Si-based GaN epitaxial growth method based on in-situ etching

Abstract

The application discloses a Si-based GaN epitaxial growth method based on in-situ etching, which comprises the following steps: growing an AlN buffer layer on a Si substrate surface; etching part of the AlN buffer layer in-situ; annealing and recrystallizing to form a nano 3D island-shaped AlN template; epitaxially growing an AlGaN buffer layer on the 3D island-shaped AlN template; epitaxially growing an AlGaN / GaN superlattice buffer layer on the AlGaN buffer layer; and epitaxially growing a GaN layer on the AlGaN / GaN superlattice buffer layer. Through the in-situ etching technology, the characteristics of low AlN bond energy at dislocations or atomic steps are utilized to generate etching pits under the action of etching gas, and then the nano 3D island-shaped pattern is formed after annealing and recrystallizing. In the subsequent epitaxial growth process, the 3D island mirror force promotes the bending and annihilation of dislocations, so that the defect and stress problems caused by lattice mismatch and thermal mismatch can be relieved, and a high-quality low-dislocation-density GaN thin film is obtained.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to a method for epitaxial growth of Si-based GaN based on in-situ etching. Background Technology

[0002] GaN, a typical representative of third-generation semiconductor materials, possesses advantages such as a large bandgap, high breakdown field strength, high saturated electron drift velocity, radiation resistance, and good chemical stability, making it a cutting-edge and hot topic in global semiconductor research. Due to the high difficulty of GaN single-crystal growth, heteroepitaxial growth is currently the primary method for fabricating GaN devices, with Si, SiC, and sapphire being commonly used substrates. During heteroepitaxial growth, factors such as lattice mismatch, thermal mismatch, and interface mismatch lead to a high density of dislocation defects in the epitaxial film. These defects become scattering centers, leakage channels, and non-radiative recombination centers, resulting in device performance degradation and reduced reliability.

[0003] In recent years, GaN heteroepitaxial technology has developed rapidly, with methods and processes such as AlGaN buffer layers, superlattice buffer layers, and patterned substrates emerging to improve the crystal quality of epitaxial materials. However, for large mismatch epitaxial systems such as Si-based GaN, the dislocation density of existing epitaxial technologies remains as high as 10-1. 8 cm -2 Therefore, in order to improve the quality of heteroepitaxial materials and reduce the difficulty and cost of the process, it is necessary to continuously develop epitaxial growth technologies with more practical value. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a Si-based GaN epitaxial growth method based on in-situ etching, which obtains high-quality GaN epitaxial films with low dislocation density through crystal plane control.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for epitaxial growth of Si-based GaN based on in-situ etching, comprising the following steps:

[0007] S1. An AlN buffer layer is grown on the surface of a Si(111) substrate;

[0008] S2. In-situ etching of the AlN buffer layer;

[0009] S3. Annealing and recrystallization to form a nano-3D island-shaped AlN template;

[0010] S4. Epitaxially grow an AlGaN buffer layer on a 3D island-shaped AlN template;

[0011] S5. Epitaxially grow an AlGaN / GaN superlattice buffer layer on the AlGaN buffer layer;

[0012] S6. Epitaxially grow a GaN layer on an AlGaN / GaN superlattice buffer layer.

[0013] Furthermore, in step S1, the thickness of the AlN buffer layer is 100–400 nm.

[0014] Furthermore, in step S2, the etching gas used for in-situ etching is one of Cl2, H2, H2 / NH3 mixture, or Cl2 / N2 mixture.

[0015] Furthermore, in step S2, the etch pits formed by the in-situ etching are inverted cone-shaped with hexagonal openings, and the etching depth is less than the thickness of the AlN buffer layer.

[0016] Furthermore, in step S2, the opening area of ​​the etching pit formed by the in-situ etching is 1×10⁻⁶. 2 ~1×10 8 nm 2 The total area of ​​the openings accounts for 25% to 75% of the area of ​​the AlN buffer layer.

[0017] Furthermore, in step S3, the annealing temperature is 1000–1400°C.

[0018] Furthermore, in step S4, the thickness of the AlGaN buffer layer is 100–1000 nm, and the molar composition of Al atoms is 20–70%.

[0019] Furthermore, in step S4, the AlGaN buffer layer has a multi-layer structure, with the thickness of each layer increasing from bottom to top, and the molar composition of Al atoms in each layer decreasing layer by layer.

[0020] Furthermore, in step S5, the thickness of the AlGaN / GaN superlattice buffer layer is 200–5000 nm, and the equivalent Al atomic molar composition is 15–35%, which is lower than the Al atomic molar composition of the AlGaN buffer layer.

[0021] Furthermore, in step S6, the thickness of the GaN layer is 200–2000 nm.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) This invention utilizes the low bond energy of AlN at dislocations or atomic steps through in-situ etching technology to generate etching pits under the action of etching gas. After annealing and recrystallization, nano-3D island-shaped patterns are formed. During subsequent epitaxial growth, the mirror force of the 3D islands causes dislocations to bend and annihilate, which can alleviate defects and stress problems caused by lattice mismatch and thermal mismatch, and obtain high-quality GaN thin films with low dislocation density.

[0024] (2) This invention performs in-situ etching and 3D patterning on the AlN buffer layer with the highest dislocation density, which is beneficial for filtering dislocations to the greatest extent and obtaining a GaN layer with low dislocation density. GaN devices fabricated on this basis have the advantages of high breakdown voltage, high current density and high on / off ratio.

[0025] (3) The entire process of the present invention adopts MOCVD technology, without the need for other equipment and processes, which is economical and convenient. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the process flow according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the etching pit distribution in the AlN buffer layer according to an embodiment of the present invention;

[0028] Figure 3 This is a cross-sectional schematic diagram of the GaN epitaxial structure of Example 1;

[0029] Figure 4 This is a cross-sectional schematic diagram of the GaN epitaxial structure in Example 2;

[0030] Figure 5 This is a cross-sectional schematic diagram of the GaN epitaxial structure in Example 3;

[0031] Figure 6 The image shows the X-ray bicrystalline diffraction curve of the GaN epitaxial structure in Example 3. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art; unless specifically specified, the technical means used are all conventional means well known to those skilled in the art.

[0033] This invention provides a method for epitaxial growth of Si-based GaN based on in-situ etching, comprising the following steps:

[0034] S1. An AlN buffer layer is grown on the surface of a Si(111) substrate;

[0035] S2. In-situ etching of the AlN buffer layer;

[0036] S3. Annealing and recrystallization to form a nano-3D island-shaped AlN template;

[0037] S4. Epitaxially grow an AlGaN buffer layer on a 3D island-shaped AlN template;

[0038] S5. Epitaxially grow an AlGaN / GaN superlattice buffer layer on the AlGaN buffer layer;

[0039] S6. Epitaxially grow a GaN layer on an AlGaN / GaN superlattice buffer layer.

[0040] This invention utilizes in-situ etching technology, taking advantage of the low bond energy of AlN at dislocations or atomic steps, to create etching pits in the AlN buffer layer under the action of etching gas. After annealing and recrystallization, nano-3D island-like patterns are formed. During the subsequent epitaxial growth of the AlGaN buffer layer, the mirror force of the 3D islands causes the dislocations to bend and annihilate towards the 3D island mirror force interface above the etching pits, reducing the dislocation density. This alleviates the defects and stress problems caused by lattice mismatch and thermal mismatch, resulting in a high-quality GaN thin film with low dislocation density.

[0041] In some embodiments, in step S1, the thickness of the AlN buffer layer is 100–400 nm.

[0042] In some embodiments, in step S2, the etching gas used for in-situ etching is one of Cl2, H2, H2 / NH3 mixture, or Cl2 / N2 mixture.

[0043] In some embodiments, in step S2, the etching pits formed by the in-situ etching are inverted cone-shaped with hexagonal openings, and the etching depth is less than the thickness of the AlN buffer layer.

[0044] In some embodiments, in step S2, the opening area of ​​the etching pit formed by the in-situ etching is 1×10⁻⁶. 2 ~1×10 8 nm 2 The total area of ​​the openings accounts for 25% to 75% of the area of ​​the AlN buffer layer.

[0045] In some embodiments, the annealing temperature in step S3 is 1000–1400°C.

[0046] In some embodiments, in step S4, the thickness of the AlGaN buffer layer is 100–1000 nm, and the molar composition of Al atoms is 20–70%.

[0047] In some embodiments, in step S4, the AlGaN buffer layer has a multilayer structure, with the thickness of each layer increasing from bottom to top and the molar composition of Al atoms decreasing layer by layer.

[0048] In some embodiments, in step S5, the thickness of the AlGaN / GaN superlattice buffer layer is 200–5000 nm, and the equivalent Al atomic molar composition is 15–35%, which is lower than the Al atomic molar composition of the AlGaN buffer layer.

[0049] In some embodiments, in step S6, the thickness of the GaN layer is 200–2000 nm.

[0050] Example 1

[0051] like Figure 1 As shown in the figure, this embodiment provides a method for epitaxial growth of Si-based GaN based on in-situ etching, which includes the following steps:

[0052] (1) An AlN buffer layer 102 is grown on the surface of a Si(111) substrate 101 using MOCVD technology. The thickness of the AlN buffer layer 102 is 250 nm.

[0053] (2) Partial etching is performed on the AlN buffer layer 102. The etching gas is a mixture of H2 / NH3. The etching pit 1022 is inverted conical in shape, and the etching depth is 10–100 nm. Figure 2 As shown, the opening shape of the etched pit 1022 is hexagonal, with a side length of 10-100 nm, and the total area of ​​the opening accounts for 25% of the area of ​​the AlN buffer layer 102.

[0054] (3) After the AlN buffer layer 102 is etched, it is annealed and recrystallized to form a nano 3D island-shaped AlN template 1021; the annealing temperature is 1200℃.

[0055] (4) An AlGaN buffer layer 103 is epitaxially grown on a 3D island-shaped AlN template 1021. The AlGaN buffer layer 103 has a thickness of 200 nm and a molar composition of Al atoms of 50%.

[0056] (5) An AlGaN / GaN superlattice buffer layer 104 is epitaxially grown on the AlGaN buffer layer 103. The thickness of the AlGaN / GaN superlattice buffer layer 104 is 500 nm and the equivalent Al atomic molar composition is 25%.

[0057] (6) An epitaxial GaN layer 105 is grown on the AlGaN / GaN superlattice buffer layer 104, and the thickness of the GaN layer 105 is 200 nm.

[0058] The cross-section of the GaN epitaxial structure obtained in this embodiment is as follows: Figure 3 As shown, after growing the AlGaN buffer layer 103, the dislocations 106 below the etch pits 1022 are filtered out. Some of the dislocations 106 between the etch pits 1022 are bent and annihilated at the 3D island mirror force interface 1031 above the etch pits 1022 under the action of the 3D island mirror force, thereby reducing the dislocation density.

[0059] Example 2

[0060] This embodiment provides a Si-based GaN epitaxial growth method based on in-situ etching, which includes the following steps:

[0061] (1) An AlN buffer layer 202 is grown on the surface of a Si(111) substrate 201 using MOCVD technology. The thickness of the AlN buffer layer 202 is 200 nm.

[0062] (2) Partial etching of AlN buffer layer 202 is performed. The etching gas is a mixture of Cl2 and N2. The etching pit 2022 is inverted cone-shaped and the etching depth is 10-100nm. The opening shape of the etching pit 2022 is hexagonal with a side length of 10-100nm. The total area of ​​the opening accounts for 50% of the area of ​​AlN buffer layer.

[0063] (3) After the AlN buffer layer 202 is etched, it is annealed and recrystallized to form a nano 3D island-shaped AlN template 2021; the annealing temperature is 1100℃.

[0064] (4) An AlGaN buffer layer 203 is epitaxially grown on a 3D island-shaped AlN template 2021, such as... Figure 4 As shown, the AlGaN buffer layer 203 has a four-layer structure. From bottom to top, the first AlGaN buffer layer 2031 has a thickness of 100 nm and an Al atom molar composition of 70%; the second AlGaN buffer layer 2032 has a thickness of 200 nm and an Al atom molar composition of 50%; the third AlGaN buffer layer 2033 has a thickness of 300 nm and an Al atom molar composition of 30%; and the fourth AlGaN buffer layer 2034 has a thickness of 400 nm and an Al atom molar composition of 20%.

[0065] (5) An AlGaN / GaN superlattice buffer layer 204 is epitaxially grown on the fourth AlGaN buffer layer 2034. The thickness of the AlGaN / GaN superlattice buffer layer 204 is 1000 nm and the equivalent Al atomic molar composition is 15%.

[0066] (6) An epitaxial GaN layer 205 is grown on the AlGaN / GaN superlattice buffer layer 204, and the thickness of the GaN layer 205 is 500 nm.

[0067] Example 3

[0068] This embodiment provides a Si-based GaN epitaxial growth method based on in-situ etching, which includes the following steps:

[0069] (1) An AlN buffer layer 302 is grown on the surface of a Si(111) substrate 301 using MOCVD technology. The thickness of the AlN buffer layer 302 is 300 nm.

[0070] (2) Partial etching of AlN buffer layer 302 is performed. The etching gas is H2. The etching pit 3022 is inverted cone shape and the etching depth is 150-220nm. The opening shape of the etching pit 3022 is hexagonal with a side length of 10-500nm. The total area of ​​the opening accounts for 75% of the area of ​​AlN buffer layer.

[0071] (3) After the AlN buffer layer 302 is etched, it is annealed and recrystallized to form a nano 3D island-shaped AlN template 3021; ​​the annealing temperature is 1300℃.

[0072] (4) An AlGaN buffer layer 303 is epitaxially grown on a 3D island-shaped AlN template 3021, such as... Figure 5 As shown, the AlGaN buffer layer 303 has a three-layer structure. From bottom to top, the first AlGaN buffer layer 3031 has a thickness of 100 nm and a molar composition of 60% Al atoms; the second AlGaN buffer layer 3032 has a thickness of 200 nm and a molar composition of 45% Al atoms; and the third AlGaN buffer layer 3033 has a thickness of 500 nm and a molar composition of 30% Al atoms.

[0073] (5) An AlGaN / GaN superlattice buffer layer 304 is epitaxially grown on the third AlGaN buffer layer 2033. The thickness of the AlGaN / GaN superlattice buffer layer 304 is 2000 nm and the equivalent Al atomic molar composition is 20%.

[0074] (6) An epitaxial GaN layer 305 is grown on the AlGaN / GaN superlattice buffer layer 304, and the thickness of the GaN layer 305 is 1000 nm.

[0075] Figure 6 (a) is the high-intensity X-ray double-crystal diffraction (002) rocking curve of the GaN epitaxial structure sample in this embodiment. Figure 6 (b) High-intensity X-ray double-crystal diffraction (002) rocking curves of GaN epitaxial structure samples obtained without in-situ etching. It can be seen that the full width at half maximum (FWHM) of the (002) rocking curve of the sample obtained by in-situ etching in this embodiment is significantly lower than that of the sample obtained without in-situ etching, indicating that the crystal quality of the GaN epitaxial film is significantly improved.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for epitaxial growth of Si-based GaN based on in-situ etching, characterized in that, Includes the following steps: S1. An AlN buffer layer is grown on the surface of a Si(111) substrate; S2. In-situ etching of the AlN buffer layer; S3. Annealing and recrystallization to form a nano-3D island-like AlN template; S4. Epitaxially grow an AlGaN buffer layer on a 3D island-shaped AlN template; S5. Epitaxially grow an AlGaN / GaN superlattice buffer layer on the AlGaN buffer layer; S6. Epitaxially growing a GaN layer on an AlGaN / GaN superlattice buffer layer; In step S2, the etching pit formed by the in-situ etching is an inverted cone shape with a hexagonal opening and an etching depth less than the thickness of the AlN buffer layer. In step S2, the opening area of ​​the etching pit formed by the in-situ etching is 1×10⁻⁶. 2 ~1×10 8 nm 2 The total area of ​​the openings accounts for 25-75% of the area of ​​the AlN buffer layer; In step S3, the annealing temperature is 1000~1400℃.

2. The method for Si-based GaN epitaxial growth based on in-situ etching according to claim 1, characterized in that, In step S1, the thickness of the AlN buffer layer is 100~400nm.

3. The method for Si-based GaN epitaxial growth based on in-situ etching according to claim 1, characterized in that, In step S2, the etching gas used for in-situ etching is one of Cl2, H2, H2 / NH3 mixture, or Cl2 / N2 mixture.

4. The method for Si-based GaN epitaxial growth based on in-situ etching according to claim 1, characterized in that, In step S4, the thickness of the AlGaN buffer layer is 100~1000nm, and the molar composition of Al atoms is 20~70%.

5. The Si-based GaN epitaxial growth method based on in-situ etching according to claim 4, characterized in that, In step S4, the AlGaN buffer layer has a multi-layer structure, with the thickness of each layer increasing from bottom to top, and the molar composition of Al atoms decreasing layer by layer.

6. The method for Si-based GaN epitaxial growth based on in-situ etching according to claim 1, characterized in that, In step S5, the thickness of the AlGaN / GaN superlattice buffer layer is 200~5000nm, and the equivalent Al atomic molar composition is 15~35%, which is lower than the Al atomic molar composition of the AlGaN buffer layer.

7. The method for Si-based GaN epitaxial growth based on in-situ etching according to claim 1, characterized in that, In step S6, the thickness of the GaN layer is 200~2000nm.

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