Silicon carbide-based GaN HEMT epitaxial wafer, device and manufacturing method thereof

Abstract

The invention belongs to the field of semiconductors, and relates to a silicon carbide-based GaN HEMT epitaxial wafer, a silicon carbide-based GaN HEMT device and a manufacturing method thereof. After the graphene layer is grown on the surface of the silicon carbide substrate by adopting the sublimation epitaxy method, the graphene and the silicon carbide are firmly combined with the substrate, the crystal quality is very high, the thermal conductivity is very high, and the performance of the GaN epitaxial wafer is improved through stress regulation and control. Then, the first AlN layer is grown on the surface of the graphene layer by adopting PVD (Physical Vapor Deposition), since AlN is of a hexagonal crystal structure and is matched with a regular hexagonal crystal structure of graphene, and the surface morphology of AlN has an inheriting effect on the morphology of graphene, a high-density AlN layer can be formed, the growth of a high-temperature AlN nucleating layer is facilitated, and a basis is provided for the subsequent growth of high-quality GaN. The preparation method disclosed by the invention is simple and easy to implement, and the repeatability and reliability of mass production can be guaranteed; and the subsequent process of the device is not influenced.

Description

Technical Field

[0001] The patent of this invention belongs to the field of semiconductors and relates to a silicon carbide-based GaN HEMT epitaxial wafer, device and its manufacturing method. Background Art

[0002] GaN HEMT (High Electron Mobility Transistor) power devices have significant advantages such as high voltage resistance, low on-resistance, fast reverse recovery, high frequency, and high FOM value. Solutions using GaN HEMT power devices are small in size and have high conversion efficiency. They can be widely used in fast charging of consumer electronics such as mobile phones, industrial power supplies, AI power supplies, automotive lidar, OBC and other applications.

[0003] Improving the power density of GaN HEMT power devices requires two prerequisites: 1. Higher crystal quality and better heat dissipation characteristics; 2. Lower trap effects to avoid current collapse. Traditional HEMT devices use a GaN buffer layer, which requires C or Fe doping of the GaN, thus introducing a large number of deep-level defects. Secondly, to ensure the high breakdown voltage and frequency characteristics of GaN HEMTs, high-quality epitaxial films are an important guarantee. Due to the high lattice mismatch, HEMTs in the current field are mainly epitaxially grown on sapphire, silicon, and silicon carbide substrates. However, sapphire and silicon have poor thermal conductivity, which affects the heat dissipation characteristics of HEMT devices under high-power operating conditions.

[0004] Therefore, from the perspective of lattice constant and thermal conductivity, silicon carbide substrates are ideal substrates for GaN HEMT epitaxy. However, single-crystal silicon carbide is expensive and the growth process is complex. Further improving the performance of GaN HEMT epitaxial wafers on silicon carbide to offset this cost disadvantage is a key prerequisite for the widespread deployment of GaN HEMT devices on silicon carbide. Graphene has a thermal conductivity 6-10 times that of silicon carbide. At GaN growth temperatures ranging from room temperature to 1000°C, the thermal expansion coefficients of GaN, graphene, and silicon carbide range from 5.59 ppm / K, -7 ppm / K, and 4.2 ppm / K to approximately 6.0 ppm / K, 0, and 5.0 ppm / K, respectively. Inserting graphene at the interface between silicon carbide and GaN can significantly improve thermal conductivity and regulate stress changes during epitaxial growth, thereby fully realizing the potential of GaN HEMT devices. Summary of the Invention

[0005] One of the objectives of the present invention is to address the problem of improving the performance of GaN HEMT on SiC and provide a method for preparing high-performance silicon carbide-based GaN HEMT epitaxial wafers to improve the power of GaN HEMT.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a silicon carbide-based GaN HEMT epitaxial wafer, comprising the following steps:

[0007] Providing silicon carbide substrates;

[0008] placing a silicon carbide substrate in a reaction chamber to grow a graphene layer;

[0009] The silicon carbide substrate on which the graphene layer has been grown is placed in a PVD reaction chamber to grow a first AlN layer;

[0010] The silicon carbide substrate on which the graphene layer and the first AlN layer have been grown is placed in an MOCVD reaction chamber to sequentially grow a second AlN layer, a U-type GaN layer, an AlN insertion layer, an AlGaN layer and a GaN cap layer.

[0011] As a further improvement to the preparation method of silicon carbide-based GaN HEMT epitaxial wafers:

[0012] Preferably, the specific process of growing the graphene layer is as follows: a silicon carbide substrate is placed in a reaction chamber, and under a high vacuum environment, the temperature of the reaction chamber is controlled to be 1300°C to 1400°C. Through the sublimation and volatilization of silicon atoms, carbon atoms are rearranged on the surface of the SiC crystal to form a graphene layer with a thickness of 1nm to 2nm.

[0013] Preferably, the specific process for growing the first AlN layer is as follows: placing the silicon carbide substrate on which the graphene layer has been grown in a PVD reaction chamber, controlling the reaction chamber temperature to 600°C to 700°C, using an Al target, introducing Ar gas and N2 gas, the introduction ratio of Ar gas to N2 gas being (4 to 6): 1, and coating a first AlN layer with a thickness of 10nm to 120nm.

[0014] Preferably, the specific process for growing the second AlN layer is as follows: control the pressure of the reaction chamber to 20mbar~200mbar, the temperature to 850℃~1050℃, introduce NH3 as the N source and TMAl as the Al source, and grow a second AlN layer with a thickness of 30nm~100nm.

[0015] Preferably, the specific process for growing a U-type GaN layer is as follows: control the pressure of the reaction chamber to 100mbar~400mbar, the temperature to 1080℃~1100℃, introduce NH3 as the N source and TMGa as the Ga source, and grow a U-type GaN layer with a thickness of 1μm~1.5μm.

[0016] Preferably, the specific process for growing the AlN insertion layer is as follows: control the pressure of the reaction chamber to 100mbar~200mbar, the temperature to 950℃~1000℃, introduce NH3 as the N source and TMAl as the Al source, and grow an AlN insertion layer with a thickness of 0.5nm~1nm.

[0017] Preferably, the specific process for growing the AlGaN layer is as follows: control the pressure of the reaction chamber to 100mbar~200mbar, the temperature to 1000℃~1100℃, introduce NH3 as the N source, TMAl as the Al source, and TMGa as the Ga source, and grow an AlGaN layer with a thickness of 15nm~30nm.

[0018] Preferably, the specific process of the GaN cap layer is as follows: control the pressure of the reaction chamber to 100mbar~200mbar, the temperature to 1080℃~1100℃, introduce NH3 as the N source and TMGa as the Ga source, and grow a GaN cap layer with a thickness of 1nm~5nm.

[0019] A second object of the present invention is to provide a silicon carbide-based GaN HEMT epitaxial wafer produced by any of the above-mentioned methods for producing a silicon carbide-based GaN HEMT epitaxial wafer, wherein the silicon carbide-based GaN HEMT epitaxial wafer structure comprises, from bottom to top, a silicon carbide substrate, a graphene layer, a first AlN layer, a second AlN layer, a U-type GaN layer, an AlN insertion layer, an AlGaN layer, and a GaN cap layer.

[0020] A third object of the present invention is to provide a silicon carbide-based GaN HEMT device, comprising the above-mentioned silicon carbide-based GaN HEMT epitaxial wafer.

[0021] The beneficial effects of the present invention compared to the prior art are:

[0022] (1) The present invention provides a method for preparing a silicon carbide-based GaN HEMT epitaxial wafer. After a graphene layer is grown on the surface of a silicon carbide substrate using sublimation epitaxy, the graphene, silicon carbide, and substrate are firmly bonded, resulting in high crystal quality and extremely high thermal conductivity. Stress regulation is also employed to improve the performance of the GaN epitaxial wafer. A first AlN layer is then grown on the surface of the graphene layer using PVD. Because AlN has a hexagonal crystal structure that matches the regular hexagonal crystal structure of graphene, the surface morphology of AlN inherits the morphology of graphene, allowing the formation of a high-density AlN layer. This is more conducive to the growth of a high-temperature AlN nucleation layer, providing a foundation for subsequent high-quality GaN growth.

[0023] (2) The method of the present invention solves the problem of low thermal conductivity of sapphire or silicon substrates in traditional GaN power devices, especially the thermal conductivity problem of high-power devices, significantly improving the heat dissipation efficiency and the efficiency of the device. The preparation method of the GaN HEMT device and the HEMT device structure adopted by the present invention can be prepared by in-situ graphene, which is simple and easy to implement, can ensure the repeatability and reliability of mass production; and has no effect on the subsequent processes of the device. The method described in the present invention has a wide range of applications and can be applied to various GaN HEMT devices. The process of the present invention is simple, stable, and highly operable, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a structural diagram of the silicon carbide-based GaN HEMT epitaxial wafer of the present invention;

[0025] The meanings of the symbols in the accompanying drawings are as follows:

[0026] 10. Silicon carbide substrate; 20. Graphene layer; 30. First AlN layer; 40. Second AlN layer; 50. U-type GaN layer; 60. AlN insertion layer; 70. AlGaN layer; 80. GaN cap layer. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] The present invention provides a method for preparing a silicon carbide-based GaN HEMT epitaxial wafer, comprising the following steps:

[0029] Providing silicon carbide substrates;

[0030] placing a silicon carbide substrate in a sublimation reaction chamber to grow a graphene layer;

[0031] The silicon carbide substrate on which the graphene layer has been grown is placed in a PVD reaction chamber to grow a first AlN layer;

[0032] The silicon carbide substrate on which the graphene layer and the first AlN layer have been grown is placed in an MOCVD reaction chamber to sequentially grow a second AlN layer, a U-type GaN layer, an AlN insertion layer, an AlGaN layer and a GaN cap layer.

[0033] The present invention provides a method for preparing a silicon carbide-based GaN HEMT epitaxial wafer. After a graphene layer is grown on the surface of a silicon carbide substrate using a sublimation epitaxial method, the graphene, silicon carbide, and substrate are firmly bonded, resulting in high crystal quality and extremely high thermal conductivity. Furthermore, stress regulation is used to improve the performance of the GaN epitaxial wafer.

[0034] Then, the first AlN layer is grown on the surface of the graphene layer using PVD. Since AlN has a hexagonal crystal structure that matches the regular hexagonal crystal structure of graphene, the surface morphology of AlN inherits the morphology of graphene, forming a high-density AlN layer, which is more conducive to the growth of a high-temperature AlN nucleation layer and provides a foundation for subsequent high-quality GaN growth.

[0035] Specifically, in some embodiments, placing the silicon carbide substrate in a sublimation reaction chamber to grow a graphene layer includes:

[0036] Under a high vacuum environment, the temperature of the reaction chamber is controlled at 1300℃~1400℃. Through the sublimation and volatilization of silicon atoms, carbon atoms are rearranged on the surface of the SiC crystal to form a graphene layer with a thickness of 1nm~2nm.

[0037] Preferably, the reaction chamber temperature is controlled at 800-900°C, CH4 gas is introduced as a C source, the C source flow rate is 20sccm-30sccm, Ar gas and H2 gas are introduced as carrier gases, the Ar gas flow rate is 190sccm-200sccm, and the H2 gas flow rate is 20sccm-90sccm, and a graphene layer with a thickness of 1nm-2nm is grown.

[0038] It should be noted that the graphene layer maintains a thickness of 1nm to 2nm, presenting a two-dimensional crystal distribution with a hexagonal lattice, which facilitates the quality of subsequent AlN thin film growth. Thickness exceeding 2nm does not significantly improve the quality of subsequent material growth. Furthermore, the graphene layer grown using the sublimation method offers high crystal quality and exceptional thermal conductivity, contributing to improved HEMT device performance.

[0039] In some embodiments, placing the silicon carbide substrate on which the graphene layer has been grown in a PVD reaction chamber to grow the first AlN layer includes:

[0040] The reaction chamber temperature is controlled at 600°C to 700°C, an Al target is used, Ar gas and N2 gas are introduced, the introduction ratio of Ar gas to N2 gas is (4 to 6):1, and a first AlN layer with a thickness of 40nm to 120nm is plated.

[0041] Preferably, the reaction chamber temperature is controlled at 600° C. to 700° C., an Al target is used, Ar gas and N 2 gas are introduced, the introduction ratio of Ar gas to N 2 gas is 5:1, and a first AlN layer with a thickness of 40 nm to 120 nm is deposited.

[0042] The thickness of the first AlN layer is maintained at 10 nm to 120 nm. In addition, the AlN layer grown using the PVD method generally has good adhesion to the substrate, and can achieve uniform growth of AlN thin films over a large area.

[0043] In some embodiments, the method for preparing the second AlN layer includes:

[0044] The pressure of the reaction chamber is controlled to be 100 mbar to 200 mbar, and the temperature is controlled to be 950° C. to 1050° C., NH 3 is introduced as the N source and TMAl is introduced as the Al source, and a second AlN layer with a thickness of 30 nm to 100 nm is grown.

[0045] It should be noted that the second AlN layer is a high-temperature growth layer. If the growth temperature is too low, the subsequent GaN cannot be completely merged, resulting in poor crystal quality. If the growth temperature is too high, TMAl and NH3 will pre-react severely, affecting the quality of AlN. The second AlN layer grown at high temperature is maintained at 30-100nm. A thickness lower than this is not conducive to the subsequent growth of the U-type GaN layer, the background electron concentration is too high, and the surface morphology and crystal quality are poor. Thickening is conducive to improving the above situation, and it tends to saturation after exceeding 100nm. The second AlN layer grown at high temperature realizes a high-quality epitaxial layer, effectively overcoming the leakage problem.

[0046] In some embodiments, the method for preparing the U-type GaN layer includes:

[0047] The pressure of the reaction chamber is controlled to be 100mbar to 400mbar, the temperature is 1080℃ to 1100℃, NH3 is introduced as the N source and TMGa is introduced as the Ga source, and a U-type GaN layer with a thickness of 1μm to 1.5μm is grown.

[0048] The U-type GaN layer realizes high-resistance GaN, and has a thickness of 1 μm to 1.5 μm. Thickness exceeding this range has a significant impact on crystal quality and dislocation density.

[0049] In some embodiments, the method for preparing the AlN insertion layer includes:

[0050] The pressure of the reaction chamber is controlled to be 100mbar to 200mbar, and the temperature is 950℃ to 1000℃. NH3 is introduced as the N source and TMAl is introduced as the Al source to grow an AlN insertion layer with a thickness of 0.5nm to 1nm.

[0051] The AlN insertion layer improves electron mobility and has a growth thickness of 0.5 nm to 1 nm. Too thick a thickness will bring great stress to the GaN layer, thereby affecting the epitaxial quality of the AlGaN layer and reducing mobility.

[0052] In some embodiments, the method for preparing the AlGaN layer includes:

[0053] The pressure of the reaction chamber is controlled to be 100mbar-200mbar, and the temperature is 1000℃-1100℃. NH3 is introduced as the N source, TMAl as the Al source, and TMGa as the Ga source to grow an AlGaN layer with a thickness of 15nm-30nm.

[0054] The AlGaN layer forms a two-dimensional electron gas. In some embodiments, the Al content is 0.25-0.3. The thickness and Al content affect the density and mobility of the two-dimensional electron gas.

[0055] In some embodiments, the method for preparing the GaN cap layer includes:

[0056] The reaction chamber is controlled at a pressure of 100mbar to 200mbar and a temperature of 1080°C to 1100°C, and NH3 is introduced as an N source and TMGa as a Ga source to grow a GaN cap layer with a thickness of 1nm to 5nm. The GaN cap layer improves the mobility of the two-dimensional electron gas.

[0057] Accordingly, if Figure 1 As shown, the present invention further provides a silicon carbide-based GaN HEMT epitaxial wafer, which is produced by the method for producing a silicon carbide-based GaN HEMT epitaxial wafer described above. The silicon carbide-based GaN HEMT epitaxial wafer includes a silicon carbide substrate 10, on which a graphene layer 20, a first AlN layer 30, a second AlN layer 40, a U-type GaN layer 50, an AlN insertion layer 60, an AlGaN layer 70, and a GaN cap layer 80 are sequentially provided. Furthermore, the present invention further provides a HEMT, which includes the silicon carbide-based GaN HEMT epitaxial wafer.

[0058] Example 1

[0059] This embodiment provides a method for preparing a silicon carbide-based GaN HEMT epitaxial wafer, comprising the following steps:

[0060] providing a silicon carbide substrate 10;

[0061] The silicon carbide substrate 10 is placed in a sublimation reaction chamber to grow a graphene layer 20, including: controlling the temperature of the reaction chamber to 1300°C in a high vacuum environment, and allowing silicon atoms to sublime and evaporate, and carbon atoms to rearrange on the SiC crystal surface to form a graphene layer 20 with a thickness of 2nm.

[0062] The silicon carbide substrate 10 on which the graphene layer 20 has been grown is placed in a PVD reaction chamber to grow a first AlN layer 30, including: controlling the reaction chamber temperature to 650°C, using an Al target, introducing Ar gas and N2 gas, with the introduction ratio of Ar gas to N2 gas being 5:1, and depositing the first AlN layer 30 with a thickness of 60 nm.

[0063] The silicon carbide substrate 10 on which the graphene layer 20 and the first AlN layer 30 are grown is placed in an MOCVD reaction chamber to sequentially grow a second AlN layer 40, a U-type GaN layer 50, an AlN insertion layer 60, an AlGaN layer 70 and a GaN cap layer 80, specifically including:

[0064] The preparation method of the second AlN layer 40 includes: controlling the pressure of the reaction chamber to 150 mbar and the temperature to 1000° C., introducing NH3 as an N source and TMAl as an Al source, and growing the second AlN layer 40 with a thickness of 70 nm;

[0065] The method for preparing the U-type GaN layer 50 includes: controlling the pressure of the reaction chamber to 150 mbar and the temperature to 1090° C., introducing NH 3 as an N source and TMGa as a Ga source, and growing the U-type GaN layer 50 with a thickness of 1.5 μm;

[0066] The preparation method of the AlN insertion layer 60 includes: controlling the pressure of the reaction chamber to 50 mbar and the temperature to 980° C., introducing NH 3 as an N source and TMAl as an Al source, and growing the AlN insertion layer 60 with a thickness of 1 nm;

[0067] The AlGaN layer 70 is prepared by controlling the pressure of the reaction chamber to 150 mbar and the temperature to 1050° C., introducing NH 3 as an N source, TMAl as an Al source, and TMGa as a Ga source, and growing the AlGaN layer 70 with a thickness of 20 nm.

[0068] The preparation method of the GaN cap layer 80 includes: controlling the pressure of the reaction chamber to 150 mbar and the temperature to 1090° C., introducing NH 3 as an N source and TMGa as a Ga source, and growing a GaN cap layer 80 with a thickness of 3 nm.

[0069] Example 2

[0070] This embodiment provides a method for preparing a silicon carbide-based GaN HEMT epitaxial wafer, comprising the following steps:

[0071] providing a silicon carbide substrate 10;

[0072] The silicon carbide substrate 10 is placed in a sublimation reaction chamber to grow a graphene layer 20, including: controlling the temperature of the reaction chamber to 1350°C under a high vacuum environment, and allowing silicon atoms to sublime and evaporate, while carbon atoms rearrange on the SiC crystal surface to form a graphene layer 20 with a thickness of 1.5 nm.

[0073] The silicon carbide substrate 10 on which the graphene layer 20 has been grown is placed in a PVD reaction chamber to grow a first AlN layer 30, including: controlling the reaction chamber temperature to 600°C, using an Al target, introducing Ar gas and N2 gas, with the introduction ratio of Ar gas to N2 gas being 5:1, and coating the first AlN layer 30 with a thickness of 40 nm.

[0074] The silicon carbide substrate 10 on which the graphene layer 20 and the first AlN layer 30 are grown is placed in an MOCVD reaction chamber to sequentially grow a second AlN layer 40, a U-type GaN layer 50, an AlN insertion layer 60, an AlGaN layer 70 and a GaN cap layer 80, specifically including:

[0075] The preparation method of the second AlN layer 40 includes: controlling the pressure of the reaction chamber to 100 mbar and the temperature to 950° C., introducing NH 3 as an N source and TMAl as an Al source, and growing the second AlN layer 40 with a thickness of 40 nm;

[0076] The method for preparing the U-type GaN layer 50 includes: controlling the pressure of the reaction chamber to 250 mbar and the temperature to 1080° C., introducing NH 3 as an N source and TMGa as a Ga source, and growing the U-type GaN layer 50 with a thickness of 1 μm;

[0077] The preparation method of the AlN insertion layer 60 includes: controlling the pressure of the reaction chamber to 100 mbar and the temperature to 950° C., introducing NH 3 as an N source and TMAl as an Al source, and growing the AlN insertion layer 60 with a thickness of 0.5 nm;

[0078] The AlGaN layer 70 is prepared by controlling the pressure of the reaction chamber to 100 mbar and the temperature to 1000° C., introducing NH 3 as an N source, TMAl as an Al source, and TMGa as a Ga source, and growing the AlGaN layer 70 with a thickness of 15 nm.

[0079] The preparation method of the GaN cap layer 80 includes: controlling the pressure of the reaction chamber to 100 mbar and the temperature to 1080° C., introducing NH 3 as an N source and TMGa as a Ga source, and growing a GaN cap layer 80 with a thickness of 1 nm.

[0080] Example 3

[0081] This embodiment provides a method for preparing a silicon carbide-based GaN HEMT epitaxial wafer, comprising the following steps:

[0082] providing a silicon carbide substrate 10;

[0083] The silicon carbide substrate 10 is placed in a sublimation reaction chamber to grow a graphene layer 20, including: controlling the temperature of the reaction chamber to 1400°C in a high vacuum environment, and allowing silicon atoms to sublime and evaporate, and carbon atoms to rearrange on the SiC crystal surface to form a graphene layer 20 with a thickness of 1 nm.

[0084] The silicon carbide substrate 10 on which the graphene layer 20 has been grown is placed in a PVD reaction chamber to grow a first AlN layer 30, including: controlling the reaction chamber temperature to 700°C, using an Al target, introducing Ar gas and N2 gas, with the introduction ratio of Ar gas to N2 gas being 5:1, and coating the first AlN layer 30 with a thickness of 120 nm.

[0085] The silicon carbide substrate 10 on which the graphene layer 20 and the first AlN layer 30 are grown is placed in an MOCVD reaction chamber to sequentially grow a second AlN layer 40, a U-type GaN layer 50, an AlN insertion layer 60, an AlGaN layer 70 and a GaN cap layer 80, specifically including:

[0086] The preparation method of the second AlN layer 40 includes: controlling the pressure of the reaction chamber to 200 mbar and the temperature to 1050° C., introducing NH 3 as an N source and TMAl as an Al source, and growing the second AlN layer 40 with a thickness of 100 nm;

[0087] The method for preparing the U-type GaN layer 50 includes: controlling the pressure of the reaction chamber to 400 mbar and the temperature to 1100° C., introducing NH 3 as an N source and TMGa as a Ga source, and growing the U-type GaN layer 50 with a thickness of 1.5 μm;

[0088] The preparation method of the AlN insertion layer 60 includes: controlling the pressure of the reaction chamber to 200 mbar and the temperature to 1000° C., introducing NH 3 as an N source and TMAl as an Al source, and growing the AlN insertion layer 60 with a thickness of 1 nm;

[0089] The AlGaN layer 70 is prepared by controlling the pressure of the reaction chamber to 200 mbar and the temperature to 1100° C., introducing NH 3 as an N source, TMAl as an Al source, and TMGa as a Ga source, and growing the AlGaN layer 70 with a thickness of 30 nm.

[0090] The preparation method of the GaN cap layer 80 includes: controlling the pressure of the reaction chamber to 200 mbar and the temperature to 1100° C., introducing NH 3 as an N source and TMGa as a Ga source, and growing a GaN cap layer 80 with a thickness of 5 nm.

[0091] The present invention provides a method for preparing a silicon carbide-based GaN HEMT epitaxial wafer. After growing a graphene layer on the surface of a silicon carbide substrate using sublimation epitaxy, the graphene, silicon carbide, and substrate are firmly bonded, resulting in high crystal quality and extremely high thermal conductivity. Stress regulation is also employed to enhance the performance of the GaN epitaxial wafer. A first AlN layer is then grown on the graphene layer using PVD. Because AlN has a hexagonal crystal structure that matches the regular hexagonal structure of graphene, the AlN's surface morphology inherits that of the graphene, resulting in a high-density AlN layer. This facilitates the growth of a high-temperature AlN nucleation layer, providing a foundation for subsequent high-quality GaN growth.

[0092] Those skilled in the art will appreciate that the foregoing descriptions are merely specific embodiments of the present invention, and not exhaustive. It should be noted that numerous variations and modifications are possible for those skilled in the art, and all such variations and modifications that do not exceed the scope of the claims should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a silicon carbide-based GaN HEMT epitaxial wafer, characterized in that: The following steps are involved: Providing a silicon carbide substrate (10); Placing a silicon carbide substrate (10) in a reaction chamber to grow a graphene layer (20); Placing the silicon carbide substrate (10) on which the graphene layer (20) has been grown in a PVD reaction chamber to grow a first AlN layer (30); The silicon carbide substrate (10) on which the graphene layer (20) and the first AlN layer (30) are grown is placed in an MOCVD reaction chamber, and a second AlN layer (40), a U-type GaN layer (50), an AlN insertion layer (60), an AlGaN layer (70) and a GaN cap layer (80) are grown in sequence.

2. The method for preparing a silicon carbide-based GaN HEMT epitaxial wafer according to claim 1, wherein: The specific process of growing the graphene layer (20) is as follows: placing a silicon carbide substrate (10) in a reaction chamber, controlling the temperature of the reaction chamber to 1300° C. to 1400° C. under a high vacuum environment, and allowing silicon atoms to sublime and volatilize, while carbon atoms are rearranged on the surface of the SiC crystal, to form a graphene layer (20) with a thickness of 1 nm to 2 nm.

3. The method for preparing a silicon carbide-based GaN HEMT epitaxial wafer according to claim 1, wherein: The specific process of growing the first AlN layer (30) is as follows: placing the silicon carbide substrate (10) on which the graphene layer (20) is grown in a PVD reaction chamber, controlling the temperature of the reaction chamber to be 600° C. to 700° C., using an Al target material, introducing Ar gas and N2 gas, wherein the introduction ratio of Ar gas to N2 gas is (4 to 6):1, and coating the first AlN layer (30) with a thickness of 10 nm to 120 nm.

4. The method for preparing a silicon carbide-based GaN HEMT epitaxial wafer according to claim 1, wherein: The specific process of growing the second AlN layer (40) is as follows: controlling the pressure of the reaction chamber to 20mbar-200mbar and the temperature to 850°C-1050°C, introducing NH3 as an N source and TMAl as an Al source, and growing the second AlN layer (40) with a thickness of 30nm-100nm.

5. The method for preparing a silicon carbide-based GaN HEMT epitaxial wafer according to claim 1, wherein: The specific process of growing the U-type GaN layer (50) is as follows: controlling the pressure of the reaction chamber to 100mbar to 400mbar and the temperature to 1080°C to 1100°C, introducing NH3 as an N source and TMGa as a Ga source, and growing the U-type GaN layer (50) with a thickness of 1μm to 1.5μm.

6. The method for preparing a silicon carbide-based GaN HEMT epitaxial wafer according to claim 1, wherein: The specific process of growing the AlN insertion layer (60) is as follows: controlling the pressure of the reaction chamber to 100mbar to 200mbar and the temperature to 950°C to 1000°C, introducing NH3 as an N source and TMAl as an Al source, and growing the AlN insertion layer (60) with a thickness of 0.5nm to 1nm.

7. The method for preparing a silicon carbide-based GaN HEMT epitaxial wafer according to claim 1, wherein: The specific process of growing the AlGaN layer (70) is as follows: controlling the pressure of the reaction chamber to 100mbar-200mbar and the temperature to 1000°C-1100°C, introducing NH3 as an N source, TMAl as an Al source, and TMGa as a Ga source, and growing the AlGaN layer (70) with a thickness of 15nm-30nm.

8. The method for preparing a silicon carbide-based GaN HEMT epitaxial wafer according to claim 1, wherein: The specific process of the GaN cap layer (80) is as follows: controlling the pressure of the reaction chamber to 100mbar-200mbar and the temperature to 1080°C-1100°C, introducing NH3 as an N source and TMGa as a Ga source, and growing a GaN cap layer (80) with a thickness of 1nm-5nm.

9. A silicon carbide-based GaN HEMT epitaxial wafer produced by the method for producing a silicon carbide-based GaN HEMT epitaxial wafer according to any one of claims 1 to 8, wherein the silicon carbide-based GaN HEMT epitaxial wafer comprises, from bottom to top: A silicon carbide substrate (10), a graphene layer (20), a first AlN layer (30), a second AlN layer (40), a U-type GaN layer (50), an AlN insertion layer (60), an AlGaN layer (70) and a GaN cap layer (80).

10. A GaN HEMT device on silicon carbide, comprising the GaN HEMT epitaxial wafer on silicon carbide according to claim 9.

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