shows a favorable deformation of the valence band structure in the case of a direct band gap. In the case of an indirect band gap Ek dispersion, such as a thin monolayer monoclinic Ga2O3, the valence band dispersion can be adjusted from indirect to a direct band gap, as shown in the transition from Figure 23A or 23B to Figure 23C. Consider the unstrained band structure 915 in Figure 23B, which has a conductivity band 916, a valence band 917, a band gap 918, and a maximum valence band value 919. Similarly, the compressed structure 910 in Figure 23A shows a conductivity band 911, a valence band 912, a band gap 913, and a maximum valence band value 914. The tensile structure 920 in Figure 23C shows a conductivity band 921, a valence band 922, a band gap 923, and a maximum valence band value 924. Detailed calculations and experimental angle-resolved photoelectron spectroscopy (ARPES) can demonstrate that applying uniaxial strains of compressive strain (valence band 912) and tensile strain (valence band 922) along the b-axis or c-axis of a monoclinic Ga2O3 unit cell can cause the valence bands to bend, as shown in structures 910 and 920.

[0286] As shown in these figures, strain plays a crucial role and typically requires the management of complex epitaxy structures. Failure to manage strain accumulation can lead to the relaxation of elastic energy within the unit cell, generating dislocations and crystallographic defects that reduce the efficiency of UV LEDs.

[0287] Formation of band structure due to stress application after growth

[0288] The techniques described above involve introducing stress in the form of uniaxial or biaxial strain during layer formation, but in other embodiments, external stress may be applied following the formation or growth of a layer or multiple layers of metal oxide to form a band structure as needed. Exemplary techniques that can be employed to introduce these stresses are disclosed in U.S. Patent No. 9,412,911.

[0289] Band structure configuration by selection of alloy composition

[0290] Another mechanism utilized in this disclosure and applied to luminescent metal oxide-based UV LEDs is the use of compositional alloying to form a ternary crystalline structure with a desired direct band gap. Generally, two different binary oxide material compositions are shown in Figures 24A and 24B. Band structure 925 includes a metal oxide AO having a crystalline structure material 930 constructed from metal atoms 928 and oxygen atoms 929, with a conductive band 926, valence band dispersion 927 and a direct band gap 931. Another binary metal oxide BO has a crystalline structure material 940 constructed from different metal cations of type B 938 and oxygen atoms 939, and has an indirect band structure 935 having a conductive band 936, a band gap 941 and a valence band dispersion 937. In this example, the common anion is oxygen, and both AO and BO have the same basic crystal symmetry type.

[0291] In other respects, metal atoms A and B are mixed with cation sites (AO) within a similar oxygen matrix. x (BO) 1-x If a ternary alloy can be formed by forming A, then this has the same basic crystal symmetry. x B 1-x This results in an O composition. Based on this, it is then possible to form a ternary metal oxide with a valence band mixing effect, as shown in Figure 25B (Note: Figures 25A and 25C reproduce Figures 24A and 24B). The direct valence band dispersion 927 of the BO crystal structure material 940 alloyed with the AO crystal structure material 930 having indirect valence band dispersion 937 exhibits improved valence band dispersion 947, and a ternary material 948 having a conductive band 946 and a band gap 949 can be produced. That is, atomic species A of material 930 incorporated into the B site of material 940 can increase the valence band dispersion. Atomic density functional theory calculation This can be used to simulate this concept, which fully explains the pseudopotential, strain energy, and crystal symmetry of the constituent atoms.

[0292] Therefore, alloying corundum Al2O3 and Ga2O3 can result in a direct band gap in the band structure of ternary metal oxide alloys, and can also improve the valence band curvature of monoclinic compositions.

[0293] Band structure configuration by digital alloy fabrication selection

[0294] While ternary alloy compositions such as AlGaO3 are desirable, an equivalent method for generating ternary alloys involves the use of digital alloy formation, which utilizes a superlattice (SL) constructed from periodic repeats of at least two different materials. If each layer constituting the repeating unit cell of the SL is below the electron de Broglie wavelength (typically around 0.1 to several tens of nm), then the periodicity of the superlattice forms a "mini-Brillouin zone" within the crystal band structure, as shown in Figure 27A. In practice, the new periodicity is superimposed on the inherent crystal structure by the formation of a given SL structure. The SL periodicity is usually one-dimensional in the direction of growth of epitaxial film formation.

[0295] In graph 950 of Figure 26, we consider the valence band state 953 inherent to material 955 and the valence band state 954 from material 956. The Ek dispersion shows the energy gap 957 along the energy axis 951 of region 958 and the first Brillouin zone edge 959 for k=0. Region 958 is the forbidden energy gap (ΔE) between energy band states 953 and 954, and is the bulk energy band of materials 955 and 956. Materials A and B form a superlattice 968 as shown in Figure 27B, with an SL period L SL However, the average lattice constant a of A and B AB Multiples of (for example, L SL =2a ABWhen selected, new states 961, 962, 963, and 964 are then generated, as shown in Figure 27A. Thus, the superlattice energy potential generates an SL band gap 967 at k=0. This effectively folds the energy band 953 from the first bulk Brillouin zone edge 959 to k=0. In other words, when the superlattice is made into an extremely thin layer (thicknesses 970 and 971, respectively) using two materials 955 and 956, a periodic repeating unit 969 is formed, and the original bulk valence band states 953 and 954 fold into new energy band states 961, 962, 963, and 964. In other words, the superlattice potential generates a new energy dispersion structure containing the band states 961, 962, 963, and 964. When the superlattice period imposes a new spatial potential, the Brillouin zone collapses into a wave vector 975.

[0296] This type of SL structure in Figure 27B is a different example of Al x Ga 1-x O / Ga2O3, Al x Ga 1-x O3 / Al2O3, Al2O3 / Ga2O3 and Al x Ga 1-x O3 / Al y Ga 1-y It can be produced using a two-layer pair containing O3.

[0297] A common use of SL for constructing optoelectronic devices is disclosed in U.S. Patent No. 10,475,956.

[0298] Figure 27C shows the SL structure for a digital binary metal oxide containing Al2O3 layer 983 and Ga2O3 layer 984. The structure is shown with respect to the electron energy 981 as a function of the epitaxial growth direction 982. The period of the SL forming the repeating unit cell 980 repeats in integer or half-integer repeats. For example, the number of repeats can vary from 3 or more periods to 100 or 1000 or more periods. Equivalent digital alloy Al x Ga 1-xThe average Al% content of O is

number

number

number

[0299] Furthermore, further examples of possible SL structures are shown in Figures 27D to 27F.

[0300] The concept of digital alloys can be extended to other different crystal symmetries, for example, cubic NiO987 and monoclinic Ga2O3986 as shown in Figure 27D, where digital alloy 985 is equivalent to ternary (NiO) x (Ga2O3) 1-x This simulates bulk alloy.

[0301] Another example is shown in the digital alloy 990 in Figure 27E, which uses cubic MgO layers 991 and cubic NiO layers 992 to constitute SL. In this example, MgO and NiO have very close lattice matching, unlike Al2O3 and Ga2O3 which have large lattice mismatch.

[0302] A four-layer periodic SL996 is shown in the digital alloy 995 of Figure 27F, where cubic MgO and NiO grown oriented along (100) can be matched to the lattice of (100)-oriented monoclinic Ga2O3. Such an SL is Ga x Ni y Mg z O n It has an effective quaternary composition.

[0303] Band structure of Al-Ga oxides

[0304] The UV LED configuration region is made of binary or ternary aluminum formed by bulk or digital alloy formation. x Ga 1-x The O3 composition can be selected. As mentioned above, advantageous valence band tuning using biaxial or uniaxial strain is also possible. An exemplary process flow 1000 describing possible selection criteria for selecting at least one of the crystal modification methods for forming the bandgap region of a UV LED is shown in Figure 29.

[0305] In step 1005, whether the band gap is direct or indirect, the band gap energy, E fermi A band structure configuration is selected that includes, but is not limited to, band structure characteristics such as carrier mobility, doping, and deflection. In step 1010, it is determined whether the binary oxide is suitable, and further in step 1015, whether the band structure of the binary oxide can be modified (i.e., adjusted) to meet the requirements. If a binary oxide material meets the requirements, this material is selected for the relevant layer of the optoelectronic device in step 1045. If a binary oxide is not suitable, it is determined in step 1025 whether a ternary oxide is suitable, and further in step 1030 whether the band structure of the ternary oxide can be modified to meet the requirements. If a ternary oxide meets the requirements, this material is selected for the relevant layer in step 1045.

[0306] If the ternary oxide is not suitable, step 1035 determines whether the digital alloy is suitable, and further step 1040 determines whether the band structure of the digital alloy can be modified to meet the requirements. If the digital alloy meets the requirements, step 1045 selects this material for the relevant layer. Following the layer determination in this manner, step 1048 fabricates the optoelectronic device stack.

[0307] Ternary alloy Al x Ga 1-xOne embodiment of the energy band lineups for Al2O3 and Ga2O3 with respect to O3 is shown in Figure 1050 of Figure 30, which varies with respect to corundum and monoclinic crystal symmetry in the offset of the conduction band and valence band. In Figure 1050, the y-axis is electron energy 1051 and the x-axis is different material types 1053 (Al2O3 1054, (Ga1Al1)O3 1055 and Ga2O3 1056). Although both corundum and monoclinic heterojunctions appear to have type I and type II offsets, Figure 30 simply plots the band alignment using existing values ​​for electron affinity of each material.

[0308] The theoretical electron band structures of corundum and monoclinic bulk crystal forms of Al2O3 and Ga2O3 are known in the prior art. However, the application of strain to thin epitaxial films remains undeveloped and is the subject of this disclosure. By referring to the bulk band structures of Ga2O31056 and Al2O31054, embodiments of this disclosure utilize how strain engineering can be advantageously applied for UV LED applications. To understand how the valence bands are affected, it is necessary to incorporate Hamiltonians such as kp into monoclinic and triclinic strain tensors. The prior art kp crystal models applied to sphalerite and wurtzite crystal symmetries lack maturity for simulations of both monoclinic and trigonal systems. Current efforts are focused on this center being point group C2 h This calculation is directed towards performing the calculation using a second-order approximation of the valence band Hamiltonian at the center of the Brillouin zone of a material with the symmetry of .

[0309] Single-crystal aluminum oxide

[0310] While two main crystal forms with monoclinic (C2m) and corundum (R3c) crystal symmetries are described herein for both Al2O3 and Ga2O3, other crystal symmetries, such as triclinic and hexagonal, are also possible. Other crystal symmetries can also be applied according to the principles described herein.

[0311] (a) Corundum symmetric Al2O3

[0312] The crystal structure of trigonal Al2O3 (corundum) 1060 is shown in Figure 31. The larger sphere represents Al atoms 1064, and the smaller sphere represents oxygen 1063. The unit cell 1062 has a crystal axis 1061. Along the c-axis, there are layers of Al and O atoms. This crystal structure has a calculated band structure 1065, as shown in Figures 32A and 32B. The electron energy 1066 is plotted as a function of the crystal wave vector 1067 in the Brillouin zone. High symmetry points in the Brillouin zone are labeled as shown near the zone center k=0, which can be applied to understand the luminescence properties of the material.

[0313] The direct band gap has a maximum value of 10⁶⁸ in the valence band and a minimum value of 10⁶⁹ in the conductivity band at k=0. The detailed diagram of the valence bands in Figure 32B shows the complex dispersion of the two uppermost valence bands. The uppermost valence bands determine the emission properties when electrons and holes can actually be injected into the Al₂O₃ band structure simultaneously.

[0314] (b) Monoclinic symmetric Al2O3

[0315] The crystal structure 1070 of monoclinic Al2O3 is shown in Figure 33. The larger sphere represents Al atoms 1064, and the smaller sphere represents oxygen atoms 1063. The unit cell 1072 has a crystal axis 1071. This crystal structure has a calculated band structure 1075, as shown in Figures 34A and 34B, where Figure 34B is a detailed view of the valence bands. Figure 34A also shows the conductivity band 1076. High symmetry points within the Brillouin zone are labeled as shown near the zone center k=0, which can be applied to understand the luminescence properties of the material.

[0316] The monoclinic crystal structure 1070 is relatively more complex than the trigonal symmetry, and has a lower density and smaller band gap than the corundum sapphire 1060 form shown in Figure 31.

[0317] The monoclinic Al2O3 form also has a direct band gap with a clearly split highest valence band 1077, which has lower curvature with respect to Ek dispersion along the GX and GN wave vectors. The monoclinic band gap is about 1.4 eV smaller than that of the corundum form. The second highest valence band 1078 splits symmetrically from the highest valence band.

[0318] Single-crystal gallium oxide

[0319] (a) Corundum Symmetric Ga2O3

[0320] Figure 35 shows the crystal structure of trigonal Ga₂O₃ (corundum) 10⁸⁰. The larger sphere represents Ga atoms 10⁸⁴, and the smaller sphere represents oxygen atoms 10⁸⁧. Unit cell 10⁸⁰ has a crystal axis 10⁸⁰. Corundum (trigonal crystal symmetry) is also known as the alpha phase. The crystal structure is identical to that of sapphire 10⁶⁰ in Figure 31. The lattice constants define unit cell 10⁸⁰, as shown in Table II of Figure 43B. The Ga₂O₃ unit cell 10⁸⁰ is larger than that of Al₂O₃. Corundum crystals have octahedral bonded Ga atoms.

[0321] The calculated band structure 1085 for corundum Ga2O3 is shown in Figures 36A and 36B, and is a pseudo-direct type with a very small energy difference between the maximum value 1087 of the valence band and the zone center k=0. The conductive band 1086 is also shown in Figure 36A.

[0322] Subsequently, the band structure and valence bands can be directly modified to the band gap using the biaxial and uniaxial strains applied to the corundum Ga2O3 using the method described above. In fact, it is possible to shift the maximum value of the valence bands towards the zone center by applying tensile strain along the b-axis and / or c-axis of the crystal. It is estimated that approximately 5% tensile strain can be accommodated within a thin Ga2O3 layer containing Al2O3 / Ga2O3SL.

[0323] (b) Monoclinic symmetric Ga2O3

[0324] Figure 37 shows the crystal structure of monoclinic Ga2O3 (corundum) 1090. The larger sphere represents Ga atoms 1084, and the smaller sphere represents oxygen atoms 1083. Unit cell 1092 is It has a crystal axis 1091. This crystal structure has a calculated band structure 1095, as shown in Figures 38A and 38B. High symmetry points within the Brillouin zone are labeled as shown near the zone center k=0, which can be applied to understand the luminescence properties of the material. The conductive band 1096 is also shown in Figure 38A.

[0325] Monoclinic Ga2O3 has a top valence of 1097 with a relatively flat Ek dispersion. Detailed examination reveals that the actual maximum position of the valence band is several eV (thermal energy k). B It becomes clear that there is variation (less than approximately 25 meV). The relatively small valence dispersion gives insight into the fact that monoclinic Ga2O3 may have a relatively large effective hole mass, and therefore low mobility and relatively localized holes. Thus, strain can be advantageously used to improve the band structure, specifically the valence electron band dispersion.

[0326] Ternary aluminum-gallium oxide

[0327] Another example of the unique properties of the AlGaO3 material system is demonstrated by the crystal structure 1100 shown in Figure 39, which has crystal axes 1101 and unit cells 1102. The ternary alloy contains a 50% Al composition.

[0328] (Al x Ga 1-x )2O3, where x=0.5 in the formula, can be deformed into a substantially different crystal symmetry having a rhomboid structure. Ga atoms 1084 and Al atoms 1064 are arranged in the crystal as shown by oxygen atoms 1083. Of particular interest is the layered structure of the atomic planes of Al and Ga. This type of structure can also be constructed using atomic layer techniques to form ordered alloys described throughout this disclosure.

[0329] The calculated band structure of 1105 is shown in Figure 40. The minimum value of the conduction band 1106 and the maximum value of the valence band 1107 directly indicate the band gap.

[0330] Regularized ternary AlGaO3 alloy

[0331] The atomic layer epitaxy method allows for the formation of even more novel types of crystalline symmetry structures. For example, some embodiments include ultrathin epitaxial layers containing alternating arrangements of the form [Al-O-Ga-O-Al-...] along the growth direction. Structure 1110 in Figure 42 shows one possible extreme case in which alternating arrangements 1115 and 1120 are used to produce an ordered ternary alloy. In connection with this disclosure, it has been demonstrated that growth conditions can be created in which self-ordering of Al and Ga can occur. These conditions can occur even when the Al and Ga fluxes are co-incident to the growth surface simultaneously, resulting in a self-assembled ordered alloy. Alternatively, ordered alloy structures can also be produced by predetermined modulation of the Al and Ga fluxes reaching the surface of the epitaxial layer.

[0332] The ability to construct the band structure of optoelectronic devices, specifically UV LEDs, by selecting from bulk metal oxides, ternary compositions, or even digital alloys, is considered to be entirely within the scope of this disclosure.

[0333] Another example is the use of biaxial and uniaxial strain to modify the band structure, one example being the use of strain layer epitaxy on an Al2O3 or Ga2O3 substrate (Al x Ga 1-x This involves the use of a 2O3 material system.

[0334] Substrate selection for AlGaO-based UV LEDs

[0335] The choice of native metal oxide substrate is to use a strain layer epitaxy on an Al2O3 or Ga2O3 substrate (Al x Ga1-x This is one advantage of the present disclosure when applied to the epitaxy of 2O3 material systems.

[0336] Examples of substrates are listed in Table I of Figure 43A. In some embodiments, intermediate AlGaO3 bulk substrates can also be used, which is advantageous for application to UV LEDs.

[0337] The beneficial use of monoclinic Ga2O3 bulk substrates lies in the high Ga% (e.g., about 30-40%) of monoclinic (Al) substrates, which are limited by strain accumulation. x Ga 1-x The ability to form a 2O3 structure is possible. This allows for the use of a conductive substrate, thus enabling vertical devices. Conversely, when using a corundum Al2O3 substrate, a corundum epitaxial film (Al) with a range of 0 ≤ x ≤ 1 can be formed. x Ga 1-x )2O3 becomes possible.

[0338] Other substrates such as MgO(100), MgAl2O4, and MgGa2O4 are also suitable for the epitaxial growth of metal oxide UV LED structures.

[0339] Selection and action of crystal growth modifiers

[0340] Examples of metal oxide structures are described here for optoelectronic applications, specifically for the manufacture of UV LEDs. The structures disclosed in Figures 44A to 44Z, which are described thereafter, are possible crystal structure modifiers for a given metal oxide MO (where M = Al, Ga), binary Ga2O3, and ternary (Al x Ga 1-x The elemental cation and anion configurations for 2O3 and binary Al2O3, etc., may be selected from either and are not limited to these.

[0341] It is theoretically and experimentally found in accordance with this disclosure that the cationic seed crystal modifier for MO as defined above can be selected from at least one of the following.

[0342] Germanium (Ge)

[0343] Ge is beneficially supplied as a pure elemental species and incorporated during the non-equilibrium crystal formation process via co-deposition of MO species. In some embodiments, elemental pure ballistic beams of atoms Ga and Ge are co-deposited together with an active oxygen beam that impacts the growth surface. For example, Ge has a valence of +4 and is introduced in a dilute atomic ratio by substitution of metal cation M sites in the MO host crystal, (Ge +4 O2) m (Ga2O3) n =(Ge +4 O2) m / (m+n) (Ga2O3) n / (m+n) =(Ge +4 O2) x (Ga2O3) 1-x =Ge x Ga 2(1-x) O 3-x A stoichiometric composition of the form can be formed, where x < 0.1 for dilute Ge plasticity.

[0344] According to this disclosure, when Ge is x < 0.1, the dilute ratio of Ge is equal to the Fermi energy (E F It has been found that sufficient electronic modification is given to the intrinsic MO to manipulate it, thereby increasing the concentration of available electron free carriers and altering the crystal lattice structure to impart favorable strain during epitaxial growth. In the case of diluted compositions, the host MO physical unit cell remains substantially undisturbed. Further increases in Ge concentration can alter the host Ga2O3 crystal structure due to lattice expansion, or even result in new material compositions.

[0345] For example, when Ge is x ≤ 1 / 3, the monoclinic crystal structure of the host Ga2O3 unit cell can be maintained. For example, at x = 0.25, monoclinic Ge 0.25 Ga 1.50 O 2.75 =Ge1Ga6O 11 It is possible to form monoclinic Ge x Ga 2(1-x) O 3-xThe (x=1 / 3) crystal exhibits an excellent direct band gap exceeding 5 eV. The lattice deformation due to the introduction of Ge is compared to that of strain-free monoclinic Ga2O3. Then, while maintaining the a-axis lattice constant, the monoclinic unit cells are preferentially increased along the b-axis and c-axis.

[0346] The lattice constants of monoclinic Ga2O3 are (a=3.08A, b=5.88A, c=6.41A), and monoclinic Ge1Ga6O 11 In this case (a=3.04A, b=6.38A, c=7.97A), therefore, introducing Ge results in biaxial expansion of the self-supporting unit cell along the b and c axes. x Ga 2(1-x) O 3-x However, when deposited epitaxially on a bulk monoclinic Ga2O3 surface oriented along the b and c axes (i.e., deposited along the a axis), then, as described herein, Ge x Ga 2(1-x) O 3-x The thin film is elastically deformed, inducing biaxial compression, and thus can favorably deflect the valence band Ek dispersion.

[0347] When x exceeds 1 / 3, the higher the Ge%, the more the crystal structure changes to a cubic crystal, such as GeGa2O5.

[0348] In some embodiments, Al2O3 and (Al x Ga 1-x It is also possible to incorporate Ge into 2O3.

[0349] For example, the direct band gap Ge x Al 2(1-x) O 3-x The ternary system can also be epitaxially formed by the co-deposition of elements Al and Ge with reactive oxygen species to form a thin film with monoclinic symmetry. According to this disclosure, it has been found that the monoclinic structure is stabilized at a Ge% of approximately 0.6x, and compared to monoclinic Al2O3, it produces a self-supporting lattice with large relative expansion along the a and c axes but moderately reduced along the b axis.

[0350] The lattice constants for monoclinic Ge2Al2O7 are (a=5.34A, b=5.34A, c=9.81A), and for monoclinic Al2O3 they are (a=2.94A, b=5.671A, c=6.14A). Therefore, Ge deposited along the growth direction oriented along the b axis and further deposited on the monoclinic Al2O3 surface x Al 2(1-x) O3 is subjected to biaxial tension if it is a thin film that can maintain its elastic deformation.

[0351] Silicon (Si)

[0352] The element Si may also be supplied as a pure elemental species for incorporation via co-deposition of MO species during the non-equilibrium crystal formation process. In some embodiments, elemental pure ballistic beams of atoms Ga and Si are co-deposited together with an active oxygen beam impacting the growth surface. For example, Si has a valence of +4 and is introduced in a dilute atomic ratio by substitution of metal cation M sites in the MO host crystal, (Si +4 O2) m (Ga2O3) n =( Si +4 O2) m / (m+n) (Ga2O3) n / (m+n) =( Si +4 O2) x (Ga2O3) 1-x =Si x Ga 2(1-x) O 3-x A stoichiometric composition of the form can be formed, where x < 0.1 for a dilute Si composition.

[0353] According to this disclosure, when Si is <0.1, the dilute ratio of Si is the Fermi energy (E FIt has been found that sufficient electronic modification is given to the intrinsic MO to manipulate it, thereby increasing the concentration of available electron free carriers and altering the crystal lattice structure to impart favorable strain during epitaxial growth. In the case of diluted compositions, the host MO physical unit cell remains substantially undisturbed. As the Si concentration increases further, the host Ga2O3 crystal structure may change due to lattice expansion, or even a new material composition may be obtained.

[0354] For example, when Si %x ≤ 1 / 3, the monoclinic crystal structure of the host Ga2O3 unit cell can be maintained. For example, when Si %x = 0.25, monoclinic Si 0.25 Ga 1.5 0O 2.75 =Si1Ga6O 11 The formation of [this] is possible. The lattice deformation caused by the introduction of Si, compared to strain-free monoclinic Ga2O3, preferentially increases monoclinic unit cells along the b and c axes while maintaining the a-axis lattice constant. Monoclinic Si1Ga6O 11 The lattice constants of this material are (a=6.40A, b=6.40A, c=9.40A), compared to (a=3.08A, b=5.88A, c=6.41A) for monoclinic Ga2O3.

[0355] Therefore, when Si is introduced, biaxial expansion occurs in the self-supporting unit cell along all three axes: a, b, and c. x Ga 2(1-x) O 3-x However, when deposited epitaxially on a bulk monoclinic Ga2O3 surface oriented along the b and c axes (i.e., deposited along the a axis), then, as described herein, Si x Ga 2(1-x) O 3-x The thin film is elastically deformable, inducing asymmetric biaxial compression, and thus can favorably deflect the valence band Ek dispersion.

[0356] When x exceeds 1 / 3, the higher the Si%, the more the crystal structure changes to a cubic crystal, such as SiGa2O5.

[0357] In some embodiments, Si Al2O3 and (Al x Ga 1-x It can also be incorporated into 2O3. For example, orthorhombic (Si +4 O2) x (Al2O3) 1-x =Si x Al 2(1-x) O 3-x This is possible by directly co-depositing elemental Si and Al onto the deposition surface with an active oxygen flux. When the deposition surface is selected from available trigonal α-Al2O3 surfaces (e.g., A-plane, R-plane, M-plane), it is then possible to form orthorhombic symmetric Al2SiO5 (i.e., x=0.5), which reports a large direct band gap at the center of the Brillouin zone. The lattice constants for orthorhombic are (a=5.61A, b=7.88A, c=7.80A) and for trigonal (R3c)Al2O3, they are (a=4.75A, b=4.75A, c=12.982A).

[0358] Therefore, the deposition of an oriented Al2SiO5 film on Al2O3 can result in significant biaxial compression of the elastically deformed film. Exceeding the elastic energy limit generally leads to the generation of harmful crystal misfit dislocations and should therefore be avoided. In particular, films with a thickness of less than approximately 10 nm are preferred to achieve elastically deformable films on Al2O3.

[0359] Magnesium (Mg)

[0360] Some embodiments involve incorporating the elemental species Mg into Ga2O3 and Al2O3 host crystals, where Mg is selected as a preferred group II metal species. Furthermore, the (Al x Ga 1-x )Incorporation into 2O3, quaternary Mg x (Al,Ga) y O z It can be used up to the formation of Mg where x < 0.1 x Ga 2(1-x) O 3-2x Specific useful compositions include Ga2O3 and (Al x Ga1-x The electronic structure of the 2O3 host is determined by Ga 3+ Mg 2+ By substituting with a cation, it is possible to make it a p-type conductive type. (Al y Ga 1-y In the case of 2O3, the band gap is approximately 6.0 eV with y = 0.3, and Mg can be incorporated up to y = approximately 0.05 to 0.1, which can change the host's conductivity type from its inherently weak excess electron n-type to excess hole p-type.

[0361] Mg x Ga 2(1-x) O 3-2x and Mg x Al 2(1-x) O 3-2x and (Ni x Mg 1-x )O-type ternary compounds are also exemplary embodiments of active region materials for light-emitting UV LEDs.

[0362] In some embodiments, Mg at x=0.5 produces a cubic crystal symmetry structure. x Ga 2(1-x) O 3-2x and Mg x Al 2(1-x) O 3-2x Both stoichiometric compositions exhibit favorable direct bandgap Ek dispersion and are suitable for the luminescence region.

[0363] Furthermore, according to this disclosure, Mg x Ga 2(1-x) O 3-2x and Mg x Al 2(1-x) O 3-2x The composition was found to be epitaxially compatible with cubic MgO and Ga2O3 in monoclinic, corundum, and hexagonal crystal symmetries.

[0364] Using non-equilibrium growth techniques allows for a wide range of Mg miscibility, from MgO to the respective M-O2 elements, within both Ga2O3 and Al2O3 hosts. This is in contrast to equilibrium growth techniques such as CZ, where phase separation occurs due to volatile Mg species.

[0365] For example, Mg when x is approximately 0.5 x Ga 2(1-x) O 3-2x The lattice constants for the cubic and monoclinic forms are (a=b=c=8.46A) and (a=10.25A, b=5.98, c=14.50A), respectively. According to this disclosure, cubic Mg x Ga 2(1-x) O 3-2x It was found that the morphology can be oriented as a thin film having (100) and (111) oriented films on monoclinic Ga2O3(100) and Ga2O3(001) substrates. Also, Mg x Ga 2(1-x) O 3-2x A thin epitaxial film can be deposited on an MgO substrate. Furthermore, Mg 0 ≤ x ≤ 1 x Ga 2(1-x) O 3-2x The film can be directly deposited on a MgAl2O4(100) spinel crystal symmetric substrate.

[0366] In further embodiments, Mg x Al 2(1-x) O 3-2x and Mg x Ga 2(1-x) O 3-2x Both high-quality (i.e., low-defect-density) epitaxial films can be directly deposited onto lithium fluoride (LiF) substrates.

[0367] Zinc (Zn)

[0368] Some embodiments involve incorporating the elemental species Zn into Ga2O3 and Al2O3 host crystals, where Zn is another preferred group II metal species. Furthermore, (Al x Ga 1-x )Incorporation into 2O3, quaternary Zng x (Al,Ga) y O z It can be used until the formation of [something].

[0369] Furthermore, the most common form of compound is a further quaternary composition that is favorable for directly adjusting the band gap structure: (Mg x Zn 1-x ) z (Al y Ga 1-y ) 2(1-z) O 3-2z , where 0≦x, y, z≦1.

[0370] According to this disclosure, it has been found that cubic crystal symmetry compositions with z of approximately 0.5 can be favorably used for a given fixed y composition between Al and Ga. By changing the Mg to Zn ratio x, the band gap can be directly increased to approximately 4 eV ≤ E G (x) can be adjusted from < 7 eV. This can be advantageously achieved by arranging separately controllable fluxes of pure elemental beams of Al, Ga, Mg, and Zn to provide an activated oxygen flux to the anionic species. Generally, it is desirable to have an excess of atomic oxygen relative to the overall impacting metal flux. Then, by controlling the Al:Ga flux ratio and Mg:Zn ratio reaching the growth surface, a composition desirable for adjusting the bandgap in the UV LED region can be pre-selected.

[0371] Surprisingly, zinc oxide (ZnO) generally has a wurtzite hexagonal crystal symmetry structure, but (Mg x Zn 1-x ) z (Al y Ga 1-y ) 2(1-z) O 3-2z When introduced, cubic and spinel crystal symmetries are readily possible using the non-equilibrium growth method described herein. The band gap properties at the center of the Brillouin zone can be tuned by the alloy composition (x, y, z) ranging from indirect to direct properties. This is advantageous for application to substantially non-absorbent electroinjection and emission regions, respectively. Furthermore, the band gap Modulation is possible for bandgap design structures such as superlattices and quantum wells described herein.

[0372] Nickel (Ni)

[0373] The incorporation of Ni elemental species into Ga2O3 and Al2O3 host crystals is yet another preferred group II metal species. Further, the incorporation of Ni into (Al x Ga 1-x )2O3 is available up to the formation of the quaternary Ni x (Al,Ga) y O z .

[0374] Further quaternary compositions that are advantageous for directly tuning the bandgap structure are the most common form of compounds: (Mg x Ni 1-x ) z (Al y Ga 1-y ) 2(1-z) O 3-2z , where 0 ≦ x, y, z ≦ 1.

[0375] According to the present disclosure, it has been found that cubic crystal symmetric compositions with z of about 0.5 can be advantageously used for a given fixed y composition between Al and Ga. By varying the ratio x of Mg to Ni, the direct bandgap can be tuned from about 4.9 eV ≦ E G (x) < 7 eV. This can be achieved advantageously by arranging the fluxes of the pure elemental beams of Al, Ga < Mg, and Ni to be separately controllable advantageously and providing an activated oxygen flux to the anion species. Then, the Al:Ga flux ratio and the Mg:Ni ratio reaching the growth surface can be controlled to pre-select the desired composition for bandgap tuning in the UVLED region.

[0376] Very useful herein is the specific band structure and intrinsic conductivity type of cubic NiO. Nickel oxide (NiO) exhibits a native p-type conductivity due to Ni d-orbital electrons. The general cubic crystal symmetric form (Mg x Ni 1-x ) z (Al y Ga 1-y ) 2(1-z) O 3-2z is possible using the non-equilibrium growth method described herein.

[0377] Ni z Ga 2(1-z) O 3-2z and Ni z Al 2(1-z) O 3-2z Both are favorable for application to UV LED formation. Dilute compositions with z < 0.1 are found to be favorable for the generation of p-type conductive materials according to this disclosure, and ternary cubic crystal symmetric compounds with z about 0.5 also exhibit a direct band gap at the center of the Brillouin zone.

[0378] Lantanid

[0379] Binary Ga2O3, ternary (Al x Ga 1-x A large selection of available lanthanide metal atoms can be incorporated into 2O3 and binary Al2O3. The lanthanide group of metals ranges from 15 elements starting with lanthanum (Z=57) to lutetium (Z=71). In some embodiments, gadolinium (Gd) (Z=64) and erbium (Er) (Z=68) are utilized due to their distinct 4f shell structure and their ability to form favorable ternary compounds with Ga2O3, GaAlO3, and Al2O3. Again, (RE x Ga 1-x )203, (RE x Ga y Al 1-x-y )2O3 and (RE x Al 1-x The incorporation of dilute impurities of only one species selected from RE={Gd or Er} into the cation sites of 2O3, where 0≦x, y, z≦1, allows for the tuning of the Fermi energy to form n-type conductive materials exhibiting corundum, hexagonal, and monoclinic crystal symmetries. The internal 4f shell orbitals of Gd provide an opportunity for electronic bonding that avoids parasitic optical 4f-4f energy level absorption at wavelengths below 250 nm.

[0380] Surprisingly, both theoretically and experimentally, according to this disclosure, (Er x Ga 1-x )2O3 and (Er x Al1-x ) When x is approximately 0.5, the ternary compound of 2O3 directly bandgates It was found to exhibit a cubic crystal symmetry structure with a pinch. Binary erbium oxide Er2O3 is known to have bixbite crystal symmetry and can be epitaxially formed as a single crystal film on a Si(111) substrate. However, the lattice constants obtained by bixbite Er2O3 are not readily applicable for seeding epitaxial films of Ga2O3, GaAlO3, and Al2O3. According to this disclosure, it was found that incorporating a gradient composition of Er increasing from 0 to 0.5 along the growth direction is necessary to generate the required final surface corresponding to the epitaxy of monoclinic Ga2O3. (Er x Ga 1-x )2O 3、 For cubic crystal symmetry with 0 ≤ x ≤ 0.5, compositions that directly exhibit a band gap may be used.

[0381] Of particular interest is the lattice constants (a=5.18A, b=5.38A, c=7.41) and a clear direct energy band gap of approximately 6.5-7 eV E G (k=0) shows that x is approximately 0.5 (Er x Al 1-x This is an orthorhombic ternary composition of )2O3. Such a structure can be deposited on a monoclinic Ga2O3 and corundum Al2O3 substrate or epitaxial layer. As mentioned above, the inner Er 3+ Since the 4f-4f transition does not exist in the Ek band structure, it is classified as non-parasitic absorption in UV LED applications.

[0382] Bismuth (Bi)

[0383] Bismuth is a known species that acts as a surfactant for GaN non-equilibrium epitaxy in thin gallium nitride (GaN) films. While surfactants reduce the surface energy of epitaxial film formation, they are generally not incorporated into the growing film. Even gallium arsenide exhibits limited Bi incorporation. Bismuth is a volatile species with high vapor pressure at low growth temperatures, and appears to be an insufficient adsorbed atom for incorporation into the growing epitaxial film. Surprisingly, however, the incorporation of Bi into Ga2O3, (Ga,Al)O3, and Al2O3 at dilute levels x<0.1 is highly efficient using the non-equilibrium growth method described in this disclosure. For example, elemental sources of Bi, Ga, and Al can be co-deposited with overpressure ratio activated oxygen (i.e., atomic oxygen, ozone, and nitrous oxide). According to this disclosure, monoclinic and corundum crystal symmetric Ga2O3 and (Ga,Al)O3 at x<0.5 are co-deposited. x , Al 1-x The incorporation of Bi into 2O3 was found to exhibit conductivity characteristics that generate an appropriate activation hole carrier concentration for the p-type conductive region of UV LED functionality.

[0384] Furthermore, for higher Bi atom embedding x > 0.1, (Bi x Ga 1-x )2O3 and (Bi x Al 1-x This allows for the adjustment of the band structure of the 2O33 composition, and indeed, it is possible all the way down to the stoichiometric binary bismuth oxide Bi2O3. Monoclinic Bi2O3 forms lattice constants (a=12.55A, b=5.28, and c=5.67A), which corresponds to directly forming a strained layer film on monoclinic Ga2O3.

[0385] Furthermore, in some embodiments, orthorhombic and trigonal morphologies exhibiting unique p-type conductivity and indirect band gaps can be utilized.

[0386] What is particularly interesting is the case of x=1 / 3 (Bi x Al 1-x The orthorhombic crystal symmetry composition of 2O3 is directly E G This means exhibiting an Ek variance of 4.78 to 4.8 eV.

[0387] Palladium (Pd)

[0388] The addition of Pd to Ga2O3, (Ga,Al)O3, and Al2O3 may be utilized in some embodiments to generate metallic behavior and is applicable to the formation of ohmic contacts. In some embodiments, palladium oxide (PdO) is used as an in-situ deposition semimetal for n-type wide-bandgap metal oxides due to the compound's inherently low work function. It can be used as an ohmic contact lens (see Figure 9).

[0389] Iridium (Ir)

[0390] Iridium is a preferred platinum group metal for incorporation into Ga2O3, (Ga,Al)O3, and Al2O3. According to this disclosure, it has been found that Ir can bond in a wide variety of valence states. Generally, rutile crystal symmetric forms of IrO2 compositions are known and exhibit semimetallic properties. Surprisingly, triple-charged Ir... 3+ Valence states are possible using non-equilibrium growth methods and are preferred for application to Ga2O3, specifically corundum crystal symmetry. Iridium has one of the highest melting points and the lowest vapor pressure when heated. This disclosure utilizes electron beam evaporation to form a pure elemental beam of the Ir species that impacts the growth surface. When reactive oxygen is supplied simultaneously and the corundum Ga2O3 surface is presented for epitaxy, a corundum crystal symmetry of Ir2O3 composition can be realized. Furthermore, by co-depositing pure elemental beams of Ir and Ga with reactive oxygen, (Ir) for 0 ≤ x ≤ 1.0 x Ga 1-x Compounds of )2O3 can be formed. Furthermore, by co-deposition of pure elemental beams of Ir and Al with reactive oxygen species, (Ir) can be formed in 0≦x≦1.0. x Al 1-xCompounds of )2O3 can be formed. The addition of Ir to a host metal oxide containing at least one of Ga2O3, (Ga,Al)O3, and Al2O3 can reduce the effective band gap. Furthermore, when the fraction of Ir is x > 0.25, the band gap becomes exclusively indirect.

[0391] Lithium (Li)

[0392] Lithium is a unique atomic species, specifically when bonded with oxygen. Pure lithium metal readily oxidizes, and lithium oxide (Li2O) is readily formed using a non-equilibrium growth method of pure elemental Li beam and reactive oxygen directed at a growth surface with clear surface crystal symmetry. Cubic crystal symmetric Li2O exhibits a large indirect band gap with Eg of approximately 6.9 eV and has lattice constants of (a=b=c=4.54A). When present in a defective crystal structure, lithium is a mobile atom, and it is this property that is utilized in lithium-ion battery technology. In contrast, this disclosure seeks to firmly incorporate Li atoms into a host crystal matrix containing at least one of Ga2O3, (Ga,Al)O3, and Al2O3. Again, dilute Li concentrations can be incorporated into substitutional metal sites in Ga2O3, (Ga,Al)O3, and Al2O3. For example, Li +1 In the case of the valence state, these compositions can be used: (Li2O) x (Ga2O3) 1-x =Li 2x Ga 2(1-x) O 3-2x , in the formula 0≦x≦1, and (Li2O) x (Al2O3) 1-x =Li 2x Al 2(1-x) O 3-2x , where 0≦x≦1.

[0393] Li at x=0.5 2x Ga 2(1-x) O 3-2x The stoichiometric form of provides LiGaO2, where x=0.5 Li 2x Al 2(1-x) O 3-2xIt provides LiAlO2.

[0394] Both LiGaO2 and LiAlO2 are E G (LiGaO2) = 5.2 eV and approximately 8 eV G (LiALO2) crystallizes in preferred orthorhombic and trigonal forms, each having direct and indirect band gap energies, respectively.

[0395] Of particular interest are the relatively small curvature of both valence bands, which suggests a smaller effective hole mass compared to Ga2O3.

[0396] The lattice constants of LiGaO2 are (a=5.09A, b=5.47, c=6.46A). In LiAlO2, (a=b=2.83A, c=14.39A). Since bulk Li(Al,Ga)O2 substrates can be used, Li(Al x Ga 1-x )Four-component compositions of orthorhombic and trigonal crystals, such as O2, can also be used, which enables UV LED operation in the light-emitting region.

[0397] Even cubic NiO, when incorporating Li impurities, exhibits improved p-type conductivity and can function as a potential electroinjection region for holes applied to UV LEDs.

[0398] Furthermore, in some embodiments, further compositions include lithium nickel oxide Li x Ni y O z It is a three-element system including . Theoretical calculations show that Ni has a higher possible valence state. 2+ and Li 2+ Provides insights into Li2. (+4) Ni +2 O3 (-6) The electronic composition containing =Li2NiO3 can be used to create it by non-equilibrium growth techniques that form monoclinic crystal symmetry. According to this disclosure, Li2NiO3 has an E of about 5 eV. G It was found to form an indirect band gap. Another composition has trigonal crystal symmetry (R3m), and Li+1 and Ni +1 Valence state is E G It forms the composition Li2NiO2 with a direct band gap between s-like and p-like states of =8eV, but the strong d-like state from Ni generates a crystal momentum-independent intermediate band gap energy state that is continuous across all Brillouin zones.

[0399] Nitrogen and fluorine anion substitution

[0400] Furthermore, according to this disclosure, it has been found that the selected anion crystal modifier for the disclosed metal oxide composition may be selected from at least one of nitrogen (N) and fluorine (F) species. Substitutional incorporation of group III metal cation sites by group II metal species into binary Ga2O3 and ternary (GaxAl 1-x Similar to the generation of p-type activated hole concentrations in 2O3, it is further possible to substitute oxygen anion sites during epitaxial growth with activated nitrogen atoms (e.g., neutral nitrogen species in some embodiments). Surprisingly, according to this disclosure, the incorporation of diluted nitrogen into the Ga2O3 host has been found to stabilize the monoclinic Ga2O3 composition during epitaxy. Prolonged exposure of growing Ga2O3 to a combination of neutral atom fluxes of oxygen and nitrogen, simultaneously with elemental Ga, has been found to form competing GaN-like precipitates.

[0401] According to this disclosure, it has also been found that by periodically modulating the growth of Ga2O3 by periodically interrupting the Ga and O fluxes and preferentially exposing the terminal surface with only activated atomic neutral nitrogen, it is possible to incorporate N into other available O sites within the Ga2O3 growth on a portion of the surface. Spacing these N layer growth interruptions by a distance of more than 5 unit cells of Ga2O3 along the growth direction allows for the incorporation of high-density impurities that help achieve p-type conductivity in Ga2O3.

[0402] This process can be used for both the corundum and trigonal forms of Ga2O3.

[0403] In some embodiments, a combined approach of group II metal cation substations and nitrogen anion substations can be used to control the p-type conductivity concentration of Ga2O3.

[0404] While it is possible to incorporate fluorine impurities into Ga2O3, elemental fluorine sources are difficult to obtain. This disclosure uniquely utilizes the sublimation of lithium fluoride (LiF) bulk crystals in a Knudsen cell to provide both Li and F compositional components that are co-deposited in elemental Ga and Al beams under an active oxygen environment supplied to the growth surface. Such a technique enables the incorporation of Li and F atoms into epitaxially formed Ga2O3 or LiGaO2 hosts.

[0405] Examples of crystalline symmetry structures formed using exemplary compositions are described here and referred to in Figures 44A–44Z. The compositions shown are not intended to be limiting, but rather to those using crystal modifiers as described in the previous section.

[0406] (Al x Ga 1-x An example of possible crystal symmetry groups 5000 for the ternary composition of 2O3 is shown in Figure 44A. The calculated equilibrium crystal formation probability 5005 is a measure of the probability that a structure will be formed for a given crystal symmetry type. The space group nomenclature 5010 used in Figure 44A is understood by those skilled in the art.

[0407] The non-equilibrium growth methods described herein can potentially select crystal symmetries that are inaccessible using other equilibrium growth methods (such as CZ). The general crystal classifications of cubic 5015, tetragonal, trigonal (rhombohedral / hexagonal) 5020, monoclinic 5025, and triclinic 5030 are shown in the inset of Figure 44A.

[0408] For example, it has been found in accordance with this disclosure that monoclinic, trigonal, and orthorhombic crystal symmetries can be energetically advantageous by providing kinematic growth conditions favorable only to specific space groups that undergo epitaxial formation. For instance, as shown in Table I in Figure 43A, the surface energy of the substrate can be selected by a sensible pre-selection of the surface orientation presented for epitaxy.

[0409] Figure 44B shows a high-quality, coherent strain, elastically deformable unit cell (i.e., the epitaxial layer is called pseudomorphic with respect to the underlying substrate) formed on a monoclinic Ga2O3(010) oriented surface 5045. x Ga 1-x The high-resolution X-ray Bragg diffraction (HRXRD) curve of the 2O3 epitaxial layer 5080 is shown exemplarily. The graph shows the intensity 5035 as a function of Ω-2θ5040. x Ga 1-x )2O3x=0.15(5050) and x=0.25(5065) are displayed. The substrate is initially placed in an ultra-high vacuum chamber (5×10 -10 It is prepared by desorbing surface impurities at high temperatures (>800°C) with a Torr value of less than 800°C.

[0410] The surface is monitored in real time by reflected high-energy electron diffraction (RHEED) to evaluate the quality of the atomic surface. Once a bright, streaky RHEED pattern is revealed indicating an atomically flat surface for a given surface reconstruction of discontinuous surface atomic dangling bonds, an activated oxygen source containing radio frequency inductively coupled plasma (RF-ICP) is ignited toward the heated surface of the substrate to generate a stream of substantially neutral atomic oxygen (O*) species and excited molecular neutral oxygen (O2*).

[0411] RHEED is monitored to indicate the oxygen-terminated surface. The source of elemental and pure Ga and Al atoms is provided by an ejection cell containing an inert ceramic crucible that is radiantly heated by a filament, and is controlled by feedback sensing of thermocouples favorably positioned relative to the crucible to monitor the metal melting temperature within the crucible. High-purity elemental metals of 6N to 7N or higher are used.

[0412] Each source beam flux is measured by a dedicated nude ion gauge, which can be spatially positioned near the center of the substrate to sample the beam flux at the substrate surface. Since the beam flux is measured for each elemental species, the relative flux ratio can be determined in advance. During the beam flux measurement, a mechanical shutter is placed between the substrate and the beam flux measurement. The mechanical shutter also intersects with atomic beams emitted from each crucible containing each elemental species selected to constitute the epitaxial film.

[0413] During deposition, the substrate is rotated to accumulate a uniform amount of atomic beam intersecting the substrate surface for a given deposition time. The substrate is radiated from behind by an electrically heated filament, and the favorable use of silicon carbide (SiC) heaters is preferred for oxide growth. SiC heaters have a unique advantage over high-melting-point metal filament heaters, as they provide a broad emissivity in the near-to-mid-infrared region.

[0414] Although not widely known among researchers in the field of epitaxial film growth, most metal oxides possess relatively large light absorption properties for near-infrared to far-infrared wavelengths. The deposition chamber is preferentially actively and continuously pumped to achieve and maintain a vacuum of around 1e-6 to 1e-5 Torr during epitaxial film growth. Operating within this vacuum range, the evaporated metal particles from the surface of each ejection vessel acquire essentially non-interacting and ballistic velocities.

[0415] By favorably positioning the ejected cell beam, which is formed by a large mean free path with a high crucible opening and a high UHV, ballistic transport without collision of ejected species with the substrate surface is ensured. The atomic beam flux from the ejected type heating source is determined by the Arrhenius behavior of the specific element species placed in the crucible. In some embodiments, 1 × 10⁻⁶ -6 Al and Ga fluxes in the Torr range are measured at the substrate surface. The oxygen plasma is controlled by the RF power coupled to the plasma and the flow rate of the source gas.

[0416] RF plasma discharges typically operate at 10 mm Torr to 1 Torr. These RF plasma pressures are incompatible with the atomic layer deposition processes reported herein. -7 Torr~1×10 -5 To achieve an activated oxygen beam flux in the Torr range, a sealed fused silica valve with a laser-perforated opening of approximately 100 microns in diameter is positioned across the circular end face of a sealed cylindrical valve. This valve is coupled to a helical-wound copper tube, a water-cooled RF antenna driven by an impedance matching network, and a high-power 100W to 1kW RF oscillator operating at, for example, 2MHz to 13.6MHz or even 20MHz.

[0417] The plasma is monitored using emission from the plasma discharge, providing accurate telemetry of the actual species generated within the valve. The size and number of openings at the valve end face, which interface the plasma to the UHV chamber, can be predetermined to achieve a suitable beam flux to maintain ballistic transport conditions over long mean free paths beyond the source-to-substrate distance. Other in-situ diagnostics that enable precise control and reproducibility of film composition and uniformity include the use of ultraviolet polarized optical reflectance measurements and ellipsometry, as well as residual gas analyzers to monitor species desorption from the substrate surface.

[0418] Other forms of reactive oxygen species include the use of oxidizing agents such as ozone (O3) and nitrous oxide (N2O). While all forms, namely RF plasma, O3, and N2O, work relatively well, RF plasma may be used in certain embodiments due to its simplicity of activation at the point of use. However, RF plasma can generate very high-energy charged ion species that affect the conductivity type of the material's background. This can be mitigated by directly removing an opening near the center of the plasma endplate coupled to the UHV chamber. The RF-induced oscillating magnetic field at the center of the solenoid of the cylindrical discharge tube is maximum along the central axis. Therefore, removing the opening that provides a line of sight from the plasma interior to the growth surface removes charged ion species that are seed-ballistically delivered to the epitaxial layer.

[0419] Referring again to Figure 44B, the growth method was briefly explained. The monoclinic Ga2O3(010) oriented substrate 5045 is cleaned in situ via high temperatures, such as approximately 800°C for 30 minutes under UHV conditions. The cleaned surface is then subjected to a process that forms a surface reconstruction containing oxygen atoms. It is terminated with an oxygen adsorption atom.

[0420] An optional homoepitaxial Ga2O3 buffer layer 5075 is deposited and monitored for crystallographic surface improvement by in-situ RHEED. Generally, Ga2O3 growth conditions using elemental Ga and reactive oxygen species require a flux ratio of φ(Ga):φ(O*)<1, i.e., atomic oxygen-rich conditions.

[0421] When the flux ratio Φ(Ga):Φ(O*)>1, the excess Ga atoms on the growth surface become potentially volatile Ga2O (g)Surface-bonded oxygen can adhere to potentially forming suboxide species, which can desorb from the surface, remove material from the surface, and even etch the surface of the Ga2O3. According to this disclosure, in the case of high Al-content AlGaO3, this etching process has been found to be reduced, although not eliminated for Al% > 50%. The etching process can be used to clean unused Ga2O3 substrates and, for example, to assist in the removal of chemical mechanical polishing (CMP) damage.

[0422] To initiate the growth of AlGaO3, an reactive oxygen species source is first optionally exposed to the surface, followed by the opening of the shutters of both the Ga and Al ejection cells. While the Al adhesion coefficient is nearly uniform, it has been experimentally found in accordance with this disclosure that the adhesion coefficient on the growth surface is kinetically dependent on the Arrhenius behavior of desorbed Ga adsorbed atoms, which depends on the growth temperature.

[0423] Epitaxial (Al x Ga 1-x The relative x=Al% of the 2O3 film is related to x=Φ(Al) / [Φ(Ga)+Φ(Al)]. x Ga 1-x During the deposition of 2O3, clear, high-quality RHEED surface reconstruction streaks are evident. Thickness can be monitored in situ by ultraviolet laser reflectance, and pseudomorphic strain states can be monitored by RHEED. Monoclinic crystal symmetry (Al x Ga 1-x The independent in-plane lattice constant of 2O3 is smaller than that of the underlying Ga2O3 lattice, therefore (Al x Ga 1-x )2O3 grows under tensile strain during elastic deformation.

[0424] The thickness 5085 of the epitaxial layer 5080, where the elastic energy can be matched or reduced by including misfit dislocations within the growth plane, is called the critical layer thickness (CLT). Beyond this point, the film can begin to grow as a partially or completely relaxed bulk film. Curves 5050 and 5065 show coherently distorted (Al) films with thicknesses less than the CLT.x Ga 1-x This is the case for a 2O3 film. When x=0.15, the CLT is >400nm, and when x=0.25, the CLT is approximately 100nm. Thickness oscillations 5070, also known as Penderosung interference fringes, indicate a highly coherent and atomically flat epitaxial film.

[0425] In experiments conducted in connection with this disclosure, a CLT < 1 nm was achieved when a pure monoclinic Al2O3 epitaxial film was grown directly on a monoclinic Ga2O3(010) surface. Furthermore, it was experimentally found that Al% > 50% achieved a low growth rate due to the unique monoclinic bonding arrangement of cations, which were divided into approximately 50% tetrahedral bonding sites and 50% octahedral bonding sites. It was found that Al-adsorbed atoms prefer to be incorporated into octahedral bonding sites during crystal growth and have a bonding affinity to tetrahedral sites.

[0426] Superlattices (SLs) are generated and can be directly applied to UV-LED operation by utilizing quantum size effect tuning mechanisms to quantize the allowable energy levels within a narrower bandgap material sandwiched between two potential energy barriers. Furthermore, SLs are exemplary media for creating pseudo-ternary alloys as discussed herein, enabling further strain control of the layers.

[0427] For example, monoclinic (Al x Ga 1-x The 2O3 ternary alloy undergoes asymmetric in-plane biaxial tensile strain when epitaxially deposited on monoclinic Ga2O3. This tensile strain can be controlled by keeping the thickness of the ternary system within each layer constituting the SL less than that of the CLT. Furthermore, the strain can be balanced by adjusting the thickness of both the Ga2O3 and the ternary layers to control the incorporated strain energy of the bilayer pair.

[0428] Furthermore, a further embodiment of the present disclosure is to produce a ternary alloy as a bulk or SL grown thick enough to form a substantially self - standing material beyond CLT and without strain. This substantially strain - free relaxed ternary layer has an effective in - plane lattice constant a parameterized by the effective Al% composition SL having. Then, when a first relaxed ternary layer is formed and subsequently another second SL is deposited directly on top of the relaxed layer, the bilayer pairs forming the second SL can then be adjusted such that the layers making up the bilayer are in equal and opposite strain states of tensile and compressive strain with respect to the first in - plane lattice constant.

[0429] FIG. 44C shows an exemplary SL 5115 formed directly on a Ga2O3(010) - oriented substrate 5100.

[0430] The bilayer pairs making up SL 5115 are both monoclinic crystal - symmetric Ga2O3 and ternary (Al x Ga 1-x )2O3(x = 0.15), and the SL period Δ SL = 18 nm. HRXRD 5090 shows symmetric Bragg diffraction and GIXR 5105 shows the grazing - incidence reflectivity of the SL. Ten periods showing very high crystal quality indicating that (Al x Ga 1-x )2O3 has a thickness beyond CLT are shown.

[0431] The multiple narrow SL diffraction peaks 5095 and 5110 indicate a coherently strained film registered at an in - plane lattice constant matching that of the monoclinic Ga2O3(010) - oriented bulk substrate 5100. The monoclinic crystal structure having an exposed growth surface of (010) (see FIG. 37) shows a complex arrangement of Ga and O atoms. In some embodiments, the starting substrate surface is prepared by an O - termination as described above. The average Al% alloy content of the SL can be considered a pseudo - bulk ternary alloy representing a regular atomic - plane ternary alloy.

[0432] [(Al xB Ga 1-xBSL containing a double layer of [2O3 / Ga2O3] has an equivalent Al% defined as follows:

number

[0433] The tensile strains shown in Figures 23A to 23C can be advantageously used for the formation of the light-emitting region.

[0434] Figure 44D further shows yet another crystal orientation of the monoclinic Ga2O3(001) substrate 5120. , ternary monoclinic 5130 alloy (Al x Ga 1-x This demonstrates greater flexibility in directly depositing 2O3.

[0435] Again, the best results are obtained by paying attention to high-quality CMP surface treatment of the cleaved substrate surface. Growth recipes in some embodiments utilize in-situ activated oxygen polishing at high temperatures (e.g., 700-800°C) using a substrate radiated through a high-power, oxygen-resistant radiative-coupled heater. SiC heaters have the unique property of high near-far-infrared emissivity. The emissivity of the SiC heater closely matches the intrinsic Ga2O3 absorption characteristics and therefore pairs well with the radiative blackbody emission spectrum exhibited by the SiC heater. Region 5125 represents the homoepitaxial growth of an O-terminated process and a high-quality Ga2O3 buffer layer. Subsequently, SL is deposited, showing two distinct growths with different ternary alloy compositions.

[0436] Shown in Fig. 44D is a coherently strained epitaxial layer of (Al x Ga 1-x )2O3 having a CLT thickness and achieving x of about 15% (5135) and x of about 30% (5140) with respect to the (002) substrate peak 5122. Again, the high-quality film is indicated by the presence of thickness interference fringes.

[0437] It has further been discovered that an SL structure is also possible on a monoclinic Ga2O3 substrate 5155 with (001) orientation, and the results are shown in Fig. 44E.

[0438] Clearly, HRXRD 5145 and GIXR 5158 show a high-quality coherently deposited SL. Peak 5156 is the substrate peak. The SL diffraction peaks 5150 and 5160 enable direct measurement of the SL period, and the SL n=0 peak enables determination of the effective Al% of the SL. In this case, a 10-period SL [(Al SL Ga 0.18 Ga 0.92 )2O3 / Ga2O3] with a period Δ

[0439] Referring to Fig. 44F, it is desired to demonstrate an application example of the versatility of the metal oxide film deposition method disclosed herein. Two different crystal symmetry type structures are epitaxially formed along the growth direction as defined by Fig. 18. A substrate 5170 (peak 5172) including a monoclinic Ga2O3 (001) oriented surface is presented for homoepitaxy of monoclinic Ga2O3 5175. Next, a cubic crystal symmetry NiO epitaxial layer 5180 is deposited. HRXRD 5165 and GIXR 5190 show that the top NiO film peak 5185 with a thickness of 50 nm has excellent atomic flatness and thickness fringes 5195.

[0440] In one example, the mixing and matching of crystal symmetry types can be favorable for a given material composition for a given function including a UVLED (see Fig. 1), thereby enhancing the flexibility for optimizing the UVLED design. Ni xO (indicating that a metal vacancy structure is possible when 0.5 < x ≤ 1), Li x Ni y O n , Mg x Ni 1-x O and Li x Mg y Ni z O n is a composition that can be advantageously utilized for integration with an AlGaO3 material containing UVLEDs.

[0441] Since NiO and MgO share very similar cubic crystal symmetries and lattice constants, they are advantageous for bandgap adjustment applications of about 3.8 - 7.8 eV. The d states of Ni affect the optical and conductivity types of the MgNiO alloy and can be adjusted for application to UVLED-type devices. A similar behavior is found in the selective incorporation of Ir into a corundum crystal symmetry ternary alloy (Ir x Ga 1-x )2O3, which exhibits favorable energy positions within the E-k dispersion due to the iridium d-state orbitals for creating p-type conductivity.

[0442] Further, additional examples of metal oxide structures are shown in FIG. 44G. The cubic crystal symmetric MgO(100) oriented surface (corresponding to peak 5206) of substrate 5205 is presented for the direct epitaxy of Ga2O3. In accordance with the present disclosure, it has been found that the surface of MgO can be selectively modified to create the cubic crystal symmetry form of a Ga2O3 epi-layer 5210 (peak 5212 of gamma Ga2O3), which functions as an intermediate transition layer for subsequent epitaxy of monoclinic Ga2O3(100)5215 (peaks 5214 and 5217). Such a structure is represented by the growth process shown in FIG. 20A.

[0443] First, a prepared clean MgO(100) surface is presented for MgO homoepitaxy. The magnesium source is a valved effusion source containing 7N purity Mg with a beam flux of about 1×10 -10 Torr in the presence of active oxygen supplied at φ(Mg):φ(O*) < 1 and a substrate surface growth temperature of 500 - 650 °C.

[0444] RHEED monitoring demonstrates improved, high-quality surface reconstruction of the MgO surface of the epitaxial film. After approximately 10–50 nm of MgO homoepitaxis, the Mg source is closed and the substrate is raised to a growth temperature of approximately 700°C under a protective O* flux. Subsequently, the Ga source is exposed on the growth surface, and RHEED is observed to show an instantaneous change in surface reconstruction toward the cubic crystal symmetric Ga2O3 epitaxial layer 5210. After approximately 10–30 nm of cubic Ga2O3 (also known as the gamma phase), direct observation of RHEED shows the appearance of a characteristic monoclinic plane reconstruction of Ga2O3(100), which remains as the most stable crystal structure. A 100 nm Ga2O3(100) oriented film is deposited, and HRXRD5200 and GIXR5220 show peaks 5214 for betaGa2O3(200) and 5217 for betaGa2O3(400). Such accidental agreements in crystal symmetry are rare, but they are extremely advantageous for applications in UV LEDs.

[0445] Another example of a complex ternary metal oxide structure applied to UV LEDs is disclosed in Figure 44H. HRXRD5225 and GIXR5245 demonstrate experimental realizations of superlattices containing ternary lanthanide-aluminum oxide integrated with a corundum Al2O3 epitaxial layer.

[0446] SL is corundum crystal symmetry (Al x Er 1-x The composition includes 2O33, and the lanthanide is selected from corundum Al2O3 and pseudomorphically grown erbium. The erbium is subjected to non-equilibrium growth via a sublimable 5N purity erbium source using an ejection cell. A flux ratio of φ(Er):φ(Al) of approximately 0.15 was used, and the growth temperature was approximately 500°C under oxygen-rich conditions where [φ(Er)+φ(Al):φ(O*)]<1.

[0447] Of particular note is Er's ability to decompose molecular oxygen on the epitaxial layer surface, and therefore the total oxygen overpressure is greater than the atomic oxygen flux. A-plane sapphire (11-20) substrate 5235 was prepared, heated to approximately 800°C, and exposed to activated oxygen polishing. In this example, activated oxygen polishing of the bare substrate surface was found to dramatically improve the quality of the subsequent epitaxial layer. Next, a homoepitaxial corundum Al2O3 layer was formed and monitored by RHEED, showing excellent crystalline quality and atomically flat layer-by-layer deposition. Subsequently, a periodic 10 SL was deposited and shown as satellite peaks 5230 and 5240 in HRXRD5225 and GIXR5245 scans. Clearly evident is the pendelosung fringe, which shows excellent coherent growth.

[0448] SL's (Er xSL Al 1-xSL The effective alloy composition of 2O3 is (110) the zero-order SL peak relative to the substrate peak 5235. n=0 It can be estimated from the position. xSl can be approximately 0.15, forming the SL period (Al x Er 1-x The 2O3 layer has been found to have corundum crystal symmetry. This discovery is particularly important for applications in UV LEDs, and Figure 44I shows corundum (Al x Er 1-x ) 203 EK Band Structure 5250 is actually E G It is disclosed that this is a direct bandgap material with ≥6eV. The electron energy 1066 is plotted as a function of the crystal wave vector 1067. The minimum value of the conduction band 5265 and the valence band 5260 are maximum at the center of the Brillouin zone 5255 (k=0).

[0449] Next, 44J is a further ternary magnesium-gallium oxide cubic crystal symmetric Mg that can be integrated with Ga2O3. x Ga 2(1-x) O 3-2xThe material composition is further demonstrated. Shown are 10-period SL[Mg] deposited on monoclinic Ga2O3(010) oriented substrate 5275 (corresponding to peak 5277) using HRXRD5270 and GIXR5290. x Ga 2(1-x) O 3-2x This is an experimental realization of a superlattice containing [Ga2O3]. The SL3 alloy composition is selected from x=0.5 with a thickness of 8nm and 8nm of Ga2O3. The SL period is

number

[0450] The ability of monoclinic Ga2O3 crystal symmetry to integrate with cubic MgAl2O4 crystal symmetry substrates is shown in Figure 44L. A high-quality single-crystal substrate 5320 (peak 5322) containing MgAl2O4 spinel is cleaved and polished to expose the (100) oriented crystal surface. The substrate is prepared and polished using active oxygen at high temperatures (~700°C) under UHV conditions (<1e-9 Torr). By maintaining the substrate at a growth temperature of 700°C, the MgGa2O4 film 5330 begins to exhibit excellent resistance to the substrate. After approximately 10-20 nm, the Mg is blocked and only Ga2O3 is deposited as the top layer film 5325. The GIXR film exhibits excellent flatness, with a thickness fringe 5340 showing a film of >150 nm. HRXRD shows the transition material MgGa2O4 corresponding to peak 5332 and the Ga2O3(100) oriented epitaxial layer at peak 5327, which exhibits monoclinic crystal symmetry. In some embodiments, hexagonal Ga2O3 can also be deposited epitaxially.

[0451] The monoclinic Ga2O3(-201) oriented crystal planes are characterized by the unique properties of a hexagonal oxygen surface matrix with in-plane lattice spacings that are acceptable for registering wurtzite-type hexagonal symmetric materials. For example, as shown in Figure 5345 of Figure 44M, wurtzite ZnO5360 (peak 5367) is a substrate Zn x Ga 2(1-x) O 3-2x It is deposited on the oxygen-terminated Ga2O3(-201) oriented surface at 5350 (peak 5352). Zn is supplied by sublimation of 7N purity Zn contained within the ejection cell. The growth temperature is selected from 450-650°C for ZnO, exhibiting very bright, sharp, narrow RHEED streaks and high crystal quality. Peak 5362 is (Al x Ga 1-x ) represents 2O3. Peak 5355 represents the transition layer.

[0452] Next, the ternary zinc gallium oxide epitaxial layer Zn x Ga 2(1-x) O 3-2x5365 is deposited by co-depositing Ga, Zn, and reactive oxygen species at 500°C. [φ(Zn)+φ(Ga)]: Flux ratio and metal beam flux ratio φ(Zn) where φ(O*)<1 φ(Ga) is selected to achieve x approximately 0.5. Zn desorbs at a much lower surface temperature than Ga and is partially controlled by a surface temperature-dependent absorption limiting process determined by the Arrhenius behavior of the adsorbed Zn atoms.

[0453] Zn is a group metal and favorably substitutes for available Ga sites in the host crystal. In some embodiments, Zn can be used to alter the conductivity type of the host for dilute concentrations of incorporated Zn such that x < 0.1. x Ga 2(1-x) O 3-2x Peak 5365, labeled as such, indicates a transition layer formed on the substrate, and Zn x Ga2(1-x)O 3-2x This shows low Ga% formation. This strongly suggests high miscibility of Ga and Zn in a ternary system, providing non-equilibrium growth of alloys over the entire range of 0 ≤ x ≤ 1. x Ga 2(1-x) O 3-2x In the case where x = 0.5, the Ek band structure provides a cubic crystal symmetry, as shown in Figure 5370 of Figure 44N.

[0454] The indirect band gap, indicated by the band extrema 5375 and 5380, can be shaped using SL band engineering, as shown in Figure 27. Using the valence band dispersion 5385, which exhibits a maximum value at k≠0, an SL period can be created in which the maximum value at the zone center can be remapped favorably to the equivalent energy, thereby creating a pseudo-direct band gap structure. Such a method is claimed in whole for its application to the formation of optoelectronic devices such as UV LEDs, as referred to in this disclosure.

[0455] As described in this disclosure, there is a large design space available for crystal modifiers for Ga2O3 and Al2O3 host crystals that can be used for application in UV LEDs.

[0456] Furthermore, here is another example in which the growth conditions can be adjusted to pre-select the intrinsic crystal symmetry of Ga2O3, namely monoclinic (beta phase) or hexagonal (epsilon or kappa phase).

[0457] Figure 44O shows a specific application of the more general method disclosed in Figure 19.

[0458] A prepared clean surface of a corundum crystal-symmetric sapphire C-plane substrate 5400 is presented for epitaxy.

[0459] The substrate surface is polished with active oxygen at high temperatures such as >750°C and approximately 800-850°C. This creates an oxygen-terminated surface 5405. While maintaining a high growth temperature, the Ga and active oxygen flux are directed to the epitaxial plane of the bare Al2O3 surface reconstruction, creating a thin template layer of corundum Ga2O3 5396 or (Al x Ga 1-x ) is modified to either 2O3x < 0.5 low Al% corundum and formed by additional co-deposited Al flux. After a template layer 5396 of approximately 10 nm, the Al flux is closed and Ga2O3 is deposited. Maintaining a high growth temperature and a low Al% template 0 ≤ x < 0.1 is favorable for the exclusive film formation of a monoclinic crystalline epitaxial layer 5397.

[0460] After the formation of the initial template layer 5396, lowering the growth temperature to approximately 650-750°C makes Ga2O3 favorable only for the growth of a new type of crystal symmetry structure with hexagonal symmetry. The hexagonal phase of Ga2O3 is favored in the x>0.1 template layer. The unique properties of the hexagonal crystal symmetry Ga2O3 5420 composition will be described later. Experimental evidence of the disclosed process for growing the epitaxial structure 5395 is provided in Figure 44P, showing HRXRD 5421 for two different growth process results for phase-pure monoclinic Ga2O3 and hexagonal crystal symmetry Ga2O3. HRXRD scans show Bragg diffraction peaks of the C-plane Al2O3(0001) oriented substrate for corundum Al2O3(0006) 5465 and Al2O3(0012) 5470. For the top epitaxial film of monoclinic Ga2O3 5445, The diffraction peaks shown at 5450, 5455, and 5460 represent sharp single-crystal monoclinic Ga2O3(-201), Ga2O3(-204), Ga2O3(-306), and Ga2O3(-408).

[0461] Orthorhombic crystal symmetry can further demonstrate the advantageous property of possessing non-inversion symmetry. This is particularly advantageous for enabling electric dipole transitions between the conductive band edge and the valence band edge of the band structure at the zone center. For example, both wurtzite (ZnO) and GaN exhibit crystal symmetry with non-inversion symmetry. Similarly, orthorhombic crystals (i.e., space group 33Pna21 crystal symmetry) possess non-inversion symmetry, enabling electric dipole optical transitions.

[0462] Conversely, the growth processes of the hexagonal Ga2O3 peaks 5425, 5430, 5435, and 5440 represent sharp single-crystal hexagonal crystal symmetric Ga2O3(002), Ga2O3(004), Ga2O3(006), and Ga2O3(008).

[0463] Hexagonal crystal symmetry Ga2O3 and hexagonal (Al x Ga 1-x The importance of achieving 203 is shown in Figure 44Q.

[0464] The energy band structure 5475 indicates that the extreme values ​​of both the conductivity band 5480 and the valence band 5490 are located at the center of the Brillouin zone 5485, and therefore are favorable for application to UV LEDs.

[0465] Single-crystal sapphire is one of the most mature crystalline oxide substrates. Further forms of sapphire are Ga2O3 and AlGaO3, as well as corundum M-plane surfaces, which can be advantageously used to form other metal oxides discussed herein.

[0466] For example, it has been experimentally discovered in this disclosure that the crystal symmetry type of Ga2O3 epitaxially formed thereon can be pre-selected using the surface energy of sapphire indicated by a specific crystal plane presented to the epitaxy.

[0467] Considering Figure 44R, the usefulness of the M-plane corundum Al2O3 substrate 5500 is disclosed. The M-plane is a (1-100) oriented surface, which can be prepared as described above and atomically polished in situ at a high growth temperature of 800°C while exposed to an activated oxygen flux. Next, the oxygen-terminated surface is cooled to 500-700°C, or 500°C in one embodiment, to epitaxially deposit a Ga2O3 film. Corundum crystal symmetric Ga2O3 with a thickness of 100-150 nm or more can be deposited on the M-plane sapphire, and corundum (Al) with a thickness of approximately 400-500 nm can be deposited. x Ga 1-x It was found that approximately 0.3 to 0.45 of 2O3x could be deposited. Of particular interest is corundum (Al 03 Ga 0.7 The 2O3 group directly exhibits a band gap, which is equivalent to the energy gap of wurtzite-type AlN.

[0468] The curves for HRXRD5495 and GIXR5540 show two separate growths on M-face sapphire 5500. High-quality single-crystal corundum Ga2O35510 and (Al 03 Ga 0.7)2O35505 is clearly shown relative to the corundum Al2O3 substrate peak 5502. Therefore, an M-plane oriented AlGaO3 film is possible on M-plane sapphire. The GIXR thickness vibration 5535 shows an atomically flat interface 5520 and film 5530. Curve 5155 indicates that there are no other crystalline phases of Ga2O3 other than the corundum phase (rhombohedral crystal symmetry).

[0469] For completeness, in accordance with this disclosure, it has also been found that various metal oxides can be used, and even the most technologically mature semiconductor substrates, namely silicon, can be utilized. For example, bulk While Ga2O3 substrates are desirable due to their crystallographic and electronic properties, they are still more expensive to manufacture than single-crystal substrates and cannot be scaled as easily as Si to substrates with large wafer diameters, such as Si's 450mm diameter.

[0470] Therefore, the embodiment includes forming a functional electronic Ga2O3 film directly on silicon. For this purpose, a process specifically developed for this application was developed.

[0471] Referring to Figure 44S, the results of an experimentally developed process for depositing monoclinic Ga2O3 films on a large-area silicon substrate are shown.

[0472] The single-crystal high-quality monoclinic Ga2O3 epitaxial layer 5565 is ternary (Ga 1-x Er x It is formed on a cubic transition layer 5570 containing 2O3. The transition layer is deposited using compositional grading that may be abrupt or continuous. The transition layer is [(Ga 1-x Er x )2O3 / (Ga 1-y Er yThe transition layer is also a digital layer containing the SL of the )2O3] layer, where x and y are selected from 0 ≤ x and y ≤ 1. The transition layer is optionally deposited on a binary bigx-byte crystal symmetric Er2O3(111) oriented template layer 5560 deposited on a Si(111) oriented substrate 5555. First, Si(111) is heated at UHV to 900°C or higher and less than 1300°C to desorb the native SiO2 oxide and remove impurities.

[0473] A clear temperature-dependent change in surface reconstruction was observed and can be used to calibrate the surface growth temperature occurring at 830°C in situ, and is only observable on the original Si surface without surface SiO2. Then, the temperature of the Si substrate was lowered to 500-700°C (Ga 1-y Er y A 2O3 film (or more) is deposited, and then the beam is slightly increased to promote epitaxial growth of a monoclinic Ga2O3(-2O1) oriented active layer film. When Er2O3 binary is used, activated oxygen is not required and can be used with pure molecular oxygen and co-deposited with a pure Er beam flux. As soon as Ga is introduced, an activated oxygen flux is required. Other transition layers are also possible and can be selected from a number of ternary oxides described herein. HRXRD5550 is a cubic (Ga 1-y Er y The 2O3 peak 5572 is shown along with the Bixbite Er2O3(111) and (222) peaks 5562. The monoclinic Ga2O3(-201), (-201), and (-402) peaks are also observed as peak 5567, and the Si(111) substrate is observed as peak 5557.

[0474] One application of this disclosure is the use of cubic symmetric metal oxides for the use of transition layers between Si(001) oriented substrate surfaces to form Ga2O3(001) and (Al,Ga)2O3(001) oriented active layer films. This is particularly advantageous for mass production.

[0475] The focus of this specification is on the development of transparent substrates that can accommodate a wide variety of metal oxide compositions and crystal symmetries. Specifically, Al2O3, (Alx Ga 1-x )2O3 and Ga2O3 materials are very interesting, and the overall miscibility reaches (Al x Ga 1-x )2O3, the range of Al%x and (Al 1-y Ga y )2O3, the range of Ga%y, can be addressed by the corundum crystal symmetry composition again and again.

[0476] Here, refer to the examples in FIGS. 44T to 44X.

[0477] FIG. 44T discloses high-quality single-crystal epitaxy of a corundum Ga2O3 (110)-oriented film on an Al2O3 (11-20)-oriented substrate (i.e., A-plane sapphire). Using the surface energy of the A-plane Al2O3 surface, very high-quality corundum Ga2O3 and corundum (Al x Ga 1-x )2O3 ternary films can be grown over the entire alloy range, where 0≦x≦1. Ga2O3 can grow up to about 45 - 80 nm of CLT, and the CLT increases dramatically with the introduction of Al to form the ternary (Al x Ga 1-x )2O3. to form.

[0478] Homoepitaxial growth of corundum Al2O3 is possible in a surprisingly wide growth window range. Corundum AlGaO3 can be grown from room temperature to about 750 °C. However, in all growths, the activated oxygen (i.e., atomic oxygen) flux must sufficiently exceed the total metal flux, that is, oxygen-rich growth conditions are required. The corundum crystal symmetry Ga2O3 film is shown by HRXRD5575 and GIXR5605 scans of two separate growths of films with different thicknesses on an A-plane Al2O3 substrate. The surface of the substrate 5590 (corresponding to peak 5592) is oriented within the (11-20) plane and is O-polished at a high temperature of about 800 °C.

[0479] While the growth temperature is lowered to an optimal range of 450 - 600 °C, such as 500 °C, reactive oxygen polishing is maintained. Then, an Al2O3 buffer 5595 is optionally deposited at 10 - 100 nm, and then a ternary (Al x Ga 1-x )2O3 epi-layer 5600 is formed by co-depositing with appropriately placed Al and Ga fluxes to achieve the desired Al%. Oxygen-rich conditions are essential. Curves 5580 and 5585 show exemplary x = 0 Ga2O3 films 5600 of 20 and 65 nm respectively.

[0480] Both HRXRD and GIXR Pendellösung fringes indicate excellent coherent growth, and transmission electron microscopy (TEM) confirms that defect densities of less than 10 7 cm -3 are possible with off-axis XRD measurements.

[0481] Corundum Ga2O3 films on A-plane Al2O3 exceeding about 65 nm show relaxation as demonstrated by reciprocal lattice mapping (RSM), but maintain excellent crystal quality for films >CLT.

[0482] Still other methods are possible to further improve the CLT of binary Ga2O3 films on A-plane Al2O3. For example, during a high-temperature O polishing step on the unused Al2O3 substrate surface, the substrate temperature can be maintained at about 750 - 800 °C. At this growth temperature, the Ga flux can coexist with reactive oxygen, and high-temperature phenomena may occur. According to the present disclosure, Ga is found to effectively diffuse to the top surface of the Al2O3 substrate to form a very high-quality corundum (Al x Ga 1-x )2O3 template layer with 0 < x < 1. Growth can be interrupted or continued while the substrate temperature is lowered to about 500 °C. The template layer functions as an in-plane lattice-matching layer closer to Ga2O3, and thus it can be seen that the CLT of the epitaxial film becomes thicker.

[0483] By establishing the unique properties of surface A and referring to the surface energy trend disclosed in Figure 20B, it is shown that a bandgap-modulated superlattice structure is also possible.

[0484] Figure 44U shows the unique attributes of the binary Ga2O3 and binary Al2O3 epitaxial layers used to form the SL structure on the A-plane Al2O3 substrate 5625 (corresponding to peak 5627). Excellent SLHRXRD5610 and GIXR5630 data show period Δ SL Multiple high-quality SL-Bragg diffraction satellite peaks 5615 and 5620 with a wavelength of 9.5 nm are shown. Not only is the full width at half maximum (FWHM) of each satellite peak 5615 very small, but the inter-peak oscillations of the Penderosung fringe are also clearly observed. During the N=10 period of SL, N-2 Penderosung oscillations are present, as shown in both HRDRD and GIXR. Zero-order SL peak SL n=0 This shows the average alloy Al% of the digital alloy formed by SL.

number

[0485] Image 5660 in Figure 44V shows the crystalline quality observed in exemplary [Al2O3 / Ga2O3]SL5645 deposited on A-plane sapphire 5625. The contrast between Ga and Al species is clearly evident, showing a sudden interface between nanometer-scale films 5650 and 5655 containing the SL period.

[0486] A closer examination of image 5660 reveals a region labeled 5635, which is due to the high-temperature Ga intermixing process described above. The Al2O3 buffer layer 5640 imparts small strain to the SL stack. Great care has been taken to create high-quality SL by keeping the Ga2O3 film thickness well below that of the CLT. However, strain accumulation can occur, and other structures are possible in some embodiments, such as growing the SL structure on a relaxed buffer composition midway between the compositional endpoints of the materials constituting the SL.

[0487] This makes it possible to design strain symmetrization such that the layer pairs forming the period of the superlattice can have equally opposite in-plane strains. Each layer is deposited beneath the CLT and subjected to biaxial elastic strain (thereby suppressing dislocation formation at the interface). Thus, some embodiments involve designing the SL to be placed on a relaxation buffer layer that allows the SL to accumulate zero strain, and therefore can be effectively grown strain-free over theoretically infinite thickness.

[0488] Furthermore, the further applications of corundum film growth can be demonstrated on yet another advantageous Al2O3 crystal surface, namely the R-plane (1-102).

[0489] Figure 44W shows a thick layer of ternary corundum (Al2O3) on an R-plane corundum Al2O3. x Ga 1-xIt demonstrates the ability to epitaxially deposit 2O3 films. HRXRD5665 shows an R-faced Al2O3 substrate 5675 prepared using high-temperature O polishing and Al and Ga co-deposition, while lowering the growth temperature from 750 to 500°C to form region 5680. Region 5680 is an optional surface layer modification for a sapphire substrate surface, such as an oxygen-terminated surface. The excellent high-quality ternary epitaxial layer 5670 (corresponding to XRD peak 5672) shows a sharp Pendero-Sung fringe 5680 and provides an alloy composition of x=0.64 with respect to the substrate peak 5677. The film thickness in this case is approximately 115 nm. Also shown in Figure 44W is the angular separation of the symmetric Bragg peak 5685 of the pseudomorphic corundum Ga2O3 epitaxial layer.

[0490] Again, it is recognized that there is high utility in producing bandgap epitaxial films that can be configured or designed to construct the functional regions required for UV LEDs. Thus, strain and composition are tools that can be used to manipulate the known functional properties of materials for application to UV LEDs according to this disclosure.

[0491] Figure 44X shows an example of a high-quality superlattice structure possible on an R-plane Al2O3(1-102) oriented substrate.

[0492] HRXRD5690 and GIXR5710 are shown as examples of SLs epitaxially formed on an R-face Al2O3(1-102) substrate 5705 (corresponding to peak 5707).

[0493] SL is [(Al x Ga 1-x It contains a 10-period [3 elements / 2 elements] 2-layer pair of 2O3 / Al2O3, where x = 0.50 in the formula. SL period Δ SL =20nm. Multiple SL-Bragg diffraction peaks 5695 and reflectance peak 5715 indicate a coherently grown pseudomorphic structure. Zero-order SL diffraction peak SL n=0 5700 is (Al xSL Ga 1-xSL ) SL effective digital alloy x containing 2O3 SL This shows that xSL = 0.2.

[0494] Such highly coherent and highly distinct bandgap materials, used to create epitaxial SLs with abrupt discontinuities at the interface, can be used to form quantum confinement structures, as disclosed herein for applications in optoelectronic devices such as UV LEDs.

[0495] The energy discontinuities of the conductive bands and valence bands available at the Al2O3 / Ga2O3 heterointerface with corundum crystal symmetry (R3c) are as follows:

number

number

[0496] Furthermore, the band offset of the monoclinic crystal symmetric (C2m) heterointerface is as follows:

number

number

[0497] Some embodiments also include generating a potential energy discontinuity by creating a Ga2O3 layer with a sudden change in crystal symmetry.

[0498] For example, it is disclosed herein that corundum crystal symmetric Ga2O3 can be directly epitaxially deposited on a monoclinic Ga2O3(110) oriented surface. Such a heterointerface generates a band offset given by the following equation:

number

number

[0499] These band offsets are sufficient to generate quantum confinement structures, as will be explained below.

[0500] As yet another example of an embodiment of the composite metal oxide heterostructure, see Figure 44Y, where a cubic MgO epitaxial layer 5730 is formed directly on a spinel MgAl2O4(100) oriented substrate 5725. HRXRD5720 shows the Bragg diffraction peak 5727 for cubic MgAl2O4(h00), h=4, 8 substrate and the epitaxial cubic MgO peak 5737 corresponding to the MgO epitaxial layer 5730. The lattice constant of MgO is almost exactly twice that of MgAl2O4, thus creating a unique epitaxial coincidence for in-plane lattice registration at the heterointerface.

[0501] Clearly, a high-quality MgO(100)-oriented epitaxial layer is formed, as evidenced by the narrow FWHM. Next, a monoclinic layer of Ga2O35735 is formed on top of the MgO layer 5730. The Ga2O3(100)-oriented film is evidenced by the Bragg diffraction peak at 5736.

[0502] Cubic MgAl2O4 and Mg x Al 2(1-x) O 3-2x The interest in ternary structures stems from the fact that they allow for direct and large band gaps.

[0503] Graph 5740 in Figure 44Z shows Mg x Al 2(1-x) O 3-2x The energy band structure (where x is approximately 0.5) is shown, and a direct band gap 5745 is formed between the extreme values ​​of the conductivity band 5750 and the valence band 5755.

[0504] Some embodiments also involve directly growing Ga2O3 on an aluminum lanthanum oxide (LaAlO3) (001) substrate.

[0505] The exemplary structures disclosed in Figures 44A–44Z are intended to demonstrate several possible configurations applicable to use in at least a portion of a UV LED structure. A wide variety of suitable mixed-symmetric heterostructures are further attributes of this disclosure. As will be understood, other configurations and structures are also possible and consistent with this disclosure.

[0506] The unique properties of the AlGaO3 material system described above can be applied to the formation of UV LEDs. Figure 45 shows an exemplary light-emitting device structure 1200 according to this disclosure. The light-emitting device 1200 is designed to operate so that optically generated light can be outcoupled perpendicularly through the device. The device 1200 consists of a substrate 1205, a first conductivity type n-type doped AlGaO3 region 1210, followed by an unintentionally doped (NID) intrinsic AlGaO3 spacer region 1215, followed by (Al x Ga 1-x )O3 / (Al y Ga 1-y ) Multiple quantum wells (MQW) or superlattice 1240 formed using periodic repetitions of O3 The barrier layer contains a larger bandgap composition 1220, while the well layer contains a narrower bandgap composition 1225.

[0507] The overall thickness of the MQW or SL1240 is selected to achieve the desired emission intensity. The thickness of the layer containing the MQW or SL1240 unit cells is configured to produce a predetermined operating wavelength based on the quantum confinement effect. An optional AlGaO3 spacer layer 1230 then separates the MQW / SL from the p-type AlGaO3 layer 1235.

[0508] The spatial energy band profiles using the k=0 representation are disclosed in Figures 46, 47, 49, 51, and 53, which are graphs of the spatial band energy 1252 as a function of the growth direction 1251. The n-type and p-type conductive regions 1210 and 1235 are (Al x Ga 1-x) is selected from the monoclinic or corundum composition of O3, where x=0.3, followed by NID1215 of the same composition with x=0.3. MQW or SL1240 is adjusted in each design 1250 (Figures 46, 47), 1350 (Figure 49), 1390 (Figure 51), and 1450 (Figure 53) by keeping the thickness of both the well and the barrier layer the same.

[0509] The well composition varies at x=0.0, 0.05, 0.10, and 0.20, and the barrier is a two-layer pair (Al x Ga 1-x )O3 / (Al y Ga 1-y ) In O3, y is fixed at 0.4. These MQW regions are located at 1275, 1360, 1400, and 1460. The thickness of the well layer is determined by the unit cell (a) of the host composition. w (Lattice constant) at least 0.5xa w ~10×a w A selection is made from the following. In this case, one unit cell is selected. Because corundum and monoclinic unit cells are relatively large, the thickness of the periodic unit cell can be relatively large. However, in some embodiments, a subunit cell assembly can be used. The MQW region 1275 in Figure 47 is Ga2O3 / (Al 0.4 Ga 0.6 ) is composed for a combination of intrinsic or unintentional doping layers containing 2O3. The MQW region 1360 in Figure 49 is (Al 0.05 Ga 0.95 )2O3 / (Al 0.4 Ga 0.6 ) is composed for a combination of intrinsic or unintentional doping layers containing 2O3. The MQW region 1400 in Figure 51 is (Al 0.1 Ga 0.9 )2O3 / (Al 0.4 Ga 0.6 ) is composed for a combination of intrinsic or unintentional doping layers containing 2O3. The MQW region 1460 in Figure 53 is (Al 0.2 Ga 0.8 )2O3 / (Al 0.4 Ga 0.6 ) Consists of a combination of inherent or unintentional doping layers containing 2O3.

[0510] Ohmic contact metals 1260 and 1280 are also shown. Conductive band end E C (z)1265 and valence band edge E V (z)1270 and the MQW region 1400 exhibit modulation of the bandgap energy for spatially modulated compositions. This is yet another special advantage of atomic layer epitaxy deposition techniques that enable such structures.

[0511] Figure 47 schematically shows the wave functions of the confined electron 1285 and hole 1290 within the MQW region 1275. The electric dipole transition due to spatial recombination of electron 1285 and hole 1290 generates photon 1295.

[0512] The emission spectrum can be calculated and plotted in graph 1300 as emission wavelength 1310 and oscillator absorption intensity 1305 (emission intensity also shown) due to the overlapping wave function integration for spatially dependent quantized electron and hole states, as shown in Figure 48. Multiple peaks 1320, 1325, and 1330 arise from recombination with the MQW of quantized energy states. Specifically, the lowest energy electron-hole recombination peak 1320 is most likely, occurring at approximately 245 nm. Region 1315 indicates that there is no absorption or emission below the energy gap of the MQW. The initial occurrence of optical activity as we move toward shorter wavelengths is due to the n=1 exciton peak determined by the MQW configuration. It is Ku 1320.

[0513] MQW configurations 1275, 1360, 1400, and 1460 result in emission energy peaks 1320 (Figure 48), 1370 (Figure 50), 1420 (Figure 52), and 1470 (Figure 54), with peak operating wavelengths of 245 nm, 237 nm, 230 nm, and 215 nm, respectively. Graph 1365 in Figure 50 also shows peaks 1375 and 1380 along with region 1385. Graph 1410 in Figure 52 also shows peaks 1425 and 1430 along with region 1435. Graph 1465 in Figure 54 also shows peak 1475 along with region 1480. Regions 1385, 1435, and 1480 indicate no optical absorption or emission of photons with energy / wavelengths below the MQW energy gap.

[0514] Furthermore, a further characteristic of metal oxide semiconductors with very wide band gaps is the configuration of ohmic contacts into the n-type and p-type regions. Exemplary diode structures 1255 include high-work-function metals 1280 and low-work-function metals 1260 (ohmic contact metals). This is due to the relative electron affinity of the metal oxides to vacuum (see Figure 9).

[0515] Figures 48, 50, 52, and 54 show the optical absorption spectra of the MQW region contained within the diode structure 1255. The MQW comprises two layers: one with a narrower bandgap and the other with a wider bandgap. The thickness of the layers, specifically the narrow-bandgap layer, is selected to be small enough to exhibit quantization effects along the growth direction within the formed conductive potential wells and valence potential wells. The absorption spectra represent the generation of electrons and holes in the quantized state of the MQW in the resonant absorption of incident photons.

[0516] In the reversible process of photon generation, electrons and holes are spatially localized at their respective quantum energy levels in the MQW and recombine directly through the band gap. This recombination generates photons with energy approximately equal to the energy of the band gap of the layer, which acts as a potential well with a direct energy gap, in addition to the energy separation of quantization levels within the potential well relative to the conduction band edge and valence band edge. Therefore, the emission / absorption spectrum shows the lowest energy resonance peak indicating the primary emission wavelength of the UV LED, which is designed to be the desired operating wavelength of the device.

[0517] Figure 55 shows a plot of known pure metal work function energies 1510 and 1500, classifying metal species (elemental metal contacts 1505) from high work function 1525 to low work function 1515 for application to p-type and n-type ohmic contacts, providing selection criteria for metal contacts for each of the conductivity type regions required by UV LEDs. The line 1520 represents the midpoint work function energy for the upper limit 1525 and lower limit 1515 shown in Figure 55.

[0518] In some embodiments, Ni, Os, Se, Pt, Pd, Ir, Au, W, and their alloys are used in the p-type region, and low work function metals selected from Ba, Na, Cs, Nd, and their alloys may be used. Other selections are also possible. For example, in some cases, common metals such as Al, Ti, Ti-Al alloys, and titanium nitride (TiN) can also be used as contacts to the n-type epitaxial oxide layer.

[0519] Intermediate contact materials such as metalloid palladium oxide (PdO), degenerately doped Si or Ge, and rare earth nitrides can be used. In some embodiments, ohmic contacts are formed in situ for at least a portion of the deposition process of the contact material to maintain the [metal contact / metal oxide] interface quality. In fact, single-crystal metal deposition is possible in some metal oxide configurations.

[0520] X-ray diffraction (XRD) is used in crystal growth analysis to directly confirm crystal quality and crystal symmetry. It is one of the most powerful tools available. Figures 56 and 57 show two-dimensional XRD data of exemplary materials of ternary AlGaO3 and binary Al2O3 / Ga2O3 superlattices. Both structures are pseudomorphically deposited on corundum crystalline symmetric substrates with A-plane oriented surfaces.

[0521] Now referring to Figure 56, a 201 nm thick epitaxial ternary (Al) on the Al2O3 substrate on side A. 0.5 Ga 0.5 The reciprocal lattice map biaxial X-ray diffraction pattern 1600 of )2O3 is shown. Clearly, the in-plane and perpendicular mismatch of the ternary film is in good agreement with the underlying substrate. The in-plane mismatch parallel to the growth plane is approximately 4088 ppm, and the perpendicular lattice mismatch of the film is approximately 23440 ppm. The ternary layer peak relative to the substrate (SUB) (Al x Ga 1-x The relative vertical displacement of 2O3 exhibits excellent film growth suitability, which is directly advantageous for UV LED applications.

[0522] Referring to Figure 57, a biaxial X-ray diffraction pattern 1700 of a 10-period SL[Al2O3 / Ga2O3] on an A-plane Al2O3 substrate exhibiting an excellent strained Ga2O3 layer (no 2-theta angle spreading) => elastically strained SL is shown. The SL period = 18.5 nm and the effective SL digital Al% is approximately 18% x_Al in a ternary alloy.

[0523] In further exemplary embodiments, the optoelectronic semiconductor devices according to the present disclosure may be implemented as metal oxide semiconductor material-based ultraviolet laser devices (UVLAS).

[0524] Metal oxide compositions with bandgap energies corresponding to operation at UVC (150–280 nm) and far / vacuum UV wavelengths (120–200 nm) generally exhibit a distinctive characteristic: they have an inherently small optical refractive index far from the fundamental band edge absorption. When operating as an optoelectronic device where the energy states are very close to the conduction band edge and the valence band edge, the effective refractive index is governed by the Kramers-Kronig relationship.

[0525] Figures 58A and 58B show cross-sections of a metal oxide semiconductor material 1820 having an optical length of 1850 along a one-dimensional optical axis, according to exemplary embodiments of the present disclosure. The incident light vector 1805 is at refractive index n Mox The material 1820 is entered from the air containing the light beam 1815. The light within the material 1820 is transmitted and reflected at the refractive index discontinuities of each surface (beam 1810).

[0526] A material slab of length 1850 can support a number of optical longitudinal modes 1825, as shown in Figure 58A. The transmittance 1815 as a function of the wavelength of light incident on the slab indicates a Fabry-Perot mode structure having modes 1825. For photons trapped in an optical cavity defined by a one-dimensional slab, according to this disclosure, it is possible to determine the round-trip losses of the slab and the minimum optical gain required to overcome these losses and enable a net gain.

[0527] The threshold gain is calculated in Figure 58B, and the transmission coefficient β is shown as a function of the optical gain in the slab for the forward 1830 and reverse 1835 directions of the optical beam 1810 propagating through it. In this simple Fabry-Perot case, the slab length L cav = 1 micrometer low refractive index n Mox At =2.5, a threshold gain of 1845 is required, calculated from the point of maximum full width at half maximum of the peak gain at 1840.

[0528] Some embodiments implement semiconductor cavities contained within vertical structures 110 (see, for example, Figure 2A) having a submicron length scale. This is for electron-hole recombination. This is due to the desire to localize the emission to a narrow region. Limiting the physical thickness of the slab where carrier recombination and emission occur helps reduce the threshold current density required to achieve laser oscillation. Therefore, it is beneficial to understand the required threshold gain by shortening the length of the gain slab.

[0529] Figures 59A to 59B show the same optical materials as Figures 58A to 58B, but L cav This is the case for 500 nm. When the cavity length 1860 is smaller than the length 1850, the number of allowable optical modes 1870 decreases. The required threshold gain needed to overcome cavity loss increases to 1865 compared to the gain 1845 in Figure 58A, referring to the peaks 1877 calculated for the forward and reverse propagation modes 1880 and 1885 shown in Figure 59B, respectively.

[0530] The increase in threshold gain required for a metal oxide material slab can be dramatically reduced by increasing the length of the slab of the optical gain medium, in this case the metal oxide semiconductor region responsible for the light emission process.

[0531] Referring again to Figures 2A and 2B, instead of using a vertical 110 light-emitting device (i.e., Figure 2A), some embodiments utilize a planar waveguide structure in which the optical modes overlap with the optical gain layer along the plane-parallel length. That is, even if the gain material is still a thin slab, the light propagation vectors are substantially parallel to the plane of the gain slab.

[0532] This is schematically shown for structure 140 in Figure 2B and structure 2360 in Figure 74. Waveguide structures with optical gain region layer thicknesses far below 500 nm are possible, and can even be as thin as 1 nanometer supporting the quantum well (see Figures 64-68). The longitudinal length of the waveguide can then be on the order of a few microns to a few millimeters, or even centimeters. This is an advantage of the waveguide structure. An additional requirement is the ability to confine and guide optical modes along the length of the long axis of the waveguide, which can be achieved by using appropriate refractive index discontinuities. It is preferable that the optical modes are guided to a medium with a higher refractive index compared to the surrounding non-absorbing cladding region. This can be achieved using the metal oxide compositions described herein, which can be pre-selected to exhibit a favorable Ek-band structure.

[0533] In its most basic configuration, UVLAS requires at least one optical gain medium and optical cavity to reuse the generated photons. The optical cavity must also include a low-loss high reflector (HR) and an output-coupled reflector (OC) capable of transmitting a portion of the optical energy generated in the gain medium. The HR and OC reflectors are generally planar and parallel, or capable of focusing the energy within the cavity into the gain medium.

[0534] Figure 60 schematically shows an embodiment of an optical cavity having HR 1900, a gain medium 1905 that substantially fills a cavity of length 1935, and an OC 1915 with a physical thickness of 1910. Standing waves 1925 and 1930 indicate two distinct optical wavelength optical fields corresponding to the cavity length. The out-coupled light 1920 is due to the OC leaking some of the energy confined within the cavity gain medium 1905. In one example, a thin aluminum metal of <15 nm is used in the far-ultraviolet or vacuum UV wavelength region, and the transmittance can be precisely adjusted by the Al film thickness 1910. The lowest energy standing wave 1925 has a node (peak intensity of the optical field) at the center node 1945 of the cavity. The first harmonic (standing wave 1930) appears at nodes 1940 and 1950 as shown.

[0535] Figure 61 shows the output wavelength 1960 and from a cavity with an energy flow of 1970. Figure 61 shows that the cavity length 1935 is the same as in Figure 60. Figure 61 shows that the cavity length 1935 can support two optical modes forming two different wavelength standing waves 1930 and 1925. Figure 61 shows the emission or outcoupling of both wavelength modes (standing waves 1930 and 1925) as wavelengths 1965 and 1960, respectively. That is, both modes propagate. The optical gain medium 1905 substantially fills the optical cavity length 1935. Only the peak optical field intensity nodes 1940, 1945, and 1950 are coupled to the spatial portion of the gain medium 1905. Thus, according to this disclosure, it is possible to configure the gain medium within the optical cavity as shown in Figure 62.

[0536] Figure 62 shows the spatially selective gain medium 1980, which is shorter in length compared to the optical gain medium 1905 in Figures 60-61 and is favorably positioned within the cavity length 1935 to amplify only mode 1925. That is, the optical gain medium 1980 supports outcoupling of wavelength 1960 as the optical mode. Thus, the cavity preferentially provides gain to the fundamental mode 1925 with the output energy selected as wavelength 1960.

[0537] Similarly, Figure 63 shows two spatially selective gain media 1990 and 1995, which are favorably positioned to amplify only the modes of standing wave 1930. The cavities preferentially provide gain to the modes of standing wave 1930 having the output energy selected as 1965.

[0538] A method comprising spatially arranging gain regions within an optical cavity is one exemplary embodiment of the present disclosure. This can be achieved by pre-determining the functional regions as a function of the growth direction during the film formation process described herein. Spacer layers between gain regions may comprise substantially non-absorbent metal oxide compositions, otherwise providing electron carrier transport functionality and assisting in the optical cavity tuning design.

[0539] Here, we focus on the design of an optical gain medium for application to UVLAS using the metal oxide composition described in this disclosure.

[0540] Figures 64A-64B and 65A-65B disclose a bandgap-designed quantum confinement structure for a single quantum well (QW). It should be understood that multiple QWs are possible, similar to a superlattice. The wide-bandgap electron barrier cladding layer is made of a metal oxide material with composition A. x B y O z The potential well material is selected from C p D q O r The metal cations A, B, C, and D are selected from the compositions described in this disclosure (0 ≤ x, y, z, p, q, r ≤ 1).

[0541] By selecting the appropriate material, the conductive band offset and valence band offset shown in Figures 64A and 64B can be achieved. (Al 0.95 B 0.05 )2O3=Al 1.9 Ga 0.1 In the case where A=Al and B=Ga form O3, and (Al 0.05 B 0.95 )2O3=Al 0.1 Ga 1.9 The case where C=Al and D=Ga form O3 is shown. Using the k=0 representation of the respective Ek curves for each material, the spatial profiles of the conductivity band 2005 and valence band 2010 along the growth direction z are shown.

[0542] Figure 64A shows L QW This shows that a QW with a thickness of 5 nm (2015) generates quantized energy states 2025 and 2035 for the allowable electron and hole states in the conduction band and valence band, respectively. The lowest quantized electron state 2020 and the highest quantized valence state 2030 participate in the spatial recombination process, generating photons with an energy equal to 2040.

[0543] Similarly, Figure 64B shows L QW This shows that a QW with a thickness of 2 nm and a value of 2050 generates quantized energy states within potential wells of electron and hole allowance states in the conduction band and valence band, respectively. The lowest quantized electron state 2055 and the highest quantized valence state 2060 participate in a spatial recombination process, generating photons with energy equal to 2065.

[0544] Further reducing the thickness of QW yields the spatial band structures shown in Figures 65A and 65B. Figure 65A shows L QWThis shows that a QW with a thickness of 1.5 nm and a thickness of 2070 generates quantized energy states within a potential well of electron and hole allowable states in the conduction band 2005 and the valence band 2010, respectively. The lowest quantized electron state 2075 and the highest quantized valence state 2080 participate in a spatial recombination process, generating a photon with an energy equal to 2085.

[0545] Figure 65B shows L QW This demonstrates that a QW with a thickness of 1.0 nm, specifically 2090, generates quantized energy states within potential wells of electron and hole allowance states in the conduction band and valence band, respectively. The QW can support only a single quantized electronic state 2095 involved in the highest quantized valence state 2100 in a spatial recombination process that generates a photon with energy equal to 2105.

[0546] The spontaneous luminescence resulting from the spatial recombination of quantized electron and hole states in the QW structures of Figures 64A, 64B, 65A, and 65B is shown in Figure 66. The annihilation of electron-hole pairs occurs at L QW For values ​​of 5.0, 2.5, 2.0, 1.5, and 1 nm, it produces photons with energy wavelengths having peaks at 2115, 2120, 2125, 2130, and 2135, respectively. What is clear from the emission spectrum of 2110 is that using the same barrier and well composition, but L QW This allows for excellent tuning of the operating wavelength possible in the gain medium by controlling [the specific factor].

[0547] Having fully explained the usefulness of constructing metal oxide compositions for direct application to UVLAS gain media, we now refer to Figures 67A and 67B, which further illustrate the electronic configuration of the gain media. Figure 67A again shows a QW constructed using a metal oxide layer to form the aforementioned QW structure example.

[0548] The QW thickness of 2160 is adjusted to achieve a recombination energy of 2145. The k=0 representation of the QW in Figure 67A represents the non-zero crystalline wave vector dispersion of quantization energy states 2165 and 2180 for the electron (conductivity band 2190) and hole (valence band 2205) states. For completeness, the underlying bulk Ek dispersion is also shown as 2170 and 2175 for k=0 and 2185 and 2200 for non-zero k. The schematic Ek diagram is important to illustrate the population inversion mechanism that creates the excess electrons and holes in the conductivity and valence bands necessary to provide optical gain.

[0549] The band structure shown in Figure 68A describes the electronic energy configuration state when the conductivity band quasi-Fermi energy level 2230 is positioned above the electronic quantization energy state 2235. Similarly, the valence band quasi-Fermi energy is selected to penetrate the valence band level 2245, generating an excess hole density 2225. The Ek curve for the conductivity band 2195 indicates that the electronic state 2220 is filled with electrons for which a non-zero crystal momentum state |k|>0 is possible. The valence band level 2240 is the valence band edge of the bulk material used in the narrow bandgap region of the MQW. When the narrow bandgap material is confined to the MQW, the energy states are quantized, resulting in a dispersion of the band structure between the conductivity band 2195 and the valence band 2205. The valence band level 2240 is the maximum value of the valence band in the MQW region. The valence band level 2245 represents the Fermi energy level of the valence band when configured as a p-type material. This fills the region with an excess hole density of 2225 with holes that can contribute to optical gain.

[0550] The photorecombination process can occur in "vertical transitions" where the change in crystal momentum between the electronic and hole states is similarly zero. Acceptable vertical transitions are shown as 2215 for k=0 and 2210 for k≠0. The calculation of the integral gain spectrum for a typical band structure in Figure 68A is shown in Figure 68. The specific input parameter for the gain spectrum is L.QW The values ​​are 2nm, electron-to-hole ratio of 1.0, carrier relaxation time τ=1ns, and operating temperature T=300K. Curves 2275~2280 represent 0≦N e ≤ 5 × 10 24 m -3 The electron color N e This shows an increase.

[0551] The net positive gain of 2250 is equal to the threshold N e Approximately 4x10 24 m -3 This can be achieved with high electron concentrations. These parameters are on the order of those achievable by other technically mature semiconductors such as GaAs and GaN. In some embodiments, metal oxide semiconductors are less susceptible to gain reduction with operating temperature due to their inherently high band gaps. This is demonstrated by conventional optically pumped high-power solid-state Ti-doped Al2O3 laser crystals.

[0552] Figure 68B shows N e The net gain 2265 and net absorption 2270 are shown as functions of . The range of crystal wave vectors that can contribute to vertical transitions determines the width of the net gain region 2250. This is basically determined by the excess electron 2220 and hole 2225 states that can be achieved by manipulating the quasi-Fermi energy.

[0553] Region 2255 lies below the fundamental bandgap of the host QW and is therefore non-absorbent. Thus, optical modulators using metal oxide semiconductor QWs are also possible. Of particular note is the induced transparency point of 2260, where the QW achieves zero loss.

[0554] Manipulating the quasi-Fermi energy is not the only method available to create excess electron-hole pairs near the zone-centered band structure that enables luminescence. Consider Figures 69A and 69B showing the Ek band structure for direct bandgap materials (Figure 69A) and pseudo-direct bandgap materials, e.g., metal oxide SL with a period selected to create a maximum valence electron value as shown in curve 2241 with hole state 2246 in Figure 69B.

[0555] Assuming a similar conduction band dispersion 2195, configurations can be achieved that allow the same vertical transitions for both valence band types 2205 and 2241. Gain spectra substantially similar to those disclosed in Figure 68B are possible for both types shown in Figures 69A and 69B.

[0556] Furthermore, a further method is disclosed for generating electronic and hole states suitable for generating light emission and optical gain in a metal oxide semiconductor structure.

[0557] Figures 70A and 70B illustrate an implosion ionization process using a metal oxide semiconductor with a direct bandgap. While implosion ionization is a known phenomenon and process in semiconductors, the advantageous properties of metal oxides with very wide energy bandgaps are not well known. One of the most promising properties discovered according to this disclosure is the extremely high dielectric breakdown strength of the metal oxide.

[0558] In conventional small-bandgap semiconductors such as Si and GaAs, when used for device functionality, the impact ionization process wears the material by generating crystallographic defects / damage. This tends to cause material degradation over time, limiting the number of dielectric breakdown events that can occur before a catastrophic device failure occurs.

[0559] Metal oxides with extremely wide band gaps (Eg > 5 eV) possess advantageous properties for fabricating shock ionization luminescence devices.

[0560] Figure 70A shows the metal oxide direct band gap of 2266, which has "hot" (high-energy) electrons injected into the conductive band in electronic state 2251, which has excess kinetic energy 2261 relative to the conductive band edge 2256. The metal oxide is subjected to an excessively high electric field (up to 10 MV / cmV) across the entire thin film. br >1) It can easily withstand this.

[0561] By operating with a metal oxide slab biased to a voltage below or close to the dielectric breakdown voltage, a shock ionization event as shown in Figure 70B becomes possible. The high-energy electron 2251 can generate lower-energy states by interacting with the host's crystal symmetry and coupling to available thermalization, which involves lattice vibration quanta called phonons and pair production. That is, the shock ionization event involving the hot electron 2251 is converted into two low-energy electron states 2276 and 2281 near the minimum of the conduction band, as well as a new hole state 2286 generated above the valence band 2271. The generated electron-hole pair 2291 is a potential recombination pair that generates a photon of energy 2266.

[0562] According to this disclosure, it has been found that impulse ionization pair production is possible at an excess electron energy of 2261, which is about half the band gap energy of 2266. For example, E G If the voltage is 5eV2266, then a hot electron relative to the approximately 2.5eV conductive band edge can initiate the pair formation process as described. This is achievable in Al2O3 / Ga2O3 heterostructures, where electrons from Al2O3 are injected into Ga2O3 across the heterojunction. Impact ionization is a stochastic process, requiring a minimum interaction length to create a finite energy distribution of electron-hole pairs. Generally, interaction lengths of 100 nm to 1 micron are sufficient to create significant pair formation.

[0563] Figures 71A and 71B demonstrate that implosion ionization is possible even in pseudo-direct and indirect band structure metal oxides. Figure 71A shows the case before the direct band gap, and Figure 71B shows the same process in the indirect band gap valence band 2294, where the generation of electron-hole pairs 2292 requires the generation of k≠0 hole states 2296 and phonons for momentum conservation. Thus, Figure 71B demonstrates that optical gain media are also possible in pseudo-direct band structures such as 2294.

[0564] Figures 72A and 72B disclose further details of a disclosure using a shock ionization process for an optical gain medium by selecting favorable characteristics of the band structure.

[0565] Figure 72A shows the band structures of Figures 68A-68B, 69A-69B, 70A-70B, and 71A-71B, along with the in-plane crystal wave vector k || and the quantization axis k parallel to the epitaxial layer growth direction z. z This explains the wave vectors along the specified line.

[0566] The dispersion of the conductive 2320 and valence electron 2329 bands is shown in k in Figure 72A. z The spatial band structure at k=0 of a material with a band gap of 2266, as depicted in Figure 72A, is plotted along the growth direction, resulting in the spatial energy band diagram shown in Figure 72B. Along the growth direction z, hot electrons 2251a are injected into the conductive band, generating impulse ionization processes and pair production 2290. When a slab of metal oxide material is exposed to a large electric field oriented along z, the band structure has a potential energy that decreases linearly along z. Quasiparticle production of electron 2276 and hole 2286 pairs. The impact ionization event that generates 2290 can undergo recombination to produce a bandgap energy photon.

[0567] The remaining electrons 2276 can be accelerated by the applied electric field to generate another hot electron 2252. The hot electron 2252 is then impulsively ionized, allowing the process to repeat. Thus, the energy supplied by the external electric field can generate pair products and a photon generation process. This process is particularly advantageous for metal oxide luminescence and photogain formation.

[0568] Finally, there are three laser topologies that can be advantageously utilized according to the principles described in this disclosure.

[0569] The basic components are (i) an electronic region that forms and generates an optical gain region, and (ii) an optical cavity containing the optical gain region.

[0570] Figure 73 shows a semiconductor optoelectronic device in the form of a vertically radiating UVLAS2300, which includes an optical gain region 2330 with a thickness of 2331, an electron injector region 2325, and a hole injector region 2335. Regions 2325 and 2335 may be n-type and p-type metal oxide semiconductors and may be substantially transparent to the operating wavelength emitted from the device along axis 2305. An electrical excitation source 200 is operably connected to the device via conductive layers 2340 and 2320, which can also function as a high reflector and an output coupler, respectively. The optical cavity between the reflectors (conductive layers 2340 and 2320) is formed by the sum of the stacks of layers 2325, 2330, and 2335.

[0571] If the reflector is a partially absorbing multilayer dielectric type, a portion of the reflector's thickness is also included as part of the cavity thickness. In the case of a pure, ideal metallic reflector, the mirror thickness is negligible. Thus, the thickness of the optical cavity is controlled by layers 2325, 2330, and 2335, of which the optical gain region 2330 is favorably positioned with respect to the cavity modes as described in Figures 61, 62, and 63. Photon recycling 2350 is indicated by mirrors / reflectors 2340 and 2320.

[0572] As shown in Figure 73, yet another choice for creating the UVLAS structure is an embodiment in which reflectors 2320 and 2340 must form part of an electrical circuit and therefore be conductive, and also be able to function as reflectors forming an optical cavity. This can be achieved by using an elemental aluminum layer to function as at least one of the HR or OC.

[0573] In alternative UVLAS configurations, the optical cavity is isolated from the electrical portion of the structure. For example, Figure 74 discloses a UVLAS 2360 having an optical cavity formed with HR2340 and OC2320 which are not part of the electrical circuit. The optical gain region 2330 is positioned with a cavity that enables photon recycling 2350. The optical axis is oriented along axis 2305. To adjust the position of the gain region 2330 between reflectors 2340 and 2320, an insulating spacer layer metal oxide region may be provided within the cavity. Electron injectors 2325 and hole injectors 2335 supply laterally transported carriers to the gain region 2330.

[0574] Such a structure can be realized for vertical emission UVLAS by creating p-type and n-type regions positioned laterally to connect only a portion of the gain region. Reflectors can also be placed in a portion of the optical gain region to generate cavity photon recycling 2350.

[0575] Furthermore, a further exemplary embodiment is the waveguide device 2370 shown in Figure 75.

[0576] Figure 75 shows a waveguide structure 2370 having a long axis 2305 with epitaxial regions sequentially formed along the growth direction z, including electron injectors 2325, an optical gain region 2330, and a hole injector region 2335. A single-mode or multi-mode waveguide structure with refractive index is selected to generate confined optical emission of forward and reverse propagation modes 2375 and 2380. The cavity length 2385 is terminated at each end with reflectors 2340 and 2320. The high reflector 2340 may be metallic or dispersion feedback type, including a multilayer dielectric conformally coated on an etched grating or raised portion. OC2320 may be a metallic translucent film of dielectric coating, or even cleavage facets of a semiconductor slab.

[0577] As understood, optical gain regions may be formed using metal oxide semiconductors according to this disclosure, which are electrically stimulated and / or optionally optically excited / stimulated, so that optical cavities can be formed in both vertical and waveguide structures as needed.

[0578] This disclosure teaches novel materials and processes for realizing metal oxide-based optoelectronic light-emitting devices capable of generating light deep into the UVC and far / vacuum ultraviolet wavelength bands. These processes include tuning or configuring the band structure of different regions of the device using a number of different methods, including, but not limited to, compositional selection to achieve a desired band structure, including forming an effective composition using a superlattice containing different layers of repeating metal oxides. This disclosure also teaches the use of biaxial or uniaxial strain to modify the band structure of relevant regions of semiconductor devices, as well as interlayer strain matching in superlattices, for example, to reduce crystal defects during the formation of optoelectronic devices.

[0579] As is understood, metal oxide-based materials are generally known in the prior art for their insulating properties. Metal oxide single-crystal compositions such as sapphire (corundum-Al2O3) are available in very high crystal quality and can be easily grown on large-diameter wafers using bulk crystal growth methods such as Czochralski (CZ), edge-feed growth (EFG), and float-zone (FZ) growth. Semiconductor gallium oxide with monoclinic crystal symmetry has been realized using essentially the same growth methods as sapphire. Since the melting point of Ga2O3 is lower than that of sapphire, the energy required for CZ, EFG, and FZ methods is slightly lower, which may help in large-scale cost reductions per wafer. Bulk alloys of AlGaO3 bulk substrates have not yet been attempted using CZ or EFG. Therefore, metal oxide layers in optoelectronic devices can be based on these metal oxide substrates according to the examples of this disclosure.

[0580] The two binary metal oxide materials Ga2O3 and Al2O3 exist in several technically related crystal symmetries. Specifically, both Al2O3 and Ga2O3 are capable of alpha phase (rhombohedral) and beta phase (monoclinic). Ga2O3 prefers the monoclinic structure energetically, while Al2O3 prefers the rhombohedral structure for bulk crystal growth. According to this disclosure, atomic beam epitaxy can be employed using high-purity metal and atomic oxygen as constituent components. As demonstrated in this disclosure, this enables many opportunities for the flexible growth of heterogeneous crystal symmetry epitaxial films.

[0581] Two exemplary classes of device structures particularly suitable for UV LEDs include high Al content Al deposited on an Al2O3 substrate. x Ga 1-x High Ga content on O3 and bulk Ga2O3 substrates It contains a large amount of AlGaO3. As demonstrated in this disclosure, the use of digital alloys and superlattices further expands the possible designs for application to UV LEDs. As demonstrated in several examples of this disclosure, the various Ga2O3 and Al2O3 surface orientations presented for AlGaO3 epitaxy can be used in conjunction with growth conditions such as temperature and metal-to-atomic oxygen ratio and relative metallicity of Al to Ga to predetermine the crystal symmetry of the epitaxial film, which can be utilized to determine the band structure of the luminescent or conductive region.

[0582] Epitaxial oxide materials and semiconductor structures

[0583] This specification describes epitaxial oxide materials, semiconductor structures containing epitaxial oxide materials, and devices containing structures containing epitaxial oxide materials.

[0584] Figures 76A-1 to 76D show charts and tables of minimum bandgap energy and lattice parameters obtained by DFT calculations for several examples of epitaxial oxide materials. The epitaxial oxide materials described herein may be any of those shown in Figure 28 and in the tables of Figures 76A-1, 76A-2, and 76B. Some examples of epitaxial oxide materials are (Al x Ga 1-x )2O3 (0≦x≦1 in the formula), (Al x Ga 1-x ) y O z (wherein the formula 0≦x≦1, 1≦y≦3 and 2≦z≦4) (having a space group of R3c (i.e. α), pna21 (i.e. κ), C2m (i.e. β), Fd3m (i.e. γ), and / or Ia3 (i.e. δ)), NiO, (Mg x Zn 1-x ) z (Al y Ga 1-y ) 2(1-z) O 3-2z (wherein the formula 0≦x≦1, 0≦y≦1 and 0≦z≦1), (Mg x Ni 1-x ) z(Al y Ga 1-y ) 2(1-z) O 3-2z (wherein the formula 0≦x≦1, 0≦y≦1 and 0≦z≦1), MgAl2O4, ZnGa2O4, (Mg x Zn y Ni 1-y-x )(Al y Ga 1-y )2O4(where 0≦x≦1, 0≦y≦1)(for example (Mg x Zn 1-x (Al)2O4) or (Mg)(Al y Ga 1-y )2O4), (Al x Ga 1-x )2(Si z Ge 1-z )O5(where 0≦x≦1 and 0≦z≦1 in the formula), (Al x Ga 1-x )2LiO2 (where 0≦x≦1 in the formula), and (Mg x Zn 1-x-y Ni y )2GeO4 (where 0≦x≦1 and 0≦y≦1).

[0585] The “epitaxial oxide” materials described herein are materials comprising oxygen and other elements (e.g., metals or nonmetals) having a regular crystalline structure configured to be formed on a single-crystal substrate or on one or more layers formed on a single-crystal substrate. Epitaxial oxide materials have defined crystalline symmetry and crystalline orientation with respect to the substrate. Epitaxial oxide materials can form coherent layers with a single-crystal substrate and / or one or more layers formed on a single-crystal substrate. Epitaxial oxide materials may exist within layers of strained semiconductor structures, where the crystals of the epitaxial oxide material are deformed compared to a relaxed state. Epitaxial oxide materials may also exist within layers of unstrained or relaxed semiconductor structures.

[0586] In some embodiments, the epitaxial oxide materials described herein are polar and piezoelectric, and as a result, the epitaxial oxide materials may have spontaneous or induced piezoelectric polarization. In some cases, induced piezoelectric polarization is caused by strain (or strain gradient) within the multilayer structure of the chirp layer. In some cases, spontaneous piezoelectric polarization is caused by a composition gradient within the multilayer structure of the chirp layer. For example, (Al x Ga 1-x ) y O z Li(Al) is a polar piezoelectric material with the Pna21 space group, where 0≦x≦1, 1≦y≦3, and 2≦z≦4. Some other polar piezoelectric epitaxial oxide materials include Li(Al) with the Pna21 or P421212 space group. x Ga 1-x )O2(0≦x≦1). Furthermore, the crystal symmetry of the epitaxial oxide layer (for example, including the materials shown in Figure 28 and the tables in Figures 76A-1, 76A-2, and 76B) is such that when the layer is in a strained state This can change. In some cases, such asymmetry in crystal symmetry caused by strain can alter the space group of epitaxial oxide materials. In some cases, epitaxial oxide layers (including, for example, the materials shown in Figure 28 and the tables in Figures 76A-1, 76A-2, and 76B) can become polar and piezoelectric when the layer is in a strained state.

[0587] In some embodiments, the epitaxial oxide materials described herein may each have cubic, tetrahedral, rhombohedral, hexagonal, and / or monoclinic crystal symmetries. In some embodiments, the epitaxial oxide material in the semiconductor structure described herein is (Al x Ga 1-x ) y O z It includes and has a space group R3c, Pna21, C2m, Fd3m, and / or Ia3, where 0≦x≦1, 1≦y≦3, and 2≦z≦4.

[0588] The epitaxial oxide materials described herein can be formed using epitaxial growth techniques such as molecular beam epitaxy (MBE), metal-organic chemical vapor deposition (MOCVD), atomic layer deposition (ALD), other physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques.

[0589] The semiconductor structures comprising epitaxial oxide materials described herein may be a single layer on a substrate or multiple layers on a substrate. Semiconductor structures comprising multiple layers may include single quantum wells, multiple quantum wells, superlattices, multiple superlattices, layers with varying (or graded) compositions, multilayer structures (or regions) with varying (or graded) compositions, doped layers (or regions) and / or multiple doped layers (or regions). Such semiconductor structures having one or more doped layers (or regions) may include layers (or regions) that are doped pn, pin, nin, pip, npn, pnp, p-metal (for forming a Schottky junction) and / or n-metal (for forming a Schottky junction). In other types of devices such as MSM (metal-semiconductor-metal), the semiconductor comprises n-type, p-type, or intentionally undoped (i-type) doped epitaxial oxide materials.

[0590] In this specification, the term “superlattice” (SL) refers to a layered structure comprising a plurality of repeating SL unit cells, each containing two or more layers, wherein the thickness of each SL unit cell may vary or remain constant, and the individual layers of the SL unit cell may vary or remain constant. Furthermore, the two or more layers of each SL unit cell may be small enough to allow the penetration of wave functions between the constituent layers of the SL unit cell, so that quantum tunneling of electrons and / or holes can easily occur. A wave function is a stochastic amplitude in quantum mechanics that describes the quantum state of a particle and the behavior of a particle.

[0591] The semiconductor structures described herein may include similar or different epitaxial oxide materials. In some cases, the crystal symmetry of the substrate and epitaxial layer within the semiconductor structure may be identical. In other cases, the crystal symmetry may differ between the substrate and epitaxial layer within the semiconductor structure.

[0592] The epitaxial oxide layers in the semiconductor structures described herein may be i-type (i.e., intrinsically or intentionally undoped), n-type, or p-type. The n-type or p-type epitaxial oxide layers may contain impurities that function as external dopants. In some cases, the n-type or p-type layer may be a polar epitaxial oxide material (e.g., (Al)). x Ga 1-x ) y O z The formula may include (where 0≦x≦1, 1≦y≦3, and 2≦z≦4, and has the Pna21 space group), and n-type or p-type conductivity can be formed by polarization doping (e.g., by strain or composition gradient within a layer(s)). can.

[0593] A semiconductor structure having a doped layer (or region) containing an epitaxial oxide material can be doped in several ways. In some embodiments, dopant impurities (e.g., acceptor impurities or donor impurities) can be co-deposited with the epitaxial oxide material so that the dopant impurities are incorporated into the crystalline layer (e.g., replaced in the lattice or interstitial position), forming active acceptors or donors to impart p-type or n-type conductivity to the material. In some embodiments, the dopant impurity layer may be deposited adjacent to the layer containing the epitaxial oxide material so that the dopant impurity layer contains active acceptors or donors that impart p-type or n-type conductivity to the epitaxial oxide material. In some cases, multiple alternating arrangements of dopant impurity layers and the layer containing the epitaxial oxide material form a doped superlattice, and the dopant impurity layers impart p-type or n-type conductivity to the doped superlattice.

[0594] Suitable substrates for forming semiconductor structures containing the epitaxial oxide materials described herein include substrates having crystal symmetry and lattice parameters compatible with the epitaxial oxide material deposited thereon. Examples of suitable substrates include Al2O3 (any crystal symmetry and C-plane, R-plane, A-plane or M-plane orientation), Ga2O3 (any crystal symmetry), MgO, LiF, MgAl2O4, MgGa2O4, LiGaO2, LiAlO2, (Al x Ga 1-x ) y O z The formula includes (wherein 0≦x≦1, 1≦y≦3 and 2≦z≦4) (for any crystal symmetry), MgF2, LaAlO3, TiO2, or quartz.

[0595] The crystal symmetries of the substrate and the epitaxial oxide material can be matched if they have the same type of crystal symmetry and in-plane (i.e., parallel to the substrate surface) lattice parameters, and the atomic positions on the substrate surface provide a suitable template for the subsequent growth of the epitaxial oxide material. For example, the substrate and the epitaxial oxide material can be matched if the in-plane lattice constant mismatch between the substrate and the epitaxial oxide material is less than 0.5%, 1%, 1.5%, 2%, 5%, or 10%. For example, in some embodiments, the crystal structure of the substrate material has a lattice mismatch of 10% or less with respect to the epitaxial layer. In some cases, the crystal symmetries of the substrate and the epitaxial oxide material can be matched if they have different types of crystal symmetry but have in-plane (i.e., parallel to the substrate surface) lattice parameters, and the atomic positions on the substrate surface provide a suitable template for the subsequent growth of the epitaxial oxide material. In some cases, multiple (e.g., 2, 4, or other integer) unit cells in the atomic arrangement of the substrate surface can provide a surface suitable for growing epitaxial oxide materials having larger unit cells than the substrate unit cells. In other cases, the epitaxial oxide layer may have a smaller lattice constant than the substrate (e.g., about half). In some cases, the unit cells of the epitaxial oxide layer may be rotated (e.g., 45 degrees) relative to the unit cells of the substrate.

[0596] In the case of epitaxial oxide materials with cubic crystal symmetry, the lattice constants are the same in all three directions of the crystal, and the lattice constants in orthogonal planes are also the same. In some cases, the epitaxial material has a crystal symmetry in which two lattice constants are the same (e.g., a=b≠c), and the crystal is oriented to be located at the interface of a heterostructure (e.g., having different compositions, different band gaps, and the same or different crystal symmetries) between epitaxial oxide materials with different lattice constants (a and b). In other cases, the epitaxial oxide material may have two different lattice constants (e.g., a≠b≠c, or a=b≠c, and the lattice constants a and c, or b and c, are oriented to be at the interface). In such cases, if the orthogonal in-plane lattice constants are different, the lattice constants in both orthogonal directions must be within a certain percentage of mismatch of the lattice constants in both orthogonal directions of the other matching material (e.g., within 0.5%, 1%, 1.5%, 2%, 5%, or 10%).

[0597] In some cases, the epitaxial oxide material for the semiconductor structure described herein and the substrate material on which the semiconductor structure is grown are selected such that the layers of the semiconductor structure have a predetermined strain or strain gradient. In some cases, the epitaxial oxide material and the substrate material are selected such that the layers of the semiconductor structure have an in-plane (i.e., parallel to the surface of the substrate) lattice constant (or interplanar spacing) within 0.5%, 1%, 1.5%, 2%, 5%, or 10% of the in-plane lattice constant (or interplanar spacing) of the substrate.

[0598] In other cases, a buffer layer containing a gradient layer or region can be used to reset the lattice constant (or interplanar spacing) of the substrate, and the layers of the semiconductor structure have in-plane lattice constants (or interplanar spacing) that are within 0.5%, 1%, 1.5%, 2%, 5%, or 10% of the final (or topmost) lattice constant (or interplanar spacing) of the buffer layer. In such cases, the material in the semiconductor structure may have a different lattice constant and / or crystal symmetry than the substrate. In such cases, even if the material in the semiconductor structure is incompatible with the substrate, the material in the semiconductor structure can be grown on the substrate using a buffer layer containing a gradient layer or region to reset the lattice constant.

[0599] Devices comprising semiconductor structures containing epitaxial oxide materials as described herein may include electronic devices and optoelectronic devices. For example, devices described herein may be resistors, capacitors, inductors, diodes, transistors, amplifiers, photodetectors, LEDs, or lasers.

[0600] In some embodiments, devic...

Claims

1. It is a semiconductor structure, Crystal substrate and A first region on a crystal substrate, comprising a superlattice of the first region having superlattice unit cells of the first region, wherein the superlattice unit cells of the first region are The first epitaxial layer, The second epitaxial layer, The first region including, An active region adjacent to the first region, comprising a superlattice of the active region having superlattice unit cells of the active region, wherein the superlattice unit cells of the active region are (Al ｘ３ Ga １－ｘ３ ) ｙ３ O ｚ３ A third epitaxial layer comprising, in the formula, x3 is 0 to 1, y3 is 1 to 3, and z3 is 2 to 4, (Al ｘ４ Ga １－ｘ４ ) ｙ４ O ｚ４ A fourth epitaxial layer comprising, where x4 is 0 to 1, y4 is 1 to 3, and z4 is 2 to 4, The active region includes, The semiconductor structure including the above.

2. The semiconductor structure according to claim 1, wherein the first epitaxial layer comprises a first epitaxial oxide material and the second epitaxial layer comprises a second epitaxial oxide material.

3. The first epitaxial layer contains (Al ｘ１ Ga １－ｘ１ ), where x1 is from 0 to 1, y1 is from 1 to 3, z1 is from 2 to 4, and the second epitaxial layer contains (Al ｘ２ Ga １－ｘ２ ), where x2 is from 0 to 1, y2 is from 1 to 3, z2 is from 2 to 4. The semiconductor structure according to any one of claims 1 to 2.​​​​​​​​

4. The first epitaxial oxide material and / or the second epitaxial oxide material is NiO, (Mg ｘａ Zn １－ｘａ ) ｚａ (Al ｙａ Ga １－ｙａ ) ２（１－ｚａ） O ３－２ｚａ (In the formula, 0 ≤ xa ≤ 1, 0 ≤ ya ≤ 1 and 0 ≤ za ≤ 1), (Mg ｘｂ Ni １－ｘｂ ) ｚｂ (Al ｙｂ Ga １－ｙｂ ) ２（１－ｚｂ） O ３－２ｚｂ (wherein the formula 0 ≤ xb ≤ 1, 0 ≤ yb ≤ 1 and 0 ≤ zb ≤ 1), MgAl ２ O ４ , ZnGa ２ O ４ , (Mg ｘｃ Zn ｙｃ Ni １－ｙｃ－ｘｃ ) (Al ｙｃ Ga １－ｙｃ ) ２ O ４ (0≦xc≦1, 0≦yc≦1), (Al ｘｄ Ga １－ｘｄ ) ２ (Si ｚｄ Ge １－ｚｄ ) O ５ (wherein the formula 0 ≤ xd ≤ 1 and 0 ≤ zd ≤ 1), (Al ｘｅ Ga １－ｘｅ ) ２ LiO ２ (where 0 ≤ x e ≤ 1 in the formula), or (Mg ｘｆ Zn １－ｘｆ－ｙｆ Ni ｙｆ ) ２ GeO ４ The semiconductor structure according to claim 3, comprising (wherein the formula 0 ≤ xf ≤ 1, 0 ≤ yf ≤ 1).

5. The semiconductor structure according to any one of claims 1 to 4, wherein the first epitaxial layer, or the second epitaxial layer, or both the first epitaxial layer and the second epitaxial layer are doped n-type.

6. The semiconductor structure according to any one of claims 1 to 4, wherein the first epitaxial layer, or the second epitaxial layer, or both the first epitaxial layer and the second epitaxial layer are p-type doped.

7. The semiconductor according to any one of claims 1 to 6, wherein the average alloy content of the superlattice unit cells in the first region and the superlattice unit cells in the active region is constant along the growth direction. structure.

8. The semiconductor structure according to any one of claims 1 to 7, wherein the first, second, third, and / or fourth epitaxial layer is distorted.

9. The semiconductor structure according to any one of claims 1 to 8, wherein the first and second epitaxial layers have opposite strains, and the third and fourth epitaxial layers have opposite strains.

10. The semiconductor structure according to any one of claims 1 to 9, further comprising a second region adjacent to the active region, wherein the second region comprises a superlattice of the second region having superlattice unit cells of the second region.

11. The second superlattice region unit cell described above is (Al ｘ５ Ga １－ｘ５ ) ｙ５ O ｚ５ A fifth epitaxial layer comprising a fifth composition, wherein x5 is 0 to 1, y5 is 1 to 3, and z5 is 2 to 4, and the fifth epitaxial layer, (Al ｘ６ Ga １－ｘ６ ) ｙ６ O ｚ６ A sixth epitaxial layer comprising a sixth composition, wherein x6 is 0 to 1, y6 is 1 to 3, and z6 is 2 to 4, and The semiconductor structure according to claim 10, including the above.

12. The semiconductor structure according to any one of claims 10 to 11, wherein the superlattice unit cell in the second region comprises a p-type epitaxial oxide material.

13. The semiconductor structure according to any one of claims 1 to 12, wherein the third epitaxial layer and / or the fourth epitaxial layer has a Pna21 space group.

14. The substrate consists of A-side sapphire, C-side sapphire, M-side sapphire, R-side sapphire, and Ga ２ O ３ The semiconductor structure according to any one of claims 1 to 13, wherein the semiconductor structure is MgO.

15. An optoelectronic semiconductor device comprising the semiconductor structure described in any one of claims 1 to 14.

16. A light-emitting diode (LED) comprising the semiconductor structure described in any one of claims 1 to 14, which emits light with a wavelength of 150 nm to 280 nm.

17. A laser comprising the semiconductor structure described in any one of claims 1 to 14, which emits light with a wavelength of 150 nm to 280 nm.

18. It is a semiconductor structure, A p-type epitaxial oxide region containing a p-type superlattice, n-type epitaxial oxide region containing an n-type superlattice, An active epitaxial oxide region comprising a superlattice of the active region, wherein the active epitaxial oxide region is located between the n-type epitaxial oxide region and the p-type epitaxial oxide region, Includes, The n-type, p-type, and active epitaxial oxide regions each contain aluminum and gallium, respectively. The aforementioned semiconductor structure.

19. The n-type, p-type, and active epitaxial oxide regions are, respectively, (Al ｘ Ga １－ｘ ) ｙ O ｚ The semiconductor structure according to claim 18, comprising the composition, wherein x is 0 to 1, y is 1 to 3, and z is 2 to 4.

20. The n-type, p-type, and active epitaxial oxide regions each have a Pna21 space group (Al ｘ Ga １－ｘ ) ｙ O ｚ The semiconductor structure according to claim 18, comprising the composition, wherein x is 0 to 1, y is 1 to 3, and z is 2 to 4.

21. A semiconductor structure comprising a substrate and a first doped superlattice on the substrate, wherein the first doped superlattice comprises alternating arrangements of a first host layer and a first dopant impurity layer, the first host layer comprises a first epitaxial oxide material, and the first dopant impurity layer comprises a first dopant material.

22. The semiconductor structure according to claim 21, wherein the first dopant impurity layer comprises a single layer of the first dopant material.

23. The semiconductor structure according to claim 21, wherein the first dopant impurity layer comprises a second epitaxial oxide material doped with the first dopant material.

24. The first epitaxial oxide material is (Al ｘ１ Ga １－ｘ１ ) ｙ１ O ｚ１ A semiconductor structure according to any one of claims 21 to 23, wherein the formula includes, where x1 is 0 to 1, y1 is 1 to 3, and z1 is 2 to 4, and the first dopant material comprises Li, Ga, Zn, N, Ir, Bi, Ni, Mg, and / or Pd.

25. The first epitaxial oxide material is (Al ｘ１ Ga １－ｘ１ ) ｙ１ O ｚ１ The semiconductor structure according to any one of claims 21 to 23, comprising, in the formula, x1 is 0 to 1, y1 is 1 to 3, z1 is 2 to 4, and the second dopant material comprises Si, Ge, Sn, and / or rare earth metals.

26. A third intrinsic region containing an epitaxial oxide material, A second doped region containing a fourth epitaxial oxide material, It further includes, The intrinsic region is located between the first doped superlattice and the second doped region. The semiconductor structure according to any one of claims 21 to 25.

27. The semiconductor structure according to claim 26, wherein the intrinsic region further comprises an intrinsic region superlattice comprising the third epitaxial oxide material and the fifth epitaxial oxide material.

28. The third epitaxial oxide material is (Al ｘ２ Ga １－ｘ２ ) ｙ２ O ｚ２ A semiconductor structure according to any one of claims 26 to 27, comprising, in the formula, where x2 is between 0 and 1, y2 is between 1 and 3, and z2 is between 2 and 4.

29. A method for forming a doped superlattice, a) Loading the substrate into the reaction chamber, b) Heating the substrate to the film formation temperature, c) Forming a host layer containing a first epitaxial oxide material on the substrate, d) Forming an impurity layer containing the first dopant material on the host layer, e) Forming a host layer containing the first epitaxial oxide material on the impurity layer, f) Repeat steps d) to e) until the superlattice reaches a desired thickness, The method, including the method described above.

30. The first epitaxial oxide material is (Al ｘ１ Ga １－ｘ１ ), ｙ１ O ｚ１ where x is from 0 to 1, y is from 1 to 3, and z is from 2 to 4, the method according to claim 29.

31. The first epitaxial oxide material is Ga having an R-3c space group ２ O ３ The method according to claim 29.

32. The method according to any one of claims 29 to 31, wherein the impurity layer comprises a single layer of the first dopant material.

33. The method according to any one of claims 29 to 31, wherein the impurity layer comprises a second epitaxial oxide material doped with the first dopant material.

34. The method according to any one of claims 29 to 33, wherein the first dopant material comprises Li, N, Ir, Bi, and / or Pd.

35. The method according to any one of claims 29 to 33, wherein the first dopant material comprises Si, Ge, Sn, and / or a rare earth metal.

36. The method according to any one of claims 29 to 35, wherein the thickness of each of the host layers in the superlattice is less than 10 nm.

37. The method according to any one of claims 29 to 36, wherein the thickness of each of the impurity layers in the superlattice is less than 1 nm.

38. It is a semiconductor structure, A substrate containing a first in-plane lattice constant, (Al ｘ１ Ga １－ｘ１ ) ｙ１ O ｚ１ A gradient buffer layer on the substrate, comprising the formula where x1 is 0 to 1, y1 is 1 to 3, z1 is 2 to 4, and x1 changes in the growth direction such that the gradient buffer layer has a first in-plane lattice constant adjacent to the substrate and a second in-plane lattice constant of the surface of the gradient buffer layer on the opposite side of the substrate. A first region on the gradient buffer region, comprising a first epitaxial oxide material including the second in-plane lattice constant, The semiconductor structure including the above.

39. The first epitaxial oxide material is (Al ｘ２ Ga １－ｘ２ ), ｙ２ O ｚ２ where x2 is from 0 to 1, y2 is from 1 to 3, and z2 is from 2 to 4. The semiconductor structure according to claim 38.

40. The first epitaxial oxide material is NiO, (Mg ｘａ Zn １－ｘａ ) ｚａ (Al ｙａ Ga １－ｙａ ) ２（１－ｚａ） O ３－２ｚａ (In the formula, 0 ≤ xa ≤ 1, 0 ≤ ya ≤ 1 and 0 ≤ za ≤ 1), (Mg ｘｂ Ni １－ｘｂ ) ｚｂ (Al ｙｂ Ga １－ｙｂ ) ２（１－ｚｂ） O ３－２ｚｂ (wherein the formula 0 ≤ xb ≤ 1, 0 ≤ yb ≤ 1 and 0 ≤ zb ≤ 1), MgAl ２ O ４ , ZnGa ２ O ４ , (Mg ｘｃ Zn ｙｃ Ni １－ｙｃ－ｘｃ ) (Al ｙｃ Ga １－ｙｃ ) ２ O ４ (0≦xc≦1, 0≦yc≦1), (Al ｘｄ Ga １－ｘｄ ) ２ (Si ｚｄ Ge １－ｚｄ ) O ５ (wherein the formula 0 ≤ xd ≤ 1 and 0 ≤ zd ≤ 1), (Al ｘｅ Ga １－ｘｅ ) ２ LiO ２ (where 0 ≤ x e ≤ 1 in the formula), or (Mg ｘｆ Zn １－ｘｆ－ｙｆ Ni ｙｆ ) ２ GeO ４ The semiconductor structure according to claim 38, comprising (wherein the formula 0 ≤ xf ≤ 1, 0 ≤ yf ≤ 1).

41. The semiconductor structure according to any one of claims 38 to 40, wherein the first epitaxial oxide material is distorted.

42. The semiconductor structure according to any one of claims 38 to 41, wherein the first epitaxial oxide material has a band gap of 4.5 eV to 9.0 eV.

43. The semiconductor structure according to any one of claims 38 to 42, wherein the first region includes one or more superlattices.

44. The semiconductor structure according to any one of claims 38 to 43, wherein the first region includes an n-type region, an i-type region, and a p-type region.

45. An optoelectronic semiconductor device comprising the semiconductor structure described in any one of claims 38 to 44, wherein the semiconductor device is a light-emitting diode (LED) that emits light with a wavelength of 150 nm to 280 nm, or a laser that emits light with a wavelength of 150 nm to 280 nm.

46. It is a semiconductor structure, A first region comprising a first epitaxial oxide material, A second region containing a second epitaxial oxide material, An inclined region located between the first region and the second region, (Al ｘ１ Ga １－ｘ１ ) ｙ１ O ｚ１ In the formula, x1 is 0 to 1, y1 is 1 to 3, z1 is 2 to 4, and the (Al) includes the Pna21 crystal symmetry in the polarization axis parallel to the growth axis. ｘ１ Ga １－ｘ１ ) ｙ１ O ｚ１ and, To induce n-type or p-type conductivity in the gradient region, the (Al) along the growth axis from the first average composition adjacent to the first region to the second average composition adjacent to the second region. ｘ１ Ga １－ｘ１ ) ｙ１ O ｚ１ The monotonic change in the average composition and The inclined region includes, The semiconductor structure including the above.

47. The first epitaxial oxide material is (Al ｘ２ Ga １－ｘ２ ) ｙ２ O ｚ２ The first composition includes x2 is 0 to 1, y2 is 1 to 3, z2 is 2 to 4, and the second epitaxial layer is (Al ｘ３ Ga １－ｘ３ ) ｙ３ O ｚ３ The semiconductor structure according to claim 46, comprising a second composition, wherein x3 is 0 to 1, y3 is 1 to 3, and z3 is 2 to 4.

48. The first epitaxial oxide material and / or the second epitaxial oxide material is NiO, (Mg ｘａ Zn １－ｘａ ) ｚａ (Al ｙａ Ga １－ｙａ ) ２（１－ｚａ） O ３－２ｚａ (In the formula, 0 ≤ xa ≤ 1, 0 ≤ ya ≤ 1 and 0 ≤ za ≤ 1), (Mg ｘｂ Ni １－ｘｂ ) ｚｂ (Al ｙｂ Ga １－ｙｂ ) ２（１－ｚｂ） O ３－２ｚｂ (wherein the formula 0 ≤ xb ≤ 1, 0 ≤ yb ≤ 1 and 0 ≤ zb ≤ 1), MgAl ２ O ４ , ZnGa ２ O ４ , (Mg ｘｃ Zn ｙｃ Ni １－ｙｃ－ｘｃ ) (Al ｙｃ Ga １－ｙｃ ) ２ O ４ (0≦xc≦1, 0≦yc≦1), (Al ｘｄ Ga １－ｘｄ ) ２ (Si ｚｄ Ge １－ｚｄ ) O ５ (wherein the formula 0 ≤ xd ≤ 1 and 0 ≤ zd ≤ 1), (Al ｘｅ Ga １－ｘｅ ) ２ LiO ２ (In the formula, 0 ≤ x e ≤ 1), (Mg ｘｆ Zn １－ｘｆ－ｙｆ Ni ｙｆ ) ２ GeO ４ The semiconductor structure according to claim 46, comprising (wherein the formula 0 ≤ xf ≤ 1, 0 ≤ yf ≤ 1).

49. The semiconductor structure according to any one of claims 46 to 48, wherein the first and / or second region is distorted.

50. The semiconductor structure according to any one of claims 46 to 49, wherein the first and second epitaxial oxide materials each have a band gap of 4.5 eV to 9.0 eV.

51. The semiconductor structure according to any one of claims 46 to 50, wherein the band gap of the first epitaxial oxide material differs from the band gap of the second epitaxial oxide material by at least 1 eV.

52. An optoelectronic semiconductor device comprising the semiconductor structure described in any one of claims 46 to 51, wherein the semiconductor device is a light-emitting diode (LED) that emits light with a wavelength of 150 nm to 280 nm, or a laser that emits light with a wavelength of 150 nm to 280 nm.

53. It is a semiconductor structure, A first region comprising a first epitaxial oxide material, A second region containing a second epitaxial oxide material, A chirp layer located between the first region and the second region, comprising an alternating layer of wide-bandgap (WBG) epitaxial oxide material layers and narrow-bandgap (NBG) epitaxial oxide material layers, wherein the thickness of the NBG layer and the WBG layer varies throughout the chirp layer, Includes, The aforementioned WBG epitaxial oxide material is (Al ｘ１ Ga １－ｘ１ ) ｙ１ O ｚ１ The formula includes, where x1 is 0 to 1, y1 is 1 to 3, z1 is 2 to 4, and the NBG epitaxial oxide material is (Al ｘ２ Ga １－ｘ２ ) ｙ２ O ｚ２ The formula includes such that x² is between 0 and 1, y² is between 1 and 3, z² is between 2 and 4, and x1 and x² differ from each other by an amount between 0.1 and 1. The aforementioned semiconductor structure.

54. The semiconductor structure according to claim 53, wherein each of the aforementioned regions contains a polar material, and there is no abrupt change in polarity at the interface between each region.

55. The first epitaxial oxide material is (Al ｘ３ Ga １－ｘ３ ) ｙ３ O ｚ３ The second epitaxial layer is (Al ｘ４ Ga １－ｘ４ ) ｙ４ O ｚ４ A semiconductor structure according to any one of claims 53 to 54, comprising a second composition, wherein x4 is 0 to 1, y4 is 1 to 3, and z4 is 2 to 4.

56. The first epitaxial oxide material and / or the second epitaxial oxide material is NiO, (Mg ｘａ Zn １－ｘａ ) ｚａ (Al ｙａ Ga １－ｙａ ) ２（１－ｚａ） O ３－２ｚａ (In the formula, 0 ≤ xa ≤ 1, 0 ≤ ya ≤ 1 and 0 ≤ za ≤ 1), (Mg ｘｂ Ni １－ｘｂ ) ｚｂ (Al ｙｂ Ga １－ｙｂ ) ２（１－ｚｂ） O ３－２ｚｂ (wherein the formula 0 ≤ xb ≤ 1, 0 ≤ yb ≤ 1 and 0 ≤ zb ≤ 1), MgAl ２ O ４ , ZnGa ２ O ４ , (Mg ｘｃ Zn ｙｃ Ni １－ｙｃ－ｘｃ ) (Al ｙｃ Ga １－ｙｃ ) ２ O ４ (0≦xc≦1, 0≦yc≦1), (Al ｘｄ Ga １－ｘｄ ) ２ (Si ｚｄ Ge １－ｚｄ ) O ５ (wherein the formula 0 ≤ xd ≤ 1 and 0 ≤ zd ≤ 1), (Al ｘｅ Ga １－ｘｅ ) ２ LiO ２ (In the formula, 0 ≤ x e ≤ 1), (Mg ｘｆ Zn １－ｘｆ－ｙｆ Ni ｙｆ ) ２ GeO ４ A semiconductor structure according to any one of claims 53 to 54, comprising (wherein the formula 0 ≤ xf ≤ 1, 0 ≤ yf ≤ 1).

57. The semiconductor structure according to any one of claims 53 to 56, wherein the first and / or second region is distorted.

58. The semiconductor structure according to any one of claims 53 to 57, wherein the second effective band gap is at least 1 eV larger than the first effective band gap.

59. An optoelectronic semiconductor device comprising the semiconductor structure described in any one of claims 53 to 58, wherein the semiconductor device is a light-emitting diode (LED) that emits light with a wavelength of 150 nm to 280 nm, or a laser that emits light with a wavelength of 150 nm to 280 nm.

60. It is a semiconductor structure, A first region including a first superlattice, the first superlattice is Multiple first epitaxial oxide layers, Multiple second epitaxial oxide layers, The first region including, A second region including a fifth epitaxial oxide layer, A chirp layer located between the first region and the second region, (Al ｘ３ Ga １－ｘ３ ) ｙ３ O ｚ３ A plurality of third epitaxial oxide layers comprising the formula, wherein x3 is 0 to 1, y3 is 1 to 3, and z3 is 2 to 4, (Al ｘ４ Ga １－ｘ４ ) ｙ４ O ｚ４ A plurality of fourth epitaxial oxide layers comprising the formula, wherein x4 is 0 to 1, y4 is 1 to 3, and z4 is 2 to 4, The chirp layer includes, The semiconductor structure including the above.

61. The plurality of first epitaxial oxide layers are (Al ｘ１ Ga １－ｘ１ ) ｙ１ O ｚ１ The formula includes, where x1 is 0 to 1, y1 is 1 to 3, z1 is 2 to 4, and the plurality of second epitaxial oxide layers are (Al ｘ２ Ga １－ｘ２ ) ｙ２ O ｚ２ The semiconductor structure according to claim 60, wherein x2 is between 0 and 1, y2 is between 1 and 3, and z2 is between 2 and 4.

62. The plurality of first epitaxial oxide layers and the plurality of second epitaxial oxide layers are NiO, (Mg ｘａ Zn １－ｘａ ) ｚａ (Al ｙａ Ga １－ｙａ ) ２（１－ｚａ） O ３－２ｚａ (In the formula, 0 ≤ xa ≤ 1, 0 ≤ ya ≤ 1 and 0 ≤ za ≤ 1), (Mg ｘｂ Ni １－ｘｂ ) ｚｂ (Al ｙｂ Ga １－ｙｂ ) ２（１－ｚｂ） O ３－２ｚｂ (wherein the formula 0 ≤ xb ≤ 1, 0 ≤ yb ≤ 1 and 0 ≤ zb ≤ 1), MgAl ２ O ４ , ZnGa ２ O ４ , (Mg ｘｃ Zn ｙｃ Ni １－ｙｃ－ｘｃ ) (Al ｙｃ Ga １－ｙｃ ) ２ O ４ (0≦xc≦1, 0≦yc≦1), (Al ｘｄ Ga １－ｘｄ ) ２ (Si ｚｄ Ge １－ｚｄ ) O ５ (wherein the formula 0 ≤ xd ≤ 1 and 0 ≤ zd ≤ 1), (Al ｘｅ Ga １－ｘｅ ) ２ LiO ２ (where 0 ≤ x e ≤ 1 in the formula), or (Mg ｘｆ Zn １－ｘｆ－ｙｆ Ni ｙｆ ) ２ GeO ４ The semiconductor structure according to claim 60, comprising (wherein the formula 0 ≤ xf ≤ 1, 0 ≤ yf ≤ 1).

63. The semiconductor structure according to any one of claims 60 to 62, wherein the plurality of first, second, third, and / or fourth epitaxial oxide layers are distorted.

64. The semiconductor structure according to any one of claims 60 to 63, wherein the superlattice includes a first effective band gap, the fifth epitaxial oxide layer includes a fifth band gap, and the first effective band gap and the fifth band gap are between 3.0 eV and 9.0 eV.

65. The semiconductor structure according to any one of claims 60 to 64, wherein the value of the overlap integral between different electron wave functions in the conductive band of the chirp layer is less than 0.05 for subband transition energies greater than 1.0 eV when the structure is biased with the operating potential.

66. The overlap value between the electron wave function and the barrier center in the conductive band of the chirp layer is 0.3 nm when the structure is biased with the operating potential. －１ A semiconductor structure according to any one of claims 60 to 65, wherein the semiconductor structure is less than [amount missing].

67. The semiconductor structure according to any one of claims 60 to 66, wherein the thickness of the plurality of third epitaxial oxide layers, or the thickness of the plurality of fourth epitaxial oxide layers, or the thickness of both the plurality of third epitaxial oxide layers and the plurality of fourth epitaxial oxide layers, varies over the entire chirp layer.

68. The semiconductor structure according to any one of claims 60 to 67, wherein the thickness of the plurality of third and / or fourth epitaxial oxide layers varies monotonically throughout the chirp layer.

69. The second area described above is Multiple fifth epitaxial oxide layers, Multiple sixth epitaxial oxide layers, A semiconductor structure according to any one of claims 60 to 68, further comprising:

70. The semiconductor structure according to claim 69, wherein the plurality of fifth and / or sixth epitaxial oxide semiconductor layers are distorted.

71. A semiconductor device comprising the semiconductor structure described in any one of claims 60 to 70, wherein the semiconductor device is a light-emitting diode (LED), a short-wavelength LED, a UV-C LED, a UV-A LED, a bipolar junction transistor, a power transistor, a vertical field-effect transistor (FET), or a semiconductor laser.

72. It is a semiconductor structure, A first region including a first epitaxial oxide layer, A second region including a second epitaxial oxide layer, A chirp layer located between the first region and the second region, (Al ｘ３ Ga １－ｘ３ ) ｙ３ O ｚ３ A plurality of third epitaxial oxide layers comprising the formula, wherein x3 is 0 to 1, y3 is 1 to 3, and z3 is 2 to 4, (Al ｘ４ Ga １－ｘ４ ) ｙ４ O ｚ４ A plurality of fourth epitaxial oxide layers comprising the formula, wherein x4 is 0 to 1, y4 is 1 to 3, and z4 is 2 to 4, The chirp layer includes, The semiconductor structure including the above.

73. The first epitaxial oxide layer is (Al ｘ１ Ga １－ｘ１ ) ｙ１ O ｚ１ Includes, In the formula, x1 is between 0 and 1, y1 is between 1 and 3, z1 is between 2 and 4, and the second epitaxial oxide layer is (Al ｘ２ Ga １－ｘ２ ) ｙ２ O ｚ２ The semiconductor structure according to claim 72, wherein the formula includes, where x2 is between 0 and 1, y2 is between 1 and 3, and z2 is between 2 and 4.

74. The first region, the second region, and / or the chirp layer are NiO, (Mg ｘａ Zn １－ｘａ ) ｚａ (Al ｙａ Ga １－ｙａ ) ２（１－ｚａ） O ３－２ｚａ (In the formula, 0 ≤ xa ≤ 1, 0 ≤ ya ≤ 1 and 0 ≤ za ≤ 1), (Mg ｘｂ Ni １－ｘｂ ) ｚｂ (Al ｙｂ Ga １－ｙｂ ) ２（１－ｚｂ） O ３－２ｚｂ (wherein the formula 0 ≤ xb ≤ 1, 0 ≤ yb ≤ 1 and 0 ≤ zb ≤ 1), MgAl ２ O ４ , ZnGa ２ O ４ , (Mg ｘｃ Zn ｙｃ Ni １－ｙｃ－ｘｃ ) (Al ｙｃ Ga １－ｙｃ ) ２ O ４ (0≦xc≦1, 0≦yc≦1), (Al ｘｄ Ga １－ｘｄ ) ２ (Si ｚｄ Ge １－ｚｄ ) O ５ (wherein the formula 0 ≤ xd ≤ 1 and 0 ≤ zd ≤ 1), (Al ｘｅ Ga １－ｘｅ ) ２ LiO ２ (where 0 ≤ x e ≤ 1 in the formula), or (Mg ｘｆ Zn １－ｘｆ－ｙｆ Ni ｙｆ ) ２ GeO ４ The semiconductor structure according to claim 72, comprising (wherein the formula 0 ≤ xf ≤ 1, 0 ≤ yf ≤ 1).

75. It is a semiconductor structure, A first epitaxial oxide semiconductor layer, Metal layer, A contact layer adjacent to the metal layer and located between the first epitaxial oxide semiconductor layer and the metal layer, Epitaxial oxide semiconductor materials, A region including a gradient of the epitaxial oxide semiconductor material composition adjacent to the metal layer, The contact layer includes, The semiconductor structure including the above.

76. The semiconductor structure according to claim 75, wherein the epitaxial oxide semiconductor material includes a piezoelectric epitaxial oxide material having spontaneously occurring piezoelectric polarization along the growth direction.

77. The semiconductor structure according to any one of claims 75 to 76, wherein the gradient of the epitaxial oxide semiconductor material composition over the region adjacent to the metal layer within the contact layer includes a smoothly changing composition gradient.

78. The aforementioned contact layer Alternating wide-bandgap sublayers and narrow-bandgap sublayers, A compositional gradient is formed by changing the thickness of the sublayer through the contact layer, Includes a CHIRP layer, The semiconductor structure according to any one of claims 75 to 77.

79. The contact layer forms a p-contact with the metal layer. The ohmic chirp layer, (Al ｘ Ga １－ｘ ) ２ O ３ Materials (where x is between 0 and 1 in the formula) The average aluminum oxide content per period, A gradient of the average aluminum oxide content per period, including a lower average aluminum oxide content per period closer to the metal layer and a higher average aluminum oxide content per period further away from the metal layer, Further including, The semiconductor structure according to any one of claims 75 to 78.

80. The contact layer forms an n-contact with the metal layer, The ohmic chirp layer, (Al ｘ Ga １－ｘ ) ２ O ３ Materials (where x is between 0 and 1 in the formula) The average aluminum oxide content per period, A gradient of the average aluminum oxide content per period, including a lower average aluminum oxide content per period closer to the metal layer and a higher average aluminum oxide content per period further away from the metal layer, Further including, The semiconductor structure according to any one of claims 75 to 78.

81. The contact layer forms a p-contact with the metal layer. The ohmic chirp layer, (Al ｘ Ga １－ｘ ) ２ O ３ Materials (where x is between 0 and 1 in the formula) The average aluminum oxide content per period, A gradient of the average aluminum oxide content per period, including a higher average aluminum oxide content per period closer to the metal layer and a lower average aluminum oxide content per period further away from the metal layer, Further including, The semiconductor structure according to any one of claims 75 to 78.

82. The contact layer forms an n-contact with the metal layer, The ohmic chirp layer, (Al ｘ Ga １－ｘ ) ２ O ３ Materials (where x is between 0 and 1 in the formula) The average aluminum oxide content per period, A gradient of the average aluminum oxide content per period, including a higher average aluminum oxide content per period closer to the metal layer and a lower average aluminum oxide content per period further away from the metal layer, Further including, The semiconductor structure according to any one of claims 75 to 78.

83. The semiconductor structure according to any one of claims 75 to 82, wherein the metal layer comprises one or more of Ni, Os, Se, Pt, Pd, Ir, W, Au, and alloys thereof.

84. The semiconductor structure according to any one of claims 75 to 83, wherein the metal layer comprises one or more of Ba, Na, Cs, Nd, and alloys thereof.

85. A semiconductor device comprising the semiconductor structure described in any one of claims 75 to 84, wherein the semiconductor device is an optoelectronic device, a light-emitting diode, a laser diode, a photodetector, a solar cell, a high-power diode, a high-power transistor, a transducer, or a high-electron-mobility transistor having wavelengths in the range from infrared to deep ultraviolet.

86. It is a semiconductor structure, A first epitaxial oxide semiconductor layer, Metal layer, A contact layer adjacent to the metal layer and located between the first epitaxial oxide semiconductor layer and the metal layer, Epitaxial oxide semiconductor materials, The gradient of strain in the epitaxial oxide semiconductor material over the region adjacent to the metal layer, The contact layer includes, The semiconductor structure including the above.

87. The semiconductor structure according to claim 86, wherein the epitaxial oxide semiconductor material includes a piezoelectric epitaxial oxide material having spontaneously occurring piezoelectric polarization along the growth direction.

88. The semiconductor structure according to any one of claims 86 to 87, wherein the region including the gradient of strain within the contact layer has a thickness greater than 0 nm and less than 20 nm.

89. The semiconductor structure according to any one of claims 86 to 88, wherein the metal layer comprises one or more of Ni, Os, Se, Pt, Pd, Ir, W, Au, and alloys thereof.

90. The semiconductor structure according to any one of claims 86 to 89, wherein the metal layer comprises one or more of Ba, Na, Cs, Nd, and alloys thereof.

91. A semiconductor device comprising the semiconductor structure described in any one of claims 86 to 90, wherein the semiconductor device is an optoelectronic device, a light-emitting diode, a laser diode, a photodetector, a solar cell, a high-power diode, a high-power transistor, a transducer, or a high-electron-mobility transistor having wavelengths in the range from infrared to deep ultraviolet.

Images