Light emitting device based on metal oxide semiconductor

Abstract

Disclosed is an optoelectronic semiconductor light emitting device configured to emit light having a wavelength in a range of about 150 nm to about 425 nm. In embodiments, the device includes a substrate having at least one epitaxial semiconductor layer disposed thereon, wherein each of the one or more epitaxial semiconductor layers comprises a metal oxide. Also disclosed is an optoelectronic semiconductor device for generating light of a predetermined wavelength, the optoelectronic semiconductor device comprising a substrate and an optical emission region. The optical emission region has an optical emission region band structure configured for generating light of the predetermined wavelength and includes one or more epitaxial metal oxide layers supported by the substrate.

Description

[0001] Related applications

[0002] This application claims priority to U.S. non-provisional patent application No. 16 / 990,349, filed August 11, 2020, entitled “Metal Oxide Semiconductor-Based Light Emitting Device,” and Australian provisional patent application No. 2020901513, filed May 11, 2020, entitled “Metal Oxide Semiconductor Based Light Emitting Device,” the contents of which are hereby incorporated by reference in their entirety.

[0003] This application references the following disclosure, the entire contents of which are hereby incorporated by reference:

[0004] • U.S. Patent No. 9,412,911, filed August 9, 2016, entitled “OPTICAL TUNING OF LIGHT EMITTINGSEMICONDUCTOR JUNCTIONS” and assigned to the applicant of this application;

[0005] • U.S. Patent No. 9,691,938, filed on June 27, 2017, entitled “Advanced Electronic Device Structures Using Semiconductor Structures and Superlattices” and assigned to the applicant of this application;

[0006] • U.S. Patent No. 10,475,956, filed November 12, 2019, entitled “OPTOELECTRONIC DEVICE” and assigned to the applicant of this application; and

[0007] The contents of each of the above applications are explicitly incorporated in their entirety by reference. Background Technology

[0008] Ultraviolet light-emitting devices (UVLEDs) have numerous applications in medicine, medical diagnostics, water purification, food processing, sterilization, aseptic packaging, and deep submicron lithography. They also enable emerging applications in biosensing, communications, pharmaceutical processes, and materials manufacturing by delivering extremely short wavelength light sources in small, lightweight packages with high electrical conversion efficiency, such as UVLEDs.

[0009] Generally, highly efficient electro-optic conversion from electrical energy to discrete wavelengths of light has been achieved using custom semiconductors that possess the properties necessary for the spatial recombination of electrons and hole charge carriers to emit light of the desired wavelengths. In applications requiring UV light, UV LEDs have been developed that utilize almost exclusively gallium indium aluminum nitride (GaInAlN) compositions forming wurtzite-type crystal structures.

[0010] Group III nitrides have been used in semiconductor-based UV LEDs, which are essentially based on heterojunction pin diodes to generate light in the UVC wavelength band (i.e., wavelengths between approximately 200 nm and 280 nm). Unfortunately, the efficiency and output optical power in the UVC region appear to be limited by the inherently low crystallinity of the AlInGaN epitaxial deposits, which is primarily due to the lack of a natural substrate such as AlN.

[0011] Sapphire (corundum Al₂O₃) has been proposed as a compromise starting surface crystal for heterogeneous seeding of two very different material systems. However, there is a significant structural mismatch between sapphire crystals and group III nitrides. This lattice and crystal symmetry mismatch results in an extremely high density of unfavorable crystallization defects, which severely impairs the final efficiency of group III nitride-based UVLEDs. Even if this defect density could be reduced by several orders of magnitude, AlN, the material with the highest bandgap, limits UVC operation to approximately 215 nm, and the output power drops sharply as the wavelength decreases below 280 nm. Summary of the Invention

[0012] In some embodiments, a photoelectric semiconductor light-emitting device includes a substrate; and a plurality of epitaxial semiconductor layers disposed on the substrate. Each of the epitaxial semiconductor layers comprises a metal oxide. The photoelectric semiconductor light-emitting device is configured to emit light having a wavelength in the range of 150 nm to 425 nm.

[0013] In some embodiments, a photoelectric semiconductor device for generating light of a predetermined wavelength includes a substrate and an optical emitting region. The optical emitting region has an optical emitting region bandgap structure configured to generate light of the predetermined wavelength. The optical emitting region has an epitaxial metal oxide layer supported by the substrate, wherein the epitaxial metal oxide layer has an optical emitting region bandgap energy capable of generating light of the predetermined wavelength. Attached Figure Description

[0014] The embodiments of this disclosure will be discussed with reference to the accompanying drawings, in which:

[0015] Figure 1This is a process flow diagram for constructing a metal-oxide-semiconductor-based LED according to an exemplary embodiment of the present disclosure;

[0016] Figure 2A and Figure 2B Two types of LED devices based on vertical optical confinement and emission and waveguide optical confinement and emission, respectively, according to exemplary embodiments of the present disclosure, are schematically depicted.

[0017] Figures 3A to 3E This is a schematic diagram of different LED device configurations including multiple areas according to an exemplary embodiment of this disclosure;

[0018] Figure 4 The illustration schematically depicts the injection of carriers with opposite charges from physically separated regions to a composite region according to an exemplary embodiment of the present disclosure;

[0019] Figure 5 The illustration shows the possible optical emission direction from the emission region of the LED according to an exemplary embodiment of the present disclosure;

[0020] Figure 6 An aperture is depicted through an opaque region according to an exemplary embodiment of the present disclosure to enable light to be emitted from an LED;

[0021] Figure 7 Exemplary selection criteria for constructing metal-oxide-semiconductor structures according to exemplary embodiments of the present disclosure are shown;

[0022] Figure 8 This is an exemplary process flow diagram for selecting and epitaxially depositing metal oxide structures according to an exemplary embodiment of the present disclosure;

[0023] Figure 9 It is a summary of the technically relevant semiconductor band gaps that vary with electron affinity, showing the relative band queues;

[0024] Figure 10 This is an exemplary schematic process flow for depositing multiple layers to form multiple regions constituting an LED, according to an exemplary embodiment of the present disclosure;

[0025] Figure 11 The optical bandgap tuning profile of a gallium oxide-based metal-oxide-semiconductor ternary composition according to an exemplary embodiment of the present disclosure is shown.

[0026] Figure 12 The optical bandgap tuning profile of a ternary alloy based on an alumina-metal oxide semiconductor ternary composition according to an exemplary embodiment of the present disclosure;

[0027] Figure 13A and Figure 13B The electron energy of a metal oxide-based optoelectronic semiconductor according to an exemplary embodiment of this disclosure is expressed in terms of crystal momentum, showing a direct band gap ( Figure 13A ) and indirect band gap ( Figure 13B );

[0028] Figures 13C to 13E The electron energy pair of the crystal momentum is represented according to an exemplary embodiment of the present disclosure, showing the permissible optical emission and absorption transitions at k=0 relative to the symmetry axis of the Ga2O3 monoclinic crystal;

[0029] Figure 14A and Figure 14B The sequential deposition of multiple heterogeneous metal-oxide-semiconductor layers with different crystal symmetry types according to an exemplary embodiment of the present disclosure is depicted for embedding into an optical emission region;

[0030] Figure 15 This is a schematic representation of an atomic deposition tool for producing a multilayer metal oxide semiconductor film comprising a variety of material compositions, according to an exemplary embodiment of the present disclosure;

[0031] Figure 16 This is a representation of the sequential deposition of layers and regions having a similar crystal symmetry type that matches the substrate, according to an exemplary embodiment of the present disclosure;

[0032] Figure 17 Sequential deposition of a region having a crystal symmetry different from the underlying first surface of the substrate, according to an exemplary embodiment of the present disclosure, wherein surface modification of the substrate is shown;

[0033] Figure 18 Depicts a buffer layer, deposited with the same crystal symmetry as the underlying substrate, according to an exemplary embodiment of the present disclosure, in order to enable subsequent heterogeneous symmetry deposition of the oxide material;

[0034] Figure 19 The structure described in the exemplary embodiment of this disclosure includes a plurality of heterogeneous symmetrical regions deposited sequentially according to the growth direction;

[0035] Figure 20A The illustration shows a crystal symmetry transition region connecting two types of deposited crystal symmetry according to an exemplary embodiment of the present disclosure;

[0036] Figure 20B The illustration shows how the specific crystal surface energy varies with crystal surface orientation for the cases of corundum-sapphire and monoclinic gallium single-crystal oxide materials according to exemplary embodiments of the present disclosure;

[0037] Figures 21A to 21CThe electronic energy configuration or band structure of a metal-oxide-semiconductor according to an exemplary embodiment of the present disclosure is schematically depicted under the influence of biaxial strain applied to a crystal cell.

[0038] Figures 22A to 22B The variation of the strip structure of a metal-oxide-semiconductor according to an exemplary embodiment of the present disclosure under the influence of uniaxial strain applied to a crystal cell is schematically depicted.

[0039] Figures 23A to 23C The effect of varying uniaxial strain applied to a crystal cell on the band structure of monoclinic gallium oxide according to an exemplary embodiment of the present disclosure is shown.

[0040] Figure 24A and Figure 24B The exemplary embodiments of the present disclosure depict two different binary metal oxide Ek-electronic configurations: one with a wide direct bandgap and the other with a narrow indirect bandgap.

[0041] Figures 25A to 25C This illustrates the valence band mixing effect of two binary different metal oxide materials in the co-formation of a ternary metal oxide alloy according to an exemplary embodiment of the present disclosure;

[0042] Figure 26 The energy originating from the dominant valence band of the two bulk metal-oxide-semiconductor materials up to the first Brillouin zone is schematically depicted as a portion of the crystal momentum according to an exemplary embodiment of the present disclosure.

[0043] Figures 27A to 27B The effect of a superlattice (SL) on the Ek configuration of a layered structure in one dimension is shown, the superlattice having a superlattice period equal to approximately twice the bulk lattice constant of the host metal-oxide-semiconductor, which depicts the formation of a superlattice Brillouin zone with an artificial bandgap opened at the center of the zone according to an exemplary embodiment of the present disclosure.

[0044] Figure 27C The illustration shows a bilayer binary superlattice according to an exemplary embodiment of the present disclosure, comprising a plurality of thin epitaxial layers of Al₂O₃ and Ga₂O₃ repeating with a fixed cell period, wherein a digital alloy simulates an equivalent ternary Al₂O₃ based on the component layer thickness ratio of the superlattice period. x Ga 1-x O3 body alloy;

[0045] Figure 27D Another bilayer binary superlattice according to an exemplary embodiment of the present disclosure is shown, comprising multiple thin epitaxial layers of NiO and Ga2O3 repeating with a fixed cell period, wherein a digital alloy simulates an equivalent ternary (NiO) based on the composition layer thickness ratio of the superlattice period. x (Ga2O3)1-x body alloy;

[0046] Figure 27E This illustration shows another ternary binary superlattice according to an exemplary embodiment of the present disclosure, comprising multiple thin epitaxial layers of MgO and NiO repeating with a fixed cell period, wherein a digital alloy simulates an equivalent ternary alloy (NiO) based on the component layer thickness ratio of the superlattice period. x (MgO) 1-x , and wherein the binary metal oxides used for repeating unit cells are each selected to vary in thickness from 1 to 10 unit cells to collectively include the unit cells of SL;

[0047] Figure 27F This illustration shows yet another possible four-material binary superlattice according to an exemplary embodiment of the present disclosure, comprising multiple thin epitaxial layers of MgO, NiO, and Ga2O3 repeating with a fixed cell period, wherein a digital alloy simulates an equivalent quaternary alloy (NiO) based on the component layer thickness ratio of the superlattice period. x (Ga2O3) y (MgO) z The binary metal oxides used for repeating unit cells are each selected to vary in thickness from 1 to 10 unit cells to include SL unit cells.

[0048] Figure 28 A diagram showing ternary metal oxide combinations that can be used in the formation of an optoelectronic device according to various exemplary embodiments of the present disclosure;

[0049] Figure 29 This is an exemplary design flowchart for tuning and constructing the optoelectronic functionality of an LED region according to an exemplary embodiment of this disclosure;

[0050] Figure 30 The diagram illustrates heterojunction bandgap sequences of binary Al2O3, ternary alloy (Al,Ga)O3, and binary Ga2O3 semiconducting oxides according to exemplary embodiments of the present disclosure.

[0051] Figure 31 The illustration shows a 3D crystal cell for calculating the Ek-band structure of corundum symmetric crystal structure (α phase) Al2O3 according to an exemplary embodiment of the present disclosure;

[0052] Figure 32A and Figure 32B The calculated energy-momentum configuration of α-Al₂O₃ near the center of the Brillouin zone is shown according to an exemplary embodiment of the present disclosure;

[0053] Figure 33A 3D crystal cell for calculating the Ek band structure of a monoclinic symmetric crystal structure Al2O3 is shown according to an exemplary embodiment of the present disclosure.

[0054] Figure 34A and Figure 34B The calculated energy-momentum configuration of θ-Al2O3 near the center of the Brillouin zone is shown according to an exemplary embodiment of the present disclosure;

[0055] Figure 35 A 3D crystal cell for calculating the Ek-band structure of corundum symmetric crystal structure (α phase) Ga2O3 is shown according to an exemplary embodiment of the present disclosure.

[0056] Figure 36A and Figure 36B The calculated energy-momentum configuration of corundum α-Ga2O3 near the center of the Brillouin zone is shown according to an exemplary embodiment of the present disclosure.

[0057] Figure 37 A 3D crystal cell of a monoclinic symmetric crystal structure (β phase) Ga2O3 for calculating the Ek band structure is shown according to an exemplary embodiment of the present disclosure.

[0058] Figure 38A and Figure 38B The calculated energy-momentum configuration of β-Ga2O3 near the center of the Brillouin zone is shown according to an exemplary embodiment of the present disclosure;

[0059] Figure 39 A 3D crystal cell for calculating the orthogonal symmetry crystal structure of a bulk ternary alloy (Al,Ga)O3 with an Ek band structure is shown according to an exemplary embodiment of the present disclosure.

[0060] Figure 40 The calculated energy-momentum configuration of (Al,Ga)O3 near the center of the Brillouin zone according to an exemplary embodiment of the present disclosure is shown, which illustrates the direct band gap;

[0061] Figure 41 This is a process flow diagram for forming an optoelectronic semiconductor device according to an exemplary embodiment of the present disclosure;

[0062] Figure 42 A cross-sectional portion of a (Al,Ga)O3 ternary 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, is depicted.

[0063] Figure 43A Table I shows the selection of substrate crystals for depositing metal oxide structures according to various exemplary embodiments of the present disclosure;

[0064] Figure 43B Table II shows the cell parameters for the selection of metal oxides according to various exemplary embodiments of the present disclosure, which show the lattice constant mismatch between Al2O3 and Ga2O3.

[0065] Figure 44A The calculated formation energy of an aluminum gallium oxide ternary alloy, which varies with composition and crystal symmetry according to an exemplary embodiment of the present disclosure, is depicted.

[0066] Figure 44B This illustrates an exemplary embodiment of the present disclosure showing a high-quality single-crystal ternary (Al2O3) epitaxial deposition on a bulk (010) oriented Ga2O3 substrate. x Ga 1-x Experimental high-resolution X-ray diffraction (HRXRD) of two exemplary dissimilar compositions of 2O3;

[0067] Figure 44C Experimental HRXRD and grazing incidence X-ray reflection (GIXR) of an exemplary superlattice according to an exemplary embodiment of the present disclosure are shown. The exemplary superlattice comprises [(Al]... x Ga 1-x The repeating unit cell of the bilayer [Ga₂O₃ / Ga₂O₃];

[0068] Figure 44D This illustrates an exemplary embodiment of the present disclosure showing a high-quality single-crystal ternary (Al2O3) epitaxial deposition on a bulk (001) oriented Ga2O3 substrate. x Ga 1-x Experimental HRXRD and GIXR of two exemplary dissimilar compositions of 2O3 layer;

[0069] Figure 44E Experimental HRXRD and GIXR of an exemplary superlattice according to an exemplary embodiment of the present disclosure are shown, the exemplary superlattice comprising [(Al] ______ selected from the elastic strain of a β-Ga2O3(001) oriented substrate. x Ga 1-x The repeating unit cell of the bilayer [Ga₂O₃ / Ga₂O₃];

[0070] Figure 44F Experimental HRXRD and GIXR of a cubic crystal symmetric binary nickel oxide (NiO) epitaxial layer elastically strained on a monoclinic crystal symmetry β-Ga2O3(001) oriented substrate according to an exemplary embodiment of the present disclosure are shown.

[0071] Figure 44GExperimental HRXRD and GIXR of a monoclinic crystal symmetry Ga2O3(100) oriented epitaxial layer with elastic strain on a cubic crystal symmetry MgO(100) oriented substrate according to an exemplary embodiment of the present disclosure are shown.

[0072] Figure 44H Experimental HRXRD and GIXR results are shown for a superlattice according to an exemplary embodiment of the present disclosure, the superlattice comprising [(Al2O3(001)] oriented substrate with elastic strain selected from corundum crystal symmetry α-Al2O3(001). x Er 1-x The repeating unit cell of the bilayer [Al₂O₃ / Al₂O₃];

[0073] Figure 44I This illustrates an exemplary embodiment of ternary aluminum erbium oxide (Al) according to the present disclosure. x Er 1-x The strainless energy-crystal momentum (Ek) dispersion in the case of )2O3 near the center of the Brillouin zone shows a direct band gap at Γ (k = 0);

[0074] Figure 44J Experimental HRXRD and GIXR of a superlattice according to an exemplary embodiment of the present disclosure are shown, the superlattice comprising a ternary magnesium gallium oxide composition coupled to a cubic (spinel) crystal symmetry. x Ga 2(1-x) O 3-2x A bilayer unit cell of a monoclinic crystal symmetry Ga2O3(100) oriented film, wherein SL is epitaxially deposited on a monoclinic Ga2O3(010) oriented substrate;

[0075] Figure 44K This illustrates an exemplary embodiment of ternary magnesium gallium oxide (MgO) according to the present disclosure. x Ga 2(1-x) O 3-2x The strainless energy-crystal momentum (Ek) dispersion near the center of the Brillouin zone shows a direct band gap at Γ (k = 0);

[0076] Figure 44L Experimental HRXRD and GIXR of an orthogonal Ga2O3 epitaxial layer with elastic strain on a cubic crystal symmetric magnesium aluminum oxide MgAl2O4(100) oriented substrate are shown according to an exemplary embodiment of the present disclosure.

[0077] Figure 44M Experimental HRXRD of a ternary zinc gallium oxide (ZnGa2O4) epitaxial layer with elastic strain on a wurtzite zinc oxide (ZnO) layer deposited on a monoclinic symmetric gallium oxide (-201) oriented substrate according to an exemplary embodiment of the present disclosure is shown.

[0078] Figure 44N This illustrates an exemplary embodiment of ternary cubic zinc gallium oxide (ZnO) according to the present disclosure. x Ga 2(1-x )O 3-2x The energy-crystal momentum (Ek) dispersion near the center of the Brillouin zone (where x = 0.5) shows the indirect band gap at Γ (k = 0);

[0079] Figure 44O The illustration shows an exemplary embodiment of the present disclosure using an intermediate layer and an epitaxial layer stack deposited along the growth direction on the substrate surface for the case of an orthorhombic Ga2O3 crystal symmetry film.

[0080] Figure 44P Experimental HRXRD of two distinctly different crystal symmetry binary Ga2O3 compositions deposited on an orthorhombic sapphire α-Al2O3(0001) oriented substrate according to an exemplary embodiment of the present disclosure, the compositions being controlled by growth conditions;

[0081] Figure 44Q The diagram illustrates the strain-free energy-crystal momentum (Ek) dispersion near the center of the Brillouin zone for the case of binary orthogonal gallium oxide according to an exemplary embodiment of the present disclosure, which shows the direct band gap at Γ (k = 0);

[0082] Figure 44R This illustrates an exemplary embodiment of the present disclosure showing a high-quality single-crystal corundum symmetric ternary (Al2O3) substrate epitaxially deposited on a bulk (1-100) oriented corundum crystal symmetric Al2O3 substrate. x Ga 1-x Experimental HRXRD and GIXR of two exemplary dissimilar compositions of 2O3 layer;

[0083] Figure 44S This illustrates a deposition in ternary erbium gallium oxide (Er gallium oxide) according to an exemplary embodiment of the present disclosure. x Ga 1-x Experimental HRXRD of the uppermost active Ga2O3 epitaxial layer on a monoclinic Ga2O3 transition layer deposited on a monocrystalline silicon (111) oriented substrate;

[0084] Figure 44T Experimental HRXRD and GIXR of exemplary high-quality single-crystal corundum-symmetric binary Ga2O3 epitaxially deposited on a bulk (11-20) oriented corundum crystal symmetry Al2O3 substrate according to an exemplary embodiment of the present disclosure are shown; wherein Ga2O3 of two thicknesses is shown as pseudoisomorphic strain (i.e., elastic deformation of the bulk Ga2O3 cell) against the underlying Al2O3 substrate.

[0085] Figure 44U Experimental HRXRD and GIXR of an exemplary high-quality single-crystal corundum symmetric superlattice comprising a binary pseudoisomorphic Ga2O3 and Al2O3 bilayers epitaxially deposited on a bulk (11-20) oriented corundum crystal symmetry Al2O3 substrate according to an exemplary embodiment of the present disclosure are shown, wherein the superlattice [Al2O3 / Ga2O3] exhibits the unique properties of corundum crystal symmetry;

[0086] Figure 44V An experimental transmission electron micrograph (TEM) of a high-quality single-crystal superlattice comprising SL[Al2O3 / Ga2O3] deposited on a corundum Al2O3 substrate according to an exemplary embodiment of the present disclosure is shown, depicting a low dislocation defect density.

[0087] Figure 44W This illustrates the uppermost active (Al) symmetry of corundum crystals epitaxially deposited on a single corundum Al2O3 (1-102) oriented substrate according to an exemplary embodiment of the present disclosure. x Ga 1-x Experimental HRXRD of 2O3 epitaxial layer;

[0088] Figure 44X This illustrates an epitaxial deposition, according to an exemplary embodiment of the present disclosure, on a bulk (1-102) oriented corundum crystal symmetry Al2O3 substrate including ternary pseudoisomorphic (Al2O3) structures. x Ga 1-x Experimental HRXRD and GIXR of exemplary high-quality single-crystal corundum symmetric superlattices of Al₂O₃ and Al₂O₃ bilayers, wherein the superlattice [Al₂O₃ / (Al₂O₃)] x Ga 1-x [2O3] exhibits the unique property of corundum crystal symmetry;

[0089] Figure 44Y The experimental wide-angle HRXRD shows an epitaxially deposited cubic symmetry uppermost active magnesium oxide (MgO) epitaxial layer on a single-crystal cubic (spinel) magnesium aluminum oxide (MgAl2O4) (100) oriented substrate according to an exemplary embodiment of the present disclosure.

[0090] Figure 44Z This illustrates an exemplary embodiment of the ternary magnesium aluminum oxide Mg according to the present disclosure. x Al 2(1-x) O 3-2x The strainless energy-crystal momentum (Ek) dispersion near the center of the Brillouin zone in the case of (x=0.5) shows a direct band gap at Γ (k=0);

[0091] Figure 45The diagram schematically illustrates the construction of an epitaxial region for a metal oxide UV LED according to an exemplary embodiment of the present disclosure, the metal oxide UV LED including a pin heterojunction diode and a plurality of quantum wells to tune optical emission energy;

[0092] Figure 46 Based on the energy band diagram of the exemplary embodiments of this disclosure... Figure 45 The growth direction of the epitaxial metal oxide UVLED structure is shown in the figure, where the band structure is represented by k=0;

[0093] Figure 47 The exemplary embodiments shown are based on this disclosure. Figure 46 A spatially confined structure of a multiple quantum well (MQW) region having quantized electron and hole wave functions that spatially recombine in the MQW region to produce a predetermined emitted photon energy determined by the corresponding quantized states in the conduction and valence bands, wherein the MQW region has a narrow bandgap material including Ga2O3;

[0094] Figure 48 The exemplary embodiments shown are based on this disclosure. Figure 47 The calculated optical absorption spectrum of the device structure, in which the lowest energy electron-hole recombination is determined by the quantized energy level within the MQW, produces sharp and discrete absorption / emission energies;

[0095] Figure 49 The growth direction of the epitaxial metal oxide UV LED structure is based on the band diagram of an exemplary embodiment of this disclosure, wherein the MQW region has (Al) 0.05 Ga 0.95 Narrow bandgap material of 2O3;

[0096] Figure 50 The exemplary embodiments shown are based on this disclosure. Figure 49 The calculated optical absorption spectrum of the device structure, in which the lowest energy electron-hole recombination is determined by the quantized energy level within the MQW, produces sharp and discrete absorption / emission energies;

[0097] Figure 51 The growth direction of the epitaxial metal oxide UV LED structure is based on the band diagram of an exemplary embodiment of this disclosure, wherein the MQW region has (Al) 0.1 Ga 0.9 Narrow bandgap material of 2O3;

[0098] Figure 52 The exemplary embodiments shown are based on this disclosure. Figure 49The calculated optical absorption spectrum of the device structure, in which the lowest energy electron-hole recombination is determined by the quantized energy level within the MQW, produces sharp and discrete absorption / emission energies;

[0099] Figure 53 The growth direction of the epitaxial metal oxide UV LED structure is based on the band diagram of an exemplary embodiment of this disclosure, wherein the MQW region has (Al) 0.2 Ga 0.8 Narrow bandgap material of 2O3;

[0100] Figure 54 The exemplary embodiments shown are based on this disclosure. Figure 53 The calculated optical absorption spectrum of the device structure, in which the lowest energy electron-hole recombination is determined by the quantized energy level within the MQW, produces sharp and discrete absorption / emission energies;

[0101] Figure 55 Plot the work function energies of pure metals according to exemplary embodiments of this disclosure, and sort the metal species from high work function to low work function for application in p-type and n-type ohmic contacts with metal oxides;

[0102] Figure 56 It is a pseudo-isomorphic ternary (Al2O3) substrate on the A-side according to an exemplary embodiment of the present disclosure. 0.5 Ga 0.5 The inverted lattice mapping of 2O3 and its 2-axis X-ray diffraction pattern;

[0103] Figure 57 The 2-axis X-ray diffraction pattern of pseudoisomorphic 10-period SL [Al2O3 / Ga2O3] on an A-side Al2O3 substrate according to an exemplary embodiment of the present disclosure shows in-plane lattice matching throughout the structure;

[0104] Figure 58A and Figure 58B The optical mode structure and threshold gain of a metal-oxide-semiconductor material plate according to an exemplary embodiment of the present disclosure are shown.

[0105] Figure 59A and Figure 59B The optical mode structure and threshold gain of a metal-oxide-semiconductor material plate according to another exemplary embodiment of the present disclosure are shown;

[0106] Figure 60 An optical cavity formed by an optical gain medium embedded between two optical reflectors is shown as an exemplary embodiment of the present disclosure.

[0107] Figure 61An exemplary embodiment of the present disclosure is shown using an optical cavity formed by an optical gain medium embedded between two optical reflectors, which shows that two optical wavelengths can be supported by the gain medium and the cavity length;

[0108] Figure 62 An exemplary embodiment of the present disclosure is shown using an optical cavity formed by a finite-thickness optical gain medium embedded between two optical reflectors and positioned at the peak electric field intensity of the fundamental wavelength mode, which shows that only one optical wavelength can be supported by the gain medium and the cavity length.

[0109] Figure 63 An exemplary embodiment of the present disclosure is shown using an optical cavity formed by two finite-thickness optical gain media embedded between two optical reflectors, the optical cavity being positioned at the peak electric field intensity of the shorter wavelength mode, which shows that only one optical wavelength can be supported by the gain media and the cavity length;

[0110] Figure 64A and Figure 64B A single quantum well structure according to an exemplary embodiment of the present disclosure is shown, the single quantum well structure comprising a metal oxide ternary material having quantized electronic states and hole states, depicting two different quantum well thicknesses;

[0111] Figure 65A and Figure 65B A single quantum well structure according to an exemplary embodiment of the present disclosure is shown, the single quantum well structure comprising a metal oxide ternary material having quantized electronic states and hole states, depicting two different quantum well thicknesses;

[0112] Figure 66 Shown from Figure 64A , Figure 64B , Figure 65A and Figure 65B The spontaneous emission spectrum of the disclosed quantum well structure;

[0113] Figure 67A and Figure 67B The spatial band structure of a metal oxide quantum well and the associated energy-crystal momentum band structure are shown according to an exemplary embodiment of the present disclosure.

[0114] Figure 68A and Figure 68B The population inversion mechanism of electrons and holes in a quantum well band structure and the resulting gain spectrum of the quantum well are shown.

[0115] Figure 69A and Figure 69BThe illustration shows the electron and hole energy states in the energy-momentum space of the conduction band and valence band filled for the direct bandgap metal oxide structure and the pseudo-direct bandgap metal oxide structure, according to the exemplary embodiments of this disclosure.

[0116] Figure 70A and Figure 70B The exemplary embodiment of this disclosure illustrates the collisional ionization process that results in the injection of hot electrons into the generated metal oxide;

[0117] Figure 71A and Figure 71B This illustrates a collisional ionization process that results in the injection of hot electrons into the generated metal oxide, according to another exemplary embodiment of the present disclosure;

[0118] Figure 72A and Figure 72B This illustrates the effect of an electric field applied to a metal oxide, according to another exemplary embodiment of the present disclosure, generating multiple impact ionization events.

[0119] Figure 73 A vertical ultraviolet laser structure according to an exemplary embodiment of the present disclosure is shown, wherein the reflector forms portions of the cavity and circuitry;

[0120] Figure 74 A vertical ultraviolet laser structure according to an exemplary embodiment of the present disclosure is shown, wherein the reflector forming the optical cavity is decoupled from the circuitry; and

[0121] Figure 75 The illustration shows a waveguide-type ultraviolet laser structure according to an exemplary embodiment of the present disclosure, wherein the reflector forming the optical cavity is decoupled from the circuit, and wherein the optical gain medium embedded in the side cavity may have a length optimized to achieve a low threshold gain.

[0122] In the following description, similar reference characters are used throughout the accompanying drawings to indicate similar or corresponding parts. Detailed Implementation

[0123] This document discloses an embodiment of a photoelectric semiconductor light-emitting device, which can be configured to emit light having a wavelength 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 substrate may contain Al₂O₃, Ga₂O₃, MgO, LiF, MgAl₂O₄, MgGa₂O₄, LiGaO₂, LiAlO₂, (Al x Ga 1-xThe semiconductor layer may contain Al2O3, MgF2, LaAlO3, TiO2, or quartz. In some embodiments, one or more of the at least one semiconductor layer may contain at least one of Al2O3 and Ga2O3.

[0124] In a first aspect, this disclosure provides a photoelectric semiconductor light-emitting device configured to emit light having a wavelength 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, wherein each of the one or more epitaxial semiconductor layers comprises a metal oxide.

[0125] In another form, the metal oxide of each of the one or more semiconductor layers is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO, Er2O3, Gd2O3, PdO, Bi2O3, IrO2 and any combination of the above metal oxides.

[0126] In another form, at least one of the one or more semiconductor layers is a single crystal.

[0127] In another form, at least one of the one or more semiconductor layers has rhombohedral, hexagonal, or monoclinic crystal symmetry.

[0128] In another form, at least one of the one or more semiconductor layers is composed of a binary metal oxide, wherein the metal oxide is selected from Al2O3 and Ga2O3.

[0129] In another form, at least one of the one or more semiconductor layers is composed of a ternary metal oxide composition, and the ternary metal oxide composition comprises at least one of Al2O3 and Ga2O3, and optionally comprises a metal oxide selected from MgO, NiO, LiO2, ZnO, SiO2, GeO, Er2O3, Gd2O3, PdO, Bi2O3 and IrO2.

[0130] In another form, at least one of the one or more semiconductor layers is composed of a ternary metal oxide composition (Al). x Ga 1-x Composed of )2O3, of which 0 <x<1。

[0131] In another form, at least one of the one or more semiconductor layers comprises a uniaxially deformed unit cell.

[0132] In another form, at least one of the one or more semiconductor layers comprises a biaxially deformed unit cell.

[0133] In another form, at least one of the one or more semiconductor layers includes a unit cell with a three - axis deformation.

[0134] 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: (i) Ga2O3 and a metal oxide selected from Al2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2; or (ii) Al2O3 and a metal oxide selected from Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO2, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2.

[0135] 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 [[ID=I3]]Ga 2(1-y) O 3-2y where 0 < x < 1 and 0 < y < 1.

[0136] In another form, the surface of the substrate is configured to achieve lattice matching of the crystal symmetry of the at least one semiconductor layer.

[0137] In another form, the substrate is a single - crystal substrate.

[0138] In another form, the substrate is selected from Al2O3, Ga2O3, MgO, LiF, MgAl2O4, MgGa2O4, LiGaO2, LiAlO2, MgF2, LaAlO3, TiO2, and quartz.

[0139] In another form, the surface of the substrate has crystal symmetry and in - plane lattice constant matching to achieve homo - epitaxy or hetero - epitaxy of the at least one semiconductor layer.

[0140] In another form, one or more of the at least one semiconductor layer are of the direct band - gap type.

[0141] In a second aspect, the present disclosure provides a photo - electric semiconductor device for generating light of a predetermined wavelength, the photo - electric semiconductor device including: a substrate; and an optical emission region having an optical emission region band structure configured to generate the light of the predetermined wavelength and including one or more epitaxial metal oxide layers supported by the substrate.

[0142] In another form, configuring the optical emission region bandgap structure to generate light of the predetermined wavelength includes selecting one or more epitaxial metal oxide layers to have an optical emission region bandgap energy capable of generating light of the predetermined wavelength.

[0143] In another form, selecting the one or more epitaxial metal oxide layers to have an optical emission region bandgap energy capable of generating light of the predetermined wavelength includes: forming a bandgap energy having form A. x O y The one or more epitaxial metal oxide layers of a binary metal oxide comprising a metal species (A) and oxygen (O) in a relative proportion of x and y.

[0144] In another form, the binary metal oxide is Al2O3.

[0145] In another form, the binary metal oxide is Ga2O3.

[0146] In another form, the binary metal oxide is selected from the group consisting of: MgO, NiO, LiO2, ZnO, SiO2, GeO, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2.

[0147] In another form, selecting the one or more epitaxial metal oxide layers to have an optical emission bandgap energy capable of generating light of the predetermined wavelength includes: forming the one or more epitaxial metal oxide layers of a ternary metal oxide.

[0148] In another form, the ternary metal oxide is having form A. x B y O n A ternary metal oxide alloy comprising metal species (A) and metal species (B) combined in relative proportions of x, y and n with oxygen (O).

[0149] In another form, the relative fraction of metal species B to metal species A is in the range of a few relative fractions to a majority relative fraction.

[0150] In another form, the ternary metal oxide has form A. × B 1-x O n , of which 0 <x<1.0。

[0151] In another form, the metal species A is Al, and the metal species B is selected from the group consisting of Zn, Mg, Ga, Ni, rare earth elements, Ir, Bi, and Li.

[0152] In another form, the metal species A is Ga, and the metal species B is selected from the group consisting of: Zn, Mg, Ni, Al, rare earths, Ir, Bi, and Li.

[0153] In another form, the ternary metal oxide has the form (Al x Ga 1-x )2O3, where 0 < x < 1. In other forms, x is about 0.1, or about 0.3, or about 0.5.

[0154] In another form, the ternary metal oxide is a ternary metal oxide ordered alloy structure, which is formed by sequential deposition of unit cells along the unit cell direction and includes alternating layers of metal species A and metal species B with an intermediate O layer to form a metal oxide ordered alloy having the form A-O-B-O-A-O-B, etc.

[0155] In another form, the metal species A is Al, and the metal species B is Ga, and the ternary metal oxide ordered alloy has the form Al-O-Ga-O-Al, etc.

[0156] In another form, the ternary metal oxide has the form of a host binary metal oxide crystal containing a crystal modifying species.

[0157] In another form, 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 modifying species is selected from the group consisting of: Ga, Al, Mg, Ni, Zn, Bi, Ge, Ir, RE, and Li.

[0158] In another form, selecting the one or more epitaxial metal oxide layers to have an optical emission region bandgap energy capable of generating light of the predetermined wavelength includes: forming the one or more epitaxial metal oxide layers into a superlattice, the superlattice including two or more metal oxide layers, the two or more metal oxide layers forming a unit cell and repeating along the growth direction with a fixed unit cell period.

[0159] In another form, the superlattice is a bilayer superlattice including repeating layers containing two different metal oxides.

[0160] In another form, the two different metal oxides include a first binary metal oxide and a second binary metal oxide.

[0161] In another form, the first binary metal oxide is Al2O3, and the second binary metal oxide is Ga2O3.

[0162] In another form, the first binary metal oxide is NiO, and the second binary metal oxide is Ga2O3.

[0163] In another form, the first binary metal oxide is MgO, and the second binary metal oxide is NiO.

[0164] In another form, the first binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO, 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, GeO, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2, except for the first selected binary metal oxide.

[0165] In another form, the two different metal oxides include binary metal oxides and ternary metal oxides.

[0166] In another form, the binary metal oxide is Ga₂O₃, and the ternary metal oxide is (Al₂O₃). x Ga 1-x )2O3, of which 0 <x<1.0。

[0167] In another form, the binary metal oxide is Ga₂O₃, and the ternary metal oxide is Al. x Ga 1-x O3, where 0 <x<1.0。

[0168] In another form, the binary metal oxide is Ga₂O₃, and the ternary metal oxide is Mg. x Ga 2(1-x) O 3-2x , of which 0 <x<1.0。

[0169] In another form, the binary metal oxide is Al₂O₃, and the ternary metal oxide is (Al₂O₃). x Ga 1-x )2O3, of which 0 <x<1.0。

[0170] In another form, the binary metal oxide is Al₂O₃, and the ternary metal oxide is Al. x Ga1-x O3, where 0 <x<1.0。

[0171] In another form, the binary metal oxide is Al₂O₃, and the ternary metal oxide is (Al₂O₃). x Er 1-x )2O3.

[0172] In another form, the 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 , of which 0 <x<1.0。

[0173] In another form, the binary metal oxide is selected from the group consisting of: Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2.

[0174] In another form, the two different metal oxides include a first ternary metal oxide and a second ternary metal oxide.

[0175] 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.

[0176] 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.

[0177] In another form, the first 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 <​​​​​​​​​​​​​​​x RE 1-x O3、(Al) 2x Li 2(1-x) )O 2x+1 and(Ga 2x Li 2(1-x) )O 2x+1 And wherein the second 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 However, the first selected ternary metal oxide is excluded, wherein 0 <x<1.0。

[0178] In another form, the superlattice is a three-layer superlattice comprising repeating layers of three different metal oxides.

[0179] 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.

[0180] In another form, the first binary metal oxide is MgO, the second binary metal oxide is NiO, and the third ternary metal oxide is Ga2O3.

[0181] In another form, the first binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO, 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, GeO, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2, excluding the first selected binary metal oxide, and the third binary metal oxide is selected from the group consisting of Al2O3, Ga2O3, MgO, NiO, LiO2, ZnO, SiO2, GeO, Er2O3, Gd2O3, PdO, Bi2O3, and IrO2, excluding the first selected binary metal oxide and the second selected binary metal oxide.

[0182] In another form, the three different metal oxides include a first binary metal oxide, a second binary metal oxide, and a ternary metal oxide.

[0183] In another form, the first binary metal oxide is selected from the group consisting of: Al₂O₃, Ga₂O₃, MgO, NiO, LiO₂, ZnO, SiO₂, GeO, 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, GeO, Er₂O₃, Gd₂O₃, PdO, Bi₂O₃, and IrO₂, except for the first selected binary metal oxide, and the 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 、(Ga2x 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 , of which 0 <x<1。

[0184] In another form, the three different metal oxides include a binary metal oxide, a first ternary metal oxide, and a second ternary metal oxide.

[0185] In another form, the binary metal oxide is selected from the group consisting of: Al₂O₃, Ga₂O₃, MgO, NiO, LiO₂, ZnO, SiO₂, GeO, Er₂O₃, Gd₂O₃, PdO, Bi₂O₃, and IrO₂, and wherein the first 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、(Alx 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 Japanese (Ga 2x Li 2(1-x) )O 2x+1 , and therein, the following two ternary metal oxides are free to choose: (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 Li2(1-x) )O 2x+1 and(Ga 2x Li 2(1-x) )O 2x+1 However, the first selected ternary metal oxide is excluded, wherein 0 <x<1。

[0186] 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.

[0187] In another form, the first 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 And wherein the second ternary metal oxide is selected from the group consisting of: (Ga 2x Ni 1-x )O 2x+1 、(Al2x 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 However, the first selected ternary metal oxide is excluded, and the 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、(Alx 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 However, the first selected ternary metal oxide and the second selected ternary metal oxide are excluded, wherein 0 <x<1。

[0188] In another form, the superlattice is a four-layer superlattice comprising repeating layers of at least three different metal oxides.

[0189] In another form, the superlattice is a four-layer superlattice comprising repeating layers of three different metal oxides, and selected metal oxide layers of the three different metal oxides are repeated in the four-layer superlattice.

[0190] 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.

[0191] In another form, the first binary metal oxide is MgO, the second binary metal oxide is NiO, and the third ternary metal oxide is Ga2O3, thereby forming a four-layer superlattice comprising MgO-Ga2O3-NiO-Ga2O3 layers.

[0192] In another form, the three different metal oxides are selected from the group consisting of: Al₂O₃, Ga₂O₃, MgO, NiO, LiO₂, ZnO, SiO₂, GeO, Er₂O₃, Gd₂O₃, PdO, Bi₂O₃, IrO₂, (Ga 2x Ni 1-x )O 2x+1 、(Al 2x Ni 1-x )O 2x+1 、(Al 2x Mg 1-x)O 2x+1 、(Ga 2x Mg 1-x )O 2x+1 、(Al 2x Zn 1-x )O 2x+1 、(Ga 2x Zn 1-x )O 2x+1 、(Ga x Bi 1-x )2O3、(Al x Bi 1-x )2O3、(Al 2x Ge 1-x )O 2+x 、(Ga 2x Ge 1-x )O 2+x 、(Al x Ir 1-x )2O3、(Ga x Ir 1-x )2O3、(Ga x RE 1-x O3、(Al) x RE 1-x O3、(Al) 2x Li 2(1-x) )O 2x+1 and(Ga 2x Li 2(1-x) )O 2x+1 , of which 0 <x<1.0。

[0193] In another form, the superlattice is a four-layer superlattice comprising repeating layers of four different metal oxides.

[0194] In another form, the four different metal oxides are selected from the group consisting of: Al₂O₃, Ga₂O₃, MgO, NiO, LiO₂, ZnO, SiO₂, GeO, Er₂O₃, Gd₂O₃, PdO, Bi₂O₃, IrO₂, (Ga 2x Ni 1-x )O 2x+1 、(Al 2x Ni 1-x )O 2x+1 、(Al 2x Mg 1-x )O 2x+1 、(Ga 2x Mg 1-x )O 2x+1 、(Al 2x Zn 1-x )O 2x+1 、(Ga2x 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 , of which 0 <x<1.0。

[0195] In another form, the respective individual layers of the two or more metal oxide layers forming the unit cell of the superlattice have a thickness less than or approximately equal to the electron de Broglie wavelength in the respective individual layer.

[0196] In another form, configuring the optical emission region band structure for generating light of the predetermined wavelength includes modifying the initial optical emission region band structure of the one or more epitaxial metal oxide layers during the formation of the optoelectronic device.

[0197] In another form, modifying the initial optical emission region band structure of the one or more epitaxial metal oxide layers during the formation of the optoelectronic device includes introducing a predetermined strain into the one or more epitaxial metal oxide layers during epitaxial deposition of the one or more epitaxial metal oxide layers.

[0198] In another form, the predetermined strain is introduced to modify the initial optical emission region band structure from an indirect bandgap to a direct bandgap.

[0199] In another form, the predetermined strain is introduced to modify the initial bandgap energy of the initial optical emission region band structure.

[0200] In another form, the predetermined strain is introduced to modify the initial valence band structure of the initial optical emission region band structure.

[0201] In another form, modifying the initial valence band structure includes raising or lowering the selected valence band relative to the Fermi level of the optical emission region.

[0202] In another form, modifying the initial valence band structure includes modifying the shape of the valence band structure to alter the localization characteristics of the holes formed in the optical emission region.

[0203] In another form, introducing the predetermined strain into the one or more epitaxial metal oxide layers includes: selecting a metal oxide layer to be strained having a composition and crystal symmetry type, wherein when epitaxially formed on an underlying layer having an underlying composition and crystal symmetry type, the composition and crystal symmetry type will introduce the predetermined strain into the metal oxide layer to be strained.

[0204] In another form, the predetermined strain is a biaxial strain.

[0205] In another form, the underlying layer is a metal oxide having a first crystal symmetry type, and the metal oxide layer to be strained also has the first crystal symmetry type but with a different lattice constant to introduce the biaxial strain into the metal oxide layer to be strained.

[0206] In another embodiment, the underlying metal oxide layer is Ga2O3, and the metal oxide layer to be strained is Al2O3, and biaxial compression is introduced into the Al2O3 layer.

[0207] In another embodiment, the underlying metal oxide layer is Al2O3, and the metal oxide layer to be strained is Ga2O3, and biaxial tension is introduced into the Ga2O3 layer.

[0208] In another form, the predetermined strain is uniaxial strain.

[0209] In another form, the underlying layer has a first crystal symmetry type comprising asymmetric unit cells.

[0210] In another form, the metal oxide layer to be strained is monoclinic Ga2O3 or Al. x Ga 1-x O or Al2O3, where x < 0 < 1.

[0211] In another form, the underlying layer and the layer to be strained form layers in a superlattice.

[0212] In another form, modifying the initial optical emission region band structure of the one or more epitaxial metal oxide layers during the formation of the optoelectronic semiconductor device includes introducing a predetermined strain into the one or more epitaxial metal oxide layers after epitaxial deposition.

[0213] In another form, the optoelectronic device includes a first conductivity type region containing one or more epitaxial metal oxide layers, the first conductivity type region having a first conductivity type region band structure configured to operate in conjunction with the optical emission region to generate light of the predetermined wavelength.

[0214] In another form, configuring the first conductivity type region bandgap structure to operate in conjunction with the optical emission region to generate light of the predetermined wavelength includes: selecting a first conductivity type region bandgap larger than the bandgap of the optical emission region.

[0215] In another form, configuring the first conductivity type region band structure to operate in conjunction with the optical emission region to generate light of the predetermined wavelength includes: selecting the first conductivity type region to have an indirect bandgap.

[0216] In another form, configuring the first conductivity type region band structure includes one or more of the following: selecting one or more suitable metal oxide materials according to the principles and techniques considered in this disclosure regarding the optical emission region; forming a superlattice according to the principles and techniques considered in this disclosure regarding the optical emission region; and / or modifying the first conductivity type region band structure by applying strain according to the principles and techniques considered in this disclosure regarding the optical emission region.

[0217] In another form, the first conductivity type region is an n-type region.

[0218] In another form, the optoelectronic device includes a second conductivity type region containing one or more epitaxial metal oxide layers, the second conductivity type region having a second conductivity type region band structure configured to operate in conjunction with the optical emitting region and the first conductivity type region to generate light of the predetermined wavelength.

[0219] In another form, configuring the second conductivity type region bandgap structure to operate in conjunction with the optical emission region to generate light of the predetermined wavelength includes: selecting a second conductivity type region bandgap larger than the bandgap of the optical emission region.

[0220] In another form, configuring the second conductivity type region band structure to operate in conjunction with the optical emission region to generate light of the predetermined wavelength includes: selecting the second conductivity type region to have an indirect bandgap.

[0221] In another form, configuring the second conductivity type region band structure includes one or more of the following: selecting one or more suitable metal oxide materials according to the principles and techniques considered in this disclosure regarding the optical emission region; forming a superlattice according to the principles and techniques considered in this disclosure regarding the optical emission region; and / or modifying the first conductivity type region band structure by applying strain according to the principles and techniques considered in this disclosure regarding the optical emission region.

[0222] In another form, the second conductivity type region is a p-type region.

[0223] In another form, the substrate is formed of a metal oxide.

[0224] In another form, the metal oxide is selected from the group consisting of: Al₂O₃, Ga₂O₃, MgO, LiF, MgAl₂O₄, MgGa₂O₄, LiGaO₂, LiAlO₂, (Al x Ga 1-x )2O3, LaAlO3, TiO2 and quartz.

[0225] In another form, the substrate is formed of a metal fluoride.

[0226] In another form, the metal fluoride is MgF2 or LiF.

[0227] In another form, the predetermined wavelength is in the wavelength range of 150 nm to 700 nm.

[0228] In another form, the predetermined wavelength is in the wavelength range of 150 nm to 280 nm.

[0229] In a third aspect, this disclosure provides a method for forming a photoelectric semiconductor device configured to emit light having a wavelength 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 comprising high-purity metal atoms and one or more atomic beams comprising oxygen atoms, while depositing two or more epitaxial metal oxide films.

[0230] In another form, the metal oxide substrate includes an Al metal oxide substrate or a Ga metal oxide substrate.

[0231] In another form, the one or more atomic beams, each containing high-purity metal atoms, comprise any one or more metals selected from the group consisting of: Al, Ga, Mg, Ni, Li, Zn, Si, Ge, Er, Gd, Pd, Bi, Ir, and any combination of the above metals.

[0232] In another form, the one or more atomic beams, each comprising high-purity metal atoms, include any one or more metals selected from the group consisting of Al and Ga, and the epitaxial metal oxide film comprises (Al... x Ga 1-x )2O3, where 0≤x≤1.

[0233] In another form, the conditions for depositing two or more epitaxial metal oxide films include: exposing the activated epitaxial growth surface to atomic beams, each containing high-purity metal atoms and an atomic beam containing oxygen atoms, wherein the oxygen:total metal flux ratio is >1.

[0234] In another form, at least one of the two or more epitaxial metal oxide films provides a first conductivity type region comprising one or more epitaxial metal oxide layers, and at least another of the two or more epitaxial metal oxide films provides a second conductivity type region comprising one or more epitaxial metal oxide layers.

[0235] In another form, the two or more extensions (Al) x Ga 1-x At least one of the 2O3 films provides one or more epitaxial layers (Al2O3). x Ga 1-x The first conductivity type region of the 2O3 layer, and the two or more epitaxial (Al) x Ga 1-x At least one of the two components in the 2O3 film provides an epitaxial layer comprising one or more Al₂O₃ layers. x Ga 1-x The second conductivity type region of the 2O3 layer.

[0236] In another embodiment, the substrate is passed through an ultra-high vacuum chamber (less than 5 × 10⁻⁶) prior to the oxidation step. -10 The epitaxial growth surface is formed by high-temperature (>800℃) desorption in the process.

[0237] In another form, the method further includes: real-time monitoring of the surface to assess atomic surface quality.

[0238] In another form, the surface is monitored in real time by reflection high-energy electron diffraction (RHEED).

[0239] In another form, oxidizing the epitaxial growth surface includes exposing the epitaxial growth surface to an oxygen source under conditions that oxidize the epitaxial growth surface.

[0240] In another form, the oxygen source is selected from one or more of the group consisting of oxygen plasma, ozone, and nitrous oxide.

[0241] In another form, the oxygen source is radio frequency inductively coupled plasma (RF-ICP).

[0242] In another form, the method further includes: real-time monitoring of the surface to assess surface oxygen density.

[0243] In another form, the surface is monitored in real time via RHEED.

[0244] In another form, the atomic beams containing high-purity Al atoms and / or high-purity Ga atoms are each provided by a bleed unit, the bleed unit comprising an inert ceramic crucible radiatively heated by a filament and controlled by feedback sensing of the molten metal temperature within the crucible.

[0245] In another form, high-purity elemental metals with a purity of 6N to 7N or higher are used.

[0246] In another form, the method further includes: measuring the beam flux of each Al and / or Ga and oxygen atom beam to determine a relative flux ratio, and then exposing the activated epitaxial growth surface to the atom beam at the determined relative flux ratio.

[0247] In another form, the method further includes rotating the substrate while exposing the activated epitaxial growth surface to the atomic beam, so as to accumulate a uniform amount of atomic beam intersecting the substrate surface within a given deposition time.

[0248] In another embodiment, the method further includes heating the substrate while exposing the activated epitaxial growth surface to the atomic beam.

[0249] In another form, the substrate is radiatively heated from behind using a blackbody emissivity that matches the lower bandgap absorption of the metal oxide substrate.

[0250] In another form, the activated epitaxial growth surface is approximately 1 × 10⁻⁶. -6 To about 1×10 -5 Torr is exposed to the atomic beam under vacuum.

[0251] In another embodiment, the Al and Ga atom beam flux at the substrate surface is approximately 1 × 10⁻⁶. -8 To about 1×10 -6 Entrust.

[0252] In another embodiment, the oxygen atom beam flux at the substrate surface is approximately 1 × 10⁻⁶. -7 To about 1×10 -5 Entrust.

[0253] In another form, the Al or Ga metal oxide substrate is A-side sapphire.

[0254] In another form, the Al or Ga metal oxide substrate is monoclinic Ga2O3.

[0255] In another form, the two or more extensions (Al) x Ga 1-x The 2O3 film contains corundum-type AlGaO3.

[0256] In another form, for the two or more extensions (Al) x Ga 1-x For each of the )2O3 membranes, x≤0.5.

[0257] In a fourth aspect, this disclosure provides a method for forming a multilayer semiconducting device, the method comprising: forming a first layer having a first crystal symmetry type and a first composition; and depositing a metal oxide layer having a second crystal symmetry type and a second composition onto the first layer in a non-equilibrium environment, wherein depositing the second layer onto the first layer comprises: initially matching the second crystal symmetry type with the first crystal symmetry type.

[0258] In another form, initially matching the second crystal symmetry type with the first crystal symmetry type includes matching a first lattice configuration of the first crystal symmetry type with a second lattice configuration of the second crystal symmetry type at a horizontal plane growth interface.

[0259] In another form, matching the first crystal symmetry type and the second crystal symmetry type includes: substantially matching the lattice constants of the corresponding end faces of the first lattice configuration and the second lattice configuration.

[0260] In another form, the first layer is corundum Al2O3 (sapphire), and the metal oxide layer is corundum Ga2O3.

[0261] In another form, the first layer is monoclinic Al2O3, and the metal oxide layer is monoclinic Ga2O3.

[0262] In another form, the first layer is R-faced corundum Al2O3 (sapphire) prepared under O-rich growth conditions, and the metal oxide layer is corundum AlGaO3 selectively grown at low temperatures (<550°C).

[0263] In another form, the first layer is M-faceted corundum Al2O3 (sapphire), and the metal oxide layer is corundum AlGaO3.

[0264] In another form, the first layer is A-side corundum Al2O3 (sapphire), and the metal oxide layer is corundum AlGaO3.

[0265] In another form, the first layer is corundum Ga2O3, and the metal oxide layer is corundum Al2O3 (sapphire).

[0266] In another form, the first layer is monoclinic Ga2O3, and the metal oxide layer is monoclinic Al2O3 (sapphire).

[0267] In another form, the first layer is (-201) oriented monoclinic Ga2O3, and the metal oxide layer is (-201) oriented monoclinic AlGaO3.

[0268] In another form, the first layer is (010) oriented monoclinic Ga2O3, and the metal oxide layer is (010) oriented monoclinic AlGaO3.

[0269] In another form, the first layer is (001) oriented monoclinic Ga2O3, and the metal oxide layer is (001) oriented monoclinic AlGaO3.

[0270] In another form, the first crystal symmetry type and the second crystal symmetry type are different, and matching the first lattice configuration and the second lattice configuration includes: reorienting the metal oxide layer to substantially match the in-plane atomic arrangement at the horizontal plane growth interface.

[0271] In another form, the first layer is C-plane corundum Al2O3 (sapphire), and the metal oxide layer is any one of monoclinic, triclinic, or hexagonal AlGaO3.

[0272] In another form, the C-faceted corundum Al2O3 (sapphire) is prepared under O-rich growth conditions to selectively grow hexagonal AlGaO3 at a lower growth temperature (<650°C).

[0273] In another form, the C-face corundum Al2O3 (sapphire) is prepared under O-rich growth conditions to selectively grow monoclinic AlGaO3 at higher growth temperatures (>650°C), wherein the Al% is limited to about 45%-50%.

[0274] In another form, the R-faced corundum Al2O3 (sapphire) is prepared under O-rich growth conditions to selectively grow monoclinic AlGaO3 at higher growth temperatures (>700°C), wherein Al% <50%.

[0275] In another form, the first layer is A-face corundum Al2O3 (sapphire), and the metal oxide layer is (110) oriented monoclinic Ga2O3.

[0276] In another form, the first layer is (110) oriented monoclinic Ga2O3, and wherein the metal oxide layer is corundum AlGaO3.

[0277] In another form, the first layer is (010) oriented monoclinic Ga2O3, and the metal oxide layer is (111) oriented cubic MgGa2O4.

[0278] In another form, the first layer is (100) oriented cubic MgO, and wherein the metal oxide layer is (100) oriented monoclinic AlGaO3.

[0279] In another form, the first layer is (100) oriented cubic NiO, and the metal oxide layer is (100) oriented monoclinic AlGaO3.

[0280] In another form, initially matching the second crystal symmetry type with the first crystal symmetry type includes depositing a buffer layer between the first layer and the metal oxide layer in a non-equilibrium environment, wherein the buffer layer has the same crystal symmetry type as the first crystal symmetry type to provide an atomically flat layer for seeding the metal oxide layer having the second crystal symmetry type.

[0281] In another form, the buffer layer includes an O-end template for seeding the metal oxide layer.

[0282] In another form, the buffer layer includes a metal end-capping template for seeding the metal oxide layer.

[0283] In another form, the first crystal symmetry type and the second crystal symmetry type are selected from the group consisting of cubic, hexagonal, orthorhombic, trigonal, rhombic, and monoclinic.

[0284] In another form, the first crystal symmetry type and the first composition of the first layer, and the second crystal symmetry type and the second composition of the second layer are selected to introduce a predetermined strain into the second layer.

[0285] In another form, the first layer is a metal oxide layer.

[0286] In another form, the first and second layers form unit cells, which repeat at a fixed unit cell period to form a superlattice.

[0287] In another form, the first and second layers are configured to have substantially equal but opposite strains to facilitate defect-free formation of the superlattice.

[0288] In another form, the method includes depositing an additional metal oxide layer having a third crystal symmetry type and a third composition onto the metal oxide layer in a non-equilibrium environment.

[0289] In another form, the third crystal type is selected from the group consisting of cubic, hexagonal, orthorhombic, trigonal, orthorhombic, and monoclinic.

[0290] In another form, the multilayer semiconductor device is a photoelectric semiconductor device for generating light of a predetermined wavelength.

[0291] In another form, the predetermined wavelength is in the wavelength range of 150 nm to 700 nm.

[0292] In another form, the predetermined wavelength is in the wavelength range of 150 nm to 280 nm.

[0293] In a fifth aspect, this disclosure provides a method for forming a photoelectric semiconductor device for generating light of a predetermined wavelength, the method comprising: introducing a substrate; depositing a first conductivity type region in a non-equilibrium environment, the conductivity type region comprising one or more epitaxial metal oxide layers; depositing an optical emission region in a non-equilibrium environment, the optical emission region comprising one or more epitaxial metal oxide layers and including an optical emission region strip structure configured for generating light of the predetermined wavelength; and depositing a second conductivity type region in a non-equilibrium environment, the second conductivity type region comprising one or more epitaxial metal oxide layers.

[0294] In another form, the predetermined wavelength is in the wavelength range of about 150 nm to about 700 nm. In yet another form, the predetermined wavelength is in the wavelength range of about 150 nm to about 425 nm. In one example, bismuth oxide can be used to generate a wavelength of up to about 425 nm.

[0295] In another form, the predetermined wavelength is in the wavelength range of about 150 nm to about 280 nm.

[0296] In another form, optical emission efficiency is controlled by selecting the crystal symmetry type of the optical emission region. The optical selection rule for electric dipole emission is controlled by the symmetry properties of the conduction band and valence band states, as well as the crystal symmetry type. An optical emission region possessing point-set symmetry in its crystal structure can have either inverted centrosymmetry or non-inverted symmetry. This document advocates for the advantageous selection of crystal symmetry to promote optical transitions of electric or magnetic dipoles for application in the optical emission region. Conversely, it is also possible to advantageously select crystal symmetry to suppress optical transitions of electric or magnetic dipoles to promote the optically non-absorbent region of the device.

[0297] In an overview manner, Figure 1 This is a process flow diagram for constructing an optoelectronic semiconductor device according to an exemplary embodiment. In one example, the optoelectronic semiconductor device is a UVLED, and in another example, the UVLED is configured to generate a predetermined wavelength in the wavelength region of about 150 nm to about 280 nm. In this example, the construction process includes: initially selecting (i) the desired operating wavelength (e.g., UVC wavelength or lower) in step 10 and (ii) the optical configuration of the device in step 60 (e.g., a vertical emitting device 70 in which the light output vector or direction is substantially perpendicular to the plane of the epitaxial layer, or a waveguide device 75 in which the light output vector is substantially parallel to the plane of the epitaxial layer). The optical emission characteristics of the device are implemented in part by selecting semiconductor material 20 and optical material 30.

[0298] Taking UVLED as an example, according to Figure 1 The optoelectronic semiconductor device constructed by the process shown will include an optical emission region based on a selected optical emission region material 35, wherein photons are generated through favorable spatial recombination of electrons in the conduction band and holes in the valence band. In one example, the optical emission region includes one or more metal oxide layers.

[0299] The optical emission region may be configured as a direct bandgap type band structure. This may be an inherent property of one or more selected materials, or it may be tuned using one or more of the techniques disclosed herein. The optical recombination or optical emission region may be covered by an electron and hole reservoir comprising n-type and p-type conductive regions. The n-type and p-type conductive regions are selected from electron and hole injection materials 45 that may have a larger bandgap relative to the optical emission region material 35, or may comprise an indirect bandgap structure that limits optical absorption at the operating wavelength. In one example, the n-type and p-type conductive regions are formed from one or more metal oxide layers.

[0300] Impurity doping is possible with both n-type and p-type materials, using Ga₂O₃ and low-Al% AlGaO₃. N-type doping is particularly advantageous for Ga₂O₃ and AlGaO₃, while p-type doping is more challenging but achievable. Suitable impurities for n-type doping are Si, Ge, Sn, and rare earth elements (e.g., erbium (Er) and gadolinium (Gd)). Using Ge flux for co-deposition doping control is particularly suitable. For p-type co-doping using group III metals, Ga sites can be filled with magnesium (Mg). 2+ ), Zinc (Zn) 2+ ) and atomic nitrogen (N 3- (Replace the O position). Further improvements can also be achieved using iridium (Ir), bismuth (Bi), nickel (Ni), and palladium (Pd).

[0301] Digital alloys using NiO, Bi₂O₃, Ir₂O₃, and PdO can also be used in some embodiments to advantageously facilitate p-type formation in Ga₂O₃-based materials. While p-type doping is possible for AlGaO₃, the use of cubic symmetry metal oxides (e.g., Li-doped NiO or Ni-vacancy NiO) is also possible. x＞1 Alternative doping strategies for wurtzite p-type Mg:GaN are also possible.

[0302] Another opportunity lies in the ability to form highly polar hexagonal crystal symmetry and directly integrate the ε-phase Ga2O3 into AlGaO3, thereby inducing polarization doping according to the principles and techniques described and mentioned in U.S. Patent No. 9,691,938. It is also necessary to select the optical material 30 required for confining light within the device, as a differential change in refractive index. For far-ultraviolet or vacuum ultraviolet light, the choice of optically transparent material ranges from MgO to metal fluorides (such as MgF2, LiF, etc.). According to this disclosure, single-crystal LiF and MgO substrates have been found to be advantageous for realizing UV LEDs.

[0303] The electrical material 50 forming the contact with the electron and hole injector regions is selected from low work function metals and high work function metals, respectively. In one example, the metal ohmic contact is formed directly in situ on the final metal oxide surface, thus reducing any intermediate traps / defects generated at the semiconducting oxide-metal interface. The device is then constructed in step 80.

[0304] Figure 2A and Figure 2B A vertical emitting device 110 and a waveguide emitting device 140 according to an exemplary embodiment are schematically shown. Device 110 has a substrate 105 and an emitting structure 135. Similarly, device 140 has a substrate 155 and an emitting structure 145. Light 125 and 130 from device 110 generated from light-generating region 120 and light 150 from device 140 propagate through the device from region 120 and are limited by the light escape cone defined by the refractive index difference at the semiconductor-air interface. Due to the extremely large bandgap energy of metal oxide semiconductors, they have a substantially lower refractive index compared to III-N materials. Therefore, the use of metal oxide materials provides an improved light escape cone and thus higher optical output coupling efficiency compared to conventional emitting devices. Waveguide devices with single-mode and multi-mode operation are also possible.

[0305] Furthermore, ultraviolet plasmon sub-guides can be directly formed at the semiconductor-metal interface using elemental metals Al or Mg to construct wide-area striped waveguides. This is an effective method for forming waveguide structures. The Ek-band structures of Al, Mg, and Ni will be discussed below. Once the desired material selection is available, the process for constructing semiconductor optoelectronic devices can be performed at step 80 (see [link to relevant documentation]). Figure 1 ).

[0306] Figure 3A The functional regions of the epitaxial structure of an optoelectronic semiconductor device 160 for generating light of a predetermined wavelength according to an exemplary embodiment are depicted.

[0307] The substrate 170 has favorable crystal symmetry and in-plane lattice constant matching at its surface to achieve homoepitaxial or heteroepitaxial growth of the first conductivity type region 175 with subsequent non-absorbing spacer region 180, optical emission region 185, optional second spacer region 190, and second conductivity type region 195. In one example, the in-plane lattice constant and lattice geometry / arrangement are matched to modify (i.e., reduce) lattice defects. Electrical excitation is provided by a source 200 connected to the electron and hole injection regions of the first conductivity type region 175 and the second conductivity type region 195. In another exemplary embodiment, an ohmic metal contact and a low bandgap or half-metal zero bandgap oxide semiconductor are used. Figure 3B The regions shown are 196, 197, and 198.

[0308] In one embodiment, a metal oxide with a wide bandgap is used to form the first conductivity type region 175 and the second conductivity type region 195, and the regions are electrically contacted using ohmic contact regions 197, 198, and 196 as described herein. In the case of the insulating substrate 170, for one conductivity type (i.e., electrons or holes), the electrical contact configuration is via ohmic contact region 198 and the first conductivity type region 175, while for another, ohmic contact region 196 and the second conductivity type region 195 are used. Optionally, the ohmic contact region 198 may be formed on the exposed portion of the first conductivity type region 175. In another embodiment, since the insulating substrate 170 can be further made transparent or opaque for operating wavelengths, in the case of a transparent substrate, the lower ohmic contact region 197 can be used as an optical reflector as part of an optical resonator.

[0309] In the case of a vertically conductive device, substrate 170 is conductive and can be transparent or opaque for the operating wavelength. Electrical or ohmic contact areas 197 and 198 are provided to advantageously achieve both electrical connection and optical propagation within the device.

[0310] Figure 3C Further possible electronic configurations of electrical contact regions 196 and 198 are schematically shown, illustrating mesa etched portions exposing the underlying conductive types of regions 175 and 198. Ohmic contact region 196 may be further patterned to expose a portion of the device for photoextraction.

[0311] Figure 3D This illustrates another electronic configuration in which an insulating substrate 170 is used to expose a first conductivity type region 175, and the electrical contact is formed on the partially exposed portion of the first conductivity type region 175. In the case of conductive and transparent substrate contacts, an ohmic contact region 198 is not required, and a spatially disposed electrical contact region 197 is used.

[0312] Figure 3E Furthermore, a possible configuration of an optical aperture 199, partially or completely etched into the optically opaque substrate 170 for optical coupling of light generated from the optical emission region 185, is shown. The optical aperture can be coupled with... Figures 3A to 3D It is used in conjunction with previous implementations.

[0313] Figure 4 The operation of the optoelectronic semiconductor device 160 is schematically illustrated, wherein an exemplary configuration includes an electron injection region 180 and a hole injection region 190, and an electrical bias 200 that transmits and directs moving electrons 230 and holes 225 into a recombination region 220. The resulting electron and hole recombination forms a spatial optical emission region 185.

[0314] Maximum band gap (E G Metal-oxide-semiconductor (E) G >4 eV) can exhibit low-mobility hole-type carriers and can even be highly localized in space, thus limiting the spatial range of hole injection. The region near the hole injection region 190 and the recombination region 220 can become favorable for the recombination process. Furthermore, the hole injection region 190 itself can be a preferred region for electron injection such that the recombination region 220 is located within a portion of the hole injection region 190.

[0315] Now refer to Figure 5 Light or optical emission is generated within device 160 by the selective spatial recombination of electrons and holes to produce high-energy photons 240, 245, and 250 of predetermined wavelengths, said predetermined wavelengths being determined by the configuration of the band structure of one or more metal oxide layers forming the optical emission region 185, as described below. Both electrons and holes are instantaneously annihilated to produce photons; this is a property of the selected metal oxide band structure.

[0316] Light generated within the optical emission region 185 can propagate within the device according to the crystal symmetry of the metal oxide host region. The crystal symmetry set of the host metal oxide semiconductor has a defined energy and crystal momentum dispersion known as the Ek configuration, which characterizes the band structure of various regions (including the optical emission region 185). Non-ordinary Ek dispersion is essentially determined by the fundamental physical atomic arrangement of the defined crystal symmetry of the host medium. In general, the possible optical polarization, the emitted light energy, and the intensity of the optical emission oscillator are directly related to the valence band dispersion of the host crystal. According to this disclosure, embodiments advantageously configure a band structure including the valence band dispersion of the selected metal oxide semiconductor for application in optoelectronic semiconductor devices (such as, in one example, for a UV LED).

[0317] The vertically generated light 240 and 245 requires adherence to the optical selection rules of the basic band structure. Similarly, there are optical selection rules for generating transverse light 250. These optical selection rules can be achieved through advantageous configuration of the crystal symmetry type and physical spatial orientation of the crystals in each region within the UVLED. The advantageous orientation of the constituent metal oxide crystals according to their growth direction is beneficial to the optimal operation of the UVLED of this disclosure. Furthermore, Figure 1 The selection of optical properties 30 (such as the refractive index for forming waveguide-type devices) in the process flow diagram shown is suitable for optical limitations and low loss.

[0318] For the sake of completeness, Figure 6Another embodiment is shown, including an optical aperture 260 disposed within the optoelectronic semiconductor device 160 to enable optical output coupling from the optical emission region 185 to be provided using a material 195 that is opaque to the operating wavelength.

[0319] In an overview manner, Figure 7 Selection criteria 270 for one or more metal oxide crystal compositions according to an exemplary embodiment are shown. 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 a binary oxide, a ternary oxide, or a quaternary oxide. A recombination region 220 is formed in the optical emission region 185 of the optoelectronic semiconductor device 160 (see, for example, [link to relevant documentation]). Figure 5 Regions of conductivity type are selected to exhibit efficient electron-hole recombination, while regions of conductivity type are selected to enable them to provide sources of electrons and holes. Even when the species of constituent metals are the same, metal-oxide semiconductors can be selectively produced from a variety of possible crystal symmetry types. A semiconductor containing one metal species with form A can be used. x O y Binary metal oxides, wherein the metal species (A) and oxygen (O) are combined in relative proportions x and y. Even with the same relative proportions x and y, it is possible to have a variety of crystal structure configurations with extremely different sets of crystal symmetries.

[0320] As will be described below, the Ga2O3 and Al2O3 compositions exhibit several advantageous and dissimilar crystal symmetries (e.g., monoclinic, rhombic, triclinic, and hexagonal), but special attention should be paid to their combination and their effectiveness in constructing UV LEDs. Other advantageous metal oxide compositions (such as MgO and NiO) exhibit less variation in practically available crystal structures (i.e., cubic crystals).

[0321] Adding a favorable second distinct metal species (B) can also expand the host binary metal oxide crystal structure to produce a form A. x B y O n Ternary metal oxides. Ternary metal oxides are rare additives of species B up to a majority relative fraction range. As described below, ternary metal oxides can be used in various embodiments to advantageously form direct bandgap optical emission structures. Other materials can be designed, including those coupled with oxygen to form quaternary compositions A. x B y C z O n Three different cation-atom species.

[0322] Generally, while it is theoretically possible to combine a large number (>4) of different metal atoms to form composite oxide materials, they rarely produce high crystallinity with particularly dissimilar crystal symmetry structures. Such composite oxides are typically polycrystalline or amorphous, and therefore lack optimal utility for use in optoelectronic devices. Clearly, this disclosure seeks, in various embodiments, configurations that are substantially single-crystal with low defect density for utilizing strip structures to form devices for UV LED epitaxial formation. Some embodiments also include achieving a desirable Ek configuration by adding another different metal species.

[0323] Selecting the desired bandgap structure for each of the UVLED regions in the optoelectronic semiconductor device 160 may also involve the integration of different crystal symmetry types. For example, a monoclinic crystal symmetry host region and a cubic crystal symmetry host region, which constitute a portion of the UVLED, may be utilized. The epitaxial formation relationship involves a focus on the formation of low-defect layer formations. The layer formation steps are then classified 285 into homogeneous symmetry formation and heterogeneous symmetry formation. To achieve the goal of providing materials for forming the epitaxial layer structure, band structure modifiers 290, such as biaxial strain, uniaxial strain, and digital alloys (such as superlattice formations), may be utilized.

[0324] The epitaxial process 295 is then defined by the type and sequence of the material composition required for deposition. This disclosure describes novel processes and compositions for achieving this objective.

[0325] Figure 8 The epitaxial process 300 is illustrated. At step 310, a substrate for supporting the optical emission region is selected, possessing a 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 compatible with the desired epitaxial crystal symmetry type. Even if equivalent crystal symmetries of both the substrate and one or more epitaxial films can be used, optimization 315 exists to match in-plane atomic arrangements, such as favorable coincidence of in-plane lattice constants or in-plane geometries of corresponding crystal planes from different crystal symmetry types.

[0326] The substrate surface has a defined two-dimensional crystal arrangement of end-capping surface atoms. In a vacuum, this discontinuity of the defined crystal structure on the fabricated surface leads to a minimization of the surface energy of the dangling bonds of the end-capping atoms. For example, a metal oxide surface can be fabricated as an oxygen-endcapping surface in one embodiment, or as a metal-endcapping surface in another embodiment. Metal oxide semiconductors can have complex crystal symmetries, and end-capping of pure species may require special care. For example, both Ga₂O₃ and Al₂O₃ can be O-endcapped by high-temperature annealing in a vacuum followed by sustained exposure to atomic or molecular oxygen at high temperatures.

[0327] The crystal surface orientation 320 of the substrate can also be selected to achieve selective film formation crystal symmetry type of epitaxial metal oxides. For example, A-side sapphire can be used to advantageously select the (110) oriented α phase to form high-quality epitaxial Ga2O3, AlGaO3, and Al2O3; while C-side sapphire produces hexagonal and monoclinic Ga2O3 and AlGaO3 films. The Ga2O3 oriented surface is also selectively used for film formation selection of AlGaO3 crystal symmetry.

[0328] The growth conditions 325 are then optimized to achieve the relative proportions of the elemental metals and activated oxygen required to realize the desired material properties. The growth temperature also plays a crucial role in determining the possible types of crystal structure symmetry. The prudent selection of the substrate surface energy, achieved through appropriate crystal surface orientation, also determines the temperature process window for the epitaxial process (during which the epitaxial structure 330 is deposited).

[0329] Figure 9 A database 350 of material selection for optoelectronic devices based on UVLEDs is disclosed. Metal oxide materials 380 are plotted as varying with their electron affinity 375 relative to vacuum. Semiconductor materials, ordered from left to right, have increasing optical band gaps and are therefore more useful for shorter wavelength operation of UVLEDs. Lithium fluoride (LiF) is used as an example in this chart; LiF has a band gap 370 (shown as a box for each material), which is the energy difference in electron volts between the conduction band minimum 360 and the valence band maximum 365. The absolute energy positions represented by the conduction band minimum 360 and the valence band maximum 365 are plotted relative to vacuum. While narrow band gap materials (such as rare earth nitrides (RE-N), germanium (Ge), palladium oxide (PdO), and silicon (Si)) do not provide suitable host properties for the optical emission region, they can be advantageously used for electrical contact formation. The use of the inherent electron affinity of a given material can be used to form ohmic contacts and metal-insulator-semiconductor junctions as needed.

[0330] A desirable material combination for use as a substrate is bismuth oxide (Bi2O). 3) Nickel oxide (NiO) and germanium oxide (GeO) x～2The substrates used include gallium oxide (Ga2O3), lithium oxide (Li2O), magnesium oxide (MgO), aluminum oxide (Al2O3), single-crystal quartz SiO2, and finally lithium fluoride 355 (LiF). In particular, Al2O3 (sapphire), Ga2O3, MgO, and LiF can be used as large, high-quality single-crystal substrates and, in some embodiments, as substrates for UVLED-type optoelectronic devices. Other embodiments of substrates for UVLED applications include single-crystal cubic symmetry magnesium aluminate (MgAl2O4) and magnesium gallate (MgGa2O4). In some embodiments, ternary AlGaO3 can be deployed as bulk substrates of monoclinic (high Ga%) and corundum (high Al%) crystal symmetry types using large-area formation methods such as the Chuklaski method (CZ) and edge-fed growth (EFG).

[0331] Considering Ga2O3 and Al2O3 host metal oxide semiconductors, in some embodiments, alloying and / or doping via elements selected from database 350 is advantageous for film formation properties.

[0332] Therefore, elements selected from silicon (Si), germanium (Ge), erbium (Er), gadolinium (Gd), palladium (Pd), bismuth (Bi), iridium (Ir), zinc (Zn), nickel (Ni), lithium (Li), and magnesium (Mg) are used to form the ternary crystal structure of Al₂O₃, AlGaO₃, or Ga₂O₃ host crystals, or as dilute additives (see [link to relevant documentation]). Figure 7 The promising crystal-modified species of semiconductor 280.

[0333] Another implementation scheme includes the selection of a crystal modifier group selected from the group consisting of Bi, Ir, Ni, Mg, and Li.

[0334] To be applied to host crystals Al₂O₃, AlGaO₃, or Ga₂O₃, multivalent states of Bi and Ir can be added to achieve p-type impurity doping. The addition of Ni and Mg cations can also achieve p-type impurity substitution doping at Ga or Al crystal sites. In one embodiment, lithium can be used as a crystal modifier, capable of increasing the band gap and modifying possible crystal symmetries, ultimately resulting in orthorhombic symmetric lithium gallate (LiGaO₂) and tetragonal symmetric aluminum gallate (LiAlO₂). For n-type doping, Si and Ge can be used as impurity dopants, with Ge providing an improved growth process for film formation.

[0335] While other materials are possible, Database 350 provides advantageous properties for application in UV LEDs.

[0336] Figure 10A process flow 400 is described for a sequential epitaxial layer formation process for epitaxially integrating a material region defined in an optoelectronic semiconductor device 160, according to an exemplary embodiment.

[0337] A substrate 405 is fabricated having a surface 410 configured to receive one or more first conductivity type crystal structure layers 415, which may include multiple epitaxial layers. Next, a first spacer region synthesis layer 420, which may include multiple epitaxial layers, is formed on layer 415. Then, an optical emitting region 425, which may include multiple epitaxial layers, is formed on layer 420. A second spacer region 430, which may include multiple epitaxial layers, is then deposited on region 425. The second conductivity type capping region 435, which may include multiple epitaxial layers, then completes most of the UVLED epitaxial structure. Other layers, such as ohmic metal layers and passive optical layers (e.g., for optical confinement or anti-reflection), may be added to complete the optoelectronic semiconductor device.

[0338] Reference Figure 11 For the case of gallium oxide-based (GaOx-based) composition 485, a possible option for ternary metal-oxide semiconductor 450 is shown. A description is provided for ternary oxide alloy A. x B 1-x The optical band gap of O is 480 for various values ​​of x. As previously mentioned, metal oxides can exhibit several stable forms of crystal symmetry structures, and adding another species to form a ternary structure further complicates the matter. However, an exemplary general trend can be found by selectively combining or alloying aluminum, group II cations {Mg, Ni, Zn}, iridium, erbium, and gadolinium atoms, as well as lithium atoms, with gallium oxide. Ni and Ir typically form deep d-bands, but can form useful optical structures for high Ga%. Ir has multiple valence states, with the Ir₂O₃ form utilized in some embodiments.

[0339] Alloying one of X = {Ir, Ni, Zn, Bi} to Ga x X 1-x O reduced the usable optical bandgap (refer to curves labeled 451, 452, 453, and 454). Conversely, alloying one of the Y = {Al, Mg, Li, RE} increased the ternary Ga... x Y 1-x Available band gaps for O (refer to curves 456, 457, 458, 459).

[0340] therefore, Figure 11 This can be understood as being applied to the formation of optical emission regions and conductivity type regions according to this disclosure.

[0341] Similarly, Figure 12Regarding the optical bandgap 480 for the alumina-based (AlOx-based) composition 485, a possible selection of the ternary metal-oxide semiconductor 490 is disclosed. A close examination of the curves reveals that alloying one of X = {Ir, Ni, Zn, Mg, Bi, Ga, RE, Li} to Al... x X 1-x The usable optical band gap is reduced in O. The group Y = {Ni,Mg,Zn} forms a spinel crystal structure, but the ternary Al band gap is completely reduced. x Y 1-x Available band gaps for O (refer to curves 491, 492, 493, 494, 495, 496, 500, 501). Figure 12 Also shown is the band gap 502 of α-phase alumina (Al2O3) with rhombic crystal symmetry.

[0342] therefore, Figure 12 This can be understood as being applied to the formation of optical emission regions and conductivity type regions according to this disclosure. Figure 28 Figure 2800 shows potential combinations of ternary oxides (0 ≤ x ≤ 1) that can be employed according to this disclosure. Figure 2800 shows crystal growth modifiers along the left column and the host crystal across the top of the figure.

[0343] Figure 13A and Figure 13B The electronic energy versus crystal momentum representation of possible metal oxide-based semiconductors (showing the direct band gap) Figure 13A ) and indirect band gap ( Figure 13B The disclosure also illustrates concepts related to the formation of optoelectronic devices according to this disclosure. Those skilled in quantum mechanics and crystal structure design know that symmetry directly determines the electronic configuration or band structure of a single crystal structure.

[0344] Generally speaking, in order to be applied to optical emission crystal structures, there exist... Figure 13A and Figure 13B The two types of electron band structures are shown. The fundamental process utilized in the optoelectronic device of this disclosure is the recombination of physical (large numbers) electrons and hole-like charge carriers, which are expressions of permissible energy and crystal momentum. The recombination process can occur, thereby conserving the crystal momentum of the incident carrier from its initial state to its final state.

[0345] To achieve the annihilation of electrons and holes to form a massless photon (i.e., the momentum k of the final state massless photon). γ k γ The final state of (=0) requires Figure 13AThe special Ek band structure is shown. Various computational techniques can be used to calculate metal-oxide-semiconductor structures with pure crystal symmetry. One such method is density function theory, where first principles can be used to construct atomic structures comprising distinguishable pseudopotentials attached to each constituent atom constituting the structure. Iterative computational schemes for calculating the total energy ab initio using a plane-wave basis can be used to calculate band structures due to crystal symmetry and spatial geometry.

[0346] Figure 13A The reciprocal space energy representing the crystal structure is related to the crystal momentum or band structure 520. This is relative to the crystal momentum vector. Energy Dispersion The lowest conduction band (525) describes the permissible configuration space of electrons. It exhibits energy dispersion. The highest valence band 535 also describes the allowable energy states of holes (positively charged crystal particles).

[0347] Dispersion 525 and 535 are relative to electron energy in electron volts (increasing direction 530, decreasing direction 585) and crystal momentum in reciprocal space (positive K). BZ 545 and negative K BZ 540 (which represents the distinct crystal wave vectors starting from the center of the Brillouin zone) is drawn. The band structure 520 is shown at the crystal's highest symmetry point, marked Γ, where Γ represents the band structure at k = 0. The band gap is defined by the energy difference between the minimum and maximum values ​​at 525 and 535, respectively. Electrons propagating through the crystal will minimize energy and relax to the conduction band minimum at 565; similarly, holes will relax to the lowest energy state at 580.

[0348] If 565 and 580 are both located at k=0, a direct recombination process can occur, in which electrons and holes annihilate and produce new massless photons 570 with energies approximately equal to the bandgap energy 560. That is, electrons and holes at k=0 can recombine and conserve crystal momentum to produce massless particles (called 'direct' bandgap materials). As will be disclosed, this situation is rare in practice, and only a small subset of semiconductors of all crystal symmetry types exhibits this favorable configuration.

[0349] Now refer to Figure 13BThe crystal structure 590, in which the primary bands 525 and 620 of the band structure have corresponding minimum values ​​565 and maximum values ​​610 that are not located at k=0, is called an 'indirect' configuration. The minimum bandgap energy 600 is still defined as the energy difference between the conduction band minimum and the valence band maximum that actually occur at the same wave vector, and is called the indirect bandgap energy 605. Obviously, optical emission is unfavorable because crystal momentum is not conserved for recombination events and secondary particles (such as crystal vibrational quantum phonons) are required to conserve crystal momentum. In metal oxides, the longitudinal optical phonon energy scales with the bandgap and is extremely large compared to those found in, for example, GaAs, Si, etc.

[0350] Therefore, achieving the goal of optical emission regions using indirect Ek configurations is challenging. This disclosure describes methods for manipulating, otherwise indirect, band gaps of specific crystal symmetry structures and transforming or modifying the k=0 characteristic of the region center of the band structure into a direct band gap dispersion suitable for optical emission. These methods are now disclosed for use in the manufacture of optoelectronic devices, and particularly in the manufacture of UV LEDs.

[0351] Even with a direct bandgap configuration, design choices are constrained by the specific crystal symmetries of a given metal oxide, which has an electric dipole selection rule controlled by a set of symmetry features assigned to each of the energy bands. In the case of Ga₂O₃ and Al₂O₃, optical absorption is controlled between the lowermost conduction band and the three uppermost valence bands.

[0352] Figures 13C to 13E The optical emission and absorption transitions at k=0 are shown relative to the symmetry of the Ga2O3 monoclinic crystal. Figures 13C to 13E Each shows three valence bands E vi (k)621, 622, and 623. In Figure 13C In the diagram, optically permissible electric dipole transitions are shown for electron 566 and hole 624, which are permissible for optical polarization vectors within the a-axis and c-axis of the monoclinic cell. This corresponds to wave vector 627 in the Γ-Y ​​branch in reciprocal space Ek. Similarly, Figure 13D The electric dipole transition between electron 566 and hole 625 is permissible for polarization along the c-axis 628 of the crystal cell. Furthermore, Figure 13E The higher energy transition between electron 566 and hole 626 is permitted for an optically polarized field along the b-axis 629 of the unit cell, which corresponds to the Ek(Γ-X) branch.

[0353] Obviously, Figure 13C , Figure 13D and Figure 13EThe magnitudes of intermediate energy transitions 630, 631, and 632 increase, but only the lowest energy transition is favorable for optical light emission. However, if the Fermi level (E... F ) is configured so that the lowest price band 621 is higher than E. F And 622 is lower than E F Optical emission can then occur at energy 631. These selection rules are particularly useful when designing waveguide devices that are optically polarization dependent for specific TE, TM, and TEM operating modes.

[0354] Referring to the explanation of the band structure above, now referring to... Figures 14A to 14B These figures illustrate how these composite elements can be incorporated into the device structure 160. Each functional region of the UVLED has a specific Ek dispersion comprising both indirect and direct materials, possibly due to significant differences in crystal symmetry types. This allows for the advantageous embedding of optical emitting regions within the device.

[0355] Figure 14A and Figure 14B A representation of the composite Ek material is shown by a single block 633, which is defined by layer thicknesses of 655, 660, and 665 and fundamental bandgap energies of 640, 645, and 650, respectively. The relative alignment of the conduction and valence band edges is shown in block 633. Figure 14B The electron energy 670 of the three dissimilar materials having bandgap energies of 640, 645, and 650 is associated with the spatial growth direction 635. For example, it is possible to deposit a first region along the growth direction 635 using an indirect crystal but with a final surface lattice constant geometry capable of providing mechanoelastic deformation of the subsequent crystal 645. This can occur, for example, by directly growing AlGaO3 on Ga2O3.

[0356] Epitaxial manufacturing methods

[0357] Non-equilibrium growth techniques are known in the prior art and are referred to as atomic and molecular beam epitaxy, chemical vapor phase epitaxy, or physical vapor phase epitaxy. Atomic and molecular beam epitaxy utilizes oriented... Figure 15 The illustrated growth surface is composed of atomic beams separated in space. Although molecular beams are also used, a combination of molecular and atomic beams can be used according to this disclosure.

[0358] One guiding principle is to use a pure source of atoms that can be multiplexed at the growth surface through favorable condensation and kinematically favorable growth conditions to physically construct crystals layer by layer. While the grown crystals can be substantially self-assembled, the method of this invention can also be controlled at the atomic level and deposit atomically thick epitaxial layers of a single species. Unlike equilibrium growth techniques that rely on thermodynamic chemical potentials to achieve bulk crystal formation, the technique of this invention can deposit very thin atomic layers at growth parameters far from the equilibrium growth temperature of bulk crystals.

[0359] In one example, the Al₂O₃ film is formed at a film-forming temperature in the range of 300°C to 800°C, while conventional bulk equilibrium growth of Al₂O₃ (sapphire) is well achieved at temperatures exceeding 1500°C. This requires a molten reservoir containing liquid Al and O, which can be configured to position a solid seed crystal close to the molten surface. The seed crystal is carefully oriented to contact the melt, resulting in a recrystallized portion near the melt. Pulling the seed crystal and the partially solidified recrystallized portion away from the melt forms a continuous crystal boule.

[0360] Such equilibrium growth methods for metal oxides limit the possible combinations of metals and the potential for composite regions to be used in heteroepitaxial formation of composite structures. The non-equilibrium growth techniques according to this disclosure operate well at growth parameters far from the melting point of the target metal oxide and can even modulate atomic species existing in a single atomic layer within a crystal cell along a pre-selected growth direction. Such non-equilibrium growth methods are not constrained by equilibrium phase diagrams. In one example, the method of the invention utilizes evaporated source material forming a beam that impacts the growth surface; this beam is ultrapure and substantially charge-neutral. Charged ions are generated in some cases, but these should be minimized as much as possible.

[0361] To grow metal oxides, the composition of the source beam can be varied in known ways to achieve their relative ratios. For example, oxygen-rich and metal-rich growth conditions can be obtained by controlling the relative beam flux measured at the growth surface. While almost all metal oxides grow optimally under oxygen-rich conditions (similar to the arsenic-rich growth of gallium arsenide (GaAs), some materials differ. For instance, GaN and AlN require metal-rich growth conditions with extremely narrow growth windows, which is one of the major reasons limiting mass production.

[0362] While metal oxides prefer oxygen-rich growth with a wide growth window, there are still opportunities to intervene and create intentionally metal-poor growth conditions. For example, both Ga₂O₃ and NiO favor cation vacancies to generate active hole conductivity types. Physical cation vacancies can generate electron-carrying holes and thus favor p-type conductivity.

[0363] Now refer to Figure 41 The process flow diagram of a method 4100 for forming a photoelectric semiconductor device according to the present disclosure is shown in an outline manner. In one example, the photoelectric semiconductor device is configured to emit light with a wavelength of about 150 nm to about 280 nm.

[0364] At step 4110, a metal oxide substrate having an epitaxial growth surface is provided. At step 4120, the epitaxial growth surface is oxidized to form an activated epitaxial growth surface. At step 4130, the activated epitaxial growth surface is exposed to one or more atomic beams each containing high-purity metal atoms and one or more atomic beams containing oxygen atoms, while depositing two or more epitaxial metal oxide films or layers.

[0365] Refer again Figure 15 This shows how to use it in one instance according to Figure 41 The method 4100 mentioned herein provides an epitaxial deposition system 680 for atomic and molecular beam epitaxy.

[0366] In one example, substrate 685 rotates about axis AX and is radiated and heated by heater 684, the emissivity of which is designed to match the absorption of the metal oxide substrate. High vacuum chamber 682 has multiple element sources 688, 689, 690, 691, and 692 capable of generating beams of atomic or molecular species as pure atomic components. A plasma source or gas source 693 and a gas feeding device 694 connected to the gas source 693 are also shown.

[0367] For example, sources 689-692 may comprise efflux sources of liquid Ga and Al and Ge or precursor-based gases. Active oxygen sources 687 and 693 may be provided 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 atomic oxygen source. Multiple gases may be injected via sources 695, 696, and 697 to provide mixtures of different species for growth. For example, atomic nitrogen and excited molecular nitrogen enable the production of n-type films, p-type films, and semi-insulating conductive films in gallium oxide-based materials. Vacuum pump 681 maintains a vacuum, and a mechanical shutter intersecting with atomic beam 686 modulates the corresponding beam flux, which provides a line of sight to the substrate deposition surface.

[0368] This deposition method has been found to have particular utility in enabling the flexible incorporation of elemental species into gallium oxide-based and aluminum oxide-based materials.

[0369] Figure 16An embodiment of an epitaxial process 700 for constructing a UV LED according to a growth direction 705 is shown. A natural substrate 710 can be used to form a homogeneous symmetry type layer 735. The substrate 710 and the crystal structure epitaxial layer 735 are homogeneous symmetry and are designated as type 1 herein. For example, a corundum-type sapphire substrate can be used to deposit corundum crystal symmetry type layers 715, 720, 725, and 730. Another example is the use of a monoclinic substrate crystal symmetry to form monoclinic crystal symmetry layers 715-730. The target materials disclosed herein are grown using a natural substrate (e.g., see...). Figure 43A This can be easily achieved using Table I. Of particular interest is the growth of epitaxial layer formations (such as corundum AlGaO3) having layers 715-730 of various compositions. Alternatively, monoclinic Ga2O3 substrate 710 can be used to form various monoclinic AlGaO3 compositions with layers 715-730.

[0370] Now refer to Figure 17 This illustrates another epitaxial process 740 using a substrate 710, which has a crystal symmetry inherently different from the crystal type of the target epitaxial metal oxide epitaxial layer 745, 750, 755, 760. That is, the substrate 710 has crystal symmetry type 1, which is heterosymmetric to the crystal structure epitaxial layer 765 composed entirely of type 2 layers 745, 750, 755, 760.

[0371] For example, C-faceted corundum sapphire can be used as a substrate to deposit at least one of monoclinic, triclinic, or hexagonal AlGaO3 structures. Another example is the epitaxial deposition of corundum AlGaO3 structures using a (110) oriented monoclinic Ga2O3 substrate. Yet another example is the epitaxial deposition of (100) oriented monoclinic AlGaO3 films using a MgO (100) oriented cubic symmetry substrate.

[0372] Process 740 can also be used to generate a corundum Ga2O3 modified surface 742 by selectively diffusing Ga atoms into the surface structure provided by the Al2O3 substrate. This can be achieved by increasing the growth temperature of the substrate 710 and exposing the Al2O3 surface to excess Ga while also providing a mixture of O atoms. Under Ga-rich conditions and at elevated temperatures, Ga adsorbed atoms selectively attach to O sites and form volatile secondary oxides Ga2O, and further, the excess Ga causes Ga adsorbed atoms to diffuse into the Al2O3 surface. Under suitable conditions, a corundum Ga2O3 surface structure is generated, thereby enabling the lattice matching of the Ga-rich AlGaO3 corundum structure or thicker layers to produce monoclinic AlGaO3 crystal symmetry.

[0373] Figure 18In another embodiment of process 770, a buffer layer 775 is deposited on a substrate 710. The buffer layer 775 has the same crystal symmetry type (type 1) as the substrate 710, thereby enabling the atomically planar layer to seed layers 780, 785, and 790 with alternating crystal symmetry types (types 2, 3, ..., N). For example, a monoclinic buffer layer 775 is deposited on a monoclinic Ga2O3 substrate 710. Cubic MgO and NiO layers 780-790 are then formed. In this figure, the heterogeneous symmetry crystal structure epitaxially with a homogeneous symmetry buffer layer is labeled as structure 800.

[0374] Figure 19 Another embodiment of the process 805 illustrates a sequential variation of various crystal symmetry types along the growth direction 705. For example, corundum Al2O3 710 (type 1) produces an O-end template 810, which is then seeded with a corundum AlGaO3 layer 815 having a substrate type 2 crystal symmetry. A hexagonal AlGaO3 layer 820 with type 3 crystal symmetry can then be formed, followed by a cubic crystal symmetry type (type N), such as MgO or NiO layer 830. In this figure, layers 815, 820, 825, and 830 are collectively labeled as a heterogeneous symmetry crystal structure epitaxy 835. Such crystal growth matching is possible using layers of very different crystal symmetry types if in-plane lattice coincidence geometry is possible. Although rare, it has been found in this disclosure that (100) oriented cubic Mg x Ni 1-x This can be achieved using a combination of O (0≤x≤1) and monoclinic AlGaO3. This procedure can then be repeated along the growth direction.

[0375] Figure 20A Another embodiment is shown, in which a substrate 710 having type 1 crystal symmetry has a fabrication surface (template 810) seeded with a first crystal symmetry type 815 (type 2), which can then be designed to transition to another symmetry type 845 (transition type 2-3) over a given layer thickness. An optional layer 850 having yet another crystal symmetry type (type N) can then be grown. For example, a corundum Ga2O3 layer 815 is formed on the C-plane sapphire substrate 710, which is then relaxed to a hexagonal Ga2O3 crystal symmetry type or a monoclinic crystal symmetry type. Further growth of layer 850 can then be used to form a high-quality relaxed layer with high crystal structure quality. In this figure, layers 815, 845, and 850 are collectively labeled as a heterosymmetric crystal structure epitaxial layer 855.

[0376] Now refer to Figure 20BA graph 860 shows the variation of a specific crystal surface energy 865 with crystal surface orientation 870 for the cases of corundum sapphire 880 and monoclinic gallium single-crystal oxide material 875. According to this disclosure, the technically relevant crystal surface energies of corundum Al2O3 880 and monoclinic substrates can be used to selectively form AlGaO3 crystal symmetry types.

[0377] For example, sapphire C-facets can be prepared under O-rich growth conditions to selectively grow hexagonal AlGaO3 at lower growth temperatures (<650°C) and monoclinic AlGaO3 at higher temperatures (>650°C). Due to the monoclinic crystal symmetry, which has approximately 50% tetrahedral coordination bonds (TCBs) and 50% octahedral coordination bonds (OCBs), monoclinic AlGaO3 is limited to approximately 45%–50% Al. While Ga can accommodate both TCBs and OCBs, Al prefers to seek OCB sites. R-facet sapphires can accommodate corundum AlGaO3 compositions with Al percentages ranging from 0%–100% when grown under O-rich conditions at low temperatures below approximately 550°C, as well as monoclinic AlGaO3 with Al <50% at high temperatures above 700°C.

[0378] Surprisingly, M-facet sapphire offers yet another, even more stable surface, which can be grown with only Al% = 0%-100% corundum AlGaO3 composition, thus providing an atomically flat surface.

[0379] Even more surprisingly, it has been discovered that A-side sapphire surfaces exhibiting AlGaO3 can possess corundum-AlGaO3 compositions and superlattices with extremely low defect densities (see discussion below). This result is essentially due to the fact that both corundum Ga2O3 and corundum Al2O3 share a unique crystal symmetry structure formed by OCB. This translates into extremely stable growth conditions within a temperature window ranging from room temperature to 800°C. This clearly demonstrates the interest in crystal symmetry designs that can produce novel structural forms suitable for LEDs, such as UV LEDs.

[0380] Similarly, natural monoclinic Ga2O3 substrates with (-201) oriented surfaces are only suitable for monoclinic AlGaO3 compositions. The Al% of the (-201) oriented film is significantly reduced due to the TCB exhibited on the grown crystal surface. This is unfavorable for large Al fractions but can be used to form very shallow MQWs in AlGaO3 / Ga2O3.

[0381] Surprisingly, the (010) and (001) oriented surfaces of monoclinic Ga2O3 can accommodate monoclinic AlGaO3 structures with extremely high crystal quality. The main limitation of Al% in AlGaO3 is the accumulation of biaxial strain. Even with careful strain management according to this disclosure using an AlGaO3 / Ga2O3 superlattice, there is still a limitation of Al% <40%, where higher quality films are obtained using a (001) oriented Ga2O3 substrate. Another example of a (010) oriented monoclinic Ga2O3 substrate is the extremely high-quality lattice matching of a MgGa2O4 (111) oriented film with a cubic crystal symmetry structure.

[0382] Similarly, the crystal symmetry of MgAl2O4 is compatible with that of corundum AlGaO3 compositions. According to this disclosure, experiments have also revealed that (100) oriented Ga2O3 provides a near-perfect lattice match for cubic MgO (100) and NiO (100) films. Even more surprisingly, the effectiveness of (110) oriented monoclinic Ga2O3 substrates in the epitaxial growth of corundum AlGaO3 is evident.

[0383] These unique properties provide selective utility for Al2O3 and Ga2O3 crystal symmetry type substrates, for example, selectively using crystal surface orientation to provide many advantages for the manufacture of LEDs, and especially UV LEDs.

[0384] In some implementations, conventional bulk crystal growth techniques can be used to form bulk substrates of corundum-AlGaO3 compositions with corundum and monoclinic crystal symmetry types. These ternary AlGaO3 substrates have also proven valuable for use in UV LED devices.

[0385] With structural modifier

[0386] By paying particular attention to structural deformations of a given crystal symmetry type, the valence band structure of AlGaO3 can be optimized. For application in solid-state, and especially semiconductor-based, electro-optically driven ultraviolet emitting devices, the valence band structure (VBS) is crucial. Typically, the VBSE-k dispersion determines the efficiency of light emission generated through the direct recombination of electrons and holes. Therefore, attention now turns to valence band tuning options to achieve UVLED operation in one instance.

[0387] Configuration of the belt structure through biaxial strain

[0388] In some embodiments, selective epitaxial deposition of AlGaO3 crystal structures can be achieved by controlling the surface crystal geometry under elastic structural deformation using a composition or by using an epitaxially registerable AlGaO3 film while maintaining the elastic deformation of the AlGaO3 unit cell.

[0389] For example, Figures 21A to 21CThe changes in the Ek band structure near the Brillouin zone center (k=0) under the influence of biaxial strain applied to the crystal cell are depicted, which favors eh recombination to generate bandgap energy photons. The band structures of both corundum and monoclinic Al2O3 are direct. According to this disclosure, Al2O3, Ga2O3, or AlGaO3 films can be deposited onto suitable surfaces that allow elastic strain on the in-plane lattice constant of the film.

[0390] Figure 43B Table II shows the lattice constant mismatch between Al2O3 and Ga2O3. For the same type of crystal symmetry, ternary alloys can be roughly intercalated between the endpoint binary alloys. Generally, Al2O3 films deposited on Ga2O3 substrates with conserved crystal orientation will produce Al2O3 films under biaxial tension, while Ga2O3 films deposited on Al2O3 substrates with the same crystal orientation will be in a compressed state.

[0391] Compared to conventional cubic crystals, zincblende crystals, or even wurtzite crystals, monoclinic and corundum crystals have non-ordinary geometries with relatively complex strain tensors. Figures 21A to 21B The diagram illustrates the general trend observed in the Ek dispersion near the center of BZ. For example, Figure 21A Diagram 890 depicts a c-plane corundum crystal cell 894 with strain-free (σ=0)Ek dispersion, wherein the conduction band 891 and the valence band 892 are separated by a band gap 893. Figure 21B The biaxial compression of cell 899 in diagram 895 alters the dispersion by hydrostatically raising the conduction band (e.g., see conduction band 896) and distorting the Ek curvature of the valence band 897. The band gap 898 typically increases after compressive strain (σ<0).

[0392] On the contrary, such as Figure 21C As shown in diagram 900, the biaxial tension applied to unit cell 904 has the effect of reducing the band gap. The effects of reducing the conduction band 901 and flattening the valence band curvature 902 are significant. Since the valence band curvature is directly related to the effective hole mass, a larger curvature decreases the effective hole mass, while a smaller curvature (i.e., a flatter Ek band) increases the effective hole mass (note: a perfectly flat valence band dispersion may result in bound holes). Therefore, it is possible to improve the valence band dispersion of Ga2O3 by wisely selecting biaxial strain performed via epitaxy on suitable crystal surface symmetry and in-plane lattice structure.

[0393] Configuration of the belt structure through uniaxial strain

[0394] Of particular interest is the possibility of using uniaxial strain to advantageously modify valence band structures, such as... Figure 22A and Figure 22B As shown, where Figure 22A The reference numbers in the text correspond to Figure 21A Reference figures. For example, in-plane uniaxial deformation of cell 894 along essentially one crystal direction (as shown in cell 909) will cause the valence band 907 to deform asymmetrically, as shown in diagram 905, which also shows the conduction band 906 and the band gap 908.

[0395] For monoclinic and corundum crystal symmetry films, similar properties will exist, and these properties can be achieved by growing Al2O3 / Ga2O3 and Al... x Ga 1-x O3 / Ga2O3 and Al x Ga 1-x This is illustrated using an elastic strain superlattice structure of O3 / Al2O3. Such structures have been grown with respect to this disclosure, and it has been found that the critical layer thickness (CLT) depends on the surface orientation of the substrate and ranges from 1-2 nm to approximately 50 nm for binary Ga2O3 on sapphire. For monoclinic Al... x Ga 1-x O 3x With x < 10%, CLT can exceed 100 nm on Ga2O3.

[0396] Uniaxial strain can be implemented by growth on a crystal symmetry surface with an asymmetric surface cell. This is possible in applications such as... Figure 20B The various surface orientations described are achieved in both corundum and monoclinic crystals, but other surface orientations and crystals are also possible, such as MgO (100), MgAl2O4 (100), 4H-SiC (0001), ZnO (111), Er2O3 (222), and AlN (0002), etc.

[0397] Figure 22B This illustrates a favorable variation of the valence band structure for the direct bandgap case. For indirect bandgap Ek dispersions (such as thin monolayer monoclinic Ga₂O₃), the valence band dispersion can be tuned from the indirect bandgap to the direct bandgap, as shown below. Figure 23A or Figure 23B Transition to Figure 23C As shown. Consider Figure 23B The strain-free band structure 915 has a conduction band 916, a valence band 917, a band gap 918, and a valence band maximum value 919. Similarly, Figure 23A The compression structure 910 shows the conduction band 911, valence band 912, band gap 913, and valence band maximum value 914. Figure 23CThe tension structure 920 shows the conduction band 921, valence band 922, band gap 923, and valence band maximum 924. Detailed calculations and experimental angle-resolved photoelectron spectroscopy (ARPES) show that compressive and tensile strain applied to the Ga2O3 film can distort the valence band, as shown in structures 910 and 920 for uniaxial strain of compressive (valence band 912) and tensile (valence band 922) strain applied along the b-axis or c-axis of the monoclinic Ga2O3 cell.

[0398] As these figures illustrate, strain plays a crucial role and is typically required to be managed in composite epitaxial structures. Unmanaged strain accumulation can lead to the release of elastic energy within the unit cell due to dislocations and crystal defects, thereby reducing the efficiency of UV LEDs.

[0399] The band structure is configured by applying post-growth stress.

[0400] While the above techniques involve introducing stress in the form of uniaxial or biaxial strain during the formation of the layers, in other embodiments, external stress may be applied after the formation or growth of the layers or metal oxide layers to configure the strip structure as needed. Exemplary techniques for introducing these stresses are disclosed in U.S. Patent No. 9,412,911.

[0401] The strip structure is configured by selecting the composition alloy.

[0402] Another mechanism utilized in this disclosure and applied to optically emitting metal oxide-based UV LEDs is the use of compositional alloying to form a ternary crystal structure with a desired direct bandgap. Generally speaking, Figure 24A and Figure 24B Two distinct binary oxide material compositions are shown. Band structure 925 comprises a metal oxide AO having a crystal structure material 930 composed of metal atoms 928 and oxygen atoms 929, with a conduction band 926, a valence band dispersion 927, and a direct band gap 931. Another binary metal oxide BO has a crystal structure material 940 composed of different metal cations 938 and oxygen atoms 939 of type B, and has an indirect band structure 935 with 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.

[0403] (AO) can be formed by mixing cation sites with metal atoms A and B in another similar oxygen-containing material. x (BO) 1-x In the case of forming a ternary alloy, this will produce A with the same basic crystal symmetry. x B 1-xO composition. Based on this, it is then possible to form ternary metal oxides with valence band mixing effects, such as... Figure 25B As shown (Note: Figure 25A and Figure 25C Reproduction Figure 24A and Figure 24B The direct valence band dispersion 927 of AO crystal structure material 930 alloyed with BO crystal structure material 940 having indirect valence band dispersion 937 can produce ternary material 948, which exhibits improved valence band dispersion 947 and has conduction band 946 and band gap 949. That is, the atomic species A of material 930 incorporated into the B sites of material 940 can expand the valence band dispersion. Atomic density function theory calculations can be used to simulate this concept, taking into full account the pseudopotentials, strain energies, and crystal symmetries of the constituent atoms.

[0404] Therefore, alloying corundum Al2O3 and Ga2O3 can produce a direct band gap in the band structure of ternary metal oxide alloys, and can also improve the valence band curvature of monoclinic crystal symmetry compositions.

[0405] The belt structure is configured by selecting digital alloy manufacturing.

[0406] While ternary alloy compositions such as AlGaO3 are desirable, an equivalent method for producing ternary alloys is through the use of digital alloying forms employing a superlattice (SL) composed of periodic repetitions of at least two different materials. If each layer of the repeating unit cell constituting the SL is less than or equal to the electron de Broglie wavelength (typically about 0.1 nm to 10 nm), the superlattice periodically forms 'mini-Brillouin zones' within the crystal band structure, such as... Figure 27A As shown. In practice, a new periodicity is superimposed on the inherent crystal structure by forming a predetermined SL structure. The SL periodicity is typically in one dimension along the epitaxial film growth direction.

[0407] exist Figure 26 In the curve 950, the valence band state 953 specific to material 955 and the valence band state 954 from material 956 are considered. Ek dispersion shows the band gap 957 along the energy axis 951 for region 958 and the first Brillouin zone edge 959 relative to k=0. Region 958 is the band gap (ΔE) between band states 953 and 954, which are the bulk bands of materials 955 and 956. If materials A and B form as... Figure 27B The superlattice shown is 968 and has a period L. SL The average lattice constant a was chosen as A and B AB Multiples of (e.g., L) SL =2a AB ), then the following will occur Figure 27AThe new states 961, 962, 963, and 964 are shown. Therefore, the superlattice energy potential produces 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. That is, when the superlattice is fabricated into an ultrathin layer (thicknesses 970 and 971) forming a periodically repeating unit cell 969 using two materials 955 and 956, the original bulk valence band states 953 and 954 are folded into new band states 961, 962, 963, and 964. In other words, the superlattice potential produces a new energy dispersion structure including band states 961, 962, 963, and 964. Due to the new spatial potential imposed by the superlattice periodicity, the Brillouin zone is contracted to a wave vector 975.

[0408] Figure 27B This type of SL structure can be generated using double pairs, which in different instances include: A1 x Ga 1-x O / Ga2O3, Al x Ga 1-x O3 / Al2O3, Al2O3 / Ga2O3 and Al x Ga 1-x O / Al y Ga 1-y O3.

[0409] The general use of an SL for configuring an optoelectronic device is disclosed in U.S. Patent No. 10,475,956.

[0410] Figure 27C The diagram illustrates an SL structure for a digital binary metal oxide, comprising an Al₂O₃ layer 983 and a Ga₂O₃ layer 984. The structure is illustrated by electron energies 981 that vary with the epitaxial growth direction 982. The SL forming the repeating unit cell 980 repeats in integer or half-integer cycles. For example, the number of repetitions can vary from three or more cycles, and even up to 100 or 1000 or more. Equivalent digital alloy Al x Ga 1-x The average Al% content of O was calculated as follows: in It is the layer thickness of Al2O3 and The thickness of the layer.

[0411] Figures 27D to 27F Some other examples of possible SL structures are shown below.

[0412] The concept of digital alloys can be extended to other different crystal symmetry types, such as... Figure 27D The cubic NiO 987 and monoclinic Ga2O3 986 are shown, with the digital alloy 985 simulating the equivalent ternary (NiO).x (Ga2O3) 1-x body alloy.

[0413] Figure 27E The use of cubic MgO layers 991 and cubic NiO layers 992 constituting the SL in the digital alloy 990 provides another example. In this example, unlike Al2O3 and Ga2O3, which have high lattice mismatch, MgO and NiO have a very close lattice match.

[0414] Figure 27F The digital alloy 995 illustrates a four-layer periodic SL996, in which cubic MgO and NiO grown along the (100) orientation are superimposed on the (100) oriented monoclinic Ga2O3 lattice. This SL will have an efficient quaternary composition of Ga x Ni y Mg z O n .

[0415] aluminum gallium oxide band structure

[0416] Binary or ternary Al can be used x Ga 1-x O3 compositions (bulk or conductor digital alloy formations) are used to select the UV LED module region. As mentioned above, advantageous valence band tuning is also possible using biaxial or uniaxial strain. Figure 29 An exemplary process flow 1000 is shown, which describes possible selection criteria for selecting at least one of the crystal modification methods to form the bandgap region of a UV LED.

[0417] At step 1005, the configuration of the band structure is selected, including but not limited to band structure characteristics (such as whether the band gap is direct or indirect), band gap energy, E... 费米 The carrier mobility, doping, and polarization are considered. At step 1010, it is determined whether a binary oxide is suitable, and at step 1015, it is further determined whether the band structure of the binary oxide can be modified (i.e., tuned) to meet the requirements. If the binary oxide material meets the requirements, it is selected for the relevant layer in the optoelectronic device at step 1045. If the binary oxide is unsuitable, it is determined at step 1025 whether a ternary oxide is suitable, and at step 1030, it is further determined whether the band structure of the ternary oxide can be modified to meet the requirements. If the ternary oxide meets the requirements, it is selected for the relevant layer at step 1045.

[0418] If the ternary oxide is unsuitable, it is determined at step 1035 whether a digital alloy is suitable, and at step 1040, it is further determined whether the strip structure of the digital alloy can be modified to meet the requirements. If the ternary oxide meets the requirements, this material is selected for the relevant layer at step 1045. After determining the layers in this way, the optoelectronic device stack is then fabricated at step 1048.

[0419] Figure 30 Figure 1050 shows Al2O3 and Ga2O3 relative to the ternary alloy Al. x Ga 1-x The implementation scheme of the band structure of O3, and for corundum and monoclinic crystal symmetry, the implementation scheme varies in conduction band and valence band shifts. In diagram 1050, the y-axis is the electron energy 1051 and the x-axis is the different material types 1053 (Al2O3 1054, (Ga1Al1)O3 1055, and Ga2O3 1056). Corundum and monoclinic heterojunctions both appear to have type I and type II shifts, while Figure 30 Simply plot the band alignment using the existing values ​​of the electron affinity for each material.

[0420] The theoretical electronic band structures of Al₂O₃ and Ga₂O₃ in monoclinic crystal form are known in the prior art. However, the application of strain to thin epitaxial films has not been studied, and this is the subject of this disclosure. By referring to the bulk band structures of Ga₂O₃ 10⁵⁶ and Al₂O₃ 10⁵⁴, embodiments of this disclosure utilize how strain design can be advantageously applied to UV LEDs. Understanding how the valence band is affected requires combining monoclinic and trigonal strain tensors into a kp-like Hamiltonian. Existing kp crystal models applied to the bulk symmetry of zincblende and wurtzite crystals are not mature enough to simulate both monoclinic and trigonal crystal systems. The current effort is to perform a second approximation of the valence band Hamiltonian at the center of the Brillouin zone of the material, where this center has the point set C₂. h Symmetry.

[0421] Single crystal alumina

[0422] This paper discusses two main crystal forms of symmetry for Al2O3 and Ga2O3: monoclinic (C2 / m) and corundum (R3c). However, other crystal symmetry types, such as triclinic and hexagonal forms, are also possible. Other crystal symmetry forms can also be applied based on the principles set forth in this disclosure.

[0423] (a) Symmetry of corundum Al2O3

[0424] Figure 31The image shows the crystal structure of trigonal Al₂O₃ (corundum) 1060. Larger spheres represent Al atoms 1064, and smaller spheres are oxygen atoms 1063. The unit cell 1062 has a crystal axis 1061. Along the c-axis are layers of Al and O atoms. This crystal structure has a calculated banding structure 1065, as shown... Figures 32A to 32B As shown, the electron energy 1066 is plotted as varying with the crystal wave vector 1067 within the Brillouin zone. High symmetry points within the Brillouin zone are marked, such as those near the center of the zone at k=0, which is useful for understanding the optical emission properties of the material.

[0425] At k=0, the direct bandgap has a maximum valence band value of 1068 and a minimum conduction band value of 1069. Figure 32B Detailed images of the valence bands show the composite dispersion of the two uppermost valence bands. In the case where electrons and holes can actually be injected simultaneously into the Al₂O₃ band structure, the uppermost valence band determines the optical emission characteristics.

[0426] (b) Monoclinic symmetry Al2O3

[0427] Figure 33 The image shows the crystal structure 1070 of monoclinic Al₂O₃. Larger spheres represent Al atoms 1064, and smaller spheres are oxygen atoms 1063. The unit cell 1072 has crystal axes 1071. This crystal structure has the calculated banding structure 1075, as shown... Figures 34A to 34B As shown, where Figure 34B This is a detailed image of the valence band. Figure 34A The conduction band 1076 is also shown. High symmetry points within the Brillouin zone are marked, as shown near the center of the zone at k=0, which is useful for understanding the optical emission properties of the material.

[0428] The monoclinic crystal structure 1070 has a more complex symmetry compared to the trigonal crystal, and compared to... Figure 31 The corundum sapphire 1060 form shown has a lower density and a smaller band gap.

[0429] The monoclinic Al₂O₃ form also has a direct bandgap with a clearly separated highest valence band 1077, which has a lower curvature relative to the Ek dispersion along the GX and GN wave vectors. The monoclinic bandgap is ~1.4 eV smaller than that of the corundum form. The second highest valence band 1078 is symmetrical and separated from the uppermost valence band.

[0430] Single-crystal gallium oxide

[0431] (a) Symmetry of corundum Ga2O3

[0432] Figure 35The image shows the crystal structure of trigonal Ga₂O₃ (corundum) 1080. Larger spheres represent Ga atoms 1084, and smaller spheres are oxygen atoms 1083. The unit cell 1082 has a crystal axis 1081. Corundum (a trigonal crystal symmetry type) is also called the α phase. The crystal structure described is similar to... Figure 31 The same as sapphire 1060, where the lattice constant is defined Figure 43B The unit cell shown in Table II is 1082. The Ga2O3 unit cell 1082 is larger than that of Al2O3. Corundum crystals have octahedral bonded Ga atoms.

[0433] Figure 36A and Figure 36B The figure shows the calculated band structure 1085 of corundum Ga2O3. The band structure is pseudo-direct, with only a very small energy difference between the valence band maximum value 1087 and the region center k=0. Figure 36A The image also shows the 1086 conduction band.

[0434] The biaxial and uniaxial strains applied to corundum Ga2O3 using the methods described above can then be used to modify the band structure and valence band into a direct bandgap. In practice, it is possible to shift the valence band maximum to the center of the region using tensile strain applied along the b-axis and / or c-axis of the crystal. It is estimated that ~5% tensile strain can be accommodated within the thin Ga2O3 layer constituting Al2O3 / Ga2O3SL.

[0435] (b) Monoclinic symmetry Ga2O3

[0436] Figure 37 The image shows the crystal structure of monoclinic Ga₂O₃ (corundum) 1090. Larger spheres represent Ga atoms 1084, and smaller spheres are oxygen atoms 1083. The unit cell 1092 has crystal axes 1091. This crystal structure has a calculated banding structure 1095, as shown... Figures 38A to 38B As shown, high-symmetry points within the Brillouin zone are marked, such as those near the center of the zone at k=0, which is useful for understanding the optical emission properties of materials. Figure 38A The image also shows the 1096 conduction band.

[0437] Monoclinic Ga₂O₃ has an uppermost valence band of 1097 with a relatively flat Ek dispersion. Closer examination reveals that the actual maximum value of the valence band is located at a position several eV (specific heat energy kJ). B The variation in T (from small to 25 meV) provides insight into the fact that monoclinic Ga₂O₃ will have a relatively large effective hole mass and therefore a relatively locally low mobility. Thus, strain can be advantageously used to improve the band structure, and particularly the valence band dispersion.

[0438] Ternary aluminum gallium oxide

[0439] Figure 39The crystal structure 1100 shown is yet another example of the unique properties of the AlGaO3 material system, having crystal axes 1101 and unit cells 1102. The ternary alloy contains 50% Al composition.

[0440] (Al x Ga 1-x )2O3, where x = 0.5, can be formed into substantially different crystal symmetry forms with an orthorhombic structure. As shown together with oxygen atom 1083, Ga atom 1084 and Al atom 1064 are disposed within the crystal. Of particular interest are the layered structures of Al and Ga atomic planes. This type of structure can also be constructed using atomic layer techniques to form ordered alloys as described throughout this disclosure.

[0441] Figure 40 The calculated band structure 1105 is shown in the figure. The minimum value of the conduction band 1106 and the maximum value of the valence band 1107 show the direct band gap.

[0442] Ordered ternary AlGaO3 alloy

[0443] The use of atomic layer epitaxy further enables the formation of novel crystal symmetry structures. For example, some embodiments include ultrathin epitaxial layers comprising alternating sequences of the form [Al-O-Ga-O-Al-…] along the growth direction. Figure 42 Structure 1110 illustrates a possible extreme case of generating an ordered ternary alloy using alternating sequences 1115 and 1120. As demonstrated in this disclosure, growth conditions can be created where Al and Ga are self-ordering. These conditions can even occur when coincident Al and Ga fluxes are simultaneously applied to the growth surface, resulting in a self-assembled ordered alloy. Alternatively, predetermined modulation of the Al and Ga fluxes reaching the epitaxial layer surface can also produce ordered alloy structures.

[0444] The ability to configure strip structures for optoelectronic devices, and in particular UV LEDs, by selecting from bulk metal oxides, ternary compositions, or even more advanced digital alloys is fully encompassed within the scope of this disclosure.

[0445] Another example is the use of biaxial and uniaxial strain to modify the strip structure, while another example is the use of strain-epitaxy (Al2O3 or Ga2O3) on a strain-exposed layer on an Al2O3 or Ga2O3 substrate. x Ga 1-x )2O3 material system.

[0446] Substrate selection for AlGaO-based UV LEDs

[0447] The choice of a natural metal oxide substrate is one aspect of this disclosure, which is suitable for utilizing the advantages of strained layer epitaxy on Al2O3 or Ga2O3 substrates (Al x Ga 1-x Epitaxy of 2O3 material system.

[0448] Figure 43A Exemplary substrates are listed in Table I. In some embodiments, intermediate AlGaO3 bulk substrates may also be used, and these are advantageous for application in UV LEDs.

[0449] The advantage of a monoclinic Ga2O3 bulk substrate is the formation of monoclinic (Al) substrates with a high Ga content (e.g., about 30%-40%, limited by strain accumulation). x Ga 1-x The ability of the Al₂O₃ structure. This enables vertical devices due to its conductive substrate capability. Conversely, corundum epitaxial films (Al₂O₃) are achieved using a corundum Al₂O₃ substrate. x Ga 1-x )2O3, where 0≤x≤1.

[0450] Other substrates such as MgO(100), MgAl2O4 and MgGa2O4 are also favorable for the epitaxial growth of metal oxide UV LED structures.

[0451] Selection and Function of Crystal Growth Modifiers

[0452] Examples of metal oxide structures used in optoelectronic applications, particularly in the fabrication of UV LEDs, will now be discussed. The following will describe... Figures 44A to 44Z The structures disclosed herein are not limiting, as possible crystal structure modifiers may be selected from those entering a given metal oxide MO (where M = Al, Ga) (such as binary Ga₂O₃, ternary (Al₂O₃)). x Ga 1-x The cation and anion components of either Al2O3 or Al2O3.

[0453] Based on both theoretical and experimental findings of this disclosure, the cationic species crystal modifier entering the MO as defined above can be selected from at least one of the following:

[0454] Germanium (Ge)

[0455] Ge is advantageously supplied as a pure elemental species for bonding during non-equilibrium crystal formation via co-deposition of MO species. In some embodiments, elementally pure shock beams of Ga and Ge atoms are co-deposited with reactive oxygen beams impacting the growth surface. For example, Ge has a +4 valence and can be introduced in a rare atomic ratio by substitution at the M-site of the metal cation in the MO host crystal to form a structure with the form (Ge... +4O2) 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, wherein for dilute Ge compositions, x < 0.1.

[0456] According to the findings of this disclosure, for Ge x < 0.1, the dilute Ge ratio provides sufficient electronic modification to intrinsic MO to manipulate the Fermi energy (E). F This increases the concentration of available electron carriers and alters the lattice structure to provide favorable strain during epitaxial growth. For dilute compositions, the host MO physical cell remains largely undisturbed. Further increases in Ge concentration lead to modification of the host Ga2O3 crystal structure via lattice expansion, or even result in entirely new material compositions.

[0457] For example, for Ge x ≤ 1 / 3, the monoclinic crystal structure of the host Ga2O3 unit cell can be maintained. For example, x = 0.25 forms a monoclinic Ge. 0.25 Ga 1.50 O 2.75 =Ge1Ga6O 11 It is possible. Advantageously, monoclinic Ge x Ga 2(1-x) O 3-x The (x = 1 / 3) crystal exhibits an excellent direct band gap exceeding 5 eV. Compared to unstrained monoclinic Ga₂O₃, the lattice deformation resulting from the introduction of Ge preferably increases the monoclinic cell size along the b-axis and c-axis while maintaining the a-axis lattice constant.

[0458] The lattice constants of monoclinic Ga₂O₃ are (a = 3.08 Å, b = 5.88 Å, c = 6.41 Å), and monoclinic Ge₁Ga₆O₃... 11 The lattice constants of Ge are (a = 3.04 Å, b = 6.38 Å, c = 7.97 Å). Therefore, introducing Ge results in biaxial expansion of the independent unit cell along the b-axis and c-axis. Thus, if Ge... x Ga 2(1-x) O 3-x Epitaxial deposition on a bulk monoclinic Ga2O3 surface oriented along the b-axis and c-axis (i.e., along the a-axis) results in Ge x Ga 2(1-x) O 3-xThe film can be elastically deformed to induce biaxial compression, and thus advantageously cause the valence band Ek to be dispersed and twisted, as discussed in this paper.

[0459] When x > 1 / 3, higher Ge% causes the crystal structure to transform into a cubic structure, such as GeGa2O5.

[0460] In some implementations, Ge is bound to Al2O3 and (Al x Ga 1-x It is also possible in )2O3.

[0461] For example, direct bandgap Ge can also be epitaxially formed by co-depositing elements Al and Ge and reactive oxygen species. x Al 2(1-x) O 3-x Ternary alloys are used to form monoclinic symmetrical thin films. According to this disclosure, for Ge%x to 0.6, the monoclinic structure is stable, resulting in independent lattices that, compared to monoclinic Al₂O₃, exhibit greater relative expansion along the a-axis and c-axis, while moderately decreasing along the b-axis.

[0462] The lattice constants of monoclinic Ge₂Al₂O₇ are (a = 5.34 Å, b = 5.34 Å, c = 9.81 Å), and those of monoclinic Al₂O₃ are (a = 2.94 Å, b = 5.671 Å, c = 6.14 Å). Therefore, to maintain the elastic deformation of a sufficiently thin film, Ge₂Al₂O₇ is deposited along the b-axis oriented growth direction and further deposited on the surface of the monoclinic Al₂O₃. x Al 2(1-x) O3 will be subjected to biaxial tension.

[0463] Silicon (Si)

[0464] Elemental Si can also be supplied as a pure elemental species for bonding during non-equilibrium crystal formation via co-deposition of MO species. In some embodiments, elementally pure impact beams of Ga and Si atoms are co-deposited with reactive oxygen beams impacting the growth surface. For example, Si has a +4 valence and can be introduced at a diluted atomic ratio by substitution at the M-site of the metal cation in the MO host crystal to form a structure with the form (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-xA stoichiometric composition, wherein for dilute Si compositions, x < 0.1.

[0465] According to the findings of this disclosure, for Si x < 0.1, the dilute Si ratio provides sufficient electronic modification to the intrinsic MO to manipulate the Fermi energy (E). F This increases the concentration of available free electron carriers and alters the lattice structure to provide favorable strain during epitaxial growth. For dilute compositions, the host MO physical cell remains largely undisturbed. Further increases in Si concentration lead to modification of the host Ga2O3 crystal structure via lattice expansion, or even result in entirely new material compositions.

[0466] For example, for Si x ≤ 1 / 3, the monoclinic crystal structure of the host Ga2O3 unit cell can be maintained. For example, for the case of Si%x = 0.25, monoclinic Si is formed. 0.25 Ga 1.50 O 2.75 =Si1Ga6O 11 It is possible. Compared to unstrained monoclinic Ga₂O₃, the lattice deformation resulting from the introduction of Si preferably increases the monoclinic cell size along the b-axis and c-axis while maintaining the a-axis lattice constant. Compared to monoclinic Ga₂O₃ (a = 3.08 Å, b = 5.88 Å, c = 6.41 Å), monoclinic Si₁Ga₆O₃ exhibits higher lattice deformation. 11 The lattice constants are (a = 6.40 Å, b = 6.40 Å, c = 9.40 Å).

[0467] Therefore, introducing Si produces biaxial expansion of independent unit cells along all a-axis, b-axis, and c-axis. Therefore, if Si... x Ga 2(1-x) O 3-x Epitaxial deposition on a bulk monoclinic Ga2O3 surface oriented along the b-axis and c-axis (i.e., along the a-axis) results in Si x Ga 2(1-x) O 3-x The film can be elastically deformed to induce asymmetric biaxial compression, and thus advantageously cause the valence band Ek to be dispersed and twisted, as discussed in this paper.

[0468] When x > 1 / 3, higher Si% causes the crystal structure to transform into a cubic structure, such as SiGa2O5.

[0469] In some implementations, Si is incorporated into Al2O3 and (Al x Ga 1-x It is also possible in )2O3. For example, orthogonal (Si) can be achieved by directly co-depositing elemental Si and Al with reactive oxygen flux onto the deposition surface. +4 O2) x (Al2O3) 1-x =Six Al 2(1-x) O 3-x It is possible. If the deposition surface is selected from available trigonal α-Al₂O₃ surfaces (e.g., A-face, R-face, M-face), it is possible to form orthorhombic crystalline symmetry Al₂SiO₅ (i.e., x = 0.5), which reports a large direct band gap at the center of the Brillouin zone. The orthorhombic lattice constants are (a = 5.61 Å, b = 7.88 Å, c = 7.80 Å), while those for trigonal (R₃c)Al₂O₃ are (a = 4.75 Å, b = 4.75 Å, c = 12.982 Å).

[0470] Therefore, depositing oriented Al₂SiO₅ films on Al₂O₃ can lead to large biaxial compression of the elastically strained film. Exceeding the elastic energy limit will produce detrimental crystal mismatch dislocations, which should generally be avoided. To obtain elastically deformable films on Al₂O₃, films with a thickness of less than about 10 nm are particularly preferred.

[0471] Magnesium (Mg)

[0472] Some implementations involve combining a Mg element species with Ga₂O₃ and Al₂O₃ host crystals, wherein Mg is selected as a preferred Group II metal species. Furthermore, it is also possible to utilize the combination of Mg with (Al₂O₃)₃... x Ga 1-x In 2O3, the most abundant and most likely to form quaternary Mg x (Al,Ga) y O z Particularly useful composition Mg x Ga 2(1-x) O 3-2x (where x < 0.1) makes it possible to use Mg 2+ Cation-substituted Ga 3+ The cation sites will combine Ga2O3 and Al x Ga 1-x The electronic structure of the Al₂O₃ host forms a p-type conductivity type. y Ga 1-y )2O3 y=0.3, the band gap is about 6.0eV, and Mg can bind up to about y~0.05-0.1, thereby enabling the host's conductivity type to change from the inherently weakly excess electron n-type to the excess hole p-type.

[0473] Type Mg x Ga 2(1-x) O 3-2x and Mg x Al 2(1-x) O 3-2x and(Ni x Mg 1-xTernary compounds of O are also an exemplary embodiment of active region materials for optically emitting UV LEDs.

[0474] In some embodiments, the stoichiometric composition Mg x Ga 2(1-x) O 3-2x and Mg x Al 2(1-x) O 3-2x (where x = 0.5, thus producing a cubic crystal symmetry structure exhibiting a favorable direct bandgap Ek dispersion) Both are suitable for the optical emission region.

[0475] Furthermore, according to the findings of this disclosure, Mg x Ga 2(1-x) O 3-2x and Mg x Al 2(1-x) O 3-2x The composition is compatible with cubic MgO and Ga2O3 epitaxial structures in monoclinic, corundum, and hexagonal crystal symmetry forms.

[0476] The use of non-equilibrium growth techniques across MgO to corresponding MO binary alloys achieved a wide range of miscibility for Mg within Ga2O3 and Al2O3 hosts. This contrasts with equilibrium growth techniques such as CZ, where phase separation occurs due to volatile Mg species.

[0477] For example, Mg in cubic and monoclinic forms x Ga 2(1-x) O 3-2x The lattice constants of (x~0.5) are (a=b=c=8.46 Å) and (a=10.25 Å, b=5.98 Å, c=14.50 Å), respectively. According to this disclosure, cubic Mg... x Ga 2(1-x) O 3-2x The form can be a thin film having a (100) or (111) oriented film on a monoclinic Ga2O3 (100) or Ga2O3 (001) substrate. Furthermore, Mg can be... x Ga 2(1-x) O 3-2x A thin epitaxial film is deposited on a MgO substrate. Furthermore, Mg... x Ga 2(1-x) O 3-2x (0≤x≤1) film is directly deposited on a MgAl2O4(100) spinel crystal symmetry substrate.

[0478] In another implementation scheme, Mg can be used x Al 2(1-x) O 3-2x and Mg x Ga 2(1-x)O 3-2x High-quality (i.e., low defect density) epitaxial films are directly deposited onto a lithium fluoride (LiF) substrate.

[0479] Zinc (Zn)

[0480] Some implementations involve incorporating the Zn element species into Ga₂O₃ and Al₂O₃ host crystals, where Zn is another preferred group II metal species. Furthermore, it is also possible to utilize the incorporation of Zn into (Al₂O₃)₃ host crystals. x Ga 1-x In 2O3, the most abundant and most likely to form quaternary Zn x (Al,Ga) y O z .

[0481] Other quaternary compositions that are advantageous for tuning direct bandgap structures are compounds having the following most general forms:

[0482] (Mg x Zn 1-x ) z (Al y Ga 1-y ) 2(1-z) O 3-2z , where 0≤x,y,z≤1.

[0483] According to this disclosure, cubic crystal symmetry compositions with z ~ 0.5 can be advantageously used for a given fixed y composition between Al and Ga. By changing the Mg to Zn ratio x, the direct band gap can be tuned to about 4 eV ≤ E. G (x) < 7 eV. This can be achieved by advantageously setting the controllable flux of pure elemental beams of Al, Ga, Mg, and Zn individually and providing an activated oxygen flux for the anionic species. Generally, excess atomic oxygen is desired relative to the total bombarding metal flux. The desired composition for bandgap tuning of the UVLED region can then be pre-selected by controlling the Al:Ga flux ratio and Mg:Zn ratio reaching the growth surface.

[0484] Surprisingly, although zinc oxide (ZnO) was introduced into (Mg) x Zn 1-x ) z (Al y Ga 1-y ) 2(1-z) O 3-2zTypically, it is a wurtzite hexagonal crystal symmetry structure, but the cubic and spinel crystal symmetry forms can be easily achieved using the non-equilibrium growth method described herein. The bandgap characteristics at the center of the Brillouin zone can be tuned within the range from indirect to direct characteristics by the alloy composition (x, y, z). This is advantageous for applications in the electron injection region and the optical emission region that are substantially non-absorbing, respectively. In addition, bandgap modulation is possible for bandgap design structures such as superlattices and quantum wells described herein.

[0485] Nickel (Ni)

[0486] Combining Ni elemental species into Ga2O3 and Al2O3 host crystals is another preferred group II metal. In addition, the use of combining Ni into (Al x Ga 1-x )2O3, up to and including forming the quaternary Ni x (Al, Ga) y O z .

[0487] Some other quaternary compositions that are beneficial for tuning the direct bandgap structure are compounds of the following most general form:

[0488] (Mg x Ni 1-x ) z (Al y Ga 1-y ) 2(1-z) O 3-2z , where 0 ≤ x, y, z ≤ 1.

[0489] According to the present disclosure, the cubic crystal symmetry composition form with z ~ 0.5 can be advantageously used for a given fixed y composition between Al and Ga. By changing the ratio x of Mg to Ni, the direct bandgap can be tuned to about 4.9 eV ≤ E G (x) < 7 eV. This can be achieved by advantageously separately setting the controllable fluxes of the pure element beams of Al, Ga <Mg, and Ni and providing an activated oxygen flux for the anion species. Then, the control of the Al:Ga flux ratio and the Mg:Ni ratio reaching the growth surface can be used to preselect the composition desired for bandgap tuning in the UVLED region.

[0490] The specific band structure and intrinsic conductivity type of cubic NiO have great utility herein. Nickel oxide (NiO) exhibits a natural p-type conductivity type due to Ni d-orbital electrons. Using the non-equilibrium growth method described herein, the general cubic crystal symmetry form (Mg x Ni 1-x ) z (Al y Ga1-y ) 2(1-z) O 3-2z .

[0491] Ni z Ga 2(1-z) O 3-2z and Ni z Al 2(1-z) O 3-2z Both are advantageous for application in UV LED formation. According to this disclosure, dilute compositions with z < 0.1 are advantageous for p-type conductivity, and for z ~ 0.5, ternary cubic symmetric compounds also exhibit a direct band gap at the center of the Brillouin zone.

[0492] Lanthanides

[0493] It can be combined with binary Ga2O3 and ternary (Al) x Ga 1-x There is a wide selection of available lanthanide element-metal atom species in Ga₂O₃ and binary Al₂O₃. The lanthanide group metals range from lanthanum (Z=57) to ruthenium (Z=71), comprising 15 elements. In some embodiments, gadolinium (Gd) (Z=64) and erbium (Er) (Z=68) are utilized due to their dissimilar 4f shell configurations and their ability to form favorable ternary compounds with Ga₂O₃, GaAlO₃, and Al₂O₃. Furthermore, only one species selected from RE = {Gd or Er} up to (RE) x Ga 1-x )2O3、(RE x Ga y Al 1-x-y )2O3 and (RE x Al 1-x The rare impurity bonding at the cation sites of Gd₂O₃ (where 0 ≤ x, y, z ≤ 1) enables the tuning of the Fermi energy to form n-type conductive materials exhibiting corundum, hexagonal, and monoclinic crystal symmetries. The internal 4f shell orbitals of Gd provide opportunities for electronic bonding to prevent parasitic optical 4f to 4f level absorption at wavelengths below 250 nm.

[0494] Surprisingly, according to this disclosure, both theoretical and experimental findings show that for x ~ 0.5, the ternary compound (Er x Ga 1-x )2O3 and (Er x Al 1-xEr₂O₃ exhibits a cubic crystal symmetry structure with a direct band gap. It is known that binary erbium oxide (Er₂O₃) possesses a manganese oxide crystal symmetry, which can be used as a single-crystal film for epitaxial formation on Si(111) substrates. However, the lattice constant achievable with manganese oxide Er₂O₃ is not readily applicable to seeding Ga₂O₃, GaAlO₃, and Al₂O₃ epitaxial films. According to this disclosure, a gradient compositional combination increasing from 0 to 0.5 along the Er growth direction is necessary to produce the desired final surface commensurate with monoclinic Ga₂O₃ epitaxy. The cubic crystal symmetry of Er₂O₃ can be utilized... x Ga 1-x )2O3 (0≤x≤0.5), such as compositions exhibiting a direct band gap.

[0495] Of particular interest is the orthogonal ternary composition (Er) in the case of x ~ 0.5. x Al 1-x ₂O₃ has lattice constants (a = 5.18 Å, b = 5.38 Å, c = 7.41 Å) and exhibits a well-defined direct energy band gap E of approximately 6.5 eV to 7 eV. G (k=0). This structure can be deposited on monoclinic Ga2O3 and corundum Al2O3 substrates or epitaxial layers. As mentioned, the internal Er 3+ The 4f-4f transition is not observed in the Ek band structure and is therefore classified as a non-parasitic absorption for UV LED applications.

[0496] Bismuth(Bi)

[0497] Bismuth is a known species that acts as a surfactant for non-equilibrium epitaxy of gallium nitride (GaN) films. Surfactants lower surface energy to facilitate epitaxial formation but typically do not bind into the grown film. Bi even binds less in gallium arsenide. Bismuth is a volatile species with high vapor pressure at low growth temperatures and appears to be a poor adsorbed atom for binding into the grown epitaxial film. Surprisingly, however, it is remarkably effective to bind Bi into Ga₂O₃, (Ga,Al)O₃, and Al₂O₃ using the non-equilibrium growth method described in this disclosure at dilution levels x < 0.1. For example, Bi, Ga, and Al element sources can be co-deposited with activated oxygen (i.e., atomic oxygen, ozone, and nitrous oxide) at overpressure ratios. According to this disclosure, binding Bi into monoclinic and corundum crystal symmetries of Ga₂O₃ and (Ga,Al)O₃ is highly effective. x Al 1-x In 2O3 (x<0.5), the conductivity type characteristics are such that the concentration of active hole carriers that produce a suitable p-type conductivity region for achieving UVLED functionality are generated.

[0498] However, higher Bi atom bonding (x > 0.1) achieves (Bi x Ga1-x )2O3 and (Bi x Al 1-x The band structure of the ternary composition of Ga₂O₃ is tuned, and in fact all the way up to the stoichiometric binary bismuth oxide Bi₂O₃. The monoclinic Bi₂O₃ forms a lattice constant (a = 12.55 Å, b = 5.28 Å, c = 5.67 Å), which is consistent with the strain layer film grown directly on monoclinic Ga₂O₃.

[0499] In addition, orthogonal and trigonal forms can be used in some implementations, which exhibit natural p-type conductivity and indirect band gap.

[0500] Of particular interest is the orthorhombic crystal symmetry composition (Bi) for the case of x = 1 / 3. x Al 1-x )2O3 exhibits direct and has E G =4.78eV-4.8eV Ek dispersion.

[0501] Palladium (Pd)

[0502] In some embodiments, the addition of Pd to Ga₂O₃, (Ga,Al)O₃, and Al₂O₃ can be used to produce metallic properties, and it is suitable for forming ohmic contacts. In some embodiments, palladium oxide (PdO) can be used as an in-situ deposited half-metal ohmic contact for n-type wide-bandgap metal oxides due to the inherently low work function of the compound (see reference). Figure 9 ).

[0503] Iridium (Ir)

[0504] Iridium is a preferred platinum group metal for bonding to Ga₂O₃, (Ga,Al)O₃, and Al₂O₃. According to this disclosure, Ir can be bonded in many valence states. Generally, IrO₂ compositions with rutile crystal symmetry are known and exhibit half-metallic characteristics. Surprisingly, tri-charged Ir can be achieved using a non-equilibrium growth method. 3+ Valence states are possible, and these valence states are preferred for application in conjunction with the crystal symmetry of Ga₂O₃, and particularly corundum. Iridium has one of the highest melting point and lowest vapor pressure upon heating. This disclosure utilizes electron beam evaporation to form a pure beam of Ir species elements impacting the growth surface. If activated oxygen is supplied simultaneously and a corundum Ga₂O₃ surface is presented for the epitaxial growth, an Ir₂O₃ composition in the form of a corundum crystal symmetry can be achieved. Furthermore, by co-depositing pure elemental beams of Ir and Ga with activated oxygen, a compound (Ir) can be formed. x Ga 1-x )2O3 (0≤x≤1.0). Furthermore, by co-depositing pure elemental bundles of Ir and Al with activated oxygen, ternary compounds (Ir) can be formed. x Al1-x (Ga,Al)O3 (0≤x≤1.0). Adding Ir to a host metal oxide containing at least one of Ga2O3, (Ga,Al)O3, and Al2O3 reduces the effective band gap. Furthermore, for Ir fractions of x > 0.25, the band gap can only be indirect in nature.

[0505] Lithium (Li)

[0506] Lithium is a unique atomic species, especially when combined with oxygen. Pure lithium metal is readily oxidized, and lithium oxide (Li₂O) can be easily formed from a pure elemental Li beam directed towards a growth surface with defined surface crystal symmetry using non-equilibrium growth methods and activated oxygen. Cubic crystal symmetry Li₂O exhibits a large indirect band gap Eg ~ 6.9 eV and a lattice constant (a = b = c = 4.54 Å). Lithium is a mobile atom in the presence of defective crystal structures, and this property is utilized in lithium-ion battery technology. Instead, this disclosure seeks to permanently bind Li atoms within a host crystal matrix comprising at least one of Ga₂O₃, (Ga,Al)O₃, and Al₂O₃. Furthermore, dilute Li concentrations can be bound to the substituted metal sites of Ga₂O₃, (Ga,Al)O₃, and Al₂O₃. For example, for Li +1 Valence states, which can be utilized by these compositions:

[0507] (Li2O) x (Ga2O3) 1-x =Li 2x Ga 2(1-x) O 3-2x where 0 ≤ x ≤ 1; and

[0508] (Li2O) x (Al2O3) 1-x =Li 2x Al 2(1-x) O 3-2x , where 0≤x≤1.

[0509] Stoichiometry of Li 2x Ga 2(1-x) O 3-2x (x = 0.5) provides LiGaO2, and the stoichiometric form of Li 2x Al 2(1-x) O 3-2x (x=0.5) provides LiAlO2.

[0510] LiGaO2 and LiAlO2 crystallize in preferred orthorhombic and trigonal forms, respectively, with direct and indirect band gap energies, where E G (LiGaO2) = 5.2 eV and E G(LiALO2)~8eV.

[0511] Of particular interest is the relatively small valence band curvature of both, which suggests that the effective mass of the holes is smaller compared to Ga2O3.

[0512] The lattice constants of LiGaO2 are (a = 5.09 Å, b = 5.47 Å, c = 6.46 Å), and the lattice constants of LiAlO2 are (a = b = 2.83 Å, c = 14.39 Å). Since bulk Li(Al,Ga)O2 substrates can be used, substrates such as Li(Al)O2 can also be used. x Ga 1-x Orthogonal and trigonal quaternary compositions of O2 are used to achieve UVLED operation in the optical emission region.

[0513] The binding of Li impurities even within cubic NiO can achieve improved p-type conductivity and can be used as a potential electron injector region for holes applied to UV LEDs.

[0514] In some embodiments, another composition comprises lithium nickel oxide (Li). x Ni y O z A ternary alloy. Theoretical calculations provide insights into possible higher valence states of Ni. 2+ and Li 2+ Understanding. Includes Li2 (+4) Ni +2 O3 (-6) =Electron compositions of Li₂NiO₃ can be produced via non-equilibrium growth techniques that form monoclinic crystal symmetry. According to this disclosure, Li₂NiO₃ forms an indirect band gap E G ~5 eV. Another composition is a trigonal crystal with symmetry (R3m), in which Li +1 and Ni +1 Valence state formation has a direct band gap E between s-like and p-like states. G The composition Li2NiO2 with a voltage of 8 eV, however, produces intermediate bandgap energy states that are continuous across all Brillouin zones and are independent of crystal momentum.

[0515] Nitrogen and fluorine anion substitution

[0516] Furthermore, according to this disclosure, the anionic crystal modifier selected for the disclosed metal oxide composition can be chosen from at least one of nitrogen (N) and fluorine (F) species. This is in contrast to the method of replacing the bound group III metal cations in binary Ga₂O₃ and ternary (GaxAl) compositions with group II metal species. 1-xThe concentration of p-type activated holes generated in Ga₂O₃ is similar, and it is further possible that oxygen anion sites will be replaced by activated nitrogen atoms (e.g., neutral nitrogen species in some embodiments) during epitaxial growth. According to this disclosure, it has been surprisingly found that dilute nitrogen binding within the Ga₂O₃ host stabilizes the monoclinic Ga₂O₃ composition during epitaxy. It has been found that prolonged exposure of Ga₂O₃ to elemental Ga and the simultaneous neutral atom fluxes of oxygen and nitrogen during growth can form competing GaN-like precipitates.

[0517] According to this disclosure, it has also been found that periodically modulating Ga₂O₃ growth by periodically interrupting the Ga and O fluxes and preferably exposing the end-cap surface only with activated atom neutral nitrogen enables a portion of the surface to bind N to additional available O sites within the Ga₂O₃ growth. Separating these N-layer growth interruptions along the growth direction by a distance greater than five or more Ga₂O₃ unit cells achieves high-density impurity bonding, thereby helping to obtain p-type conductivity characteristics in Ga₂O₃.

[0518] This process can be used for both corundum and trigonal forms of Ga2O3.

[0519] In some implementations, a combination of group II metal cation substitution and nitrogen anion substitution can be used to control the concentration of p-type conductivity in Ga2O3.

[0520] Incorporating fluorine impurities into Ga2O3 is also possible; however, elemental fluorine sources are challenging. This disclosure uniquely utilizes the sublimation of lithium fluoride (LiF) bulk crystals within a Knudsen cell to provide the composition of both Li and F co-deposited during elemental Ga and Al beams under activated oxygen conditions, thereby supplying the growth surface. This technique enables the incorporation of Li and F atoms within the epitaxially formed Ga2O3 or LiGaO2 host.

[0521] Examples of crystal symmetry structures formed using exemplary compositions are now described, and... Figures 44A to 44Z They are mentioned in the text. The compositions shown are not intended to be limiting, as discussed in previous chapters regarding crystal modifiers.

[0522] Figure 44A The diagram shows the ternary composition (Al). x Ga 1-x Examples of possible crystal symmetry groups 5000 for )2O3. The calculated equilibrium crystal formation probability 5005 is a measure of the probability that a structure will form for a given crystal symmetry type. Figure 44A The space group name 5010 used here is as understood by those skilled in the art.

[0523] The non-equilibrium growth methods described in this paper can potentially select crystal symmetry types that are otherwise unattainable using equilibrium growth methods (such as CZ). Figure 44A The illustrations show common crystal categories: cubic 5015, tetragonal, trigonal (rhombohedral / hexagonal) 5020, monoclinic 5025, and triclinic 5030.

[0524] For example, according to this disclosure, by providing growth conditions for motion that are only favorable to a specific spatial group to be epitaxially formed, monoclinic, trigonal, and orthorhombic crystal symmetry types can be made energy-favorable. For example, as Figure 43A As illustrated in Table I, the surface energy of the substrate can be selected by intelligently pre-selecting the surface orientation for the epitaxial presentation.

[0525] Figure 44B This illustrates the strained ternary (Al) ternary structure formed on a monoclinic Ga2O3(010) oriented surface 5045, exhibiting high-quality, coherent strained, elastically deformed cell (i.e., the epitaxial layer is referred to as pseudoisomorphic relative to the underlying substrate). x Ga 1-x Exemplary high-resolution X-ray Bragg diffraction (HRXRD) curves of the Al₂O₃ epitaxial layer 5080. The graph shows the intensity 5040 as a function of Ω⁻²θ 5035. Two compositions (Al₂O₃, Al ... x Ga 1-x )2O3x=0.15(5050) and x=0.25(5065). Initially through an ultra-high vacuum chamber (less than 5×10 -10 The substrate is prepared by desorbing surface impurities in a high-temperature (>800℃) environment.

[0526] The surface is monitored in real time by reflected high-energy electron diffraction (RHEED) to assess atomic surface quality. Once a bright and striped RHEED pattern indicating the predetermined surface reconstruction of atomically flat surfaces indicating discontinuous surface atomic dangling bonds is clearly visible, an activated oxygen source, including radio frequency inductively coupled plasma (RF-ICP), is ignited to generate a flow of substantially neutral atomic oxygen (O*) species and excited molecularly neutral oxygen (O2*) directed towards the heated surface of the substrate.

[0527] RHEED was monitored to show the oxygen-sealed end surface. The source of elemental Ga and Al atoms, as well as pure Ga and Al atoms, was provided by a bleed unit comprising an inert ceramic crucible radiatively heated by a filament and controlled by feedback sensing of a thermocouple monitoring the molten metal temperature within the crucible, which was advantageously positioned relative to the crucible. High-purity elemental metals, such as 6N to 7N or higher, were used.

[0528] The flux of each source beam is measured using a dedicated bare ion gauge, which can be spatially positioned near the center of the substrate to sample the beam flux at the substrate surface. The beam flux is measured for each element species, thus allowing the relative flux ratio to be predetermined. During beam flux measurement, a mechanical shutter is positioned between the substrate and the beam flux measurement point. The mechanical shutter also intersects with the atomic beams emitted from each crucible containing each element species selected to constitute the epitaxial film.

[0529] During deposition, the substrate is rotated to accumulate a uniform amount of atomic beams intersecting the substrate surface within a given deposition time. The substrate is radiated from behind by an electrically heated filament; for oxide growth, a silicon carbide (SiC) heater is advantageously preferred. A unique advantage of SiC heaters over refractory metal filament heaters is the availability of a wide near-mid-infrared emissivity.

[0530] What is not well known to those working in the field of epitaxial film growth is that most metal oxides have relatively large optical absorption properties for near- and far-infrared wavelengths. During epitaxial film growth, it is preferable to actively and continuously evacuate the deposition chamber to obtain and maintain a vacuum of approximately 1e-6 to 1e-5 Torr. When operating within this vacuum range, the metal particles evaporating from the surface of each effluent crucible achieve substantially non-interacting and impingement-like velocities.

[0531] Advantageously positioned catenary unit bundles, formed by the Clausien factor of the crucible orifice and the large mean free path of UHV, ensure collision-free, impact-based transport of catenary species to the substrate surface. The atomic beam flux from the catenary-type heated source is determined by the Arenis properties of the specific element species placed in the crucible. In some embodiments, the flux is measured at the substrate surface at 1 × 10⁻⁶. -6 The fluxes of Al and Ga within the Torr range. Oxygen plasma is controlled by the RF power coupled to the plasma and the flow rate of the feed gas.

[0532] RF plasma discharges typically operate in the range of 10 mTorr to 1 Torr. These RF plasma pressures are incompatible with the atomic layer deposition process reported in this paper. To achieve a pressure of 1 × 10⁻⁶ mTorr, [further details are needed]. -7 Up to 1×10 -5 The activated oxygen beam flux within the range of Torque is used to mount a sealed fused silica bulb with a laser-drilled hole of approximately 100 micrometers in diameter on the circular end face of a sealed cylindrical bulb. The bulb is coupled to a helical-wound copper tube and a water-cooled RF antenna, which are driven by an impedance matching network and a high-power 100W-1kW RF oscillator operating, for example, from 2MHz to 13.6MHz or even 20MHz.

[0533] Plasma is monitored using optical emission from the plasma discharge, providing precise telemetry of the actual species generated within the bulb. The size and number of orifices on the bulb end face represent the interface between the plasma and the UHV chamber and can be predetermined to obtain compatible beam flux, maintaining impulsive transport conditions for long mean free paths exceeding the source-to-substrate distance. Further field diagnostics enabling precise control and repeatability of the film composition and uniformity include monitoring species desorption from the substrate surface using ultraviolet polarized optical reflectometers and ellipsometers, as well as residual gas analyzers.

[0534] Other forms of activated oxygen include the use of oxidants such as ozone (O3) and nitrous oxide (N2O). While all forms (i.e., RF plasma, O3, and N2O) work relatively well, RF plasma is used in some embodiments due to the simplicity of point activation. However, RF plasma can potentially generate extremely high-energy charged ion species, which can affect the type of background conductivity of the material. This effect is mitigated by removing a hole located just near the center of the plasma endplate coupled to the UHV chamber. The RF inductive oscillating magnetic field will be at its maximum at the center of the solenoid of the cylindrical discharge tube along the central axis. Therefore, removing the hole, which provides a view from the inside of the plasma to the growth surface, removes the charged ions that are impulsively transported to the epitaxial layer.

[0535] The growth method has been briefly described; please refer to [link / reference] again. Figure 44B The monoclinic Ga2O3(010) oriented substrate 5045 was cleaned in situ for 30 minutes under UHV conditions at high temperatures (e.g., ~800°C). The cleaned surface was then end-capped with activated oxygen adsorption atoms to form a surface reconstruction containing oxygen atoms.

[0536] A homoepitaxial Ga2O3 buffer layer 5075 was deposited, and its crystal surface improvement was monitored by in-situ RHEED. Generally, Ga2O3 growth conditions using elemental Ga and activated oxygen require a flux ratio φ(Ga):φ(O*) < 1, i.e., atomic oxygen-rich conditions.

[0537] For a flux ratio Φ(Ga):Φ(O*) > 1, excess Ga atoms on the growth surface can attach to surface-bonded oxygen, which can potentially form volatile Ga2O. (g) Suboxide species are then desorbed from the surface, and material can be removed from the surface and even etched onto the surface of Ga2O3. According to this disclosure, for high Al content AlGaO3, this etching process (if not removed) is reduced to make Al% > 50%. The etching process can be used to clean the original Ga2O3 substrate, for example, to help remove chemical mechanical polishing (CMP) damage.

[0538] To initiate the growth of AlGaO3, optionally, an activated oxygen source is initially exposed to the surface, and then two shutters are opened for each of the Ga and Al outflow units. According to this disclosure, it has been experimentally found that the adhesion coefficient of Al is close to one, while the adhesion coefficient on the growth surface is kinetically dependent on the Arenis properties of the desorbed Ga adsorbed atoms, which depends on the growth temperature.

[0539] Extensional (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 Al₂O₃, clear, high-quality RHEED surface reconstruction fringes are evident. Thickness can be monitored using an in-situ ultraviolet laser reflectometer, and the pseudoisomorphic strain state can be monitored via RHEED. This is due to the monoclinic crystal symmetry (Al₂O₃). x Ga 1-x The in-plane lattice constant of Al₂O₃ is smaller than that of the underlying Ga₂O₃ lattice, thus allowing it to grow under tensile strain during elastic deformation (Al₂O₃). x Ga 1-x )2O3.

[0540] The thickness 5085 of the epitaxial layer 5080, which can be matched or reduced by including mismatch 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 fully relaxed bulk film. Curves 5050 and 5065 represent the coherent strain (Al) for thicknesses below the CLT. x Ga 1-x The case of )2O3 films. For x = 0.15, CLT > 400 nm, and for x = 0.25, CLT ~ 100 nm. Thickness oscillations 5070 are also known as Pendellosung interference fringes and indicate highly coherent and atomically flat epitaxial films.

[0541] In experiments conducted regarding this disclosure, a pure monoclinic Al2O3 epitaxial film was directly grown on a monoclinic Ga2O3(010) surface, achieving a CLT < 1 nm. Further experiments revealed that due to the unique monoclinic bonding configuration of the cations, approximately 50% tetrahedral bonding sites and 50% octahedral bonding sites were formed, resulting in an Al% > 50% growth rate. It was found that Al adsorbed atoms preferentially bind to octahedral bonding sites during crystal growth and exhibit bonding affinity to tetrahedral bonding sites.

[0542] A superlattice (SL) is generated, and a quantum size effect tuning mechanism is utilized to quantize the allowed energy levels within a narrower bandgap material sandwiched between two potential barriers, enabling the direct application of the superlattice to UVLED operation. Additionally, the SL is an exemplary vehicle for generating pseudo - ternary alloys as discussed herein and for further implementing strain management of the layers.

[0543] For example, monoclinic (Al x Ga 1-x )2O3 ternary alloy experiences asymmetric in - plane biaxial tensile strain when epitaxially deposited on monoclinic Ga2O3. This tensile strain can be managed by ensuring that the thickness of the ternary alloy remains below the critical layer thickness (CLT) within each layer constituting the SL. Additionally, the strain can be balanced by tuning the thicknesses of both the Ga2O3 and ternary alloy layers to manage the intrinsic strain energy of the bilayer pair.

[0544] Another embodiment of the present disclosure is to generate the ternary alloy as a bulk or SL, grow it thick enough to exceed the CLT, and form a substantially strain - free and independent material. This virtually strain - free relaxed ternary alloy layer has an effective in - plane lattice constant a SL parameterized by the effective Al% composition. If a first relaxed ternary alloy layer is then formed, followed by another second SL directly deposited on the relaxed layer, the bilayer pair forming the second SL can be tuned such that the layers constituting the bilayer are in a strain state where the tensile and compressive strains are equal and opposite with respect to the first in - plane lattice constant.

[0545] Figure 44C An exemplary SL 5115 directly formed on a Ga2O3(010) - oriented substrate 5100 is shown.

[0546] The bilayer pair constituting the SL 5115 is both monoclinic crystal symmetry Ga2O3 and ternary (Al x [[ID=2l]]Ga 1-x [[ID=2r]])2O3(x = 0.15), where the SL period Δ SL = 18 nm. HRXRD 5090 shows symmetric Bragg diffraction, and GIXR 5105 shows the grazing - incidence reflectivity of the SL. Ten periods are shown, where the extremely high crystal quality indicates (Al x Ga 1-x )2O3 with a thickness < CLT.

[0547] Multiple narrow SL diffraction peaks 5095 and 5110 indicate coherently strained films registered using the in - plane lattice constant of the matching monoclinic Ga2O3(010) - oriented bulk substrate 5100. The monoclinic crystal structure has a growth surface exposed to (010) (refer to Figure 37This demonstrates a composite array of Ga and O atoms. In some embodiments, the starting substrate surface is prepared by O end-capping as previously described. The average Al% alloy content of SL represents a pseudo-bulk ternary alloy, which can be considered as an ordered atomic planar ternary alloy.

[0548] Including [(Al xB Ga 1-xB The SL of the 2O3 / Ga2O3 bilayer has an equivalent Al%, which is defined as:

[0549]

[0550] Where L B It is a wider bandwidth (Al) xB Ga 1-xB The thickness of the 2O3 layer was determined by referring to the zero-order diffraction peak of SL. n＝0 This can be directly determined by the angular separation and position of the substrate peak 5102. The inverted lattice mapping shows that the in-plane lattice constant is pseudoisomorphic with the underlying substrate and provides excellent application for UV LEDs.

[0551] like Figures 23A to 23C The tension strain shown can be advantageously used to form optical emission regions.

[0552] Figure 44D This demonstrates a more flexible direct deposition of ternary monoclinic 5130 alloy (Al) on a monoclinic Ga2O3(001) substrate 5120 with another crystal orientation. x Ga 1-x )2O3.

[0553] Furthermore, optimal results are obtained by focusing specifically on high-quality CMP surface preparation from the split substrate surface. In some embodiments, the growth formulation utilizes in-situ activated oxygen milling of the substrate radiatively heated at high temperatures (e.g., 700°C to 800°C) using a high-power, oxygen-resistant radiation-coupled heater. The SiC heater possesses a unique property: high near- and far-infrared emissivity. The emissivity of the SiC heater closely matches the intrinsic absorption characteristics of Ga2O3 and is therefore well coupled with the radiometric blackbody emission spectrum exhibited by the SiC heater. Region 5125 represents the O-end treatment of the high-quality Ga2O3 buffer layer and homoepitaxial growth. SL is then deposited, showing two separate growths with different ternary alloy compositions.

[0554] Figure 44D Yes (Al) x Ga 1-x)A coherent strained epitaxial layer of 2O3 having a thickness <CLT and achieving x~15% (5135) and x~30% (5140) relative to the (002) substrate peak 5122. Furthermore, the presence of thickness interference fringes indicates a high-quality film.

[0555] It was further found that it is also possible to implement the SL structure on the (001)-oriented monoclinic Ga2O3 substrate 5155, with the results shown in Figure 44E as shown.

[0556] Obviously, HRXRD 5145 and GIXR 5158 demonstrate high-quality coherent deposited SLs. 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 peaks enable determination of the effective Al% of the SL. For this case, a ten-period SL [(Al SL Ga 0.18 Ga 0.92 )2O3 / Ga2O3 with a period Δ

[0557] Referring to Figure 44F , an exemplary application demonstrating the versatility of the metal oxide film deposition method disclosed herein is shown. Two different crystal symmetry type structures are epitaxially formed along the growth direction defined as Figure 18 . A substrate 5170 (peak 5172) presenting a monoclinic Ga2O3 (001)-oriented surface is used for homoepitaxy of monoclinic Ga2O3 5175. Next, a cubic crystal symmetry NiO epitaxial layer 5180 is deposited. HRXRD 5165 and GIXR 5190 show that the peak 5185 of the uppermost NiO film with a thickness of 50 nm has excellent atomic flatness and thickness fringes 5195.

[0558] In one example, a mixed and matched crystal symmetry type may be beneficial for a given material composition, which is beneficial for a given function including a UVLED (referring to Figure 1 ), thereby increasing the flexibility to optimize the UVLED design. Ni x O (0.5 < x ≤ 1, indicating that a metal vacancy structure is possible), Li x Ni y O n , Mg x Ni 1-x O and Li x Mg y Ni z O n are compositions that can be advantageously used for integration with the AlGaO3 material constituting the UVLED.

[0559] Because NiO and MgO share very similar cubic crystal symmetry and lattice constants, they are advantageous for bandgap tuning applications from approximately 3.8 eV to 7.8 eV. The d-state of Ni influences the optical and electrical conductivity types of MgNiO alloys and can be tuned for use in UV LED devices. For selectively incorporating Ir into corundum crystal-symmetric ternary alloys (Ir... x Ga 1-x Similar properties were found in 2O3, which exhibited favorable energy positions within the Ek dispersion due to the iridium d-state orbitals, thus enabling p-type conductivity.

[0560] Figure 44G Another example of a metal oxide structure is shown. A cubic crystal symmetry MgO(100) oriented surface is presented on substrate 5205 (corresponding to peak 5206) for direct epitaxy of Ga2O3. According to this disclosure, the surface of MgO can be selectively modified to produce a Ga2O3 epitaxial layer 5210 (peak 5212 of γ-Ga2O3) in cubic crystal symmetry form, which acts as an intermediate transition layer for subsequent epitaxy of monoclinic Ga2O3(100) 5215 (peaks 5214 and 5217). This structure is formed by… Figure 20A The growth process is shown in the diagram.

[0561] First, the prepared clean MgO(100) surface is presented for MgO homoepitaxialization. The magnesium source is a valved bleed source containing Mg of 7N purity, with a beam flux of ~1×10⁻⁶ in the presence of active oxygen. -10 The substrate is supplied with φ(Mg):φ(O*)<1 and the substrate surface growth temperature is 500°C to 650°C.

[0562] RHEED was monitored to demonstrate improved and high-quality surface reconstruction of the MgO surface of the epitaxial film. After homoepitaxial growth of MgO from approximately 10 nm to 50 nm on the substrate, the Mg source was turned off and the temperature was raised to approximately 700 °C under a protective O* flux. The Ga source was then exposed to the growth surface, and RHEED was observed to instantly transform the surface reconstruction into a cubic crystal-symmetric Ga2O3 epitaxial layer 5210. After approximately 10 nm to 30 nm of cubic Ga2O3 (also referred to as the γ phase), a characteristic monoclinic surface reconstruction of Ga2O3 (100) appeared and remained as the most stable crystal structure, as can be observed by direct observation of RHEED. A 100 nm Ga2O3 (100) oriented film was deposited, where HRXRD 5200 and GIXR 5220 showed peaks 5214 for β-Ga2O3 (200) and 5217 for β-Ga2O3 (400). Such sporadic crystal symmetry alignments are rare, but highly advantageous for applications in UV LEDs.

[0563] Figure 44H This paper discloses yet another example of a composite ternary metal oxide structure for use in UV LEDs. HRXRD 5225 and GIXR 5245 demonstrate experimental realizations of a superlattice comprising a lanthanide aluminum oxide ternary alloy integrated with a corundum Al2O3 epitaxial layer.

[0564] SL includes the symmetry of corundum crystals that grow pseudoisomorphically with Al2O3 (Al x Er 1-x A ternary composition of 2O3, wherein the lanthanide element is selected from erbium. Erbium is presented for non-equilibrium growth via a sublimated 5N purity erbium source using a bleed unit. The flux ratio φ(Er):φ(Al) ~0.15 is used with oxygen-enriched conditions [φ(Er)+φ(Al)]:φ(O*)]<1 at a growth temperature of approximately 500°C.

[0565] Of particular note is that Er enables molecular oxygen to split at the epitaxial layer surface, resulting in a total oxygen overpressure greater than the atomic oxygen flux. A sapphire (11-20) substrate 5235 with A-side was prepared and heated to approximately 800°C, then exposed to activated oxygen polishing. In this example, activated oxygen polishing of the bare substrate surface was found to significantly improve the quality of subsequent epitaxial layers. Next, a homoepitaxial corundum Al2O3 layer was formed and monitored by RHEED, revealing excellent crystal quality and atomically flat layer-by-layer deposition. Ten-cycle SL was then deposited, and these ten-cycle SLs were observed as co-peaks at 5230 and 5240 in HRXRD 5225 and GIXR 5245 scans. Pendellosung fringes are clearly visible, indicating excellent coherent growth.

[0566] SL's effective alloy composition (Er xSL Al 1-xSL )2O3 can pass through the zero-order SL peak SL n＝0 It was derived from the position of the (110) substrate peak 5235. It has been found that xSl ~ 0.15 is possible, and SL-periods (Al) are formed. x Er 1-x The 2O3 layer exhibits corundum crystal symmetry. This discovery is particularly important for its application in UV LEDs, where... Figure 44I Public corundum (Al) x Er 1-x The EK band structure of 2O3 5250 actually has E G Direct bandgap material with a voltage ≥6 eV. The electron energy 1066 is plotted as varying with the crystal wave vector 1067. At the center of the Brillouin zone 5255 (k = 0), the conduction band has a minimum value at 5265 and the valence band has a maximum value at 5260.

[0567] Next, Figure 44JThe text showcases another ternary magnesium gallium oxide cubic crystal with symmetry that can be integrated with Ga2O3. x Ga 2(1-x) O 3-2x Material composition. A 10-period SL[Mg] composition is shown deposited on a monoclinic Ga2O3(010) oriented substrate 5275 (corresponding to peak 5277). x Ga 2(1-x) O 3-2x The superlattice of [Ga2O3] was experimentally realized using HRXRD 5270 and GIXR 5290. The SL ternary alloy composition was selected with x = 0.5 and a thickness of 8 nm, and the Ga2O3 was 8 nm thick. The SL period was Δ SL =16nm, of which the average Mg% is Diffraction peaks at 5280 and 5295 report slight diffusion of Mg across the SL interface, which can be mitigated by growth at lower temperatures. x Ga 2(1-x) O 3-2x The strip structure with x=0.5 is particularly suitable for use with UV LEDs. Figure 44K The band structure calculated in the report is characteristically straightforward (referencing band extrema 5315 and 5310 and k = 0 5305), with a band gap of E. G ~5.5eV.

[0568] Figure 44L The ability to integrate monoclinic Ga2O3 crystal symmetry with cubic MgAl2O4 crystal symmetry is demonstrated. A high-quality single-crystal substrate 5320 (peak 5322) including MgAl2O4 spinel was cleaved and polished to expose the (100) oriented crystal surface. The substrate was prepared and polished at high temperature (~700°C) under UHV conditions (<1e-9 Torr). The substrate was held at a growth temperature of 700°C to initiate a MgGa2O4 film 5330, which showed excellent registration with the substrate. After about 10 nm to 20 nm, Mg was turned off and only Ga2O3 was deposited as the uppermost film 5325. The GIXR film has excellent flatness, showing thickness stripes 5340 indicating films >150 nm. HRXRD shows the transition material MgGa2O4 corresponding to peak 5332 and the Ga2O3 (100) oriented epitaxial layer with peak 5327 indicating monoclinic crystal symmetry. In some implementations, hexagonal Ga2O3 can also be epitaxially deposited.

[0569] The monoclinic Ga₂O₃(-201) oriented crystal plane is characterized by the unique properties of its hexagonal oxygen surface matrix, and its in-plane lattice spacing is suitable for registering wurtzite-type hexagonal crystal symmetry materials. For example, Figure 44MAs shown in Figure 5345, wurtzite ZnO 5360 (peak 5367) is deposited on the substrate Zn x Ga 2(1-x) O 3-2x Peak 5350 (5352) is on the oxygen-sealed Ga2O3 (-201) surface. Zn is supplied by sublimation of 7N purity Zn contained in the efflux unit. The growth temperature of ZnO is selected from 450℃ to 650℃, and it exhibits extremely bright and sharp narrow RHEED stripes, indicating high crystal quality. Peak 5362 indicates (Al x Ga 1-x )2O3. Peak 5355 indicates the transition layer.

[0570] Next, a ternary zinc gallium oxide epitaxial layer Zn was deposited by co-depositing Ga and Zn with active oxygen at 500°C. x Ga 2(1-x) O 3-2x 5365. A flux ratio [φ(Zn)+φ(Ga)]:φ(O*)<1 and a metal beam flux ratio φ(Zn):φ(Ga) were chosen to achieve x ~ 0.5. Compared to Ga, Zn desorbs at much lower surface temperatures and is partially controlled by a process with limited absorption, which depends on the surface temperature determined by the Arenis properties of the zinc adsorbed atoms.

[0571] Zn is a group metal and is advantageously substituted at available Ga sites in the host crystal. In some embodiments, for dilute x < 0.1 concentrations of the bound Zn, Zn can be used to alter the conductivity type of the host. Peak 5365 labeled Zn x Ga 2(1-x) O 3-2x The transition layer formed on the substrate is shown, thereby showing Zn x Ga 2(1-x) O 3-2x The low Ga% formation strongly suggests that the high miscibility of Ga and Zn in ternary alloys provides for non-equilibrium growth across the entire alloy range (0 ≤ x ≤ 1). For the case of x = 0.5, Zn... x Ga 2(1-x) O 3-2x Provides cubic crystal symmetry forms, Ek-band structures such as Figure 44N The diagram is shown in Figure 5370.

[0572] The indirect bandgap indicated by the extreme values ​​5375 and 5380 can be shaped using the SL band design shown in Figure 27. The valence band dispersion 5385, which shows a maximum value at k≠0, can be used to generate SL periods that advantageously map the maximum value to the equivalent energy at the center of the region, thereby producing a pseudo-direct bandgap structure. The entire method for application in forming optoelectronic devices (such as the UV LEDs mentioned in this disclosure) is claimed.

[0573] As explained in this disclosure, there is a considerable design space available for crystal modifiers of Ga2O3 and Al2O3 host crystals, which can be utilized for application in UV LEDs.

[0574] Now, another example is disclosed, in which the growth conditions can be tuned to preselect the unique crystal symmetry type of Ga2O3, namely monoclinic (β phase) or hexagonal (ε phase or κ phase).

[0575] Figure 44O Show Figure 19 The specific application of the more general methods disclosed herein.

[0576] The prepared and cleaned surface of a sapphire C-plane substrate 5400 exhibiting corundum crystal symmetry is used for epitaxy.

[0577] The substrate surface is polished with active oxygen at temperatures above 750°C and such as ~800°C to 850°C. This produces an oxygen-sealed end surface 5405. While maintaining a high growth temperature, Ga and active oxygen flux are directed toward the epitaxial surface, and the exposed Al2O3 surface is reconstructed and modified into a corundum Ga2O3 thin template layer 5396 or low-Al% corundum (Al x Ga 1-x Ga₂O₃ is formed by additional co-deposition of Al flux, resulting in x < 0.5. After a template layer of approximately 10 nm (5396), the Al flux is turned off and Ga₂O₃ is deposited. Maintaining a high growth temperature and a low Al% template (0 ≤ x < 0.1) is only beneficial for the formation of the monoclinic crystal structure epitaxial layer (5397).

[0578] If the growth temperature is lowered to approximately 650°C to 750°C after the formation of the initial template layer 5396, Ga2O3 only favors the growth of novel crystal symmetry structures with hexagonal symmetry. Hexagonal Ga2O3 also benefits from template layers with x > 0.1. The unique properties of the hexagonal crystal symmetry Ga2O35420 composition will be discussed later. Figure 44P Experimental evidence for the disclosed process of growing epitaxial structure 5395 is provided, showing HRXRD 5420 results for two different growth processes for single-phase monoclinic Ga2O3 and hexagonal symmetry Ga2O3. HRXRD scans show Bragg diffraction peaks on the C-plane Al2O3(0001) oriented substrate of corundum Al2O3(0006) 5465 and Al2O3(0012) 5470. For the uppermost epitaxial film of monoclinic Ga2O3, diffraction peaks indicated by 5445, 5450, 5455, and 5460 represent sharp single-crystal monoclinic Ga2O3(-201), Ga2O3(-204), Ga2O3(-306), and Ga2O3(-408).

[0579] Orthorhombic crystal symmetry can further exhibit the advantageous property of possessing non-inverted symmetry. This is particularly advantageous for allowing electric dipole transitions between the conduction band edge and the valence band edge at the center of the zone. For example, wurtzite ZnO and GaN both exhibit crystal symmetry with non-inverted symmetry. Similarly, orthorhombic (i.e., space group 33Pna21 crystal symmetry) possesses non-inverted symmetry that enables optical transitions of electric dipoles.

[0580] Conversely, for the growth process of hexagonal Ga2O3, peaks 5425, 5430, 5435 and 5440 represent sharp single-crystal hexagonal crystal symmetries Ga2O3(002), Ga2O3(004), Ga2O3(006) and Ga2O3(008).

[0581] Figure 44Q The diagram shows Ga2O3 achieving hexagonal crystal symmetry and also achieving hexagonal (Al) crystal symmetry. x Ga 1-x The importance of )2O3.

[0582] The band structure 5475 shows that the extrema of the conduction band 5480 and the valence band 5490 are both located at the center of the Brillouin zone 5485, and is therefore advantageous for application in UV LEDs.

[0583] Single-crystal sapphire is one of the most mature crystalline oxide substrates. Another form of sapphire is the corundum M-face, which can be advantageously used to form Ga2O3 and AlGaO3, as well as other metal oxides discussed herein.

[0584] For example, according to the present disclosure, it has been experimentally discovered that the surface energy of sapphire exhibited for a specific crystal facet of epitaxy can be used to preselect the crystal symmetry type of Ga2O3 epitaxially formed thereon.

[0585] Now consider Figure 44R The invention discloses the utility of an M-plane corundum Al2O3 substrate 5500. The M-plane is a (1-100) oriented surface and can be prepared as previously discussed, and atomically ground in situ at a high growth temperature of 800°C while exposed to an activated oxygen flux. The oxygen-sealed surface is then cooled to 500°C-700°C (e.g., 500°C in one embodiment), and a Ga2O3 film is epitaxially deposited. It has been found that sapphire and corundum (Al2O3) with a thickness of approximately 400 nm to 500 nm can be deposited on the M-plane. x Ga 1-x Symmetric Ga₂O₃ crystals exceeding 100 nm to 150 nm were deposited on Al₂O₃ (x ~ 0.3-0.45). Of particular interest are the deposition of Al₂O₃ crystals with symmetry exceeding 100 nm to 150 nm on Al₂O₃. 03 Ga 0.7)2O3 exhibits a direct band gap and is equivalent to the band gap of wurtzite AlN.

[0586] HRXRD 5495 and GIXR 5540 curves show two separate growth patterns on the M-plane sapphire 5500. The peak 5502 relative to the corundum Al2O3 substrate clearly indicates high-quality single-crystal corundum Ga2O3 5510 and (Al2O3) growth. 03 Ga 0.7 Therefore, it is possible to achieve an M-plane oriented AlGaO3 film on M-plane sapphire. GIXR thickness oscillation 5535 indicates atomically flat interfaces 5520 and films 5530. Curve 5155 shows Ga2O3 with no other crystalline phases besides the corundum phase (rhombic crystal symmetry).

[0587] For completeness, it has also been found according to this disclosure that various metal oxides can be used to develop even the most technologically mature semiconductor substrates, namely silicon. For example, while bulk Ga2O3 substrates are desirable due to their crystallinity and electronic properties, their production is still more expensive than that of single-crystal substrates, and they cannot be scaled up to large wafer diameter substrates as easily as silicon, for example, up to 450 mm for Si.

[0588] Therefore, the implementation scheme includes opening up functional electrons directly on a Ga2O3 film on silicon. To this end, a process has been specifically developed for this application.

[0589] Now refer to Figure 44S The results of an experimentally developed process for depositing monoclinic Ga2O3 films on large-area silicon substrates are shown.

[0590] Including ternary (Ga 1-x Er x A single-crystal high-quality monoclinic Ga₂O₃ epitaxial layer 5565 is formed on a cubic transition layer 5570 of Ga₂O₃. The transition layer is deposited using a compositional stepwise deposition process that can be abrupt or continuous. The transition layer may also include [(Ga₂O₃)]. 1- x Er x )2O3 / (Ga 1-y Er y The SL layer of the [2O3] layer, where x and y are selected from 0 ≤ x, y ≤ 1. A transition layer is optionally deposited on a binary ferromagnetic crystal symmetry Er2O3(111) oriented template layer 5560, which is deposited on a Si(111) oriented substrate 5555. Initially, Si(111) is heated in UHV to 900°C or higher but below 1300°C to desorb native SiO2 oxide and remove impurities.

[0591] A clear temperature-dependent surface reconstruction change was observed, and it can be used for in-situ calibration of the surface growth temperature occurring at 830 °C, and is only observable for pristine Si surfaces without surface SiO2. The Si substrate temperature was then lowered to 500 °C to 700 °C to deposit one or more Ga... 1-y Er y A Ga₂O₃ film is formed, and then the temperature is slightly increased to facilitate the epitaxial growth of a monoclinic Ga₂O₃(-201) oriented active layer film. If an Er₂O₃ binary alloy is used, activation oxygen is not required, and pure molecular oxygen can be used for co-deposition with a pure Er beam flux. Once Ga is introduced, an activation oxygen flux is required. Other transition layers are also possible and can be selected from several ternary oxides described herein. HRXRD 5550 shows a cubic (Ga₂O₃) film. 1-y Er y The peaks 5572 of 2O3 and (111) and (222) of argumentite Er2O3 were observed at 5562. The (-201), (-201), and (-402) peaks of monoclinic Ga2O3 were also observed as peak 5567, and the Si (111) substrate was observed as peak 5557.

[0592] One application of this disclosure is the use of cubic symmetric metal oxides to form Ga₂O₃(001) and (Al,Ga)₂O₃(001) oriented active layer films between the surfaces of a Si(001) oriented substrate using a transition layer. This is particularly advantageous for mass production.

[0593] This paper focuses on developing transparent substrates adaptable to a wide variety of metal oxide compositions and crystal symmetry types. In particular, to reiterate, Al₂O₃, (Al₂O₃) x Ga 1-x The materials )2O3 and Ga2O3 are of great interest and are close to Al%x in (Al x Ga 1-x In 2O3 and Ga%y in (Al) 1-y Ga y The opportunity for the entire range of miscibility in 2O3 can be addressed by compositions of corundum crystal symmetry type.

[0594] Now refer to Figures 44T to 44X Examples in [the text].

[0595] Figure 44T High-quality single-crystal epitaxy of corundum Ga2O3 (110) oriented films on Al2O3 (11-20) oriented substrates (i.e., A-side sapphire) is disclosed. The surface energy of the A-side Al2O3 surface can be used to grow particularly high-quality corundum Ga2O3 and ternary corundum (Al2O3). x Ga 1-xGa₂O₃ films, where 0 ≤ x ≤ 1 for the entire alloy range. Ga₂O₃ can grow CLTs up to approximately 45 nm to 80 nm, and with the introduction of Al to form ternary (Al₂O₃) films. x Ga 1-x )2O3, CLT increased significantly.

[0596] Homoetropic growth of corundum Al₂O₃ is possible over a surprisingly wide growth window. Corundum AlGaO₃ can be grown from room temperature to a maximum of about 750 °C. However, all growth requires an activation oxygen (i.e., atomic oxygen) flux that greatly exceeds the total metal flux, i.e., oxygen-rich growth conditions. Two separately grown films of different thicknesses on an Al₂O₃ substrate with different surfaces are shown in HRXRD 5575 and GIXR 5605 scans, revealing corundum crystal-symmetric Ga₂O₃ films. The substrate surface 5590 (corresponding to peak 5592) is oriented in the (11–20) plane and oxygen-milled at a high temperature of about 800 °C.

[0597] While maintaining the optimal growth temperature within the range of 450°C to 600°C (such as 500°C), active oxygen grinding is kept in place. An Al₂O₃ buffer layer of 10 nm to 100 nm is then optionally deposited, and a ternary (Al₂O₃) layer is then formed by co-deposition with Al and Ga fluxes appropriately configured to achieve the desired Al% x Ga 1-x Ga2O3 epitaxial layer 5600. Oxygen-rich conditions are mandatory. Curves 5580 and 5585 show exemplary Ga2O3 films 5600 at 20 nm and 65 nm, respectively (x = 0).

[0598] Both HRXRD and GIXR exhibit excellent coherent Pendellosung interference fringes, and transmission electron microscopy (TEM) confirms that the defect density measured by off-axis XRD may be less than 10. 7 cm -3 .

[0599] As confirmed by inverted lattice mapping (RSM), corundum Ga2O3 films exceeding approximately 65 nm on the A-side Al2O3 exhibit relaxation, but still maintain excellent crystal quality for films with a crystal lattice depth greater than CLT.

[0600] Several other methods are also possible for further improving the CLT of binary Ga2O3 films on the A-side Al2O3. For example, during the high-temperature oxygen polishing step on the surface of the pristine Al2O3 substrate, the substrate temperature can be maintained at approximately 750°C to 800°C. At this growth temperature, Ga flux can be present along with activated oxygen, and high-temperature phenomena may occur. According to this disclosure, Ga effectively diffuses into the uppermost surface of the Al2O3 substrate, thereby forming extremely high-quality corundum (Al2O3). x Ga1-x ) A Ga2O3 template layer (0 < x < 1). Growth can be interrupted or continued when the substrate temperature is reduced to about 500 °C. Then, the template layer acts as an in-plane lattice-matching layer closer to Ga2O3, and thus the CLT of the epitaxial film is found to be thicker.

[0601] After establishing the unique properties of the A-plane surface and referring to Figure 20B the disclosed surface energy trends, a superlattice structure with bandgap modulation is also shown to be possible.

[0602] Figure 44U Shows the unique properties of binary Ga2O3 and binary Al2O3 epitaxial layers used to form an SL structure on an A-plane Al2O3 substrate 5625 (corresponding to peak 5627). Excellent SL HRXRD 5610 and GIXR 5630 data show multiple high-quality SL Bragg diffraction side peaks 5615 and 5620 with a period Δ SL = 9.5 nm. Not only is the full width at half maximum (FWHM) of each side peak 5615 small, but also the inter-peak oscillations of Pendellosung fringes are clearly observed. For N = 10 SL periods, there are N - 2 Pendellosung oscillations, as shown in both HRDRD and GIXR. The zero-order SL peak SL n＝0 indicates the average alloy Al% of the digital alloy formed by the SL and is This degree of crystalline perfection is rarely observed in many other commercially relevant material systems of non-oxides, and it should be noted that it is comparable to the very mature GaAs / AlAs group III arsenide material system deposited on a GaAs substrate. Such a low-defect-density SL structure is necessary for high-performance UVLED operation.

[0603] Figure 44V The image 5660 in shows the crystal quality observed for an exemplary [Al2O3 / Ga2O3] SL 5645 deposited on an A-plane sapphire 5625. Clearly visible is that the contrast of Ga and Al species shows a sharp interface between the nanoscale films 5650 and 5655 constituting the SL period.

[0604] Examining the image 5660 more closely shows regions, labeled 5635, that result from the above-described high-temperature Ga mixing process. The Al2O3 buffer layer 5640 gives a small strain to the SL stack. Special attention should be paid to keeping the Ga2O3 film thickness well below the CLT to produce high-quality SLs. However, strain accumulation may occur, and in some embodiments, other structures are possible, such as growing an SL structure on a relaxed buffer composition intermediate the composition endpoints of the materials constituting the SL.

[0605] This allows for the design of strain symmetry, where the layer pairs forming the superlattice period can have equal and opposite in-plane strains. Each layer is deposited below the CLT and undergoes biaxial elastic strain (thus suppressing dislocation formation at the interface). Therefore, some embodiments involve designing SLs disposed on a relaxation buffer layer, which allows the SLs to accumulate zero strain and thus can be efficiently grown without strain, with a theoretically infinite thickness.

[0606] This allows for another application of corundum film growth on a favorable Al2O3 crystal surface (i.e., the R-plane (1-102)).

[0607] Figure 44W This shows the epitaxial deposition of a thick ternary corundum (Al2O3) layer on R-face corundum Al2O3. x Ga 1-x The capability of the Al₂O₃ film. HRXRD5665 shows an R-side Al₂O₃ substrate 5675, which is prepared using high-temperature oxygen polishing and co-deposition of Al and Ga (thus forming region 5680) while reducing the growth temperature from 750°C to 500°C. Region 5680 is an optional surface layer modification of the sapphire substrate surface (such as the oxygen-sealed surface). The excellent high-quality ternary epitaxial layer 5670 (corresponding to XRD peak 5672) exhibits sharp Pendellosung stripes 5680 and provides an alloy composition with x = 0.64 relative to the substrate peak 5677. The film thickness in this case is approximately 115 nm. Figure 44W The image also shows the angular separation of the symmetrical Bragg peak 5685 in the pseudoisomorphic corundum Ga2O3 epitaxial layer.

[0608] Furthermore, the generation of bandgap epitaxial films is highly efficient, and these films can be configured or designed to construct the functional regions required for UV LEDs. In this way, strain and composition are tools that, according to this disclosure, can be used to manipulate the known functional properties of materials for application in UV LEDs.

[0609] Figure 44X Examples of possible high-quality superlattice structures for R-plane Al2O3(1-102) oriented substrates are shown.

[0610] Exemplary SLs shown for epitaxial formation on an Al2O3(1-102) substrate 5705 (corresponding to peak 5707) on the R-plane are HRXRD 5690 and GIXR 5710.

[0611] The SL includes 10-period [ternary / binary] bilayer pairs [(Al] x Ga 1-x [2O3 / Al2O3], where x = 0.50. SL period Δ SL=20nm. Multiple SL Bragg diffraction peaks at 5695 and a reflectance peak at 5715 indicate a coherently grown pseudoisomorphic structure. The zero-order SL diffraction peak SL... n＝0 5700 indicates that it includes (Al) xSL Ga 1-xSL The effective number of alloys of SL in 2O3 x SL , where x SL =0.2.

[0612] Such highly coherent and largely different bandgap materials used to generate epitaxial SLs with abrupt discontinuities at the interface can be used to form quantum confinement structures as disclosed herein for application in optoelectronic devices such as UV LEDs.

[0613] For the corundum crystal symmetry (R3c), the discontinuities in the conduction band and valence band energies obtainable at the Al2O3 / Ga2O3 heterointerface are as follows:

[0614]

[0615]

[0616] Furthermore, for a monoclinic crystal symmetry (C2m) heterointerface, the band shift is:

[0617]

[0618]

[0619] Some implementations also include generating potential discontinuities by producing Ga2O3 layers with abrupt changes in crystal symmetry.

[0620] For example, this paper discloses that corundum crystal-symmetric Ga2O3 can be directly epitaxially deposited on a monoclinic Ga2O3(110) oriented surface. The band shift generated by this heterojunction is given by the following:

[0621]

[0622]

[0623] These band shifts are sufficient to produce quantum confined structures, as will be described below.

[0624] As another example of an implementation scheme for a composite metal oxide heterostructure, refer to Figure 44YIn this process, a cubic MgO epitaxial layer 5730 is formed directly on a spinel MgAl2O4(100) oriented substrate 5725. HRXRD 5720 shows the Bragg diffraction peak 5727 of the cubic MgAl2O4(h 0 0) (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, and thus a unique epitaxial coincidence is achieved to realize in-plane lattice registration at the heterojunction.

[0625] Clearly, a high-quality MgO(100) oriented epitaxial layer was formed, as confirmed by the narrow FWHM. Next, a monoclinic Ga2O3 layer 5735 was formed on the MgO layer 5730. The Ga2O3(100) oriented film was confirmed by the Bragg diffraction peak at 5736.

[0626] cubic MgAl2O4 and Mg x Al 2(1-x) O 3-2x The ternary structure is of interest due to its potential for direct and large band gaps.

[0627] Figure 44Z The curve 5740 shows Mg x Al 2(1-x) O 3-2x The band structure (x ~ 0.5) shows a direct band gap 5745 formed between the conduction band 5750 and the valence band 5755 extreme.

[0628] Some implementations also include the direct growth of Ga2O3 on a lanthanum aluminum oxide LaAlO3(001) substrate.

[0629] Figures 44A to 44Z The exemplary examples disclosed herein are intended to demonstrate some possible configurations suitable for use in at least a portion of a UVLED structure. A wide variety of compatible heterostructures of mixed symmetry types are another property of this disclosure. As will be understood, other configurations and structures are also possible and consistent with this disclosure.

[0630] The aforementioned unique properties of AlGaO3 material systems can be applied to the formation of UV LEDs. Figure 45 An exemplary light-emitting device structure 1200 according to the present disclosure is shown. The light-emitting device 1200 is designed to operate such that optically generated light can be coupled outwardly perpendicularly through the device. The device 1200 includes a substrate 1205, a first conductive n-type doped AlGaO3 region 1210, followed by an unintentionally doped (NID) intrinsic AlGaO3 spacer region 1215, and then a region using (Al... x Ga 1-x )O3 / (Al y Ga1-y A multiple quantum well (MQW) or superlattice 1240 formed by the periodic repetition of O3, wherein the barrier layer comprises a larger band gap composition 1220 and the well layer comprises a narrower band gap composition 1225.

[0631] The total thickness of the MQW or SL 1240 is selected to obtain the desired emission intensity. The layer thickness of the unit cell constituting the MQW or SL 1240 is configured to generate a predetermined operating wavelength based on the quantum confinement effect. Next, an optional AlGaO3 spacer layer 1230 separates the MQW / SL from the p-type AlGaO3 layer 1235.

[0632] Figure 46 , Figure 47 , Figure 49 , Figure 51 and Figure 53 The diagram discloses a spatial band structure represented by k=0, and is a graph showing the spatial band energy 1252 varying with the growth direction 1251. The n-type conductive region 1210 and the p-type conductive region 1235 are selected from monoclinic or corundum compositions (Al). x Ga 1-x O3 (where x = 0.3), followed by NID 1215 with the same composition (x = 0.3). The thickness of both the well layer and the barrier layer was adjusted in each design to 1250 ( Figure 46 , Figure 47 ), 1350 Figure 49 ), 1390 Figure 51 ) and 1450 ( Figure 53 Keep the same in tune to either the MQW or SL1240.

[0633] The trap composition varies from x = 0.0, 0.05, 0.10, and 0.20, and the barrier is targeted at bilayer pairs (Al). x Ga 1-x )O3 / (Al y Ga 1-y O3 was fixed at y = 0.4. These MQW regions are located at 1275, 1360, 1400, and 1460. The thickness of the well layer is selected from at least 0.5 xa of the host composition. w Up to 10xa w a unit cell (a w (where is the lattice constant). For the current case, a unit cell is selected. When the corundum and monoclinic unit cells are relatively large, the periodic unit cell thickness can be relatively large. However, in some embodiments, subcell assemblies can be utilized. Figure 47 MQW region 1275 in the middle is configured to include Ga2O3 / (Al 0.4 Ga 0.6 The nature or unintentional combination of doped layers of 2O3. Figure 49MQW region 1360 in the configuration is configured to contain (A1) 0.05 Ga 0.95 )2O3 / (Al 0.4 Ga 0.6 The nature or unintentional combination of doped layers of 2O3. Figure 51 MQW region 1400 in the configuration is configured to contain (A1) 0.1 Ga 0.9 )2O3 / (Al 0.4 Ga 0.6 The nature or unintentional combination of doped layers of 2O3. Figure 53 MQW region 1460 in the configuration is configured to contain (Al) 0.2 Ga 0.8 )2O3 / (Al 0.4 Ga 0.6 The nature or unintentional combination of doped layers of 2O3.

[0634] Also shown are ohmic contact metals 1260 and 1280. Conductor edge E C (z)1265 and the edge of the valence band E V (z)1270 and MQW region 1400 show bandgap energy modulation relative to the spatially modulated composition. This is another particular advantage of atomic layer epitaxial deposition techniques that make such structures possible.

[0635] Figure 47 The wave functions of confined electrons 1285 and holes 1290 within the MQW region 1275 are schematically shown. Photon 1295 is generated by electric dipole transitions caused by the spatial recombination of electrons 1285 and holes 1290.

[0636] The emission spectrum can be calculated and Figure 48 This is illustrated in Figure 1300, where the emission spectrum is plotted as emission wavelength 1310 and oscillator absorption intensity 1305 due to the overlapping integral of the wave functions of the spatially dependent quantized electron and hole states (which also indicate emission intensity). Using the MQW, multiple peaks 1320, 1325, and 1330 arise due to the recombination of quantized energy states. In particular, the lowest-energy electron-hole recombination peak 1320 is the most likely and appears at ~245 nm. Region 1315 shows that there is no absorption or optical emission below the MQW bandgap. The initial onset of optical activity as it moves toward shorter wavelengths is the n=1 exciton peak 1320, determined by the MQW configuration.

[0637] MQW configurations of 1275, 1360, 1400, and 1460 generate light emission energy peaks of 1320 nm with peak operating wavelengths of 245 nm, 237 nm, 230 nm, and 215 nm, respectively. Figure 48 ), 1370 Figure 50 ), 1420 Figure 52 ) and 1470 ( Figure 54 ). Figure 50 The curve 1365 also shows peaks at 1375 and 1380 and region at 1385. Figure 52 The curve 1410 also shows peaks 1425 and 1430, as well as region 1435. Figure 54 The curve 1465 also shows peak 1475 and region 1480. Regions 1385, 1435 and 1480 show that for photon energies / wavelengths below the MQW bandgap, there is no optical absorption or emission.

[0638] Another feature of extremely wide bandgap metal-oxide semiconductors is the configuration of ohmic contacts with both n-type and p-type regions. An exemplary diode structure 1255 includes a high work function metal 1280 and a low work function metal 1260 (ohmic contact metal). This is due to the relative electron affinity of the metal oxide relative to vacuum (see reference). Figure 9 ).

[0639] Figure 48 , Figure 50 , Figure 52 and Figure 54 The optical absorption spectrum of the MQW region contained within diode structure 1255 is shown. The MQW comprises two layers: a narrower bandgap material and a wider bandgap material. The thickness of the layers, particularly the narrower bandgap layer, is chosen to be small enough to exhibit quantization effects along the growth direction within the formed conduction and valence potential wells. The absorption spectrum indicates the generation of electrons and holes in the quantized state of the MQW following the resonant absorption of the incident photon.

[0640] The reversible photon generation process involves the spatial localization of electrons and holes in their respective MQW quantum energy levels and their recombination via a direct band gap. The recombination of photons is approximately equivalent to the layer acting as a potential well, which, in addition to the energy separation of the quantized energy levels within the potential well relative to the conduction and valence band edges, also possesses a direct band gap. Therefore, the emission / absorption spectra reveal a lowest-order energy resonance peak, which indicates the main emission wavelength of the UV LED and is designed as the desired operating wavelength of the device.

[0641] Figure 55 A plot 1500 shows the known work function energy 1510 of a pure metal, and sorts the 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, and provides selection criteria for metal contacts for each of the conductivity type regions required for UV LEDs. Line 1520 represents relative to... Figure 55 The work function energy at the midpoint of the upper limit 1525 and the lower limit 1515 is depicted in the figure.

[0642] In some implementations, Os, Pt, Ir, and Ni are used in the p-type region, and low work function metals selected from rare earth elements, Li, and Cs can be used. Other options are also possible.

[0643] Intermediate contact materials such as half-metallic palladium oxide (PdO), degraded doped Si or Ge, and rare-earth nitrides can be used. In some embodiments, for at least a portion of the contact material, the ohmic contact is formed in situ during the deposition process to preserve the [metal contact / metal oxide] interface quality. In fact, for some metal oxide configurations, single-crystal metal deposition is possible.

[0644] X-ray diffraction (XRD) is one of the most powerful tools available for analyzing crystal growth to directly confirm crystal quality and crystal symmetry type. Figure 56 and Figure 57 Two-dimensional XRD data of exemplary materials, including ternary AlGaO3 and binary Al2O3 / Ga2O3 superlattices, are shown. Both structures were pseudoisomorphically deposited on a corundum crystal symmetry substrate with an A-plane oriented surface.

[0645] Reference Figure 56 This shows a 201nm thick epitaxial ternary (Al2O3) substrate on the A-side Al2O3 substrate. 0.5 Ga 0.5 The inverted lattice map of Al₂O₃ and the 2-axis X-ray diffraction pattern at 1600° are shown. Clearly, the in-plane and perpendicular mismatches of the ternary film are well matched to the underlying substrate. The in-plane mismatch parallel to the growth plane is ~4088 ppm, and the perpendicular lattice mismatch is ~23440 ppm. The ternary layer peaks (Al₂O₃) are also shown. x Ga 1-x The relative vertical displacement of O2O3 with respect to the substrate (SUB) shows excellent film growth compatibility and is directly beneficial for UV LED applications.

[0646] Now refer to Figure 57 The diagram shows a 10-period 2-axis X-ray diffraction pattern 1700 of SL [Al2O3 / Ga2O3] on an Al2O3 substrate on the A-side, which shows a Ga2O3 layer with excellent strain (no extension at the 2θ angle) => elastic strain SL. The SL period is 18.5 nm, and the effective SL number is Al% ternary alloy x_Al ~ 18%.

[0647] In another exemplary embodiment, the optoelectronic semiconductor device according to this disclosure can be implemented as an ultraviolet laser device (UVLAS) based on a metal oxide semiconducting material.

[0648] Metal oxide compositions possessing bandgap energies commensurate with their operation in UVC (150 nm to 280 nm) and far / vacuum UV wavelengths (120 nm to 200 nm) share a generally distinguishing characteristic: an inherently small optical refractive index with absorption far from the fundamental band edge. The effective refractive index is controlled by the Krammers-Kronig relation for operation as an optoelectronic device with energy states adjacent to the conduction and valence band edges.

[0649] Figures 58A to 58B The diagram shows a cross-section of a metal-oxide-semiconductor material 1820 having an optical length 1850 along a one-dimensional optical axis, according to an exemplary embodiment of the present disclosure. The incident light vector 1805 originates from a source with a refractive index of n. MOx Air enters material 1820. Light within material 1820 is transmitted and reflected (beam 1810) at refractive index discontinuities at each surface as a transmitted beam 1815.

[0650] A material plate with a length of 1850 mm can support several optical longitudinal modes 1825, such as... Figure 58A As shown. Transmission 1815, varying with the wavelength of light incident on the plate, illustrates a Fabry-Perot mode structure with mode 1825. Because photons are trapped within an optical cavity defined by a one-dimensional plate, it is possible, according to this disclosure, to determine the round-trip losses of the plate and the minimum optical gain required to overcome these losses and achieve net gain.

[0651] Figure 58B The threshold gain calculated in the figure shows the transmission factor β of the forward 1830 and reverse 1835 propagating beam 1810 as a function of the in-plate optical gain. For this simple Fabry-Perot case, the plate length L cav =1 micrometer low refractive index n MOx =2.5 requires a threshold gain of 1845, which is calculated from the half-peak full amplitude point of the peak gain at 1840.

[0652] Some implementation schemes implement a vertical structure 110 with a sub-micron length scale (e.g., see...). Figure 2A The semiconductor cavity contained within the plate is designed to localize electron and hole recombination into a narrow region. Limiting the physical thickness of the plate to the extent that carrier recombination occurs and light emission is generated helps reduce the threshold current density required to achieve laser emission. Therefore, it is advantageous to estimate the required threshold gain by reducing the length of the gain plate.

[0653] Figures 59A to 59B Showing with Figures 58A to 58B Same optical material, but used for L cav=500nm. The smaller cavity length 1860 results in fewer permissible optical modes 1870 compared to a length of 1850. (See reference...) Figure 59B The peak 1877 shown is calculated for forward propagation mode 1880 and backward propagation mode 1885, respectively, and Figure 58A Compared to the gain of 1845, the required threshold gain to overcome cavity loss increases to 1865.

[0654] By increasing the length of the optical gain medium (in this case, the metal oxide semiconducting region responsible for the optical emission process), the increase in the required threshold gain of the metal oxide material plate can be significantly reduced.

[0655] Refer again Figure 2A and Figure 2B Instead of using a vertical 110 launcher (i.e., Figure 2A Some implementations utilize planar waveguide structures in which the optical modes overlap the optical gain layer along a length parallel to the plane. That is, even though the gain material is still a thin plate, the optical propagation vector is substantially parallel to the plane of the gain plate.

[0656] for Figure 2B Structure 140 and Figure 74 Structure 2360 in the diagram schematically illustrates this. Waveguide structures with optical gain layer thicknesses much less than 500 nm are possible, and can even be as thin as 1 nanometer, supporting quantum wells (see Figures 64 to 68). The longitudinal length of the waveguide can then be from a few micrometers to even a few millimeters or even a centimeter. This is an advantage of waveguide structures. An additional requirement is the ability to confine and guide optical modes along the principal axis of the waveguide, which can be achieved by using suitable refractive index discontinuities. Optical modes are preferably guided in a higher refractive index medium compared to the surrounding non-absorbing cladding region. This can be achieved using metal oxide compositions, as described in this disclosure, that can be pre-selected to exhibit advantageous Ek-band structures.

[0657] In its most basic configuration, UVLAS requires at least one optical gain medium and an optical cavity for recycling the generated photons. The optical cavity must also feature a high reflector (HR) with low loss and an output coupling reflector (OC) capable of transmitting a portion of the light energy generated within the gain medium. The HR and OC reflectors are generally planar parallel or designed to focus the energy within the cavity into the gain medium.

[0658] Figure 60An embodiment of the optical cavity is schematically shown, having an HR 1900, a gain medium 1905 substantially filling the cavity length 1935, and an OC 1915 with a physical thickness 1910. Standing waves 1925 and 1930 show two dissimilar optical wavelengths matching the cavity length. Outwardly coupled light 1920 is due to a portion of the trapped energy within the cavity gain medium 1905 leaking from the OC. In one example, a low-thickness (<15 nm) aluminum metal is used in the far UV wavelength region or the vacuum UV wavelength region, and transmission can be precisely tuned through the Al film thickness 1910. The lowest energy standing wave 1925 has a node (peak intensity of the optical field) at the cavity's central node 1945. As shown, the first harmonic (standing wave 1930) is shown to nodes 1940 and 1950.

[0659] Figure 61 The output wavelengths from the cavity at 1960 and 1965 are shown with the energy flow at 1970. The cavity length at 1935 is also shown. Figure 60 The same as in [the previous sentence]. Figure 61 The cavity length of 1935 mm supports two optical modes that form two different standing waves, 1930 mm and 1925 mm. Figure 61 The emission or outward coupling of the two wavelength modes (standing waves 1930 and 1925) is shown 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. Therefore, according to this disclosure, it is possible to configure the gain medium within the optical cavity as follows: Figure 62 As shown.

[0660] Figure 62 This shows a space-selective gain medium 1980, which is related to... Figures 60 to 61 The optical gain medium 1905 is shorter in length and advantageously positioned within the cavity length 1935 to amplify only the mode 1925. That is, the optical gain medium 1980 facilitates outward coupling at wavelength 1960, which is the optical mode. Therefore, the cavity preferably provides gain to the fundamental mode 1925 using the output energy selected for wavelength 1960.

[0661] Similarly, Figure 63 Two spatially selective gain media 1990 and 1995 are shown, advantageously positioned to amplify only the standing wave mode 1930. The cavity preferably utilizes the output energy selected as 1965 to provide gain to the standing wave mode 1930.

[0662] This method, which involves spatially positioning gain regions within an optical cavity, is an exemplary embodiment of this disclosure. This can be achieved by pre-determining functional regions that vary with the growth direction during the film formation process as described herein. The spacer layers between gain segments may comprise substantially non-absorbing metal oxide compositions and, in other cases, provide electron carrier transport functionality and facilitate optical cavity tuning design.

[0663] Now attention is turned to the design of optical gain media for UVLAS using metal oxide compositions as described in this disclosure.

[0664] Figures 64A to 64B and Figures 65A to 65B A bandgap-designed quantum confinement structure of a single quantum well (QW) is disclosed. It should be understood that multiple QWs are possible, and superlattices are also possible. The wide bandgap electronic barrier coating is selected from metal oxide material composition A. x B y O z Furthermore, the potential well material was chosen to be 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).

[0665] Pre-selection of materials can achieve, for example Figure 64A and Figure 64B The conduction band offset and valence band offset are shown. A = Al, B = Ga are shown to form (Al... 0.95 B 0.05 )2O3=Al 1.9 Ga 0.1 O3 and C=Al, D=Ga to form (Al) 0.05 B 0.95 )2O3=Al 0.1 Ga 1.9 The case of O3. The conduction band spatial profile 2005 and the valence band spatial profile 2010 along the growth direction z are shown using the k=0 representation of the corresponding Ek curve for each material.

[0666] Figure 64A Showing a thickness of 2015L QW =5nm, which are the allowed states of electrons and holes in the conduction and valence bands, respectively, generating quantized energy states 2025 and 2035. The lowest quantized electronic state 2020 and the highest quantized valence state 2030 participate in the spatial recombination process to produce a photon with energy equal to 2040.

[0667] Similarly, Figure 64B It shows a thickness of 2050L QWA QW of 2 nm generates quantized energy states within the potential well, representing the allowed states of electrons and holes in the conduction and valence bands, respectively. The lowest quantized electronic state 2055 and the highest quantized valence state 2060 participate in a spatial recombination process to produce a photon with energy equal to 2065.

[0668] Reducing the QW thickness further leads to Figure 65A and Figure 65B Spatial zone structure. Figure 65A It shows a thickness of 2070L QW A QW of 1.5 nm generates quantized energy states by allowing electrons and holes in the conduction band 2005 and valence band 2010, respectively, within the potential well. The lowest quantized electronic state 2075 and the highest quantized valence state 2080 participate in a spatial recombination process to produce a photon with energy equal to 2085.

[0669] Figure 65B It shows a thickness of 2090L QW A QW with a wavelength of 1.0 nm generates quantized energy states within the potential well by allowing electrons and holes in the conduction and valence bands, respectively. The QW can support only a single quantized electronic state 2095, which, together with the highest quantized valence state 2100, participates in a spatial recombination process to produce a photon with energy equal to 2105.

[0670] Figure 66 The middle shows Figure 64A , Figure 64B , Figure 65A and Figure 65B The spontaneous emission of the QW structure is due to the spatial recombination of quantized electron and hole states. The annihilation of electron-hole pairs produces high-energy photons with wavelength peaks relative to L. QW The values ​​for 5.0 nm, 2.5 nm, 2.0 nm, 1.5 nm, and 1 nm are at 2115, 2120, 2125, 2130, and 2135, respectively. The self-emission spectrum 2110 clearly shows that, by using the same barrier and trap composition but controlling L... QW Excellent tunability of the operating wavelength is possible for the gain medium.

[0671] The utility of configuring metal oxide compositions for direct application to UVLAS gain media has been fully described; now, refer to Figure 67A and Figure 67B It describes the electronic configuration of the gain medium in more detail. Figure 67A A QW is again shown that uses a metal oxide layer to form an exemplary QW structure as previously described.

[0672] The QW thickness of 2160 was tuned to achieve a composite energy of 2145. Figure 67AIn the diagram, k=0 in QW represents the non-zero crystal wave vector dispersion of quantized energy states 2165 and 2180, representing electronic (conduction band 2190) and hole (valence band 2205) states. For completeness, the fundamental Ek dispersion is also shown as 2170 and 2175 at k=0 and 2185 and 2200 for non-zero k. This schematic Ek diagram is crucial for describing the population inversion mechanism, which generates the excess electrons and holes necessary to provide optical gain in the conduction and valence bands.

[0673] Figure 68A The band structure shown describes the electronic energy configuration when the conduction band quasi-Fermi level 2230 is positioned such that it is above the electronic quantized state 2235. Similarly, the valence band quasi-Fermi level is selected to penetrate the valence band level 2245, resulting in an excess hole density 2225. The Ek curve of the conduction band 2195 shows that the electronic state 2220 is filled with electrons, making the non-zero crystal momentum state |k|>0 possible. The valence band level 2240 is the valence band edge of the bulk material used in the narrow bandgap region of the MQW. When the narrow bandgap material is confined in the MQW, the energy states are quantized, resulting in a band structure dispersion of conduction band 2195 and valence band 2205. The valence band level 2240 is the valence band maximum in the MQW region. The valence band level 2245 represents the Fermi level of the valence band when configured as a p-type material. This allows the excess hole density 2225 region to be filled with holes that can participate in optical gain.

[0674] Optical recombination can occur for 'vertical transitions', where the change in crystal momentum between electronic and hole states is also zero. Allowable vertical transitions are shown as 2210 at k=0 and 2215 at k≠0. Figure 68B The middle shows Figure 68A The calculation of the integrated gain spectrum of a representative band structure. Specific input parameters for the gain spectrum are: L QW =2nm, electron-to-hole concentration ratio of 1.0, carrier relaxation time of τ = 1ns, and operating temperature of T = 300K. Curves 2275 to 2280 show the electron concentration N. e The increase of, where 0≤N e ≤5x10 24 m -3 .

[0675] A net positive gain of 2250 can be achieved at high electron concentrations, where the threshold is N. e ~4x10 24 m -3These parameters are roughly achievable with other technologically mature semiconductors, such as GaAs and GaN. In some implementations, thanks to their inherently high band gaps, metal-oxide-semiconductor systems are also less prone to gain degradation with operating temperature. This can be demonstrated by conventional optically pumped high-power solid-state Ti-doped Al₂O₃ laser crystals.

[0676] Figure 68B Showing N e The net gain 2265 and net absorption 2270 change. The range of crystal wave vectors that can facilitate vertical transitions determines the width of the net gain region 2250. This is essentially determined by the excess electronic state 2220 and the hole state 2225 that are achievable by manipulating the quasi-Fermi energy.

[0677] Region 2255 is below the fundamental bandgap of the host QW and therefore does not absorb. Therefore, it is also possible to implement an optical modulator using a metal-oxide-semiconductor QW. Notably, inductive transparency 2260 is achieved with zero loss in the QW.

[0678] Manipulating the quasi-Fermi energy is not the only method that can be used to generate excess electron-hole pairs near the central band structure of the region, thereby achieving optical emission. Consider... Figure 69A and Figure 69B They show that for direct bandgap materials ( Figure 69A Ek band structures in the case of pseudo-direct bandgap materials, such as those selected to produce valence maxima (e.g.) Figure 69B The periodic metal oxide SL (as shown by curve 2241 and hole state 2246).

[0679] Assuming a similar conduction band dispersion at 2195, the same vertical transitions are possible configurations for both valence band types 2205 and 2241. For example... Figure 68B The published essentially similar gain spectra are for Figure 69A and Figure 69B Both types shown are possible.

[0680] Another method is disclosed as an alternative to generating electronic and hole states suitable for optical emission and optical gain using metal oxide semiconductor structures.

[0681] consider Figure 70A and Figure 70B These demonstrate the impact ionization process of metal oxide semiconductors with direct band gaps. While impact ionization is a known phenomenon and process in semiconductors, the advantageous properties of metal oxides with extremely wide band gaps are not well known. One of the most promising properties discovered according to this disclosure is the extremely high dielectric breakdown strength of metal oxides.

[0682] In existing small-bandgap semiconductors (such as Si, GaAs, etc.), impact ionization processes often lead to material wear due to the generation of crystal defects / damage when functioning in a device. Over time, this degrades the material and limits the number of potential breakdown events that can occur before a catastrophic device failure.

[0683] Extremely wide bandgap metal oxides with Eg > 5eV possess advantageous properties for generating impact ionization light emitting devices.

[0684] Figure 70A The diagram illustrates a direct bandgap 2266 in a metal oxide, where 'hot' (high-energy) electrons are injected into the conduction band in electronic states 2251 with excess kinetic energy 2261 relative to the edge of the conduction band 2256. The metal oxide can readily withstand excessively high electric fields (V0) applied to the thin film. br >1MV / cm-10MV / cm).

[0685] Impact ionization events are achieved by operating a metal oxide plate biased at voltages below or near the breakdown voltage, such as... Figure 70B As shown, the high-energy electron 2251 interacts with the crystal symmetry of the host and can generate lower-energy states by coupling to available thermal states using lattice vibrational quantum pairs called phonons. Specifically, a collisional ionization event involving the hot electron 2251 is converted into two lower-energy electronic states 2276 and 2281 near the conduction band minimum, and a new hole state 2286 is generated at the top of the valence band 2271. The generated electron-hole pair 2291 is a potential recombination pair to produce a photon with energy 2266.

[0686] According to this disclosure, it has been found that for an excess electron energy 2261 that is approximately half the bandgap energy 2266, collisional ionization pairs can be generated. For example, if E G =5 eV 2266, then hot electrons relative to the ~2.5 eV conduction band edge can initiate the pair generation process as described. This is achievable for Al2O3 / Ga2O3 heterostructures, where electrons from Al2O3 are injected across the heterojunction into Ga2O3. Collisive ionization is a stochastic process and requires a minimum interaction length to create a finite energy distribution of electron-hole pairs. Generally, interaction lengths from 100 nm to 1 micrometer can be used to create significant pair generation.

[0687] Figure 71A and Figure 71B It is shown that collisional ionization is also possible in pseudo-direct band structure metal oxides and indirect band structure metal oxides. Figure 71A Describe the situation prior to the direct bandgap, and Figure 71BThe same process is shown for the indirect bandgap valence band 2294, where the generation of electron-hole pairs 2292 requires the creation of a hole state 2296 with k ≠ 0, thus necessitating the presence of phonons to conserve momentum. Therefore, Figure 71B It is also possible to realize optical gain media in pseudo-direct band structures such as 2294.

[0688] Figure 72A and Figure 72B Further details of this disclosure are disclosed regarding the use of impact ionization processes for optical gain media by selecting the advantageous properties of the band structure.

[0689] Figure 72A Wave vector description for in-plane crystal wave vector k|| and wave vector along quantization axis kZ parallel to epitaxial growth direction z. Figures 68A to 68B , Figures 69A to 69B , Figures 70A to 70B and Figures 71A to 71B The belt structure.

[0690] Figure 72A Along kZ, the conduction band dispersion 2320 and the valence band dispersion 2329 are shown. If... Figure 72A The band structure of the material with a band gap of 2266, depicted in the figure, with k=0 spatial band structure drawn along the growth direction, is then... Figure 72B The resulting spatial band structure is shown in the diagram. Along the growth direction z, hot electrons 2251a are injected into the conduction band, causing a collisional ionization process and generating 2290. If the metal oxide material plate is subjected to a large electric field along the z-direction, the band structure has a linearly decreasing potential energy along z. The collisional ionization event that causes electrons 2276 and holes 2286 to align with particles and generate 2290 can undergo recombination and produce bandgap photons.

[0691] The remaining electron 2276 can be accelerated by the applied electric field to generate another hot electron 2252. The hot electron 2252 can then be ionized by collision and the process is repeated. Therefore, the energy supplied by the external electric field can induce the generation of electrons and photons. This process is particularly advantageous for metal oxide light emission and optical gain formation.

[0692] Finally, there are three laser topologies that can be advantageously utilized based on the principles set forth in this disclosure.

[0693] The basic components are: (i) an electronic region that forms and generates the optical gain region; and (ii) an optical cavity containing the optical gain region.

[0694] Figure 73A semiconductor optoelectronic device in the form of a vertical emission UVLAS 2300 is shown, comprising: an optical gain region 2330 with a thickness of 2331; an electron injector region 2325 (2310); and a hole injector region 2335 (2315). Regions 2325 and 2335 may be n-type and p-type metal-oxide semiconductors, and are substantially transparent to the operating wavelength emitted from the device along axis 2305. An electrical excitation source 200 is operatively connected to the device via conductive layers 2340 and 2320, which may also function as a high reflector and an output coupler, respectively. The optical cavity between the reflectors (conductive layers 2340 and 2320) is formed by the sum of the stacked layers 2325, 2330, and 2335.

[0695] If the reflector is partially absorptive and has a multilayer dielectric type, a portion of the reflector's thickness is also included as the cavity thickness. For a pure and ideal metallic reflector, the mirror thickness is negligible. Therefore, the optical cavity thickness is controlled by layers 2325, 2330, and 2335, where the optical gain region 2330 is relative to... Figure 61 , Figure 62 and Figure 63 The cavity mode is advantageously positioned. Photon recirculation 2350 is shown by optical reflections from mirrors / reflectors 2340 and 2320.

[0696] Used to generate such Figure 73 Another option for the UVLAS structure shown is the following implementation: in which reflectors 2320 and 2340 form part of the circuit and therefore must be conductive and must also function as reflectors forming the optical cavity. This can be achieved by using an elemental aluminum layer as at least one of HR or OC.

[0697] An alternative UVLAS configuration decouples the optical cavity from the electrical components of the structure. For example, Figure 74 A UVLAS 2360 with an optical cavity is disclosed, the optical cavity being formed to include HR 2340 and OC 2320, which are not part of the circuitry. An optical gain region 2330 is positioned with the cavity to enable photon recirculation 2350. The optical axis is oriented along axis 2305. An insulating spacer layer of metal oxide region may be provided within the cavity to adjust the position of the gain region 2330 between reflectors 2340 and 2320. An electron injector 2325 and a hole injector 2335 provide laterally transported carriers to the gain region 2330.

[0698] This structure for vertically emitting UVLAS can be achieved by creating p-type and n-type regions laterally configured to connect only a portion of the gain region. The reflector can also be positioned on a portion of the optical gain region to generate cavity photon recirculation 2350.

[0699] Even another exemplary implementation plan is Figure 75 The waveguide device shown is 2370.

[0700] Figure 75 A waveguide structure 2370 is shown, having a main axis 2305 and epitaxial regions sequentially formed along the growth direction z. These epitaxial regions include an electron injector 2325, an optical gain region 2330, and a hole injector region 2335. A single-mode or multimode waveguide structure with a refractive index is selected to produce confined optical radiation of a forward propagation mode 2375 and a backward propagation mode 2380. The cavity length 2385 terminates at each end with reflectors 2340 and 2320. The high reflector 2340 may be metallic or of a distributed feedback type, comprising an etched grating or a multilayer dielectric conformally coated to the ridge. OC 2320 may be a dielectric-coated metallic translucent film or even a cleaved facet of a semiconductor substrate.

[0701] As will be understood, an optical gain region can be formed using an electrically excited and / or optically pumped / excited metal-oxide semiconductor according to the present disclosure, wherein an optical cavity can be formed in both the vertical structure and the waveguide structure as needed.

[0702] This disclosure teaches novel materials and processes for realizing photoelectric light-emitting devices based on metal oxides, which are capable of generating light deep into the UVC and far / vacuum UV wavelength bands. These processes include using a variety of different methods to tune or configure the band structure of different regions of the device, including but not limited to composition selection to achieve a desired band structure, including forming an effective composition by using a superlattice comprising different repeating layers of metal oxide. This disclosure also teaches the use of biaxial or uniaxial strain to modify the band structure of relevant regions of a semiconductor device and the use, for example, strain matching between layers in a superlattice to reduce crystal defects during the formation of the photoelectric device.

[0703] As will be understood, metal oxide-based materials are well known in the art due to their insulating properties. Metal oxide single-crystal compositions such as sapphire (corundum Al₂O₃) can be obtained with extremely high crystal quality and can be readily grown in large-diameter wafers using bulk crystal growth methods such as the Chuklaski method (CZ), edge-feed growth (EFG), and floating region (FZ). Semiconducting gallium oxide with monoclinic crystal symmetry has been achieved using essentially the same growth methods as sapphire. Ga₂O₃ has a lower melting point than sapphire, therefore the energy required for CZ, EFG, and FZ methods is slightly lower, and this helps reduce the cost per wafer at scale. Bulk alloys of AlGaO₃ bulk substrates have not yet been explored using CZ or EFG. Therefore, according to examples of this disclosure, metal oxide layers for optoelectronic devices can be based on these metal oxide substrates.

[0704] Two binary metal oxide materials, Ga₂O₃ and Al₂O₃, exist in several technically relevant crystal symmetry forms. Specifically, both α-phase (rhombic) and β-phase (monoclinic) are possible for both Al₂O₃ and Ga₂O₃. Ga₂O₃ is energy-favored for a monoclinic structure, while Al₂O₃ favors a rhombic structure for bulk crystal growth. According to this disclosure, atomic beam epitaxy using high-purity metals and atomic oxygen can be employed. As shown in this disclosure, this enables numerous opportunities for the flexible growth of heterogeneous crystal symmetry epitaxial films.

[0705] Two exemplary categories of device structures particularly suitable for UV LEDs include: high-Al content Al deposited on an Al2O3 substrate. x Ga 1-x O3; and high-Ga-content AlGaO3 on a bulk Ga2O3 substrate. As shown in this disclosure, the use of digital alloys and superlattices further expands the possible designs for application in UV LEDs. As shown in some examples of this disclosure, the selection of various Ga2O3 and Al2O3 surface orientations for AlGaO3 epitaxy can be combined with growth conditions (such as temperature and metal-to-atomic oxygen ratio and Al-to-Ga relative metal ratio) to predetermine the crystal symmetry type of the epitaxial film, which can be used to determine the band structure of the optical emission region or the conductivity type region.

[0706] Throughout this specification and the following claims, unless the context otherwise requires, the words “comprise” and “include”, as well as variations such as “comprising” and “including”, shall be understood to imply inclusion of the stated integers or groups of integers, but not to exclude any other integers or groups of integers.

[0707] Unless otherwise defined, all terms used in this disclosure (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. Further guidance, including term definitions, is provided to better understand the teachings of this disclosure.

[0708] As used herein, the following terms have the following meanings:

[0709] Unless the context clearly indicates otherwise, as used herein, “a,” “an,” and “described” refer to both the singular and plural references. For example, “metal oxide” refers to one or more metal oxides.

[0710] As used herein, the term "about" is intended to encompass variations from a specified value of + / -20% or less, preferably + / -10% or less, more preferably + / -5% or less, even more preferably + / -1% or less, and even more preferably + / -0.1% or less, since such variations are suitable for implementation in the disclosed embodiments. However, it should be understood that the values ​​referred to by the modifier "about" are themselves specifically disclosed.

[0711] Unless otherwise defined, "weight %" (weight percentage) means the relative weight of the corresponding component based on the total weight of the formulation or elements involved.

[0712] The range of values ​​described by endpoints includes all numbers and fractions contained within the range and the endpoints described, unless otherwise expressly stated in a disclaimer or similar document.

[0713] Any reference to prior art in this specification is not and should not be construed as an admission or in any way an implication that such prior art is part of common general knowledge.

[0714] Reference has been made to embodiments of the disclosed invention. Each example has been provided by way of explanation of the inventive technique and is not intended to limit the technique of the invention. In fact, although this specification has been described in detail with respect to specific embodiments of the invention, it will be understood that those skilled in the art will readily conceive of alternatives, variations, and equivalents of these embodiments upon gaining an understanding of the foregoing. For example, a feature illustrated or described as part of one embodiment may be used with another embodiment to obtain other embodiments. Therefore, the subject matter of the invention is intended to cover all such modifications and variations within the scope of the appended claims and their equivalents. These and other modifications and variations may be made to the invention by those skilled in the art without departing from the scope of the invention, the scope of which is more specifically set forth in the appended claims. Furthermore, those skilled in the art will understand that the foregoing description is merely illustrative and is not intended to limit the invention.

Claims

1. An optoelectronic semiconductor light emitting device comprising: a substrate; and a plurality of epitaxial semiconductor layers disposed on a substrate, wherein each of the epitaxial semiconductor layers comprises an epitaxial oxide, wherein at least one of the epitaxial semiconductor layers comprises an optical emissive material of a direct bandgap type, and wherein at least one of the epitaxial semiconductor layers comprises (Al x1 Ga 1-x1 )2O3, wherein 0≤x1≤1, wherein the plurality of epitaxial semiconductor layers comprises: a first region comprising a first conductivity type; a second region comprising a non-intentionally doped (NID) intrinsic region; and a third region comprising a second conductivity type, wherein the second region is between the first region and the third region, wherein the substrate and the plurality of epitaxial semiconductor layers are monocrystalline epitaxially formed, wherein the optoelectronic semiconductor light emitting device is configured to emit light having a wavelength in a range from 150 nanometers to 425 nanometers, wherein the first region, the second region, or the third region comprises a superlattice, and wherein the superlattice comprises (Al x1 Ga 1-x1 )2O3 and comprises (Al x2 Ga 1-x2 )2O3, where 0≤x2≤1, where x1 is not equal to x2.

2. The optoelectronic semiconductor light emitting device of claim 1, wherein at least one of the plurality of epitaxial semiconductor layers has rhombohedral crystal symmetry.

3. The optoelectronic semiconductor light emitting device of claim 1, wherein at least one of the plurality of epitaxial semiconductor layers comprises a uniaxially strained unit cell.

4. The optoelectronic semiconductor light emitting device of claim 1, wherein at least one of the plurality of epitaxial semiconductor layers comprises a biaxially strained unit cell.

5. The optoelectronic semiconductor light emitting device of claim 1, wherein at least one of the plurality of epitaxial semiconductor layers comprises a traxially strained unit cell.

6. The optoelectronic semiconductor light emitting device of claim 1, wherein the substrate has a surface on which the plurality of epitaxial semiconductor layers are disposed, wherein the surface of the substrate is configured to enable lattice matching with the plurality of epitaxial semiconductor layers.

7. The optoelectronic semiconductor light emitting device of claim 1, wherein the substrate is a monocrystalline substrate.

8. The optoelectronic semiconductor light emitting device of claim 7, wherein the substrate is selected from the group consisting of AI2O3, MgO, LiF, MgAl2O4, MgGa2O4, LiGaO2, LiAlO2, MgF2, LaAlO3, TiO2, quartz, and SiC.

9. The optoelectronic semiconductor light emitting device of claim 1, wherein the substrate has a surface on which the plurality of epitaxial semiconductor layers are disposed, wherein the surface of the substrate has a crystal symmetry and in-plane lattice constants configured to enable homoepitaxy or heteroepitaxy of the plurality of epitaxial semiconductor layers.

10. The optoelectronic semiconductor light emitting device of claim 1, wherein at least one of the plurality of epitaxial semiconductor layers has hexagonal crystal symmetry.

11. The optoelectronic semiconductor light emitting device of claim 1, wherein at least one of the plurality of epitaxial semiconductor layers has monoclinic crystal symmetry.

12. The optoelectronic semiconductor light emitting device of claim 1, wherein at least one of the plurality of epitaxial semiconductor layers has orthorhombic crystal symmetry.

13. The optoelectronic semiconductor light emitting device of claim 1, wherein at least one of the plurality of epitaxial semiconductor layers has cubic crystal symmetry.

14. The optoelectronic semiconductor light emitting device of claim 1, wherein at least one of the plurality of epitaxial semiconductor layers has trigonal crystal symmetry.

15. The optoelectronic semiconductor light emitting device of claim 1, wherein one of the plurality of epitaxial semiconductor layers has a crystal symmetry that is different than a crystal symmetry of another of the plurality of epitaxial semiconductor layers.

16. The optoelectronic semiconductor light emitting device of claim 1, wherein xi is greater than 0, x2 is greater than 0, or both xi and x2 are greater than 0.

17. The photoelectric semiconductor light-emitting device of claim 1, wherein the second region comprises a superlattice, and the superlattice comprises (Al) x1 Ga 1-x1 The first layer of 2O3 and containing (Al) x2 Ga 1-x2 The second layer of )2O3 repeats periodically, where 0≤x2≤1, and x1 is not equal to x2.

18. The optoelectronic semiconductor light emitting device of claim 1, wherein the substrate comprises Ga2O3.

19. The optoelectronic semiconductor light emitting device of claim 1, wherein the substrate comprises AlGaO3.

20. An optoelectronic semiconductor device for generating light of a predetermined wavelength, comprising: a substrate; a first epitaxial oxide layer, a second epitaxial oxide layer, and a third epitaxial oxide layer supported by a substrate, wherein at least one of the first epitaxial oxide layer, the second epitaxial oxide layer, and the third epitaxial oxide layer comprises (Al x1 Ga 1-x1 )2O3, where 0≤x1≤1; an optical emission region having an optical emission region band structure configured for generating light of the predetermined wavelength, the optical emission region comprising the first epitaxial oxide layer supported by the substrate, wherein the first epitaxial oxide layer has an optical emission region bandgap energy capable of generating light of the predetermined wavelength, wherein the first epitaxial oxide layer is direct bandgap type; a first conductivity type region having the second epitaxial oxide layer, the first conductivity type region having a first conductivity type region band structure configured to operate in conjunction with the optical emission region to generate light of the predetermined wavelength; and a second conductivity type region having the third epitaxial oxide layer, the second conductivity type region having a second conductivity type region band structure configured to operate in conjunction with the optical emission region and the first conductivity type region to generate light of the predetermined wavelength, wherein the optical emission region is between the first conductivity type region and the second conductivity type region, wherein the substrate, the first conductivity type region, the second conductivity type region, and the optical emission region are monocrystalline epitaxially formed devices, wherein the first epitaxial oxide layer, the second epitaxial oxide layer, or the third epitaxial oxide layer comprises a superlattice, the superlattice comprising two or more epitaxial oxide layers forming a unit cell and repeating with a fixed unit cell period along a growth direction, and 21. The optoelectronic semiconductor device of claim 20, wherein each individual layer of the unit cell forming the superlattice has a thickness that is less than or equal to an electron de Broglie wavelength in the individual layer. wherein one of the two or more layers of epitaxial oxide forming a unit cell of a superlattice comprises (Al x1 Ga 1-x1 )2O3, and wherein another of the two or more layers of epitaxial oxide forming a unit cell of a superlattice comprises (Al x2 Ga 1-x2 )2O3, wherein 0 < x2 < 1, wherein xi is not equal to x2.

22. The optoelectronic semiconductor device of claim 20, wherein the optical emission region band structure includes a predetermined strain introduced into the first epitaxial oxide layer.

23. The optoelectronic semiconductor device of claim 20, wherein the first conductivity type region band structure has a first conductivity type region bandgap energy that is greater than the optical emission region bandgap energy.

24. The optoelectronic semiconductor device of claim 20, wherein the second epitaxial oxide layer of the first conductivity type region comprises a superlattice. ​ 25. The optoelectronic semiconductor device of claim 20, wherein the second conductivity type region band structure has a second conductivity type region energy band gap that is greater than the optical emission region band gap energy band gap.

26. The optoelectronic semiconductor device of claim 20, wherein the substrate is selected from the group consisting of Al2O3, MgO, LiF, MgAl2O4, and SiC.

27. The optoelectronic semiconductor device of claim 20, wherein the substrate is formed from a metal fluoride.

28. The optoelectronic semiconductor device of claim 20, wherein the predetermined wavelength is in a wavelength range of 150 nanometers to 280 nanometers.

29. The optoelectronic semiconductor device of claim 20, wherein xi is greater than 0, x2 is greater than 0, or both xi and x2 are greater than 0.

30. The optoelectronic semiconductor device of claim 20, wherein the first epitaxial oxide layer comprises a superlattice, and the superlattice comprises (Al... x1 Ga 1-x1 The first layer of 2O3 and containing (Al) x2 Ga 1-x2 The second layer of )2O3 repeats periodically, where 0≤x2≤1, and x1 is not equal to x2.

31. The optoelectronic semiconductor device of claim 20, wherein the substrate comprises Ga2O3.

32. The optoelectronic semiconductor device of claim 20, wherein the substrate comprises AlGaO3.

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