Preparation method of raw material for growing aluminum nitride crystal by physical vapor transport method

Abstract

The present application relates to the technical field of aluminum nitride crystal, in particular to a raw material preparation method suitable for growing aluminum nitride crystal by physical vapor transport method, comprising the following steps: sintering aluminum nitride powder to form an intermediate in an inert atmosphere; sintering the intermediate in a nitrogen atmosphere, and the temperature difference between the bottom and the top of the container containing the intermediate is 10-20 DEG C. In the present application, the impurity atoms in the sintered aluminum nitride powder are separated from the aluminum nitride lattice in the high temperature process for the first time, and new nitrogen vacancies are generated inside. Through the second sintering, the material is shaped and nitrogen is supplemented. In the nitrogen atmosphere, through high temperature treatment and reducing the temperature difference of the container containing the intermediate, on the one hand, it can promote the combination of nitrogen atoms and aluminum atoms in aluminum nitride, fill the nitrogen vacancies and increase the content of nitrogen atoms; on the other hand, it can reduce the sublimation of aluminum nitride raw material, reduce the loss of the intermediate, and at the same time, it can also form aluminum nitride raw material with a certain porosity and increase the effective surface area.

Description

Technical Field

[0001] This invention relates to the field of aluminum nitride crystal technology, and more specifically to a method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport. Background Technology

[0002] Aluminum nitride, as one of the representatives of ultra-wide bandgap semiconductor materials, has a large bandgap (6.2 eV) and high thermal conductivity (3.4 W·cm). -1 ·K -1 High breakdown field strength (1.17×10⁻⁶) 7 V·cm -1 Aluminum nitride (AN) exhibits excellent properties such as resistance to acid and alkali corrosion and radiation. Physical vapor transport (PVT) is widely recognized as one of the most effective methods for growing AN crystals. The PVT method involves sublimating the AN feedstock in a high-temperature zone, then transporting the sublimated AN feedstock within a crucible for deposition in a low-temperature zone, ultimately obtaining AN crystals. Currently, high-quality AN crystals have been successfully prepared using tungsten resistance heating systems both domestically and internationally, but there are no reports of high-quality AN crystal preparation in China. This is because high-quality AN crystal growth faces numerous challenges, one of the most significant being the difficulty in achieving V / III balance and effective supply of the feedstock during sublimation. The specific reasons are as follows:

[0003] Direct nitriding and carbothermal reduction nitriding are currently the main technical routes for the production of commercial-grade aluminum nitride powder. However, for the physical vapor transport method, commercial-grade aluminum nitride powder suffers from high impurity content, uneven particle size distribution, and easy oxidation. The unstable properties of the raw material can affect the efficiency and quality of aluminum nitride crystal growth. Therefore, directly using commercial aluminum nitride powder in the physical vapor transport method can lead to agglomeration during crystal growth, significantly reducing the effective sublimation area and causing a decrease in the amount of material sublimation in the later stages of crystal growth, resulting in a sharp decline in the growth rate of aluminum nitride crystals in the later stages. Furthermore, the material also contains a small amount of oxygen impurities, necessitating purification treatment before using commercially purchased aluminum nitride powder. In the physical vapor transport method for growing aluminum nitride crystals, during the later stages of raw material sublimation, the coarsening and shrinkage of the aluminum nitride feedstock lead to aluminum atom enrichment, resulting in a severe imbalance in the supersaturation of aluminum and nitrogen vapors—specifically, an excess of aluminum atoms and a deficiency of nitrogen atoms. This further leads to a nitrogen deficiency in the aluminum nitride crystals, forming nitrogen vacancy defects and causing the grown aluminum nitride crystals to exhibit a deep amber color. Insufficient nitrogen atom supply during aluminum nitride crystal formation severely hinders the growth of high-quality aluminum nitride crystals. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the nitrogen deficiency in aluminum nitride raw materials in the prior art, which leads to nitrogen vacancy defects in the formation of aluminum nitride crystals, thereby providing a raw material preparation method suitable for growing aluminum nitride crystals by physical vapor transport method.

[0005] Therefore, the present invention provides a raw material preparation method suitable for growing aluminum nitride crystals by physical vapor transport method, comprising the following steps: sintering aluminum nitride powder in an inert atmosphere to form an intermediate; sintering the intermediate in a nitrogen atmosphere, wherein the temperature difference between the bottom and top of the container holding the intermediate during sintering is 10℃-20℃.

[0006] In some embodiments, the temperature at the bottom of the container holding the intermediate is higher than the temperature at the top.

[0007] Due to the integration effect of heat, even among heating instruments of different models and specifications, the temperature is highest in the middle and lowest at both ends. In some embodiments, when the intermediate body is sintered, the heating element of the heating instrument is set inside the heating instrument, and the container holding the intermediate body is placed in the middle position of the heating area formed by the heating element. This can maintain the temperature difference between the bottom and top of the container holding the intermediate body at 10℃-20℃. It should be noted that the container holding the intermediate body is placed in the middle position of the heating area formed by the heating element, which refers to the middle position in the axial direction. The radial position will not affect the temperature difference between the bottom and top of the container holding the intermediate body.

[0008] In some embodiments, the specific steps for sintering the intermediate include raising the temperature to 2100℃-2200℃ at a heating rate of 4℃ / min-10℃ / min, holding at that temperature for 10h-15h, and then lowering the temperature to 15℃-35℃ at a cooling rate of 3℃ / min-8℃ / min. The nitrogen atmosphere pressure inside the heating apparatus before sintering is 1×10⁻⁶. 5 Pa-3×10 5 Pa.

[0009] In some embodiments, the nitrogen atom content of the aluminum nitride raw material is 51wt%-56wt%, and the oxygen atom content is less than 100ppm.

[0010] In some embodiments, the specific steps for sintering aluminum nitride powder include raising the temperature to 2000℃-2050℃ at a heating rate of 3℃ / min-8℃ / min, holding at that temperature for 5h-10h, and then lowering the temperature to 15℃-35℃ at a cooling rate of 3℃ / min-8℃ / min.

[0011] In some embodiments, the temperature difference between the bottom and top of the container holding the aluminum nitride powder is 20°C-50°C. Specifically, the temperature at the bottom of the container holding the aluminum nitride powder is higher than the temperature at the top.

[0012] Due to the integration effect of the heat source, even among heating instruments of different models and specifications, the temperature is highest in the middle and lowest at both ends. In some embodiments, when the aluminum nitride powder is sintered, the heating element of the heating instrument is set inside the heating instrument, and the container holding the aluminum nitride powder is placed in the upper middle part of the heating area formed by the heating element. This can maintain a temperature difference of 20℃-50℃ between the bottom and top of the container holding the intermediate body. It should be noted that the height of the heating area formed by the heating element is H, and the distance between the bottom of the container holding the aluminum nitride powder and the bottom of the heating area formed by the heating element is greater than 1 / 2H.

[0013] In some embodiments, the pressure of the inert atmosphere is 0.8 × 10⁻⁶. 5 Pa-1.0×10 5 Pa.

[0014] Preferably, the inert atmosphere includes at least one of nitrogen, helium, and argon.

[0015] In some of these embodiments, the aluminum nitride powder has a particle size of 0.1 mm to 2 mm.

[0016] In some embodiments, before sintering the intermediate, a step of pulverizing the intermediate under an inert atmosphere is included, wherein the particle size of the pulverized intermediate is 0.1 mm to 1.0 mm.

[0017] In some embodiments, the container for containing aluminum nitride powder and / or containing intermediates is made of at least one of tungsten, tantalum, tantalum carbide, and rhenium.

[0018] On the other hand, the present invention also provides a method for growing aluminum nitride crystals, wherein the aluminum nitride raw material prepared by the above-mentioned raw material preparation method suitable for growing aluminum nitride crystals by physical vapor transport is used as the raw material for growing aluminum nitride crystals.

[0019] In some embodiments, the reaction temperature of the physical vapor transport method is 1900℃-2350℃, and the reaction time is 5h-30h.

[0020] The technical solution of this invention has the following advantages:

[0021] 1. This invention provides a method for preparing raw materials suitable for growing aluminum nitride crystals using physical vapor transport, comprising the following steps: sintering aluminum nitride powder in an inert atmosphere to form an intermediate; sintering the intermediate in a nitrogen atmosphere, wherein the temperature difference between the bottom and top of the container holding the intermediate during sintering is 10℃-20℃. This invention sintersing aluminum nitride through two high-temperature treatments. In the first sintering, impurity atoms in the aluminum nitride powder detach from the aluminum nitride lattice during the high-temperature process, creating new nitrogen vacancies within the aluminum nitride lattice. The second sintering performs high-temperature shaping and nitrogen replenishment. Under a nitrogen atmosphere, the high-temperature treatment and reduced temperature difference in the container holding the intermediate promote the bonding of nitrogen atoms with aluminum atoms in aluminum chloride, filling nitrogen vacancies and increasing the nitrogen content. Furthermore, it reduces the sublimation of the aluminum nitride raw material, lowering the loss of the intermediate. Through two sintering processes, not only is the aluminum nitride powder formed into a polycrystalline form, but the probability of coarse crystal formation and material clustering of aluminum nitride is also effectively reduced, increasing the effective surface area for sublimation of the aluminum nitride raw material.

[0022] When the aluminum nitride raw material provided by this invention is used in the preparation of aluminum nitride crystals by physical vapor transport, the effective supply of nitrogen atoms is increased during the sublimation process, the imbalance between group V and group III during the growth of aluminum nitride crystals is reduced, nitrogen vacancy defects are reduced, the crystal growth process is stable, and the quality of the formed aluminum nitride crystals is high.

[0023] 2. This invention provides a method for preparing raw materials suitable for growing aluminum nitride crystals using physical vapor transport. In the sintering of aluminum nitride powder, the temperature difference between the bottom and top of the container holding the powder is 20℃-50℃. By increasing the temperature difference in the container during the sintering of aluminum nitride powder, this invention accelerates the detachment rate of oxygen atoms from the aluminum nitride lattice, simultaneously increasing the sublimation rate of the aluminum nitride powder, reducing powder loss, and shortening the holding time.

[0024] 3. The present invention provides a method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport. The specific steps for sintering the intermediate include: raising the temperature to 2100℃-2200℃ at a heating rate of 4℃ / min-10℃ / min, holding at that temperature for 10h-15h, and then lowering the temperature to 15℃-35℃ at a cooling rate of 3℃ / min-8℃ / min, with a nitrogen atmosphere pressure of 1×10⁻⁶. 5 Pa-3×10 5 Pa. This invention, through high temperature and high nitrogen pressure conditions, not only promotes the bonding rate of aluminum and nitrogen atoms in the raw material and fills nitrogen vacancies, but also forms polycrystalline aluminum nitride with a certain porosity, effectively reducing the clustering of aluminum nitride raw materials, increasing the effective sublimation area of ​​the raw materials, and ensuring sublimation stability at high temperatures, further increasing the probability of nitrogen atom adsorption in the raw materials. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the heating apparatus and crucible used in sintering aluminum nitride powder in Embodiment 1 of the present invention;

[0027] Figure 2 This is a schematic diagram of the heating apparatus and crucible used during the sintering of the intermediate in Embodiment 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of aluminum nitride crystal growth in Application Example 1 of the present invention;

[0029] Figure 4 This is a physical image of the aluminum nitride crystal obtained in Application Example 1 of this invention;

[0030] Figure 5 This is the XRD pattern of the aluminum nitride crystal obtained in Application Example 1 of this invention;

[0031] Figure 6 This is a physical image of the aluminum nitride crystal obtained in Application Example 4 of this invention;

[0032] Figure label:

[0033] 1-Heating apparatus; 2-Heating element; 3-Crucible; 31-Crucible lid; 4-Support;

[0034] 51-Aluminum nitride powder; 52-Intermediate; 53-Aluminum nitride raw material; 6-Aluminum nitride seed crystal. Detailed Implementation

[0035] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0036] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0037] In the embodiments and application examples of this invention,

[0038] The yield % of aluminum nitride raw material = aluminum nitride raw material / aluminum nitride powder × 100%;

[0039] Aluminum nitride feedstock sublimation rate (g / h) = Aluminum nitride feedstock sublimation rate (g) / time (h);

[0040] Crystal sublimation condensation rate % = Crystal deposition amount / Aluminum nitride feed sublimation amount × 100%;

[0041] The aluminum nitride raw material in the above calculation formula is the raw material obtained in this embodiment that is suitable for growing aluminum nitride crystals by physical vapor transport method.

[0042] Example 1

[0043] This embodiment provides a method for preparing raw materials suitable for growing aluminum nitride crystals using the physical vapor transport method, including specific steps and methods:

[0044] (1) Please refer to Figure 1 As shown, aluminum nitride powder 51 (particle size 1 mm) is placed in crucible 3, and crucible lid 31 is placed on top. The crucible lid and crucible are concentric. Heating element 2 of heating instrument 1 is suspended inside the heating instrument. The crucible is placed on top of the heating area formed by the heating element through support 4. The chamber is closed, and the vacuum degree of the chamber is evacuated to 5 × 10⁻⁶. -4 After Pa, nitrogen gas is introduced until the pressure reaches 0.8 × 10⁻⁶. 5 Pa.

[0045] (2) The aluminum nitride powder is sintered by resistance heating. The specific steps are as follows: the temperature is raised to 2000℃ at a heating rate of 5℃ / min, held for 5h, and then the temperature is lowered to 25℃ at a cooling rate of 5℃ / min. During the sintering process, the crucible is placed on the top of the heating instrument to maintain a temperature difference of 30℃ between the bottom and top of the crucible, so as to obtain the pretreated material.

[0046] (3) Remove the crucible containing the pretreated material and place it in a glove box. Once the vacuum level in the glove box drops to 100 Pa, purge it with nitrogen until the pressure reaches 1 × 10⁻⁶ Pa. 5 Pa, open the crucible lid, crush the pretreated material, and screen to obtain an intermediate with a particle size range of 0.5-1.0 mm.

[0047] (4) Please refer to Figure 2 As shown, the intermediate 52 obtained from screening is placed back into the crucible 3, and the crucible lid 31 is placed on top. The heating element 2 of the heating instrument 1 is suspended inside the heating instrument. The crucible is placed into the heating instrument through the support 4, with the heating area formed by the heating element in the middle position. The chamber is closed, and the vacuum degree of the chamber is evacuated to 5 × 10⁻⁶. -4 Pa, the pressure of nitrogen gas filling the chamber is 1×10 Pa.5 After Pa, the material is subjected to high-temperature plasticizing and nitrogen supplementation. The specific steps are as follows: the temperature is raised to 2100℃ at a heating rate of 5℃ / min, held for 10h, and then the temperature is lowered to 25℃ at a heating rate of 5℃ / min. During the sintering process, the crucible is placed in the middle of the heater to maintain a temperature difference of 10℃ between the bottom and top of the crucible, thus obtaining aluminum nitride raw material.

[0048] The aluminum nitride raw material prepared in this example was measured using an energy dispersive spectroscopy (Supra 55Sapphire) instrument at an accelerating voltage of 15kV. The nitrogen atom content of the aluminum nitride raw material was found to be 54wt%, the oxygen impurity content was less than 100ppm, and the yield of aluminum nitride raw material was 93%.

[0049] Example 2

[0050] This embodiment provides a method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method. The specific steps and methods are the same as in embodiment 1, except that in step (2), the temperature difference between the bottom and top of the crucible is maintained at 20°C.

[0051] The aluminum nitride raw material obtained in this embodiment has a nitrogen atom content of 54wt%, an oxygen impurity content of less than 100ppm, and a yield of 92%.

[0052] Example 3

[0053] This embodiment provides a method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method. The specific steps and methods are the same as in embodiment 1, except that the temperature difference between the bottom and top of the crucible is maintained at 50°C in step (2).

[0054] The aluminum nitride raw material obtained in this embodiment has a nitrogen atom content of 54wt%, an oxygen impurity content of less than 100ppm, and an aluminum nitride raw material yield of 85%.

[0055] Example 4

[0056] This embodiment provides a method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method. The specific steps and methods are the same as in embodiment 1, except that the temperature difference between the bottom and top of the crucible is maintained at 20°C in step (4).

[0057] The aluminum nitride raw material obtained in this embodiment has a nitrogen atom content of 56 wt%, an oxygen impurity content of less than 100 ppm, and a yield of 90%.

[0058] Example 5

[0059] This embodiment provides a method for preparing raw materials suitable for growing aluminum nitride crystals using the physical vapor transport method, including specific steps and methods:

[0060] (1) Place aluminum nitride powder (particle size 0.1 mm) into the crucible, cover it with the crucible lid, ensuring the lid and crucible are concentric. The heating element 2 of heating instrument 1 is suspended inside the heating instrument. The crucible is placed in the upper-middle part of the heating area formed by the heating element. Close the chamber and evacuate the chamber to a vacuum level of 5 × 10⁻⁶. -4 After Pa, argon gas is introduced until the pressure reaches 1.0 × 10⁻⁶. 5 Pa.

[0061] (2) The aluminum nitride powder is sintered by resistance heating. The specific steps are as follows: the temperature is raised to 2050℃ at a heating rate of 3℃ / min, held for 5 hours, and then the temperature is lowered to 30℃ at a cooling rate of 8℃ / min. During the sintering process, the crucible is placed in the middle and upper part of the heating instrument to maintain a temperature difference of 30℃ between the bottom and top of the crucible to obtain the pretreated material.

[0062] (3) Remove the crucible containing the pretreated material and place it in a glove box. Once the vacuum level in the glove box drops to 100 Pa, purge it with nitrogen until the pressure reaches 1 × 10⁻⁶ Pa. 5 Pa, open the crucible lid, crush the pretreated material, and screen to obtain material with a particle size range of 0.1-0.5mm.

[0063] (4) Continue to put the screened material into the crucible, cover the crucible, suspend the heating element 2 of heating instrument 1 inside the heating instrument, place the crucible in the middle of the heating area formed by the heating element, close the chamber, and evacuate the chamber to a vacuum degree of 5×10. -4 Pa, the pressure of nitrogen gas filling the chamber is 3 × 10 Pa. 5 After Pa, the material is subjected to high-temperature plasticizing and nitrogen supplementation. The specific steps are as follows: the temperature is raised to 2200℃ at a heating rate of 10℃ / min, held for 10h, and then the temperature is lowered to 35℃ at a heating rate of 3℃ / min. During the sintering process, the crucible is placed in the middle of the heater to maintain a temperature difference of 10℃ between the bottom and top of the crucible, thus obtaining aluminum nitride raw material.

[0064] The aluminum nitride raw material prepared in this example was measured using an energy dispersive spectroscopy (Supra 55Sapphire) instrument at an accelerating voltage of 15kV. The nitrogen atom content of the aluminum nitride raw material was found to be 52wt%, the oxygen impurity content was less than 100ppm, and the yield of the aluminum nitride raw material was 88%.

[0065] Example 6

[0066] This embodiment provides a method for preparing raw materials suitable for growing aluminum nitride crystals using the physical vapor transport method, including specific steps and methods:

[0067] (1) Place aluminum nitride powder (particle size 2 mm) into the crucible, cover it with the crucible lid, ensuring the lid and crucible are concentric. The heating element 2 of heating instrument 1 is suspended inside the heating instrument. The crucible is placed on top of the heating area formed by the heating element. Close the chamber and evacuate the chamber to a vacuum level of 5 × 10⁻⁶. -4 After Pa, helium gas is introduced until the pressure reaches 1.0 × 10⁻⁶. 5 Pa.

[0068] (2) The aluminum nitride powder is sintered by resistance heating. The specific steps are as follows: the temperature is raised to 2000℃ at a heating rate of 8℃ / min, held for 10h, and then the temperature is lowered to 15℃ at a cooling rate of 3℃ / min. During the sintering process, the crucible is placed on top of the heating area formed by the heating body, and the temperature difference between the bottom and top of the crucible is kept at 40℃ to obtain the pretreated material.

[0069] (3) Remove the crucible containing the pretreated material and place it in a glove box. Once the vacuum level in the glove box drops to 100 Pa, purge it with nitrogen until the pressure reaches 1 × 10⁻⁶ Pa. 5 Pa, open the crucible lid, crush the pretreated material, and screen to obtain material with a particle size range of 0.5-1.0 mm.

[0070] (4) Continue to put the screened material into the crucible, cover the crucible, place the crucible in the middle of the heating area formed by the heating element, close the chamber, and evacuate the chamber to a vacuum level of 5×10⁻⁶. -4 Pa, the pressure of nitrogen gas filling the chamber is 1×10 Pa. 5 After Pa, the material is subjected to high-temperature plasticizing and nitrogen supplementation. The specific steps are as follows: the temperature is raised to 2100℃ at a heating rate of 4℃ / min, held for 15h, and then the temperature is lowered to 15℃ at a heating rate of 8℃ / min. During the sintering process, the crucible is placed in the middle of the heater to maintain a temperature difference of 10℃ between the bottom and top of the crucible, thus obtaining aluminum nitride raw material.

[0071] The aluminum nitride raw material prepared in this example was measured using an energy dispersive spectroscopy (Supra 55Sapphire) instrument at an accelerating voltage of 15kV. The nitrogen atom content of the aluminum nitride raw material was found to be 53wt%, the oxygen impurity content was less than 100ppm, and the yield of the aluminum nitride raw material was 90%.

[0072] Application Example 1

[0073] See Figure 3 As shown, this application example provides a method for preparing aluminum nitride crystals, with the specific steps and parameters as follows:

[0074] Aluminum nitride raw material 53 was placed in crucible 3, and aluminum nitride seed crystal 6 was attached to the inner wall of crucible lid 31. The crucible lid was then placed on top, and the crucible was placed in a heating apparatus and treated at 2340°C for 10 hours. The aluminum nitride raw material was the aluminum nitride raw material obtained in Example 1.

[0075] The aluminum nitride crystals prepared in this application example can be found in [reference needed]. Figure 4 As can be seen, the aluminum nitride crystals prepared in this application example are transparent and exhibit a pale amber color; the photoluminescence spectrum of the crystal shows a decrease in luminescence intensity due to the lack of nitrogen vacancies, and the XRD pattern of the crystal shows... Figure 5 The half-maximum width of aluminum nitride crystals was found to be 80 arcsec. The data before and after growth were calculated, and the sublimation rate of aluminum nitride raw material was found to be 1.8 g / h, and the sublimation-condensation ratio of aluminum nitride crystals was 70%.

[0076] Application Example 2

[0077] This application example provides a method for preparing aluminum nitride crystals. The specific steps and parameters are the same as in application example 1, except that the aluminum nitride raw material is the aluminum nitride raw material obtained in example 2.

[0078] The aluminum nitride crystals prepared in this application example are transparent and have a light amber color. The lack of nitrogen vacancies in the photoluminescence spectrum of the crystals weakens the luminescence intensity. The full width at half maximum (FWHM) of the aluminum nitride crystals was 85 arcsec. Calculations of the data before and after growth showed that the sublimation rate of the aluminum nitride raw material was 1.6 g / h and the sublimation-condensation ratio of the aluminum nitride crystals was 67%.

[0079] Application Example 3

[0080] This application example provides a method for preparing aluminum nitride crystals. The specific steps and parameters are the same as in application example 1, except that the aluminum nitride raw material is the aluminum nitride raw material obtained in example 3.

[0081] The aluminum nitride crystals prepared in this application example are transparent and have a light amber color. The lack of nitrogen vacancies in the photoluminescence spectrum of the crystals weakens the luminescence intensity. The XRD pattern of the aluminum nitride crystals shows a full width at half maximum (FWHM) of 90 arcsec. Calculations of the data before and after growth show that the sublimation rate of the aluminum nitride raw material is 1.3 g / h and the sublimation-condensation ratio of the aluminum nitride crystals is 63%.

[0082] Application Example 4

[0083] This application example provides a method for preparing aluminum nitride crystals. The specific steps and parameters are the same as in application example 1. The difference is that the aluminum nitride raw material is aluminum nitride powder that has not been treated in step (1) of the example.

[0084] In this application example, after the growth of aluminum nitride seed crystals, the aluminum nitride raw material exhibited severe clustering, resulting in a sublimation rate reduced to 0.2 g / h. (See [link to relevant documentation]). Figure 6The grown aluminum nitride crystals are dark amber in color. The photoluminescence spectrum of the crystals shows high luminescence intensity of nitrogen vacancy defects. The XRD pattern of the aluminum nitride crystals shows a full width at half maximum (FWHM) of 250 arcsec and a sublimation-condensation ratio of 35%.

[0085] Application Example 5

[0086] This application example provides a method for preparing aluminum nitride crystals. The specific steps and parameters are the same as in application example 1. The difference is that the aluminum nitride raw material is aluminum nitride powder that has been purified and pulverized in step (3) of example 1.

[0087] In this application example, after the growth of aluminum nitride seed crystals, the aluminum nitride raw material exhibited severe clustering, and the sublimation rate decreased to 0.3 g / h. The grown aluminum nitride crystals were generally dark amber in color, and the photoluminescence spectrum of the crystals showed high luminescence intensity of nitrogen vacancy defects. The XRD pattern of the aluminum nitride crystals showed a full width at half maximum (FWHM) of 180 arcsec, and the sublimation-condensation ratio of the aluminum nitride crystals was 40%.

[0088] Application Example 6

[0089] This application example provides a method for preparing aluminum nitride crystals. The specific steps and parameters are the same as in application example 1, except that the aluminum nitride raw material is prepared by the following method.

[0090] The preparation method of aluminum nitride raw material is the same as that in Example 1. The difference is that in step (4), the crucible is placed on the top of the heating instrument. During the sintering process, the temperature difference between the bottom and top of the crucible is 30°C, and the yield of aluminum nitride raw material is 70%.

[0091] In this application example, after the aluminum nitride seed crystals were grown, the aluminum nitride raw material exhibited severe clustering, and the sublimation rate decreased to 0.5 g / h. The grown aluminum nitride crystals were generally dark amber in color, and the nitrogen vacancy defects in the photoluminescence spectrum of the crystals showed high luminescence intensity. The XRD pattern of the aluminum nitride crystals showed a full width at half maximum (FWHM) of 150 arcsec, and the sublimation-to-condensation ratio of the aluminum nitride crystals was 45%.

[0092] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport, characterized in that, Includes the following steps, Aluminum nitride powder is sintered in an inert atmosphere to form an intermediate; the temperature difference between the bottom and top of the container holding the aluminum nitride powder is 20℃-50℃; wherein the temperature at the bottom of the container holding the aluminum nitride powder is higher than the temperature at the top. The specific steps for sintering aluminum nitride powder include: The temperature is raised to 2000℃-2050℃ at a heating rate of 3℃ / min-8℃ / min, held for 5h-10h, and then the temperature is lowered to 15℃-35℃ at a cooling rate of 3℃ / min-8℃ / min. In a nitrogen atmosphere, the intermediate is sintered. During the sintering of the intermediate, the temperature difference between the bottom and top of the container holding the intermediate is 10℃-20℃. The specific steps for sintering the intermediate include: The temperature is increased to 2100℃-2200℃ at a heating rate of 4℃ / min - 10℃ / min, held for 10h-15h, and then decreased to 15℃-35℃ at a cooling rate of 3℃ / min - 8℃ / min. The nitrogen atmosphere pressure is 1×10 5 Pa-3×10 5 Pa.

2. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport according to claim 1, characterized in that, The pressure of the inert atmosphere is 0.8 × 10⁻⁶. 5 Pa-1.0×10 5 Pa.

3. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport according to claim 2, characterized in that, The inert atmosphere includes at least one of nitrogen, helium, or argon; and / or, The particle size of aluminum nitride powder is 0.1 mm-2 mm.

4. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport according to claim 3, characterized in that, During the sintering of the aluminum nitride powder, the heating element of the heating instrument is located inside the heating instrument, and the container holding the aluminum nitride powder is placed in the upper middle part of the heating area formed by the heating element.

5. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport according to claim 1, characterized in that, Before sintering the intermediate, the process also includes crushing and screening the intermediate under an inert atmosphere, with the particle size of the screened intermediate being 0.1mm-1.0mm.

6. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport according to claim 1, characterized in that, During the sintering of the intermediate, the heating element of the heating instrument is located inside the heating instrument, and the container holding the intermediate is placed in the middle of the heating area formed by the heating element.

7. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport according to any one of claims 1-6, characterized in that, The container for containing aluminum nitride powder and / or containing intermediates is made of at least one of tungsten, tantalum, tantalum carbide, and rhenium.

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