Hemt epitaxial wafer and preparation method thereof, hemt

Abstract

The application discloses a HEMT epitaxial wafer and a preparation method thereof and a HEMT, and the HEMT epitaxial wafer comprises a substrate, a nucleation layer, a buffer layer, a channel layer, an insertion layer, a barrier layer and a cap layer which are sequentially stacked on the substrate; the nucleation layer comprises a BN layer and an AlN layer which are sequentially stacked; the buffer layer comprises a carbon-doped YAlGaN layer, a carbon-doped GaN layer, a Si3N4 layer and an undoped GaN layer which are sequentially stacked; and the doping concentration of the carbon-doped YAlGaN layer is greater than that of the carbon-doped GaN layer. The application can improve the growth quality of the epitaxial layer, thereby improving the performance of the HEMT device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a HEMT epitaxial wafer and its preparation method, and HEMT. Background Technology

[0002] The conventional epitaxial structure of gallium nitride (GaN)-based HEMT devices includes a substrate, buffer layer, channel layer, insertion layer, and barrier layer. Commonly used substrates for epitaxial growth are sapphire, silicon carbide (SiC), and silicon. However, regardless of whether GaN films are grown on sapphire, SiC, or silicon substrates, lattice mismatch and thermal mismatch problems exist. When growing GaN films on silicon substrates, a relatively thick AlGaN layer is typically grown as a buffer layer, but heteroepitaxially grown GaN films still contain a large number of dislocations and defects, with defect densities as high as 10-1. 9 cm -2 This can lead to the formation of leakage current channels in the epitaxial layer. Increased leakage current in the buffer layer results in a decrease in the device's breakdown tolerance and performance failure, severely impacting the lifespan and efficiency of gallium nitride-based HEMT devices. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a HEMT epitaxial wafer that can alleviate the lattice mismatch between the substrate and the GaN epitaxial structure and improve the crystal quality of the epitaxial wafer.

[0004] The technical problem to be solved by the present invention is to provide a method for preparing HEMT epitaxial wafers, which has a simple process and produces HEMT epitaxial wafers with good performance.

[0005] To achieve the above-mentioned technical effects, the present invention provides a HEMT epitaxial wafer, comprising a substrate and a nucleation layer, a buffer layer, a channel layer, an insertion layer, a barrier layer and a capping layer sequentially stacked on the substrate;

[0006] The nucleation layer comprises sequentially stacked BN and AlN layers;

[0007] The buffer layer comprises a carbon-doped YAlGaN layer, a carbon-doped GaN layer, a Si3N4 layer, and an undoped GaN layer stacked sequentially.

[0008] The doping concentration of the carbon-doped YAlGaN layer is greater than that of the carbon-doped GaN layer.

[0009] As an improvement to the above technical solution, the lattice constant of the carbon-doped YAlGaN layer is smaller than that of the carbon-doped GaN layer.

[0010] As an improvement to the above technical solution, the lattice constant of the carbon-doped YAlGaN layer gradually increases along the epitaxial growth direction.

[0011] As an improvement to the above technical solution, the Y component in the carbon-doped YAlGaN layer has a proportion of 0 to 0.15, and the Al component has a proportion of 0 to 0.25.

[0012] As an improvement to the above technical solution, the doping concentration of the carbon-doped YAlGaN layer is 1×10⁻⁶. 19 cm -3 ~1×10 20 cm -3 ;

[0013] The doping concentration of the carbon-doped GaN layer is 1×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .

[0014] As an improvement to the above technical solution, the thickness of the BN layer is 10nm to 100nm; the thickness of the AlN layer is 20nm to 200nm; the thickness of the carbon-doped YAlGaN layer is 400nm to 1000nm; the thickness of the carbon-doped GaN layer is 200nm to 600nm; the thickness of the Si3N4 layer is 5nm to 50nm; and the thickness of the undoped GaN layer is 20nm to 100nm.

[0015] Accordingly, the present invention also discloses a method for preparing a HEMT epitaxial wafer, which includes the following steps:

[0016] A substrate is provided on which a core layer, a buffer layer, a channel layer, an insertion layer, a barrier layer, and a capping layer are sequentially grown.

[0017] The nucleation layer comprises sequentially stacked BN and AlN layers;

[0018] The buffer layer comprises a carbon-doped YAlGaN layer, a carbon-doped GaN layer, a Si3N4 layer, and an undoped GaN layer stacked sequentially.

[0019] The doping concentration of the carbon-doped YAlGaN layer is greater than that of the carbon-doped GaN layer.

[0020] As an improvement to the above technical solution, the growth temperature of the BN layer is 650℃~850℃, and the growth pressure is 70Torr~150Torr;

[0021] The growth temperature of the AlN layer is 700℃~900℃, and the growth pressure is 70Torr~150Torr.

[0022] As an improvement to the above technical solution, the growth temperature of the carbon-doped YAlGaN layer is 800℃~1000℃, and the growth pressure is 100Torr~150Torr;

[0023] The growth temperature of the carbon-doped GaN layer is 800℃~1000℃, and the growth pressure is 100Torr~150Torr;

[0024] The growth temperature of the Si3N4 layer is 900℃~1100℃, and the growth pressure is 100Torr~200Torr;

[0025] The growth temperature of the undoped GaN layer is 1000℃~1200℃, and the growth pressure is 150Torr~250Torr.

[0026] Accordingly, the present invention also discloses a HEMT, including the above-mentioned HEMT epitaxial wafer.

[0027] Implementing the embodiments of the present invention has the following beneficial effects:

[0028] In this invention, BN and AlN layers are deposited as nucleation layers. The BN layer has a large conduction band shift and a small valence band shift, which can improve the problem of electron leakage. Furthermore, the BN layer tends to grow in a two-dimensional layered manner, and its layers are connected by van der Waals forces. Growing an AlN layer on the BN layer can effectively alleviate mismatch stress and improve the crystal quality of the nucleation layer.

[0029] Carbon-doped YAlGaN layers and the introduction of carbon doping into carbon-doped GaN layers can increase the resistance of the buffer layer, reduce the leakage current of the buffer layer, and improve device performance. They can also introduce compressive stress to some extent, alleviating the tensile stress caused by lattice mismatch between the substrate and the buffer layer. High-doped YAlGaN layers and low-doped GaN layers reduce the leakage current of the buffer layer while having little impact on the crystal quality of the epitaxial layer. The introduction of a Si3N4 layer can block dislocation propagation and prevent carbon and oxygen impurities from entering subsequent epitaxial layers, thereby reducing the dislocation density of the epitaxial layer and improving device performance. Finally, an undoped GaN layer is grown to fill surface defects in the buffer layer, providing a high-quality growth platform for the subsequent epitaxial layers. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the HEMT epitaxial wafer provided in an embodiment of the present invention;

[0031] Figure 2 This is a flowchart of the preparation method of HEMT epitaxial wafer provided in the embodiments of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments.

[0033] like Figure 1 As shown, this embodiment of the invention provides a HEMT epitaxial wafer, including a substrate 1 and a nucleation layer 2, a buffer layer 3, a channel layer 4, an insertion layer 5, a barrier layer 6, and a capping layer 7 sequentially stacked on the substrate 1; the nucleation layer 2 includes a BN layer and an AlN layer sequentially stacked; the buffer layer 3 includes a carbon-doped YAlGaN layer, a carbon-doped GaN layer, a Si3N4 layer, and an undoped GaN layer sequentially stacked; the doping concentration of the carbon-doped YAlGaN layer is greater than the doping concentration of the carbon-doped GaN layer.

[0034] The boron nitride (BN) layer, with its hexagonal boron nitride structure, exhibits a larger conduction band shift and a smaller valence band shift compared to AlN, thus mitigating electron leakage. Furthermore, the BN layer tends to grow in a two-dimensional layered manner, with layers connected by van der Waals forces. Growing an AlN layer on this BN layer effectively alleviates mismatch stress and improves the crystal quality of the nucleation layer. Introducing carbon doping into carbon-doped YAlGaN layers and carbon-doped GaN layers increases the resistance of the buffer layer, reduces leakage current, and enhances device performance. Since the radius of carbon atoms is smaller than that of nitrogen atoms, carbon doping in these layers also introduces compressive stress to some extent, alleviating tensile stress caused by lattice mismatch between the substrate and the buffer layer, thereby improving the crystal quality of the buffer layer. High-doped YAlGaN layers reduce buffer layer leakage current, while low-doped GaN layers reduce leakage current with minimal impact on the crystal quality of the epitaxial layer. The introduction of a Si3N4 layer can block dislocation extension and prevent carbon and oxygen impurities from forming subsequent epitaxial layers, thereby reducing the dislocation density in the epitaxial layer and improving device performance. Finally, growing an undoped GaN layer in an H2 atmosphere can fill the surface defects of the buffer layer and provide a high-quality growth platform for the subsequent epitaxial layer.

[0035] In one embodiment, the lattice constant of the carbon-doped YAlGaN layer is smaller than that of the carbon-doped GaN layer. The smaller lattice constant of the carbon-doped YAlGaN layer and the larger lattice constant of the carbon-doped GaN layer, when stacked sequentially, can further increase the compressive stress introduced by the buffer layer, reduce the tensile stress of the substrate on the buffer layer, and improve the crystal quality of the buffer layer.

[0036] In one embodiment, the lattice constant of the carbon-doped YAlGaN layer gradually increases along the epitaxial growth direction. Specifically, the lattice constant of the carbon-doped YAlGaN layer increases linearly or stepwise along the epitaxial growth direction. As the buffer layer continues to grow and its thickness increases, the tensile stress on the epitaxial layer from the substrate gradually accumulates and increases. The gradual increase in the lattice constant of the carbon-doped YAlGaN layer leads to a gradual increase in the compressive stress introduced by the buffer layer, thereby reducing the tensile stress exerted on the buffer layer by the substrate and further improving the crystal quality of the buffer layer.

[0037] In one embodiment, the Y component in the carbon-doped YAlGaN layer has a proportion of 0 to 0.15. If the proportion of Y component is too large, it will cause a decrease in quality. For example, the proportion of Y component in the carbon-doped YAlGaN layer is 0, 0.05, 0.08, 0.1, 0.12, or 0.15, but is not limited to these. The Al component in the carbon-doped YAlGaN layer has a proportion of 0 to 0.25. If the proportion of Al component is too large, it will increase the mismatch with the subsequent epitaxial layers. For example, the proportion of Al component in the carbon-doped YAlGaN layer is 0, 0.08, 0.1, 0.15, 0.18, 0.2, or 0.25, but is not limited to these.

[0038] In one embodiment, the doping concentration of the carbon-doped YAlGaN layer is 1 × 10⁻⁶. 19 cm -3 ~1×10 20 cm -3 The doping concentration of the carbon-doped GaN layer is 1×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 By controlling the doping concentrations of the carbon-doped YAlGaN layer and the carbon-doped GaN layer within this range, the growth quality can be improved while ensuring sufficient doping concentration. For example, the doping concentration of the carbon-doped YAlGaN layer is 1 × 10⁻⁶. 19 cm -3 5×10 19 cm -3 8×10 19 cm -3 Or 1×10 20 cm -3 However, this is not the only possibility. For example, the doping concentration of the carbon-doped GaN layer is 1 × 10⁻⁶. 18 cm -3 5×10 18 cm -3 8×10 18 cm -3 Or 1×10 19 cm -3However, it is not limited to this.

[0039] In one embodiment, the thickness of the BN layer is 10 nm to 100 nm. If the thickness of the BN layer is less than 10 nm, it is not conducive to stress relief; if the thickness of the BN layer is greater than 100 nm, the band gap will decrease due to electron band dispersion. For example, the thickness of the BN layer is 10 nm, 20 nm, 30 nm, 50 nm, 60 nm, 80 nm, or 100 nm, but is not limited to these. The thickness of the AlN layer is 20 nm to 200 nm. For example, the thickness of the AlN layer is 20 nm, 30 nm, 50 nm, 80 nm, 100 nm, 150 nm, or 200 nm, but is not limited to these.

[0040] In one embodiment, the thickness of the carbon-doped YAlGaN layer is 400 nm to 1000 nm. If the thickness of the carbon-doped YAlGaN layer is less than 400 nm, it cannot provide sufficient compressive stress; if the thickness of the carbon-doped YAlGaN layer is greater than 1000 nm, it will cause a decrease in lattice quality. For example, the thickness of the carbon-doped YAlGaN layer is 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, or 1000 nm, but is not limited thereto. The thickness of the carbon-doped GaN layer is 200 nm to 600 nm. For example, the thickness of the carbon-doped GaN layer is 200 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or 600 nm, but is not limited thereto. The thickness of the Si3N4 layer is 5nm to 50nm. If the thickness of the Si3N4 layer is less than 5nm, it cannot effectively prevent dislocations and impurities from spreading. If the thickness of the Si3N4 layer is greater than 50nm, lattice mismatch will cause cracking in the subsequently grown undoped GaN layer. For example, the thickness of the Si3N4 layer is 5nm, 10nm, 15nm, 20nm, 30nm, 40nm, or 50nm, but is not limited to these. The thickness of the undoped GaN layer is 20nm to 100nm. For example, the thickness of the undoped GaN layer is 20nm, 30nm, 50nm, 70nm, 90nm, or 100nm, but is not limited to these.

[0041] In addition to the nucleating layer and buffer layer structures described above, the other layered structures of the present invention have the following characteristics:

[0042] The substrate 1 includes, but is not limited to, a Si substrate, a sapphire substrate, a SiC substrate, and a GaN substrate. In one embodiment, the substrate is a Si substrate.

[0043] The channel layer 4 includes, but is not limited to, a GaN channel layer and an InGaN channel layer. In one embodiment, the channel layer 4 is an InGaN channel layer with a thickness of 50 nm to 300 nm.

[0044] In one embodiment, the insertion layer 5 is an AlN insertion layer with a thickness of 1 nm to 6 nm.

[0045] In one embodiment, the barrier layer 6 is an AlGaN barrier layer with a thickness of 5nm to 40nm.

[0046] In one embodiment, the capping layer 7 is a GaN capping layer with a thickness of 15nm to 50nm.

[0047] Correspondingly, such as Figure 2 As shown, the present invention also provides a method for preparing a HEMT epitaxial wafer, comprising the following steps:

[0048] S100 provides a substrate:

[0049] The substrate can be selected from Si substrate, sapphire substrate, SiC substrate, and GaN substrate. In one embodiment, a Si substrate is selected.

[0050] S200 nucleation layer:

[0051] Growth can be achieved through PVD, MOCVD, MBE, or HVPE. Specifically, in one embodiment, the growth of the nucleation layer includes the following steps:

[0052] S201 BN layer growth:

[0053] MOCVD growth was employed, with the reaction chamber temperature controlled at 650℃~850℃ and the pressure at 70Torr~150Torr, and N and B sources introduced.

[0054] AlN layers are grown using S202:

[0055] MOCVD growth was employed, with the reaction chamber temperature controlled at 700℃~900℃ and the pressure at 70Torr~150Torr, and N source and Al source were introduced.

[0056] S300 growth buffer layer:

[0057] The growth can be performed using PVD, MOCVD, MBE, or HVPE. Specifically, in one embodiment, the growth of the buffer layer includes the following steps:

[0058] S301 grows carbon-doped YAlGaN layers:

[0059] MOCVD growth was employed, with the reaction chamber temperature controlled at 800℃~1000℃ and the pressure at 100Torr~150Torr. N source, Ga source, Al source, Y source and C source were introduced.

[0060] S302 grows carbon-doped GaN layers:

[0061] MOCVD growth was employed, with the reaction chamber temperature controlled at 800℃~1000℃ and the pressure at 100Torr~150Torr, and N source, Ga source and C source were introduced.

[0062] Si3N4 layer grown in S303:

[0063] MOCVD growth was employed, with the reaction chamber temperature controlled at 900℃~1100℃ and the pressure at 100Torr~200Torr, and N source and Si source were introduced.

[0064] S304 for growing undoped GaN layers:

[0065] MOCVD growth was employed, with the reaction chamber temperature controlled at 1000℃~1200℃ and the pressure at 150Torr~250Torr, and N source and Ga source were introduced.

[0066] S400 growth channel layer:

[0067] In one embodiment, MOCVD growth is employed, with the reaction chamber temperature controlled at 650°C to 950°C and the pressure at 50 Torr to 250 Torr, and N, Ga, and In sources introduced.

[0068] S500 growth insertion layer:

[0069] In one embodiment, MOCVD growth is employed, with the reaction chamber temperature controlled at 700°C to 1100°C and the pressure at 100 Torr to 200 Torr, and N and Al sources introduced.

[0070] S600 growth barrier layer:

[0071] In one embodiment, MOCVD growth is employed, with the reaction chamber temperature controlled at 800°C to 1200°C and the pressure at 100 Torr to 200 Torr, and N source, Ga source, and Al source introduced.

[0072] S700 growth cap layer:

[0073] In one embodiment, MOCVD growth is employed, with the reaction chamber temperature controlled at 700°C to 1100°C and the pressure at 100 Torr to 200 Torr, and an N source and a Ga source introduced.

[0074] During growth, the Al source can be TMAl, the In source can be TMIn, the Ga source can be TMGa, the N source can be NH3, the B source can be TEB, and the Y source can be C. 33 H 57 O6Y, the C source can be CCl4, the Si source can be SiH4, and the Mg source can be CP2Mg, but it is not limited to these.

[0075] The present invention will be further illustrated below with specific embodiments.

[0076] Example 1

[0077] This embodiment provides a HEMT epitaxial wafer, including a substrate and a nucleation layer, a buffer layer, a channel layer, an insertion layer, a barrier layer and a capping layer sequentially stacked on the substrate.

[0078] The substrate is a Si substrate.

[0079] The nucleation layer consists of a BN layer and an AlN layer deposited sequentially, with the BN layer having a thickness of 35 nm and the AlN layer having a thickness of 100 nm.

[0080] The buffer layer consists of a carbon-doped YAlGaN layer, a carbon-doped GaN layer, a Si3N4 layer, and an undoped GaN layer deposited sequentially. The doping concentration of the carbon-doped YAlGaN layer is 1.5 × 10⁻⁶. 20 cm -3 The thickness is 100 nm, the Y composition is 0.16%, the Al composition is 0.26%, and the lattice constant of the carbon-doped YAlGaN layer remains unchanged. The doping concentration of the carbon-doped GaN layer is 1.5 × 10⁻⁶. 19 cm -3 The thickness of the Si3N4 layer is 450 nm. The thickness of the Si3N4 layer is 20 nm. The thickness of the undoped GaN layer is 55 nm.

[0081] The channel layer is an InGaN channel layer with a thickness of 100nm.

[0082] The insertion layer is an AlN insertion layer with a thickness of 3 nm.

[0083] The barrier layer is an AlGaN barrier layer with a thickness of 10 nm.

[0084] The capping layer is a GaN capping layer with a thickness of 20nm.

[0085] The above-mentioned method for preparing HEMT epitaxial wafers includes the following steps:

[0086] S100 provides a substrate:

[0087] The substrate used is a Si substrate.

[0088] The S200 nucleation layer growth process specifically includes the following steps:

[0089] S201 BN layer growth:

[0090] MOCVD growth was employed, with the reaction chamber temperature controlled at 750℃ and the pressure at 120 Torr, and N and B sources introduced.

[0091] AlN layers are grown using S202:

[0092] MOCVD growth was employed, with the reaction chamber temperature controlled at 800℃ and the pressure at 100 Torr, and N and Al sources introduced.

[0093] The S300 growth buffer layer specifically includes the following steps:

[0094] S301 grows carbon-doped YAlGaN layers:

[0095] MOCVD growth was employed, with the reaction chamber temperature controlled at 900℃ and the pressure at 100 Torr. N, Ga, Al, Y, and C sources were introduced.

[0096] S302 grows carbon-doped GaN layers:

[0097] MOCVD growth was employed, with the reaction chamber temperature controlled at 900℃ and the pressure at 120 Torr, and N, Ga, and C sources introduced.

[0098] Si3N4 layer grown in S303:

[0099] MOCVD growth was employed, with the reaction chamber temperature controlled at 1000℃ and the pressure at 150 Torr, and N and Si sources introduced.

[0100] S304 for growing undoped GaN layers:

[0101] MOCVD growth was employed, with the reaction chamber temperature controlled at 1100℃ and the pressure at 200 Torr, and N and Ga sources introduced.

[0102] S400 growth channel layer:

[0103] MOCVD growth was employed, with the reaction chamber temperature controlled at 800℃ and the pressure at 120 Torr, and N, Ga, and In sources introduced.

[0104] S500 growth insertion layer:

[0105] MOCVD growth was employed, with the reaction chamber temperature controlled at 900℃ and the pressure at 120 Torr, and N and Al sources introduced.

[0106] S600 growth barrier layer:

[0107] MOCVD growth was employed, with the reaction chamber temperature controlled at 1000℃ and the pressure at 150 Torr, and N, Ga, and Al sources introduced.

[0108] S700 growth cap layer:

[0109] MOCVD growth was employed, with the reaction chamber temperature controlled at 900℃ and the pressure at 120 Torr, and N and Ga sources introduced.

[0110] Example 2

[0111] This embodiment provides a HEMT epitaxial wafer, which differs from Embodiment 1 in that the Y composition of the carbon-doped YAlGaN layer is 0.12, the Al composition is 0.25, and the lattice constant of the carbon-doped YAlGaN layer remains unchanged. All other aspects are the same as in Embodiment 1.

[0112] Example 3

[0113] This embodiment provides a HEMT epitaxial wafer, which differs from Embodiment 1 in that the Y composition percentage of the carbon-doped YAlGaN layer along the epitaxial growth direction is 0.12, 0.08, and 0.04, respectively, and the Al composition percentage is 0.25, 0.15, and 0.05, respectively, resulting in a stepwise increase in the lattice constant of the carbon-doped YAlGaN layer along the epitaxial growth direction. All other aspects are the same as in Embodiment 1.

[0114] Example 4

[0115] This embodiment provides a HEMT epitaxial wafer, which differs from Embodiment 3 in that the doping concentration of the carbon-doped YAlGaN layer is 4.5 × 10⁻⁶. 19 cm -3 The doping concentration of the carbon-doped GaN layer is 4 × 10⁻⁶. 18 cm -3 Everything else is the same as in Example 3.

[0116] Comparative Example 1

[0117] This comparative example provides a HEMT epitaxial wafer, which differs from Example 1 in that the nucleation layer is an AlN layer, the buffer layer is an AlGaN / GaN layer, the AlGaN layer has a thickness of 10 nm, the GaN layer has a thickness of 15 nm, and the number of periods is 10. Correspondingly, in the fabrication method, the nucleation layer does not include the preparation step of the BN layer. The preparation step of the buffer layer involves controlling the reaction chamber temperature at 800°C and the pressure at 150 Torr, introducing Al, Ga, and N sources to grow the AlGaN layer; maintaining the temperature and pressure constant, introducing Ga and N sources to grow the GaN layer; and repeating the stacking and periodic growth of the AlGaN and GaN layers. All other steps are the same as in Example 1.

[0118] Comparative Example 2

[0119] This comparative example provides a HEMT epitaxial wafer, which differs from Example 1 in that the nucleation layer does not contain a BN layer; correspondingly, the preparation method does not include a BN layer preparation step. All other aspects are the same as in Example 1.

[0120] Comparative Example 3

[0121] This comparative example provides a HEMT epitaxial wafer, which differs from Example 1 in that the nucleation layer does not contain an AlN layer; correspondingly, the preparation method does not include an AlN layer preparation step. All other aspects are the same as in Example 1.

[0122] Comparative Example 4

[0123] This comparative example provides a HEMT epitaxial wafer, which differs from Example 1 in that the buffer layer does not contain a carbon-doped YAlGaN layer; correspondingly, the fabrication method does not include the step of preparing a carbon-doped YAlGaN layer. All other aspects are the same as in Example 1.

[0124] Comparative Example 5

[0125] This comparative example provides a HEMT epitaxial wafer, which differs from Example 1 in that the buffer layer does not contain a carbon-doped GaN layer; correspondingly, the fabrication method does not include a step for preparing a carbon-doped GaN layer. All other aspects are the same as in Example 1.

[0126] Comparative Example 6

[0127] This comparative example provides a HEMT epitaxial wafer, which differs from Example 1 in that the buffer layer does not contain a Si3N4 layer; correspondingly, the preparation method does not include the Si3N4 layer preparation step. All other aspects are the same as in Example 1.

[0128] Comparative Example 7

[0129] This comparative example provides a HEMT epitaxial wafer, which differs from Example 1 in that the buffer layer does not contain an undoped GaN layer; correspondingly, the fabrication method also does not include a step for preparing an undoped GaN layer. All other aspects are the same as in Example 1.

[0130] Performance testing:

[0131] HEMT epitaxial wafers prepared in Examples 1 to 4 and Comparative Examples 1 to 7 were fabricated into HEMT devices for testing. The rocking curves of the GaN(102) surface were obtained by XRD, and the edge dislocation density was calculated as the dislocation density of Examples 1 to 4 and Comparative Examples 1 to 7 according to the following formula. The results are shown in Table 1.

[0132]

[0133] In the formula N edge Edge dislocation density (EDD); Δω e is the FWHM of the (102) plane; a is the Burgers vector, a = 0.3189 nm.

[0134] Table 1 Performance test results of HEMT epitaxial wafers

[0135] Example 1 <![CDATA[2.3×10 7 ]]> Example 2 <![CDATA[1.8×10 7 ]]> Example 3 <![CDATA[1.2×10 7 ]]> Example 4 <![CDATA[9.7×10 6 ]]> Comparative Example 1 <![CDATA[1.8×10 9 ]]> Comparative Example 2 <![CDATA[7.1×10 7 ]]> Comparative Example 3 <![CDATA[9.4×10 7 ]]> Comparative Example 4 <![CDATA[3.6×10 7 ]]> Comparative Example 5 <![CDATA[2.9×10 8 ]]> Comparative Example 6 <![CDATA[6.5×10 7 ]]> Comparative Example 7 <![CDATA[7.1×10 7 ]]>

[0136] As can be seen from the table, the nucleation layer and buffer layer structure of the present invention can effectively reduce dislocation density and improve the performance of HEMT devices.

[0137] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A HEMT epitaxial wafer, characterized in that, It includes a substrate and a nucleation layer, a buffer layer, a channel layer, an insertion layer, a barrier layer and a capping layer sequentially stacked on the substrate; The nucleation layer comprises sequentially stacked BN and AlN layers; The buffer layer comprises a carbon-doped YAlGaN layer, a carbon-doped GaN layer, a Si3N4 layer, and an undoped GaN layer stacked sequentially. The doping concentration of the carbon-doped YAlGaN layer is greater than that of the carbon-doped GaN layer.

2. The HEMT epitaxial wafer as described in claim 1, characterized in that, The lattice constant of the carbon-doped YAlGaN layer is smaller than that of the carbon-doped GaN layer.

3. The HEMT epitaxial wafer as described in claim 1, characterized in that, The lattice constant of the carbon-doped YAlGaN layer gradually increases along the epitaxial growth direction.

4. The HEMT epitaxial wafer as described in claim 1, characterized in that, The Y component in the carbon-doped YAlGaN layer accounts for 0.05~0.15%, and the Al component accounts for 0.08~0.25%.

5. The HEMT epitaxial wafer as described in claim 1, characterized in that, The doping concentration of the carbon-doped YAlGaN layer is 1×10⁻⁶. 19 cm -3 ~1×10 20 cm -3 ; The doping concentration of the carbon-doped GaN layer is 1×10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .

6. The HEMT epitaxial wafer as described in claim 1, characterized in that, The thickness of the BN layer is 10nm~100nm; the thickness of the AlN layer is 20nm~200nm; the thickness of the carbon-doped YAlGaN layer is 400nm~1000nm; the thickness of the carbon-doped GaN layer is 200nm~600nm; the thickness of the Si3N4 layer is 5nm~50nm; and the thickness of the undoped GaN layer is 20nm~100nm.

7. A method for preparing a HEMT epitaxial wafer, used to prepare the HEMT epitaxial wafer as described in any one of claims 1 to 6, characterized in that, Includes the following steps: A substrate is provided on which a core layer, a buffer layer, a channel layer, an insertion layer, a barrier layer, and a capping layer are sequentially grown. The nucleation layer comprises sequentially stacked BN and AlN layers; The buffer layer comprises a carbon-doped YAlGaN layer, a carbon-doped GaN layer, a Si3N4 layer, and an undoped GaN layer stacked sequentially. The doping concentration of the carbon-doped YAlGaN layer is greater than that of the carbon-doped GaN layer.

8. The method for preparing a HEMT epitaxial wafer as described in claim 7, characterized in that, The growth temperature of the BN layer is 650℃~850℃, and the growth pressure is 70Torr~150Torr. The growth temperature of the AlN layer is 700℃~900℃, and the growth pressure is 70Torr~150Torr.

9. The method for preparing a HEMT epitaxial wafer as described in claim 7, characterized in that, The growth temperature of the carbon-doped YAlGaN layer is 800℃~1000℃, and the growth pressure is 100Torr~150Torr; The growth temperature of the carbon-doped GaN layer is 800℃~1000℃, and the growth pressure is 100Torr~150Torr; The growth temperature of the Si3N4 layer is 900℃~1100℃, and the growth pressure is 100Torr~200Torr. The growth temperature of the undoped GaN layer is 1000℃~1200℃, and the growth pressure is 150Torr~250Torr.

10. A HEMT, characterized in that, The HEMT includes the HEMT epitaxial wafer as described in any one of claims 1 to 6.

Images