A GaN-based HEMT epitaxial structure and preparation method thereof

Abstract

The present invention discloses a GaN-based HEMT epitaxial structure and a preparation method thereof. The structure comprises a substrate; a buffer layer is epitaxially grown on the upper surface of the substrate; a channel layer is epitaxially grown on the upper surface of the buffer layer; a barrier layer is epitaxially grown on the upper surface of the channel layer; and an intentionally doped p-type gallium nitride layer is epitaxially grown on the upper surface of the barrier layer. The intentionally doped p-type gallium nitride layer has a periodic structure and is cyclically grown from bottom to top by an intentionally doped magnesiumocene GaN layer, a magnesiumocene layer, and an undoped GaN layer. By utilizing the diffusion effect and memory effect of magnesium atoms, uniform distribution of magnesium atoms in the intentionally doped p-type gallium nitride layer is achieved, clustering of magnesium atoms in the structure is reduced, and the hole concentration of the p-type layer can be effectively increased without deteriorating the appearance of the GaN wafer and the crystal quality of the p-type layer, and without affecting the ohmic contact in the subsequent device manufacturing process.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and in particular relates to a GaN-based HEMT epitaxial structure and a preparation method thereof. Background Art

[0002] As a third-generation compound semiconductor material, GaN has been widely used in the fields of microelectronics and optoelectronics due to its wide bandgap width and breakdown field strength, as well as its direct bandgap characteristics. Under the current international and domestic situation of energy shortages and heavy environmental pressures, the successful commercial application of GaN has made outstanding contributions to energy conservation and emission reduction and the realization of the dual carbon tasks, and has broad market prospects.

[0003] HEMTs (High Electron Mobility Transition), one of GaN's key applications, consist of a substrate, buffer layer, channel layer, barrier layer, and p-type gallium nitride layer. However, obtaining p-type materials with high hole concentrations during the fabrication process is challenging. Conventional methods for fabricating HEMTs use magnesium cyclopentadienyl as a dopant for the p-type material, followed by epitaxial growth of the bulk p-type layer. The inventors believe that simply increasing the molar concentration of magnesium cyclopentadienyl can lead to poor GaN wafer appearance, such as roughness and yield degradation. Furthermore, simply increasing the dopant concentration does not result in a higher hole concentration. Instead, the hole concentration decreases with increasing magnesium cyclopentadienyl doping concentration, compromising ohmic contact in subsequent device fabrication. Furthermore, higher dopant concentrations lead to poorer crystal quality in the p-type layer of the GaN wafer, hindering the electrical performance of the HEMT device. Therefore, a GaN-based HEMT epitaxial structure and fabrication method are needed.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance understanding of the background of the present disclosure and therefore may contain information that does not constitute prior art. Summary of the Invention

[0005] The inventors have found through research that reducing the clustering of magnesium atoms in the structure, thereby reducing the magnesium doping self-compensation effect caused by the uneven distribution of local magnesium atoms in the entire p-type layer, can effectively increase the hole concentration of the p-type layer.

[0006] In view of at least one of the above technical problems, the present disclosure provides a GaN-based HEMT epitaxial structure and a preparation method thereof. The specific technical solutions are as follows:

[0007] A GaN-based HEMT epitaxial structure comprises a substrate, a buffer layer epitaxially grown on the upper surface of the substrate; a channel layer epitaxially grown on the upper surface of the buffer layer; a barrier layer epitaxially grown on the upper surface of the channel layer; and an intentionally doped p-type gallium nitride layer epitaxially grown on the upper surface of the barrier layer. The intentionally doped p-type gallium nitride layer has a periodic structure and is cyclically grown from bottom to top by an intentionally doped magnesiumcyclopentadienyl GaN layer, a magnesiumcyclopentadienyl GaN layer, and an undoped GaN layer. By utilizing the diffusion and memory effects of magnesium atoms, uniform distribution of magnesium atoms in the intentionally doped p-type gallium nitride layer is achieved, reducing clustering of magnesium atoms in the structure and thus reducing the self-compensation effect of magnesium doping. This effectively increases the hole concentration of the p-type layer without degrading the appearance of the GaN wafer or the crystal quality of the p-type layer, and without affecting the ohmic contact in subsequent device fabrication processes.

[0008] In some embodiments of the present disclosure, the substrate is a silicon substrate, a silicon carbide substrate, or a sapphire substrate.

[0009] In some embodiments of the present disclosure, the buffer layer is an AlN / AlGaN composite structure.

[0010] In some embodiments of the present disclosure, the buffer layer has a thickness of 100 to 300 nm.

[0011] In some embodiments of the present disclosure, the channel layer is an unintentionally doped GaN layer, and the thickness of the channel layer is 1000-2000 nm.

[0012] In some embodiments of the present disclosure, the barrier layer has a thickness of 15 to 20 nm.

[0013] In some embodiments of the present disclosure, the intentionally doped magnesiumocene GaN layer has a thickness of 2.5 to 3.0 nm, the magnesiumocene layer has a thickness of 0.6 to 0.8 nm, and the undoped GaN layer has a thickness of 1.5 to 2.0 nm.

[0014] In some embodiments of the present disclosure, the total number of periods of the intentionally doped p-type gallium nitride layer is 15-20.

[0015] A method for preparing a GaN-based HEMT epitaxial structure comprises the following steps:

[0016] The first step is to use a substrate as a substrate for epitaxial growth, use a metal organic chemical vapor deposition system as the epitaxial growth system, place the substrate in a reaction chamber of the metal organic chemical vapor deposition system, adjust the temperature of the reaction chamber to 1000-1100°C, and clean the substrate in a hydrogen atmosphere.

[0017] In the second step, trimethylgallium, trimethylaluminum and ammonia are introduced as raw materials onto the substrate treated in the first step to grow a buffer layer. The temperature in the reaction chamber is adjusted to 950-1050°C, the pressure is adjusted to 50-100 mbar, and the V / III ratio is 1000-1500.

[0018] In the third step, trimethylgallium and ammonia are introduced as raw materials onto the buffer layer obtained in the second step to grow a channel layer. The temperature in the reaction chamber is adjusted to 1050-1100° C., the pressure in the reaction chamber is adjusted to 200-300 mbar, and the V / III ratio is 35000-40000.

[0019] In the fourth step, trimethylgallium, trimethylaluminum and ammonia are introduced into the channel layer obtained in the third step to grow a barrier layer. The temperature in the reaction chamber is adjusted to 1040-1060° C., the pressure in the reaction chamber is adjusted to 50-100 mbar, and the V / III ratio is 3000-4500.

[0020] In the fifth step, a deliberately doped p-type gallium nitride layer is grown on the barrier layer obtained in the fourth step. The temperature in the reaction chamber is adjusted to 950-1000°C, the pressure in the reaction chamber is 150-300 mbar, the V / III ratio is 30,000-50,000, and the p-type dopant is bis(cyclopentadienyl)magnesium.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention utilizes the diffusion and memory effects of magnesium atoms to achieve uniform distribution of magnesium atoms in the intentionally doped p-type gallium nitride layer, reducing the clustering of magnesium atoms in the structure and the self-compensation effect of magnesium doping. This effectively increases the hole concentration in the p-type layer without increasing the amount of magnesium atoms used during the growth process, thereby maintaining the appearance of the GaN wafer and the crystal quality of the p-type layer. In theory, a higher hole concentration will facilitate ohmic contact in subsequent device fabrication. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the epitaxial structure of the GaN-based HEMT of the present invention;

[0024] Explanation of the numbers in the figure: 1. substrate; 2. buffer layer; 3. channel layer; 4. barrier layer; 5. intentionally doped p-type gallium nitride layer; 51. intentionally doped bismuth magnesiumocene GaN layer; 52. bismuth magnesiumocene layer; 53. undoped GaN layer. DETAILED DESCRIPTION

[0025] In order to better understand the purpose, structure and function of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0026] The serial numbers assigned to the components herein are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" mentioned in this disclosure includes direct and indirect "connections" unless otherwise specified. In the description of this application, it should be understood that the orientation terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and brief description, and do not indicate or imply that the device or unit referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as a limitation on this application.

[0027] like Figure 1 As shown, a GaN-based HEMT epitaxial structure is designed, comprising a substrate 1, a buffer layer 2 epitaxially grown on the upper surface of the substrate 1; a channel layer 3 epitaxially grown on the upper surface of the buffer layer 2; a barrier layer 4 epitaxially grown on the upper surface of the channel layer 3; and an intentionally doped p-type gallium nitride layer 5 epitaxially grown on the upper surface of the barrier layer 4. The intentionally doped p-type gallium nitride layer 5 has a periodic structure, cyclically grown from bottom to top by an intentionally doped magnesium cyclopentadienyl GaN layer 51, a magnesium cyclopentadienyl GaN layer 52, and an undoped GaN layer 53. The present invention utilizes the diffusion and memory effects of magnesium atoms to achieve uniform distribution of magnesium atoms in the intentionally doped p-type gallium nitride layer, reducing magnesium atom clustering in the structure and the self-compensation effect of magnesium doping. This effectively increases the hole concentration of the p-type layer without increasing the amount of magnesium atoms used during the growth process, thereby maintaining the appearance of the GaN wafer and the crystal quality of the p-type layer. Theoretically, a higher hole concentration will facilitate ohmic contact in subsequent device fabrication.

[0028] A method for preparing a GaN-based HEMT epitaxial structure as described above is designed, comprising the following steps: first, using a substrate 1 as a substrate for epitaxial growth, using a metal organic chemical vapor deposition system as the epitaxial growth system, placing the substrate 1 in a reaction chamber of the metal organic chemical vapor deposition system, adjusting the temperature of the reaction chamber to 1000-1100° C., and cleaning the substrate 1 in a hydrogen atmosphere;

[0029] In the second step, trimethylgallium, trimethylaluminum and ammonia are introduced as raw materials onto the substrate 1 processed in the first step to grow a buffer layer 2. The temperature in the reaction chamber is adjusted to 950-1050°C, the pressure is adjusted to 50-100 mbar, and the V / III ratio is 1000-1500.

[0030] In the third step, trimethyl gallium and ammonia are introduced as raw materials onto the buffer layer 2 obtained in the second step to grow the channel layer 3. The temperature in the reaction chamber is adjusted to 1050-1100° C., the pressure in the reaction chamber is adjusted to 200-300 mbar, and the V / III ratio is 35000-40000.

[0031] In the fourth step, trimethylgallium, trimethylaluminum and ammonia are introduced onto the channel layer 3 obtained in the third step to grow a barrier layer 4. The temperature in the reaction chamber is adjusted to 1040-1060° C., the pressure in the reaction chamber is adjusted to 50-100 mbar, and the V / III ratio is 3000-4500.

[0032] In the fifth step, a deliberately doped p-type gallium nitride layer 5 is grown on the barrier layer 4 obtained in the fourth step. The temperature in the reaction chamber is adjusted to 950-1000° C., the pressure in the reaction chamber is 150-300 mbar, the V / III ratio is 30,000-50,000, and the p-type dopant is bis(cyclopentadienyl)magnesium.

[0033] Among them, ammonia is used as the Group V source material, and trimethylgallium and trimethylaluminum are used as the Group III raw materials.

[0034] In the above implementation, three embodiments are listed to implement the above technical solution:

[0035] Example 1

[0036] This embodiment provides a GaN-based HEMT epitaxial structure, wherein:

[0037] A single crystal silicon substrate is selected as the substrate 1;

[0038] Using a metal organic chemical vapor deposition system as an epitaxial growth system, placing a substrate 1 in a reaction chamber of the metal organic chemical vapor deposition system, adjusting the temperature of the reaction chamber to 1000° C., and cleaning the substrate 1 in an environment where hydrogen is used as the chamber atmosphere gas;

[0039] A buffer layer 2 is grown on the silicon substrate by introducing trimethylgallium, trimethylaluminum, and ammonia as raw materials. The temperature in the reaction chamber is adjusted to 1000°C, the pressure is adjusted to 50 mbar, and the V / III ratio is 1000. The buffer layer adopts a composite structure composed of AlN / AlGaN and has a thickness of 100 nm.

[0040] TMGa (trimethyl gallium) and NH3 (ammonia) are introduced as raw materials onto the buffer layer 2 to grow a channel layer 3, i.e., an unintentionally doped GaN layer. The temperature in the reaction chamber is adjusted to 1050°C, the pressure is adjusted to 300 mbar, the V / III ratio is 40,000, and the thickness of the unintentionally doped GaN layer is 2000 nm.

[0041] A barrier layer 4 is formed on the unintentionally doped GaN layer by introducing TMGa (trimethyl gallium), TMAl (trimethyl aluminum), and NH3 (ammonia). The temperature in the reaction chamber is adjusted to 1040°C, the pressure is adjusted to 100 mbar, the V / III ratio is 4500, and the thickness of the barrier layer is 15 nm.

[0042] An intentionally doped p-type GaN layer 5 is grown on the barrier layer 4. The reaction chamber temperature is adjusted to 1000°C, the pressure is adjusted to 150 mbar, the V / III ratio is 50,000, and the p-type dopant is cyclopentadienyl magnesium (Cp2Mg). The intentionally doped p-type GaN layer has a periodic sandwich structure. The intentionally doped p-type GaN layer 5 is cyclically grown from bottom to top, comprising an intentionally doped cyclopentadienyl magnesium (GaN) layer 51, a cyclopentadienyl magnesium (Mg) layer 52, and an undoped GaN layer 53. The thicknesses are 2.5 nm, 0.6 nm, and 1.5 nm, respectively, and the total number of cycles is 20.

[0043] Example 2

[0044] This embodiment provides a GaN-based HEMT epitaxial structure, wherein:

[0045] A sapphire substrate is selected as the base substrate 1;

[0046] Using a metal organic chemical vapor deposition system as an epitaxial growth system, placing a substrate 1 in a reaction chamber of the metal organic chemical vapor deposition system, adjusting the temperature of the reaction chamber to 1080° C., and cleaning the substrate 1 in an environment where hydrogen is used as the chamber atmosphere gas;

[0047] TMGa (trimethyl gallium), TMAl (trimethyl aluminum), and NH3 (ammonia) are introduced as raw materials onto the sapphire substrate to grow a buffer layer 2. The temperature in the reaction chamber is adjusted to 1050°C, the pressure is adjusted to 100 mbar, and the V / III ratio is 1500. The buffer layer adopts a composite structure composed of AlN / AlGaN and has a thickness of 200 nm.

[0048] TMGa (trimethyl gallium) and NH3 (ammonia) are introduced as raw materials onto the buffer layer 2 to grow a channel layer 3, i.e., an unintentionally doped GaN layer. The temperature in the reaction chamber is adjusted to 1100°C, the pressure is adjusted to 200 mbar, the V / III ratio is 35000, and the thickness of the unintentionally doped GaN layer is 1500 nm.

[0049] TMGa (trimethyl gallium), TMAl (trimethyl aluminum), and NH3 (ammonia) are introduced onto the unintentionally doped GaN layer to form a barrier layer 4. The temperature in the reaction chamber is adjusted to 1060°C, the pressure is adjusted to 50 mbar, the V / III ratio is 3000, and the thickness of the barrier layer is 18.5 nm.

[0050] An intentionally doped p-type GaN layer 5 is grown on the barrier layer 4. The reaction chamber temperature is 950°C, the system chamber pressure is 300 mbar, the V / III ratio is 30,000, and the p-type dopant is cyclopentadienyl magnesium (Cp2Mg). The intentionally doped p-type GaN layer has a periodic sandwich structure. The intentionally doped p-type GaN layer 5 is cyclically grown from bottom to top by an intentionally doped cyclopentadienyl magnesium (GaN) layer 51, a cyclopentadienyl magnesium (Mg) layer 52, and an undoped GaN layer 53. The thicknesses are 3.0 nm, 0.7 nm, and 2.0 nm, respectively, and the total number of cycles is 18.

[0051] Example 3

[0052] This embodiment provides a GaN-based HEMT epitaxial structure, wherein:

[0053] A silicon carbide substrate is selected as the substrate 1;

[0054] Using a metal organic chemical vapor deposition system as an epitaxial growth system, placing a substrate 1 in a reaction chamber of the metal organic chemical vapor deposition system, adjusting the temperature of the reaction chamber to 1100° C., and cleaning the substrate 1 in an environment where hydrogen is used as the chamber atmosphere gas;

[0055] TMGa (trimethyl gallium), TMAl (trimethyl aluminum), and NH3 (ammonia) are introduced as raw materials to grow a buffer layer 2 on the silicon carbide substrate. The temperature in the reaction chamber is adjusted to 950°C, the pressure is adjusted to 80 mbar, and the V / III ratio is 1350. The buffer layer adopts a composite structure composed of AlN / AlGaN and has a thickness of 300 nm.

[0056] TMGa (trimethyl gallium) and NH3 (ammonia) are introduced as raw materials onto the buffer layer 2 to grow a channel layer 3, i.e., an unintentionally doped GaN layer. The temperature in the reaction chamber is adjusted to 1080°C, the pressure is adjusted to 266 mbar, the V / III ratio is 38000, and the thickness of the unintentionally doped GaN layer is 1000 nm.

[0057] TMGa (trimethyl gallium), TMAl (trimethyl aluminum), and NH3 (ammonia) are introduced onto the unintentionally doped GaN layer to form a barrier layer 4. The temperature in the reaction chamber is adjusted to 1055°C, the pressure is adjusted to 85 mbar, the V / III ratio is 4000, and the thickness of the barrier layer is 20 nm.

[0058] An intentionally doped p-type GaN layer 5 is grown on the barrier layer 4. The temperature and pressure in the reaction chamber are adjusted to 975°C, 250 mbar, and a V / III ratio of 40,000. The p-type dopant is cyclopentadienyl magnesium (Cp2Mg). The intentionally doped p-type GaN layer has a periodic sandwich structure. The intentionally doped p-type GaN layer 5 is cyclically grown from bottom to top, comprising an intentionally doped cyclopentadienyl magnesium (GaN) layer 51, a cyclopentadienyl magnesium (Mg) layer 52, and an undoped GaN layer 53. The thicknesses are 2.5 nm, 0.6 nm, and 1.5 nm, respectively, and the total number of cycles is 15.

[0059] Comparative Example 1

[0060] A single crystal silicon substrate is selected as the substrate 1;

[0061] Using a metal organic chemical vapor deposition (MOCVD) system as an epitaxial growth system, raising the temperature in a reaction chamber of the metal organic chemical vapor deposition system to 1000° C., and cleaning the substrate 1 in an environment where hydrogen is used as an ambient gas;

[0062] TMGa (trimethyl gallium), TMAl (trimethyl aluminum), and NH3 (ammonia) are introduced as raw materials onto the silicon substrate to grow a buffer layer. The temperature in the reaction chamber of the metal organic compound deposition system is adjusted to 1000°C, the pressure is adjusted to 100 mbar, and the V / III ratio is 1000. The buffer layer adopts a composite structure composed of AlN / AlGaN and has a thickness of 100 nm.

[0063] TMGa (trimethyl gallium) and NH3 (ammonia) are introduced as raw materials to grow an unintentionally doped GaN layer on the buffer layer. The temperature in the reaction chamber is adjusted to 1050°C, the pressure is adjusted to 200 mbar, the V / III ratio is 35000, and the thickness of the unintentionally doped GaN layer is 2000 nm.

[0064] A barrier layer of TMGa (trimethyl gallium), TMAl (trimethyl aluminum), and NH3 (ammonia) is introduced onto the unintentionally doped GaN layer. The temperature in the reaction chamber is adjusted to 1040°C, the pressure is adjusted to 50 mbar, the V / III ratio is 3000, and the thickness of the barrier layer is 15 nm.

[0065] A deliberately doped p-type GaN layer was grown on top of the barrier layer. The reaction chamber temperature was adjusted to 950°C, the pressure was adjusted to 300 mbar, the V / III ratio was 50,000, and the p-type dopant was bismuthocene magnesium (Cp2Mg). The deliberately doped p-type GaN layer had a bulk structure (a monomeric structure type grown entirely from a single material) and a total thickness of 90 nm.

[0066] Comparative Example 2

[0067] A silicon carbide substrate is selected as the substrate 1;

[0068] A metal organic chemical vapor deposition (MOCVD) system is used as an epitaxial growth system, the temperature in the reaction chamber of the system is increased to 1100° C., and the substrate 1 is cleaned in an environment of hydrogen as an ambient gas;

[0069] A buffer layer was grown on the silicon carbide substrate using TMGa (trimethyl gallium), TMAl (trimethyl aluminum), and NH3 (ammonia) as raw materials. The temperature in the reaction chamber was adjusted to 1050°C, the pressure was adjusted to 50 mbar, and the V / III ratio was 1500. The buffer layer was a composite structure of AlN / AlGaN with a thickness of 200 nm.

[0070] A non-intentionally doped GaN layer was grown on the buffer layer using TMGa (trimethyl gallium) and NH3 (ammonia) as raw materials. The temperature in the reaction chamber was adjusted to 1100°C, the pressure was adjusted to 300 mbar, the V / III ratio was 40,000, and the thickness of the non-intentionally doped GaN layer was 1500 nm.

[0071] A barrier layer of TMGa (trimethyl gallium), TMAl (trimethyl aluminum), and NH3 (ammonia) is grown on top of the unintentionally doped GaN layer. The temperature in the reaction chamber is adjusted to 1060°C, the pressure is adjusted to 100 mbar, the V / III ratio is 4500, and the thickness of the barrier layer is 18.5 nm.

[0072] A deliberately doped p-type GaN layer was grown on top of the barrier layer. The reaction chamber temperature was adjusted to 1000°C, the pressure was adjusted to 150 mbar, the V / III ratio was 30,000, and the p-type dopant was bismuthocene magnesium (Cp2Mg). The deliberately doped p-type GaN layer was a bulk structure with a total thickness of 90 nm.

[0073] It should be noted that in the above embodiments and the comparative example, the molar amount of magnesium cyclopentadienyl and the molar ratio of Mg / Ga used in the growth and preparation process of the p-type gallium nitride layer are the same.

[0074] After performing HALL concentration tests on the samples produced in the above examples and control examples, the following experimental data were obtained:

[0075]

[0076] The data obtained from the above experimental tests show that the Hall hole concentrations of Examples 1, 2, and 3 are significantly increased compared to those of Control Examples 1 and 2. This increase in hole concentration not only meets the requirements for a p-type functional layer in a HEMT device, but also facilitates ohmic contact during subsequent device fabrication without causing any additional damage to the appearance and performance of the GaN wafer. Therefore, the present invention solves the aforementioned problem of difficulty in obtaining a p-type gallium nitride layer with a high hole concentration.

[0077] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A GaN-based HEMT epitaxial structure, comprising a substrate (1), characterized in that: A buffer layer (2) is epitaxially grown on the upper surface of the substrate (1); a channel layer (3) is epitaxially grown on the upper surface of the buffer layer (2); a barrier layer (4) is epitaxially grown on the upper surface of the channel layer (3); an intentionally doped p-type gallium nitride layer (5) is epitaxially grown on the upper surface of the barrier layer (4); the intentionally doped p-type gallium nitride layer (5) is a periodic structure, and the intentionally doped p-type gallium nitride layer (5) is cyclically grown from bottom to top by an intentionally doped magnesium cyclopentadienyl GaN layer (51), a magnesium cyclopentadienyl GaN layer (52), and an undoped GaN layer (53).

2. The GaN-based HEMT epitaxial structure according to claim 1, characterized in that: The substrate (1) is a silicon substrate, a silicon carbide substrate, or a sapphire substrate.

3. The GaN-based HEMT epitaxial structure according to claim 1, wherein: The buffer layer (2) is an AlN / AlGaN composite structure.

4. The GaN-based HEMT epitaxial structure according to claim 1, wherein: The buffer layer (2) has a thickness of 100 to 300 nm.

5. The GaN-based HEMT epitaxial structure according to claim 1, wherein: The channel layer (3) is an unintentionally doped GaN layer, and the thickness of the channel layer is 1000-2000 nm.

6. The GaN-based HEMT epitaxial structure according to claim 1, characterized in that: The barrier layer (4) has a thickness of 15 to 20 nm.

7. The GaN-based HEMT epitaxial structure according to claim 1, wherein: The thickness of the intentionally doped magnesiumocene GaN layer (51) is 2.5 to 3.0 nm, the thickness of the magnesiumocene layer (52) is 0.6 to 0.8 nm, and the thickness of the undoped GaN layer (53) is 1.5 to 2.0 nm.

8. The GaN-based HEMT epitaxial structure according to claim 1, wherein: The total number of periods of the intentionally doped p-type gallium nitride layer (5) is 15 to 20.

9. A method for preparing a GaN-based HEMT epitaxial structure according to any one of claims 1 to 8, characterized in that: The steps include: The first step is to use a substrate (1) as a substrate for epitaxial growth, use a metal organic chemical vapor deposition system as an epitaxial growth system, place the substrate (1) in a reaction chamber of the metal organic chemical vapor deposition system, adjust the temperature of the reaction chamber to 1000-1100° C., and clean the substrate (1) in an environment where hydrogen is used as a chamber atmosphere gas; In the second step, trimethylgallium, trimethylaluminum and ammonia are introduced as raw materials onto the substrate (1) processed in the first step to grow a buffer layer (2), the temperature in the reaction chamber is adjusted to 950-1050° C., the pressure is adjusted to 50-100 mbar, and V / III is 1000-1500; In the third step, trimethyl gallium and ammonia are introduced as raw materials onto the buffer layer (2) obtained in the second step to grow a channel layer (3), the temperature in the reaction chamber is adjusted to 1050-1100° C., the pressure in the reaction chamber is adjusted to 200-300 mbar, and V / III is 35000-40000; In the fourth step, trimethylgallium, trimethylaluminum and ammonia are introduced into the channel layer (3) obtained in the third step to grow a barrier layer (4), the temperature in the reaction chamber is adjusted to 1040-1060° C., the pressure in the reaction chamber is adjusted to 50-100 mbar, and V / III is 3000-4500; In the fifth step, a deliberately doped p-type gallium nitride layer (5) is grown on the barrier layer (4) obtained in the fourth step. The temperature in the reaction chamber is adjusted to 950-1000° C., the pressure in the reaction chamber is 150-300 mbar, the V / III ratio is 30000-50000, and the p-type dopant is bis(cyclopentadienyl)magnesium.

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