Gallium nitride-based high electron mobility transistor epitaxial structure and preparation method thereof

Abstract

The epitaxial structure comprises a substrate layer, a polymerization layer, a high-resistance layer, a middle layer, a channel layer and a barrier layer which are sequentially arranged from bottom to top, the polymerization layer comprises a combination of a buffer layer and a transition layer, the channel layer is provided with a two-dimensional electron conducting channel, and the high-resistance layer is arranged between the high-resistance layer and the middle layer. The material composition of the barrier layer is ALInGaN, and the channel layer is formed at the interface of the barrier layer and the intermediate layer. According to the epitaxial structure disclosed in the technical scheme, AlInGaN is adopted as a barrier layer material to replace a traditional AlGaN barrier layer, the lattice constant of the barrier layer can be adjusted by introducing the In element, lattice mismatch between the barrier layer and a GaN channel layer is reduced, and meanwhile high polarization intensity is kept, so that the two-dimensional electron gas concentration is improved, and meanwhile the performance of the epitaxial structure is improved. The interface defects are reduced, and the electron mobility is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor preparation technology, and in particular to a gallium nitride-based high electron mobility transistor epitaxial structure and a preparation method thereof. Background Art

[0002] Gallium nitride-based high electron mobility transistors (GaN HEMTs) have broad application prospects in high-frequency, high-power electronic devices due to their excellent properties, including high breakdown electric field, high electron saturation velocity, and high electron mobility. The core structure of GaN HEMTs is the two-dimensional electron gas (2DEG) formed at the heterojunction interface, whose concentration and mobility directly determine the performance of the device.

[0003] Traditional GaN HEMT epitaxial structures usually adopt AlGaN / GaN heterostructures to form a two-dimensional electron gas at the interface between AlGaN and GaN. As research deepens, researchers have developed a variety of improved heterostructures to improve device performance. For example, CN103123934B discloses a gallium nitride-based high electron mobility transistor structure with a barrier layer, which includes a substrate, a nucleation layer, an unintentionally doped high-resistance layer, an unintentionally doped high-mobility channel layer, an unintentionally doped aluminum nitride space layer, an unintentionally doped barrier layer, and an unintentionally doped gallium nitride cap layer. This structural design increases the confinement effect on the channel two-dimensional electron gas and improves the output power of the device.

[0004] However, there are still some technical problems with the GaN HEMT structure in the existing technology. First, in the traditional AlGaN / GaN heterojunction, the polarization strength of AlGaN is limited, which makes it difficult to further increase the concentration of the two-dimensional electron gas, limiting the current density and output power of the device. Secondly, there is a large lattice mismatch between AlGaN and GaN, which easily introduces stress and defects at the interface, reduces the mobility of the two-dimensional electron gas, and thus affects the high-frequency performance of the device. In addition, in order to obtain a higher two-dimensional electron gas concentration, it is usually necessary to increase the Al component in the AlGaN barrier layer, but the AlGaN barrier layer with a high Al component may lead to an increase in the surface roughness of the epitaxial layer and a decrease in the crystal quality, which is not conducive to subsequent device preparation and reliability. Summary of the Invention

[0005] The purpose of the present invention is to solve the above technical problems and provide a gallium nitride-based high electron mobility transistor epitaxial structure and preparation method that can provide a high concentration of two-dimensional electron gas while maintaining good crystal quality and interface characteristics.

[0006] In order to achieve the above-mentioned objectives, the present invention provides a gallium nitride-based high electron mobility transistor epitaxial structure, which includes a substrate layer, a polymerization layer, a high resistance layer, an intermediate layer, a channel layer and a barrier layer arranged in sequence from bottom to top, the polymerization layer includes a combination of a buffer layer and a transition layer, the channel layer has a two-dimensional electron conduction channel, the material composition of the barrier layer is AlInGaN, and the channel layer is formed at the interface between the barrier layer and the intermediate layer.

[0007] Preferably, the material composition of the barrier layer is Al x In y Ga 1-x-y N, where 0 <x<1, 0<y<1, x + y<1。

[0008] Preferably, the material composition of the barrier layer is Al 0.73 In 0.08 Ga 0.19 N.

[0009] Preferably, the barrier layer has a thickness of 10-30 nm.

[0010] Preferably, the two-dimensional electron gas concentration on the channel layer is greater than or equal to 1.5×10 13 / cm -2 .

[0011] Preferably, the mobility of the two-dimensional electron gas on the channel layer is greater than or equal to 2200 cm 2 / V·s.

[0012] The present invention also provides a method for preparing a gallium nitride-based high electron mobility transistor epitaxial structure, which comprises: Providing a substrate and cleaning the surface of the substrate; Growing a polymer layer comprising a buffer layer and a transition layer on the substrate at a growth temperature of 950-1050° C.; A high resistance layer, an intermediate layer, a channel layer and a barrier layer are grown on the polymer layer, wherein the channel layer has a two-dimensional electron conductive channel, the material of the barrier layer is AlInGaN, and the channel layer is formed at the interface between the barrier layer and the intermediate layer, wherein the temperature for growing the barrier layer is 750~850°C.

[0013] Preferably, during the growth of the barrier layer, the composition of the barrier layer is controlled by adjusting the flow rates of ammonia, trimethylaluminum, trimethylindium and triethylgallium, so that the material composition of the barrier layer satisfies: Al x In y Ga 1-x-y N, where 0 <x<1, 0<y<1, x + y<1。

[0014] Preferably, the barrier layer has a thickness of 10-30 nm.

[0015] Preferably, the two-dimensional electron gas concentration on the channel layer is greater than or equal to 1.5×10 13 / cm -2 The mobility of the two-dimensional electron gas on the channel layer is greater than or equal to 2200 cm 2 / V·s.

[0016] Compared with the prior art, the epitaxial structure and preparation method disclosed in the above technical solution of the present invention adopt AlInGaN as the barrier layer material to replace the traditional AlGaN barrier layer. The introduction of the In element can adjust the lattice constant of the barrier layer, reduce the lattice mismatch between the barrier layer and the GaN channel layer, and maintain a high polarization strength, thereby increasing the two-dimensional electron gas concentration while reducing interface defects and improving electron mobility. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the layer structure of the transistor epitaxial structure in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the embodiments and the accompanying drawings.

[0019] This embodiment discloses a gallium nitride (GaN)-based high electron mobility transistor (HEMT) epitaxial structure, such as Figure 1 , including a substrate layer, a polymer layer, a high resistance layer, an intermediate layer, a channel layer and a barrier layer arranged in sequence from bottom to top.

[0020] The polymer layer includes a combination of a buffer layer and a transition layer. In this embodiment, the polymer layer also includes an SLS GaN layer, also known as a superlattice GaN strain relief layer. This layer is composed of periodically alternating thin layers (such as an AlGaN / GaN superlattice), further reducing dislocation density and controlling stress distribution.

[0021] The channel layer has a two-dimensional electron conductive channel, the material composition of the barrier layer is AlInGaN, and the channel layer is formed at the interface between the barrier layer and the intermediate layer.

[0022] The substrate layer can be made of materials such as silicon substrate, silicon carbide substrate or sapphire substrate.

[0023] The buffer layer is grown directly on the substrate layer to alleviate the lattice mismatch and thermal expansion coefficient difference between the substrate layer and the subsequent growth layer, and reduce the dislocation density.

[0024] The transition layer serves as the initial layer for epitaxial growth, providing a crystal template for subsequent growth, and may include a nucleation layer or a low-temperature GaN layer.

[0025] A high-resistance layer is grown on the polymer layer to increase the breakdown voltage of the device and reduce leakage current. The high-resistance layer can be made of carbon-doped GaN material.

[0026] The intermediate layer is grown on the high-resistance layer to further improve the crystal quality of the channel layer. The intermediate layer can be made of GaN material.

[0027] The channel layer is actually a two-dimensional electron gas region formed at the interface between the barrier layer and the intermediate layer, not a separate layer of material. The two-dimensional electron gas is a high-concentration electron region formed due to the polarization effect and band bending between the barrier layer and the intermediate layer.

[0028] Wherein, the material component of the barrier layer is Al x In y Ga 1-x-y N, where 0 <x<1, 0<y<1, x + y<1。

[0029] Specifically, the material composition of the barrier layer is Al 0.73 In 0.08 Ga 0.19 N.

[0030] In addition, the barrier layer has a thickness of 10-30 nm.

[0031] The transistor epitaxial structure has the above structure, and the two-dimensional electron gas concentration on the channel layer is greater than or equal to 1.5×10 13 / cm -2 The mobility of the two-dimensional electron gas on the channel layer is greater than or equal to 2200 cm 2 / V·s.

[0032] The GaN-based high-electron-mobility transistor epitaxial structure employing the aforementioned structure utilizes AlInGaN quaternary materials in the barrier layer, allowing for more flexible adjustment of the lattice constant and band structure compared to traditional AlGaN ternary materials, thereby achieving higher two-dimensional electron gas concentration and mobility. Furthermore, the introduction of indium into the barrier layer reduces stress, improves crystal quality, and further enhances device performance.

[0033] In another preferred embodiment of the present invention, a method for preparing a gallium nitride-based high electron mobility transistor epitaxial structure is provided, which comprises the following steps: Providing a substrate and cleaning the surface of the substrate; Growing a polymer layer comprising a buffer layer and a transition layer on a substrate at a growth temperature of 950-1050° C.; A high-resistance layer, an intermediate layer, a channel layer and a barrier layer are grown on the polymer layer. The channel layer has a two-dimensional electron conductive channel. The material of the barrier layer is AlInGaN. The channel layer is formed at the interface between the barrier layer and the intermediate layer. The temperature for growing the barrier layer is 750~850℃.

[0034] Specifically, a sapphire substrate with a thickness of 500 μm is first provided. The surface of the substrate is cleaned, and the cleaning steps include: ultrasonic cleaning with acetone for 10 minutes, ultrasonic cleaning with isopropyl alcohol for 10 minutes, rinsing with deionized water for 5 minutes, and finally drying with nitrogen.

[0035] The cleaned silicon substrate was placed in a reaction chamber of a metal organic chemical vapor deposition (MOCVD) device, heated to 1000° C., and the surface of the silicon substrate was thermally cleaned for 5 minutes in a hydrogen atmosphere to remove the surface oxide layer.

[0036] Then, a GaN buffer layer is grown on the substrate, and then a GaN superlattice transition layer is grown on the buffer layer. The growth temperature is 1000° C., and the total thickness of the transition layer is 1 μm.

[0037] Then, an SLS GaN layer (superlattice strain relief layer) is grown on the superlattice transition layer. Next, a carbon-doped GaN high-resistance layer is grown on the SLS GaN layer at a growth temperature of 1000° C. During the growth of the high-resistance layer, ammonia, trimethylgallium, and propane are introduced as reaction gases.

[0038] Then, a GaN intermediate layer is grown on the carbon-doped GaN high-resistance layer at a growth temperature of 1000° C. During the growth of the intermediate layer, ammonia and trimethylgallium are introduced as reaction gases.

[0039] Then, an AlInGaN barrier layer is grown on the GaN intermediate layer at a growth temperature of 800°C for 10 minutes, with a barrier layer thickness of 20 nm. During the barrier layer growth process, the composition of the barrier layer is controlled by adjusting the flow rates of ammonia, trimethylaluminum, trimethylindium, and triethylgallium, so that the material composition of the barrier layer satisfies the following requirements: Al 0.73 In 0.08 Ga 0.19 N.

[0040] Finally, a passivation layer may also be grown on the barrier layer.

[0041] The GaN-based high electron mobility transistor epitaxial structure obtained by the above preparation method has a two-dimensional electron gas concentration on the channel layer of 1.8×10 13 / cm -2 The mobility of the two-dimensional electron gas in the channel layer is 2300 cm 2 / V·s.

[0042] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention are still within the scope of the present invention.

Claims

1. A gallium nitride-based high electron mobility transistor epitaxial structure, characterized in that: The invention comprises a substrate layer, a polymerization layer, a high resistance layer, an intermediate layer, a channel layer and a barrier layer arranged in sequence from bottom to top. The polymerization layer comprises a combination of a buffer layer and a transition layer. The channel layer has a two-dimensional electron conductive channel. The material composition of the barrier layer is AlInGaN. The channel layer is formed at the interface between the barrier layer and the intermediate layer.

2. The GaN-based high electron mobility transistor epitaxial structure according to claim 1, wherein: The material composition of the barrier layer is Al x In y Ga 1-x-y N, where 0 < x < 1, 0 < y < 1, x + y < 1.

3. The GaN-based high electron mobility transistor epitaxial structure according to claim 2, wherein: The material composition of the barrier layer is Al 0.73 In 0.08 Ga 0.19 N.

4. The GaN-based high electron mobility transistor epitaxial structure according to claim 1, wherein: The thickness of the barrier layer is 10-30 nm.

5. The GaN-based high electron mobility transistor epitaxial structure according to claim 1, wherein: The two-dimensional electron gas concentration on the channel layer is greater than or equal to 1.5×10 13 / cm -2 .

6. The GaN-based high electron mobility transistor epitaxial structure according to claim 1, wherein: The mobility of the two-dimensional electron gas on the channel layer is greater than or equal to 2200 cm 2 / V·s.

7. A method for preparing a gallium nitride-based high electron mobility transistor epitaxial structure, characterized in that: include: Providing a substrate and cleaning the surface of the substrate; Growing a polymer layer comprising a buffer layer and a transition layer on the substrate at a growth temperature of 950-1050° C.; A high resistance layer, an intermediate layer, a channel layer and a barrier layer are grown on the polymer layer, wherein the channel layer has a two-dimensional electron conductive channel, the material of the barrier layer is AlInGaN, and the channel layer is formed at the interface between the barrier layer and the intermediate layer, wherein the temperature for growing the barrier layer is 750~850°C.

8. The method for preparing a gallium nitride-based high electron mobility transistor epitaxial structure according to claim 7, characterized in that: During the growth of the barrier layer, the composition of the barrier layer is controlled by adjusting the flow rates of ammonia, trimethylaluminum, trimethylindium and triethylgallium, so that the material composition of the barrier layer satisfies: Al x In y Ga 1-x-y N, where 0 < x < 1, 0 < y < 1, x + y < 1.

9. The method for preparing a gallium nitride-based high electron mobility transistor epitaxial structure according to claim 7, characterized in that: The thickness of the barrier layer is 10-30 nm.

10. The method for preparing a gallium nitride-based high electron mobility transistor epitaxial structure according to claim 7, characterized in that: The two-dimensional electron gas concentration on the channel layer is greater than or equal to 1.5×10 13 / cm -2 The mobility of the two-dimensional electron gas on the channel layer is greater than or equal to 2200 cm 2 / V·s.

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