GaN-based heterostructure, manufacturing method and application thereof

Abstract

The application discloses a GaN-based heterostructure, a manufacturing method and application thereof, and grows a cubic phase BN film layer on a GaN substrate through a radio frequency magnetron sputtering technology; grows a diamond film layer on the cubic phase BN film layer through a microwave plasma assisted CVD technology, and finally manufactures the GaN-based heterostructure. Structural similarity between the diamond and the cubic phase BN can avoid film stress generated on a grown heteroepitaxial diamond film. Since each film layer in the GaN-based heterostructure has high thermal conductivity, and there is a covalent bonding mechanism between the layers, heat generated is distributed to the lateral and vertical directions through the diamond film layer, so that the GaN-based heterostructure has good heat dissipation performance. The GaN-based heterostructure has high thermal conductivity, can solve heat dissipation problems in a series of applications such as power electronics and high-speed devices, and avoid film stress, so that the device has good mechanical stability, and has good heat dissipation effect when applied to a HEMT device.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and in particular to a GaN-based heterostructure, its fabrication method, and its applications. Background Technology

[0002] In recent years, group III nitride semiconductor devices have been widely used not only in optical devices but also in electronic devices, such as high electron mobility transistors (hereinafter referred to as "HEMT").

[0003] Due to GaN's inherent advantages in breakdown voltage and operating frequency, and the growing demand for power electronics and RF applications, GaN is expected to become the preferred device for manufacturing a variety of optoelectronic, power electronics, and RF devices. GaN-based semiconductor devices possess advantages such as high temperature resistance, thermal stability, low power consumption, high breakdown voltage, and high electron mobility, making them suitable for various applications in power electronics, automotive / hybrid electric vehicles (HEVs), wireless communications, and micro-LED displays. However, major technical and economic challenges, such as high defect density, limited scalability, and high production costs, limit the application of GaN-based semiconductor devices in the electronics and optoelectronic equipment industries. Furthermore, the poor thermal conductivity of the GaN buffer layer and its growth template leads to poor heat dissipation issues during operation of GaN-based semiconductor devices.

[0004] As power density increases, high-power GaN-based semiconductor devices (such as GaN-based high electron mobility transistors (HEMTs) exhibit significant self-heating effects, leading to a noticeable temperature rise. If this heat cannot be dissipated quickly and effectively, it will severely impact the device's electrical and thermal performance, and even its safety and reliability. Heat dissipation is primarily achieved through heat conduction via the epitaxial layer, semiconductor substrate, bonding layer, and packaging shell. Since the active region, which generates heat, is very small, the heat dissipation capacity of the epitaxial layer and semiconductor substrate, which are adjacent to the active layer, becomes the main factor affecting the device's overall heat dissipation performance.

[0005] Therefore, heat dissipation and device reliability have become urgent issues to be addressed in the fabrication of high-power GaN devices. Summary of the Invention

[0006] To address the current issues of heat dissipation, structural stability, and reliability in GaN-based semiconductor devices, embodiments of this application propose a GaN-based heterostructure, its fabrication method, and its application to solve these problems.

[0007] In a first aspect, this application proposes a method for fabricating a GaN-based heterostructure, comprising the following steps:

[0008] A cubic phase BN thin film was grown on a GaN substrate using radio frequency magnetron sputtering. The magnetron sputtering conditions included operating pressure, radio frequency power, first substrate temperature, and bias voltage applied to the GaN substrate. The operating pressure included base pressure and process pressure, with the base pressure being below 7*10⁻⁶. -4 Pa, process pressure range of 5-20 mTorr, RF power range of 100W-300W, first substrate temperature range of 200-600℃, bias voltage range of 0-200V;

[0009] Diamond films were grown on cubic BN thin films using microwave plasma CVD technology. The conditions used in the microwave plasma CVD technology included chamber pressure and a second substrate temperature. The chamber pressure ranged from 100 to 175 Torr, and the second substrate temperature ranged from 800 to 1150 °C.

[0010] In some embodiments, the target material in the radio frequency magnetron sputtering technology is hexagonal BN, and the sputtering gas is a mixture of argon and nitrogen in a volume ratio of 1-5:1. Under these conditions, BN thin films with a cubic phase close to stoichiometry can be generated.

[0011] In some embodiments, the growth rate of the cubic phase BN thin film layer ranges from 3 to 5 nm / min.

[0012] In some embodiments, the microwave frequency used in the microwave plasma-assisted CVD technology is 915MHz, and the microwave power ranges from 4 to 7kW.

[0013] In some embodiments, the reaction gases used in the microwave plasma-assisted CVD technology are CH4 and H2, wherein the gas flow rate of CH4 is 1%-6% of the gas flow rate of H2. Under this reaction gas and flow rate ratio, the diamond film layer grown on the cubic phase BN film layer has a uniform thickness and the particle size inside the diamond film layer is relatively uniform.

[0014] In some embodiments, the growth rate of the diamond film layer ranges from 2 to 5 μm / h.

[0015] Secondly, embodiments of this application propose a GaN-based heterostructure, which is fabricated using the aforementioned method for fabricating GaN-based heterostructures.

[0016] In some embodiments, the thickness of the cubic phase BN thin film ranges from 1 nm to 100 nm. The cubic phase BN thin film can be amorphous, polycrystalline, or single-crystal.

[0017] In some embodiments, the thickness of the diamond film layer ranges from 1µm to 100µm. The diamond film is a heat-resistant polycrystalline or monocrystalline material.

[0018] Thirdly, embodiments of this application propose an application of the GaN-based heterostructure described above in HEMT devices.

[0019] This application discloses a GaN-based heterostructure, its fabrication method, and its applications. A high-quality cubic phase BN thin film layer is grown on a GaN substrate, followed by a diamond thin film layer, thus forming a GaN-based heterostructure. The cubic phase BN thin film layer has tetrahedral coordination with sp3 bonds, which is beneficial for forming heterostructures in nitride semiconductors. The structural similarity between diamond and cubic phase BN avoids film stress on the grown heteroepitaxial diamond film. Since each layer in the GaN-based heterostructure has high thermal conductivity and there is a covalent bonding mechanism between the layers, the generated heat is distributed in the lateral and vertical directions through the diamond thin film layer, giving the GaN-based heterostructure excellent heat dissipation performance. The high thermal conductivity of the GaN-based heterostructure will solve heat dissipation problems in a range of applications such as power electronics and high-speed devices, and avoid film stress, resulting in devices with good mechanical stability. Attached Figure Description

[0020] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of the invention. Other embodiments and many anticipated advantages of the embodiments will be readily recognized as they become better understood through reference to the following detailed description. Elements in the drawings are not necessarily to scale. The same reference numerals refer to corresponding similar parts.

[0021] Figure 1 This is a schematic diagram illustrating a method for fabricating a GaN-based heterostructure according to an embodiment of this application;

[0022] Figure 2 This is a schematic diagram of a GaN substrate according to an embodiment of this application;

[0023] Figure 3 This is a schematic diagram of the growth of a cubic phase BN thin film layer on a GaN substrate, as an embodiment of this application.

[0024] Figure 4 This is a schematic diagram of a GaN-based heterostructure according to an embodiment of this application;

[0025] Figure 5 This is an external view of a GaN-based heterostructure according to an embodiment of this application;

[0026] Figure 6 The Fourier transform infrared spectroscopy results are for the GaN-based heterostructure BN thin film layer of Example 1 of this application.

[0027] Figure 7 The image shows a scanning electron microscope (SEM) image of a diamond thin film layer with a GaN-based heterostructure as described in Example 1 of this application.

[0028] Figure 8 The Fourier transform infrared spectroscopy results are for the GaN-based heterostructure BN thin film layer of Example 2 of this application.

[0029] Figure 9 XPS test results for the GaN-based heterostructure BN thin film layer of Example 2 of this application;

[0030] Figure 10 The image shows the XRD pattern of the GaN-based heterostructure of Example 3 of this application.

[0031] Figure 11 The Fourier transform infrared spectroscopy results are shown for a comparative GaN-based heterostructure BN thin film.

[0032] Figure 12 XPS test results for BN thin films with GaN-based heterostructures as a comparative example;

[0033] Figure 13 The results of thermal mapping comparison of HEMT devices. Figure 13 a is a schematic diagram of the HEMT device. Figure 13 b is a thermal diagram of HEMT devices fabricated using a GaN substrate; Figure 13 c is a thermal diagram of the application of GaN-based heterostructures in HEMT devices according to an embodiment of this application. Detailed Implementation

[0034] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] An embodiment of the present invention proposes a method for fabricating GaN-based heterostructures, such as... Figure 1 As shown, it includes the following steps:

[0037] S1: A cubic phase BN thin film layer is grown on a GaN substrate using radio frequency magnetron sputtering technology;

[0038] S2: Diamond thin film layer is grown on cubic phase BN thin film layer by microwave plasma-assisted CVD technology.

[0039] For GaN substrates, commercially available self-supporting GaN substrates or GaN substrates heteroepitaxially fabricated on sapphire, SiC, Si, or other substrates can be used. Among GaN substrate growth technologies, hydride vapor phase epitaxy (HVPE) is the preferred process due to its high growth rate (reaching over 800 μm / h), low cost, ability to grow large areas, and good uniformity. Other fabrication processes, such as the ammoniathermal method, HNPSG, and NaFlux, can also be used, but will not be elaborated upon here. Figure 2 The diagram shown is of a GaN substrate.

[0040] Cubic boron nitride (c-BN) has tetrahedral coordination with sp3 bonds, which can provide high thermal conductivity and large band gap. The tetrahedral coordination of c-BN is conducive to forming heterostructures with nitride semiconductors. Therefore, bare GaN substrates are used for the growth of c-BN.

[0041] Since diamond and cubic boron nitride (c-BN) share the same structural characteristics and have very small differences in lattice constants (Δa = 1.3%), forming a diamond thin film on cubic boron nitride (c-BN) has significant advantages. Furthermore, microwave plasma-assisted CVD (MPACVD) is the most economical and efficient method for growing high-quality diamond thin films. Therefore, this application employs MPACVD technology to grow a high-quality diamond thin film on a cubic BN thin film, ultimately forming a diamond / c-BN / GaN heterostructure with good heat dissipation performance and low film stress.

[0042] like Figure 1 S1 and Figure 3 As shown, step S1 is performed first, in which a cubic phase BN thin film layer 200 is grown on a GaN substrate 100 by radio frequency magnetron sputtering.

[0043] The process of growing a cubic BN thin film layer 200 on a GaN substrate 100 in this application employs an radio frequency magnetron sputtering system, using hexagonal BN as the target material. Applying a negative bias voltage to the GaN substrate 100 facilitates the formation of a high-quality cubic BN thin film layer 200 on the GaN substrate 100. During this process, the magnetron sputtering conditions include operating pressure, radio frequency power, first substrate temperature, and the bias voltage applied to the GaN substrate 100. The operating pressure includes a base pressure and a process pressure, with the base pressure being below 7*10⁻⁶. -4The process pressure is 5-20 mTorr, the first substrate temperature is 200-600℃, and the bias voltage is 0-200V. The RF power ranges from 100W to 300W, more preferably 150W to 250W. Within this RF power range, good cubic phase BN thin films can be grown using 3-6 inch hexagonal BN. When using 3-inch hexagonal BN as the target, the RF power is 300W, which allows for the growth of a good cubic phase BN thin film 200. The sputtering gas is a mixture of argon and nitrogen in a volume ratio of 1-5:1. Under these conditions, a cubic phase BN thin film 200 with near-stoichiometric proportions can be generated. Under precise growth conditions, the growth rate of the cubic phase BN thin film 200 is 3-5 nm / min. The thickness of the cubic phase BN thin film 200 produced through the above steps ranges from 1 nm to 100 nm. The cubic phase BN thin film layer 200 can be amorphous, polycrystalline, or monocrystalline.

[0044] Then proceed to step S2, such as Figure 1 S2 and Figure 4As shown, a diamond thin film layer 300 is grown on a cubic BN thin film layer 200 using microwave plasma-assisted CVD (CPCVD). The conditions used in the CPCVD technique include chamber pressure and a second substrate temperature. The chamber pressure is 100-175 Torr. When the pressure is too low, insufficient gas dissociation leads to more secondary nucleation and poor surface quality. When the pressure is too high, electrons collide frequently with gas molecules, preventing effective electron acceleration and thus reducing energy and surface quality. The second substrate temperature ranges from 800-1150℃. Temperatures below 800℃ result in very low nucleation density of the diamond thin film layer 300, hindering continuous growth. Temperatures above 1150℃ cause severe overheating of the substrate during diamond deposition, also negatively impacting the formation of the diamond thin film layer 300. The microwave frequency is 915MHz. The reaction gases used in the microwave plasma-assisted CVD technology are CH4 and H2. The gas flow rate of CH4 is 1%-6% of the gas flow rate of H2, specifically, the gas flow rates of CH4 and H2 range from 30:3000 to 30:500 sccm. When the CH4 / H2 flow rate is <1.0%, secondary nucleation is obvious in the diamond film layer 300, resulting in small grain size, which is not conducive to improving the thermal conductivity of the diamond film layer 300. When the CH4 / H2 flow rate is >6.0%, larger grains can be obtained in the diamond film layer 300, but twins are easily generated between crystal faces and grains, and the non-diamond phase increases significantly. Under this reaction gas and flow rate, the microwave power of this microwave plasma-assisted CVD technology is adjusted between 4-7kW. When the microwave power is below 4kW, the grain size on the diamond film surface is small, with many grain boundaries, and the growth quality is relatively poor. When the microwave power is above 7kW, the grain size on the diamond surface increases, but the growth of twins becomes very obvious. The final grown diamond film layer 300 has a thickness ranging from 1µm to 100µm. The diamond film layer 300 is a heat-resistant polycrystalline or single-crystal material. After the growth of the diamond film layer 300, a GaN-based heterostructure with a structure of diamond / c-BN / GaN can be obtained, such as... Figure 5 The image shown is an external view of a GaN-based heterostructure.

[0045] The GaN-based heterostructure with diamond / c-BN / GaN structure obtained by the above method has high purity, uniform grain distribution, high growth quality, and good bonding quality between film layers. Therefore, the GaN-based heterostructure has high overall interface strength and good heat dissipation.

[0046] The technical solution of this application will be illustrated by the following embodiments.

[0047] Example 1

[0048] First, a GaN substrate is provided and placed in an RF magnetron sputtering chamber. A cubic phase BN thin film is grown on the GaN substrate using RF magnetron sputtering technology, employing a 4-inch hexagonal BN film, with the base pressure set to below 7*10. -4 The substrate temperature was raised to 300°C, and a gas mixture with an argon-nitrogen ratio of 2:1 (by volume) was introduced. The process pressure was adjusted to 5 mTorr, the RF power was controlled at 150 W, and the sputtering time was 15 minutes. A bias voltage of 50 V was applied to the GaN on the substrate. A BN thin film was grown under these conditions, and the resulting BN thin film was subjected to Fourier transform infrared spectroscopy (FTIR) analysis. Figure 6 The Fourier transform infrared spectroscopy test results shown indicate that at 1100 cm⁻¹ -1 A peak corresponding to c-BN appears nearby, at 1400 cm⁻¹. -1 No peaks corresponding to h-BN were found nearby, therefore c-BN exists in the BN film layer grown under these conditions, and no h-BN was found.

[0049] A GaN substrate with a cubic BN thin film layer was placed in a microwave plasma CVD reaction chamber. A diamond thin film layer was grown using microwave plasma CVD technology. CH4 and H2 were introduced at flow rates of 30 sccm and 1000 sccm, respectively. The chamber pressure was adjusted to 120 Torr, the second substrate temperature to 900℃, and the microwave power to 5 kW. Finally, a diamond thin film layer was grown on the cubic BN thin film layer. Figure 7 The scanning electron microscope images shown indicate that a diamond film layer with uniform surface grains was grown under these conditions, and the grains were tightly bonded together, demonstrating that a dense diamond film layer can be grown on the c-BN film layer.

[0050] Example 2

[0051] First, a GaN substrate is provided and placed in an RF magnetron sputtering reaction chamber. A cubic phase BN thin film is grown on the GaN substrate using RF magnetron sputtering technology, employing a 5-inch hexagonal BN film, with the base pressure set to below 7*10. -4 The substrate temperature was raised to 400℃, and a gas mixture with an argon-nitrogen ratio of 4:1 (by volume) was introduced. The process pressure was adjusted to 15 mTorr, the RF power was controlled at 200 W, and the sputtering time was 30 minutes. A bias voltage of 150 V was applied to the GaN on the substrate. A BN thin film was grown under these conditions, and the resulting BN thin film was subjected to Fourier transform infrared spectroscopy (FTIR) analysis. Figure 8 The Fourier transform infrared spectroscopy test results shown indicate that at 1100 cm⁻¹ -1 A peak corresponding to c-BN appears nearby, at 1400 cm⁻¹. -1No peaks corresponding to h-BN were found nearby. Furthermore, as... Figure 9 The XPS test results show that the BN film layer contains c-BN, and no h-BN phase was found. Therefore, the BN film layer grown under these conditions contains c-BN, and no h-BN phase was found.

[0052] A GaN substrate with a cubic BN thin film layer was placed in a microwave plasma CVD reaction chamber, and a diamond thin film layer was grown using microwave plasma CVD technology. CH4 and H2 were introduced at flow rates of 30 sccm and 1500 sccm, respectively. The chamber pressure was adjusted to 150 Torr, the second substrate temperature was 1000℃, and the microwave power was 6 kW. Finally, a diamond thin film layer was grown on the cubic BN thin film layer. Under these conditions, the diamond thin film layer exhibited uniform surface grains and tight bonding between grains, demonstrating that a dense diamond thin film layer can be grown on the c-BN thin film layer.

[0053] Example 3

[0054] First, a GaN substrate is provided and placed in an RF magnetron sputtering chamber. A cubic phase BN thin film is grown on the GaN substrate using RF magnetron sputtering technology, employing a 3-inch hexagonal BN film, with the base pressure set to below 7*10. -4 The substrate temperature was raised to 350°C, and a mixture of argon and nitrogen in a volume ratio of 3:1 was introduced. The process pressure was adjusted to 16 mTorr, the RF power was controlled at 300 W, and the sputtering time was 15 minutes. A bias voltage of 120 V was applied to GaN on the substrate. A cubic phase BN thin film was grown under these conditions.

[0055] A GaN substrate with a cubic BN thin film layer was placed in a microwave plasma CVD reaction chamber. A diamond thin film layer was grown using microwave plasma CVD technology. CH4 and H2 were introduced at flow rates of 30 sccm and 3000 sccm, respectively. The chamber pressure was adjusted to 120 Torr, the second substrate temperature to 1150℃, and the microwave power to 5.5 kW. Finally, a diamond thin film layer was grown on the cubic BN thin film layer. Figure 10 The XRD results shown indicate that the diamond grown on c-BN has high purity.

[0056] Comparative Example

[0057] First, a GaN substrate is provided and placed in an RF magnetron sputtering reaction chamber. A cubic phase BN thin film is grown on the GaN substrate using RF magnetron sputtering technology. The magnetron sputtering conditions are controlled as follows: the base pressure is below 7*10. -4The substrate temperature was raised to 350°C, and a gas mixture with an argon-nitrogen ratio of 3:1 (by volume) was introduced. The process pressure was adjusted to 10 mTorr, the RF power was controlled at 350 W, and the sputtering time was 15 minutes. A bias voltage of 100 V was applied to the GaN on the substrate. A BN thin film was grown under these conditions, and the resulting BN thin film was subjected to Fourier transform infrared spectroscopy (FTIR) analysis. Figure 11 The Fourier transform infrared spectroscopy test results shown indicate that at 1100 cm⁻¹ -1 A peak corresponding to c-BN appears nearby, at 1400 cm⁻¹. -1 A peak corresponding to h-BN appears nearby, and further, such as Figure 12 The XPS test results show that c-BN exists in the BN film layer, but a weak and relatively broad π-bond co-peak appears in front of B1s, indicating the presence of the h-BN phase in the product. Therefore, a small amount of h-BN phase exists in the BN film layer grown under these conditions.

[0058] A GaN substrate with a BN thin film was placed in a microwave plasma CVD chamber, and a diamond thin film was grown using microwave plasma CVD technology. CH4 and H2 were introduced at flow rates of 30 sccm and 2000 sccm, respectively. The chamber pressure was adjusted to 10 Torr, the second substrate temperature was 950℃, and the microwave power was 5.5 kW. A diamond thin film was ultimately grown on the BN thin film. However, due to the excessively high radio frequency power in magnetron sputtering, an h-BN phase was introduced into the BN thin film. The h-BN phase has a different crystal structure and lattice constant than diamond, making it difficult to grow a dense diamond thin film under these conditions, thus affecting diamond growth.

[0059] This embodiment also provides a GaN-based heterostructure, which can be prepared using the preparation method described in the above embodiment. The GaN-based heterostructure includes a GaN substrate 100, a cubic BN thin film layer 200, and a diamond thin film layer 300. The thickness of the cubic BN thin film layer 200 in the GaN-based heterostructure ranges from 1 nm to 100 nm, and the cubic BN thin film layer 200 can be amorphous, polycrystalline, or single-crystal. The thickness of the diamond thin film layer 300 in the GaN-based heterostructure ranges from 1 μm to 100 μm. The diamond thin film layer 300 is a heat-resistant polycrystalline or single-crystal. The final GaN-based heterostructure has a thermal conductivity of 500-1000 W / (m*K), while the thermal conductivity of GaN is 130 W / (m*K). Therefore, the GaN-based heterostructure with the structure diamond / c-BN / GaN has good thermal performance.

[0060] The GaN-based heterostructure of this application can be used in HEMT devices, providing excellent heat dissipation. The surface temperature of the HEMT device was measured under both the use of a GaN substrate and the GaN-based heterostructure of this application. Figure 13 Heat map, Figure 13 a is a schematic diagram of a HEMT device. Figure 13 b is a thermal diagram of a HEMT device using a GaN substrate. Figure 13 Figure c shows a thermal diagram of the HEMT device using the GaN-based heterostructure of this application. It is evident that the HEMT device using the GaN-based heterostructure of this application exhibits excellent heat dissipation. The generated heat is distributed laterally and vertically through the diamond thin film layer, preventing heat concentration within the device and minimizing its impact on electrical and mechanical properties, thereby improving device reliability and stability. This high thermal conductivity structure will solve heat dissipation problems in a range of applications, including power electronics and high-speed devices.

[0061] This application discloses a GaN-based heterostructure, its fabrication method, and its applications. A high-quality cubic phase BN thin film layer is grown on a GaN substrate, followed by a diamond thin film layer, thus forming a GaN-based heterostructure. The cubic phase BN thin film layer has tetrahedral coordination with sp3 bonds, which is beneficial for forming heterostructures in nitride semiconductors. The structural similarity between diamond and cubic phase BN avoids film stress on the grown heteroepitaxial diamond film. Since each layer in the GaN-based heterostructure has high thermal conductivity and there is a covalent bonding mechanism between the layers, the generated heat is distributed in the lateral and vertical directions through the diamond thin film layer, giving the GaN-based heterostructure excellent heat dissipation performance. The high thermal conductivity of the GaN-based heterostructure will solve heat dissipation problems in a range of applications such as power electronics and high-speed devices, and avoids film stress, resulting in devices fabricated from GaN-based heterostructures with good mechanical stability.

[0062] The specific embodiments of this application have been described above, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0063] In the description of this application, it should be understood that the terms "upper," "lower," "inner," "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and for simplification, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The simple fact that certain measures are recited in mutually different dependent claims does not indicate that combinations of these measures cannot be used for improvement. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A method for fabricating a GaN-based heterostructure, characterized in that, Includes the following steps: A cubic phase BN thin film was grown on a GaN substrate using radio frequency magnetron sputtering. The magnetron sputtering conditions included operating pressure, radio frequency power, a first substrate temperature, and a bias voltage applied to the GaN substrate. The operating pressure included a base pressure and a process pressure, with the base pressure ranging from less than 7 * 10⁻⁶. -4 Pa, the process pressure ranges from 5 to 20 mTorr, the radio frequency power ranges from 100 W to 300 W, the first substrate temperature ranges from 200 to 600 °C, the bias voltage ranges from 0 to 200 V, the target material in the radio frequency magnetron sputtering technology is hexagonal BN, and the sputtering gas is a mixture of argon and nitrogen with a volume ratio of 1 to 5:

1. A diamond thin film layer is grown on the cubic phase BN thin film layer by microwave plasma CVD technology. The conditions used in the microwave plasma CVD technology include chamber pressure and a second substrate temperature. The chamber pressure ranges from 100 to 175 Torr, and the second substrate temperature ranges from 800 to 1150 °C.

2. The method for fabricating a GaN-based heterostructure according to claim 1, characterized in that, The growth rate of the cubic phase BN thin film is in the range of 3-5 nm / min.

3. The method for fabricating a GaN-based heterostructure according to claim 1, characterized in that, The microwave plasma-assisted CVD technology uses a microwave frequency of 915 MHz and a microwave power range of 4-7 kW.

4. The method for fabricating a GaN-based heterostructure according to claim 1, characterized in that, The reaction gases used in the microwave plasma-assisted CVD technology are CH4 and H2, wherein the gas flow rate of CH4 is 1%-6% of the gas flow rate of H2.

5. The method for fabricating a GaN-based heterostructure according to claim 1, characterized in that, The growth rate of the diamond film layer ranges from 2 to 5 µm / h.

6. A GaN-based heterostructure, characterized in that, It is fabricated using the method for fabricating GaN-based heterostructures according to any one of claims 1-5.

7. The GaN-based heterostructure according to claim 6, characterized in that, The thickness of the cubic phase BN thin film layer ranges from 1 nm to 100 nm.

8. The GaN-based heterostructure according to claim 6, characterized in that, The thickness of the diamond film layer ranges from 1 µm to 100 µm.

9. The application of a GaN-based heterostructure according to any one of claims 6-8 in a HEMT device.

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