Large area group iii nitride crystal and substrate, method for manufacturing the same and method for using the same

Abstract

To provide a large area group III metal nitride substrate having low defective density and formed by a technique capable of improving a crystal growth process, and a method for growing the same.SOLUTION: A nitride substrate includes: at least two crystals having a first surface allowing crystal growth and a second surface on the side opposite to the first surface and including group III metal selected from at least one of gallium, aluminum and indium, and nitrogen; and a matrix member directly or indirectly contacting at least a part of the at least two crystals and constituted of a polycrystal member including gallium and nitrogen. The at least part of the matrix member is positioned between the at least two crystals.SELECTED DRAWING: Figure 19G

Description

Technical Field

[0001] The present disclosure generally relates to techniques for processing materials for manufacturing gallium-containing nitride substrates, and to the use of these substrates in optoelectronic and electronic devices. More particularly, embodiments of the present disclosure include techniques for growing large-area crystals and substrates using a combination of processing techniques. It should be noted that this application is a divisional application of Japanese Patent Application No. 2022-548644 filed on February 10, 2021.

Background Art

[0002] Gallium nitride (GaN)-based optoelectronic and electronic devices are of great commercial importance. However, the quality and reliability of these devices are endangered by high defect levels, particularly threading dislocations, grain boundaries, and strain in the semiconductor layers of the devices. Threading dislocations can arise from lattice mismatches of GaN-based semiconductor layers with respect to non-GaN substrates such as sapphire or silicon carbide. Grain boundaries can arise from the coalescence front of epitaxially overgrown layers. Additional defects can arise from thermal expansion mismatches, impurities, and tilt boundaries, depending on the details of layer growth.

[0003] The presence of defects adversely affects epitaxially grown layers. Such effects include a decrease in electronic device performance. To overcome these defects, techniques have been proposed that require complex and tedious manufacturing processes to reduce the concentration and / or effect of defects. A significant number of conventional growth methods for gallium nitride crystals have been proposed, but there are still limitations. That is, conventional methods are worthy of improvement to be cost-effective and efficient.

[0004] Progress has been made in the growth of large-area gallium nitride crystals, with significantly lower defect levels than heteroepitaxial GaN layers. However, most techniques for growing large-area GaN substrates involve the deposition of GaN on non-GaN substrates such as sapphire or GaAs. This approach generally results in threading dislocations with an average density of 10 5 ~10 7 cm -2 −2 on the surface of the thick boule, causing large warping, stress, and strain. Threading dislocations with a reduced density are desirable for many applications. Warping, stress, and strain can reduce the yield when slicing the boule into wafers and may cause the wafers to crack during downstream processing, potentially affecting the reliability and lifetime of the devices. Another consequence of warping, stress, and strain is that even techniques close to equilibrium, such as ammonothermal growth, can generate a significant density of stacking defects during growth in the m-plane and semi-polar directions. In addition, due to crack formation, multiple crystallographic domains, etc., the quality of c-plane growth may be insufficient. The ability to fabricate substrates larger than 2 inches, like the ability to fabricate large-area GaN substrates with non-polar or semi-polar crystal orientations, is currently very limited. Most large-area substrates are fabricated by vapor-phase methods such as relatively expensive hydride vapor-phase epitaxy (HVPE). A more inexpensive method is desired while achieving large area and low threading dislocation density as quickly as possible.

[0005] Ammonothermal crystal growth has several advantages over HVPE as a means of manufacturing GaN boules. However, the performance of the ammonothermal GaN crystal growth process can strongly depend on the size and quality of the seed crystal. Seed crystals produced by HVPE can suffer from many of the above limitations, and crystals grown ammonothermally are not widely available.

[0006] Conventional techniques have proposed methods of fusing simple GaN seed crystals into larger compound crystals by tiling methods. Some of the conventional methods involve using simple GaN seed crystals grown by hydride vapor epitaxy (HVPE), polishing the edges of the simple crystals at an inclined angle, and fusing them in the direction of rapid growth. Many or most of the conventional methods use HVPE as the crystal growth method for bonding the seed crystals. However, such conventional techniques have limitations. Typically, for example, conventional techniques do not specify the accuracy of the crystal orientation in both the polar direction and azimuthal angle between the fused simple seed crystals, nor do they provide a method for generating a high-precision crystallographic position between the basic seed crystals and minimizing the defects caused by the fusion of the simple seed crystals. Ammonothermal GaN usually has a lattice constant that is at least slightly different from that of HVPE GaN. Even the presence of a slight mismatch in the lattice constant can cause stress and cracks in the crystals grown ammonothermally on HVPE seed crystals, especially when tiling and coalescence are involved. Furthermore, cracks may occur during subsequent sawing or polishing of the crystals grown ammonothermally formed on one or more HVPE seed crystals.

Summary of the Invention

Problems to be Solved by the Invention

[0007] Due at least to the above problems, there is a need for a substrate formed by a technique that has a low defect density and improves the crystal growth process. Also, from the above, it can be seen that a technique for improving crystal growth is highly desired.

Means for Solving the Problems

[0008] Embodiments of the present disclosure include self-supporting group III metal nitride crystals. The self-supporting crystals have a wurtzite crystal structure, a first surface having a maximum dimension exceeding 40 millimeters in a first direction, an average density of stacking defects of less than 10 3 cm -1 and an average density of stacking defects of less than 10 1 cm -2 to 106 cm -2 including the average density of threading dislocations between, wherein the average density of threading dislocations on the first surface varies periodically at least two times in the first direction, and the period of the variation in the first direction is between 5 micrometers and 20 millimeters, and the misorientation angle varies within 0.1 degrees at the center 80% of the first surface of the crystal along the first direction and within 0.1 degrees at the center 80% of the first surface of the crystal along the second direction orthogonal to the first direction. The first surface includes a plurality of first regions, and each of the plurality of first regions has a locally substantially linear array of threading dislocations for 5 cm -1 to 10 5 cm -1 in density, and the first surface further includes a plurality of second regions, each of the plurality of second regions being disposed between adjacent pairs of the plurality of first regions and having a density of threading dislocations less than 10 5 cm -2 and a density of stacking faults less than 10 3 cm -1 and the first surface further includes a plurality of third regions, each of the plurality of third regions being disposed within one of the plurality of second regions or between adjacent second pairs and having a minimum dimension between 10 micrometers and 500 micrometers and a density of threading dislocations between 10 3 cm -2 to 10 8 cm -2 in density.

[0009] Embodiments of the present disclosure include a self-supporting group III metal nitride crystal including at least two domains. Each of the at least two domains includes a group III metal selected from gallium, aluminum, and indium, or a combination thereof, and nitrogen. Each of the at least two domains has a wurtzite crystal structure, and also has a maximum dimension exceeding 10 millimeters in the first direction, 10 1 cm -2 to 1×10 6 cm -2 in the average density of threading dislocations, 10 3 cm -1The average density of stacking defects less than, the full width at half maximum of the symmetric X-ray rocking curve less than 200 seconds of arc, 10 17 cm -3 The impurity concentration of H exceeding, and quantified by calibrated secondary ion mass spectrometry to be 10 15 cm -3 The impurity concentration of at least one of Li, Na, K, F, Cl, Br, and I exceeding, includes a first surface. The concentration of through dislocations in the first surface of the domain on the first surface can vary periodically by at least a factor of 2 in the first direction, and the period of the variation in the first direction is between 5 micrometers and 5 millimeters. The first surface includes a plurality of first regions, each of the plurality of first regions having a locally substantially linear array of through dislocations at a concentration between 5 cm -1 and 10 5 cm -1 The first surface can further include a plurality of second regions, each of the plurality of second regions being disposed between adjacent pairs of the plurality of first regions and having a through dislocation concentration of less than 10 5 cm -2 and a stacking defect concentration of less than 10 3 cm -1 The first surface further includes a plurality of first regions, each of the plurality of third regions being disposed between one of the plurality of second regions or adjacent pairs of the second regions, having a minimum dimension between 10 micrometers and 500 micrometers, and a through dislocation at a concentration between 10 1 cm -2 and 10 6 cm -2 The free-standing group III metal nitride crystal has a maximum dimension in the first direction exceeding 40 millimeters, the crystallographic misorientation varies by 0.2 degrees or less in two orthogonal directions over the central 80% of the crystal along the first direction, and by 0.1 degrees or less in two orthogonal directions over the central 80% of the crystal along a second direction orthogonal to the first direction, and at least two domains are from about 50 cm -1 to about 5×10 5 cm -1separated by dislocation lines with a linear density therebetween, and the polar azimuthal difference angle γ between the first domain and the second domain is greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuthal difference angles α and β are greater than about 0.01 degrees and less than about 1 degree.

[0010] Embodiments of the present disclosure include a method of forming a Group III metal nitride crystal, including performing a bulk crystal growth process on a tiled array of at least two seed crystals within a crystal growth apparatus, where the bulk crystal growth process fuses a bulk crystal layer grown from a first surface of a first seed crystal and a bulk crystal layer grown from a first surface of a second seed crystal to form a compound crystal, and the polar azimuthal difference angle γ between the crystal orientations of the first surface of the first seed crystal and the first surface of the second seed crystal is greater than about 0.005 degrees and less than about 0.2 degrees, the azimuthal difference angles α and β of the azimuthal angles between the crystal orientations of the first surfaces of the first and second seed crystals are greater than about 0.01 degrees and less than about 1 degree, and each of the seed crystals includes at least one of gallium, aluminum, and indium and nitrogen, and has a wurtzite crystal structure and a maximum dimension of at least 5 millimeters. In some embodiments, the bulk crystal growth process is performed at a first temperature, and the tiled array of at least two seed crystals is positioned on a first surface of a mechanical fixture during the bulk crystal growth process, the mechanical fixture including at least a backing plate member and a clamp member, each of which has a coefficient of thermal expansion that is between 80% and 99% of the coefficient of thermal expansion of the at least two seed crystals averaged over the range from room temperature to the first temperature, the coefficient of thermal expansion being measured in a plane parallel to the first surface.

[0011] Embodiments of the present disclosure include a method for forming a Group III metal nitride crystal, the method comprising the steps of arranging at least two seed crystals each having a first surface on a mechanical fixture, arranging the mechanical fixture within a crystal growth apparatus, and performing a bulk crystal growth process at a second temperature to fuse the first seed crystal and the second seed crystal into a compound crystal, each of the seed crystals comprising at least one of gallium, aluminum, and indium and nitrogen, having a wurtzite crystal structure and a maximum dimension of at least 5 millimeters. The mechanical fixture includes at least a backing plate member and a clamp member, each of which has a coefficient of thermal expansion that is between 80% and 99% of the coefficient of thermal expansion of the first surfaces of the at least two seed crystals averaged over the range between room temperature and the second temperature, the polar orientation difference angle γ between the crystal orientation of the first surface of the first seed crystal and the crystal orientation of the first surface of the second seed crystal is greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β of the azimuth of the crystal orientation between the first surfaces of the first and second seed crystals are greater than about 0.01 degrees and less than about 1 degree.

[0012] Embodiments of the present disclosure include a method of forming a Group III metal nitride crystal, the method comprising growing a polycrystalline Group III metal nitride on a tiled array of at least two seed crystals, the tiled array of at least two seed crystals including a first seed crystal having a first surface and a second surface and a second seed crystal having a first surface and a second surface, and fusing a polycrystalline Group III metal nitride layer grown from the second surfaces of the first and second seed crystals by a process of growing a polycrystalline Group III metal nitride on the tiled array of at least two seed crystals to form a tiled assembly; and performing a bulk crystal growth process on the tiled assembly within a crystal growth apparatus. The bulk crystal growth process fuses a bulk crystal layer grown on the first surface of the first seed crystal and a bulk crystal layer grown on the first surface of the second seed crystal to form a compound crystal, the polar azimuthal difference angle γ between the crystal azimuths of the first surfaces of the first and second seed crystals is greater than about 0.005 degrees and less than about 0.2 degrees, the azimuthal difference angles α and β of the azimuths of the crystal azimuths between the first surfaces of the first and second seed crystals are greater than about 0.01 degrees and less than about 1 degree, each of the seed crystals includes at least one of gallium, aluminum, and indium and nitrogen, and has a wurtzite crystal structure and a maximum dimension of at least 5 millimeters.

[0013] Embodiments of the present disclosure include a method of forming a Group III metal nitride crystal, the method including growing polycrystalline Group III metal nitride on a tiled array of at least two seed crystals, separating the tiled assembly from a susceptor; and performing a bulk crystal growth process on the tiled assembly within a crystal growth apparatus. The tiled array of at least two seed crystals includes a first seed crystal having a first surface and a second surface; and a second seed crystal having a first surface and a second surface, the tiled array of at least two seed crystals being disposed on a susceptor, and a tiled assembly being formed by fusing a polycrystalline Group III metal nitride layer deposited on the second surfaces of the first and second seed crystals by a process of growing polycrystalline Group III metal nitride on the tiled array of at least two seed crystals. The bulk crystal growth process forms a compound crystal by fusing a bulk crystal layer grown on the first surface of the first seed crystal and a bulk crystal layer grown on the first surface of the second seed crystal. The polar azimuth difference angle γ between the crystal orientations of the first surfaces of the first and second seed crystals is greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β of the azimuth angles between the crystal orientations of the first surfaces of the first and second seed crystals are greater than about 0.01 degrees and less than about 1 degree, each of the seed crystals including at least one of gallium, aluminum, and indium and nitrogen, and having a wurtzite crystal structure and a maximum dimension of at least 5 millimeters.

[0014] Embodiments of the present disclosure include a method of forming a Group III metal nitride crystal, the method comprising: placing at least two seed crystals, each having a first surface and a second surface opposite the first surface, in a susceptor; placing the susceptor in a growth reactor and growing polycrystalline Group III metal nitride on the second surfaces of the at least two seed crystals to form a tile-like assembly; separating the tile-like assembly from the susceptor; placing the tile-like assembly in a crystal growth apparatus; and performing a bulk crystal growth process, including fusing a first seed crystal and a second seed crystal into a compound crystal, wherein each of the seed crystals comprises at least one of gallium, aluminum, and indium and nitrogen, and has a wurtzite crystal structure and a maximum dimension of at least 5 millimeters. Each of the seed crystals comprises at least one of gallium, aluminum, and indium and nitrogen, and has a wurtzite crystal structure and a maximum dimension of at least 5 millimeters. The polar orientation difference angle γ between the crystal orientations of the first surfaces of the first and second seed crystals is greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β of the azimuths between the crystal orientations of the first surfaces of the first and second seed crystals are greater than about 0.01 degrees and less than about 1 degree.

[0015] Embodiments of the present disclosure include a method of forming a Group III metal nitride crystal. The method includes growing a Group III metal nitride crystal layer on an array of at least two first seed crystals, wherein each of the first seed crystals in the array of at least two first seed crystals is aligned in an array extending in a first direction, and a first tile-shaped crystal is formed by a process of growing the Group III metal nitride crystal layer; slicing the first tile-shaped crystal along a second direction orthogonal to the first direction, wherein slicing the first tile-shaped crystal forms at least two second seed crystals and the at least two second seed crystals have a first surface; and growing a Group III metal nitride crystal layer on an array of at least two second seed crystals, wherein each of the second seed crystals in the array of at least two second seed crystals is aligned in an array extending in the first direction, and a second tile-shaped crystal is formed by a process of growing the Group III metal nitride crystal layer on the array of at least two second seed crystals. The method further includes slicing the second tile-shaped crystal along both the second direction and the first direction to form at least two third seed crystals, and growing a Group III metal nitride crystal layer on an array of the at least two third seed crystals, wherein each of the third seed crystals in the array of at least two third seed crystals is aligned in an array extending in the first direction, and a third tile-shaped crystal is formed by a process of growing the Group III metal nitride crystal layer on the array of at least two second seed crystals.

[0016] Embodiments of the present disclosure include a method of forming a Group III metal nitride crystal, the method comprising arranging at least two first seed crystals, each having a first surface and a second surface opposite the first surface, along a first direction on a support structure; performing a first bulk crystal growth operation to combine the at least two first seed crystals to form a first one-dimensional tile-shaped crystal; slicing the first one-dimensional tile-shaped crystal into at least two second seed crystals along a second direction orthogonal to the first direction; arranging at least two second seed crystals, each having a first surface and a second surface opposite the first surface, on the support structure along a third direction orthogonal to the first and second directions; performing a second bulk crystal growth operation to combine the at least two second seed crystals to form a second one-dimensional tile-shaped crystal; slicing the second one-dimensional tile-shaped crystal along both the second direction and the first direction to form at least two third seed crystals; arranging at least two third seed crystals, each having a first surface and a second surface opposite the first surface, on the support structure along the first direction; and performing a third bulk crystal growth operation to combine the at least two third seed crystals to form a third one-dimensional tile-shaped crystal having a first surface, a second surface opposite the first surface, and at least two domains. Each of the at least two domains in the third one-dimensional tile-shaped crystal surrounds at least a portion of the two third seed crystals. The polar azimuth difference angle γ between the crystal azimuth of the first surface of the first domain of the third one-dimensional tile-shaped crystal and the crystal azimuth of the first surface of the second domain of the third one-dimensional tile-shaped crystal is greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β of the azimuth between the crystal azimuths of the first surfaces of the first and second seed crystals are greater than about 0.01 degrees and less than about 1 degree. Each of the first seed crystal, the second seed crystal, and the third seed crystal contains at least one of gallium, aluminum, and indium and nitrogen, and has a wurtzite crystal structure. Each of the first seed crystal, the second seed crystal, and the third seed crystal includes a maximum dimension of at least 5 millimeters, and the crystal azimuths of the first surfaces of the first seed crystal, the second seed crystal, and the third seed crystal are the same and are within about 1 degree of being identical.

[0017] Embodiments of the present disclosure include a self-supporting group III metal nitride substrate including at least two crystals, each of the at least two crystals including a group III metal selected from gallium, aluminum, and indium, or a combination thereof, and nitrogen. Each of the at least two crystals having a wurtzite crystal structure has a first surface having a maximum dimension exceeding 10 millimeters in a first direction and a maximum dimension exceeding 4 millimeters in a second direction orthogonal to the first direction, 10 1 cm -2 to 1×10 6 cm -2 and having an average density of threading dislocations between, 10 3 cm -1 and having an average density of stacking defects less than, and a symmetric X-ray rocking curve full width at half maximum of less than 200 seconds of arc. The self-supporting group III metal nitride substrate has a maximum dimension in the first direction exceeding 40 millimeters. The magnitude of the crystallographic misorientation of the first surface of each of the at least two crystals is equal within 0.5 degrees, and the direction of the crystallographic misorientation of the first surface of each of the at least two crystals is equal within 10 degrees. Each of the at least two crystals is bonded to a matrix member including polycrystalline GaN, and the polar azimuth difference angle γ between the first domain and the second domain is greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β are greater than about 0.01 degrees and less than about 1 degree.

[0018] Embodiments of the present disclosure include a method of manufacturing a freestanding group III metal nitride substrate including at least two domains, the method including depositing a layer of polycrystalline GaN on an array of at least two seed crystals deposited on a susceptor to form a tile-shaped composite member, and separating the tile-shaped composite member from the susceptor. The layer of polycrystalline GaN is formed on a second surface opposite the first surface of each of the at least two seed crystals. Each of the at least two seed crystals includes a group III metal selected from gallium, aluminum, and indium, or a combination thereof, and nitrogen, and at least two seed crystals having a wurtzite crystal structure have a first surface with a maximum dimension exceeding 10 millimeters in a first direction and a maximum dimension exceeding 4 millimeters in a second direction orthogonal to the first direction, an average concentration of through dislocations of less than about 2×10 7 cm -2 an average concentration of stacking defects of less than 10 3 cm -1 and a symmetric X-ray rocking curve full width at half maximum of less than 200 seconds of arc.

[0019] Embodiments of the present disclosure include a method of manufacturing a freestanding group III metal nitride substrate including at least two domains, the method including providing at least two seed crystals, each of the at least two seed crystals including a group III metal selected from gallium, aluminum, and indium, or a combination thereof, and nitrogen, disposing the at least two seed crystals on a susceptor, depositing a layer of polycrystalline GaN on a second surface opposite the first surface of each of the at least two seed crystals to form a tile-shaped composite member, and removing the tile-shaped composite member from the susceptor. At least two seed crystals having a wurtzite crystal structure have a first surface with a maximum dimension exceeding 10 millimeters in a first direction and a maximum dimension exceeding 4 millimeters in a second direction orthogonal to the first direction, an average concentration of through dislocations of less than about 2×10 7 cm -2 an average concentration of stacking defects of less than 10 3 cm -1It includes the average density of stacking defects less than a certain value, and the full width at half maximum of the symmetric X-ray rocking curve less than 200 seconds of arc. The polar azimuth difference angle γ between the first surface of the first seed crystal and the first surface of the second seed crystal is greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β are greater than about 0.01 degrees and less than about 1 degree.

[0020] Embodiments of the present disclosure are self-supporting group III metal nitride substrates including an array of seed crystals, where each of the seed crystals in the array of seed crystals contains a group III metal selected from gallium, aluminum, and indium, or a combination thereof, and nitrogen, and a polycrystalline GaN layer disposed on at least one surface of each of the seed crystals in the array of seed crystals. Each of the seed crystals having a wurtzite crystal structure has an average density of threading dislocations between 10 1 cm -2 and 1×10 6 cm -2 , and includes a first surface having an average density of stacking defects less than 10 3 cm -1 . The magnitude of the crystallographic misorientation of the first surface of each of the seed crystals is equal within 0.5 degrees, and the direction of the crystallographic misorientation of the first surface of each of the seed crystals is equal within 10 degrees. The polar azimuth difference angle γ between the first seed crystal and the second seed crystal in the array of seed crystals is greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β are greater than about 0.01 degrees and less than about 1 degree.

[0021] Embodiments of the present disclosure have a wurtzite crystal structure, at least two domains, each of which contains a group III metal selected from gallium, aluminum, and indium, or a combination thereof, and nitrogen; a first surface having a maximum dimension greater than 40 millimeters in a first direction, including the domain surfaces of each of the at least two domains, and the domain surfaces of each of the at least two domains having a dimension of at least 10 millimeters in the first direction, 10 3 cm -1 less than the average density of stacking defects, and 10 1 cm -2 to 106 cm -2 comprising a self - standing group - III metal nitride crystal including a first surface having an average density of threading dislocations between -2 and -1 . The average density of threading dislocations on the domain surface of each of at least two domains can vary periodically by at least a factor of 2 in a first direction, and the period of the variation in the first direction is between 5 micrometers and 20 millimeters. The domain surface of each of at least two domains includes a plurality of first regions, each of the plurality of first regions having a locally substantially linear array of threading dislocations at a density between 5 cm -1 and 10 5 cm -1 The domain surface of each of at least two domains further includes a plurality of second regions, each of the plurality of second regions being disposed between adjacent pairs of the plurality of first regions and having a threading dislocation density of less than 10 5 cm -2 and a stacking fault density of less than 10 3 cm -1 The domain surface of each of at least two domains further includes a plurality of third regions, each of the plurality of third regions being disposed between one of the plurality of second regions or adjacent pairs of the second regions, having a minimum dimension between 10 micrometers and 500 micrometers, and having a threading dislocation density between 10 3 cm -2 and 10 8 cm -2 The self - standing group - III metal nitride crystal has a crystallographic misorientation that varies by 0.5 degrees or less in two orthogonal directions over the central 80% of the crystal along a first direction and varies by 0.5 degrees or less in two orthogonal directions over the central 80% of the crystal along a second direction orthogonal to the first direction. At least two domains are separated by dislocation lines having a linear density between about 50 cm -1 and about 5×10 5 cm -1 The polar azimuthal difference angle γ between the first domain and the second domain is greater than about 0.005 degrees and less than about 0.3 degrees, and the azimuthal difference angles α and β are greater than about 0.01 degrees and less than about 1 degree.

[0022] To better understand the above features of the present disclosure, a more detailed description of the present disclosure, briefly summarized above, can be obtained by referring to the embodiments shown in the accompanying drawings, some of which are presented herein. It should be noted, however, that the accompanying drawings show only exemplary embodiments and should not be construed as limiting the scope of the present disclosure, as other equally valid embodiments are possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0023]

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Mode for Carrying Out the Invention

[0024] According to the present disclosure, techniques related to techniques for processing materials for manufacturing group III metal nitride and gallium-based substrates are provided. More specifically, embodiments of the present disclosure include techniques for growing large-area substrates using a combination of processing techniques. In some embodiments of the present disclosure, the large-area substrate is referred to herein as a free-standing group III metal nitride wafer. In addition, in some embodiments, the formed or grown components configured to be further processed to form one or more free-standing group III metal nitride wafers are referred to herein as free-standing group III metal nitride boules. By way of example only, the present disclosure can be applied to the growth of crystals of GaN, AlN, InN, InGaN, AlGaN, and AlInGaN, as well as other crystals for manufacturing bulk substrates or patterned substrates. Such bulk substrates or patterned substrates can be used in a variety of applications including optoelectronic devices, laser diodes, light-emitting diodes, photodiodes, solar cells, photoelectrochemical water splitting and hydrogen generation, photodetectors, integrated circuits, and transistors.

[0025] Threading dislocations in GaN are known to act as strong non-radiative recombination centers, which can significantly limit the efficiency of GaN-based light-emitting diodes (LEDs) and laser diodes. Non-radiative recombination causes local heating, which may lead to accelerated device degradation (Cao et al., Microelectronics Reliability, 2003, 43(12), 1987-1991). In high-power applications, GaN-based devices suffer from a decrease in efficiency with increasing current density, known as droop. There is evidence suggesting a correlation between the dislocation density and the magnitude of droop in LEDs (Schubert et al., Applied Physics Letters, 2007, 91(23), 231114). In the case of GaN-based laser diodes, a negative correlation between the dislocation density and the mean time to failure (MTTF) has been well demonstrated (Tomiya et al., IEEE Journal of Selected Topics in Quantum Electronics, 2004, 10(6), 1277-1286). This is thought to be due to the diffusion of impurities along the dislocations (Orita et al., IEEE International Reliability Physics Symposium Proceedings, 2009, 736-740). In electronic devices, dislocations have been shown to significantly increase the leakage current (Kaun et al., Applied Physics Express, 2011, 4(2), 024101) and shorten the device lifetime of high electron mobility transistor (HEMT) structures (Tapajna et al., Applied Physics Letters, 2011, 99(22), 223501-223503). One of the main advantages of using bulk GaN as a substrate material for epitaxial thin-film growth is a significant reduction in the density of threading dislocations in the film. Therefore, the dislocation density of bulk GaN substrates has a major impact on device efficiency and reliability.

[0026] Lateral epitaxial overgrowth (LEO) is a method widely applied to improve the crystal quality of films grown by vapor-phase methods. For example, a GaN layer is nucleated on a sapphire substrate, a SiO2 mask with a periodic array of openings is deposited on the GaN layer, and then GaN is grown by metalorganic chemical vapor deposition (MOCVD) through the openings of the SiO2 mask layer, grown laterally on the mask, and merged. The dislocation density in the region above the opening of the mask was very high as well as that of the layer under the mask, but the dislocation density in the laterally overgrown region was significantly lower. This method is attractive because it can be applied to large-area substrates and can significantly reduce the dislocation density. Similar methods have been applied to the vapor-phase growth of GaN layers by many groups in various forms. These methods are variously called LEO, epitaxial lateral overgrowth (ELO or ELOG), selective area growth (SAG), and dislocation elimination by epitaxial growth with inverted pyramid-shaped pits (DEEP), etc. In essentially all variations of this method, a thin heteroepitaxial GaN layer is grown on a non-GaN substrate, a patterned mask is deposited on the GaN layer, and growth is resumed in a one-dimensional or two-dimensional array of openings in the mask. The period or pitch of the growth positions defined by the openings of the mask is typically between 2 and 100 micrometers, typically between about 5 and 20 micrometers. Individual GaN crystallites or regions grow and then merge. Then, epitaxial growth can be continued on the merged GaN material to produce a thick film or "ingot". By HVPE, a relatively thick GaN layer can be deposited on the merged GaN material. The LEO process reduces the dislocation concentration, typically to about 10 5 ~10 7 cm -2It can be significantly reduced to a certain level. However, in many cases, the laterally grown wings of the formed LEO layer are crystallographically inclined several degrees from the underlying substrate ( "wing tilt"), which may be acceptable in thin film processes but may not be acceptable in bulk crystal growth processes as it can cause unacceptable stress and cracking, as well as unacceptable variations in surface crystal orientation.

[0027] The average dislocation density can be reduced to about 10 5 ~10 7 cm -2 less, or to reduce the misorientation variation across a 50 or 100 mm wafer to less than about 0.1 degrees, the capabilities of the conventionally applied LEO method are limited by several factors. First, the pitch of the pattern of the openings formed in the mask layer tends to be conservative, but a larger pitch may be desirable for certain applications. Second, c-plane LEO growth is carried out by excluding, in the (0001) or Ga-plane direction, and at least two limitations occur. One limitation is that the growth rate in the M direction tends to be slower than the growth rate in the (0001) direction, and semi-polar (10-11) facets are often formed, resulting in a decrease in the overall crystal diameter with increasing thickness and difficulty in coalescing large pitch patterns. In addition, another limitation is that, in contrast to growth in other crystal directions, growth in the (0001) direction tends to exclude oxygen. As a result, there may be a significant lattice mismatch between the HVPE crystal grown in (0001) used as a seed and the crystal grown on top of it by another technique. In addition, when semi-polar facets are formed during the LEO process, the oxygen (or other dopant) levels vary significantly, causing lateral variations in lattice constant and stress and potentially causing cracking in the LEO crystal itself or the crystal grown on top of the latter used as a seed.

[0028] Regarding III-nitride growth techniques other than HVPE, a modification of the LEO method is disclosed. In a first example, Jiang et al. (U.S. Patent Application Publication No. 2014 / 0147650, now the specification of U.S. Patent No. 9,589,792) disclosed a process for the ammonothermal LEO growth of III-nitride by replacing the mask layer of a typical vapor-phase LEO-type process (SiO2 or SiN x ) with a combination of an adhesion layer, a diffusion barrier layer, and an inert layer. In a second example, Mori et al. (U.S. Patent Application Publication No. 2014 / 0328742, now the specification of U.S. Patent No. 9,834,859) disclosed a process for the LEO growth of III-nitride in a sodium-gallium flux. However, in this method, the coalescing crystallites usually have significant semi-polar facets, resulting in large lateral variations in the impurity content of the coalesced crystal, causing a thermal expansion mismatch between the coalescing nitride layer and a hetero-substrate containing a material different from the coalescing nitride, which may cause uncontrollable cracking.

[0029] Several authors, e.g., Linthicum et al. (Applied Physics Letters, 75, 196, (1999)), Chen et al. (Applied Physics Letters 75, 2062 (1999)), and Wang et al. (U.S. Patent No. 6,500,257), have noted that threading dislocations in GaN growth typically propagate mainly in the growth direction, and that by growing through the sidewalls of trenches in a thin and defect-rich c-plane GaN layer rather than vertically through the window of a patterned mask, the dislocation density can be further reduced compared to the conventional LEO method. These methods have been extended by other authors, e.g., Chen et al. (Japanese Journal of Applied Physics 42, L818 (2003)), and Imer et al. (U.S. Patent No. 7,361,576), to nonpolar and semipolar oriented GaN thin films. However, to the inventors' knowledge, the sidewall LEO method has not yet been extended to the growth of bulk GaN or N-sector GaN. In particular, we have found that the various methods used in thin film research are optimal for forming trenches with a depth of several hundred micrometers at a millimeter-scale pitch and produce several unexpected advantages.

[0030] Figures 1A - 1T are schematic cross - sectional views of a seed crystal or substrate at various stages of a method for forming a patterned mask seed layer for ammonothermal sidewall lateral epitaxial overgrowth. Referring to Figure 1A, a photoresist layer 103 is disposed on a substrate 101. The substrate 101 and the subsequently formed layers described with respect to Figures 1A - 1T can be used in subsequent tiling operations as further described with respect to Figures 2A - 2C, Figures 3A - 3E, and Figures 17A - 22F. In certain embodiments, some of the layer - forming process steps described in connection with Figures 1A - 1T are carried out subsequent to some of the process steps of the tiling operation, as further described, for example, in connection with Figures 17A - F. In certain embodiments, the substrate 101 consists of or includes a substrate material that is a single - crystal group III metal nitride, a gallium - containing nitride, or gallium nitride. The substrate 101 can be grown by HVPE, ammonothermally, or by the flux method. One or both of the large - area surfaces of the substrate 101 may be polished and / or chemically - mechanically polished. The large - area surface 102 of the substrate 101 can have a crystal orientation within 5 degrees, within 2 degrees, within 1 degree, or within 0.5 degrees of the (0001)+c plane, (000 - 1)-c plane, {10 - 10}m plane, {11 - 2±2}, {60 - 6±1}, {50 - 5±1}, {40 - 4±1}, {30 - 3±1}, {50 - 5±2}, {70 - 7±3}, {20 - 2±1}, {30 - 3±2}, {40 - 4±3}, {50 - 5±4}, {10 - 1±1}, {10 - 1±2}, {10 - 1±3}, {21 - 3±1}, or {30 - 3±4}. It will be understood that the plane {30 - 3±4} means the {30 - 34} plane and the {30 - 3 - 4} plane. The large - area surface 102 can have a (hkil) semi - polar orientation, where i =-(h + k) and l, and at least one of h and k is non - zero. The large - area surface 102 can have a maximum lateral dimension between about 5 millimeters and about 600 millimeters and a minimum lateral dimension between about 1 millimeter and about 600 millimeters, and the substrate 101 can have a thickness between about 10 micrometers and about 10 millimeters, or between about 100 micrometers and about 2 millimeters.

[0031] The substrate 101 may have a surface penetration dislocation density of less than about 10 7 cm -2 less than, less than about 10 6 cm -2 less than, less than about 10 5 cm -2 less than, less than about 10 4 cm -2 less than, less than about 10 3 cm -2 less than, or less than about 10 2 cm -2 less than. The substrate 101 may have a stacking defect concentration of less than about 10 4 cm -1 less than, less than about 10 3 cm -1 less than, less than about 10 2 cm -1 less than, less than about 10 cm -1 less than or less than about 1 cm -1 less than. The substrate 101 may have a symmetric X-ray rocking curve (e.g., (002) for the c-plane) full width at half maximum (FWHM) of less than about 500 arcseconds, less than about 300 arcseconds, less than about 200 arcseconds, less than about 100 arcseconds, less than about 50 arcseconds, less than about 35 arcseconds, less than about 25 arcseconds, or less than about 15 arcseconds. The substrate 101 may have an asymmetric X-ray rocking curve (e.g., (201) for the c-plane) full width at half maximum (FWHM) of less than about 500 arcseconds, less than about 300 arcseconds, less than about 200 arcseconds, less than about 100 arcseconds, less than about 50 arcseconds, less than about 35 arcseconds, less than about 25 arcseconds, or less than about 15 arcseconds. The substrate 101 may have a crystal curvature radius of greater than 0.1 meter, greater than 1 meter, greater than 10 meters, greater than 100 meters, or greater than 1000 meters in at least one, at least two, or three independent or orthogonal directions.

[0032] The substrate 101 may include regions having a relatively high concentration of through dislocations separated by regions having a relatively low concentration of through dislocations. The concentration of through dislocations in the relatively high concentration regions is greater than about 10 5 cm -2 greater than, greater than about 10 6 cm -2 greater than, greater than about 10 7 cm -2 greater than, or greater than about 10 8 cm-2 can be super. The concentration of through dislocations in the relatively low concentration region can be about 10 6 cm -2 less than, about 10 5 cm -2 less than, or about 10 4 cm -2 less than. The substrate 101 can include regions having relatively high electrical conductivity separated by regions having relatively low electrical conductivity. The substrate 101 can have a thickness between about 10 micrometers and about 100 millimeters, or between about 0.1 millimeter and about 10 millimeters. The substrate 101 can have a maximum dimension (including diameter) of at least about 5 millimeters, at least about 10 millimeters, at least about 25 millimeters, at least about 50 millimeters, at least about 75 millimeters, at least about 100 millimeters, at least about 150 millimeters, at least about 200 millimeters, at least about 300 millimeters, at least about 400 millimeters, or at least about 600 millimeters.

[0033] The large area surface 102 (FIG. 1A) can have a crystal orientation within about 5 degrees of the (000-1)N plane, c-plane orientation, and can have an X-ray diffraction ω-scan rocking curve full width at half maximum (FWHM) of less than about 200 arcseconds, less than about 100 arcseconds, less than about 50 arcseconds, or less than about 30 arcseconds for the (002) and / or (102) and / or (201) reflections, and about 10 7 cm -2 less than, about 10 6 cm -2 less than, about 10 5 cm -2 less than, or about 10 4 cm -2It is possible to have an average dislocation density below. In some embodiments, the threading dislocations on the large area surface 102 are distributed substantially uniformly. In other embodiments, the threading dislocations on the large area surface 102 are non-uniformly arranged as a one-dimensional array of rows of relatively high and relatively low concentration regions or as a two-dimensional array of high dislocation density regions within a matrix of low dislocation density regions. The crystal orientation of the large area surface 102 can be constant at less than about 1 degree, less than about 0.5 degree, less than about 0.2 degree, less than about 0.1 degree, or less than about 0.05 degree, less than about 0.02 degree, or less than about 0.01 degree. In certain embodiments, the large area surface 102 is roughened, for example, by wet etching to enhance the adhesion of the mask layer and form a matte finish.

[0034] Referring again to FIG. 1A, the photoresist layer 103 can be deposited on the large area surface 102 by methods known in the art. For example, in certain embodiments of the lift-off process, a solution of negative photoresist is first applied to the large area surface 102. Next, the substrate 101 is rotated at high speed (e.g., between 1000 and 6000 revolutions per minute for 30 to 60 seconds) to produce a uniform photoresist layer 103 on the large area surface 102. The photoresist layer 103 can be baked (e.g., between about 90 and about 120 degrees Celsius) to remove excess photoresist solvent. After baking, the photoresist layer 103 is then exposed to UV light through a photomask (not shown) to form a patterned photoresist layer 104 (FIG. 1B) having a predetermined pattern of cross-linked photoresist, such as region 104A, formed within the unexposed region 104B. The regions 104B of the patterned photoresist can form stripes or dots having a characteristic width or diameter W and pitch L. Next, the patterned photoresist layer 104 can be developed to remove the non-cross-linked material seen in region 104B, leaving region 104A as shown in FIG. 1C.

[0035] Referring to FIG. 1D, one or more patterned mask layers 111 may be deposited on the large area surface 102 and on the region 104A of the patterned photoresist layer 104. The one or more patterned mask layers 111 may include an adhesion layer 105 deposited on the large area surface 102, a diffusion barrier layer 107 deposited on the adhesion layer 105, and an inert layer 109 deposited on the diffusion barrier layer 107. The adhesion layer 105 may include one or more of Ti, TiN, TiN y TiSi2, Ta, TaN y Al, Ge, Al x Ge y Cu, Si, Cr, V, Ni, W, TiW x TiW x N y etc., and may have a thickness between about 1 nanometer and about 1 micrometer. The diffusion barrier layer 107 may include TiN, TiN y TiSi2, W, TiW x TiN y WN y TaN y TiW x N y TiW x Si z N yIt may contain one or more of TiC, TiCN, Pd, Rh, Cr, etc., and has a thickness between about 1 nanometer and about 10 micrometers. The inert layer 109 may contain one or more of Au, Ag, Pt, Pd, Rh, Ru, Ir, Ni, Cr, V, Ti, or Ta, and may have a thickness between about 10 nanometers and about 100 micrometers. One or more patterned mask layers 111 can be deposited by sputter deposition, thermal evaporation, electron beam evaporation, etc. After the deposition of the (one or more) patterned mask layers 111, as shown in FIG. 1D, the portion of the (one or more) patterned mask layers 111 present on the region 104A of the patterned photoresist layer 104 does not directly contact the substrate 101. Next, as shown in FIG. 1E, the region 104A and the portion of the (one or more) patterned mask layers 111 disposed thereon are lifted off by a method known in the art to form openings 112 in the (one or more) patterned mask layers 111. In certain embodiments, a relatively thin inert layer, for example, having a thickness of 10 to 500 nanometers, is deposited before the lift-off process. After the lift-off process is carried out, an additional thicker inert layer, for example, having a thickness of 5 to 100 micrometers, can be deposited on the already patterned inert layer by electroplating, electroless deposition, etc.

[0036] The patterned mask layer 111 can be formed using other methods other than the above lift-off procedure, including shadow masking, positive resist reactive ion etching, wet chemical etching, ion milling, and nanoimprint lithography, and variations of the above negative resist lift-off procedure.

[0037] In certain embodiments, the (one or more) patterned mask layers 111 are deposited on both the front and back surfaces of the substrate 101.

[0038] Figures 1F - 1L are top views of the arrangement of the exposed regions 120 on the substrate 101 formed by one or more of the above - described processes. For example, the exposed regions 120 (or also referred to herein as growth centers) shown in Figures 1F - 1L can be defined by the openings 112 formed in the (one or more) patterned mask layer 111 shown in Figure 1E. In certain embodiments, the exposed regions 120 are arranged in a one - dimensional (1D) array in the y - direction, such as a single row of exposed regions 120 as shown in Figure 1I. In certain embodiments, the exposed regions 120 are arranged in a two - dimensional (2D) array in the x and y directions, as shown in Figures 1F - 1H and Figures 1J - 1L. The openings 112, and thus the exposed regions 120, can be circular, square, rectangular, triangular, hexagonal, etc., and can have an opening dimension or diameter W between about 1 micrometer and about 5 millimeters, or between about 10 micrometers and about 500 micrometers, as shown in Figures 1F - 1L. The exposed regions 120 can be arranged in a 2D hexagonal or square array having a pitch dimension L between about 5 micrometers and about 20 millimeters, between about 200 micrometers and about 15 millimeters, or between about 500 micrometers and about 10 millimeters, or between about 0.8 millimeters and about 5 millimeters, as shown in Figures 1F and 1G. The exposed regions 120 can be arranged in a 2D array, and as shown in Figures 1H and 1J - 1L, the pitch dimension L1 in the y - direction and the pitch dimension L2 in the x - direction may be different from each other. The exposed regions 120 can be arranged in an array of rectangles, parallelograms, hexagons, or trapezoids (not shown), and as shown in Figures 1H and 1J - 1L, the pitch dimension L1 in the y - direction and L2 in the x - direction may be different from each other. The array of exposed regions 120 can be linear or irregular in shape. The exposed regions 120 of the (one or more) patterned mask layer 111 can be arranged in alignment with the structure of the substrate 101.For example, in certain embodiments, the large area surface 102 is hexagonal, e.g., in the (0001) or (000-1) crystal orientation, and the openings of the (one or more) patterned mask layer 111 include a 2D hexagonal array such that the separation between the closest adjacent openings is parallel to the <11-20> or <10-10> direction of the large area surface 102. In certain embodiments, the large area surface 102 of the substrate is non-polar or semi-polar, and the exposed regions 120 include a 2D square or rectangular array such that the separation between the closest adjacent openings is parallel to the projection of two of the c-axis, m-axis, and a-axis on the large area surface 102 of the substrate 101. In certain embodiments, the pattern of the exposed regions 120 is oriented obliquely with respect to the structure of the substrate 101. For example, the exposed regions 120 are rotated between about 1 degree and about 44 degrees with respect to the high symmetry axes of the substrate, such as the projection of the c-axis, m-axis, and a-axis on the large area surface 102 of the substrate 101 having a hexagonal crystal structure such as a wurtzite crystal structure. In certain embodiments, the exposed regions 120 are substantially linear rather than substantially circular. In certain embodiments, the exposed regions 120 are slits having a width W and a period L that extend across the entire length of the substrate 101 as shown in FIG. 1I. In certain embodiments, the exposed regions 120 are slits having a width W1 in the y direction and a predetermined length W2 in the x direction that is shorter than the length of the substrate 101, and can be arranged in a 2D linear array having a period L1 in the y direction and a period L2 in the x direction as shown in FIGS. 1J-1L. In some embodiments, adjacent rows of the exposed regions 120 (e.g., slits) may be offset from each other in the x direction rather than being arranged directly adjacent to each other as shown in FIG. 1K. In certain embodiments, adjacent rows of the exposed regions 120 (e.g., slits) may be offset from each other in the longitudinal y direction. In certain embodiments, the exposed regions 120 include slits that extend in two or more different directions, such as in the x direction and the y direction as shown in FIG. 1L. In certain embodiments, the exposed regions 120 (e.g., slits) can be arranged to reflect the hexagonal symmetry of the substrate. In certain embodiments, the exposed regions 120 (e.g., slits) can extend to the edge of the substrate 101.

[0039] In certain embodiments, the pattern of the openings terminates at a distance from the edge of the substrate, for example, between 10 micrometers and 5 millimeters, between 20 micrometers and 2 millimeters, between 50 micrometers and 1 millimeter, or between 100 micrometers and 500 micrometers. The termination of the (one or more) patterns forms a rim surrounding the edge of the substrate. The rim can have a width equal to the predetermined distance, which can be used, for example, to improve the integrity and robustness of the edge of the patterned mask layer. Not only the edge of the substrate, but also the rim may be covered by the patterned mask layer 111.

[0040] In an alternative embodiment, as shown in FIG. 1M, the large area surface 102 of the substrate 101 is covered with a blanket mask 116 that includes one, two, or more of an adhesive layer 105, a diffusion barrier layer 107, and an inert layer 109, followed by a positive photoresist layer 113. The photoresist layer is exposed to UV light through a photomask (not shown) to form soluble exposed regions 106B and unexposed regions 106A, as shown in FIG. 1N (basically, a negative pattern as shown in FIG. 1B). Next, the exposed regions 106B are removed by development. As shown in FIG. 1O, the openings 112 of the blanket mask 116 (including the adhesive layer 105, the diffusion barrier layer 107, and the inert layer 109) are formed by wet etching or dry etching through the openings of the patterned photoresist layer 113A to form a patterned mask layer 111. After the formation of the openings 112, the photoresist layer 113 is removed, and a structure similar or identical to the structure shown in FIG. 1E is generated, as shown in FIG. 1P.

[0041] Next, as shown in FIG. 1Q, trenches 115 are formed in the exposed area 120 of the substrate 101 through the openings 112 (or "windows") formed in the patterned mask layer 111. In certain embodiments, the depth of the trenches 115 is between 50 micrometers and about 1 millimeter, or between about 100 micrometers and about 300 micrometers. In certain embodiments, the trenches 115 penetrate through the entire thickness of the substrate 101, forming a patterned hole or slit that extends from the back side 118 of the substrate 101 through the opening 112 of the patterned mask layer 111. The width of the individual trenches can be between about 10 micrometers and about 500 micrometers, or between about 20 micrometers and about 200 micrometers. The individual trenches 115 can be linear or curved and can have a length between about 100 micrometers and about 50 millimeters, or between about 200 micrometers and about 10 millimeters, or between about 500 micrometers and about 5 millimeters in the X direction and / or Y direction. In a particular embodiment, the large surface 102 of the substrate 101 has a (000-1)N plane orientation and the trenches 115 are formed by wet etching. In a particular embodiment, the etchant composition or solution comprises a solution of 85% phosphoric acid (H3PO4) and sulfuric acid (H2SO4) with an H2SO4 / H3PO4 ratio between 0 and about 1:1. In certain embodiments, the phosphoric acid solution is adjusted to form polyphosphoric acid, which raises its boiling point. For example, reagent grade (85%) H3PO4 can be adjusted by stirring and heating at a temperature between about 200 degrees Celsius and about 450 degrees Celsius in a beaker for about 5 minutes to about 5 hours. In certain embodiments, the trenches 115 are formed by heating the masked substrate 101 in one of the aforementioned etching solutions at a temperature between about 200 degrees Celsius and about 350 degrees Celsius for about 15 minutes to about 6 hours. In another embodiment, the trenches 115 are formed by electrochemical wet etching.

[0042] Figures 1R - 1T illustrate alternative techniques for forming an array of patterned and masked trenches in substrate 101. As shown in Figure 1R, a blanket mask 116 (including an adhesive layer 105, a diffusion barrier layer 107, and an inert layer 109) can be deposited on the large - area surface 102 of substrate 101. To form the patterned mask layer 111, as shown in Figure 1S, incipient trenches 114 can be formed by laser ablation. The laser ablation process is also known as, or referred to as, a laser processing process or a laser beam processing process. Laser ablation can be performed with a watt - level laser such as a neodymium - doped yttrium - aluminum - garnet (Nd:YAG) laser, a CO2 laser, an excimer laser, a Ti:sapphire laser, etc. The laser can emit pulses having a pulse length in the range of nanoseconds, picoseconds, or femtoseconds. In certain embodiments, the frequency of the output light of the laser can be doubled, tripled, or quadrupled using appropriate nonlinear optics. The beam width, output, and scan speed of the laser on the surface of substrate 101 having the patterned mask layer 111 can be varied to adjust the width, depth, and aspect ratio of the incipient trenches 114. The laser can scan repeatedly over a single trench or over the entire array of trenches.

[0043] The surface and sidewalls of the trench 114 in the as-formed state may contain damage remaining from the laser ablation process. In certain embodiments, the substrate 101 including the trench 114 in the as-formed state is further processed by wet etching, dry etching, or photoelectrochemical etching to remove residual damage within the trench 114 in the as-formed state, as shown in FIG. 1T. In certain embodiments, the large area surface 102 of the substrate 101 has a (000-1)N plane orientation, and the trench 115 is formed from the trench 114 in the as-formed state by wet etching. In certain embodiments, the etchant composition or solution includes a solution of 85% phosphoric acid (H3PO4) and sulfuric acid (H2SO4) with an H2SO4 / H3PO4 ratio between 0 and about 1:1. In certain embodiments, the phosphoric acid solution is adjusted to form polyphosphoric acid, and its boiling point increases. For example, reagent grade (85%) H3PO4 can be adjusted by stirring and heating at a temperature between about 200° C. and about 450° C. in a beaker for about 5 minutes to about 5 hours. In certain embodiments, the trench 115 is formed by heating the substrate 101 in one of the above-described etching solutions at a temperature between about 200° C. and about 350° C. for about 15 minutes to about 6 hours.

[0044] After performing one or more of the above-described processes on the substrate 101, the crystal growth process can be simultaneously performed on a single substrate 101 or an array of substrates 101. The single substrate 101 or the array of substrates 101 each act as one or more seed crystals during the crystal growth process. FIGS. 17A-17F show some examples of various arrays of seed crystals 370, such as the substrate 101, that can be used during the crystal growth process. Referring to FIGS. 17A-17F, at least some of the edges 395 of two or more seed crystals 370 are prepared for tessellation to form a one-dimensional or two-dimensional array of tile crystals. Each of the seed crystals 370 can be prepared in a square (FIG. 17A), rectangular (FIG. 17B), hexagonal (FIG. 17C), a mixture of rhombus and triangle (FIG. 17D), a mixture of hexagon and pentagon (FIG. 17E), a mixture of hexagon and rhombus (FIG. 17F), or other shapes, or combinations thereof. When the surface 102 has a non-polar or semi-polar orientation, a square or rectangle may be preferred. When the surface 102 has a (000±1)c-plane orientation, a hexagonal, rhombic, triangular, rhombohedral, pentagonal, or trapezoidal shape may be preferred. Triangular, quadrilateral, or pentagonal shapes can serve to define the outer perimeter of the array of seed crystals. In certain embodiments, a portion or all of the edges 395 of the seed crystal 370 are such that the intersection of the edge and the large area surface 102 is within 0.5 degrees, 0.2 degrees, 0.1 degrees, 0.05 degrees, 0.02 degrees, or 0.01 degrees parallel to a plane defined by a plane selected from the {11-20}a-plane, (000±1)c-plane, {10-10}m-plane, {10-1±1}, or a plane perpendicular to the large area surface 102 and an axis selected from the c-axis, m-axis, or a-axis. In certain embodiments, the edge 395 is prepared with a root mean square surface roughness of less than 10 micrometers, less than 5 micrometers, less than 2 micrometers, or less than 1 micrometer. In certain embodiments, the edge 395 is prepared prior to pattern deposition and patterning as described above and in FIGS. 1A-1T such that the patterned mask layer 111 extends from the large area surface 102 over at least a portion of the edge. In certain embodiments, the edge 395 is prepared by at least one of a dicing saw, a wire saw, and a laser.In certain embodiments, the edge 395 also includes an orientation flat, such as a notch angle or an orientation groove, to simplify the tracking of the crystal orientations of the various crystals 370.

[0045] In certain embodiments, many, most, or all of the seed crystals 370 positioned in the array are prepared to have exactly the same size and shape. For example, the X-direction dimension 380 of each of the nominally identical seed crystals 370 within the array can be equal within 0.5 millimeters, 0.2 millimeters, 0.1 millimeters, 50 micrometers, 20 micrometers, 10 micrometers, 5 micrometers, 2 micrometers, or 1 micrometer. In certain embodiments, the X-direction dimension 380 is between 4 millimeters and 10 millimeters, between 10 millimeters and 15 millimeters, between 15 millimeters and 25 millimeters, between 25 millimeters and 50 millimeters, between 50 millimeters and 100 millimeters, or between 100 millimeters and 150 millimeters. Similarly, the Y-direction dimension 390 of each of the nominally identical seed crystals within the array can be equal within 0.5 millimeters, 0.2 millimeters, 0.1 millimeters, 50 micrometers, 20 micrometers, 10 micrometers, 5 micrometers, 2 micrometers, or 1 micrometer. Similarly, the Y-direction dimension 390 of each of the nominally identical seed crystals within the array can be equal within 0.5 millimeters, 0.2 millimeters, 0.1 millimeters, 50 micrometers, 20 micrometers, 10 micrometers, 5 micrometers, 2 micrometers, or 1 micrometer. In certain embodiments, the Y-direction dimension 390 is between 8 millimeters and 10 millimeters, between 10 millimeters and 15 millimeters, between 15 millimeters and 25 millimeters, between 25 millimeters and 50 millimeters, between 50 millimeters and 100 millimeters, or between 100 millimeters and 150 millimeters. In certain embodiments, a portion of the edge 395, specifically, the outer edge of the array of seed crystals, can be cut to have a circular or elliptical cross-section rather than a straight line in order to allow for a curved, or substantially circular or elliptical perimeter of the array of seed crystals 370, as shown in FIG. 19G.In certain embodiments, the starting point of the seed crystal 370 is a wafer having a mostly circular perimeter, with a portion of the original edge retained while the other edges are prepared as described above for tessellation.

[0046] In certain embodiments, the back surface of one or more seed crystals, and optionally one or more edges and / or front surfaces, are coated with a mechanically compliant coating or interface layer 1921 (FIG. 19E), which is configured to accommodate extrinsic or intrinsic stresses formed between the seed crystal 370 and a deposited layer or structure thereon without either the seed crystal 370 or the deposited layer or structure suffering from cracks or other defects. The mechanically compliant coating can include or be composed of one or more of graphite, pyrolytic graphite, boron nitride, pyrolytic boron nitride, molybdenum disulfide, and tungsten disulfide. In certain embodiments, the mechanically compliant coating is deposited by at least one of sputtering, chemical vapor deposition, plasma enhanced chemical vapor deposition, high density plasma enhanced chemical vapor deposition, and electron beam evaporation. In certain embodiments, the mechanically compliant coating is not completely dense and is deposited by one or more of spraying of particles suspended in a slurry, screen printing of particles suspended in a slurry, painting of particles suspended in a slurry, plasma spraying, etc. In certain embodiments, the mechanically compliant coating is subjected to a heat treatment process in which the particles within the mechanically compliant coating are partially or fully sintered.

[0047] In some embodiments, the thickness of each of the seed crystals 370 is equal to within 50 micrometers, within 25 micrometers, within 10 micrometers (μm), within 5 micrometers, within 2 micrometers, or within 1 micrometer. In certain embodiments, the uniform seed thickness improves the mechanical integrity of the clamped array of seed crystals. In certain embodiments, the uniform seed thickness enhances the coplanarity of the upper surface of the seed crystals. In certain embodiments, the uniform seed thickness can improve both the mechanical integrity and the thermal uniformity of the composite structure being manufactured. Each crystallographic misorientation of the large area surface 102 of the seed crystal 370 has a magnitude and a direction 397. For example, if a particular c-plane seed crystal is misoriented 0.50 degrees in the m direction and 0.06 degrees in the orthogonal a direction, the magnitude of the misorientation is approximately 0.504 degrees and the direction is 6.8 degrees away from a particular m direction. In some embodiments, the magnitude of each of the crystallographic misorientations of the seed crystal 370 is equal to within 0.2 degrees, within 0.1 degrees, within 0.05 degrees, within 0.02 degrees, or within 0.01 degrees. In some embodiments, the direction 397 of each of the crystallographic misorientations of the seed crystal is aligned within 10 degrees, within 5 degrees, within 2 degrees, within 1 degree, within 0.5 degrees, within 0.2 degrees, or within 0.1 degrees.

[0048] In certain embodiments, the array of seed crystals 370 is disposed within a mechanical fixture, as schematically shown in FIGS. 18A - 18D. This embodiment may be suitable when the number of seed crystals is small or when each seed crystal in the array of seed crystals can be held in place by clamping a portion around each seed crystal. For example, this technique can be used for the seed crystal arrays shown in FIGS. 17E and 17F, but cannot be used for the seed crystal arrays shown in FIGS. 17A - D. The seed crystals 370 can be disposed on a backing plate 1810 (FIG. 18A), a retaining ring 1830 (FIG. 18B) can be disposed around the array of seed crystals 370, and a clamping ring 1840 (FIG. 18C) can be disposed on top of the retaining ring 1830. Each of the backing plate 1810, the retaining ring 1830, and the clamping ring 1840 can have three or more through - holes 1820, 1825 for attachment by a set of fasteners such as screws, bolts, or threaded rods. In certain embodiments, the through - holes 1820 are tapped, while the through - holes 1825 are drilled. In a preferred embodiment, each of the backing plate 1810, the retaining ring 1830, and the clamping ring 1840 is made of a material having a coefficient of thermal expansion (CTE) slightly less than that of the seed crystal 370, such as molybdenum. In certain embodiments, the through - holes 1820 are located around the seed crystal 370. In certain embodiments, at least one seed crystal 370 has a through - hole aligned with at least one of the through - holes 1820 or 1825 in the backing plate 1810 passing through it. In certain embodiments, one or more of the backing plate 1810, the retaining ring 1830, and the clamping ring 1840 are coated with a release coating to easily remove the fused crystals from the fixture components. In certain embodiments, the release coating inhibits the deposition or adhesion of GaN on the mechanical parts. In certain embodiments, the release coating provides mechanical compliance between the seed crystal and the fixture components and adapts to stresses due to residual CTE mismatches without cracking or defects.The release coating can include or be composed of one or more of graphite, boron nitride, molybdenum disulfide, or tungsten disulfide. In certain embodiments, the release coating is not completely dense and is deposited by one or more of spraying particles suspended in a slurry, screen printing particles suspended in a slurry, painting particles suspended in a slurry, etc.

[0049] In some embodiments, molybdenum (Mo) is known to have a CTE of about 5.8×10 -6 / K when averaged over a temperature range from 20 degrees Celsius to 1000 degrees Celsius. Thus, it is desirable to form at least a part of the mechanical fixture from molybdenum (Mo). In some embodiments, the alloy of Mo is selected such that its recrystallization temperature exceeds the highest temperature that the mechanical fixture reaches during the crystal growth process. Exceeding the recrystallization temperature during processing can cause grain growth in the Mo substrate, change the stress state of the material, and potentially lead to embrittlement of the material after subsequent cooling. When Mo is doped with titanium and zirconium to produce what is commercially called a titanium-zirconium-molybdenum (TZM) alloy, it is known that the recrystallization temperature increases to a range of 1200 degrees Celsius to 1400 degrees Celsius compared to Mo, which is 200 degrees Celsius to 300 degrees Celsius higher than the recrystallization temperature of elemental Mo and 100 degrees Celsius to 600 degrees Celsius higher than the epitaxial growth temperature. TZM is a dilute alloy of Mo (more than 98%, preferably at least 99%), Ti (between 0.2% and 1.0%), Zr (between 0% and 0.3%), and C (between 0% and 0.1%). Other alloys are possible. For example, the CTE of an alloy of MoW can be designed to fall within a range of 4.9×10 -6 / K to 5.8×10 -6 / K when averaged over a temperature range from 20 degrees Celsius to 1000 degrees Celsius. The CTE of the mechanical fixture constituent material can be designed to be between 80% and 99%, between 85% and 98%, between 90% and 97%, or between 94% and 96% of the CTE of the crystal in the plane of the first surface.

[0050] The flatness of the mechanical fixture components shall be such that the amount of warpage over their entire diameter shall not exceed 0.1% of their diameter, preferably not exceed 0.02% of their diameter. Warpage is defined herein as the sum of the positive maximum deviation and the negative maximum deviation of the upper surface of the fixture component from a virtual plane, where this imaginary plane intersects the upper surface of the fixture component and is selected to be the plane that minimizes the magnitude of the warpage.

[0051] The clearance between the retainer ring and the array of seed crystals 370 can be selected such that the clearance shrinks to substantially zero at a predetermined temperature used for bulk crystal growth, and each of the seed crystals 370 is positioned such that there is little or no gap between adjacent edges of adjacent crystals, ensuring accurate crystallographic alignment of the seed crystals 370. In one example, the gap 1711 (FIGS. 17A - 17F) between adjacent edges of the seed crystals 370 is between zero and 200 micrometers, between 0.1 micrometer and 50 micrometers, or between 0.2 micrometer and 50 micrometers. In certain embodiments, each of the backing plate 1810, the retainer ring 1830, and the clamping ring 1840 is made of molybdenum, or a molybdenum alloy, such as MoW or TZM, or silver-coated or silver-coated Mo, W, or Ni, etc. In certain embodiments, the material used to prepare at least one of the backing plate 1810, the retainer ring 1830, and the clamping ring 1840 is annealed to remove residual stress before machining. In certain embodiments, a mesa structure is incorporated into the backing plate 1810 at the intersection of two, three, or more seed crystals. In certain embodiments, the top of the mesa is ground to be precisely flat and coplanar so as to improve the alignment accuracy or planarity of the surface of the seed crystal 370 parallel to the plane or coplanar plane of the mesa. In certain embodiments, additional components are incorporated into mechanical fixtures such as spacer pads or springs. The additional components can be manufactured from materials compatible with an ammonothermal crystal growth environment, such as at least one of molybdenum, tungsten, tantalum, niobium, silver, gold, platinum, or iridium.

[0052] After assembling an array of seed crystals within the fixture, the fixture can be secured together using at least three screws, bolts, threaded rods and nuts, or similar fasteners 1855 to form a tiled array 1860 (FIG. 18D).

[0053] The mechanical fixture is designed and manufactured in such a manner that the crystal orientations between each of the group-III nitride crystals positioned on or within the fixture are substantially the same. Referring again to FIG. 18D, the first coordinate system 1821 (x1y1z1) represents the crystal orientation of the first group-III nitride crystal 1801, where z1 is the negative surface normal of the nominal orientation of the surface 1811 of the first group-III nitride crystal 1801, and x1 and y1 are vectors orthogonal to z1. For example, if the surface 1801 has a (0001) orientation, z1 is the unit vector along [000-1], and x1 and y1 can be selected along [10-10] and [1-210], respectively. If the surface 1811 has a (10-10) orientation, z1 is the unit vector along [-1010], and x1 and y1 can be selected along [1-210] and

[0001] , respectively. Similarly, the second coordinate system 1822 (x2y2z2) represents the crystal orientation of the second nitride crystal 1802, where z2 is the negative surface normal of the nominal orientation of the surface 1812 of the second nitride crystal 1802, and x2 and y2 are vectors orthogonal to z2, and the same rules as for (x1y1z1) are applied to the crystallographic directions corresponding to (x2y2z2). The crystal orientation difference between the surface of the first nitride crystal and the surface of the second nitride crystal can be specified by three angles α, β, and γ, where α is the angle between x1 and x2, β is the angle between y1 and y2, and γ is the angle between z1 and z2. Since the surface orientations of the first and second nitride crystals are substantially the same, the polar orientation difference angle γ is very small, for example, less than 0.5 degrees, less than 0.2 degrees, less than 0.15 degrees, less than 0.1 degrees, less than 0.05 degrees, less than 0.02 degrees, or less than 0.01 degrees. Due to the precise control of the orientation of the nitride crystals during placement, the orientation difference angles α and β are also very small, for example, less than 1 degree, less than 0.5 degrees, less than 0.2 degrees, less than 0.1 degrees, less than 0.05 degrees, less than 0.02 degrees, or less than 0.01 degrees. Typically, γ is less than or equal to α and β. The crystal orientation differences between additional adjacent nitride crystals are similarly very small.However, the crystallographic misorientation angles α, β, and γ may be detectable by x-ray measurement and may be greater than about 0.005 degrees, greater than about 0.01 degrees, greater than about 0.02 degrees, greater than about 0.05 degrees, greater than about 0.1 degrees, or greater than about 0.2 degrees.

[0054] In the above-described embodiments, the mechanical fixture that supports the array of seed crystals may have a CTE that is similar to, but slightly less than, the CTE of those seed crystals. In another embodiment, a polycrystalline group III nitride-containing support structure is used in place of the molybdenum material of the mechanical fixture. The polycrystalline group III nitride may be textured or highly textured. Since the CTE of GaN differs by about 12% between the a-axis and the c-axis, for example, polycrystalline GaN does not have a CTE that exactly matches that of a single-crystalline GaN seed crystal. However, the mismatch is small, and the temperature dependencies of the CTEs in the a-axis and c-axis directions are similar. In addition, to the extent that the polycrystalline GaN material is highly textured in the c-axis direction, its lateral CTE becomes very close to the CTE of single-crystalline GaN in the a-axis direction. Exemplary methods for manufacturing textured polycrystalline group III metal nitrides are described in the specifications of U.S. Patent Nos. 8,039,41, 8,461,071, U.S. Reissue Patent 47114, U.S. Patent Nos. 10,094,017, and 10,619,239, each of which is incorporated herein by reference.

[0055] In certain embodiments, used to support the array of seed crystals 370 during processing, the array of seed crystals 370 is disposed on the support surface 1915 of the susceptor 1910, as shown in FIG. 19A. This embodiment may be suitable for each of the seed arrays schematically shown in FIGS. 17A - F. In some embodiments, spacers (not shown) of a desired size are disposed between adjacent edges of each of the seed crystals 370 so that a defined regular spacing can be maintained in at least one direction, such as the X direction, or the X and Y directions. The spacers can include machined blocks or wires of a desired diameter. The spacing between adjacent edges of each of the seed crystals 370 can be set so that the spacing is less than 2 millimeters (mm), such as between 0.1 micrometer (μm) and 1 millimeter (mm), or between 0.1 micrometer and 200 micrometers, between 0.1 micrometer and 50 micrometers, or between 0.2 micrometer and 50 micrometers.

[0056] The susceptor 1910 can include or be composed of one or more of SiO2, graphite, pyrolytic boron nitride (PBN), SiC-coated graphite, PBN-coated graphite, TaC-coated graphite, molybdenum, or a molybdenum alloy. In certain embodiments, the surface 1915 of the susceptor 1910 facing the one or more seed crystals can be coated with a release coating 1923. The release coating 1923 can include or be composed of one or more of graphite, boron nitride, molybdenum disulfide, or tungsten disulfide. In certain embodiments, the release coating 1923 is not completely dense and is deposited by one or more of spraying particles suspended in a slurry, screen printing particles suspended in a slurry, painting particles suspended in a slurry, etc. In certain embodiments, the array of seed crystals 370 is surrounded by a retainer ring 1930 disposed on the support surface 1915. In certain embodiments, the retainer ring 1930 can include or be composed of a material having a coefficient of thermal expansion (CTE) slightly less than that of GaN, such as, for example, molybdenum or a molybdenum alloy. In certain embodiments, the susceptor 1910 is machined to have a hollow region formed in the shape of the seed crystal 370 or a depression formed in the support surface 1915 to facilitate accurate alignment of the seed crystal and the crystal plane formed thereon. In certain embodiments, the retainer ring 1930 can include or be composed of wires. In certain embodiments, the large-area surfaces of one or more seed crystals having a mechanically compliant coating (e.g., the interface layer 1921 in FIG. 19E) formed therebetween are disposed in contact with the support surface 1915 of the susceptor 1910. In certain embodiments, the large-area surfaces of one or more seed crystals having a mechanically compliant coating (e.g., the interface layer 1921) are positioned on the side opposite the support surface 1915 of the susceptor 1910.The mechanically compliant coating is used to reduce some of the extrinsic and intrinsic stresses that form between the (one or more) seed crystals 370 and the susceptor 1910 and / or between the (one or more) seed crystals 370 and the porous member 1940 and / or the polycrystalline GaN layer 1950 disposed on the opposite side (these are discussed below).

[0057] In certain embodiments, the porous member 1940 is disposed over one or more of the seed crystals 370 and is configured to minimize the extrinsic stress induced in the seed crystals 370 due to the CTE mismatch that occurs between the seed crystals 370 and the porous member 1940. The porous member 1940 is also useful for reducing the stress induced in the seed crystals 370 due to the CTE mismatch that occurs between the seed crystals 370 and the polycrystalline GaN layer 1950 formed thereon and subsequently deposited thereon. In certain embodiments, the porous member 1940 has a honeycomb structure as shown in FIG. 19F. The porous member 1940 can include or be composed of one or more of graphite, carbon fiber, silica fiber, aluminosilicate fiber, borosilicate fiber, silicon carbide coating, pyrolytic boron nitride coating, pyrolytic graphite coating, or polymer.

[0058] As part of the process used to form the support for the array of seed crystals 370, a susceptor 1910 on which the array of seed crystals 370 is accurately positioned can be placed within a reactor capable of polycrystalline GaN synthesis. Next, the polycrystalline GaN reactor can be closed, evacuated, and backfilled with nitrogen. The temperature of the susceptor 1910 within the reactor can be raised to about 900 °C and a bake-out in a mixture of 5% H2 in N2 can be carried out for about 24 hours to remove oxygen and moisture from the furnace. After the nitrogen bake-out, for example, 1.2 standard liters per minute of Cl2 can be flowed through a source chamber containing gallium at a temperature of about 850 degrees Celsius, and the effluent can be mixed with a flow of 15 standard liters per minute of NH3 in a nitrogen carrier gas. The process can be carried out for about 30 hours, the reactive gases can be stopped, and the reactor can be cooled. A textured polycrystalline GaN layer 1950 about 1 millimeter thick can be deposited on the array of seed crystals 370 to produce a structure similar to that schematically shown in FIG. 19B. The openings, gaps 1941, or pores within the porous member 1940, if present, are partially or completely filled with polycrystalline GaN. In certain embodiments, the porous member 1940 is completely encapsulated within the polycrystalline GaN (not shown). In certain embodiments, one or more components of the porous member 1940, such as a polymer disposed within the material used to form the porous member 1940, for example, undergo partial or complete decomposition during the deposition of the polycrystalline GaN layer 1950, thus enabling the material within the porous member 1940 to exhibit one or more desirable mechanical properties.

[0059] After the formation of the polycrystalline GaN layer 1950, the tile-shaped composite structure 1960 including the seed crystal 370 bonded with the polycrystalline GaN layer 1950 can then be separated from the susceptor 1910 as schematically shown in FIG. 19C. As a component of the tile-shaped composite structure 1960 including at least the array of the seed crystal 370, the polycrystalline GaN layer 1950 is often referred to herein as a matrix member. The tile-shaped composite structure 1960 and the polycrystalline GaN layer or matrix member 1950 shown in FIGS. 19C to 19F include the porous member 1940, but this configuration is not intended to be limiting with respect to the scope of the disclosure provided herein. In some embodiments, the matrix member may optionally include the porous member 1940. In certain embodiments, the susceptor 1910 is separated from the tile-shaped composite structure 1960 by using a mechanical process that is used to break any bond formed between the susceptor 1910 and the components within the tile-shaped composite structure 1960. In one example, a mechanical shear force is applied between the susceptor 1910 and the tile-shaped composite structure 1960, causing cracks and damage to a part of the release coating 1923 or the interface layer 1921 disposed therebetween, and thus, the susceptor 1910 and the tile-shaped composite structure 1960 can be separated. In other embodiments, the susceptor 1910 is dissolved in, for example, a mineral acid or a base.

[0060] In certain embodiments of the tiled composite structure 1960, as schematically shown in FIG. 19D, a gap 1970 is formed between adjacent tiled seed crystals 370. The formed gap 1970 can serve to inhibit the growth of the polycrystalline GaN layer 1950 from impeding lateral growth from the seed crystals 370 during subsequent processing steps such as a merge process. The gap 1970 can have a width between about 1 micrometer and about 5 millimeters, between about 5 micrometers and about 1 millimeter, between about 10 micrometers and about 500 micrometers, or between about 20 micrometers and about 200 micrometers. The gap 1970 can have a depth between about 1 micrometer and about 1 millimeter, between about 5 micrometers and about 300 micrometers, or between about 10 micrometers and about 100 micrometers. The gap 1970 can be formed, for example, by laser machining such as a dicing saw. In certain embodiments, the gap forming process includes a masking operation that prevents the polycrystalline group III nitride material from being formed between adjacent seed crystals 370 instead of or in addition to etching. In certain embodiments, the patterning and etching of the seed crystals 370 are performed after the formation of the tiled composite structure 1960, as schematically shown in FIGS. 1A - 1T, rather than before.

[0061] A tile array 1860 and / or a tile-like composite structure 1960 comprising an array of properly oriented seed crystals 370 can be used as a substrate for bulk crystal growth, including, for example, ammonothermal growth, HVPE growth, or flux growth. In the following description, the grown GaN layer is referred to as an ammonothermal layer, although alternatively, other bulk growth methods such as HVPE or flux growth may be used. In certain embodiments involving ammonothermal bulk growth, one or more tile arrays 1860 and / or tile-like composite structures 1960 are then suspended on a seed rack and placed within a sealable container such as a capsule, autoclave, or liner within an autoclave. In certain embodiments, one or more pairs of tile arrays are suspended back-to-back with the open and / or patterned large area surfaces facing outward. Next, a group III metal source such as a polycrystalline group III metal nitride, at least one mineralizer composition, and ammonia (or other nitrogen-containing solvent) are added to the sealable container and the sealable container is sealed. The mineralizer composition can include an alkali metal such as Li, Na, K, Rb, or Cs, an alkaline earth metal such as Mg, Ca, Sr, or Ba, or a hydride, amide, imide, amide imide, nitride, or azide of an alkali or alkaline earth. The mineralizer can include an ammonium halide such as NH4F, NH4Cl, NH4Br, or NH4I, a gallium halide such as GaF3, GaCl3, GaBr3, or GaI3, or any compound that can be formed by reaction of one or more of F, Cl, Br, I, HF, HCl, HBr, HI, Ga, GaN, and NH3. The mineralizer can include other alkali, alkaline earth, or ammonium salts, other halides, urea, sulfur or sulfide salts, or phosphorus or phosphorus-containing salts. The sealable container (e.g., capsule) is then placed within a high pressure apparatus such as an internally heated high pressure apparatus or autoclave and the high pressure apparatus can be sealed. Next, the sealable container containing the tile array 1860 and / or tile-like composite structure 1960 is heated to a temperature above about 400 degrees Celsius and pressurized above about 50 megapascals to perform ammonothermal crystal growth.

[0062] Figures 2A - 2C show different steps within a bulk crystal growth process carried out on an array of adjacent tile - shaped seed crystals. The patterned seed crystals are formed by a LEO process without trenches under the mask openings. During the bulk crystal growth process, the group - III metal nitride layer 213 grows through the openings 112 of the patterned mask layer 111, grows outward through the openings as shown in Figure 2B, grows laterally on the patterned mask layer 111, first coalesces between adjacent mask openings, and then coalesces between adjacent tiles or seed crystals (Figure 2C). After coalescence, the group - III metal nitride layer 213 includes a window region 215 that grows perpendicular to the openings of the patterned mask layer 111, a wing region 217 that grows laterally on the patterned mask layer 111, a core - coalescence front 219 formed at the boundary between wings growing from adjacent openings of the patterned mask layer 111, and a second core - coalescence front 235 formed at the boundary between wings growing from adjacent tiles or seed crystals. The through - dislocation 214 may exist in the window region 215, originating from the through - dislocations present on the surface of the substrate 101.

[0063] Figures 3A - 3C illustrate the sidewall LEO process for bulk III - nitride. Figures 3D - 3E show bulk crystal growth on adjacent tiled seed crystals, where the patterned seed crystals are formed by the sidewall LEO process. Figure 3A shows a substrate including a patterned and masked trench 115 formed by one of the processes described herein. In the sidewall LEO process, the group - III metal nitride material 221 grows on the sides and bottom of the patterned and masked trench 115 as shown in Figure 3B. As the group - III metal nitride material 221 grows inwardly on the sidewalls of the trench 115, it becomes increasingly difficult for the group - III nitride raw material to reach the bottom of the trench, regardless of whether the raw material includes a group - III metal ammonothermal complex (in the case of ammonothermal growth), a group - III metal halide (in the case of HVPE), or a group - III metal alloy or inorganic complex (in the case of flux growth). Eventually, the group - III metal nitride material 221 pinches off the lower region of the trench and forms a void 225 as shown in Figure 3C. It has been found that the concentration of threading dislocations in the laterally grown group - III metal nitride material 221 is lower than that in the substrate 101. Many threading dislocations 223 originating from the substrate 101 terminate at the surface of the void 225. Subsequently, the group - III metal nitride layer 213 grows upward through the opening 112 (or window) of the patterned mask layer 111. However, since the laterally grown group - III metal nitride material 221 has a lower concentration of threading dislocations than the substrate 101 and many dislocations originating from the substrate 101 terminate at the surface of the void 225, the dislocation density of the vertically grown group - III metal nitride layer 213 is significantly reduced compared to the conventional LEO process, as described above in connection with Figures 2A - 2C.

[0064] Figures 3D - 3E show the continuation of the sidewall LEO growth process and the fusion between adjacent tiles or seed crystals. Similar to the conventional LEO process (Figures 2A - 2C), the group III metal nitride layer 213 grows within the opening 112 of the patterned mask layer 111, grows outward through the opening as shown in Figure 3D, grows laterally on the patterned mask layer 111, first coalesces between adjacent mask openings, and then coalesces between adjacent tiles or seed crystals (Figure 3E). After coalescence, the group III metal nitride layer 213 includes a window region 215 that grows perpendicular to the opening of the patterned mask layer 111 as shown in Figure 3E, a wing region 217 that grows laterally on the patterned mask layer 111, a core coalescence front 219 formed at the boundary between wings growing from adjacent openings of the patterned mask layer 111, and a second core coalescence front 235 formed at the boundary between wings growing from adjacent tiles or seed crystals. The laterally grown group III metal nitride material 221 has a lower density of threading dislocations than the substrate 101, and since many threading dislocations originating from the substrate 101 terminate at voids 225, the density of threading dislocations in the window region 215 is significantly lower than in the case of conventional LEO.

[0065] The ammonothermal group III metal nitride layer 213 can have a thickness between about 10 micrometers and about 100 millimeters, or between about 100 micrometers and about 20 millimeters.

[0066] In certain embodiments, the ammonothermal group III metal nitride layer 213 is subjected to one or more processes such as at least one of sawing, lapping, grinding, polishing, chemical mechanical polishing, or etching.

[0067] In certain embodiments, the concentration of extended defects, such as threading dislocations and stacking defects, in the ammonothermal group III metal nitride layer 213 can be quantified by defect selective etching. Defect selective etching can be performed using, for example, a solution containing one or more of H3PO4, H3PO4 adjusted by long-term heat treatment to form polyphosphoric acid, and H2SO4, or one or more of a molten flux containing one or more of NaOH and KOH. Defect selective etching can be performed at a temperature between about 100 degrees Celsius and about 500 degrees Celsius for about 5 minutes to about 5 hours, and the treatment temperature and time are selected to result in the formation of etch pits having a diameter between about 1 micrometer and about 25 micrometers, and then the ammonothermal group III metal nitride layer, crystal, or wafer is removed from the etchant solution.

[0068] The concentration of threading dislocations on the surface of the window region 215 can be about 10 times to about 10 4 times lower than the concentration in the underlying substrate 101. The concentration of threading dislocations on the surface of the window region 215 can be less than about 10 8 cm -2 −1, less than about 10 7 cm -2 −2, less than about 10 6 cm -2 −3, less than about 10 5 cm -2 −4, or less than about 10 4 cm -2 −5. The concentration of threading dislocations on the surface of the wing region 217 can be about one to about three orders of magnitude lower than the concentration of threading dislocations on the surface of the window region 215, and can be less than about 10 5 cm -2 −1, less than about 10 4 cm -2 −2, less than about 10 3 cm -2 −3, less than about 10 2 cm -2 −4, or less than about 10 cm -2 −5. Some stacking defects can be, for example, from about 1 cm -1 to about 10 4 cm -1at a concentration between them and may exist on the surface of the window region 215. The concentration of stacking defects on the surface of the wing region 217 may be about one to about three orders of magnitude lower than that on the surface of the wing region 217 on the surface of the window region 215, about 10 2 cm -1 less than, about 10 cm -1 less than, about 1 cm -1 less than, or about 0.1 cm -1 less than and may be undetectable. For example, through dislocations such as edge dislocations are, for example, about 1×10 5 cm -1 less than, about 3×10 4 cm -1 less than, about 1×10 4 cm -1 less than, about 3×10 3 cm -1 less than, about 1×10 3 cm -1 less than, about 3×10 2 cm -1 , less than or 1×10 2 cm -1 less than and may exist in the core coalescence fronts 219 and 235 at a line density. The dislocation density along the core coalescence front is greater than 5 cm -1 greater than, 10 cm -1 greater than, 20 cm -1 greater than, 50 cm -1 greater than, 100 cm -1 greater than, 200 cm -1 greater than, or 500 cm -1 greater than and may be.

[0069] In certain embodiments, the masking and the growth process of the bulk group III nitride crystal are repeated one, two, three, or more times. In some embodiments, these operations are performed with the first bulk group III metal nitride layer remaining bonded to the substrate 101. In other embodiments, the substrate 101 is removed, for example, by sawing, lapping, grinding, and / or etching, before subsequent masking and bulk crystal growth operations.

[0070] Figures 4A, 4B, and 4C are schematic diagrams showing a method of forming a self-supporting group III metal nitride boule and a self-supporting group III metal nitride wafer. In certain embodiments, substrate 101 is removed from an ammonothermal group III metal nitride layer 213 (configured as in FIG. 3E, FIG. 4A), or the last such layer deposited, to form a self-supporting fused ammonothermal group III metal nitride boule 413 that includes at least a portion of the ammonothermal group III metal nitride layer 213. Removal of substrate 101 is accomplished by one or more of sawing, grinding, lapping, polishing, laser lift-off, self-separation, and etching, and a processed self-supporting laterally grown group III metal nitride boule 413 can be formed. The processed self-supporting laterally grown group III metal nitride boule 413 can include a composition similar or substantially identical to the ammonothermal group III metal nitride layer, and the etching can be performed under conditions where the etching rate on the back side of substrate 101 is much faster than the etching rate on the front side of the ammonothermal group III metal nitride layer. In certain embodiments, a portion of the ammonothermal group III metal nitride layer 213, or the last such layer deposited, can be protected from attack by an etchant by deposition of a mask layer, wrapping a portion of the layer with Teflon®, clamping a portion of the layer against the "Teflon®", painting with a "Teflon®" paint, etc. In certain embodiments, substrate 101 includes single crystal gallium nitride, the large area surface 102 of substrate 101 has a crystal orientation within about 5 degrees of the (0001) crystal orientation, and substrate 101 is preferentially etched by heating in a solution containing one or more of H3PO4, H3PO4 adjusted by a long heat treatment to form polyphosphoric acid, and H2SO4 at a temperature between about 150 degrees Celsius and about 500 degrees Celsius for about 30 minutes to about 5 hours, or by heating in a molten flux containing one or more of NaOH and KOH. Surprisingly, the (one or more) patterned mask layer 111 can facilitate preferential removal of substrate 101 by acting as an etch stop.The processed self-supporting fused ammonothermal group-III metal nitride boule 413 can include one or more window regions 415 formed over an exposed region 120, such as an opening 112 of a (one or more) patterned mask layer 111 of a substrate 101. The processed self-supporting laterally grown fused group-III metal nitride boule 413 can also include one or more wing regions 417 formed over a non-opening region of the (one or more) patterned mask layer 111, and a pattern of a locally substantially linear array 419 of threading dislocations as shown in FIG. 4B, and one or more second core coalescence fronts 435. One or more of a front face 421 and a back face 423 of the self-supporting fused ammonothermal group-III metal nitride boule 413 can be lapped, polished, etched, and chemically mechanically polished. As discussed above, the pattern of the locally substantially linear array 419 and the one or more second core coalescence fronts 435 can include a core coalescence front region including a "sharp boundary" having a width of less than about 25 micrometers or less than about 10 micrometers disposed between adjacent wing regions 417, or an "extended boundary" having a width between about 25 micrometers and about 1000 micrometers, or between about 30 micrometers and about 250 micrometers, disposed between adjacent wing regions 417, depending on growth conditions.

[0071] In certain embodiments, the edges of the self - supporting fused ammonothermal group III metal nitride boule 413 are ground to form a cylindrically shaped ammonothermal group III metal nitride boule. In certain embodiments, one or more flat portions are ground onto the side surface of the self - supporting fused ammonothermal group III metal nitride boule 413. In certain embodiments, the self - supporting fused ammonothermal group III metal nitride boule 413 is sliced into one or more self - supporting fused ammonothermal group III metal nitride wafers 431, as shown in FIG. 4C. Slicing can be performed by, among other things, multi - wire saw cutting, multi - wire slurry saw cutting, slicing, inner diameter saw cutting, outer diameter saw cutting, cleavage, ion implantation followed by lift - off, scribing, laser cutting, etc. One or more large - area surfaces of the self - supporting fused ammonothermal group III metal nitride wafer 431 can be lapped, polished, etched, electro - chemically polished, photoelectro - chemically polished, reactive ion etched, and / or chemically mechanically polished according to methods known in the art. In certain embodiments, chamfered, beveled, or rounded edges are ground onto the edges of the self - supporting fused ammonothermal group III metal nitride wafer 431. The self - supporting fused ammonothermal group III metal nitride wafer can have a diameter of at least about 10 millimeters, at least about 25 millimeters, at least about 50 millimeters, at least about 75 millimeters, at least about 100 millimeters, at least about 150 millimeters, at least about 200 millimeters, at least about 300 millimeters, at least about 400 millimeters, or at least about 600 millimeters and can have a thickness between about 50 micrometers and about 20 millimeters, or between about 150 micrometers and about 5 millimeters. One or more large - area surfaces of the self - supporting fused ammonothermal group III metal nitride wafer 431 can be used as a substrate for group III metal nitride growth, among other things, by chemical vapor deposition, metal - organic chemical vapor deposition, hydride vapor epitaxy, molecular beam epitaxy, flux growth, solution growth, ammonothermal growth, etc.

[0072] Configuration example of a tile-shaped seed crystal array In some embodiments of the present disclosure, the crystal layer grown from the formed tile-shaped seed crystal array has a reduced number of crystal defects, particularly at the core coalescence front, and a reduced misalignment between adjacent particles or seed crystals, such that the tile-shaped array of seed crystals used during the crystal growth process or in one or more of the multiple steps of the crystal growth process may involve the use and alignment of seed crystals having desirable crystallographic and structural attributes. In certain embodiments, the array of seed crystals 370 is aligned, oriented, and arranged in a one-dimensional array as shown in FIGS. 20B-20C, rather than in a two-dimensional array as shown in FIGS. 17A-19G. As will be described in more detail below, tiling in one dimension at a time can provide certain advantages over tiling two-dimensionally simultaneously. Generally, a fixture or handle substrate that supports two or more seed crystals positioned in an array has a CTE that is approximately matched to that of the seed crystals. However, when tiling non-polar or semi-polar GaN crystals with different CTEs in the c-direction and a-direction, due to the wurtzite crystal structure, the handle substrate is unlikely to have a CTE match in both directions unless it is a single-crystalline GaN having the same crystal orientation. The advantage of forming and combining a one-dimensional array of seed crystals is that it may be more difficult to combine crystals in two directions simultaneously than to do so in only one growth direction at a time. Further, the defect level at the core coalescence boundary and the angular misalignment between tiles depend greatly on the accuracy of the polishing and alignment operations, and thus it may be easier to align and configure a one-dimensional array of seed crystals so that a very high-quality combined GaN crystal can be formed in subsequent operations.

[0073] In certain embodiments of the present disclosure, as shown in FIGS. 20A - 20C, a plurality of first GaN tiles or seed crystals 2001 are provided to be tiled in a first direction to form a one - dimensional array of seed crystals. In certain embodiments, each of the tile crystals 2001 that may include or be composed of the seed crystal 370 is prepared from a common single crystal, for example, by multi - wire sawing, grinding, polishing, and chemical - mechanical polishing. The formed tile crystals 2001 can be tiled one - dimensionally, joined, and grown into a substantially equilibrium shape, for example, along the c - direction of an m - plane seed crystal, as shown in FIGS. 20A - 20C. In another particular embodiment, the c - plane seed crystals can be tiled along a direction and grown into a substantially equilibrium shape. The original seed may have been grown ammono - thermally or by HVPE.

[0074] During the process of forming the one - dimensional array of seed crystals, after positioning and aligning the seed crystals in a desired orientation, a coalescence process is used to bond the seed crystals arranged in the one - dimensional array to each other (in the Y - direction). During the coalescence process, the gap 2011 (FIG. 20B, similar to the gap 1711 in FIGS. 17A - 17F) between adjacent tile crystals 2001 is filled, and a core - coalescence front 2015 can be formed at the same position as the gap 2011 (FIGS. 20B and 20D). The coalescence process can be performed in separate steps, for example, by using a mechanical fixture as shown in FIGS. 18A - 18D, by bonding using a polycrystalline group - III nitride layer as shown in FIGS. 19A - 19C, or by bonding to a handle substrate as described below. Next, the coalesced array of seed crystals can be removed from the handle substrate and used as a seed for subsequent ammono - thermal crystal growth. In a subsequent ammono - thermal crystal growth process, as shown in FIGS. 20D - 20E, a grown crystal layer 2045 formed on the coalesced array of seed crystals can be grown into a substantially equilibrium shape to form grown tile - like seed crystals 2050.

[0075] In some embodiments, rather than using mechanical fixtures (Figs. 18A - 18D) or polycrystalline group III nitride bonding layers (Figs. 19A - 19C), the coalescence process is performed using a handle substrate that consists of, or includes, a support component formed from one or more of molybdenum, molybdenum alloys, single - crystal or polycrystalline group III metal nitrides, or another material with a CTE that closely matches the seed crystal and is compatible with the crystal growth environment. An adhesive layer can be deposited on the front surface of the handle substrate and the back surface of the seed crystal. The adhesive layer can include one or more of SiO2, GeO2, SiNx, AlNx, or B, Al, Si, P, Zn, Ga, Si, Ge, Au, Ag, Ni, Ti, Cr, Zn, Cd, In, Sn, Sb, Tl, W, In, Cu, or Pb, or their oxides, nitrides, or oxynitrides. In certain embodiments, the composition of the adhesive layer on at least one of the handle substrate and the seed crystal can have a melting point that can be selected such that it undergoes incipient melting at a temperature of less than about 300°C, less than about 400°C, or less than about 500°C. In certain embodiments, the composition of the adhesive layer on at least one of the handle substrate and the seed crystal can be selected such that it undergoes incipient melting at a temperature of less than about 300°C, less than about 400°C, or less than about 500°C and can be selected to have a melting point that exceeds about 600°C, exceeds about 700°C, exceeds about 800°C, or exceeds about 900°C. The composition and structure of the adhesive layer can be selected such that it undergoes incipient melting at a temperature of less than about 300°C, less than about 400°C, less than about 500°C, or less than about 600°C, then bonds to the paired adhesive layer and remains unmelted after heat treatment at a temperature below the solidus temperature, or maintains a melt volume fraction of less than about 20%, less than about 10%, or less than about 5% at a temperature that exceeds about 600°C, exceeds about 700°C, exceeds about 800°C, or exceeds about 900°C. The seed crystal is bonded to the handle substrate at a first temperature at which at least one of the adhesive layer compositions can melt, then heat - treated to remain unmelted at a second, higher temperature at which the crystal growth process is performed, and the crystal growth process is carried out at this temperature to coalesce the seed crystal into a single crystal.Further details are described in U.S. Patent No. 10,400,352, which is hereby incorporated by reference in its entirety.

[0076] In some embodiments of the crystal formation process, next, as schematically shown in FIG. 21A, the grown tile-shaped seed crystal 2050 is sliced. In one example, the slicing is performed parallel to the m-plane and parallel to the original seed surface, forming the long and narrow portions of the grown tile-shaped seed crystal 2050, such as crystals 2101, 2102, 2103, 2104, 2105, 2106, 2107, and 2108. Next, the long and narrow portions of the grown tile-shaped seed crystal 2050 are tiled side by side. Since adjacent strips are formed from the crystals above or below each other, even if the original one-dimensional tiling process shown in FIGS. 20A-20E is not very accurate, the crystal orientation along the rows is very accurate, for example, better than 0.3°, better than 0.1°, better than 0.05°, better than 0.02°, or better than 0.01°.

[0077] During the process of forming an array of seed crystals, as shown in FIGS. 21B - 21C, the narrow portions of the grown tile - shaped seed crystals are positioned and aligned in a desired orientation, and then, using a coalescence process, the narrow portions of the grown tile - shaped seed crystals are joined (in the X - direction). During the coalescence process, the gap 2112 (FIG. 21B) between adjacent tile crystals 2001 is filled, and a core - coalescence front 2115 is formed at the same position as the gap 2112 (FIGS. 21B and 21D). After coalescence, as shown in FIGS. 21D - 21E, the first two - dimensional tile - shaped crystal can be detached from the fixture or handle substrate and regrown into a substantially equilibrium shape surrounding the regrown crystal layer 2145. The regrown crystal 2150 includes a grown crystal layer 2145 that includes a core - coalescence front 2115 formed within or above the gap 2112, similar to the crystal array seen in the above - mentioned second core - coalescence front 435, along with the core - coalescence front 2015 formed by the extension of the existing core - coalescence front 2015 in the seed crystals 2101, 2102, etc. The inaccuracies of the original tiling may appear as Y - or axial - direction crystal grain boundaries (i.e., the core - coalescence front 2015; in the specific example shown, the c - direction), but the azimuthal difference in the X - direction (i.e., the core - coalescence front 2115; in the specific example shown, the a - direction) needs to be minimized.

[0078] Next, the regrown crystal 2150 is sliced in the X-Y plane (parallel to the m-plane in the particular example shown) as schematically shown in FIG. 22A to form, for example, slices 2201, 2202, 2203, 2204, 2205, 2206, 2207, and 2208. In addition, as shown in FIG. 22B, the regrown crystal 2150 or slices 2201-2208 are then sliced at a position 2220 corresponding to a defective grain boundary seen at the core coalescence front 2015, which is parallel to the c-plane in the particular example (FIG. 21D), to form, for example, slabs 2201A, 2201B, 2201C, …, 2202A, 2202B, 2202C, … 2208C, 2208D, and 2208E (e.g., a total of 40 slabs). After forming slices 2201-2208 and dividing the slices at position 2220, the resulting slabs 2201A-2208E can then be re-tiled in a direction orthogonal to the previous tiling operation as shown in FIG. 22C. In this configuration, the slabs adjacent to each other in the Z direction are arranged side by side to form a one-dimensional array in the Y direction, and the edges prepared at position 2220 are arranged adjacent to each other. This formed array of slabs 2201A-2208A (FIGS. 22C-22D) enables a very small misorientation seen in the regrown crystal 2150 to be replicated throughout the subsequently formed mosaic crystal 2250.

[0079] During the process of forming the array of slabs 2201A - 2208A shown in FIGS. 22B - 22C, after positioning and aligning the slabs 2201A - 2208A in a desired orientation, a coalescence process is used to bond the array of slabs 2201A - 2208A together (in the Y direction). During the coalescence process, the gap 2212 (FIG. 22C) between adjacent slabs 2201A - 2208A is filled, and a core coalescence front 2215 is formed at the same position as the gap 2212 (FIGS. 22C and 22E). Each of the slabs 2201A - 2208A disposed within the array is bonded by at least one core coalescence front 2215 (FIG. 22C). When the array of slabs 2201A - 2208A is recombined, next, as shown in FIG. 22E, they are peeled from the fixture or handle substrate and regrown to form an equilibrium shape having a grown crystal layer 2245 with a significantly reduced defect density associated with the core coalescence front 2215. Following a similar procedure, slabs 2201B - 2208B, 2201C - 2208C, … and 2201E - 2208E can be coalesced and grown.

[0080] Using the procedures schematically shown in FIGS. 20A - 22F, large - area and low - defect m - plane GaN crystals suitable for use as seeds in subsequent ammonothermal crystal growth of m - plane boules or in subsequent bulk crystal growth by another method such as HVPE or flux growth can be fabricated. Similarly, using a continuous 1 - D tiling operation, large - area and low - defect c - plane or semi - polar GaN crystals suitable for use as seeds in subsequent bulk crystal growth or suitable for use as substrates for the manufacture of electronic or optoelectronic devices can be prepared.

[0081] In certain embodiments, for further use in one - dimensional or two - dimensional tiling processes or for use as substrates in the manufacture of electronic or optoelectronic devices, the mosaic crystal 2250 is sliced along a short dimension or at an oblique angle to form a seed crystal suitable for use as a seed in subsequent ammonothermal crystal growth or subsequent bulk crystal growth by another method such as HVPE or flux growth.

[0082] In an alternative embodiment, for example, for the growth of c-plane or semi-polar crystals, the first one-dimensional tiling operation (Figs. 20A - 20D) is omitted and the isolated m-plane crystals are simply grown to approximately an equilibrium shape. The formed crystals may be sliced and tiled parallel to the m-plane as shown in Figs. 21A - 21E to form the regrown crystals 2150. Alternatively, the formed crystals can be sliced parallel to the c-plane or in a semi-polar orientation to prepare seeds for the one-dimensional tiling operation. Crystals sliced from the grown boule region in the +c

[0001] direction have a significantly reduced dislocation density and are particularly well-suited for the growth of c-plane and / or semi-polar crystals, where the dislocation density is less than 10 6 cm -2 less than 10 5 cm -2 less than 10 4 cm -2 less than, or 10 3 cm -2 less than.

[0083] As schematically shown in Figs. 17A - 19F, for a one-step process of two-dimensional tiles, a sequential 1-D tiling approach can have several advantages including making it easier to select, prepare, and stack the tiles; more accurately aligning a single crystal domain; reducing the CTE mismatch to the handle substrate or fixture, thereby reducing the risk of cracking; and reducing the risk that individual tiles will be misaligned in orientation by more than, for example, a 0.1° target specification.

[0084] Examples of grown freestanding crystals Figures 5A - 5E are schematic diagrams showing through - dislocation patterns formed on individual tile crystals formed by the patterned growth method summarized in FIGS. 1A - 4C. The individual tile crystals shown in FIGS. 5A - 5E can form part of a self - standing fused group - III metal nitride boule 413 or wafer 431, as described in connection with FIGS. 4A - 4C, or can form part of a self - standing fused ammonothermal group - III nitride boule or wafer shown in FIGS. 6A - 6G, which will be further described below. The large - area surface of the self - standing ammonothermal group - III metal nitride boule 413 or wafer 431 can be characterized by a pattern of a locally substantially linear array 419 of through - dislocations propagated from a coalescence front 219 formed during an epitaxial lateral overgrowth process, as described above in connection with FIGS. 3A - 3E. The pattern of the locally substantially linear array of through - dislocations can be an irregular pattern formed at least in part due to the pattern of exposed regions 120 (FIGS. 1F - 1L) used in the process to form a 2D hexagonal, square, rectangular, trapezoidal, triangular, 1D linear, or self - standing laterally grown group - III metal nitride boule 413. One or more window regions 415 are formed over the exposed regions 120 (FIGS. 1F - 1L), and one or more wing regions 417 are formed in portions that are not over the exposed regions 120, i.e., in portions formed by lateral growth. As discussed above, the pattern of the formed coalescence front 219 or the locally substantially linear array 419 can include a coalescence front region having a width (i.e., measured parallel to the surface of the page including FIGS. 5A - 5E) that can vary depending on the growth conditions.

[0085] More complex patterns are also possible, which may be advantageous in that they are, for example, more resistant to cracking or cleavage. Pattern 502 may be longer in one direction compared to another orthogonal direction, for example, due to self-standing coalesced and laterally grown group III metal nitride boules 413 being sliced at an inclined angle with respect to the large area surface of self-standing ammonothermal group III metal nitride boules 413. The pattern 502 of a locally substantially linear array of through dislocations can be characterized by a linear array of through dislocations (FIG. 5D) having a pitch dimension L between about 5 micrometers and about 20 millimeters, or between about 200 micrometers and about 5 millimeters. The pattern 502 of a locally substantially linear array of through dislocations can be characterized by a pitch dimension L (FIGS. 5A, 5B) between about 5 micrometers and about 20 millimeters, or between about 200 micrometers and about 5 millimeters, or between about 500 micrometers and about 2 millimeters, or by pitch dimensions L1 and L2 (FIGS. 5C and 5E) in two orthogonal directions. In certain embodiments, the pattern 502 of a locally substantially linear array of through dislocations is substantially aligned with the underlying crystal structure of the group III metal nitride, for example, the locally substantially linear array is within about 5 degrees, within about 2 degrees, or within about 1 degree of the projection thereof in the plane of the surface of the self-standing ammonothermal group III metal nitride boule 413 or group III metal nitride wafer 431, such as <10-10>, <11-20>, or [000±1]. The linear density of the through dislocations within the pattern is less than about 1×10 5 cm -1 less than, less than about 3×10 4 cm -1 less than, less than about 1×10 4 cm -1 less than, less than about 3×10 3 cm -1 less than, less than about 1×10 3 cm -1 less than, less than about 3×10 2 cm -1 less than, or less than about 1×10 2 cm -1 less than and may be. The linear density of the through dislocations within pattern 502 is greater than 5 cm -1 and greater than 10 cm-1 Greater than 20 cm -1 Greater than 50 cm -1 Greater than 100 cm -1 Greater than 200 cm -1 Greater than or 500 cm -1 May be greater than

[0086] Referring again to FIGS. 5A-5E, the large area surface of the individual particles or domains within the self-supporting fused ammonothermal Group III metal nitride boule or wafer can be further characterized by an array of wing regions 417 and an array of window regions 415. Each domain (or sometimes referred to herein as a particle) can be formed by growth on an individual tile crystal (e.g., seed crystal 370). The domains generally include a wing region, a window region, a core coalescence front, and a locally generally linear array of dislocations, and are generally surrounded by a core coalescence front. Each wing region 417 can be positioned between adjacent locally generally linear arrays 419 of through dislocations. Each window region 415 may be disposed within a single wing region 417, or may be positioned between two adjacent wing regions 417, and can have a minimum dimension between 10 micrometers and 500 micrometers, and 10 3 cm -2 to 10 8 cm -2 and can be characterized by a through dislocation concentration between, which results from residual through dislocations propagating vertically from the window region during the bulk crystal growth process and a concentration of stacking defects less than 10 3 cm -1 In some embodiments, the boundary between the window region and the wing region may be dislocated with a line density between about 5 cm -1 to 10 5 cm -1

[0087] ​The array can be elongated in one direction compared to another orthogonal direction, for example, due to the boules being sliced at an angle with respect to the large area surface of a self - supporting, fused ammonothermal group - III metal nitride boule. The pattern of a locally substantially linear array 419 of through - dislocations can be characterized by a pitch dimension L between about 5 micrometers and about 20 millimeters, or between about 200 micrometers and about 2 millimeters, or pitch dimensions L1 and L2 in two orthogonal directions. In certain embodiments, a first pattern of a locally substantially linear array 419 of through - dislocations is substantially aligned with the underlying crystal structure of the group - III metal nitride. For example, the locally substantially linear array is within about 5 degrees, within about 2 degrees, or within about 1 degree of one or more of <10 - 10>, <11 - 20>, or [000±1], or their projections in the plane of the surface of a self - supporting ammonothermal group - III nitride boule or wafer. The linear density of through - dislocations within the pattern is less than about 1×10 5 cm -1 −1, less than about 3×10 4 cm -1 −1, less than about 1×10 4 cm -1 −1, less than about 3×10 3 cm -1 −1, less than about 1×10 3 cm -1 −1, less than about 3×10 2 cm -1 −1, less than about 1×10 2 cm -1 −1, or less than about 1×10 -1 cm -1 −1 may be. The linear density of through - dislocations within the pattern is greater than 5 cm -1 −1, greater than 10 cm -1 −1, greater than 20 cm -1 −1, greater than 50 cm -1 −1, greater than 100 cm -1 −1, greater than 200 cm -1 −1, or greater than 500 cm -1 −1 may be.

[0088] The density of through - dislocations in the wing region 417 between locally substantially linear arrays of through - dislocations is less than about 10 5 cm -2 −1, less than about 10 4 cm -2 −1, less than about 103 cm -2 less than, about 10 2 cm -1 less than, or about 10 cm -2 less than. The density of through - dislocations on the surface of the window region 415 is about 10 8 cm -2 less than, about 10 7 cm -2 less than, about 10 6 cm -2 less than, about 10 5 cm -2 less than, or about 10 4 cm -2 less than. The density of through - dislocations on the surface of the window region can be at least 2 times, at least 3 times, at least 10 times, at least 30 times, or at least 100 times higher than the density of through - dislocations on the surface of the wing region. The density of through - dislocations on the surface of the window region can be less than 10 4 times less, less than 3000 times, less than 1000 times, less than 300 times, less than 100 times, or less than 30 times higher than the density of through - dislocations on the surface of the wing region. In some embodiments, the boundary between the window region 415 and the wing region 417 may be, for example, about 5 cm -1 to 10 5 cm -1 with a line density between, and may be dislocated. The density of through - dislocations averaged over the large - area surface of a self - standing ammonothermal group - III nitride boule or wafer is about 10 7 cm -2 less than, about 10 6 cm -2 less than, about 10 5 cm -2 less than, about 10 4 cm -2 less than, about 10 3 cm -2 less than, or about 10 2 cm -2 less than. The density of stacking defects averaged over the large - area surface of a self - standing ammonothermal group - III nitride boule or wafer is about 10 3 cm -1 less than, about 10 2 cm -1Less than, about 10 cm -1 Less than, about 1 cm -1 Less than, or about 0.1 cm -1 It may be less than or undetectable. In some embodiments, for example, after repeated regrowth on a seed crystal having a patterned array of dislocations and / or growth to a thickness greater than 2 millimeters, greater than 3 millimeters, greater than 5 millimeters, or greater than 10 millimeters, the position of the through dislocations may be somewhat shifted laterally with respect to the pattern of the seed crystal. In such cases, the region of higher through dislocation concentration may be somewhat more diffuse than the relatively sharp lines schematically shown in FIGS. 5A - 5E. However, the concentration of through dislocations as a function of the lateral position along a line on the surface varies periodically with a period between about 5 micrometers and about 20 millimeters, or between about 200 micrometers and about 5 millimeters. The concentration of through dislocations within the periodically varying region can vary by at least 2 times, at least 5 times, at least 10 times, at least 30 times, at least 100 times, at least 300 times, or at least 1000 times.

[0089] Referring to FIGS. 6A - 6F, as discussed above, the self - standing fused ammonothermal group - III nitride boule or wafer can be formed by using one or more of the tiling processes described in connection with FIGS. 3A - 4C and 17A - 22F. The self - standing fused ammonothermal group - III nitride boule or wafer can include two or more domains or grains separated by one or more second lines of dislocations 635, the latter being derived from a second coalescence front 235 or 2215 formed during the lateral growth of the ammonothermal group - III metal nitride material from one seed to its adjacent seed, as schematically shown in FIGS. 2C, 3E, and 22E. Depending on the shape of the original nitride crystal, the pattern of the domains can be, for example, (a) square (FIGS. 6A and 17A), (b) rectangular (FIGS. 6B and 17B), (c) hexagonal (FIGS. 6C and 17C), (d) rhombohedral (FIGS. 6D and 17D), (e) a mixture of hexagonal and pentagonal (FIGS. 6E and 17E); or (f) a mixture of hexagonal and rhombohedral (FIGS. 6F and 17F). Other patterns are also possible. FIG. 6G shows an example of a square self - standing fused ammonothermal group - III nitride boule or wafer formed using a plurality of tile - like seed crystals (e.g., seed crystal 370) shown in FIG. 1G during the crystal growth process, where each of the domains resulting from a single tile crystal (e.g., seed crystal 370) includes a window region, a wing region, and a coalescence front. The domains can have a first lateral tile dimension 680 and a second lateral tile dimension 690 that approximately correspond to the original tile crystal dimensions 380 and 390, respectively (see FIGS. 17A - 17F), the lateral dimensions defining a plane perpendicular to the thickness, where each of the first lateral tile dimension 680 and the second lateral tile dimension 690 can be at least about 5 millimeters, 10 millimeters, 15 millimeters, 20 millimeters, 25 millimeters, 35 millimeters, 50 millimeters, 75 millimeters, 100 millimeters, 150 millimeters, or at least about 200 millimeters. The polar azimuthal difference angle γ between adjacent domains can be less than 0.5 degrees, less than 0.2 degrees, less than 0.1 degrees, less than 0.05 degrees, less than 0.02 degrees, or less than 0.01 degrees.The first horizontal tile dimension 680 can be approximately the same as the first horizontal seed dimension (i.e., the dimension 380 in the X direction). Similarly, the second horizontal tile dimension 690 can be approximately equal to the second horizontal seed dimension (i.e., the dimension 390 in the Y direction). The azimuth difference angles α and β between adjacent domains can be less than 0.5 degrees, less than 0.2 degrees, less than 0.1 degrees, less than 0.05 degrees, less than 0.02 degrees, or less than 0.01 degrees. Typically, γ is less than or equal to α and β. The crystal azimuth difference angles α, β, and γ can be greater than about 0.01 degrees, greater than about 0.02 degrees, greater than about 0.05 degrees, or greater than about 0.1 degrees. The dislocation density along the line between adjacent domains is about 5×10. 5 cm -1 less than, about 2×10 5 cm -1 less than, about 1×10 5 cm -1 less than, about 5×10 4 cm -1 less than, about 2×10 4 cm -1 less than, about 1×10 3 cm -1 less than, about 5×10 3 cm -1 less than, about 2×10 3 cm -1 less than, or about 1×10 3 cm -1 less than and can be. The dislocation density along the line between adjacent domains is 50 cm -1 greater than, 100 cm -1 greater than, 200 cm -1 greater than, 500 cm -1 greater than, 1,000 cm -1 greater than, 2000 cm -1 greater than, or 5000 cm -1 greater than and can be.

[0090] A self - supporting fused ammonothermal Group III nitride boule or wafer can have a symmetric X - ray rocking curve (e.g., (002) for the c - plane) full - width at half - maximum (FWHM) of less than about 300 arcseconds, less than about 200 arcseconds, less than about 100 arcseconds, less than about 50 arcseconds, less than about 35 arcseconds, less than about 25 arcseconds, or less than about 15 arcseconds. A self - supporting fused ammonothermal Group III nitride boule or wafer can have an asymmetric X - ray rocking curve (e.g., (201) or (102) for the c - plane) full - width at half - maximum (FWHM) of less than about 300 arcseconds, less than about 200 arcseconds, less than about 100 arcseconds, less than about 50 arcseconds, less than about 35 arcseconds, less than about 25 arcseconds, or less than about 15 arcseconds. A self - supporting fused ammonothermal Group III nitride boule or wafer can have a thickness between about 100 micrometers and about 100 millimeters, or between about 1 millimeter and about 10 millimeters. A self - supporting fused ammonothermal Group III nitride boule or wafer can have a diameter of at least about 15 millimeters, at least about 20 millimeters, at least about 25 millimeters, at least about 35 millimeters, at least about 50 millimeters, at least about 75 millimeters, at least about 100 millimeters, at least about 150 millimeters, at least about 200 millimeters, or at least about 400 millimeters. The surface of a self - supporting fused ammonothermal Group III nitride boule or wafer can have a crystal orientation within 10 degrees, within 5 degrees, within 2 degrees, within 1 degree, within 0.5 degree, within 0.2 degree, within 0.1 degree, within 0.05 degree, within 0.02 degree, or within 0.01 degree of the (0001) Ga - polar, (000 - 1) N - polar, {10 - 10} non - polar, or {11 - 20} non - polar a - plane. The surface of a self - supporting fused ammonothermal Group III nitride boule or wafer can have an (hkil) semi - polar orientation, where i =-(h + k) and l, and at least one of h and k is non - zero.In certain embodiments, the crystal orientation of a self-supporting fused ammonothermal group-III nitride boule or wafer is within 10 degrees, 5 degrees, 2 degrees, 1 degree, 0.5 degree, 0.2 degree, 0.1 degree, 0.05 degree, 0.02 degree, or 0.01 degree of {11-2±2}, {60-6±1}, {50-5±1}, {40-4±1}, {30-3±1}, {50-5±2}, {70-7±3}, {20-2±1}, {30-3±2}, {40-4±3}, {50-5±4}, {10-1±1}, {10-1±2}, {10-1±3}, {21-3±1}, or {30-3±4}. The self-supporting fused ammonothermal group-III nitride boule or wafer has a minimum lateral dimension of at least 10 millimeters. In some embodiments, the fused nitride crystal has a minimum lateral dimension of at least 2 centimeters, at least 3 centimeters, at least 4 centimeters, at least 5 centimeters, at least 6 centimeters, at least 8 centimeters, at least 10 centimeters, or at least 20 centimeters. In some embodiments, the self-supporting fused ammonothermal group-III nitride boule or wafer is used as a substrate for epitaxy to form a semiconductor structure. The self-supporting fused ammonothermal group-III nitride boule can be saw cut, lapped, polished, dry etched, and / or chemically mechanically polished by methods known in the art. One or more edges of the self-supporting fused ammonothermal group-III nitride boule or wafer may be ground. The self-supporting fused ammonothermal group-III nitride boule or wafer can be placed in a suitable reactor and an epitaxial layer can be grown by MOCVD, MBE, HVPE, etc. In certain embodiments, the epitaxial layer comprises GaN or Al x In y Ga (1-x-y) N, where 0≦x, y≦1. The morphology of the epitaxial layer is uniform between domains on the surface because the surface orientations are substantially the same.

[0091] In some embodiments, the self-supporting fused ammonothermal group-III nitride boule or wafer is used as a substrate for further tiling. For example, referring to FIGS. 17A-19D, the seed crystal 370 itself can be selected to be a self-supporting fused ammonothermal group-III metal nitride boule or wafer. The tiling, coalescing, and re-tiling operations can be repeated more than two times, more than four times, more than eight times, or more than sixteen times. Thus, fused nitride crystals having excellent crystal quality and a very large diameter can be produced by successive tiling operations.

[0092] The self-supporting fused ammonothermal group-III nitride boule or wafer can be used as a substrate for manufacturing optoelectronic devices and electronic devices such as at least one of a light-emitting diode, a laser diode, a photodetector, an avalanche photodiode, a transistor, a rectifier, a Schottky rectifier, a thyristor, a p-i-n diode, a metal-semiconductor-metal diode, a high electron mobility transistor, a metal semiconductor field effect transistor, a metal oxide field effect transistor, a power metal oxide semiconductor field effect transistor, a power metal insulated gate semiconductor field effect transistor, a bipolar junction transistor, a metal insulated gate field effect transistor, a heterojunction bipolar transistor, a power insulated gate bipolar transistor, a power vertical junction field effect transistor, a cascode switch, an inner subband emitter, a quantum well infrared photodetector, a quantum dot infrared photodetector, a solar cell, or a diode for photoelectrochemical water splitting and hydrogen generation devices. In some embodiments, the position of the device relative to the domain structure in the self-supporting fused ammonothermal group-III nitride boule or wafer is selected such that the active region of each individual device lies within a single domain or particle of the self-supporting fused ammonothermal group-III nitride boule or wafer.

[0093] Self-supporting, fused ammonothermal group III metal nitride boules or wafers can have a large area crystal orientation within 5 degrees, 2 degrees, 1 degree, 0.5 degree, 0.2 degree, 0.1 degree, 0.05 degree, 0.02 degree, or 0.01 degree of the (0001)+c plane, (000-1)-c plane, {10-10}m plane, {11-20}a plane, {11-2±2}, {60-6±1}, {50-5±1}, {40-4±1}, {30-3±1}, {50-5±2}, {70-7±3}, {20-2±1}, {30-3±2}, {40-4±3}, {50-5±4}, {10-1±1}, {10-1±2}, {10-1±3}, {21-3±1}, or {30-3±4}. Self-supporting ammonothermal group III metal nitride boules or wafers can have an (hkil) semi-polar large area surface orientation, where i = -(h + k) and l, and at least one of h and k is non-zero.

[0094] In certain embodiments, the large area surface of a self-supporting ammonothermal group III metal nitride crystal or wafer has a misoriented crystal orientation between about -60 degrees and about +60 degrees from the {10-10}m plane towards the

[0001] +c direction and up to about 10 degrees maximum towards the orthogonal <1-210>a direction. In certain embodiments, the large area surface of a self-supporting ammonothermal group III metal nitride crystal or wafer has a misoriented crystal orientation between about -30 degrees and about +30 degrees from the {10-10}m plane towards the

[0001] +c direction and up to about 5 degrees maximum towards the orthogonal <1-210>a direction. In certain embodiments, the large area surface of a self-supporting ammonothermal group III metal nitride crystal or wafer has a misoriented crystal orientation between about -5 degrees and about +5 degrees from the {10-10}m plane towards the

[0001] +c direction and up to about 1 degree maximum towards the orthogonal <1-210>a direction. The self-supporting ammonothermal group III metal nitride crystal or wafer is 10 2 cm -1 less than, 10 cm -1 less than, or 1 cm -1 less than stacking defect density, and on one or both of the two large area surfaces, about 10 5 cm-2 less than about 10 4 cm -2 less than about 10 3 cm -2 less than about 10 2 cm -2 less than, or about 10 cm -2 It may have a very low dislocation density of less than.

[0095] Free-standing, fused ammonothermal Group III metal nitride boules or wafers may have a symmetric X-ray rocking curve full width at half maximum (FWHM) of less than about 200 arcseconds, less than about 100 arcseconds, less than about 50 arcseconds, less than about 35 arcseconds, less than about 25 arcseconds, or less than about 15 arcseconds. Free-standing, fused ammonothermal Group III metal nitride boules or wafers may have a crystal curvature radius of greater than 0.1 meter, greater than 1 meter, greater than 10 meters, greater than 100 meters, or greater than 1000 meters in at least one, at least two, or three independent or orthogonal directions.

[0096] In certain embodiments, at least one surface of a free-standing, fused ammonothermal Group III metal nitride boule or wafer has an atomic impurity concentration of at least one of oxygen (O) and hydrogen (H) greater than about 1×10 16 cm -3 greater than, about 1×10 17 cm -3 greater than, or about 1×10 18 cm -3 greater than. In certain embodiments, the ratio of the atomic impurity concentration of H to the atomic impurity concentration of O is between about 0.3 and about 1000, between about 0.4 and about 10, or between about 10 and about 100. In certain embodiments, at least one surface of a free-standing, fused ammonothermal Group III metal nitride boule or wafer has an impurity concentration of at least one of lithium (Li), sodium (Na), potassium (K), fluorine (F), chlorine (Cl), bromine (Br), or iodine (I) greater than about 1×10 15 cm -3 greater than, about 1×10 16 cm -3 greater than, or about 1×10 17 cm-3 Greater than, approximately 1×10 18 cm -3 is greater than. In certain embodiments, the top and bottom surfaces of a freestanding, fused ammonothermal Group III metal nitride boule or wafer have impurity concentrations of O, H, carbon (C), Na, and K that are quantified by calibrated secondary ion mass spectrometry (SIMS) and are, respectively, between about 1×10 16 cm -3 and 1×10 19 cm -3 between, between about 1×10 16 cm -3 and 2×10 19 cm -3 between, 1×10 17 cm -3 less than, 1×10 16 cm -3 less than, and 1×10 16 cm -3 less than. In another embodiment, the top and bottom surfaces of a freestanding, fused ammonothermal Group III metal nitride boule or wafer have impurity concentrations of at least one of O, H, C, and Na and K that are quantified by calibrated secondary ion mass spectrometry (SIMS) and are, respectively, between about 1×10 16 cm -3 and 1×10 19 cm -3 between, between about 1×10 16 cm -3 and 2×10 19 cm -3 between, 1×10 17 cm -3 less than, and about 3×10 15 cm -3 and 1×10 18 cm -3 between. In yet another embodiment, the top and bottom surfaces of a freestanding, fused ammonothermal Group III metal nitride boule or wafer have impurity concentrations of at least one of O, H, C, and F and Cl that are quantified by calibrated secondary ion mass spectrometry (SIMS) and are, respectively, between about 1×10 16 cm -3 and 1×10 19 cm -3 between, between about 1×10 16 cm-3 to 2×10 19 cm -3 and between 1×10 17 cm -3 less than and about 1×10 15 cm -3 to 1×10 19 cm -3 it can be. In some embodiments, the top and bottom surfaces of a self-supporting fused ammonothermal group III metal nitride boule or wafer have an H impurity concentration quantified by calibrated secondary ion mass spectrometry (SIMS) of about 5×10 17 cm -3 to 1×10 19 cm -3 it can be. In certain embodiments, at least one surface of a self-supporting ammonothermal group III metal nitride boule or wafer has an impurity concentration of copper (Cu), manganese (Mn), and iron (Fe) between about 1×10 16 cm -3 to 1×10 19 cm -3 . In a particular embodiment, a self-supporting fused ammonothermal group III metal nitride boule or wafer has an infrared absorption peak at about 3175 cm -1 and the absorbance per unit thickness is greater than about 0.01 cm -1 .

[0097] A self-supporting fused ammonothermal group III metal nitride crystal or wafer can be characterized by a wurtzite structure that does not substantially include a cubic or other crystal structure, and the other crystal structure is less than about 0.1 volume % relative to the substantial wurtzite structure.

[0098] Surprisingly, given the lattice mismatch between HVPE GaN and ammonothermal GaN, the results of using the techniques disclosed herein show that ammonothermal lateral epitaxial overgrowth can produce thick, large-area GaN layers without cracks. In certain embodiments, a self-supporting, fused ammonothermal group III metal nitride crystal or wafer has a diameter of greater than about 25 millimeters, greater than about 50 millimeters, greater than about 75 millimeters, greater than about 100 millimeters, greater than about 150 millimeters, greater than about 200 millimeters, greater than about 300 millimeters, or greater than about 600 millimeters, and a thickness of greater than about 0.1 millimeter, greater than about 0.2 millimeter, greater than about 0.3 millimeter, greater than about 0.5 millimeter, greater than about 1 millimeter, greater than about 2 millimeters, greater than about 3 millimeters, greater than about 5 millimeters, greater than about 10 millimeters, or greater than about 20 millimeters, and is substantially crack-free. In contrast, we have found that ammonothermal growth in large-area, unpatterned HVPE GaN seed crystals results in cracking when the layer is thicker than a few hundred micrometers, even when a patterning process was used to form the HVPE GaN seed crystals.

[0099] Self-supporting, fused ammonothermal group III metal nitride wafers can be characterized by a total thickness variation (TTV) of less than about 25 micrometers, less than about 10 micrometers, less than about 5 micrometers, less than about 2 micrometers, or less than about 1 micrometer, and a macroscopic warp of less than about 200 micrometers, less than about 100 micrometers, less than about 50 micrometers, less than about 25 micrometers, or less than about 10 micrometers. The large-area surface of the self-supporting, fused ammonothermal group III metal nitride wafer has a diameter greater than about 100 micrometers or a characteristic dimension of less than about 2 cm -2 less than about 1 cm -2 less than about 0.5 cm -2 less than about 0.25 cm -2 less than, or about 0.1 cm -2It may have a macro defect density below. The misorientation angle variation across the large-area surface of a self-supporting ammonothermal group III metal nitride crystal or wafer can be less than about 1 degree, less than about 0.5 degree, less than about 0.2 degree, less than about 0.1 degree, less than about 0.05 degree, or less than about 0.025 degree in each of two orthogonal crystallographic directions. The root mean square surface roughness of the large-area surface of a self-supporting fused ammonothermal group III metal nitride wafer, measured over an area of at least 10 μm × 10 μm, can be less than about 0.5 nanometer, less than about 0.2 nanometer, less than about 0.15 nanometer, less than about 0.1 nanometer, or less than about 0.10 nanometer. A self-supporting fused ammonothermal group III metal nitride wafer can be characterized by n-type electrical conductivity having a carrier concentration between about 1×10 17 cm -3 and about 3×10 19 cm -3 and a carrier mobility exceeding about 100 cm 2 / V-s. In an alternative embodiment, a self-supporting fused ammonothermal group III metal nitride wafer is characterized by p-type electrical conductivity having a carrier concentration between about 1×10 15 cm -3 and about 1×10 19 cm -3 . In yet another embodiment, a self-supporting fused ammonothermal group III metal nitride wafer is characterized by semi-insulating electrical behavior and has a room temperature resistivity greater than about 10 7 ohm·centimeter, greater than about 10 8 ohm·centimeter, greater than about 10 9 ohm·centimeter, greater than about 10 10 ohm·centimeter, or greater than about 10 11 ohm·centimeter. In certain embodiments, a self-supporting fused ammonothermal group III metal nitride wafer is highly transparent and has an optical absorption coefficient at a wavelength of 400 nanometers less than about 10 cm -1 , less than about 5 cm -1 , less than about 2 cm -1 , less than about 1 cm -1 , less than about 0.5 cm -1 , less than about 0.2 cm-1 less than, or about 0.1 cm -1 is less than.

[0100] In some embodiments, a self-supporting fused ammonothermal group III metal nitride crystal or wafer is used as a seed crystal for further bulk growth. In one particular embodiment, the further bulk growth includes fused ammonothermal bulk crystal growth. In another particular embodiment, the further bulk growth includes high temperature solution crystal growth, also known as flux crystal growth. In yet another particular embodiment, the further bulk growth includes HVPE. The further grown crystal can be sliced, lapped, polished, etched, and / or chemically mechanically polished into a wafer by methods known in the art. The surface of the wafer can be characterized by a root mean square surface roughness measured over an area of 10 micrometers × 10 micrometers that is less than about 1 nanometer or less than about 0.2 nanometer.

[0101] The wafer can be incorporated into a semiconductor structure. The semiconductor structure includes at least one Al x In y Ga (1-x-y)It may include an N epitaxial layer, where 0 ≦ x, y, x + y ≦ 1. The epitaxial layer can be deposited on a wafer by methods known in the art, such as metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). At least a part of the semiconductor structure can be part of a gallium nitride-based electronic device or optoelectronic device, such as a light-emitting diode, a laser diode, a power conversion photodiode, a photodetector, an avalanche photodiode, a photovoltaic cell, a solar cell, a cell for photoelectrochemically decomposing water, a transistor, a rectifier, and a thyristor, etc.; a transistor, a rectifier, a Schottky rectifier, a thyristor, a p-i-n diode, a metal-semiconductor-metal diode, a high electron mobility transistor, a metal semiconductor field effect transistor, a metal oxide field effect transistor, a power metal oxide semiconductor field effect transistor, a power metal insulated gate semiconductor field effect transistor, a bipolar junction transistor, a metal insulated gate field effect transistor, a heterojunction bipolar transistor, a power insulated gate bipolar transistor, a power vertical junction field effect transistor, a cascode switch, an inner subband emitter, a quantum well infrared photodetector, a quantum dot infrared photodetector, and one of their combinations can be formed. The gallium nitride-based electronic device or optoelectronic device can be incorporated into equipment such as a lamp or a lighting fixture. After being individualized, the gallium nitride-based electronic device or optoelectronic device can have a lateral dimension of at least 0.1 millimeter × 0.1 millimeter. The gallium nitride-based electronic device or optoelectronic device can have a maximum dimension of at least 8 millimeters and can include, for example, a laser diode. The gallium nitride-based electronic device or optoelectronic device may not completely contain dislocations throughout its volume. For example, at a dislocation density of 10 4 cm -2 −2, it can be expected that there are no dislocations in a significant part of a 0.1 × 0.1 mm 2 device. At a dislocation density of 10 2 cm -2 −1, for a 1 × 1 mm 2It can be expected that there are no dislocations in a significant portion of the device. Gallium nitride-based electronic or optoelectronic devices may not contain stacking defects throughout their volume. For example, at a stacking defect density of 1 cm -1 , it can be expected that there are no stacking defects in a significant portion of a 10×1 mm 2 striped device such as a laser diode with non-polar or semi-polar large area surfaces s and c facets.

[0102] Figures 7A-7D are cross-sectional views showing a method according to an embodiment of the present disclosure, as well as the resulting optoelectronic and electronic devices. A two-terminal or three-terminal device such as an optoelectronic or electronic device can be formed by a series of steps including having a self-supporting fused ammonothermal group III metal nitride wafer 431 or a locally substantially linear array 419 of threading dislocations, and depositing an epitaxial layer on a substrate including at least one AlInGaN active layer 631 by MOCVD as shown, for example, in Figure 7B. In certain embodiments, the deposited layer includes an n-type or n+ layer 633, a doped or unintentionally doped single quantum well (SQW), multiple quantum well (MQW) structure, double heterostructure (DH structure), or n-drift layer, and, as shown, a p-type layer 636. The device structure can be vertical as schematically shown in Figures 7B and 7D or horizontal as schematically shown in Figure 7C. The device can be electrically connected to an external circuit to provide a potential between an n-type contact 639 and a p-type contact 637. In particular, additional layers such as a separate confinement heterostructure (SCH) layer, a cladding layer, an AlGaN electron blocking layer, and a p+ contact layer can be deposited. In many cases, threading dislocations in the substrate such as a locally substantially linear array 419 pattern propagate into the deposited layer and potentially affect the performance of the device.

[0103] In certain embodiments, the method also deposits n-type contact 639 and p-type contact 637, as shown in FIGS. 7B and 7C. In some embodiments, at least one of the set of n-type and p-type contacts is disposed with a particular alignment with respect to the core recombination front, the wing region, and / or the window region. The light-emitting portion may be on the core recombination front or at the center between the core recombination fronts. In one particular embodiment, a transparent p-type contact is deposited and arranged to avoid contact with the core recombination front, which may have a high threading dislocation density. In this way, a light-emitting structure or photodiode structure having a relatively low density of threading dislocations can be formed. In this way, a light-emitting structure, PN diode, photodiode, or Schottky barrier diode having a relatively low density of threading dislocations can be formed. In a preferred embodiment, the region of light emission and / or maximum electric field overlaps over the wing region 417 and is designed to avoid the pattern of a locally substantially linear array 419. In certain embodiments, a defect region associated with the core recombination front or window region is utilized as a shunt path to reduce series resistance. In certain embodiments, the n-type contact has a knife-edge dislocation density greater than 10 3 cm -1 and / or a threading dislocation density greater than about 10 5 cm -2 and is disposed over the core recombination front or window region.

[0104] Next, referring to FIG. 7C, in some embodiments, such as a laser diode, a PN diode, a photodiode, or a Schottky barrier diode, etc., the p-contact can be disposed in a region substantially without a core recombination front. In certain embodiments such as a laser diode, the laser ridge or stripe structure 740 can be disposed in a region substantially without a core recombination front. A mesa can be formed by conventional lithography and an n-contact disposed in electrical contact with the n-type layer and / or the substrate. Additional structures such as sidewall passivation, ion implantation regions, field plates, etc. can be disposed in alignment with the core recombination front.

[0105] Next, referring to FIG. 7D, in some embodiments, such as a current aperture vertical electron transistor (CAVET), etc., the n-drift layer 731 is deposited on the n+ contact layer 730, which in turn is deposited on the self-supporting fused ammonothermal group III metal nitride boule 413. The P-type layer 636 is formed on the n-layer 731 having the opening 736. Following the remaining regrowth of the n-layer 731, the AlGaN 2D electron gas layer 738 is deposited. Finally, the source contact 737, the drain contact 739, the dielectric layer 741, and the gate contact 743 are deposited. In a preferred embodiment, the opening 736 is disposed away from the first core recombination front 419 and the second core recombination front 435. In a preferred embodiment, the opening 736 is disposed away from the window region 415. In a preferred embodiment, the opening 736 is disposed over the wing region 417. Other types of three-terminal devices such as trench CAVET, MOSFET, etc. are positioned such that the region of maximum electric field is located within the wing region 417.

[0106] FIG. 8 shows a top view (plan view) of a self-standing GaN substrate formed by ammonothermal lateral epitaxial growth using a mask in the form of a two-dimensional array. The GaN layer was grown through a two-dimensional array of openings in the original mask layer to form the window region 415. The coalescence of the GaN layers can form a two-dimensional grid of a pattern of a locally substantially linear array 419 of threading dislocations.

[0107] FIG. 9A shows a top view of a device structure, e.g., an LED, where a transparent p-contact 970 is aligned and arranged so as not to contact either the window region 415 or the pattern of the locally substantially linear array 419 of threading dislocations. FIG. 9B shows a top view of an alternative embodiment of a device structure, e.g., an LED, where an electrical contact 980 is realigned with respect to the window region 415 and the pattern of the locally substantially linear array 419 of threading dislocations, but is arranged here on top of the pattern of the locally substantially linear array 419 of threading dislocations. FIG. 9C shows a top view of an alternative embodiment of a device structure, e.g., a flip-chip LED, where an n-type electrical contact 990 is aligned with respect to the window region 415 and a p-type electrical contact 995 is aligned between the window regions 415.

[0108] Individual dies, such as light emitting diodes or laser diodes, can be formed by sawing, cleaving, slicing, singulating, etc. between adjacent sets of electrical contacts. Referring again to FIG. 9A, slicing can be performed along the pattern of a locally substantially linear array 419 of dislocations. Slicing can also be performed through window region 415. Referring now to FIG. 9B, in certain embodiments, slicing can be performed through window region 415, but not along the pattern of a locally substantially linear array 419 of dislocations. Referring again to FIG. 9C, in certain embodiments, slicing is neither performed through a seed region nor along all core coalescence fronts. Depending on the arrangement of the one-dimensional or two-dimensional array of seed regions, the singulated dies can have three corners, four corners, or six corners.

[0109] The methods described herein have several potential defect regions, but provide a means for manufacturing large area group III metal nitride substrates. The methods described herein provide a means for manufacturing high performance light emitting diodes and / or laser diodes that avoid potential problems associated with defect regions of large area group III metal nitride substrates.

[0110] Examples of tile-shaped crystal array substrates Referring again to FIGS. 19D and 19G, in certain embodiments, instead of using the tile-like composite structure 1960 as a seed crystal for further bulk crystal growth, the tile-like composite structure 1960 is further processed to form a tile-like composite substrate 1980 and used directly as a substrate for manufacturing optical or electronic devices. The formed tile-like composite substrate 1980 includes an array of seed crystals 370 bonded by a polycrystalline GaN layer 1950, also referred to as a matrix member. In some embodiments, the array of seed crystals 370 is positioned such that the surface 1975 of each seed crystal is parallel to a first plane, such as the X-Y plane shown in FIG. 19G. The array of seed crystals 370 can be positioned such that a gap 1986 (FIG. 19G) is formed between adjacent edges of the seed crystals 370. In one example, the gap 1986 is less than 2 millimeters (mm), for example, between 0.1 micrometer (μm) and 1 millimeter (mm), or between 0.1 micrometer and 200 micrometers, between 0.1 micrometer and 50 micrometers, or between 0.2 micrometer and 50 micrometers. In certain embodiments, the gap 1986 is completely filled with the matrix member material 1950. In certain embodiments, as shown in FIG. 19D, the upper surface of the matrix member material 1950 is below the upper surface of the seed crystal surface 1975. In certain embodiments, the matrix member material 1950 is not present within the gap 1986, and thus, the seed crystals 370 are held in place only by their bonding from their back sides to the matrix member 1950. In certain embodiments, the surface 1975 of the seed crystals 370 within the array is planarized, such as by grinding, lapping, polishing, etc. In certain embodiments, the surface 1975 is chemically mechanically polished and subjected to a final cleaning operation in a clean room environment. In certain embodiments, during the process used to form the tile-like composite substrate 1980, the back surface of the tile-like composite structure 1960 is thinned and planarized, such as by grinding, lapping, and / or polishing. In certain embodiments, the thickness of the tile-like composite substrate 1980 is the same as the thickness of the seed crystals 370, and thus, the matrix member 1950 is present only within the gap 1986.In other embodiments, the thickness of the tile-shaped composite substrate 1980 is greater than the thickness of the seed crystal 370, in which case the matrix member 1950 is bonded to the back side of the seed crystal 370. The perimeter of the tile-shaped composite structure 1960 can be ground to form the outer edge 1990 of the tile-shaped composite substrate 1980. In certain embodiments, a chamfered, beveled, or rounded edge is ground into the edge 1990 of the tile-shaped composite substrate 1980. In some embodiments, the outer edge 1990 surrounding the array of seed crystals 370 has a circular shape. In certain embodiments, one or more orientation flats 1995 can be ground into the edge 1990 of the tile-shaped composite substrate 1980. In certain embodiments, the tile-shaped composite substrate 1980 has a diameter between 20 millimeters and 210 millimeters, between 20 millimeters and 30 millimeters, between 45 millimeters and 55 millimeters, between 90 millimeters and 110 millimeters, between 140 millimeters and 160 millimeters, or between 190 millimeters and 210 millimeters, and a thickness between 150 micrometers and about 5 millimeters, between about 200 micrometers and about 2 millimeters, or between about 250 micrometers and about 1.5 millimeters.

[0111] In certain embodiments, the thickness of each of the seed crystals 370 within the tile - shaped composite substrate 1980 is equal within 50 micrometers, within 25 micrometers, within 10 micrometers, within 5 micrometers, within 2 micrometers, or within 1 micrometer. In certain embodiments, each surface 1975 of the seed crystals 370 is coplanar within 10 micrometers, within 5 micrometers, within 2 micrometers, or within 1 micrometer. Each crystallographic mis - cut of the surfaces 1975 of the seed crystals 370 can have a magnitude equal within 0.5 degrees, within 0.3 degrees, within 0.2 degrees, within 0.1 degrees, within 0.05 degrees, within 0.02 degrees, or within 0.01 degrees. In a preferred embodiment, the direction of each crystallographic mis - cut of the seed crystals 370 is aligned within 10 degrees, within 5 degrees, within 2 degrees, within 1 degree, within 0.5 degrees, within 0.2 degrees, or within 0.1 degrees. In certain embodiments, each of the surfaces 1975 of the seed crystals 370 has an orientation within 5 degrees, within 2 degrees, within 1 degree, or within 0.5 degrees of an orientation selected from {20 - 2±1}, {30 - 3±1}, and {10 - 10}, and a mis - cut in the a - direction of less than 0.5 degrees, less than 0.2 degrees, less than 0.1 degrees, or less than 0.05 degrees.

[0112] The tile - shaped composite substrate 1980 can be characterized by a total thickness variation (TTV) of less than about 25 micrometers, less than about 10 micrometers, less than about 5 micrometers, less than about 2 micrometers, or less than about 1 micrometer, and by a macroscopic warp of less than about 200 micrometers, less than about 100 micrometers, less than about 50 micrometers, less than about 25 micrometers, or less than about 10 micrometers. The small values of TTV and macroscopic warp are useful for the manufacture of electronic devices because they allow for the deposition of epitaxial layers with uniform properties and high device yield. At least one surface 1975 (FIG. 19D) of the tile - shaped composite substrate 1980 has a diameter or characteristic dimension greater than about 100 micrometers and less than about 2 cm -2 less than about 1 cm -2 less than about 0.5 cm -2 less than about 0.25 cm -2less than, or about 0.1 cm -2 It may have a macro defect concentration of less than. The variation in the misorientation angle across the entire surface 1975 of the seed crystal 370 may be less than about 1 degree, less than about 0.5 degree, less than about 0.2 degree, less than about 0.1 degree, less than about 0.05 degree, or less than about 0.025 degree in each of two orthogonal crystallographic directions. The root mean square average surface roughness of at least one surface 1975 of the tile-shaped composite substrate 1980, measured over an area of at least 10 μm × 10 μm, may be less than about 0.5 nanometer, less than about 0.2 nanometer, less than about 0.15 nanometer, less than about 0.1 nanometer, or less than about 0.10 nanometer. At least one seed crystal 370 within the tile-shaped composite substrate 1980 may be characterized by an n-type electrical conductivity having a carrier concentration between about 1 × 10 17 cm -3 and about 3 × 10 19 cm -3 and a carrier mobility exceeding about 100 cm 2 / V-s. In an alternative embodiment, at least one seed crystal 370 within the tile-shaped composite substrate 1980 is characterized by a p-type electrical conductivity having a carrier concentration between about 1 × 10 15 cm -3 and about 1 × 10 19 cm -3 . In yet another embodiment, at least one seed crystal 370 within the tile-shaped composite substrate 1980 wafer is characterized by a semi-insulating electrical behavior and has a room temperature resistivity exceeding about 10 7 ohm·centimeter, exceeding about 10 8 ohm·centimeter, exceeding about 10 9 ohm·centimeter, exceeding about 10 10 ohm·centimeter, or exceeding about 10 11 ohm·centimeter.

[0113] One or more device structures can be grown or deposited on one or more of the seed crystals 370 within the tile-shaped composite substrate 1980, as schematically shown in FIG. 23A. In certain embodiments, for example, following deposition of the first layer 2310 by MOCVD, MBE, or HVPE, a release layer 2320 can be deposited thereon. In some embodiments, the first layer 2310 can include a layer doped with an n-type dopant. The release layer 2320 can include InGaN or be composed of InGaN. The release layer 2320 can include or be composed of multiple quantum wells or strained layer superlattices.

[0114] In certain embodiments, a device layer 2340 is then deposited and overlays the release layer 2320. The device layer 2340 can include one or more of a low nGaN drift layer, one or more AlInGaN active layers, one or more AlInGaN cladding layers, a p-type layer, and a p-type electrical contact. Other layers can also be present in the device layer 2340 as it can be suitable for the manufacture of devices such as light emitting diodes, laser diodes, photodiodes, diodes, transistors, etc. In certain embodiments, an adhesive layer 2350 can be deposited on the device layer 2340. In some embodiments, trenches 2355 are formed through the adhesive layer 2350, the device layer 2340, and into or through the release layer 2320. As schematically shown in FIG. 23B, a handle substrate 2360 is then bonded to the adhesive layer 2350. The process of bonding the handle substrate 2360 to the adhesive layer 2350 can be achieved by one or more of thermocompression bonding, soldering, non-sintered silver bonding, or adhesive bonding. In some embodiments, the release layer 2320 is then removed, as schematically shown in FIG. 23C, separating one or more device layers 2340 bonded to the handle substrate 2360 from one or more seed crystals 370. In certain embodiments, the release layer 2320 is removed by photoelectrochemical etching. In certain embodiments, the order of these operations is changed. In one particular embodiment, a portion or all of the release layer 2320 is removed before bonding the handle substrate 2360 to the adhesive layer 2350.

[0115] In certain embodiments, the surface 2370 of the seed crystal 370 may have a portion of the first layer 2310 or other layers present and may be re-planarized by one or more of grinding, lapping, and polishing. The surface 2370 may be further prepared by chemical mechanical polishing and final cleaning in a clean room environment. After removing the device layer 2340 from the tiled composite substrate 1980 and re-preparing the surface 2370 of the seed crystal 370 within the tiled composite substrate 1980, the tiled composite substrate is reused directly again as a substrate for manufacturing optical or electronic devices. The tiled composite substrate 1980 can be reused at least once, at least twice, at least three times, at least five times, or at least ten times as a substrate used for forming optical or electronic devices. FIGS. 19A-19E and FIGS. 23A-23C show a configuration in which the polycrystalline GaN layer 1950 of the tiled composite substrate 1980 extends on the surface of the seed crystal 370 (e.g., the lower surface in FIGS. 23A-23C). However, in some configurations, the polycrystalline GaN layer 1950 is positioned only at the edge of the seed crystal 370 and is not disposed on any of the main surfaces (e.g., the upper and lower surfaces in FIGS. 23A-23B) of the seed crystal 370. This configuration is not intended to limit the scope of the present disclosure.

[0116] The above-described series of steps provides a method according to an embodiment of the present disclosure. In certain embodiments, the present disclosure provides a method and resulting crystalline material provided by a high-pressure apparatus having a structured support member. Other alternatives can also be provided in which steps are added, one or more steps are deleted, or one or more steps are provided in a different order without departing from the scope of the claims herein.

Examples

[0117] Embodiments provided by the present disclosure are further illustrated by reference to the following examples. It will be apparent to those skilled in the art that many modifications can be made to both the materials and methods without departing from the scope of the present disclosure.

[0118] Example 1 A c-plane oriented bulk GaN crystal grown by HVPE with a thickness of about 0.3 millimeters was provided for use as a substrate 101 for patterning and ammonothermal crystal growth. A layer of TiW with a thickness of 100 nanometers was sputter deposited as an adhesive layer on the (000-1)N plane of the substrate, followed by deposition of an inert layer with a thickness of 780 nanometers containing Au. Next, a 6-micrometer thick Au layer was electroplated on the sputter layer to increase the thickness of the inert layer (e.g., blanket mask 116). AZ-4300 was used as a photoresist (e.g., photoresist layer 103) to define a pattern including a linear array of slits (e.g., openings 112) with a width of 3 micrometers and a length of 1 centimeter, and a pitch diameter of 1200 micrometers. As schematically shown in FIGS. 1M to 1P, a wet etching process was carried out using a commercially available TFA gold etching solution at room temperature to obtain a substrate having a patterned mask layer 111. The mask pattern was composed of an m-stripe domain with linear openings having a width of about 30 to 40 micrometers and oriented parallel to <10-10>. Next, the substrate having the patterned mask layer 111 was placed in a stirring beaker containing concentrated H3PO4. The beaker was heated to about 280 degrees Celsius over about 30 minutes, held at this temperature for about 90 minutes, and then cooled. The cross-section of the trench 115 formed by this procedure, having a depth of about 162 micrometers and an upper width of about 105 micrometers, is shown in FIG. 10. Surprisingly, the sidewalls of the trench 115 are substantially vertical.

[0119] Example 2 A patterned c-plane oriented bulk GaN substrate 101 with trenches formed therein was prepared in the same procedure as described in Example 1. The patterned substrate was placed in a silver capsule together with a baffle having an open area of 15%, polycrystalline GaN raw material, NH4F mineralizer, and ammonia, and the capsule was sealed. The ratios of the GaN raw material and the NH4F mineralizer to ammonia were about 1.69 and 0.099 by weight, respectively. The capsule was placed in an internally heated high-pressure apparatus and heated to about 666 degrees Celsius in the upper raw material zone and about 681 degrees Celsius in the lower crystal growth zone, maintained at these temperatures for about 215 hours, then cooled and taken out. The ammonothermal GaN filled most of the volume in the trenches, grew through the linear openings of the patterned mask on the HVPE GaN substrate, grew laterally, and completely merged to form an ammonothermal GaN layer about 1200 micrometers thick with a smooth upper surface. Two parallel cuts were made perpendicular to both the surface of the ammonothermal GaN layer and the pattern to create a rod-shaped test piece having an m-plane surface. As shown in FIGS. 11A and 11B, one m-plane surface of the test piece was polished and examined with an optical microscope. As indicated by the dashed line in the enlarged view on the right side of FIG. 11B, an interface can be seen between the substrate 101 and the laterally grown group III metal nitride material 221. Both the patterned mask layer 111 and the void 225 appear black in the image and are under the ammonothermal group III metal nitride layer 213.

[0120] Example 3 A patterned c-plane oriented bulk GaN substrate with trenches formed was prepared in the same procedure as described in Examples 1 and 2, and the final group III metal nitride layer 213 is shown in FIG. 12B (i.e., the right figure). A second patterned substrate was prepared in a similar procedure except that no trenches were prepared under the mask openings, and the final group III metal nitride layer is shown in FIG. 12A (i.e., the left figure). The patterned substrate was placed in a silver capsule together with a baffle with an open area of 15%, polycrystalline GaN raw material, NH4F mineralizer, and ammonia, and the capsule was sealed. The ratios of the GaN raw material and the NH4F mineralizer to ammonia were about 2.05 and 0.099 by weight, respectively. The capsule was placed in an internally heated high-pressure apparatus and heated to about 666 degrees Celsius in the upper raw material zone and about 678 degrees Celsius in the lower crystal growth zone, maintained at these temperatures for about 427 hours, then cooled and taken out. The ammonothermal GaN filled most of the volume in the trenches of the substrate with trenches formed (FIG. 12B), grew through the linear openings of the patterned mask on the HVPE GaN substrate, grew laterally, and completely merged to form an ammonothermal GaN layer with a smooth upper surface and a thickness of about 2100 micrometers. The ammonothermal GaN layer grew similarly through the linear openings of the patterned mask on the patterned HVPE GaN substrate without trenches formed (FIG. 12A), grew laterally, and completely merged to form an ammonothermal GaN layer with a smooth upper surface and a thickness of about 2100 micrometers. The surfaces of both ammonothermal GaN layers were lightly etched and examined with an optical microscope. Differential interference contrast (Nomarski) micrographs and transmission micrographs of both layers are shown in FIGS. 12A - 12B. The average etch pit density (thought to accurately represent the threading dislocation density) of the ammonothermal GaN layer grown on the patterned substrate without trenches (FIG. 12A) was about 1.0×10 5 cm -2 . The average etch pit density of the ammonothermal GaN layer grown on the patterned substrate with trenches formed (FIG. 12B) was about 1.0×10 4 cm -2and was improved by at least 10 times.

[0121] Example 4 A patterned c-plane oriented bulk GaN substrate with trenches was prepared in the same procedure as described in Examples 1 and 2, but with a pitch of 800 micrometers. The patterned substrate with trenches was placed in a silver capsule together with a baffle with 15% open area, polycrystalline GaN raw material, NH4F mineralizer, and ammonia, and the capsule was sealed. The ratios of the GaN raw material and the NH4F mineralizer to ammonia were approximately 1.71 and 0.099 by weight, respectively. The capsule was placed in an internally heated high-pressure apparatus and heated to approximately 668 degrees Celsius in the upper raw material zone and approximately 678 degrees Celsius in the lower crystal growth zone, and maintained at these temperatures for approximately 485 hours, then cooled and removed. The ammonothermal GaN filled most of the volume in the trenches of the substrate with trenches, grew through the linear openings of the patterned mask on the HVPE GaN substrate, grew laterally, and completely merged to form an ammonothermal GaN layer approximately 980 micrometers thick with a smooth upper surface. The HVPE GaN substrate was removed by grinding, and the obtained free-standing ammonothermal GaN substrate was polished and chemically mechanically polished. Next, a PANalytical X’Pert PRO diffractometer was used with an electron energy of 45 kV, a line focus of 40 mA, a step of 0.0002 degrees, a dwell time of 1 second, a Ge(220) mirror, a slit height of 1.0 mm, and a slit width of 1.0 mm at nine different positions across the substrate to characterize the free-standing ammonothermal GaN substrate by X-ray diffraction. The analysis results of the formed GaN substrate are summarized in FIG. 13. The range of the misorientation along [1-100] was measured to be 0.078 degrees in the central 80% of the large-area surface of the crystal, and the range of the misorientation along [11-20] was measured to be 0.063 degrees in the central 80% of the large-area surface of the crystal. Thus, in some embodiments, the free-standing crystal has a misorientation angle that varies by 0.1 degrees or less in the central 80% of the large-area surface of the crystal along a first direction, and a misorientation angle that varies by 0.1 degrees or less in the central 80% of the large-area surface of the crystal along a second direction orthogonal to the first direction.In contrast, as a result of performing the same measurements on commercially available HVPE wafers, misorientation ranges of 0.224 degrees along [1-100] and 0.236 degrees along [11-20] were obtained. As summarized in the table and graph shown in FIG. 14, the full width at half maximum of the rocking curve for the (002) reflection was measured to be 36 arcseconds, while the full width at half maximum of the rocking curve for the (201) reflection was measured to be 32 arcseconds. In contrast, the same measurements on commercially available HVPE substrates with a diameter of 50 mm produced values of 48 arcseconds and 53 arcseconds, respectively, and the same measurements on commercially available HVPE substrates with a diameter of 100 mm produced values of 78 arcseconds and 93 arcseconds, respectively.

[0122] Example 5 A c-plane oriented bulk GaN crystal grown by HVPE with a thickness of about 0.3 millimeters was provided for use as a substrate for patterning and ammonothermal crystal growth. A 100-nanometer-thick layer of TiW was sputter deposited as an adhesion layer on the (000-1)N surface of the substrate, followed by deposition of an inert layer with a thickness of 780 nanometers containing Au. Next, a 6-micrometer-thick Au layer was electroplated on the sputter layer to increase the thickness of the inert layer. A nanosecond pulsed frequency-doubled YAG laser was used to form a pattern on the N surface of the substrate. The pattern consisted of an m-trench domain with linear openings approximately 50-60 micrometers wide and oriented parallel to <10-10> with a pitch of 1200 micrometers. Next, the patterned substrate was placed in a stirring beaker containing concentrated H3PO4. The beaker was heated to approximately 280 degrees Celsius over about 30 minutes, held at this temperature for about 60 minutes, and then cooled. The cross-section of the trench formed by this procedure, having a depth of approximately 200 micrometers and an upper width of approximately 80 micrometers, is shown in FIG. 15. The sidewalls of the trench are surprisingly nearly vertical.

[0123] Example 6 A patterned c-plane oriented bulk GaN substrate with trenches was prepared in a procedure similar to that described in Example 5, except that a high output of laser was used to form slots that completely penetrate the substrate. After etching with concentrated H3PO4 at about 280 degrees Celsius for about 30 minutes, the width of the slots was about 115 micrometers. The patterned substrate was placed in a silver capsule together with a baffle with 15% open area, polycrystalline GaN raw material, NH4F mineralizer, and ammonia, and the capsule was sealed. The ratios of the GaN raw material and the NH4F mineralizer to ammonia were about 1.74 and 0.099 by weight, respectively. The capsule was placed in an internally heated high-pressure apparatus, heated to about 667 degrees Celsius in the upper raw material zone and about 681 degrees Celsius in the lower crystal growth zone, maintained at these temperatures for about 500 hours, then cooled and removed. Ammonothermal GaN filled most of the volume in the trenches of the substrate with formed trenches, grew through the linear openings of the patterned mask on the HVPE GaN substrate, grew laterally, and completely merged to form an ammonothermal GaN layer about 2010 micrometers thick with a smooth upper surface. The surface of the ammonothermal GaN layer was lightly etched and examined with an optical microscope. A photomicrograph of this layer is shown in Figure 16. The etch pits within rectangles A, B, C, D, E, F, and G shown in Figure 16 were counted, and the average etch pit density (thought to accurately represent the threading dislocation density) of the ammonothermal GaN layer grown on the patterned, laser-trenched substrate was about 6.0×10 3 cm -2 resulted in the determination that it was.

[0124] Example 7 Similar to the configuration shown in FIG. 17E, four c-plane oriented bulk GaN seed crystals were laser cut from three 100 mm diameter bulk GaN wafers such that the linear cut edges were approximately the a-plane. A 100 nanometer thick layer of TiW was sputter deposited as an adhesive layer on the (000-1)N plane of the seed crystal, followed by deposition of a 2.6 micrometer thick layer containing Ag. A nanosecond pulsed frequency doubled YAG laser was used to form a pattern on the N plane of the seed crystal. The pattern consisted of an m-trench domain with linear openings oriented parallel to <10-10> that formed a triangular pattern. Four tiles were placed on a flat Mo backing plate within a Mo alignment ring such that the linear tile edges and off-cut directions were aligned. Similar to the configuration shown in FIG. 18D, an Ag circular ring gasket and a Mo circular ring clamp were placed on top of the seed crystal and clamped to the backing plate using four Mo bolts to secure the seed crystal. Four additional Mo bolts were attached to through holes in two of the larger seed crystals to secure the latter to the backing plate and suggest tile warping. The assembled fixture had an exposed circular tile area of approximately 5.3 inches (about 13.462 cm) in diameter. The assembled fixture was placed in a silver capsule together with a baffle with a 7% open area, polycrystalline GaN feedstock, NH4F mineralizer, and ammonia, and the capsule was sealed. The ratios of the GaN feedstock and NH4F mineralizer to ammonia were approximately 2.53 and 0.094 by weight, respectively. The capsule was placed in an internally heated high pressure apparatus and heated to approximately 667 degrees Celsius in the upper feedstock zone and approximately 680 degrees Celsius in the lower crystal growth zone, maintained at these temperatures for approximately 500 hours, then cooled and removed. Ammonothermal GaN grew through the linear openings of the patterned mask on the seed crystal, grew laterally, and coalesced between the patterned trenches and between the seed crystals to form an ammonothermal GaN layer approximately 2600 micrometers thick, circular in diameter approximately 5.3 inches (about 13.462 cm), and containing four domains. X-ray diffraction measurements performed across the entire tile-like interface after growth showed a crystal orientation difference of approximately 0.2 degrees between adjacent tile-like domains.

[0125] Example 8 Similar to the configuration shown in FIG. 17E, four c-plane oriented bulk GaN seed crystals are laser cut from three 100 mm diameter bulk GaN wafers such that the linear cut edges are approximately the a-plane. An AlN layer with a thickness of 200 nanometers is sputtered onto the (0001)Ga plane of the seed crystal. A very fine BN particle suspected to be a volatile organic carrier is sprayed onto a Mo susceptor composed of a backing plate and an alignment ring to form a release layer. The four seed crystals are placed with the (000-1)N plane down on a flat Mo susceptor within the Mo alignment ring such that the linear tile edges and the off-cut directions are accurately aligned. The susceptor is horizontally placed in a poly-GaN reactor to grow a conformal polycrystalline GaN layer with a thickness of about 1 mm to form a continuous polycrystalline GaN handle on the (0001)Ga plane of the four seed crystals. After the growth of the polycrystalline GaN is completed and the reactor is cooled, the susceptor is removed from the poly-GaN reactor with the seed crystal and the polycrystalline GaN intact. The seed crystal embedded in the polycrystalline GaN matrix is separated from the Mo backing plate by separation in the release layer. A nanosecond pulsed frequency-doubled YAG laser trims the edges of the tile-shaped composite structure to form a circular tile-shaped composite with a diameter of about 5.3 inches (about 13.462 cm). The large-area exposed polycrystalline GaN handle and the surface of the (000-1)N plane are subjected to grinding, polishing, and chemical mechanical polishing. A 100 nanometer thick layer of TiW is sputter deposited as an adhesive layer on the (000-1)N plane of the seed crystal, followed by the deposition of a 1.3 micrometer thick layer containing Ag. Next, a 6 micrometer thick Au layer is electroplated on the (000-1)N plane of the seed crystal and the surface of the exposed polycrystalline GaN handle. A nanosecond pulsed frequency-doubled YAG laser is used to form a pattern on the N plane of the tile piece. The pattern includes an m-trench domain with linear openings oriented parallel to <10-10> that form a triangular pattern. Next, the patterned, tile-shaped composite structure is placed in a silver capsule together with a baffle with a 15% open area, polycrystalline GaN raw material, NH4F mineralizer, and ammonia, and the capsule is sealed.The ratios of GaN raw material and NH4F mineralizer to ammonia are approximately 1.74 and 0.099 by weight, respectively. The capsule was placed in an internally heated high-pressure apparatus and heated to approximately 667 degrees Celsius in the upper raw material zone and approximately 681 degrees Celsius in the lower crystal growth zone, maintained at these temperatures for about 500 hours, then cooled and removed. Ammonothermal GaN grows through the linear openings of the patterned mask on the seed crystal, grows laterally, and coalesces between the patterned trenches and tile pieces to form an ammonothermal GaN layer with a thickness of approximately 3000 micrometers.

[0126] Example 9 A tile-like composite structure similar to that described in Example 8 is prepared, except that 38 seed crystals having an orientation of (30-3-1), dimensions of 10 millimeters in a direction parallel to the c-axis projection and 20 millimeters in the m direction, and a thickness of 300 micrometers are used. The edges of the seed crystals constituting the periphery of the array are laser trimmed to a circle with a diameter of 95 millimeters before placing the seed crystals on the Mo susceptor with the (30-3-1) plane facing down. After depositing a 1-millimeter-thick polycrystalline GaN matrix on the (30-31) side of the seed crystal and the susceptor, the tile-like composite structure is removed from the susceptor by separating it with a release layer. The periphery of the tile-like composite structure is ground to a diameter of 100 millimeters, and a plane parallel to the m plane of the seed crystal is ground at one edge. Following a 1000-grit grinding wheel, a 4800-grit grinding wheel is used to grind the back side of the tile-like composite structure to form a plane exactly parallel to the front surface. Next, the front surface of the tile-like composite structure is chemically mechanically polished to remove about 15 micrometers of material to produce a tile-like composite substrate with a thickness of 600 micrometers similar to the substrate shown in Figure 19G.

[0127] Next, the tile-shaped composite substrate is placed on a susceptor in a commercially available MOCVD reactor. An n-type GaN layer is deposited, followed by deposition of an InGaN strained-layer superlattice release layer, followed by deposition of another n-type GaN layer, followed by deposition of an n-type InGaN cladding layer, followed by deposition of an undoped InGaN multiple quantum well, followed by deposition of a p-type cladding layer, followed by deposition of a p-type layer and a p-contact layer. Next, trenches are formed by conventional lithography, and a mesa having a length of about 1200 micrometers along the projection of the c-direction of the (30-3-1) plane and a width of 100 micrometers along the orthogonal m-direction is formed. About 95% of the release layer is etched away by a photoelectrochemical process using a KOH solution and illumination of 405 nanometers. Next, a gold-containing adhesive layer is deposited on the p-contact layer, the mesa structure is transferred to a silicon carbide handle substrate in a continuous process by thermocompression bonding, and then the remaining release layer is fractured. After removal of the mesa structure, the surface of the tile-shaped composite substrate is re-prepared by chemical mechanical polishing.

[0128] The above is directed to embodiments of the present disclosure, but other and further embodiments of the present disclosure can be devised without departing from the basic scope thereof, which is determined by the following claims.

[0129] Hereinafter, preferred embodiments of the present invention will be described item by item.

[0130] Embodiment 1 A self-supporting group III metal nitride substrate including at least two crystals, each of the at least two crystals comprising a group III metal selected from gallium, aluminum, and indium, or a combination thereof, and nitrogen, wherein each of the at least two crystals having a wurtzite crystal structure has a first surface having a maximum dimension exceeding 10 millimeters in a first direction and a maximum dimension exceeding 4 millimeters in a second direction orthogonal to the first direction, 10 2 cm -2 from 1×10 6 cm -2The average density of threading dislocations between, 10 3 cm -1 The average density of stacking defects less than, the full width at half maximum of the symmetric X-ray rocking curve less than 200 seconds of arc, including The magnitude of the crystallographic misorientation of the first surface of each of the at least two crystals is equal within 0.5 degrees, The direction of the crystallographic misorientation of the first surface of each of the at least two crystals is equal within 10 degrees, Each of the at least two crystals is bonded to a matrix member containing polycrystalline GaN, and The polar azimuth difference angle γ between the first surface of the first crystal of the at least two crystals and the first surface of the second crystal of the at least two crystals is greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β are greater than about 0.01 degrees and less than about 1 degree, A self-supporting group III metal nitride substrate.

[0131] Embodiment 2 The self-supporting group III metal nitride substrate according to Embodiment 1, wherein the self-supporting group III metal nitride substrate has a maximum dimension in the first direction exceeding 40 millimeters.

[0132] Embodiment 3 The self-supporting group III metal nitride substrate according to Embodiment 2, wherein the magnitude of the crystallographic misorientation of the first surface of each of the at least two crystals is equal within 0.2 degrees, and the direction of the crystallographic misorientation of the first surface of each of the at least two crystals is equal within 2 degrees.

[0133] Embodiment 4 The self-supporting group III metal nitride substrate according to Embodiment 2, wherein each of the first surfaces has a crystal orientation within 5 degrees of an orientation selected from {20 - 2 ± 1}, {30 - 3 ± 1}, and {10 - 10}, and a misorientation in the a direction of less than 0.5 degrees.

[0134] Embodiment 5 The self-supporting group-III metal nitride substrate according to Embodiment 4, wherein each of the first surfaces has a crystal orientation within 1 degree of an orientation selected from {20-2±1}, {30-3±1}, and {10-10}, and a misorientation in the a direction of less than 0.1 degree.

[0135] Embodiment 6 The self-supporting group-III metal nitride substrate according to Embodiment 2, wherein the maximum dimension in the first direction is between 45 and 110 millimeters.

[0136] Embodiment 7 The self-supporting group-III metal nitride substrate has a thickness of from about 150 micrometers to about 2 millimeters, a total thickness variation of less than about 25 micrometers, and a macroscopic warp of less than about 50 micrometers and further includes the self-supporting group-III metal nitride substrate according to Embodiment 2.

[0137] Embodiment 8 The self-supporting group-III metal nitride substrate according to Embodiment 1, wherein a gap is formed between adjacent edges of each of the at least two crystals, and the matrix member at least partially fills the gap.

[0138] Embodiment 9 The self-supporting group-III metal nitride substrate according to Embodiment 1, wherein each of the first surfaces of the at least two crystals has a crystal orientation within 5 degrees of the {10-10} m-plane.

[0139] Embodiment 10 The self-supporting group-III metal nitride substrate according to Embodiment 1, wherein each of the first surfaces of the at least two crystals has a crystal orientation within 5 degrees of the (0001)+c plane or within 5 degrees of the (000-1)-c plane.

[0140] Embodiment 11 The self-supporting group-III metal nitride substrate according to Embodiment 1, wherein each of the first surfaces of the at least two crystals has a crystal orientation within 5 degrees from a semi-polar orientation selected from {60-6±1}, {50-5±1}, {40-4±1}, {30-3±1}, {50-5±2}, {70-7±3}, {20-2±1}, {30-3±2}, {40-4±3}, {50-5±4}, {10-1±1}, {10-1±2}, {10-1±3}, {21-3±1}, and {30-3±4}.

[0141] Embodiment 12 The first surface is 1×10 16 cm -3 to 1×10 19 cm -3 of oxygen (O), 1×10 16 cm -3 to 2×10 19 cm -3 of hydrogen (H), and 1×10 15 cm -3 to 1×10 19 cm -3 of at least one of fluorine (F) and chlorine (Cl) having an impurity concentration, the self-supporting group-III metal nitride substrate according to Embodiment 1.

[0142] Embodiment 13 The first surface is 1×10 16 cm -3 to 1×10 19 cm -3 of oxygen (O), 1×10 16 cm -3 to 2×10 19 cm -3 of hydrogen (H), and 3×10 15 cm -3 to 1×10 18 cm -3 of at least one of sodium (Na) and potassium (K) The self-supporting group-III metal nitride substrate according to Embodiment 1, having the impurity concentration of

[0143] Embodiment 14 The self-supporting group-III metal nitride substrate according to Embodiment 1, further including an interface layer at an interface between at least one of the at least two crystals and the matrix member.

[0144] Embodiment 15 The self-supporting group-III metal nitride substrate according to Embodiment 14, wherein the interface layer includes at least one of graphite, boron nitride, molybdenum disulfide, and tungsten disulfide.

[0145] Embodiment 16 The self-supporting group-III metal nitride substrate according to Embodiment 1, wherein each of the first surfaces of the at least two crystals is substantially parallel to a first plane.

[0146] Embodiment 17 The self-supporting group-III metal nitride substrate according to Embodiment 1, wherein the matrix member has a diameter exceeding 40 mm.

[0147] Embodiment 18 The self-supporting group-III metal nitride substrate according to Embodiment 1, wherein the matrix member further includes a porous member.

[0148] Embodiment 19 The self-supporting group-III metal nitride substrate according to Embodiment 18, wherein the porous member includes at least one of graphite, carbon fiber, silica fiber, aluminosilicate fiber, borosilicate fiber, silicon carbide coating, pyrolytic boron nitride coating, or pyrolytic graphite coating.

[0149] Embodiment 20 In a self-supporting group-III metal nitride substrate, An array of seed crystals, each of the seed crystals in the array of seed crystals comprising a Group III metal selected from gallium, aluminum, and indium, or a combination thereof, and nitrogen; and A polycrystalline GaN layer disposed on at least one surface of each of the seed crystals in the array of seed crystals comprising, wherein each of the seed crystals having a wurtzite crystal structure has an average density of threading dislocations between 10 2 cm -2 and 1×10 6 cm -2 , and an average density of stacking defects of less than 10 3 cm -1 , and includes a first surface having the magnitude of the crystallographic misorientation of the first surface of each of the seed crystals being equal within 0.5 degrees, the direction of the crystallographic misorientation of the first surface of each of the seed crystals being equal within 10 degrees, and the polar azimuth difference angle γ between a first seed crystal of the array of seed crystals and a second seed crystal of the array of seed crystals being greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β being greater than about 0.01 degrees and less than about 1 degree, a self - supporting Group III metal nitride substrate.

[0150] Embodiment 21 each of the seed crystals being comprising a symmetric X - ray rocking curve full - width at half - maximum of less than 200 seconds of arc, and a maximum dimension greater than 10 millimeters in the first direction and a maximum dimension greater than 4 millimeters in a second direction orthogonal to the first direction The self - supporting Group III metal nitride substrate according to embodiment 20.

[0151] Embodiment 22 The self - supporting Group III metal nitride substrate according to embodiment 20, wherein the matrix member has a diameter greater than 40 mm.

[0152] Embodiment 23 The self-supporting group-III metal nitride substrate according to embodiment 20, wherein each of the first surfaces has a crystal orientation within 5 degrees of an orientation selected from {20-2±1}, {30-3±1}, and {10-10}, and a miscut in the a direction of less than 0.5 degrees.

[0153] Embodiment 24 The self-supporting group-III metal nitride substrate has a thickness between about 150 micrometers and about 2 millimeters, a total thickness variation of less than about 25 micrometers, and a macroscopic warp of less than about 50 micrometers and further includes the self-supporting group-III metal nitride substrate according to embodiment 20.

[0154] Embodiment 25 A self-supporting group-III metal nitride substrate including at least two crystals, wherein each of the at least two crystals contains a group-III metal selected from gallium, aluminum, and indium, or a combination thereof, and nitrogen, where each of the at least two crystals having a wurtzite crystal structure has a first surface having a maximum dimension exceeding 10 millimeters in a first direction and a maximum dimension exceeding 4 millimeters in a second direction orthogonal to the first direction, 10 2 cm -2 to 1×10 6 cm -2 and an average density of threading dislocations between, 10 3 cm -1 an average density of stacking defects of less than, and a symmetric X-ray rocking curve full width at half maximum of less than 200 seconds of arc, the magnitude of the crystallographic miscut of the first surface of each of the at least two crystals is equal within 0.5 degrees, the direction of the crystallographic miscut of the first surface of each of the at least two crystals is equal within 10 degrees, each of the at least two crystals is bonded to a matrix member containing polycrystalline GaN, and The polar azimuth difference angle γ between the first surface of the first crystal of the at least two crystals and the first surface of the second crystal of the at least two crystals is greater than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β are greater than about 0.01 degrees and less than about 1 degree. Self-supporting group-III metal nitride substrate.

[0155] Embodiment 26 The self-supporting group-III metal nitride substrate according to Embodiment 25, wherein the self-supporting group-III metal nitride substrate has a maximum dimension in the first direction exceeding 40 millimeters.

[0156] Embodiment 27 The self-supporting group-III metal nitride substrate according to Embodiment 26, wherein the magnitude of the crystallographic misorientation of each of the first surfaces of the at least two crystals is equal within 0.2 degrees, and the direction of the crystallographic misorientation of each of the first surfaces of the at least two crystals is equal within 2 degrees.

[0157] Embodiment 27 The self-supporting group-III metal nitride substrate according to Embodiment 26, wherein each of the first surfaces has a crystal orientation within 5 degrees of an orientation selected from {20-2±1}, {30-3±1}, and {10-10}, and a misorientation in the a direction of less than 0.5 degrees.

[0158] Embodiment 28 The self-supporting group-III metal nitride substrate according to Embodiment 27, wherein each of the first surfaces has a crystal orientation within 1 degree of an orientation selected from {20-2±1}, {30-3±1}, and {10-10}, and a misorientation in the a direction of less than 0.1 degree.

[0159] Embodiment 29 The self-supporting group-III metal nitride substrate according to Embodiment 26, wherein the maximum dimension in the first direction is between 45 and 110 millimeters.

[0160] Embodiment 30 The self-supporting group-III metal nitride substrate is A thickness of from about 150 micrometers to about 2 millimeters, a total thickness variation of less than about 25 micrometers, and a macroscopic warp of less than about 50 micrometers The self-supporting group-III metal nitride substrate according to Embodiment 26, further comprising.

[0161] Embodiment 31 The self-supporting group-III metal nitride substrate according to Embodiment 25, wherein a gap is formed between adjacent edges of each of the at least two crystals, and the matrix member fills at least partially the gap.

[0162] Embodiment 32 The self-supporting group-III metal nitride substrate according to Embodiment 25, wherein the first surface of each of the at least two crystals has a crystal orientation within 5 degrees from the {10-10}m plane.

[0163] Embodiment 33 The self-supporting group-III metal nitride substrate according to Embodiment 25, wherein the first surface of each of the at least two crystals has a crystal orientation within 5 degrees from the (0001)+c plane or within 5 degrees from the (000-1)-c plane.

[0164] Embodiment 34 The self-supporting group-III metal nitride substrate according to Embodiment 25, wherein the first surface of each of the at least two crystals has a crystal orientation within 5 degrees from a semi-polar orientation selected from {60-6±1}, {50-5±1}, {40-4±1}, {30-3±1}, {50-5±2}, {70-7±3}, {20-2±1}, {30-3±2}, {40-4±3}, {50-5±4}, {10-1±1}, {10-1±2}, {10-1±3}, {21-3±1}, and {30-3±4}.

[0165] Embodiment 35 The first surface is 1×10 16 cm -3 to 1×10 19 cm -3Oxygen (O) between 1×10 16 cm -3 to 2×10 19 cm -3 Hydrogen (H) between, and 1×10 15 cm -3 to 1×10 19 cm -3 At least one of fluorine (F) and chlorine (Cl) between The self-supporting group-III metal nitride substrate according to Embodiment 25, having an impurity concentration of

[0166] Embodiment 36 The first surface is 1×10 16 cm -3 to 1×10 19 cm -3 Oxygen (O) between 1×10 16 cm -3 to 2×10 19 cm -3 Hydrogen (H) between, and 3×10 15 cm -3 to 1×10 18 cm -3 At least one of sodium (Na) and potassium (K) between The self-supporting group-III metal nitride substrate according to Embodiment 25, having an impurity concentration of

[0167] Embodiment 37 The self-supporting group-III metal nitride substrate according to Embodiment 25, further including an interface layer at an interface between at least one of the at least two crystals and the matrix member.

[0168] Embodiment 38 The self-supporting group-III metal nitride substrate according to Embodiment 37, wherein the interface layer includes at least one of graphite, boron nitride, molybdenum disulfide, and tungsten disulfide.

[0169] Embodiment 39 The self-supporting group-III metal nitride substrate according to embodiment 25, wherein each of the first surfaces of the at least two crystals is substantially parallel to a first plane.

[0170] Embodiment 40 The self-supporting group-III metal nitride substrate according to embodiment 25, wherein the matrix member has a diameter exceeding 40 mm.

[0171] Embodiment 41 The self-supporting group-III metal nitride substrate according to embodiment 25, wherein the matrix member further includes a porous member.

[0172] Embodiment 42 The self-supporting group-III metal nitride substrate according to embodiment 41, wherein the porous member includes at least one of graphite, carbon fiber, silica fiber, aluminosilicate fiber, borosilicate fiber, silicon carbide coating, pyrolytic boron nitride coating, or pyrolytic graphite coating.

[0173] Embodiment 43 In a self-supporting group-III metal nitride substrate, An array of seed crystals, wherein each of the seed crystals in the array of seed crystals includes a group-III metal selected from gallium, aluminum, and indium, or a combination thereof, and nitrogen; and A polycrystalline GaN layer disposed on at least one surface of each of the seed crystals in the array of seed crystals wherein, Each of the seed crystals having a wurtzite crystal structure includes a first surface having an average density of threading dislocations between 10 2 cm -2 and 1×10 6 cm -2 and an average density of stacking defects less than 10 3 cm -1 and the magnitude of the crystallographic misorientation of the first surface of each of the seed crystals is equal to within 0.5 degrees. The crystallographic misorientation directions of the first surfaces of each of the seed crystals are equal within 10 degrees, and a self-supporting group III metal nitride substrate, wherein a polar azimuth difference angle γ between a first seed crystal of the array of seed crystals and a second seed crystal of the array of seed crystals is greater than about 0.005 degrees and less than about 0.2 degrees, and azimuth difference angles α and β are greater than about 0.01 degrees and less than about 1 degree.

[0174] Embodiment 44 each of the seed crystals has a symmetric X-ray rocking curve full width at half maximum of less than 200 seconds of arc, and a maximum dimension exceeding 10 millimeters in the first direction and a maximum dimension exceeding 4 millimeters in a second direction orthogonal to the first direction The self-supporting group III metal nitride substrate according to Embodiment 43, comprising:

[0175] Embodiment 45 The self-supporting group III metal nitride substrate according to Embodiment 43, wherein the matrix member has a diameter exceeding 40 mm.

[0176] Embodiment 46 The self-supporting group III metal nitride substrate according to Embodiment 43, wherein each of the first surfaces has a crystal orientation within 5 degrees of an orientation selected from {20 - 2 ± 1}, {30 - 3 ± 1}, and {10 - 10}, and a misorientation in the a direction of less than 0.5 degrees.

[0177] Embodiment 47 The self-supporting group III metal nitride substrate has a thickness between about 150 micrometers and about 2 millimeters, a total thickness variation of less than about 25 micrometers, and a macroscopic warp of less than about 50 micrometers The self-supporting group III metal nitride substrate according to Embodiment 43, further comprising:

Explanation of Reference Numerals

[0178] 101 Substrate 102 Large-area surface 103, 104 Photoresist layer 105 Adhesive layer 107 Diffusion barrier layer 109 Inactive layer 111 Mask layer 112 Opening 113 Photoresist layer 115 Trench 120 Exposed area 221 Group III metal nitride material 213 Group III metal nitride layer 215 Window area 217 Wing area 219 Core coalescence front 225 Void 370 Seed crystal 395 Edge 1810 Backing plate 1820, 1825 Through hole 1830 Retaining ring 1840 Clamping ring 1910 Susceptor 1921 Interface layer 1923 Release coating 1940 Porous member 1950 Polycrystalline GaN layer 1960 Tile-like composite structure 1970 Gap

Claims

1. It has a first surface capable of crystal growth and a second surface on the opposite side of the first surface, and at least two crystals containing a group III metal selected from at least one of gallium, aluminum, and indium and nitrogen, a matrix member that is in direct or indirect contact with at least a part of the at least two crystals and is composed of a polycrystalline member containing gallium and nitrogen, A nitride substrate in which at least a part of the matrix member is also located between the at least two crystals.

2. The nitride substrate according to claim 1, wherein the matrix member has a porous member that is in direct or indirect contact with the second surface of the at least two crystals.

3. The nitride substrate according to claim 2, wherein the porous member has through holes penetrating in the thickness direction, and the polycrystalline member is located in the through holes of the porous member and is in direct or indirect contact with the second surface.

4. The nitride substrate according to claim 3, wherein the interval between the at least two crystals is smaller than the width of the through hole of the porous member.

5. The nitride substrate according to any one of claims 1 to 4, wherein the interval between the at least two crystals is smaller than the lateral width of the crystal.

6. The nitride substrate according to any one of claims 1 to 5, wherein the matrix member further has a holding member located outside the at least two crystals.

7. The at least two crystals have a wurtzite crystal structure, a first surface having a maximum dimension exceeding 10 millimeters in a first direction and a maximum dimension exceeding 4 millimeters in a second direction orthogonal to the first direction, 10 １ cm －２ to 1×10 ６ cm －２ average density of threading dislocations between, 10 ３ cm －１ average density of stacking defects less than, and a symmetric X-ray rocking curve full width at half maximum of less than 200 seconds of arc, the nitride substrate according to any one of claims 1 to 6.

8. For each of the at least two crystals, the magnitude of the crystallographic misorientation of the first surface is equal to within 0.5 degrees, and the direction of the crystallographic misorientation of the first surface is equal to within 10 degrees. The nitride substrate according to any one of claims 1 to 7.

9. The at least two crystals have a first crystal and a second crystal, The polar orientation difference angle γ between the crystal orientation of the first surface of the first crystal and the crystal orientation of the first surface of the second crystal of the at least two crystals is more than about 0.005 degrees and less than about 0.2 degrees, and the azimuth difference angles α and β of the azimuth angles between the crystal orientations of the first surfaces of the first and second seed crystals are more than about 0.01 degrees and less than about 1 degree. The nitride substrate according to any one of claims 1 to 8.

10. The nitride substrate according to any one of claims 1 to 9, wherein the matrix member has a maximum dimension exceeding 40 millimeters.

11. The at least two crystals each have a crystal orientation within 5 degrees of an orientation selected from {20 - 2 ± 1}, {30 - 3 ± 1}, and {10 - 10} on each of the first surfaces and a misorientation in the a direction of less than 0.5 degrees, for the nitride substrate according to any one of claims 1 to 10.

12. The polycrystalline member is oriented in the c-axis direction, for the nitride substrate according to any one of claims 1 to 11.

13. The at least two crystals each have a crystal orientation within 5 degrees from the (0001)+c plane or within 5 degrees from the (000 - 1)-c plane on each of the first surfaces, for the nitride substrate according to any one of claims 1 to 12.

14. Each of the at least two crystals has an oxygen (O) concentration between 1×10 １６ cm －３ and 1×10 １９ cm －３ , a hydrogen (H) concentration between 1×10 １６ cm －３ and 2×10 １９ cm －３ , and an impurity concentration of at least one of fluorine (F) and chlorine (Cl) between 1×10 １５ cm －３ and 1×10 １９ cm －３ . The nitride substrate according to any one of claims 1 to 13.

15. Each of the at least two crystals has an oxygen (O) content between 1×10 １６ cm －３ and 1×10 １９ cm －３ , a hydrogen (H) content between 1×10 １６ cm －３ and 2×10 １９ cm －３ , and an impurity concentration of at least one of sodium (Na) and potassium (K) between 3×10 １５ cm －３ and 1×10 １８ cm －３ . The nitride substrate according to any one of claims 1 to 14.

16. The at least two crystals further include an interface layer at an interface between at least one of the at least two crystals and the matrix member, for the nitride substrate according to any one of claims 1 to 15.

17. The nitride substrate according to claim 16, wherein the interface layer includes at least one of graphite, boron nitride, molybdenum disulfide, and tungsten disulfide.

18. The at least two crystals further have a core coalescence front region where semiconductor layers extending from each of the first surfaces meet, and the core coalescence front region has threading dislocations, for the nitride substrate according to any one of claims 1 to 17.

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