Raw material preparation method suitable for growing aluminum nitride crystal by physical vapor transport method

Abstract

The invention relates to the technical field of aluminum nitride crystals, in particular to a raw material preparation method suitable for growing aluminum nitride crystals by a physical vapor transport method, which comprises the following steps: sintering aluminum nitride powder in an inert atmosphere to form an intermediate; sintering the intermediate in a nitrogen atmosphere, and controlling the temperature difference between the bottom and the top of a container for accommodating the intermediate to be 10-20 DEG C; impurity atoms in the aluminum nitride powder sintered for the first time are separated from aluminum nitride crystal lattices in the high-temperature process, new nitrogen vacancies are generated in the aluminum nitride powder, materials are molded and nitrogen is supplemented through the second time of sintering, and in the nitrogen atmosphere, through high-temperature treatment and reduction of the temperature difference of a container for containing an intermediate, the nitrogen vacancies are formed. On one hand, combination of nitrogen atoms and aluminum atoms in aluminum nitride can be promoted, nitrogen vacancies are filled, the content of the nitrogen atoms is increased, on the other hand, sublimation of the aluminum nitride raw material can be reduced, loss of an intermediate is reduced, meanwhile, the aluminum nitride raw material with a certain porosity can be formed, and the effective surface area is increased.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum nitride crystals, and in particular to a method for preparing raw materials suitable for growing aluminum nitride crystals by a physical vapor transport method. Background Art

[0002] As one of the representatives of ultra-wide bandgap semiconductor materials, aluminum nitride has a large bandgap width (6.2eV), high thermal conductivity (3.4W·cm -1 ·K -1 ), high breakdown field strength (1.17×10 7 V cm -1 ), acid and alkali corrosion resistance, radiation resistance and other excellent properties. The physical vapor transport (PVT) method is recognized as one of the most effective methods for growing aluminum nitride crystals. The PVT method for growing aluminum nitride is that the aluminum nitride raw material is sublimated in a high temperature zone, the sublimated aluminum nitride raw material is transported in a crucible, and deposited in a low temperature zone to finally obtain aluminum nitride crystals. At present, the preparation of high-quality aluminum nitride crystals has been achieved in tungsten resistance heating systems both domestically and internationally, but there are no reports on the preparation of high-quality aluminum nitride crystals in China. This is because aluminum nitride crystals face many problems in high-quality growth. One of the more important problems is that it is difficult to achieve V / III balance and effective supply of raw materials during the sublimation process. The specific reasons are as follows:

[0003] Direct nitridation and carbon thermal reduction nitridation 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 has problems such as high impurity content, uneven particle size distribution, and easy oxidation. The unstable nature of the raw materials will affect the efficiency and quality of aluminum nitride crystal growth. Therefore, when commercial aluminum nitride powder is used directly in the physical vapor transport method, agglomeration will occur during the crystal growth process, and the effective sublimation area will be greatly reduced, resulting in a decrease in the sublimation amount of the material in the middle and late stages of crystal growth, and a sharp decrease in the growth rate of aluminum nitride crystals in the middle and late stages of growth; and the material also contains a small amount of oxygen impurities, so commercially purchased aluminum nitride powder must be purified before use. In the process of growing aluminum nitride crystals by physical vapor transport, in the later stage of raw material sublimation, the aluminum nitride raw material coarsening and sublimation shrinkage will lead to the enrichment of aluminum atoms, resulting in a serious imbalance in the supersaturation of aluminum vapor and nitrogen vapor, specifically, more aluminum atoms and fewer nitrogen atoms, which will further lead to a lack of nitrogen in the aluminum nitride crystals, thereby forming nitrogen vacancy defects, making the grown aluminum nitride crystals dark amber. In the process of aluminum nitride crystal formation, the insufficient supply of nitrogen atoms seriously 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 problem in the prior art that insufficient nitrogen in the aluminum nitride raw materials leads to the presence of nitrogen vacancy defects in the aluminum nitride crystal formation process, thereby providing a raw material preparation method suitable for growing aluminum nitride crystals by physical vapor transport method.

[0005] To this end, the present invention provides a method for preparing raw materials 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, and when sintering the intermediate, the temperature difference between the bottom and the top of the container containing the intermediate is 10°C-20°C.

[0006] In some of these embodiments, the temperature at the bottom of the vessel containing the intermediate product is higher than the temperature at the top.

[0007] Due to the integrating effect of the heater, even in heating instruments of different models and specifications, the temperature in the middle is the highest and at both ends is the lowest. In some embodiments, when the intermediate is sintered, the heating body of the heating instrument is arranged inside the heating instrument, and the container containing the intermediate is placed in the middle position of the heating area formed by the heating body, so that the temperature difference between the bottom and the top of the container containing the intermediate can be maintained at 10°C-20°C. It should be noted that the middle position of the container containing the intermediate in the heating area formed by the heating body refers to the middle position in the axial direction, and the radial position will not affect the temperature difference between the bottom and the top of the container containing the intermediate.

[0008] In some of the embodiments, the specific steps of sintering the intermediate include raising the temperature to 2100°C-2200°C at a heating rate of 4°C / min-10°C / min, keeping the temperature for 10h-15h, and then cooling the temperature to 15°C-35°C at a cooling rate of 3°C / min-8°C / min. The nitrogen atmosphere pressure in the heating instrument before sintering is 1×10 5 Pa-3×10 5 Pa.

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

[0010] In some of the embodiments, the specific steps for sintering aluminum nitride powder include increasing the temperature to 2000°C-2050°C at a heating rate of 3°C / min-8°C / min, keeping the temperature for 5h-10h, and then reducing the temperature to 15°C-35°C at a cooling rate of 3°C / min-8°C / min.

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

[0012] Due to the integrating effect of the heater, even in heating instruments of different models and specifications, the temperature in the middle is the highest and the temperature at both ends is the lowest. In some embodiments, when the aluminum nitride powder is sintered, the heating body of the heating instrument is arranged inside the heating instrument, and the container containing the aluminum nitride powder is placed in the middle and upper part of the heating area formed by the heating body, so that the temperature difference between the bottom and the top of the container containing the intermediate body can be maintained at 20°C-50°C. It should be noted that the height of the heating area formed by the heating body is H, and the distance between the bottom of the container containing the aluminum nitride powder and the bottom of the heating area formed by the heating body is greater than 1 / 2H.

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

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

[0015] In some embodiments, the particle size of the aluminum nitride powder is 0.1 mm-2 mm.

[0016] In some of the embodiments, before sintering the intermediate, the process further includes crushing the intermediate under an inert atmosphere, wherein the particle size of the crushed intermediate is 0.1 mm-1.0 mm.

[0017] In some embodiments, the container for containing aluminum nitride powder and / or containing the intermediate 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, using the aluminum nitride raw material prepared by the above-mentioned raw material preparation method suitable for growing aluminum nitride crystals by physical vapor transport as the raw material for growing aluminum nitride crystals;

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

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

[0021] 1. The present invention provides a method for preparing raw materials suitable for growing aluminum nitride crystals by 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, and when sintering the intermediate, the temperature difference between the bottom and top of the container containing the intermediate is 10°C-20°C. The present invention sinters aluminum nitride by two high-temperature treatments. The impurity atoms in the aluminum nitride powder are separated from the aluminum nitride lattice during the high-temperature process during the first sintering, and new nitrogen vacancies are generated inside the aluminum nitride lattice. High-temperature shaping and nitrogen supplementation are performed by the second sintering. In a nitrogen atmosphere, by high-temperature treatment and reducing the temperature difference of the container containing the intermediate, on the one hand, nitrogen atoms can be promoted to combine with aluminum atoms in aluminum chloride, fill nitrogen vacancies, and increase the content of nitrogen atoms. On the other hand, the sublimation of aluminum nitride raw materials can be reduced, and the loss of intermediates can be reduced. Through two sinterings, not only the aluminum nitride powder is formed into a polycrystalline form, but also the probability of aluminum nitride coarsening and material clustering can be effectively reduced, and the effective surface area of ​​aluminum nitride raw material sublimation is increased.

[0022] The aluminum nitride raw material provided by the present invention is used in the preparation of aluminum nitride crystals by a physical vapor transport method, which increases the effective supply of nitrogen atoms during the sublimation process, reduces the imbalance degree of group V and group III during the growth of the aluminum nitride crystal, reduces nitrogen vacancy defects, stabilizes the crystal growth process, and produces aluminum nitride crystals of high quality.

[0023] 2. The present invention provides a method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method. When sintering aluminum nitride powder, the temperature difference between the bottom and the top of the container containing the aluminum nitride powder is 20°C-50°C. When sintering aluminum nitride powder, the present invention can accelerate the rate of oxygen atoms leaving the aluminum nitride lattice by increasing the temperature difference of the container containing the aluminum nitride powder, and at the same time increase the sublimation rate of the aluminum nitride powder, reduce the loss of aluminum nitride powder, and shorten the heat preservation time.

[0024] 3. The present invention provides a method for preparing a raw material suitable for growing aluminum nitride crystals by a physical vapor transport method. The specific steps of sintering the intermediate include: raising the temperature to 2100°C-2200°C at a heating rate of 4°C / min-10°C / min, keeping the temperature for 10h-15h, and then lowering the temperature to 15°C-35°C at a cooling rate of 3°C / min-8°C / min. The nitrogen atmosphere pressure is 1×10 5 Pa-3×10 5 Pa. The present invention can not only promote the bonding rate of aluminum atoms and nitrogen atoms in the raw material and fill nitrogen vacancies in the raw material under the conditions of high temperature and high nitrogen pressure, but also form aluminum nitride polycrystalline material with a certain porosity, effectively reduce the clusters of aluminum nitride raw material, increase the effective sublimation area of ​​the raw material, and stabilize the sublimation at high temperature, further increasing the probability of the raw material adsorbing nitrogen atoms. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

[0027] Figure 2 is a schematic diagram of a heating apparatus and a crucible when sintering an intermediate in Example 1 of the present invention;

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

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

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

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

[0032] Reference numerals:

[0033] 1-heating device; 2-heating body; 3-crucible; 31-crucible cover; 4-support;

[0034] 51-aluminum nitride powder; 52-intermediate; 53-aluminum nitride raw material; 6-aluminum nitride seed crystal. DETAILED DESCRIPTION

[0035] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0036] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

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

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

[0039] Sublimation amount of aluminum nitride raw material g / h = sublimation amount of aluminum nitride raw material g / time h;

[0040] Crystal sublimation condensation ratio % = crystal deposition amount / aluminum nitride raw material sublimation amount × 100%;

[0041] The aluminum nitride raw material in the above calculation formula is the raw material prepared in this embodiment and 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 by physical vapor transport method, and the specific steps and methods are as follows:

[0044] (1) Please refer to Figure 1 As shown, aluminum nitride powder 51 (with a particle size of 1 mm) is placed in the crucible 3, and the crucible cover 31 is put on. The crucible cover and the crucible are concentric. The heating body 2 of the heating device 1 is suspended inside the heating device. The crucible is placed on the top of the heating area formed by the heating body through the bracket 4. The chamber is closed and the vacuum degree of the chamber is pumped to 5×10 -4 Pa, and then filled with nitrogen until the pressure was 0.8×10 5 Pa.

[0045] (2) The aluminum nitride powder is sintered by resistance heating. The specific steps are: raising the temperature to 2000°C at a heating rate of 5°C / min, keeping it at that temperature for 5 hours, and then lowering the temperature to 25°C at a cooling rate of 5°C / min. During the sintering process, the crucible is placed on the top of the heating instrument to maintain the temperature difference between the bottom and the top of the crucible at 30°C to obtain the pretreated material.

[0046] (3) Take out the crucible containing the pre-treated material and put it into the glove box. When the vacuum degree of the glove box drops to 100 Pa, fill it with nitrogen until the pressure reaches 1×10 5 Pa, open the crucible cover, 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 screened intermediate 52 is further placed in the crucible 3, and the crucible cover 31 is covered. The heating body 2 of the heating apparatus 1 is suspended inside the heating apparatus. The crucible is placed in the heating apparatus through the bracket 4, in the middle of the heating area formed by the heating body, and the chamber is closed, and the vacuum degree of the chamber is pumped to 5×10 -4 Pa, nitrogen was filled into the chamber until the pressure was 1×105 After Pa, the material is subjected to high-temperature molding and nitrogen supplementation. The specific steps are to increase the temperature to 2100°C at a heating rate of 5°C / min, keep it warm for 10 hours, and then reduce the temperature to 25°C at a heating rate of 5°C / min. During the sintering process, the crucible is placed in the middle position of the heater and the temperature difference between the bottom and the top of the crucible is maintained at 10°C to obtain aluminum nitride raw material.

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

[0049] Example 2

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

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

[0052] Example 3

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

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

[0055] Example 4

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

[0057] The aluminum nitride raw material prepared 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% of the aluminum nitride raw material.

[0058] Example 5

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

[0060] (1) Aluminum nitride powder (particle size of 0.1 mm) is placed in a crucible, and the crucible cover is put on. The crucible cover and the crucible are concentric. The heating body 2 of the heating device 1 is suspended in the interior of the heating device. The crucible is placed in the middle and upper part of the heating area formed by the heating body. The chamber is closed and the vacuum degree of the chamber is evacuated to 5×10 -4 Pa, and then filled with argon gas to a pressure of 1.0×10 5 Pa.

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

[0062] (3) Take out the crucible containing the pre-treated material and put it into the glove box. When the vacuum degree of the glove box drops to 100 Pa, fill it with nitrogen until the pressure reaches 1×10 5 Pa, open the crucible cover, crush the pretreated material, and screen to obtain material with a particle size range of 0.1-0.5 mm.

[0063] (4) The screened materials are further placed in the crucible, and the crucible cover is closed. The heating body 2 of the heating device 1 is suspended in the interior of the heating device, and the crucible is placed in the middle of the heating area formed by the heating body. The chamber is closed and the vacuum degree of the chamber is pumped to 5×10 -4 Pa, nitrogen was filled into the chamber until the pressure was 3×10 5 After Pa, the material is subjected to high-temperature molding and nitrogen supplementation. The specific steps are to increase the temperature to 2200°C at a heating rate of 10°C / min, keep it warm for 10 hours, and then reduce the temperature to 35°C at a heating rate of 3°C / min. During the sintering process, the crucible is placed in the middle position of the heater to maintain a temperature difference of 10°C between the bottom and the top of the crucible to obtain aluminum nitride raw material.

[0064] The aluminum nitride raw material prepared in this embodiment was measured using an energy spectrum analyzer (Supra 55Sapphire) at an acceleration voltage of 15 kV, and the nitrogen atom content of the aluminum nitride raw material was found to be 52 wt %, the oxygen impurity content was less than 100 ppm, 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 by physical vapor transport method, and the specific steps and methods are as follows:

[0067] (1) Aluminum nitride powder (particle size of 2 mm) is placed in a crucible, and the crucible cover is put on. The crucible cover and the crucible are concentric. The heating body 2 of the heating device 1 is suspended in the interior of the heating device. The crucible is placed on the top of the heating area formed by the heating body. The chamber is closed and the vacuum degree of the chamber is evacuated to 5×10 -4 Pa, and then filled with helium to a pressure of 1.0×10 5 Pa.

[0068] (2) The aluminum nitride powder is sintered by resistance heating. The specific steps are: raising the temperature to 2000°C at a heating rate of 8°C / min, keeping it warm for 10 hours, and then reducing the temperature to 15°C at a cooling rate of 3°C / min. During the sintering process, the crucible is placed on the top of the heating area formed by the heating body to maintain the temperature difference between the bottom and the top of the crucible at 40°C, thereby obtaining a pretreated material.

[0069] (3) Take out the crucible containing the pre-treated material and put it into the glove box. When the vacuum degree of the glove box drops to 100 Pa, fill it with nitrogen until the pressure reaches 1×10 5 Pa, open the crucible cover, crush the pretreated material, and screen to obtain material with a particle size range of 0.5-1.0 mm.

[0070] (4) The screened materials are put into the crucible, the crucible cover is put on, the crucible is placed in the middle of the heating area formed by the heating body, the chamber is closed, and the vacuum degree of the chamber is pumped to 5×10 -4 Pa, nitrogen was filled into the chamber until the pressure was 1×10 5 After Pa, the material is subjected to high-temperature molding and nitrogen supplementation. The specific steps are to increase the temperature to 2100°C at a heating rate of 4°C / min, keep it warm for 15 hours, and then reduce the temperature to 15°C at a heating rate of 8°C / min. During the sintering process, the crucible is placed in the middle position of the heater and the temperature difference between the bottom and the top of the crucible is maintained at 10°C to obtain aluminum nitride raw material.

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

[0072] Application Example 1

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

[0074] The aluminum nitride raw material 53 is placed in the crucible 3, the aluminum nitride seed crystal 6 is attached to the inner wall of the crucible cover 31, the crucible cover is closed, and the crucible is placed in a heating apparatus at 2340° C. for 10 hours. The aluminum nitride raw material is the aluminum nitride raw material prepared in Example 1.

[0075] The aluminum nitride crystal prepared in this application example is shown in Figure 4 It can be seen that the aluminum nitride crystal prepared in this application example is transparent and presents a light amber color; the luminescence intensity is weakened by the lack of nitrogen vacancies in the photoluminescence spectrum of the crystal, and the XRD of the crystal shows Figure 5 , and the half-peak width of the aluminum nitride crystal was obtained to be 80 arcsec. By calculating the data before and after the growth, the sublimation amount of the aluminum nitride raw material was obtained to be 1.8 g / h, and the sublimation and condensation ratio of the aluminum nitride crystal 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 those of Application Example 1, except that the aluminum nitride raw material is the aluminum nitride raw material prepared in Example 2.

[0078] The aluminum nitride crystals prepared in this application example are translucent and light amber in color. The lack of nitrogen vacancies in the photoluminescence spectrum of the crystal weakens the luminescence intensity. The half-peak width obtained from the XRD diagram of the aluminum nitride crystal is 85 arcsec. By calculating the data before and after growth, the sublimation amount of the aluminum nitride raw material is 1.6 g / h, and the sublimation condensation ratio of the aluminum nitride crystal is 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 those of Application Example 1, except that the aluminum nitride raw material is the aluminum nitride raw material prepared in Example 3.

[0081] The aluminum nitride crystals prepared in this application example are translucent and light amber in color. The lack of nitrogen vacancies in the photoluminescence spectrum of the crystal weakens the luminescence intensity. The half-peak width obtained from the XRD diagram of the aluminum nitride crystal is 90 arcsec. By calculating the data before and after growth, the sublimation amount of the aluminum nitride raw material is 1.3 g / h, and the sublimation condensation ratio of the aluminum nitride crystal 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 those of Application Example 1, except that the aluminum nitride raw material is the aluminum nitride powder in step (1) of the embodiment without any treatment.

[0084] In this application example, after the aluminum nitride seed crystals were grown, the aluminum nitride raw material state had serious clustering phenomenon, and the sublimation rate was reduced to 0.2g / h. Figure 6The grown aluminum nitride crystals are dark amber in color as a whole, and the nitrogen vacancy defect luminescence intensity in the photoluminescence spectrum of the crystal is high. The half-peak width obtained from the XRD diagram of the aluminum nitride crystal is 250 arcsec, and the sublimation condensation ratio of the aluminum nitride crystal is 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 those of Application Example 1, except that the aluminum nitride raw material is the aluminum nitride powder that has been de-impurified and crushed in step (3) of Example 1.

[0087] After the aluminum nitride seed crystals in this application example are grown, the aluminum nitride raw material state has serious clustering phenomenon, the sublimation amount is reduced to 0.3g / h, and the grown aluminum nitride crystals are dark amber in color as a whole. The nitrogen vacancy defect luminescence intensity in the photoluminescence spectrum of the crystal is high. The half-peak width obtained from the XRD diagram of the aluminum nitride crystal is 180arcsec, and the sublimation condensation ratio of the aluminum nitride crystal is 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 those of Application Example 1, except that the aluminum nitride raw material is prepared by the following preparation method.

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

[0091] After the aluminum nitride seed crystals in this application example are grown, the aluminum nitride raw material state has serious clustering phenomenon, the sublimation amount is reduced to 0.5g / h, and the grown aluminum nitride crystals are dark amber in color as a whole. The nitrogen vacancy defect luminescence intensity in the photoluminescence spectrum of the crystal is high. The half-peak width obtained from the XRD diagram of the aluminum nitride crystal is 150arcsec, and the sublimation condensation ratio of the aluminum nitride crystal is 45%.

[0092] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport, characterized in that: The following steps are included: In an inert atmosphere, sintering aluminum nitride powder to form an intermediate; The intermediate body is sintered in a nitrogen atmosphere. When the intermediate body is sintered, the temperature difference between the bottom and the top of the container containing the intermediate body is 10°C-20°C.

2. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method according to claim 1, characterized in that: The specific steps for sintering aluminum nitride powder include: Raise the temperature to 2000-2050°C at a heating rate of 3°C / min-8°C / min, keep it warm for 5h-10h, and then lower the temperature to 15°C-35°C at a cooling rate of 3°C / min-8°C / min.

3. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method according to claim 2, characterized in that: The temperature difference between the bottom and top of the container containing the aluminum nitride powder is 20°C-50°C.

4. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method according to claim 3, characterized in that: The pressure of the inert atmosphere is 0.8×10 5 Pa-1.0×10 5 Pa.

5. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method according to claim 4, characterized in that: The inert atmosphere comprises at least one of nitrogen, helium or argon; and / or, The particle size of aluminum nitride powder is 0.1mm-2mm.

6. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method according to claim 5, characterized in that: When the aluminum nitride powder is sintered, the heating body of the heating device is arranged inside the heating device, and the container containing the aluminum nitride powder is placed in the middle and upper part of the heating area formed by the heating body.

7. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method according to claim 1, characterized in that: Before the intermediate is sintered, the process also includes the steps of crushing and screening the intermediate under an inert atmosphere, wherein the particle size of the intermediate after screening is 0.1 mm to 1.0 mm.

8. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method according to claim 7, characterized in that: The specific steps for sintering the intermediate include: Raise the temperature to 2100-2200°C at a heating rate of 4°C / min-10°C / min, keep it warm for 10h-15h, and then lower the temperature to 15°C-35°C at a cooling rate of 3°C / min-8°C / min. The nitrogen atmosphere pressure is 1×10 5 Pa-3×10 5 Pa.

9. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method according to claim 1, characterized in that: When the intermediate body is sintered, the heating body of the heating device is arranged inside the heating device, and the container for accommodating the intermediate body is placed in the middle position of the heating area formed by the heating body.

10. The method for preparing raw materials suitable for growing aluminum nitride crystals by physical vapor transport method according to any one of claims 1 to 9, characterized in that: The material of the container for containing the aluminum nitride powder and / or the intermediate is at least one of tungsten, tantalum, tantalum carbide and rhenium.

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