Epitaxial structure, power device and manufacturing method of epitaxial structure

Abstract

This invention provides an epitaxial structure, mainly comprising two graded-layer layers, an aluminum-containing graded-layer layer, a gallium-containing graded-layer layer, and a buffer layer between the two graded-layer layers. The aluminum-containing graded-layer layer is disposed on a silicon 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 silicon substrate and grown by a partial graded-layer to form the aluminum-containing two-dimensional structure. The gallium-containing graded-layer layer is disposed on the 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 buffer layer and grown by a partial graded-layer to form the gallium-containing two-dimensional structure. The two-layer three-dimensional to two-dimensional graded-layer structure alleviates the lattice difference between the silicon substrate and the epitaxial layers and reduces internal stress.

Description

Technical Field

[0001] This 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. Prior Technology

[0002] In recent years, with advancements in materials and structures, high electron mobility transistors (HEMTs) have made significant progress, particularly in power electronics and high-frequency devices. HEMTs primarily utilize the wide bandgap of gallium nitride (GaN) material, which generates a two-dimensional electron gas (2DEG) at the heterojunction. This provides excellent device performance, including high breakdown voltage, outstanding electron mobility, and low on-resistance, thereby achieving high switching speeds and power densities.

[0003] However, manufacturing gallium nitride (GaN) epitaxial substrates presents numerous technical challenges and difficulties, primarily related to material properties, growth processes, and substrate selection. Specifically, GaN exhibits significant lattice differences compared to commonly used substrates (such as sapphire, silicon, and silicon carbide). For instance, the lattice difference between GaN and sapphire is approximately 16%, and with silicon, it reaches as high as 17%. Such lattice differences lead to high-density dislocation formation, typically reaching 10⁹ to 10¹⁰ cm⁻², thereby reducing the performance of high-electron-mobility transistors. Therefore, the industry urgently needs an innovative epitaxial structure to overcome the performance limitations of next-generation wide-bandgap semiconductor materials due to the difficulties in epitaxial manufacturing. Summary of the Invention

[0004] The main objective of this invention is to provide an epitaxial structure, a power device, and a method for manufacturing the epitaxial structure. This epitaxial structure primarily comprises two gradient layers: an aluminum-containing gradient layer and a gallium-containing gradient layer. By transforming two three-dimensional layers into two-dimensional gradient layers of different materials, the significant lattice differences between the silicon wafer and the gallium nitride epitaxial layer are adjusted, reducing lattice stress and improving the mass production yield of epitaxial wafers, as well as the epitaxial quality and electrical performance of the device channel layer.

[0005] To achieve the above objectives, the present invention provides an epitaxial structure comprising an aluminum-containing gradient layer, an aluminum-containing homogeneous layer, a first buffer layer, a gallium-containing gradient layer, a gallium-containing homogeneous layer, and a second buffer layer. The aluminum-containing gradient layer is disposed on a substrate. The aluminum-containing 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 the substrate and grown with a partial gradient to form the aluminum-containing two-dimensional structure. The aluminum-containing homogeneous layer is disposed on the aluminum-containing two-dimensional structure, and the first buffer layer is disposed on the aluminum-containing homogeneous layer. The gallium-containing gradient layer is disposed 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 grown with a partial gradient to form the gallium-containing two-dimensional structure. The gallium-containing homogeneous layer is disposed on the gallium-containing two-dimensional structure, and the second buffer layer is disposed on the gallium-containing homogeneous layer.

[0006] In one embodiment of the epitaxial structure of the present invention, a plurality of aluminum-containing seed crystals are disposed on a substrate, wherein the aluminum-containing three-dimensional structure is formed by the growth of these aluminum-containing seed crystals.

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

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

[0009] In one embodiment of the epitaxial structure of the present invention, the aluminum homogeneous layer is an aluminum nitride layer, and the thickness of the aluminum nitride layer is 30~300 nanometers (nm).

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

[0011] In one embodiment of the epitaxial structure of the present invention, a plurality of gallium-containing seed crystals are disposed on the first buffer layer, wherein the gallium-containing three-dimensional structure is formed by the growth of these gallium-containing seed crystals.

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

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

[0014] In one embodiment of the epitaxial structure of the present invention, the gallium homolayer is a gallium nitride layer, and the thickness of the gallium nitride layer is 30~300 nanometers (nm).

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

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

[0017] To achieve the above objectives, the present invention provides a method for manufacturing an epitaxial structure, comprising the following steps: First, forming an aluminum-containing gradient layer on a substrate, wherein the aluminum-containing gradient layer has an aluminum-containing three-dimensional structure and an aluminum-containing two-dimensional structure, the aluminum-containing three-dimensional structure being formed on the substrate and grown with a partial gradient to form the aluminum-containing two-dimensional structure. Second, forming an aluminum-containing homogeneous layer on the aluminum-containing two-dimensional structure, and forming a first buffer layer on the aluminum-containing homogeneous layer. Next, forming a gallium-containing gradient layer on the first buffer layer, wherein the gallium-containing gradient layer has a gallium-containing three-dimensional structure and a gallium-containing two-dimensional structure, the gallium-containing three-dimensional structure being formed on the first buffer layer and grown with a partial gradient to form the gallium-containing two-dimensional structure. Finally, forming a gallium-containing homogeneous layer on the gallium-containing two-dimensional structure, and forming a second buffer layer on the gallium-containing homogeneous layer.

[0018] In one embodiment of the method for manufacturing the epitaxial structure of the present invention, a step is further included in providing a plurality of aluminum nitride seed crystals on a substrate, wherein the aluminum-containing three-dimensional structure is formed by growing the aluminum nitride seed crystals.

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

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

[0021] In one embodiment of the method for manufacturing the epitaxial structure of the present invention, a step is further included in providing a plurality of gallium nitride seed crystals on a first buffer layer, wherein the gallium-containing three-dimensional structure is formed by growing the gallium nitride seed crystals.

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

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

[0024] After referring to the drawings and the embodiments described below, those skilled in the art will understand other objects of the present invention, as well as the technical means and implementation of the present invention. Simple Explanation of the Diagram

[0025] Figures 1A to 1I show schematic diagrams of manufacturing an epitaxial structure according to an embodiment of the present invention; Figure 2 shows a magnified scanning electron microscope image of the epitaxial structure in one embodiment of the present invention; Figure 3 shows a schematic diagram of an epitaxial structure in another embodiment of the present invention; Figure 4 shows a schematic diagram of a power device using an epitaxial structure in one embodiment of the present invention; and Figure 5 shows a schematic diagram of the fabrication process steps of the epitaxial structure of the present invention. Implementation

[0026] The present invention will be explained below through embodiments. These embodiments are not intended to limit the implementation of the invention to any specific environment, application, or special method as described in the embodiments. Therefore, the descriptions of the embodiments are for illustrative purposes only and are not intended to limit the invention. It should be noted that in the following embodiments and drawings, elements not directly related to the present invention have been omitted and are not shown, and the dimensional relationships between the elements in the drawings are for ease of understanding only and are not intended to limit the actual scale.

[0027] This invention discloses an epitaxial structure suitable for power devices and its manufacturing method, thereby improving the performance of power devices. Referring to Figure 1A, firstly, a plurality of aluminum-containing seed crystals 10 are provided on a substrate 1. The substrate 1 can be a silicon (Si) substrate, a silicon-on-insulator (SOI) substrate, but is not limited thereto. For example, ammonia (NH₃) and trimethylaluminum (TMAl) gas are introduced into the silicon substrate using metal-organic chemical vapor deposition (MOCVD) to precipitate the silicon substrate. <111> Complex aluminum nitride (AlN) seed crystals are slowly and evenly distributed on the crystal plane. Then, these aluminum-containing seed crystals 10 continue to grow at a low temperature of 400–600°C, causing the seed crystal volume to continuously expand, as shown in Figure 1B. After a period of growth, due to the large difference in lattice constants and high lattice dislocation density between the silicon substrate and aluminum nitride, aluminum nitride cannot grow into a flat thin film on the substrate. Instead, it forms many island-like three-dimensional aluminum-containing structures 112, as shown in Figure 1C. This stage is defined as the "3D growth" stage.

[0028] Next, the growth temperature is raised to a high temperature of 1000~1200°C. At this temperature, because aluminum and nitrogen atoms gain sufficient kinetic energy, they can move along the substrate surface to the most suitable lattice position. Therefore, the lateral growth rate will be greater than the vertical growth rate, and the island-shaped aluminum-containing three-dimensional structure 112 will grow longer and larger. This stage can be called the "2D growth" stage. When the island-shaped aluminum-containing three-dimensional structure 112 grows to a certain extent laterally, it begins to coalescence with adjacent island-shaped aluminum-containing three-dimensional structures 112. After all the island-shaped structures become blocky and coalesce with each other, the crystal surface begins to flatten. At this time, the aluminum-containing three-dimensional structure 112 begins to grow upward to partially form an aluminum-containing two-dimensional structure 114, as shown in Figure 1D. At this point, an aluminum-containing gradient layer 110 is formed on the substrate 1. This aluminum-containing gradient layer 110 has the aluminum-containing three-dimensional structure 112 formed on the substrate 1, and the aluminum-containing two-dimensional structure 114 formed by the partial gradient growth of the aluminum-containing three-dimensional structure 112. Specifically, the aluminum gradient layer 110 series aluminum nitride gradient layer has a thickness of 10~20 nanometers (nm), which allows the silicon lattice on the substrate to be significantly adjusted through the process of the aluminum nitride gradually changing from a three-dimensional structure to a two-dimensional structure.

[0029] Referring to Figure 1E, an aluminum homogeneous layer 120 is then grown on the flat surface of the aluminum-containing two-dimensional structure 114 of the aluminum-containing gradient layer 110. This aluminum homogeneous layer contains an aluminum nitride layer, and the thickness of this aluminum nitride layer is at least 30-300 nanometers (nm), which gradually stabilizes the defects of the aluminum nitride material. Referring to Figure 1F, a first buffer layer 130 is then formed on the aluminum homogeneous layer 120 to further modulate the internal stress. The first buffer layer 130 can be a block type or a layered stacked structure, for example, a layered stacked structure composed of aluminum (Al), gallium (Ga), and nitrogen (N) in different proportions. Specifically, it can be a superlattice structure composed of alternating stacks of high-energy bandgap materials (such as aluminum nitride or aluminum gallium nitride with high aluminum content) and low-energy bandgap materials (such as gallium nitride or aluminum gallium nitride with low aluminum content), with a total thickness between 20 and 5000 nanometers (nm), to further reduce the internal stress caused by lattice differences and reduce the defect density.

[0030] Next, a second large-scale lattice modulation epitaxial structure layout is performed. Specifically, a gallium-containing gradient layer 140 is formed on the first buffer layer 130. Referring to Figures 1G and 1H, these figures show that ammonia (NH3) and trimethylgallium (TMGa) gas are introduced using organometallic chemical vapor deposition to nucleate a plurality of gallium-containing seed crystals 20 evenly distributed on the surface of the first buffer layer 130. These gallium-containing seed crystals 20 are specifically gallium nitride seed crystals. Then, these gallium-containing seed crystals 20 continue to grow at a low temperature of 400-600°C, causing the seed crystal volume to continuously increase. Subsequently, the aforementioned "3D growth" and "2D growth" stages are performed, allowing a blocky gallium-containing three-dimensional structure (not shown) to gradually grow from the gallium-containing seed crystals on the first buffer layer 130, and further forming a gallium-containing gradient layer 140. This gallium-containing gradient layer 140 has a gallium-containing three-dimensional structure formed on the first buffer layer, and a gallium-containing two-dimensional structure (not shown) grown from the gallium-containing three-dimensional structure to form a flat surface through partial gradient. Specifically, the gallium-containing gradient layer 140 is a gallium nitride gradient layer with a total thickness of 10 to 20 nanometers (nm). This allows the aluminum gallium nitride lattice in the buffer layer to be significantly adjusted again through the process of the gallium nitride three-dimensional structure gradually transforming into a gallium nitride two-dimensional structure, thereby alleviating the corresponding internal stress.

[0031] Referring to Figure 1H, a gallium-containing homogeneous layer 150 is grown on the flat surface of the gallium-containing two-dimensional structure in the gallium-containing gradient layer 140. This gallium-containing homogeneous layer contains a gallium nitride layer, and the thickness of this gallium nitride layer is at least 30-300 nanometers (nm) or even thicker, to further reduce the number of defects in the gallium nitride material. Referring to Figure 1I, a second buffer layer 160 is then formed on the gallium-containing homogeneous layer 150 to further modulate the internal stress. The second buffer layer 160, similar to the first buffer layer 130, can be a block type or a layered stacked structure, for example, a layered stacked structure composed of aluminum (Al), gallium (Ga), and nitrogen (N) in different proportions. Specifically, it can be a superlattice structure consisting of alternating stacks of high-energy bandgap materials (such as aluminum nitride or aluminum gallium nitride with high aluminum content) and low-energy bandgap materials (such as gallium nitride or aluminum gallium nitride with low aluminum content), with a total thickness between 20 and 5000 nanometers (nm), to further reduce internal stress caused by lattice differences and reduce defect density. Please refer to Figure 2, which shows a scanning electron microscope magnified cross-section of an epitaxial structure of the present invention. The total thickness of the aluminum-containing graded layer 110 and the aluminum-containing homogeneous layer 120 shown in the figure is approximately 107 nanometers (nm), and the total thickness of the gallium-containing graded layer 140 is approximately 12 nanometers (nm). Clearly, the number of lattice cracks shown above the gallium-containing graded layer 140 in the figure is significantly reduced compared to the number of cracks below the gallium-containing graded layer 140. Moreover, unlike traditional superlattice structures that use small-amplitude lattice modulation in their stacked structure, Figure 2 clearly shows that by using two layers of three-dimensional transition two-dimensional gradient layers with different materials (such as aluminum nitride and gallium nitride), the purpose of significantly modulating lattice differences can be achieved.

[0032] The aforementioned arrangement of at least two three-dimensional transition two-dimensional gradient layers of different materials in the epitaxial structure of the power device is for illustrative purposes only. In practical applications, depending on the required amount of lattice stress modulation in the power device, the process steps shown in Figures 1G to 1I can be repeated until the quality of the gallium nitride epitaxial film meets the specifications set for the power device. The evaluation criteria for the quality of the epitaxial film can be, for example, measuring the X-ray rocking curve (XRC) of a 1-micron gallium nitride epitaxial layer <10. 2> A full width at half maximum (FWHM) of less than 1000 arc seconds is used as the criterion for determining whether to repeat the process steps shown in Figures 1G to 1I. For example, as shown in Figure 3, the epitaxial structure 100 on the display substrate 1 has three three-dimensional transition two-dimensional gradient layers (110, 140, 170) to further alleviate lattice stress and reduce lattice misalignment. Specifically, in addition to the structure shown in Figure 1I, it also includes a gallium-containing gradient layer 170, a gallium-containing homogeneous layer 180, and a third buffer layer 190 repeatedly grown on the second buffer layer 160. The materials corresponding to each epitaxial layer can be referred to the above content and will not be repeated here.

[0033] Please refer to Figure 4, which 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, which includes a substrate 1 and an epitaxial structure 100 as described above, and further includes a channel layer 200 on the epitaxial structure 100, and a gate 302, a source 304 and a drain 306 on the channel layer 200, wherein a two-dimensional electron gas (2DEG) channel 202 is provided in the channel layer 200 adjacent to the upper barrier layer. In addition, the epitaxial structure of the present invention can be applied to other power devices. For example, power devices that can use 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] Please refer to Figure 5, which shows a schematic diagram of the fabrication process steps of the epitaxial structure of the present invention. First, in step S01, an aluminum-containing gradient layer is formed on a substrate. The aluminum-containing gradient layer has an aluminum-containing three-dimensional structure and an aluminum-containing two-dimensional structure, wherein the aluminum-containing three-dimensional structure is formed on the substrate and grown with a partial gradient to form the aluminum-containing two-dimensional structure. Next, in step S02, an aluminum-containing homogeneous layer is formed on the aluminum-containing two-dimensional structure. In step S03, a first buffer layer is formed on the aluminum-containing homogeneous layer. Next, in step S04, a gallium-containing gradient layer is formed on the first buffer layer. The gallium-containing gradient layer has a gallium-containing three-dimensional structure and a gallium-containing two-dimensional structure, wherein the gallium-containing three-dimensional structure is formed on the first buffer layer and grown with a partial gradient to form the gallium-containing two-dimensional structure. In step S05, a gallium-containing homogeneous layer is formed on the gallium-containing two-dimensional structure. Finally, in step S06, a second buffer layer is formed on the gallium-containing homogeneous layer. The descriptions of the relevant components can be found in the foregoing content and will not be repeated here.

[0035] The above embodiments are merely illustrative of the implementation of the present invention and to explain its technical features, and are not intended to limit the scope of protection of the present invention. Any changes or equivalent arrangements that can be easily made by those skilled in the art are within the scope of the present invention, and the scope of protection of the present invention shall be determined by the scope of the patent application.

[0036] 1:Substrate 10: Aluminum-containing seed crystals 20: Gallium-containing seed crystals 100: Epitaxial structure 110: Aluminum-containing 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 graded layer 150: Gallium-containing homolayer 160: Second Buffer Layer 170: Gallium-containing graded layer 180: Gallium-containing homolayer 190: Third Buffer Layer 200: Channel Layer 202: Two-dimensional electron gas channel 302: Gate 304: Source 306: Jiji

Claims

1. An epitaxial structure comprising: an aluminum-containing gradient layer disposed on a substrate, the aluminum-containing gradient layer having an aluminum-containing three-dimensional structure and an aluminum-containing two-dimensional structure, wherein the aluminum-containing three-dimensional structure is formed on the substrate and grown with a partial gradient to form the aluminum-containing two-dimensional structure; an aluminum-containing homogeneous layer disposed on the aluminum-containing two-dimensional structure; a first buffer layer disposed on the aluminum-containing homogeneous layer; a gallium-containing gradient layer disposed on the first buffer layer, the gallium-containing gradient layer having a gallium-containing three-dimensional structure and a gallium-containing two-dimensional structure, wherein the gallium-containing three-dimensional structure is formed on the first buffer layer and grown with a partial gradient to form the gallium-containing two-dimensional structure; a gallium-containing homogeneous layer disposed on the gallium-containing two-dimensional structure; and a second buffer layer disposed on the gallium-containing homogeneous layer.

2. The epitaxial structure as described in claim 1 further includes a plurality of aluminum-containing seed crystals disposed on the substrate, wherein the aluminum-containing three-dimensional structure is formed by growing the aluminum-containing seed crystals.

3. The epitaxial structure as described in claim 2, wherein each of the aluminum-containing seed crystals is an aluminum nitride (AlN) seed crystal.

4. The epitaxial structure as described in claim 3, wherein the aluminum-containing gradient layer is an aluminum nitride gradient layer, and the thickness of the aluminum nitride gradient layer is 10~20 nanometers (nm).

5. The epitaxial structure as described in claim 4, wherein the aluminum-containing homogeneous layer is an aluminum nitride layer, and the thickness of the aluminum nitride layer is 30 to 300 nanometers (nm).

6. The epitaxial structure as described in claim 1, wherein the material of 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 epitaxial structure as described in claim 1 further includes a plurality of gallium-containing seed crystals disposed on the first buffer layer, wherein the gallium-containing three-dimensional structure is formed by growing the gallium-containing seed crystals.

8. The epitaxial structure as described in claim 7, wherein each gallium-containing seed crystal is a gallium nitride (GaN) seed crystal.

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

10. The epitaxial structure as described in claim 9, wherein the gallium-containing homopolymer layer is a gallium nitride layer, and the thickness of the gallium nitride layer is 30 to 300 nanometers (nm).

11. The epitaxial structure as described in claim 1, wherein the material of 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. A power device comprising: a substrate; an epitaxial structure as described in any one of claims 1 to 11, the epitaxial structure being disposed on the substrate; and a channel layer disposed on the epitaxial structure, wherein the channel layer has a two-dimensional electron gas (2DEG) channel therein.

13. A method for manufacturing an epitaxial structure, comprising: forming an aluminum-containing gradient layer on a substrate, the aluminum-containing gradient layer having an aluminum-containing three-dimensional structure and an aluminum-containing two-dimensional structure, wherein the aluminum-containing three-dimensional structure is formed on the substrate and grown with a partial gradient to form the aluminum-containing two-dimensional structure; forming an aluminum-containing homogeneous layer on the aluminum-containing two-dimensional structure; forming a first buffer layer on the aluminum-containing homogeneous layer; forming a gallium-containing gradient layer on the first buffer layer, the gallium-containing gradient layer having a gallium-containing three-dimensional structure and a gallium-containing two-dimensional structure, wherein the gallium-containing three-dimensional structure is formed on the first buffer layer and grown with a partial gradient to form the gallium-containing two-dimensional structure; forming a gallium-containing homogeneous layer on the gallium-containing two-dimensional structure; and forming a second buffer layer on the gallium-containing homogeneous layer.

14. The method for manufacturing an epitaxial structure as described in claim 13 further includes a step of providing a plurality of aluminum nitride seed crystals on the substrate, wherein the aluminum-containing three-dimensional structure is formed by growing the aluminum nitride seed crystals.

15. The method for manufacturing an epitaxial structure as claimed in claim 14, wherein the step of forming an aluminum-containing gradient layer is to form an aluminum nitride gradient layer, wherein the thickness of the aluminum nitride gradient layer is 10 to 20 nanometers (nm).

16. The method for manufacturing an epitaxial structure as claimed in claim 15, wherein the step of forming an aluminum-containing homogeneous layer is to form an aluminum nitride layer, wherein the thickness of the aluminum nitride layer is 30 to 300 nanometers (nm).

17. The method for manufacturing the epitaxial structure as described in claim 13 further includes a step of providing a plurality of gallium nitride seed crystals on the first buffer layer, wherein the gallium-containing three-dimensional structure is formed by growing the gallium nitride seed crystals.

18. The method for manufacturing an epitaxial structure as claimed in claim 17, wherein the step of forming a gallium-containing gradient layer is to form a gallium nitride gradient layer, wherein the thickness of the gallium nitride gradient layer is 10 to 20 nanometers (nm).

19. The method for manufacturing an epitaxial structure as claimed in claim 18, wherein the step of forming a gallium-containing homogeneous layer is to form a gallium nitride layer, wherein the thickness of the gallium nitride layer is 30 to 300 nanometers (nm).

Images