Method for regulating polarity of aluminum nitride film

Abstract

The invention provides a method for regulating and controlling polarity of an aluminum nitride film. The method comprises the following steps: depositing a hexagonal boron nitride buffer layer on a substrate; pretreating the hexagonal boron nitride buffer layer by adopting oxygen plasma to form the hexagonal boron nitride buffer layer with an oxygen dangling bond on the surface; and depositing aluminum nitride on the pretreated hexagonal boron nitride buffer layer by adopting a metal organic chemical vapor deposition method to obtain the aluminum nitride film. Wherein aluminum nitride is deposited on the pretreated hexagonal boron nitride buffer layer by adopting a metal organic chemical vapor deposition method to sequentially obtain nitrogen polar aluminum nitride, mixed polar aluminum nitride and aluminum polar aluminum nitride. And by controlling the number of the hexagonal boron nitride buffer layers, the distribution interval of the mixed polarity aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is controlled.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor technology, and in particular, to a method for regulating the polarity of aluminum nitride thin films. Background Art

[0002] III-nitride semiconductor materials with a wurtzite structure have a hexagonal crystal structure, and the positive and negative charge centers in the C-axis direction are not centrosymmetric. Therefore, they can exhibit nitrogen (N)-polar surfaces or metal-polar (Al, Ga, In) surfaces. Since the spontaneous polarization vector of III-nitrides is determined by the polar orientation, different polar surfaces will generate different types of charges. Therefore, although N-polar and metal-polar nitride have the same overall properties, these two polarities have obvious differences in terms of chemical inertness, growth mode, surface morphology, and nonlinear optical characteristics.

[0003] Aluminum nitride (AlN) is an important basis for preparing aluminum gallium nitride (AlGaN)-based optoelectronic devices. The polar surface and material quality of AlN will also directly determine the performance of the devices. Different polarization directions will result in different polarization carriers, which have important application prospects in the regulation of the polarization field and injection efficiency of light-emitting devices. However, the growth window of AlN thin films with an N-polar surface is very narrow. Especially for nitride thin films grown by metalorganic chemical vapor deposition (MOCVD), due to the special metal-rich growth environment, usually only a single aluminum (Al)-polar AlN can be obtained, and it is very difficult to regulate the polarity of AlN. In addition, the dislocation density and strain state of the AlN template are also very important for the performance of AlGaN-based optoelectronic devices. Dislocations will provide non-radiative recombination channels to reduce the internal quantum efficiency of the devices, and the strain state will determine the initial strain state of the subsequent AlGaN layer, affecting the uniformity of the Al component. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] To solve at least one of the above technical problems of AlN thin films in the prior art, the present disclosure provides a method for regulating the polarity of aluminum nitride thin films. By introducing a hexagonal boron nitride (h-BN) buffer layer, it is used to regulate the polarity of the AlN epitaxial layer and prepare high-quality and low-stress AlN thin films.

[0006] (2) Technical Solutions

[0007] In view of the above technical problems, an embodiment of the present disclosure provides a method and a preparation method for regulating the polarity of an AlN thin film with a low dislocation density and no strain.

[0008] According to one aspect of the present disclosure, a method for regulating the polarity of aluminum nitride thin films is provided. The method includes the following steps: depositing a hexagonal boron nitride buffer layer on a substrate; pretreating the hexagonal boron nitride buffer layer with oxygen plasma to form a hexagonal boron nitride buffer layer with oxygen dangling bonds on the surface; and depositing aluminum nitride on the pretreated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain an aluminum nitride thin film.

[0009] Among them, the depositing aluminum nitride on the pretreated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain an aluminum nitride thin film includes: depositing aluminum nitride on the pretreated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain a nitrogen-polar aluminum nitride thin film; continuously depositing aluminum nitride on the nitrogen-polar aluminum nitride to obtain a mixed-polarity aluminum nitride thin film; and continuously depositing aluminum nitride on the mixed-polarity aluminum nitride thin film to a preset thickness to obtain an aluminum-polar aluminum nitride thin film.

[0010] Specifically, the O dangling bonds formed on the h-BN surface by oxygen plasma pretreatment will promote the adsorption of Al atoms, and the special interface configuration leads to the formation of a N-polar AlN epitaxial layer in the initial stage of growth. Driven by the special metal-rich growth environment and surface energy anisotropy of MOCVD, the initial N-polar AlN undergoes polarity inversion during the subsequent growth process to form mixed-polarity AlN. Among them, the thickness of the h-BN buffer layer will affect the polarity inversion process of the AlN epitaxial layer. Continuing to epitaxially grow AlN on the mixed-polarity AlN to a preset thickness (>800 nm), the N-polar AlN is completely inverted to form Al-polar AlN. If Al-polar AlN is directly deposited on the h-BN / substrate without oxygen plasma pretreatment.

[0011] Preferably, the plasma equipment includes a glue applicator.

[0012] Preferably, by controlling the number of layers of the hexagonal boron nitride buffer layer, the distribution interval of the mixed-polarity aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is controlled.

[0013] Preferably, the material of the substrate includes one of sapphire, silicon carbide, aluminum nitride, and metal materials.

[0014] Preferably, the method for depositing the hexagonal boron nitride buffer layer on the substrate includes one of low-pressure chemical vapor deposition and metal-organic chemical vapor deposition.

[0015] Preferably, the hexagonal boron nitride buffer layer is at least 1 layer, and the total thickness of the boron nitride buffer layer is greater than 0 and less than or equal to 10 nm.

[0016] Preferably, the hexagonal boron nitride buffer layer is pretreated with oxygen plasma to form a hexagonal boron nitride buffer layer with oxygen dangling bonds on the surface, specifically including: the flow rate of the oxygen plasma is 100 sccm - 300 sccm, the power of the oxygen plasma is 50 w - 200 w, and the pretreatment time is 1 min - 3 min.

[0017] Preferably, metal-organic chemical vapor deposition is used to deposit aluminum nitride on the pretreated hexagonal boron nitride buffer layer to obtain an aluminum nitride thin film, specifically including: the equipment used is a metal-organic chemical vapor deposition equipment, the deposition process temperature is 1100 °C - 1300 °C, the chamber pressure is 40 torr - 50 torr, the aluminum source is trimethylaluminum, the flow rate of the aluminum source is 50 sccm - 150 sccm, the nitrogen source is ammonia, the flow rate of the nitrogen source is 300 sccm - 1000 sccm, and the carrier gas is hydrogen.

[0018] Preferably, the distribution range of the nitrogen-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is 10 nm - 200 nm.

[0019] Preferably, the distribution range of the mixed-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is 200 nm - 800 nm.

[0020] Preferably, the distribution range of the aluminum-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is in the region greater than 800 nm.

[0021] Preferably, the deposition time of the nitrogen-polar aluminum nitride thin film is 2 min - 12 min.

[0022] Preferably, an aluminum nitride thin film is continuously deposited on the nitrogen-polar aluminum nitride thin film, and the deposition time is 2 min - 36 min to obtain the mixed-polar aluminum nitride thin film.

[0023] According to another aspect of the present disclosure, an aluminum nitride thin film is provided, and the aluminum nitride thin film is prepared by any one of the above methods.

[0024] (III) Beneficial effects

[0025] It can be seen from the above technical solutions that a method for regulating the polarity of an aluminum nitride thin film provided by the present disclosure has at least one of the following beneficial effects:

[0026] (1) A high-quality h-BN buffer layer with controllable number of layers is grown on a high-temperature resistant substrate, and the h-BN buffer layer is used to effectively regulate the polarity of the AlN epitaxial layer;

[0027] (2) The h-BN buffer layer alleviates the lattice mismatch and thermal mismatch between the epitaxial layer and the substrate, reduces the dislocation density of the AlN epitaxial layer, and effectively releases the residual stress of the epitaxial layer. Description of the Drawings

[0028] Figure 1 Schematically shows a flowchart of a method for regulating the polarity of an aluminum nitride thin film according to an embodiment of the present disclosure.

[0029] Figure 2 Schematically shows a structural diagram of the polarity of an AlN thin film according to an embodiment of the present disclosure.

[0030] Figure 3 Schematically shows a Raman and Fourier infrared spectroscopy characterization diagram of h-BN directly grown on a sapphire substrate according to an embodiment of the present disclosure.

[0031] Figure 4 Schematically shows an X-ray photoelectron spectroscopy diagram of h-BN before and after oxygen plasma treatment according to an embodiment of the present disclosure.

[0032] Figure 5 Schematically shows a HAADF-STEM image of an N-polarity AlN thin film according to an embodiment of the present disclosure.

[0033] Figure 6 Schematically shows an atomic diagram of the boundary structure of the polarity inversion region of a mixed-polarity AlN thin film according to an embodiment of the present disclosure.

[0034] Figure 7 Schematically shows a geometric phase analysis diagram of the polarity inversion region of a mixed-polarity AlN thin film according to an embodiment of the present disclosure.

[0035] Figure 8 Schematically shows a HAADF-STEM image and a KOH etching image of an Al-polarity AlN thin film according to an embodiment of the present disclosure. Detailed Description of the Embodiments

[0036] To make the objectives, technical solutions, and advantages of the present disclosure clearer and more understandable, the following further elaborates on the present disclosure in detail with reference to specific embodiments and the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts fall within the scope of protection of the present disclosure.

[0037] Due to the very narrow growth window of AlN thin films on the nitrogen (N) polar surface, especially for nitride thin films grown by metalorganic chemical vapor deposition, due to the special metal-rich growth environment, existing methods for preparing AlN thin films usually can only obtain single aluminum (Al) polar AlN, and it is very difficult to control the polarity of AlN. In addition, the dislocation density and strain state of the AlN template are also very important for the performance of AlGaN-based optoelectronic devices. Dislocations will provide non-radiative recombination channels to reduce the internal quantum efficiency of the device, and the strain state will determine the initial strain state of the subsequent AlGaN layer, affecting the uniformity of the Al composition.

[0038] To solve at least one of the above technical problems of AlN thin films in the prior art, embodiments of the present disclosure provide a method for controlling the polarity of high-quality AlN thin films. By introducing a hexagonal boron nitride (h-BN) buffer layer, it is used to control the polarity of the AlN epitaxial layer and prepare high-quality and low-stress AlN thin films.

[0039] An embodiment of the present disclosure shows a method for controlling the polarity of AlN thin films, and a detailed description of the method for controlling the polarity of AlN thin films is given.

[0040] The first step is to deposit a hexagonal boron nitride (i.e., h-BN) buffer layer on the substrate.

[0041] The second step is to deposit aluminum nitride on the pretreated hexagonal boron nitride buffer layer by metalorganic chemical vapor deposition to directly obtain an aluminum-polar aluminum nitride thin film.

[0042] An embodiment of the present disclosure shows a method for controlling the polarity of AlN thin films. Refer to Figure 1 , and a detailed description of the method for controlling the polarity of AlN thin films is given.

[0043] In step S1, a hexagonal boron nitride buffer layer is deposited on the substrate.

[0044] In some exemplary embodiments, the material of the substrate includes one of sapphire, silicon carbide, aluminum nitride, and metal materials, and the substrate has an atomically smooth plane.

[0045] In some exemplary embodiments, the method for depositing the hexagonal boron nitride buffer layer on the substrate includes one of low-pressure chemical vapor deposition and metalorganic chemical vapor deposition.

[0046] In some exemplary embodiments, the hexagonal boron nitride buffer layer is at least 1 layer, and the total thickness of the boron nitride buffer layer is greater than 0 and less than or equal to 10 nm.

[0047] In step S2, the hexagonal boron nitride buffer layer is pretreated with oxygen plasma to form a hexagonal boron nitride buffer layer with oxygen dangling bonds on the surface.

[0048] In some exemplary embodiments, the oxygen plasma pretreatment device includes a dicing machine.

[0049] In some exemplary embodiments, the oxygen plasma flow rate is 100 sccm - 300 sccm, the oxygen plasma power is 50 W - 200 W, and the pretreatment time is 1 min - 3 min.

[0050] In step S3, aluminum nitride is deposited on the pretreated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain an aluminum nitride thin film, including:

[0051] Aluminum nitride is deposited on the pretreated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain a nitrogen-polar aluminum nitride thin film;

[0052] Aluminum nitride is continuously deposited on the nitrogen-polar aluminum nitride to obtain a mixed-polar aluminum nitride thin film; and

[0053] Aluminum nitride is continuously deposited on the mixed-polar aluminum nitride thin film to a preset thickness to obtain an aluminum-polar aluminum nitride thin film.

[0054] In some exemplary embodiments, by controlling the number of layers of the hexagonal boron nitride buffer layer, the distribution range of the mixed-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is controlled.

[0055] In some exemplary embodiments, the deposition of aluminum nitride on the pretreated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain an aluminum nitride thin film specifically includes: the equipment used is a metal-organic chemical vapor deposition equipment, the deposition process temperature is 1100 °C - 1300 °C, the chamber pressure is 40 torr - 50 torr, the aluminum source is trimethylaluminum, the aluminum source flow rate is 50 sccm - 150 sccm, the nitrogen source is ammonia, the nitrogen source flow rate is 300 sccm - 1000 sccm, and the carrier gas is hydrogen.

[0056] In some exemplary embodiments, the distribution range of the nitrogen-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is 10 nm - 200 nm; the distribution range of the mixed-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is 200 nm - 800 nm; the distribution range of the aluminum-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is in the region greater than 800 nm.

[0057] In some exemplary embodiments, the deposition time of the nitrogen-polar aluminum nitride thin film is 2 min - 12 min; an aluminum nitride thin film is continuously deposited on the nitrogen-polar aluminum nitride thin film for a deposition time of 2 min - 36 min to obtain the mixed-polarity aluminum nitride thin film.

[0058] For example, in step S1, a 3 - 10 nm thick h-BN buffer layer is deposited on a sapphire substrate by low-pressure chemical vapor deposition.

[0059] Perform Raman spectroscopy and Fourier transform infrared spectroscopy analysis on the h-BN buffer layer, refer to Figure 3 , wherein, Figure 3 a in Figure 3 is the Raman spectrum of h-BN, the abscissa represents the Raman shift, and the ordinate represents the Raman intensity. As can be seen from -1 a in Figure 3 a peak appears at the 1372 cm -1 position. Figure 3 b in Figure 3 is the Fourier transform infrared spectrum, the abscissa represents the absorption peak position, and the ordinate represents the absorption peak intensity. Figure 3 The upper curve in Figure 3 b is the Fourier transform infrared spectrum of the 3 - 10 nm thick h-BN buffer layer deposited on the sapphire substrate, Figure 3 The lower curve in -1 b is the Fourier transform infrared spectrum of the sapphire substrate without the deposited h-BN buffer layer. Compared with the lower curve, an additional absorption peak appears in the upper curve, and the absorption peak position is approximately at 1371 cm -1 position. Combining Figure 3 a in Figure 3 and the equipment error, it can be known that this absorption peak is the absorption peak of h-BN. Thus, it can be known that the h-BN buffer layer is deposited on the sapphire substrate.

[0060] For example, in step S2, the h-BN / sapphire substrate obtained in step S1 is placed in a glue applicator for oxygen plasma treatment. The oxygen flow rate is 300 sccm, the plasma power is 50 - 200 w, and the treatment time is 3 min.

[0061] X-ray photoelectron spectroscopy diagrams of the h-BN buffer layer before and after oxygen plasma treatment, refer to Figure 4 , the abscissa represents the binding energy, and the ordinate represents the relative intensity. Figure 4 shows the intensities of the peaks of Al 2p, Al 2s, B 1s, C1s, N 1s, and O 1s before and after oxygen plasma treatment. As can be seen from Figure 4It can be seen that after oxygen plasma treatment, the peak intensities of B 1s and N 1s also slightly decreased, and the peak intensity of O 1s increased. It was further measured that the surface roughness of h-BN treated with oxygen plasma increased from 0.43nm to 0.58nm. This shows that oxygen plasma treatment will destroy some BN bonds and introduce O-related dangling bonds on the h-BN surface to provide nucleation sites for the subsequent growth of AlN, but it has little effect on the surface roughness of h-BN and will not affect the subsequent growth of AlN.

[0062] For example, in step S3, a metal organic chemical vapor deposition method is used to grow an AlN film on the substrate obtained in step S2, the growth temperature is 1200°C to 1300°C, the chamber pressure is 40-50 tort, trimethylaluminum is used as the aluminum source during growth, the flow rate is 70-90sccm, ammonia is used as the nitrogen source, the flow rate is 500sccm, and the carrier gas is hydrogen.

[0063] For example, the growth time is 2min-12min, and the thickness of the obtained AlN film is 10nm-200nm. Figure 5 , it can be seen from the high-angle annular dark field scanning transmission image that AlN is N-polar. Therefore, AlN with a thickness of <200nm grown on h-BN is N-polar.

[0064] For example, the AlN film with a thickness of 200 nm to 800 nm is obtained by continuing to grow on the N-polar AlN film for 2 min to 36 min.

[0065] The 200-800nm AlN epitaxial layer boundary structure, see Figure 6 , Figure 6 This indicates that N-polar AlN and Al-polar AlN exist simultaneously, confirming the polarity reversal process of the AlN epitaxial layer during its growth. The distribution range of the mixed polarity aluminum nitride film in the thickness direction of the aluminum nitride film is 200nm-800nm.

[0066] The strain state of AlN epilayers was measured using Geometric Phase Analysis (GPA), see Figure 7 .in, Figure 7 a in the equation is the strain state in the x-axis direction. Figure 7 b in the figure is the strain state in the y direction. The horizontal axis of the curve in the figure represents the position, and the vertical axis represents the strain magnitude. The measurement area is the area indicated by the horizontal line in the figure, and the boundary position is the position indicated by the oblique line in the figure. Figure 7 a and Figure 7 From b in the figure, we can see that the peak position of strain appears at the intersection of the horizontal line and the oblique line in the figure, that is, the boundary position of the polarity reversal domain. It can be seen that the boundary of the polarity reversal domain is the strain concentration area, so strain may be an important reason affecting polarity reversal.

[0067] Further analysis shows that the main reasons affecting the polarity inversion of AlN are as follows: the special interface structure between AlN and h-BN, the special metal-rich growth environment of MOCVD, and the strain state of the AlN epitaxial layer. The B-O-N and B-O bonds generated on the h-BN surface by oxygen plasma treatment are more conducive to adsorbing Al atoms to form a special and stable interfacial configuration of B-O-Al-N, enabling the stable existence of N-polar AlN. The special metal-rich growth environment of MOCVD is more conducive to the growth of metal-polar nitrides. Driven by the metal-rich growth environment and surface energy anisotropy, N-polar AlN spontaneously inverses to metal polarity in the presence of defects. The weak strain state of the epitaxial layer will delay the process of polarity inversion.

[0068] Furthermore, by comparing the strain states and polarity inversion processes of the AlN epitaxial layers on bare sapphire, single-layer h-BN / sapphire, and thick-layer h-BN / sapphire, it is found that the AlN epitaxial layer on bare sapphire is always in a large strain state. Therefore, the N-polar AlN on bare sapphire has completely inverted to Al polarity when it is less than 100 nm. The AlN epitaxial layer on single-layer h-BN / sapphire is in a small compressive strain state. Therefore, the polarity inversion of AlN on single-layer h-BN is delayed to 200 - 600 nm, while the AlN epitaxial layer on thick-layer h-BN / sapphire is always in a weak strain state. Therefore, the polarity inversion of AlN on thick-layer h-BN is further delayed to 200 - 800 nm.

[0069] For example, continue to deposit aluminum nitride on the mixed-polarity aluminum nitride thin film to a preset thickness to obtain an AlN thin film with a thickness greater than 800 nm. The HAADF-STEM image thereof is referred to Figure 8 a in Figure 8 and the (scanning) SEM image of the AlN thin film after being etched by potassium hydroxide (KOH) is referred to Figure 8 a in Figure 8 and b in

[0070] An embodiment of the present disclosure shows an AlN thin film, and the corresponding product structure is successively a substrate, an h-BN buffer layer, an N-polar AlN thin film, a mixed-polarity AlN thin film, and an Al-polar AlN thin film.

[0071] In some exemplary embodiments, the material of the substrate includes one of sapphire, silicon carbide, aluminum nitride, and metal materials.

[0072] In some exemplary embodiments, there is at least 1 layer of the h-BN buffer layer, and the total thickness of the boron nitride buffer layer is greater than 0 and less than or equal to 10 nm. In some exemplary embodiments, the distribution range of the nitrogen-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is 10 nm - 200 nm; the distribution range of the mixed-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is 200 nm - 800 nm; the distribution range of the aluminum-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is the region greater than 800 nm.

[0073] For example, the product structure of the AlN thin film is, in sequence, a sapphire substrate, an h-BN buffer layer, an N-polar AlN thin film, a mixed-polar AlN thin film, and an aluminum-polar AlN thin film.

[0074] A method for regulating the polarity of an AlN thin film according to the present disclosure can regulate the initially grown AlN to be a stable N-polar AlN by using an h-BN buffer layer pretreated with oxygen plasma. And by regulating the number of layers of the h-BN buffer layer, the polarity inversion process of the AlN epitaxial layer can be regulated. Finally, a high-quality and low-stress aluminum-polar AlN thin film is prepared, which is beneficial to the subsequent preparation of a high-quality and polarity-controllable AlN template and has strong practicability.

[0075] So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings.

[0076] The above specific embodiments have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for regulating the polarity of aluminum nitride thin films, wherein, The method includes the following steps: Depositing a hexagonal boron nitride buffer layer on a substrate; Pre-treating the hexagonal boron nitride buffer layer with oxygen plasma to form a hexagonal boron nitride buffer layer having oxygen dangling bonds on the surface; and Depositing aluminum nitride on the pre-treated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain an aluminum nitride thin film; Wherein, depositing aluminum nitride on the pre-treated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain an aluminum nitride thin film includes: Depositing aluminum nitride on the pre-treated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain a nitrogen-polar aluminum nitride thin film; Continuing to deposit aluminum nitride on the nitrogen-polar aluminum nitride to obtain a mixed-polarity aluminum nitride thin film; and Continuing to deposit aluminum nitride on the mixed-polarity aluminum nitride thin film to a preset thickness to obtain an aluminum-polar aluminum nitride thin film.

2. The method for regulating the polarity of aluminum nitride thin films according to claim 1, wherein, Depositing aluminum nitride on the pre-treated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain an aluminum nitride thin film specifically includes: Controlling the distribution range of the mixed-polarity aluminum nitride thin film in the thickness direction of the aluminum nitride thin film by controlling the number of layers of the hexagonal boron nitride buffer layer.

3. The method for regulating the polarity of aluminum nitride thin films according to claim 1 or 2, wherein, The material of the substrate includes one of sapphire, silicon carbide, aluminum nitride, and metal materials.

4. The method for regulating the polarity of aluminum nitride thin films according to claim 1 or 2, wherein, The method for depositing the hexagonal boron nitride buffer layer on the substrate includes one of low-pressure chemical vapor deposition and metal-organic chemical vapor deposition.

5. The method for regulating the polarity of an aluminum nitride thin film according to claim 1 or 2, wherein, The hexagonal boron nitride buffer layer is at least 1 layer, and the total thickness of the boron nitride buffer layer is greater than 0 and less than or equal to 10 nm.

6. The method for regulating the polarity of an aluminum nitride thin film according to claim 1 or 2, wherein, Pre-treating the hexagonal boron nitride buffer layer with oxygen plasma to form a hexagonal boron nitride buffer layer having oxygen dangling bonds on the surface specifically includes: The flow rate of the oxygen plasma is 100 sccm - 300 sccm, the power of the oxygen plasma is 50 w - 200 w, and the pre-treatment time is 1 min - 3 min.

7. The method for regulating the polarity of aluminum nitride thin films according to claim 1 or 2, wherein, Depositing aluminum nitride on the pre-treated hexagonal boron nitride buffer layer by metal-organic chemical vapor deposition to obtain an aluminum nitride thin film specifically includes: The equipment used is a metal-organic chemical vapor deposition equipment, the deposition process temperature is 1100 °C - 1300 °C, the chamber pressure is 40 torr - 50 torr, the aluminum source is trimethylaluminum, the flow rate of the aluminum source is 50 sccm - 150 sccm, the nitrogen source is ammonia, the flow rate of the nitrogen source is 300 sccm - 1000 sccm, and the carrier gas is hydrogen.

8. According to the method for regulating the polarity of an aluminum nitride thin film according to claim 1 or 2, wherein, The distribution range of the nitrogen-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is 10 nm - 200 nm; The distribution range of the mixed-polarity aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is 200 nm - 800 nm; The distribution range of the aluminum-polar aluminum nitride thin film in the thickness direction of the aluminum nitride thin film is in the region greater than 800 nm.

9. According to the method for regulating the polarity of an aluminum nitride thin film according to claim 8, wherein, The deposition time of the nitrogen-polar aluminum nitride thin film is 2 min - 12 min; An aluminum nitride thin film is continuously deposited on the nitrogen-polar aluminum nitride thin film, and the deposition time is 2 min - 36 min to obtain the mixed-polarity aluminum nitride thin film.

10. An aluminum nitride thin film, wherein, The aluminum nitride thin film is prepared by any one of the methods described in claims 1-9.

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