Crystals and devices

Abstract

Embodiments of this disclosure include self-supporting crystals containing a group III metal and nitrogen. The self-supporting crystals have a wurtzite-type crystal structure, a growth direction (one of [0 0 0 ±1], {1 0 -1 0}, {1 0 -1 ±1}, {1 0 -1 ±2}), and a first surface (dislocation density in the growth direction of 1 cm³). -2 ~10^7 cm -2 Dislocation direction within 30 degrees, impurity H concentration 10^17 cm -3 It contains (super) and has at least four sets of bands, each band containing a first subband and a second subband, the first subband containing at least one impurity selected from H, O, Li, Na, K, F, Cl, Br, I, and each of the at least four sets of bands is partially nearly parallel.

Description

Cross-reference of related applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 440,059, filed on 19 January 2023, which is incorporated herein by reference in its entirety. [Technical Field]

[0002] This disclosure relates to the processing of materials in a supercritical fluid used for growing crystals that can be used to form bulk substrates, which can be used to form various optoelectronic devices, integrated circuits, power devices, lasers, light-emitting diodes, solar cells, and other related devices. [Background technology]

[0003] This disclosure generally relates to material processing techniques in supercritical fluids, such as single crystal growth. Examples of such crystals include metal oxides (e.g., MXO4 crystals, where M represents Al or Ga and X represents P or As) and metal nitrides (e.g., GaN, AlN, InN, InGaN, AlGaN, AlInGaN, etc.). More specifically, embodiments of this disclosure include techniques for controlling parameters related to material processing in capsules or liners installed within the housing of high-pressure equipment. Crystalline materials, including gallium nitride, are useful as substrates for the manufacture of optoelectronic and electronic devices such as lasers, light-emitting diodes, solar cells, photoelectrochemical hydrolysis and hydrogen production devices, photodetectors, integrated circuits, and transistors.

[0004] Supercritical fluids are used to process a variety of materials. Supercritical fluids are often defined as substances that have exceeded their critical point, i.e., their critical temperature and critical pressure. The critical point represents the highest temperature and pressure at which a substance can exist in equilibrium as both vapor and liquid. In certain supercritical fluid applications, the material being processed may be placed inside a pressure vessel or other high-pressure device. In some cases, it may be preferable to first place the material inside a container, liner, or capsule, and then place it inside the high-pressure device. During operation, the high-pressure device provides structural support against the high pressure generated within the container or capsule holding the material. The container, liner, or capsule provides a closed / sealed environment that is chemically inert and impermeable to solvents, solutes, and any gases that may be involved in or generated during the process.

[0005] Supercritical fluids offer an ideal environment for high-quality crystal growth, particularly in solvothermal processes, providing high volume and low cost. Supercritical fluids often possess both liquid dissolving capabilities and gaseous transport properties. Therefore, on the one hand, supercritical fluids can dissolve large amounts of solute for recrystallization. On the other hand, their high diffusion coefficient, a favorable transport property, allows the solute to be rapidly transported across the boundary layer between the supercritical fluid bulk and the growing crystal. Furthermore, their low viscosity results in a very thin boundary layer, easily leading to self-convection and self-stirring within the reactor even with slight temperature gradients. This combination of properties allows, for example, the growth of hundreds or thousands of large α-quartz crystals in a single growth run in supercritical water.

[0006] In some applications, such as crystal growth, the pressure vessel or capsule also includes a baffle plate that divides its interior into different chambers (e.g., an upper and lower half). The baffle plate often has numerous randomly or regularly spaced holes to allow fluid flow and heat / mass transfer between these different chambers. Each of these chambers holds a different material to be processed with the supercritical fluid. For example, in a typical crystal growth application, a seed crystal is placed at one end of the capsule and nutrients at the other. In addition to the material to be processed, the capsule typically contains a solid or liquid that forms a supercritical fluid under high temperature and pressure, as well as a mineralizer to increase the solubility of the material to be processed in the supercritical fluid. In some cases, the mineralizer may be a mixture of two or more substances (e.g., S. Tysoe et al., Patent Document 1 (2010)). During operation, the capsule is heated and pressurized to near or above its critical point, thereby transforming the solid and / or liquid into a supercritical fluid. In some applications, the fluid may remain subcritical, i.e., the pressure or temperature may be below the critical point. However, in all cases covered herein, the fluid is heated, i.e., at a temperature higher than its boiling point at atmospheric pressure. The term “supercritical” is used throughout to mean “heated state,” including cases where the critical point is not necessarily known due to the solute dissolved in the fluid composition.

[0007] In many solvothermal crystal growth systems, "normal" solubility is observed, meaning that the solubility of the substance to be crystallized increases with increasing temperature of the supercritical fluid. In such cases, nutrients are placed at the high-temperature end of the growth chamber and seed crystals at the low-temperature end, with the low-temperature end positioned above the high-temperature end to allow fluid mixing by natural convection. Examples of these systems include α-quartz in supercritical water using NaOH as a mineralizer, and GaN in supercritical ammonia using acidic mineralizers NH4Cl, NH4Br, and NH4I (Non-Patent Literature 1). On the other hand, "reverse solubility" can occur, meaning that solubility decreases with increasing temperature, in which case the relative positions of nutrients and seeds within the growth chamber may be reversed. Examples of systems exhibiting reverse solubility include AlPO4 (berlinite) in supercritical water using HCl as a mineralizer (ED Kolb and RA Laudise, Patent Literature 2 (1981)), and AlN in supercritical ammonia using the basic mineralizer KNH2 (Non-Patent Literature 2). GaN treated with the basic mineralizer KNH2 in supercritical ammonia also exhibits reverse solubility (Non-Patent Document 3). GaN treated with the acidic mineralizer NH4F in supercritical ammonia also exhibits reverse solubility, but in contrast to the other acidic mineralizers mentioned above (M. D'Evelyn et al., Patent Document 3 (2006)). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] U.S. Patent No. 7,642,122 [Patent Document 2] U.S. Patent No. 4300979 [Patent Document 3] U.S. Patent No. 7078731 [Non-patent literature]

[0009] [Non-Patent Document 1] D. Tomida et al., J. Crystal Growth 325, 52 (2011) [Non-Patent Document 2] D. Peters, J. Crystal Growth 104, 411 (1990) [Non-Patent Document 3] R. Dwilinski et al., J. Crystal Growth 310, 3911 (2008) [Overview of the project] [Problems that the invention aims to solve]

[0010] A challenge in crystal growth in reverse solubility systems is that the hottest point in the growth chamber is usually on the wall surrounding the seed crystal. This can lead to accidental nucleation on these walls, where crystals may grow preferentially over the seed crystal. Wall crystallization reduces the material deposition efficiency in the process, i.e., the proportion of dissolved nutrients that crystallize on the seed crystal, and can also interfere with crystal growth near the walls. The severity of this wall deposition problem can be sensitive to the temperature distribution within the crystal growth region and the temperature difference between the nutrient zone and the crystal growth zone. Material deposition efficiency is a crucial factor in economically forming self-supporting crystals.

[0011] Therefore, what is needed is an improved apparatus and method for improving the yield of the crystal growth process and the properties of the formed crystals by controlling the internal temperature distribution and its time evolution during solvothermal crystal growth exhibiting reverse solubility, thereby reducing accidental wall deposition on the inner surface of the growth zone and improving the crystal growth process.

[0012] This disclosure provides techniques for material processing for crystal growth. More specifically, this disclosure provides apparatus and methods for seed crystal heating suitable for use in combination with a high-pressure vessel for crystal growth of materials having reverse solubility in a supercritical fluid. This includes, but may also include, the growth of Group III metal nitride crystals by ammonium-based or ammonium-acidic techniques. In other embodiments, this disclosure also provides methods suitable for the synthesis of crystalline nitride materials, although it will be recognized that other crystals and materials can also be processed. These crystals and materials include, but are not limited to, GaN, AlN, InN, InGaN, AlGaN, AlInGaN, BN, and other materials for the manufacture of bulk or patterned substrates. Such bulk or patterned substrates can be used in a variety of applications, including optoelectronic devices, lasers, light-emitting diodes, solar cells, photoelectrochemical hydrolysis and hydrogen production, photodetectors, integrated circuits, and transistors.

[0013] Embodiments of the present disclosure include a self-supporting crystal containing a group III metal and nitrogen. The self-supporting crystal may include: a wurtzite-type crystal structure; a growth direction, which is selected from [0 0 0 ±1], {1 0 -1 0}, {1 0 -1 ±1}, or {1 0 -1 ±2}; a first surface having the maximum dimension in the first direction; and a second surface located opposite to the first surface. The second surface is separated from the first surface by a second direction perpendicular to the first direction, which is within 10 degrees of the growth direction. The first surface is 1 cm -2 ~10^7 cm -2 Dislocation density, at least 50% of dislocations oriented within 30 degrees from the growth direction, and average impurity concentration H of 10^17 cm⁻¹ -3 The average impurity concentration exceeds 10^15 cm⁻¹, and at least one of Li, Na, K, F, Cl, Br, or I is 10^15 cm⁻¹. -3They are characterized by exceeding (these are quantified by calibrated secondary ion mass spectrometry). Self-supporting crystals are characterized by having at least four sets of bands, each band set containing a first subband and a second subband, where the concentration of at least one impurity selected from H, O, Li, Na, K, F, Cl, Br, and I in the first subband is about 1.05 to about 100 times higher than the concentration in the second subband within the same subband; each of the at least four sets of bands is at least partially nearly parallel, and the thickness of each band set in the growth direction is about 0.1 micrometers to about 500 micrometers.

[0014] Embodiments of the present disclosure include a method for forming a group III metal nitride boule or wafer. The method includes forming a single crystal layer at least 1 mm thick on the surface of at least one seed crystal, the formation of which includes: heating a sealable container to a temperature above about 200°C, wherein the internal region of the sealable container contains at least one seed crystal, a polycrystalline group III metal nitride nutrient, a mineralizer, and ammonia, wherein a first region of the internal region contains the polycrystalline group III metal nitride nutrient and a second region contains at least one seed crystal, and the heating of the container causes the pressure in the internal region to exceed about 50 MPa. The temperature difference between the first and second regions is sequentially adjusted, which has a magnitude of about 1°C to about 100°C and a positive or negative sign, and this sequential adjustment of the magnitude and / or sign of the temperature difference is performed at least once during the formation of the single crystal layer. The thickness of the formed single crystal layer can be measured in a first growth direction, and at least 50% of the dislocations formed in the formed single crystal layer have an orientation within 30 degrees from the first growth direction. The thickness of the single crystal layer can be measured in a first growth direction, and the formed single crystal layer may have an oxygen gradient that decreases along the first growth direction extending from the surface of at least one seed crystal. In some embodiments, the single crystal layer formation process further includes: sequentially depositing multiple subbands with a material efficiency of more than 60% (where material efficiency is defined as the weight increase of the group III metal nitride material deposited on at least one seed crystal divided by the weight increase of the group III metal material deposited on the entire surface in a second region).

[0015] Embodiments of the present disclosure include a method for forming a group III metal nitride boule or wafer. The method involves placing at least one seed crystal, a polycrystalline group III metal nitride nutrient, a mineralizer, and ammonia in a sealable container, heating the container to a temperature above about 200°C and creating a pressure inside the container above about 50 MPa, thereby creating a temperature difference between a first region containing the polycrystalline group III metal nitride nutrient and a second region containing at least one seed crystal. This temperature difference has a magnitude and sign between about 1°C and about 100°C, which allows etching of the polycrystalline group III metal nitride nutrient and single crystal growth on at least one seed crystal. The magnitude of the temperature difference between the first and second regions is periodically reduced or its sign is reversed to etch accidental group III metal nitride nuclei that form on the surface within the second region, thereby depositing a single crystal layer at least 1 mm thick on the surface of at least one seed crystal. In this case, the material efficiency (also called material layer deposition efficiency, which is the value obtained by dividing the weight increase of the group III metal nitride material deposited on at least one seed crystal by the weight increase of the group III metal material deposited on the entire surface within the second region) exceeds 60%.

[0016] This disclosure achieves these and other advantages in the context of known process technologies. However, a further understanding of the nature and advantages of this disclosure will be obtained by referring to the latter part of the specification and the accompanying drawings. [Brief explanation of the drawing]

[0017] To enable a more detailed understanding of the features of this disclosure described above, a more specific description of the disclosure, which has been briefly summarized above, is provided with reference to several embodiments shown in the accompanying drawings. However, it should be noted that the accompanying drawings are merely illustrative examples of embodiments and do not limit their scope, and other equally effective embodiments are also recognized. [Figure 1A]This is a schematic diagram showing the heat flux to a crystal growth chamber by a solvothermal process having reverse solubility and associated wall deposition, according to one embodiment of the present disclosure. [Figure 1B] This is a schematic diagram showing the heat flux to a crystal growth chamber by a solvothermal process having reverse solubility and associated wall deposition, according to one embodiment of the present disclosure. [Figure 1C] This is a schematic diagram showing the heat flux to a crystal growth chamber by a solvothermal process having reverse solubility and associated wall deposition, according to one embodiment of the present disclosure. [Figure 2] This is a schematic diagram showing a pressure vessel apparatus according to one embodiment of the present disclosure. [Figure 3] This is a schematic diagram showing an internally heated pressure vessel device according to one embodiment of the present disclosure. [Figure 4] This is a schematic diagram showing the temperature-time profile of a solvothermal process according to one embodiment of the prior art. [Figure 5] This is a schematic diagram showing an enlarged view of the temperature-time profile of a solvothermal process according to one embodiment of the present disclosure. [Figure 6] This is a schematic diagram showing an enlarged view of the temperature-versus-time profile of a solvothermal process according to another embodiment of the present disclosure. [Figure 7] This is a schematic diagram showing an enlarged view of the temperature-versus-time profile of a solvothermal process according to yet another embodiment of the present disclosure. [Figure 8A] This is a schematic diagram showing an enlarged view of the temperature-versus-time profile of a solvothermal process having hot zone sectors in multiple azimuthal directions, according to an embodiment of the present disclosure. [Figure 8B] This is a schematic diagram showing an enlarged view of the temperature-versus-time profile of a solvothermal process having hot zone sectors in multiple azimuthal directions, according to an embodiment of the present disclosure. [Figure 9]This is a schematic diagram showing an enlarged view of the temperature-versus-time profile of a solvothermal process having hot zone sectors in multiple azimuthal directions, according to an embodiment of the present disclosure. [Figure 10] This is a schematic diagram showing a simplified flow diagram of a method for processing a material in a supercritical fluid according to one embodiment of the present disclosure. [Figure 11] This is a schematic diagram showing the impurity concentration as a function of depth within the crystal, according to a particular embodiment of the present disclosure. [Figure 12] This is a schematic diagram showing the impurity concentration as a function of depth within the crystal, according to a particular embodiment of the present disclosure. [Figure 13] This is a schematic diagram showing the impurity concentration as a function of depth within the crystal, according to a particular embodiment of the present disclosure. [Figure 14] This is a schematic diagram showing the impurity concentration as a function of depth within the crystal, according to a particular embodiment of the present disclosure. [Figure 15] This is a schematic diagram showing the impurity concentration as a function of depth within the crystal, according to a particular embodiment of the present disclosure. [Figure 16] This is a schematic diagram illustrating a method for slicing a grown crystal to produce a wafer, according to a specific embodiment of the present disclosure. [Figure 17] This is a schematic diagram showing a wafer fabricated according to a specific embodiment of this disclosure. [Figure 18A] This is a schematic diagram showing a wafer fabricated according to a specific embodiment of this disclosure. [Figure 18B] This is a schematic diagram showing a wafer fabricated according to a specific embodiment of this disclosure. [Figure 18C] This is a schematic diagram showing a wafer fabricated according to a specific embodiment of this disclosure.

[0018] For ease of understanding, identical elements common to all figures are given the same reference numeral whenever possible. It is also conceivable, and is not limited to, that elements and features of one embodiment may be usefully incorporated into other embodiments. [Modes for carrying out the invention]

[0019] This disclosure provides techniques for material processing for crystal growth. More specifically, this disclosure provides improved heater designs and thermal control systems suitable for use in combination with high-pressure vessels for crystal growth of materials having reverse solubility in supercritical fluids. This includes, but may also include, the growth of Group III metal nitride crystals by ammonium-based or ammonium-acidic techniques. In other embodiments, this disclosure also provides methods suitable for the synthesis of crystalline nitride materials, although it will be recognized that other crystals and materials can also be processed. These crystals and materials include, but are not limited to, GaN, AlN, InN, InGaN, AlGaN, AlInGaN, BN, and other materials for the manufacture of bulk or patterned substrates. Such bulk or patterned substrates can be used in a variety of applications, including optoelectronic devices, lasers, light-emitting diodes, solar cells, photoelectrochemical hydrolysis and hydrogen production, photodetectors, integrated circuits, and transistors.

[0020] This disclosure includes embodiments relating to apparatus for manufacturing compositions. This disclosure also includes embodiments relating to methods for manufacturing and / or using compositions.

[0021] The approximate expressions used throughout this specification and the claims are applied to modify quantitative expressions that may vary within an acceptable range without altering the fundamental function. Therefore, values ​​modified with "approximately" may not be limited to the specified exact value. In at least one case, the range of variation indicated by "approximately" may be determined based on the precision of the measuring instrument. Similarly, when the word "free" is combined with other words, unless explicitly stated, what is modified by that word may be considered free if it is substantially nonexistent or only a trace amount.

[0022] The technical challenges addressed by this disclosure are schematically shown in Figures 1A-1C. Referring to Figure 1A, the growth chamber 101 may include the inner surface of an autoclave or pressure vessel, the inner surface of a liner within an autoclave, or the inner surface of a capsule within an autoclave or internally heated high-pressure device. As used herein, “autoclave” refers to a thick-walled pressure vessel for processing materials at high temperature and pressure. Internally heated high-pressure devices can also process materials at high temperature and pressure and can be considered pressure vessels, although their structure may differ significantly from conventional pressure vessels. Autoclaves, pressure vessels, or internally heated high-pressure devices are typically cylindrical and oriented vertically. The internal space 103 is filled with a supercritical fluid (such as ammonia or water) in which a mineralizer is dissolved. The growth chamber 101 may be divided into an upper chamber 105 and a lower chamber 107 by a baffle 109. The baffle 109 includes one or more disks, cones, spherical portions, etc., and has one or more holes or annular gaps relative to the growth chamber 101, allowing restricted fluid movement through the baffle. One or more seed crystals 111 are suspended in the lower chamber 107 (from a device not shown), and one or more clumps of polycrystalline nutrient material 113 are placed in the upper chamber 105. In certain embodiments, the polycrystalline nutrient material 113 is placed in one or more baskets (not shown). This configuration is suitable for crystal growth in a system with reverse solubility, where etching of the polycrystalline nutrient material 113 occurs in the upper chamber 105, and growth of crystalline material onto the seed crystal 111 occurs in the lower chamber 107.

[0023] The growth chamber 101 is heated to a temperature distribution suitable for crystal growth by one or more electric heaters (not shown). An exemplary (prior art) heater for an autoclave is described in Dwilinski (U.S. Patent No. 6656615) and includes a cylindrical, independently controllable hot zone surrounding the upper chamber 105 and the lower chamber 107. An exemplary (prior art) heater suitable for an internally heated high-pressure apparatus is described in Giddings (U.S. Patent No. 7705276) and includes a cylindrical, independently controllable hot zone surrounding the upper chamber 105 and the lower chamber 107, and is located within a high-strength cylindrical enclosure. Conditions suitable for crystal growth are achieved by heating the lower chamber 107 to a higher temperature than the upper chamber 105, resulting in free convection 127 in the growth zone within the lower chamber 107 and free convection 125 in the nutrient zone within the upper chamber 105. The temperature difference between the lower chamber 107 and the upper chamber 105 can range from approximately 1°C to 100°C, 3°C to 30°C, or 5°C to 20°C. Under steady-state growth conditions, the temperature distribution within the growth chamber 101 becomes quasi-steady, and the deposition rate of crystalline material in the lower chamber 107 equals the etching rate of polycrystalline nutrients in the upper chamber 105. Therefore, under steady-state conditions, the net heat flux passing through the boundary of the growth chamber 101 is zero; that is, the inward heat flux passing through a specific portion of the boundary of the growth chamber 101 is offset by the outward heat flux in other portions. The details of the heat flux distribution depend on the details of the power distribution to the heater, but generally, the growth zone heat flux 137 passing around the cylinder of the lower chamber 107 flows inward, allowing the lower chamber 107 to be hotter than the upper chamber 105. For the same reason, the baffle heat flux 139 flows upward from the lower chamber 107 to the upper chamber 105. If the heater is cylindrical, the bottom heat flux 134 and top heat flux 132 (passing through the bottom and top of the growth chamber 101) flow outward. Depending on the details, the nutrient zone heat flux 135 passing around the cylinder of the upper chamber 105 can be outward or inward.

[0024] As a result of the heat flux schematically shown in Figure 1A, the hottest surface in the growth chamber 101 is typically around the lower chamber 107. In the case of the reverse solubility system, the thermodynamic driving force for deposition is maximum at these surfaces, and nuclei 141 may form on these surfaces, as schematically shown in Figure 1B. Furthermore, since the surface on which nuclei 141 form is the hottest in the growth chamber 101, the nuclei 141 grow faster than the seed crystal 111. Therefore, as the crystal growth process progresses, the nuclei 141 may coalesce into a continuous polycrystalline film 143 (see Figure 1C). The roughness and thickness of the continuous polycrystalline film 143 can alter the growth zone free convection 147. Growth to the seed crystal 111 may be hindered by competition for dissolved nutrients or disturbance in the growth zone free convection 147. In extreme cases, if the temperature difference between the continuous polycrystalline film 143 and the seed crystal 111 becomes large, and the flux of dissolved nutrients from the upper chamber 105 to the lower chamber 107 is obstructed by the depletion of polycrystalline nutrients 113 or clogging of pores or annular gaps in the baffle 109, the seed crystal may be etched instead of growing, while the continuous polycrystalline film 143 continues to grow.

[0025] As a further consequence of the suboptimal temperature distribution, such as excessively high sidewall temperatures in the lower chamber 107, a temperature minimum may occur at the bottom of the lower chamber 107, suppressing or disrupting convective flow, causing fluid stagnation, and resulting in suboptimal fluid flow over the seed crystal 111.

[0026] Figure 2 is a simplified diagram of a high-pressure apparatus according to one embodiment of the present disclosure. This figure is merely an example and does not unduly limit the scope of the claims herein. Those skilled in the art will be able to recognize other variations, modifications, and alternatives. As shown in the figures, the present disclosure provides apparatus for processing crystals or materials under high pressure (e.g., GaN, AlN, InN, InGaN, AlGaN, AlInGaN, BN, etc.). Other processing methods include hydrothermal crystal growth of oxides and other crystalline materials, hydrothermal or ammonia thermal synthesis, hydrothermal decomposition, etc. Of course, there may be a variety of other variations, modifications, and alternatives.

[0027] Referring to Figure 2, a high-pressure apparatus and associated methods for processing materials in a supercritical fluid are disclosed. In certain embodiments, an improved heater is used as a component of the autoclave. The autoclave may be able to process materials in a fluid at a pressure of about 5 MPa to less than about 500 MPa, less than about 400 MPa, less than about 300 MPa, less than about 200 MPa, or less than about 100 MPa, or about 5 MPa to 100 MPa (e.g., about 50 MPa) at a temperature of about 50°C to about 900°C, e.g., about 100°C to about 600°C, about 150°C to about 500°C, or about 200°C to about 400°C. Referring to Figure 2, the autoclave 200 includes an autoclave body 201 consisting of walls 201a with an inner surface 201b. The upper part of the autoclave body 201 is surrounded by at least one upper heater 205, and the lower part is surrounded by at least one lower heater 207, each of which may include insulation. The upper heater 205 may include one or more independently controllable hot zones (e.g., a top tail zone 205a and a top main zone 205b). Similarly, the lower heater 207 may include one or more independently controllable hot zones (e.g., a bottom main zone 207a and a bottom tail zone 207b). The upper heater 205 and the lower heater 207 are typically controlled independently, even though they are physically integrated. In certain embodiments, a liner 211 is located within the cavity of the autoclave body 201. The inner surface of the liner 211, or, if there is no liner 211, the inner surface 201b of the autoclave body 201, is used to form a cylindrical chamber 225 in which a method of processing material in a supercritical fluid is carried out. The cylindrical chamber 225 (also called a growth chamber) includes a central axis 221 that runs through the top and bottom of the autoclave body 201. Liner 211 may be formed from or contain one or more of the following: platinum, palladium, iridium, Pt / Ir alloy, gold, or silver. For example, Liner 211 may consist of a solid sheet material of pure silver or a silver alloy. Liner 211 may also consist of one or more of the following: titanium, rhenium, copper, iron, nickel, stainless steel, zirconium, tantalum, molybdenum, niobium, or alloys thereof.The baffle 109 may be located inside the liner 211 (if present) or the autoclave body 201. The baffle 109 includes one or more discs, conical portions, spherical portions, etc., and has one or more holes or annular gaps relative to the inner diameter of the liner 211 (if present) to restrict fluid movement through the baffle. In certain embodiments, a bottom baffle 213 is provided at a predetermined distance from the bottom surface 215 of the liner 211 (if present) or the inner bottom surface of the autoclave body 201. The baffle 109 and bottom baffle 213 may be formed from one or more materials such as platinum, palladium, iridium, Pt / Ir alloy, gold, silver, titanium, rhenium, copper, iron, nickel, stainless steel, zirconium, tantalum, molybdenum, niobium, or alloys thereof. The bottom baffle 213 may have the shape of a flat disc and have one or more holes with a diameter of approximately 1 mm to approximately 25 mm. There may be an annular gap of approximately 0.5 mm to 25 mm between the outer diameter of the bottom baffle 213 and the inner diameter of the liner 211 (if present) or the autoclave body 201 (if the liner 211 is absent).

[0028] A cylindrical chamber, such as the cylindrical chamber 225, is provided with multiple seed mounts (not shown) in which seed crystals 111 are arranged at intervals as a vertical array 223. In other words, the seed mounts are configured as a vertical array 223 at intervals to support the seed crystals during processing. Multiple crystal-supporting seed mounts may be arranged as a horizontal array at each level of the vertical array 223 and aligned in a direction perpendicular to the vertical array 223 (radial direction).

[0029] In certain embodiments, the autoclave 200 includes an autoclave cap 217 and a closure 219, as shown, and a gasket (not shown). The configuration in Figure 2 is a schematic diagram of a Grayloc® seal. In other embodiments, the autoclave 200 includes one or more of the following: an unsupported Bridgman seal, an O-ring seal, a C-ring seal, a restrained gasket seal, a bolted closure, an AE® closure, an EZE-Seal®, a Keuntzel closure, a ZipperClave® closure, a threadless pin closure, or a Gasche® gasket seal. In certain embodiments, the autoclave 200 has a cap, closure, and seal not only on the top but also on the bottom.

[0030] The autoclave body 201, autoclave cap 217, and closure 219 may be made of a material selected from steel, low carbon steel, SA723 steel, SA266 carbon steel, 4340 steel, A-286 steel, iron-based superalloys, nickel-based superalloys, cobalt-based superalloys, Inconel 718, Rene 41, 304 stainless steel, 310 stainless steel, 316 stainless steel, 340 stainless steel, 410 stainless steel, 17-4 precipitation-hardening stainless steel, zirconium and its alloys, titanium and its alloys, and other materials commonly known as Monel®, Inconel®, Hastelloy®, Udimet® 500, Stellite®, Rene® 41, and “Rene” 88. Any component of the autoclave body 201, autoclave cap 217, or closure 219 may be heat-treated. In certain embodiments, the autoclave body 201 is equipped with a removable seal not only at the top but also at the bottom.

[0031] The autoclave 200 may further include a bottom edge heater 231 and an insulating material 232 thermally coupled to the bottom of the autoclave body 201. The bottom edge heater 231 generates a nearly azimuthally uniform power distribution around the central axis of the autoclave body 201. The power level of the bottom edge heater 231 may be selected to maintain uniformity of the temperature distribution across the bottom surface 215 within 10°C, 5°C, 2°C, 1°C, 0.5°C, or 0.2°C, based on its relative relationship to the power levels of the lower heater 207 and upper heater 205, and the radial dependence of the power density within the bottom edge heater 231. In certain embodiments, the power level of the bottom edge heater 231 is selected based on its relative relationship to the power levels of the lower heater 207 and upper heater 205, and the radial dependence of the power density within the bottom edge heater 231, such that the average temperature of the bottom surface 215 is within 20°C, 10°C, 5°C, 2°C, or 1°C of the average temperature within a specified height range of the inner surface of the liner 211 or, if the liner 211 is absent, the inner surface of the autoclave body 201. The specified height range is measured from the bottom surface 215. In certain embodiments, the specified height is approximately 1 cm, 5 cm, 10 cm, 20 cm, or 25 cm. In certain embodiments, the bottom edge heater 231 has at least two or more independently controllable hot zones.

[0032] In certain embodiments, the autoclave 200 further includes a top insulator / heater 209. The top insulator / heater 209 may include, or consist of, a load-bearing thermal insulator made of, for example, zirconia or other ceramic material with low thermal conductivity. In certain embodiments, the top insulator / heater 209 may be able to generate heat by an electrical connection through the autoclave cap 217. In certain embodiments, the top insulator / heater 209 includes one or more such as a cartridge heater, cable heater, or disc heater. The dimensions and power level (if any) of the top insulator / heater 209, as well as the power levels of the lower heater 207 and upper heater 205, and the radial dependence of the power density within the top insulator / heater 209, may be selected to maintain a uniform temperature distribution across the top surface 245 within 10°C, 5°C, 2°C, or 1°C. Furthermore, by adjusting the dimensions of the top insulation / heater 209 and the power levels of the upper heater 205 and lower heater 207, the average temperature of the top surface 245 can be set to be within 20°C, 10°C, 5°C, 2°C, or 1°C of the average temperature of a specified height range measured from the top surface 245 on the inner surface of the liner 211 or, if the liner 211 is absent, on the inner surface of the autoclave body 201. In certain embodiments, the specified height is approximately 1 cm, 5 cm, 10 cm, 20 cm, or 25 cm. In certain embodiments, the top insulation / heater 209 has at least two or three independently controllable hot zones.

[0033] Details relating to the manufacture and characteristics of the bottom end heater 131 and the top insulation / heater 209 are described in U.S. Patent Application No. 17 / 963004, which is incorporated herein by reference in its entirety.

[0034] Figure 3 is a simplified diagram of an internally heated high-pressure apparatus according to one embodiment of the present disclosure. This figure is merely an example and does not unduly limit the scope of the claims herein. Those skilled in the art will be able to recognize other variations, modifications, and alternatives. As shown in the figures, the present disclosure provides apparatus for processing crystals or materials under high pressure (e.g., GaN, AlN, InN, InGaN, AlGaN, AlInGaN, BN, etc.). Other processing methods include hydrothermal crystal growth of oxides and other crystalline materials, hydrothermal or ammonia thermal synthesis, hydrothermal decomposition, etc. Of course, there may be a variety of other variations, modifications, and alternatives.

[0035] Referring to Figure 3, a high-pressure apparatus and related methods for handling supercritical fluids are disclosed. In certain embodiments, an improved heater is used as a component of the internally heated high-pressure apparatus. The apparatus provides adequate containment in all directions (radial and axial directions for a typical cylindrical vessel). Furthermore, depending on the details of the design parameters, the apparatus can operate at 200°C to 1500°C and pressures of about 5 MPa to about 2000 MPa for the required period, for example, about 1 hour to about 180 days, to grow a satisfactory bulk crystal. The internally heated high-pressure apparatus 300 can be constructed by stacking one or more ring assemblies (high-strength enclosure ring 301 and ceramic ring 303) to provide radial containment. The stack may include more than 2, more than 5, more than 10, more than 20, more than 30, more than 50, or more than 100 ring assemblies. The heater or heating member 305 and capsule 307 are surrounded and may be mechanically supported by at least one support plate (not shown). The laminate provides radial containment against pressure generated within the capsule 307 and transmitted to the outside via the heater 305. The heater 305 includes an upper heater 305a and a lower heater 305b. The upper heater 305a and the lower heater 305b may each have one or more independently controllable hot zones. Even if the upper heater 305a and the lower heater 305b are physically integrated, they are usually controlled independently. The interior of the heater 305 forms a processing chamber in which the capsule 307 is placed. If the ring assembly of the die laminate consists of a high-strength enclosure ring 301 and a ceramic ring 303, an interference fit may exist between the two members of each ring assembly. External cooling means may be provided for one or more ring assemblies or radial restraints. In certain embodiments, the capsule 307 includes an inner capsule member and an outer capsule member (not shown).

[0036] Axial containment of the pressure generated within the capsule 307 may be provided by an end plug 311, a crown member 317, a tie rod, or a tie rod fastener 315. The end plug 311 may be made of zirconium oxide or zirconia. The end plug 311 may be surrounded by an end plug jacket 313. The end plug jacket may provide mechanical support and / or radial containment for the end plug 311, and mechanical support and / or axial containment for the heater 305. The end plug jacket 313 may be made of steel, stainless steel, iron-based alloy, nickel-based alloy, etc. In certain embodiments, the tie rod fastener 315 is provided in an arrangement that provides axial loads to two or more ring assemblies. Further details are described in U.S. Patent No. 9,724,666 and No. 1,017,4438, which are incorporated herein by reference.

[0037] The crown member 317 and tie rod fastener 315 may consist of a material selected from steel, low carbon steel, SA723 steel, SA266 carbon steel, 4340 steel, A-286 steel, iron-based superalloys, 304 stainless steel, 310 stainless steel, 316 stainless steel, 340 stainless steel, 410 stainless steel, 17-4 precipitation-hardening stainless steel, zirconium and its alloys, titanium and its alloys, or materials commonly known as "Monel," "Inconel," "Hastelloy," "Udimet" 500, "Stellite," "Rene" 41, "Rene" 88.

[0038] In certain embodiments, the internally heated high-pressure device 300 may include a pressure transmission medium 309 near the axial end of the capsule 307 and the end plug 311. The pressure transmission medium 309 may include multiple components, such as one or more discs. The pressure transmission medium may include sodium chloride, other salts, or phyllosilicate minerals such as aluminum silicate hydroxide or pyrophyllite, or other materials.

[0039] Capsule 307 (also called process capsule) consists of or may contain one or more of platinum, palladium, iridium, Pt / Ir alloy, gold, or silver. For example, capsule 307 may contain a solid sheet material of pure silver or a silver alloy. Capsule 307 also consists of or may contain one or more of titanium, rhenium, copper, iron, nickel, stainless steel, zirconium, tantalum, molybdenum, niobium, or alloys thereof. Capsule 307 may further contain an outer support capsule to provide additional mechanical strength. The support capsule may consist of one or more of the following materials: steel, stainless steel, carbon steel, iron-based alloys or superalloys, nickel, nickel-based alloys or superalloys, "Inconel" nickel-chromium-iron alloy, "Hastelloy" nickel-molybdenum-chromium alloy, "Rene" 41 nickel-based alloy, Waspalloy® nickel-based alloy, Mar-M 247® polycrystalline cast nickel-based alloy, "Monel" nickel-copper alloy, "Stellite" cobalt-chromium alloy, copper, copper-based alloy, zirconium, niobium, molybdenum, tantalum, tungsten, rhenium, platinum, platinum-based alloy, palladium, iridium, ruthenium, rhodium, osmium, titanium, vanadium, chromium, gold, silver, aluminum, or combinations thereof. Details of Capsule 307 are described in U.S. Patent No. 1,0029955, which is incorporated herein by reference.

[0040] The baffle 109 is positioned inside the capsule 307 and may divide the internal space of the capsule 307 into an upper chamber and a lower chamber. The baffle 109 includes one or more discs, conical portions, spherical portions, etc., and has one or more holes or annular gaps relative to the inner diameter of the capsule 307, allowing restricted fluid movement through the baffle. The baffle 109 may be formed from or contain one or more of the following materials: platinum, palladium, iridium, Pt / Ir alloy, gold, silver, titanium, rhenium, copper, iron, nickel, stainless steel, zirconium, tantalum, molybdenum, niobium, or alloys thereof. As an example, the baffle 109 may contain a solid sheet material of pure silver or a silver alloy.

[0041] The internally heated high-pressure device 300 may further include a bottom end heater 331 and / or an upper end heater 341 thermally coupled to the bottom and top of the capsule 307. The bottom end heater 331 generates a power distribution that is substantially azimuthally uniform around the axis of heater 305. The power level of the bottom end heater 331 may be selected to maintain uniformity of the temperature distribution of the bottom surface 215 or alternatively the bottom baffle 213 within 10°C, 5°C, 2°C, or 1°C, based on its relative relationship to the power levels of the lower heater 305b and upper heater 305a, and the radial dependence of the power density within the bottom end heater 331. In certain embodiments, the power level of the bottom end heater 331 is selected based on its relative relationship to the power levels of the lower heater 305b and the upper heater 305a, and the radial dependence of the power density within the bottom end heater 331, such that the average temperature of the bottom surface 215 or alternatively the bottom baffle 213 is within 20°C, 10°C, 5°C, 2°C, or 1°C of the average temperature of a specified height range on the inner surface of the capsule 307. The specified height range is measured from the bottom surface 215. In certain embodiments, the specified height is approximately 1 cm, 5 cm, 10 cm, 20 cm, or 25 cm. The upper end heater 341 (if present) generates a nearly azimuthally uniform power distribution around the axis of heater 305, and the power level of the upper end heater 341 may be selected to maintain uniformity of the temperature distribution across the entire upper surface 345 to within 10°C, 5°C, 2°C, or 1°C, based on its relative relationship to the power levels of the lower heater 305b and upper heater 305a, and the radial dependence of the power density within the upper end heater 341. In certain embodiments, the power level of the upper end heater 341 is selected to be within 20°C, 10°C, 5°C, 2°C, or 1°C of the average temperature of the upper surface 345 compared to the average temperature of a specified height range measured from the upper surface 345 on the inner surface of the capsule 307, based on its relative relationship to the power levels of the lower heater 305b and upper heater 305a, and the radial dependence of the power density within the upper end heater 341.

[0042] Referring back to Fig. 1B, due to the thermodynamic driving force of preferential deposition on the wall compared to the seed crystal, the small nuclei formed on the wall then grow faster than the seed crystal. The main focus of the present disclosure is to etch and remove these wall nuclei before they merge and grow faster than the seed crystal.

[0043] Fig. 4 schematically shows the temperature profile of a conventional solvothermal crystal growth process having inverse solubility. Here, the average temperature of the upper chamber 105 is shown by the dashed line, and the average temperature of the lower chamber 107 is shown by the solid line. The upper chamber 105 (containing the nutrient 113) is heated from room temperature to the target nutrient temperature T ramp-up during the period of t nutrient . The lower chamber 107 (containing the seed crystal 111) is similarly heated from room temperature to the target growth temperature Tgrowth. In the case of GaN growth, T growth is in the range of about 400 °C to about 1000 °C or about 450 °C to about 800 °C, and the temperature difference ΔT = T growth - T nutrient is in the range of about 1 °C to about 100 °C, about 2 °C to about 50 °C, or about 3 °C to about 25 °C. For the growth of other nitrides (such as AlN and InN), oxides, and other crystalline compositions, the set temperatures may be different. The heating (ramp-up) time t ramp-up is in the range of about 0.1 hour to about 200 hours, or about 5 hours to about 96 hours. The soak time t soak (the time when crystal growth mainly occurs) is in the range of about 1 hour to about 10,000 hours, about 12 hours to about 7,500 hours, or about 100 hours to about 5,000 hours. At the end of the growth cycle, the upper chamber 105 and the lower chamber 107 are cooled to, for example, room temperature (during the period of t ramp-down ). The cooling (ramp-down) time t ramp-down is in the range of about 0.1 hour to about 200 hours, or about 5 hours to about 96 hours.

[0044] More complex versions of this simple profile are also possible. For example, instead of heating at a constant rate, the upper and / or lower chambers can be heated faster initially and slower later (e.g., to reduce the load on heaters 205, 207 and 305a, 305b). In certain embodiments, the upper zone 105 may be heated before the lower zone 107 to accelerate the partial dissolution of nutrients 113. The magnitude and spatial distribution of ΔT during ramp-up can be adjusted to control the amount of back-etch of the seed crystal 111. Similarly, the magnitude and spatial distribution of ΔT during cooling can also be adjusted to minimize or optimize the amount of back-etch of the growing crystal. The magnitude of ΔT during soaking can also be increased midway through the run to increase the growth rate after initial nucleation and does not need to be kept constant. In addition, the profile is generally height-dependent. For example, the T near the bottom of the lower zone 107 growth The temperature can be about 1°C to 20°C higher than near the top, which promotes fluid transport and equalizes the growth rate with respect to height. Similarly, the T near the bottom of the upper zone 105 nutrient The temperature in this area may be approximately 1°C to 20°C higher than near the top, in order to facilitate fluid transport within the upper zone 105. ramp-up t soak t ramp-down The values ​​may differ between the lower (growth) zone and the upper (nutrient) zone.

[0045] However, the inventors found that, regardless of the details of the heating profile used, it is extremely difficult to avoid the formation of wall nuclei 141 at realistic values ​​of ΔT during soaking.

[0046] In certain embodiments, one or more surfaces within a growth region are cooled from the “growth” temperature, held at a lower (”etch”) temperature, reheated back to the growth temperature, and held at the growth temperature for a predetermined time. This cool-etch-reheat-grow sequence may be performed at least two, four, five, ten, twenty, fifty, one hundred, two hundred, or four hundred times or more during the growth process. This cooling, low-temperature holding, reheating, and high-temperature holding may be performed sequentially, either periodically or aperiodicly.

[0047] Figure 5 shows an enlarged view of the initial portion of a cooling-etch-reheating-grow sequence according to a particular embodiment of the present disclosure. The average temperature of the upper zone 105 is set to a desired value T. u,nutrient After raising the temperature, it is maintained at this temperature during the soak period (dotted line in Figure 5). The average temperature of the lower zone 107 is set to the desired value T. l,growth After raising the temperature to a certain level and holding it for a predetermined period, the average temperature is lowered to a lower T l,etch until l,cool Cool for a certain amount of time, and at this low ("etch back") temperature t etchback Hold for the time, t l,heat T l,growth Reheat until t growth This value is maintained for the duration of T. As shown in Figure 5, l,etch is T u,nutrient At lower levels, ΔT becomes negative during the etch-back period. In other embodiments, T l,etch is T l,growth Lower but T u,nutrient At higher temperatures, ΔT remains positive, which may still be sufficient for etching the wall nucleus 141. Cooling time t l,cool The duration is approximately 0.2 minutes to 4 hours, 0.5 minutes to 1 hour, or 1 minute to 20 minutes. etchback The heating time is approximately 1 minute to 48 hours, approximately 2 minutes to 10 hours, or approximately 3 minutes to 4 hours. l,heat The time ranges from approximately 0.5 minutes to approximately 8 hours, approximately 1 minute to approximately 4 hours, or approximately 2 minutes to approximately 1 hour. l,growth and T l,etch The temperature difference is approximately 2°C to 100°C, 5°C to 75°C, or 10°C to 50°C. u,nutrient and T l,etch The temperature difference is approximately -20°C to 20°C, approximately -5°C to 15°C, or approximately 0°C to 10°C. Growth time t growth The timeframes are approximately 5 minutes to 500 hours, 10 minutes to 100 hours, 15 minutes to 50 hours, or 20 minutes to 24 hours. The overall cycle of the cooling-etch-reheating-growth sequence is approximately 6 minutes to 536 hours, 15 minutes to 200 hours, or 30 minutes to 28 hours.

[0048] In certain embodiments, instead of cooling and etching back the surface within the growth region, the surface within the nutrient region is heated from the “nutrient” temperature to a higher (“etch”) temperature, held at this high temperature, recooled back to the growth conditions (nutrient temperature), and held at the nutrient temperature for a predetermined period. This heating-etch-cooling-growth sequence may be performed at least 2, 5, 10, 20, 50, 100, 200, or 400 or more times during the growth process. This heating, etch temperature holding, recooling, and low temperature holding may be performed sequentially, cyclically, or aperiodically.

[0049] Figure 6 shows an enlarged view of the initial portion of the heating-etch-recooling-grow sequence according to a particular embodiment of the present disclosure. The average temperature of the lower zone 107 is set to a desired value T. l,growth After raising the temperature, it is maintained at this temperature during the soak period (solid line in Figure 6). The average temperature of the upper zone 105 is set to the desired value T. u,nutrient After raising the temperature to a certain level and holding it for a predetermined period, the average temperature of the upper zone 107 is raised to a higher T u,etch Heat for the specified time, and at this high ("etch back") temperature etchback Hold for the time, t u,cool T u,nutrient Cool down to this value and maintain it for the duration of tgrowth. As shown in Figure 5, T l,etch is T l,growth At higher levels, ΔT becomes negative during the etch-back period. In other embodiments, T u,etch is T u,nutrient Higher than T l,growth At lower temperatures, ΔT remains positive, which may still be sufficient for etching the wall nucleus 141. The heating-etch-recooling-growth sequence is repeated multiple times, periodically, cyclically, or aperiodically. Heating time t u,heat The cooling time is approximately 0.5 minutes to 8 hours, 1 minute to 4 hours, or 2 minutes to 1 hour. u,cool The time ranges from approximately 0.2 minutes to approximately 4 hours, approximately 0.5 minutes to approximately 1 hour, or approximately 1 minute to approximately 20 minutes. u,etch and T u,nutrient The temperature difference is approximately 2°C to 100°C, 5°C to 75°C, or 10°C to 50°C. u,etch and Tl,growth The temperature difference is approximately -20°C to 20°C, approximately -5°C to 15°C, or approximately 0°C to 10°C.

[0050] In certain embodiments, etching of the nucleus 141 can be performed by varying both average temperatures, rather than keeping one average temperature constant and modulating the other. For example, one or more surfaces in the growth region may be cooled, one or more surfaces in the nutrient region may be heated and etched back, and then returned to growth conditions and held for a predetermined time. This cooling-heating-etching-heating-cooling-growth sequence may be performed at least 2, 5, 10, 20, 50, 100, 200, or 400 or more times during the growth process. The heating-etching-recooling-growth sequence may be performed sequentially, cyclically, or aperiodically.

[0051] Figure 7 shows an enlarged view of the initial portion of a cooling + heating-etch-heating + cooling-growth sequence according to a particular embodiment of the present disclosure. The average temperature of the lower zone 107 is set to a desired value T. l,growth Raise the temperature to the desired value T, and set the average temperature of the upper zone 105 to the desired value T. u,nutrient Raise the temperature to a higher T after holding for a predetermined period. u,etch until u,heat Heat for a certain amount of time, and at this high ("etch back") temperature t etchback Hold for the time, t u,cool T u,nutrient Cool it down to t growth This value is maintained for the duration of T. As shown in Figure 7, l,etch is T u,etch At lower levels, ΔT becomes negative during the etch-back period. In other embodiments, T u,etch is T u,nutrient Higher than T l,etch At lower temperatures, ΔT remains positive, which may still be sufficient for etching the wall nucleus 141. Heating time t u,heat The cooling time is approximately 0.5 minutes to 8 hours, 1 minute to 4 hours, or 2 minutes to 1 hour. u,cool The time ranges from approximately 0.2 minutes to approximately 4 hours, approximately 0.5 minutes to approximately 1 hour, or approximately 1 minute to approximately 20 minutes. u,etch and T u,nutrientThe temperature difference is approximately 2°C to 100°C, 5°C to 75°C, or 10°C to 50°C. u,etch and T l,growth The temperature difference is approximately -20°C to 20°C, approximately -5°C to 15°C, or approximately 0°C to 10°C. The cooling + heating - etching - heating + cooling - growth sequence may be performed sequentially, cyclically, or aperiodically.

[0052] As shown in Figure 5, T l,etch is T u,nutrient At lower levels, ΔT becomes negative during the etch-back period. In other embodiments, T l,etch is T l,growth Lower but T u,nutrient At higher temperatures, ΔT remains positive, which may still be sufficient for etching the wall nucleus 141.

[0053] In each process schematically shown above and in Figures 5, 6, and 7, the fluid flow pattern during the growth period is similar to that schematically shown in Figure 1A. During the etching period, the driving force for free convection flow may decrease or disappear. In certain embodiments, flow may stagnate during the etching period. If there is a modest negative temperature gradient within the growth zone during the etching period, where the upper part is about 1°C to about 10°C lower than the lower part, some free convection will occur within the growth zone 107 even during the etching period. In other embodiments, there may be no temperature gradient or a positive gradient (the upper part is the same temperature as or hotter than the lower part, about 0°C to about 10°C) within the growth zone during the etching period, and little or no free convection may occur.

[0054] In certain embodiments, the growth-etch-growth process is carried out non-uniformly within the growth region. For example, the upper zone heaters 205a, 205b (Figure 2), 305a (Figure 3) and the lower zone heaters 207a, 207b (Figure 2), 305b (Figure 3) can be divided in the azimuthal direction (2 divisions, 3 divisions, 4 divisions, 8 divisions, etc.). Instead of periodically cooling and heating the lower zone heaters in all azimuthal directions, heating and cooling are performed at different timings for each different azimuthal zone. As shown in Figures 8A and 8B, the average temperature of the upper zone 105 is set to T u,nutrientRaise the temperature and maintain it during the soaking period, and set the average temperature of the lower zone 107 to T l,growth After raising the temperature to a certain level and holding it for a predetermined period, the average temperature of the first quadrant in the lower zone 107 is set to T l,etch Cool to the desired temperature, hold the etch back, then reheat and T l,growth The process is returned to the starting position and held for a predetermined period. If the same process is performed sequentially in the second, third, and fourth quadrants with time lags, the temperature distribution in the lower zone 107 becomes asymmetric, and complex lateral and vertical convective flow may occur. The non-uniform growth-etch-regrowth process may allow for sequential and positional "agitation" of the supercritical solvent in the growth zone 107 in an advantageous manner, and may allow for complete etch removal of the wall nuclei 141 while reducing the amount of etch on the seed 111 compared to the azimuthal uniform process (Figures 5-7). The non-azimuthal uniform analogs shown in Figures 6 and 7 are also possible.

[0055] In an embodiment like that shown in Figure 8A, the adjacent quadrant reaches the growth temperature T before one quadrant begins to cool. l,growth In some cases, the crystal may not be completely reheated. This method may be advantageous in completely etching away the wall nuclei 141 near the quadrant boundary, but it may also increase the amount of etch on the seed crystal 111. In another embodiment (Figure 8B), the growth setting for one quadrant is changed after the setting for another quadrant has been fully recovered.

[0056] In an embodiment as shown in Figure 9, when changing the setting value of one quadrant, the setting values ​​of other quadrants are changed in the opposite direction to partially or completely compensate for the temperature change experienced by the seed crystal 111. This method has the potential to completely remove the wall nuclei 141 by etching while minimizing etching to the seed 111 and the reduction in growth rate.

[0057] In the above embodiment, the temperature program for the growth-etch-growth cycle is implemented during the entire "soak" period. In certain embodiments, the growth-etch-growth cycle, which reverses the temperatures of the upper zone 105 and the lower zone 107, may be implemented during the heating process. The magnitude of ΔT and the cycle duration may also be changed as the soak progresses (for example, the growth period may be extended while the etching period remains nearly constant), and the etching cycle may be terminated midway through the soak.

[0058] In the embodiments shown in Figures 5-9, the setting value of only one quadrant or azimuth sector is changed at once, but in other embodiments, two or more may be changed simultaneously. For example, quadrants 1 and 3 may be cooled and reheated, quadrants 2 and 4 may be kept at a constant temperature, then quadrants 2 and 4 may be cooled and reheated, and quadrants 1 and 3 may be kept at a constant temperature.

[0059] In the embodiments shown in Figures 1A, 1B, and 1C, an example is shown in which the seed crystal 111 is suspended in the center of the lower zone 107. Various suspension methods are known, such as drilling a hole in the seed crystal 111 and suspending it with a wire, or fixing one or two sides with clips or the like. In other embodiments, the seed crystal 111 may be placed close to (within approximately 5 mm, 2 mm, 1 mm, 0.3 mm, 0.1 mm) or in direct contact with the mounting surface of the growth zone. For example, one or more sides of the seed crystal 111 can be pressed against the mounting surface with clips or the like. Even with such a configuration, the same process as the above-described method of etching the wall nucleus 141 by periodically changing the mounting surface temperature can be carried out. These processes are also within the scope of this disclosure.

[0060] While the above discussion primarily focuses on reverse solubility solvothermal systems, a similar process of obtaining a growth-etch-growth cycle by periodically changing the relative temperature between zones is also applicable to solvothermal systems of normal solubility and falls within the scope of this disclosure.

[0061] For example, single crystals of Group III metal nitrides such as gallium nitride can be grown in the growth chamber 101 by following the procedure below.

[0062] For example, a seed crystal such as a high-quality group III metal nitride single crystal is suspended or attached from furniture or the like by a conventionally well-known method. The seed crystal has a dislocation density on the surface of less than about 10^7 cm -2 less than, 10^6 cm -2 less than, 10^5 cm -2 less than, 10^4 cm -2 less than, 10^3 cm -2 less than, or 10^2 cm -2 less than, and a stacking fault density of less than about 10^4 cm -1 less than, 10^3 cm -1 less than, 10^2 cm -1 less than, 10 cm -1 less than, or 1 cm -1 less than. For example, a polycrystalline nutrient such as a group III metal nitride polycrystal is put into a basket in the growth chamber 101.

[0063] A solid mineralizer (for example, an alkali metal such as Li, Na, K, Rb, Cs, an alkaline earth metal such as Be, Mg, Ca, Sr, Ba, a hydride, amide, imide, amide imide, nitride, azide, ammonium halide (NH4F, NH4Cl, NH4Br, NH4I), metal halide, or a compound formed by the reaction of one or more of F, Cl, Br, I, HF, HCl, HBr, HI, Ga, Al, In, GaN, AlN, InN, NH3 with a metal, etc.) is put into the growth chamber 101.

[0064] The growth chamber 101 is closed, for example, by attaching an autoclave cap 217 to an autoclave body 201 or welding the end of a capsule 307. Then, the growth chamber 101 is evacuated through a tube or the like. To remove residual air, moisture, and other volatile impurities, the growth chamber 101 is evacuated and heated to about 25°C to about 900°C, or about 100°C to about 500°C with a heater 205 / 207 or 305 for 1 hour to 1,000 hours, or 24 hours to 250 hours. Multiple evacuation and purge cycles may be performed.

[0065] In certain embodiments, a gaseous or liquid-phase mineralizer is introduced into the growth chamber 101 by a known method. For example, if the mineralizer is HF, it is introduced using the method disclosed in U.S. Patent Application No. 2022 / 0136128. In certain embodiments, a solvent is introduced into an internally heated high-pressure device by a known method. For example, if the solvent is ammonia, it is introduced under high pressure using the method disclosed in U.S. Patent No. 8021481.

[0066] The growth chamber 101 is heated to a temperature exceeding approximately 400°C and pressurized to a pressure exceeding approximately 50 MPa to carry out ammonia thermal crystal growth, and the temperature program described in one of the processes described above is applied.

[0067] In some embodiments, the crystal growth process includes: applying a temperature difference between a first region containing polycrystalline group III metal nitride nutrients in a sealable container and a second region containing at least one seed crystal, having a magnitude of about 1°C to about 100°C and a sign that allows etching and single crystal growth; periodically decreasing the magnitude or reversing the sign of the temperature difference to etch accidental group III metal nitride nuclei formed on the inner surface of the second region; and depositing a single crystal layer at least 1 mm thick on the surface of at least one seed crystal (where the material layer deposition efficiency, or simply "material efficiency," is defined as the ratio of the weight increase of the group III metal nitride material deposited on at least one seed crystal to the weight increase of the group III metal material deposited on the entire inner surface of the second region, and is greater than 60%, greater than 75%, or greater than 90%).

[0068] Over periods ranging from 24 to 9,000 hours, 48 ​​to 4,000 hours, and 96 to 2,000 hours, each of the multiple seed crystals grows into a thick, self-supporting ammonia thermal group III metal nitride Boule.

[0069] In certain embodiments, the material efficiency (the value obtained by dividing the net weight increase of the seed crystal 111 by the weight reduction of the polycrystalline nutrient 113 consumed in the chemical reaction with the mineralizer during the single crystal growth run) is greater than 50%, greater than 60%, greater than 70%, greater than 80%, greater than 90%, or greater than 95%.

[0070] One or more self - standing ammonia thermal group III metal nitride boules may increase the thickness of the seed crystal 111 by more than 2 mm, more than 3 mm, more than 5 mm, more than 10 mm, more than 15 mm, more than 20 mm, more than 25 mm, more than 40 mm, or more than 100 mm during a single crystal growth run. In certain embodiments, the thickness direction is selected from any of [000 - 1], [0 0 0 1], {1 0 -1 0}, {1 0 -1 ±1}.

[0071] The distribution of various impurities within the self - standing ammonia thermal group III metal nitride boule can be evaluated by creating test wafers sliced parallel to the thickness direction and performing line scans or discrete point sampling by calibrated secondary ion mass spectrometry (SIMS). In certain embodiments, the product wafers are created by slicing the self - standing ammonia thermal group III metal nitride boule at an angle within 32 degrees, 24 degrees, 16 degrees,​​​​​​​​​​​​​​​​​​​​​Characterized as less than . In certain embodiments, the average impurity concentrations of O, H, carbon (C), Na, and K on the surface of a test wafer or product wafer are approximately 1 × 10^16 cm⁻¹ each. -3 ~5 × 10^19 cm -3 , about 1×10^16 cm -3 ~8 × 10^19 cm -3 , 1 × 10^17 cm -3 Less than 1 × 10^16 cm -3 Less than 1 × 10^16 cm -3 It is less than. In certain embodiments, the impurity concentrations of O, H, C, at least one F, and Cl on the surface of a test wafer or product wafer are approximately 1 × 10^16 cm⁻¹ each. -3 ~5 × 10^19 cm -3 , about 1×10^16 cm -3 ~8 × 10^19 cm -3 , 1 × 10^17 cm -3 Less than approximately 1 × 10^15 cm -3 ~1 × 10^19 cm -3 That is the case.

[0072] Generally, fluctuations in growth conditions, represented by temperature profiles schematically shown in Figures 5, 6, 7, 8A-B, and 9, cause local impurity levels within self-supporting thermal ammonia group III metal nitride boules. These fluctuations are usually large enough to be measurable, but they do not significantly adversely affect properties such as crystallinity or fracture resistance. Elements whose impurity concentrations may fluctuate include O, H, C, F, Cl, Na, K, Si, Ge, and Mg. In addition, carrier concentrations, Fermi levels (e.g., optical absorption coefficients at one or more wavelengths between approximately 360 nm and 750 nm), and work functions, secondary electron emission rates, cathodoluminescence, or photoluminescence intensity and spectrum can fluctuate in conjunction with the growth-etch cycle. When the growth condition fluctuation cycle is relatively short (approximately 6 minutes to 8 hours), for example, changes in the concentrations of O, H, C, F, Cl, Na, and K can be quantified by performing a SIMS sputtering depth profile in the growth direction (perpendicular to the growth surface). Another method involves fabricating a test wafer sliced ​​parallel to the thickness direction. When the variation cycle is relatively long (approximately 12 to 500 hours), the change in impurity concentration can be quantified on the thickness-oriented test wafer by SIMS line scanning or discrete-point sampling. By fabricating a second slice (parallel to the first slice) and aligning the large-area surface parallel to the growth direction, both sides can be polished or chemically mechanically polished to quantify the optical absorption coefficient at wavelengths of approximately 360 nm to 750 nm, for example. Alternatively, the test wafer can be observed with a scanning electron microscope, which provides sufficient spatial resolution regardless of the growth and etch variation cycle period. The secondary electron emission rate and backscattered electron cross-section are sensitive to carrier concentration and work function, and cycle-dependent bands may be observed. Similarly, the intensity and wavelength of cathodoluminescence (CL) also change in conjunction with the growth direction variation of impurity levels. By scanning the growth direction of the test wafer surface with light exceeding the band gap using a CL observation device, a dedicated CL device, or a He-Cd laser, changes in the intensity and wavelength of photoluminescence (PL) can also be observed.

[0073] The fluctuations in impurity concentration associated with varying growth conditions are similar to those observed in crystals and wafers using two-plane growth as described in, for example, U.S. Patent No. 1,0145,026. In the latter method, crystals are grown in a semipolar direction intermediate between the <1 0 -1 0> m direction and the [0 0 0 -1] -c direction, resulting in alternating {1 0 -1 0} m planes and {1 0 -1 -1} planes on the growth front. Because these growth planes have slightly different impurity incorporation rates, the resulting semipolar wafers exhibit alternating bands of high and low impurity concentrations. However, a key difference is that in conventional methods, the high and low concentration bands appear almost perpendicular to the growth direction, whereas in crystals formed by the process disclosed herein, the high and low concentration regions are distributed parallel to the growth direction. This difference in distribution does not adversely affect the crystal structure, and the process described herein enables high material efficiency, growth rate, and large crystal formation.

[0074] All Group III metal nitride crystals grown with current technology contain measurable dislocations, such as edge, screw, and mixed dislocations. Typically, the majority of dislocations on the preparation surface of bulk-grown Group III metal nitride crystals (over 50%, over 65%, over 80%, etc.) are threading dislocations, mainly aligned with the crystal growth direction (locally within 30 degrees). The three-dimensional dislocation distribution can be determined by creating multiple surfaces perpendicular to the growth direction and comparing the dislocation locations and concentrations on each. These parallel surfaces can be created by continuous chemical mechanical polishing. For example, a test wafer is prepared, and subsurface damage is removed from the surface by chemical mechanical polishing. Dislocation locations and concentrations can be determined by measuring the etch pit density using an optical microscope or scanning electron microscope. For example, if the crystal orientation of the test wafer surface is within 5 degrees from (0 0 0 1), defect-selective etch pits can be formed by heating with a KOH / NaOH molten solution or a concentrated H3PO4 or H3PO4 / H2SO4 mixture. When the surface orientation is intermediate between the m plane and {1 0 -1 -1}, selective etching is possible with concentrated H3PO4 or H3PO4 / H2SO4 mixture or Na2O2 / NaOH molten flux. After recording the distribution of etch pits with a digital image, the surface is chemically and mechanically polished again by h, and selective etching is performed again to record the pit positions. Defining the deviation from the surface normal by the threading dislocation inclination angle α, the pits after regrinding move by h tan(α) from the reference point. By comparing the pit distribution images of the original surface and the regrinding surface, the threading dislocation inclination angle α distribution can be quantified. For example, if 10 μm is removed after the first etching to create a second surface, and selective etching is performed again, the α dislocation moves approximately 5.8 μm on the second surface. Therefore, in certain embodiments, at least 50%, 65%, or 80% of the etch pits on the second surface are located within approximately 5.8 μm of the pits on the first surface.

[0075] In certain embodiments, the three-dimensional distribution of dislocations can be measured using multiphoton photoluminescence (e.g., T. Tanikawa et al., Appl. Phys. Express 11, 031004 (2018)), and the orientation direction can be directly determined.

[0076] As disclosed in U.S. Patent Application No. 2023 / 0167586, growing ammonia thermal group III nitride crystals with an intentional oxygen gradient in the growth direction offers specific advantages. For example, the growth rate in the <1 1 -2 0>a direction and <1 0 -1 0>m direction increases at higher oxygen levels compared to the [0 0 0 -1] growth rate, promoting coreless growth during pattern growth and resulting in a flatter, more complete c-plane surface morphology. The oxygen gradient is also useful in device applications because it maintains optical transmittance and thermal conductivity while achieving both low ohmic loss and low contact resistance. The maximum oxygen concentration in ammonia thermal group III nitride crystals is approximately 1 × 10^20 cm⁻¹. -3 Less than 5 × 10^19 cm -3 Less than 3 × 10^19 cm -3 Less than 2 × 10^19 cm -3 Less than 1 × 10^19 cm -3 If less than 2 × 10^18 cm⁻¹, the minimum oxygen concentration is 2 × 10^ -3 Super, 1×10^18 cm -3 Super, 5×10^17 cm -3 A method for maintaining this is disclosed. Depending on the application, it can reach 2 × 10^17 cm. -3 Less than 1 × 10^17 cm -3 In some cases, a minimum oxygen concentration of less than [0 0 0 1] is desirable. The maximum oxygen gradient in the direction is 1 × 10^21 cm. -4 Less than 5 × 10^20 cm -4 Less than 2 × 10^20 cm -4 Less than 5 × 10^16 cm, minimum oxygen gradient -4 Super, 2×10^17 cm -4 Super, 5×10^17 cm -4 Super, 1×10^18 cm -4Methods for maintaining this state are also disclosed. The oxygen concentration and its gradient during ammonia thermal crystal growth can be controlled by (1) controlling the oxygen concentration and its gradient in the polycrystalline group III nitride raw material, (2) controlling the time, temperature, and atmosphere for calcining the polycrystalline raw material before ammonia thermal crystal growth, (3) adding Ga2O3 or water to the ammonia thermal growth environment, (4) controlling the oxygen concentration of silver (chamber liner / capsule / baffle / furniture material), and (5) controlling the time, temperature, and atmosphere for autoclaving or calcining the capsule after loading the polycrystalline nutrients and seed crystals and before filling with ammonia.

[0077] The method of use in a particular embodiment can be briefly summarized as follows: An apparatus for high-pressure crystal growth or material processing (e.g., as described above) is provided, wherein the apparatus has an internal region (e.g., cylindrical) enclosed by radial and axial constraint structures, and the opening to the internal region can be closed. One or more raw materials are supplied to the internal region, the opening is closed and sealed, a solvent is supplied to the internal region, thermal energy is applied to the apparatus to raise the temperature of the internal region to over 200°C and heat the solvent. A crystalline material is formed from the heated solvent, thermal energy is removed from the apparatus to change the capsule temperature from a first temperature to a lower second temperature, the solvent is released from the internal region, the opening to the internal region of the high-pressure apparatus is opened, the crystalline material is removed from the internal region, and other steps are performed as necessary. This set of steps provides a method according to one embodiment of the present disclosure. In a particular embodiment, a method and crystalline material provided in a high-pressure apparatus that applies high temperature directly to a seed crystal are disclosed. As other alternatives, the addition, deletion, or reordering of steps will not depart from the scope of this claim. Details of the method and structure are described throughout this specification, and in particular are detailed below.

[0078] Figure 10 shows a simplified flow diagram of a method for processing a material in a supercritical fluid. This figure is an example and does not unduly limit the claims of this specification.

[0079] In certain embodiments, the process begins with step 1001. This method begins with providing a high-pressure crystal or material processing apparatus (step 1003) as described above, but other methods are also possible. The apparatus may have an internal region (e.g., cylindrical) surrounded by radial and axial constraint structures. Openings to the internal region may be closed with lids or welded structures.

[0080] In a particular embodiment, at least one raw material is supplied to the internal region (step 1005), the opening is closed (step 1007), and a solvent such as ammonia is supplied to the internal region (step 1009). In a particular embodiment, the raw material includes seed crystals and polycrystalline nutrients. The method involves heating the internal region to raise the temperature to over 200°C, heating the solvent, and processing at least one raw material within the internal region (step 1011).

[0081] Referring again to Figure 10, the method forms a crystalline material from a process with a heated solvent (step 1013). In certain embodiments, the crystalline material includes gallium-containing nitride crystals such as GaN, AlGaN, and InGaN. In certain embodiments, the method removes thermal energy from the capsule (step 1015) and changes the temperature of the internal region from a first temperature to a lower second temperature. After energy removal and temperature reduction, the solvent is removed from the internal region (step 1017).

[0082] In certain embodiments, the internal region is released (step 1019). In certain embodiments, the crystalline material is removed from the internal region (step 1021). Depending on the embodiment, other steps may be added or removed. In certain embodiments, the method terminates with a stop (step 1023).

[0083] The above set of steps provides a method according to one embodiment of the present disclosure. In a particular embodiment, a method and crystalline material provided in a high-pressure apparatus that applies high temperature directly to a seed crystal are disclosed. As other alternatives, adding, deleting, or rearranging steps will not depart from the scope of the claims.

[0084] In certain embodiments, gallium-containing nitride crystals or boules grown in the manner described above are sliced ​​or divided for wafer fabrication. Slicing, dividing, and cutting can be performed using conventionally known methods, such as internal diameter cutting, external diameter cutting, fixed abrasive multiwire cutting, fixed abrasive multiblade cutting, multiblade slurry cutting, multiwire slurry cutting, ion implantation, and layer separation. The wafers are then lapped, polished, and chemically and mechanically polished using conventionally known methods.

[0085] One or more active layers can be deposited on a well-crystalline gallium-containing nitride wafer. The active layer can be incorporated into at least one optoelectronic device such as a light-emitting diode, laser diode, photodetector, photodiode, avalanche photodiode, transistor, rectifier, or thyristor, or into any of the following devices: transistor, rectifier, Schottky rectifier, thyristor, PIN diode, metal-semiconductor-metal diode, high electron-mobility transistor, metal-semiconductor field-effect transistor, metal-oxide field-effect transistor, power metal-oxide-semiconductor field-effect transistor, power metal-insulator-semiconductor field-effect transistor, bipolar junction transistor, metal-insulator field-effect transistor, heterojunction bipolar transistor, power insulated-gate bipolar transistor, power vertical junction field-effect transistor, cascode switch, inner subband emitter, quantum well infrared photodetector, quantum dot infrared photodetector, solar cell, or diode for photoelectrochemical water splitting and hydrogen production. example

[0086] Embodiments of the present disclosure are further illustrated by the following examples. It will be apparent to those skilled in the art that many modifications to the materials and methods are possible.

[0087] Example 1 In this example, 28 c-plane GaN seed crystals were suspended by silver wire and placed in a 5.6-inch inner diameter silver capsule along with approximately 3.1 kg of polycrystalline GaN nutrients (sintered at 210°C for approximately 16 hours). The capsule was baked out under vacuum at approximately 200°C for approximately 6 hours. The capsule was then filled with 97.2 g of HF mineralizer and 2.36 kg of ammonia and sealed. The lower end of the capsule was heated to approximately 684°C, and the upper end to approximately 669°C. The upper end temperature was maintained for approximately 200 hours. The lower end temperature was maintained at 684°C for 1.5 hours, then cooled to 664°C in approximately 4 minutes, held at this lower "etch" temperature for approximately 10 minutes, and then reheated to the "growth" temperature of 684°C in approximately 5 minutes, where it was held for another 1.5 hours. This cycle was repeated 111 more times. After cooling, the capsule was opened, and the grown crystals were removed. The average growth rate of the seed crystal was approximately 4.5 μm / h. The material efficiency (the percentage of GaN transported from the nutrient region to the growth region and reaching the seed crystal) was 100%. No nucleated GaN crystals were observed on the inner diameter of the capsule.

[0088] One of the growing crystals was sliced ​​at an angle of approximately 3 degrees from the c-plane, exposing the growth thickness to a wide wedge-shaped surface. Approximately 10⁹ bright-colored fringes were observed on this wedge surface, which are thought to indicate the start of each growth cycle. The average spacing between growth cycle fringes was approximately 4.9 μm in the direction normal to the c-plane surface of this crystal. SIMS analysis was performed at several locations on the wedge surface to measure the concentrations of O and H in the [0 0 0 -1] direction from the seed surface. The results for this example are shown in Figures 11 and 12. As shown in Figure 12, a band was formed within the growing crystal layer by the cycle process in this example.

[0089] Another N-plane surface of the grown crystal was polished nearly parallel to the (0 0 0 -1) orientation, and the outermost 30 μm layer was analyzed using depth profile SIMS. The oxygen and fluorine concentrations in the depth direction are shown in Figure 12. During the growth / etch cycle, the oxygen concentration was approximately 1.5 × 10^19 cm⁻¹. -3 ~Approx. 2.5×10^19 cm -3 The fluorine concentration is approximately 3.6 × 10^17 cm⁻¹ -3 ~Approx. 2.1×10^18 cm -3The concentration fluctuated periodically within this range. In this region, the period of the impurity concentration fluctuation was approximately 10 μm. As shown in Figure 11, the O and H concentrations in the grown crystal layer decreased on a scale of several hundred μm as the growth thickness increased. As shown in Figure 12, multiple bands showing a bimodal distribution of O and F concentration levels were formed within the grown crystal layer. The gradual decrease in oxygen concentration, which was prominent in Figure 11, was not observed in the 30 μm range in Figure 12, and the analysis point was located approximately 700 μm away from the seed.

[0090] Example 2 In this example, 34 c-plane GaN seed crystals were suspended by silver wire and placed in a 5.6-inch inner diameter silver capsule along with 3.8 kg of polycrystalline GaN nutrients that had been calcined in ammonia at approximately 835°C for approximately 4 hours. The capsule was baked out under vacuum at approximately 250°C for approximately 40 hours. The capsule was then filled with 94.0 g of HF mineralizer and 2.43 kg of ammonia and sealed. The lower end of the capsule was heated to approximately 685°C, and the upper end to approximately 669°C. The upper end temperature was maintained for approximately 620 hours. The lower end temperature was maintained at 684°C for 1.5 hours, then cooled to 664.5°C in approximately 4.2 minutes, held at this lower "etch" temperature for approximately 12 minutes, and then reheated to the "growth" temperature of 684°C in approximately 4.8 minutes, where it was held for another 1.5 hours. This cycle was repeated 310 times. After cooling, the capsule was opened and the grown crystals were removed. The average growth rate of the seed crystal was approximately 2.5 micrometers per hour. The material efficiency (the percentage of GaN transported from the nutrient region to the growth region and reaching the seed crystal) was 100%. At the end of the process, no nucleated GaN crystals were observed on the inner diameter of the capsule.

[0091] One of the grown crystals was sliced ​​at an angle of approximately 6 degrees from the c-plane, exposing the grown thickness to a wide wedge-shaped surface. SIMS analysis was performed at several points on the wedge surface to measure the O and H concentrations with respect to distance from the growth surface. The results for this example are shown in Figures 13 and 14. Similar to Figure 11, Figure 13 shows that the O and H concentrations in the grown crystal layer decrease as the thickness of the grown layer increases, which is desirable.

[0092] Another N-plane surface of the grown crystal was polished nearly parallel to the (0 0 0 -1) orientation, and the outermost 40 micrometers were analyzed using depth profile SIMS. The oxygen and fluorine concentrations in the depth direction are shown in Figure 14. During the growth / etch cycle, the oxygen concentration was approximately 9 × 10^18 cm⁻¹⁸ -3 From approximately 1.1 × 10^19 cm -3 It fluctuates periodically, and the fluorine concentration, in phase, is approximately 1.1 × 10^17 cm⁻¹. -3 From approximately 1.5 × 10^17 cm -3 The values ​​fluctuated periodically. As shown in Figure 14, the grown crystal layer contained multiple formation bands exhibiting a bimodal distribution of O and F concentration levels. In Figure 14, unlike Figure 12, a slight increase in oxygen concentration with depth (i.e., in the direction of decreasing distance to the seed) is observed.

[0093] Example 3 In this example, 27 c-plane GaN seed crystals were suspended by silver wire and placed in a 5.6-inch inner diameter silver capsule along with 2.2 kg of polycrystalline GaN nutrients that had been calcined in ammonia at approximately 835°C for approximately 4 hours. The capsule was baked out under vacuum at approximately 250°C for approximately 40 hours. The capsule was then filled with 97.5 g of HF mineralizer and 2.36 kg of ammonia and sealed. The bottom of the capsule was heated to approximately 680°C and the top to approximately 669°C. The top temperature was maintained for approximately 357 hours. The bottom temperature was maintained at 680°C for 12 hours, then cooled to 664.5°C in approximately 2 minutes, held at this lower "etch" temperature for approximately 12 minutes, and then reheated to the "growth" temperature of 680°C in approximately 5 minutes, where it was held for another 12 hours. This cycle was repeated 27 more times. After cooling, the capsule was opened and the grown crystals were removed. The average growth rate of the seed crystal was approximately 3.9 micrometers per hour. The material efficiency (the percentage of GaN transported from the nutrient region to the growth region and reaching the seed crystal) was approximately 87%. Nucleation of isolated GaN crystals, similar to the schematic diagram in Figure 1B, was observed on the inner diameter of the capsule, but its distribution density was modest across the exposed surface of the capsule wall.

[0094] One of the grown crystals was sliced ​​at an angle of approximately 3 degrees from the c-plane, exposing the grown thickness to a wide wedge-shaped surface. SIMS analysis was performed at several points on the wedge surface to measure the O and H concentrations with respect to distance from the growth surface. The results for this example are shown in Figure 15. Similar to Figures 11 and 13, Figure 15 shows that the O and H concentrations in the grown crystal layer decrease as the thickness of the grown layer increases, which is desirable.

[0095] In this example, the growth time during the cycle was long (12 hours, compared to 1.5 hours in Examples 1 and 2), making it impractical to observe the bands associated with the growth cycle using sputter depth profiles. However, when a cross-section was cut from another crystal and observed with a scanning electron microscope, thin, bright bands corresponding to the growth / etch cycle were observed locally at intervals of approximately 38 micrometers under channeling contrast conditions.

[0096] Without being bound by theory, several possible mechanisms for the behavior shown in Figures 12 and 14 can be considered. Firstly, the etching process may cause localized roughening of the growing crystal surface. Re-growth on a roughened surface may increase the level of impurity incorporation. Subsequently, as the surface morphology returns to a smooth steady state, the level of impurities in the growing crystal may decrease. Secondly, the growth rate on the seed may decrease during the etching period of the cycle compared to the growth period, but the seed may not actually be etched (unlike in the case of wall nuclei). The decrease in growth rate during the etching period may be accompanied by a reduction in impurity incorporation, but conversely, a lower growth temperature may increase impurity incorporation. Thirdly, flow reversal during the etching cycle (circulation during the growth cycle as shown in Figure 1A, stagnation during the etching cycle) may reintroduce impurities into the growth environment, increasing the level of impurities when growth resumes. Subsequently, the level of impurities in the growth environment may decrease, and the level of impurities in the crystal may also return to a local baseline.

[0097] Note that the detailed concentration profiles in Figure 14 and Figure 12 are different. In Figure 14, the impurity concentration rises sharply and then decays slowly (the growth direction is from a large sputtering depth to a shallow sputtering depth). On the other hand, Figure 12 is more bimodal (high and low). The detailed explanation for this is unclear, but the cooling time, etching time, heating time, and the details of the temperature values ​​for each cycle may be influencing factors. For example, if the etching cycle is long (as in Example 2), more impurities may be released from the already grown and dissolving crystal and added to the solution surrounding the crystal. This may increase the overall impurity concentration in the solution, and the rectangular profile as in Figure 12 may change to a sawtooth profile as in Figure 14.

[0098] In the case of a three-dimensional seed crystal, bands with alternating impurity levels associated with the growth-etch-regrowth process can be formed on all seed surfaces exposed to the crystal growth environment. Typically, the seed crystal 111 has one or two faces with a larger surface area than its sides, and in sectors formed on these, the bands are nearly parallel as long as the growth surface is smooth and planar. In certain embodiments, the large-area seed surface has a crystal orientation within 5 degrees, 2 degrees, or 1 degree from (0 0 0 ±1) or (1 0 -1 0), and the bands are nearly parallel to this orientation. Depending on the length of the growth-etch cycle, the period of high and low impurity levels within the subbands may vary in the range of approximately 0.1 micrometers to approximately 500 micrometers, 0.5 micrometers to 250 micrometers, 1 micrometer to 100 micrometers, or 3 micrometers to 50 micrometers.

[0099] Figure 16 is a schematic diagram of a grown crystal 1601 formed on a large-area surface 1603 of a seed crystal 1605. For simplicity, growth on other surfaces of the seed crystal 1605 and the formation of other facets such as semipolar surfaces are not shown. In this example, the seed crystal 1605 is hexagonal, and the large-area surface 1603 has a crystal orientation within 5 degrees from (0 0 0 -1), but other seed shapes are also possible. The large-area surface 1603 may also have any of the orientations (0 0 0 1), {1 0 -1 0}, {1 0 -1 ±1}, or {1 0 -1 ±2}.

[0100] In certain embodiments, a crystal or wafer containing alternating impurity concentration bands 1615 can be sliced ​​at a first cutting orientation 1607 to produce a wafer having a surface 1721 with normals 1719 within 10 degrees, 5 degrees, 2 degrees, or 1 degree from the growth direction 1617 (e.g., [0 0 0 ±1], <1 0 -1 0>, <1 0 -1 ±1>, <1 0 -1 ±2>). The edges of the cut crystal are ground to obtain a wafer 1701 as shown in Figure 17. As is well known, one or more orientation flats or chamfers can also be added. The number of parallel bands in the wafer is significantly reduced compared to the number of bands in the growing crystal, to at least 4, 8, 10, etc. In certain embodiments, each band has a first subband in which the concentration of at least one impurity selected from H, O, Li, Na, K, F, Cl, Br, and I is about 1.05 times, 1.1 times, 1.2 times, 1.5 times or more, 5 times, 10 times, and less than 100 times higher than the concentration of the same impurity in the second subband.

[0101] In certain embodiments, the first surface 1721 of the wafer 1701 has a normal 1719 within 10 degrees, 5 degrees, 2 degrees, and 1 degree from the growth direction 1617 of the ammonia thermal group III nitride crystal ([0 0 0 -1], [0 0 0 1], {1 0 -1 0}, {1 0 -1 ±1}, {1 0 -1 ±2}), the diameter 1725 (maximum side length) is 40 mm or more, 70 mm or more, 90 mm or more, 140 mm or more, and 190 mm or more, and the thickness is 200 micrometers to 2000 micrometers, 225 micrometers to 1000 micrometers, and 250 micrometers to 600 micrometers. In certain embodiments, at least 50%, 65%, and 80% of the dislocations on the first surface are threading dislocations within 30 degrees from the growth direction 1617 or the first surface normal 1719.

[0102] As described above, the yield and quality of crystals with alternating impurity concentration bands 1615 and, for example, wafers near the c-plane, can be improved by the presence of an oxygen concentration gradient (and associated hydrogen and fluorine gradients) in the thickness direction. The average oxygen concentration at a depth of 2 to 10 micrometers on the first surface 1721 is 1.1 to 10 times and 1.1 to 3 times higher than the average oxygen concentration at the same depth on the second surface 1723, as quantified by calibrated SIMS. The stacking fault concentration on the first surface 1721 is 10^3 cm⁻³. -1 Less than 10^2 cm -1 Less than 10 cm -1 Less than 1 cm -1 Characterized by being less than the following: Total wafer thickness variation (TTV) is less than 30 micrometers, less than 20 micrometers, less than 10 micrometers, and less than 5 micrometers.

[0103] Referring to Figures 16 and 18A-18C, in a particular embodiment, a grown crystal 1601 containing alternating impurity concentration bands 1615 is sliced ​​at a second cutting orientation 1609 to produce a wafer 1801 in which the first surface 1721 has a crystal orientation (e.g., nonpolar or semipolar orientation) that is nearly perpendicular (within 30 degrees) to the crystal growth direction 1617, the maximum side length 1825 along the first direction 1831 is greater than 5 mm, the first direction 1831 is within 30 degrees of the growth direction 1617, and the maximum side length 1827 along the second direction 1833 (perpendicular to the first direction 1831) is greater than 15 mm. Figure 18A is a perspective view of the first surface 1721 of the wafer 1801 sliced ​​at the second cutting orientation 1609, Figure 18B is a plan view, and Figure 18C is a side view from the negative direction of the second direction 1833. In this example, the wafer is nearly rectangular, but other shapes are also possible. The thickness of wafer 1701 (in the third direction 1835 perpendicular to the first and second directions) is 100 to 1000 micrometers or 200 to 600 micrometers between the first surface and the opposing second surface 1723. In certain embodiments, at least 50%, 65%, and 80% of the dislocations on the first surface are threading dislocations within 30 degrees from the growth direction 1617. The presence and orientation of threading dislocations can be observed and quantified by selective etching of the third surface (orientations perpendicular to the first direction 1831, within 60 degrees, within 45 degrees, within 30 degrees, and within 20 degrees). The wafer has bands such as 4 to 10,000, 10 to 5,000, and 25 to 1,000 along the first direction 1831. In certain embodiments, each band has an impurity concentration in the first subband (at least one of H, O, Li, Na, K, F, Cl, Br, I) that is 1.05 times, 1.1 times, 1.2 times, 1.5 times or more, 5 times, 10 times, and less than 100 times higher than the same impurity in the second subband. In addition, due to the oxygen gradient in the [0 0 0 1] direction, the minimum oxygen concentration when scanning the first surface in the first direction is 2 × 10^17 cm -3 ~1 × 10^19 cm -3 , 5 × 10^17 cm -3 ~6 × 10^18 cm -3 Therefore, at the second position, which is 1mm to 25mm and 2mm to 10mm away, the maximum value is 1 × 10^18 cm. -3 ~5 × 10^19 cm -3, 1.5 × 10^18 cm -3 ~2 × 10^19 cm -3 , 2 × 10^18 cm -3 ~1.2 × 10^19 cm -3 It increases to [value]. Furthermore, due to the correlation between the oxygen concentration and the light absorption coefficient of ammonia thermal group III nitride, the minimum value of the light absorption coefficient at 450 nm is 0.1 cm at the first position on the first surface. -1 ~5 cm -1 , 0.25 cm -1 ~3 cm -1 The maximum value is 1mm to 25mm, and at the second position, which is 2mm to 10mm away, it is 0.5cm. -1 ~25 cm -1 , 0.75 cm -1 ~10 cm -1 , 1 cm -1 ~6 cm -1 This is the result.

[0104] One or more processing systems described herein, such as the autoclave 200 or the internally heated high-pressure apparatus 300, may include a system controller capable of executing the methods described herein. The system controller includes a central processing unit (CPU), memory, and support circuits. The system controller is used for process sequence control in the formation of free-standing crystals (including Group III metals and nitrogen). The CPU is a general-purpose industrial computer processor configured for controlling the processing chamber and associated subprocessors. Memory, as used herein, is generally non-volatile memory and includes RAM, ROM, floppy disks, hard disk drives, and other local or remote digital storage. Support circuits are typically connected to the CPU and include caches, clock circuits, input / output subsystems, power supplies, and combinations thereof. Software instructions (programs) and data can be coded and stored in memory to direct the processor within the CPU. Programs readable by the CPU within the system controller determine the tasks that can be executed by the components within the processing system.

[0105] Typically, a program read by the CPU within a system controller contains code that causes the processor (CPU) to perform tasks related to the methods described herein. The program contains instructions for controlling various hardware and electrical components within the processing system to carry out the methods and sequences described herein. In one embodiment, the program contains instructions for performing one or more operations related to Figures 4 to 10.

[0106] Embodiments of the present disclosure may include an apparatus for solvothermal crystal growth. The apparatus includes a pressure vessel (with a cylindrical portion extending from the top to the bottom), a cylindrical heater (upper and lower zones around the cylindrical portion), a sealable container placed in the cylindrical portion inside the pressure vessel, and a computer-readable medium (for storing program instructions), which, by executing the program instructions, carries out a method for forming a group III metal nitride boule or wafer. The method involves forming a single crystal layer at least 1 mm thick on the surface of a seed crystal, for which a sealable container is heated to over 200°C, containing a seed crystal, polycrystalline group III metal nitride nutrients, a mineralizer, and ammonia in its internal region, with the nutrients in the first internal region and the seed crystal in the second internal region, and heating to an internal pressure of over 50 MPa, and sequentially adjusting the temperature difference between the first and second regions (1°C to 100°C, positive or negative sign), which is performed at least once during single crystal layer formation. The thickness of the formed single crystal layer is measured in the growth direction, and at least 50% of the formed dislocations have orientations within 60, 45, 30, and 20 degrees from the growth direction. The formed single crystal layer measured in the growth direction has an oxygen gradient decreasing from the seed crystal surface. In some embodiments, multiple subbands are deposited sequentially with a material efficiency of over 60% (material efficiency = weight increase of group III metal nitride material deposited on the seed crystal / weight increase of group III metal material on the entire surface within the second region).

[0107] While embodiments of the present disclosure have been described above, further embodiments may be conceived without departing from the basic scope of the present disclosure. The scope is defined by the following claims.

Claims

1. The free-standing crystal comprising a group III metal and nitrogen, characterized in that the free-standing crystal comprises the following: wurtzite-type crystal structure; Growth direction, the growth direction being selected from [0 0 0 ±1], {1 0 -1 0}, {1 0 -1 ±1}, or {1 0 -1 ±2}; A first surface having the maximum end-to-end dimension in the first direction; and The second surface located on the opposite side of the first surface, It is separated from the first surface in the first direction and in a second direction perpendicular to the first surface, and the second direction is within 10 degrees from the growth direction. Here: The first surface has a dislocation density of 1 cm -2 from 10 7 cm -2 The range is such that at least 50% of the dislocations are oriented within 30 degrees from the growth direction, and the average hydrogen impurity concentration is 10 17 cm -3 Furthermore, the average impurity concentration of at least one of lithium, sodium, potassium, fluorine, chlorine, bromine, and iodine is 10 15 cm -3 Larger than (quantified by calibrated secondary ion mass spectrometry), and The freestanding crystal has at least four sets of bands, Each set of bands includes a first subband and a second subband, wherein the first subband contains at least one impurity selected from hydrogen, oxygen, lithium, sodium, potassium, fluorine, chlorine, bromine, and iodine, with a concentration approximately 1.05 to 100 times higher than the concentration of the same impurity in the second subband. Each of the four sets of bandwidths is substantially parallel in at least part, and the thickness of each bandwidth along the growth direction ranges from about 0.1 micrometers to about 500 micrometers.

2. The freestanding crystal according to claim 1, The maximum end-to-end dimension of the first surface exceeds 40 millimeters in the first direction. The distance between the first surface and the second surface is approximately 200 micrometers to approximately 2000 micrometers in the second direction.

3. The freestanding crystal according to claim 1, The average oxygen concentration in the range of 2 to 10 micrometers in depth from the first surface (measured in at least 4 regions, by calibrated secondary ion mass spectrometry) is from 1×10 16 cm -3 to 5×10 19 cm -3 and is about 1.1 times to about 10 times higher than the average oxygen concentration in the same depth range from the second surface (also measured in 4 regions).

4. The free-standing crystal comprising a group III metal and nitrogen, characterized in that the free-standing crystal comprises the following: wurtzite-type crystal structure; Growth direction, the growth direction being selected from [0 0 0 ±1], {1 0 -1 0}, {1 0 -1 ±1}, or {1 0 -1 ±2}; A first surface having a maximum end-to-end dimension exceeding 5 millimeters in a first direction, wherein the first direction is within 30 degrees of the growth direction; The second surface located on the opposite side of the first surface, It is separated from the first surface in the first direction and in a second direction perpendicular to the first surface; and A third surface having an orientation that is nearly perpendicular (within 60 degrees) to the first direction, Here: The third surface has a dislocation density of 1 cm -2 from 10 7 cm -2 Within this range, at least 50% of the dislocations have an orientation within 30 degrees from the growth direction. The first surface described above has an average hydrogen impurity concentration of 10 17 cm -3 Larger than 10, and with an average impurity concentration of at least one of lithium, sodium, potassium, fluorine, chlorine, bromine, and iodine. 15 cm -3 Larger than (quantified by calibrated secondary ion mass spectrometry), The freestanding crystal has at least four sets of bands, Each set of bands includes a first subband and a second subband, wherein the first subband contains at least one impurity selected from hydrogen, oxygen, lithium, sodium, potassium, fluorine, chlorine, bromine, and iodine, with a concentration approximately 1.05 to 100 times higher than the concentration of the same impurity in the second subband. Each of the four sets of bandwidths is substantially parallel in at least part, and the thickness of each bandwidth along the growth direction ranges from about 0.1 micrometers to about 500 micrometers.

5. The freestanding crystal according to claim 4, wherein the distance between the first surface and the second surface is about 200 micrometers to about 2000 micrometers in the second direction.

6. The freestanding crystal according to claim 4 or 5, wherein the average concentration of stacking faults on the first surface is 10 3 cm -1 The minimum value of the oxygen concentration in the crystal is less than 2 × 10 at the first position. 17 cm -3 from 1 x 10 19 cm -3 The range is such that it increases along the first direction to the second position, and the maximum value of the second position is 1 × 10⁻⁶. 18 cm -3 From approximately 5 x 10 19 cm -3 The range is such that the distance between the first position and the second position is in the range of 1 millimeter to 25 millimeters.

7. The freestanding crystal according to any one of claims 1 to 6, wherein the crystal orientation of the first surface is within 10 degrees from (000±1).

8. The freestanding crystal according to any one of claims 1 to 7, wherein the thickness along the growth direction of the at least four sets of bands is about 1 micrometer to about 250 micrometers.

9. The freestanding crystal according to any one of claims 1 to 8, wherein the thickness along the growth direction of the at least four sets of bands is about 2 micrometers to about 100 micrometers.

10. The freestanding crystal according to any one of claims 1 to 9, wherein the at least four sets of bandwidths include at least ten sets of bandwidths.

11. The freestanding crystal according to any one of claims 1 to 10, wherein each set of bands comprises a first subband and a second subband, wherein the first subband has an impurity concentration of at least one selected from hydrogen, oxygen, lithium, sodium, potassium, fluorine, chlorine, bromine, and iodine that is about 1.1 to about 5 times higher than the concentration of the same impurity in the second subband.

12. A method for forming a group III metal nitride ingot or wafer, comprising: A step of forming a single crystal layer at least 1 millimeter thick on the surface of at least one seed crystal, wherein the formation of the single crystal layer includes the following: A process of heating a sealable container to a temperature exceeding approximately 200°C, here The internal region of the sealable container comprises the at least one seed crystal, polycrystalline group III metal nitride nutrient, mineralizer, and ammonia. The first region contains the polycrystalline group III metal nitride nutrient, The second region includes the at least one seed crystal, The heating of the sealable container causes the pressure inside the sealable container to exceed approximately 50 megapascals; and A process of sequentially adjusting the temperature difference between the first and second regions, here The magnitude of the aforementioned temperature difference is in the range of approximately 1°C to approximately 100°C, and has a positive or negative sign. During the formation of the single crystal layer, the magnitude and / or sign of the sequentially adjusted temperature difference is changed at least once.

13. A method according to claim 12, wherein the thickness of the formed single crystal layer is measured along a first growth direction, and at least 50% of the dislocations generated in the formed single crystal layer are oriented within 30 degrees from the first growth direction.

14. A method according to claim 12 or 13, wherein the thickness of the formed single crystal layer is measured along a first growth direction, and the formed single crystal layer has an oxygen concentration gradient that decreases along the first growth direction extending from the surface of at least one seed crystal.

15. A method according to any one of claims 12 to 14, wherein the formation of the single crystal layer further comprises: A process of sequentially depositing multiple subbands under conditions where the material efficiency exceeds 60%, where the material efficiency is defined as the value obtained by dividing the weight increase of the group III metal nitride material deposited on at least one seed crystal by the weight increase of the group III metal material deposited on the entire surface within the second region.

16. The method according to claim 15, wherein the single crystal layer is at least 3 millimeters thick and the material efficiency exceeds 75%.

17. The method according to claim 15, wherein the single crystal layer is at least 4 millimeters thick and the material efficiency exceeds 90%.

18. A method according to any one of claims 12 to 17, wherein the sequential adjustment of the temperature difference between the first region and the second region further includes the step of periodically cooling and then reheating at least one surface within the second region.

19. A method according to any one of claims 12 to 17, wherein the sequential adjustment of the temperature difference between the first region and the second region further includes the step of periodically heating and then recooling at least one surface within the first region.

20. A method according to any one of claims 12 to 17, wherein the sequential adjustment of the temperature difference between the first region and the second region is A step of periodically cooling at least one surface in the first orientation sector of the second region and at least one surface in the second orientation sector of the second region, and then reheating them, or A process of periodically heating at least one surface in the first orientation sector of the first region and at least one surface in the second orientation sector of the first region, and then recooling them. The further comprising at least one of the above, wherein there is a time difference between the heating and recooling steps between the first orientation sector and the second orientation sector.

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