Epitaxial wafer, epitaxial wafer growth method and high electron mobility transistor

Abstract

The present invention provides an epitaxial wafer, an epitaxial wafer growth method, and a high electron mobility transistor. The epitaxial wafer comprises a sequentially stacked Si substrate, an AlN nucleation layer, a high-resistance buffer layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer, and a GaN cap layer. The high-resistance buffer layer comprises a first carbon-doped AlGaN layer, a second carbon-doped AlGaN layer, and a third carbon-doped AlGaN layer, the first carbon-doped AlGaN layer being disposed proximal to the AlN nucleation layer. The doping concentration of the first carbon-doped AlGaN layer uniformly changes from high to low, the doping concentration of the second carbon-doped AlGaN layer remains constant, and the doping concentration of the third carbon-doped AlGaN layer uniformly changes from low to high. Compared with the prior art, the epitaxial wafer proposed by the present invention achieves both high resistance and high crystal quality.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an epitaxial wafer, an epitaxial wafer growth method and a high electron mobility transistor. Background Art

[0002] As a third-generation semiconductor material, GaN-based materials have become the preferred material for manufacturing high-temperature, high-frequency, high-power, and radiation-resistant high electron mobility transistor (HEMT) structures due to their advantages such as large bandgap, large electron saturation drift velocity, good chemical stability, radiation resistance, high temperature resistance, and easy formation of heterojunctions. On the other hand, since GaN-based heterostructures have high carrier concentration and electron mobility, their on-resistance is small, and the advantage of large bandgap enables them to withstand very high operating voltages. Therefore, GaN-based high electron mobility transistors are also suitable for applications such as high-temperature, high-frequency, high-power devices, and low-loss switching devices.

[0003] Common substrates for growing GaN thin films in the aforementioned fields are sapphire (Al2O3), silicon carbide (SiC), and silicon (Si). Epitaxial growth of GaN thin films on sapphire and SiC substrates is highly established, but their relative price, particularly SiC, significantly increases production costs. Furthermore, sapphire itself has poor heat dissipation, making large-scale epitaxial growth difficult. Therefore, Si substrates are typically used for epitaxial growth of GaN thin films. Their excellent thermal conductivity allows for large-scale epitaxial growth, particularly on 6-inch, 8-inch, and 12-inch epitaxial wafers, reducing production costs and offering significant market competitiveness. However, the oxygen atoms released by the oxides (e.g., SiO2) contained on the Si substrate surface decompose at high temperatures and diffuse into the buffer layer during epitaxial layer growth, causing leakage in the buffer layer and preventing high resistance, thus reducing device performance. Furthermore, the high concentration of two-dimensional electron gas near the channel layer easily overflows into the buffer layer, further preventing the buffer layer from achieving high resistance.

[0004] In order to solve the above problems, the existing technology usually achieves high resistance and reduces leakage of the buffer layer by high-concentration Fe or C doping of the buffer layer. However, high-concentration doping affects the crystal quality of the epitaxial layer and is not conducive to improving device performance. Although low-concentration doping can improve the crystal quality of the epitaxial layer, it is difficult to achieve high resistance. Summary of the Invention

[0005] In view of this, an object of the present invention is to provide an epitaxial wafer, an epitaxial wafer growth method and a high electron mobility transistor, so as to achieve high resistance of the epitaxial layer and improve the crystal quality of the epitaxial layer.

[0006] An embodiment of the present invention is implemented as follows: an epitaxial wafer includes a Si substrate, an AlN nucleation layer, a high-resistance buffer layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer, and a GaN cap layer stacked in sequence, wherein the high-resistance buffer layer includes a first carbon-doped AlGaN layer, a second carbon-doped AlGaN layer, and a third carbon-doped AlGaN layer stacked in sequence, wherein the first carbon-doped AlGaN layer is disposed on a side close to the AlN nucleation layer;

[0007] The doping concentration of the first carbon-doped AlGaN layer changes uniformly from high to low, the doping concentration of the second carbon-doped AlGaN layer remains constant, and the doping concentration of the third carbon-doped AlGaN layer changes uniformly from low to high.

[0008] Furthermore, in the epitaxial wafer, the Al composition of AlGaN in the first carbon-doped AlGaN layer is 0.50-0.80, and the doping concentration of the first carbon-doped AlGaN layer is 5*10 17 cm -3 -5*10 20 cm -3 .

[0009] Furthermore, in the epitaxial wafer, the Al composition of AlGaN in the second carbon-doped AlGaN layer is 0.40-0.50, and the doping concentration of the second carbon-doped AlGaN layer is 5*10 15 cm -3 -5*10 16 cm -3 .

[0010] Furthermore, the Al composition of AlGaN in the third carbon-doped AlGaN layer is 0.20-0.40, and the doping concentration of the second carbon-doped AlGaN layer is 5*10 17 cm -3 -5*10 20 cm -3 .

[0011] Furthermore, in the above-mentioned epitaxial wafer, the thickness of the first carbon-doped AlGaN layer is 0.5-1.0 μm, the thickness of the second carbon-doped AlGaN layer is 0.5-1.0 μm, and the thickness of the third carbon-doped AlGaN layer is 300-600 nm.

[0012] Furthermore, in the above-mentioned epitaxial wafer, a pre-laid Al layer is provided between the Si substrate and the AlN nucleation layer, and the thickness of the pre-laid Al layer is 1 to 5 nm.

[0013] Another object of the present invention is to provide an epitaxial wafer growth method for growing the above-mentioned epitaxial wafer, the method comprising:

[0014] Providing a Si substrate, and pre-laying an Al layer on the Si substrate;

[0015] An AlN nucleation layer, a first carbon-doped AlGaN layer, a second carbon-doped AlGaN layer, a third carbon-doped AlGaN layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer and a GaN cap layer are sequentially grown on the pre-laid Al layer.

[0016] Furthermore, in the above-mentioned epitaxial wafer growth method, in which, in the step of sequentially growing an AlN nucleation layer, a first carbon-doped AlGaN layer, a second carbon-doped AlGaN layer, a third carbon-doped AlGaN layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer and a GaN cap layer on the pre-laid Al layer, the growth temperature of the first carbon-doped AlGaN layer and the second carbon-doped AlGaN layer are both 1000°C-1200°C, and the pressure is both 40-70 mbar, and the growth temperature of the third carbon-doped AlGaN layer is 1050°C-1150°C, and the pressure is 150-250 mbar.

[0017] Furthermore, the above-mentioned epitaxial wafer growth method, wherein the step of providing a Si substrate and pre-laying an Al layer on the Si substrate further comprises:

[0018] The Si substrate is deoxidized by high-temperature treatment for 5 to 10 minutes in a chamber temperature of 1000 to 1200° C., a chamber pressure of 50 to 150 mbar, and a H 2 atmosphere.

[0019] Another object of the present invention is to provide a high electron mobility transistor, comprising the above-mentioned epitaxial wafer.

[0020] Compared with the prior art, the present invention avoids the need to perform high-concentration carbon doping on the entire buffer layer to achieve high resistance by providing an AlGaN buffer layer and performing carbon doping and changing the carbon doping method, thereby improving the overall epitaxial crystal quality of the buffer layer; and the carbon doping concentration of the first carbon-doped AlGaN buffer layer gradually changes from high to low, which can block impurities such as Si atoms and oxygen atoms that diffuse from the substrate to the epitaxial layer. Since the impurity concentration is higher on the side close to the substrate, the concentration of impurities diffused into the epitaxial layer will gradually decrease as the epitaxial layer grows, which can effectively block the diffusion of impurities to achieve high resistance in the buffer layer without reducing the crystal quality; due to the first carbon doping The AlGaN buffer layer has already blocked the diffusion of most impurities. Constant carbon doping of the second carbon-doped AlGaN buffer layer can take into account both crystal quality and high resistance characteristics. The carbon doping concentration of the third carbon-doped AlGaN buffer layer gradually changes from low to high. Since the two-dimensional electron gas concentration close to the GaN channel layer is high, it is easy to overflow into the buffer layer. The carbon doping concentration of the third carbon-doped AlGaN buffer layer is set to gradually change from low to high to block the two-dimensional electron gas from overflowing into the buffer layer, so that the buffer layer achieves high resistance, reduces buffer layer leakage, and improves the pinch-off characteristics and voltage resistance characteristics of the device, thereby achieving high resistance of the epitaxial growth while ensuring the crystal quality of the epitaxial growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the epitaxial wafer in the first embodiment of the present invention;

[0022] Figure 2 This is a flow chart of a method for growing an epitaxial wafer according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0024] Furthermore, as used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. In the detailed description and claims, a list of items connected by the term "one of" may mean any of the listed items. For example, if items A and B are listed, the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements. In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" or "at least one of A or B" means only A; only B; or both A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" or "at least one of A, B, or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0025] Example 1

[0026] See also Figure 1 , is an epitaxial wafer provided in the first embodiment of the present invention, comprising a Si substrate 1, an AlN nucleation layer 3, a high-resistance buffer layer 4, a GaN channel layer 5, an AlN insertion layer 6, an AlGaN barrier layer 7, and a GaN cap layer 8 stacked in sequence, wherein the high-resistance buffer layer 4 comprises a first carbon-doped AlGaN layer 40, a second carbon-doped AlGaN layer 41, and a third carbon-doped AlGaN layer 42 stacked in sequence, wherein the first carbon-doped AlGaN layer 40 is disposed on a side close to the AlN nucleation layer 3;

[0027] The doping concentration of the first carbon-doped AlGaN layer 40 changes uniformly from high to low, the doping concentration of the second carbon-doped AlGaN layer 41 remains constant, and the doping concentration of the third carbon-doped AlGaN layer 42 changes uniformly from low to high.

[0028] It can be understood that by providing multiple carbon-doped AlGaN buffer layers and gradually doping the carbon doping concentration of the first carbon-doped AlGaN layer 40 from high to low, the carbon doping concentration of the second carbon-doped AlGaN layer 41 is constantly doped, and the carbon doping concentration of the third carbon-doped AlGaN layer 42 is gradually changed from low to high, the first carbon-doped AlGaN layer 40 can block impurities such as Si atoms and oxygen atoms that diffuse from the substrate to the epitaxial layer. Moreover, since the first carbon-doped AlGaN layer 40 has already blocked the diffusion of most impurities, the constant carbon doping of the second carbon-doped AlGaN layer 41 can take into account both crystal quality and high resistance characteristics. Since the two-dimensional electron gas concentration close to the GaN channel layer is relatively high and easily overflows into the buffer layer, the carbon doping concentration of the third carbon-doped AlGaN layer 42 is gradually changed from low to high to block the two-dimensional electron gas from overflowing into the buffer layer, thereby achieving high resistance in the buffer layer, reducing leakage current in the buffer layer, and improving the pinch-off characteristics and withstand voltage characteristics of the device, thereby achieving high resistance of the epitaxial layer and ensuring the crystal quality of the epitaxial layer.

[0029] By way of example and not limitation, in some preferred embodiments of the present invention, the Al composition of AlGaN in the first carbon-doped AlGaN layer 40 is 0.50-0.80, and the doping concentration of the first carbon-doped AlGaN layer 40 is 5*10 17 cm -3 -5*10 20 cm -3 The Al composition of AlGaN in the second carbon-doped AlGaN layer 41 is 0.40-0.50, and the doping concentration of the second carbon-doped AlGaN layer 41 is 5*10 15 cm -3 -5*10 16 cm -3 The Al composition of AlGaN in the third carbon-doped AlGaN layer 42 is 0.20-0.40, and the doping concentration of the second carbon-doped AlGaN layer 42 is 5*10 17 cm -3 -5*10 20 cm -3 .

[0030] Specifically, the thickness of the first carbon-doped AlGaN layer 40 is 0.5-1.0 μm, the thickness of the second carbon-doped AlGaN layer 41 is 0.5-1.0 μm, and the thickness of the third carbon-doped AlGaN layer 42 is 300-600 nm.

[0031] Furthermore, a pre-laid Al layer 2 is provided between the Si substrate 1 and the AlN nucleation layer 3 . The thickness of the pre-laid Al layer 2 is 1 to 5 nm. By providing the pre-laid Al layer 2 , the interface reaction between the Si substrate 1 and the AlN nucleation layer 3 can be suppressed.

[0032] Example 2

[0033] See also Figure 2 , is a method for growing an epitaxial wafer provided in a second embodiment of the present invention, which is used to grow the epitaxial wafer in the above-mentioned embodiment 1, and the method includes steps S20 to S21:

[0034] Step S20, providing a Si substrate, and pre-laying an Al layer on the Si substrate;

[0035] Among them, a layer of Al is first pre-laid on the substrate to suppress the interface reaction between the Si substrate and the epitaxial layer. Specifically, the growth temperature of the pre-laid Al layer is 1000-1100°C, the pressure is 40-70mbar, and the flow rate of the Al source is 50-200sccm.

[0036] In addition, in order to improve the growth effect of the epitaxial wafer, in some optional embodiments of the present invention, the step of providing a Si substrate and pre-laying an Al layer on the Si substrate further includes:

[0037] The Si substrate is deoxidized by high-temperature treatment for 5 to 10 minutes in a chamber temperature of 1000 to 1200° C., a chamber pressure of 50 to 150 mbar, and a H 2 atmosphere.

[0038] The processing method includes but is not limited to MOCVD.

[0039] Step S21 , sequentially growing an AlN nucleation layer, a first carbon-doped AlGaN layer, a second carbon-doped AlGaN layer, a third carbon-doped AlGaN layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer, and a GaN capping layer on the pre-laid Al layer.

[0040] Specifically, the first carbon-doped AlGaN layer and the second carbon-doped AlGaN layer are grown at temperatures of 1000° C.-1200° C. and pressures of 40-70 mbar, and the third carbon-doped AlGaN layer is grown at temperatures of 1050° C.-1150° C. and pressures of 150-250 mbar.

[0041] In addition, in a specific implementation, the growth temperature of the AlN nucleation layer is 1100°C-1200°C, the thickness is 150-300nm, and the growth pressure is between 40-70mbar; the thickness of the GaN channel layer is between 300-600nm, the growth temperature is 1050°C-1150°C, and the growth pressure is 150-250mbar; the thickness of the AlN insertion layer is 1nm, the growth temperature is 1050°C-1150°C, and the growth pressure is 40-70mbar; the thickness of the AlGaN barrier layer is 20-25nm The growth temperature is between 1050℃ and 1150℃, the growth pressure is between 40 and 70mbar, and the Al component is between 0.20 and 0.25; the thickness of the GaN cap layer is 3 to 10nm, the growth temperature is 1050℃ and 1150℃, and the pressure is 40 to 70mbar; wherein trimethylaluminum (TMAl), trimethylgallium (TMGa) or triethylgallium (TEGa), and NH3 are respectively used as precursors of group III and group V sources, carbon tetrabromide (CBr4) is used as a precursor of the carbon (C) source, and N2 and H2 are used as carrier gases.

[0042] In summary, the epitaxial wafer and epitaxial wafer growth method in the embodiment of the present invention, by providing an AlGaN buffer layer and performing carbon doping and changing the carbon doping method, avoids the need to perform high-concentration carbon doping on the entire buffer layer to achieve high resistance, and can improve the overall epitaxial crystal quality of the buffer layer; and the carbon doping concentration of the first carbon-doped AlGaN layer gradually changes from high to low, which can block impurities such as Si atoms and oxygen atoms that diffuse from the substrate to the epitaxial layer. Since the impurity concentration is higher on the side close to the substrate, as the epitaxial layer grows, the concentration of impurities diffused into the epitaxial layer will gradually decrease, which can effectively block the diffusion of impurities to achieve high resistance in the buffer layer, and will not reduce the crystal quality. Since the first carbon-doped AlGaN layer has blocked the diffusion of most impurities, constant carbon doping of the second carbon-doped AlGaN layer can take into account both crystal quality and high resistance characteristics. The carbon doping concentration of the third carbon-doped AlGaN layer gradually changes from low to high. Since the two-dimensional electron gas concentration close to the GaN channel layer is high, it is easy to overflow into the buffer layer. The carbon doping concentration of the third carbon-doped AlGaN layer is set to gradually change from low to high to block the two-dimensional electron gas from overflowing into the buffer layer, so that the buffer layer achieves high resistance, reduces buffer layer leakage, and improves the pinch-off characteristics and withstand voltage characteristics of the device, thereby achieving high resistance of the epitaxial growth and ensuring the crystal quality of the epitaxial growth.

[0043] Example 3

[0044] A third embodiment of the present invention provides a high electron mobility transistor, comprising the epitaxial wafer of the first embodiment. The epitaxial wafer can be obtained by epitaxial growth using the epitaxial growth method of the second embodiment.

[0045] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. An epitaxial wafer, characterized in that: It comprises a Si substrate, an AlN nucleation layer, a high-resistance buffer layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer and a GaN cap layer stacked in sequence, wherein the high-resistance buffer layer comprises a first carbon-doped AlGaN layer, a second carbon-doped AlGaN layer and a third carbon-doped AlGaN layer stacked in sequence, wherein the first carbon-doped AlGaN layer is arranged on a side close to the AlN nucleation layer; The doping concentration of the first carbon-doped AlGaN layer uniformly changes from high to low along the side close to the Si substrate to the side away from the Si substrate, the doping concentration of the second carbon-doped AlGaN layer remains constant, and the doping concentration of the third carbon-doped AlGaN layer uniformly changes from low to high along the side close to the Si substrate to the side away from the Si substrate.

2. The epitaxial wafer according to claim 1, characterized in that The Al composition of AlGaN in the first carbon-doped AlGaN layer is 0.50-0.80, and the doping concentration of the first carbon-doped AlGaN layer is 5*10 17 cm -3 -5*10 20 cm -3 .

3. The epitaxial wafer according to claim 1, characterized in that The Al composition of AlGaN in the second carbon-doped AlGaN layer is 0.40-0.50, and the doping concentration of the second carbon-doped AlGaN layer is 5*10 15 cm -3 -5*10 16 cm -3 .

4. The epitaxial wafer according to claim 1, characterized in that The Al composition of AlGaN in the third carbon-doped AlGaN layer is 0.20-0.40, and the doping concentration of the second carbon-doped AlGaN layer is 5*10 17 cm -3 -5*10 20 cm -3 .

5. The epitaxial wafer according to claim 1, characterized in that The thickness of the first carbon-doped AlGaN layer is 0.5-1.0 μm, the thickness of the second carbon-doped AlGaN layer is 0.5-1.0 μm, and the thickness of the third carbon-doped AlGaN layer is 300-600 nm.

6. The epitaxial wafer according to claim 1, characterized in that A pre-laid Al layer is further provided between the Si substrate and the AlN nucleation layer, and the thickness of the pre-laid Al layer is 1-5 nm.

7. A method for growing an epitaxial wafer, for growing the epitaxial wafer according to any one of claims 1 to 6, characterized in that: The method comprises: Providing a Si substrate, and pre-laying an Al layer on the Si substrate; An AlN nucleation layer, a first carbon-doped AlGaN layer, a second carbon-doped AlGaN layer, a third carbon-doped AlGaN layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer and a GaN cap layer are sequentially grown on the pre-laid Al layer.

8. The epitaxial wafer growth method according to claim 7, characterized in that: In the steps of sequentially growing an AlN nucleation layer, a first carbon-doped AlGaN layer, a second carbon-doped AlGaN layer, a third carbon-doped AlGaN layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer, and a GaN cap layer on the pre-laid Al layer, the growth temperatures of the first carbon-doped AlGaN layer and the second carbon-doped AlGaN layer are both 1000°C-1200°C and the pressures are both 40-70 mbar, and the growth temperature of the third carbon-doped AlGaN layer is 1050°C-1150°C and the pressure is 150-250 mbar.

9. The epitaxial wafer growth method according to claim 7, wherein: The step of providing a Si substrate, before the step of pre-laying an Al layer on the Si substrate, further comprises: The Si substrate is deoxidized by high-temperature treatment for 5 to 10 minutes at a chamber temperature of 1000 to 1200° C., a chamber pressure of 50 to 150 mbar, and a H 2 atmosphere.

10. A high electron mobility transistor, characterized in that: The epitaxial wafer comprises the epitaxial wafer according to any one of claims 1 to 6.

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