Ultrawide bandgap semiconductor devices including magnesium germanium oxides

Abstract

Various forms of Mg xGe 1-xO 2-x are disclosed, wherein the Mg xGe 1-xO 2-x is an epitaxial layer formed on a substrate comprising a substantially single-crystal substrate material. The Mg xGe 1-xO 2-x epitaxial layer has crystal symmetry compatible with the substrate material. Semiconductor structures and devices including the Mg xGe 1-xO 2-x epitaxial layer are disclosed, as well as methods for manufacturing such epitaxial layers and semiconductor structures and devices.

Description

Technical Field

[0001] Related applications

[0002] This application claims priority to International Patent Application No. PCT / IB2021 / 060414, filed on November 10, 2021, entitled “Ultrawide Bandgap Semiconductor Devices Including Magnesium Germanium Oxides”, which is incorporated herein by reference for all purposes.

[0003] This application relates to U.S. Patent No. 11,342,484, filed August 11, 2020, entitled "Metal Oxide Semiconductor-Based Light Emitting Device"; International Application No. PCT / IB2021 / 060413, filed November 10, 2021, entitled "Epitaxial Oxide Materials, Structures and Devices"; and International Application No. PCT / IB2021 / 060466, filed November 11, 2021, entitled "Epitaxial Oxide Materials, Structures and Devices"; all of these applications are incorporated herein by reference for all purposes.

[0004] This invention relates to an ultrawide bandgap semiconductor device comprising magnesium germanium oxide. Prior Technology

[0005] Electronic and optoelectronic devices rely on semiconductor materials to provide the characteristics that enable them to function in a variety of ways for different applications. Optoelectronic devices include light-emitting diodes (LEDs), which emit infrared, visible, or ultraviolet wavelengths of light depending on the bandgap of the material used in the LED. For example, ultraviolet (UV) emitting LEDs utilize wide bandgap (WBG) semiconductors, such as gallium nitride (GaN) and aluminum nitride (AlN). Photodetectors are another type of optoelectronic device that senses the presence of light. For example, UV light detection is used in various applications such as communication systems, data storage, biosensing, and fluorescence measurement. Laser and solar blind detectors are other types of optoelectronic devices.

[0006] Digital power management systems use electronic devices to convert direct current (DC) to alternating current (AC), such as DC-DC and AC-DC converters. These power converters and power conversion devices are essentially constructed using high breakdown voltage and fast switching time power transistors. The characteristics of the semiconductor materials used in the electronic devices affect performance characteristics, such as breakdown voltage tolerance, conduction-state electrical losses, transistor switching speed, and overall switching efficiency. High-frequency switching transistors are used in telecommunications and radar systems and also require low insertion loss materials and high signal gain.

[0007] The continuous development of semiconductor materials is extremely important for the ongoing improvement and advancement of electronic and optoelectronic devices. Summary of the Invention

[0008] In some embodiments, the semiconductor structure includes a substrate containing a substantially single-crystal substrate material and a Mg xGe 1-xO 2-x epitaxial layer on the substrate, wherein x has a value of 0 ≤ x < 1. The Mg xGe 1-xO 2-x epitaxial layer has crystal symmetry compatible with the substrate material.

[0009] In some embodiments, the semiconductor device includes a substrate containing a substantially single-crystal substrate material and an active region on the substrate. The active region comprises a MgxGe 1-xO 2-x epitaxial layer, wherein x has a value of 0 ≤ x < 1. The MgxGe 1-xO 2-x epitaxial layer has crystal symmetry compatible with the substrate material.

[0010] In some embodiments, a method of forming a semiconductor device includes providing a substrate comprising a substantially single-crystal substrate material having crystal symmetry with respect to the Mg xGe 1-xO 2-x epitaxial layer. The material is co-deposited onto the substrate to form the Mg xGe 1-xO 2-x epitaxial layer, wherein x has a value of 0 ≤ x < 1. Depending on the value of x, the material comprises at least two elements selected from Mg, Ge, and oxygen, wherein Mg, Ge, and oxygen are supplied from a Mg source, a Ge source, and an active oxygen source, respectively.

[0011] In other embodiments, other elements are incorporated into the MgxGe 1-xO 2-x crystal to alter electronic properties, such as conductivity type. Simple Explanation of the Diagram

[0012] Figure 1A is a perspective view of a cubic symmetrical MgO structure according to some embodiments, showing the atomic positions of magnesium and oxygen atoms in the unit cell.

[0013] Figure 1B is a plan view along the axis of the cubic MgO illustrated in Figure 1A.

[0014] Figure 2A is a perspective view of a single crystal cell containing trigonal germanium oxide (GeO2) according to some embodiments.

[0015] Figure 2B is a plan view of a single crystal cell of trigonal germanium oxide (GeO2) illustrated in Figure 2A.

[0016] Figure 3A is a perspective view of a single crystal cell containing tetragonal germanium oxide (GeO2) according to some embodiments.

[0017] Figure 3B is a plan view of a single crystal cell of tetragonal germanium oxide (GeO2) illustrated in Figure 3A.

[0018] Figure 4 is a table of single-crystal compositions that can be formed from Mg, Ge and O in different proportions according to some embodiments.

[0019] Figure 5 is a table showing examples of possible single-crystal compositions that can be formed from Mg, Ge and O, exhibiting low formation energy and thus exhibiting stable structures, according to some embodiments.

[0020] Figure 6 is a plot showing the calculated formation energies of different single-crystal compositions (i.e., Mg xGe yO z) formed from Mg, Ge and O according to some embodiments.

[0021] Figure 7A is a symbolic view of the basic unit cell of a Mg2GeO4(Pnma) type single crystal composition as defined in some embodiments.

[0022] Figure 7B is a symbolic view of the basic unit cell of a MgGeO 3 (C2 / c) type single crystal composition as defined in some embodiments.

[0023] Figure 7C is a symbolic view of the basic unit cell of a Mg2GeO4(Fd3m) type single crystal composition as defined in some embodiments.

[0024] Figure 8A shows the electron energy-momentum (E-) of Mg2GeO4(Fd3m) according to some embodiments. [k]) Figure 7C shows the calculated valence band and conduction band structure at the critical point in the Brillouin zone of the crystal.

[0025] Figure 8B shows the E- of Mg2GeO4(Fd3m) illustrated in Figure 8A according to some embodiments. [k] Detailed valence band structure of E- [k] diagram.

[0026] Figure 9A shows the E- of Mg2GeO4(Pnma) according to some examples. Figure [k] shows the calculated valence and conduction band structures at the critical point in the Brillouin zone of the crystal revealed in Figure 7A.

[0027] Figure 9B shows the E- of Mg2GeO4(Pnma) illustrated in Figure 9A according to some embodiments. [k] Detailed valence band structure of E- [k] diagram.

[0028] Figure 10A shows the E- of MgGeO 3(C2 / c) according to some embodiments. Figure [k] shows the calculated valence and conduction band structures at the critical point in the Brillouin zone of the crystal revealed in Figure 7B.

[0029] Figure 10B shows the E- of MgGeO 3(C2 / c) illustrated in Figure 10A according to some embodiments. [k] Detailed valence band structure of E- [k] diagram.

[0030] Figure 11 reveals a local bond structure within an Fd3m cubic crystal of form AB2O4 according to some embodiments, wherein the A and B cations are bonded to oxygen (O) atoms.

[0031] Figure 12 is a table showing examples of the composition and orientation of compatible substrates on which single-crystal compositions Mg2GeO4(Pnma), MgGeO3(C2 / c) and Mg2GeO4(Fd3m) can be epitaxially formed according to some embodiments.

[0032] Figure 13A shows schematic diagrams of two different independent crystal structures corresponding to the film and the substrate (both having cubic or tetrahedral symmetry) according to some embodiments, wherein the film has a parallel (i.e., in-plane) lattice constant greater than that of the substrate. .

[0033] Figure 13B is a schematic diagram showing the effect of epitaxially forming a cubically symmetric layer on a substrate that also has cubic symmetry (as shown in Figure 13A) according to some embodiments, wherein the in-plane lattice constant of the original film is greater than the in-plane lattice constant of the substrate.

[0034] Figure 14A shows schematic diagrams of two different independent crystal structures corresponding to the film and the substrate (both having cubic or tetrahedral symmetry) according to some embodiments, wherein the film has an in-plane lattice constant smaller than that of the substrate.

[0035] Figure 14B is a schematic diagram showing the effect of epitaxially forming a cubically symmetric layer on a substrate that also has cubic symmetry (as shown in Figure 14A) according to some embodiments, wherein the in-plane lattice constant of the original film is smaller than the in-plane lattice constant of the substrate.

[0036] Figure 15A illustrates the unit cell of a cubic Fd3m Mg2GeO4 crystal according to some embodiments, which is uniformly elastically deformed along the in-plane ab axis, matching twice the lattice constant of an independent cubic MgO crystal.

[0037] Figure 15B is a symbolic diagram of the lattice mismatch formation of a Mg2GeO4(Fd3m) epitaxial layer formed on a substrate containing cubic magnesium oxide MgO (001) according to some embodiments, showing that the in-plane lattice constant of the film is approximately matched with an integer multiple of the smaller MgO unit cell.

[0038] Figure 16 illustrates the electronic band structure (E-) of a cubic space group Fd3m Mg2GeO4 epitaxial layer formed on a substrate or rigid layer of cubic Fd3m space group magnesium aluminate MgAl2O4 according to some embodiments. [k] diagram.

[0039] Figure 17 illustrates the electronic band structure (E-) of a cubic space group Fd3m Mg2GeO4 epitaxial layer formed on a substrate or rigid layer of cubic Fd3m space group magnesium oxide (MgO) according to some embodiments. [k] diagram.

[0040] Figure 18A shows a table of normalized x, y, and z positions of cation sites in a Mg2GeO4(Fd3m) cell according to some embodiments.

[0041] Figure 18B shows a table of normalized x, y, and z positions of anion sites in a Mg2GeO4(Fd3m) cell according to some embodiments.

[0042] Figure 19 is a table summarizing the semiconductor properties of single-site trivalent gallium impurity atom substitution in a Mg2GeO4(Fd3m) lattice according to some embodiments. It shows that single-site substitution of Ge sites by Ga produces p-type conductivity and retains the direct bandgap characteristics.

[0043] Figure 20 is a crystal structure diagram of Ga-doped Mg2GeO4(Fd3m) according to some embodiments, showing that in this example, the Ge23 site is substituted by Ga.

[0044] Figure 21A is an illustration of E-doped Mg2GeO4(Fd3m) according to Figure 20 of some embodiments. [k] Figure shows the valence band and conduction band structure.

[0045] Figure 21B is a detailed view of the valence band structure illustrated in Figure 21A according to some embodiments. [k] diagram.

[0046] Figure 22 is a table showing the semiconductor properties of Ga-doped Mg2GeO4 (Fd3m) derived from Ga replacing multiple Mg sites at different sites according to some embodiments.

[0047] Figure 23 shows the crystal structure diagram and related E- of doped Mg2GeO4(Fd3m) according to some embodiments. [k] Figure shows that in this example, the Mg 1 site is substituted with Ga.

[0048] Figure 24 shows the crystal structure diagram and related E- of doped Mg2GeO4(Fd3m) according to some embodiments. [k] Figure shows that in this example, the Mg2 site is substituted with Ga.

[0049] Figure 25 shows the E- of doped Mg2GeO4(Fd3m) derived from some embodiments, in which trivalent Al replaces the octahedral Mg1 sites. [k] diagram.

[0050] Figure 26 shows the E- of doped Mg2GeO4(Fd3m) derived from some embodiments, in which the tetrahedral Ge17 sites are replaced with trivalent Al. [k] diagram.

[0051] Figure 27 is a cell crystal structure diagram of cubic lithium oxide Li₂O (Fm3m) according to some embodiments, showing the tetrahedral Li⁺ atoms bonded to oxygen.

[0052] Figure 28 is a cell crystal structure diagram of doped Mg 2GeO 4 (Fd3m) according to some embodiments, which shows that in this example, the tetrahedral sites of Ge 17 are intentionally substituted with Li.

[0053] Figure 29A illustrates the E- of Li-doped Mg2GeO4(Fd3m) according to Figure 28 of some embodiments. [k] diagram.

[0054] Figure 29B shows the E- illustrated in Figure 29A according to some embodiments. [k] Detailed valence band structure of E- [k] diagram.

[0055] Figure 30 shows the E- values ​​corresponding to Li-doped Mg₂GeO₄(Fd₃m) according to some embodiments. [k] diagram, where the Mg 1 site is substituted with Li.

[0056] Figure 31 is a unit cell crystal structure diagram of cubic nickel oxide (NiO, space group Fd3m) according to some embodiments, showing the octahedral bonding between Ni and oxygen atoms.

[0057] Figure 32 is a cell crystal structure diagram of Ni-doped Mg2GeO4 (Fd3m) according to some embodiments, which shows that in this example, the octahedral Mg1 sites are substituted with Ni.

[0058] Figure 33A illustrates the E- of Ni-doped Mg2GeO4(Fd3m) according to Figure 32 of some embodiments. [k] diagram.

[0059] Figure 33B is a density of states diagram of Ni-doped Mg2GeO4(Fd3m) illustrated in Figure 32 of some embodiments.

[0060] Figure 34 is a cell crystal structure diagram of nitrogen (N) atoms substituted at one of the possible 32 oxygen sites in Mg 2GeO 4 (Fd3m) according to some embodiments.

[0061] Figure 35A illustrates the E- of N-doped Mg2GeO4(Fd3m) according to Figure 34 of some embodiments. [k] diagram.

[0062] Figure 35B shows a detailed view of the valence band structure illustrated in Figure 35A according to some embodiments.

[0063] Figure 36A shows the stoichiometric cell crystal structure of cubic Mg2GeO4 (Fd3m) according to some embodiments, identifying the nominal structural positions of selected Mg and Ge atomic sites.

[0064] Figure 36B shows an example of an anti-site cross-substitution process according to some embodiments, wherein the exchange process includes exchanging a nominal Mg 12 site with a Ge atom and a nominal Ge 20 site with a Mg atom.

[0065] Figure 37A shows the E-value obtained from the reverse site exchange within Mg2GeO4(Fd3m) as illustrated in Figure 36B of some embodiments. [k] diagram.

[0066] Figure 37B is an electronic density of states diagram illustrating the Mg↔Ge anti-site exchange according to Figure 36B of some embodiments.

[0067] Figure 37C shows a skewed unit cell generated by geometry optimization of an energy-minimizing process of single Mg↔Ge antisite atomic exchange, as illustrated in Figure 36B, according to some embodiments.

[0068] Figure 37D is a schematic diagram of the cubic bonding environment of Ge atoms in a nominal Fd3m crystal according to some embodiments, and the skewed crystal field obtained when Ge atoms are substituted into octahedral bonding sites.

[0069] Figure 37E is a table showing the positions of cations and anions in a distorted crystal structure under single anti-site substitution according to some embodiments.

[0070] Figure 37F shows the E- substituted with a single anti-site based on geometrically optimized methods according to some embodiments. [k] with structure diagram.

[0071] Figure 38 is a crystal structure diagram of a cell in which the cation lattice position changes from the normal configuration to a germanium-rich configuration for space group Fd3m according to some embodiments.

[0072] Figure 39A is a table of possible compositions of Mg xGe yO z having various crystal space groups and relative amounts of cations and anions within crystal cells, according to some embodiments.

[0073] Figure 39B is a table showing the formation energy and lowest band gap of the MgxGeyOz compound mentioned in Figure 39A of some embodiments.

[0074] Figure 39C is a table indicating the atomic positions within a Ge-excess Fd3m crystal formed by replacing Mg sites with Ge according to some embodiments.

[0075] Figure 40 shows the E- of Ge-doped Mg2GeO4(Fd3m) with excess Ge according to some embodiments. [k] diagram.

[0076] Figure 41 shows the E- of Mg-doped Mg₂GeO₄(Fd₃m) with excess Mg according to some embodiments. [k] diagram.

[0077] Figure 42A is a diagram showing the possible conductivity types (n-type or p-type) of Mg2GeO4(Fd3m) using the doping strategies disclosed herein, according to several embodiments.

[0078] Figure 42B shows a graph of the relative formation energies of selected substitutional impurities at Mg sites or Ge sites in Mg 2GeO 4 (Fd3m) according to some embodiments.

[0079] Figure 43A shows a binary oxide according to some embodiments. and ternary oxides The Ellingham diagram for the thermodynamic formation of oxidation.

[0080] Figures 43B, 43C, and 43D schematically illustrate the surface dynamics of film formation on an epitaxial surface using elemental fluxes of constituent materials according to some embodiments.

[0081] Figure 43E is a summary ternary phase diagram of the Mg-Ge-O system calculated using density functional theory (DFT) according to some embodiments, showing a stable composition of MgO, GeO 2, Mg 2GeO 4 and MgGeO 3.

[0082] Figure 44A is a representative growth phase diagram of epitaxial co-deposition of Mg 1-yGe yO 1+y compounds using elemental Ge, Mg and active O flux as a function of surface growth temperature according to some embodiments.

[0083] Figure 44B is a growth phase diagram illustrating the experimentally determined growth window of a high-quality single-crystal Mg2GeO4 with an Fd3m crystal structure deposited on an MgO substrate, similar to the illustration in Figure 44A, based on some embodiments.

[0084] Figure 45 is based on some embodiments for... The changes in the growth phase diagram and film growth rate of Mg 1-yGe yO 1+y under the condition were obtained.

[0085] Figure 46A is a cross-sectional view of an epitaxially formed layered semiconductor structure according to some embodiments, the layered semiconductor structure including a substrate, an epitaxial layer comprising a substantially single crystal of Mg2GeO4 (Fd3m) and a cap formed of MgO, which may be present.

[0086] Figure 46B is a table showing the crystal structure characteristics of epitaxial films and substrates compatible with Mg2GeO4 according to some embodiments.

[0087] Figure 46C is a cubic crystal structure diagram of a substrate made of MgO or LiF with a symmetry lattice constant a according to some embodiments.

[0088] Figure 46D is a cubic crystal structure diagram of a substrate or epitaxial layer according to some embodiments, wherein the symmetry lattice constant of the substrate or epitaxial layer is approximately twice the lattice constant illustrated in Figure 46C.

[0089] Figure 46E illustrates a schematic diagram of the formation of coherent epitaxial layers along the growth directions of two different cubic crystal structures with significantly different lattice constants according to some embodiments.

[0090] Figure 47 is an experimentally determined triaxial X-ray diffraction (XRD) pattern of a layered semiconductor structure illustrated in Figure 46A according to some embodiments, wherein the Mg2GeO4(Fd3m) layer system is used. form.

[0091] Figure 48 shows the experimentally determined triaxial XRD pattern of a layered semiconductor structure illustrated in Figure 46A according to some embodiments, wherein the Mg2GeO4(Fd3m) layer system is used. form.

[0092] Figure 49 shows an experimentally determined triaxial XRD pattern of a layered semiconductor structure illustrated in Figure 46A according to some embodiments, wherein the Mg2GeO4(Fd3m) layer system is used. 0.5 is formed.

[0093] Figure 50 shows experimentally determined triaxial XRD patterns of semiconductor structures according to some embodiments, in which attempts are made to use... A Mg 2GeO 4(Fd3m) layer is formed.

[0094] Figure 51 is a cross-sectional view of an epitaxially formed layered semiconductor structure according to some embodiments, the layered semiconductor structure including a substrate, a buffer layer as appropriate, and a superlattice or multilayer periodic structure.

[0095] Figure 52A is an experimentally determined XRD pattern of a layered semiconductor structure of a superlattice as illustrated in Figure 51 according to some embodiments, wherein one layer is MgO and the other layer is Mg2GeO4(Fd3m), and the superlattice is deposited on an MgO buffer layer and an MgO(100) substrate.

[0096] Figure 52B is an experimentally determined XRD pattern of a layered semiconductor structure of a superlattice according to some embodiments, illustrated in Figure 51, wherein one layer is Mg2GeO4(Fd3m) and the other layer is MgGa2O4(Fd3m), and the superlattice is deposited on an MgO buffer layer and an MgO(100) substrate.

[0097] Figure 52C is an experimentally determined XRD pattern of a layered semiconductor structure of a superlattice according to some embodiments, illustrated in Figure 51, wherein one layer is Mg2GeO4(Fd3m) and the other layer is MgO(Fm3m), and the superlattice is deposited on an MgO buffer layer and an MgO(100) substrate.

[0098] Figure 52D is an experimentally determined XRD pattern of a layered semiconductor structure of a superlattice according to some embodiments, illustrated in Figure 51, wherein one layer is Mg2GeO4(Fd3m) and the other layer is MgO(Fm3m), and the superlattice is deposited on an MgO buffer layer and an MgO(100) substrate.

[0099] Figure 52E is an experimentally determined XRD pattern of a layered semiconductor structure illustrated in Figure 51, based on a superlattice of some embodiments, wherein one layer is Mg2GeO4(Fd3m) and the other layer is a stable cubic γ-Ga2O3, the superlattice being deposited on an MgO buffer layer and an MgO(100) substrate.

[0100] Figure 52F is an experimentally determined XRD pattern of a layered semiconductor structure of a superlattice as illustrated in Figure 51 according to some embodiments, wherein one layer is Mg2GeO4(Fd3m) and the other layer is a stable cubic γ-Ga2O3, the superlattice being deposited on an MgO buffer layer and an MgO(100) substrate.

[0101] Figure 52G shows a complex epitaxial layer structure of different cubic oxide layers integrated into a superlattice or multi-heterojunction structure according to some embodiments.

[0102] Figure 52H shows experimental XRD data of the Fd3m crystal structure GeMg2O4 according to some embodiments, which is deposited as a high-quality bulk layer on an Fm3m MgO(100) substrate and further includes an MgO cap.

[0103] Figure 52I shows experimental XRD data of the Fd3m crystal structure GeMg2O4 when an SL structure including a 20× periodic SL[GeMg2O4 / MgO] is incorporated on an Fm3m MgO(100) substrate, according to some embodiments.

[0104] Figure 53 is a summary table of superlattice properties of example structures including MgGeO epitaxial layers according to some embodiments.

[0105] Figure 54A shows an epitaxial multilayer structure for forming an electronic or optoelectronic device according to some embodiments, which includes a substrate, a buffer layer (if present), a first conductivity type layer, a second conductivity type region, a third conductivity type region, and an electrical contact layer.

[0106] Figure 54B is a symbolic diagram showing the possible conductivity types of Mg aGe bO c modified by co-doping or crystal growth during epitaxial layer formation according to some embodiments.

[0107] Figure 55A shows a multilayer structure for forming an electronic device according to some embodiments, the electronic device having different regions including at least one layer of Mg aGe bO c.

[0108] Figure 55B shows a symbolic diagram of example materials that can be combined with Mg, aGe, bO, and c to form heterostructures according to some embodiments.

[0109] Figure 55C is a plot of the band gap energy as a function of the lattice constant for various materials that can be used in semiconductor structures according to some embodiments.

[0110] Figure 56A shows a structural diagram of a homogeneous interface device including a pin structure according to some embodiments.

[0111] Figure 56B shows a structural diagram of a homogeneous interface device including a nin structure according to some embodiments.

[0112] Figure 56C shows a structural diagram of a heterojunction device including a pin structure according to some embodiments.

[0113] Figure 56D shows a structural diagram of a dual heterojunction device according to some embodiments.

[0114] Figure 56E shows a strip structure diagram of a metal-insulator-semiconductor (MIS) structure according to some embodiments.

[0115] Figure 56F shows a structural diagram of a multi-heterojunction device including a pin structure and a quantum well according to some embodiments.

[0116] Figure 56G shows a strip structure diagram of a pin structure having a superlattice in region i according to some embodiments.

[0117] Figures 56H and 56I show strip structure diagrams of pin structures having superlattices in the p, i, and n regions according to some embodiments.

[0118] Figure 57 is a symbolic cross-sectional view of an in-plane conductive device according to some embodiments, the in-plane conductive device including an insulating substrate and a semiconductor layer region formed on the substrate, wherein electrical contacts are located on the top semiconductor layer of the device.

[0119] Figure 58 is a symbolic cross-sectional view of a vertical conductive device according to some embodiments, the vertical conductive device including a conductive substrate and a semiconductor layer region formed on the substrate, wherein electrical contacts are located on the top and bottom of the device.

[0120] Figure 59 is a symbolic cross-sectional view of a vertically conductive device for emitting light according to some embodiments, which has the electrical contact configuration illustrated in Figure 58, which is a planar parallel waveguide for emitting light.

[0121] Figure 60 is a symbolic cross-sectional view of a vertical conductive device for light emission according to some embodiments, which has the electrical contact configuration illustrated in Figure 58, and is configured as a vertical light emission device.

[0122] Figure 61 is a symbolic cross-sectional view of an in-plane conductive device for photodetection according to some embodiments, the in-plane conductive device having the electrical contact configuration illustrated in Figure 57, configured to receive light passing through the semiconductor layer region and / or the substrate.

[0123] Figure 62 is a symbolic cross-sectional view of an in-plane conductive device for light emission according to some embodiments, the in-plane conductive device having the electrical contact configuration illustrated in Figure 57, configured to emit light vertically or in-plane.

[0124] Figure 63 is a symbolic cross-sectional view of an in-plane surface metal-semiconductor-metal (MSM) conductive device according to some embodiments, the conductive device including a substrate and a semiconductor layer region including a plurality of semiconductor layers, wherein the top layer includes a pair of planar forked electrical contacts.

[0125] Figure 64A is a top view of an in-plane bimetallic MSM conductive device according to some embodiments, the conductive device including a first electrical contact formed of a first metal material that is forked with a second electrical contact formed of a second metal material.

[0126] Figure 64B is a symbolic cross-sectional view of an in-plane bimetallic MSM conductive device illustrated in Figure 64A according to some embodiments, the conductive device being formed from a substrate showing the cell arrangement and a semiconductor layer region.

[0127] Figure 65 is a symbolic cross-sectional view of a multilayer semiconductor device according to some embodiments, the multilayer semiconductor device having a first electrical contact formed on a mesa surface and a second electrical contact horizontally and vertically spaced from the first electrical contact.

[0128] Figure 66 is a symbolic cross-sectional view of an in-plane MSM conductive device according to some embodiments, the conductive device comprising multiple cells arranged laterally to form the mesa structure illustrated in Figure 65.

[0129] Figure 67 is a symbolic cross-sectional view of a multi-terminal device having a multi-platform structure according to some embodiments.

[0130] Figure 68A is a symbolic cross-sectional view of a planar field-effect transistor (FET) including source, gate and drain electrical contacts according to some embodiments, wherein the source and drain electrical contacts are formed on a semiconductor layer region formed on an insulating substrate, and the gate electrical contact is formed on a gate layer formed on the semiconductor layer region.

[0131] Figure 68B is a top view of a planar FET illustrated in Figure 68A according to some embodiments, showing the distance between the source-to-gate electrical contact and the drain-to-gate electrical contact.

[0132] Figure 69A is a symbolic cross-sectional view of a planar field-effect transistor (FET) with a configuration similar to that illustrated in Figures 68A and 68B, according to some embodiments, except that the source electrical contact is implanted in the substrate through the semiconductor layer region, and the drain electrical contact is implanted only in the semiconductor layer region.

[0133] Figure 69B is a top view of the planar FET illustrated in Figure 69A.

[0134] Figure 70 is a top view of a planar FET according to some embodiments, the planar FET including multiple interconnect cells of the planar FET illustrated in Figure 68A or Figure 69A.

[0135] Figure 71 is a process flow diagram of forming a conductive device according to some embodiments, the conductive device including a regenerated conformal semiconductor layer region on an exposed etched mesa sidewall. Implementation

[0136] Semiconductor structures with magnesium germanium oxide epitaxial layers are disclosed, wherein the magnesium germanium oxide layer and substrate materials are carefully designed and used in a specific combination to enable the formation of high-quality crystal structures. Embodiments of the semiconductor structure include a substantially single-crystal substrate having a predetermined crystal symmetry compatible with a specific form of magnesium germanium oxide in the epitaxial layer. The semiconductor structure relates to novel forms of magnesium germanium oxide, wherein a substantially single-crystal structure is formed. The semiconductor structure includes at least one magnesium germanium oxide region having a predetermined single-crystal symmetry type. Embodiments of conductive doping of magnesium germanium oxide materials and methods for forming semiconductor structures are disclosed. Embodiments of magnesium germanium oxide materials exhibit ultra-wide band gaps, such as 5.2 eV (for monoclinic crystal forms) to 6.4 eV (for orthorhombic forms). Some embodiments have direct band gaps, such as cubic magnesium germanium oxide having a direct band gap of 5.8 eV. The disclosed materials, structures, and methods enable high-quality and efficient semiconductor devices, including optoelectronic devices operating in the deep ultraviolet range and electronic devices for radio frequency (RF) communication, digital computing, and power switching.

[0137] In this disclosure, magnesium germanium oxide (MgxGeyOz) comprises germanium (Ge), magnesium (Mg), and oxygen (O), wherein x, y, and z are molar fractions, where x has any value in the range of 0 ≤ x ≤ 1.5, y has any value in the range of 1.0 ≤ y ≤ 2.5, and z has any value in the range of 2 ≤ z ≤ 5. In this disclosure, embodiments are also represented as MgaGebOc (where a, b, and c correspond to x, y, and z of MgxGeyOz), or as MgxGe1-xO2-x, where x has any value in the range of 0 ≤ x < 1, or as Mg1-yGeyO1+y, where 0 < y ≤ 1. It should be understood that an example of a magnesium germanium oxide (e.g., Mg x Ge y O z) listed in this disclosure can be replaced by another expression as described in this paragraph (e.g., Mg xGe 1-xO 2-x).

[0138] In the electronics and optoelectronics industries, an increasing number of modern applications require semiconductors with new materials and functional properties. While silicon remains the mainstay of digital computing and power switching industries, there is a need to increase the performance of power switches in digital power management systems to enable commercial progress in new application areas. Specifically, the industry needs to develop wide bandgap (WBG) semiconductor materials. Furthermore, optoelectronic devices (such as light-emitting diodes (LEDs)) require a unique set of material-specific standards to achieve effective light emission at infrared, visible, and ultraviolet wavelengths. UVLEDs utilize WBG semiconductors, such as GaN and AlN. Those familiar with this technology know that effective optical emission from semiconductor materials requires the fundamental characteristic of a direct bandgap energy-momentum configuration.

[0139] However, favorable direct band gaps may only be applicable to the crystal structure type and small subgroup of atoms constituting the single-crystal composition of the semiconductor. There are technical and fundamental physics challenges preventing conventional UV LEDs (e.g., AlN-based UV LEDs) from achieving far-ultraviolet wavelengths shorter than about 260 nm, for example, shorter than about 220 nanometers (nm). There is a desire to provide UV LEDs that can generate wavelengths far below 250 nm and increase the optical output power of UV LEDs for applications such as the inactivation of viruses and germicidal contaminants on surfaces, in liquids, and in the air.

[0140] Short UV wavelength sensors are another type of device that can benefit from further development of WBG semiconductor materials, as short UV wavelength sensors are typically limited by the available semiconductor bandgap energy and available technology.

[0141] Another anticipated application of WBG semiconductor materials relates to digital power management systems, such as DC-DC and AC-DC converters. Power switches used in these systems are typically implemented using semiconductors of the following forms: Si (Eg = 1.1 eV), GaN (Eg = 3.4 eV), and silicon carbide (SiC, Eg = 3.1 eV), where Eg is the bandgap between the minimum conduction band and the maximum valence band. Although GaN and SiC are classified as WBG, there is a pressing need in the industry to further increase the available bandgap energy to improve electrical breakdown voltage tolerance, reduce conduction-state electrical losses, increase transistor switching speed, and thus increase overall switching efficiency.

[0142] Clearly, conventional WBG materials are technically limited for many applications, including extremely short UV LEDs and lasers, high-efficiency power switching systems, and solar blind detectors. There is an urgent need in the industry to develop new materials to overcome these drawbacks and limitations. The wide bandgap of epitaxial oxide materials provides them with high dielectric breakdown voltages, and therefore they can be used in electronic devices requiring large bias voltages and high electric fields (e.g., high-voltage switches and impact ionization devices). The bandgap of epitaxial oxide materials is also well-suited for optoelectronic devices that emit or detect light in the UV range, where materials with bandgap ranges from about 4.5 eV to about 8 eV can be used to emit or detect UV light with wavelengths from about 150 nm to 280 nm. Other ultrawide-bandgap oxide materials disclosed can be used for extreme UV applications <150 nm. Semiconductor heterostructures can also be formed using wide-bandgap materials as emitter or absorber layers, and materials with bandgap wider than the emitter or absorber layers can be used in other layers of the structure to be transparent to the emitted or absorbed wavelengths.

[0143] The magnesium germanium oxide materials disclosed herein can be used in a variety of electronic and optoelectronic devices, such as (but not limited to) light-emitting devices (e.g., UV LEDs), photosensors (e.g., short UV wavelength sensors), and power switches as described above. Other applications include functionalizing oxide surfaces to form bioelectronic interfaces for biosensing. In embodiments, as will be set forth herein, the magnesium germanium oxide materials can be used in one or more layers of active regions (e.g., n-type active regions or layers, i-type active regions or layers, and / or p-type active regions or layers) of semiconductor devices. i-type regions should also be referred to as intrinsic regions or unintentionally doped regions.

[0144] The "epitaphedral oxide" material described herein is a material containing oxygen and other elements (e.g., metals (e.g., gallium) or non-metals (e.g., germanium and silicon)) that has an ordered crystalline structure configured to be formed on a single-crystal substrate or on one or more layers formed on a single-crystal substrate. The epitaxial oxide material has a defined crystal symmetry and crystal orientation relative to the substrate. The epitaxial oxide material can be formed as a layer coherent with the single-crystal substrate and / or with one or more layers formed on the single-crystal substrate. The epitaxial oxide material can be located in a strained layer of a semiconductor structure, wherein the crystal of the epitaxial oxide material is deformed compared to a relaxed state. The epitaxial oxide material can also be located in an unstrained or relaxed layer of a semiconductor structure.

[0145] In this disclosure, if the substrate and the epitaxial oxide material have compatible crystal symmetry, and the in-plane (i.e., parallel to the substrate surface) lattice parameters and atomic positions on the substrate surface provide a suitable template for the subsequent growth of the epitaxial oxide material, then the crystal symmetry of the substrate and the epitaxial oxide material can be compatible. For example, if the in-plane lattice constant mismatch between the substrate and the epitaxial oxide material is less than 0.5%, 1%, 1.5%, 2%, 5%, or 10%, then the substrate and the epitaxial oxide material can be compatible. For example, in some embodiments, the crystal structure of the substrate material has a lattice mismatch of less than or equal to 10% with the epitaxial layer. In some cases, if the substrate and the epitaxial oxide material have different types of crystal symmetry, but the in-plane (i.e., parallel to the substrate surface) lattice parameters and atomic positions on the substrate surface provide a suitable template for the subsequent growth of the epitaxial oxide material, then the crystal symmetry of the substrate and the epitaxial oxide material can be compatible. In some cases, the multiple (e.g., 2, 4, or other integer) unit cells of the atomic arrangement on the substrate surface can provide a suitable surface for the growth of epitaxial oxide materials having unit cells larger than those of the substrate. In other cases, the epitaxial oxide layer may have a lattice constant smaller than that of the substrate (e.g., about half). In some cases, the unit cells of the epitaxial oxide layer may be rotated (e.g., rotated 45°) compared to the unit cells of the substrate.

[0146] The epitaxial oxide materials described herein can be formed using epitaxial growth techniques such as molecular beam epitaxy (MBE), metal-organic chemical vapor deposition (MOCVD), atomic layer deposition (ALD), and other physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques.

[0147] [Crystal Structure]

[0148] This paper reveals the discovery of the ability to generate specific forms of epitaxial single-crystal semiconductor structures of MgxGeyOz using carefully selected substrates based on their compatibility with the crystal symmetry of the formed epitaxial MgxGeyOz films. Insights relating to crystal structures will now be presented to provide background for the formation of these epitaxial MgxGeyOz films and the tuning of exemplary characteristics.

[0149] Density functional theory (DFT) enables the prediction and calculation of band structures in crystalline oxides based on quantum mechanics without phenomenological parameters. DFT calculations applied to understanding the electronic properties of solid oxide crystals are fundamentally based on treating the nuclei of the atoms constituting the crystal as fixed via the Boehm-Oppenheimer approximation, thereby generating a static external potential in which many-body electron fields are embedded. Atomic positions and the crystal structure of the matter impose a fundamental structural effective potential on the interacting electrons. The effective potential of many-body electron interactions in three-dimensional space can be implemented using electron density functional theory. This effective potential includes exchange and correlation interactions, representing interacting and non-interacting electrons. For applications in solid-state semiconductors and oxides, a series of modified exchange functionals (XCFs) exist to improve the accuracy of DFT results. Within the DFT framework, the many-electron Schrödinger equation is divided into two groups: (i) valence electrons; and (ii) core electrons. Inner-shell electrons are strongly bound and partially shield the nucleus, thus forming an inert core. Atomic bonds in crystals are primarily attributed to valence electrons. Therefore, in many cases, internal electrons can be neglected, thereby reducing the atoms constituting the crystal to ionic cores that interact with valence electrons. This effective interaction is called a pseudopotential and approximates the potential felt by the valence electrons. A notable exception to the core electron effect is in the case of lanthanide oxides, where the partially filled lanthanide atoms' 4f- orbitals are surrounded by closed electron orbitals. The DFT band structure revealed in this paper explains this effect. Many improvements to the XCF exist to achieve greater accuracy in applying band structures to oxides. For example, improvements to the historical XCF of known local density approximations (LDA), generalized gradient approximations (GGA) mixed exchanges (e.g., HSE (Heyd-Scuseria-Ernzerhof), PBE (Perdew-Burke-Ernzerhof), and BLYP (Becke, Lee, Yang, Parr)) include the use of the Becke-Johnson (TBmBJ) exchange functional modified by Tran-Blaha and further modifications, such as the KTBmBJ, JTBSm, and GLLBsc forms. According to the findings of this disclosure, specifically for the materials disclosed herein, the TBmBJ exchange potential can predict the electronic energy-momentum (E-) of the epitaxial oxide materials. [k]) Band structure, band gap, lattice constant, and some mechanical properties. Another advantage of TBmBJ compared to HSE is its lower computational cost when applied to a large number of atoms in large supercells used to simulate smaller perturbations to idealized crystal structures, such as impurity inclusions. Further improvements to TBmBJ specifically applied to this oxide system are also expected. DTF calculations are extensively used in this disclosure to provide de novo insights into the electronic and physical properties of the epitaxial oxide materials described herein, such as band gap and whether the band gap characteristics are direct or indirect. The electronic and physical properties of epitaxial oxide materials can be used to design semiconductor structures and devices using epitaxial oxide materials. In some cases, experimental data have also been used to verify the properties of the epitaxial oxide materials and structures described herein.

[0150] This article describes the calculated Ek band structure of epitaxial oxide materials derived using DFT calculations. [, k Several features of the figure can be used to provide insights into the electronic and physical properties of epitaxial oxide materials. For example, the energies of the valence band and conduction band extrema and [, k The ]-vector indicates the approximate energy width of the band gap and whether the band gap has direct or indirect characteristics. The curvature of the valence band and conduction band branches near the extrema is related to the effective mass of holes and electrons, which is related to the carrier mobility in the material. Compared with previous exchange functionals, DFT calculations using the TBmBJ exchange functional more accurately show the magnitude of the material's band gap, as verified by experimental data. In this disclosure, the calculated band diagram of the epitaxial material may differ from the actual band diagram of the epitaxial material in some respects. However, certain characteristics (such as valence band and conduction band extrema, and the curvature of the valence band and conduction band branches near the extrema) closely correspond to the actual band diagram of the epitaxial material. Therefore, even though some details of the band diagram are not accurate, the calculated band diagram of the epitaxial material in this disclosure still provides useful insights into the electronic and physical properties of epitaxial oxide materials and can be used to design semiconductor structures and devices using epitaxial oxide materials.

[0151] Figures 1A and 1B show the perspective view and plan view of a cubic symmetrical MgO structure, respectively. The figures highlight the characteristic lattice constant. The atomic positions of magnesium atoms ("Mg") and oxygen atoms ("O") in a single unit cell. Cubic MgO is the most stable form of this composition, and it rarely forms any other polymorphs in which the unit cell is classified in the cubic Fm3m space group. In this crystal structure, Mg atoms are octahedral bonded to oxygen atoms. Cubic MgO is known and can be readily formed into bulk substrates or films. However, embodiments of this disclosure provide unique insights into using materials such as MgO as low lattice mismatch substrates for growing certain forms of epitaxial MgxGeyOz as single-crystal structures.

[0152] Figures 2A and 2B show a perspective view and a plan view, respectively, of an example of a low-formation-energy crystal structure of GeO₂ according to some embodiments. Low formation energy corresponds to a composition with a stable structure. The structures in Figures 2A and 2B are characterized by their lattice constants. The three-sided GeO 2, of which As can be seen, Ge atoms ("Ge") are tetrahedral bonded to oxygen atoms ("O").

[0153] Figures 3A and 3B show a perspective view and a plan view, respectively, of a second example of a low-formation-energy crystal structure of GeO₂ according to some embodiments. The structure is characterized by its lattice constant. and The tetragonal GeO 2, in which Once again, Ge atoms are tetrahedral bonded to O atoms. The low-energy forms shown in Figures 2A-2B and 3A-3B provide a stable structure. Other types of GeO₂ crystal structures also exist, but these structures are not as stable as those shown in Figures 2A-2B and 3A-3B.

[0154] In reality, forming large GeO₂ single crystals is challenging and at best results in polycrystalline or amorphous films. According to this disclosure, after studying detailed growth parameters, it was found that crystalline GeO₂ can be stabilized by adding other elements (such as Mg and Zn, and even Al and Ga).

[0155] This disclosure uniquely utilizes the relatively stable forms of octahedral Mg-O bonds and tetrahedral Ge-O bonds to achieve the growth of MgxGeyOz layers in the formation of single-crystal structures using carefully selected substrates. The embodiments also enable the doping of MgxGeyOz materials in various ways by leveraging the characteristics of octahedral and tetrahedral bond sites.

[0156] Regarding this disclosure, many possible structures of MgxGeyOz are investigated. Figure 4 shows a table 400 of examples of potential single-crystal compositions that can be formed from Mg, Ge, and O, listed in order from GeO2 at the top to MgO at the bottom. In this table, the unit cells are classified according to MgxGe1-xO2-x, where x is in the range of 0 to 1, where x = 0 represents binary GeO2 and x = 1 represents binary MgO. As can be seen, the most stable composition corresponds to The resulting composition is Mg₂GeO₄. A specific unit cell of a crystal structure comprises a series of unique spatial positions for Mg and Ge cations and oxygen anions. The space group and point group of a specific crystal are determined by the atomic arrangement within the unit cell. The general formula in Figure 4 is used to illustrate various possible configurations.

[0157] Based on possible combinations of Mg, Ge, and O (e.g., those shown in Figure 4), modeling was performed on the selection of possible single-crystal compositions formed from Mg, Ge, and O, taking into account the stability of the compositions. Example single-crystal compositions are shown in Table 500 of Figure 5, where the structure of group 510 is the most stable among the structures studied, and the structure of group 520 is the second most stable. Table 500 shows the relevant space group and symmetry classification for each composition (or structure). Table 500 also shows the bonding types of Ge and Mg, where Td indicates tetrahedral bonding to O atoms, and Oh indicates octahedral bonding to O atoms. For Mg14Ge5O24, the bonding between Ge and O atoms is a combination of Td and Oh bonds. The most stable MgxGe1-xO2-x structure exhibits the following types of crystal symmetry groups: x = 2 / 3 cubic (Fd3m), x = 2 / 3 orthorhombic (Pnma), and x = 1 / 2 monoclinic (C2 / c), which is of particular interest.

[0158] Density function theory (DFT) of the Tran-Blaha modified Becke-Johnson (TBmBJ) exchange potential can be used to predict the electron energy-momentum (E-) of epitaxial oxide materials. [k]) diagram, band gap, lattice constant and some mechanical properties.

[0159] Figure 6 graphically illustrates the structural characteristics of Table 500. Figure 600 shows the calculated relative energies (expressed in electron volts eV) above the Hall level for different single-crystal compositions and space groups (i.e., Mg xGe yO z) formed from Mg, Ge, and O. Thermodynamically stable compounds exhibit energies above the convex hull, E Hall = 0.0 eV / atom, with higher values ​​indicating increased metastability. Energy values ​​above the Hall level of 0 represent the most stable crystal form, progressing to less stable forms as the energy above the Hall level increases (i.e., formation energy increases). The most stable compositions (i.e., low formation energy) are shown starting from the left side of Figure 600, with less stable compositions (i.e., higher formation energy) progressing to the right side of Figure 600. As can be seen, the single-crystal composition Mg₂GeO₄ with the Pnma space group (orthorhombic symmetry) at point 610 in Figure 600, MgGeO₃ with the C2 / c space group (monoclinic symmetry) at point 620, and Mg₂GeO₄ with the Fd3m space group (cubic symmetry) at point 630 are all equivalent in stability, possessing a thermodynamically stable structure with low formation energy. Figure 600 also illustrates that changing the crystal structure can produce different levels of stability even with the same stoichiometry of MgₓGe₂yO₂z. For example, MgGeO₃ with the R3 space group (point 650) is less stable than MgGeO₃ with the Pbca space group (point 640), and MgGeO₃ with the Cmcm space group (point 660) is even less stable.

[0160] Figures 7A, 7B, and 7C are lattice diagrams of examples of Mg x Ge y O z that can be formed in single-crystal semiconductor structures according to some embodiments. Each figure shows the basic unit cell of a single-crystal composition formed from Mg, Ge, and oxygen (O). Figure 7A shows unit cell 710 of Mg 2GeO 4 (Pnma space group), which has a band gap E g of 6.4066 eV and a formation energy of -163.1986 eV / atom. Figure 7B shows unit cell 720 of MgGeO 3 (C2 / c space group), which has a band gap E g of 5.1694 eV and a formation energy of -117.6576 eV / atom. Figure 7C shows unit cell 730 of Mg 2GeO 4 (Fd3m space group), which has a band gap E g of 5.8056 eV and a formation energy of -81.9710 eV / atom. Of the three forms shown, Mg2GeO4(Fd3m) has the following combination: the band gap may be in the UVC band (i.e., about 200-280 nm) and exhibits a direct band gap, optimal formation energy and cubic crystal symmetry, and it is expected to be easier to grow by epitaxial methods.

[0161] The bandgap characteristics of various forms of Mg₂Ge₄yO₂z in Figures 7A, 7B, and 7C are calculated and shown in Figures 9A-9B, 10A-10B, and 8A-8B, respectively. Figures 8A and 8B show the bandgap modeling of the Mg₂GeO₄(Fd₃m) structure in Figure 7C. Figure 8A shows the E- bandgap characteristics of Mg₂GeO₄(Fd₃m). [k] Figure 800 shows the calculated structure of the valence band 820 and conduction band 810. Figure 800 shows the energy (eV) on the y-axis along the Brillouin zone (BZ) path on the x-axis. The direct bandgap between the conduction band 810 and the valence band 820 is shown at the center of the Brillouin zone, where the bandgap energy Eg is 5.8056 eV. Figure 8A illustrates that Mg2GeO4 (Fd3m) is a direct bandgap semiconductor material, where the maximum value of the valence band 820 and the minimum value of the conduction band 810 occur at the center of the region. Figure 8B is an enlarged view of the valence band structure, 825. As can be seen in Figure 8B, the valence band structure in region 827 at the center of the region has a relatively large curvature and is parabolic, indicating that holes will have good mobility (e.g., greater than 1 cm² / Vs, or greater than 10 cm² / Vs, or greater than 100 cm² / Vs). As can also be seen from Figure 8A, the Fermi energy... =0) is located in the approximate middle band gap between the valence band and the conduction band, which indicates that Mg2GeO4(Fd3m) will be a semiconductor with high resistivity (e.g., an intrinsic or lightly doped semiconductor).

[0162] Figure 9A shows the E- of Mg₂GeO₄(Pnma) (see Figure 7A) with a calculated valence band 920 and conduction band 910 structure. [k] Figure 900. Figure 9B is an enlarged view of the valence band structure. 925. The direct bandgap is shown at the center of the Brillouin zone, with a bandgap energy of Eg 6.4066 eV. As can be seen, Mg2GeO4(Pnm) is a direct bandgap semiconductor material, in which the maximum value of the valence band and the minimum value of the conduction band occur at the center of the zone. Figure 9B illustrates that the valence band structure in region 927 at the center of the region has high curvature, indicating that holes will have good mobility. As can also be seen from Figure 9A, the Fermi energy ( The band gap, located roughly between the valence band and the conduction band, indicates that Mg2GeO4(Pnma) will be a semiconductor with high resistivity (e.g., an intrinsic or lightly doped semiconductor).

[0163] Figure 10A shows the E- of MgGeO 3(C2 / c) (see Figure 7B) with a calculated valence band 1020 and conduction band 1010 structure. [k] Figure 1000. Figure 10B is an enlarged view of the valence band structure. 1025. As can be seen, MgGeO 3 (C2 / c) is an indirect bandgap semiconductor material, because the maximum value of the valence band and the minimum value of the conduction band occur at different points. This value indicates a poor optical emitter. Specifically, in some embodiments, MgxGe1-xO2-x is MgGeO3 with the C2 / c space group and is an indirect bandgap material. The difference between the conduction band minimum and the valence band maximum... The [k]-vector reveals an indirect bandgap, one instance of which is indicated by arrow 1005. As can be seen in Figure 10B, the valence band structure in region 1027 at the center of the region exhibits curvature, indicating good electron-hole mobility. Also visible from Figure 10A, the Fermi energy ( The band gap, located roughly in the middle between the valence band and the conduction band, indicates that MgGeO3(C2 / c) will be a semiconductor with high resistivity (e.g., an intrinsic or lightly doped semiconductor).

[0164] Referring now to Figure 11, a local tetrahedral bond structure (shape 1100) within the Fd3m cubic crystal of form AB₂O₄ is shown, in which the A and B cations are tetrahedral and octahedral bonded to the oxygen (O) atom, respectively. The critical bond length between the A and O atoms is shown. Annotated in Figure 11. Equation 1 is presented according to this disclosure to investigate the stability and cation interchangeability of possible configurations of the MgxGeyOz structure. For the ideal Fd3m unit cell, cations in tetrahedral coordination occupy special positions 8a (Wyckoff positions). The point symmetry is 43m, while the octahedral coordinated cation resides at a specific position for 16d ( The anion is located at the equivalent point position 32e, which requires a position parameter u. For u = 0.25, an ideal cubic close packing of anions is achieved, and therefore changes in u reflect adjustments to the structure to accommodate cations of different sizes in octahedral and tetrahedral positions. For example, decreasing the value of u to below 0.25 causes the anion to move along the

[0111] direction toward the nearest tetrahedral cation, thereby reducing the size of the tetrahedron within the range of octahedral sizes.

[0165] Bond length between tetrahedral Ge cations and O anions It is given by the following formula: (Equation 1) in It is the lattice constant of a cubic unit cell. For the case of a bulk, independent Fd3mMg2GeO4 crystal structure, it is found that... And therefore .

[0166] For example, if the B atom has a coordination number of +2, such as magnesium (i.e., cation site B = Mg), and the A atom has a coordination number of +4, such as germanium (i.e., cation site A = Ge), then a cubic composition AB₂O₄ = GeMg₂O₄ (i.e., Mg₂GeO₄) is formed. Based on the considerations for the growth of the MgₓGe₂O₄ structure studied in this disclosure, Mg₂GeO₄ will adopt a normal spinel structure or, alternatively, a less stable spinel structure with some interchangeability between cations at tetrahedral and octahedral sites. That is, it is expected that the normal spinel structure will only be able to self-assemble with the Mg cations located at the octahedral sites and the Ge cations located at the tetrahedral sites within the crystal, and generally achieve the co-deposition desired for epitaxial growth.

[0167] The deformation of the Fd3m unit cell can also alter the oxygen u parameter, for example, through biaxial strain during mimicry epitaxial deposition on a lattice-mismatched surface. Tetragonal distortion will significantly affect the structure and electronic properties of Mg2GeO4.

[0168] Using these crystal structure considerations, various forms of Mg₂Ge₂O₄ were studied. In Figure 12, Table 1200 illustrates examples of compatible substrate compositions and orientations for single-crystal compositions 1210 on which (001) or (100) orientations of Mg₂GeO₄ (Pnma), MgGeO₃ (C₂ / c), and Mg₂GeO₄ (Fd₃m) can be epitaxially formed. Currently, there are no examples of bulk, large-area single-crystal natural Mg₂GeO₄ substrates in industry, thus requiring heteroepitaxial methods. The space group "SG" and crystal symmetry type of each composition are listed. Possible substrates 1230 for composition 1210 are revealed, noting that the seed substrate may not have an ideal lattice match with the MgGeO composition to be epitaxially formed (i.e., a non-natural lattice match). The crystal structure of individual cells of MgxGeyOz is also revealed, as shown by the cell configuration parameters 1220 (including lattice constants a, b, c and angles α, β, γ). The lattice mismatch between the MgxGeyOz film and the substrate is preferably selected to enable the growth of single-crystal epitaxial films with low defect density.

[0169] In some embodiments, the crystal symmetry of the substrate material may be cubic or tetrahedral. In some embodiments, the substrate material comprises MgO (001), MgGa₂O₄ (001), MgAl₂O₄ (001), or LiF (100). In some embodiments, the substrate material comprises β-Ga₂O₃ (100), LiAlO₂ (100), ZrO₂ (100), LiNbO₃ (001), LiTaO₃ (001), Fe₂O₃ (100), BN (001), LiGaO₂ (001), TiO₂ (001), AlN (100), SiC (100), BaF₂ (100), BN (100), or CdWO₄ (001).

[0170] A schematic diagram of the single-crystal structure of the Mg xGe yO z film (i.e., epitaxial layer) on the substrate is shown in Figures 13A-13B and 14A-14B, wherein the substrate material is selected (i.e. predetermined) based on its compatibility with the type of Mg xGe yO z grown.

[0171] Figure 13A shows schematic diagrams of two different independent crystal structures corresponding to film 1310 and substrate 1300 (both having cubic or tetrahedral symmetry). The growth direction Z is shown. Film 1310 has a larger in-plane lattice constant (also called parallel lattice constant) than the substrate; that is, It should be noted that independent cubic crystals exhibit equal in-plane and perpendicular lattice constants. , where i = {sub, film}. That is, before any epitaxial layer is formed (i.e., if the film material is in an independent state and not grown on the substrate), the parallel and perpendicular lattice constants of the film will be affected by the cubic or tetrahedral nature of the film material ( Symmetrical and equal to each other ( Similarly, the parallel and perpendicular lattice constants of the substrate will be equal due to the cubic or tetrahedral symmetry of the substrate. ).

[0172] Figure 13B is a schematic diagram showing the epitaxial growth of the film 1310 of Figure 13A on substrate 1300. Figure 13B illustrates the effect of epitaxially forming a layer with cubic symmetry on a substrate that also has cubic symmetry, wherein the in-plane lattice constant of the independent film is greater than the in-plane lattice constant of the substrate. During the formation of the epitaxial layer 1310', the film material will undergo elastic deformation and will be in a strained state compared to its independent (or relaxed) state (film 1310), so that the parallel or in-plane lattice constant of the epitaxial layer ( The lattice constant will be matched with the parallel or in-plane lattice constant of the substrate 1300 (i.e.) ,and The resulting epitaxial layer 1310' was formed during compression. Due to the Poisson effect, this deformation will affect the vertical lattice constant of the resulting epitaxial layer 1310'. Increase, based on the fact that the Poisson's ratio of the material is greater than the vertical lattice constant of the original membrane material (i.e., ).

[0173] Therefore, a high-quality epitaxial layer can be formed during growth via elastic deformation of the film cell to accommodate in-plane lattice mismatch. This is defined herein as mimicry epitaxy. Figures 13A-13B illustrate that designs in which both the epitaxial layer and the substrate have cubic and tetrahedral symmetries in semiconductor structures are advantageously used in embodiments of this disclosure. In some embodiments, the substrate and film have cubic or tetrahedral crystal symmetry such that the in-plane lattice constants are equal ( Furthermore, the in-plane lattice constant of the film is greater than that of the substrate. In such cases, when grown on a substrate, the vertical lattice constant of the epitaxial film increases, leading to the accumulation of in-plane compressive stress. Furthermore, in some cases, compression has been observed to contribute to the growth of the epitaxial layer.

[0174] Figures 14A-14B are similar to Figures 13A-13B, but depict tensile strain in the epitaxial layer system. Figure 14A shows schematic diagrams corresponding to two different independent crystal structures: film 1410 and substrate 1400 (both having cubic or tetrahedral symmetry). Film 1410 has a smaller in-plane (i.e., parallel) lattice constant than substrate 1400; that is, Before any epitaxial layer is formed, the parallel and perpendicular lattice constants of the film will be equal. Similarly, the parallel and perpendicular lattice constants of the substrate will be equal due to the cubic or tetrahedral symmetry of the material. ).

[0175] Figure 14B is a schematic diagram showing the effect of epitaxial formation of a layer with cubic (or tetrahedral) symmetry on a substrate that also has cubic (or tetrahedral) symmetry, wherein the in-plane lattice constant of the original film 1410 is smaller than the in-plane lattice constant of the substrate 1400 (i.e., (As shown in Figure 14A). During the formation of the epitaxial layer 1410', the film material will undergo elastic deformation to maintain the in-plane lattice constant. It will match the in-plane lattice constant of the substrate (i.e.) ,and Due to the Poisson effect, this deformation will cause the vertical lattice constant of the resulting epitaxial layer to decrease to less than the vertical lattice constant of the original film material (i.e., The elastic tetragonal distortion of the film cell caused by the matching of the in-plane lattice constant with the in-plane lattice constant of the substrate leads to a decrease in the vertical lattice constant of the film (i.e., The resulting epitaxial layer system is formed during stretching, in which layers typically accumulate in-plane tensile stress.

[0176] Figures 15A-15B show the crystal structure of cubic Fd3m Mg2GeO4 crystal 1510 formed individually and on substrate 1500. In Figure 15A, the unit cell of cubic Fd3m Mg2GeO4 crystal 1510 undergoes uniform elastic deformation along the in-plane a-axis and b-axis, matching twice the lattice constant of an independent cubic MgO crystal. That is, Mg2GeO4 crystal 1510 has a tensile biaxial strain matching that of MgO (001). The crystal symmetry tetragonal transformation of the cubic Fd3m space group resulting from this tensile elastic deformation forms a new I4amd space group. The lattice constants a, b, and c (expressed in Angstrom (Å)) and angles α, β, and γ are shown in Figure 15A.

[0177] Figure 15B is a symbolic diagram illustrating the lattice mismatch formation of an epitaxial layer 1511 of Mg2GeO4(Fd3m) crystal formed on a cubic MgO (001) substrate 1500, showing that the in-plane lattice constant of the film approximately matches an integer multiple of the smaller MgO unit cell. In this example, the epitaxial layer 1511 will have tetragonal symmetry with space group I4amd. In this example, the formation of the epitaxial layer produces a 2x unit cell match, where... This results in the formation of a Mg2GeO4(Fd3m) epitaxial layer 1511 on the MgO substrate 1500 in a stretched state.

[0178] Figures 16 and 17 show the effect of strain on the band gap of cubic Mg₂GeO₄ (Fd₃m) epitaxial layers on different cubic substrate materials. Figure 16 shows the electronic band structure (E-) of a cubic space group Fd₃m Mg₂GeO₄ epitaxial layer formed on a substrate or rigid layer of cubic Fd₃m space group magnesium aluminate MgAl₂O₄. [k] Fig. 1600. In this example, the lattice constant mismatch of Mg₂GeO₄ and MgAl₂O₄ is approximately +2.2%, resulting in in-plane compressive stress, and Mg₂GeO₄ is formed under compressive conditions. The cubic space group Fd₃m Mg₂GeO₄ epitaxial layer still has a direct band gap, and the minimum value of the conduction band 1610 and the maximum value of the valence band 1620 occur at the center of the Brillouin zone, where... The same applies to the unstrained Mg₂GeO₄Fd₃m in Figure 8A. However, compared to Eg of 5.8056 eV in Figure 8A, the band gap Eg of the Mg₂GeO₄ layer at the center of the region in Figure 1600 has increased to 6.004 eV.

[0179] Figure 17 shows the electron band structure (E-) of a cubic space group Fd3m Mg2GeO4 epitaxial layer formed on a substrate or rigid layer of cubic Fd3m space group magnesium oxide (MgO). [k] Figure 1700. In this example, the lattice constant mismatch between Mg₂GeO₄ and MgO is approximately -1.9%, resulting in in-plane stress during tension, meaning that Mg₂GeO₄ is formed during tension. Compared to Figure 16, the strain-dependent band gap Eg of Mg₂GeO₄ between the conduction band 1710 and the valence band 1720 at the center of the Brillouin zone is observed to decrease to 5.806 eV.

[0180] As can be understood from this disclosure, a compatible (i.e., low lattice mismatch) combination of MgxGeyOz crystal structure and substrate material is disclosed, which enables the MgxGeyOz epitaxial layer to form an epitaxial single crystal structure with the substrate. In the embodiments, the epitaxial oxide material and substrate material are selected such that the in-plane (i.e., parallel to the substrate surface) lattice constant (or interplanar spacing) of the epitaxial layer of the semiconductor structure is within 0.5%, 1%, 1.5%, 2%, 5%, or 10% of the in-plane lattice constant (or interplanar spacing) of the substrate.

[0181] [Doping]

[0182] Examples provide doping of MgxGeyOz, which enables the material to be used as an epitaxial layer in various types of electronic and optoelectronic devices, such as n-type or p-type layers. In several embodiments, MgxGeyOz can be a direct bandgap material or an indirect bandgap material. In some embodiments, the direct bandgap material Mg2GeO4(Fd3m) is doped. In the crystal structure of Mg2GeO4(Fd3m), Ge sites have tetrahedral (Td) bonds with oxygen and Mg sites have octahedral (Oh) bonds with oxygen. The following are some embodiments of this disclosure: ● Ga doping can potentially replace Ge Td sites, and calculations show that Ge Td sites replaced by Ga Td sites (e.g., all individual Ge Td sites) produce direct bandgap p-type materials. ● Ga doping can potentially replace Mg Oh sites, and calculations show that Mg Oh sites replaced by Ga Oh sites (e.g., all single Mg Oh sites) produce direct bandgap n-type materials. ● Al doping can potentially replace Mg Oh sites, and calculations show that this produces direct bandgap n-type materials. ● Al doping can potentially replace Ge Td sites, and calculations show that this produces direct bandgap p-type materials. ● Li doping can potentially substitute Ge Td or Mg Oh sites, and calculations show that it is a direct bandgap p-type material. ● Ni doping can potentially replace Mg Oh sites, and calculations show the formation of defect bands and a reduced band gap. ● N doping can potentially replace O sites, and calculations show that it is a direct bandgap p-type material. ● Inverse site substitution can be performed within the unit cell, and calculations show that it is a p-type material. Inverse site substitution can involve the switching between Mg and Ge atoms, which results in Ge Td atoms being placed at octahedral bonding sites (Ge Td → Ge Oh) and Mg Oh atoms being placed at tetrahedral bonding sites (Mg Oh → Mg Td). ● Doping can be achieved by using excess Mg or excess Ge.

[0183] Although Mg₂GeO₄ is used as an example to illustrate the embodiments, these embodiments can be applied to other forms of MgxGe₁ ...

[0184] Referring now to Figures 18A and 18B, a table showing the normalized x, y, and z positions in Cartesian coordinates for the cation (i.e., Mg and Ge) sites (Figure 18A) and anion (i.e., O) sites (Figure 18B) of the Mg₂GeO₄(Fd₃m) unit cell is displayed, as will be mentioned throughout this disclosure. In this example, the cation unit cell includes 16 distinct Mg sites (Mgₐ, i = 0-15) and 8 distinct Ge sites (Geₘ, j = 16-23). ​​The anion unit cell includes 32 distinct sites (Oₘk, k = 24-55). Therefore, Figures 18A-18B disclose the crystal structure of Mg₂GeO₄(Fd₃m) according to an embodiment of this disclosure.

[0185] In some embodiments, Ga atoms (creating Ga Td sites) can be used to replace Ge Td sites to produce direct bandgap p-type materials, as illustrated in Figures 19-21B. Figure 19 is Table 1900 summarizing the semiconductor properties of single-site trivalent gallium impurity atom substitutions in Mg2GeO4(Fd3m), which originate from multiple single-site substitutions of Ge sites by Ga. Table 1900 shows specific substituted Ge sites 1910, corresponding to the Ge i cation sites in Figure 18A. For example, in the first column of Table 1900, the Ge site "Ge16" is substituted with Ga atoms to become the Ga site "Ga16". Table 1900 also shows normalized x, y, and z coordinates and calculated semiconductor properties, such as bandgap classification 1920 and bandgap energy value 1925, semiconductor type 1930 (E Fermi) and formation energy 1940 (E Formation). As can be seen, for each indicated Ge site, the resulting doped Mg₂GeO₄(Fd₃m) is a direct bandgap p-type material. Examples include semiconductor structures and devices in which the MgₓGe₁ ...

[0186] Figure 20 shows the crystal structure of doped Mg₂GeO₄(Fd₃m), illustrating Ga substitution at the Ge₂₃ site in this example. Figures 21A and 21B show the E-structure of Mg₂GeO₄(Fd₃m) derived from Ga substitution at the Ge site, as illustrated in Figure 20. [k] Figure. Figure 21A, Figure 2100 shows the structure of the valence band 2120 and conduction band 2110, and Figure 21B, Figure 2125 shows an enlarged view of the valence band structure. As can be seen, doped Mg2GeO4(Fd3m) is a direct bandgap semiconductor material, in which the maximum value of the valence band 2120 and the minimum value of the conduction band 2110 occur at... At the center of the time zone. As shown in Figure 21B, it is best visible in the middle, and the maximum value of the valence band, 2127, is higher than the Fermi energy ( This indicates that the doped Mg₂GeO₄(Fd₃m) is a p-type material in this example. In summary, the degenerate Fermi energy Ef lies within the valence band, and the direct band gap is reduced by approximately 140 meV. Compared to the 5.8056 eV Eg of the undoped case in Figure 8A, the Eg of this Ge-site substituted form is 5.6650 eV. The doped Mg₂GeO₄(Fd₃m) still possesses an ultrawide band gap greater than 4 eV.

[0187] In some embodiments, Mg Oh sites can be substituted with Ga (generating Ga Oh sites) to produce a direct bandgap n-type material, as illustrated in Figures 22-24. In Figure 22, Table 2200 reveals the calculated semiconductor properties of Ga-doped Mg₂GeO₄(Fd₃m) derived from multiple single-site substitutions of Ga at different Mg sites. Table 2200 shows the substituted Mg sites 2210 and their normalized x, y, and z coordinates. Example semiconductor properties of the selected substitution cases are shown, such as bandgap classification 2220 and bandgap energy 2225, semiconductor type 2230, and formation energy 2240. The values ​​of the semiconductor properties shown are very similar to each other; similar results are expected for other substitution embodiments shown in Table 2200. As can be seen, for each indicated Mg site, the resulting doped Mg₂GeO₄(Fd₃m) is a direct bandgap n-type material. That is, single-site substitution of trivalent cations at divalent Mg sites produces n-type conductivity. Examples include semiconductor structures and devices in which the MgxGe 1-xO 2-x epitaxial layer is a direct bandgap n-type material and contains a Ga dopant (e.g., Ga atoms). The Ga dopant is located at Mg sites in the corresponding undoped (i.e., compared to nominal) MgxGe 1-xO 2-x crystal structure. Methods of doping the MgxGe 1-xO 2-x epitaxial layer include replacing the Mg sites in the corresponding undoped MgxGe 1-xO 2-x crystal structure with Ga to produce n-type conductivity.

[0188] Figure 23 shows the crystal structure of doped Mg₂GeO₄(Fd₃m) (Figure 2350), where in this example, the Mg₁ sites are substituted with Ga. Figure 23 also shows the relevant E- spectral density of the n-type doped semiconductor material. [k] Figure 2300. As can be seen, the resulting doped Mg2GeO4(Fd3m) is a direct bandgap semiconductor material. The minimum value of the conduction band 2310 is 2315, which is lower than the Fermi energy ( This indicates that the doped Mg2GeO4(Fd3m) is an n-type material in this example.

[0189] Figure 24 is similar to Figure 23, but the Mg2 sites are replaced by Ga. Figure 24 includes the crystal structure diagram 2450 of the doped Mg2GeO4 (Fd3m) and the relevant E- spectral density of the n-type doped semiconductor material. [k] Figure 2400. As can be seen, the resulting doped Mg2GeO4(Fd3m) is a direct bandgap semiconductor material, and the minimum value of the conduction band 2410, 2415, is lower than the Fermi energy ( This indicates that the doped Mg2GeO4(Fd3m) is an n-type material in this example.

[0190] In some embodiments, by co-depositing with another elemental aluminum source in one instance, Al can be substituted at Mg00 sites to produce a direct bandgap n-type material (see, for example, Figure 42B). Figure 25 shows the E-wave structure of doped Mg2GeO4 (Fd3m) with Al-substituted octahedral Mg1 sites, representing the valence band 2520 and conduction band 2510. [k] Figure 2500. As can be seen, the resulting doped Mg2GeO4(Fd3m) is a direct bandgap semiconductor material. The minimum value of the conduction band 2510 is 2515, which is lower than the Fermi energy ( This indicates that the doped Mg₂GeO₄(Fd₃m) in this example is an n-type material. That is, the Fermi energy is located within the conduction band 2150 and is expected to exhibit n-type conductivity. Embodiments include semiconductor structures and devices in which the MgₓGe₁ ...

[0191] In some embodiments, Al can be substituted at Ge Td sites to produce direct bandgap p-type materials. Figure 26 shows the E-band structure of doped Mg₂GeO₄(Fd₃m) with valence band 2620 and conduction band 2610 derived from Al-substituted tetrahedral Ge 17 sites. [k] Figure 2600. As can be seen, the resulting doped Mg2GeO4(Fd3m) is a direct bandgap semiconductor material. The maximum value of the valence band at 2620 is 2625, which is higher than the Fermi energy ( This indicates that the doped Mg₂GeO₄(Fd₃m) in this example is a p-type material. That is, the Fermi energy is located within the valence band 2620 and is expected to exhibit p-type conductivity. Embodiments include semiconductor structures and devices in which the MgₓGe₁ₓO₂ₓ epitaxial layer is a direct bandgap p-type material and contains an Al dopant (e.g., Al atoms). The Al dopant is located at the Ge sites of the corresponding undoped MgₓGe₁ₓO₂ₓ crystal structure. The method of doping the MgₓGe₁ₓO₂ₓ epitaxial layer includes replacing the Ge sites of the corresponding undoped MgₓGe₁ₓO₂ₓ crystal structure with Al to produce p-type conductivity.

[0192] In some embodiments, Ge Td or Mg Oh sites can be substituted with Li to produce direct bandgap p-type materials, as illustrated in Figures 27-30. Figure 27 shows the unit cell crystal structure of cubic lithium oxide Li₂O (Fm3m), which shows tetrahedral monovalent Li⁺ atoms bonded to oxygen. Li₂O is a stable oxide in which Li atoms are tetrahedrally bonded (Td) to oxygen atoms.

[0193] Figure 28 shows the unit cell crystal structure of doped Mg₂GeO₄(Fd₃m), which illustrates the tetrahedral Ge⁷ sites substituted by Li⁺ as impurity atoms in this example. Both Li⁺ and Ge⁴⁺ oxides are energy-preferring to tetrahedral bonds with oxygen, and therefore it is expected that Li⁺ will preferentially substitute for Ge sites compared to octahedral sites.

[0194] Figure 29A shows the E- of Li-doped Mg₂GeO₄(Fd₃m) with Li substitution at the Ge site illustrated in Figure 28. [k] Figure 2900. Shows the valence band 2920 and conduction band 2910 structure. Figure 29B is an enlarged view 2925 of the valence band structure 2920 in Figure 29A. As can be seen, the doped Mg2GeO4(Fd3m) is an intermediate bandgap semiconductor with a bandgap energy of 5.5563 eV, between the conduction band minimum 2915 and the valence band maximum 2927. As best seen in Figure 29B, the doped Mg2GeO4(Fd3m) in this example is a degenerate p-type material. That is, the Fermi energy ( It is located within the valence band 2920 (view 2925) and thus produces p-type conductivity, and the valence band maximum 2927 is no longer at the center of the Brillouin zone.

[0195] Figure 30 corresponds to the E- of doped Mg2GeO4(Fd3m). [k] Figure 3000 shows Li substitution at the Mg 1 site. The conduction band 3010 and valence band 3020 structures are shown. Figure 30 shows that Li doping at the Mg 1 site produces an indirect bandgap semiconductor. Observing Figures 29A and 30, both show the effect of replacing Ge 17 or Mg 1 atoms with Li to produce p-type materials, where Ge substitution produces degenerate p-type materials. Examples include semiconductor structures and devices in which the Mg xGe 1-xO 2-x epitaxial layer is a direct bandgap p-type material and contains a Li+ dopant (e.g., Li+ atoms). The Li+ dopant is located at the Ge or Mg sites of the corresponding undoped Mg xGe 1-xO 2-x crystal structure. The method of doping the Mg xGe 1-xO 2-x epitaxial layer includes replacing the Ge or Mg sites of the corresponding undoped Mg xGe 1-xO 2-x crystal structure with Li+ to produce p-type conductivity.

[0196] In some embodiments, compared to the undoped form, Mg Oh sites can be substituted with Ni atoms to create defect bands and a reduced band gap, as illustrated in Figures 31-33B. Figure 31 shows the crystal structure of a cubic NiO (space group Fd3m) unit cell. NiO is a stable oxide in which Ni atoms are octahedrally bonded (Ni Oh) to oxygen atoms. Ni Oh atoms are chosen to replace Mg.

[0197] Figure 32 shows the unit cell crystal structure of Ni-doped Mg2GeO4 (Fd3m), which shows the octahedral Mg1 sites substituted by Ni+ as impurity atoms in this example.

[0198] Figure 33A illustrates the E- of Ni-doped Mg2GeO4(Fd3m) as shown in Figure 32. [k] Figure 3300 shows the structure of the valence band 3320 and conduction band 3310. As can be seen, the resulting doped material has a band gap where the band gap energy Eg is reduced to approximately 2 eV. In addition to the normal valence band 3320, there are multiple defect bands 3328 and 3329, and parasitic absorption also exists in the gaps between the defect bands. Ni atom substitution at Mg sites generates deep energy levels within the band gap due to Ni p-orbitals and d-orbitals. These calculations show that Ni does not significantly change the conductivity type of Mg₂GeO₄, but it does introduce parasitic optical absorption into the band gap.

[0199] Figure 33B is the density of states (DOS) diagram of Ni-doped Mg₂GeO₄ (Fd₃m) illustrated in Figure 32. The DOS indicates the unfavorable subbandgap energy states caused by Ni p-orbitals and d-orbitals. Examples include semiconductor structures and devices in which the MgₓGe₁ ...

[0200] In some embodiments, O sites can be substituted with N atoms (nitrogen doping, N³⁺) to produce direct bandgap p-type materials, as illustrated in Figures 34-35B. Figure 34 shows a cell crystal structure of N atoms substituted at oxygen sites within Mg₂GeO₄(Fd₃m). In this example, the anion O₄⁵ site is substituted with trivalent nitrogen as an impurity atom, labeled as... .

[0201] Figure 35A is derived from the N-doped Mg2GeO4(Fd3m) with N-site substitution illustrated in Figure 34. [k] Figure 3500. Shows the structure of the valence band 3520 and conduction band 3510. Figure 35B is an enlarged view of the valence band structure 3525 in Figure 35B. As can be seen from Figure 35A, compared with the undoped Eg of 5.8056 eV in Figure 8A, the band gap energy of N-doped Mg2GeO4(Fd3m) is reduced to a direct band gap semiconductor of approximately 4.88 eV. As best seen in Figure 35B, for N-doped Mg2GeO4(Fd3m), the energy approaches the Fermi level due to nitrogen impurities. The relatively flat bandgap at 3528 induces the formation of p-type materials. Examples include semiconductor structures and devices in which the MgxGe 1-xO 2-x epitaxial layers are direct bandgap p-type materials and contain N 3+ dopants (e.g., N 3+ atoms). The N 3+ dopants are located in the oxygen sites of the corresponding undoped MgxGe 1-xO 2-x crystal structure. A method of doping the MgxGe 1-xO 2-x epitaxial layer includes replacing the oxygen sites of the corresponding undoped MgxGe 1-xO 2-x crystal structure with N 3+.

[0202] In some embodiments, atoms within a unit cell may be substituted for each other to produce a p-type material. This substitution technique should be referred to in this disclosure as anti-site substitution or anti-site doping, for example, Mg and Ge being substituted at their respective tetrahedral and octahedral bond sites by another type of atom (Ge and Mg, respectively). Anti-site substitution will be illustrated in Figures 36A-37F.

[0203] Figure 36A shows the stoichiometric unit cell crystal structure of cubic Mg₂GeO₄ (Fd₃m), identifying the normal structural positions of the selected Mg and Ge atomic sites to be used in the cation anti-site doping process. In this example, the tetrahedral Ge₂O sites ( ) and the Mg 12 sites of octahedral bonds ( One atom in the atom will be replaced by another atom.

[0204] Figure 36B shows an example of anti-site cross-substitution, wherein in this example the exchange process includes replacing the nominal Mg 12 site with a Ge atom during crystal structure formation to become Furthermore, the nominal Ge 20 sites were also replaced by Mg atoms during the formation of the crystal structure, thus becoming... It should be noted that the total number of Mg and Ge cations within the unit cell remains unchanged, thus maintaining the total number of Mg and Ge atoms in the unit cell. Due to anti-site substitution, the original Fd3m (cubic) space group crystal becomes Cm (monoclinic) space group.

[0205] Figure 37A shows the E- obtained by the reverse site exchange within Mg2GeO4(Fd3m) as illustrated in Figure 36B. [k] Figure 3700 shows the structure of the valence band 3720 and conduction band 3710. In this example, selective Mg↔Ge anti-site cross-substitution generates E- by changing the new unit cell space group symmetry from normal cubic (i.e., without anti-site exchange) to a monoclinic structure. [k] The undesirable characteristics of the band structure. Reverse site exchange is energy-inefficient in replacing the atomic position of a Mg atom with a local tetrahedral site, and conversely, in replacing a Ge atom with a local octahedral site. Compared to the most stable normal Fd3m configuration, the band structure is significantly reduced in magnitude. The intermediate bands generated deep within the interstitial spaces (e.g., defect bands 3728, 3729) indicate that the electronic structure is self-compensating, due to the Fermi level (…). It is located between the lowest energy s-orbital and the highest p-orbital energy on the k-vector in the Brillouin zone. Figure 37B is the electronic density of states diagram of the Mg↔Ge anti-site exchange example in Figure 36B.

[0206] Figure 37C shows the skewed unit cell 3740, which is geometrically optimized through the energy minimization process of the single Mg↔Ge antisite atomic exchange in the Mg₂GeO₄ crystal structure illustrated in Figure 36B. The example Ge atom local environment 3750 is highlighted.

[0207] Figure 37D is a schematic diagram of the cubic bonding environment 3750 of Ge atoms (tetrahedral bonding) in a nominal Fd3m crystal and the distorted crystal field 3751 obtained when Ge atoms are substituted into octahedral bonding sites. The lattice distortion minimizes the resulting unit cell formation energy.

[0208] Figure 37E shows the cases of single anti-site substitution for the skewed crystal structure, as shown in Tables 3760 and 3770 for cation and anion positions, respectively. In this example of Figure 37E, the Mg 10 site is substituted with Ge (Ge 10), and the Ge 23 site is substituted with Mg (Mg 23).

[0209] Figure 37 shows the E-type geometrically optimized single anti-site substitution of the F series. [k] band structure, wherein the Mg 11 site is substituted with Ge (Ge 11) and the Ge 24 site is substituted with Mg (Mg 24). The resulting band gap E g is of the indirect type and is less than the nominal stoichiometric Fd3m case. Examples include semiconductor structures and devices in which the Mg xGe 1-xO 2-x epitaxial layer has a doped cell structure and a corresponding undoped cell structure (i.e., the corresponding undoped structure is the undoped nominal Mg xGe 1-xO 2-x structure). In the case of the doped cell structure, Mg xGe 1-xO 2-x is an indirect band gap p-type material; wherein the doped cell structure contains Ge atoms at the first position occupied by Mg in the corresponding undoped cell structure; and the doped cell structure contains Mg atoms at the second position occupied by Ge in the corresponding undoped cell structure. In the doped cell structure, the Ge atoms are octahedral and the Mg atoms at the second position are tetrahedral. The method of doping a Mg xGe 1-xO 2-x epitaxial layer includes placing Ge atoms in a first position occupied by Mg in the corresponding undoped unit cell structure of Mg xGe 1-xO 2-x, and placing Mg atoms in a second position occupied by Ge in the corresponding undoped unit cell structure.

[0210] In some embodiments, excess Mg atoms or excess Ge atoms can be used to generate doped materials, as illustrated in Figures 38-41. Examples include semiconductor structures and devices in which the Mg xGe 1-xO 2-x epitaxial layer is doped with excess Ge atoms or excess Mg atoms. Methods of doping the Mg xGe 1-xO 2-x epitaxial layer include doping with excess Ge atoms or excess Mg atoms. Figure 38 shows a cell crystal structure diagram of the cation lattice positions of space group Fd3m, which transforms from a normal configuration to a germanium-rich configuration. In this example, the excess Ge atoms are generated, for example, by transforming the Mg 4 site into another Ge atom. The resulting composition exhibits a new space group symmetry of R3m, and the resulting composition is equivalent to:

[0211] Figure 39A is Table 3900 of possible compositions (Formula 3910) of Mg xGe yO z having various crystal space groups 3920 according to some embodiments. The number of Mg atoms (N_Mg), Ge atoms (N_Ge), and oxygen atoms (N_O) in each unit cell, as well as the relative number of cations and anions within the crystal cell, are listed 3940. The Mg:Ge atom ratio in each unit cell for a given space group is calculated 3930. For the example case of the nominal Mg 2GeO 4Fd3m crystal space group, the cation to anion ratio Mg:Ge is 2.0 (marked by arrow 3932). Using excess Ge atoms (9 atoms instead of the nominal 8 atoms), the ratio Mg:Ge is 1.7 (arrow 3934), and using excess Mg atoms (17 atoms instead of the nominal 16 atoms), the ratio Mg:Ge is 2.4 (arrow 3936).

[0212] Figure 39B is Table 3901 showing the formation energy 3950 and minimum band gap 3960 of the MgxGeyOz compound mentioned in Figure 39A. For the Fd3m Mg2GeO4 crystal, when modified with excess Mg, this composition exhibits P-43m symmetry (marked by arrow 3926), and with excess Ge, the composition exhibits R-3m symmetry (marked by arrow 3924). Both Mg-rich and Ge-rich structures are less energy-favorable and inherently have higher formation energies; that is, the doped form is less stable.

[0213] In Figure 39C, Table 3902a shows the atomic positions within a normal Fd3m crystal, and Table 3902b shows an Fd3m crystal with an excess of Ge. In this embodiment, the excess Ge atoms are inserted by replacing Mg sites (Mg4 in this example) with Ge. Although the total number of cations (Mg and Ge) is maintained, the number of Ge atoms per unit cell is increased.

[0214] Figure 40 shows the E- of Ge-doped Mg2GeO4(Fd3m) containing excess Ge. [k] Figure 4000. As can be seen, the doped Mg₂GeO₄(Fd₃m) is a direct bandgap semiconductor, with a bandgap energy of 4.3942 eV at the center of the region, which is less than that of the undoped case in Figure 8A. Fermi energy ( It is located deep within the conduction band 4010 and therefore exhibits n-type conductivity.

[0215] Figure 41 shows the E- of Mg-doped Mg₂GeO₄(Fd₃m) containing excess Mg. [k] Figure 4100. As can be seen, the doped Mg₂GeO₄ (Fd₃m) is a direct bandgap semiconductor with a bandgap energy of 5.6405 eV, which is less than that of the undoped case in Figure 8A. Fermi energy ( It is located near the edge of the valence band 4120 and therefore exhibits p-type conductivity.

[0216] Figure 42A summarizes some examples of doping strategies illustrated in Figures 19 to 41. This figure indicates the type (i.e., n-type or p-type) of the resulting doped Mg₂GeO₄(Fd₃m). Examples can also be applied to other forms of MgₓGe₁ ... For example, MgxGe 1-xO 2-x structures (e.g., epitaxial layers) can be grown to be Ge-deficient, thereby providing open Ge sites for Ga substitution. Similarly, Ga substitution at Mg sites can be achieved by growing MgxGe 1-xO 2-x structures in a Mg-deficient manner. Aluminum doping (not shown in this figure) can be achieved using similar techniques, where Mg-deficient growth induces Al substitution at Mg sites to produce n-type materials, and Ge-deficient growth induces Al substitution at Ge sites to produce p-type materials. These substitution strategies are further explained by the formation energies in Figure 42B.

[0217] Figure 42B is a graph showing the relative formation energies of selected substitution impurity examples at Mg sites or Ge sites in Mg 2GeO 4 (Fd3m). In this figure, the impurity material is selected from Li, Al, Ga, and Ge; however, other materials are also possible, such as Si, Bi, and / or Zn. Using Li as a dopant as an example, bar 4210 represents the formation energy (in eV) of Li substitution at Ge sites, and bar 4220 represents the formation energy (in eV) of Li substitution at Mg sites. The graph in Figure 42B shows that the Li-doped case exhibits the lowest formation energy of the impurity material, and both cases produce p-type conductivity. In another example considering Ga as a dopant, Figure 42B shows that inserting Ga at Ge sites requires more energy than inserting Ge at Ge sites. However, growing a Ge-deficient Mg xGe 1-xO 2-x structure will allow Ga atoms to substitute at Ge sites.

[0218] [Mg, x , Ge , y , O , z , ] [Growth of membranes and semiconductor structures]

[0219] The methods for forming MgxGeyOz epitaxial layers require the thermodynamic insights described herein to appropriately grow the structure, for example, using molecular beam epitaxy (MBE). Figure 43A shows the methods used to form binary oxides. and ternary oxides A plot of the thermodynamic oxidation Ellingham diagram. For a given growth temperature and metallic material, there exists an oxygen partial pressure at which the metal begins to oxidize. For each oxide reaction, the boundary line is shown between the metal remaining oxide-free (below the boundary line) and forming individual oxides (above the boundary line).

[0220] Generally, the growth phase diagram of the selected oxide compound deposited by the self-constituent material indicates that sufficient oxygen is required at a given growth temperature to optimize the reaction pathway. The oxygen source can be selected from molecular oxygen, excited metastable molecular oxygen, and atomic oxygen. In one embodiment, active oxygen (e.g., atomic oxygen) is used to grow the oxide described in this disclosure. The active oxygen can be derived from an excited plasma source or an ozone source. For MgxGeyOz film growth from an elemental source (e.g., a solid effluent source, such as a Knudsen cell), the Ellingham diagram of Figure 43A (oxygen partial pressure in Torr versus 1000 / T in Kelvin) supports the requirement to supply a large incident excess of Ge flux to the surface relative to the Mg flux over the entire temperature range to produce the MgxGeyOz compound. If sufficient Ge is not supplied during co-deposition, the germanium oxide formed on the surface will be reduced to elemental Ge in the presence of Mg.

[0221] Figures 43B, 43C, and 43D illustrate the surface dynamics of film formation on the outer surface 4310 using the elemental flux of the constituent materials. Figure 43B shows the surface dynamics of incident Ge or Mg atoms in the absence of oxygen. The net deposition surface coverage is obtained by subtracting the desorption rate from the arrival rate of the incident atoms. The desorption rate depends on the surface temperature. For the growth conditions of interest in this disclosure, Mg desorption is dominant due to its lower activation energy compared to Ge, and follows Arrhenius behavior. Furthermore, both Ge and Mg exhibit adhesion probabilities of less than 1 for both chemisorption and physisorption to the outer surface 4310, which also depends on the binding energy of the crystal-surface complex (which is closely related to the surface restoration of the bound surface atoms and is a function of crystal symmetry, surface temperature, and oxygen environment). Generally, higher growth temperatures favor the surface migration of cations, which is beneficial for layer-by-layer growth schemes. At the high growth temperature of surface 4310, molecular oxygen readily dissociates; however, it has been found that the active form of oxygen, ideally neutral atoms or ionized oxygen atoms, is preferred, with neutral substances being even better. Figure 43B shows the co-deposition of cations and anions onto the surface. In the case of Ge and O co-deposition, the Ge:O ratio determines where oxides can form. Furthermore, GeO bound to the surface in crystalline form can readily decompose into GeO(g) vapor at sufficiently high temperatures (e.g., >500°C). In the example of growth on a MgO substrate, considering the adhesion coefficients δi of Mg and Ge, it has been experimentally found, according to this disclosure, that δMg is approximately 10 × δGe and δMg is approximately 0.5. That is, Mg tends to deposit more readily on the MgO substrate than Ge.

[0222] Figure 43C shows the arrival of cations (solid circles) and anions (hollow circles) at the outer surface 4310. In the case where the cation = Mg and the anion = O, MgO is formed. Similarly, in the case where the cation = Ge, GeO₂ may form on the surface. At sufficiently high surface temperatures, the solid GeO₂ formed on the outer surface will decompose into volatile GeO vapor, and the activation temperature for GeO₂ decomposition is approximately 500°C.

[0223] Figure 43D shows the case of high Ge flux relative to co-deposited oxygen flux incidence. In this scenario, Ge can etch GeO₂ or MgO formed on the outer surface 4310. The growth limit between deposition and etching can be controlled by the Ge:[active O] ratio, where deposition occurs under conditions where Ge:O < 1 and the growth temperature is less than approximately 600°C. For the surface etching process, at surface temperatures of 400°C–800°C, Ge:O > 1 with increasing etching rate.

[0224] Figures 43C and 43D illustrate that, to successfully form the desired Mg xGe yO z layer, a careful balance must be maintained between the growth temperature and the flux ratio of Mg, Ge, and O to allow Ge deposition while preventing Ge and / or Mg removal from the surface. For example, as shown in Figure 43A, a large incident excess of Ge flux relative to the Mg flux is required to generate and stabilize the Mg xGe yO z compound. However, excessive Ge flux can lead to temperature-dependent effects, which are counterproductive to Mg xGe yO z formation, such as Ge becoming a volatile vapor (explained in Figure 43C) or causing Ge to etch away GeO 2 or MgO (explained in Figure 43D). Furthermore, pure GeO 2 single-crystal films are found to be challenging due to surface dynamics and, similarly, polymorphism, resulting in polycrystalline and amorphous structures. In the embodiments of this disclosure, Mg and Zn are ideal crystal growth modifiers for stabilizing the formation of GeO-based compounds, and these compounds can achieve extremely high crystallinity in a predetermined crystal structure.

[0225] Figure 43E shows a summary ternary phase diagram of the Mg-Ge-O system calculated using DFT, displaying stable compositions of MgO, GeO2, Mg2GeO4, and MgGeO3, all along the same line from point 4322 (MgO) to point 4324 (GeO2). The configuration points on the phase diagram represent relative mole fractions. It should be noted that there are no continuous alloy compositions, as the displayed compositions represent the most stable forms.

[0226] Figure 44A shows a representative growth phase diagram 4400 for epitaxial co-deposition of the compound Mg 1-yGe yO 1+y (0 ≤ y < 1) (equivalent to Mg xGe 1-xO 2-x, 0 < x ≤ 1) as a function of elemental Ge, Mg, and active O flux, using the surface growth temperature. It should be noted that the above formula does not include x=0 and y<1, only to emphasize that the single-crystal form of GeO 2 is difficult to achieve as a single-crystal film. However, it is possible that a small amount of stabilizing material, acting as a surfactant, can indeed stabilize crystalline GeO 2 films. For example, Bi can be used as a surfactant. The resulting surface adsorption atomic ratio yGe for a given growth temperature and incident Ge:Mg flux ratio is plotted in Figure 44A.

[0227] Displaying the incident flux ratio in the range of 1 to 10. The isotherms are shown. A phase diagram (yGe, Tg, k) is constructed to illustrate the underlying kinematic processes, in which Mg deposited on the surface exhibits the Arenis desorption rate as a function of temperature. Ge deposited on the outer surface reacts with oxygen to form oxide compounds or decomposes into GeO monooxide vapor, with an activation temperature of approximately 500℃-550℃. Therefore, the elemental incident flux ratio... It is through the deposition surface temperature that the material is modified to maintain its properties. The ratio of adsorbed surface material is given.

[0228] Figure 44B shows the same growth phase diagram 4400 as Figure 44A, but illustrates the experimentally determined growth window 4410 of high-quality single-crystal Mg₂GeO₄ with an Fd₃m crystal structure deposited on an MgO substrate. The surface growth temperature in this window 4410 is approximately 400°C to approximately 500°C. The value is approximately The surface adsorption atom ratio yGe is approximately 0.28 to approximately 0.4. The line marked by arrow 4420 indicates the stoichiometric value yGe = 1 / 3 (i.e., achieving the desired stoichiometry of Mg₂GeO₄). Growth window 4410 shows the experimental verification of the actual growth conditions of Mg₂GeO₄, with growth window 4410 overlaid on the theoretical projection depicted in the figure.

[0229] Figure 45 shows the target Figure 4500 shows the growth phase diagram of Mg 1-yGe yO 1+y. Figure 4510 shows the resulting change in film growth rate, with units on the right-hand y-axis related to relative growth rate, where 0 corresponds to negligible adsorption on the growth surface, and values ​​greater than 1 indicate net accumulation of surface material. Two kinetic effects limit the growth rate: Mg surface desorption and GeO decomposition. For a fixed incident Ge:Mg flux ratio, the stoichiometric control window for Mg 2GeO 4 with yGe = 1 / 3 has an optimal growth temperature of 450 °C < Tg < 500 °C, as discussed above. During co-deposition, the inherent self-assembly of stable Mg 2GeO 4 allows slight deviations from the optimal flux and temperature. In Figure 45, the growth rate decreases significantly as the growth temperature increases and exceeds the growth window, as indicated by arrow 4515. Arrow 4525 indicates that the yGe ratio of adsorbed atoms decreases as the temperature decreases.

[0230] A method of forming a semiconductor device includes providing a substrate comprising a substantially single-crystal substrate material having crystal symmetry compatible with a Mg xGe 1-xO 2-x epitaxial layer; and co-depositing the material onto the substrate to form a Mg xGe 1-xO 2-x epitaxial layer, wherein x has a value of 0 ≤ x < 1. Depending on the value of x, the material comprises at least two elements selected from Mg, Ge, and oxygen, wherein Mg, Ge, and oxygen are supplied by a Mg source, a Ge source, and an active oxygen source, respectively. In some embodiments, the epitaxial layer has a substantially single-crystal structure and may be a lattice-mismatched layer or a substrate. In another embodiment, the epitaxial film and the substrate may each have different space group symmetries by being configured to have surface configurations that favor low lattice-mismatch heterojunction interfaces. In some embodiments, co-deposition is carried out using a molecular beam epitaxy process or an element flux co-deposition process. Organometallic or other precursor materials may also be used to transport Ge, Mg, and O to the growth surface. In some embodiments, the method includes depositing a buffer layer between a substrate and a MgxGe 1-xO 2-x epitaxial layer (e.g., a buffer layer comprising MgO or other forms of magnesium germanium oxide). In some embodiments, the MgxGe 1-xO 2 epitaxial layer may self-assemble during co-deposition. Examples may include determining the elemental incident flux ratio of the Ge source to the Mg source based on the deposition surface temperature. ), in order to maintain the ratio of Ge to Mg adsorbed surface material ( In some embodiments, co-deposition includes using a growth temperature of 400°C-500°C and a Ge source flux ratio k=3 to 9 to the Mg source. For example, the flux ratio k can have a value from 3 to 7.5 and Mg xGe 1-xO 2-x can be Mg 2GeO 4. The method may include forming a superlattice on a substrate, wherein the superlattice has unit cells comprising a first layer and a second layer, wherein the first layer in the superlattice is a Mg xGe 1-xO 2-x epitaxial layer. In some embodiments, the second layer of the superlattice is a second Mg yGe 1-yO 2-y epitaxial layer, wherein y is in the range of 0 to 1 and x ≠ y.

[0231] According to this disclosure, various semiconductor structures for electronic and optoelectronic devices can be formed by growing an epitaxial single-crystal Mg xGe 1-xO 2-x ultrawide bandgap epitaxial layer on a substrate of intentional selection. For example, any of the substrate materials listed in FIG12 can be used, such as for growing Mg 2GeO 4 or MgGeO 3 epitaxial layers. In some embodiments, the semiconductor structure includes a substrate containing a substantially single-crystal substrate material; and a Mg xGe 1-xO 2-x epitaxial layer on the substrate, wherein x has a value of 0 ≤ x < 1; wherein the Mg xGe 1-xO 2-x epitaxial layer has crystal symmetry compatible with the substrate material.

[0232] Figure 46A shows a cross-sectional view of an epitaxially formed layered semiconductor structure 4600, which includes a substrate 4601, a substantially single-crystal epitaxial layer (i.e., epitaxial layer) 4602 (which may include one or more epitaxial layers), and a cap 4603, which may be present as appropriate. In some embodiments, the substrate 4601 may be MgO, the epitaxial layer 4602 may contain Mg₂GeO₄ (Fd₃m), and the cap 4603 may be formed of MgO. In this example, the epitaxial layer 4602 is formed via a deposition process on the prepared substrate 4601 having a surface crystal structure conducive to the growth of epitaxial layers as described herein.

[0233] Figure 46B shows Table 4605 of the crystal structure characteristics of example epitaxial film material 4610 and a substrate compatible with Mg₂GeO₄ according to some embodiments. Experiments revealed that lattice mismatches between Mg₂GeO₄ and the substrate or other listed cubic oxides can be controlled to form a structure with extremely low defect density and high coherence. The minimum lattice mismatch between Mg₂GeO₄ and the substrate was found to be for the substrate material MgO (row 4620), followed by Al₂MgO₄ (row 4622) and LiF (row 4624). These substrates are crucial due to their high optical transparency in the extreme ultraviolet range. All listed compounds are cubic compounds, with MgO and LiF having approximately half the lattice constant of the AB₂O₄ compound, where {A, B} are selected from {Al, Ga, Ge, Zn}.

[0234] Figure 46C shows a cubic crystal structure of a substrate selected from MgO, LiF, or similar crystal structures, with each unit cell 4650 having a symmetry lattice constant a. Other substrates (e.g., monoclinic β-phase Ga₂O₃) with unique (100) oriented surfaces are also possible.

[0235] Figure 46D shows a cubic crystal structure of a substrate or epitaxial layer selected from Mg2GeO4, MgGa2O4, ZnGa2O4 or MgAl2O4 (or similar). The symmetry lattice constant of each unit cell 4652 is approximately twice the symmetry lattice constant illustrated in Figure 46C, i.e., 2a.

[0236] Figure 46E shows a schematic diagram illustrating the formation of coherent epitaxial layers along the growth directions of two different cubic crystal structures with significantly different lattice constants. Layer 4660 has a lattice constant a (see Figure 46C), and layer 4670 has a lattice constant of approximately 2 × a (see Figure 46D). For example, an epitaxial layer 4670 of Mg₂GeO₄ (or γ-Ga₂O₃, MgGa₂O₄, ZnGa₂O₄, or MgAl₂O₄) can be formed at the growth interface between layers 4660 and 4670 with a low misalignment density by matching the lattice constant of the epitaxial layer to a multiple (e.g., an integer multiple) of the lattice constant of the underlying film or substrate (layer 4660). In the example of Figure 46E, the lattice constant is matched to an integer multiple of approximately 2 in the plane of the heterojunction; that is, the lattice constant a of layer 4660 is matched to the lattice constant 2a of layer 4670. In other words, within the xy growth plane perpendicular to the growth direction, the lattice constant matches an integer multiple of 2 corresponding to a 2×2 array of unit cells. For example, this can be achieved in cubic Mg₂GeO₄ deposited on an MgO substrate.

[0237] Figures 47-50 show some embodiments. X-ray diffraction (XRD) images (intensity versus angle in Ω-2θ scan) of layered semiconductor structures with different flux values, illustrating the effect of flux ratio of impacting material on the resulting grown layer.

[0238] Figure 47 shows the experimentally determined triaxial XRD pattern of the layered semiconductor structure illustrated in Figure 46A. A 240 nm Mg₂GeO₄ (Fd₃m) epitaxial layer system was used. The structure was formed by incident Ge and Mg fluxes and a growth temperature of 425 °C. A thin MgO cap (approximately 11 nm) was deposited on the surface to form an X-ray Fabry-Perot structure. In this example, the extremely narrow full width at half maximum (FWHM) of the Mg₂GeO₄ peak at 4710, compared to the MgO substrate peak at 4720, clearly demonstrates the high quality of the structure. Furthermore, the MgO cap layer further induced a high-frequency Pendellosung oscillation at 4730 in the XRD pattern, indicating a fully coherent structure with extremely high quality and low defect density. The MgO substrate, cubic Mg₂GeO₄ film, and MgO cap are highly crystalline and planar parallel at the atomic scale and coherent throughout the structure, thereby inducing the X-ray Fabry-Perot effect, as shown. The interval between the 4710 peak of bulk Mg2GeO4(400) and the 4720 peak of substrate MgO(200) is 1395.9 s.

[0239] Figure 48 shows the experimentally determined triaxial XRD pattern of the layered semiconductor structure illustrated in Figure 46A, in which the approximately 254 nm thick Mg₂GeO₄(Fd₃m) layer is used. The formation is achieved by incident Ge and Mg fluxes and a growth temperature of 425°C. The MgO substrate (peak 4820) and Mg₂GeO₄ peak 4810 show the formation of a crystalline film of Mg₂GeO₄. The structure also includes an MgO cap similar to that in Figure 47; however, fewer high-frequency streaks are present, indicating that the crystal structure is not as coherent as in Figure 47.

[0240] Figure 49 shows the experimentally determined triaxial XRD pattern of the layered semiconductor structure illustrated in Figure 46A, where the Mg₂GeO₄(Fd₃m) layer system is used. The formation is achieved by an incident Ge and Mg flux of 0.5 and a growth temperature of 425°C. As can be seen from the substrate peak 4920 and the Mg 2GeO 4 peak 4910, only the minimum formation of the Mg 2GeO 4 (Fd3m) layer is observed.

[0241] Figure 50 shows the experimentally determined triaxial XRD pattern of the layered semiconductor structure illustrated in Figure 46A, where the incident Ge and Mg fluxes are... The growth temperature was 425℃. As can be seen, no Mg₂GeO₄ (Fd₃m) layer was formed; the layered semiconductor structure consisted only of MgO (peak 5020). Figures 47-50 illustrate that, for the growth conditions used, the relatively high Ge flux in the molecular beam epitaxy process (…) This will improve the quality of the epitaxial Mg2GeO4(Fd3m) layer. A very high-quality Mg2GeO4(Fd3m) epitaxial layer is achieved on MgO, as shown in Figure 47.

[0242] [Multi-layer structure]

[0243] The MgxGeyOz epitaxial layers disclosed herein can be used in various semiconductor device structures, including multilayer structures and chirped layers. Multilayer structures can be, for example, superlattices ("SL", which may include short-period superlattices), multiple superlattices, compositionally varied (or hierarchical) layers, or compositionally varied (or hierarchical) multilayer structures (or regions). Examples of multilayer structures will be illustrated with reference to Figures 51-53. Although certain combinations of substrate materials, buffer layers, and multilayers will be described, other combinations using the MgxGeyOz materials and compatible substrates as described throughout this disclosure are possible.

[0244] The embodiments include semiconductor structures and devices having a superlattice, the superlattice comprising a unit cell having a first layer, wherein the Mg xGe 1-xO 2-x epitaxial layer is the first layer in the superlattice. In some embodiments, the unit cell of the superlattice further comprises a second Mg yGe 1-yO 2-y layer, wherein y is in the range of 0 to 1 and x ≠ y. For example, the first layer may be MgO having the Fm3m space group, and in some embodiments, the unit cell of the superlattice further comprises a second layer, which is made of Mg 2GeO 4 having the Fd3m space group. In some embodiments, the unit cell of the superlattice further comprises a second MgGa 2O 4 or γ-Ga 2O 3 layer.

[0245] Figure 51 shows a cross-sectional view of an epitaxially formed layered semiconductor structure 5100, which includes a substrate 5110, a buffer layer 5120 (if applicable), a superlattice or multilayer periodic structure 5130, and a cap 5140 (if applicable). In this example, the periodic structure 5130 (e.g., a superlattice) includes repeating cells 5135 consisting of two layers 5132 and 5134. The figure shows that layer 5132 is thicker than layer 5134; however, in other embodiments, layer 5132 may be thinner than layer 5134, or the thicknesses of layers 5132 and 5134 may be equal. In an exemplary embodiment, the layered semiconductor structure 5100 includes a MgO (100) oriented substrate 5110, a superlattice (periodic structure 5130) including cells 5135 of MgGeO and MgO with a defined period, and a final cap 5140 of MgO. An oxygen plasma source can be used to prepare a substrate 5110 for deposition to terminate the MgO surface with oxygen.

[0246] Figures 52A-52F show experimentally measured XRD patterns of embodiments of the semiconductor structures illustrated in Figure 51, wherein such structures include superlattices. In Figures 52A-52F, the peaks representing the substrate are labeled "SUB". Additional arrows point to "satellite peaks," which are characteristic of the XRD pattern generated by the periodic SL structure. Figures 52H-52I show experimentally measured XRD patterns of embodiments of the semiconductor structures illustrated in Figure 52G.

[0247] Figure 52A shows the experimentally determined XRD pattern 5200 of the layered semiconductor structure illustrated in Figure 51 of the superlattice 5130, where layer 5132 is Fd3m MgGa2O4 and layer 5134 is Mg2GeO4 (Fd3m). The Mg2GeO4 (Fd3m) layer system is deposited on the MgO buffer layer 5120. The incident Ge and Mg fluxes form a MgO buffer layer deposited on a MgO(100) substrate 5110. As can be seen, high-frequency fringes (one example labeled as fringe 5210) indicate extremely high crystal quality, suggesting an excellent match between the in-plane lattice constants of the MgGa₂O₄ layer and the Mg₂GeO₄(Fd₃m) layer forming the superlattice. Sharp satellite peaks (marked by arrows) The markers continue to higher orders without broadening and indicate a coherent growth structure with high structural quality. The SL period is 26 nm and the interval between the MgO (200) substrate and the SL n=0 peak is 1024.8 s.

[0248] Figure 52B shows the experimentally determined XRD pattern 5201 of the layered semiconductor structure illustrated in Figure 51, where layer 5132 is Mg2GeO4(Fd3m) and layer 5134 is MgGa2O4(Fd3m). The superlattice is deposited on the MgO buffer layer 5120 and the MgO (100) substrate 5110. Sharp satellite peaks ( This again indicates a coherent growth structure with high structural quality. Figure 52B shows a superlattice with unit cells, where the first layer of the unit cell is Mg₂GeO₄ with the Fd3m space group, and the second layer of the unit cell is MgGa₂O₄ with the Fd3m space group. The SL period is 27.2 nm with 10 periods, and the interval between the MgO(200) substrate and the SL n=0 peak is 1206.7 s, indicating that the MgGe₂O₄ layer is thicker than that in Figure 52A.

[0249] Figure 5202 shows the experimentally determined XRD pattern of the layered semiconductor structure illustrated in Figure 51 of the C-type superlattice 5130, where layer 5132 is Mg2GeO4 (Fd3m) and layer 5134 is MgO (Fm3m). The superlattice is deposited on the MgO buffer layer 5120 and the MgO (100) substrate 5110. Sharp satellite peaks ( The diagram shows a coherent growth structure indicating high structural quality. Figure 52C illustrates a superlattice with unit cells, where the first layer of the unit cell is MgO with space group Fm3m, and the second layer is made of Mg2GeO4 with space group Fd3m. This confirms that Mg2GeO4 can be formed on MgO and MgO can also be formed on Mg2GeO4. The SL period is 26.6 nm with N=10 periods and N-2 thickness oscillations between satellite peaks. The SL n=0 interval with the MgO(200) substrate is 614.2 s, indicating... SL effective alloy system .

[0250] Figure 52D shows the experimentally determined XRD pattern 5203 of the layered semiconductor structure of superlattice 5130 illustrated in Figure 51, where layer 5132 is Mg2GeO4 (Fd3m) and layer 5134 is MgO (Fm3m). The layers of the structure represented in Figure 52D are thicker than those in Figure 52C, as evidenced by the presence of more satellite peaks in Figure 52D than in Figure 52C. This is used to demonstrate the superlattice deposition on the MgO buffer layer 5120 and the MgO(100) substrate 5110. Sharp satellite peaks indicate a coherent growth structure with high structural quality. The SL period is 35.6 nm and consists of 10 periods.

[0251] Figure 5204 shows the experimentally determined XRD pattern of the layered semiconductor structure illustrated in Figure 51, where layer 5132 is Mg2GeO4 (Fd3m) and layer 5134 is a stable cubic γ-Ga2O3. The superlattice is deposited on an MgO buffer layer 5120 and an MgO (100) substrate 5110. Sharp satellite peaks ( This indicates a coherently grown structure with high structural quality. The superlattice period is 18.4 nm and has 10 periods. The spacing between the MgO(200) substrate and the SL n=0 peak is 1337.6 s. This indication includes... Effective digital alloy. Cubic. The layer system is stabilized by intentionally growing layers below the critical layer thickness (CLT), in which, unless stabilized with another substance, it becomes energy-favorable for formation. .

[0252] Figure 5205 shows the experimentally determined XRD pattern of the layered semiconductor structure illustrated in Figure 51 of the F-type superlattice 5130, where layer 5132 is Mg2GeO4 (Fd3m) and layer 5134 is MgO. After depositing 10× period SL [MgO / Mg2GeO4], a thick β-Ga2O3 capping layer was formed with a thickness exceeding CLT (Note: below CLT, stable γ-Ga2O3 can be formed). The superlattice was deposited on the MgO buffer layer 5120 and the MgO(100) substrate 5110. In this example, the thick β-phase Ga2O3 film 5220 was grown as the capping layer 5140, showing a highly coherent structure. Sharp satellite peaks ( The text indicates a coherent growth structure with high structural quality. SL acts as a dummy substrate for forming high-quality β-Ga₂O₃(100) oriented films, which have biaxial strain suitable for tuning the valence band edges. Figure 52F shows a superlattice with cells, where the first layer of the cells is Mg₂GeO₄ with the Fd3m space group, and the second layer of the cells is cubic MgO, and another thick epitaxial β-phase Ga₂O₃ is grown on SL, which acts as a dummy substrate.

[0253] Figure 52G shows a complex epitaxial layer structure 5206 of different cubic oxide layers integrated into a superlattice or multi-heterojunction structure in another example. It shows a large lattice constant cubic GeMg₂O₄ (i.e., Mg₂GeO₄) and a small lattice constant MgO layer, forming a superlattice with repeating periods Λ and N repeats, grown along the growth direction. The MgO(100) oriented substrate allows the lattice to be matched with the GeMg₂O₄ "2×" cubic-to-cubic structure. The direct band gap E- of the two materials... [, k This allows for unique electronic band structure tuning using pre-selected quantized energy levels with specific layer thicknesses that constitute the SL period. If the layer thickness "L" constituting the SL is thin, such that each of LGeMgO and LMgO is less than about 10⁻²⁰ × their respective unit cell thickness (i.e., layer thickness less than about 150 nm), then an effective composition can be formed. Digital pseudo-alloys, among which This indicates the presence of an MgO capping layer, which can be used to protect the final surface of the structure.

[0254] Figure 52H shows experimental XRD data 5207 of Fd3m crystal structure Mg2GeO4 deposited as a high-quality bulk layer and further including MgO cap on an Fm3m MgO(100) substrate.

[0255] Figure 52I shows the experimental XRD data of the Fd3m crystal structure Mg2GeO4 when incorporated as an SL structure including a 20× periodic SL[Mg2GeO4 / MgO] on an Fm3m MgO(100) substrate.

[0256] As shown in Figure 52H, the extremely high quality Mg₂GeO₄ is demonstrated by the diffraction peaks of the small FWHM epitaxial layer (labeled "GeMgO 4400") and the high-frequency thickness oscillations generated by the X-ray Fabry-Bohr effect of the parallel atomic planes of the film and MgO capping layer, indicating that the film and MgO capping layer are strain-strained and coherent with the underlying substrate crystal structure. As shown in Figure 52I, this high lattice matching between Mg₂GeO₄ and MgO can be further used to form complex SL structures. Figure 52I shows the SL including a 20× periodic SL[Mg₂GeO₄ / MgO] / MgO sub(100). In addition, numerous sharp SL satellite peaks SLn are evidence of a coherent strain structure. Both Mg₂GeO₄ and MgO are constituent materials with The direct band gap.

[0257] For thin layers of materials with small band gaps, approximately 1-5 crystal cells thick, when sandwiched between materials with larger band gaps (e.g., MgO), the conduction band minimum and valence band maximum values ​​can be quantum confined. The transition energy between the lowest quantized level in the conduction band and the highest quantized level in the valence band of Mg₂GeO₄ can be tuned by changing the thickness through the quantum confinement effect. This tuning method allows the transition energy to be freely adjusted. to Variation. This energy range is ideal for photoelectron emitting devices operating in the deep ultraviolet (161-213 nm) portion of the electromagnetic spectrum.

[0258] Figure 53 is a summary table of the characteristics of example structures of physically realized MgxGeyOz epitaxial layers according to embodiments of this disclosure. The table lists the constructed epitaxial layer structures, the space group of the structures, whether the structural layers are bulk or superlattices, the quality, and the substrate material. As demonstrated by these examples, the compatibility of MgGa₂O₄, Mg₂GeO₄, MgO, β-Ga₂O₃, and γ-Ga₂O₃ is beneficial for the bandgap energy design of electronic and optoelectronic devices.

[0259] [Conductive device]

[0260] Semiconductor structures, such as conductive devices, including the MgxGeyOz epitaxial oxide materials and compatible substrates disclosed herein, will be described. Semiconductor structures including the epitaxial oxide materials described herein can be a single layer or multiple layers on a substrate. Multilayer semiconductor structures may include single quantum wells, multiple quantum wells, superlattices, multiple superlattices, compositionally varied (or hierarchical) layers, compositionally varied (or hierarchical) multilayer structures (or regions), doped layers (or regions), and / or multiple doped layers (or regions). Semiconductor structures having one or more doped layers (or regions) may include layers (or regions) doped with pn, pin, nin, pip, npn, pnp, p-metals (to form Schottky junctions) and / or n-metals (to form Schottky junctions).

[0261] In some embodiments, the semiconductor device includes a substrate containing a substantially single-crystal substrate material; and an active region on the substrate comprising a Mg xGe 1-xO 2-x epitaxial layer, wherein x has a value of 0 ≤ x < 1. The Mg xGe 1-xO 2-x epitaxial layer has crystal symmetry compatible with the substrate material. In some embodiments, the semiconductor device is an optoelectronic device comprising a light-emitting diode or a photodetector. For example, the optoelectronic device emits or absorbs light with wavelengths in the range of 150 nm to 280 nm (e.g., 150 nm to 260 nm, or less than about 260 nm, or less than about 250 nm, or less than about 220 nm). In some embodiments, the semiconductor device is an electronic device comprising a diode or a transistor. In some embodiments, the Mg xGe 1-xO 2-x epitaxial layer is the intrinsic layer of the semiconductor device. In some embodiments, the Mg xGe 1-xO 2-x epitaxial layer is a doped layer comprising n-type or p-type conductivity, doped by methods disclosed herein.

[0262] Devices comprising semiconductor structures containing the magnesium germanium oxide material described herein may include electronic and optoelectronic devices. For example, the devices described herein may be resistors, capacitors, inductors, diodes, transistors (switches, such as field-effect transistors, RF power switches), amplifiers, sensors, photodetectors, LEDs, and lasers. In some embodiments, devices comprising semiconductor structures containing the magnesium germanium oxide material described herein are optoelectronic devices that detect or emit UV light (e.g., wavelengths from 150 nm to 280 nm), such as photodetectors, LEDs, and lasers. In some cases, the device includes an active region in which light is detected or emitted, and the active region contains magnesium germanium oxide material having a bandgap selected for detecting or emitting UV light (e.g., wavelengths from 150 nm to 280 nm).

[0263] The doped layer in a conductive device may include donor (n-type) or acceptor (p-type) impurity (or dopant) material. The impurity can act as a foreign dopant to provide n-type or p-type conductivity to the doped layer. For example, the doped layer can be formed by co-depositing an epitaxial oxide semiconductor with a high concentration (e.g., about 1e17 cm⁻³ to about 1e20 cm⁻³ or greater than about 1e20 cm⁻³) of impurities (or dopant) that can act as donor (n-type) or acceptor (p-type) materials (e.g., using molecular beam epitaxy or chemical vapor deposition). Doping can be achieved by the various doping strategies disclosed herein, for example, with respect to Figures 18A-42B.

[0264] Referring now to FIG54A, an epitaxial multilayer structure 5400 for forming an electronic or optoelectronic device is shown, comprising a substrate 5410, a buffer layer 5420 (if applicable), a first conductivity type layer 5430, a second conductivity type region 5440, a third conductivity type region 5450, and an electrical contact layer 5460. Structure 5400 is formed layer by layer sequentially along the growth direction Z. The first, second, and third conductivity types can be selected from p-type, i-type, and n-type, and can be used in various combinations (e.g., pn, np, pin, nin, pip, npn, or pnp). The bulk or superlattice of the MgxGeyOz epitaxial oxide material disclosed herein can be used for layers 5420, 5430, 5440, 5450, and / or 5460.

[0265] Figure 54B shows the possible conductivity types of Mg aGe bO c that can be used in semiconductor structure 5400. The process for generating conductivity is schematically illustrated, showing the addition of doping Mg aGe bO c 5490 to 5492 to generate conductivity type 5494. In one example, Mg aGe bO c can be Mg 2GeO 4 (a=2, b=0, c=4). The conductivity types in Figure 54B can be modified during epitaxial layer formation using co-doping or crystal growth. The doped layer can be formed in any of the regions shown in Figure 54A. In some embodiments, the electrically activated doped or conductivity type regions can have atomically abrupt interfaces with other different regions, or these regions can be graded within a predetermined distance.

[0266] Figure 55A shows a multilayer structure 5500 for forming an electronic device having different regions including at least one MgaGebOc layer. A substrate 5510 has an epitaxial layer 5520n (e.g., a film or region) deposited along the growth direction Z. The layer 5520n constituting the device is selected from at least one Mg2Ge4 form and can be integrated with compositions selected from, for example, the following types: ZnxGeyOz, ZnxGayOz, AlxGeyOz, AlxZnyOz, AlxMgyOz, MgxGayOz, MgxZnyOz, and GaxOz, where x, y, and z represent relative molar fractions.

[0267] Figure 55B shows a symbolic diagram of an example composition that can be combined with MgaGebOc to form a heterostructure. The combination is schematically drawn, illustrating MgaGebOc 5590 plus heterostructure material 5592, wherein in this example, the heterostructure material composition 5594 comprises MgxGeyOz, ZnxGeyOz, ZnxGayOz, AlxGeyOz, AlxZnyOz, AlxMgyOz, MgxGayOz, MgxZnyOz, and GaxOz. Figure 55C is a plot of the minimum bandgap (eV) versus lattice constant (c, in angstroms) of Mg2GeO and other materials that can be used in heterostructures of the semiconductor structures disclosed herein. This plot can be used to determine the compatibility of the crystal structure lattice matching of the material combinations. The embodiments include semiconductor structures and devices (and methods of manufacturing such structures and devices) wherein a Mg xGe 1-xO 2-x epitaxial layer is disposed on a substrate, wherein x has a value of 0 ≤ x < 1 and a second epitaxial layer forms a heterostructure with the Mg xGe 1-xO 2-x epitaxial layer. The second epitaxial layer may comprise Zn xGe yO z, Zn xGa yO z, Al xGe yO z, Al xZn yO z, Al xMg yO z, Mg xGa yO z, Mg xZn yO z, or Ga xO z, wherein x, y, and z are molar fractions.

[0268] Figure 56A is a bandgap energy (eV) diagram showing the variation of bandgap energy (eV) along the growth direction Z, representing a homogeneous junction device including a pin structure. This structure is formed along the growth direction Z using spatial control of the doped regions. Moving from left to right along the growth direction, an n-type region is formed first, followed by an unintentionally doped region (the intrinsic "i" region), and then a p-type region. In several embodiments, the doping transitions between the n, i, and p regions can be abrupt or hierarchical within a certain distance. The bandgap height of each region is the same, indicating that the bandgap energies Eg of the n, i, and p regions are equal. The p and n regions form diodes. An electric field between the p and n regions is applied along the Z-axis to the central intrinsic region, causing electrons and holes to be injected into the i region. In embodiments, for one or more pin layers, a device having the structure of Figure 56A may include MgxGeyOz, such as Mg2GeO4.

[0269] Figure 56B is a diagram illustrating the structure of a homogeneous junction device (e.g., a diode) with a nin structure. The nin structure is formed along the growth direction Z using spatial control of the doped regions. In various examples, the doping concentration of the nin local junctions can be abrupt or graded within a predetermined distance. In embodiments, for one or more layers, a device having the structure of Figure 56B may include MgxGeyOz, for example, Mg2GeO4.

[0270] Figure 56C represents a band structure diagram of a heterojunction device (e.g., a diode) with a pin structure. This structure is formed along the growth direction Z using spatially controlled composition and doping in different regions. In several embodiments, the composition and doping can be abrupt or hierarchical within a predetermined distance. The band gap energies Eg of the p-region and n-region do not necessarily have to be the same, where in this example the band gap of the n-region is greater than that of the p-region. Heterojunction conduction band offset. and price band offset An energy barrier is provided to control / confine carrier flow. The pin structure forms a diode, and a built-in electric field applies an electric field in the i-region along the Z direction, as shown. The heterojunction structure can be used in light-emitting devices because light generated from the central region will not be absorbed by the p-region and n-region and will therefore escape. In other words, the heterojunction structure in FIG. 56C can be advantageously used as a light-emitting device (e.g., an LED) because the wider bandgap n-region and p-region have a lower absorption coefficient for light emitted from the narrower bandgap i-layer. In embodiments, for one or more layers, a device having the structure of FIG. 56C may include Mg xGe yO z, such as Mg 2GeO 4.

[0271] Figure 56D is a diagram representing a band structure of a double heterojunction device (e.g., a quantum well). This structure, including a wide bandgap, is sequentially formed along the growth direction Z using spatial control of the composition. Layer composition and narrow bandgap region / layer , making The narrow bandgap region lies between two wide bandgap regions. For a sufficiently thin narrow bandgap region, the energy levels allowed within the quantum well are quantized. In many instances, this can be used in optoelectronic and electronic devices. In embodiments, devices having the structure of FIG. 56D for one or more layers may include MgxGeyOz, such as Mg2GeO4. Since Mg2GeO4 is a direct bandgap material, optical emission can be used for electron and hole space recombination.

[0272] Figure 56E shows a band structure diagram of a metal-insulator-semiconductor (MIS) structure. The semiconductor region has a band gap E g1, and the insulating region has a band gap E g2. In embodiments, for one or more layers, a device having the structure of Figure 56E may include Mg xGe yO z, such as Mg 2GeO 4. For example, the Mg 2GeO 4 layer can be used as an insulator or a semiconductor. If a Mg 2GeO 4 semiconductor is used to form the metal-insulator-semiconductor structure, the insulator can be selected from a wider band gap material compatible with that shown in Figure 55C.

[0273] Figure 56F represents a band structure diagram of a multi-heterojunction device (e.g., a diode) with a pin structure and a single quantum well (QW). In this example, the band gaps of the n-region and p-region are respectively... The band gap of the barrier greater than QW region (band gap) ) and the band gap of quantum wells ( ),in Electrons and holes are injected from their respective storage regions into the intrinsic region. The conduction band at the heterojunction shifts. and price band offset It provides an energy barrier for controlling / confining charge carrier flow. Heterojunction structures can be used in light-emitting devices because light generated from the central region will not be absorbed by the p- and n-regions and will therefore escape; that is, the wider bandgap n- and p-regions have lower absorption coefficients for light emitted from quantum wells in the narrower bandgap i-layer. It has a bandgap. The quantum well design allows for tunable confinement of thickness LQW within a bandgap. The quantized energy levels in the conduction and valence bands between the barriers. In other embodiments, the structure may have one or more quantum wells in the intrinsic region. The energy levels in a multi-quantum-well structure affect several properties of the structure, such as the minimum effective band gap. In some cases, such as in light-emitting devices, having one or more quantum wells can improve optical emission, for example, due to the increased quantum well trapping rate of carriers injected from the p-region and n-region into the i-region. In embodiments, for one or more layers, a device having the structure of FIG56F may include MgxGeyOz, for example Mg2GeO4.

[0274] Figure 56G is a diagram of a pin structure with a superlattice (SL) in region i. The pin structure has multiple quantum wells, wherein the barrier layer of the multi-quantum-well structure in region i has a band gap greater than that of the n-layer and p-layer. In other cases, the band gap of the barrier layer in the multiple quantum wells may be narrower than that of the n-layer and p-layer. The lower half of Figure 56G shows a single quantum well of the multi-quantum-well structure. The thickness LQB of the barrier layer can be made thin enough that electrons and holes can pass through the barrier layer (e.g., within region i, and / or when transferring between the n-layer and / or p-layer into and / or out of region i). The multi-quantum-well structure can be a digital alloy, the properties of which depend on the materials constituting the barriers and wells and the thickness of the barriers and wells. In embodiments, for one or more layers, a device having the structure of Figure 56G may include MgxGeyOz, for example Mg2GeO4.

[0275] Figure 56H shows the band structure of a pin structure with a superlattice in the p, i, and n regions. For this fully superlattice structure of p(SL)-i(SL)-n(SL), the p, i, and n regions can have the same or different compositions. The n region includes N n SL pairs of wells (thickness L 1 and band gap E gW 1) and a barrier (thickness L 2 and band gap E gB 1). The i region includes Ni SL pairs of wells (thickness L 3 and band gap E gW 2) and a barrier (thickness L 4 and band gap E gB 2). The p region includes N p SL pairs of wells (thickness L 5 and band gap E gW 3) and a barrier (thickness L 6 and band gap E gB 3). In this example, the band gaps of the barrier and wells in the i region are narrower than those of the barrier and wells in the n and p layers. In other cases with structures having multiple quantum wells, the band gap of the barrier layer can be wider than that of the n and p layers. Additionally, in some cases, the thickness and / or bandgap of the barriers and / or wells in the n-region, i-region, and / or p-region can vary throughout the individual regions (e.g., to form a hierarchical structure or chirped layers). The thicknesses L2, L4, and / or L6 of the barrier layers can be made thin enough that electrons and holes can pass through these barrier layers (e.g., within the i-region, and / or when transferring between the n-layer and / or p-layer into and / or out of the i-region). Each region in the structure can behave as a digital alloy, the properties of which depend on the materials constituting the barriers and wells and the thickness of the barriers and wells. For example, the materials and layer thicknesses can be selected such that the n-region and p-region have wider bandgap and are therefore transparent (or have a low absorption coefficient) to the wavelength of light emitted from the i-region superlattice. In embodiments, for one or more layers, a device having the structure of FIG. 56H may include MgxGeyOz, for example Mg2GeO4.

[0276] Figure 56I is a band structure diagram similar to the pin structure in Figure 56H. The band gaps and thicknesses of the barriers and wells in the n, i, and p regions are defined in Figure 56H. In this example, the superlattices in the n, i, and p regions have the same alternating material pairs, and different well (or well and barrier) thicknesses for tuning optical properties in the i region. The structure has material A and material B, wherein the barrier of the superlattice in the n region includes material A and the well in the superlattice in the n region includes material B. In this example, the barriers in the i and p regions also include material A, and the wells in the i and p regions also include material B. The wells in the i region are fabricated to be thicker so that the energy of the quantized level in the potential well is lower than the band edge of the main well, thereby making the effective band gap of the superlattice in the i region narrower than the band gaps of the superlattices in the n and p regions (i.e., close to the band gap of the bulk material A). Therefore, this structure can be used in light-emitting devices (e.g., LEDs), as described herein. In an embodiment, for one or more layers, a device having the structure of FIG56I may include Mg xGe yO z, such as Mg 2GeO 4.

[0277] In the conductive devices described in Figures 57-71, one or more layers of the active region may comprise MgxGeyOz. The semiconductor layer region may be formed as a single layer of a single composition, or may comprise multiple layers of different compositions, or a multilayer structure comprising repeating layers each formed from individual sublayers. In the conductive device, the electrical materials forming the contacts with the electron and hole injection regions are selected from low-work-function and high-work-function metals, respectively. In one example, the metal ohmic contact is formed directly in situ on the surface of the final metal oxide, thus reducing any intermediate traps / defects generated at the semiconductor oxide-metal interface. Some examples of high-work-function metals that can be used for ohmic (or low-resistance) contacts with p-type epitaxial oxide layers are Ni, Os, Se, Pt, Pd, Ir, Au, and their alloys. Some examples of low-work-function materials that can be used for ohmic (or low-resistance) contacts with n-type epitaxial oxide layers are Cs, Na, and lanthanides; however, Al, Ti, Ti-Al alloys, and titanium nitride (TiN), which are common metals, can also be used. In some cases, the metal contact layer may contain two or more metal layers with different compositions (e.g., Ti layer and Al layer).

[0278] Figure 57 shows an in-plane conductive device, which in this example includes an insulating substrate and a semiconductor layer region formed on the substrate, wherein electrical contacts are positioned on the top semiconductor layer of the device. In this example, a first electrical contact or electrode (contact 1) is located on the top surface of the semiconductor layer, and a second electrical contact (contact 2) is laterally spaced from the first electrical contact and embedded in the semiconductor layer to induce an in-plane current, as indicated by the large arrow.

[0279] Figure 58 shows a vertically conductive device, which in this example includes a conductive substrate and a semiconductor layer region formed on the substrate, wherein electrical contacts are located at the top and bottom of the device. In this example, the first electrical contact (contact 1) is located at the top of the semiconductor layer region (embedded in or on the top surface). The second electrical contact (contact 2) is located on the underside of the substrate, perpendicularly spaced from the first electrical contact, to generate a vertical current as indicated by the large arrow.

[0280] Figure 59 shows a symbolic cross-sectional view of a vertically conductive device (e.g., a light-emitting diode) for light emission, having the electrical contact configuration illustrated in Figure 58, which is a planar parallel waveguide for emitting light. The device includes a substrate, a first semiconductor layer (Semi1) having a first conductivity type, a second semiconductor layer (Semi2) having a second conductivity type, and a third semiconductor layer (Semi3) having a second conductivity type. For example, the first, second, and third conductivity types can be n-type, i-type, and p-type, as described throughout this disclosure. A first electrical contact (contact 1) is located on the top surface of the device, and a second electrical contact (contact 2) is located on the bottom surface. Electrons and holes are injected into the central semiconductor layer, wherein light is emitted in a plane parallel to the layer plane (i.e., perpendicular to the growth direction).

[0281] Figure 60 shows a symbolic cross-sectional view of a vertically conductive device (e.g., a light-emitting diode) for light emission, having the electrical contact configuration illustrated in Figure 58, which is a vertical light-emitting device. The device includes a substrate, a first semiconductor layer (Semi1) having a first conductivity type, a second semiconductor layer (Semi2) having a second conductivity type, and a third semiconductor layer (Semi3) having a second conductivity type. For example, the first, second, and third conductivity types can be n-type, i-type, and p-type, as described throughout this disclosure. The first electrical contact (contact 1) is located on the top surface of the device, and the second electrical contact (contact 2) is located on the bottom surface. Electrons and holes are injected into the central semiconductor layer. The substrate and other layers of the device can be designed to be transparent to the wavelength of the emitted light, allowing light to be emitted through one or both of the top and / or bottom surfaces of the device. As can be seen, the first and second electrical contacts are arranged on their respective surfaces to allow light to pass through.

[0282] Figure 61 shows a symbolic cross-sectional view of an in-plane conductive device (e.g., a photodetector) for photodetection, having the electrical contact configuration illustrated in Figure 57, configured to receive light passing through a semiconductor layer region and / or a substrate. The device includes a substrate and a semiconductor layer region formed on the substrate, wherein the electrical contacts are positioned on the top semiconductor layer of the device. In this example, a first electrical contact or electrode (contact 1) is located on the top surface of the semiconductor layer, and a second electrical contact (contact 2) is laterally spaced from the first electrical contact and embedded in the semiconductor layer. The substrate material is transparent to the wavelength of interest. The light received by the device generates a current, which can be measured at the first and second electrical contacts.

[0283] Figure 62 shows a symbolic cross-sectional view of an in-plane conductive device (e.g., a light-emitting diode) for light emission, having the electrical contact configuration illustrated in Figure 57, configured to emit light vertically or in-plane. The device includes a substrate and a semiconductor layer region formed on the substrate, wherein the electrical contacts are positioned on the top semiconductor layer of the device. In this example, a first electrical contact or electrode (contact 1) is located on the top surface of the semiconductor layer, and a second electrical contact (contact 2) is laterally spaced from the first electrical contact and embedded in the semiconductor layer. In the embodiment of vertically emitted light, the substrate material is transparent to the generated wavelength.

[0284] Figure 63 shows a symbolic cross-sectional view of an in-plane surface-mount conductive device (MSM), which includes a substrate and a semiconductor layer region comprising multiple semiconductor layers (Semi1, Semi2, Semi3). The top metal layer includes a pair of planar forked electrical contacts (contact 1, contact 2) spaced apart by a distance "a". The width of the repeating portion of the device is shown as a Λ cell. In this example, the in-plane MSM conductive device includes a third electrical contact (contact 3) located on the bottom surface of the substrate, which may be present as needed. In the case of a conductive substrate, contact 3 may serve as a vertically conductive collector or drain. In the case of an insulating substrate, contact 3 may serve as the back gate of a field-effect device.

[0285] Figure 64A shows a top view of an in-plane bimetallic MSM conductive device, which includes a first electrical contact (contact 1) formed of a first metal material that is forked with a second electrical contact (contact 2) formed of a second metal material. As can be seen in an enlarged view of a portion of the forked contact, the finger width of the first electrical contact is... And the width of the second electrical contact is The distance between contacts is The lateral gap g between the individual electrodes determines the in-plane electric field strength. Contact 1 and contact 2 can be formed of different metals, such as high work function metals and low work function metals. In other embodiments, the metal-Semi1 heterojunction interface can form a Schottky barrier.

[0286] Figure 64B shows a symbolic cross-sectional view of the in-plane bimetallic MSM conductive device illustrated in Figure 64A. The conductive device is formed from a substrate and a semiconductor layer region epitaxially formed on the substrate. The cross-sectional view shows the arrangement of electrical contact cells.

[0287] Figure 65 shows a symbolic cross-sectional view of a multilayer semiconductor device having a first electrical contact (contact 1) formed on a mesa surface and a second electrical contact (contact 2) horizontally and vertically spaced from the first electrical contact. The device includes a substrate and semiconductor layers (Semi1, Semi2, Semi3, Semi4). In this illustrative embodiment, the first electrical contact is formed on an initial top surface of a semiconductor layer region, which is etched to expose a sublayer for positioning the second electrical contact. In this example, the multilayer semiconductor device further includes a third electrical contact (contact 3) located on the underside of the substrate. The three-terminal device including contacts 1, 2, and 3 can function as a vertical heterojunction bipolar transistor or a vertical conduction FET switch.

[0288] Figure 66 shows a symbolic cross-sectional view of an in-plane MSM conductive device comprising multiple unit cells of the mesa-structured device illustrated in Figure 65. The unit cells are arranged adjacent to each other in the lateral direction. These unit cells can form elongated fingers in the plane of the figure.

[0289] Figure 67 shows a symbolic cross-sectional view of a multi-terminal device having multiple semiconductor layers (Semi1, Semi2, Semi3, Semi4). The device has a first electrical contact (contact 1) formed on a first mesa structure (mesa 1). A second electrical contact (contact 2) is horizontally and vertically spaced from the first electrical contact and formed on a second mesa structure (mesa 2). A third electrical contact (contact 3) is horizontally and vertically spaced from the second electrical contact. In this illustrative embodiment, the first electrical contact is formed on the initial top surface of a semiconductor layer region (Semi4), which is etched to expose a first sublayer (Semi3) for positioning the second electrical contact. The first sublayer is further etched to expose another second sublayer (Semi2) for positioning the third electrical contact. In this example, the multi-terminal device further includes a fourth electrical contact (contact 4) located on the underside of the substrate. For electrically insulating substrates, the fourth electrical contact is present as appropriate.

[0290] Figure 68A shows a symbolic cross-sectional view of a planar field-effect transistor (FET) including source (S), gate (G), and drain (D) electrical contacts. The source and drain electrical contacts are formed on a semiconductor layer region (Semi1), which is formed on an insulating substrate. The gate electrical contacts are formed on a gate layer formed on the semiconductor layer region. The MgxGeyOy material layer can be used in two different ways. One function of the MgxGeyOy layer is to serve as a conductive channel region Semi1 with a wider bandgap material for forming the gate layer. For example, the gate layer itself can be epitaxially formed on the Semi1 (e.g., cubic γ-Al₂O₃, MgO, or MgAl₂O₄), or it can be substantially amorphous (e.g., amorphous Al₂O₃). Compositions of MgxGeyOy can alternatively be used as the gate layer, wherein, for example, the conductive channel Semi1 is a material with a smaller bandgap. The metal forming the S and D contacts is ideally ohmic, and the gate metal can be selected to control the threshold voltage of the FET.

[0291] Figure 68B shows a top view of the planar FET illustrated in Figure 68A, illustrating the distance D1 between the source contact and the gate contact, and the distance D2 between the drain contact and the gate contact. Section BB indicates a cross-section according to Figure 68A. The distance D2 > D1 can be used to control the breakdown voltage of the channel Semi1 along the G region and D region.

[0292] Figure 69A shows a symbolic cross-sectional view of a planar FET with a configuration similar to that illustrated in Figures 68A and 68B. In Figure 69A, the source contact (S) is implanted into the substrate (implant 1) via a semiconductor layer region (Semi1), and the drain contact is implanted only in the semiconductor layer region (implant 2). Using selective region ion implantation to spatially alter the conductivity of specific regions (e.g., S-regions and D-regions) facilitates improved lateral contact to the channel layer Semi1. The selection of ion implantation materials such as Ga, Al, Li, and Ge is anticipated to be used to impart p-type and n-type conductive regions. O implantation can also be used to create compositions with localized insulation. An alternative to the ion implantation method is the use of a diffusion process, in which material can be spatially formed on the surface of Semi1 and then driven into the interior of Semi1 via a thermally activated diffusion process. For example, a Li-based glass can be deposited, and Li can be driven into Semi1 via an annealing process in an inert environment. This rapid thermal annealing process is possible.

[0293] Figure 69B shows a top view of the planar FET illustrated in Figure 69A. Section BB indicates the cross-section according to Figure 69A.

[0294] Figure 70 shows a top view of a planar FET, which includes multiple interconnect cells of the planar FET illustrated in Figure 68A or Figure 69A. Repeating cells Λ are shown, with this embodiment illustrating a 3-terminal device.

[0295] Figure 71 shows a process flow diagram for forming a conductive device including a regenerated conformal semiconductor layer region on an exposed etched mesa sidewall. Initially, a semiconductor device with a substrate (SUB) and an epitaxially formed semiconductor layer region (EPI) is formed. This semiconductor layer region is then etched to leave the remaining mesa-structured semiconductor layer region. Another conformal semiconductor layer region (Semi2) is then grown on the mesa structure, which can then be planarized as needed in a subsequent planarization step. For example, the conformal coating Semi2 can be another oxide deposited via atomic layer deposition. Semi2 can be used as a passivation region or as an active region for forming a FET.

[0296] It should be understood that, unless otherwise stated or implied, the terms "comprise" and "include" and any derivative thereof (e.g., includes, comprising, including, including) used in this specification are intended to include the features referred to by the terms and are not intended to exclude the existence of any additional features.

[0297] References to any prior art in this specification are not, and should not be construed as, endorsements of any form of advice that would form part of common common sense regarding such prior art.

[0298] The embodiments of the disclosed invention have been described in detail with reference to the accompanying drawings, one or more of which are illustrated therein. Each example has been provided by way of explanation and not as a limitation thereof. In fact, although this specification has been described in detail with respect to specific embodiments of the invention, it should be understood that modifications, variations, and equivalents of such embodiments will readily conceive of by those skilled in the art upon gaining an understanding of the foregoing. For example, a feature illustrated or described in part as one embodiment may be used with another embodiment to produce yet another embodiment. Therefore, this subject matter is intended to cover all such modifications and variations within the scope of the appended claims and their equivalents. Such and other modifications and variations of the invention may be practiced by those skilled in the art without departing from the scope of the invention (which is more specifically set forth in the appended claims). Furthermore, those skilled in the art should understand that the foregoing description is by way of example only and is not intended to limit the invention.

[0299] 400: Instance Table 500: Table 510: Group 520: Group 600: Drawing 610: points 620: points 630: points 640: points 650: points 660: points 710: Unit cell 720: Unit cell 730: Unit cell 800: Electron Energy-Momentum Diagram / Figure 810: Conductor belt 820: Price Band 825: Enlarged view of the valence band structure 827: Area in the center of the district 900: Electron Energy-Momentum Diagram 910: Conductor belt 920: Price Band 925: Enlarged view of the valence band structure 927: Area in the center of the district 1000: Electron Energy-Momentum Diagram 1005: Arrow 1010: Conductor belt 1020: Price Band 1025: Enlarged view of valence band structure 1027: Area at the center of the district 1100: Local tetrahedral bond structure 1200: Table 1210: Single Crystal Composition / Composition 1220: Cell configuration parameters 1230: Possible substrate 1300:Substrate 1310: Membrane 1310': Epitaxial layer 1400:Substrate 1410: Original membrane / membrane 1410': Epitaxial layer 1500:Substrate 1510: Cubic Fd3m Mg2GeO4 crystal / Mg2GeO4 crystal 1511: Epitaxial layer 1600: Electron band structure electron energy-momentum diagram / figure 1610: Conductor belt 1620: Price Band 1700: Electron energy-momentum diagram of electron band structure 1710: Conductor belt 1720: Price Band 1900: Table 1910: Specific Ge site 1920: Bandgap Classification 1925: Bandgap energy value 1930: Semiconductors 1940: Formation Energy 2100: Figure 2110: Conductor belt 2120: Price Band 2125: Image 2127: Maximum value 2200: Table 2210: Mg site 2220: Bandgap Classification 2225: Bandgap energy 2230: Semiconductors 2240: Formation Energy 2300: Correlated electron energy-momentum diagram 2310: Conductor belt 2315: Minimum value 2350: Crystal Structure Diagram 2400: Correlated electron energy-momentum diagram 2410: Conductor belt 2415: Minimum value 2450: Crystal Structure Diagram 2500: Electron Energy-Momentum Diagram 2510: Conductor belt 2515: Minimum value 2520: Price Band 2600: Electron Energy-Momentum Diagram 2610: Conductor belt 2620: Price Band 2625: Maximum value 2900: Electron Energy-Momentum Diagram 2910: Conductor belt 2915: Minimum value of conduction band 2920: Price Band / Price Band Structure 2925: Enlarged view / view of valence band structure 2927: Maximum price band 3000: Electron Energy-Momentum Diagram 3010: Conductor belt 3020: Price Range 3300: Electron Energy-Momentum Diagram 3310: Conductor belt 3320: Price Range / Normal Price Range 3328: Defect zone 3329: Defect zone 3500: Electron Energy-Momentum Diagram 3510: Conductor belt 3520: Price Range 3525: Enlarged view of the price band structure 3528: The relatively flat energy band induced 3700: Electron Energy-Momentum Diagram 3710: Conductor belt 3720: Price Range 3728: Defect zone 3729: Defect zone 3740: Distorted crystal cell 3750: Example Ge atomic local environment / cubic bond end local environment 3751: Wicked Crystal Field 3760: Table 3770: Table 3900: Table 3901: Table 3902a: Table 3902b: Table 3910: Style 3920: Crystallization Space Group 3924: Arrow 3926: Arrow 3930:Mg:Ge atomic ratio 3932: Arrow 3934: Arrow 3936: Arrow 3940: The relative number of cations and anions within a crystal cell 3950: Formation Energy 3960: Lowest band gap 4000: Electron Energy-Momentum Diagram 4010: Conductor belt 4100: Electron Energy-Momentum Diagram 4120: Price Band 4202: Conductor belt 4204: Price Band 4210: items 4220: items 4310: Outer surface / surface 4322: points 4324: points 4400: Representative growth phase diagram / growth phase diagram 4410: Experimental determination of growth window / growth window / window 4420: Arrow 4500: Growth Phase Diagram 4510: Growth rate 4515: Arrow 4525: Arrow 4600: Layered semiconductor structure 4601: Substrate / Substrate to be prepared 4602: Essentially an epitaxial layer of a single crystal / epitaxial layer 4603: Cover / Cap as needed 4605: Table 4610: Examples of epitaxial film materials 4620: line 4622: line 4624: line 4650: unit cell 4652: Unit cell 4660: Layer 4670: Layer / Epitec Layer 4710: Mg 2GeO 4 peak / bulk Mg 2GeO 4 (400) 4720:MgO substrate peak / substrate MgO(200) peak 4730: High-frequency Pendelosson oscillation 4810:Mg 2GeO 4 peaks 4820:MgO substrate peak 4910:Mg 2GeO 4 peaks 4920:Substrate peak 5020: Peak 5100: Layered semiconductor structure 5110: Substrate / MgO(100) oriented substrate 5120: Buffer layer, depending on the situation 5130: Superlattice or multilayer periodic structure / periodic structure / superlattice 5132: Layer 5134: Layer 5135: Unit cell / Repeating unit cell 5140: Final cap / capping layer / capping as needed 5200: Experimentally measured X-ray diffraction pattern 5201: X-ray diffraction diagram 5202: X-ray diffraction diagram 5203: X-ray diffraction diagram 5204: X-ray diffraction diagram 5205: X-ray diffraction diagram 5206: Complex epitaxial layer structure 5207: Experimental X-ray diffraction data 5208: Experimental X-ray diffraction data 5210: Stripes 5400: Epitaxial multilayer structure / structure / semiconductor structure 5410:Substrate 5420: Buffer layer / layer, depending on the situation 5430: First conductivity type layer / layer 5440: Second conductivity type region / layer 5450: Third conductivity type region / layer 5460: Electrical contact layer / layer 5490:Mg aGe bO c 5492: Doped 5494: Conductivity type 5500: Multi-layer structure 5510:Substrate 5520: Epitaxial layer / layer 5590:Mg aGe bO c 5592: Heterogeneous structural materials 5594: Heterogeneous structural material composition

Claims

1. A semiconductor structure comprising: a substrate comprising a substantially single-crystal substrate material; and a Mg xGe 1-xO 2-x epitaxial layer on the substrate, wherein x has a value of 0 ≤ x < 1; wherein the Mg xGe 1-xO 2-x epitaxial layer has crystal symmetry compatible with the substrate material.

2. The semiconductor structure of claim 1, wherein the crystal structure of the substrate material has a lattice mismatch of less than or equal to 10% with respect to the epitaxial layer.

3. The semiconductor structure of claim 1, wherein the crystal symmetry of the substrate material is cubic or tetrahedral.

4. The semiconductor structure of claim 3, wherein the substrate material comprises MgO(001), MgGa2O4(001), MgAl2O4(001) or LiF(100).

5. The semiconductor structure of claim 4, wherein the semiconductor structure further includes a buffer layer between the substrate and the Mg xGe 1-xO 2-x epitaxial layer, wherein the buffer layer comprises MgO.

6. The semiconductor structure of claim 1, wherein the substrate material comprises β-Ga₂O₃(100), LiAlO₂(100), ZrO₂(100), LiNbO₃(001), LiTaO₃(001), Fe₂O₃(100), BN(001), LiGaO₂(001), TiO₂(001), AlN(100), SiC(100), BaF₂(100), BN(100), or CdWO₄(001).

7. The semiconductor structure of claim 1, wherein the Mg xGe 1-xO 2-x is Mg 2GeO 4.

8. The semiconductor structure of claim 1, wherein x = 2 / 3 and the Mg xGe 1-xO 2-x epitaxial layer comprises Mg 2GeO 4 having cubic symmetry and Fd3m space group.

9. The semiconductor structure of claim 1, wherein x = 2 / 3 and the Mg xGe 1-xO 2-x epitaxial layer comprises Mg 2GeO 4 having orthorhombic symmetry and Pnma space group.

10. The semiconductor structure of claim 1, wherein x = 1 / 2 and the Mg xGe 1-xO 2-x epitaxial layer comprises MgGeO 3 having monoclinic symmetry and C2 / c space group.

11. The semiconductor structure of claim 1, wherein the Mg xGe 1-xO 2-x is a direct bandgap material.

12. The semiconductor structure of claim 1, wherein the Mg xGe 1-xO 2-x is an indirect bandgap material.

13. The semiconductor structure of claim 1, wherein the Mg xGe 1-xO 2-x is MgGeO 3 having the C2 / c space group and is an indirect bandgap material.

14. The semiconductor structure of claim 1, wherein the Mg xGe 1-xO 2-x epitaxial layer is doped.

15. The semiconductor structure of claim 14, wherein the Mg xGe 1-xO 2-x is a direct bandgap p-type material and contains Ga dopant.

16. The semiconductor structure of claim 15, wherein the Ga dopant is located at the Ge site of the corresponding undoped Mg xGe 1-xO 2-x crystal structure.

17. The semiconductor structure of claim 14, wherein the Mg xGe 1-xO 2-x is a direct bandgap n-type material and contains Ga dopant.

18. The semiconductor structure of claim 17, wherein the Ga dopant is located at the Mg site of the corresponding undoped Mg xGe 1-xO 2-x crystal structure.

19. The semiconductor structure of claim 14, wherein the Mg xGe 1-xO 2-x is a direct bandgap p-type material and contains an Al dopant.

20. The semiconductor structure of claim 19, wherein the Al dopant is located at the Ge site of the corresponding undoped Mg xGe 1-xO 2-x crystal structure.

21. The semiconductor structure of claim 14, wherein the Mg xGe 1-xO 2-x is a direct bandgap n-type material and contains an Al dopant.

22. The semiconductor structure of claim 21, wherein the Al dopant is located at the Mg site of the corresponding undoped Mg xGe 1-xO 2-x crystal structure.

23. The semiconductor structure of claim 14, wherein the MgxGe 1-xO 2-x is a direct bandgap p-type material and contains Li+ dopant.

24. The semiconductor structure of claim 23, wherein the Li+ dopant is located at a Ge site or a Mg site in the corresponding undoped Mg xGe 1-xO 2-x crystal structure.

25. The semiconductor structure of claim 14, wherein the Mg xGe 1-xO 2-x contains a Ni+ dopant.

26. The semiconductor structure of claim 25, wherein the Ni+ dopant is located at the Mg site of the corresponding undoped MgxGe 1-xO 2-x crystal structure.

27. The semiconductor structure of claim 14, wherein the MgxGe 1-xO 2-x is a direct bandgap p-type material and contains N 3+ dopant.

28. The semiconductor structure of claim 27, wherein the N3+ dopant is located at the oxygen site of the corresponding undoped MgxGe1-xO2-x crystal structure.

29. The semiconductor structure as described in claim 14, wherein: The Mg xGe 1-xO 2-x epitaxial layer has a doped cell structure and a corresponding undoped cell structure; in the case of the doped cell structure, the Mg xGe 1-xO 2-x is an indirect bandgap p-type material; the doped cell structure contains Ge atoms at the first position occupied by Mg in the corresponding undoped cell structure; and the doped cell structure contains Mg atoms at the second position occupied by Ge in the corresponding undoped cell structure.

30. The semiconductor structure of claim 29, wherein in the doped cell structure, the Ge atoms are octahedral and the Mg atoms at the second position are tetrahedral.

31. The semiconductor structure of claim 14, wherein the unit cell of the Mg xGe 1-xO 2-x is doped with excess Ge atoms or excess Mg atoms.

32. The semiconductor structure of claim 1, further comprising a superlattice having a unit cell having a first layer; wherein the Mg xGe 1-xO 2-x epitaxial layer is the first layer in the superlattice.

33. The semiconductor structure of claim 32, wherein the cell of the superlattice further comprises a second layer of Mg yGe 1-yO 2-y, wherein y is in the range of 0 to 1 and x ≠ y.

34. The semiconductor structure of claim 32, wherein the first layer is MgO having the space group Fm3m.

35. The semiconductor structure of claim 34, wherein the cell of the superlattice further comprises a second layer made of Mg2GeO4 having the space group Fd3m.

36. The semiconductor structure of claim 32, wherein the unit cell of the superlattice further comprises a second layer of MgGa₂O₄ or γ-Ga₂O₃.

37. The semiconductor structure of claim 1, wherein the Mg xGe 1-xO 2-x epitaxial layer is the active region of the optoelectronic device.

38. The semiconductor structure of claim 37, wherein the optoelectronic device is a light-emitting diode or a photodetector.

39. The semiconductor structure of claim 38, wherein the optoelectronic device emits or absorbs light with wavelengths in the range of 150 nm to 280 nm.

40. The semiconductor structure of claim 1, wherein the Mg xGe 1-xO 2-x epitaxial layer is the active region of an electronic device.

41. The semiconductor structure of claim 1, further comprising a second epitaxial layer forming a heterostructure with the Mg xGe 1-xO 2-x epitaxial layer.

42. The semiconductor structure of claim 41, wherein the second epitaxial layer comprises Zn xGe yO z, Zn xGa yO z, Al xGe yO z, Al xZn yO z, Al xMg yO z, Mg xGa yO z, Mg xZn yO z or Ga xO z, wherein x, y and z are molar fractions.

43. A semiconductor device comprising: A substrate comprising a substantially single-crystal substrate material; and an active region on the substrate comprising a Mg xGe 1-xO 2-x epitaxial layer, wherein x has a value of 0 ≤ x < 1; wherein the Mg xGe 1-xO 2-x epitaxial layer has crystal symmetry compatible with the substrate material.

44. The semiconductor device of claim 43, wherein the semiconductor device is an optoelectronic device comprising a light-emitting diode or a photodetector.

45. The semiconductor device of claim 44, wherein the optoelectronic device emits or absorbs light with wavelengths in the range of 150 nm to 280 nm.

46. ​​The semiconductor device of claim 43, wherein the semiconductor device is an electronic device comprising a diode or a transistor.

47. The semiconductor device of claim 43, wherein the Mg xGe 1-xO 2-x epitaxial layer is an intrinsic layer.

48. The semiconductor device of claim 43, wherein the Mg xGe 1-xO 2-x epitaxial layer system includes an n-type or p-type conductive doped layer.

49. The semiconductor device of claim 43, wherein the Mg xGe 1-xO 2-x is Mg 2GeO 4.

50. A method for forming a semiconductor device, the method comprising: A substrate is provided comprising a substantially single-crystal substrate material having crystal symmetry compatible with the Mg xGe 1-xO 2-x epitaxial layer; The material is co-deposited onto the substrate to form the Mg xGe 1-xO 2-x epitaxial layer, wherein x has a value of 0 ≤ x < 1; wherein, according to the x value, the material contains at least two elements selected from Mg, Ge and oxygen, wherein the Mg, the Ge and the oxygen are supplied by a Mg source, a Ge source and an active oxygen source, respectively.

51. The method of claim 50, further comprising depositing a buffer layer between the substrate and the Mg xGe 1-xO 2-x epitaxial layer.

52. The method of claim 50, wherein the co-deposition system is implemented using a molecular beam epitaxy process.

53. The method of claim 50, wherein the Mg xGe 1-xO 2 epitaxial layer self-assembles in the co-deposition.

54. The method of claim 50 further includes determining the elemental incident flux ratio of the Ge source to the Mg source based on the deposition surface temperature, so as to maintain the surface material ratio of the Ge source to the Mg source.

55. The method of claim 50, wherein the Mg xGe 1-xO 2-x is Mg 2GeO 4.

56. The method of claim 50, wherein the co-deposition includes using a growth temperature of 400°C-500°C and a flux ratio k( ) of the Ge source to the Mg source of k=3 to 9.

57. The method of claim 56, wherein the flux ratio k has a value of 3 to 7.5 and the Mg xGe 1-xO 2-x system is Mg 2GeO 4.

58. The method of claim 50, wherein the co-deposition includes doping the epitaxial layer.

59. The method of claim 58, wherein the doping comprises replacing the Ge sites of the corresponding undoped MgxGe 1-xO 2-x crystal structure with Ga to produce p-type conductivity.

60. The method of claim 58, wherein the doping comprises replacing the Mg sites of the corresponding undoped MgxGe 1-xO 2-x crystal structure with Ga to produce n-type conductivity.

61. The method of claim 58, wherein the doping comprises replacing the Ge sites of the corresponding undoped MgxGe 1-xO 2-x crystal structure with Al to produce p-type conductivity.

62. The method of claim 58, wherein the doping comprises replacing the Mg sites of the corresponding undoped MgxGe 1-xO 2-x crystal structure with Al to produce n-type conductivity.

63. The method of claim 58, wherein the doping comprises replacing the Ge or Mg sites of the corresponding undoped MgxGe 1-xO 2-x crystal structure with Li+ to produce p-type conductivity.

64. The method of claim 58, wherein the doping comprises replacing the Mg sites of the corresponding undoped MgxGe 1-xO 2-x crystal structure with Ni+.

65. The method of claim 58, wherein the doping comprises replacing oxygen sites in the corresponding undoped MgxGe 1-xO 2-x crystal structure with N 3+.

66. The method of claim 58, wherein the doping includes: Ge atoms are placed in the first position occupied by Mg in the corresponding undoped unit cell structure of Mg xGe 1-xO 2-x; and Mg atoms are placed in the second position occupied by Ge in the corresponding undoped unit cell structure.

67. The method of claim 50, further comprising forming a superlattice on the substrate, wherein the superlattice has a cell comprising a first layer and a second layer, wherein the first layer in the superlattice is the Mg xGe 1-xO 2-x epitaxial layer.

68. The method of claim 67, wherein the second layer of the superlattice is a second Mg yGe 1-yO 2-y epitaxial layer, wherein y is in the range of 0 to 1 and x ≠ y.

69. The method of claim 50, further comprising forming the semiconductor device from the substrate and the Mg xGe 1-xO 2-x epitaxial layer.