Crack-free ultrawide-bandgap group-iii-nitride semiconductor films deposited on silicon substrate

Abstract

A method of forming a single-crystalline group-III-nitride (III-N) thick film includes epitaxially growing or depositing, on a silicon (Si) (111) substrate, one or more metallic interlayers or a superlattice structure including a plurality of pairs of a metallic layer and a semiconductor layer, epitaxially growing or depositing, on a top layer of the superlattice structure that is located opposite to the Si (111) substrate or on a top layer of the one or more metallic interlayers that is located opposite to the Si (111) substrate, the single-crystalline group-III-N thick film, epitaxially growing or depositing, on a top layer of the single-crystalline group-III-N thick film, a secondary substrate, removing the one or more metallic interlayers or the metallic layers from the superlattice structure to separate the Si (111) substrate, and transferring the single-crystalline group-III-N thick film on to the secondary substrate.

Description

2483-14801 CRACK-FREE ULTRAWIDE-BANDGAP GROUP-III-NITRIDE SEMICONDUCTOR FILMS DEPOSITED ON SILICON SUBSTRATE CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims priority to U.S. Provisional Application Serial No. 63 / 532,595 filed August 14, 2023 and entitled “CRACK-FREE ULTRAWIDE-BANDGAP GROUP-III-NITERIDE SEMICONDUCTOR FILMS DEPOSITED ON SILICON SUBSTRATE,” which is incorporated herein by reference in its entirety for all purposes. TECHNICAL FIELD

[0002] The present disclosure relates generally to group-III-nitride (N) semiconductor films. In particular, the present disclosure relates to epitaxial growth of crack-free group-III- nitride semiconductor films on silicon (Si) substrate. BACKGROUND

[0003] Group-III-nitride (III-N) materials, such as indium nitride (InN), gallium nitride (GaN), aluminum nitride (AlN), and their alloys of InxGa1-xN, AlxGa1-x N, AlxIn1-x N, and AlxInyGa1-x-yN where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1, possess excellent properties for electronic, photonic, sensing, and energy harvesting applications, including high dielectric breakdown voltage, high piezoelectric coefficients, excellent thermal, mechanical, and chemical stability, and bandgap energies that span from an infrared to a deep ultraviolet spectrum, which makes them unique among the semiconductor materials. Specifically, AlN and AlxGa1-xN with high mole fraction of AlN have great technological potential for high-power high-voltage electronics, harsh-environment sensing, self-powered system, electro-mechanical transducers and actuators, environment sensing, secure communication, and chemical-free sanitization. To fabricate the devices for such applications, single-crystalline AlN and AlxGa1-xN have been epitaxially grown on a limited choice of substrates such as sapphire (Al2O3), silicon carbide (SiC), and AlN that can offer relatively small (or zero) lattice mismatch with AlN. However, those substrates are small and expensive, which limits the throughput and cost reduction of the manufacturing process.

[0004] It is desirable to use Si substrates that offer large wafer size, low cost, good thermal and electrical conductivity, potential integration with matured Si-based circuits / technology, and an easy layer-transfer process. A major obstacle in epitaxial growth of AlN on Si substrate is that the AlN films are easily cracked during epitaxial growth due to in-plane tensile strain in2483-14801 the film. For example, cracks typically formed in the AlN layer with a thickness exceeding ~200-400 nanometers (nm) in most chemical vapor epitaxy carried out higher than 1000 degrees Celsius (°C) and in any AlN layers thicker than ~1 micrometer (μm), which is not thick enough for most device applications.

[0005] The in-plane strain in AlN film that is induced by lattice and thermal expansion mismatches, that is, the differences in lattice constants and thermal expansion coefficients between substrate [e.g., (111) plane of Si] and epitaxial film [e.g., (0001) plane of AlN], as shown in

[0006] Table 1. Table 1 Liner thermal In-plane lattice Cr stal ex ansion Strain on Si Strain in AlN, [000 ] S att ce constant on ( ) p ane o damond structure s ca cu ated rom a ormula ^^^^^^^⁄√2 , where ^^^^^^^is a lattice constant of the Si unit cell.

[0008] Strain in film on a substrate is calculated by a formula ^^ ൌ^ೞି^^^^, where ^^^is the in-plane lattice constant of film and ^^^is the in-plane lattice constant of the substrate which is the same as the in-plane lattice constant of pseudomorph epitaxial film (fully strained).

[0009] The in-plane tensile strain-induced cracks can alter the mechanical and electrical properties of materials. For example, the in-plane tensile strain-induced cracks can change the stiffness, strength, and ductility of AlN films, and further can affect carrier mobility and device performance of AlN films. As such, an ongoing need exists to develop epitaxial growth / deposition of crack-free thick films of AlN or aluminum gallium nitride (AlGaN) with high mole fractions of AlN having ultrawide-bandgap. SUMMARY

[0010] An embodiment of a method of forming a single-crystalline group-III-nitride (III-N) thick film comprises epitaxially growing or depositing, on a silicon (Si) (111) substrate, one or more metallic interlayers, and epitaxially growing or depositing, on a top layer of the one or2483-14801 more metallic interlayers that is located opposite to the Si (111) substrate, the single-crystalline group-III-N thick film. In some embodiments, before epitaxially growing or depositing, on the Si (111) substrate, the one or more metallic interlayers, the method further comprises epitaxially growing or depositing, on the Si (111) substrate, a single-crystalline group-III-N thin film. In certain embodiments, the one or more metallic interlayers comprise face-centered cubic (FCC) structures oriented in

[0111] and / or hexagonal closed packed (HCP) structures oriented in

[0001] , and wherein metals of the one or more metallic interlayers comprise aluminum (Al), gold (Au), thorium (Th), silver (Ag), ytterbium (Yb), cadmium (Cd), magnesium (Mg), scandium (Sc), lanthanum (La), titanium (Ti), zirconium (Zr), terbium (Tb), yttrium (Y), or any mixture of metals thereof. In some embodiments, the method further comprises epitaxially growing or depositing, on a top layer of the single-crystalline group-III- N thick film, a secondary substrate, removing the one or more metallic interlayers to separate the Si (111) substrate, and transferring the single-crystalline group-III-N thick film on to the secondary substrate.

[0011] An embodiment of a method of forming a single-crystalline group-III-nitride (III-N) thick film comprises epitaxially growing or depositing, on the Si (111) substrate, a superlattice structure comprising a plurality of pairs of a metallic layer and a semiconductor layer, and epitaxially growing or depositing, on a top layer of the superlattice structure that is located opposite to the Si (111) substrate, the single-crystalline group-III-N thick film. In some embodiments, the metallic layers in the superlattice structure comprise face-centered cubic (FCC) structures oriented in

[0111] and / or hexagonal closed packed (HCP) structures oriented in

[0001] , and wherein metals of the metallic layers comprise aluminum (Al), gold (Au), thorium (Th), silver (Ag), ytterbium (Yb), cadmium (Cd), magnesium (Mg), scandium (Sc), lanthanum (La), titanium (Ti), zirconium (Zr), terbium (Tb), yttrium (Y), or any mixture of metals thereof. In certain embodiments, the semiconductor layers of the superlattice structure comprise an aluminum nitride (AlN), a gallium nitride (GaN), an aluminum gallium nitride (AlGaN), or a combination thereof. In certain embodiments, the pairs of the metallic layer and the semiconductor layer comprises periods of 2 to 200. In some embodiments, before epitaxially growing or depositing, on the Si (111) substrate, the superlattice structure, the method further comprises epitaxially growing or depositing, on the Si (111) substrate, a single- crystalline group-III-N thin film. In some other embodiments, a thickness of the single- crystalline group-III-N thin film is in a range of 1 nm to 500 nm.

[0012] In any of the previous embodiments, the single-crystalline group-III-N thick film comprises aluminum nitride (AlN) layers, gallium nitride (GaN) layers, and / or alloys of2483-14801 aluminum gallium nitride (AlxGa1-xN) with high mole fraction of AlN layers, wherein a thickness of the single-crystalline group-III-N thick film is in a range of 1 μm to 50 cm, and wherein 0 ≤ x ≤ 1.

[0013] In any of the previous embodiments, the method further comprises epitaxially growing or depositing, on a top layer of the single-crystalline group-III-N thick film, a secondary substrate, removing the metallic layers from the superlattice structure to separate the Si (111) substrate, and transferring the single-crystalline group-III-N thick film on to the secondary substrate. In some embodiments, the method further comprises reusing the Si (111) substrate for a production process of the single-crystalline group-III-N thick film. In certain embodiment, the secondary substrate comprises a flexible substrate made of polymeric, metallic, ceramic elements, or a combination of thereof. In certain embodiment, the secondary substrate comprises a rigid substrate made of polymeric, metallic, ceramic elements, or a combination of thereof.   BRIEF DESCRIPTION OF DRAWINGS

[0014] The following figures form part of the present specification and are included to further demonstrate certain aspects of the present disclosure. The subject matter of the present disclosure may be better understood by reference to the figure in combination with the detailed description of specific aspects presented herein.

[0015] FIG. 1 depicts a schematic structure of a thick film layer of AlN / AlGaN on Si substrate with single or multiple metallic interlayers according to an embodiment of this disclosure;

[0016] FIG.2 depicts the strain in the film for gold (Au) on Si and AlN on Au as a function of temperature;

[0017] FIG. 3 depicts the experimental result confirming that a metal interlayer is epitaxially grown on Si substrate to achieve single-crystalline AlN films;

[0018] FIG. 4 depicts X-ray diffraction (XRD) φ (rotational) scan around AlN {101ത2} planes;

[0019] FIG. 5 depicts a schematic structure of AlN on Si substrate with a superlattice consisting of AlN and metal layers according to an embodiment of this disclosure;

[0020] FIG. 6 depicts a schematic structure of AlN / metal superlattice according to an embodiment of this disclosure.

[0021] FIG.7 schematically shows processing steps for film transfer of the AlN layer from the Si substrate to a secondary substrate;2483-14801

[0022] FIG. 8 is a flowchart illustrating methods of epitaxial growth or deposition of the AlN / AlGaN layer according to an embodiment of this disclosure;

[0023] FIG. 9 depicts a schematic layer structure of alternative method of using a thin separation layer of AlN before using single or multiple metallic interlayers to grow AlN thick film on Si substrate; and

[0024] FIG.10A and FIG.10B depict the role of adding the thin separation layer of AlN. DETAILED DESCRIPTION OF EMBODIMENTS

[0025] Disclosed herein are methods to overcome limitations of the epitaxial growth / deposition of crack-free thick films of AlN or AlGaN with high mole fractions of AlN having ultrawide-bandgap. In one or more aspects, the methods include introduction of single or multiple interlayer(s) for strain management between Si substrate and group-III-N semiconductor epitaxial layers. Selected elements or compounds used in the interlayers are chemically less stable than Si and group-III-N materials. Therefore, the layers can be selectively removed for the epitaxial lift-off process.

[0026] Embodiments of this disclosure describe methods addressing a critical issue to realize crack-free single-crystalline group-III-N film on Si with targeting film thickness of 1 μm up to several centimeters (cm). In this disclosure, interlayers between Si substrate and the group-III-N film that are introduced to reduce the lattice mismatch and thermal expansion coefficient differences between the Si substrate and the group-III-N film by mitigating the in- plane tensile strain in the film or converting the strain status of epitaxial film from tensile to compressive strain are discussed below. This disclosure comprises various schemes of (1) structures using single or multiple metallic interlayer(s); (2) superlattice structures consisting of alternating metallic and semiconductor layers, which can mitigate the induced strain in the heteroepitaxial growth of group-III-N film layers on Si substrate; and (3) transferring method of the group-III-N film from Si substrate to another substrate using epitaxial lift-off process.

[0027] In an embodiment, FIG. 1 illustrates a structure and FIG. 8 illustrates a corresponding production process or method 1 using single or multiple metallic interlayer(s), which can mitigate the induced strain in the heteroepitaxial growth of group-III-N film layers on Si substrate.

[0028] Method 1: Metallic interlayer(s):

[0029] Step S801: Providing a single-crystalline silicon (111) as a substrate of AlN and AlGaN epitaxial growth.2483-14801

[0030] The single-crystalline silicon (111) substrate is pivotal in semiconductor technology due to their unique surface characteristics and orientation. The (111) plane of silicon features a high density of surface atoms, which enhances surface stability and uniformity. This orientation is particularly advantageous for growing films and achieving epitaxial growth, which are crucial for high-performance electronic devices. Additionally, the (111) plane influences thermal and electrical properties, allowing for optimized device performance. In silicon-based technologies such as applications ranging from metal-oxide-semiconductor field- effect transistors (MOSFETs) and complementary metal-oxide-semiconductor (CMOS) circuits to advanced technologies like quantum computing and photonics, the (111) substrate orientation is chosen for its ability to meet specific material and device requirements, ensuring consistent and reliable results.

[0031] Step S802: Growing the first metallic interlayer having low lattice mismatch with the substrate or AlN layer and being single crystalline.

[0032] Step S803: If necessary, growing the second metallic interlayer having low lattice mismatch with the first metallic layer or AlN and being single crystalline.

[0033] We introduce different single crystalline metallic interlayer(s) that are structurally matched with group-III-N and Si. In this method, relatively ductile metallic layers are used as interlayers to mitigate the strain in the AlN epitaxial layer from the substrate.

[0034] Step S804: Growing a thick group-III-N semiconductor film due to strain- management of metallic interlayers.

[0035] Error! Reference source not found. shows a schematic structure of AlN on Si with single or multiple metallic interlayers. Metallic interlayer(s) 102 is epitaxially grown on Si (111) substrate 101 before the epitaxial growth of group-III-N layer 103. The group-III-N layer 103 is grown on a top layer 104 of the metallic interlayer(s) 102.

[0036] Metals having face-centered cubic (FCC) structure oriented in

[0111] and hexagonal closed packed (HCP) structure oriented in

[0001] offer similar planar atomic configure to group-III-N (0001) and Si (111) to achieve the epitaxial growth of single crystal thick film of group-III-N semiconductor. The metals including aluminum (Al), gold (Au), thorium (Th), silver (Ag), ytterbium (Yb), cadmium (Cd), magnesium (Mg), scandium (Sc), lanthanum (La), titanium (Ti), zirconium (Zr), terbium (Tb), yttrium (Y), and a combination of those layers can be used as an interlayer(s). Table 2 lists the detailed physical properties of the metals for interlayers.2483-14801 Table 2 Liner In-plane thermal Strain N [ mula^^^^^^^⁄√2 , where ^^^^^^^is a lattice constant of the FCC metal unit cell.

[0038] Strain in film on a substrate is calculated by a formula ^^ ൌ^ೞି^^^^, where ^^^is thein-plane lattice constant of film and ^^^is the in-plane lattice constant substrate which is the same as the in-plane lattice constant of pseudomorph epitaxial film (fully strained).

[0039] The epitaxial interlayers either mitigate the tensile strain in AlN film or change the strain status in AlN from tensile to compressive strain. For example, Zr used in as the interlayer reduces the tensile strain to 0.0386 from 0.235 in the case of AlN on Si. Also, Au used in as the interlayer changes strain in AlN to compressive strain (-0.0746), which cannot induce crack formation in the film. The epitaxial growth of the interlayer and group-III-N film is typically carried out at elevated temperatures as high as ~1400 °C. Due to the thermal expansion of materials, in-plane lattice constants and resulting strains are changed with temperature.

[0040] In an embodiment, gold is used to modify the strain in AlN and prevent crack formation when a thick group-III-N film is grown. First, the Si substrate is cleaned to remove2483-14801 its native oxide. Then the initial thin AlN layer is deposited on the Si substrate by direct current (DC) magnetron reactive sputtering using an Al target at 110 watts (W) of DC cathode power with a mixture of argon (Ar) and nitrogen (N) gases introduced by independent mass flow controllers. In some embodiments, the sample holder is rotated (e.g., at approximately 20 revolutions per minute (rpm)) during sputtering to ensure film homogeneity. The partial pressures of oxygen (O) and water vapor (H2O) in the chamber may be analyzed using a residual gas analyzer (RGA) and kept as low as 10-10Torr and 10-11Torr, respectively. Subsequently, a thin ductile metallic Au layer (a thickness range of ~1 nm to 10 μm) may be deposited by E-beam evaporation. After the initial deposition of the thin Au and AlN films, a second layer of AlN is deposited with a thickness range of ~10 nm to 1 μm using a similar deposition condition as the first AlN. Finally, a thick layer of AlN layer with a thickness range of 1 μm to 50 cm may be epitaxially grown onto the sputtered AlN by plasma-assisted Molecular Beam Epitaxy (MBE) (or PA-MBE), Metalorganic Chemical Vapor Deposition (MOCVD), or Hydride Vapor Phase Epitaxy (HVPE). In some embodiments, PA-MBE is used due to its ability to enable precise control and high-quality growth of single-crystal materials. The AlN / Au / AlN / Si substrate may then be prepared using a standard solvent cleaning procedure before the MBE growth, followed by outgassing at a first temperature (e.g., outgassing at 250 °C for 12 hours) in a load-lock chamber and then at a second temperature (e.g., at 600 °C for 12 hours) in a buffer chamber. In an embodiment, the AlN epitaxial layer is grown at a substrate temperature of ~800‒1400 °C, as measured by the thermocouple, with Al beam equivalent pressure (BEP) of approximately 7.21×10-8Torr and 0.4 standard cubic cm (sccm) per minute of N2 flow rate with 350 W radio frequency (RF) power for plasma. The chamber pressure may be approximately 3.7×10-6Torr with a corresponding growth rate of ~200 nm / hour (hr). In some embodiments, the epitaxial structures are characterized by high- resolution X-ray diffraction (XRD) and transmission electron microscopy (TEM).

[0041] FIG. 2 shows the strain in the film for Au on Si and AlN on Au as a function of temperature. The strain calculation indicates that even at elevated temperatures, the compressive strain of AlN induced by the Au interlayer remains relatively stable, preventing the formation of cracks. The metallic interlayer is epitaxially grown with Si and AlN to offer single-crystalline thick group-III-N semiconductor films.

[0042] In some cases, especially when the intermixing, alloying, formation of compounds, or eutectic transformation occurs at the interface between the metallic layer and Si. Therefore, referring to FIG.9, a thin AlN layer 901 can be inserted between the metallic interlayer(s) 102 and Si substrate 101 for separation and protection. The additional thin AlN layer 901 can be a2483-14801 crack-free AlN layer with a thickness of approximately between 1 nm and 500 nm to prevent the aforementioned phase transformation reactions at the interface.

[0043] The first AlN layer serves not only as a seed layer for the succeeding epitaxial layers but also as a chemical isolation layer to prevent a possible eutectic reaction between Au and Si. FIG.10A and FIG.10B show the experimental results to validate the role of the separation and protection layer. As shown in FIG. 10A, the surface of AlN is not smooth in the case of AlN and Au interlayer on Si substrate 101 and without an AlN separation and protection layer. Furthermore, as shown in FIG. 10B, the surface of AlN is smooth in the case of AlN and Au interlayer on Si substrate and with an AlN separation and protection layer.

[0044] FIG.3 shows the experimental result confirming that a metal interlayer is epitaxially grown on Si to achieve single-crystalline AlN films. XRD shows single-crystalline Au film epitaxially grown along

[0111] in the out-of-plane direction on Si (111) substrate from the diffraction peaks of Au (111) and Au (222) but no other peaks. Furthermore, AlN film is also epitaxially grown along

[0001] in the out-of-plane direction on Au (111) surface from the diffraction peaks of AlN (0002) and AlN (0004).

[0045] FIG. 4 depicts XRD φ (rotational) scan around AlN {101ത2} planes. Six separatepeaks 60 degrees (°) apart indicate both the in-plane and out-of-plane alignments, supporting the epitaxial growth of a single-crystalline AlN film.

[0046] In an embodiment, FIG. 5 and a method 2 in FIG. 8 depict superlattice structures consisting of alternating metallic and semiconductor layers, which can mitigate the induced strain in the heteroepitaxial growth of group-III-N film layers on Si substrate.

[0047] Method 2: Metal / semiconductor superlattice:

[0048] Step S805: Growing superlattice structure consisting of AlN and metallic layer having low lattice mismatch with the substrate or AlN layer and being single crystalline.

[0049] The concept of metallic interlayer is further extended in this method. Strain mitigation and / or modification is achieved by the superlattice structure with multiple pairs consisting of AlN and metal layers.

[0050] FIG.5 depicts a schematic structure of AlN on Si with a superlattice consisting of multiple pairs each of which consisting a metallic layer and a semiconductor layer. Herein, the semiconducting layer is AlN, GaN, or AlGaN. The superlattice structure 502 is epitaxially grown on Si (111) substrate 501 before the epitaxial growth of group-III-N layer 503. Specifically, the group-III-N layer 503 is grown on a top layer 504 of the superlattice structure 502.2483-14801

[0051] FIG. 6 shows a schematic structure of AlN / metal superlattice. Aluminum (Al) layer, gold (Au) layer, thorium (Th) layer, silver (Ag) layer, ytterbium (Yb) layer, cadmium (Cd) layer, magnesium (Mg) layer, scandium (Sc) layer, lanthanum (La) layer, titanium (Ti) layer, zirconium (Zr) layer, terbium (Tb) layer, yttrium (Y) layer, and a combination of those layers can be used as a metal layer 602 in the superlattice structure 502. Furthermore, the superlattice structure can filter the propagating threading dislocations at the AlN / metal interfaces to decrease the density of threading dislocations in AlN film 503. Still refereeing to FIG.6, the superlattice structure 502 includes multiple pairs of alternating AlN layers 601 and the metal layers 602 with periods of two to several hundreds.

[0052] In an embodiment, FIG.7 and an optional method 3 in FIG. 8 depict a production process in the form of a new epitaxial lift-off process.

[0053] Method 3: A new epitaxial lift-off process:

[0054] Step S806: Epitaxial water-liftoff from the metallic interlayers to reuse the Si substrate.

[0055] The metallic layers 602 used in the interlayers 102 and superlattice structure 502 in FIG.1 and FIG.5 further offer an additional advantage of an easy epitaxial lift-off process for film layer transfer. FIG. 7 schematically shows the processing steps for film transfer of the AlN layer 103 or 503 from the Si substrate 101 or 501 to a secondary substrate 701. The secondary substrate 701 is attached to AlN layer 103 or 503. The secondary substrate 701 can be mechanically flexible or rigid made of polymeric, metallic, ceramic elements, and a combination of them. Then, the Si substrate 101 or 501 is detached from the AlN layer 103 or 503 by removing the metallic interlayer 102 or metal layers 602 in the superlattice structure 502.

[0056] Due to their less chemical stability than that of Si and AlN, the metals used in interlayer 102 and superlattice structure 502 can be easily removed or dissolved by chemical etching with less toxic / dangerous solutions. For example, selected metal interlayers such as Yb can be dissolved in water by the formation of an aqueous form of ytterbium (III) hydroxide (Yb(OH)3), which enables the water-lift-off process: 2 Yb (s) + 6 H2O (g) → 2 Yb (OH)3(aq) + 3 H2(g)

[0057] Once the lift-off process is performed from the Yb layer, the thick AlN layer (103 or 503) can be successfully separated from the Si (111) substrate 101 or 501, while ensuring the preservation of its structural integrity.2483-14801 ADDITIONAL DISCLOSURE

[0058] An embodiment of a method of forming a single-crystalline group-III-nitride (III-N) thick film comprises epitaxially growing or depositing, on a silicon (Si) (111) substrate, one or more metallic interlayers, and epitaxially growing or depositing, on a top layer of the one or more metallic interlayers that is located opposite to the Si (111) substrate, the single-crystalline group-III-N thick film. In some embodiments, before epitaxially growing or depositing, on the Si (111) substrate, the one or more metallic interlayers, the method further comprises epitaxially growing or depositing, on the Si (111) substrate, a single-crystalline group-III-N thin film. In certain embodiments, the one or more metallic interlayers comprise face-centered cubic (FCC) structures oriented in

[0111] and / or hexagonal closed packed (HCP) structures oriented in

[0001] , and wherein metals of the one or more metallic interlayers comprise aluminum (Al), gold (Au), thorium (Th), silver (Ag), ytterbium (Yb), cadmium (Cd), magnesium (Mg), scandium (Sc), lanthanum (La), titanium (Ti), zirconium (Zr), terbium (Tb), yttrium (Y), or any mixture of metals thereof. In some embodiments, the method further comprises epitaxially growing or depositing, on a top layer of the single-crystalline group-III- N thick film, a secondary substrate, removing the one or more metallic interlayers to separate the Si (111) substrate, and transferring the single-crystalline group-III-N thick film on to the secondary substrate.

[0059] An embodiment of a method of forming a single-crystalline group-III-nitride (III-N) thick film comprises epitaxially growing or depositing, on the Si (111) substrate, a superlattice structure comprising a plurality of pairs of a metallic layer and a semiconductor layer, and epitaxially growing or depositing, on a top layer of the superlattice structure that is located opposite to the Si (111) substrate, the single-crystalline group-III-N thick film. In some embodiments, the metallic layers in the superlattice structure comprise face-centered cubic (FCC) structures oriented in

[0111] and / or hexagonal closed packed (HCP) structures oriented in

[0001] , and wherein metals of the metallic layers comprise aluminum (Al), gold (Au), thorium (Th), silver (Ag), ytterbium (Yb), cadmium (Cd), magnesium (Mg), scandium (Sc), lanthanum (La), titanium (Ti), zirconium (Zr), terbium (Tb), yttrium (Y), or any mixture of metals thereof. In certain embodiments, the semiconductor layers of the superlattice structure comprise an aluminum nitride (AlN), a gallium nitride (GaN), an aluminum gallium nitride (AlGaN), or a combination thereof. In certain embodiments, the pairs of the metallic layer and the semiconductor layer comprises periods of 2 to 200. In some embodiments, before epitaxially growing or depositing, on the Si (111) substrate, the superlattice structure, the method further comprises epitaxially growing or depositing, on the Si (111) substrate, a single-2483-14801 crystalline group-III-N thin film. In some other embodiments, a thickness of the single- crystalline group-III-N thin film is in a range of 1 nm to 500 nm.

[0060] In any of the previous embodiments, the single-crystalline group-III-N thick film comprises aluminum nitride (AlN) layers, gallium nitride (GaN) layers, and / or alloys of aluminum gallium nitride (AlxGa1-xN) with high mole fraction of AlN layers, wherein a thickness of the single-crystalline group-III-N thick film is in a range of 1 μm to 50 cm, and wherein 0 ≤ x ≤ 1. In any of the previous embodiments, the method further comprises epitaxially growing or depositing, on a top layer of the single-crystalline group-III-N thick film, a secondary substrate, removing the metallic layers from the superlattice structure to separate the Si (111) substrate, and transferring the single-crystalline group-III-N thick film on to the secondary substrate. In some embodiments, the method further comprises reusing the Si (111) substrate for a production process of the single-crystalline group-III-N thick film. In certain embodiment, the secondary substrate comprises a flexible substrate made of polymeric, metallic, ceramic elements, or a combination of thereof. In certain embodiment, the secondary substrate comprises a rigid substrate made of polymeric, metallic, ceramic elements, or a combination of thereof.

[0061] While aspects of the presently disclosed subject matter have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the subject matter. The aspects described herein are exemplary only and are not intended to be limiting. Many variations and modifications of the subject matter disclosed herein are possible and are within the scope of the disclosed subject matter. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). Use of the term "optionally" with respect to any element of a claim is intended to mean that the subject element is required, or alternatively, is not required. Both alternatives are intended to be within the scope of the claim. Use of broader terms such as comprises, includes, having, etc. should be understood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, etc.

[0062] Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an2483-14801 aspect of the present disclosure. Thus, the claims are a further description and are an addition to the aspects of the presently disclosed subject matter. The discussion of a reference herein is not an admission that it is prior art to the presently disclosed subject matter, especially any reference that may have a publication date after the priority date of this application. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference, to the extent that they provide exemplary, procedural or other details supplementary to those set forth herein.

Claims

2483-14801 CLAIMS What is claimed is:

1. A method of forming a single-crystalline group-III-nitride (III-N) thick film comprising: epitaxially growing or depositing, on a silicon (Si) (111) substrate, one or more metallic interlayers; and epitaxially growing or depositing, on a top layer of the one or more metallic interlayers that is located opposite to the Si (111) substrate, the single-crystalline group-III-N thick film.

2. The method of claim 1, further comprising: epitaxially growing or depositing, on the Si (111) substrate, a superlattice structure comprising a plurality of pairs of a metallic layer and a semiconductor layer; and epitaxially growing or depositing, on a top layer of the superlattice structure that is located opposite to the Si (111) substrate, the single-crystalline group-III-N thick film.

3. The method of claim 2, wherein the metallic layers in the superlattice structure comprise face-centered cubic (FCC) structures oriented in [111] and / or hexagonal closed packed (HCP) structures oriented in [0001], and wherein metals of the metallic layers comprise aluminum (Al), gold (Au), thorium (Th), silver (Ag), ytterbium (Yb), cadmium (Cd), magnesium (Mg), scandium (Sc), lanthanum (La), titanium (Ti), zirconium (Zr), terbium (Tb), yttrium (Y), or any mixture of metals thereof.

4. The method of claim 2, wherein the semiconductor layers of the superlattice structure comprise an aluminum nitride (AlN), a gallium nitride (GaN), an aluminum gallium nitride (AlGaN), or a combination thereof.

5. The method of claim 2, wherein the pairs of the metallic layer and the semiconductor layer comprises periods of 2 to 200.

6. The method of claim 2, wherein before epitaxially growing or depositing, on the Si (111) substrate, the superlattice structure, the method further comprises epitaxially growing or depositing, on the Si (111) substrate, a single-crystalline group-III-N thin film.2483-14801 7. The method of claim 1, wherein before epitaxially growing or depositing, on the Si (111) substrate, the one or more metallic interlayers, the method further comprises epitaxially growing or depositing, on the Si (111) substrate, a single-crystalline group-III-N thin film.

8. The method of claim 6 or 7, wherein a thickness of the single-crystalline group-III-N thin film is in a range of 1 nanometer (nm) to 500 nm.

9. The method of claim 1 or 2, wherein the single-crystalline group-III-N thick film comprises aluminum nitride (AlN) layers, gallium nitride (GaN) layers, and / or alloys of aluminum gallium nitride (AlxGa1-xN) with high mole fraction of AlN layers, wherein a thickness of the single-crystalline group-III-N thick film is in a range of 1 micrometer (μm) to 50 centimeters (cm), and wherein 0 ≤ x ≤ 1.

10. The method of claim 1, wherein the one or more metallic interlayers comprise face- centered cubic (FCC) structures oriented in [111] and / or hexagonal closed packed (HCP) structures oriented in [0001], and wherein metals of the one or more metallic interlayers comprise aluminum (Al), gold (Au), thorium (Th), silver (Ag), ytterbium (Yb), cadmium (Cd), magnesium (Mg), scandium (Sc), lanthanum (La), titanium (Ti), zirconium (Zr), terbium (Tb), yttrium (Y), or any mixture of metals thereof.

11. The method of claim 1, further comprising: epitaxially growing or depositing, on a top layer of the single-crystalline group-III-N thick film, a secondary substrate; removing the one or more metallic interlayers to separate the Si (111) substrate; and transferring the single-crystalline group-III-N thick film on to the secondary substrate.

12. The method of claim 2, further comprising: epitaxially growing or depositing, on a top layer of the single-crystalline group-III-N thick film, a secondary substrate; removing the metallic layers from the superlattice structure to separate the Si (111) substrate; and transferring the single-crystalline group-III-N thick film on to the secondary substrate.2483-14801 13. The method of claim 11 or 12, further comprising reusing the Si (111) substrate for a production process of the single-crystalline group-III-N thick film.

14. The method of claim 11 or 12, wherein the secondary substrate comprises a flexible substrate made of polymeric, metallic, ceramic elements, or a combination of thereof.

15. The method of claim 11 or 12, wherein the secondary substrate comprises a rigid substrate made of polymeric, metallic, ceramic elements, or a combination of thereof.

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