Micron flip-chip LED device for suppressing SRH non-radiative recombination, preparation method and application thereof

Abstract

The present invention provides a micron flip-chip LED device for suppressing SRH non-radiative recombination, a preparation method and an application thereof. By fabricating a micron hole array on a micro-sized device and injecting an N-type material, the function is to form a high-resistance region around the edge of the P-type semiconductor material transport layer, thereby restricting the expansion of current to the region with more sidewall defects at the edge of the device. When carriers diffuse to the edge, SRH recombination will be caused due to the existence of etching defects. Therefore, SRH recombination of carriers can be fundamentally reduced, and the external quantum efficiency can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of Micro-LED devices for display, and particularly relates to a micron flip-chip LED device for suppressing SRH non-radiative recombination, and a preparation method and application thereof. Background Art

[0002] With the development of the information age, display technology has become a key link for realizing information interaction. Micro-LED has become a hot topic of concern for many companies and researchers at present due to its advantages of self-luminescence, high integration, high efficiency, high stability and low power consumption. Compared with liquid crystal display (LCD) and organic light-emitting diode (OLED), Micro-LED can have more obvious display advantages.

[0003] When the size of the LED chip is reduced to the micron level, the ratio of its specific surface area (sidewall area / volume) will gradually increase, so that the overall influence of sidewall dangling bonds will increase. Moreover, during the chip preparation process, the etching process will cause damage to the chip sidewalls, making Micro-LED face more serious surface defect problems, ultimately reducing the external quantum efficiency (EQE) of the device. At the same time, sidewall defects are prone to generate leakage channels, making the carriers in the device easily diffuse towards the edge direction, thus increasing SRH recombination and leakage current, and affecting the performance of the device. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. For this reason, the first aspect of the present invention proposes a micron-sized flip-chip LED device for suppressing SRH non-radiative recombination, which can suppress the diffusion of current towards the edge direction, so that more holes in the P-type region flow into the MQWs to participate in the radiative recombination effect, and improve the hole injection efficiency and external quantum efficiency (EQE) of the device.

[0005] The second aspect of the present invention proposes a preparation method of the micron-sized flip-chip LED device for suppressing SRH non-radiative recombination.

[0006] The third aspect of the present invention proposes a preparation method of the micron-sized flip-chip LED device for suppressing SRH non-radiative recombination.

[0007] The fourth aspect of the present invention proposes an application of the micron-sized flip-chip LED device for suppressing SRH non-radiative recombination.

[0008] According to a first aspect of the present invention, a micron-sized flip-chip LED device for suppressing SRH non-radiative recombination is provided. The epitaxial structure of the device sequentially includes a substrate, an undoped GaN buffer layer, and an N-type GaN layer along the epitaxial growth direction; the N-type GaN layer includes a first N-type GaN layer and a second N-type GaN layer; the second N-type GaN layer covers a part of the first N-type GaN layer; a multi-quantum well layer, an electron blocking layer, a P-type GaN layer, and a current spreading layer are sequentially disposed on the second N-type GaN layer; the current spreading layer covers a part of the P-type GaN layer; an N electrode is distributed on the part of the first N-type GaN layer that is not covered by the second N-type GaN layer, and a P electrode is distributed on the surface of the current spreading layer; a passivation layer covers the area of the device except for the P electrode and the N electrode; from top to bottom, the P-type GaN layer, the electron blocking layer, the multi-quantum well layer, and the second N-type GaN layer form a Mesa mesa; micron holes are provided in a partial area of the Mesa mesa from the mesa edge towards the center direction, and the micron holes are filled with an N-type material.

[0009] In the present invention, an N-type material is injected near the edge of the Mesa mesa. The N-type material can form a reverse junction with the P-type GaN layer at the edge of the Mesa mesa, thereby suppressing the diffusion of current in the edge direction, enabling more holes in the P-type region to flow into the MQWs to participate in the radiative recombination effect, and further improving the hole injection efficiency and external quantum efficiency (EQE) of the device.

[0010] In some embodiments of the present invention, the depth of the micron holes is adjustable, and the depth is 100 nm to 1400 nm; the micron holes are etched from the device current spreading layer downwards, specifically one of etching to the P-type GaN layer, etching to the electron blocking layer, or etching to the quantum well layer.

[0011] In some preferred embodiments of the present invention, the N-type material is selected from transparent materials and / or non-transparent materials; preferably, the transparent material is at least one selected from ITO, IGZO, ZTO, or IZO; the non-transparent material is at least one selected from N-type GaN or N-type ZnO. When the N-type material is a transparent material, the probability of light emission can be increased, thereby improving the light extraction efficiency and further improving the external quantum efficiency.

[0012] In some more preferred embodiments of the present invention, the Mesa mesa is a semiconductor material, the Mesa mesa is a light-emitting region, and has a cylindrical structure; the bottom radius of the Mesa mesa is 5 μm to 20 μm; preferably, the Mesa mesa is provided with micron holes in a partial area from the mesa edge towards the center of the device, and the micron holes are distributed in a circular array on the Mesa mesa, close to but not in contact with the mesa edge.

[0013] In some more preferred embodiments of the present invention, the micron holes are distributed in the middle region between the edge of the current spreading layer and the edge of the Mesa mesa or in a partial region in the direction from the edge of the Mesa mesa towards the center of the device, including the middle region between the edge of the current spreading layer and the edge of the Mesa mesa and the region extending 0 μm to 10 μm towards the center of the current spreading layer.

[0014] In some more preferred embodiments of the present invention, the micron holes are distributed at a position 1 μm to 3 μm in the direction from the edge of the Mesa mesa towards the center of the device.

[0015] In some more preferred embodiments of the present invention, the shape of the micron holes is one of a circle, a triangle, a square or a hexagon; when the micron holes are circular, the size of the micron holes is in the micron scale, and the diameter is 500 nm to 2 μm; when the micron holes are triangular, square or hexagonal, the diameter of the inscribed circle is 500 nm to 2 μm.

[0016] In some more preferred embodiments of the present invention, the P electrode is any one of a hexagon, a circle, a triangle or a pentagon; the current spreading layer is a cylindrical structure, and the bottom area thereof is smaller than the bottom area of the P-type GaN layer, and it plays a role in current spreading and can be ITO.

[0017] In some more preferred embodiments of the present invention, the N electrode has a Y-shaped double-ring structure, and both the inner ring and the outer ring of the N electrode surrounding the Mesa mesa structure part are 1 / 2 to 3 / 4 of a circle, and a rectangular parallelepiped and a cylindrical electrode pad structure are sequentially extended along the outer ring. The length of the rectangular parallelepiped is 5 μm to 10 μm, and the diameter of the extended bottom surface of the cylinder is 6 μm to 10 μm.

[0018] In some more preferred embodiments of the present invention, the N electrode or the P electrode adopts a four-layer metal alloy of Cr / Al / Ti / Au, and the thickness is 1 μm to 1.25 μm.

[0019] In some more preferred embodiments of the present invention, the region covered by the passivation layer includes the side walls of the current spreading layer, the P-type GaN layer, the electron blocking layer, the quantum well layer and the second N-type GaN layer, the part of the first N-type GaN layer except the part covered by the second N-type GaN layer and the N electrode, the part of the P-type GaN layer except the part covered by the current spreading layer and the surface of the current spreading layer; preferably, the passivation layer is SiO2, and the thickness is 500 nm to 1 μm.

[0020] In some more preferred embodiments of the present invention, the electron blocking layer is an AlGaN electron blocking layer, and the electron blocking layer has a cylindrical structure.

[0021] According to a second aspect of the present invention, a method for fabricating a micron-sized flip-chip LED device for suppressing SRH non-radiative recombination is provided, comprising the following steps:

[0022] A1: Sampling wafer, the wafer includes a substrate, an undoped GaN buffer layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer arranged in sequence from bottom to top. Deposit and anneal on the P-type GaN layer to prepare a current spreading layer precursor, and form a photoresist mask layer with a Mesa mesa structure on the upper surface of the current spreading layer precursor, and wet-etch to obtain the current spreading layer;

[0023] A2: Transfer the Mesa mesa structure to the GaN-based epitaxial layer by ICP etching, expose the second N-type GaN layer, and remove the photoresist;

[0024] A3: Photolithographically form a photoresist mask layer with a micron hole array structure, transfer the micron hole array structure to the GaN-based epitaxial layer by ICP etching, grow N-type material into the micron holes, and remove the photoresist;

[0025] A4: Deposit a passivation layer, photolithographically form a photoresist mask layer, expose the electrode growth region by ICP etching, remove the photoresist, and form a P electrode and an N electrode by evaporation and lift-off respectively.

[0026] In some preferred embodiments of the present invention, in A1, the evaporation is carried out in two steps. In the first step, no oxygen is doped; in the second step, oxygen is doped, and the oxygen evaporation flow rate is 2 sccm.

[0027] In some more preferred embodiments of the present invention, in A3, the growing of the N-type material into the micron holes specifically refers to selectively growing the N-type material into the micron holes by electron beam evaporation or magnetron sputtering or MOCVD reactor.

[0028] In some more preferred embodiments of the present invention, the specific operation of the annealing is to continuously introduce 200 sccm of nitrogen and 35 sccm of oxygen under pure nitrogen, and perform annealing treatment at 550 °C for 5 minutes.

[0029] In some more preferred embodiments of the present invention, the wet-etching is specifically carried out by soaking step by step for 10 min under the condition of water bath heating at 40 °C in the etching solution.

[0030] In some more preferred embodiments of the present invention, the photoresist is removed using acetone for resist stripping.

[0031] According to a third aspect of the present invention, a method for fabricating a micron-sized flip-chip LED device for suppressing SRH non-radiative recombination is provided, comprising the following steps:

[0032] B1: Sampling wafer. The wafer includes a substrate, an undoped GaN buffer layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer arranged in sequence from bottom to top. A photoresist mask layer with a micron hole array structure is formed by photolithography. The micron hole array structure is transferred to the GaN-based epitaxial layer by ICP etching, and the photoresist is removed.

[0033] B2: Evaporate N-type material into the micron holes using electron beam evaporation technology, and evaporate and anneal on the P-type GaN layer to prepare a current spreading layer precursor. A photoresist mask layer with a Mesa mesa structure is formed by photolithography on the upper surface of the current spreading layer precursor, and the current spreading layer is obtained by wet etching; the photoresist is removed.

[0034] B3: A photoresist mask layer with a Mesa mesa structure is formed by photolithography. The Mesa mesa structure is transferred to the GaN-based epitaxial layer by ICP etching to expose the second N-type GaN layer, and the photoresist is removed.

[0035] B4: Deposit a passivation layer, form a photoresist mask layer by photolithography, expose the electrode growth region by ICP etching, remove the photoresist, and form a P electrode and an N electrode by evaporation and lift-off respectively.

[0036] In some more preferred embodiments of the present invention, the specific operation of the annealing is to continuously introduce 200 sccm of nitrogen and 35 sccm of oxygen under pure nitrogen, and perform annealing treatment at 550 °C for 5 minutes.

[0037] In some more preferred embodiments of the present invention, the wet etching is specifically to soak step by step for 10 min under the condition of 40 °C water bath heating in the etching solution.

[0038] In some more preferred embodiments of the present invention, the photoresist is removed using acetone for resist stripping.

[0039] According to the fourth aspect of the present invention, an electronic device is proposed, which includes the micron-sized flip-chip LED device for suppressing SRH non-radiative recombination.

[0040] The beneficial effects of the present invention are as follows:

[0041] 1. The micron-sized flip-chip LED device prepared by the present invention for suppressing SRH non-radiative recombination forms a micron hole array on the micro-sized device and injects N-type material, whose function is to form a high-resistance region around the edge of the P-type semiconductor material transmission layer, thereby restricting the current from spreading to the region with more sidewall defects at the edge of the device. When carriers diffuse to the edge, SRH recombination will be caused due to the existence of etching defects. Therefore, SRH recombination of carriers can be fundamentally reduced, and the external quantum efficiency can be improved.

[0042] 2. The micron-sized surface-emitting LED device prepared by the present invention, which inhibits SRH non-radiative recombination, is injected with a transparent N-type material such as ITO, IGZO, ZTO, IZO, etc., so that photons can be emitted from the etched micron holes, thereby increasing the light emission probability.

[0043] 3. The micron-sized surface-emitting LED device prepared by the present invention, which inhibits SRH non-radiative recombination, adopts a micron hole array, which can allow more holes to participate in the radiative recombination in the multi-quantum well while minimizing the volume of P-GaN to the greatest extent. Brief Description of the Drawings

[0044] The present invention will be further described below in conjunction with the drawings and embodiments, where:

[0045] Figure 1 is a top view schematic diagram of the micron-sized surface-emitting LED device of the present invention, which inhibits SRH non-radiative recombination.

[0046] Figure 2 is at Figure 1 a cross-sectional schematic diagram at the cut line CC'.

[0047] Figure 3 is a cross-sectional schematic diagram of the current spreading layer of the micron-sized surface-emitting LED device of Example 1, which inhibits SRH non-radiative recombination.

[0048] Figure 4 is a cross-sectional schematic diagram of the Mesa mesa of the micron-sized surface-emitting LED device of Example 1, which inhibits SRH non-radiative recombination.

[0049] Figure 5 is a cross-sectional schematic diagram of the micron hole array structure of the micron-sized surface-emitting LED device of Example 1, which inhibits SRH non-radiative recombination.

[0050] Figure 6 is a cross-sectional schematic diagram of the N-type material structure of the micron-sized surface-emitting LED device of Example 1, which inhibits SRH non-radiative recombination.

[0051] Figure 7 is a cross-sectional schematic diagram of the passivation layer of the micron-sized surface-emitting LED device of Example 1, which inhibits SRH non-radiative recombination.

[0052] Figure 8 is a cross-sectional schematic diagram of the micron holes of the micron-sized surface-emitting LED device of Example 2, which inhibits SRH non-radiative recombination.

[0053] Figure 9Schematic cross-sectional view of the current spreading layer and N-type material structure for fabricating a micron-sized flip-chip LED device with suppressed SRH non-radiative recombination in Example 2.

[0054] Figure 10 Schematic cross-sectional view of the Mesa mesa for fabricating a micron-sized flip-chip LED device with suppressed SRH non-radiative recombination in Example 2.

[0055] Figure 11 Schematic cross-sectional view of the passivation layer for fabricating a micron-sized flip-chip LED device with suppressed SRH non-radiative recombination in Example 2.

[0056] Figure 12 Optical output power test results of the Micro LED structure in the embodiment of the present invention and the comparative example

[0057] Figure 13 Internal quantum efficiency test results of the Micro LED structure in the embodiment of the present invention and the comparative example

[0058] Reference numerals: 1, substrate; 12, undoped GaN buffer layer; 2, N-type GaN layer; 21, first N-type GaN layer; 22, second N-type GaN layer; 3, multiple quantum well layer; 4, P-type GaN layer; 5, current spreading layer; 6, passivation layer; 7, P electrode; 8, N electrode; 9, micro-holes, 10, Mesa mesa; 11, electron blocking layer. Detailed implementation manners

[0059] The following will clearly and completely describe the concept and technical effects of the present invention in combination with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of the present invention.

[0060] A micron-sized flip-chip LED device with suppressed SRH non-radiative recombination, as Figure 1 , Figure 2 shown. The epitaxial structure of the device sequentially includes a substrate 1, an undoped GaN buffer layer 12, and an N-type GaN layer 2 along the epitaxial growth direction; the N-type GaN layer 2 is divided into a first N-type GaN layer 21 and a second N-type GaN layer 22;

[0061] The second N-type GaN layer 22 covers part of the first N-type GaN layer 21;

[0062] A multiple quantum well layer 3, an electron blocking layer 11, a P-type GaN layer 4, and a current spreading layer 5 are sequentially arranged on the second N-type GaN layer 22;

[0063] The current spreading layer 5 covers a part of the P-type GaN layer 4;

[0064] An N electrode 8 is also distributed on the uncovered part of the first N-type GaN layer 21 that is not covered by the second N-type GaN layer 22, and a P electrode 7 is distributed at the center of the surface of the current spreading layer 5; the area of the device except for the P electrode 7 and the N electrode 8 is covered with a passivation layer 6; from top to bottom, the P-type GaN layer 4, the electron blocking layer 11, the multi-quantum well layer 3, and the second N-type GaN layer 22 form a Mesa mesa 10;

[0065] Micron holes 9 are provided in a partial area of the Mesa mesa 10 from the mesa edge towards the center direction, and the micropores are filled with an N-type material.

[0066] Example 1

[0067] In this example, a micron-sized flip-chip LED device for suppressing SRH non-radiative recombination is prepared. The specific process is as follows:

[0068] A1. Select a 2-inch epitaxial wafer. The substrate of the epitaxial wafer is a sapphire structure with a thickness of 300 μm. On the substrate, there are arranged a 3.5-μm undoped GaN buffer layer, a 2.5-μm N-type GaN layer, a 166.5-nm multi-quantum well layer, a 20-nm P-type electron blocking layer, and a 300-nm P-type GaN layer. Use electron beam evaporation coating technology to deposit ITO on the GaN-based epitaxial layer. The thickness of the ITO is 100 nm, and it is deposited in two steps. The thickness of the first step of deposition is 16.7 nm without oxygen doping, and the thickness of the second step of deposition is 83.3 nm with an oxygen flow rate of 2 sccm. Subsequently, annealing treatment is carried out using rapid thermal annealing technology, that is, in an environment of pure nitrogen, continuously introduce 200 sccm of nitrogen and 35 sccm of oxygen, and perform annealing treatment at 550 °C for 5 minutes; then coat HMDS as an adhesion promoter at 150 °C, select a positive photoresist as a mask layer for photolithography, and soak it step by step in an ITO etching solution at 40 °C in a water bath for 10 min to form a cylindrical current spreading layer 5 with a bottom radius smaller than the P-type GaN layer 4 and located in the central area of the surface of the P-type GaN layer 4. The radius is 1 μm smaller than the mesa radius. Subsequently, use acetone for degluing and acetone for cleaning to remove the photoresist, as Figure 3 shown;

[0069] A2. Using a mask plate with the structure of the Mesa mesa 10, combine photolithography technology to form a photoresist mask layer, and use ICP etching technology to transfer the Mesa mesa 10 structure with a bottom radius of 20 μm to the GaN-based epitaxial layer until the exposed N-type GaN layer 21 is exposed by etching, and then remove the photoresist, as Figure 4 shown;

[0070] A3. Use a mask plate with a micron pore array structure, combine it with ordinary ultraviolet lithography technology to form a photoresist mask layer, and then use ICP etching technology to transfer the micron pore array structure to the GaN-based epitaxial layer. The depth of the micron pores is etched to the lower surface of the AlGaN electron blocking layer 11, as Figure 5 shown;

[0071] A4. Use MOCVD to selectively grow N-GaN in the micron pores 9 so that the N-GaN material fills the entire micron pores as the N-type material structure. Use acetone to clean the photoresist and strip the ITO outside the micron pore area. As Figure 6 shown;

[0072] A5. Use plasma-enhanced chemical vapor deposition technology to grow a SiO2 passivation layer 6 with a growth time of 9 min and a passivation layer thickness of 500 nm. Combine lithography technology to form a photoresist mask layer. The mask layer has openings at the top center area of the current spreading layer 5 and the exposed N-type GaN layer 21 area exposed by etching the Mesa mesa 10 structure. Then use ICP etching technology to etch the SiO2 passivation layer 6 in these two areas until the SiO2 passivation layer 6 in this area is completely removed. The etching time is 7 minutes. Then use acetone and photoresist remover to remove the photoresist, as Figure 7 shown;

[0073] A5. Use negative photoresist and electron beam evaporation technology to prepare a Cr / Al / Ti / Au metal with a thickness of 1.25 μm, and combine metal stripping technology, that is, first soak in 60°C acetone for 10 minutes, and then use a blue film to strip the metal. Prepare a P electrode 7 and an N electrode 8 on the exposed top center area of the current spreading layer 5 and the exposed N-type GaN layer 21 area exposed by etching the Mesa mesa 10 structure respectively, as Figure 2 shown.

[0074] Example 2

[0075] In this example, a micron-sized surface-emitting LED device that suppresses SRH non-radiative recombination was prepared. The specific process is as follows:

[0076] B1. Select a 2-inch epitaxial wafer. The substrate of the epitaxial wafer is a sapphire structure with a thickness of 300 μm. There are a 3.5-μm undoped GaN buffer layer, a 2.5-μm N-type GaN layer, a 166.5-nm multi-quantum well layer, a 20-nm P-type electron blocking layer, and a 300-nm P-type GaN layer arranged on the substrate. Use a mask plate with a micron pore array structure, combine it with ordinary ultraviolet lithography technology to form a photoresist mask layer, and then use ICP etching technology to transfer the micron pore array structure to the GaN-based epitaxial layer. The depth of the micron pores is etched to the lower surface of the AlGaN electron blocking layer 11, and then use acetone and photoresist remover to remove the photoresist, as Figure 8as shown;

[0077] B2. Use electron beam evaporation coating technology to deposit ITO on the GaN-based epitaxial layer and in the micro-holes; subsequently, in an environment of pure nitrogen, continuously introduce 200 sccm of nitrogen and 35 sccm of oxygen, and perform annealing treatment at 550 °C for 5 minutes; then coat HMDS as an adhesion promoter at 150 °C, select a positive photoresist as the mask layer for photolithography, and soak step by step in an ITO etching solution at 40 °C in a water bath for 10 min to form a cylindrical current spreading layer 5 with a bottom radius smaller than the P-type GaN layer 4 and located in the central region of the surface of the P-type GaN layer 4, with a radius 1 μm smaller than the mesa radius. Subsequently, use acetone for degluing and acetone for cleaning to remove the photoresist, as Figure 9 shown;

[0078] B3. Using a mask plate with a Mesa mesa 10 structure, combine photolithography technology to form a photoresist mask layer, and use ICP etching technology to transfer the Mesa mesa 10 structure with a bottom radius of 20 μm to the GaN-based epitaxial layer until the exposed N-type GaN layer 21 is etched and exposed. Subsequently, remove the photoresist, as Figure 10 shown;

[0079] B4. Use plasma-enhanced chemical vapor deposition technology to grow a SiO2 passivation layer 6 with a growth time of 9 min and a passivation layer thickness of 500 nm; combine photolithography technology to form a photoresist mask layer, and the mask layer has openings at the top central region of the current spreading layer 5 and the region of the exposed N-type GaN layer 21 where the Mesa mesa 10 structure is etched and exposed. Subsequently, use ICP etching technology to etch the SiO2 passivation layer 6 in these two regions until the SiO2 passivation layer 6 in this region is completely removed, with an etching time of 7 minutes. Then use acetone and a photoresist remover to remove the photoresist, as Figure 11 shown;

[0080] B5. Use negative photoresist and electron beam evaporation technology to prepare a Cr / Al / Ti / Au metal with a thickness of 1.25 μm, and combine the lift-off technology, that is, first soak in acetone at 60 °C for 10 minutes, and then use a blue film to strip the metal. Prepare a P electrode 7 and an N electrode 8 respectively on the top central region of the exposed current spreading layer 5 and the region of the exposed N-type GaN layer 21 where the Mesa mesa 10 structure is etched and exposed, as Figure 2 shown.

[0081] Comparative Example

[0082] This comparative example prepared a micron-sized flip-chip LED device, which was the same as the preparation steps of Example 1 except that no N-type material was grown in the micro-holes.

[0083] Test Example

[0084] Apsys simulation comparison diagrams of the optical output power (LOP) and internal quantum efficiency (IQE) of the Micro-LED structures prepared in Example 1, Example 2 and the comparative example. Through the Apsys simulation data, the results are as Figure 12 , Figure 13 shown.

[0085] From Figure 12 , Figure 13 it can be seen that for the chip with a Mesa mesa radius of 20 μm, when the current density is 50 A / cm 2 , the optical output power of the Micro-LED structure injecting N-type GaN non-transparent material is 4 W / cm 2 , the internal quantum efficiency is 26%, the optical output power of the Micro-LED structure injecting ITO transparent material is 12 W / cm 2 , the internal quantum efficiency is 79%, and the optical output power of the Micro-LED structure without injecting N-type material is 2 W / cm 2 , the internal quantum efficiency is 19%. Compared with the Micro-LED without injecting N-type material, the Micro-LED devices after injecting transparent and non-transparent N-type materials have obvious improvements, and injecting transparent material will have more improvement than non-transparent material.

[0086] The above has described the embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the purpose of the present invention. In addition, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

Claims

1. A micron-sized flip-chip LED device for suppressing SRH non-radiative recombination, characterized in that: The epitaxial structure of the device sequentially includes a substrate, an undoped GaN buffer layer, and an N-type GaN layer along the epitaxial growth direction; the N-type GaN layer includes a first N-type GaN layer and a second N-type GaN layer; the second N-type GaN layer covers part of the first N-type GaN layer; a multi-quantum well layer, an electron blocking layer, a P-type GaN layer, and a current spreading layer are sequentially disposed on the second N-type GaN layer; the current spreading layer covers part of the P-type GaN layer; an N electrode is distributed on the part of the first N-type GaN layer that is not covered by the second N-type GaN layer, and a P electrode is distributed on the surface of the current spreading layer; the area of the device except for the P electrode and the N electrode is covered with a passivation layer; from top to bottom, the P-type GaN layer, the electron blocking layer, the multi-quantum well layer, and the second N-type GaN layer form a Mesa mesa; In some areas of the Mesa mesa from the mesa edge towards the center direction, micron holes are provided, and the micron holes are filled with an N-type material; the micron holes are etched downwards from the current spreading layer, specifically formed by etching to the P-type GaN layer, etching to the electron blocking layer, or etching to the quantum well layer; the N-type material is a transparent material; the transparent material is selected from at least one of ITO, IGZO, ZTO, or IZO; The micron holes are arranged in a circular ring array on the Mesa mesa, close to but not in contact with the mesa edge.

2. The micron-sized flip-chip LED device for suppressing SRH non-radiative recombination according to claim 1, wherein: The micron holes are arranged in a circular ring array on the Mesa mesa, close to but not in contact with the mesa edge.

3. The micron-sized flip-chip LED device for suppressing SRH non-radiative recombination according to claim 1, characterized in that: The micron holes are distributed at a position 1 μm to 3 μm from the Mesa mesa edge towards the center of the device.

4. The micron-sized flip-chip LED device for suppressing SRH non-radiative recombination according to claim 1, wherein: The shape of the micron holes is one of a circle, a triangle, a square, or a hexagon; when the micron holes are circular, the size of the micron holes is in the micron scale, and the diameter is 500 nm to 2 μm; when the micron holes are triangular, square, or hexagonal, the diameter of the inscribed circle is 500 nm to 2 μm.

5. The micron-sized flip-chip LED device for suppressing SRH non-radiative recombination according to claim 1, wherein: The electron blocking layer is an AlGaN electron blocking layer, and the electron blocking layer has a cylindrical structure.

6. The micron-sized flip-chip LED device for suppressing SRH non-radiative recombination according to claim 1, characterized in that: The N electrode has a Y-shaped double-ring structure. The inner and outer circles of the part of the N electrode surrounding the Mesa mesa structure are each 1 / 2 to 3 / 4 of a circle, and a rectangular body and a cylindrical electrode pad structure are sequentially extended along the outer circle.

7. A method for preparing a micron-sized flip-chip LED device for suppressing SRH non-radiative recombination according to any one of claims 1 to 6, characterized in that: Including the following steps: A1: Sampling wafer, the wafer includes a substrate, an undoped GaN buffer layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer arranged from bottom to top. Evaporate and anneal on the P-type GaN layer to prepare a precursor of the current spreading layer, and lithographically form a photoresist mask layer with a Mesa mesa structure on the upper surface of the precursor of the current spreading layer, and wet-etch to obtain the current spreading layer; A2: Use ICP etching to transfer the Mesa mesa structure to the GaN-based epitaxial layer, expose the second N-type GaN layer, and remove the photoresist; A3: Lithographically form a photoresist mask layer with a micron hole array structure, use ICP etching to transfer the micron hole array structure to the GaN-based epitaxial layer, grow the N-type material into the micron holes, and remove the photoresist; A4: Deposit a passivation layer, form a photoresist mask layer by lithography, use ICP etching to expose the electrode growth region, remove the photoresist, and form the P electrode and the N electrode by evaporation and lift-off respectively.

8. A method for preparing a micron-sized flip-chip LED device for suppressing SRH non-radiative recombination according to any one of claims 1 to 6, characterized in that: It includes the following steps: B1: Take a sample wafer. The sample wafer includes a substrate, an undoped GaN buffer layer, an N-type GaN layer, a multi-quantum well layer, an electron blocking layer, and a P-type GaN layer arranged in sequence from bottom to top. Form a photoresist mask layer with a micron hole array structure by lithography, transfer the micron hole array structure to the GaN-based epitaxial layer by ICP etching, and remove the photoresist; B2: Evaporate an N-type material into the micron holes using an electron beam evaporation technique, evaporate and anneal on the P-type GaN layer to prepare a current spreading layer precursor, and form a photoresist mask layer with a Mesa mesa structure by lithography on the upper surface of the current spreading layer precursor, and obtain the current spreading layer by wet etching; Remove the photoresist; B3: Transfer the Mesa mesa structure to the GaN-based epitaxial layer by ICP etching to expose the second N-type GaN layer, and remove the photoresist; B4: Deposit a passivation layer, form a photoresist mask layer by lithography, use ICP etching to expose the electrode growth region, remove the photoresist, and form the P electrode and the N electrode by evaporation and lift-off respectively.

9. An electronic device, characterized in that: It is composed of a micron-sized surface-emitting LED device for suppressing SRH non-radiative recombination according to any one of claims 1 to 6.

Images