III-nitride substrate and method for producing same

Abstract

Embodiments of the present disclosure include techniques related to processing materials to produce III-metal nitride and gallium-based substrates. More particularly, embodiments of the present disclosure include techniques for growing large area substrates using a combination of processing techniques. By way of example only, the present disclosure can be adapted to the growth of crystals such as GaN, AlN, InN, InGaN, and AlInGaN for the production of bulk or patterned substrates. Such bulk or patterned substrates can be used in a variety of applications including optoelectronic and electronic devices, lasers, light emitting diodes, solar cells, photoelectrochemical water splitting and hydrogen production, photodetectors, integrated circuits, and transistors.

Description

Description of Related Applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 321,530, filed March 18, 2022, which is incorporated herein by reference. [Technical field]

[0002] The present disclosure relates generally to techniques for processing materials to produce gallium-containing nitride substrates and the use of these substrates in optoelectronic and electronic devices. More specifically, embodiments of the present disclosure include techniques for growing large area substrates using a combination of processing techniques. [Background technology]

[0003] Gallium nitride (GaN) based optoelectronic and electronic devices are of great commercial importance. However, the quality and reliability of these devices are compromised by high defect levels, specifically threading dislocations, grain boundaries, and strain in the semiconductor layers of the devices. Threading dislocations can arise from the lattice mismatch of GaN based semiconductor layers to non-GaN substrates such as sapphire or silicon carbide. Grain boundaries can arise from coalescence fronts of epitaxially overgrown layers. Depending on the details of the growth of those layers, additional defects can arise from thermal expansion mismatch, impurities, and tilt boundaries.

[0004] The presence of defects can have a detrimental effect on epitaxial growth layers. Some of these defects can even lead to poor performance of electronic devices. Although techniques to eliminate the above-mentioned defects have already been proposed, these techniques require complex and cumbersome fabrication processes to reduce the density and effect of defects. Although many methods for growing gallium nitride crystals have been proposed, there are still limitations. In other words, conventional methods still need to be improved in terms of cost-effectiveness and efficiency.

[0005] The presence of defects has a detrimental effect on epitaxially grown layers. Such detrimental effects can impair the performance of electronic devices. To overcome these defects, techniques have been proposed that require complex and cumbersome manufacturing processes to reduce the concentration and / or effect of the defects. Numerous methods for growing gallium nitride crystals have been proposed in the past, but they still have limitations; that is, conventional methods have room for improvement in terms of cost-effectiveness and efficiency.

[0006] Advances have been made in growing large-area gallium nitride crystals with significantly lower defect levels than heteroepitaxial GaN layers. However, most techniques for growing large-area GaN substrates involve deposition of GaN on non-GaN substrates such as sapphire or GaAs. This approach typically results in threading dislocations of up to 10 times the thickness across the surface of a thick boule. 5 ~10 7 cm -2 Dislocations occur at an average concentration of 1000 Å, resulting in significant bow, stress, and distortion. A reduction in the concentration of threading dislocations is desirable for many applications. Bow, stress, and distortion can reduce yields when slicing the boule into wafers and can also lead to wafers being more susceptible to cracking in downstream processes, adversely affecting device reliability and lifetime. Another consequence of bow, stress, and distortion is that significant concentrations of stacking faults can occur during growth in m-plane and semipolar orientations, even when near equilibrium growth techniques such as ammonothermal growth are used. In addition, the quality of c-plane growth can be poor due to the formation of cracks and multiple crystallographic domains. The ability to produce substrates larger than 2 inches is currently very limited, as is the ability to produce large area GaN substrates with nonpolar or semipolar crystallographic orientations. Most large area substrates are produced by relatively expensive vapor phase techniques such as hydride vapor phase epitaxy (HVPE). A less expensive method that also achieves large area and low threading dislocation density as quickly as possible is desirable.

[0007] Ammonothermal crystal growth has many advantages over HVPE as a means of producing GaN boules. However, the performance of the ammonothermal GaN crystal growth process will depend heavily on the size and quality of the seed crystal. Seed crystals produced by HVPE may suffer from many of the limitations mentioned above, and large area ammonothermal grown crystals are not currently widely available. Numerous techniques, such as lateral epitaxial overgrowth (LEO), could beneficiate HVPE-derived seeds, but would still suffer from problems related to distortion, crack formation, and low yields. Several inventors, including Jiang et al. (Patent Documents 1 and 2), have disclosed methods to apply LEO techniques to ammonothermal growth, but these methods have several limitations and require improvement. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Pat. No. 9,589,792 [Patent Document 2] US Patent Application Publication No. 2021 / 0249252 Summary of the Invention [Problem to be solved by the invention]

[0009] Due to at least the problems discussed above, there is a need for lower defect density substrates formed by techniques that improve the crystal growth process, and in view of the above, techniques that improve crystal growth are highly desirable. [Means for solving the problem]

[0010] Embodiments of the present disclosure may provide a crystal comprising a Group III metal and nitrogen, the crystal being free-standing and having a wurtzite crystal structure; a first face having a maximum dimension in a first direction of greater than 40 millimeters and having a crystallographic orientation within 5 degrees of one of (0001) and (000-1); 3 cm-1 average concentration of stacking faults less than 10 1 cm -2 and 10 6 cm -2 , the average concentration of threading dislocations on the first surface varies in a first direction within the first domains with a period of at least two, the period of the variation in the first direction being between 5 micrometers and 20 millimeters, and the first domains have a maximum dimension in the first direction greater than 500 micrometers. -1 and 10 5 cm -1 and wherein at least 50% of the intersections between adjacent locally substantially linear arrays of threading dislocations substantially consist of three locally substantially linear arrays of threading dislocations that meet at an intersection angle of 120°±3°. 5 cm -2 Concentration of threading dislocations less than 10 3 cm -1 The first surface further includes a plurality of second regions, each disposed within one of the plurality of second regions or between an adjacent pair of the second regions, each having a minimum dimension between 10 micrometers and 500 micrometers and a minimum dimension between 10 micrometers and 500 micrometers. 3 cm -2 and 10 8 cm -2 The first domain is surrounded by six domains, where the orientation of between 55% and 100% of the plurality of third regions is oriented along a third direction, rotated by 60°±3° from the first direction, or along a fourth direction, rotated by 120°±3° from the first direction, and the orientation of between 55% and 100% of the plurality of third regions within the third domain of the six surrounding domains alternates between the third direction and the fourth direction.

[0011] An embodiment of the present disclosure provides a crystal comprising a Group III metal and nitrogen, the crystal being free-standing and having a wurtzite crystal structure; a first face having a maximum dimension greater than 5 millimeters in a first direction, the first face having a crystallographic orientation within 5 degrees of one of (0001) and (000-1); 3 cm -1 average concentration of stacking faults less than 10 1 cm -2 and 10 6 cm -2 , the average concentration of threading dislocations on the first face varies in a first direction within the first domains with a period of at least two, the period of the variation in the first direction being between 5 micrometers and 20 millimeters, and the first domains have a maximum dimension in the first direction of greater than 500 micrometers. -1 and 10 5 cm -1 and wherein at least 50% of the intersections between adjacent locally substantially linear arrays of threading dislocations meet at an intersection angle of 120°±3°. The first surface includes a plurality of first regions each having a locally substantially linear array of threading dislocations having a concentration between 10 5 cm -2 Concentration of threading dislocations less than 10 3 cm -1 The first surface further includes a plurality of second regions each disposed within one of the plurality of second regions or between an adjacent pair of the second regions, the first surface having a minimum dimension between 10 micrometers and 5 millimeters and a minimum dimension between 10 micrometers and 5 millimeters. 3 cm -2 and 10 8 cm -2 The third region further includes a plurality of threading dislocations having a concentration between.

[0012] In some embodiments, the plurality of third regions comprises a two-dimensional pattern of third regions comprising repeating units of the third regions, each repeating unit comprising a portion of a first linear array of primary third regions extending in a first direction, a portion of a second linear array of primary third regions extending in a second direction, and a portion of a third linear array of two or more primary third regions extending in a third direction, the first linear array, the second linear array, and the third linear array of primary third regions intersecting at a plurality of intersection points. Each of the primary third regions may have a rectangular shape with a minor dimension between about 3 micrometers and about 100 micrometers and a major dimension between about 200 micrometers and about 5 millimeters.

[0013] In some other embodiments, the plurality of third regions includes a two-dimensional array of major third regions having a rectangular shape with a minor dimension between about 3 micrometers and about 100 micrometers and a major dimension between about 200 micrometers and about 5 millimeters, a first end of each of the major third regions positioned a first distance from a center point, each major third region extending through a center of each major third region, and oriented such that a line parallel to the major dimension of the major third region does not coincide with the center point.

[0014] An embodiment of the present disclosure provides a crystal comprising a Group III metal and nitrogen, the crystal being freestanding and having a wurtzite crystal structure; a first face having a largest dimension greater than 5 millimeters in a first direction, the first face having a crystallographic orientation within 5 degrees of one of (0001) and (000-1), the first direction being aligned within ±3° of a crystallographic orientation selected from <10-10> and <11-20>; 3 cm -1 average concentration of stacking faults less than 10 1 cm -2 and 10 6 cm -2and the average concentration of threading dislocations on the first surface has a period of variation that varies by a period of at least two in each of a first direction, a second direction rotated 60 degrees from the first direction, and a third direction rotated 120 degrees from the first direction, and the periods of variation in the first direction, second direction, and third direction are equal to within a factor of two and each is between 5 micrometers and 20 millimeters. The first surface includes a plurality of first regions, each of the plurality of first regions being equal to or greater than 5 cm. -1 and 10 5 cm -1 and between 5% and 75% of the intersections between adjacent locally substantially linear arrays of threading dislocations include only three locally substantially linear arrays of threading dislocations that meet at an intersection angle of 120°±3°. 5 cm -2 Concentration of threading dislocations less than 10 3 cm -1 The first surface further includes a plurality of second regions, each of which is disposed within one of the plurality of second regions or at least partially between an adjacent pair of the second regions, and has a minimum dimension between 10 micrometers and 5 millimeters and a minimum dimension between 10 micrometers and 5 millimeters. 3 cm -2 and 10 8 cm -2 The third region further includes a plurality of threading dislocations having a concentration between. [Brief description of the drawings]

[0015] Having briefly summarized the present disclosure above, in order that the above-listed features of the present disclosure may be understood in detail, the present disclosure will now be described in more detail with reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings only illustrate exemplary embodiments, and therefore should not be considered as limiting the scope thereof, as other embodiments having similar effect may be recognized. [Figure 1A]FIG. 1 is a simplified diagram illustrating certain stages in a method for forming a patterned photoresist layer on a seed crystal or substrate, according to an embodiment of the present disclosure. [Figure 1B] FIG. 1 is a simplified diagram illustrating the next steps in a method for forming a patterned photoresist layer on a seed crystal or substrate, according to an embodiment of the present disclosure. [Figure 1C] FIG. 1 is a simplified diagram illustrating the next steps in a method for forming a patterned photoresist layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1D] FIG. 1 is a simplified diagram illustrating a method of forming a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1E] FIG. 1 is a simplified diagram illustrating a method of forming a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1F] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1G] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1H] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1I] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1J] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1K] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1L] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1M] 1 is a simplified diagram illustrating certain stages in a method for forming a patterned photoresist layer on a seed crystal or substrate according to an alternative embodiment of the present disclosure. [Figure 1N]FIG. 1 is a simplified diagram illustrating the next steps in a method of forming a patterned photoresist layer on a seed crystal or substrate, according to an alternative embodiment of the present disclosure. [Figure 1O] FIG. 1 is a simplified diagram illustrating a method of forming a patterned mask layer on a seed crystal or substrate according to an alternative embodiment of the present disclosure. [Figure 1P] FIG. 1 is a simplified diagram illustrating a method of forming a patterned mask layer on a seed crystal or substrate according to an alternative embodiment of the present disclosure. [Figure 1Q] FIG. 1 is a simplified diagram illustrating a method for forming a patterned trench in a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1R] FIG. 1 is a simplified diagram illustrating an alternative method of forming patterned trenches in a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1S] FIG. 1 is a simplified diagram illustrating an alternative method of forming patterned trenches in a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 1T] FIG. 1 is a simplified diagram illustrating an alternative method of forming patterned trenches in a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 2A] FIG. 1 is a simplified diagram illustrating an epitaxial lateral overgrowth process for forming large area group III metal nitride crystals according to an embodiment of the present disclosure. [Figure 2B] FIG. 1 is a simplified diagram illustrating an epitaxial lateral overgrowth process for forming large area group III metal nitride crystals according to an embodiment of the present disclosure. [Figure 2C] FIG. 1 is a simplified diagram illustrating an epitaxial lateral overgrowth process for forming large area group III metal nitride crystals according to an embodiment of the present disclosure. [Figure 3A] FIG. 1 is a simplified diagram illustrating an improved epitaxial lateral overgrowth process for forming large area group III metal nitride crystals according to an embodiment of the present disclosure. [Figure 3B] FIG. 1 is a simplified diagram illustrating an improved epitaxial lateral overgrowth process for forming large area group III metal nitride crystals according to an embodiment of the present disclosure. [Figure 3C]FIG. 1 is a simplified diagram illustrating an improved epitaxial lateral overgrowth process for forming large area group III metal nitride crystals according to an embodiment of the present disclosure. [Figure 3D] FIG. 1 is a simplified diagram illustrating an improved epitaxial lateral overgrowth process for forming large area group III metal nitride crystals according to an embodiment of the present disclosure. [Figure 3E] FIG. 1 is a simplified diagram illustrating an improved epitaxial lateral overgrowth process for forming large area group III metal nitride crystals according to an embodiment of the present disclosure. [Figure 3F] FIG. 1 is a simplified diagram illustrating an improved epitaxial lateral overgrowth process for forming large area group III metal nitride crystals according to an embodiment of the present disclosure. [Figure 4A] Simplified diagram showing a method for forming a free-standing ammonothermal group III metal nitride boule and a free-standing ammonothermal group III metal nitride wafer. [Figure 4B] Simplified diagram showing a method for forming a free-standing ammonothermal group III metal nitride boule and a free-standing ammonothermal group III metal nitride wafer. [Figure 5A] FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 5B] FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 5C] FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 5D] FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 5E] FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 5F]FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 5G] FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 6] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 7A] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 7B] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 7C] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 7D] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 7E] FIG. 1 is a top view of an arrangement of exposed areas in a patterned mask layer on a seed crystal or substrate according to an embodiment of the present disclosure. [Figure 8A] FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 8B] FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 8C] FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 8D] FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a free-standing ammonothermal group III metal nitride boule or wafer according to an embodiment of the present disclosure. [Figure 8E]FIG. 1 is a simplified diagram showing threading dislocation patterns and regions on a freestanding ammonothermal Group III metal nitride boule or wafer according to an embodiment of the present disclosure. To facilitate understanding, identical reference numbers have been used, where possible, to designate identical elements common to the figures. It is contemplated that elements and features of one embodiment may be incorporated into other embodiments, as appropriate, unless specifically noted otherwise. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present disclosure provides techniques for processing materials to produce III-metal nitride and gallium-based substrates. More specifically, embodiments of the present disclosure include techniques for growing large area substrates using a combination of processing techniques. By way of example only, the present disclosure can be applied to the growth of crystals such as GaN, AlN, InN, InGaN, AlGaN, and AlInGaN for the production of bulk or patterned substrates. Such bulk and 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 production, photodetectors, integrated circuits, and transistors.

[0017] 1A-1E are schematic cross-sectional views of a seed crystal or substrate during various stages of a method for forming a patterned mask seed layer for ammonothermal sidewall lateral epitaxial overgrowth. Referring to FIG. 1A, a substrate 101 is provided with a photoresist layer 103 disposed thereon. In certain embodiments, the substrate 101 is made of or includes a substrate material that is a monocrystalline group III metal nitride, a gallium-containing nitride, or a gallium nitride. The substrate 101 may be grown by HVPE, ammonothermal, or flux methods. One or both large area surfaces of the substrate 101 may be polished and / or chemically mechanically polished. The large area surface 102 of the substrate 101 may have a crystallographic orientation within 5 degrees, within 2 degrees, within 1 degree, or within 0.5 degrees of the (001)+c-plane, the (000-1)-c-plane, the {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}. Planes {30-3±4} will be understood to mean {30-34} planes and {30-3-4} planes. The large area surface 102 may have a (hkil) semipolar orientation, where i=-(h+k) and l and at least one of h and k are non-zero. The large area surface 102 may 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 may have a thickness between about 10 micrometers and about 10 millimeters, or between about 100 micrometers and about 2 millimeters.

[0018] The substrate 101 is approximately 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 The surface may have a surface threading dislocation density of less than 100 nm.

[0019] The large area surface 102 (FIG. 1A) may have a crystallographic orientation within about 5 degrees of the (000-1) N-plane, c-plane orientation, and may have an x-ray diffraction omega-scan rocking curve full width at half maximum (FWHM) for the (002) and / or (102) reflections of less than about 200 arc seconds, less than about 100 arc seconds, less than about 50 arc seconds, or less than about 30 arc seconds, and may have an x-ray diffraction omega-scan rocking curve full width at half maximum (FWHM) for the (002) and / or (102) reflections of less than about 10 7 cm -2 Less than, about 10 6 cm -2 Less than or about 10 5 cm -2 In some embodiments, the threading dislocations in the large area surface 102 are approximately uniformly distributed. In other embodiments, the threading dislocations in the large area surface 102 are arranged non-uniformly, such as as a one-dimensional array of rows of regions of relatively high and relatively low concentration, or as a two-dimensional array of high dislocation density regions within a matrix of low dislocation density regions. The crystallographic orientation of the large area surface 102 may be constant to less than about 5 degrees, less than about 2 degrees, less than about 1 degree, less than about 0.5 degrees, less than about 0.2 degrees, less than about 0.1 degrees, or less than about 0.05 degrees.

[0020] In certain embodiments, the large area surface 102 is roughened to enhance adhesion of the mask layer and to form a matte morphology, for example, by wet etching in at least a first etchant. In certain embodiments, the wet etching is performed in at least a first etchant, and optionally followed by a second etchant. In certain embodiments, the roughening is performed by etching in a solution of H2O2:NH4OH in a ratio of between about 1:3 and about 3:1 at a temperature between about 15°C and about 50°C for a time between about 10 minutes and about 100 hours. In certain embodiments, the roughening is performed by etching in a solution containing at least one of NaOH and KOH in a concentration between about 0.01 molar and about 5 molar at a temperature between about 15°C and about 95°C for a time between about 10 minutes and about 100 hours. In certain embodiments, at least one of the first etchant and the second etchant comprises one or more of silicic acid hydrate, orthosilicic acid, boric acid, nitric acid, chlorosulfonic acid, sulfamic acid, nitrosylsulfuric acid, methanesulfonic acid, potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, and the like. In certain embodiments, the roughening process comprises or consists of a photochemical and / or photoelectrochemical process including above band gap irradiation of the surface 102. In certain embodiments, the roughened surface comprises pyramidal, pyramidal-like, and / or conical features. In certain embodiments, the roughened surface has a root mean square roughness between about 100 nanometers and about 500 micrometers, between about 1 micrometer and about 200 micrometers, or between about 10 micrometers and about 100 micrometers. In certain embodiments, the roughening process is performed after forming the surface 102 by wire-sawing and / or grinding. In certain embodiments, surface 102 is not chemically mechanically polished and has a root mean square roughness of between about 1 micrometer and about 500 micrometers, or between about 10 micrometers and about 100 micrometers, prior to undergoing a roughening process. In certain embodiments, some smoothing of surface 102 occurs along with some roughening of features of different length scales or different morphologies, for example.

[0021] Referring again to FIG. 1A, a photoresist layer 103 may be deposited on the large area surface 102 by methods known in the art. For example, in a particular embodiment of a lift-off process, a solution of negative photoresist is first applied to the large area surface 102. The substrate 101 is then spun at high speed (e.g., between 1000 and 6000 revolutions per minute for 30 to 60 seconds) to form a uniform photoresist layer 103 on the large area surface 102. The photoresist layer 103 may then be baked (e.g., between about 90° C. and about 120° C.) to remove excess photoresist solvent. After baking, the photoresist layer 103 may then be exposed to ultraviolet light through a photomask (not shown) to form a patterned photoresist layer 104 (FIG. 1B) having a predetermined pattern of crosslinked photoresist, such as regions 104A, formed in unexposed regions 104B. The regions 104B of the patterned photoresist may form stripes or dots having a representative width or diameter W and a pitch L. Patterned photoresist layer 104 can then be developed to remove the uncrosslinked material found in areas 104B, leaving behind areas 104A, as shown in FIG. 1C.

[0022] 1D , one or more patterned mask layers 111 may be deposited on the large area surface 102 and regions 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 a passivation layer 109 deposited on the diffusion barrier layer 107.

[0023] In certain embodiments, the adhesion and cohesion strength of the patterned mask layer 111 is optimized by adjusting one or more process parameters. In certain embodiments, the adhesion strength of the patterned mask layer 111 is increased by rigorous cleaning of the surface 102 prior to deposition. In certain embodiments, the rigorous cleaning includes one or more of washing in one or more of deionized water, isopropyl alcohol, ethanol, acetone, 1-methyl-2-pyrrolidone, dimethylsulfoxide, trichloroethylene, methylene chloride, Microposit™ Remover 1165, another organic solvent, aqueous HCl, or another aqueous acid, or ultrasonic treatment. In particular embodiments, the adhesion and cohesion strength is increased by optimizing the pressure during the sputtering deposition process of one or more of the adhesion layer 105, the diffusion barrier layer 107, and the passivation layer 109. In certain embodiments, the sputtering pressure is adjusted to control the level of stress in one or more of the coatings, for example, by measuring the induced warpage either on the actual substrate 101 or on a test deposition surface. For example, the stress can be made more tensile by decreasing the sputtering gas pressure and more compressive by increasing the sputtering gas pressure. The stress can also be altered by changing the electrical bias present on the substrate 101 during the sputtering deposition process. In certain embodiments, the adhesion and / or bond strength of the patterned mask layer 111 is evaluated using a pull-off test, such as one or more of ASTM D903 and D3359. In certain embodiments, the adhesion and / or bond strength of the patterned mask layer 111 is evaluated by peel resistance during one or more of water rinsing, ultrasonic treatment in water, cleaning in an aqueous HCl solution, and ultrasonic treatment in an aqueous HCl solution, cleaving the substrate and examining the fracture cross-section, and scratching the surface 102 with a sharp point.

[0024] 1F-1L are top views of an array of exposed regions 120 on a substrate 101 formed by one or more of the processes described above. For example, the exposed regions 120 (also referred to herein as growth centers or primary growth centers) shown in FIGS. 1F-1L may be defined by and / or include openings 112 formed in a patterned mask layer 111 shown in FIG. 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 FIG. 1I. In certain embodiments, the exposed regions 120 are arranged in a two-dimensional (2D) array in the X and Y directions, such as shown in FIGS. 1F-1H and 1J-1L. The openings 112, and therefore the exposed areas 120, may be circular, square, rectangular, triangular, hexagonal, etc., and may have an opening dimension W (or diameter W) between about 1 micrometer and about 5 millimeters, between about 3 micrometers and about 5 millimeters, or between about 10 micrometers and about 500 micrometers, as shown in Figures 1F-1L. The exposed areas 120 may be arranged in a 2D hexagonal or square array with 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 areas 120 may be arranged in a 2D array, where the pitch dimension L1 in the Y direction and the pitch dimension L2 in the X direction may differ from each other, as shown in Figures 1H and 1J-1L. The exposed regions 120 may be arranged in a rectangular, parallelogram, hexagonal, or trapezoidal array (not shown), where the pitch dimension L1 in the Y direction and the pitch dimension L2 in the X direction may differ from each other, as shown in Figures 1H and 1J-1L. The array of exposed regions 120 may be linear or irregular. The exposed regions 120 in the patterned mask layer 111 may be positioned to match the structure of the substrate 101.For example, in certain embodiments, the large-area surface 102 has a hexagonal crystal orientation, e.g., a (0001) or (000-1) crystal orientation, and the openings in the patterned mask layer 111 have a 2D hexagonal array such that the spacing between nearest adjacent openings is parallel to within ±5°, ±3°, ±2°, or ±1° of the <11-20> or <10-10> directions on 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 have a 2D square or rectangular array such that the spacing between nearest 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 exposed regions 120 is oriented obliquely with respect to the structure of substrate 101, e.g., exposed regions 120 are rotated by an angle between about 1 degree and about 44 degrees with respect to a high symmetry axis of the substrate, such as a projection of the c-axis, m-axis, or a-axis on large area surface 102 of substrate 101 having a hexagonal crystal structure, such as a wurtzite crystal structure. In certain embodiments, exposed regions 120 are substantially linear rather than substantially circular. In certain embodiments, exposed regions 120 are slits having a width W and period L that span the entire length of substrate 101, as shown in FIG. 1I. In certain embodiments, exposed regions 120 are slits having a width W1 in the Y direction and a predetermined length W2 in the X direction that is less than the length of substrate 101, and may be arranged in a 2D linear array with period L1 in the Y direction and period L2 in the X direction, as shown in FIGS. 1J-1L. In certain embodiments, the slits are oriented within ±5°, ±3°, ±2°, or ±1° towards the <11-20> or <10-10> direction across the large area surface 102. In some embodiments, adjacent rows of exposed regions 120 (e.g., slits) may be offset from one another in the X direction rather than being aligned directly adjacent to one another, as shown in FIG. 1K.In particular embodiments, exposed regions 120 include or consist of slits oriented within ±3°, ±2°, or ±1° toward the <10-10> (X) direction, and the spacing L1-W1 between adjacent rows of slits in the y, or <11-20>, direction is less than or equal to (W2-1 / 2L2) / √3 and greater than or equal to (W2-1 / 2L2) / (3√3). In other words, the overlap s between exposed regions 120 in adjacent rows can be greater than or equal to √3(L1-W1) and less than or equal to 3√3(L1-W1). In this way, wings growing lateral from adjacent growth centers can be joined after growth in only the <11-20> direction, without <10-10> growth being required. In particular embodiments, the axial spacing (L2-W2) between the slits is between about 5 micrometers and about 200 micrometers, or between about 10 micrometers and about 150 micrometers, or between about 25 micrometers and about 125 micrometers. In FIG. 1J, the actual period of the array of exposed regions 120 in the X direction is equal to the period L2 between adjacent rows of exposed regions. The period in the X direction is also equal to L2 in FIG. 1K, but the unit cell is a parallelogram rather than a rectangle as in FIG. 1J. In other embodiments, the actual period in the X direction may be L2 in multiples of L2, e.g., 2L2, 3L2, 4L2, 5L2, or 6. In certain embodiments, adjacent rows of exposed regions 120 (e.g., slits) may be offset from one another in the longitudinal Y direction, as shown in FIG. 1K. In certain embodiments, exposed regions 120 include slits extending in two or more different directions, e.g., in the X direction and the Y direction, as shown in FIG. 1L. In certain embodiments, the exposed areas 120 (e.g., slits) may be arranged in a manner that reflects the hexagonal symmetry of the substrate. In certain embodiments, the exposed areas 120 (e.g., slits) may extend to the edge of the substrate 101. In certain embodiments, the surface 102 is masked with edges adjacent its edges, and thus, no exposed areas may extend to the edge of the substrate 101. In certain embodiments, the masked edges have a width between about 25 micrometers and about 1 millimeter.

[0025] In certain embodiments, the surface 102 has an orientation within about 10 degrees, within about 5 degrees, within about 2 degrees, within about 1 degree, or within about 0.5 degrees of the (0001) or (000-1) c-plane. In certain embodiments, as shown generally in Figure 6, the domains of a pattern of exposed regions 120, each having linear features, such as those shown generally in Figures 1J and 1K, are arranged in a two-dimensional periodic tessellated array in three different orientations on the surface 102. Each domain may include an array of exposed regions 120. As shown in Figure 6, the surface 102 may include a tessellated array of hexagonal domains 600 that include an array of exposed regions 120, with adjacent domains characterized by exposed regions 120 having different orientations. In certain embodiments, approximately one third of each of the domains have exposed regions or growth centers that may include or consist of slits aligned within ±3°, ±2°, or ±1° toward the [10-10], [01-10], and [-1100] directions. In certain embodiments, approximately one third of each of the domains have growth centers aligned within ±3°, ±2°, or ±1° toward the [11-20], [1-210], and [-2110] directions. In certain embodiments, the domains have hexagonal boundaries, as shown generally in FIG. 6. In certain embodiments, at least 90% of the domains having a first orientation are surrounded by six domains having alternating second and third orientations. In certain embodiments, the domains have a dimension in each of the first and second perpendicular directions between about 500 micrometers and about 10 millimeters, or between about 1 millimeter and about 5 millimeters.

[0026] In certain embodiments, the surface 102 has an orientation within about 10 degrees, within about 5 degrees, within about 2 degrees, within about 1 degree, or within about 0.5 degrees of the (0001) or (000-1) c-plane. In certain embodiments, as shown generally in FIG. 7A, the growth centers (i.e., exposed regions 120), which may include slits formed in a mask layer as shown, are disposed along each of three directions, rotated 120 degrees from each other, and have a common period L2 along each of the three directions. In certain embodiments, approximately one-third of each of the growth centers are aligned within ±3°, ±2°, or ±1° toward the [10-10], [01-10], and [-1100] directions. In certain embodiments, approximately one-third of each of the growth centers are aligned within ±3°, ±2°, or ±1° toward the [11-20], [1-210], and [-2110] directions. In certain embodiments, the length of the growth center is long compared to L2, so that the intersection 701 between the three lines of the growth center is contained within the growth center. The intersections are also referred to herein as vertices, and the intersection points are also referred to herein as vertices. In certain embodiments, the basic unit cell 709 of the pattern contains only one intersection 701, around which six growth centers are arranged with an angle of 60° between them. In certain embodiments, the growth center extends to the edge of the surface 102. In certain embodiments, the growth center extends to and terminates at an edge parallel to the edge of the surface 102, the edge having a width between about 25 micrometers and about 2 millimeters.

[0027] A potential drawback of having growth centers with lengths comparable to the lateral dimension or diameter of the substrate 101, as in Figures 1I or 7A, is that relaxation may occur only in material grown along the growth center, rather than in a direction parallel to the growth center. For example, as shown generally in Figures 1J, 1K, and 1L, a growth center may be blocked to allow relaxation in each of two perpendicular directions. Blocking may be similarly introduced in the pattern shown generally in Figure 7A. In the pattern shown generally in Figure 7B, rather than opening up the intersections 701, they are masked. The presence of masked intersections 701 from which slit-shaped growth centers radiate may result in slower coupling over the intersections, as growth in the <10-10> direction may need to cover them. In certain embodiments, the basic unit cell 709 of the pattern includes only one intersection 701, around which six growth centers are arranged with angles of 60° between them.

[0028] The pattern shown in FIG. 7B includes multiple linear arrays of growth centers formed in a regular repeating pattern. In the example shown in FIG. 7B, the multiple linear arrays of growth centers include a first linear array of growth centers 751, a second linear array of growth centers 752, and a third linear array of growth centers 753. The first linear array of growth centers 751 includes multiple growth centers 761 aligned in a first direction, such as the X direction. The second linear array of growth centers 752 includes multiple growth centers 762 aligned in a second direction, which is adjusted at an angle of 60 degrees from the first direction. The third linear array of growth centers 753 includes multiple growth centers 763 aligned in a third direction, which is adjusted at an angle of 120 degrees from the first direction. The pattern shown in Figure 7B also includes a plurality of intersections 701 (also referred to as vertices) formed at each of the points where the first linear array of growth centers, the second linear array of growth centers, and the third linear array of growth centers intersect in the formed repeating pattern. For clarity, intersections 701 refer to locations where lines having a width equal to five times the width of the growth centers, passing through the centers of the first linear array of growth centers, the second linear array of growth centers, and the third linear array of growth centers, and oriented along the directions of the first linear array of growth centers, the second linear array of growth centers, and the third linear array of growth centers, respectively, intersect.

[0029] As described further below with respect to the examples shown in Figures 8A-8E, portions of the crystals that grow vertically from a growth center (e.g., an exposed region) in the pattern of the linear array of growth centers form a plurality of primary window regions, or primary tertiary regions, that are oriented in the pattern of the linear array of growth centers from which they are grown.

[0030] In certain embodiments, as shown generally in Figure 7C, each vertex or intersection has a single growth center of a specific orientation therethrough. In a special embodiment, adjacent intersections 703, 705, and 707 have slit-shaped growth centers aligned within ±3°, ±2°, or ±1° toward the [10-10], [01-10], and [-1100] directions, respectively. In another special embodiment, adjacent intersections 703, 705, and 707 have slit-shaped growth centers aligned within ±3°, ±2°, or ±1° toward the [11-20], [1-210], and [-2110] directions, respectively. In the special embodiment shown in Figure 7C, the period L3 in the X direction is 3L2, where L2 is the spacing between adjacent intersections in the X direction, regardless of the type of intersection. In a particular embodiment, the period of each of the X direction and the two directions rotated 120 degrees relative to the X direction is equal to at least one of L2, 2L2, 3L2, 4L2, 5L2, 6L2, or a larger multiple of L2. In a particular embodiment, the period of each of the Y direction and the two directions rotated 120 degrees relative to the Y direction is equal to at least one of L1, 2L1, 3L1, 4L1, 5L1, 6L1, or a larger multiple of L1. The growth centers may have a width W1. Short growth centers that do not pass through any vertices may have a length W2. Long growth centers that pass through only one intersection may have a length W3. In a particular embodiment, the basic unit cell 709 of the pattern includes only nine vertices, including three of each of the types of adjacent intersections 703, 705, and 707, and the six growth centers around them are arranged at an angle of 60° between them.

[0031] The pattern shown in FIG. 7C includes multiple linear arrays of growth centers formed in a regular repeating pattern of alternative growth centers. In the example shown in FIG. 7C, the multiple linear arrays of growth centers include a first linear array of growth centers 751a, a second linear array of growth centers 752a, and a third linear array of growth centers 753a. In the example shown in FIG. 7C, the first, second, and third linear arrays of growth centers include two different types of growth centers, such as long growth centers 761a, 762a, 763a, and short growth centers 761b, 762b, 763b, respectively, each aligned in a respective linear array direction. Each linear array of growth centers includes at least one growth center (e.g., long growth center 761a, 762a, 763a) that passes through one out of three intersections 701 taken in the direction in which the linear array of growth centers extends. For example, the first linear array of growth centers 751a includes multiple growth centers 761a and 761b, and the first linear array of growth centers extends in a first direction (e.g., the X direction) such that growth center 761a passes through first intersection 703 and fourth intersection 719. Long growth centers 761a, 762a, 763a positioned in the linear array of intersections 701, such as intersections 703, 705, 707 in Figure 7C, include intersections where the long growth centers 761a, 762a, 763a pass sequentially through the centers of the intersections and are oriented in a first direction, a second direction, and a third direction, respectively.

[0032] In certain embodiments, the rows of growth centers from the morphology as shown generally in FIG. 7B are offset to avoid intersections 701 of adjacent growth centers. An example of these embodiments is shown generally in FIG. 7D. In certain embodiments, approximately one third of each of the growth centers are aligned within ±3°, ±2°, or ±1° toward the [10-10], [01-10], and [-1100] directions. In certain embodiments, approximately one third of each of the growth centers are aligned within ±3°, ±2°, or ±1° toward the [11-20], [1-210], and [-2110] directions. In certain embodiments, one end of each of the growth centers points to a central portion of an adjacent growth center or slit, and the other end points to an edge portion of an adjacent growth center or slit. In certain embodiments, the period L1 is the same in each of three directions, e.g., the Y direction and directions rotated ±120° relative to the Y direction. In certain embodiments, at least six growth centers are contained within the basic unit cell 709. In certain embodiments, exactly six growth centers are contained within the basic unit cell 709.

[0033] 7D includes a plurality of linear arrays of growth centers formed in a regular repeating pattern of alternative growth centers. In this example, the plurality of linear arrays of growth centers are formed in a two-dimensional array of growth centers, where growth centers 781 in the two-dimensional array are rectangular having short and long dimensions, a first end 781a of each of the growth centers 781 is positioned a first distance 785 from a center point 786, and each growth center is oriented such that a line 787 (only one shown) passing through the center of each growth center 781 and parallel to the long dimension of the growth center does not coincide with the center point 786.

[0034] The pattern shown in FIG. 7E includes multiple linear arrays of growth centers formed in a regular repeating pattern of growth centers that also includes multiple sub-apertures. In one example, the pattern shown in FIG. 7E includes multiple linear arrays of primary growth centers made similar to the configuration shown in FIG. 7C, and also includes multiple sub-apertures 711. In some cases, it has been found that depending on the pitch of the pattern (e.g., L1 and L2) and the growth conditions, the coupling may be slower than desired. In some embodiments, as shown in FIG. 7E, sub-apertures 711 (or sub-growth centers), or additional growth centers, may be included within a larger pattern that consists of or includes a primary growth center within a triangular feature, for example, as shown generally in FIG. 7E. In certain embodiments, the sub-apertures 711 are circular, square, rectangular, triangular, hexagonal, etc. In certain embodiments, the sub-apertures 711 include or consist of slit-shaped features. In certain embodiments, the slits in the sub-aperture 711 are aligned within ±3°, ±2°, or ±1° toward the [10-10], [01-10], and / or [-1100] directions. In certain embodiments, the slits in the sub-aperture 711 are aligned within ±3°, ±2°, or ±1° toward the [11-20], [1-210], and [-2110] directions. In certain embodiments, as shown generally in FIG. 7E, the sub-aperture 711 has a V-shape and is positioned within a triangular region of the pattern. In certain embodiments, the sub-aperture 711 includes two intersecting slit-shaped features oriented at an angle to each other. In certain embodiments, the sub-aperture 711 includes two slit-shaped features that meet at one end at an angle of about 60 degrees, for example, between about 55 degrees and about 65 degrees. The width W4 of the sub-aperture 711 may be similar to or smaller than the width W1 of the main aperture. In certain embodiments, the ratio of the length W5 of the minor aperture to the length W2 of the shorter major aperture is between about 0.9 and about 0.01, or between about 0.5 and about 0.05, or between about 0.3 and about 0.1. In certain embodiments, at least 3, at least 9, at least 18, at least 27, or at least 50 minor apertures 711 are included within a basic unit cell 709 defined by a major aperture.

[0035] In an alternative set of embodiments, as shown in FIG. 1M, the large area surface 102 of the substrate 101 is covered with a blanket mask 116, including one, two or more of an adhesion layer 105, a diffusion barrier layer 107, and a passivation layer 109, followed by a positive photoresist layer 113. The photoresist layer is exposed to ultraviolet light through a photomask (not shown) to form dissolvable exposed regions 106B and unexposed regions 106A (substantially the negative of the pattern shown in FIG. 1B), as shown in FIG. 1N. The exposed regions 106B are then removed by development. As shown in FIG. 1O, openings 112 in the blanket mask 116 (including the adhesion layer 105, the diffusion barrier layer 107, and the passivation layer 109) can then be formed by wet or dry etching through the openings in the patterned photoresist layer 113A to form a patterned mask layer 111. After forming opening 112, as shown in FIG. 1P, photoresist layer 113 is removed to produce a structure similar or identical to that shown in FIG. 1E.

[0036] Next, trenches 115 are formed in the exposed regions 120 of the substrate 101 through the openings 112 (or "windows") formed in the patterned mask layer 111, as shown in FIG. 1Q. In certain embodiments, the depth of the trenches 115 is between about 50 micrometers and about 1 millimeter, or between about 100 micrometers and about 300 micrometers. In certain embodiments, the trenches 115 extend through the entire thickness of the substrate 101 to form patterned holes extending from the back surface 118 of the substrate 101 through the openings 112 in the patterned mask layer 111. The width of the individual trenches may be between about 10 micrometers and about 500 micrometers, or between about 20 micrometers and about 200 micrometers. The individual trenches 115 may be straight or curved and may have lengths in the X and / or Y directions of 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 a particular embodiment, the large area surface 102 of the substrate 101 has a (000-1), N-face orientation, and the trench 115 is formed by wet etching. In a particular embodiment, the etching composition or etchant comprises a solution of 85% phosphoric acid (H3PO4) and sulfuric acid (H2SO4), with an H2SO4 / H3PO4 ratio between 0 and about 1:1. In a particular embodiment, the phosphoric acid solution is conditioned to form polyphosphoric acid and elevate the boiling point. For example, reagent grade (85%) H3PO4 can be conditioned by stirring and heating in a beaker at a temperature between about 200° C. and about 450° C. for a period between about 5 minutes and about 5 hours. In a particular embodiment, the trench 115 is formed by heating the masked substrate 101 in one of the above-mentioned etchants at a temperature between about 200° C. and about 350° C. for a period between about 15 minutes and about 6 hours. In another embodiment, the trench 115 is formed by electrochemical wet etching.

[0037] 1R-1T show an alternative approach to forming an array of patterned masked trenches in a substrate 101. As shown in FIG. 1R, a blanket mask 116 (including an adhesion layer 105, a diffusion barrier layer 107, and a passivation layer 109) can be deposited on the large area surface 102 of the substrate 101. As shown in FIG. 1S, initial trenches 114 can be formed by laser ablation to form a patterned mask layer 111. Laser ablation techniques are also known or referred to as laser machining techniques or laser beam machining techniques. Laser ablation can be performed by watt level lasers such as neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers, CO2 lasers, excimer lasers, Ti:sapphire lasers, and the like. The laser can emit pulses with pulse lengths in the nanosecond, picosecond, and femtosecond ranges. In certain embodiments, the frequency of the output light of the laser can be doubled, tripled, or quadrupled using appropriate nonlinear optical elements. The beam width, power, and scanning speed of the laser over the surface of the substrate 101 with the patterned mask layer 111 can be varied to adjust the width, depth, and aspect ratio of the initial trenches 114. The laser may be scanned repeatedly over one trench or over an array of trenches.

[0038] The surface and sidewalls of the initial trench 114 may contain damage left by the laser ablation process. In certain embodiments, the substrate 101 containing the initial trench 114 is further processed by wet etching, dry etching, or photoelectrochemical etching to remove residual damage within the initial trench 114, as shown in FIG. 1T. In a particular embodiment, the large area surface 102 of the substrate 101 has a (000-1) N-face orientation, and the trench 115 is formed from the initial trench 114 by wet etching. In a particular embodiment, the etching composition or etchant comprises a solution of 85% phosphoric acid (H3PO4) and sulfuric acid (H2SO4), with the H2SO4 / H3PO4 ratio being between 0 and about 1:1. In a particular embodiment, the phosphoric acid solution is conditioned to form polyphosphoric acid and increase its boiling point. For example, reagent grade (85%) H3PO4 can be conditioned by stirring and heating in a beaker at a temperature between about 200° C. and about 450° C. for between about 5 minutes and about 5 hours. In a particular embodiment, trench 115 is formed by heating substrate 101 in one of the above-mentioned etchants at a temperature between about 200° C. and about 350° C. for a time between about 15 minutes and about 6 hours.

[0039] The pattern of the mask layer under which trenches 115 are formed may be selected from any of the patterns described above, such as those shown generally in Figures 1F-1L, 6, or 7A-7E.

[0040] The substrate 101 with the patterned mask layer and, optionally, masked patterned trenches 115 is then used as a substrate for bulk crystal growth, including, for example, ammonothermal growth, HVPE growth, or flux growth. In the discussion below, the grown GaN layer will be referred to as an ammonothermal layer, although other bulk growth methods such as HVPE or flux growth may be used instead. In certain embodiments, including ammonothermal bulk growth, the patterned substrate 101 may then be suspended on a crystal seed rack and placed in a sealable container, such as a capsule, an autoclave, or a liner in an autoclave. In certain embodiments, one or more pairs of patterned substrates are suspended back-to-back with the large area patterned surfaces facing outward. 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 then added to the sealable container, and the sealable container is sealed. The mineralizer composition may include an alkali metal such as Li, Na, K, Rb, or Cs, an alkaline earth metal such as Mg, Ca, Sr, or Ba, or an alkali or alkaline earth hydride, amide, imide, amide-imide, nitride, or azide. The mineralizer may include an ammonium halide such as NHF, NH4Cl, NH4Br, or NHI, a gallium halide such as GaF3, GaCl3, GaBr3, GaI3, or any compound that can be formed by the reaction of one or more of F, Cl, Br, I, HF, HCl, HBr, HI, Ga, GaN, and NH3. The mineralizer may include other alkali salts, alkaline earth salts, ammonium salts, other halides, urea, sulfur or sulfide salts, or phosphorus or phosphorus-containing salts. The sealable container (e.g., capsule) can then be placed in a high pressure apparatus such as an internally heated high pressure apparatus or an autoclave, and the high pressure apparatus can be sealed. The sealable container containing the patterned substrate 101 is then heated to a temperature in excess of about 400° C. and pressures in excess of about 50 megapascals to effect ammonothermal crystal growth.

[0041] 2A-2C show bulk crystal growth by a conventional LEO process with no trenches under the mask openings. During the bulk crystal growth process, III-metal nitride layer 213 grows through openings 112 in patterned mask layer 111, grows outward through the openings as shown in FIG. 2B, grows lateral on patterned mask layer 111, and bonds as shown in FIG. 2C. After bonding, III-metal nitride layer 213 includes window regions 215 grown perpendicular to the openings in patterned mask layer 111, wing regions 117 grown lateral on patterned mask layer 111, and bonds 219 at the boundaries between wings grown from adjacent openings in patterned mask layer 111. Threading dislocations 214 originating from threading dislocations present at the surface of substrate 101 may be present in window regions 215.

[0042] 3A-3C illustrate a bulk III-nitride sidewall LEO process. FIG. 3A illustrates a substrate with a patterned and masked trench 115 formed by one of the processes described herein. In a sidewall LEO process, III-metal nitride material 221 grows on the sides and bottom of the patterned and masked trench 115, as shown in FIG. 3B. As the III-metal nitride material 221 on the sidewall of the trench 115 grows inward, it becomes increasingly more difficult for the III-nitride nutrient material to reach the bottom of the trench, whether the III-nitride nutrient material comprises an ammonothermal complex of a III-metal (in the case of ammonothermal growth), a III-metal halide (in the case of HVPE), or a III-metal alloy or inorganic complex (in the case of flux growth). Eventually, the III-metal nitride material 221 pinches off the lower region of the trench to form a cavity 225 as shown in FIG. 3C. It has been found that the concentration of threading dislocations in the lateral grown group-III metal nitride material 221 is lower than in the substrate 101. Many threading dislocations 223 originating from the substrate 101 terminate at the surface of the cavity 225. Concomitantly, the group-III metal nitride layer 213 grows upward through the openings 112 (or windows) in the patterned mask layer 111. However, since the lateral grown group-III metal nitride material 221 has a lower concentration of threading dislocations than the substrate 101 and many dislocations from the substrate 101 terminate at the surface of the cavity 225, the dislocation density in the vertically grown group-III metal nitride layer 213 is significantly reduced with respect to the conventional LEO process as described above with respect to FIGS. 2A-2C.

[0043] 3D-3F show a continuation of the sidewall LEO growth process. As in the conventional LEO process (FIGS. 2A-2C), III-metal nitride layer 213 grows in opening 112 in patterned mask layer 111, grows outward through the opening as shown in FIG. 3D, grows lateral on patterned mask layer 111, and bonds as shown in FIG. 3E. After bonding, III-metal nitride layer 213 includes window regions 215 grown perpendicular to the opening in patterned mask layer 111, wing regions 217 grown lateral on patterned mask layer 111, and bonds 219 that occur at the boundaries between wings grown from adjacent openings in patterned mask layer 111 as shown in FIG. 3F. The lateral grown group III metal nitride material 221 has a lower concentration of threading dislocations than the substrate 101, and because many threading dislocations from the substrate 101 terminate within the cavities 225, the concentration of threading dislocations in the window regions 215 is significantly lower than in the conventional LEO case.

[0044] The ammonothermal Group III metal nitride layer 213 may have a thickness between about 10 micrometers and about 100 millimeters, or between about 100 micrometers and about 20 millimeters.

[0045] 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.

[0046] In certain embodiments, the concentration of extended defects, such as threading dislocations and stacking faults, in the ammonothermal grown group III metal nitride layer 213 can be quantified by a defect-selective etch. The defect-selective etch can be performed, for example, using a solution containing one or more of H3PO4, H3PO4 conditioned to polyphosphoric acid by extended heat treatment, and H2SO4, or a molten flux containing one or more of NaOH and KOH. The defect-selective etch can be performed at a temperature between about 100° C. and about 500° C. for a time between about 5 minutes and about 5 hours, with the process temperature and time selected to cause the formation of etch pits having a diameter between about 1 micrometer and about 25 micrometers. The ammonothermal group III metal nitride layer, crystal, or wafer is then removed from the etchant.

[0047] The concentration of threading dislocations at the surface of the window region 215 is about 10 and about 10 lower than that in the underlying substrate 101. 4 The concentration of threading dislocations at the surface of the window region 215 may be lower by a factor between 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 The concentration of threading dislocations at the surface of the wing regions 217 may be about one to about three orders of magnitude lower than the concentration of threading dislocations at the surface of the window regions 215, and may be 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 10cm -2 The surface of the window area 215 may be, for example, less than about 1 cm -1 and about 10 4 cm -1The concentration of stacking faults at the surface of the wing region 217 may be about one to about three orders of magnitude lower than the concentration of stacking faults at the surface of the window region 215, and may be about 10 2 cm -1 Less than 10cm -1 Less than 1cm -1 Less than or about 0.1 cm -1 The bond 219 may have a linear density of less than about 1×10 5 cm -1 Less than 3×10 4 cm -1 Less than 1×10 4 cm -1 Less than 3×10 3 cm -1 Less than 1×10 3 cm -1 Less than 3×10 2 cm -1 Less than or equal to 1 × 10 2 cm -1 The dislocation density along the joint is less than 5 cm -1 Super, 10cm -1 Super, 20cm -1 Super, 50cm -1 Super, 100cm -1 Super, 200cm -1 Over or 500cm -1 Sometimes it's super.

[0048] In certain embodiments, the process of masking and bulk III-nitride crystal growth is repeated one, two, three or more times. In some embodiments, these operations are performed while the first bulk III-nitride metal layer remains bonded to the substrate 101. In other embodiments, the substrate 101 is removed, for example by sawing, lapping, grinding, and / or etching, prior to the subsequent masking and bulk crystal growth operations.

[0049] 4A and 4B are simplified diagrams illustrating the formation of a free-standing group-III metal nitride boule and a free-standing group-III metal nitride wafer. In certain embodiments, the substrate 101 is removed from the ammonothermal group-III metal nitride layer 213 (FIG. 3F), or the last such layer deposited, to form a free-standing ammonothermal group-III metal nitride boule 413. The substrate 101 may be removed by one or more of sawing, grinding, lapping, polishing, laser lift-off, self-detachment, and etching to form a processed free-standing, side-grown group-III metal nitride boule 413. The processed free-standing, side-grown group-III metal nitride boule 413 may have a similar or substantially identical composition to the ammonothermal group-III metal nitride layer, and etching may be performed under conditions where the etch rate of the backside of the substrate 101 is much faster than the etch rate of the frontside of the ammonothermal group-III metal nitride layer. The processed freestanding ammonothermal group III metal nitride boule 413 may include one or more window regions 415 formed on the substrate 101 over exposed regions 120, such as openings 112 in the patterned mask layer 111. The processed freestanding ammonothermal group III metal nitride boule 413 may also include one or more wing regions 417 formed over non-open regions in the patterned mask layer 111, and a pattern of locally approximately linear arrays 419 of threading dislocations, as shown in Figure 4A. One or more of the front surface 421 and back surface 423 of the freestanding ammonothermal group III metal nitride boule 413 may be lapped, polished, etched, and chemically mechanically polished. As also noted above, the pattern of the locally substantially linear array 419 may include, depending on the growth conditions, a junction region that includes 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 of between about 25 micrometers and about 1000 micrometers, or between about 30 micrometers and about 250 micrometers disposed between adjacent wing regions 417.

[0050] In certain embodiments, the edges of the freestanding ammonothermal group III metal nitride boule 413 are ground to form a cylindrical ammonothermal group III metal nitride boule. In certain embodiments, one or more flats are ground into the sides of the freestanding ammonothermal group III metal nitride boule 413. In certain embodiments, the freestanding ammonothermal group III metal nitride boule 413 is sliced ​​into one or more freestanding ammonothermal group III metal nitride wafers 431, as shown in FIG. 4B. This slicing can be done by sawing with a multi-wire saw or a multi-wire slurry saw, slicing, ID sawing, OD sawing, cleaving, ion implantation followed by exfoliation, spalling, laser cutting, or the like. One or more large area surfaces of the freestanding ammonothermal group III metal nitride wafer 431 may be lapped, polished, etched, electrochemically polished, photoelectrochemically polished, reactive ion etched, and / or chemically mechanically polished according to methods known in the art. In certain embodiments, the edges of the freestanding ammonothermal group III metal nitride wafer 413 are ground to provide chamfered, beveled, or rounded edges. The freestanding ammonothermal group III metal nitride wafer may have a diameter of at least about 5 millimeters, at least about 10 millimeters, at least about 25 millimeters, at least about 40 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 may have a thickness between about 50 micrometers and about 10 millimeters, or between about 150 micrometers and about 1 millimeter. One or more large area surfaces of the freestanding ammonothermal Group III metal nitride wafer 431 can be used as a substrate for growing Group III metal nitrides by chemical vapor deposition, metalorganic chemical vapor deposition, hydride vapor phase deposition, molecular beam epitaxy, flux growth, solution growth, ammonothermal growth, among others.

[0051] 5A-5G and 8A-8E are simplified diagrams illustrating threading dislocation patterns formed in a freestanding group III metal nitride boule 413 or wafer 431 after growth on a crystal seed having a pattern of growth centers similar to those shown generally in FIGS. 1F-1L and 7A-7E, respectively. Crystals having various patterns may have certain advantages and disadvantages, as described above and below. The large area surface of the freestanding ammonothermal group III metal nitride boule 413 or wafer 431 may be characterized by a pattern of locally nearly linear arrays 419 of threading dislocations propagated from bonds 219 formed during the epitaxial lateral overgrowth process, as described above with respect to FIGS. 3A-3F. The pattern of the locally substantially linear array of threading dislocations may be 2D hexagonal, square, rectangular, trapezoidal, triangular, 1D linear, or an irregular pattern formed at least in part due to the pattern of exposed regions 120 (FIGS. 1F-1L, 7A-7E) used during the process of forming the free-standing ammonothermal group III metal nitride boule 413. One or more window regions 415 are formed over the exposed regions 120 (FIGS. 1F-1L, 7A-7E), and one or more wing regions 417 are formed over the portions of the exposed regions 120 that are not over the exposed regions 120, i.e., formed by lateral growth. As previously mentioned, the pattern of bonds 219 or locally substantially linear arrays 419 formed may include bond regions having lateral widths (i.e., measured parallel to the surface of the page and perpendicular to the locally substantially linear arrays 419, including FIGS. 5A-5G and 8A-8E) that may vary depending on the growth conditions. In certain embodiments, the creepage width of the bond is between about 5 micrometers and about 500 micrometers, between about 10 micrometers and about 250 micrometers, or between about 20 micrometers and about 100 micrometers.

[0052] At least 15%, at least 40%, or at least 75% of the intersections 521 between adjacent bonds 419 (also referred to herein as first regions) include or consist of only three bonds that meet at a cross angle of 120°±3°, as shown in Figures 5A, 5F, 5G, 8A, 8B, 8C, 8D, and 8E. For example, for a crystal species having a near c-plane orientation, the three bond intersections may be formed by a-direction growth from adjacent growth centers, which tends to be faster. In certain embodiments, at least 50%, at least 75%, or at least 90% of the intersections 523 between adjacent bonds 419 include or consist of only four bonds that meet at a cross angle of 90°±3°, as shown in Figures 5B, 5C, and 5E. These patterns with four bond vertices may be particularly useful for the growth of low defect crystals with non-polar or semi-polar orientations. In certain embodiments, at least 10%, at least 20%, or at least 30% of the intersections 525 between adjacent bonds 419 include or consist of six bonds that meet at an intersection angle of 60°±3°, as shown in Figures 8B, 8D, and 8E. Formation of six bond intersections may be useful for achieving maximum strain relief, but may require lateral growth in a relatively gentle direction to close the cavity. In certain embodiments, at least 10%, at least 15%, or at least 20% of the intersections 527 between adjacent bonds 419 include or consist of only two bonds that meet at an intersection angle of 120°±3°, as shown in Figures 8C and 8D. In certain embodiments, at least 10%, at least 15%, or at least 20% of the intersections 529 between adjacent joints 419 include or consist of only three joints, where two of the joints meet at an angle of 120°±3° and two of the joints meet at an angle of 90°±3°, as shown in Figure 8D. In certain embodiments, at least 10%, at least 15%, or at least 20% of the intersections 531 between adjacent joints 419 include or consist of only two joints that meet at an angle of 150°±5°, as shown in Figure 8E.In certain embodiments, at least 10%, at least 15%, or at least 20% of the intersections 533 between adjacent joints 419 include or consist of only three joints, two of the joints meeting at an angle of 60°±3° and two of the joints meeting at an angle of 90°±3°, as shown in FIGURE 8E. In certain embodiments, between about 3% and about 10% of the intersections 535 between adjacent joints 419 include or consist of only four joints, two of the joints meeting at an angle of 60°±3°, two of the joints meeting at an angle of 90°±3°, and two of the joints meeting at an angle of 120°±3°, as shown in FIGURE 8E. In certain embodiments, intersection type 535 spans two intersections connected by a short joint, where the first intersection includes two joints that meet at an angle of 60°±3° and the second intersection includes two joints that meet at an angle of 120°±3°. The latter set of more complex joint intersections can result from the use of more complex mask patterns, such as those shown in Figures 7C-7E, and can allow for an ideal combination of reliable bonding and stress relief.

[0053] In certain embodiments, the mask pattern includes multiple domains with different orientations of growth centers 120, such as those shown diagrammatically in FIG. 6. In such cases, the resulting crystal may have a pattern of dislocations within a domain that is rotated with respect to adjacent domains. For example, locally, within a single domain, the distribution of threading dislocations may resemble that shown in FIG. 5F, with the orientations of adjacent domains rotated with respect to each other. In a particular embodiment, a first domain may be characterized by a window region 415 oriented in a first direction that is aligned within ±3° of a crystal orientation selected from <10-10> and <11-20>. A first domain may be surrounded by six domains, where the orientations of between 55% and 100% of the plurality of window regions 415 are oriented along a second direction rotated by 60°±3° from the first direction or along a third direction rotated by 120°±3° from the first direction, and the orientations of between 55% and 100% of the plurality of window regions 415 within the six surrounding domains alternate between the second direction and the third direction.

[0054] In certain embodiments, in the distributions of threading dislocations shown in Figures 5A and 8A-E resulting from patterns of trigonal or hexagonal symmetry, e.g., as shown in Figures 1F and 7A-E, the average concentration of threading dislocations in a first direction (e.g., along the Y direction in Figure 5A and along the X direction in Figures 8A-E) includes a period of variation that varies with a period of at least 2. In certain embodiments, the average concentration of threading dislocations also includes a period of variation that varies with a period of at least 2 in each of a second direction and a third direction, where the second direction is rotated or angled 60 degrees from the first direction and the third direction is rotated or angled 120 degrees from the first direction. In certain embodiments, the periods of change in each of the first direction, the second direction, and the third direction are equal to within 2x, 1.5x, 1.1x (i.e., within ±10%), or 1.05x (i.e., within ±5%).

[0055] In general, the distribution of window regions 415 within the basic unit cell 509, as shown generally in Figures 5A-5G and 8A-8E, mirrors the distribution of the pattern of openings or growth centers in the mask, as shown generally in Figures 1F-1L, 6, and 7A-7E and described above.

[0056] More complex patterns are possible and may have advantages, such as, for example, increased resistance to cracking and cleaving. For example, one direction of the pattern 502 may be elongated relative to the other orthogonal direction due to the freestanding longitudinally grown group III metal nitride boule 413 being sliced ​​at an oblique angle relative to the large area surface (e.g., front surface 421, which is parallel to the XY plane) of the freestanding ammonothermal group III metal nitride boule 413. The pattern 502 of locally substantially linear arrays of threading dislocations may be characterized by a linear array of threading 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, in certain embodiments. The locally substantially linear array pattern 502 of threading dislocations may be characterized in certain embodiments by a pitch dimension L (FIGS. 5A, 5B), or pitch dimensions L1 and L2 in two orthogonal directions (FIGS. 5C, 5E, 5F, and 5G), 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. In certain embodiments, the locally substantially linear array pattern 502 of threading dislocations is substantially aligned with the underlying crystal structure of the group-III metal nitride, e.g., the locally substantially linear array extends in a direction 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 projections thereof, in the plane of the surface of the freestanding ammonothermal group-III metal nitride boule 413 or group-III metal nitride wafer 431. The linear concentration of threading dislocations in this pattern is approximately 1 × 10 5 cm -1 Less than 3×10 4 cm -1Less than 1×10 4 cm -1 Less than 3×10 3 cm -1 Less than 1×10 3 cm -1 Less than 3×10 2 cm -1 Less than or about 1 × 10 2 cm -1 The linear concentration of threading dislocations in this pattern 502 may be less than 5 cm -1 Super, 10cm -1 Super, 20cm -1 Super, 50cm -1 Super, 100cm -1 Super, 200cm -1 Over or 500cm -1 Sometimes it's super.

[0057] 5A-5G and 8A-8E, the large area surface of the freestanding ammonothermal group III metal nitride boule or wafer may be further characterized by an array of wing regions 417 and an array of window regions 415. Each wing region 417 may be positioned between adjacent locally substantially linear arrays 419 of threading dislocations. Each window region 415 may be positioned within one wing region 417 or may be positioned between two adjacent wing regions 417 and may have a minimum dimension between about 3 micrometers and about 500 micrometers and may have a minimum dimension of about 10 micrometers or more that arise from residual threading dislocations that propagated vertically from the exposed regions (i.e., primary growth centers) during the bulk crystal growth process. 3 cm -2 and 10 8 cm -2 The concentration of threading dislocations between 10 3 cm -1 The portion of the growing crystal that propagates vertically from the exposed region (e.g., the window region) may also be referred to herein as the primary window region, or alternatively, the primary tertiary region. In some embodiments, the boundary between the window region and the wing region may be characterized by, for example, a linear density of about 5 cm -1 and 10 5 cm -1It may be decorated with transitions between.

[0058] One direction of the array may be longer than the other orthogonal direction, for example, due to slicing the boule at an oblique angle relative to the large area surface of the freestanding ammonothermal Group III metal nitride boule. The pattern of the locally substantially linear array of threading dislocations 419 may be characterized by a pitch dimension L, or pitch dimensions L1 and L2 in two orthogonal directions, between about 5 micrometers and about 20 millimeters, or between about 200 micrometers and about 5 millimeters. In certain embodiments, the pattern of the locally substantially linear array of threading dislocations 419 is substantially aligned with the underlying crystal structure of the Group III metal nitride, for example, the locally substantially linear array is oriented 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 projections thereof, in the plane of the surface of the freestanding ammonothermal Group III nitride boule or wafer. The linear concentration of threading dislocations in the pattern is about 1×10 5 cm -1 Less than 3×10 4 cm -1 Less than 1×10 4 cm -1 Less than 3×10 3 cm -1 Less than 1×10 3 cm -1 Less than 3×10 2 cm -1 Less than or about 1 × 10 2 cm -1 The linear concentration of threading dislocations in this pattern can be less than 5 cm -1 Super, 10cm -1 Super, 20cm -1 Super, 50cm -1 Super, 100cm -1 Super, 200cm -1 Over or 500cm -1 Sometimes it's super.

[0059] The concentration of threading dislocations in the wing regions 417 between the locally nearly linear arrays of threading dislocations is 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 10cm -2 The concentration of threading dislocations at the surface of the window region 415 may be less than 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 The concentration of threading dislocations at the surface of the window region may 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 concentration of threading dislocations at the surface of the wing region. The concentration of threading dislocations at the surface of the window region may be at least 10 4 The interface between the window region 415 and the wing region 417 may be less than 1000 times, 300 times, 100 times, or 30 times higher than the concentration of threading dislocations at the surface of the wing region. In some embodiments, the interface between the window region 415 and the wing region 417 may be less than 100 times, 30 times, or 30 times higher than the concentration of threading dislocations at the surface of the wing region. -1 and 10 5 cm -1 The density of threading dislocations averaged over a large area surface of a freestanding ammonothermal III-nitride boule or wafer is approximately 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 -1The concentration of stacking faults averaged over a large area surface of a freestanding ammonothermal III-nitride boule or wafer can be less than about 10 3 cm -1 Less than, about 10 2 cm -1 Less than 10cm -1 Less than 1cm -1 Less than or about 0.1 cm -1 The thickness of the seed crystal may be less than 100 μm, or may be undetectable. In some embodiments, for example, after repeated regrowth on a seed crystal having a patterned array of dislocations and / or after growth to a thickness of more than 2 mm, more than 3 mm, more than 5 mm, or more than 10 mm, the location of the threading dislocations may be displaced lateral to some extent relative to the pattern on the seed crystal. In such cases, the regions of higher concentration of threading dislocations will be somewhat more diffuse than the relatively sharp lines outlined in FIGS. 5A-5G and 8A-8E. However, the concentration of threading dislocations as a function of lateral position along a particular direction on the surface will vary periodically, with a period between about 5 micrometers and about 20 millimeters, or between about 200 micrometers and about 5 millimeters. The concentration of threading dislocations in the periodically varying regions may vary by at least 2-fold, at least 5-fold, at least 10-fold, at least 30-fold, at least 100-fold, at least 300-fold, or at least 1000-fold.

[0060] Freestanding ammonothermal group III metal nitride boules or wafers are available in the following configurations: (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 The freestanding ammonothermal Group III metal nitride boule or wafer may have a large area crystallographic orientation within 5 degrees, within 2 degrees, within 1 degree, within 0.5 degrees, within 0.2 degrees, within 0.1 degrees, within 0.05 degrees, within 0.02 degrees, or within 0.01 degrees of {10-1±1}, {10-1±2}, {10-1±3}, {21-3±1}, or {30-3±4}. The freestanding ammonothermal Group III metal nitride boule or wafer may have a (hkil) semipolar large area surface orientation, where i=-(h+k), and at least one of l and h and k is non-zero.

[0061] In certain embodiments, the large area surface of the freestanding ammonothermal Group III metal nitride crystal or wafer has a crystal orientation miscut between about -60 degrees and about +60 degrees from the {10-10}m-plane in the

[0001] +c direction and by about 10 degrees in the orthogonal <1-210>a direction. In certain embodiments, the large area surface of the freestanding ammonothermal Group III metal nitride crystal or wafer has a crystal orientation miscut between about -30 degrees and about +30 degrees from the {10-10}m-plane in the

[0001] +c direction and by about 5 degrees in the orthogonal <1-210>a direction. In certain embodiments, the large area surface of the freestanding ammonothermal Group III metal nitride crystal or wafer has a crystal orientation miscut between about -5 degrees and about +5 degrees from the {10-10}m-plane in the

[0001] +c direction and by about 1 degree in the orthogonal <1-210>a direction. The free-standing ammonothermal group III metal nitride crystal or wafer is 10 2 cm -1 Less than 10cm -1 Less than or equal to 1 cm -1 stacking fault concentration of less than 10 5 cm -2 Less than, about 104 cm -2 Less than, about 10 3 cm -2 Less than, about 10 2 cm -2 Less than or about 10cm -2 The dislocation density may be very low, less than 100 nm.

[0062] The freestanding ammonothermal Group III metal nitride boule or wafer may have a symmetrical x-ray rocking curve full width at half maximum (FWHM) of less than about 200 arc seconds, less than about 100 arc seconds, less than about 50 arc seconds, less than about 35 arc seconds, less than about 25 arc seconds, or less than about 15 arc seconds. The freestanding ammonothermal Group III metal nitride boule or wafer may have a crystal radius of curvature 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.

[0063] In certain embodiments, at least one surface of the freestanding ammonothermal Group III metal nitride boule or wafer is at least about 1×10 16 cm -3 Super, about 1×10 17 cm -3 More than or about 1×10 18 cm -3 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 the freestanding 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 15 cm -3 Super, about 1×10 16 cm -3 Super, about 1×10 17 cm -3 More than or about 1×10 18 cm -3In certain embodiments, the top and bottom surfaces of the freestanding ammonothermal Group III metal nitride boule or wafer each have an impurity concentration of at least one of lithium (Li), sodium (Na), potassium (K), fluorine (F), chlorine (Cl), bromine (Br), or iodine (I) of greater than about 1×10, as quantified by calibrated secondary ion mass spectrometry (SIMS). 16 cm -3 and 1×10 19 cm -3 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 or equal to 1 × 10 16 cm -3 In another embodiment, the top and bottom surfaces of the freestanding ammonothermal Group III metal nitride boule or wafer may each have an impurity concentration of less than about 1×10, as quantified by calibrated secondary ion mass spectrometry (SIMS). 16 cm -3 and 1×10 19 cm -3 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 In yet another embodiment, the top and bottom surfaces of the freestanding ammonothermal Group III metal nitride boule or wafer may each have an impurity concentration of between about 1×10 and about 1×10, as quantified by calibrated secondary ion mass spectrometry (SIMS). 16 cm -3 and 1×10 19 cm -3 Between, about 1 × 10 16 cm -3 and 2×10 19cm -3 Between 1×10 17 cm -3 Less than and about 1 × 10 15 cm -3 and 1×10 19 cm -3 In some embodiments, the top and bottom surfaces of the freestanding ammonothermal Group III metal nitride boule or wafer may have an impurity concentration of between about 5×10, as quantified by calibrated secondary ion mass spectrometry (SIMS), and about 5×10 17 cm -3 and 1×10 19 cm -3 In certain embodiments, at least one surface of the freestanding ammonothermal group III metal nitride boule or wafer may have an impurity concentration of H between about 1×10 16 cm -3 and 1×10 19 cm -3 In particular embodiments, the freestanding ammonothermal Group III metal nitride boule or wafer has an impurity concentration of between about 0.01 cm -1 The absorbance per unit thickness is about 3175 cm -1 It has an infrared absorption peak of

[0064] Freestanding ammonothermal Group III metal nitride crystals or wafers may be characterized by a wurtzite structure that is substantially free of cubic entities or other crystalline structures (other structures being less than about 0.1% by volume of the substantially wurtzite structure).

[0065] Surprisingly, given the lattice mismatch between HVPE GaN and ammonothermal GaN, ammonothermal lateral epitaxial overgrowth as a result of using the techniques disclosed herein shows that it is possible to produce thick, large area GaN layers that are free of cracks. In certain embodiments, the freestanding ammonothermal Group III metal nitride crystal or wafer has a diameter 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 greater than about 0.1 millimeters, greater than about 0.2 millimeters, greater than about 0.3 millimeters, greater than about 0.5 millimeters, 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 free of cracks. In contrast, it has been found that ammonothermal growth on large area, unpatterned HVPE GaN seeds often results in cracking when the layers are thicker than a few hundred micrometers, even when a patterned process is used to form the HVPE GaN seeds.

[0066] The freestanding ammonothermal Group III metal nitride wafer may 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 measure of bow 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 concentration of macroscopic defects having a diameter or feature size of greater than about 100 micrometers on the large area surface of the freestanding ammonothermal Group III metal nitride wafer is less than about 2 cm. -2 Less than 1cm -2 Less than 0.5cm -2 Less than 0.25cm -2Less than or about 0.1 cm -2 The variation in miscut angle across the large area surface of the freestanding ammonothermal Group III metal nitride crystal or wafer may be less than about 5 degrees, less than about 2 degrees, less than about 1 degree, less than about 0.5 degrees, less than about 0.2 degrees, less than about 0.1 degrees, less than about 0.05 degrees, or less than about 0.025 degrees in each of two orthogonal crystallographic directions. The large area surface of the freestanding ammonothermal Group III metal nitride wafer may have a root mean square surface roughness measured over an area of ​​at least 10 μm×10 μm of less than about 0.5 nanometers, less than about 0.2 nanometers, less than about 0.15 nanometers, less than about 0.1 nanometers, or less than about 0.10 nanometers. The freestanding ammonothermal Group III metal nitride wafer is of n-type conductivity and has a root mean square surface roughness of less than about 1×10 17 cm -3 and about 3 × 10 19 cm -3 and the carrier concentration between about 100cm 2 In an alternative embodiment, the freestanding ammonothermal Group III metal nitride wafer may be characterized by having a carrier mobility of greater than about 1×10 15 cm -3 and about 1×10 19 cm -3 In yet another embodiment, the freestanding ammonothermal group III metal nitride wafer may be characterized as having an electrically semi-insulating behavior and a room temperature resistivity of about 10 7 Over ohm-centimeters, about 10 8 Over ohm-centimeters, about 10 9 Over ohm-centimeters, about 10 10 More than ohm-centimeters, or about 10 11 In certain embodiments, the freestanding ammonothermal group III metal nitride wafer is highly transparent and has an optical absorption coefficient at a wavelength of 400 nanometers of about 10 cm. -1 Less than 5cm -1 Less than 2cm -1 Less than 1cm-1 Less than 0.5cm -1 Less than 0.2cm -1 Less than or about 0.1 cm -1 is less than.

[0067] In some embodiments, the free-standing 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 comprises ammonothermal bulk crystal growth. In another particular embodiment, the further bulk growth comprises high temperature solution crystal growth, also known as flux crystal growth. In yet another particular embodiment, the further bulk growth comprises HVPE. The further grown crystal can then be sliced, lapped, polished, etched, and / or chemically mechanically polished into wafers by methods known in the art. The surface of the wafer may be characterized by a root mean square surface roughness measured over an area of ​​10 micrometers by 10 micrometers of less than about 1 nanometer or less than about 0.2 nanometers.

[0068] The above sequence of steps provides a method according to an embodiment of the present disclosure. In a particular embodiment, the present disclosure provides a method and resulting crystalline material provided by a high pressure apparatus having a structured support member. Other alternatives may be provided in which steps are added, one or more steps are removed, or one or more steps are provided in a different order without departing from the scope of the claims.

[0069] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of which is determined by the following claims. [Explanation of symbols]

[0070] 101 Substrate 102 large area surface 103 Photoresist layer 104 Patterned photoresist layer 104A area 104B Unexposed area 105 Adhesive layer 106A Unexposed area 106B Exposure area 107 Diffusion Barrier Layer 109 Inactive layer 111 Pattern Mask Layer 112 Aperture, exposed area 114 Initial Trench 115 Trench 116 Blanket Mask 117, 217, 417 Wing Area 118 Back 213 Group III metal nitride layers 214, 223 Threading dislocations 215, 415 Window area 219 Joint 221 Group III Metal Nitride Materials 225 Cavity 413 Group III Metal Nitride Boules 419 Locally Nearly Linear Array 431 Freestanding Ammonothermal Group III Metal Nitride Wafers 521, 523, 525, 527, 529, 531 Intersection 600 Hexagonal Domain 701, 703, 705, 707 intersection 709 Basic unit cell 711 Secondary opening 751, 751a First linear array 752, 752a Second linear array 753, 753a Third linear array 761 Growth centers aligned in the first direction 762 Growth centers aligned in the second direction 763 Growth centers aligned in the third direction 761a, 762a, 763a Long growth center 761b, 762b, 763b Short growth center 785 First Distance 786 center point

Claims

1. In a crystal comprising a group III metal and nitrogen, the crystal is free-standing; Wurtzite crystal structure, a first face having a largest dimension greater than 5 millimeters in a first direction, the first face having a crystallographic orientation within 5 degrees of one of (0001) and (000-1); 10 ３ cm －１ the average concentration of stacking faults less than 10 １ cm －２ and 10 ６ cm －２ The average concentration of threading dislocations between having the average concentration of threading dislocations on the first surface varies in a first domain with a period of at least two in the first direction, the period of the variation in the first direction being between 5 micrometers and 20 millimeters, and the first domain having a maximum dimension in the first direction greater than 500 micrometers; The first surfaces each have a thickness of 5 cm －１ and 10 ５ cm －１ wherein at least 50% of the intersections between adjacent locally substantially linear arrays of threading dislocations consist essentially of three locally substantially linear arrays of threading dislocations that meet at a crossing angle of 120°±3°; The first surfaces are each disposed between adjacent pairs of the plurality of first regions, ５ cm －２ Concentration of threading dislocations less than 10 ３ cm －１ a plurality of second regions having a concentration of stacking faults less than The first surfaces are each disposed within one of the plurality of second regions or between adjacent pairs of the second regions and have a minimum dimension between 3 micrometers and 5 millimeters and a minimum width of 10 micrometers and 5 millimeters. ３ cm －２ and 10 ８ cm －２ a plurality of third regions having threading dislocations having a concentration between

2. The crystals were quantified by calibrated secondary ion mass spectrometry to determine １７ cm －３ H impurity concentration of more than 1×10 １５ cm －３ 2. The crystal of claim 1, further comprising an impurity concentration of at least one of Li, Na, K, F, Cl, Br, and I of greater than 1000.

3. The first surface is 1x10 １６ cm －３ and 1 x 10 １９ cm －３ Oxygen (O) between 1x10 １６ cm －３ and 2 x 10 １９ cm －３ Hydrogen (H) between 1x10 １５ cm －３ and 1 x 10 １９ cm －３ At least one of fluorine (F) and chlorine (Cl) between The crystal of claim 2, characterized by an impurity concentration of:

4. The first surface is 1x10 １６ cm －３ and 1 x 10 １９ cm －３ Oxygen (O) between 1x10 １６ cm －３ and 2 x 10 １９ cm －３ Hydrogen (H) between 3×10 １５ cm －３ and 1 x 10 １８ cm －３ At least one of sodium (Na) and potassium (K) between The crystal of claim 2, characterized by an impurity concentration of:

5. 2. The crystal of claim 1, wherein the overlap between adjacent third regions included in the plurality of third regions aligned in a second direction perpendicular to the first direction and adjacent in the first direction is between √3 and 3√3 times the spacing between adjacent third regions in the first direction.

6. 2. The crystal of claim 1, wherein the first domain is surrounded by six domains, wherein the orientation of between 55% and 100% of the third regions is oriented along a second direction aligned at an angle of 60°±3° from the first direction or along a third direction aligned at an angle of 120°±3° from the first direction, and the orientation of between 55% and 100% of the third regions within the six surrounding domains alternates between the second direction and the third direction.

7. A crystal comprising a Group III metal and nitrogen, the crystal being free-standing; Wurtzite crystal structure, a first face having a maximum dimension of greater than 5 millimeters in a first direction aligned within ±3° of a crystallographic orientation selected from <10-10> and <11-20>, the first face having a crystallographic orientation within 5 degrees of one of (0001) and (000-1); 10 ３ cm －１ the average concentration of stacking faults less than 10 １ cm －２ and 10 ６ cm －２ The average concentration of threading dislocations between having an average concentration of threading dislocations on the first surface has a period of variation that varies by at least a factor of two in each of the first direction, a second direction aligned at an angle of 60 degrees from the first direction, and a third direction aligned at an angle of 120 degrees from the first direction, the periods of variation in the first direction, the second direction, and the third direction being equal to within a factor of two and each being between 5 micrometers and 20 millimeters; The first surfaces each have a thickness of 5 cm －１ and 10 ５ cm －１ and wherein between 5% and 75% of the intersections between adjacent locally substantially linear arrays of threading dislocations include only three locally substantially linear arrays of threading dislocations that meet at an intersection angle of 120°±3°; The first surfaces are each disposed at least partially between adjacent pairs of the plurality of first regions, ５ cm －２ Concentration of threading dislocations less than 10 ３ cm －１ a plurality of second regions having a concentration of stacking faults less than The first surfaces each are disposed within one of the plurality of second regions or at least partially disposed between an adjacent pair of the second regions, and each have a minimum dimension between 3 micrometers and 5 millimeters and a minimum dimension between 10 micrometers and 5 millimeters. ３ cm －２ and 10 ８ cm －２ a plurality of third regions having threading dislocations having a concentration between

8. The crystals were quantified by calibrated secondary ion mass spectrometry to determine １７ cm －３ H impurity concentration of more than 1×10 １５ cm －３ 8. The crystal of claim 7, further having an impurity concentration of at least one of Li, Na, K, F, Cl, Br, and I of greater than 1000.

9. The first surface is 1x10 １６ cm －３ and 1 x 10 １９ cm －３ Oxygen (O) between 1x10 １６ cm －３ and 2 x 10 １９ cm －３ Hydrogen (H) between 1x10 １５ cm －３ and 1 x 10 １９ cm －３ At least one of fluorine (F) and chlorine (Cl) between The crystal of claim 8, characterized by an impurity concentration of:

10. The first surface is 1x10 １６ cm －３ and 1 x 10 １９ cm －３ Oxygen (O) between 1x10 １６ cm －３ and 2 x 10 １９ cm －３ Hydrogen (H) between 3×10 １５ cm －３ and 1 x 10 １８ cm －３ At least one of sodium (Na) and potassium (K) between The crystal of claim 8, characterized by an impurity concentration of:

11. 8. The crystal of claim 7, wherein the periods of change in each of the first direction, the second direction, and the third direction are equal to within 10%.

12. the plurality of third regions includes a plurality of main third regions each of which is rectangular having a minor dimension between about 3 micrometers and about 100 micrometers and a major dimension between about 200 micrometers and about 5 millimeters; The plurality of main third regions include a first linear array of primary third regions aligned parallel to the first direction; a second linear array of primary third regions aligned parallel to the second direction; and a third linear array of primary third regions aligned parallel to the third direction; Including, a first linear array of the primary third regions intersecting linear arrays of the primary third regions aligned parallel to the two other directions; 8. The crystal of claim 7, wherein the linear array of intersections includes intersections such that a major third region of the first linear array passes through a first intersection in the array of intersections, a major third region of the second linear array passes through a second intersection in the array of intersections, and a major third region of the third linear array passes through a third intersection in the array of intersections.

13. 8. The crystal of claim 7, wherein the plurality of third regions comprises a plurality of main third regions defining a basic unit cell, the basic unit cell comprising three intersections where a first main third region of the plurality of main third regions in the first direction intersects a line that spans the main third region in the second direction and the third direction, three intersections where a first main third region in the second direction intersects a line that spans the main third region in the first direction and the third direction, and three intersections where a first main third region in the third direction intersects a line that spans the main third region in the first direction and the second direction.

14. 8. The crystal of claim 7, wherein the plurality of third regions comprises a plurality of main third regions each rectangular in shape having a minor dimension between about 3 micrometers and about 100 micrometers and a major dimension between about 200 micrometers and about 5 millimeters, each of the plurality of main third regions being parallel to a line in the first direction, the second direction, or the third direction, a first end of each of the main third regions pointing to a central portion of an adjacent main third region and a second end of each of the main third regions pointing to an end portion of another adjacent main third region.

15. The crystal of claim 7, wherein the plurality of third regions includes a plurality of main third regions and a plurality of minor third regions, the plurality of main third regions defining a two-dimensional periodic array having a basic unit cell, and at least three minor third regions are contained within the basic unit cell.

16. The plurality of third regions are a two-dimensional pattern of a third region comprising third region repeat units, each repeat unit comprising: a portion of a first linear array of primary third regions extending in the first direction; a portion of a second linear array of primary third regions extending in the second direction; a portion of a third linear array of two or more primary third regions extending in the third direction, the first linear array, the second linear array, and the third linear array of primary third regions intersecting at intersections; Including, 8. The crystal of claim 7, wherein each of said major third regions is rectangular with a minor dimension between about 3 micrometers and about 100 micrometers and a major dimension between about 200 micrometers and about 5 millimeters.

17. 17. The crystal of claim 16, wherein the repeat units of the third region are formed in a linear array of repeat units, and a portion of the major third region within the linear array of repeat units are successively aligned in the first direction, aligned at an angle of 60 degrees from the first direction, and aligned at an angle of 120 degrees from the first direction.

18. 17. The crystal of claim 16, wherein the repeat unit of the third region further comprises a plurality of sub-third regions, the sub-third regions comprising two intersecting third regions oriented at an angle relative to each other.

19. 17. The crystal of claim 16, wherein a main third region of the first linear array of main third regions passes through the intersection point.

20. The plurality of third regions are A two-dimensional array of primary third regions, the major third regions in the two-dimensional array are rectangular with a minor dimension between about 3 micrometers and about 100 micrometers and a major dimension between about 200 micrometers and about 5 millimeters; a first end of each of the major third regions is positioned a first distance from a center point; a two-dimensional array of major third regions, each major third region being oriented such that a line passing through a center of each major third region and parallel to a major dimension of the major third region is not coincident with said center point; The crystal of claim 7, comprising:

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