Light emitting diode chip with transmission barrier layer and preparation method thereof

Abstract

The invention discloses a light-emitting diode chip with a transmission barrier layer and a preparation method of the light-emitting diode chip, and belongs to the technical field of semiconductors. The light-emitting diode chip comprises a substrate, an epitaxial unit, a transmission barrier layer and a reflecting layer, the epitaxial units are sequentially arranged on one surface of the substrate at intervals; the transmission barrier layer covers each epitaxial unit, and the transmission barrier layer can transmit light emitted by the epitaxial units; the reflection layer covers the transmission barrier layer, and the reflection layer can reflect the light emitted by the epitaxial unit. According to the light-emitting diode chip provided by the embodiment of the invention, the brightness of the light-emitting diode chip can be improved even under the condition that the size is very small.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor technology, and in particular to a light emitting diode chip with a transmission barrier layer and a preparation method thereof. Background Art

[0002] A light emitting diode chip is a common semiconductor chip that can convert electrical energy into light energy.

[0003] In the related art, in order to improve the brightness of the LED chip, a reflector structure, such as a Distributed Bragg Reflector (DBR), is configured inside the LED chip. The Bragg reflector can efficiently reflect the light generated in the epitaxial layer of the LED chip.

[0004] However, with the advancement of miniaturization of LED chips, some have reached sizes of 50µm or even below 10µm. Since the brightness enhancement effect of a Bragg reflector on an LED chip is proportional to its size, the smaller the LED chip, the less effective the Bragg reflector is. Therefore, the brightness enhancement effect of a Bragg reflector on miniature LED chips is relatively poor. Summary of the Invention

[0005] The present disclosure provides a light-emitting diode chip with a transmissive barrier layer and a method for manufacturing the same, which can improve the brightness of the light-emitting diode chip even when the chip is very small. The technical solution is as follows:

[0006] In one aspect, an embodiment of the present disclosure provides a light-emitting diode chip with a transmission barrier layer, comprising a substrate, an epitaxial unit, a transmission barrier layer, and a reflective layer;

[0007] The epitaxial units are sequentially arranged at intervals on one side of the substrate;

[0008] The transmission blocking layer covers the outside of each of the epitaxial units, and the transmission blocking layer can transmit the light emitted by the epitaxial unit;

[0009] The reflective layer covers the transmission blocking layer, and the reflective layer can reflect the light emitted by the epitaxial unit.

[0010] In one implementation of the present disclosure, the transmission blocking layer includes a plurality of transmission blocking sub-units;

[0011] The transmission blocking sub-units are arranged at intervals from each other, and each transmission blocking sub-unit corresponds to each epitaxial unit one by one, and each transmission blocking sub-unit covers the outside of the corresponding epitaxial unit.

[0012] In one implementation of the present disclosure, the reflective layer includes a plurality of reflective subunits;

[0013] The reflective subunits are arranged at intervals from each other, and each reflective subunit corresponds to each transmission blocking subunit one by one, and each reflective subunit covers the outside of the corresponding transmission blocking subunit.

[0014] In an implementation of the present disclosure, the transmission barrier layer is an integral structural component, and the transmission barrier layer is filled in the gaps between the epitaxial units.

[0015] In one implementation of the present disclosure, the reflective layer is an integral structural component.

[0016] In one implementation of the present disclosure, the transmission blocking layer is an inorganic material or an organic material, the inorganic material includes at least one of silicon oxide and silicon nitride, and the organic material includes at least one of phenolic resin, negative photoresist, photosensitive polyimide, and acrylic resin.

[0017] In one implementation of the present disclosure, the refractive index of the transmission blocking layer is 1.4 to 2.1.

[0018] In one implementation of the present disclosure, the epitaxial unit includes a first semiconductor layer, an active layer, and a second semiconductor layer stacked in sequence;

[0019] The etching mesas of the first semiconductor layer and the second semiconductor layer both have contact electrodes;

[0020] The transmission barrier layer covers the contact electrodes of the first semiconductor layer and the second semiconductor layer.

[0021] In another aspect, an embodiment of the present disclosure provides a method for preparing a light-emitting diode chip, wherein the method is used to prepare the light-emitting diode chip described in the previous aspect, and the method comprises:

[0022] providing a substrate;

[0023] preparing each epitaxial unit on one side of the substrate;

[0024] preparing a transmission blocking layer on a side of each epitaxial unit facing away from the substrate, such that the transmission blocking layer covers the outside of each epitaxial unit;

[0025] A reflective layer is prepared on a side of the transmission blocking layer facing away from the substrate, so that the reflective layer covers the transmission blocking layer.

[0026] In one implementation of the present disclosure, a transmission blocking layer is formed on a side of each epitaxial unit facing away from the substrate, comprising:

[0027] Spin coating or depositing the transmission blocking layer on a side of each epitaxial unit facing away from the substrate;

[0028] Etching the transmission blocking layer to the substrate to obtain a plurality of transmission blocking sub-units spaced apart from each other;

[0029] A reflective subunit is prepared on a side of each transmission blocking layer facing away from the substrate, and each reflective subunit corresponds to each transmission blocking subunit one by one.

[0030] The beneficial effects of the technical solutions provided by the embodiments of the present disclosure include at least:

[0031] The light-emitting diode chip provided by the embodiment of the present disclosure mainly includes a substrate, an epitaxial unit, a transmission blocking layer and a reflective layer. Among them, each epitaxial unit is arranged in sequence and spaced apart on one side of the substrate and can emit light under the action of electric current. The transmission blocking layer covers the outside of each epitaxial unit. On the one hand, the transmission blocking layer can play the role of passivation, buffering and filling. On the other hand, it can transmit the light emitted by the epitaxial unit, so that as much light as possible emitted by the epitaxial unit is transmitted through. The reflective layer covers the outside of the transmission blocking layer and can reflect the light transmitted by the transmission blocking layer, thereby effectively improving the brightness of the light-emitting diode chip.

[0032] That is to say, the light-emitting diode chip provided in the embodiment of the present disclosure can, through the cooperation between the transmission blocking layer and the reflective layer, on the one hand transmit as much light as possible emitted by the epitaxial unit, and on the other hand reflect the transmitted light to improve the brightness of the light-emitting diode chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, 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 disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0034] Figure 1 is a structural schematic diagram of a light-emitting diode chip provided by an embodiment of the present disclosure;

[0035] Figure 2is a structural schematic diagram of another light-emitting diode chip provided by an embodiment of the present disclosure;

[0036] Figure 3 This is a flow chart of a method for preparing a light-emitting diode chip provided by an embodiment of the present disclosure;

[0037] Figure 4 is a flow chart of another method for preparing a light-emitting diode chip provided by an embodiment of the present disclosure;

[0038] Figure 5 is a schematic diagram of the preparation process provided by an embodiment of the present disclosure;

[0039] Figure 6 is a schematic diagram of the preparation process provided by an embodiment of the present disclosure;

[0040] Figure 7 is a schematic diagram of the preparation process provided by an embodiment of the present disclosure;

[0041] Figure 8 It is a schematic diagram of the preparation process provided by the embodiment of the present disclosure.

[0042] Figure Number:

[0043] 10. Substrate;

[0044] 20. Epitaxial unit;

[0045] 210, first semiconductor layer; 220, active layer; 230, second semiconductor layer;

[0046] 30. Transmission blocking layer;

[0047] 310, transmission blocking subunit;

[0048] 40. Reflective layer;

[0049] 410, reflection subunit;

[0050] 50. Contact electrode. DETAILED DESCRIPTION

[0051] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0052] Figure 1 This is a schematic diagram of the structure of a light-emitting diode chip provided by an embodiment of the present disclosure, see Figure 1In this embodiment, the light-emitting diode chip includes a substrate 10, epitaxial units 20, a transmission barrier layer 30, and a reflective layer 40. The epitaxial units 20 are sequentially arranged on one side of the substrate 10. The transmission barrier layer 30 covers the outside of each epitaxial unit 20 and can transmit the light emitted by the epitaxial unit 20. The reflective layer 40 covers the outside of the transmission barrier layer 30 and can reflect the light emitted by the epitaxial unit 20.

[0053] The light-emitting diode chip provided by the embodiment of the present disclosure mainly includes a substrate 10, an epitaxial unit 20, a transmission barrier layer 30 and a reflective layer 40. Among them, each epitaxial unit 20 is arranged in sequence and spaced apart on one side of the substrate 10, and can emit light under the action of electric current. The transmission barrier layer 30 covers the outside of each epitaxial unit 20. On the one hand, the transmission barrier layer 30 can play the role of passivation, buffering and filling. On the other hand, it can transmit the light emitted by the epitaxial unit 20, so that as much light as possible emitted by the epitaxial unit 20 is transmitted through. The reflective layer 40 covers the outside of the transmission barrier layer 30 and can reflect the light transmitted by the transmission barrier layer 30, thereby effectively improving the brightness of the light-emitting diode chip.

[0054] That is to say, the light-emitting diode chip provided in the embodiment of the present disclosure can, through the cooperation between the transmission blocking layer 30 and the reflection layer 40, on the one hand transmit as much light as possible emitted by the epitaxial unit 20, and on the other hand reflect the transmitted light to improve the brightness of the light-emitting diode chip.

[0055] In this embodiment, the substrate 10 is one of a sapphire substrate 10, a SiC substrate 10, a Si substrate 10, and a GaN substrate 10, which can be selected according to actual needs and is not limited in this disclosure.

[0056] In this embodiment, the transmission blocking layer 30 is made of an inorganic material or an organic material. The inorganic material includes silicon oxide and silicon nitride, and the organic material includes phenolic resin, negative photoresist, photosensitive polyimide, and acrylic resin.

[0057] In the above implementation, the transmission blocking layer 30 is designed to be the above semiconductor packaging material, which can have the effects of passivation, buffering and filling on one hand, and the effect of transmitting light on the other hand.

[0058] Phenolic resin is a synthetic resin formed by the polycondensation of phenol and formaldehyde under acid or base catalysis. It has excellent high temperature resistance, resistance to weak acids and bases, corrosion resistance, and good insulation properties.

[0059] Negative photoresist (SU8) is a photosensitive epoxy resin characterized by high resolution, high temperature resistance and chemical stability.

[0060] Photosensitive polyimide (PSPI) is a modified material that incorporates photosensitive groups into the polyimide backbone, combining the high-temperature resistance and photosensitivity of polyimide. Of course, in other embodiments, polyimide can be substituted for the photosensitive polyimide. Polyimide is a high-performance thermosetting resin formed by the polycondensation of aromatic dianhydrides and diamine monomers.

[0061] Acrylic resin is a thermoplastic or thermosetting resin made by polymerizing acrylic acid and its ester monomers. It has the characteristics of high transparency and strong weather resistance.

[0062] In order to ensure the light transmittance of the transmission blocking layer 30 , illustratively, the refractive index of the transmission blocking layer 30 is 1.4 to 2.1.

[0063] In the above implementation, the refractive index directly affects the material's reflection, refraction, and transmission of light, thereby determining light transmittance. If the refractive index of the transmission-blocking layer 30 is too high, it will result in increased surface reflection, thereby reducing light transmittance. If the refractive index of the transmission-blocking layer 30 is too low, it will cause scattering losses, which will also reduce light transmittance. Therefore, designing the refractive index of the transmission-blocking layer 30 within the above range can achieve higher light transmittance.

[0064] In this embodiment, the refractive index of the transmission blocking layer 30 is 1.8. Of course, in other embodiments, the refractive index of the transmission blocking layer 30 can also be other values ​​within the above numerical range, and the present disclosure does not limit this.

[0065] In this embodiment, the epitaxial unit 20 includes a first semiconductor layer 210 , an active layer 220 , and a second semiconductor layer 230 , which are stacked in sequence.

[0066] Illustratively, the first semiconductor layer 210 is of a first conductivity type, the second semiconductor layer 230 is of a second conductivity type, and the second conductivity type is different from the first conductivity type.

[0067] When the light emitting diode chip is working, electron transition occurs between the first semiconductor layer 210 and the second semiconductor layer 230 , and the active layer 220 emits light.

[0068] In this embodiment, the first semiconductor layer 210 is an N-type semiconductor layer, the active layer 220 is a quantum well layer, and the second semiconductor layer 230 is a P-type semiconductor layer. Of course, in other embodiments, the first semiconductor layer 210 may also be a P-type semiconductor layer, the second semiconductor layer 230 may be an N-type semiconductor layer, and the active layer 220 may be a quantum well layer, and this disclosure is not limited thereto.

[0069] In this embodiment, both the first semiconductor layer 210 and the second semiconductor layer 230 have etched mesas. The etched mesa of the first semiconductor is the side of the first semiconductor layer 210 that faces away from the substrate 10 and is exposed to the outside (not blocked by the active layer 220). The etched mesa of the second semiconductor is the side of the second semiconductor layer 230 that faces away from the substrate 10. The etched mesas of the first semiconductor layer 210 and the second semiconductor layer 230 both have contact electrodes 50.

[0070] The transmission barrier layer 30 covers the outside of the contact electrode 50 of the first semiconductor layer 210 and the second semiconductor layer 230 .

[0071] It is worth noting that the transmissive barrier layer 30 covers the contact electrode 50, which means that the transmissive barrier layer 30 covers the contact electrode 50, but is not limited to covering the contact electrode 50. In this embodiment, the transmissive barrier layer 30 at least covers the first semiconductor layer 210, the second semiconductor layer 230 and the contact electrode 50.

[0072] In the above implementation, the contact electrode 50 is covered by the transmission barrier layer 30 , so that the passivation effect of the transmission barrier layer 30 can be effectively exerted.

[0073] As can be seen from the foregoing, the transmission barrier layer 30 and the reflection layer 40 are key to improving the brightness of the light-emitting diode chip. Two arrangements of the two are introduced below.

[0074] For the first arrangement.

[0075] Continue to see Figure 1 In this embodiment, the transmission blocking layer 30 includes a plurality of transmission blocking sub-units 310, and the transmission blocking sub-units 310 are arranged at intervals from each other. Each transmission blocking sub-unit 310 corresponds to each epitaxial unit 20 one by one, and each transmission blocking sub-unit 310 covers the outside of its corresponding epitaxial unit 20.

[0076] In the above implementation, the transmission blocking layer 30 is composed of a plurality of transmission blocking sub-units 310, with one transmission blocking sub-unit 310 corresponding to one epitaxial unit 20. This arrangement of the transmission blocking sub-units 310 effectively ensures that light emitted from each epitaxial unit 20 is transmitted through its corresponding transmission blocking sub-unit 310.

[0077] In this embodiment, the reflective layer 40 includes a plurality of reflective subunits 410 , which are arranged at intervals with each other. Each reflective subunit 410 corresponds one-to-one to each transmission blocking subunit 310 , and each reflective subunit 410 covers the outside of its corresponding transmission blocking subunit 310 .

[0078] In the above implementation, the reflective layer 40 is composed of a plurality of reflective subunits 410, with one reflective subunit 410 corresponding to one transmission blocking subunit 310. This arrangement of the reflective subunits 410 effectively ensures that light transmitted by each transmission blocking subunit 310 is reflected by its corresponding reflective subunit 410.

[0079] That is, a transmission blocking subunit 310 and a reflection subunit 410 form a group, and together correspond to one epitaxial unit 20 , and by ensuring the reflection of light in each epitaxial unit 20 , the brightness of the light emitting diode chip is improved.

[0080] Regarding the second arrangement.

[0081] Figure 2 This is a schematic diagram of the structure of another light-emitting diode chip provided in the embodiment of the present disclosure, see Figure 2 In this embodiment, the transmission barrier layer 30 is an integral structural component, and the transmission barrier layer 30 fills the gaps between the epitaxial units 20 .

[0082] In the above implementation, the transmission barrier layer 30 is a single unit, which not only covers each epitaxial unit 20 but also fills the gaps between the epitaxial units 20. In this way, it is not necessary to target each epitaxial unit 20, but rather all epitaxial units 20 in general. This makes it effectively applicable to very small epitaxial units 20 while still ensuring overall brightness.

[0083] In this embodiment, the reflective layer 40 is an integral structural component.

[0084] In the above implementation, the reflective layer 40 is a whole and directly covers the entire transmission barrier layer 30 , which can effectively simplify the process steps while ensuring functionality.

[0085] Figure 3 A flowchart of a method for preparing a light emitting diode chip provided in an embodiment of the present disclosure, combined with Figure 3 In this embodiment, the preparation method includes:

[0086] Step 301: Provide a substrate 10.

[0087] Step 302 : Prepare each epitaxial unit 20 on one side of the substrate 10 .

[0088] Step 303 : forming a transmission barrier layer 30 on a side of each epitaxial unit 20 facing away from the substrate 10 , such that the transmission barrier layer 30 covers the outside of each epitaxial unit 20 .

[0089] Step 304 : preparing a reflective layer 40 on the side of the transmission barrier layer 30 facing away from the substrate 10 , such that the reflective layer 40 covers the outside of the transmission barrier layer 30 .

[0090] The manufacturing method provided in the embodiments of the present disclosure can produce a light-emitting diode chip including a transmission barrier layer 30 and a reflective layer 40. The cooperation between the transmission barrier layer 30 and the reflective layer 40 allows for the transmission of as much light as possible from the epitaxial unit 20, while also reflecting the transmitted light to increase the brightness of the light-emitting diode chip.

[0091] Figure 4 A flow chart of another method for preparing a light emitting diode chip provided in an embodiment of the present disclosure, combined with Figure 4 In this embodiment, the preparation method includes:

[0092] Step 401: Provide a substrate 10.

[0093] Step 402 : Prepare an epitaxial layer on one side of the substrate 10 .

[0094] In this embodiment, step 402 includes:

[0095] The first semiconductor layer 210 , the active layer 220 and the second semiconductor layer 230 are sequentially prepared.

[0096] The first semiconductor layer 210 is an N-type semiconductor layer, the active layer 220 is a quantum well layer, and the second semiconductor layer 230 is a P-type semiconductor layer.

[0097] Step 403: Etch the epitaxial layer by photolithography until the substrate 10 is etched to expose the etched mesa of the first semiconductor layer 210 (see Figure 5 ).

[0098] In step 403 , the epitaxial layer is etched into a plurality of epitaxial units 20 that are sequentially spaced apart by a photolithography process.

[0099] Step 404: Prepare contact electrodes 50 on the etched mesas of the first semiconductor layer 210 and the second semiconductor layer 230 (see Figure 6 ).

[0100] Step 405 : forming a transmission barrier layer 30 on a side of each epitaxial unit 20 facing away from the substrate 10 , such that the transmission barrier layer 30 covers the outside of each epitaxial unit 20 .

[0101] In this embodiment, step 405 includes:

[0102] Step 4051: Spin-coat or deposit a transmission barrier layer 30 on the side of each epitaxial unit 20 facing away from the substrate 10 (see Figure 7 ).

[0103] Step 4052: Etching the transmission barrier layer 30 to the substrate 10 to obtain a plurality of transmission barrier sub-units 310 spaced apart from each other (see Figure 8 ).

[0104] It is worth noting that step 4052 is not a mandatory step. If step 4052 is not performed, the transmission barrier layer 30 is a single integral structure. If step 4052 is performed, the transmission barrier layer 30 is divided into a plurality of transmission barrier sub-units 310.

[0105] Step 406 : forming a reflective layer 40 on the side of the transmission barrier layer 30 facing away from the substrate 10 , such that the reflective layer 40 covers the outside of the transmission barrier layer 30 .

[0106] In this embodiment, step 406 includes:

[0107] Step 4061: Deposit a reflective layer 40 on the side of the transmission barrier layer 30 facing away from the substrate 10 (see Figure 2 ).

[0108] Step 4062: Etching the reflective layer 40 to the substrate 10 to obtain a plurality of reflective subunits 410 arranged at intervals from each other, each reflective subunit 410 corresponding to each transmission blocking subunit 310 (see Figure 1 ).

[0109] It is worth noting that step 4062 is not a must-do step. If step 4052 is not performed in step 405, then step 4062 is not performed in step 406. If step 4052 is performed in step 405, then step 4062 is performed in step 406.

[0110] Step 407: Prepare pad electrodes.

[0111] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by a person of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," "third," and similar words used in the patent specification and claims of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish between different components. Similarly, terms such as "a" or "an" do not indicate a quantitative limitation, but rather indicate the presence of at least one. Terms such as "include" or "comprise" mean that the elements or objects preceding "include" or "comprises" encompass the elements or objects listed after "include" or "comprises," and their equivalents, and do not exclude other elements or objects. Terms such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," "right," "top," and "bottom" are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0112] The above does not limit the present disclosure in any form. Although the present disclosure has been disclosed as above through the embodiments, it is not intended to limit the present disclosure. Any technician familiar with the profession can make slight changes or modifications to equivalent embodiments with equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present disclosure. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present disclosure without departing from the content of the technical solution of the present disclosure are still within the scope of the technical solution of the present disclosure.

Claims

1. A light-emitting diode chip having a transmission barrier layer, characterized in that: It comprises a substrate (10), an epitaxial unit (20), a transmission blocking layer (30) and a reflection layer (40); The epitaxial units (20) are sequentially arranged at intervals on one side of the substrate (10); The transmission blocking layer (30) covers the outside of each of the epitaxial units (20), and the transmission blocking layer (30) is capable of transmitting light emitted by the epitaxial unit (20); The reflective layer (40) covers the outside of the transmission blocking layer (30), and the reflective layer (40) is capable of reflecting light emitted by the epitaxial unit (20).

2. The light-emitting diode chip according to claim 1, characterized in that The transmission blocking layer (30) includes a plurality of transmission blocking subunits (310); The transmission blocking subunits (310) are arranged at intervals with each other, each transmission blocking subunit (310) corresponds to each epitaxial unit (20) one by one, and each transmission blocking subunit (310) covers the outside of the corresponding epitaxial unit (20).

3. The light-emitting diode chip according to claim 2, characterized in that: The reflective layer (40) includes a plurality of reflective subunits (410); The reflective subunits (410) are arranged at intervals from each other, each reflective subunit (410) corresponds to each transmission blocking subunit (310) one by one, and each reflective subunit (410) covers the outside of the corresponding transmission blocking subunit (310).

4. The light-emitting diode chip according to claim 1, characterized in that The transmission barrier layer (30) is an integral structural component, and the transmission barrier layer (30) is filled in the gaps between the epitaxial units (20).

5. The light-emitting diode chip according to claim 4, characterized in that: The reflective layer (40) is an integral structural component.

6. The light-emitting diode chip according to any one of claims 1 to 5, characterized in that: The transmission blocking layer (30) is made of an inorganic material or an organic material. The inorganic material includes at least one of silicon oxide and silicon nitride, and the organic material includes at least one of phenolic resin, negative photoresist, photosensitive polyimide, and acrylic resin.

7. The light-emitting diode chip according to any one of claims 1 to 5, characterized in that: The refractive index of the transmission blocking layer (30) is 1.4 to 2.

1.

8. The light emitting diode chip according to any one of claims 1 to 5, characterized in that: The epitaxial unit (20) comprises a first semiconductor layer (210), an active layer (220) and a second semiconductor layer (230) stacked in sequence; The etched mesas of the first semiconductor layer (210) and the second semiconductor layer (230) both have contact electrodes (50); The transmission blocking layer (30) covers the outside of the contact electrodes (50) of the first semiconductor layer (210) and the second semiconductor layer (230).

9. A method for preparing a light emitting diode chip, characterized in that: The preparation method is used to prepare the light-emitting diode chip according to claim 1, and the preparation method comprises: Providing a substrate (10); preparing each epitaxial unit (20) on one side of the substrate (10); A transmission blocking layer (30) is prepared on a side of each epitaxial unit (20) facing away from the substrate (10), such that the transmission blocking layer (30) covers the outside of each epitaxial unit (20); A reflective layer (40) is prepared on the side of the transmission blocking layer (30) facing away from the substrate (10), so that the reflective layer (40) covers the outside of the transmission blocking layer (30).

10. The preparation method according to claim 9, characterized in that A transmission blocking layer (30) is prepared on a side of each epitaxial unit (20) facing away from the substrate (10), comprising: Spin coating or depositing the transmission blocking layer (30) on a side of each epitaxial unit (20) facing away from the substrate (10); Etching the transmission blocking layer (30) to the substrate (10) to obtain a plurality of transmission blocking subunits (310) spaced apart from each other; A reflective subunit (410) is prepared on a side of each transmission blocking layer (30) facing away from the substrate (10), and each reflective subunit (410) corresponds one-to-one to each transmission blocking subunit (310).

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