LED epitaxial structure, LED chip and LED epitaxial structure manufacturing method

Abstract

The present invention provides an LED epitaxial structure, an LED chip and a method for manufacturing an LED epitaxial structure. The LED epitaxial structure includes a substrate and a buffer layer and a semiconductor layer arranged thereon. A plurality of raised microstructures are arranged on the surface of the substrate. The buffer layer includes a first buffer layer covering the microstructure, the first buffer layer forms a first through hole at the top of the microstructure, and a second through hole is formed on the side wall of the microstructure. A hollow structure extending upward along the first through hole is formed in the semiconductor layer, and the medium in the hollow structure is air. The air column hollow structure located at the top of the microstructure formed based on the through hole structure increases the refractive index difference at the interface, effectively enhances the reflection effect of light at the interface, and improves the light extraction efficiency of the LED device. Moreover, since the hollow structure is a slender cylindrical structure extending upward, it has little effect on the structure in the semiconductor layer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor light emitting devices, and in particular to an LED epitaxial structure, an LED chip and a method for manufacturing the LED epitaxial structure. Background Art

[0002] Light Emitting Diode (LED) is a new type of energy-saving and environmentally friendly solid-state lighting source. It has the advantages of high energy efficiency, small size, light weight, fast response speed and long life, making it widely used in many fields.

[0003] The current mainstream semiconductor light-emitting materials, such as gallium nitride, have problems such as lattice mismatch and thermal mismatch with the substrate, which affects the service life and luminous efficiency of the device. To solve this problem, an aluminum nitride buffer layer is usually grown on the substrate as a transition layer to reduce lattice mismatch and other problems.

[0004] At the same time, the technology of patterning sapphire substrates has also been developing rapidly in recent years. It prepares micro / nano-sized microstructure pattern arrays on sapphire substrates. On the one hand, the microstructure enables the semiconductor layer to achieve lateral epitaxial growth, reducing the dislocation density of the semiconductor layer and relaxing the stress generated during the growth process; on the other hand, the microstructure reflects and diffracts the light generated by the active layer, thereby reducing the internal total reflection caused by the refractive index difference of the material, thereby improving the light output efficiency of the LED chip through multiple effects.

[0005] However, although growing an aluminum nitride buffer layer on the surface of a patterned substrate reduces problems such as lattice mismatch between the semiconductor layer and the substrate, due to the weak bond energy of aluminum atoms, the surface of the aluminum nitride buffer layer is flat, which reduces the refractive index difference between the interfaces, which is not conducive to further improving the light extraction efficiency of the LED chip. Summary of the invention

[0006] The object of the present invention is to provide an LED epitaxial structure, an LED chip and a method for manufacturing the LED epitaxial structure.

[0007] The present invention provides an LED epitaxial structure, comprising a substrate, a buffer layer and a semiconductor layer arranged thereon, wherein a plurality of protruding microstructures are arranged on the surface of the substrate; the buffer layer comprises a first buffer layer covering the microstructure, wherein the first buffer layer forms a first through hole at the top of the microstructure, and forms a plurality of second through holes on the side wall of the microstructure; a hollow structure extending upward along the first through hole is formed in the semiconductor layer, and the medium in the hollow structure is air.

[0008] As a further improvement of the present invention, the buffer layer also includes a second buffer layer located between the substrate and the first buffer layer, and the lattice constant difference between the material of the first buffer layer and the material of the substrate is greater than the lattice constant difference between the material of the second buffer layer and the material of the substrate.

[0009] As a further improvement of the present invention, the substrate is a sapphire substrate, and the microstructure thereon is conical, or pyramidal, or a quasi-conical shape with raised or depressed side walls, or a quasi-pyramid shape with raised or depressed side walls, and its height ranges from 1.5 to 2 μm.

[0010] As a further improvement of the present invention, the first buffer layer is a gallium aluminum nitride layer or a gallium nitride layer, and its thickness ranges from 10 to 20 nm.

[0011] As a further improvement of the present invention, the second buffer layer is an aluminum nitride layer with a thickness of 10-30 nm.

[0012] As a further improvement of the present invention, a roughening layer is provided between the first buffer layer and the semiconductor layer, the roughening layer is a gallium nitride layer, the hollow structure penetrates the roughening layer, and the difference between the thickness of the roughening layer and the height of the microstructure is less than 0.5 μm.

[0013] As a further improvement of the present invention, the hollow structure is cylindrical, with a height ranging from 0.5 to 4 μm and a pore size ranging from 0.01 to 0.1 μm.

[0014] As a further improvement of the present invention, the size of the second through hole is smaller than that of the first through hole.

[0015] The present invention also provides an LED chip, including an LED epitaxial structure, and a current blocking layer, a transparent conductive layer and a connecting electrode sequentially formed on the LED epitaxial structure, wherein the LED epitaxial structure adopts the LED epitaxial structure as described above.

[0016] The present invention also provides a method for manufacturing an LED epitaxial structure, comprising the steps of:

[0017] Providing a substrate, and forming a plurality of protruding microstructures on the surface of the substrate;

[0018] Forming a first buffer layer on a side of the substrate having the microstructure, annealing the first buffer layer, and forming a first through hole located at the top of the microstructure and a plurality of second through holes located at the sidewalls of the microstructure in the first buffer layer;

[0019] A semiconductor layer is grown on the first buffer layer, and the temperature is continuously raised after the growth of the semiconductor layer is completed, so that the semiconductor layer forms a cylindrical hollow structure on the first through hole.

[0020] As a further improvement of the present invention, the growth temperature range of the semiconductor layer is 1100-1150°C.

[0021] As a further improvement of the present invention, after the semiconductor layer is grown, the temperature range for continuing to rise is 25-50°C.

[0022] As a further improvement of the present invention, before forming the first buffer layer, the method further includes the step of: forming a second buffer layer on the microstructured side of the substrate, wherein the lattice constant difference between the material of the first buffer layer and the material of the substrate is greater than the lattice constant difference between the material of the second buffer layer and the material of the substrate.

[0023] As a further improvement of the present invention, the substrate is a sapphire substrate, and the microstructure formed thereon is conical, pyramidal, or quasi-conical with raised or depressed side walls, or quasi-pyramidal with raised or depressed side walls, and its height ranges from 1.5 to 2 μm.

[0024] As a further improvement of the present invention, the first buffer layer is a gallium aluminum nitride layer or a gallium nitride layer, and the growth thickness ranges from 10 to 20 nm, and the second buffer layer is an aluminum nitride layer, and the thickness of the second buffer layer is from 10 to 30 nm.

[0025] As a further improvement of the present invention, before forming the semiconductor layer, the method further includes forming a roughening layer on the first buffer layer, wherein the roughening layer is a gallium nitride layer, and the difference between the growth thickness of the roughening layer and the height of the microstructure is less than 0.5 μm.

[0026] The beneficial effects of the present invention are as follows: the present invention forms a transition layer with a large lattice constant difference with the patterned substrate on the patterned substrate, and forms a plurality of through-hole structures on the transition layer. The air column hollow structure located at the top of the substrate microstructure formed based on the through-hole structure, and the plurality of air holes located on the sidewall of the substrate microstructure increase the refractive index difference at the above interface, effectively enhance the reflection effect of light at the interface, and improve the light extraction efficiency of the LED device; and, since the hollow structure is a slender cylindrical structure extending upward, it has little effect on the structure in the semiconductor layer. In addition, the method for forming the hollow structure is simple, and there is no need to finely etch the holes, which can be suitable for large-scale process production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of an LED epitaxial structure in one embodiment of the present invention.

[0028] Figure 2 is a schematic diagram of an LED chip in one embodiment of the present invention.

[0029] Figure 3 It is a schematic flow chart of a method for manufacturing an LED epitaxial structure in the present invention.

[0030] Figures 4 to 6 It is a schematic diagram of each step of a method for manufacturing an LED epitaxial structure in the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in combination with the specific implementation methods of this application and the corresponding drawings. Obviously, the described implementation methods are only part of the implementation methods of this application, not all of the implementation methods. Based on the implementation methods in this application, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0032] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0033] For ease of explanation, this document uses terms that represent relative positions in space for description, such as "above", "below", "back", "front", etc., to describe the relationship of one unit or feature shown in the drawings relative to another unit or feature. Terms of relative positions in space can include different orientations of the device in use or operation other than the orientation shown in the figure. For example, if the device in the figure is turned over, the unit described as being "below" or "above" other units or features will be located "below" or "above" the other units or features. Therefore, the exemplary term "below" can encompass both the spatial orientations of below and above.

[0034] like Figure 1 As shown, the present invention provides an LED epitaxial structure, which includes a substrate 1 and a buffer layer 2 and a semiconductor layer 3 arranged thereon.

[0035] The surface of the substrate 1 is provided with a plurality of raised microstructures 11, the buffer layer 2 includes a first buffer layer 21 covering the surface of the microstructure 11, the first buffer layer 21 forms a first through hole 211 at the top of the microstructure 11, and forms a plurality of second through holes 212 on the side wall of the microstructure 11, and a hollow structure 31 extending upward along the first through hole 211 is formed in the semiconductor layer 3, and the medium in the hollow structure 31 is air.

[0036] The substrate 1 is a sapphire substrate, a silicon-based substrate, a silicon carbide substrate, or a composite substrate composed of the above substrates, or other common LED substrate materials.

[0037] Specifically, in this embodiment, the substrate 1 is a sapphire substrate, and a plurality of periodically arranged microstructures 11 are formed on its surface, and the microstructures 11 are cone-shaped, pyramid-shaped, or quasi-cone-shaped with raised or depressed sidewalls, or quasi-pyramid-shaped with raised or depressed sidewalls, and the height range is 1.5-2 μm. In other embodiments of the present invention, the microstructure 11 may also be a patterned silicon dioxide layer formed on the surface of the substrate 1, as long as a raised microstructure 11 can be formed on the surface of the substrate 1.

[0038] By forming the raised microstructure 11, on the one hand, the semiconductor layer 3 grown based thereon can be changed from longitudinal epitaxy to lateral epitaxy, thereby effectively reducing the dislocation density within the semiconductor layer 3; on the other hand, the interface that produces scattering or refraction on the surface of the substrate 1 is increased, thereby improving the luminous efficiency of the LED chip.

[0039] In some embodiments of the present invention, the buffer layer 2 also includes a second buffer layer 22, and the second buffer layer 22 is covered on the side of the substrate 1 where the microstructure 11 is formed, and the first buffer layer 21 is covered on the second buffer layer 22, that is, the second buffer layer 22 is located between the substrate 1 and the first buffer layer 21.

[0040] Furthermore, the lattice constant difference between the material of the first buffer layer 21 and the material of the substrate 1 is greater than the lattice constant difference between the material of the second buffer layer 22 and the material of the substrate 1. The second buffer layer 22 is made of a common buffer layer material on a substrate 1 for LEDs. Compared with the second buffer layer 22, the lattice constant difference between the material of the first buffer layer 21 and the substrate 1 is larger, and after annealing, it is easier to form a large gap structure on the microstructure 11.

[0041] Specifically, in this embodiment, the first buffer layer 21 is a gallium nitride aluminum layer or a gallium nitride layer, and its thickness ranges from 10 to 20 nm. Since there is an obvious lattice mismatch between gallium nitride aluminum or gallium nitride and the sapphire substrate 1, after the first buffer layer 21 is formed, it is annealed, and the first buffer layer 21 will form a plurality of island structures with large gaps, and the gaps between different island structures form a through-hole structure that penetrates the first buffer layer 21. Since the microstructure 11 is in an upwardly convex shape and its top is sharp, the first buffer layer 21 will form the largest gap space at the top of the microstructure 11, that is, the first through hole 211, and the first through hole 211 provides a structural basis for the formation of the hollow structure 31 in the semiconductor; the side wall of the microstructure 11 is relatively flat, and the first buffer layer 21 will form a plurality of smaller gap spaces, that is, the second through hole 212, on the side wall of the microstructure 11, and the size of the second through hole 212 is smaller than the first through hole 211.

[0042] In other embodiments of the present invention, the material of the first buffer layer 21 may also be other materials such as gallium-containing materials, or different materials may be selected according to the material of the substrate 1. It is sufficient as long as the lattice constant difference between the material of the first buffer layer 21 and the material of the substrate 1 is greater than the lattice constant difference between the material of the buffer layer 2 on a common LED substrate 1 and the material of the substrate 1.

[0043] Specifically, in this embodiment, the second buffer layer 22 is a single-layer aluminum nitride buffer layer 2, and its thickness ranges from 10 to 30 nm. By arranging the second buffer layer 22 on the substrate 1 as a transition layer between the first buffer layer 21 and the semiconductor layer 3, the lattice mismatch between the substrate 1 and the semiconductor layer 3 can be reduced, thereby reducing defects such as dislocations generated during the growth of the semiconductor layer 3. In other embodiments of the present invention, the second buffer layer 22 can also be made of other materials such as nitrides, or a multi-layer composite structure, as long as it can be used as a transition layer to reduce the lattice mismatch between the substrate 1 and the semiconductor layer 3.

[0044] In some other embodiments of the present invention, a roughening layer 4 is further provided between the first buffer layer 21 and the semiconductor layer 3 , and the roughening layer 4 is used to make a further transition for growing the semiconductor layer 3 , so that the structure of the hollow structure 31 is more stable.

[0045] Specifically, in this embodiment, the roughening layer 4 is a gallium nitride layer. During the formation process, the island-like structures formed by the first buffer layer 21 are used as the basic nucleation layer for the growth of the roughening layer 4, and the roughening layer 4 grows laterally epitaxially along the island-like structures. During the growth of the roughening layer 4, its growth thickness is controlled so that the hollow structure 31 penetrates the roughening layer 4. On the one hand, if the thickness of the roughening layer 4 is too thin, the structure of the roughening layer 4 grown laterally epitaxially is not complete, so that the hollow structure 31 located above the first through hole 211 is irregular in shape, thereby affecting the growth quality of the semiconductor layer 3; on the other hand, if the thickness of the roughening layer 4 is too thick, the roughening layer 4 may grow laterally epitaxially above the first through hole 211 until the structure is completely merged, and the hollow structure 31 disappears.

[0046] More specifically, in this embodiment, the difference between the height of the roughening layer 4 and the height of the microstructure 11 is less than 0.5 μm, that is, the thickness of the roughening layer 4 is plus or minus 5 μm of the height of the microstructure 11. In other embodiments, the thickness of the roughening layer 4 can also be adaptively adjusted according to the morphology of the substrate 1 and the size of the LED chip.

[0047] In addition, since the size of the second through hole 212 is smaller than that of the first through hole 211, the roughening layer 4 grown on the side wall of the microstructure 11 gradually grows and merges above the second through hole 212, and the medium in the second through hole 212 is air, thereby forming a plurality of air holes on the side wall of the microstructure 11.

[0048] The semiconductor layer 3 is formed on the roughening layer 4. When growing, the semiconductor layer 3 adopts a temperature higher than the conventional growth temperature, so that the semiconductor layer 3 continues to grow at a higher growth rate based on the hollow structure 31 of the roughening layer 4, gradually forming a complete hollow structure 31 without filling the hollow structure 31.

[0049] Specifically, in this embodiment, the semiconductor layer 3 is a doped gallium nitride layer, which includes an N-type semiconductor layer 31 , a light emitting layer 32 and a P-type semiconductor layer 33 , and the hollow structure 31 is located in the N-type semiconductor layer 31 .

[0050] The hollow structure 31 is cylindrical, with a height ranging from 0.5 to 4 μm, a pore size ranging from 0.01 to 0.1 μm, and the inner filling medium is air, that is, a regular air column is formed above the first through hole 211. It can be understood that the height of the hollow structure 31 is the common height of the two parts located in the roughening layer 4 and the semiconductor layer 3.

[0051] By forming a hollow structure 31 between the semiconductor layer 3 and the substrate 1, and combining the plurality of second through holes 212 formed on the side wall of the microstructure 11, the refractive index difference at the interface is increased, and the reflection effect of light at the interface is effectively enhanced, thereby improving the light extraction efficiency of the LED device. In addition, since the hollow structure 31 is a slender cylindrical structure extending upward, it has little effect on the structure in the semiconductor layer 3.

[0052] like Figure 2 As shown, the present invention also provides an LED chip, including an LED epitaxial structure, and structures such as a current blocking layer 7, a transparent conductive layer 6 and a connecting electrode 5 formed in sequence on the LED epitaxial structure, wherein the LED epitaxial structure adopts the above-mentioned LED epitaxial structure.

[0053] like Figure 3 As shown, the present invention also provides a method for manufacturing an LED epitaxial structure, comprising the steps of:

[0054] S1: providing a substrate 1 and forming a plurality of protruding microstructures 11 on the surface of the substrate 1 .

[0055] The substrate 1 is a sapphire substrate, a silicon-based substrate, a silicon carbide substrate, or a composite substrate composed of the above substrates, or other common LED substrate materials.

[0056] Specifically, in this embodiment, the substrate 1 is a sapphire substrate 1, and a plurality of periodically arranged microstructures 11 are formed on its surface by etching, and the microstructure 11 is conical, pyramidal, or quasi-conical with raised or depressed sidewalls, or quasi-pyramidal with raised or depressed sidewalls, and its height ranges from 1.5 to 2 μm. In other embodiments of the present invention, the microstructure 11 can also be formed by depositing a silicon dioxide layer on the surface of the substrate 1, and then etching the silicon dioxide layer, etc., as long as a raised microstructure 11 can be formed on the surface of the substrate 1.

[0057] S2: forming a first buffer layer 21 on the side of the substrate 1 having the microstructure 11, annealing the first buffer layer 21, and forming a first through hole 211 located at the top of the microstructure 11 and a plurality of second through holes 212 located at the sidewalls of the microstructure 11 in the first buffer layer 21.

[0058] Specifically, in this embodiment, the first buffer layer 21 is a gallium aluminum nitride layer or a gallium nitride layer, and the growth thickness ranges from 10 to 20 nm. Aluminum gallium nitride or gallium nitride having a large lattice constant difference with the substrate 1 is selected as the material of the first buffer layer 21, so as to form an island structure with a large gap after annealing.

[0059] In some embodiments of the present invention, before forming the first buffer layer 21, the step of forming a second buffer layer 22 on the side of the substrate 1 having the microstructure 11 is also included, and the lattice constant difference between the material of the first buffer layer 21 and the material of the substrate 1 is greater than the lattice constant difference between the material of the second buffer layer 22 and the material of the substrate 1.

[0060] Specifically, in this embodiment, the second buffer layer 22 is an aluminum nitride layer, and the thickness of the second buffer layer 22 is in the range of 10-30 nm.

[0061] S3 : growing a semiconductor layer 3 on the first buffer layer 21 , and continuing to increase the temperature after the growth of the semiconductor layer 3 is completed, so that the semiconductor layer 3 forms a cylindrical hollow structure 31 on the first through hole 211 .

[0062] Specifically, in this embodiment, the semiconductor layer 3 is a doped gallium nitride layer, and the growth temperature range of the semiconductor layer 3 is 1100-1150°C. After the growth of the semiconductor layer 3, the temperature range of continuing to rise is 25-50°C. Compared with the conventional gallium nitride layer growth temperature, the present invention adopts a higher growth temperature, so that the semiconductor layer 3 maintains a higher longitudinal epitaxial growth rate, and grows rapidly upward based on the first through hole 211, thereby forming a complete hollow structure 31, rather than lateral epitaxial growth and merging and filling the hollow structure 31. After the growth of the semiconductor layer 3 is completed, the temperature continues to rise to further stabilize the shape of the hollow structure 31.

[0063] In some embodiments of the present invention, before forming the semiconductor layer 3 , the method further includes forming a roughening layer 4 on the first buffer layer 21 .

[0064] Specifically, in this embodiment, the roughening layer 4 is a gallium nitride layer, and the difference between the growth thickness of the roughening layer 4 and the height of the microstructure 11 is less than 0.5 μm.

[0065] The manufacturing method adopted in the present invention can form a hollow structure for enhancing refraction and local reflection in the LED chip by only adjusting the growth temperature without the need for a sophisticated through-hole etching step, which is simple and convenient and can be applied to large-scale process production.

[0066] In summary, the present invention forms a transition layer with a large lattice constant difference with the patterned substrate on the patterned substrate, and forms multiple through-hole structures on the transition layer. The air column hollow structure located at the top of the substrate microstructure formed based on the through-hole structure, and multiple air holes located on the sidewall of the substrate microstructure, increase the refractive index difference at the above interface, effectively enhance the reflection effect of light at the interface, and improve the light extraction efficiency of the LED device; and, because the hollow structure is a slender cylindrical structure extending upward, it has little effect on the structure in the semiconductor layer. In addition, the method for forming the hollow structure is simple, and there is no need to etch holes in a refined manner, which can be suitable for large-scale process production.

[0067] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0068] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. An LED epitaxial structure, comprising a substrate and a buffer layer and a semiconductor layer arranged thereon, characterized in that: The substrate surface is provided with a plurality of raised microstructures; The buffer layer includes a first buffer layer covering the microstructure, wherein the first buffer layer forms a first through hole at the top of the microstructure and forms a plurality of second through holes on the sidewall of the microstructure, wherein the plurality of second through holes are air holes; A hollow structure extending upward along the first through hole is formed in the semiconductor layer. The medium in the hollow structure is air. The hollow structure is cylindrical, with a height ranging from 0.5 to 4 um and an aperture ranging from 0.01 to 0.1 um.

2. The LED epitaxial structure according to claim 1, characterized in that: The buffer layer further includes a second buffer layer located between the substrate and the first buffer layer, and a lattice constant difference between a material of the first buffer layer and a material of the substrate is greater than a lattice constant difference between a material of the second buffer layer and a material of the substrate.

3. The LED epitaxial structure according to claim 2, characterized in that: The substrate is a sapphire substrate, and the microstructure thereon is in the shape of a cone, a pyramid, a quasi-cone with a convex or concave side wall, or a quasi-pyramid with a convex or concave side wall, and the height range is 1.5-2 μm.

4. The LED epitaxial structure according to claim 3, characterized in that: The first buffer layer is a gallium aluminum nitride layer or a gallium nitride layer, and its thickness ranges from 10 to 20 nm.

5. The LED epitaxial structure according to claim 4, characterized in that: The second buffer layer is an aluminum nitride layer, and the thickness of the second buffer layer is 10-30 nm.

6. The LED epitaxial structure according to claim 4, characterized in that: A roughening layer is further provided between the first buffer layer and the semiconductor layer. The roughening layer is a gallium nitride layer. The hollow structure penetrates the roughening layer. The difference between the thickness of the roughening layer and the height of the microstructure is less than 0.5 μm.

7. The LED epitaxial structure according to claim 1, characterized in that: The second through hole has a smaller size than the first through hole.

8. An LED chip, comprising an LED epitaxial structure, and a current blocking layer, a transparent conductive layer and a connecting electrode formed in sequence on the LED epitaxial structure, characterized in that: The LED epitaxial structure adopts the LED epitaxial structure as claimed in any one of claims 1 to 7.

9. A method for manufacturing an LED epitaxial structure, characterized in that: Includes steps: Providing a substrate, and forming a plurality of protruding microstructures on the surface of the substrate; Forming a first buffer layer on a side of the substrate having the microstructure, annealing the first buffer layer, and forming a first through hole located at the top of the microstructure and a plurality of second through holes located at the sidewalls of the microstructure in the first buffer layer, wherein the plurality of second through holes are air holes; A semiconductor layer is grown on the first buffer layer, and the temperature is continued to rise after the growth of the semiconductor layer is completed. The semiconductor layer forms a cylindrical hollow structure on the first through hole. The hollow structure is cylindrical, with a height range of 0.5-4um and an aperture range of 0.01-0.1um. The medium in the hollow structure is air.

10. The method for manufacturing an LED epitaxial structure according to claim 9, characterized in that: The growth temperature of the semiconductor layer is in the range of 1100-1150°C.

11. The method for manufacturing an LED epitaxial structure according to claim 10, characterized in that: After the semiconductor layer is grown, the temperature is continued to rise in the range of 25-50°C.

12. The method for manufacturing an LED epitaxial structure according to claim 9, characterized in that: Before forming the first buffer layer, the method further includes forming a second buffer layer on the microstructured side of the substrate, wherein the lattice constant difference between the material of the first buffer layer and the material of the substrate is greater than the lattice constant difference between the material of the second buffer layer and the material of the substrate.

13. The method for manufacturing an LED epitaxial structure according to claim 12, characterized in that: The substrate is a sapphire substrate, and the microstructure formed thereon is in the shape of a cone, a pyramid, a quasi-cone with a raised or recessed side wall, or a quasi-pyramid with a raised or recessed side wall, and the height range is 1.5-2 μm.

14. The method for manufacturing an LED epitaxial structure according to claim 13, characterized in that: The first buffer layer is a gallium aluminum nitride layer or a gallium nitride layer, and the growth thickness ranges from 10 to 20 nm. The second buffer layer is an aluminum nitride layer, and the thickness of the second buffer layer is from 10 to 30 nm.

15. The method for manufacturing an LED epitaxial structure according to claim 12, characterized in that: Before forming the semiconductor layer, the method further includes forming a roughening layer on the first buffer layer, wherein the roughening layer is a gallium nitride layer, and the difference between the growth thickness of the roughening layer and the height of the microstructure is less than 0.5 μm.

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