Molecular beam epitaxy method for epitaxially growing high-quality AlN on Si substrate and AlN epitaxial wafer

Abstract

The application relates to a molecular beam epitaxy preparation method of epitaxial high-quality AlN on a Si substrate and an AlN epitaxial wafer, and the preparation method comprises the following steps: S1, obtaining a substrate, performing infrared lamp baking on the substrate, performing high-temperature deoxidization after heating pretreatment, and obtaining a pretreated substrate; S2, adopting a molecular beam epitaxy method to pre-deposit an Al layer on the pretreated substrate; S3, adopting the molecular beam epitaxy method to grow an AlN epitaxial layer on the pre-deposited Al layer; and S4, continuously introducing a nitrogen plasma post-treatment, and cooling to a wafer transfer temperature to obtain an epitaxial wafer. In the technical scheme, the pre-deposited Al layer can inhibit the reaction between the substrate and N in the AlN layer, the formation of amorphous particles is avoided, the AlN morphology is improved, meanwhile, the pre-deposited Al layer not only relieves the lattice mismatch problem between the substrate material and the AlN, but also improves the Al atom migration rate for the growth of the subsequent AlN layer, promotes two-dimensional growth, and thus the AlN crystal quality is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor process technology, specifically to a molecular beam epitaxy method for preparing high-quality AlN on a Si substrate and an AlN epitaxial wafer. Background Technology

[0002] Aluminum nitride (AlN), as a fourth-generation wide-bandgap semiconductor, possesses advantages such as a large bandgap (6.2 eV), high thermal stability, and high breakdown field strength. These properties make it ideal for optoelectronic and electronic devices, such as light-emitting diodes (LEDs) and high-electron-mobility transistors (HEMTs). In the overall device structure, the quality of the AlN epitaxial layer has a crucial impact on device performance.

[0003] Currently, AlN is typically grown as a buffer layer on Si(111) substrates. The main method for large-scale production of AlN epitaxial layers is metal-organic chemical vapor deposition (MOCVD). Although MOCVD technology is mature, suitable for large-scale production, and has low cost, molecular beam epitaxy (MBE) can achieve AlN epitaxial growth at relatively low temperatures, significantly reducing the stress between AlN and the Si substrate caused by thermal expansion mismatch, thereby effectively suppressing crack formation in the epitaxial layer. Furthermore, the lower growth temperature and atomic-level precision control offered by MBE technology help suppress interdiffusion between Al and Si atoms, thus improving the quality of the AlN epitaxial layer. Therefore, AlN grown on Si substrates using MBE technology exhibits superior interface quality and lower defect density, which is crucial for improving the performance of devices such as HEMTs.

[0004] Currently, the growth of AlN on Si using MBE technology is still in the experimental research and development stage. Reported MBE epitaxial AlN methods include direct growth, two-step growth, and metal modulation. While these methods have made some progress, challenges remain in balancing low-temperature growth with high-quality crystallization, completely avoiding Si interfacial reactions, and achieving stable and reproducible processes. Summary of the Invention

[0005] Based on the above description, this invention provides a molecular beam epitaxy method for preparing high-quality AlN on a Si substrate and an AlN epitaxial wafer, aiming to propose a method for growing AlN epitaxial layers using the pre-lay Al method to further improve the crystal quality of AlN.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] This invention provides a method for preparing high-quality AlN on a substrate via molecular beam epitaxy, comprising:

[0008] S1. Obtain the substrate, bake the substrate with an infrared lamp, perform high-temperature deoxidation after heating pretreatment, and obtain the pretreated substrate;

[0009] S2. An Al layer is pre-deposited on a pretreated substrate using molecular beam epitaxy.

[0010] S3. An AlN epitaxial layer is grown on a pre-laid Al layer using molecular beam epitaxy.

[0011] S4. After continuous nitrogen plasma injection, the temperature is lowered to the wafer transfer temperature to obtain the epitaxial wafer.

[0012] Furthermore, in step S1, the substrate is made of silicon.

[0013] Furthermore, in step S1, the infrared lamp baking temperature is 150℃-250℃, and the infrared lamp baking time is 1 h-2 h.

[0014] Furthermore, in step S1, the target temperature for the heating pretreatment is 400℃-600℃, and the heating pretreatment time is not less than 2 hours.

[0015] Furthermore, in step S1, the high-temperature deoxidation temperature is 900℃-1200℃.

[0016] Furthermore, in step S2, the substrate temperature is 900℃-1000℃ during the pre-deposition of the Al layer.

[0017] Furthermore, in step S3, when growing the AlN epitaxial layer, the substrate temperature is 900℃-1000℃, and the growth mode adopts the Al-rich mode with a 3:5 ratio of 1-1.2.

[0018] Furthermore, in step S4, the process time is 5 min-20 min.

[0019] Furthermore, in step S4, the transfer temperature does not exceed 300°C.

[0020] The present invention also proposes an AlN epitaxial wafer, which is prepared by molecular beam epitaxy of high-quality AlN on a substrate as described above.

[0021] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0022] (1) In the technical solution of the present invention, the reaction between the substrate and the N in the AlN layer can be suppressed by pre-laying the Al layer, thus avoiding the formation of amorphous particles and improving the morphology of AlN. At the same time, the pre-layed Al layer not only alleviates the problem of lattice mismatch between the substrate material and AlN, but also improves the Al atom mobility for the subsequent growth of AlN layer, promotes two-dimensional growth, and thus improves the quality of AlN crystal.

[0023] (2) During the epitaxial growth of AlN, due to excessive aluminum source or insufficient reaction, tiny aluminum droplets often form on the surface, resulting in rough and uneven surface. In step S4 of this invention, nitrogen plasma is continuously introduced to utilize its highly active nitrogen species to conduct an in-situ nitriding reaction with the surface Al droplets, converting metallic Al into AlN, thereby effectively eliminating small-sized Al droplets on the surface, significantly reducing the surface roughness of the epitaxial layer, obtaining a smooth and uniform AlN film, optimizing the surface morphology of AlN, and thus improving the quality of AlN crystals. Nitrogen plasma not only participates in the elimination of Al droplets, but also performs slight nitriding repair on the AlN surface, filling possible nitrogen vacancies on the surface, enhancing surface chemical stability, and further improving the compositional uniformity and interface quality of the epitaxial layer. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the direct growth method in the prior art;

[0025] Figure 2 This is a schematic diagram of the two-step growth method in the prior art;

[0026] Figure 3 This is a schematic diagram illustrating the flow rate variation over time in the metal modulation method of the prior art.

[0027] Figure 4 This is a schematic flowchart of an embodiment of the molecular beam epitaxy method for preparing high-quality AlN on a Si substrate according to this application.

[0028] Figure 5 The image shows the XRD (002) FWHM crystal quality test results of the AlN epitaxial wafers provided in Example 1 and Comparative Example 1 of this application. Detailed Implementation

[0029] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0031] Aluminum nitride (AlN), as a fourth-generation wide-bandgap semiconductor, possesses advantages such as a large bandgap (6.2 eV), high thermal stability, and high breakdown field strength. These properties make it ideal for optoelectronic and electronic devices, such as light-emitting diodes (LEDs) and high-electron-mobility transistors (HEMTs). In the overall device structure, the quality of the AlN epitaxial layer has a crucial impact on device performance.

[0032] Currently, AlN is typically grown as a buffer layer on Si substrates. The main method for large-scale production of AlN epitaxial layers is metal-organic chemical vapor deposition (MOCVD). Although MOCVD technology is mature, suitable for large-scale production, and relatively inexpensive, molecular beam epitaxy (MBE) can achieve AlN epitaxial growth at relatively lower temperatures, significantly reducing stress between AlN and the Si substrate caused by thermal expansion mismatch, thereby effectively suppressing crack formation in the epitaxial layer. Furthermore, the lower growth temperature and atomic-level precision control offered by MBE technology help suppress interdiffusion between Al and Si atoms, thus improving the quality of the AlN epitaxial layer. Therefore, AlN grown on Si substrates using MBE technology exhibits superior interface quality and lower defect density, which is crucial for improving the performance of devices such as HEMTs.

[0033] Currently, the growth of AlN on Si using MBE technology is still in the experimental research and development stage. Reported MBE epitaxial AlN methods include direct growth, two-step growth, and metal modulation.

[0034] Among them, such as Figure 1 As shown, the direct growth method is the most basic method for growing AlN using MBE. It involves no changes to the epitaxial structure and only adjusts the growth temperature and the 3:5 ratio to obtain relatively favorable process conditions. However, the direct growth method easily forms amorphous SiN, resulting in poor AlN morphology. When Al and N atoms are simultaneously introduced into the Si substrate, amorphous SiN is easily formed, which is detrimental to the formation of the two-dimensional AlN morphology, thus leading to poor AlN morphology.

[0035] like Figure 2 As shown, the two-step growth method involves first epitaxially growing an AlN starter layer on a Si substrate using a lower 3:5 ratio (N-rich mode), and then epitaxially growing an AlN buffer layer using a 3:5 ratio close to 1 using a slightly metal-rich mode. The starter layer AlN uses the N-rich mode, while the buffer layer AlN uses the metal-rich mode. This process requires strict and precise switching of the process 3:5 ratio, which places high demands on accuracy. Furthermore, when the starter layer is in the N-rich mode, it is easy to form more pit morphologies, which can easily introduce defects.

[0036] like Figure 3As shown, the metal modulation method involves: a) first, opening only the Al baffle, allowing Al atoms to deposit and migrate; b) then opening the N baffle, where N consumes Al atoms to form AlN; c) then closing the Al baffle, allowing N to consume excess Al on the AlN surface; d) finally closing the N baffle, forming AlN within one cycle; e) repeating the above four steps to obtain AlN of the desired thickness. However, the metal modulation method has a complex growth process, requiring precise control of the switching timing; and the growth process necessitates repeated baffle switching, demanding high precision in equipment control and resulting in a relatively slow growth rate.

[0037] While the aforementioned methods have achieved some progress, challenges remain in balancing low-temperature growth with high-quality crystallization, completely avoiding Si interfacial reactions, and achieving a stable and reproducible process. Therefore, this patent aims to propose a method for growing AlN epitaxial layers using the pre-lay Al method to further improve the crystal quality of AlN.

[0038] In view of this, see Figure 4 This invention provides a method for preparing high-quality AlN on a substrate using molecular beam epitaxy, comprising:

[0039] S1. Obtain the substrate, bake the substrate with an infrared lamp, perform high-temperature deoxidation after heating pretreatment, and obtain the pretreated substrate;

[0040] S2. An Al layer is pre-deposited on a pretreated substrate using molecular beam epitaxy.

[0041] S3. An AlN epitaxial layer is grown on a pre-laid Al layer using molecular beam epitaxy.

[0042] S4. After continuous nitrogen plasma injection, the temperature is lowered to the wafer transfer temperature to obtain the epitaxial wafer.

[0043] In the technical solution of this invention, the pre-laid Al layer can suppress the reaction between the substrate and the N in the AlN layer, avoiding the formation of amorphous particles and thus improving the AlN morphology. At the same time, the pre-laid Al layer not only alleviates the lattice mismatch problem between the substrate material and AlN, but also improves the Al atom mobility for the subsequent growth of the AlN layer, promoting two-dimensional growth and thus improving the AlN crystal quality. During the AlN epitaxial growth process, due to excessive aluminum source or insufficient reaction, tiny aluminum droplets often form on the surface, resulting in rough and uneven surface. In step S4 of this invention, nitrogen plasma is continuously introduced, utilizing its highly active nitrogen species to undergo in-situ nitriding reaction with the surface Al droplets, converting metallic Al into AlN, thereby effectively eliminating small-sized Al droplets on the surface, significantly reducing the surface roughness of the epitaxial layer, obtaining a flat and uniform AlN film, optimizing the AlN surface morphology, and thus improving the AlN crystal quality. Nitrogen plasma not only participates in the elimination of Al droplets, but also performs slight nitriding repair on the AlN surface, filling possible nitrogen vacancies on the surface, enhancing surface chemical stability, and further improving the compositional uniformity and interface quality of the epitaxial layer.

[0044] Furthermore, in step S1, the substrate is made of silicon.

[0045] In the technical solution of this invention, by using infrared lamp rapid heating combined with high-temperature deoxidation process, in-situ cleaning of silicon substrate can be achieved within the molecular beam epitaxy system, effectively avoiding re-oxidation and carbon contamination of Si substrate, ensuring atomically clean Si surface, and laying the foundation for high-quality AlN nucleation. Significant lattice mismatch and thermal expansion coefficient differences exist between Si and AlN, easily leading to high-density penetrating dislocations and cracks in the epitaxial layer. This invention effectively removes the natural oxide layer and adsorbed impurities on the silicon substrate surface through infrared baking and high-temperature deoxidation treatment, enhancing surface activity. Combined with the introduction of Al pre-lay layers, it can regulate interface nucleation behavior, promote two-dimensional nucleation mode, alleviate interface stress concentration, and significantly suppress the generation of cracks and defects.

[0046] Furthermore, in step S1, the infrared lamp baking temperature is 150℃-250℃, and the infrared lamp baking time is 1 h-2 h.

[0047] In the technical solution of the present invention, a large number of adsorbent impurities can be eliminated in advance during the low-temperature pre-baking step, which significantly reduces the load on the subsequent high-temperature deoxidation stage and prevents surface blistering, contamination or vacuum fluctuations caused by the violent volatilization of moisture or organic matter during high-temperature rapid heating, thereby ensuring the stability and cleaning effect of the high-temperature deoxidation process.

[0048] Furthermore, in step S1, the target temperature for the heating pretreatment is 400℃-600℃, and the heating pretreatment time is not less than 2 hours.

[0049] In the technical solution of this invention, by maintaining the temperature for a long time within the range of 400℃-600℃, most of the volatile pollutants can be effectively removed, and the silicon wafer surface can be prevented from being severely oxidized, thus providing an ideal interface basis for the subsequent high-temperature deoxidation process.

[0050] Furthermore, in step S1, the high-temperature deoxidation temperature is 900℃-1200℃.

[0051] In the technical solution of this invention, under high temperature conditions of 900℃-1200℃, the SiO2 natural oxide layer and chemically adsorbed oxygen species on the silicon surface undergo thermal decomposition and are effectively discharged through an ultra-high vacuum environment. This temperature range fully covers the thermodynamic window for significant SiO2 volatilization, enabling atomically clean silicon surfaces to be achieved in a short time. This facilitates atomic rearrangement on the silicon surface and provides an oxide-free interface for the uniform nucleation of subsequent Al pre-lays and AlN epitaxy.

[0052] Furthermore, in step S2, the substrate temperature is 900℃-1000℃ during the pre-deposition of the Al layer.

[0053] In the technical solution of the present invention, by adopting the above-mentioned substrate temperature, the pre-laid Al layer has higher chemical activity and can react rapidly with active nitrogen in nitrogen plasma to generate AlN, thereby achieving a smooth phase transition from the metal layer to the nitride and reducing interface defects.

[0054] Furthermore, in step S3, when growing the AlN epitaxial layer, the substrate temperature is 900 ℃-1000 ℃, and the growth mode adopts the Al-rich mode with a 3:5 ratio of 1-1.2.

[0055] In the technical solution of this invention, the reactivity of nitrogen is significantly enhanced by a growth temperature of 900℃-1000℃, making it easier for nitrogen to combine with Al atoms to generate high-quality AlN. By adopting an Al-rich growth mode with a 3:5 ratio of 1-1.2 (i.e., slightly excess Al), an Al-rich environment can be formed, which effectively suppresses the formation of acceptor defects such as nitrogen vacancies. At the same time, it promotes the two-dimensional diffusion of Al atoms on the surface, which is conducive to planar layer-by-layer growth, reduces stacking faults and through dislocations, and significantly improves crystal integrity.

[0056] In some embodiments of the present invention, in step S2, when pre-laying the Al layer, the substrate temperature is 900℃-1000℃, and in step S3, when growing the AlN epitaxial layer, the substrate temperature is 900℃-1000℃. With the pre-laying temperature close to the subsequent AlN growth temperature, the system can directly introduce nitrogen plasma to start AlN nucleation without significant temperature adjustment, shortening the process transition time, achieving a smooth phase transition from the metal layer to the nitride, and reducing interface defects.

[0057] It should be noted that the 3:5 ratio refers to the ratio of the beam currents of group III elements (Al) to group V elements (N) during the molecular beam epitaxy growth of AlN.

[0058] Furthermore, in step S4, the process time is 5 min-20 min.

[0059] In the technical solution of this invention, after AlN epitaxial growth is completed, trace amounts of metallic Al droplets or Al-rich regions may remain on the surface. By continuously applying high-power nitrogen plasma during the initial cooling phase, a high concentration of active nitrogen atoms is generated, which can undergo a rapid nitriding reaction with the surface Al droplets, transforming them into AlN crystals. This effectively eliminates surface metal clusters, significantly reduces the surface roughness of the epitaxial layer, and obtains a uniform and dense final surface morphology. During the process time of 5-20 minutes, active nitrogen continuously acts on the AlN surface, promoting surface atomic rearrangement and forming a more stable N-terminated surface structure. During this period, it is ensured that sufficient active nitrogen is continuously supplied to form a gradient nitriding protective layer, preventing surface decomposition or re-oxidation caused by excessively rapid cooling or interruption of the nitrogen source.

[0060] Furthermore, in step S4, the transfer temperature does not exceed 300°C.

[0061] In the technical solution of this invention, by adjusting the wafer transfer temperature to no higher than 300°C, the surface oxidation of the epitaxial wafer before and after removal from the cavity is suppressed, ensuring that an atomically clean AlN surface is obtained. AlN is prone to thermal desorption of nitrogen at high temperatures, leading to surface denitrification, formation of nitrogen vacancies or precipitation of metallic Al, resulting in surface roughening and crystal quality degradation. By controlling the wafer transfer temperature to no higher than 300°C, the driving force of thermal decomposition is significantly reduced, effectively maintaining the structural integrity and chemical stability of the AlN epitaxial layer after growth.

[0062] The present invention also proposes an AlN epitaxial wafer, which is prepared by molecular beam epitaxy of high-quality AlN on a substrate as described above.

[0063] Since this AlN epitaxial wafer adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0064] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0065] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0066] Example 1

[0067] This embodiment provides a method for preparing high-quality AlN on a substrate using molecular beam epitaxy. (See reference...) Figure 4 The steps are as follows:

[0068] Step 1: Select a Si substrate;

[0069] Step 2: Transfer the Si substrate into the sample injection chamber and bake it with an infrared lamp at 200°C for 90 minutes;

[0070] Step 3: Transfer the Si substrate into the pretreatment chamber, target temperature 500℃, pretreatment for 4 h;

[0071] Step 4: Transfer the Si substrate into the growth chamber for high-temperature deoxidation, with a target temperature of 1000℃;

[0072] Step 5: Epitaxially deposit an Al layer on the Si substrate at a growth temperature of 950℃.

[0073] Step 6: Growing AlN epitaxial layer: Growing AlN epitaxial layer on the pre-laid Al layer at a growth temperature of 950℃, using Al-rich mode, with a 3:5 ratio of 1.1.

[0074] Step 7: Turn off the Al baffle and continue to maintain N plasma for 10 min. The purpose is to allow active nitrogen to eliminate small Al droplets on the AlN surface, reduce AlN roughness, and optimize the AlN surface morphology.

[0075] Step 8: After the AlN epitaxial layer growth is completed, the temperature of the Si substrate is lowered to 280℃, and the substrate is removed.

[0076] Comparative Example 1

[0077] This comparative example uses a direct growth method to grow AlN on a Si substrate, and the steps are as follows:

[0078] Step 1: Select a Si substrate;

[0079] Step 2: Transfer the Si substrate into the sample injection chamber and bake it with an infrared lamp at 200°C for 90 minutes;

[0080] Step 3: Transfer the Si substrate into the pretreatment chamber, target temperature 500℃, pretreatment for 4 h;

[0081] Step 4: Transfer the Si substrate into the growth chamber for high-temperature deoxidation;

[0082] Step 5: Growing an AlN epitaxial layer: An AlN epitaxial layer is grown on the Si substrate described above, using an Al-rich growth mode;

[0083] Step 6: Close the Al baffle and continue to maintain N plasma. The purpose is to allow active nitrogen to eliminate small Al droplets on the AlN surface, reduce AlN roughness, and optimize the AlN surface morphology.

[0084] Step 7: After the AlN epitaxial layer growth is completed, the temperature of the Si substrate is reduced to 280°C, and the substrate is removed.

[0085] The AlN epitaxial wafers provided in Example 1 and Comparative Example 1 were subjected to XRD (002) FWHM crystal quality testing, and the results are as follows: Figure 5 As shown.

[0086] according to Figure 5 The test results show that the (002) FWHM of the AlN epitaxial wafer prepared in Example 1 is only 972 arcsec, while the (002) FWHM of the AlN epitaxial wafer prepared in Comparative Example 1 is 1404 arcsec, indicating that the AlN epitaxial wafer prepared by the method in this scheme is of better quality.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0088] In summary, the technical solution of this application has the following beneficial technical effects:

[0089] (1) In the technical solution of the present invention, the reaction between the substrate and the N in the AlN layer can be suppressed by pre-laying the Al layer, thus avoiding the formation of amorphous particles and improving the morphology of AlN. At the same time, the pre-layed Al layer not only alleviates the problem of lattice mismatch between the substrate material and AlN, but also improves the Al atom mobility for the subsequent growth of AlN layer, promotes two-dimensional growth, and thus improves the quality of AlN crystal.

[0090] (2) During the epitaxial growth of AlN, due to excessive aluminum source or insufficient reaction, tiny aluminum droplets often form on the surface, resulting in rough and uneven surface. In step S4 of this invention, nitrogen plasma is continuously introduced to utilize its highly active nitrogen species to conduct an in-situ nitriding reaction with the surface Al droplets, converting metallic Al into AlN, thereby effectively eliminating small-sized Al droplets on the surface, significantly reducing the surface roughness of the epitaxial layer, obtaining a smooth and uniform AlN film, optimizing the surface morphology of AlN, and thus improving the quality of AlN crystals. Nitrogen plasma not only participates in the elimination of Al droplets, but also performs slight nitriding repair on the AlN surface, filling possible nitrogen vacancies on the surface, enhancing surface chemical stability, and further improving the compositional uniformity and interface quality of the epitaxial layer.

Claims

1. A molecular beam epitaxy method of epitaxially growing high quality AIN on a substrate, characterized by, The method comprises the following steps: S1. obtaining a substrate, performing infrared lamp baking on the substrate, and performing high-temperature deoxidization after heating pretreatment to obtain a pretreated substrate; S2. using a molecular beam epitaxy method to pre-deposit an Al layer on the pretreated substrate; S3. using a molecular beam epitaxy method to grow an AlN epitaxial layer on the pre-deposited Al layer; S4. continuously introducing a nitrogen plasma post-treatment, and cooling to a wafer transfer temperature to obtain an epitaxial wafer.

2. The molecular beam epitaxy method for fabricating high-quality AlN epitaxial on substrate according to claim 1, wherein, In step S1, the material of the substrate is silicon.

3. The molecular beam epitaxy method for fabricating high-quality AlN epitaxial on substrate of claim 1, wherein, In step S1, the infrared lamp baking temperature is 150-250°C, and the infrared lamp baking time is 1-2 h.

4. The molecular beam epitaxy method for fabricating high-quality AlN epitaxial on substrate of claim 1, wherein, In step S1, the target temperature of the heating pretreatment is 400-600°C, and the heating pretreatment time is not less than 2 h.

5. The molecular beam epitaxy method for epitaxial high-quality A1N on a substrate according to claim 1, wherein In step S1, the high-temperature deoxidization temperature is 900-1200°C.

6. The molecular beam epitaxy method for epitaxial high-quality A1N on a substrate according to claim 1, wherein In step S2, when the Al layer is pre-deposited, the substrate temperature is 900-1000°C.

7. The molecular beam epitaxy method for epitaxial high quality A1N on substrate of claim 1, wherein, In step S3, when the AlN epitaxial layer is grown, the substrate temperature is 900-1000°C, and the growth mode is an Al-rich mode, and the three-five ratio is 1-1.

2.

8. The molecular beam epitaxy method for epitaxial high quality A1N on substrate of claim 1, wherein, In step S4, the process time is 5-20 min.

9. The molecular beam epitaxy method for epitaxial high quality A1N on substrate of claim 1, wherein, In step S4, the wafer transfer temperature is not higher than 300°C.

10. An AlN epitaxial wafer, characterized by, The epitaxial high-quality AlN on a substrate prepared by the molecular beam epitaxy method according to any one of claims 1 to 9.

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