Epitaxial oxide materials, structures, and devices

Abstract

It provides an epitaxial semiconductor structure with a wide bandgap. [Solution] The semiconductor structure may include two or more epitaxial oxide materials having different properties such as composition, crystal symmetry, and band gap. The semiconductor structure may include one or more epitaxial oxide layers formed on a compatible substrate having in-plane lattice parameters and atomic positions that provide a suitable template for growing the epitaxial oxide material. Strain may occur in one or more epitaxial oxide materials. One or more epitaxial oxide materials can be doped to n-type or p-type. The semiconductor structure may include a superlattice having the epitaxial oxide material. The semiconductor structure may include a chirp layer having 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, or solar cell.

Description

[Technical Field]

[0001] Related applications This application claims priority to International Application No. PCT / IB2021 / 060414, entitled "Ultrawide Bandgap Semiconductor Devices Including Magnesium Germanium Oxides," filed on November 10, 2021; International Application No. PCT / IB2021 / 060413, entitled "Epitaxial Oxide Materials, Structures and Devices," filed on November 10, 2021; and International Application No. PCT / IB2021 / 060427, entitled "Epitaxial Oxide Materials, Structures, and Devices," filed on November 10, 2021, all of which are incorporated herein by reference for all purposes.

[0002] This application, filed on 11 August 2020, relates to U.S. Non-Provisional Patent Application No. 16 / 990,349, entitled "Metal Oxide Semiconductor-Based Light Emitting Device," all of which are incorporated herein by reference for all purposes.

[0003] 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.

[0004] The contents of each of the above publications are explicitly incorporated in their entirety by reference. [Background technology]

[0005] 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. Broad-bandgap semiconductor materials, such as those with a bandgap greater than approximately 4 eV, are useful in several applications, including high-power and optoelectronic devices that detect or emit ultraviolet (UV) wavelength light.

[0006] 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. In this case, UV LEDs were developed using almost exclusively gallium-indium-aluminum-nitride (GaInAlN) compositions that form a wurtzite-type crystal structure.

[0007] In another example, high-power RF switches are used in transceivers of wireless communication systems to separate, amplify, and filter transmitted and received signals. A requirement for the transistor devices that make up such RF switches is that they 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, wider-bandgap semiconductors (e.g., GaN) with higher breakdown voltages are used. A further advantage of using wider-bandgap semiconductors such as GaN in RF switches is that impedance matching with microwave circuits can be simplified. [Overview of the project] [Means for solving the problem]

[0008] In some embodiments, the semiconductor structure includes an epitaxial oxide material. In some embodiments, the semiconductor structure includes two or more epitaxial oxide materials having different properties such as composition, crystal symmetry, or band gap. The semiconductor structure may include one or more epitaxial oxide layers formed on a compatible substrate having in-plane lattice parameters and atomic positions that provide a suitable template for growing the epitaxial oxide material. In some embodiments, one or more of the epitaxial oxide materials are strained. In some embodiments, one or more of the epitaxial oxide materials are doped to be n-type or p-type. In some embodiments, the semiconductor structure includes a superlattice having the epitaxial oxide material. In some embodiments, the semiconductor structure includes a chirp layer having the epitaxial oxide material.

[0009] The semiconductor structures described herein may be part of semiconductor devices such as optoelectronic devices having wavelengths from infrared to deep ultraviolet, light-emitting diodes, laser diodes, photodetectors, solar cells, high-power diodes, high-power transistors, transducers, or high-electron-mobility transistors. In some embodiments, the semiconductor device has high breakdown voltage due to the properties of the epitaxial oxide material therein. In some embodiments, the semiconductor device uses a shock ionization mechanism for carrier multiplication.

[0010] Embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. [Brief explanation of the drawing]

[0011] [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, representing the electron energy versus crystal momentum 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 the underlying 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] An exemplary embodiment of the present disclosure shows a three-dimensional crystal unit cell of a corundum symmetric crystal structure (alpha phase) Ga2O3 used to calculate the Ek band structure. [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 disclosure shows a three-dimensional crystal unit cell of monoclinic symmetric crystal structure (beta phase) Ga2O3 used to calculate the Ek band structure according to exemplary embodiments of this 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) images 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 the present 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 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 (Al0.05Ga0.95)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 electronic 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] This table shows the crystal symmetry (or space group), lattice constants ("a", "b", and "c" for different crystal directions, in angstroms), band gap (minimum band gap energy, in eV units), and wavelength of light ("λ_g", in nm units) corresponding to the band gap energy of various materials. [Figure 76A-2] This table shows the crystal symmetry (or space group), lattice constants ("a", "b", and "c" for different crystal directions, in angstroms), band gap (minimum band gap energy, in eV units), and wavelength of light ("λ_g", in nm units) corresponding to the band gap energy of various materials. [Figure 76B]The chart shows pairs of band gaps (minimum band gap energy, in eV units) for several epitaxial oxide materials, and, in some cases, crystal symmetries (e.g., α-, β-, γ-, and κ-AlxGa1-xOy) for the lattice constants (in angstroms) of the epitaxial oxide materials. [Figure 76C] The chart shown in Figure 76B further illustrates the classification of epitaxial oxides based on their lattice constants. [Figure 76D] The plot shows the lattice constant "a" versus lattice constant "b" of the selected epitaxial oxide. [Figure 76E] The chart shows the band gap (minimum band gap energy, in eV units) for several calculated epitaxial oxide materials. [Figure 76F] The chart shows the band gap (minimum band gap energy, in eV units) for several calculated epitaxial oxide materials. [Figure 76G] The chart shows the band gap (minimum band gap energy, in eV units) for several calculated epitaxial oxide materials. [Figure 76H] The chart shows the band gap (minimum band gap energy, in eV units) for several calculated epitaxial oxide materials. [Figure 77] This is a flowchart showing the process for forming the epitaxial material described in this disclosure, including those shown in the tables in Figures 76A-1 and 76A-2. [Figure 78] This is a schematic diagram illustrating the situation that occurs when an element is added to an epitaxial oxide, using the analogy of a seesaw. [Figure 79] This is a plot of shear modulus (in GPa) versus bulk modulus (in GPa) for several examples of epitaxial oxide materials. [Figure 80] This is a plot of the Poisson's ratio of several epitaxial oxide materials. [Figure 81A] An example of a semiconductor structure containing an epitaxial oxide material in a layer or region is shown. [Figure 81B] An example of a semiconductor structure containing an epitaxial oxide material in a layer or region is shown. [Figure 81C] An example of a semiconductor structure containing an epitaxial oxide material in a layer or region is shown. [Figure 81D] An example of a semiconductor structure containing an epitaxial oxide material in a layer or region is shown. [Figure 81E] An example of a semiconductor structure containing an epitaxial oxide material in a layer or region is shown. [Figure 81F] An example of a semiconductor structure containing an epitaxial oxide material in a layer or region is shown. [Figure 81G] An example of a semiconductor structure containing an epitaxial oxide material in a layer or region is shown. [Figure 81H] An example of a semiconductor structure containing an epitaxial oxide material in a layer or region is shown. [Figure 81I] An example of a semiconductor structure containing an epitaxial oxide material in a layer or region is shown. [Figure 81J] An example of adding an epitaxial oxide material to a semiconductor structure in a layer or region is shown. [Figure 81K] An example of adding an epitaxial oxide material to a semiconductor structure in a layer or region is shown. [Figure 81L] An example of adding an epitaxial oxide material to a semiconductor structure in a layer or region is shown. [Figure 82A] This is a schematic diagram of an example of a semiconductor structure containing an epitaxial oxide layer on a suitable substrate. [Figure 82B] This plot shows the electron energy (y-axis) versus the growth direction (x-axis) for an embodiment of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials. [Figure 82C] This plot shows the electron energy (y-axis) versus the growth direction (x-axis) for an embodiment of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials. [Figure 82D]This plot shows the electron energy (y-axis) versus the growth direction (x-axis) for an embodiment of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials. [Figure 82E] This plot shows the electron energy (y-axis) versus the growth direction (x-axis) for an embodiment of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials. [Figure 82F] This plot shows the electron energy (y-axis) versus the growth direction (x-axis) for an embodiment of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials. [Figure 82G] This plot shows the electron energy (y-axis) versus the growth direction (x-axis) for an embodiment of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials. [Figure 82H] This plot shows the electron energy (y-axis) versus the growth direction (x-axis) for an embodiment of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials. [Figure 82I] This plot shows the electron energy (y-axis) versus the growth direction (x-axis) for an embodiment of an epitaxial oxide heterostructure containing layers of different epitaxial oxide materials. [Figure 83A] The relationship between electron energy and growth direction in three different digital alloy examples, and examples of confined electron and hole wave functions in each case are shown. [Figure 83B] The relationship between electron energy and growth direction in three different digital alloy examples, and examples of confined electron and hole wave functions in each case are shown. [Figure 83C] The relationship between electron energy and growth direction in three different digital alloy examples, and examples of confined electron and hole wave functions in each case are shown. [Figure 84] Figures 83A to 83C are charts showing the plot of the effective band gap versus the average composition (x) for the digital alloys. [Figure 85]The charts show pairs of band gaps (minimum band gap energy, in eV units) and, in some cases, crystal symmetry pairs of lattice constants for epitaxial oxide materials calculated using several DFTs. [Figure 86] A schematic diagram illustrates how epitaxial oxide materials with monoclinic unit cells are interchangeable with epitaxial oxide materials with cubic unit cells. [Figure 87] The chart shows pairs of band gaps (minimum band gap energy, in eV units) and, in some cases, crystal symmetry pairs of epitaxial oxide materials calculated using several DFTs, as well as charts of lattice constants of epitaxial oxide materials that further demonstrate the grouping of epitaxial oxide materials within each group, where they are compatible with other materials within the group. [Figure 88A] The charts of band gaps (minimum band gap energy, in eV units) versus lattice constants for epitaxial oxide materials calculated using several DFTs are shown, and all epitaxial oxide materials have a crystalline symmetry with either an Fd3m or Fm3m space group. [Figure 88B-1] This is a schematic diagram illustrating how epitaxial oxide materials with cubic symmetry and relatively small lattice constants (e.g., equivalent to about 4 angstroms) can be lattice-matched (or have small lattice mismatches) with epitaxial oxide materials with relatively large lattice constants (e.g., equivalent to about 8 angstroms). [Figure 88B-2] This shows the crystal structure of NiAl2O4 having an Fd3m space group. [Figure 88C] Figure 88A shows a chart with lines connecting subsets of epitaxial oxide materials having the composition (NixMgyZn1-xy)(AlqGa1-q)2O4, where 0≦x≦1, 0≦y≦1, 0≦z≦1, and 0≦q≦1, or (NixMgyZn1-xy)GeO4, where 0≦x≦1, 0≦y≦1, and 0≦z≦1. The shaded areas represent the convex hulls of the connected materials shown on the plot. [Figure 88D]Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including MgAl2O4, ZnAl2O4, NiAl2O4, and several alloys thereof. [Figure 88E] Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including "2ax MgO", γ-Ga2O3, MgAl2O4, ZnAl2O4, NiAl2O4, and several alloys thereof. [Figure 88F] Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including MgAl2O4, MgGa2O4, ZnGa2O4, and several alloys thereof. [Figure 88G] Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including "2ax NiO" (NiO whose plotted lattice constant is twice that of the NiO unit cell), "2ax MgO", γ-Al2O3, γ-Ga2O3, MgAl2O4, and several alloys thereof. [Figure 88H] Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including γ-Ga2O3, MgGa2O4, Mg2GeO4, and several alloys thereof. [Figure 88I] Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including γ-Ga2O3, MgGa2O4, "2ax MgO", and several alloys thereof. [Figure 88J] Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including γ-Ga2O3, Mg2GeO4, "2ax MgO", and several alloys thereof. [Figure 88K] Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including Ni2GeO4, Mg2GeO4, (Mg0.5Zn0.5)2GeO4, Zn(Al0.5Ga0.5)2O4, Mg(Al0.5Ga0.5)2O4, "2ax MgO", and several alloys thereof. [Figure 88L]Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including γ-Ga2O3, γ-Al2O3, MgAl2O4, ZnAl2O4, and several alloys thereof. [Figure 88M] Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including γ-Ga2O3, γ-Al2O3, MgAl2O4, ZnAl2O4, "2ax MgO", and several alloys thereof, with the bulk alloy γ-(AlxGa1-x)2O3 shown along one of the lines. [Figure 88N] Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including γ-Ga2O3, γ-Al2O3, MgAl2O4, ZnAl2O4, "2ax MgO", and several alloys thereof, and the digital alloy compositions, including layers of (MgO)z((AlxGa1-x)2O3)1-z material, are shown within the shaded area enclosed by the lines. [Figure 880] Figure 88A shows a chart with lines connecting a subset of epitaxial oxide materials, including MgGa2O4, ZnGa2O4, (Mg0.5Zn0.5)Ga2O4, (Mg0.5Ni0.5)Ga2O4, (Zn0.5Ni0.5)Ga2O4, "2ax NiO", "2ax MgO", and several alloys thereof. [Figure 89A] The charts of band gaps (minimum band gap energy, in eV units) versus lattice constants for epitaxial oxide materials calculated using several DFTs are shown, with lattice constants ranging from approximately 4.5 angstroms to 5.3 angstroms, indicating that the materials possess non-cubic symmetries such as hexagonal and orthorhombic. [Figure 89B] The table shows the properties of the Li(AlxGa1-x)O2 film calculated by DFT (space group ("SG"), lattice constants in angstroms ("a" and "b"), and lattice mismatch rates ("%Δa" and "%Δb") between the LiGaO2 film and the listed possible substrates ("sub"). [Figure 90A] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for LiAlO2 with the P41212 space group. [Figure 90B] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Li(Al0.5Ga0.5)O2 with the Pna21 space group. [Figure 90C] This shows a calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone in LiGaO2 with the Pna21 space group. [Figure 90D] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for ZnAl2O4 with the Fd3m space group. [Figure 90E] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for ZnGa2O4 with the Fd3m space group. [Figure 90F] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for MgGa2O4 with the Fd3m space group. [Figure 90G] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for GeMg2O4 with the Fd3m space group. [Figure 90H] This shows a calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for NiO with the Fm3m space group. [Figure 90I] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for MgO with the Fm3m space group. [Figure 90J] This shows a calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for SiO2 with the P3221 space group. [Figure 90K] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for NiAl2O4 with the Imma space group. [Figure 90L] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for αAl2O3 with the R3c space group. [Figure 90M]The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for α(Al0.75Ga0.25)2O3 with the R3c space group is shown. [Figure 90N] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for α(Al0.5Ga0.5)2O3 with the R3c space group is shown. [Figure 90O] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for α(Al0.25Ga0.75)2O3 with the R3c space group is shown. [Figure 90P] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for αGa2O3 with the R3c space group. [Figure 90Q] This shows a calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for κGa2O3 with the Pna21 space group. [Figure 90R] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for κ(Al0.5Ga0.5)2O3 with the Pna21 space group is shown. [Figure 90S] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for κAl2O3 with the Pna21 space group. [Figure 90T] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for γGa2O3 with the Fd3m space group. [Figure 90U] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for MgAl2O4 with the Fd3m space group. [Figure 90V] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for NiAl2O4 with the Fd3m space group. [Figure 90W] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for MgNi2O4 with the Fd3m space group. [Figure 90X] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for GeNi2O4 with the Fd3m space group. [Figure 90Y] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Li2O with the Fm3m space group. [Figure 90Z] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Al2Ge2O7 with a C2c space group. [Figure 90AA] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Ga4Ge1O8 with a C2m space group. [Figure 90BB] This shows a calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for NiGa2O4 with the Fd3m space group. [Figure 90CC] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Ga3N1O3 with the R3m space group. [Figure 90DD] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Ga3N1O3 with a C2m space group. [Figure 90EE] This shows a calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for MgF2 with a P42mnm space group. [Figure 90FF] This shows a calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for NaCl with the Fm3m space group. [Figure 90GG] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Mg0.75Zn0.25O with the Fd3m space group is shown. [Figure 90HH] This shows a calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for ErAlO3 with a P63mcm space group. [Figure 90II]This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Zn2Ge1O4 with the R3 space group. [Figure 90JJ] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for LiNi2O4 with the P4332 space group. [Figure 90KK] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for GeLi4O4 with a Cmcm space group. [Figure 90LL] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for GeLi2O3 with the Cmc21 space group. [Figure 90MM] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Zn(Al0.5Ga0.5)2O4 with an Fd3m space group. [Figure 90NN] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Mg(Al0.5Ga0.5)2O4 with an Fd3m space group. [Figure 9000] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for (Mg0.5Zn0.5)Al2O4 with the Fd3m space group. [Figure 90PP] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for (Mg0.5Ni0.5)Al2O4 with an Fd3m space group. [Figure 90QQ] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for β(Al0Ga1.0)2O3 (i.e., β(Ga2O3)) which has a C2m space group. [Figure 90RR] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for β(Al0.125Ga0.875)2O3 with a C2m space group. [Figure 90SS]The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for β(Al0.25Ga0.75)2O3 with a C2m space group is shown. [Figure 90TT] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for β(Al0.375Ga0.625)2O3 with a C2m space group is shown. [Figure 90UU] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for β(Al0.5Ga0.5)2O3 with a C2m space group is shown. [Figure 90VV] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for β(Al1.0Ga0.0)2O3 (i.e., θ-aluminum oxide) with a C2m space group is shown. [Figure 90WW] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for GeO2 with a P42mnm space group. [Figure 90XX] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for Ge(Mg0.5Zn0.5)2O4(with an Fd3m space group). [Figure 90YY] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for (Ni0.5Zn0.5)Al2O4 with an Fd3m space group. [Figure 90ZZ] This shows the calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone for a LiF with the Fm3m space group. [Figure 91] This shows the atomic crystal structure of the heterojunction between MgGa2O4 and MgAl2O4 epitaxial oxide materials. [Figure 92A] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone of a superlattice containing [MgAl2O4]1|[MgGa2O4]1 with an Fd3m space group in the unit cell is shown. [Figure 92B]The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone of a superlattice containing [MgAl2O4]1|[Mg(Al0.5Ga0.5)2O4]1 with an Fd3m space group in the unit cell is shown. [Figure 92C] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone of a superlattice containing [MgAl2O4]1|[ZnAl2O4]1 with an Fd3m space group in the unit cell is shown. [Figure 92D] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone of a superlattice containing [MgGa2O4]1|[(Mg0.5Zn0.5)O]1 with an Fd3m space group in the unit cell is shown. [Figure 92E] This shows a calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone of a superlattice containing [αAl2O3]2|[αGa2O3]2, where the unit cell has an R3c space group and the growth direction is A-plane. [Figure 92F] This shows a calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone of a superlattice containing [αAl2O3]1|[αGa2O3]1, where the unit cell has an R3c space group and the growth direction is A-plane. [Figure 92G] The calculated energy-crystal momentum (Ek) dispersion plot near the center of the Brillouin zone of a superlattice containing [GeMg2O4]1|[MgO]1 with an Fd3m / Fd3m space group in its unit cell is shown. [Figure 93] This shows the atomic crystal structure of β-(Al0.5Ga0.5)2O3 having the space group C2m. [Figure 94] The energy-crystal momentum (Ek) dispersion plots calculated by DFT near the center of the Brillouin zone for superlattices containing β-(Al0.5Ga0.5)2O3 and β-Ga2O3 are shown. [Figure 95A] This is a schematic diagram of a coherently (and pseudomorphically) distorted β-Ga2O3(100) film on an MgO(100) substrate, showing the in-plane unit cell arrangement (along the "b" and "c" directions in the plan view). [Figure 95B] This is a schematic diagram of a coherently (and pseudomorphically) distorted β-Ga2O3(100) film on an MgO(100) substrate, showing a unit cell arrangement in the growth direction ("a") where the film lattice is rotated 45° relative to the substrate lattice. [Figure 96] This shows an energy-crystal momentum (Ek) dispersion plot calculated by DFT near the center of the Brillouin zone of pseudomorphically distorted β-Ga2O3 on a 45° rotated MgO lattice. [Figure 97] A schematic diagram of a superlattice formed from alternating layers of β-Ga2O3 and MgO (each layer containing one or more unit cells) is shown, where the β-Ga2O3 layer is pseudomorphically distorted with respect to the MgO lattice rotated by 45°. [Figure 98A] This is a table showing the crystalline structure properties of exemplary epitaxial films and substrates compatible with Mg2GeO4. [Figure 98B] This table shows the compatibility of β-Ga2O3 with various heterostructure materials. [Figure 99] This table illustrates the selection of possible oxide material compositions containing the constituent elements (Mg, Zn, Al, Ga, O). [Figure 100] Figure 99 shows a schematic diagram of an epitaxial layer structure formed from at least two different materials further selected from the Oxide_type_A and Oxide_type_B categories shown. [Figure 101] This shows the single-crystal orientation of an ultra-broadbandgap cubic oxide composition containing ZnGa2O4(ZGO), which is formed by epitaxial deposition on the wurtzite-type crystal surface of SiC-4H with a smaller bandgap. [Figure 102] The shaded triangular region represents the atomic arrangement of the ZnGa2O4(111) surface. [Figure 103] Figures A and B show experimental XRD and XRR data of a ZGa2O4(111) oriented film epitaxially formed on a prepared SiC-4H(0001) surface. [Figure 104A]A schematic diagram of a cubic oxide with a large lattice constant, represented by ZnGa2O4, formed on an oxide with a smaller cubic lattice constant, represented by MgO, is shown. [Figure 104B] The crystal structures of the epitaxial growth surfaces presented for the structure in Figure 104A are shown, including the upper and lower atomic structures of MgO(100) and ZnGa2O4(100), respectively. [Figure 105] Figures A and B show experimental XRD data of high structural quality epitaxial layers of ZnGa2O4 films deposited on an MgO substrate. [Figure 106] This shows experimental XRD data of a high-structural-quality epitaxial layer of a NiO film deposited on a MgO substrate. [Figure 107] A schematic diagram of a cubic oxide with a large lattice constant, represented by MgGa2O4, formed on an oxide with a smaller cubic lattice constant, represented by MgO, is shown. [Figure 108] Figures A and B show experimental XRD data for forming an ultrawide bandgap cubic MgGa2O4(100) oriented epitaxial layer on a prepared MgO(100) substrate. [Figure 109] This shows a further epitaxial layer structure containing two UWBG large lattice constant cubic oxide layers integrated into a heterogeneous bandgap oxide structure deposited on a large lattice constant cubic MgAl2O4(100) oriented substrate. [Figure 110] Figures A and B show experimental XRD data of MgO, ZnAl2O4, and ZnGa2O4 cubic oxide films on an MgAl2O4(100) oriented substrate. [Figure 111] The surface atomic configurations of the cubic LiF(111) oriented surface and the cubic γGa2O3(111) oriented surface are shown. [Figure 112] A and B show experimental XRD data of gallium oxide that demonstrate the crystal symmetry group of the epitaxial layer, controlled by the symmetry of the underlying substrate or seed surface. [Figure 113] This shows the epitaxial structure of Ga2O3 formed on a cubic MgO substrate. [Figure 114]Figures A and B show experimental XRD data for low growth temperature (LT) and high growth temperature (HT) Ga2O3 film formation on prepared MgO(100) oriented substrates, respectively. [Figure 115] It exhibits a complex epitaxial layer structure of heterogeneous cubic oxide layers integrated into a superlattice or multiple heterojunction structure. [Figure 116] Figures A and B show experimental XRD data of SL structures formed using MgGa2O4 and ZnGa2O4 layers deposited on an MgO(100) substrate but with different periodicities. [Figure 117] Figures A and B show experimentally determined grazing incidence XRR data that demonstrate the extremely high crystal structure quality of the SL[MgGa2O4 / ZnGa2O4] / / MgO(100) structure shown in Figures 116A and 116B, respectively. [Figure 118] As another example, we show a complex epitaxial layer structure of heterogeneous cubic oxide layers integrated into a superlattice or multiple heterojunction structure. [Figure 119] Figures A and B show experimental XRD and XRR data of the epitaxial SL structure that forms SL[MgAl2O4 / MgO] / / MgAl2O4(100) as described in Figure 118. [Figure 120] As a further example, we show a complex epitaxial layer structure of heterogeneous cubic oxide layers integrated into a superlattice or multiple heterojunction structure. [Figure 121] This shows experimental XRD data of GeMg2O4, an Fd3m crystal structure containing MgO caps, deposited as a high-quality bulk layer on an Fm3m MgO(100) substrate. [Figure 122] This shows experimental XRD data of the Fd3m crystal structure GeMg2O4 when incorporated as an SL structure containing a 20-fold periodic SL[GeMg2O4 / MgO] on an Fm3m MgO(100) substrate. [Figure 123] As another example, we show a complex epitaxial layer structure of heterogeneous cubic oxide layers integrated into a superlattice or multiple heterojunction structure. [Figure 124] The (100) crystal plane representation of Fd3m cubic symmetry unit cells of GeMg2O4 and MgGa2O4 is shown. [Figure 125] Experimental XRD data of an SL structure containing a 20-fold periodic SL[Mg2GeO4 / MgGa2O4] on an MgO(100) substrate are shown. [Figure 126] Experimental XRD data of an SL structure containing a 10-fold periodic SL[Mg2GeO4 / MgGa2O4] on an MgO(100) substrate are shown. [Figure 127] As a further example, we show a complex epitaxial layer structure of heterogeneous cubic oxide layers integrated into a superlattice or multiple heterojunction structure. [Figure 128] A and B show experimental XRD data of superlattice structures including SL[GeMg2O4 / γGa2O3] / / MgOsub(100). [Figure 129] As another example, we show a complex epitaxial layer structure of heterogeneous cubic oxide layers integrated into a superlattice or multiple heterojunction structure. [Figure 130] Figures A and B show experimental XRD and XRR data for heterostructures and superlattice structures containing SL[ZnGa2O4 / MgO] / / MgOsub(100). [Figure 131] As another example, we show a complex epitaxial layer structure of heterogeneous cubic oxide layers integrated into a superlattice or multiple heterojunction structure. [Figure 132] A and B show experimental XRD data of superlattice structures including SL[MgGa2O4 / MgO] / / MgOsub(100). [Figure 133] The material exhibits a complex epitaxial layer structure in which heterogeneous cubic oxide layers are integrated to form heterostructures and SLs, with the SLs containing SL[Ga2O3 / MgO] / / MgOsub(100). [Figure 134] Figures A and B show experimental XRD data of the SL structure in Figure 133, where the growth temperature was selected to achieve the cubic phase γGa2O3 during the MBE deposition process. [Figure 135] As a further example, we show a complex epitaxial layer structure of heterogeneous cubic oxide layers integrated into a superlattice or multiple heterojunction structure. [Figure 136]Experimental XRD data of a pseudomorphically distorted bulk RS-Mg0.9Zn0.1O epitaxial layer on a cubic Fm3m MgO(100) oriented substrate are shown. [Figure 137] The experimental XRD data for the bulk RS-Mg0.9Zn0.1O composition shown in Figure 136, incorporated into a digital alloy in the form SL[RS-Mg0.9Zn0.1O / MgO] / / MgOsub(100), is shown. [Figure 138A] The plot shows the minimum band gap energy versus the small lattice constant for monoclinic β(AlxGa1-x)2O3. [Figure 138B] The plot shows the minimum band gap energy versus the small lattice constant for hexagonal α(AlxGa1-x)2O3. [Figure 138C] An example of a possible R3c α(AlxGa1-x)2O3 epitaxial structure is shown. [Figure 139A] This shows an epitaxial layer structure in which the effective alloy composition of each SL region is incrementally adjusted in stages along the growth direction. [Figure 139B] (110) Experimental XRD data of the stepped gradient SL (SGSL) structure shown in Figure 139A is shown using a digital alloy containing a bilayer of αGa2O3 and αAl2O3 deposited on oriented sapphire (no miscuts). [Figure 140] As an example, we show another stepped gradient SL structure that can be used to form a pseudo-substrate with a tuned in-plane lattice constant for a subsequent high-quality, near-lattice-matched active layer. [Figure 141A] This exhibits another stepped gradient SL structure, including a highly complex digital alloy gradient interleaved by wide bandgap spacers. [Figure 141B] Figure 141A shows experimental high-resolution XRD data of a stepped-slope (i.e., chirp) SL structure with an interposer. [Figure 141C] Figure 141A shows high-resolution XRD data of a stepped-slope (i.e., chirp) SL structure with an interposer. [Figure 142A] The electron band diagram is shown as a function of the growth direction of the chirp layer structure. [Figure 142B] The electron band diagram is shown as a function of the growth direction of the chirp layer structure. [Figure 142C] The electron band diagram is shown as a function of the growth direction of the chirp layer structure. [Figure 142D] Figures 142A to 142C show the wavelength spectra of oscillator intensities of electric dipole transitions between the conduction band and valence band of the chirp layer, as modeled. [Figure 143A] An example of the full Ek band structure of an epitaxial oxide material derived from the atomic structure of the crystal is shown. [Figure 143B] As shown in the Ek diagram of Figure 143A, a simplified band structure is shown that represents the minimum band gap of the material with space (z) as the x-axis, rather than the wave vector. [Figure 144A] This shows a simplified band structure of a homojunction device containing a pin structure with an epitaxial oxide layer. [Figure 144B] This shows a simplified band structure of a homojunction device containing a nin structure with an epitaxial oxide layer. [Figure 145A] This shows a simplified band structure of a heterojunction pin device containing an epitaxial oxide layer. [Figure 145B] The band structure diagram of a double heterojunction device containing an epitaxial oxide layer is shown. [Figure 145C] This shows a simplified band structure of a multiple heterojunction PIN device containing an epitaxial oxide layer. [Figure 146] The band structure diagram of a metal-insulator-semiconductor (MIS) structure containing an epitaxial oxide layer is shown. [Figure 147A] A simplified band structure of another example of a pin structure with a superlattice in the i-region is shown. [Figure 147B] A single quantum well with the structure shown in Figure 147A is shown. [Figure 148] A simplified band structure of another example of a pin structure with superlattices in the n, i, and p layers is shown. [Figure 149]A simplified band structure of another example of a pin structure with superlattices in the n, i, and p layers, similar to the structure in Figure 148, is shown. [Figure 150A] An example of a semiconductor structure containing an epitaxial oxide layer is shown. [Figure 150B] Figure 150A shows a structure having etched layers that can contact any of the layers of the semiconductor structure. [Figure 150C] Figure 150B shows the structure having an additional contact area that contacts the back surface of the substrate (opposite the epitaxial oxide layer). [Figure 151] This shows a multilayer structure used to form an electronic device having separate regions containing at least one layer of MgaGebOc. [Figure 152] This is an illustrative diagram showing an example of a material that can form a heterostructure when combined with MgaGebOc. [Figure 153] This is a plot of the bandgap energy as a function of the lattice constant for examples of materials that can be used in heterostructures of semiconductor structures. [Figure 154] This is a schematic cross-sectional view of an in-plane conductive device, including an insulating substrate and a semiconductor layer region formed on a substrate having electrical contacts disposed on the upper semiconductor layer of the device. [Figure 155] This is a schematic cross-sectional view of a vertical conduction device, including a conductive substrate and semiconductor layer regions formed on a substrate having electrical contacts located on the top and bottom of the device. [Figure 156A] Figure 155 shows a schematic cross-sectional view of a vertical conduction device for light emission, which has an electrical contact configuration and is configured as a planar parallel waveguide for emitted light. [Figure 156B] Figure 155 shows a schematic cross-sectional view of a vertical conduction device for light emission, which has an electrical contact configuration and is configured as a vertical light emission device. [Figure 157A] Figure 154 shows a schematic cross-sectional view of an in-plane conductive device for photodetection, having an electrical contact configuration and configured to receive light passing through a semiconductor layer region and / or substrate. [Figure 157B]Figure 154 is a schematic cross-sectional view of a planar conductive device for light emission, having an electrical contact configuration and configured to emit light in a vertical or planar direction. [Figure 158A] This is a semiconductor structure that can be used as part of a light-emitting device. [Figure 158B] This is a schematic cross-sectional view of a light-emitting device that can be formed using the semiconductor structure shown in Figure 158A. [Figure 159A] This is a semiconductor structure that can be used as part of a light-emitting device. [Figure 159B] This is a schematic cross-sectional view of a light-emitting device that can be formed using the semiconductor structure shown in Figure 159A. [Figure 160] This is a schematic cross-sectional view of an in-plane surface metal-semiconductor-metal (MSM) conductive device having a substrate and a semiconductor layer region including multiple semiconductor layers, the uppermost layer including a pair of planar mutually mating electrical contacts. [Figure 161A] The image shows a top view of an in-plane dual-metal MSM conduction device, which comprises a second electrical contact made of a second metallic material and a first electrical contact made of a first metallic material that mates with it. [Figure 161B] Figure 64A is a schematic cross-sectional view of an in-plane bimetallic MSM conduction device formed from the substrate and semiconductor layer regions shown, illustrating the unit cell arrangement. [Figure 162] This is a schematic cross-sectional view of a multilayer semiconductor device having a first electrical contact formed on a mesa surface, and a second electrical contact spaced horizontally and vertically from the first electrical contact. [Figure 163] Figure 162 is a schematic cross-sectional view of an in-plane MSM conduction device formed by arranging multiple mesa-structured unit cells laterally. [Figure 164] This is a schematic cross-sectional view of a multi-terminal device having multiple mesa structures. [Figure 165A]This is a schematic cross-sectional view of a planar field-effect transistor (FET) including source, gate, and drain electrical contacts, wherein the source and drain electrical contacts are formed on a semiconductor layer region formed on an insulating substrate, and the gate electrical contact is formed on a gate layer formed on the semiconductor layer region. [Figure 165B] Figure 165A is a top view of a planar FET, showing the distance between the electrical contacts from the source to the gate and from the drain to the gate. [Figure 166A] This is a schematic cross-sectional view of a planar field-effect transistor (FET) having a configuration similar to that shown in Figures 165A and 165B, except that the source electrical contact is embedded in the substrate through a semiconductor layer region, and the drain electrical contact is embedded only in the semiconductor layer region, according to some embodiments. [Figure 166B] Figure 166A is a top view of the planar FET shown. [Figure 167] Figure 165A or Figure 166A is a top view of a planar FET including multiple interconnected unit cells of the planar FET shown. [Figure 168] This is a process flow diagram for forming a conductive device that includes a regrowthed isotropic semiconductor layer region on an exposed, etched mesa sidewall. [Figure 169A] This chart shows the center frequencies of RF operating bands that can be used in various applications. [Figure 169B] A typical RF switch circuit diagram is shown. [Figure 170A] The circuit diagram and equivalent circuit diagram of an FET having a source terminal ("S"), a drain terminal ("D"), and a gate terminal ("G") are shown. [Figure 170B] The circuit diagram and equivalent circuit diagram of an RF switch that uses multiple FETs in series to achieve high voltage resistance are shown. [Figure 170C] The circuit diagram and equivalent circuit diagram of an RF switch that uses multiple FETs in series to achieve high voltage resistance are shown. [Figure 170D]The circuit diagram and equivalent circuit diagram of an RF switch that uses multiple FETs in series to achieve high voltage resistance are shown. [Figure 171] This chart shows the calculated on-resistance of a specific RF switch, and the calculated breakdown voltages associated with the various semiconductors that make up the RF switch. [Figure 172A] The circuit diagram shows multiple Si-based FETs connected in series to achieve high voltage resistance. [Figure 172B] Figure 172A shows a circuit diagram of a single Ga2O3-based FET that can achieve the same high voltage rating as the series Si-based FETs. [Figure 173] This chart shows the calculated off-state FET capacitance (in F) versus the calculated specific on-resistance (RON) for Si (low bandgap material) and epitaxial oxide materials with a high bandgap. [Figure 174] This chart shows the difference between the thickness of the complete depletion layer (tFD) of the channel of an FET containing α-Ga2O3 and the doping density of α-Ga2O3 in the channel (ND CH). [Figure 175] A schematic diagram of an example of a FET containing an epitaxial oxide material is shown. [Figure 176A] This is an Ek diagram showing the calculated band structure of an epitaxial oxide material that can be used in the FETs and RF switches of this disclosure, and in this example, it shows that α-Al2O3 can be used as a gate layer or additional oxide encapsulation. [Figure 176B] This is an Ek diagram showing the calculated band structure of an epitaxial oxide material that can be used in the FET and RF switch of this disclosure, and in this example, it shows that α-Ga2O3 can be used as the channel layer. [Figure 177] This chart shows the calculated minimum bandgap energy (in eV) versus lattice constant (in angstroms) for α- and κ-(AlxGa1-x)2O3 materials compatible with sapphire (α-Al2O3) substrates. [Figure 178] A schematic diagram of a part of an FET and a chart of the energy-to-channel distance (in the "x" direction) are shown. [Figure 179] To illustrate the operation of an FET using an epitaxial oxide material, a schematic diagram of a part of the FET and a chart of energy versus distance along the channel ("z" direction) are shown. [Figure 180] A schematic diagram of a part of an FET and a chart of the energy-to-channel distance ("z" direction) are shown. [Figure 181] A schematic diagram of the atomic surface of α-Al2O3 oriented in plane A (i.e., the (110) plane) is shown. [Figure 182] A schematic diagram of an example of an FET including an epitaxial oxide material and an integrated phase shifter is shown. [Figure 183] A and B show schematic diagrams of a system including one or more switches (e.g., including the FET in Figure 182) having an integrated phase shifter. [Figure 184] A schematic diagram of an example of a FET including an epitaxial oxide material and an epitaxial oxide embedded ground plane is shown. [Figure 185] A and B are energy band diagrams along the gate stack direction ("z" as shown in the schematic diagram of Figure 179) of an example of a FET having a structure like the FET in Figure 184, where the layers are formed of α-(AlxGa1-x)2O3 and α-Al2O3. [Figure 186] This shows several RF waveguide structures that can be formed using an embedded ground plane containing epitaxial oxide material. [Figure 187] A schematic diagram of an example of an FET including an epitaxial oxide material and an electric field shield on the gate electrode is shown. [Figure 188] Schematic diagrams of epitaxial oxides and dielectric materials that form integrated FET and coplanar (CP) waveguide structures are shown. [Figure 189] A schematic diagram of an example of an FET including an epitaxial oxide material and an integrated phase shifter is shown. [Figure 190] A to C show energy band diagrams along the channel direction (as shown in Figure 178, "x") for the S-tunnel junction and D-tunnel junction described for the FET shown in Figure 189. [Figure 191A] Figure 189 is a schematic diagram of an example process flow for manufacturing an epitaxial oxide material such as an FET. [Figure 191B] Figure 189 is a schematic diagram of an example process flow for manufacturing an epitaxial oxide material such as an FET. [Figure 191C] Figure 189 is a schematic diagram of an example process flow for manufacturing an epitaxial oxide material such as an FET. [Figure 191D] Figure 189 is a schematic diagram of an example process flow for manufacturing an epitaxial oxide material such as an FET. [Figure 191E] Figure 189 is a schematic diagram of an example process flow for manufacturing an epitaxial oxide material such as an FET. [Figure 191F] Figure 189 is a schematic diagram of an example process flow for manufacturing an epitaxial oxide material such as an FET. [Figure 191G] Figure 189 is a schematic diagram of an example process flow for manufacturing an epitaxial oxide material such as an FET. [Figure 192] The atomic structure of κ-Ga2O3 (i.e., Ga2O3 with the Pna21 space group) calculated by DFT is shown. [Figure 193A] The band structures calculated by DFT for κ-(AlxGa1-x)2O3 with x=1, 0.5, and 0 are shown. [Figure 193B] The band structures calculated by DFT for κ-(AlxGa1-x)2O3 with x=1, 0.5, and 0 are shown. [Figure 193C] The band structures calculated by DFT for κ-(AlxGa1-x)2O3 with x=1, 0.5, and 0 are shown. [Figure 193D] The minimum bandgap energy calculated by DFT for κ-(AlxGa1-x)2O3 with x=1, 0.5, and 0 is shown. [Figure 194A]This shows a schematic diagram of the energy versus growth direction "z" in the κ-(AlxGa1-x)2O3 / κ-Ga2O3 heterostructure, along with the calculated band diagram (edges of the conduction and valence bands), the calculated electron wave function, and the calculated electron density. [Figure 194B] This shows a schematic diagram of the energy versus growth direction "z" in the κ-(AlxGa1-x)2O3 / κ-Ga2O3 heterostructure, along with the calculated band diagram (edges of the conduction and valence bands), the calculated electron wave function, and the calculated electron density. [Figure 194C] This shows a schematic diagram of the energy versus growth direction "z" in the κ-(AlxGa1-x)2O3 / κ-Ga2O3 heterostructure, along with the calculated band diagram (edges of the conduction and valence bands), the calculated electron wave function, and the calculated electron density. [Figure 194D] The image shows the electron density in a thin layer within a confined energy well formed in the κ-(AlxGa1-x)2O3 / κ-Ga2O3 heterostructure at x=0.3, 0.5, and 1. [Figure 194E] The image shows the electron density in a thin layer within a confined energy well formed in the κ-(AlxGa1-x)2O3 / κ-Ga2O3 heterostructure at x=0.3, 0.5, and 1. [Figure 195] The band structure calculated by DFT of Li-doped κ-Ga2O3 is shown. [Figure 196] This chart summarizes the band structure results calculated by DFT for (Al,Ga)xOy doped with different dopants. [Figure 197A] An example of a PIN structure with multiple quantum wells in the n, i, and p layers is shown (similar to the structure shown in Figure 149). [Figure 197B] Figure 197A shows the calculated band diagram for a portion of the n-domain superlattice with a structure similar to that of Figures 194B and 194C, as well as the wave functions of the confined electrons and holes. [Figure 197C]Figure 197A shows the calculated band diagram for a portion of the n-domain superlattice with a structure similar to that of Figures 194B and 194C, as well as the wave functions of the confined electrons and holes. [Figure 198A] The diagram shows a crystalline substrate having a specific orientation (hkl) with respect to the growth direction, and a structure having an epitaxial layer ("film epitaxial layer") having an orientation (h' k' l'). [Figure 198B] This table shows several substrates compatible with the κ-AlxGa1-xOy epitaxial layer, the substrate space group ("SG"), the substrate orientation, the orientation of the κ-AlxGa1-xOy film grown on the substrate, and the elastic strain energy due to mismatch. [Figure 199] An example is shown that includes a substrate (C-plane α-Al2O3) and a template (low-temperature "LT" grown Al(111)) structure used to match the in-plane lattice constant to κ-AlxGa1-xOy ("Pna21 AlGaO"). [Figure 200] We present several DFT-calculated epitaxial oxide materials that can serve as substrates for κ-AlxGa1-xOy and / or form heterostructures with κ-AlxGa1-xOy, using lattice constants ranging from approximately 4.8 angstroms to approximately 5.3 angstroms, in various examples. [Figure 201] We present several additional DFT-calculated epitaxial oxide materials that can serve as substrates for κ-AlxGa1-xOy and / or form heterostructures with κ-AlxGa1-xOy, using possible in-plane lattice constants ranging from approximately 4.8 angstroms to approximately 5.3 angstroms, in various examples. [Figure 202A] This shows the rectangular arrangement of atoms within a unit cell on the (001) surface of κ-Ga2O3. [Figure 202B] This shows the surface of α-SiO2 formed by stacking rectangular unit cells of κ-Ga2O3(001). [Figure 202C] This shows the surface of LiGaO2(011) formed by stacking rectangular unit cells of κ-Ga2O3(001). [Figure 202D]This shows the surface of Al(111) formed by stacking rectangular unit cells of κ-Ga2O3(001). [Figure 202E] This shows the surface of α-Al2O2(001) (i.e., C-face sapphire) formed by stacking rectangular unit cells of κ-Ga2O3(001). [Figure 203] A flowchart of an example method for forming a semiconductor structure containing κ-AlxGa1-xOy is shown. [Figure 204A] The image shows two superimposed experimental XRD scans: one of κ-Al2O3 grown on an Al(111) template, and the other of κ-Al2O3 grown on a Ni(111) template. [Figure 204B] The images show two superimposed experimental XRD scans (shifted to the y-axis) of the shown structure, one containing a κ-Ga2O3 layer grown on an α-Al2O3 substrate with an Al(111) template layer, and the other containing a β-Ga2O3 layer grown on an α-Al2O3 substrate without a template layer. [Figure 204C] Figure 204B shows two superimposed scans at high resolution, where fringing due to the improved layer quality was observed. [Figure 205] Figures A and B show simplified Ek diagrams of the Brillouin zone center of epitaxial oxide materials, as shown in Figures 28, 76A-1, 76A-2, and 76B, illustrating the impact ionization process. [Figure 206A] The graph shows the energy versus band gap plots for epitaxial oxide materials (including the conduction 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 206B] An example using α-Ga2O3 with a band gap of approximately 5 eV is shown. [Figure 207A] A schematic diagram of an epitaxial oxide material having two planar contact layers (e.g., a metal or a highly doped semiconductor contact material and a metal contact) coupled to an applied voltage Va is shown. [Figure 207B] The band diagram of the structure shown in Figure 207A is shown along the growth direction ("z" direction) of the epitaxial oxide material. [Figure 207C] Figure 207A shows the band diagram of the epitaxial oxide material with the structure shown, along the growth direction ("z"), where the epitaxial oxide has a band gap gradient (i.e., a gradient band gap), Ec(z), in the growth direction ("z"). [Figure 208] A schematic diagram of an example of an electroluminescent device including a high work function metal ("metal #1"), an ultra-high bandgap ("UWBG") layer, a wide bandgap ("WBG") epitaxial oxide layer, and a second metal contact ("metal #2"). [Figure 209] Figures A and B show schematic diagrams of an example of a PIN diode, which is a PIN diode comprising a p-type semiconductor layer, an epitaxial oxide layer that is not intentionally doped (NID) and contains an impulse ionization region (IIR), and an n-type semiconductor layer. [Modes for carrying out the invention]

[0012] This specification discloses embodiments of epitaxial oxide materials having structures and electronic devices comprising epitaxial oxide materials. Several embodiments disclose 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.

[0013] 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.

[0014] In another form, each metal oxide in one or more semiconductor layers is Al2O3, Ga2O 3、 The material is selected from the group consisting of MgO, NiO, Li2O, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, IrO2, and any combination of the aforementioned metal oxides.

[0015] In another embodiment, at least one of the one or more semiconductor layers is a single crystal.

[0016] In another embodiment, at least one of the one or more semiconductor layers has rhombohedral, hexagonal, or monoclinic crystal symmetry.

[0017] In another embodiment, at least one of the one or more semiconductor layers is composed of a binary metal oxide, the metal oxide selected from Al2O3 and Ga2O3.

[0018] In another embodiment, at least one of one or more semiconductor layers is composed of a ternary metal oxide composition comprising 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.

[0019] In another form, at least one of the one or more semiconductor layers is (Al x Ga 1-x ) is composed of a ternary metal oxide composition of 2O3, where 0 <x<1である。

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

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

[0022] In another form, at least one of the one or more semiconductor layers includes a triaxially deformed unit cell.

[0023] 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.

[0024] In another form, at least one of the one or more semiconductor layers is composed of a quaternary metal oxide composition (Ni x Mg 1-x ) y Ga 2(1-y) O 3-2y where 0 < x < 1 and 0 < y < 1.

[0025] In another form, the surface of the substrate is configured to enable lattice matching of the crystal symmetry of at least one semiconductor layer.

[0026] In another form, the substrate is a single crystal substrate.

[0027] In another form, the substrate is selected from Al2O3, Ga2O3, MgO, LiF, MgAl2O4, MgGa2O4, LiGaO2, LiAlO2, MgF2, LaAlO3, TiO2, and quartz.

[0028] In another embodiment, the surface of the substrate has a match between crystal symmetry and in-plane lattice constants to allow homoepitaxy or heteroepitaxy of at least one semiconductor layer.

[0029] In another form, at least one or more of the semiconductor layers are of the direct bandgap type.

[0030] 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.

[0031] 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.

[0032] 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 configuration 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].

[0033] In another form, the binary metal oxide is Al2O3.

[0034] In another form, the binary metal oxide is Ga2O3.

[0035] 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.

[0036] In another form, selecting one or more epitaxial metal oxide layers to have a light-emitting 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.

[0037] In another form, the ternary metal oxide includes metal species (A) and (B) bonded to oxygen (O) in relative ratios x, y, and n, A x B y O n is a ternary metal oxide bulk alloy in the form of.

[0038] 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.

[0039] In another form, the ternary metal oxide is A x B 1-x O n is in the form of, where 0 < x < 1.0.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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- and so on.

[0044] In another form, metal species A is Al, metal species B is Ga, and the ternary metal oxide ordered alloy takes the form of Al-O-Ga-O-Al-, etc.

[0045] In another form, a ternary metal oxide is a host binary metal oxide crystal containing a crystal-modifying species.

[0046] 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.

[0047] 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 involves forming one or more epitaxial metal oxide layers as a superlattice comprising two or more layers of metal oxide that form unit cells and repeat along the growth direction with a fixed unit cell period. This includes the following.

[0048] In another form, the superlattice is a bilayer superlattice containing repeating layers of two different metal oxides.

[0049] In another form, the two different metal oxides include a first binary metal oxide and a second binary metal oxide.

[0050] In another form, the first binary metal oxide is Al2O3 and the second binary metal oxide is Ga2O3.

[0051] In another form, the first binary metal oxide is NiO, and the second binary metal oxide is Ga2O3.

[0052] In another form, the first binary metal oxide is MgO and the second binary metal oxide is NiO.

[0053] In another form, the first binary metal oxide is Al2O3,Ga2O 3、 The first binary metal oxide is selected from the group consisting of 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.

[0054] In another form, the two different metal oxides include binary metal oxides and ternary metal oxides.

[0055] 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。

[0056] 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。

[0057] 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。

[0058] 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。

[0059] 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。

[0060] In another form, the binary metal oxide is Al2O3, and the ternary metal oxide is (Al x Er 1-x It is 2O3.

[0061] 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 Ir1 -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。

[0062] In another form, binary metal oxides are Al2O3, Ga2O 3、 It is selected from the group consisting of MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2.

[0063] In another form, the two different metal oxides include a first ternary metal oxide and a second ternary metal oxide.

[0064] 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.

[0065] 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.

[0066] 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, (Gax 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 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。

[0067] In another form, the superlattice is a three-layer superlattice containing repeating layers of three different metal oxides.

[0068] 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.

[0069] 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.

[0070] In another form, the first binary metal oxide is Al2O3,Ga2O 3、 The first binary metal oxide is selected from the group consisting of 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, and the third binary metal oxide is selected from the group consisting of the first and second selected binary metal oxides No, Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O 3、 It is selected from the group consisting of Gd2O3, PdO, Bi2O3, and IrO2.

[0071] In another form, the three different metal oxides include a first binary metal oxide, a second binary metal oxide, and a ternary metal oxide.

[0072] In another form, the first binary metal oxide is Al2O3,Ga2O 3、 The second binary metal oxide is selected from the group consisting of MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2, and if the first selected binary metal oxide is not present, then Al2O3, Ga2O 3、The ternary metal oxide is selected from the group consisting of MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2, and the 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, (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。

[0073] In another form, the three different metal oxides include a binary metal oxide, a first ternary metal oxide, and a second ternary metal oxide.

[0074] In another form, binary metal oxides are Al2O3, Ga2O 3、The first ternary metal oxide is selected from the group consisting of 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 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 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 , (Al2x 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。

[0075] 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.

[0076] 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 xBi 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 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, (Al2x 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 , (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である。

[0077] In another form, the superlattice is a four-layer superlattice containing repeating layers of at least three different metal oxides.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] In another form, the three different metal oxides are Al2O3, Ga2O 3、 MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, IrO 2、 (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 Selected from the group consisting of, where 0 <x<1.0である。

[0082] In another form, the superlattice is a four-layer superlattice containing repeating layers of four different metal oxides.

[0083] In another form, the four different metal oxides are Al2O3, Ga2O 3、 MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, IrO 2、 (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。

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

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

[0089] In another configuration, a predetermined strain is introduced to modify the initial valence electron band structure of the initial emission region band structure.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] In another form, the given strain is a biaxial strain.

[0094] 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.

[0095] 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.

[0096] The underlying metal oxide layer is Al2O3, the strained metal oxide layer is Ga2O3, and biaxial tension is introduced into the Ga2O3 layer.

[0097] In another form, the given strain is a uniaxial strain.

[0098] In another form, the underlying layer has a first crystal symmetry type with asymmetric unit cells.

[0099] In another form, the strained metal oxide layer is monoclinic Ga2O 3、 Al x Ga 1-x It is either O or Al2O3, and in the formula x < 0 < 1.

[0100] In another form, the underlying layer and the strained layer form a superlattice layer.

[0101] In another embodiment, modifying the initial luminescence region band structure of one or more epitaxial metal oxide layers when forming an optoelectronic device includes 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.

[0102] In another embodiment, the optoelectronic device comprises a first conduction region having one or more epitaxial metal oxide layers having a first conduction region band structure configured to work in conjunction with an emitting region to generate light of a predetermined wavelength.

[0103] In another embodiment, configuring a first conduction region band structure to work in combination with an emission region to produce light of a predetermined wavelength involves selecting a first conduction region energy band gap that is larger than the emission region energy band gap.

[0104] In another embodiment, configuring a first conduction-type region band structure to operate in combination with an emission region to produce light of a predetermined wavelength includes selecting the first conduction-type region to have an indirect band gap.

[0105] In another embodiment, constructing a first conduction-type region band structure includes one or more of the following: selecting a suitable metal oxide material or multiple material in accordance with the principles and techniques considered in this disclosure in relation to the light-emitting region; forming a superlattice in accordance with the principles and techniques considered in this disclosure in relation to the light-emitting region; and / or modifying the first conduction-type region band structure by applying strain in accordance with the principles and techniques considered in this disclosure in relation to the light-emitting region.

[0106] In another form, the first conduction-type region is an n-type region.

[0107] In another embodiment, the optoelectronic device comprises a second conduction region having one or more epitaxial metal oxide layers having a second conduction region band structure configured to operate in combination with a light-emitting region and a first conduction region to generate light of a predetermined wavelength.

[0108] In another embodiment, configuring a second conduction region band structure to work in conjunction with an emission region to produce light of a predetermined wavelength involves selecting a second conduction region energy band gap that is larger than the emission region energy band gap.

[0109] In another embodiment, configuring a second conduction region band structure to operate in combination with an emission region to produce light of a predetermined wavelength includes selecting the second conduction region to have an indirect band gap.

[0110] In another embodiment, constructing a second conduction-type region band structure includes one or more of the following: selecting a suitable metal oxide material or a plurality of materials in accordance with the principles and techniques considered in this disclosure in relation to the light-emitting region; forming a superlattice in accordance with the principles and techniques considered in this disclosure in relation to the light-emitting region; and / or modifying the first conduction-type region band structure by applying strain in accordance with the principles and techniques considered in this disclosure in relation to the light-emitting region.

[0111] In another form, the second conduction-type region is a p-type region.

[0112] In another form, the substrate is formed from a metal oxide.

[0113] 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.

[0114] In another form, the substrate is formed from a metal fluoride.

[0115] In other forms, metal fluorides are MgF2 or LiF.

[0116] In another form, the given wavelength is in the wavelength range of 150 nm to 700 nm.

[0117] In another form, the given wavelength is in the wavelength range of 150 nm to 280 nm.

[0118] 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.

[0119] In another form, the metal oxide substrate includes an Al or Ga metal oxide substrate.

[0120] In another form, one or more atomic beams, each containing high-purity metal atoms, are used to represent 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.

[0121] In another embodiment, 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.

[0122] 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.

[0123] In another embodiment, at least one of two or more epitaxial metal oxide films provides a first conduction-type region comprising one or more epitaxial metal oxide layers, and at least another film of the two or more epitaxial metal oxide films comprises one or more epitaxial metal oxide layers It provides a second conduction-type region containing an ionized layer.

[0124] 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 conduction type region including a 2O3 layer, and two or more epitaxial (Al x Ga 1-x ) At least one other of the 2O3 film is one or more epitaxial (Al x Ga 1-x ) Provides a second conductive region including a 2O3 layer.

[0125] In another configuration, the substrate is placed in an ultra-high vacuum chamber (5) before the oxidation step. × 10 -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.

[0126] In another form, the method further includes monitoring the surface in real time to evaluate the quality of the atomic surface.

[0127] In another configuration, the surface is monitored in real time by reflected high-energy electron diffraction (RHEED).

[0128] 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.

[0129] In another configuration, the oxygen source is selected from one or more of the group consisting of oxygen plasma, ozone, and nitrous oxide.

[0130] In another configuration, the oxygen source is radio-frequency inductively coupled plasma (RF-ICP).

[0131] In another form, the method further includes monitoring the surface in real time to assess the oxygen density of the surface.

[0132] In another configuration, the surface is monitored in real time by RHEED.

[0133] In another embodiment, atomic beams containing high-purity Al atoms and / or high-purity Ga atoms are each emitted and heated 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 in the crucible.

[0134] In another form, high-purity elemental metals with a purity of 6N to 7N or higher are used.

[0135] 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.

[0136] 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.

[0137] In another embodiment, the method further includes heating the substrate when the activated epitaxial growth surface is exposed to an atomic beam.

[0138] In another form, a blackbody emissivity suitable for absorption below the band gap of a metal oxide substrate is used. When used, the substrate is heated by radiating heat from the rear.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] In another form, the Al or Ga metal oxide substrate is A-plane sapphire.

[0143] In another form, the Al or Ga metal oxide substrate is monoclinic Ga2O3.

[0144] In another form, two or more epitaxial (Al x Ga 1-x The 2O3 film contains corundum-type AlGaO3.

[0145] In another form, two or more epitaxial (Al x Ga 1-x For each of the 2O3 membranes, x ≤ 0.5.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] In another configuration, the first layer is corundum Al2O3 (sapphire), and the metal oxide layer is corundum Ga2O3.

[0150] In another configuration, the first layer is monoclinic Al2O3, and the metal oxide layer is monoclinic Ga2O3.

[0151] 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).

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

[0153] In another configuration, the first layer is A-plane corundum Al2O3 (sapphire), and the metal oxide layer is corundum AlGaO3.

[0154] In another configuration, the first layer is corundum Ga2O3, and the metal oxide layer is corundum Al2O3.

[0155] In another configuration, the first layer is monoclinic Ga2O3, and the metal oxide layer is monoclinic Al2O3 (sapphire).

[0156] In another configuration, the first layer is (-201) oriented monoclinic Ga2O3, and the metal oxide layer is (-201) oriented monoclinic AlGaO3.

[0157] In another configuration, the first layer is (010) oriented monoclinic Ga2O3, and the metal oxide layer is (010) oriented monoclinic AlGaO3.

[0158] In another configuration, the first layer is (001) oriented monoclinic Ga2O3, and the metal oxide layer is (001) oriented monoclinic AlGaO3.

[0159] 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.

[0160] 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.

[0161] 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).

[0162] 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%.

[0163] 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%.

[0164] In another configuration, the first layer is A-plane corundum Al2O3 (sapphire), and the metal oxide layer is (110)-oriented monoclinic Ga2O3.

[0165] In another configuration, the first layer is (110) oriented monoclinic Ga2O3, and the metal oxide layer is corundum AlGaO3.

[0166] In another configuration, the first layer is (010) oriented monoclinic Ga2O3, and the metal oxide layer is (111) oriented cubic MgGa2O4.

[0167] In another configuration, the first layer is (100)-oriented cubic MgO, and the metal oxide layer is (100)-oriented monoclinic AlGaO3.

[0168] The first layer is (100) oriented cubic NiO, and the metal oxide layer is (100) oriented monoclinic AlGaO3.

[0169] In another form, 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, and the buffer layer The crystal symmetry type is the same as the first crystal symmetry type, providing an atomically planar layer for seeding a metal oxide layer having the second crystal symmetry type.

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

[0171] In another configuration, the buffer layer includes a metal-terminated template for seeding the metal oxide layer.

[0172] In another embodiment, the first and second crystal symmetries are selected from the group consisting of cubic, hexagonal, orthorhombic, trigonal, rhombic, and monoclinic crystals.

[0173] 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.

[0174] In another form, the first layer is a metal oxide layer.

[0175] In another configuration, the first and second layers form a superlattice by creating repeating unit cells with a fixed unit cell period.

[0176] 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.

[0177] 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.

[0178] In another form, the third crystal form is selected from the group consisting of cubic, hexagonal, orthorhombic, trigonal, rhombic, and monoclinic crystals.

[0179] In another form, a multilayer semiconductor device is an optoelectronic semiconductor device that generates light of a predetermined wavelength.

[0180] In another form, the given wavelength is in the wavelength range of 150 nm to 700 nm.

[0181] In another form, the given wavelength is in the wavelength range of 150 nm to 280 nm.

[0182] 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 conduction region comprising one or more epitaxial layers of a metal oxide in a non-equilibrium environment; depositing an emission region comprising one or more epitaxial layers of a 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 conduction region comprising one or more epitaxial layers of a metal oxide in a non-equilibrium environment.

[0183] 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.

[0184] In another form, the specified wavelength is in the wavelength range of approximately 150 nm to approximately 280 nm.

[0185] 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 conduction band and valence band states, 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.

[0186] 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.

[0187] 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.

[0188] The luminescent 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 luminescent region may be clad by electron and hole reservoirs including n-type and p-type conduction regions. The n-type and p-type conduction regions are selected from electron and hole injection materials 45 that may have a larger bandgap than the luminescent region material 35 or may include an indirect bandgap structure that limits light absorption at the operating wavelength. In one example, the n-type and p-type conduction regions are formed from one or more metal oxide layers.

[0189] Impurity doping of Ga2O3 and low Al% AlGaO3 is possible for both n-type and p-type materials. 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).

[0190] 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.

[0191] 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.

[0192] 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.

[0193] 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.

[0194] 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).

[0195] 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.

[0196] The substrate 170 is provided with a favorable crystal symmetry and in-plane lattice constant matching on its surface, enabling homoepitaxy or heteroepitaxy of the first conduction region 175 having a non-absorbent spacer region 180, an emitting region 185, an optional second spacer region 190, and a second conduction 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 conduction region 175 and the second conduction 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.

[0197] The first and second conduction regions 175 and 195 are, in one example, formed using a metal oxide having a wide band gap 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 by using the ohmic contact region 198 and the first conduction region 175 for one conduction type (i.e., electrons or holes) and the ohmic contact region 196 and the second conduction region 195 for the other. 198 may optionally be created on an exposed portion of the first conductive 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.

[0198] In the case of a vertical conduction device, the substrate 170 is conductive and may be either transparent or opaque with respect to the operating wavelength. Electrical or ohmic contact regions 197 and 198 are arranged to favorably enable both electrical connections and optical propagation within the device.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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, ternary, 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 conduction 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.

[0209] 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.

[0210] 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 the form of tertiary metal oxides. The ternary metal oxides range from dilute additions of type B to the majority relative proportion. As described below, ternary metal oxides can be employed in various embodiments to advantageously form bandgap emission structures directly. Furthermore, 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.

[0211] 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.

[0212] 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, by utilizing monoclinic and cubic crystal symmetry host regions that include a portion of the UVLED. This can be done. Next, the epitaxial formation relationship requires attention to the formation of low-defect layers. Then, the types of layer formation steps are classified as homosymmetric and heterosymmetric formation285. To achieve the goal of providing a material that forms an epitaxial layer structure, band structure modifiers290 such as digital alloys can be used for biaxial strain, uniaxial strain, and superlattice formation.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] Next, the growth conditions 325 are optimized for the relative ratio of elemental metals and activated oxygen required to achieve the desired material properties. The growth temperature also plays a crucial role in determining the possible crystal structure symmetry types. A wise selection of the substrate surface energy due to appropriate crystal surface orientation also determines the temperature process window of the epitaxial process in which the epitaxial structure 330 is deposited.

[0218] A database of material selections 350 for applications in UVLED-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 UVLEDs. 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 conduction band 360 and the maximum valence band 365. The absolute energy positions represented by the minimum conduction band 360 and the maximum valence band 365 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 they are useful for forming electrical contacts. It can be used for practical purposes. The inherent electron affinity of a given material can be used to form ohmic contacts and metal-insulator-semiconductor junctions as needed.

[0219] 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).

[0220] 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.

[0221] 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).

[0222] Further embodiments include selection from the group of crystal modifiers selected from the group consisting of Bi, Ir, Ni, Mg, and Li.

[0223] 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 leading to 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.

[0224] Other materials are also possible, but database 350 offers properties that are advantageous for application to UV LEDs.

[0225] 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.

[0226] The substrate 405 is prepared using a surface 410 configured to receive a first conductive crystal structure layer (or more) 415 which may contain multiple epitaxial layers. Next, a first spacer region composition layer (or more) 420 which may contain multiple epitaxial layers is prepared Next, a light-emitting region 425 is formed on layer 420, and region 425 may contain multiple epitaxial layers. Then, 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.

[0227] 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.

[0228] 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).

[0229] Therefore, Figure 11 can be understood as an application of the present disclosure toward the formation of luminescent and conductive regions.

[0230] 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 also shows the energy gap 502 of alpha-phase aluminum oxide (Al2O3) with rhombohedral crystal symmetry.

[0231] 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.

[0232] 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.

[0233] Generally, when applied to a luminescent crystal structure, as shown in Figures 13A and 13B, two k A lath electron band structure exists. 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.

[0234] 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.

[0235] Figure 13A shows the reciprocal space energy versus crystal momentum or band structure of the crystal structure.

number

number

number

[0236] 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 conduction band value of 565. Similarly, holes relax to the lowest energy state of 580.

[0237] 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. In other words, the electron and hole at k=0 recombine and recombine, preserving the crystal moment, and this is called a “direct” bandgap material. It is possible to generate massless particles. As disclosed, this situation is actually rare, and only a small subset of all crystal-symmetric semiconductors exhibit this favorable configuration.

[0238] 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 conduction 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. Since crystal momentum cannot be conserved in recombination events, and secondary particles such as crystal vibrational quantum phonons are required to conserve crystal momentum, the luminescence process is clearly undesirable. 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.

[0239] 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.

[0240] 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 conduction band and the three uppermost valence bands.

[0241] 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.

[0242] 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 ( EF ) 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.

[0243] 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.

[0244] Figures 14A and 14B show a single block 63 defined by layer thicknesses of 655, 660, and 665, and fundamental bandgap energies of 640, 645, and 650, respectively. Figure 3 shows a representation of the composite Ek material. The relative alignment of the conduction band edge and the valence band edge is shown in block 633. Figure 14B represents the electron energy 670 versus the spatial growth direction 635 for three distinct materials having band gap energies 640, 645, and 650. For example, an indirect crystal is deposited along the growth direction 635, otherwise a first region with a final surface lattice geometry that can provide mechanical-elastic deformation of the subsequent crystal 645 is possible. For example, this can occur when growing AlGaO3 directly on Ga2O3.

[0245] Epitaxial manufacturing method

[0246] 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.

[0247] 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.

[0248] 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.

[0249] Such equilibrium growth methods for metal oxides limit the possible combinations of metals and the complexity of discontinuous regions that can lead to the heteroepitaxial formation of complex structures. The non-equilibrium growth techniques of this disclosure can operate with growth parameters far enough away 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 constrained by the equilibrium phase diagram. In one example, the method utilizes an evaporation source material including a beam that strikes the growth surface to be ultra-high purity and substantially charge-neutral. Charged ions may be generated, but these should be kept to a minimum as much as possible.

[0250] 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.

[0251] 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 conduction types. Physical cation vacancies are electron carriers. It can generate holes of type p, and therefore prefers p-type conductivity.

[0252] 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.

[0253] 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.

[0254] 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.

[0255] 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.

[0256] For example, sources 689-692 may include ejection 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 refine 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.

[0257] This deposition method has proven particularly useful in enabling the flexibility to incorporate elemental species into Ga oxide-based and Al oxide-based materials.

[0258] 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.

[0259] 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.

[0260] 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.

[0261] 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.

[0262] 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.

[0263] 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 collectively labeled in this figure as a heterosymmetric crystal structure epitaxy 835. Such crystal growth matching is possible using layers of very different crystal symmetries, if a co-incident shape of the in-plane lattice 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.

[0264] 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. Then, an optional layer 850 can 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 Ga2O3 crystal symmetry type or a monoclinic crystal symmetry type. Then, further growth of layer 850 can be used to form a high-quality relaxed layer with high crystal structure quality. Layers 815, 845 and 850 are... In the figure, the heterosymmetric crystal structure is collectively labeled as epitaxy-855.

[0265] 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.

[0266] 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.

[0267] 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.

[0268] 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.

[0269] 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.

[0270] Remarkably, the (010) and (001) oriented surfaces of monoclinic Ga2O3 can accommodate monoclinic AlGaO3 structures of very high crystal quality. The main limitation of Al% in AlGaO3 is the accumulation of biaxial strain. Careful strain control in this disclosure using AlGaO3 / Ga2O3 superlattices has allowed us to find a limit of Al% < 40%, enabling higher quality films using (001) oriented Ga2O3 substrates. Furthermore, a further example of (010) oriented monoclinic Ga2O3 substrates is the very high-quality lattice matching of MgGa2O4 (111) oriented films with a cubic crystal symmetry structure.

[0271] 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 correspondence lattice matching 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.

[0272] These unique properties provide selective utility for Al2O3 and Ga2O3 crystal symmetric substrates, for example, through the selective use of crystal surface orientation, in LEDs, specifically UVLs. Many advantages are offered in the manufacture of EDs.

[0273] 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.

[0274] Band structure modifier

[0275] 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 photoemission generation through direct electron-hole recombination. Therefore, attention is focused on valence band tuning options to achieve one exemplary UVLED operation.

[0276] Band structure formation due to biaxial strain

[0277] 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.

[0278] 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.

[0279] 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.

[0280] 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, having conduction bands 891 and valence bands 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 conduction bands, for example, referring to the conduction 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

[0281] Conversely, as shown in Figure 900 of Figure 21C, the biaxial tension applied to the unit cell 904 is the band gap 903

number

[0282] Band structure formation due to uniaxial strain

[0283] 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 conduction band 906 and the band gap 908.

[0284] 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.

[0285] 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).

[0286] 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 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 conduction 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 conduction 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 conduction 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.

[0287] 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.

[0288] Formation of band structure due to stress application after growth

[0289] 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.

[0290] Band structure configuration by selection of alloy composition

[0291] 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 conduction 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 type B metal cations 938 and oxygen atoms 939, and has an indirect band structure 935 having a conduction 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.

[0292] 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 it is possible to produce a ternary material 948 having a conduction band 946 and a band gap 949. That is, the atomic species A of material 930 incorporated into the B site of material 940 can increase the valence band dispersion. Using calculations of atomic density functional theory, this concept can be simulated to fully explain the pseudopotential, strain energy, and crystal symmetry of the constituent atoms.

[0293] 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.

[0294] Band structure configuration by digital alloy fabrication selection

[0295] While ternary alloy compositions such as AlGaO3 are desirable, an equivalent method for producing ternary alloys involves the use of digital alloy formation, which utilizes a superlattice (SL) constructed from periodic repetitions 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 about 0.1 to several tens of nm), then, due to the periodicity of the superlattice, "mini-brillianzo" forms within the crystal band structure, as shown in Figure 27A. A "sequence" is formed. In reality, a new periodicity is superimposed on the inherent crystal structure by the formation of a predetermined SL structure. The SL periodicity is usually one-dimensional in the growth direction of epitaxial film formation.

[0296] 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 S L=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.

[0297] 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.

[0298] A common use of SL for constructing optoelectronic devices is disclosed in U.S. Patent No. 10,475,956.

[0299] 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

[0300] Furthermore, further examples of possible SL structures are shown in Figures 27D to 27F.

[0301] 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.

[0302] 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.

[0303] 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 made lattice-matched to (100)-oriented monoclinic Ga2O3. Such an SL is Ga x Ni y Mg z O n It has an effective quaternary composition.

[0304] Band structure of Al-Ga oxides

[0305] 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.

[0306] 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 properties such as carrier mobility, doping, and deflection. In step 1010, it is determined whether a 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 the binary oxide material meets the requirements, this material is selected in step 1045 for the relevant layer of the optoelectronic device. If the 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 the ternary oxide meets the requirements, this material is selected in step 1045 for the relevant layer.

[0307] 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.

[0308] 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 the corundum and monoclinic crystal symmetries due to the offset between the conduction band and the valence band. In this graph, the y-axis represents the electron energy 1051, and the x-axis represents different material types 1053 (Al2O31054, (Ga1Al1)O31055, and Ga2O31056). While 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.

[0309] 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 symmetry systems lack maturity for simulations of both monoclinic and tricgonal 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 .

[0310] Single-crystal aluminum oxide

[0311] 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.

[0312] (a) Corundum symmetric Al2O3

[0313] 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.

[0314] The direct band gap has a maximum value of 10⁶⁸ in the valence band and a minimum value of 10⁶⁹ in the conduction 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.

[0315] (b) Monoclinic symmetric Al2O3

[0316] 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 band. Figure 34A also shows the conduction 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.

[0317] 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.

[0318] 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.

[0319] Single-crystal gallium oxide

[0320] (a) Corundum Symmetric Ga2O3

[0321] 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.

[0322] 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 conduction band 1086 is also shown in Figure 36A.

[0323] 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.

[0324] (b) Monoclinic symmetric Ga2O3

[0325] The crystal structure of monoclinic Ga2O3 (corundum) 1090 is shown in Figure 37. The larger sphere represents Ga atoms 1084, and the smaller sphere represents oxygen atoms 1083. The unit cell 1092 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 conduction band 1096 is also shown in Figure 38A.

[0326] 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.

[0327] ternary aluminum-gallium oxide

[0328] 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.

[0329] (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.

[0330] 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.

[0331] Regularized ternary AlGaO3 alloy

[0332] 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.

[0333] The ability to construct the band structure of optoelectronic devices, specifically UV LEDs, by selecting from bulk metal oxides, ternary compositions, or even still digital alloys, is all considered to be within the scope of this disclosure.

[0334] 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.

[0335] Substrate selection for AlGaO-based UV LEDs

[0336] 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.

[0337] 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.

[0338] The beneficial use of monoclinic Ga2O3 bulk substrates lies in their high Ga% (e.g., about 30-40%), which is limited by strain accumulation. x Ga 1-x The ability to form a 2O3 structure is possible. This allows for the creation 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.

[0339] Other substrates such as MgO(100), MgAl2O4, and MgGa2O4 also use metal oxides. It is suitable for epitaxial growth of VLED structures.

[0340] Selection and action of crystal growth modifiers

[0341] 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 next, 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.

[0342] 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.

[0343] Germanium (Ge)

[0344] 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 in the formula.

[0345] 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.

[0346] 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 caused by the introduction of Ge preferentially increases monoclinic unit cells along the b and c axes while maintaining the a-axis lattice constant, compared to strain-free monoclinic Ga2O3.

[0347] 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.

[0348] When x exceeds 1 / 3, the higher the Ge%, the more the crystal structure changes to a cubic crystal, such as GeGa2O5.

[0349] In some embodiments, Al2O3 and (Al x Ga 1-x It is also possible to incorporate Ge into 2O3.

[0350] 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.

[0351] 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.

[0352] Silicon (Si)

[0353] 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 the dilute Si composition in the formula.

[0354] 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.

[0355] 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 1.50 O 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.

[0356] 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.

[0357] When x exceeds 1 / 3, the higher the Si%, the more the crystal structure becomes cubic, for example, SiGa2O It changes to 5.

[0358] 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).

[0359] 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.

[0360] Magnesium (Mg)

[0361] 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 conduction type. (Al y Ga 1-y In the case of 2O3, y=0.3, the band gap is approximately 6.0 eV, and Mg can incorporate y up to about 0.05-0.1, which can change the host's conduction type from its inherently weak excess electron n-type to excess hole p-type.

[0362] 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.

[0363] 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.

[0364] 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.

[0365] 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.

[0366] 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. 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.

[0367] 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.

[0368] Zinc (Zn)

[0369] 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].

[0370] 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.

[0371] 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.

[0372] 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 bandgap 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 luminescence regions, respectively. Furthermore, bandgap modulation is possible for bandgap-designed structures such as superlattices and quantum wells described herein.

[0373] Nickel (Ni)

[0374] 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 .

[0375] Furthermore, additional quaternary compositions advantageous for tuning the direct bandgap structure are the most common form of the compound: (Mg x Ni 1-x ) z (Al y Ga 1-y ) 2(1-z) O 3-2z , where 0 ≤ x, y, z ≤ 1.

[0376] According to the present disclosure, it has been found that cubic crystal symmetry 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, 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.

[0377] 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 symmetry form (Mg x Ni 1-x ) z (Al y Ga 1-y ) 2(1-z) O 3-2zThis is possible using the non-equilibrium growth method described herein.

[0378] 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 conductivity 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.

[0379] Lantanid

[0380] 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 conducting 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.

[0381] Surprisingly, both theoretically and experimentally, according to this disclosure, (Er x Ga1-x )2O3 and (Er x Al 1-x It has been found that the ternary compound of )2O3 exhibits a cubic crystal symmetry structure with a direct band gap when x is approximately 0.5. The binary erbium oxide Er2O3 is known to have bixbyte crystal symmetry and can be epitaxially formed as a single crystal film on a Si(111) substrate. However, the lattice constants obtained by bixbyte Er2O3 are not readily applicable for seeding epitaxial films of Ga2O3, GaAlO3, and Al2O3. According to this disclosure, it has been 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.

[0382] 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.

[0383] Bismuth (Bi)

[0384] 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 conduction-type properties that generate an appropriate activation hole carrier concentration for the p-type conduction region of UV LED functionality.

[0385] 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.

[0386] Furthermore, in some embodiments, orthorhombic and trigonal morphologies exhibiting unique p-type conductivity and indirect band gaps can be utilized.

[0387] 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 =4.78-4.8eV.

[0388] Palladium (Pd)

[0389] The addition of Pd to Ga2O3, (Ga,Al)O3, and Al2O3 may be used in some embodiments to generate metallic behavior and is applicable to the formation of ohmic contacts. In some embodiments, palladium oxide (PdO) can be used as an in-situ deposited semimetallic ohmic contact for n-type broad bandgap metal oxides due to the compound's inherently low work function (see Figure 9).

[0390] Iridium (Ir)

[0391] 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, (I) for 0 ≤ x ≤ 1.0 r 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.

[0392] Lithium (Li)

[0393] 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.

[0394] 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.

[0395] 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.

[0396] Of particular interest are the relatively small curvature of both valence bands, which suggests a smaller effective hole mass compared to Ga2O3.

[0397] The lattice constants of LiGaO2 are (a=5.09A, b=5.47, c=6.46A), and for LiAlO2 they are (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.

[0398] 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.

[0399] 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 in 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 =8eV direct band between s-like and p-like states Although it forms a Li2NiO2 composition with a gap, the strong d-like state from Ni generates a crystal momentum-independent intermediate bandgap energy state that is continuous across all Brillouin zones.

[0400] Nitrogen and fluorine anion substitution

[0401] 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.

[0402] 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.

[0403] This process can be used for both the corundum and trigonal forms of Ga2O3.

[0404] 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.

[0405] 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.

[0406] 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.

[0407] (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.

[0408] 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.

[0409] 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.

[0410] 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.

[0411] 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*).

[0412] 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 radiated and heated by a filament, and 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.

[0413] 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.

[0414] 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 emitted-heated 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.

[0415] 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.

[0416] Formed by the crucible opening's clausing coefficient and the large mean free path of the UHV. By favorably positioning the ejection cell beam, ballistic transport without collision of ejected species with the substrate surface is ensured. The atomic beam flux from the ejection-type heating source is determined by the Arrhenius behavior of 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.

[0417] 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.

[0418] 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.

[0419] 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 conduction 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.

[0420] Referring again to Figure 44B, the growth method was briefly described. 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 terminated with reactive oxygen adsorbed atoms that form a surface reconstruction containing oxygen atoms.

[0421] 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.

[0422] 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.

[0423] 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.

[0424] 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.

[0425] 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.

[0426] 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.

[0427] 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.

[0428] 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.

[0429] 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 strain-free and self-standing material beyond CLT. This substantially strain-free relaxed ternary layer has an effective in-plane lattice constant a parameterized by the effective Al% composition SL which is. When a first relaxed ternary layer is formed and then another second SL is deposited directly on top of the relaxed layer, then the bilayer pair forming the second SL can 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.

[0430] FIG. 44C shows an exemplary SL 5115 formed directly on a Ga2O3(010)-oriented substrate 5100.

[0431] The bilayer pair constituting SL 5115 is both a monoclinic crystal symmetric Ga2O3 and a 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 small-angle grazing incidence reflectivity of the SL. Ten periods showing very high crystal quality indicating that (Al x Ga 1-x )2O3 has a thickness of <CLT are shown.

[0432] The plurality of narrow SL diffraction peaks 5095 and 5110 indicate a coherently strained film registered with an in-plane lattice constant matching 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.

[0433] [(Al xB Ga 1-xB)The SL containing the bilayer of [2O3 / Ga2O3] has an equivalent Al% defined as follows:

Number

[0434] FIG. 44D further shows further flexibility for directly depositing the ternary monoclinic 5130 alloy (Al

[0435] Ga x Ga 1-x )2O3 on yet another crystal orientation of the monoclinic Ga2O3(001) substrate 5120.

[0436] Again, the best results are obtained by paying attention to the high-quality CMP surface treatment of the cleaved substrate surface. The growth recipe in some embodiments uses in-situ activated oxygen polishing at high temperature (e.g., 700 - 800 °C) using a substrate that is radiation heated through a high-power, oxygen-resistant emissive heater. The SiC heater has the unique property of a high near and far infrared emissivity. The emissivity of the SiC heater almost matches the inherent Ga2O3 absorption characteristics, thus well coupling with the blackbody radiation spectrum shown by the SiC heater. Region 5125 represents the O-terminated process and the homoepitaxial growth of a high-quality Ga2O3 buffer layer. Then, the SL is deposited, and two separate growths with different ternary alloy compositions are shown.

[0437] Shown in Fig. 44D is a coherently strained epitaxial layer of (Al Ga x )2O3 that has a CLT thickness and achieves x of about 15% (5135) and x of about 30% (5140) relative to the (002) substrate peak 5122. Again, the high-quality film is indicated by the presence of thickness interference fringes. 1-x

[0438] 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.

[0439] Clearly, HRXRD 5145 and GIXR 5158 indicate 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 )2O3 / Ga2O3] with a period Δ 0.92 = 8.6 nm is shown.

[0440] 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 indicate that the top NiO film peak 5185 with a thickness of 50 nm has excellent atomic flatness and thickness fringes 5195.

[0441] In one example, the mixing and matching of crystal symmetry types can be favorable for a given material composition that is advantageous for a given function including a UVLED (see Fig. 1), thereby enhancing the flexibility for optimizing the UVLED design. Ni​x O (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 including a UVLED.

[0442] 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.

[0443] Further, a further example of a metal oxide structure is 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 a cubic crystal symmetric form of a Ga2O3 epitaxial layer 5210 (peak 5212 of gamma Ga2O3) that 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.

[0444] First, a prepared clean MgO(100) surface is presented for MgO homoepitaxy. The magnesium source is a valved ejection 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.

[0445] 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 converted to O* The growth temperature was raised to approximately 700°C under protective flux. Subsequently, the Ga source was exposed on the growth surface, and RHEED was observed to show an instantaneous change in surface reconstruction toward the cubic crystal symmetry of the Ga2O3 epitaxial layer 5210. After approximately 10-30 nm of cubic Ga2O3 (also known as the gamma phase), direct observation with RHEED revealed the characteristic monoclinic plane reconstruction of Ga2O3(100), which remained as the most stable crystal structure. A 100 nm Ga2O3(100) aligned film was deposited, and HRXRD5200 and GIXR5220 showed peaks 5214 for betaGa2O3(200) and 5217 for betaGa2O3(400). Such a coincidental agreement of crystal symmetry is rare, but it is very advantageous for UV LED applications.

[0446] 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.

[0447] 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.

[0448] 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, approximately 800 The substrate is heated to °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 is formed and monitored by RHEED, showing excellent crystalline quality and atomically flat layer-by-layer deposition. Subsequently, a 10-period SL is deposited, shown as satellite peaks 5230 and 5240 in HRXRD5225 and GIXR5245 scans. Clearly evident is the pendelosung fringe, which shows excellent coherent growth.

[0449] 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 ) The EK band structure of 2O3 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).

[0450] 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

[0451] 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.

[0452] 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.

[0453] 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. A flux ratio of [φ(Zn)+φ(Ga)]:φ(O*)<1 and a metal beam flux ratio φ(Zn):φ(Ga) are 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 Zn adsorbed atoms.

[0454] 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 conduction 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.

[0455] 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.

[0456] 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.

[0457] Furthermore, we here disclose yet another example in which growth conditions can be adjusted to pre-select the intrinsic crystal symmetry of Ga2O3, namely monoclinic (beta phase) or hexagonal (epsilon or kappa phase).

[0458] Figure 44O shows a specific application of the more general method disclosed in Figure 19.

[0459] A prepared clean surface of a corundum crystal-symmetric sapphire C-plane substrate 5400 is presented for epitaxy.

[0460] 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.

[0461] 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 C-plane Al2O3(0001) oriented substrates for corundum Al2O3(0006) 5465 and Al2O3(0012) 5470. In the case of the top epitaxial film of monoclinic Ga2O3, the diffraction peaks shown at 5445, 5450, 5455, and 5460 represent sharp single-crystal monoclinic Ga2O3(-201), Ga2O3(-204), Ga2O3(-306), and Ga2O3(-408).

[0462] 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 conduction 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.

[0463] Conversely, in the growth process of hexagonal Ga2O3 peaks 5425, 5430, 5435, and 5440, sharp single-crystal hexagonal crystal symmetric Ga2O3(002), Ga2O3(00 4) Represents Ga2O3(006) and Ga2O3(008).

[0464] Hexagonal crystal symmetry Ga2O3 and hexagonal (Al x Ga 1-x The importance of achieving 2O3 is shown in Figure 44Q.

[0465] The energy band structure 5475 indicates that the extreme values ​​of both the conduction 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.

[0466] 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.

[0467] 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.

[0468] 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.

[0469] 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, it is possible to form an M-plane oriented AlGaO3 film on an M-plane sapphire. The GIXR thickness oscillation 5535 indicates 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).

[0470] To complete, in accordance with the present disclosure, various metal oxides have also been found to be usable, even the most technically mature semiconductor substrate, i.e., silicon. For example, bulk Ga2O3 substrates are desirable for their crystallographic and electronic properties, but they are still more expensive to manufacture than single crystal substrates and, for example, cannot be scaled as easily to large wafer diameter substrates such as 450 mm in diameter as Si.

[0471] Therefore, embodiments include forming a functional electronic Ga2O3 film directly on silicon. For this purpose, a process has been developed specifically for this application.

[0472] Referring now to FIG. 44S, the results of a process experimentally developed to deposit a monoclinic Ga2O3 film on a large area silicon substrate are shown.

[0473] A single crystal high quality monoclinic Ga2O3 epi-layer 5565 is formed on a cubic transition layer 5570 containing ternary (Ga 1-x Er x )2O3. The transition layer is deposited using a composition grading that can be abrupt or continuous. The transition layer is [(Ga Er 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.

[0474] 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.

[0475] 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.

[0476] 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 is (Al x Ga 1-x )Al%x and (Al in 2O3 1-y Ga y It was reiterated that the range of Ga%y in 2O3 can be addressed by corundum crystal symmetric composition.

[0477] Here, refer to the examples in Figures 44T to 44X.

[0478] Figure 44T discloses high-quality single-crystal epitaxy of corundum Ga2O3(110) oriented films 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 A ternary film of 2O3 can be grown across the entire alloy range, where 0 ≤ x ≤ 1. Ga2O3 can be grown up to CLT of approximately 45-80 nm, and CLT can be dramatically increased by the introduction of Al to form a ternary (Al x Ga 1-x ) Forms 2O3.

[0479] Homoepitaxial growth of corundum Al2O3 is possible within a surprisingly wide growth window range. Corundum AlGaO3 can be grown from room temperature up to approximately 750°C. However, all growths require oxygen-rich growth conditions, i.e., the activated oxygen (i.e., atomic oxygen) flux well exceeding the total metal flux. Corundum crystal symmetric Ga2O3 films are shown in HRXRD5575 and GIXR5605 scans of two separate growths of films of different thicknesses on an A-plane Al2O3 substrate. The substrate surface at 5590 (corresponding to peak 5592) is oriented in the (11-20) plane and polished at a high temperature of approximately 800°C.

[0480] While the growth temperature is lowered to an optimal range of 450-600°C, such as 500°C, activated oxygen Polishing is maintained. Then, Al2O3 buffer 5595 is optionally deposited at 10 - 100 nm, and then ternary (Al x Ga 1-x )2O3 epi-layer 5600 is formed by co-deposition 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.

[0481] Both Pendellösung interference fringes of HRXRD and GIXR show excellent coherent growth, and transmission electron microscopy (TEM) confirms that defect densities of less than 10 7 cm -3 are possible.

[0482] Colloidal 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.

[0483] Further other methods are possible to further improve the CLT of binary Ga2O3 films on A-plane Al2O3. For example, during the high-temperature O polishing step of 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 activated 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 colloidal (Al x Ga 1-x )2O3 template layer with 0 < x < 1. Growth can be interrupted or continued while the substrate temperature is decreasing 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.

[0484] Establishing the unique properties of the A-plane and referring to the surface energy trends disclosed in FIG. 20B, it is shown that a bandgap-modulated superlattice structure is also possible.

[0485] 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

[0486] 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.

[0487] 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.

[0488] 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.

[0489] Furthermore, the further applications of corundum film growth can be demonstrated on yet another advantageous Al2O3 crystal surface, namely the R-plane (1-102).

[0490] 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.

[0491] 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.

[0492] Figure 44X shows an example of a high-quality superlattice structure possible on an R-plane Al2O3(1-102) oriented substrate.

[0493] HRXRD5690 and GIXR5710 are shown as examples of SLs epitaxially formed on an R-face Al2O3(1-102) substrate 5705 (corresponding to peak 5707).

[0494] 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.

[0495] Such highly coherent and vastly different bandgap materials are used to create epitaxial SLs with abrupt discontinuities at the interface, such as UV LEDs. For applications to electronic devices, it can be used to form quantum confinement structures, as disclosed herein.

[0496] The energy discontinuities of the conduction band and valence band available at the Al2O3 / Ga2O3 heterointerface with corundum crystal symmetry (R3c) are as follows:

number

[0497] Furthermore, the band offset of the monoclinic crystal symmetric (C2m) heterointerface is as follows:

number

[0498] Some embodiments also include generating a potential energy discontinuity by creating a Ga2O3 layer with a sudden change in crystal symmetry.

[0499] 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

[0500] These band offsets are sufficient to generate quantum confinement structures, as will be explained below.

[0501] 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.

[0502] 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.

[0503] Cubic MgAl2O4 and Mg x Al 2(1-x) O 3-2x Interest in the three-part structure is, This is due to the possibility of a direct and large band gap.

[0504] 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 conduction band 5750 and the valence band 5755.

[0505] Some embodiments also involve directly growing Ga2O3 on an aluminum lanthanum oxide (LaAlO3) (001) substrate.

[0506] 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.

[0507] 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 conduction-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 ) comprises multiple quantum wells (MQW) or superlattice 1240 formed using periodic repetitions of O3, the barrier layer comprising a larger bandgap composition 1220 and the well layer comprising a narrower bandgap composition 1225.

[0508] 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.

[0509] 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 conduction 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.

[0510] 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 ) containing 2O3 Alternatively, it is configured for a combination of unintentional doping layers. 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.

[0511] Ohmic contact metals 1260 and 1280 are also shown. Conduction 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.

[0512] 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.

[0513] 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 the 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 first occurrence of optical activity as we move toward shorter wavelengths is the n=1 exciton peak 1320, determined by the MQW configuration.

[0514] 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.

[0515] 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).

[0516] 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 conduction potential well and valence potential well. The absorption spectra represent the generation of electrons and holes in the quantized state of the MQW in the resonant absorption of incident photons.

[0517] 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, in addition to the energy separation of quantization levels within the potential well relative to the conduction and valence band edges, generates photons with energy approximately equal to the energy of the band gap of the layer acting as a potential well with a direct energy gap. Therefore, the emission / absorption spectrum shows the lowest energy resonance peak, which indicates the primary emission wavelength of the UV LED. It is designed to achieve the desired operating wavelength of the device.

[0518] 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 conduction 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.

[0519] 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.

[0520] 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.

[0521] X-ray diffraction (XRD) is one of the most powerful tools available in crystal growth analysis to directly confirm crystal quality and crystal symmetry. Figures 56 and 57 show two-dimensional XRD data for exemplary materials of ternary AlGaO3 and binary Al2O3 / Ga2O3 superlattices. Both structures are pseudomorphically deposited on corundum crystal-symmetric substrates with A-plane oriented surfaces.

[0522] 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.

[0523] 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.

[0524] 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).

[0525] 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 valence band edge, the effective refractive index is governed by the Kramers-Kronig relationship.

[0526] 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).

[0527] 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.

[0528] 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 length of the slab 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.

[0529] Some embodiments implement semiconductor cavities contained within vertical structures 110 (see, for example, Figure 2A) having submicron length scales. This is due to the desire to localize electron-hole recombination to a narrow region. Limiting the physical thickness of the slab where carrier recombination occurs and light emission is generated 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.

[0530] 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.

[0531] 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.

[0532] 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.

[0533] 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 is advantageous. This can be achieved using the metal oxide compositions described in this disclosure, which can be pre-selected to exhibit a specific structure.

[0534] 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.

[0535] Figure 60 schematically illustrates an embodiment of an optical cavity having HR1900, a gain medium 1905 substantially filling 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 tuned 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. 1The harmonics (standing wave 1930) appear at nodes 1940 and 1950, as shown in the diagram.

[0536] Figure 61 shows output wavelengths 1960 and 1965 from a cavity having an energy flow of 1970. 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 a gain medium within the optical cavity as shown in Figure 62.

[0537] 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.

[0538] 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.

[0539] 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.

[0540] Here, we focus on the design of an optical gain medium for application to UVLAS using the metal oxide composition described in this disclosure.

[0541] 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 broad 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).

[0542] By selecting the appropriate material, conduction band offset and valence band offset as 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 conduction band 2005 and valence band 2010 along the growth direction z are shown.

[0543] Figure 64A shows LQW This shows that a QW with a thickness of 5 nm (2015) generates quantized energy states 2025 and 2035 for the allowed electron and hole states in the conduction band and valence band, respectively. The lowest quantized electronic state 2020 and the highest quantized valence state 2030 participate in the spatial recombination process, generating photons with energy equal to 2040.

[0544] 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 electronic state 2055 and the highest quantized valence state 2060 participate in a spatial recombination process, generating a photon with an energy equal to 2065.

[0545] Further reducing the thickness of QW yields the spatial band structures shown in Figures 65A and 65B. Figure 65A shows L QW This 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 high...

Claims

1. A semiconductor structure comprising an epitaxial oxide heterostructure, circuit board and (Ni ｘ１ Mg ｙ１ Zn １－ｘ１－ｙ１ ) (Al ｑ１ Ga １－ｑ１ ) ２ O ４ A first epitaxial oxide layer containing (wherein the formula 0 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 1 and 0 ≤ q1 ≤ 1), (Ni ｘ２ Mg ｙ２ Zn １－ｘ２－ｙ２ )(Al ｑ２ Ga １－ｑ２ ) ２ O ４ (where 0 ≦ x2 ≦ 1, 0 ≦ y2 ≦ 1 and 0 ≦ q2 ≦ 1), and a second epitaxial oxide layer At least one condition selected from x1 ≠ x2, y1 ≠ y2, and q1 ≠ q2 is satisfied. The aforementioned semiconductor structure.

2. The substrate is MgO, LiF, or MgAl ２ O ４ The semiconductor structure according to claim 1, including the above.

3. The first epitaxial oxide layer is MgAl ２ O ４ A semiconductor structure according to any one of claims 1 to 2, including the semiconductor structure described in any one of claims 1 to 2.

4. The second epitaxial oxide layer is NiAl ２ O ４ A semiconductor structure according to any one of claims 1 to 3, including the above.

5. The first epitaxial oxide layer is (Mg ｙ１ Zn １－ｙ１ ) Al ２ O ４ The second epitaxial oxide layer includes (Ni ｘ１ Zn １－ｘ１ ) Al ２ O ４ A semiconductor structure according to any one of claims 1 to 2, including the semiconductor structure described in any one of claims 1 to 2.

6. The semiconductor structure according to any one of claims 1 to 5, wherein at least one of the first and second epitaxial oxide layers has cubic symmetry.

7. The semiconductor structure according to any one of claims 1 to 6, wherein at least one of the first and second epitaxial oxide layers is distorted.

8. The semiconductor structure according to any one of claims 1 to 7, wherein at least one of the first and second epitaxial oxide layers is doped in an n-type or p-type manner.

9. The semiconductor structure according to any one of claims 1 to 8, wherein the first and second epitaxial oxide layers are layers of a superlattice unit cell.

10. The semiconductor structure according to any one of claims 1 to 8, wherein the first and second epitaxial oxide layers are layers of the chirp layer that include alternating layers whose thickness changes throughout the entire chirp layer.

11. A light-emitting diode (LED) comprising the semiconductor structure described in any one of claims 1 to 10, which emits light with a wavelength of 150 nm to 280 nm.

12. A laser comprising the semiconductor structure described in any one of claims 1 to 10, which emits light with a wavelength of 150 nm to 280 nm.

13. A radio frequency (RF) switch comprising the semiconductor structure according to any one of claims 1 to 10.

14. A high electron-mobility transistor (HEMT) comprising the semiconductor structure described in any one of claims 1 to 10.

15. A semiconductor structure comprising an epitaxial oxide heterostructure, circuit board and (Ni ｘ１ Mg ｙ１ Zn １－ｘ１－ｙ１ ) ２ GeO ４ A first epitaxial oxide layer containing (wherein 0 ≤ x1 ≤ 1 and 0 ≤ y1 ≤ 1), (Ni ｘ２ Mg ｙ２ Zn １－ｘ２－ｙ２ ) ２ GeO ４ It includes a second epitaxial oxide layer (wherein the formula 0 ≤ x² ≤ 1 and 0 ≤ y² ≤ 1), x1 ≠ x2 and y1 = y2, x1 = x2 and y1 ≠ y2, or x1 ≠ x2 and y1 ≠ y2. The aforementioned semiconductor structure.

16. The substrate is MgO, LiF, or MgAl ２ O ４ The semiconductor structure according to claim 15, including the above.

17. The first epitaxial oxide layer is Ni ２ GeO ４ A semiconductor structure according to any one of claims 15 to 16, including the semiconductor structure described in any one of claims 15 to 16.

18. The second epitaxial oxide layer is Mg ２ GeO ４ A semiconductor structure according to any one of claims 15 to 17, including the above.

19. The first epitaxial oxide layer is (Ni ｘ１ Mg ｙ１ ) ２ GeO ４ The second epitaxial oxide layer includes (Mg ｙ１ Zn １－ｘ１－ｙ１ ) ２ GeO ４ A semiconductor structure according to any one of claims 15 to 16, including the semiconductor structure described in any one of claims 15 to 16.

20. The semiconductor structure according to any one of claims 15 to 19, wherein at least one of the first and second epitaxial oxide layers has cubic symmetry.

21. The semiconductor structure according to any one of claims 15 to 20, wherein at least one of the first and second epitaxial oxide layers is distorted.

22. The semiconductor structure according to any one of claims 15 to 21, wherein at least one of the first and second epitaxial oxide layers is doped in an n-type or p-type manner.

23. The semiconductor structure according to any one of claims 15 to 22, wherein the first and second epitaxial oxide layers are layers of a superlattice unit cell.

24. The semiconductor structure according to any one of claims 15 to 22, wherein the first and second epitaxial oxide layers are layers of the chirp layer that include alternating layers whose thickness varies throughout the entire chirp layer.

25. A light-emitting diode (LED) comprising the semiconductor structure described in any one of claims 15 to 24, which emits light with a wavelength of 150 nm to 280 nm.

26. A laser comprising the semiconductor structure described in any one of claims 15 to 24, which emits light with a wavelength of 150 nm to 280 nm.

27. A radio frequency (RF) switch comprising the semiconductor structure described in any one of claims 15 to 24 blood.

28. A high electron-mobility transistor (HEMT) comprising the semiconductor structure described in any one of claims 15 to 24.

29. A semiconductor structure comprising an epitaxial oxide heterostructure, circuit board and (Mg ｘ１ Zn １－ｘ１ ) (Al ｙ１ Ga １－ｙ１ ) ２ O ４ A first epitaxial oxide layer containing (wherein 0 ≤ x1 ≤ 1 and 0 ≤ y1 ≤ 1), (Ni ｘ２ Mg ｙ２ Zn １－ｘ２－ｙ２ ) ２ GeO ４ A second epitaxial oxide layer (wherein the formula 0 ≤ x² ≤ 1 and 0 ≤ y² ≤ 1) is included, The aforementioned semiconductor structure.

30. The substrate is MgO, LiF, or MgAl ２ O ４ The semiconductor structure according to claim 29, including the semiconductor structure described in claim 29.

31. The first epitaxial oxide layer is MgGa ２ O ４ or MgAl ２ O ４ A semiconductor structure according to any one of claims 29 to 30, including the above.

32. The second epitaxial oxide layer is Ni ２ GeO ４ or Mg ２ GeO ４ A semiconductor structure according to any one of claims 29 to 31, including the above.

33. The first epitaxial oxide layer is (Mg ｘ１ ) (Al ｙ１ Ga １－ｙ１ ) ２ O ４ The second epitaxial oxide layer includes (Ni ｘ２ Mg ｙ２ ) ２ GeO ４ A semiconductor structure according to any one of claims 29 to 30, including the above.

34. The semiconductor structure according to any one of claims 29 to 33, wherein at least one of the first and second epitaxial oxide layers has cubic symmetry.

35. The semiconductor structure according to any one of claims 29 to 34, wherein at least one of the first and second epitaxial oxide layers is distorted.

36. The semiconductor structure according to any one of claims 29 to 35, wherein at least one of the first and second epitaxial oxide layers is doped in an n-type or p-type manner.

37. The semiconductor structure according to any one of claims 29 to 36, wherein the first and second epitaxial oxide layers are layers of a superlattice unit cell.

38. The semiconductor structure according to any one of claims 29 to 36, wherein the first and second epitaxial oxide layers are layers of the chirp layer that include alternating layers whose thickness changes throughout the entire chirp layer.

39. A light-emitting diode (LED) comprising the semiconductor structure described in any one of claims 29 to 38, which emits light with a wavelength of 150 nm to 280 nm.

40. A laser comprising the semiconductor structure described in any one of claims 29 to 38, which emits light with a wavelength of 150 nm to 280 nm.

41. A radio frequency (RF) switch comprising the semiconductor structure described in any one of claims 29 to 38.

42. A high electron-mobility transistor (HEMT) comprising the semiconductor structure described in any one of claims 29 to 38.

43. A semiconductor structure comprising an epitaxial oxide heterostructure, circuit board and A first epitaxial oxide layer containing MgO, (Ni ｘ１ Mg ｙ１ Zn １－ｘ１－ｙ１ ) (Al ｑ１ Ga １－ｑ１ ) ２ O ４ A second epitaxial oxide layer (wherein the formula 0 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 1, and 0 ≤ q1 ≤ 1) is included. The aforementioned semiconductor structure.

44. The substrate is MgO, LiF, or MgAl ２ O ４ The semiconductor structure according to claim 43, comprising the same.

45. The second epitaxial oxide layer is MgNi ２ O ４ Or NiAl ２ O ４ A semiconductor structure according to any one of claims 43 to 44, including the above.

46. The second epitaxial oxide layer contains (Ni ｘ１ Mg ｙ１ )(Al ｑ１ Ga １－ｑ１ ) ２ O ４ and is the semiconductor structure according to any one of claims 43 to 44.

47. The semiconductor structure according to any one of claims 43 to 46, wherein at least one of the first and second epitaxial oxide layers has cubic symmetry.

48. The semiconductor structure according to any one of claims 43 to 47, wherein at least one of the first and second epitaxial oxide layers is distorted.

49. The semiconductor structure according to any one of claims 43 to 48, wherein at least one of the first and second epitaxial oxide layers is doped in an n-type or p-type manner.

50. The semiconductor structure according to any one of claims 43 to 49, wherein the first and second epitaxial oxide layers are layers of a superlattice unit cell.

51. The semiconductor structure according to any one of claims 43 to 49, wherein the first and second epitaxial oxide layers are layers of the chirp layer that include alternating layers whose thickness changes throughout the entire chirp layer.

52. A light-emitting diode (LED) comprising the semiconductor structure described in any one of claims 43 to 51, which emits light with a wavelength of 150 nm to 280 nm.

53. A laser comprising the semiconductor structure described in any one of claims 43 to 51, which emits light with a wavelength of 150 nm to 280 nm.

54. A radio frequency (RF) switch comprising the semiconductor structure described in any one of claims 43 to 51.

55. A high electron-mobility transistor (HEMT) comprising the semiconductor structure described in any one of claims 43 to 51.

56. A semiconductor structure comprising an epitaxial oxide heterostructure, circuit board and A first epitaxial oxide layer containing MgO, (Ni ｘ２ Mg ｙ２ Zn １－ｘ２－ｙ２ ) ２ GeO ４ A second epitaxial oxide layer (wherein the formula 0 ≤ x² ≤ 1 and 0 ≤ y² ≤ 1) is included, The aforementioned semiconductor structure.

57. The substrate is MgO, LiF, or MgAl ２ O ４ The semiconductor structure according to claim 56, including the above.

58. The second epitaxial oxide layer is Ni ２ GeO ４ or Mg ２ GeO ４ A semiconductor structure according to any one of claims 56 to 57, including the semiconductor structure described in any one of claims 56 to 57.

59. The second epitaxial oxide layer is (Ni ｘ２ Mg ｙ２ ) ２ GeO ４ A semiconductor structure according to any one of claims 56 to 57, including the semiconductor structure described in any one of claims 56 to 57.

60. The semiconductor structure according to any one of claims 56 to 59, wherein at least one of the first and second epitaxial oxide layers has cubic symmetry.

61. The semiconductor structure according to any one of claims 56 to 60, wherein at least one of the first and second epitaxial oxide layers is distorted.

62. The semiconductor structure according to any one of claims 56 to 61, wherein at least one of the first and second epitaxial oxide layers is doped in an n-type or p-type manner.

63. The semiconductor structure according to any one of claims 56 to 62, wherein the first and second epitaxial oxide layers are layers of a superlattice unit cell.

64. The semiconductor structure according to any one of claims 56 to 62, wherein the first and second epitaxial oxide layers are layers of the chirp layer that include alternating layers whose thickness varies throughout the entire chirp layer.

65. A light-emitting diode (LED) comprising the semiconductor structure described in any one of claims 56 to 64, which emits light with a wavelength of 150 nm to 280 nm.

66. A laser comprising the semiconductor structure described in any one of claims 56 to 64, which emits light with a wavelength of 150 nm to 280 nm.

67. A radio frequency (RF) switch comprising the semiconductor structure described in any one of claims 56 to 64.

68. A high electron-mobility transistor (HEMT) comprising the semiconductor structure described in any one of claims 56 to 64.

69. A semiconductor structure comprising an epitaxial oxide heterostructure, circuit board and Li(Al ｘ１ Ga １－ｘ１ ) O ２ A first epitaxial oxide layer containing (where 0 ≤ x 1 ≤ 1 in the formula), (Al ｘ２ Ga １－ｘ２ ) ２ O ３ A second epitaxial oxide layer containing (wherein the formula 0 ≤ x² ≤ 1) The aforementioned semiconductor structure.

70. The substrate is LiGaO ２ (001), LiAlO ２ (001), AlN(110), or SiO ２ The semiconductor structure according to claim 69, comprising (100).

71. The semiconductor structure according to claim 69, wherein the substrate includes a crystalline material and an Al(111) template layer.

72. The first epitaxial oxide layer is LiGaO ２ A semiconductor structure according to any one of claims 69 to 71, including the above.

73. The second epitaxial oxide layer is LiAlO ２ A semiconductor structure according to any one of claims 69 to 72, including the semiconductor structure described in any one of claims 69 to 72.

74. The semiconductor structure according to any one of claims 69 to 73, wherein at least one of the first and second epitaxial oxide layers has cubic symmetry.

75. The semiconductor structure according to any one of claims 69 to 74, wherein at least one of the first and second epitaxial oxide layers is distorted.

76. The semiconductor structure according to any one of claims 69 to 75, wherein at least one of the first and second epitaxial oxide layers is doped in an n-type or p-type manner.

77. The semiconductor structure according to any one of claims 69 to 76, wherein the first and second epitaxial oxide layers are layers of a superlattice unit cell.

78. The semiconductor structure according to any one of claims 69 to 77, wherein the first and second epitaxial oxide layers are layers of the chirp layer that include alternating layers whose thickness changes throughout the entire chirp layer.

79. A light-emitting diode (LED) comprising the semiconductor structure described in any one of claims 69 to 78, which emits light with a wavelength of 150 nm to 280 nm.

80. A laser comprising the semiconductor structure described in any one of claims 69 to 78, which emits light with a wavelength of 150 nm to 280 nm.

81. A radio frequency (RF) switch comprising the semiconductor structure described in any one of claims 69 to 78.

82. A high electron-mobility transistor (HEMT) comprising the semiconductor structure described in any one of claims 69 to 78.

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