Epitaxial structure, power device, and method for manufacturing an epitaxial structure

Abstract

The present invention provides an epitaxial structure and a method for manufacturing the same that alleviates lattice mismatch between a silicon wafer and a gallium nitride epitaxial layer and reduces internal lattice stress. [Solution] An epitaxial structure mainly comprising two composition gradient layers, an aluminum-containing composition gradient layer 110 and a gallium-containing composition gradient layer 140, and a buffer layer between them, wherein the aluminum-containing composition gradient layer 110 is placed on a silicon substrate 1 and has an aluminum-containing three-dimensional structure and an aluminum-containing two-dimensional structure. The aluminum-containing three-dimensional structure is formed on the silicon substrate, and the aluminum-containing two-dimensional structure is formed by partial composition gradient growth. The two layers of composition gradient layers from the three-dimensional structure to the two-dimensional structure alleviate lattice mismatch between the silicon substrate and the epitaxial layer, and reduce internal stress.

Description

Technical Field

[0001] The present invention relates to an epitaxial structure, a power device, and a method for manufacturing an epitaxial structure, and particularly to a gallium nitride epitaxial structure, a gallium nitride power device, and a method for manufacturing a gallium nitride epitaxial structure.

Background Art

[0002] In recent years, with the progress of materials and structure technologies, high electron mobility transistors (HEMTs) have achieved remarkable development and are particularly applied in the fields of power electronics and high-frequency equipment. High electron mobility transistors mainly utilize the wide bandgap characteristics of gallium nitride (GaN) materials. This material generates a two-dimensional electron gas (2DEG) at the heterointerface, provides a high breakdown voltage, excellent electron mobility, and low on-resistance, and realizes a high switching speed and high output density.

[0003] However, there are many technical problems in the manufacture of gallium nitride epitaxial substrates, mainly related to aspects such as material properties, growth processes, and substrate selection. Specifically, there is a significant lattice mismatch between the lattice constant of gallium nitride and that of common substrates (sapphire, silicon, silicon carbide). For example, the lattice mismatch between gallium nitride and sapphire reaches about 16%, and the mismatch with silicon also reaches 17%. This lattice mismatch forms a high density of dislocations, and the dislocation density usually reaches 10 9 ~10 10 cm -2 and degrades the performance of high electron mobility transistors. Based on this, the semiconductor industry requires an innovative epitaxial structure in next-generation wide bandgap semiconductor materials to overcome technical barriers that affect device performance in the epitaxial manufacturing process.

Summary of the Invention

[0004] The main object of the present invention is to provide an epitaxial structure, a power device, and a method for manufacturing the epitaxial structure. This epitaxial structure mainly comprises two composition gradient layers, namely an aluminum-containing composition gradient layer and a gallium-containing composition gradient layer. Through two composition gradient layers of different materials that transition from a three-dimensional structure to a two-dimensional structure, lattice mismatch between the silicon wafer and the gallium nitride epitaxial layer is mitigated, and internal lattice stress is reduced. This structure improves the yield of epitaxial wafers and simultaneously improves the epitaxial quality and electrical performance of the device channel layer.

[0005] To achieve the above objective, the present invention provides an epitaxial structure comprising an aluminum-containing composition gradient layer, an aluminum-containing homo-layer, a first buffer layer, a gallium-containing composition gradient layer, a gallium-containing homo-layer, and a second buffer layer. The aluminum-containing composition gradient layer is placed on a substrate. The aluminum-containing composition gradient layer has an aluminum-containing three-dimensional structure and an aluminum-containing two-dimensional structure. The aluminum-containing three-dimensional structure is formed on a substrate, and the aluminum-containing two-dimensional structure is formed by partial composition gradient growth. The aluminum-containing homo-layer is placed on the aluminum-containing two-dimensional structure. The first buffer layer is placed on the aluminum-containing homo-layer. The gallium-containing composition gradient layer is placed on the first buffer layer. The gallium-containing composition gradient layer has a gallium-containing three-dimensional structure and a gallium-containing two-dimensional structure. The gallium-containing three-dimensional structure is formed on the first buffer layer, and the gallium-containing two-dimensional structure is formed by partial composition gradient growth. The gallium-containing homo-layer is placed on the gallium-containing two-dimensional structure. The second buffer layer is placed on the gallium-containing homo-layer.

[0006] In embodiments of the epitaxial structure of the present invention, a plurality of aluminum-containing seed crystals are further placed on a substrate, and the aluminum-containing three-dimensional structure is grown and formed from these aluminum-containing seed crystals.

[0007] In the embodiment of the epitaxial structure of the present invention, each aluminum-containing seed crystal is an aluminum nitride (AlN) seed crystal.

[0008] In an embodiment of the epitaxial structure of the present invention, the aluminum-containing composition gradient layer is an aluminum nitride composition gradient layer, and the thickness of the aluminum nitride composition gradient layer is 10 to 20 nanometers (nm).

[0009] In an embodiment of the epitaxial structure of the present invention, the aluminum-containing homo-layer is an aluminum nitride layer, and the thickness of the aluminum nitride layer is 30 to 300 nanometers (nm).

[0010] In embodiments of the epitaxial structure of the present invention, the first buffer layer is composed of aluminum (Al), gallium (Ga), and nitrogen (N), and the thickness of the first buffer layer is 20 to 5000 nanometers (nm).

[0011] In embodiments of the epitaxial structure of the present invention, a plurality of gallium-containing seed crystals are further placed on the first buffer layer, and the gallium-containing three-dimensional structure is grown and formed from these gallium-containing seed crystals.

[0012] In the embodiment of the epitaxial structure of the present invention, each gallium-containing seed crystal is a gallium nitride (GaN) seed crystal.

[0013] In embodiments of the epitaxial structure of the present invention, the gallium-containing composition gradient layer is a gallium nitride composition gradient layer, and the thickness of the gallium nitride composition gradient layer is 10 to 20 nanometers (nm).

[0014] In embodiments of the epitaxial structure of the present invention, the gallium-containing homo-layer is a gallium nitride layer, and the thickness of the gallium nitride layer is 30 to 300 nanometers (nm).

[0015] In embodiments of the epitaxial structure of the present invention, the second buffer layer is composed of aluminum (Al), gallium (Ga), and nitrogen (N), and the thickness of the second buffer layer is 20 to 5000 nanometers (nm).

[0016] To achieve the above objective, the present invention provides a power device comprising a substrate, one of the above-described epitaxial structures placed on the substrate, and a channel layer placed on the epitaxial structure. The channel layer has a two-dimensional electron gas (2DEG) channel.

[0017] To achieve the above objective, the present invention provides a method for manufacturing an epitaxial structure. First, an aluminum-containing composition gradient layer having an aluminum-containing three-dimensional structure and an aluminum-containing two-dimensional structure is formed on a substrate. The aluminum-containing three-dimensional structure is formed on the substrate, and the aluminum-containing two-dimensional structure is formed by partial composition gradient growth. Next, an aluminum-containing homo-layer is formed on the aluminum-containing two-dimensional structure, and a first buffer layer is formed on the aluminum-containing homo-layer. Next, a gallium-containing composition gradient layer is formed on the first buffer layer. The gallium-containing composition gradient layer has a gallium-containing three-dimensional structure and a gallium-containing two-dimensional structure. The gallium-containing three-dimensional structure is formed on the first buffer layer, and the gallium-containing two-dimensional structure is formed by partial composition gradient growth. Finally, a gallium-containing homo-layer is formed on the gallium-containing two-dimensional structure, and a second buffer layer is formed on the gallium-containing homo-layer.

[0018] In an embodiment of the method for manufacturing an epitaxial structure according to the present invention, the process further includes the step of placing a plurality of aluminum nitride seed crystals on a substrate, and the aluminum-containing three-dimensional structure is grown and formed from these aluminum nitride seed crystals.

[0019] In an embodiment of the method for manufacturing an epitaxial structure according to the present invention, the step of forming an aluminum-containing composition gradient layer is to form an aluminum nitride composition gradient layer, and the thickness of the aluminum nitride composition gradient layer is 10 to 20 nanometers (nm).

[0020] In an embodiment of the method for manufacturing an epitaxial structure according to the present invention, the step of forming an aluminum-containing homo-layer is to form an aluminum nitride layer, and the thickness of the aluminum nitride layer is 30 to 300 nanometers (nm).

[0021] In an embodiment of the method for manufacturing an epitaxial structure of the present invention, the method further includes a step of disposing a plurality of gallium nitride seed crystals on the first buffer layer, and the gallium-containing three-dimensional structure is grown and formed from these gallium nitride seed crystals.

[0022] In an embodiment of the method for manufacturing an epitaxial structure of the present invention, the step of forming a gallium-containing composition gradient layer is to form a gallium nitride composition gradient layer, and the thickness of the gallium nitride composition gradient layer is 10 to 20 nanometers (nm).

[0023] In an embodiment of the method for manufacturing an epitaxial structure of the present invention, the step of forming a gallium-containing homo layer is to form a gallium nitride layer, and the thickness of the gallium nitride layer is 30 to 300 nanometers (nm).

[0024] Those skilled in the art can understand other objects of the present invention, as well as the technical means and embodiments of the present invention, by referring to the drawings and the embodiments described below.

Brief Description of the Drawings

[0025] [Figure 1A] Schematic diagram of the epitaxial structure in an embodiment of the present invention [Figure 1B] Schematic diagram of the epitaxial structure in an embodiment of the present invention [Figure 1C] Schematic diagram of the epitaxial structure in an embodiment of the present invention [Figure 1D] Schematic diagram of the epitaxial structure in an embodiment of the present invention [Figure 1E] Schematic diagram of the epitaxial structure in an embodiment of the present invention [Figure 1F] Schematic diagram of the epitaxial structure in an embodiment of the present invention [Figure 1G] Schematic diagram of the epitaxial structure in an embodiment of the present invention [Figure 1H] Schematic diagram of the epitaxial structure in an embodiment of the present invention [Figure 1I] Schematic diagram of the epitaxial structure in an embodiment of the present invention [Figure 2] Scanning electron microscope magnified view of the epitaxial structure in an embodiment of the present invention. [Figure 3] Schematic diagram of the epitaxial structure in another embodiment of the present invention [Figure 4] Schematic diagram of a power device utilizing an epitaxial structure in an embodiment of the present invention. [Figure 5] Flowchart of the manufacturing process for the epitaxial structure of the present invention [Modes for carrying out the invention]

[0026] The present invention will be described below through examples. These examples illustrate the embodiments of the present invention and are not intended to limit the invention to any particular environment, application, or specific configuration described therein. Therefore, while the examples illustrate the present invention, they do not limit it. Components not directly related to the present invention are omitted and not shown in the embodiments and drawings. The dimensional relationships of the components in the drawings are for ease of understanding and do not limit the actual dimensions.

[0027] The present invention discloses an epitaxial structure applicable to power devices and capable of improving the product performance of power devices, and a method for manufacturing the same. As shown in Figure 1A, first, a plurality of aluminum-containing seed crystals 10 are placed on a substrate. The substrate 1 is a silicon (Si) substrate, a silicon on insulator (SOI) substrate, but is not limited thereto. For example, ammonia gas (NH3) and trimethylaluminum (TMAl) gas are introduced using metal-organic chemical vapor deposition (MOCVD) on the silicon substrate. <111> Multiple aluminum nitride (AlN) seed crystals are slowly formed, evenly distributed on the directional plane. Next, the growth of these aluminum-containing seed crystals 10 is continued at a low temperature of 400-600°C, continuously expanding the volume of the seed crystals as shown in Figure 1B. After growth for a certain period of time, due to the large difference in lattice constants between the silicon substrate and the aluminum nitride, and the high density of lattice defects, the aluminum nitride does not grow as a flat thin film on the substrate. Instead, as shown in Figure 1C, only numerous island-like aluminum-containing three-dimensional structures 112 are formed. This stage is the "3D growth" stage.

[0028] Next, the growth temperature is increased to 1000-1200°C. At this high temperature, aluminum and nitrogen atoms gain sufficient energy to move along the substrate surface to the optimal lattice position. As a result, the rate of lateral growth becomes greater than the rate of vertical growth, and the island-like aluminum-containing three-dimensional structures 112 grow larger. This stage is the "2D growth" stage. When the island-like aluminum-containing three-dimensional structures 112 grow laterally to a certain extent, they coalesce with adjacent island-like aluminum-containing three-dimensional structures 112. When all the island-like structures become block-like and coalesce with each other, the crystal surface becomes flat. At this time, as shown in Figure 1D, the aluminum-containing three-dimensional structures 112 begin to grow upward, forming aluminum-containing two-dimensional structures 114 through partial compositional gradient growth. At this time, an aluminum-containing compositional gradient layer 110 is formed on the substrate 1. This aluminum-containing composition gradient layer 110 has an aluminum-containing three-dimensional structure 112 formed on the substrate 1, and an aluminum-containing two-dimensional structure 114 formed from the aluminum-containing three-dimensional structure 112 by partial composition gradient growth. Specifically, the aluminum-containing composition gradient layer 110 is an aluminum nitride composition gradient layer with a thickness of 10 to 20 nanometers (nm). The degree of lattice mismatch in the silicon substrate is significantly reduced by the composition gradient change from a three-dimensional structure to a two-dimensional structure using aluminum nitride material.

[0029] As shown in Figure 1E, an aluminum-containing homo-layer 120 is then grown on the flat surface of the aluminum-containing two-dimensional structure 114 of the aluminum-containing composition gradient layer 110. Specifically, this aluminum-containing homo-layer is an aluminum nitride layer. The thickness of this aluminum nitride layer is 30 to 300 nanometers (nm). By forming the aluminum nitride layer within the aforementioned thickness range, defects in the aluminum nitride material are stabilized. As shown in Figure 1F, a first buffer layer 130 is then formed on the aluminum-containing homo-layer 120 to further relieve internal stress. The first buffer layer 130 is in the form of a block or a layered structure. This layered structure is composed of, for example, different ratios of aluminum (Al), gallium (Ga), and nitrogen (N). Specifically, the first buffer layer is a superlattice structure in which high-bandgap material (aluminum nitride or aluminum gallium nitride with a high aluminum content) and low-bandgap material (gallium nitride or aluminum gallium nitride with a low aluminum content) are alternately stacked, and its total thickness is 20 to 5000 nanometers (nm). This structure further reduces internal stress caused by lattice mismatch, thereby decreasing defect density.

[0030] Next, the epitaxial structure configuration for the second major lattice adjustment is as follows. Specifically, a gallium-containing composition gradient layer 140 is formed on the first buffer layer 130. Figures 1G and 1H show that multiple gallium-containing seed crystals 20 are nucleated and uniformly distributed on the surface of the first buffer layer 130 by introducing ammonia gas (NH3) and trimethylgallium (TMGa) gas using organometallic compound chemical vapor deposition. These gallium-containing seed crystals 20 are gallium nitride seed crystals. Next, the growth of these gallium-containing seed crystals 20 is continued at a low temperature of 400°C to 600°C, continuously expanding the volume of the seed crystals. Subsequently, the aforementioned "3D growth" and "2D growth" stages are performed, and the gallium-containing seed crystals gradually grow on the first buffer layer 130 to form a block-like gallium-containing three-dimensional structure (not shown), and further form the gallium-containing composition gradient layer 140. The gallium-containing composition gradient layer 140 includes a gallium-containing three-dimensional structure formed on the first buffer layer, and a gallium-containing two-dimensional structure (not shown) with a flat surface that grows from the gallium-containing three-dimensional structure and is partially formed by the composition gradient. Specifically, the gallium-containing composition gradient layer 140 is a gallium nitride composition gradient layer with a total thickness of 10 to 20 nanometers (nm). In this process, the aluminum gallium nitride lattice in the buffer layer undergoes a composition gradient change from a gallium nitride three-dimensional structure to a gallium nitride two-dimensional structure, achieving a second major lattice adjustment and effectively relieving internal stress.

[0031] As shown in Figure 1H, a gallium-containing homo-layer 150 is grown on the flat surface of the gallium-containing two-dimensional structure of the gallium-containing composition gradient layer 140. This gallium-containing homo-layer is a gallium nitride layer with a thickness of 30-300 nanometers (nm) or more. This thickness range can further reduce the number of defects in the gallium nitride material. As shown in Figure 1I, a second buffer layer 160 is formed on the gallium-containing homo-layer 150 to further relieve internal stress. The second buffer layer 160, like the first buffer layer 130, is in a block-like form or a layered structure. The layered structure is composed of aluminum (Al), gallium (Ga), and nitrogen (N) in different ratios. Specifically, the second buffer layer is a superlattice structure, composed of alternating layers of high-bandgap material (aluminum nitride or aluminum gallium nitride with a high aluminum content) and low-bandgap material (gallium nitride or aluminum gallium nitride with a low aluminum content). The total thickness of the second buffer layer is 20-5000 nanometers (nm). This structure reduces internal stress due to lattice mismatch and decreases defect density. Figure 2 is a scanning electron microscope magnified view of the epitaxial structure cross-section of the present invention. In the figure, the total thickness of the aluminum-containing composition gradient layer 110 and the aluminum-containing homo-layer 120 is approximately 107 nanometers (nm). The total thickness of the gallium-containing composition gradient layer 140 is approximately 12 nanometers (nm). The figure shows that the number of lattice cracks in the upper region of the gallium-containing composition gradient layer 140 is significantly less than the number of cracks in the lower region of the gallium-containing composition gradient layer 140. Unlike conventional superlattice structures that employ a stacked structure with a narrow lattice adjustment method, Figure 2 shows that lattice mismatch can be significantly mitigated by using two layers of different materials (aluminum nitride and gallium nitride) with a composition gradient from three to two dimensions.

[0032] The aforementioned embodiment, in which at least two layers of different materials are arranged in a three-dimensional to two-dimensional compositional gradient within the epitaxial structure of a power device, is merely illustrative. In actual applications, the process shown in Figures 1G to 1I is repeated, depending on the degree of lattice stress relaxation required for the power device, until the quality of the gallium nitride epitaxial thin film meets the specifications of the power device. The evaluation criterion for epitaxial thin film quality is, for example, the X-ray rocking curve of the 1-micrometer gallium nitride epitaxial layer. The image quality of JPEG2026103833000002.jpg16166 is less than 1000 arcseconds. This evaluation criterion is used to determine whether it is necessary to repeatedly perform the processes shown in Figures 1G through 1I. For example, Figure 3 shows that the epitaxial structure 100 on substrate 1 has three layers of compositional gradient from three-dimensional to two-dimensional (110, 140, 170). This structure further relaxes internal lattice stress and reduces lattice defects. Specifically, the structure in Figure 3 includes the structure shown in Figure 1I, with an additional gallium-containing compositional gradient layer 170, a gallium-containing homo-layer 180, and a third buffer layer 190 grown on the second buffer layer 160. The material composition of each epitaxial layer is the same as described above, so a repeated explanation is omitted.

[0033] Figure 4 shows a schematic diagram of the application of the epitaxial structure of the present invention to a power device. Specifically, the power device shown in Figure 4 is a high electron mobility transistor and includes a substrate 1 and the aforementioned epitaxial structure 100, and further includes a channel layer 200 placed on the epitaxial structure 100, a gate 302, a source 304, and a drain 306 placed on the channel layer 200. In the channel layer 200, there is a two-dimensional electron gas (2DEG) channel 202 in the portion adjacent to the upper barrier layer. The epitaxial structure of the present invention can also be applied to other power devices. For example, power devices that apply the epitaxial structure of the present invention include Schottky diodes, metal oxide semiconductor field-effect transistors, junction field-effect transistors (JFETs), insulated gate bipolar transistors (IGBTs), or light-emitting diodes (LEDs).

[0034] Figure 5 is a flowchart of the manufacturing process for the epitaxial structure of the present invention. In step S01, an aluminum-containing composition gradient layer is formed on a substrate. The aluminum-containing composition gradient layer includes an aluminum-containing three-dimensional structure and an aluminum-containing two-dimensional structure. The aluminum-containing three-dimensional structure is formed on the substrate. The aluminum-containing two-dimensional structure is formed from the aluminum-containing three-dimensional structure by partial composition gradient growth. Next, in step S02, an aluminum-containing homo-layer is formed on the aluminum-containing two-dimensional structure. In step S03, a first buffer layer is formed on the aluminum-containing homo-layer. Next, in step S04, a gallium-containing composition gradient layer is formed on the first buffer layer. This gallium-containing composition gradient layer includes a gallium-containing three-dimensional structure and a gallium-containing two-dimensional structure. The gallium-containing three-dimensional structure is formed on the first buffer layer. The gallium-containing two-dimensional structure is formed from the gallium-containing three-dimensional structure by partial composition gradient growth. In step S05, a gallium-containing homo-layer is formed on the gallium-containing two-dimensional structure. Finally, in step S06, a second buffer layer is formed on the gallium-containing homo-layer. The detailed contents of each of the above elements have been described above and will not be repeated here.

[0035] The above-described embodiments illustrate embodiments of the present invention and describe the characteristic configuration of the present invention. The present invention is not limited to the above embodiments. Modifications or equivalent arrangements that can be easily made by those skilled in the art are also within the scope of the present invention. The scope of protection of the rights of the present invention shall be based on the claims. [Explanation of Symbols]

[0036] 1 circuit board 10. Aluminum-containing seed crystals 20 Gallium-containing seed crystals 100 Epitaxial Structure 110 Aluminum-containing composition gradient layer 112 Aluminum-containing three-dimensional structure 114 Aluminum-containing two-dimensional structure 120 Aluminum-containing homogeneous layer 130 First Buffer Layer 140 Gallium-containing composition gradient layers 150 Gallium-containing homogeneous layer 160 Second Buffer Layer 170 Gallium-containing composition gradient layers 180 Gallium-containing homogeneous layer 190 Third Buffer Layer 200 channel layer 202 Two-dimensional electron gas channel Gate 302 304 Source 306 Drain

Claims

1. An epitaxial structure comprising an aluminum-containing composition gradient layer, an aluminum-containing homo-layer, a first buffer layer, a gallium-containing composition gradient layer, a gallium-containing homo-layer, and a second buffer layer, The aluminum-containing composition gradient layer is placed on a substrate and has an aluminum-containing three-dimensional structure and an aluminum-containing two-dimensional structure, the aluminum-containing three-dimensional structure is formed on the substrate and the aluminum-containing two-dimensional structure is formed by partial composition gradient growth. The aluminum-containing homo-layer is placed on the aluminum-containing two-dimensional structure, The first buffer layer is placed on the aluminum-containing homo-layer, The gallium-containing composition gradient layer is placed on the first buffer layer and has a gallium-containing three-dimensional structure and a gallium-containing two-dimensional structure, the gallium-containing three-dimensional structure is formed on the first buffer layer and the gallium-containing two-dimensional structure is formed by partial composition gradient growth. The gallium-containing homo-layer is placed on the gallium-containing two-dimensional structure, The second buffer layer has an epitaxial structure and is placed on the gallium-containing homo-layer.

2. The substrate further comprises a plurality of aluminum-containing seed crystals placed on the substrate, The epitaxial structure according to claim 1, characterized in that the aluminum-containing three-dimensional structure is grown and formed from the aluminum-containing seed crystal.

3. The epitaxial structure according to claim 2, characterized in that each of the aluminum-containing seed crystals is an aluminum nitride (AlN) seed crystal.

4. The epitaxial structure according to claim 3, characterized in that the aluminum-containing composition gradient layer is an aluminum nitride composition gradient layer, and the thickness of the aluminum nitride composition gradient layer is 10 to 20 nanometers (nm).

5. The epitaxial structure according to claim 4, characterized in that the aluminum-containing homo-layer is an aluminum nitride layer, and the thickness of the aluminum nitride layer is 30 to 300 nanometers (nm).

6. The epitaxial structure according to claim 1, characterized in that the first buffer layer is composed of aluminum (Al), gallium (Ga), and nitrogen (N), and the thickness of the first buffer layer is 20 to 5000 nanometers (nm).

7. The first buffer layer further comprises a plurality of gallium-containing seed crystals placed on the buffer layer, The epitaxial structure according to claim 1, characterized in that the gallium-containing three-dimensional structure is grown from the gallium-containing seed crystal.

8. The epitaxial structure according to claim 7, characterized in that each of the gallium-containing seed crystals is a gallium nitride (GaN) seed crystal.

9. The epitaxial structure according to claim 8, characterized in that the gallium-containing composition gradient layer is a gallium nitride composition gradient layer, and the thickness of the gallium nitride composition gradient layer is 10 to 20 nanometers (nm).

10. The epitaxial structure according to claim 9, characterized in that the gallium-containing homo-layer is a gallium nitride layer, and the thickness of the gallium nitride layer is 30 to 300 nanometers (nm).

11. The epitaxial structure according to claim 1, characterized in that the second buffer layer is composed of aluminum (Al), gallium (Ga), and nitrogen (N), and the thickness of the second buffer layer is 20 to 5000 nanometers (nm).

12. It is a power device, circuit board and An epitaxial structure according to any one of claims 1 to 11 is installed on the substrate, A power device comprising a channel layer having a two-dimensional electron gas (2DEG) channel, which is mounted on the epitaxial structure.

13. A method for manufacturing an epitaxial structure, A step of forming an aluminum-containing composition gradient layer having an aluminum-containing three-dimensional structure formed on the substrate and an aluminum-containing two-dimensional structure formed from the aluminum-containing three-dimensional structure by partial composition gradient growth, The process of forming an aluminum-containing homo-layer on the aforementioned aluminum-containing two-dimensional structure, The steps include forming a first buffer layer on the aluminum-containing homo-layer, A step of forming a gallium-containing composition gradient layer having a gallium-containing three-dimensional structure formed on the first buffer layer and a gallium-containing two-dimensional structure formed from the gallium-containing three-dimensional structure by partial composition gradient growth, The steps include forming a gallium-containing homo-layer on the gallium-containing two-dimensional structure, A method for producing an epitaxial structure, comprising the step of forming a second buffer layer on the gallium-containing homo-layer.

14. The process further includes the step of placing a plurality of aluminum nitride seed crystals on the substrate, The method for producing an epitaxial structure according to claim 13, characterized in that the aluminum-containing three-dimensional structure is grown and formed from the aluminum nitride seed crystal.

15. The step of forming the aluminum-containing composition gradient layer is to form an aluminum nitride composition gradient layer. The method for producing an epitaxial structure according to claim 14, characterized in that the thickness of the aluminum nitride composition gradient layer is 10 to 20 nanometers (nm).

16. The step of forming the aluminum-containing homo-layer involves forming an aluminum nitride layer. The method for producing an epitaxial structure according to claim 15, characterized in that the thickness of the aluminum nitride layer is 30 to 300 nanometers (nm).

17. The process further includes the step of placing a plurality of gallium nitride seed crystals on the first buffer layer, The method for producing an epitaxial structure according to claim 13, characterized in that the gallium-containing three-dimensional structure is grown from the gallium nitride seed crystal.

18. The step of forming the gallium-containing composition gradient layer is to form a gallium nitride composition gradient layer. The method for producing an epitaxial structure according to claim 17, characterized in that the thickness of the gallium nitride composition gradient layer is 10 to 20 nanometers (nm).

19. The step of forming the gallium-containing homo-layer involves forming a gallium nitride layer. The method for producing an epitaxial structure according to claim 18, characterized in that the thickness of the gallium nitride layer is 30 to 300 nanometers (nm).

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