Preparation method for growing GaN crystal by eliminating interference of water and oxygen

Abstract

The invention belongs to the technical field of growth and preparation of gallium nitride crystals, and particularly relates to a preparation method for growing GaN crystals by eliminating interference of water and oxygen. The method comprises the following steps: putting a sodium-containing cosolvent, metal gallium and an additive into a transfer crucible in a glove box filled with protective gas, heating the transfer crucible, stopping heating after melting, and cooling to obtain a metal gallium sheet; placing the GaN seed crystal in a growth crucible, inversely buckling the transfer crucible on the growth crucible, transferring the metal gallium sheet into the growth crucible, heating, melting, cooling and solidifying; and transferring the growth crucible from the glove box to a reaction kettle of crystal growth equipment, introducing nitrogen under a vacuum condition, heating for reaction, cooling, washing and drying to obtain the GaN crystal. The transfer crucible process provided by the invention can simply and effectively eliminate the influence of water and oxygen in the environment on growth of GaN crystals by a flux method, and is simple in process method, low in cost, good in repeatability and suitable for commercialized mass production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gallium nitride crystal growth preparation, and particularly relates to a preparation method for growing GaN crystals by eliminating water and oxygen interference. BACKGROUND

[0002] As a third-generation semiconductor material, gallium nitride (GaN) crystals have the characteristics of wide band gap, high breakdown electric field, high saturated electron mobility, small dielectric constant, strong radiation resistance, good chemical stability, and the like, and have an irreplaceable position in optoelectronic devices, high-power electronic devices, and high-temperature and high-frequency applications, and are one of the core materials of energy-saving industries and high-end military electronic devices.

[0003] At present, the preparation of GaN devices is still mainly based on heteroepitaxial growth methods, such as using sapphire, SiC or Si as a substrate to grow GaN crystals. However, this heteroepitaxial growth method inevitably has a large lattice mismatch and thermal mismatch, resulting in a large number of defects and residual stress in the epitaxial layer, which limits the further improvement of the performance of GaN devices. Therefore, the preparation of GaN bulk crystals with excellent performance can realize the homoepitaxial growth of GaN thin films, and fundamentally solve the defect and stress problems caused by heteroepitaxial growth.

[0004] Since the Na flux method for growing GaN bulk crystals has the advantages of low equipment cost, relatively mild growth conditions, relatively large growth rate, and simple growth process, and the growth process is in a near-equilibrium state in thermodynamics, it can prepare thin films, thick films or bulk single crystals with high purity, low dislocation density and high crystalline quality, and can reduce the dislocation density of GaN to the order of 10 -3 ~ 10 -2 cm -2 order, and therefore is considered as an economical and practical epitaxial growth technology that can be industrialized. In recent years, this technology has developed rapidly, and in January 2025, Osaka University and Toyota Synthetic in Japan grew an 8-inch hexagonal gallium nitride crystal by using a multi-point seed crystal method and a Na flux method. However, in the process of growing GaN crystals by the Na flux method, the growth crucible containing sodium flux and metal gallium and the like needs to be transferred from the glove box to the reaction kettle. At this time, water and oxygen in the environment will react violently with the active metals such as sodium in the crucible, thereby introducing a large number of oxygen-containing defects into the GaN crystal, and the activity of the flux metal sodium and the like will also be greatly reduced, which reduces the growth rate of the GaN crystal, and this is also one of the main reasons why the GaN crystal grown by the sodium flux method is black.

[0005] Therefore, it is necessary to develop a flux method for growing GaN crystals that reduces or eliminates the interference of water and oxygen in the environment on active metals such as sodium. SUMMARY

[0006] The application aims at solving the problems of the prior art, and provides a preparation method for growing GaN crystals by eliminating water-oxygen interference. In a first aspect, the application provides a preparation method for growing GaN crystals by eliminating water-oxygen interference, comprising the following steps: S1, placing a sodium-containing fluxing agent, metallic gallium and an additive into a transfer crucible in a glove box filled with a protective gas, and heating the transfer crucible until the metallic gallium is fully melted, stopping heating after melting, and cooling to solidify the metallic gallium to obtain a metallic gallium sheet inlaid with metallic sodium and the additive; S2, placing a GaN seed crystal in a growth crucible, and inverting the transfer crucible containing the metallic gallium sheet on the growth crucible, transferring the metallic gallium sheet in the transfer crucible to the growth crucible by extrusion stretching, and then placing the growth crucible in a heating kettle until the side surface of the metallic gallium sheet is melted and adheres to the growth crucible, and cooling and solidifying; S3, transferring the growth crucible after cooling and solidification from the glove box to a reaction kettle of a crystal growth device, filling nitrogen under vacuum, heating and reacting, naturally cooling to room temperature after the reaction, washing, and drying to obtain the GaN crystal.

[0007] The application proposes a transfer crucible process, which utilizes the physical properties of metallic gallium and sodium to pre-prepare a metallic gallium sheet inlaid with fluxing agents and additives on the surface, then locally warms the side surface of the metallic gallium sheet to adhere to the growth crucible, so that the fluxing agents and additives are isolated from water and oxygen, thereby solving the influence of water and oxygen on the active metals such as fluxing agent sodium during the transfer of the loaded growth crucible from the glove box to the reaction kettle in the prior art, eliminating the oxygen-containing defects in the fluxing agent method for growing GaN crystals, and improving the effective activity of the fluxing agent. The transfer crucible process is simple and practical in operation, has good repeatability, and is conducive to the later industrialization promotion.

[0008] As a further preferred embodiment, the sodium-containing fluxing agent includes any one of metallic sodium or a nitride containing metallic sodium.

[0009] As a further preferred embodiment, the additive includes one or more of carbon, carbon composite material, and graphite.

[0010] As a further preferred embodiment, the molar ratio of the sodium-containing fluxing agent, the metallic gallium and the additive is 1-9:1-9:0.1-1.

[0011] As a further preferred embodiment, the heating temperature in S1 is 30-97.72℃. The heating temperature is between the melting points of metallic gallium and sodium, which ensures that the gallium is fully melted, and the metallic sodium solid and the additive float on the surface of the gallium solution due to the much smaller density than the metallic gallium.

[0012] As a further preferred embodiment, the protective gas comprises one or both of nitrogen or argon.

[0013] As a further preferred embodiment, the vacuum degree in the vacuum condition in S3 is less than 1 Pa.

[0014] As a further preferred embodiment, the transit crucible is made of silica gel, silicone rubber or plastic. The growth crucible comprises a boron nitride, alumina, yttria, zirconia, tungsten carbide, graphite, nickel, tantalum, tungsten or molybdenum crucible. The transit crucible is smaller in size than the growth crucible.

[0015] As a further preferred embodiment, the specific procedure of the temperature rising reaction is as follows: First, the temperature is raised to 500-700°C, then the temperature is raised to 700-900°C, nitrogen is filled to a pressure of 1-10 MPa, and finally the temperature is maintained at 1-10 MPa and 700-900°C for 1-200 hours.

[0016] As a further preferred embodiment, the specific procedure of the washing comprises the following: The GaN crystal is sequentially washed with anhydrous ethanol, deionized water, hot deionized water and hydrochloric acid.

[0017] The present application has the following advantages: (1) The transit crucible process provided by the present application can effectively eliminate the influence of water and oxygen in the environment on the flux method for growing GaN crystals, and the process is simple, low in cost, and good in repeatability, and is suitable for commercial mass production.

[0018] (2) The transit crucible used in the present application has elastic properties, which makes it easy to transfer the thin sheet of metallic gallium to the growth crucible by extrusion or stretching or direct shearing, and the transit crucible process simultaneously causes the surface of the thin sheet of metallic gallium to naturally flip once, coats the flux and additives to isolate water and oxygen, and the elastic properties of the transit crucible enable the thin sheet of metallic gallium to be effectively transferred, and the process is simple and efficient.

[0019] (3) The transit crucible of the present application is made of silica gel, silicone rubber or plastic, which is easy to obtain, and the manufacturing process is simple and low in cost. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 The figure shows a process flow chart for eliminating the interference of water and oxygen in growing GaN crystals provided by the present invention; Figure 2 FIG2 is a schematic diagram of a process for growing GaN crystals by eliminating the interference of water and oxygen provided by the present invention; Among them, 10: transfer crucible, 11: metal gallium, 12: metal sodium, 13: graphite particles, 20: growth crucible, 21: GaN seed crystal. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0023] Example 1 A preparation method for eliminating water and oxygen interference in growing GaN crystals, which specifically includes the following steps: (1) In an argon-filled glove box, metal gallium, sodium, and graphite particles with a molar ratio of 25:75:0.5 were placed in a silicone rubber transfer crucible (such as Figure 2 (as shown in a in the figure); (2) Place the silicone rubber transfer crucible loaded with the raw materials in step (1) on a constant temperature horizontal heating platform and heat it (temperature 50°C, 20 minutes) to fully melt the metal gallium. At this time, the metal sodium and graphite particles float on the metal gallium solution. Stop heating and cool it to 20°C to allow the metal gallium to fully cool and solidify, thereby obtaining a metal gallium sheet embedded with metal sodium and graphite particles (such as Figure 2 (as shown in b); (3) Place the GaN seed crystal in the center of the boron nitride growth crucible (such as Figure 2 Then, make the silicone rubber transfer crucible surface face downward (as shown in c in the figure). Figure 2 As shown in d in the figure), the raw materials in the silicone rubber transfer crucible are transferred to the boron nitride growth crucible by extrusion and stretching (as shown in d in the figure). Figure 2 (as shown in e); (4) Put the boron nitride growth crucible into the cylindrical ring-shaped heating furnace and heat (temperature 32℃, 5 minutes) to melt the gallium sheet side surface and adhere to the growth crucible, and after cooling and solidification, the gallium sheet covers the metal sodium and graphite particles, and the metal sodium flux is isolated from water and oxygen (as shown in f of Figure 2 ); (5) Transfer the boron nitride growth crucible from the glove box to the reaction kettle of the high-temperature high-pressure crystal growth equipment, seal and vacuumize to below 1 Pa, fill in nitrogen with a purity higher than 99.999%, then quickly heat to 600℃, then slowly heat to 870℃, continue to fill in high-purity nitrogen to maintain the pressure at 3.5 MPa, keep at 3.5 MPa pressure and 870℃ temperature for 200 hours; (6) Cut off the power, naturally cool to room temperature, release the pressure and open the furnace, then take out the boron nitride growth crucible, wash the GaN crystal in the boron nitride crucible with anhydrous ethanol, deionized water, hot deionized water, hydrochloric acid, etc. in sequence, remove the surface residues of the GaN crystal, then get the GaN crystal at the bottom of the boron nitride crucible, and then dry the GaN crystal, finally get the GaN crystal.

[0024] The embodiments of the present application are described above in combination with the drawings, the principles and implementation modes of the present application are described by applying specific examples, the above embodiment descriptions are only used to help understand the core idea of the present application, but the present application is not limited to the above specific implementation modes, the above specific implementation modes are only illustrative, but not restrictive, and those skilled in the art can make many forms under the inspiration of the present application without departing from the scope of the present application and the protection scope of the claims, all of which belong to the protection of the present application.

Claims

1. A method for preparing GaN crystals by eliminating the interference of water and oxygen in growing the GaN crystals, characterized in that: The following steps are involved: S1. In a glove box filled with protective gas, a sodium-containing cosolvent, metal gallium, and an additive are placed in a transfer crucible, and the transfer crucible is heated until the metal gallium is fully melted. After melting, heating is stopped, and the crucible is cooled until the metal gallium solidifies to obtain a metal gallium sheet embedded with metal sodium and the additive; S2. Placing a GaN seed crystal in a growth crucible, and placing the transfer crucible containing the metal gallium flake upside down on the growth crucible, transferring the metal gallium flake in the transfer crucible to the growth crucible by extrusion and stretching, and then placing the growth crucible in a heating kettle until the side surface of the metal gallium flake melts and adheres to the growth crucible, and then cooling and solidifying; S3. Transfer the cooled and solidified growth crucible from the glove box to a reactor in a crystal growth device, fill it with nitrogen under vacuum conditions, heat it up for reaction, and naturally cool it to room temperature after the reaction is completed. Wash it, and dry it to obtain the GaN crystal.

2. The preparation method according to claim 1, characterized in that The sodium-containing co-solvent includes any one of metallic sodium or a nitride containing metallic sodium.

3. The preparation method according to claim 2, characterized in that The additive includes one or more of carbon, carbon composite material, and graphite.

4. The preparation method according to claim 3, characterized in that The molar ratio of the sodium-containing cosolvent, the metal gallium and the additive is 1-9:1-9:0.1-1.

5. The preparation method according to claim 1, characterized in that The heating temperature in S1 is 30°C to 97.72°C.

6. The preparation method according to claim 1, characterized in that The protective gas includes one or both of nitrogen and argon.

7. The preparation method according to claim 1, characterized in that The vacuum degree under vacuum conditions in S3 is less than 1Pa.

8. The preparation method according to claim 1, characterized in that The transfer crucible is made of silica gel, silicone rubber, or plastic; The growth crucible includes a boron nitride, aluminum oxide, yttrium oxide, zirconium oxide, tungsten carbide, graphite, nickel, tantalum, tungsten or molybdenum crucible; The transfer crucible is smaller than the growth crucible.

9. The preparation method according to claim 1, characterized in that The specific procedures of the temperature-raising reaction are as follows: First, the temperature is raised to 500°C to 700°C, then raised to 700°C to 900°C, nitrogen is introduced to make the pressure 1MPa to 10MPa, and finally, the temperature is maintained at 1MPa to 10MPa and 700°C to 900°C for 1 to 200 hours.

10. The preparation method according to claim 1, characterized in that The specific process of the washing comprises the following: The GaN crystal was washed with anhydrous ethanol, deionized water, hot deionized water, and hydrochloric acid in sequence.

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