A multi-groove diamond substrate surrounded AlN / GaN heterojunction and a preparation method thereof

Abstract

The application discloses a multi-groove diamond substrate surrounded AlN / GaN heterojunction and a preparation method thereof. The heterojunction comprises a diamond substrate with a plurality of grooves, an AlN layer in the grooves, and a GaN epitaxial layer and an AlN epitaxial layer on the surface of the diamond substrate. The multi-groove diamond substrate surrounded AlN / GaN heterojunction provided by the application adopts a multi-groove diamond substrate as a heat dissipation material, greatly increases the heat dissipation capacity of the device, and improves the performance of the device. The diamond substrate has stable chemical properties, and is beneficial to improving the service life of the device.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microelectronics, and particularly relates to a multi-groove diamond substrate surrounded AlN / GaN heterojunction and a preparation method thereof. BACKGROUND

[0002] With the development of microelectronics technology, the third generation of wide bandgap semiconductor materials represented by GaN are widely used for preparing microwave power devices due to their stable chemical properties and physical properties such as high temperature resistance and radiation resistance. With the continuous improvement and improvement of the design and process of GaN microwave power devices, the theoretical output power is higher and higher, the frequency is larger and larger, and the volume is smaller and smaller. At the same time, the heat of the chip active region is continuously accumulated, so that the heat dissipation of the device becomes one of the main problems hindering the development of GaN-based power devices.

[0003] Traditional GaN-based power devices are mainly grown on sapphire, SiC and other substrate materials, and the thermal conductivity of these materials is relatively low, which cannot timely dissipate the large amount of heat generated by the device, thereby causing the junction temperature of the device to rise, and the output power density and efficiency and other performances to deteriorate rapidly. In addition, in the fields of automobile engines and spacecraft, the performance of devices prepared using sapphire and SiC substrates is greatly limited in extremely high power and high temperature environments.

[0004] In recent years, diamond materials have attracted widespread attention as preferred materials for preparing high-performance electronic devices due to their excellent physical and chemical properties such as breakdown electric field strength and high thermal conductivity. In terms of the combination of diamond and GaN, there are currently mainly the following ways, one is a substrate transfer technology of directly growing diamond on the back of a GaN epitaxial layer; two is a low-temperature bonding technology; three is a technology of epitaxially growing GaN on a single crystal diamond.

[0005] However, there are technical difficulties such as large wafer stress and high interface thermal resistance in directly growing diamond on the back of a GaN epitaxial layer, thereby causing poor heat dissipation performance of the diamond device and affecting the performance of the device; in the low-temperature bonding technology, there are problems of high-precision processing of large-size diamond substrates and poor interface bonding strength; in addition, the technology of epitaxially growing GaN on a single crystal diamond is limited by the small size and high cost of single crystal diamond, thereby limiting the development and large-scale application of GaN-based microwave power devices. SUMMARY

[0006] In order to solve the above problems in the prior art, the application provides a multi-groove diamond substrate surrounded AlN / GaN heterojunction and a preparation method thereof. The technical problems to be solved by the application are solved by the following technical scheme:

[0007] A multi-groove diamond substrate surrounded AlN / GaN heterojunction, comprising: a diamond substrate with a plurality of grooves, an AlN layer in the grooves, and a GaN epitaxial layer and an AlN epitaxial layer on the surface of the diamond substrate.

[0008] In one embodiment of the present application, the cross-sectional shape of the groove is U-shaped.

[0009] In one embodiment of the present application, the area of a single groove is 1-4mm 2 , and the depth is 1-3um.

[0010] In one embodiment of the present application, a GaN layer is further provided on the AlN layer in the groove.

[0011] In one embodiment of the present application, the GaN layer comprises an LT-GaN layer and an HT-GaN layer, and the sum of the thicknesses of the AlN layer, the LT-GaN layer and the HT-GaN layer is the same as the depth of the groove.

[0012] In one embodiment of the present application, the thickness of the AlN layer is 20-50nm.

[0013] In one embodiment of the present application, the thickness of the LT-GaN layer is 500-1000nm, and the thickness of the HT-GaN layer is 500-2000nm.

[0014] In one embodiment of the present application, the thickness of the GaN epitaxial layer is 100-200nm, and the thickness of the AlN epitaxial layer is 200-300nm.

[0015] Another embodiment of the present application further provides a preparation method of a multi-groove diamond substrate surrounded AlN / GaN heterojunction, comprising the following steps:

[0016] Cutting the diamond substrate to form a plurality of grooves on the surface thereof;

[0017] Growing an AlN layer in the grooves by a magnetron sputtering process;

[0018] Growing a GaN epitaxial layer and an AlN epitaxial layer on the surface of the diamond substrate in sequence to form a multi-groove diamond substrate surrounded AlN / GaN heterojunction.

[0019] In one embodiment of the present application, after growing the AlN layer in the grooves by the magnetron sputtering process, further comprising:

[0020] An LT-GaN layer and an HT-GaN layer are sequentially grown on the AlN layer by using a MOCVD process; wherein the sum of thicknesses of the AlN layer, the LT-GaN layer and the HT-GaN layer is the same as the depth of the groove.

[0021] Advantages of the present application:

[0022] 1. The AlN / GaN heterojunction surrounded by the multi-groove diamond substrate provided by the present application adopts the multi-groove diamond substrate as a heat dissipation material, greatly increases the heat dissipation capacity of the device, and improves the device performance; and the diamond substrate has stable chemical properties, which is conducive to improving the service life of the device.

[0023] 2. The LT-GaN layer and the HT-GaN layer are introduced into the groove of the diamond substrate, which relieves the stress generated in the subsequent growth process, improves the crystal quality of the epitaxial layer, and greatly improves the device performance.

[0024] 3. The AlN layer is grown by using a magnetron sputtering process, which solves the problem of difficult combination between the diamond substrate and GaN, and increases the bonding strength.

[0025] 4. The polycrystalline diamond is used as a substrate material, which has lower cost and higher thermal conductivity compared with single crystal diamond, can be better introduced into the structure of a semiconductor power device, significantly improves the heat dissipation capacity and working stability of the device, and is suitable for large-scale application of GaN-based microwave power devices.

[0026] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a structure schematic diagram of an AlN / GaN heterojunction surrounded by a multi-groove diamond substrate provided by an embodiment of the present application;

[0028] Figure 2 is a structure schematic diagram of another AlN / GaN heterojunction surrounded by a multi-groove diamond substrate provided by an embodiment of the present application;

[0029] Figure 3 is a flow chart of a preparation method of an AlN / GaN heterojunction surrounded by a multi-groove diamond substrate provided by an embodiment of the present application;

[0030] Figures 4a-4i is a process process schematic diagram of preparing an AlN / GaN heterojunction surrounded by a multi-groove diamond substrate provided by an embodiment of the present application. DETAILED DESCRIPTION

[0031] The application will be described in further detail below with reference to specific embodiments, but the embodiments of the application are not limited thereto.

[0032] Embodiment one

[0033] Please refer to Figure 1 , Figure 1 is a structure schematic diagram of a multi-groove diamond substrate surrounded AlN / GaN heterojunction provided by an embodiment of the application, comprising: a diamond substrate 1 with several grooves, an AlN layer 2 located in the grooves, and a GaN epitaxial layer 3 and an AlN epitaxial layer 4 located on the surface of the diamond substrate 1.

[0034] Specifically, the embodiment adopts polycrystalline diamond material as the substrate material, and sets 2 or more grooves on it, and forms an AlN layer, also known as a magnetron sputtering AlN layer, in the grooves through a magnetron sputtering process. The cross-sectional shape of the groove is U-shaped, the area of a single groove is 1-4mm 2 , and the depth is 1-3um.

[0035] The embodiment adopts a multi-groove diamond substrate as a heat dissipation material, greatly increases the heat dissipation capacity of the device, and improves the device performance; at the same time, the AlN layer is grown by a magnetron sputtering process, which solves the problem of difficult combination between the diamond substrate and GaN, and increases the bonding strength.

[0036] In addition, the embodiment preferably adopts polycrystalline diamond as the substrate material, which has lower cost and higher thermal conductivity compared with traditional single crystal diamond, can be better introduced into the structure of the semiconductor power device, and significantly improves the heat dissipation capacity and working stability of the device; at the same time, the diamond substrate has stable chemical properties, which is conducive to improving the working life of the device, and is suitable for large-scale application of GaN-based microwave power devices.

[0037] Further, please refer to Figure 2 , Figure 2 is another structure schematic diagram of a multi-groove diamond substrate surrounded AlN / GaN heterojunction provided by an embodiment of the application, wherein a GaN layer 5 is further arranged on the AlN layer 2 in the groove.

[0038] Further, the embodiment sets the GaN layer 5 into a multi-layer structure comprising an LT-GaN layer 51 and an HT-GaN layer 52, wherein the LT-GaN layer 51 is a low-temperature GaN layer, the HT-GaN layer 52 is a high-temperature GaN layer, and the sum of the thicknesses of the LT-GaN layer 51 and the HT-GaN layer 52 is the same as the depth of the groove, that is, the upper surface of the HT-GaN layer 52 is flush with the upper surface of the diamond substrate 1.

[0039] Specifically, the thickness of the AlN layer 2 can be set to 20-50 nm, the thickness of the LT-GaN layer 3 can be set to 500-1000 nm, and the thickness of the HT-GaN layer 4 can be set to 500-2000 nm. The thickness of the GaN epitaxial layer 3 can be set to 100-200 nm, and the thickness of the AlN epitaxial layer 4 can be set to 200-300 nm.

[0040] The embodiment introduces the LT-GaN layer and the HT-GaN layer in the groove of the diamond substrate, alleviates the stress generated in the subsequent growth process, improves the crystal quality of the epitaxial layer, and greatly improves the device performance.

[0041] Embodiment Two

[0042] On the basis of the above-mentioned embodiment one, the embodiment provides a preparation method of a multi-groove diamond substrate surrounded AlN / GaN heterojunction. Please refer to Figure 3 , Figure 3 is a preparation method flow chart of a multi-groove diamond substrate surrounded AlN / GaN heterojunction provided by the embodiment, and specifically includes the following steps:

[0043] S1: cutting the diamond substrate to form a plurality of grooves on the surface thereof.

[0044] Firstly, laser high-energy ablation is adopted to cut the high-thermal-conductivity diamond substrate to form a plurality of U-shaped grooves.

[0045] Then, the inner wall of the groove is ground, polished and cleaned to remove residual diamond powder.

[0046] Finally, a hydrogen plasma etching method is adopted to remove the graphite generated by cutting the diamond, and an air oxidation method is further adopted to remove the hydrogen termination on the surface of the diamond.

[0047] S2: growing an AlN layer in the groove by adopting a magnetron sputtering process.

[0048] Specifically, the embodiment adopts a standard magnetron sputtering process to sputter and grow an AlN layer with a thickness of 20-50 nm at the bottom of each groove.

[0049] Further, after the AlN layer is grown, the following steps are further included:

[0050] adopting a MOCVD process to grow a LT-GaN layer and a HT-GaN layer on the AlN layer in sequence; wherein the sum of the thicknesses of the AlN layer, the LT-GaN layer and the HT-GaN layer is the same as the depth of the groove.

[0051] S3: growing a GaN epitaxial layer and an AlN epitaxial layer on the surface of the diamond substrate in sequence to form a multi-groove diamond substrate surrounded AlN / GaN heterojunction.

[0052] Specifically, the embodiment adopts MOCVD process to grow GaN layer with thickness of 100-200nm on the surface of diamond substrate; and further adopts MOCVD process to grow AlN layer with thickness of 200-300nm on the GaN epitaxial layer, so as to complete the preparation of the AlN / GaN heterojunction surrounded by the multi-groove diamond substrate.

[0053] Embodiment three

[0054] The preparation method of the present application will be described in detail below by taking the preparation of the AlN / GaN heterojunction surrounded by the multi-groove diamond substrate with the thickness of 20nm of the magnetron sputtering AlN layer, 500nm of the LT-GaN layer, 1000nm of the HT-GaN layer, 100nm of the GaN epitaxial layer and 200nm of the AlN epitaxial layer as an example.

[0055] Please refer to Figures 4a-4i , Figures 4a-4i which is the process flow diagram of the preparation of the AlN / GaN heterojunction surrounded by the multi-groove diamond substrate provided by the embodiment of the present application.

[0056] Step one: making the multi-groove diamond

[0057] The current is set to 60A, the pulse width is set to 300us, the frequency is set to 200Hz, the cutting speed is set to 200mm / min, and the cutting time is set to 7 minutes. The laser high-energy ablation is used to perform selected cutting on the diamond, and two grooves with an area of 2mm 2 and a cutting depth of 1.4um are cut out, as shown in Figure 4a .

[0058] Step two: grinding, polishing and cleaning of the inner wall of the groove

[0059] After the inner wall of the laser high-energy ablation diamond groove is ground and polished, until the roughness of the inner wall of the diamond groove is less than 1.5nm, the polished diamond film is sequentially cleaned by ultrasonic cleaning using acetone, alcohol and deionized water, and the ultrasonic power is 200w. After cleaning for 30 minutes, it is blown dry, as shown in Figure 4b .

[0060] Step three: removing graphite and hydrogen termination

[0061] 3a) The method of hydrogen plasma etching is used to remove the graphite generated by cutting the diamond, and the H2 flow is set to 200sccm, the pressure is set to 5KPa, and the temperature is set to 350℃. Etching for 5min, and cooling to room temperature in a hydrogen atmosphere after etching, as shown in Figure 4c .

[0062] 3b) removing the hydrogen termination on the surface of the diamond by oxidation in air. The grooved diamond is placed in an oven and heated at 220°C in an O2 atmosphere for 20 min. As shown in Fig. 3b. Figure 4d

[0063] Step four: making a magnetron sputtering AlN layer

[0064] The multi-groove diamond is taken out and placed on a magnetron sputtering table, and the reaction temperature is set to 370°C, the reaction pressure is set to 2.0 Pa, the sputtering power is set to 300 W, and aluminum nitride is used as the target material and nitrogen gas is used as the sputtering gas. An AlN layer with a thickness of 20 nm is sputtered and grown at the bottom of the groove by using a standard magnetron sputtering process, as shown in Fig. 4. Figure 4e

[0065] Step five: making an LT-GaN layer

[0066] The sample after magnetron sputtering of AlN is placed in the reaction furnace of the MOCVD equipment, the reaction chamber temperature is set to 900°C, the reaction chamber pressure is set to 20 Torr, and the reaction chamber is simultaneously supplied with ammonia gas with a flow rate of 2500 sccm and a gallium source with a flow rate of 50 sccm. An LT-GaN layer with a thickness of 500 nm is grown, as shown in Fig. 5. Figure 4f

[0067] Step six: making an HT-GaN layer

[0068] The reaction chamber temperature is set to 1100°C, the reaction chamber pressure is set to 70 Torr, and the reaction chamber is simultaneously supplied with ammonia gas with a flow rate of 5000 sccm and a gallium source with a flow rate of 80 sccm. An HT-GaN layer with a thickness of 1000 nm is grown, as shown in Fig. 6. Figure 4g

[0069] Step seven: making a GaN epitaxial layer

[0070] The reaction chamber temperature is set to 1050°C, the reaction chamber pressure is set to 50 Torr, and the reaction chamber is simultaneously supplied with ammonia gas with a flow rate of 5000 sccm and a gallium source with a flow rate of 20 sccm. A GaN epitaxial layer with a thickness of 100 nm is grown, as shown in Fig. 7. Figure 4h

[0071] Step eight: making an AlN epitaxial layer

[0072] The reaction chamber temperature is set to 1100°C, the reaction chamber pressure is set to 50 Torr, and the reaction chamber is simultaneously supplied with ammonia gas with a flow rate of 5000 sccm and an aluminum source with a flow rate of 190 sccm. An AlN epitaxial layer with a thickness of 200 nm is grown, as shown in Fig. 8. Figure 4i

[0073] ​​​​​​The preparation of the AlN / GaN heterojunction surrounded by the multi-groove diamond substrate is completed, with the thickness of the AlN layer being 20 nm, the thickness of the LT-GaN layer being 500 nm, the thickness of the HT-GaN layer being 1000 nm, the thickness of the GaN epitaxial layer being 100 nm, and the thickness of the AlN epitaxial layer being 200 nm.

[0074] Example Four

[0075] The preparation method of the present application is described in detail below by taking the preparation of the AlN / GaN heterojunction surrounded by the multi-groove diamond substrate as an example, with the thickness of the AlN layer being 25 nm, the thickness of the LT-GaN layer being 600 nm, the thickness of the HT-GaN layer being 1500 nm, the thickness of the GaN epitaxial layer being 150 nm, and the thickness of the AlN epitaxial layer being 250 nm. The specific steps include the following steps:

[0076] Step 1: Making the multi-groove diamond

[0077] The current is set to 60 A, the pulse width is 300 us, the frequency is 200 Hz, the cutting speed is 200 mm / min, and the cutting time is 5 minutes. The laser high-energy ablation is used to perform selective cutting on the diamond, and two grooves with an area of 1 mm 2 and a cutting depth of 1 um are cut out.

[0078] Step 2: Grinding, polishing, and cleaning the inner wall of the groove

[0079] Step 3: Removing graphite and hydrogen termination

[0080] In this embodiment, the detailed processes of steps 2 and 3 are the same as those of steps 2 and 3 in the above-described example three, and thus are not described here again.

[0081] Step 4: Making the AlN layer by magnetron sputtering

[0082] The multi-groove diamond is taken out and placed on the magnetron sputtering table, the reaction temperature is set to 400℃, the reaction pressure is set to 2.0 Pa, the sputtering power is set to 300 W, aluminum nitride is used as the target material, nitrogen is used as the sputtering gas, and the standard magnetron sputtering process is adopted to sputter and grow the AlN with a thickness of 25 nm at the bottom of the groove.

[0083] Step 5: Making the LT-GaN layer

[0084] The sample after the magnetron sputtering of the AlN is placed in the reaction furnace of the MOCVD equipment, the reaction chamber temperature is set to 850℃, the reaction chamber pressure is set to 25 Torr, the two gases of ammonia with a flow rate of 2500 sccm and gallium source with a flow rate of 60 sccm are simultaneously introduced into the reaction chamber, and the LT-GaN layer with a thickness of 600 nm is grown.

[0085] Step 6: Making the HT-GaN layer

[0086] The reaction chamber temperature is set to 1100°C, the reaction chamber pressure is set to 80 Torr, the reaction chamber is supplied with ammonia gas at a flow rate of 5000 seem and gallium source gas at a flow rate of 80 seem, and a 1500 nm thick HT-GaN layer is grown.

[0087] Step 7: Making a GaN epitaxial layer

[0088] The reaction chamber temperature is set to 1050°C, the reaction chamber pressure is set to 70 Torr, the reaction chamber is supplied with ammonia gas at a flow rate of 5000 seem and gallium source gas at a flow rate of 30 seem, and a 150 nm thick GaN epitaxial layer is grown.

[0089] Step 8: Making an AlN epitaxial layer

[0090] The reaction chamber temperature is set to 1150°C, the reaction chamber pressure is set to 50 Torr, the reaction chamber is supplied with ammonia gas at a flow rate of 5000 seem and aluminum source gas at a flow rate of 150 seem, and a 250 nm thick AlN epitaxial layer is grown, completing the preparation of the multi-groove diamond substrate-encircled AlN / GaN heterojunction.

[0091] Example Five

[0092] The preparation method of the present application will be described in detail below with reference to the preparation of a multi-groove diamond substrate-encircled AlN / GaN heterojunction having an AlN layer with a thickness of 30 nm, an LT-GaN layer with a thickness of 800 nm, an HT-GaN layer with a thickness of 2000 nm, a GaN epitaxial layer with a thickness of 200 nm, and an AlN epitaxial layer with a thickness of 300 nm. The specific steps include:

[0093] Step A: Making a multi-groove diamond

[0094] The current is set to 60 A, the pulse width is set to 300 us, the frequency is set to 200 Hz, the cutting speed is set to 200 mm / min, and the cutting time is set to 10 minutes. Laser high-energy ablation is used to perform selective cutting on the diamond, cutting out two grooves with an area of 4 mm 2 and a depth of 2 um.

[0095] Step B: Grinding, polishing, and cleaning the inner wall of the groove

[0096] Step C: Removing graphite and hydrogen termination

[0097] In this embodiment, the detailed procedures of steps B and C are the same as steps two and three in the above-described example three, and will not be described again here.

[0098] Step D: Making a magnetron sputtering AlN layer

[0099] The multi-groove diamond is taken out and placed on a magnetron sputtering table, a reaction temperature of 330 DEG C is set, a reaction pressure of 2.0 Pa is set, a sputtering power of 300 W is set, aluminum nitride is used as a target material, nitrogen is used as a sputtering gas, and a standard magnetron sputtering process is used to sputter and grow an AlN layer with a thickness of 30 nm at the bottom of the groove.

[0100] Step E: LT-GaN layer preparation

[0101] The sample after the magnetron sputtering of AlN is placed in a MOCVD device reaction furnace, a reaction chamber temperature of 800 DEG C is set, a reaction chamber pressure of 20 Torr is set, 2500 sccm of ammonia gas and 50 sccm of gallium source are simultaneously introduced into the reaction chamber, and an LT-GaN layer with a thickness of 800 nm is grown.

[0102] Step F: HT-GaN layer preparation

[0103] A reaction chamber temperature of 1050 DEG C is set, a reaction chamber pressure of 80 Torr is set, 5000 sccm of ammonia gas and 80 sccm of gallium source are simultaneously introduced into the reaction chamber, and an HT-GaN layer with a thickness of 2000 nm is grown.

[0104] Step G: GaN epitaxial layer preparation

[0105] A reaction chamber temperature of 1080 DEG C is set, a reaction chamber pressure of 70 Torr is set, 5000 sccm of ammonia gas and 30 sccm of gallium source are simultaneously introduced into the reaction chamber, and a GaN epitaxial layer with a thickness of 200 nm is grown.

[0106] Step H: AlN epitaxial layer preparation

[0107] A reaction chamber temperature of 1200 DEG C is set, a reaction chamber pressure of 50 Torr is set, 5000 sccm of ammonia gas and 200 sccm of aluminum source are simultaneously introduced into the reaction chamber, and an AlN epitaxial layer with a thickness of 300 nm is grown, and the preparation of the AlN / GaN heterojunction around the multi-groove diamond substrate is completed.

[0108] It should be noted that although the embodiments of the present application provide examples of parameters containing specific values, it should be understood that the parameters do not necessarily equal the corresponding values, but are approximately equal to the corresponding values within an acceptable error tolerance or design constraint.

[0109] The above is further detailed description of the present application in combination with specific preferred embodiments, and cannot be deemed as limitation of the specific implementation of the present application to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, and all should be deemed as falling within the protection scope of the present application.

Claims

1. An AlN / GaN heterojunction surrounded by a multi-groove diamond substrate, characterized in that, include: A diamond substrate (1) with several grooves, an AlN layer (2) located in the grooves, and a GaN epitaxial layer (3) and an AlN epitaxial layer (4) located on the surface of the diamond substrate (1); The groove has a U-shaped cross-section; and the area of ​​a single groove is 1-4 mm². 2 The depth is 1-3 μm; A GaN layer (5) is also provided on the AlN layer (2) in the groove; the GaN layer (5) includes an LT-GaN layer (51) and an HT-GaN layer (52), and the sum of the thicknesses of the AlN layer (2), the LT-GaN layer (51) and the HT-GaN layer (52) is the same as the depth of the groove; the growth temperature of the LT-GaN layer (51) is 900℃ and the reaction chamber pressure is 20 Torr; the growth temperature of the HT-GaN layer (52) is 1050℃ and the reaction chamber pressure is 70 Torr.

2. The AlN / GaN heterojunction surrounded by a multi-groove diamond substrate according to claim 1, characterized in that, The thickness of the AlN layer (2) is 20-50 nm.

3. The AlN / GaN heterojunction surrounded by a multi-groove diamond substrate according to claim 1, characterized in that, The thickness of the LT-GaN layer (51) is 500-1000 nm, and the thickness of the HT-GaN layer (52) is 500-2000 nm.

4. The AlN / GaN heterojunction surrounded by a multi-groove diamond substrate according to claim 1, characterized in that, The thickness of the GaN epitaxial layer (3) is 100-200 nm, and the thickness of the AlN epitaxial layer (4) is 200-300 nm.

5. A method for fabricating an AlN / GaN heterojunction surrounded by a multi-groove diamond substrate, characterized in that, Includes the following steps: A diamond substrate is cut to form several grooves on its surface; wherein the cross-sectional shape of the grooves is U-shaped; and the area of ​​a single groove is 1-4 mm². 2 The depth is 1-3 μm; An AlN layer was grown in the groove using a magnetron sputtering process. An LT-GaN layer and an HT-GaN layer are sequentially grown on the AlN layer using MOCVD technology; wherein the sum of the thicknesses of the AlN layer, the LT-GaN layer, and the HT-GaN layer is the same as the depth of the groove; the growth temperature of the LT-GaN layer (51) is 900℃, and the reaction chamber pressure is 20 Torr; the growth temperature of the HT-GaN layer (52) is 1050℃, and the reaction chamber pressure is 70 Torr. GaN epitaxial layers and AlN epitaxial layers are sequentially grown on the surface of the diamond substrate to form an AlN / GaN heterojunction surrounded by a multi-groove diamond substrate.

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