Epitaxial structure and preparation method thereof

Abstract

The invention discloses an epitaxial structure and a preparation method thereof. The preparation method of the epitaxial structure comprises the steps that a corrosion layer is formed on one side of a substrate, the corrosion layer comprises a first face opposite to the substrate and a second face adjacent to the first face, and the second face of the corrosion layer is a non-polar face; forming an epitaxial layer on one side, far away from the substrate, of the corrosion layer; and corroding the second surface of the corrosion layer by using a chemical solution. According to the invention, the substrate of the epitaxial structure can be stripped on the basis of not damaging the epitaxial layer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an epitaxial structure and a preparation method thereof. Background Art

[0002] Epitaxial structures, such as GaN-based optoelectronic devices and power devices, have important applications in the field of semiconductor technology. Currently, sapphire substrates are mainly used to manufacture GaN-based optoelectronic devices and power devices.

[0003] However, with the increase in integration and power, the disadvantage of poor thermal conductivity of sapphire substrates has become increasingly obvious, greatly restricting the further application of epitaxial structures. To solve this problem, laser lift-off technology can be used to lift off the substrate. However, when using laser lift-off technology, the high temperature generated during the lift-off process damages GaN, increasing the defect density of GaN and the reverse leakage, which reduces the performance of the epitaxial structure. Summary of the invention

[0004] The invention provides an epitaxial structure and a preparation method thereof, so as to peel off a substrate without damaging an epitaxial layer.

[0005] According to one aspect of the present invention, a method for preparing an epitaxial structure is provided, the method for preparing the epitaxial structure comprising:

[0006] forming a corrosion layer on one side of the substrate, wherein the corrosion layer comprises a first surface opposite to the substrate and a second surface adjacent to the first surface, and the second surface of the corrosion layer is a non-polar surface;

[0007] forming an epitaxial layer on a side of the etching layer away from the substrate;

[0008] The second surface of the etching layer is etched by using a chemical solution.

[0009] Optionally, forming a corrosion layer on one side of the substrate includes:

[0010] An etching layer matching the lattice constant of the epitaxial layer is formed on one side of the substrate.

[0011] Optionally, forming an etching layer on one side of the substrate that matches the lattice constant of the epitaxial layer includes:

[0012] In is formed on one side of the substrate x Al 1-x The corrosion layer composed of N;

[0013] The step of forming an epitaxial layer on a side of the etching layer away from the substrate comprises:

[0014] An epitaxial layer consisting of one or more combinations of AlN, GaN, AlGaN and InGaN is formed on the side of the corrosion layer away from the substrate.

[0015] Optionally, before forming the corrosion layer on one side of the substrate, the method further includes:

[0016] forming a transition layer on one side of the substrate;

[0017] The step of forming a corrosion layer on one side of the substrate comprises:

[0018] The corrosion layer is formed on a side of the transition layer away from the substrate.

[0019] Optionally, before forming the epitaxial layer on the side of the etching layer away from the substrate, the method further includes:

[0020] forming a buffer layer on a side of the corrosion layer away from the substrate;

[0021] The step of forming an epitaxial layer on a side of the etching layer away from the substrate comprises:

[0022] The epitaxial layer is formed on a side of the buffer layer away from the corrosion layer.

[0023] Optionally, the corroding the second surface of the corrosion layer by using a chemical solution comprises:

[0024] The corrosion layer is corroded by using a chemical solution for a time period of T, wherein S÷4×t≤T≤2×S÷4×t, S is the size of the substrate, and t is a reference time for etching when the substrate is of a preset size.

[0025] Optionally, forming a corrosion layer on one side of the substrate includes:

[0026] Forming the corrosion layer on one side of the substrate by using at least one of metal organic compound chemical vapor deposition method and molecular beam epitaxy method;

[0027] Alternatively, the etching layer is formed on one side of the substrate by using a pulse growth method.

[0028] Optionally, after forming the epitaxial layer on the side of the etching layer away from the substrate, the method further includes:

[0029] forming a channel layer on a side of the epitaxial layer away from the substrate;

[0030] forming a spacer layer on a side of the channel layer away from the epitaxial layer;

[0031] forming a barrier layer on a side of the spacer layer away from the channel layer;

[0032] A cap layer is formed on a side of the barrier layer away from the spacer layer.

[0033] Optionally, the material of the barrier layer is different from that of the corrosion layer.

[0034] According to another aspect of the present invention, an epitaxial structure is provided. The epitaxial structure is manufactured by the method for manufacturing an epitaxial structure as described above.

[0035] The technical solution of the embodiment of the present invention adopts a method for preparing an epitaxial structure, which includes: forming a corrosion layer on one side of a substrate, wherein the corrosion layer includes a first surface opposite to the substrate and a second surface adjacent to the first surface, and the second surface of the corrosion layer is a non-polar surface; forming an epitaxial layer on the side of the corrosion layer away from the substrate; and corroding the second surface of the corrosion layer using a chemical solution. The corrosion layer is corroded by a chemical solution, thereby separating the substrate from the epitaxial layer, and the epitaxial layer will not be damaged during the separation process, thereby not reducing the performance of the epitaxial structure. In addition, since laser lift-off is not used, the substrate can be a transparent substrate or a non-transparent substrate, and the range of choices for substrate materials is also wider.

[0036] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 A flow chart of a method for preparing an epitaxial structure provided in an embodiment of the present invention;

[0039] Figure 2 A schematic diagram of a product structure formed by the main steps of a method for preparing an epitaxial structure provided by an embodiment of the present invention;

[0040] Figure 3 A flow chart of another method for preparing an epitaxial structure provided in an embodiment of the present invention;

[0041] Figure 4 A schematic diagram of a product structure formed by the main steps of another method for preparing an epitaxial structure provided by an embodiment of the present invention;

[0042] Figure 5 A flow chart of another method for preparing an epitaxial structure provided in an embodiment of the present invention;

[0043] Figure 6 A schematic diagram of a product structure formed by the main steps of another method for preparing an epitaxial structure provided by an embodiment of the present invention;

[0044] Figure 7 A flow chart of another method for preparing an epitaxial structure provided in an embodiment of the present invention;

[0045] Figure 8 A schematic diagram of a product structure formed by the main steps of another method for preparing an epitaxial structure provided by an embodiment of the present invention;

[0046] Fig. 9 A flow chart of another method for preparing an epitaxial structure provided in an embodiment of the present invention;

[0047] Fig.10 A schematic diagram of a product structure formed by main steps of another method for preparing an epitaxial structure provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0049] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0050] Figure 1 A flowchart of a method for preparing an epitaxial structure provided in an embodiment of the present invention, Figure 2 A schematic diagram of a product structure formed by the main steps of a method for preparing an epitaxial structure provided in an embodiment of the present invention, combined with Figure 1 and Figure 2 The method for preparing the epitaxial structure comprises:

[0051] Step S110, forming a corrosion layer on one side of the substrate, wherein the corrosion layer 13 includes a first surface opposite to the substrate and a second surface adjacent to the first surface, and the second surface of the corrosion layer 13 is a non-polar surface;

[0052] Specifically, Figure 2 As shown, a substrate 11 may be provided first, and the substrate 11 may be a transparent substrate or a non-transparent substrate. Subsequently, a corrosion layer 13 is formed on one side of the substrate 11, and the corrosion layer 13 is subsequently used for corrosion to peel off the substrate 11. The first surface of the corrosion layer 13 may be understood as the bottom surface of the corrosion layer 13, and the second surface of the corrosion layer 13 may be understood as the side surface of the corrosion layer 13. When the corrosion layer 13 is corroded, since at this time in the epitaxial structure, the top surface and the bottom surface of the corrosion layer 13 are not exposed to the outside, and only the side surface is exposed to the outside, the second surface of the corrosion layer 13 is set as a non-polar surface, which can facilitate the subsequent corrosion of the corrosion layer from the side without corroding other film layers.

[0053] Step S120, forming an epitaxial layer 15 on a side of the etching layer 13 away from the substrate 11;

[0054] Specifically, Figure 2 As shown, after the etching layer is formed, the epitaxial layer 15 can be formed by growth or the like.

[0055] Step S130: using a chemical solution to etch the second surface of the corrosion layer 13.

[0056] Specifically, if the substrate 11 and the epitaxial layer 15 are not separated in the epitaxial structure, the application of the epitaxial structure will be limited due to the poor thermal conductivity of the substrate 11. In this embodiment, the substrate 11 and the epitaxial layer 15 are separated so that the epitaxial structure of the final product no longer contains the substrate 11, thereby avoiding the problem caused by the poor thermal conductivity of the substrate 11. In addition, in this embodiment, a corrosion layer 13 is added and the corrosion layer 13 is corroded by chemical solution corrosion. When the corrosion layer 13 is completely corroded, the substrate 11 falls off the epitaxial layer 15. Compared with the traditional laser peeling method, the chemical solution corrosion method does not generate excessive heat, and thus does not damage the structure of the epitaxial layer and does not reduce the performance of the epitaxial structure. And because the second surface of the corrosion layer 13 is a non-polar structure, during chemical solution corrosion, the corrosion can be carried out from the second surface of the corrosion layer without damaging the epitaxial layer.

[0057] The technical solution of this embodiment adopts a method for preparing an epitaxial structure, which includes: forming a corrosion layer on one side of a substrate, wherein the corrosion layer includes a first surface opposite to the substrate and a second surface adjacent to the first surface, and the second surface of the corrosion layer is a non-polar surface; forming an epitaxial layer on the side of the corrosion layer away from the substrate; and corroding the second surface of the corrosion layer using a chemical solution. The corrosion layer is corroded by a chemical solution, thereby separating the substrate from the epitaxial layer. During the separation process, the epitaxial layer will not be damaged, and the performance of the epitaxial structure will not be reduced. In addition, since laser lift-off is not adopted, the substrate can be a transparent substrate or a non-transparent substrate, and the range of choices for substrate materials is also wider.

[0058] It should be noted that the material of the chemical solution in this embodiment is not specifically limited, as long as it can etch away the corrosion layer. Different corrosion layer materials may correspond to different chemical solutions.

[0059] Optionally, forming a corrosion layer on one side of the substrate includes:

[0060] An etching layer having a lattice constant matching that of the epitaxial layer is formed on one side of the substrate.

[0061] Specifically, when the epitaxial layer is directly made on the substrate, the lattice constants between the substrate and the epitaxial layer do not match. When the substrate is peeled off, the stress release on the substrate will cause damage to the epitaxial layer. In addition, when the corrosion layer is corroded, if the lattice constants of the corrosion layer and the epitaxial layer do not match, the corrosion layer and the epitaxial layer will cause stress release problems. When the stress of the epitaxial layer is released, the epitaxial layer may be damaged, thereby reducing the performance of the epitaxial structure. In this embodiment, the lattice constant of the corrosion layer is matched with the lattice constant of the epitaxial layer. When the corrosion layer is corroded, the problem of stress release of the epitaxial layer will be greatly suppressed, thereby further preventing damage to the epitaxial layer and ensuring that the performance of the epitaxial structure will not be reduced; in addition, although the substrate will also release stress, since a corrosion layer is provided between the substrate and the epitaxial layer, the stress released by the substrate will not affect the epitaxial layer, and thus will not damage the epitaxial layer.

[0062] Optionally, forming an etching layer on one side of the substrate that matches the lattice constant of the epitaxial layer includes:

[0063] In is formed on one side of the substrate x Al 1-x N, wherein the value range of x is 0<x<1, preferably, the value range of x is 0.15 to 0.19;

[0064] Forming an epitaxial layer on a side of the etching layer away from the substrate includes:

[0065] An epitaxial layer consisting of one or more combinations of AlN, GaN, AlGaN and InGaN is formed on the side of the etching layer away from the substrate.

[0066] Specifically, in this embodiment, the epitaxial layer can be a stacked structure of one or more of AlN, GaN, AlGaN and InGaN. x Al 1-x N, and when x is in the range of 0.15 to 0.19, the lattice constants of the corrosion layer and the epitaxial layer are well matched. Therefore, when the corrosion layer is corroded, the problem of stress release of the epitaxial layer can be greatly suppressed, and damage to the epitaxial layer can be further prevented, ensuring that the performance of the epitaxial structure will not be reduced. Of course, it should be noted that the corrosion layer can also be made of other materials whose lattice constants match the lattice constants of the epitaxial layer. Lattice constant matching can be understood as the same lattice constants.

[0067] Optionally, Figure 3 A flowchart of another method for preparing an epitaxial structure provided in an embodiment of the present invention, Figure 4 A schematic diagram of a product structure formed by the main steps of another method for preparing an epitaxial structure provided in an embodiment of the present invention, referring to Figure 3 and Figure 4 In this embodiment, the method for preparing the epitaxial structure includes:

[0068] Step S210, forming a transition layer 12 on one side of the substrate;

[0069] Specifically, the substrate 11 can be a combination of one or more of gallium nitride, aluminum gallium nitride, indium gallium nitride, aluminum indium gallium nitride, indium phosphide, gallium arsenide, silicon carbide, diamond, sapphire, germanium, silicon, or any other material capable of growing group III nitrides. The transition layer 12 can be a combination of one or more of AlN, GaN, AlGaN and InGaN. The transition layer 12 is used to enable the corrosion layer 13 to grow smoothly, avoiding the problem of poor quality of the corrosion layer grown directly on the substrate. In this embodiment, the transition layer 12 is grown directly on the substrate 11.

[0070] Step S220, forming an etching layer on a side of the transition layer away from the substrate;

[0071] Specifically, in this embodiment, forming the corrosion layer on one side of the substrate includes forming the corrosion layer 13 on the side of the transition layer away from the substrate. The corrosion layer 13 is directly grown on the transition layer 12, and a corrosion layer with better quality can be grown.

[0072] Step S120, forming an epitaxial layer on a side of the etching layer away from the substrate;

[0073] Step S130: using a chemical solution to etch the second surface of the corrosion layer.

[0074] Optionally, Figure 5A flowchart of another method for preparing an epitaxial structure provided in an embodiment of the present invention, Figure 6 A schematic diagram of a product structure formed by the main steps of another method for preparing an epitaxial structure provided in an embodiment of the present invention, combined with Figure 5 and Figure 6 The method for preparing the epitaxial structure comprises:

[0075] Step S110, forming a corrosion layer on one side of the substrate, wherein the corrosion layer includes a first surface opposite to the substrate and a second surface adjacent to the first surface, and the second surface of the corrosion layer is a non-polar surface;

[0076] Step S310, forming a buffer layer on a side of the etching layer away from the substrate;

[0077] Specifically, the material of the buffer layer 14 may be GaN, and the buffer layer 14 may improve the quality of the subsequently grown semiconductor material layer, thereby greatly improving the quality of the epitaxial structure. In this embodiment, the buffer layer is directly grown on the surface of the corrosion layer.

[0078] Step S320, forming an epitaxial layer on a side of the buffer layer away from the corrosion layer;

[0079] Specifically, compared with the above-mentioned implementation manner, in this embodiment, the epitaxial layer is not grown directly on the corrosion layer, but is grown on the buffer layer, so that the quality of the epitaxial layer is better.

[0080] Step S130: using a chemical solution to etch the second surface of the corrosion layer.

[0081] Optionally, Figure 7 A flowchart of another method for preparing an epitaxial structure provided in an embodiment of the present invention, Figure 8 A schematic diagram of a product structure formed by the main steps of another method for preparing an epitaxial structure provided in an embodiment of the present invention, referring to Figure 7 and Figure 8 The method for preparing the epitaxial structure comprises:

[0082] Step S210, forming a transition layer on one side of the substrate;

[0083] Step S220, forming an etching layer on a side of the transition layer away from the substrate;

[0084] Step S310, forming a buffer layer on a side of the etching layer away from the substrate;

[0085] Step S320, forming an epitaxial layer on a side of the buffer layer away from the corrosion layer;

[0086] Step S130: using a chemical solution to etch the second surface of the corrosion layer.

[0087] Specifically, in this embodiment, both a transition layer and a buffer layer are formed in the epitaxial structure, so that the quality of the grown corrosion layer and epitaxial layer are good, thereby further reducing the risk of damage to the epitaxial layer when stripping the substrate and improving the performance of the epitaxial structure.

[0088] Optionally, corroding the second surface of the corrosion layer by using a chemical solution comprises:

[0089] The corrosion layer is corroded by using a chemical solution for a time period of T, wherein S÷4×t≤T≤2×S÷4×t, S is the size of the substrate, and t is a reference time for etching when the substrate is of a preset size.

[0090] Specifically, the preset size can be 4 inches. t is the reference time required to etch the corrosion layer when the substrate is 4 inches. It can be understood that t is the minimum time required for the corrosion layer to be completely etched. S can be 2 inches, 6 inches, 8 inches or 12 inches, etc. If T is small, such as less than S÷4×t, the corrosion layer may not be etched cleanly, making it impossible to completely strip the substrate. If T is large, such as greater than 2×S÷4×t, it will cause a large waste of time and reduce the yield of the epitaxial structure. It should be noted that in this embodiment, the corrosion layer is corroded from the second side, that is, the side, so the corrosion time is mainly related to the substrate size, and the thickness of the corrosion layer has little effect on the corrosion time. Under the same substrate size conditions, the thickness of the corrosion layer has a negligible effect on the corrosion time.

[0091] Illustratively, in the above embodiment, forming a corrosion layer on one side of the substrate includes: forming the corrosion layer on one side of the substrate using at least one of metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE); or forming the corrosion layer on one side of the substrate using a pulsed growth method.

[0092] Specifically, in this embodiment, the corrosion layer can be grown by MOCVD, or by MBE, or by a mixture of MOCVD and MBE, for example, a certain thickness is first grown by MOCVD, and then the corrosion layer of the remaining thickness is grown by MBE. Of course, a pulse growth method can also be used, such as NH3 is always introduced into the cavity during the entire growth process, and the In source and Al source are sequentially introduced into the cavity in the form of pulses, the first pulse is the Al source introduced into the cavity, at which time the In source is not introduced into the cavity, and then the second pulse turns off the Al source and turns on the In source, and the cycle continues. It should be noted that the corrosion layer can also be grown by other methods.

[0093] Optionally, Fig. 9A flowchart of another method for preparing an epitaxial structure provided in an embodiment of the present invention, Fig.10 A schematic diagram of a product structure formed by the main steps of another method for preparing an epitaxial structure provided in an embodiment of the present invention, referring to Fig. 9 and Fig.10 The method for preparing the epitaxial structure comprises:

[0094] Step S110, forming a corrosion layer on one side of the substrate, wherein the corrosion layer includes a first surface opposite to the substrate and a second surface adjacent to the first surface, and the second surface of the corrosion layer is a non-polar surface;

[0095] Step S120, forming an epitaxial layer on a side of the etching layer away from the substrate;

[0096] After step S120, the method further includes:

[0097] Step S410, forming a channel layer on a side of the epitaxial layer away from the substrate;

[0098] Specifically, the channel layer 16 is directly grown on the epitaxial layer to obtain a better two-dimensional electron gas interface, reduce interface scattering, and improve mobility and two-dimensional electron gas concentration.

[0099] Step S420, forming a spacer layer on a side of the channel layer away from the epitaxial layer;

[0100] Specifically, the spacer layer 17 is directly grown on the channel layer 16 . The spacer layer 17 is an AlN spacer layer, which can raise the potential barrier to increase the confinement of the two-dimensional electron gas, while reducing alloy scattering and improving mobility.

[0101] Step S430, forming a barrier layer on a side of the spacer layer away from the channel layer;

[0102] Specifically, the barrier layer 18 is directly grown on the spacer layer 17, and the barrier layer can be AlGaN. The barrier layer 18 forms a heterojunction structure with the channel layer 16, so that the channel layer 16 can provide a channel for the movement of the two-dimensional electron gas. It should be noted that the barrier layer 18 is made of a different material from the corrosion layer 13, so as to prevent the chemical solution from corroding the barrier layer 18 when the corrosion layer 13 is corroded.

[0103] Step S440, forming a cap layer on a side of the barrier layer away from the spacer layer;

[0104] Specifically, the cap layer 19 can be used to reduce surface states, reduce surface leakage of subsequent devices, and inhibit current collapse, thereby improving device performance and reliability. It should be noted that in some optional implementations, the cap layer 19 may not be provided.

[0105] Step S130: using a chemical solution to etch the second surface of the corrosion layer.

[0106] The embodiment of the present invention further provides an epitaxial structure, which is made by the method for making an epitaxial structure provided by any embodiment of the present invention. The epitaxial structure provided by this embodiment has good performance because the epitaxial layer will not be lost when the substrate is peeled off.

[0107] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0108] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an epitaxial structure, characterized in that: The method for preparing the epitaxial structure comprises: forming a corrosion layer on one side of the substrate, wherein the corrosion layer comprises a first surface opposite to the substrate and a second surface adjacent to the first surface, and the second surface of the corrosion layer is a non-polar surface; forming an epitaxial layer on a side of the etching layer away from the substrate; The second surface of the etching layer is etched by using a chemical solution.

2. The method for preparing an epitaxial structure according to claim 1, characterized in that: The step of forming a corrosion layer on one side of the substrate comprises: An etching layer matching the lattice constant of the epitaxial layer is formed on one side of the substrate.

3. The method for preparing an epitaxial structure according to claim 2, characterized in that: The step of forming an etching layer on one side of the substrate and matching the lattice constant of the epitaxial layer comprises: In is formed on one side of the substrate x Al 1-x The corrosion layer composed of N; The step of forming an epitaxial layer on a side of the etching layer away from the substrate comprises: An epitaxial layer consisting of one or more combinations of AlN, GaN, AlGaN and InGaN is formed on the side of the corrosion layer away from the substrate.

4. The method for preparing an epitaxial structure according to claim 1, characterized in that: Before forming the corrosion layer on one side of the substrate, the method further includes: forming a transition layer on one side of the substrate; The step of forming a corrosion layer on one side of the substrate comprises: The corrosion layer is formed on a side of the transition layer away from the substrate.

5. The method for preparing an epitaxial structure according to claim 1 or 4, characterized in that: Before forming an epitaxial layer on a side of the etching layer away from the substrate, the method further comprises: forming a buffer layer on a side of the corrosion layer away from the substrate; The step of forming an epitaxial layer on a side of the etching layer away from the substrate comprises: The epitaxial layer is formed on a side of the buffer layer away from the corrosion layer.

6. The method for preparing an epitaxial structure according to claim 1, characterized in that: The method of corroding the second surface of the corrosion layer by using a chemical solution comprises: The corrosion layer is corroded by using a chemical solution for a time period of T, wherein S÷4×t≤T≤2×S÷4×t, S is the size of the substrate, and t is a reference time for etching when the substrate is of a preset size.

7. The method for preparing an epitaxial structure according to claim 1, characterized in that: The step of forming a corrosion layer on one side of the substrate comprises: Forming the corrosion layer on one side of the substrate by using at least one of metal organic compound chemical vapor deposition method and molecular beam epitaxy method; Alternatively, the etching layer is formed on one side of the substrate by using a pulse growth method.

8. The method for preparing an epitaxial structure according to claim 1, characterized in that: After forming the epitaxial layer on the side of the etching layer away from the substrate, the method further comprises: forming a channel layer on a side of the epitaxial layer away from the substrate; forming a spacer layer on a side of the channel layer away from the epitaxial layer; forming a barrier layer on a side of the spacer layer away from the channel layer; A cap layer is formed on a side of the barrier layer away from the spacer layer.

9. The method for preparing an epitaxial structure according to claim 8, characterized in that: The material of the barrier layer is different from that of the corrosion layer.

10. An epitaxial structure, characterized in that: The epitaxial structure is made by the method for making an epitaxial structure according to any one of claims 1 to 9.

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