LED chip, preparation method thereof and display device

Abstract

The invention provides an LED chip, a preparation method thereof and a display device. The preparation method of the LED chip comprises the following steps: providing a substrate; growing a non-doped GaN layer on the substrate; an epitaxial layer is formed on the surface of the side, away from the substrate, of the non-doped GaN layer, the epitaxial layer is etched to form a plurality of light-emitting tables arranged at intervals, and each light-emitting table comprises a table top away from the side of the substrate and a side face connected with the table top; and growing a quantum dot layer on the surface of one side, far away from the substrate, of the light-emitting table, wherein the quantum dot layer at least comprises a plurality of quantum dots distributed on the side surface. The etching damage, introduced by etching, on the side surface of the light-emitting table can be efficiently and precisely repaired in a targeted manner; the high-density quantum dots grown on the side face of the light-emitting table can increase the scattering sectional area of light emitted by the active area of the light-emitting table, so that the light-emitting efficiency is enhanced, and the light-emitting intensity of the LED is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of LED chips, and in particular to an LED chip and a preparation method thereof, and a display device. Background Art

[0002] The emergence of GaN-based Micro / Nano LED technology provides a new display solution for augmented reality (AR) applications with high brightness, long life, low power consumption, easy integration, and ultra-high resolution. Micro / Nano LED forms a light-emitting micro-table (Mesa) on an LED epitaxial wafer through photolithography, etching, and other methods, thereby achieving high display resolution and high pixel density (PPI). In order to achieve the goal of miniaturization of AR terminal form, the size of Mesa needs to be continuously reduced to meet the display requirements of high PPI.

[0003] However, the plasma (ICP-RIE) etching process commonly used in existing semiconductor processes will introduce a large amount of plasma etching damage to the Mesa sidewall, thereby forming a high-density non-radiative composite defect center (NRC). The density of NRC will further increase with the reduction of the size of the light-emitting platform and the increase of the specific surface area, resulting in a sharp drop in the external quantum efficiency and luminous intensity of the LED chip. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one object of the present invention is to provide an LED chip and a preparation method thereof, and a display device, which can achieve enhanced luminous efficiency and luminous intensity.

[0005] In one aspect of the present invention, the present invention provides a method for preparing an LED chip, the method comprising: providing a substrate; growing an undoped GaN layer on the substrate; etching to form an epitaxial layer on a surface of the undoped GaN layer on a side away from the substrate, etching the epitaxial layer to form a plurality of spaced-apart light-emitting tables, the light-emitting tables comprising a table top away from a side of the substrate and a side surface connected to the table top; growing a quantum dot layer on a surface of the light-emitting table on a side away from the substrate, the quantum dot layer comprising at least a plurality of quantum dots distributed on the side surface; growing a first electrode layer on the table top of the light-emitting table; peeling off the substrate and growing a second electrode layer on a side of the epitaxial layer away from the table top.

[0006] According to an embodiment of the present invention, an epitaxial layer is formed on a surface of the non-doped GaN layer away from the substrate, and the epitaxial layer is etched to form a plurality of light-emitting tables arranged at intervals. The method comprises: sequentially growing an N-type semiconductor layer, a quantum well light-emitting layer, and a P-type semiconductor layer on a surface of the non-doped GaN layer away from the substrate to form the epitaxial layer; etching the epitaxial layer to form the light-emitting table, wherein the side surface is arranged at an angle with the substrate, and the angle ranges from 70° to 90°.

[0007] According to an embodiment of the present invention, the material of the substrate includes any one of sapphire, silicon, gallium nitride, gallium oxide or silicon carbide; the thickness of the undoped GaN layer is 1 to 5 μm; the N-type semiconductor layer is an n-GaN layer, and the thickness of the N-type semiconductor layer is 1 to 2 μm; the quantum well light-emitting layer is an InGaN multi-quantum well layer, and the total thickness of the quantum well light-emitting layer is 100 to 200 nm; the P-type semiconductor layer includes an electron blocking layer and a P-GaN layer grown in sequence on the surface of the quantum well light-emitting layer away from the substrate, and the total thickness of the P-type semiconductor layer is 50 to 150 nm.

[0008] According to an embodiment of the present invention, before growing a quantum dot layer on a surface of the light-emitting table away from the substrate, the method further comprises: performing GaN material decomposition on the p-GaN layer on the surface of the light-emitting table, and the specific steps include: in a vacuum growth chamber, evaporating and removing organic matter and water molecules on the surface of the light-emitting table at a first temperature; heating to a second temperature to perform GaN material decomposition on the p-GaN layer on the surface of the light-emitting table, and removing the decomposed Ga atoms and N atoms.

[0009] According to an embodiment of the present invention, the first temperature is 150-250°C, and the evaporation time is 15-25 minutes; the second temperature is 650-1000°C; the method for heating the vacuum growth chamber to the second temperature includes: continuously introducing an N source into the vacuum growth chamber during the heating process to prevent decomposition of the GaN material during the heating process, and stopping the introduction of the N source after the heating is completed.

[0010] According to an embodiment of the present invention, the material of the quantum dots is MGaN, wherein M is Al or In, and a quantum dot layer is grown on a surface of the light-emitting platform away from the substrate. The method comprises: growing an MGaN single crystal film on a surface of the light-emitting platform away from the substrate in an island / layered growth mode, and after the MGaN single crystal film is grown to a preset thickness, the MGaN single crystal film forms an MGaN wetting layer on the surface of the light-emitting platform after energy relaxation, and an MGaN quantum dot layer attached to the surface of the MGaN wetting layer away from the light-emitting platform, wherein the MGaN quantum dot layer comprises a plurality of MGaN quantum dots.

[0011] According to an embodiment of the present invention, a MGaN single crystal thin film is grown on a surface of the light-emitting platform away from the substrate in an island / layered growth mode, the method comprising: after the GaN material in the p-GaN layer on the surface of the light-emitting platform is decomposed for a preset time, an M source, a Ga source, and an N source are continuously introduced into the vacuum growth chamber at a second temperature, the atomic stoichiometry is controlled, and MGaN is grown on the surface of the light-emitting platform. x Ga 1-x N single crystal film, x is 0.05-0.4; the preset thickness of the MGaN single crystal film is 25-30nm; the diameter of the MGaN quantum dots in the direction parallel to the side surface is less than 20nm, and the height of the MGaN quantum dots in the direction perpendicular to the side surface is less than 10nm; the thickness of the MGaN wetting layer in the direction perpendicular to the side surface is 10-20nm.

[0012] According to an embodiment of the present invention, the quantum dots are GaN, and a quantum dot layer is grown on the surface of the light-emitting table away from the substrate. The method includes: forming Ga droplets on the surface of the light-emitting table away from the substrate, and forming a GaN quantum dot layer on the surface of the light-emitting table away from the substrate after irradiation in a nitrogen atomic atmosphere, wherein the GaN quantum dot layer includes a plurality of GaN quantum dots.

[0013] According to an embodiment of the present invention, a GaN quantum dot layer is grown on a surface of the light-emitting table away from the substrate, and the method includes: after the GaN material in the p-GaN layer on the surface of the light-emitting table is decomposed for a preset time, continuing to introduce a Ga source into a vacuum growth chamber, and depositing a Ga atomic layer on the surface of the light-emitting table after a certain period of time; stopping the introduction of the Ga source, and maintaining the second temperature for a preset time so that the Ga atomic layer forms Ga droplets; continuing to introduce an N source into the vacuum growth chamber, and forming the GaN quantum dots after irradiation in a nitrogen atomic atmosphere; the diameter of the GaN quantum dots in a direction parallel to the side surface is 20 to 30 nm, and the height of the GaN quantum dots in a direction perpendicular to the side surface is 40 to 50 nm.

[0014] According to an embodiment of the present invention, growing a first electrode layer on the table top of the light-emitting table includes: growing an insulating layer on the surface of the non-doped GaN layer away from the substrate, the thickness of the insulating layer in a direction perpendicular to the substrate being 2 to 3 μm; removing at least part of the insulating layer and the quantum dot layer on the table top of the light-emitting table to form a first via hole exposing the P-type semiconductor layer; growing the first electrode layer on the table top of the light-emitting table, the first electrode layer contacting the P-type semiconductor layer through the first via hole, the surface of the first electrode layer away from the substrate being flush with the surface of the insulating layer away from the substrate.

[0015] According to an embodiment of the present invention, the method further includes: providing a driving backplane, on which a plurality of spaced metal contacts are disposed; and bonding the first electrode layer to the metal contacts of the driving backplane.

[0016] According to an embodiment of the present invention, the method further includes: after peeling off the substrate, using a hydrochloric acid solution to spin-coat the surface of the side of the non-doped GaN layer away from the light-emitting table, so as to remove and clean the Ga residue generated on the surface of the side of the non-doped GaN layer away from the substrate and close to the light-emitting table. According to an embodiment of the present invention, the method further includes: peeling off the substrate; after peeling off the substrate, removing at least part of the non-doped GaN layer on the surface of the side of the light-emitting table away from the table, forming a second via hole exposing the N-type semiconductor layer, forming a second electrode layer grown on the surface of the side of the non-doped GaN layer away from the light-emitting table and in the second via hole, and the second electrode layer contacts the N-type semiconductor layer through the second via hole.

[0017] According to an embodiment of the present invention, a reflective layer is grown on a surface of the second electrode layer away from the undoped GaN layer, and at least a portion of the reflective layer corresponding to the light-emitting stage is removed to form a transmission hole.

[0018] In another aspect of the present invention, the present invention provides an LED chip, which is prepared by any of the methods described above.

[0019] In another aspect of the present invention, the present invention provides a display device, comprising an LED chip prepared by any of the methods described above. The LED chip formed by the above-mentioned LED chip preparation method can efficiently and precisely repair the etching damage on the side of the light-emitting platform introduced by etching; the high-density quantum dots grown on the side of the light-emitting platform can increase the scattering cross-sectional area of ​​the light emitted from the active area of ​​the light-emitting platform, thereby enhancing the light extraction efficiency and light output efficiency, which is conducive to significantly improving the luminous intensity of the LED. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0021] Figure 1 is a flow chart of a partial structure of preparing an LED chip in one embodiment of the present invention;

[0022] Figure 2 is a flow chart of a partial structure of preparing an LED chip in another embodiment of the present invention;

[0023] Figure 3is a flow chart of a partial structure of preparing an LED chip in another embodiment of the present invention;

[0024] Figure 4 is a flow chart of a partial structure of preparing an LED chip in another embodiment of the present invention;

[0025] Figure 5 is a flow chart of a partial structure of preparing an LED chip in another embodiment of the present invention;

[0026] Figure 6 is a flow chart of a partial structure of preparing an LED chip in another embodiment of the present invention;

[0027] Figure 7 It is a flow chart of a partial structure of preparing an LED chip in another embodiment of the present invention. DETAILED DESCRIPTION

[0028] The scheme of the present invention will be explained below in conjunction with embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are followed. The present invention will be described below with reference to specific embodiments, it should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0029] In one aspect of the present invention, the present invention provides a method for preparing an LED chip, the method comprising:

[0030] S100: providing a substrate 100.

[0031] Among them, the specific type of substrate 100 can be a sapphire substrate 100, a silicon substrate 100, an n-type doped silicon carbide substrate 100 or an n-type doped gallium nitride substrate 100. Those skilled in the art can flexibly select a suitable type of substrate 100 according to the specific structural type of the LED chip.

[0032] In some embodiments, after the substrate 100 is cleaned and decontaminated, a buffer layer with a thickness of 10 to 100 nm may be grown thereon. The material of the buffer layer may be aluminum nitride or aluminum gallium nitride, which may be deposited by physical vapor deposition (PVD). The material of the buffer layer may also be gallium nitride, and a portion of the undoped GaN layer 200 may be used as the buffer layer.

[0033] S200: growing an undoped GaN layer 200 on the substrate 100. The undoped GaN layer 200 (un-intentionallydoped GaN, u-GaN) refers to a gallium nitride layer that does not include any dopant but may include contaminants or impurities that are not intentionally incorporated into the film, and serves as the bulk layer of the N-type GaN layer to be epitaxially grown in the next step. The undoped GaN layer 200 has a thickness of 1 to 5 μm; specifically, it can be epitaxially grown using MOCVD (Metal Organic Chemical Vapor Deposition, a high-purity chemical vapor deposition technology used to prepare semiconductor materials and devices) equipment.

[0034] S300: forming an epitaxial layer on a surface of the non-doped GaN layer 200 away from the substrate 100, and etching the epitaxial layer to form a plurality of light-emitting platforms 300 arranged at intervals, wherein the light-emitting platforms 300 include a platform 302 away from the substrate 100 and a side surface 301 connected to the platform 302. Specifically, the method includes:

[0035] S330: On the surface of the non-doped GaN layer 200 away from the substrate 100, an N-type semiconductor layer 310, a quantum well light emitting layer 320, and a P-type semiconductor layer 330 are sequentially grown to form an epitaxial layer. The thickness of the non-doped GaN layer 200 is 1 to 5 μm; the N-type semiconductor layer 310 is a Si-doped n-GaN layer with a Si doping concentration of 10 18 cm -3 ~10 19 cm -3 The thickness of the N-type semiconductor layer 310 is 1 to 2 μm; the quantum well light-emitting layer 320 is an InGaN multi-quantum well layer, including 5 to 8 periods of alternately grown InGaN and GaN, and the total thickness of the quantum well light-emitting layer 320 is 100 to 200 nm; the P-type semiconductor layer 330 includes an electron blocking layer and a Mg-doped P-GaN layer sequentially grown on the surface of the quantum well light-emitting layer 320 away from the substrate 100, and the total thickness of the P-type semiconductor layer 330 is 50 to 150 nm.

[0036] The component of In in the quantum well light emitting layer 320 InGaN determines the color of the light emitted by the LED structure, which can generally be designed to be blue and green. The emission wavelength of the blue light quantum well light emitting layer 320 is 455-465nm, and the emission wavelength of the green light quantum well light emitting layer 320 is 520-535nm.

[0037] After the epitaxial wafer is grown, it is ultrasonicated in an acetone solution for 10 minutes and then rinsed with deionized water for 15 minutes to make the surface of the epitaxial wafer clean. Figure 1 (a) shown.

[0038] S320: Etch the epitaxial layer to form a light-emitting platform 300. The side surface 301 of the light-emitting platform 300 is set at an angle with the substrate 100, and the angle ranges from 70° to 90°. The light-emitting platform 300 (Mesa) is prepared on the 4-inch GaN-based LED epitaxial wafer prepared in step S330 by using a photolithography process and a plasma (ICP-RIE) etching process. The cross-sectional shape of the light-emitting platform 300 in a direction parallel to the substrate 100 can be circular or square. The diameter of the circle or the side length of the square is preferably 500 to 3000 nm, and the height of the light-emitting platform 300 is preferably 1.45 to 1.5 μm. The light-emitting platform 300 is formed on the undoped GaN layer 200, which can ensure the electrical insulation characteristics of the LED chip and reduce the influence of optical crosstalk between the light-emitting platforms 300. The structure after preparation is as follows Figure 1 (b) as shown.

[0039] S400 : growing a quantum dot layer 400 on a surface of the light-emitting stage 300 away from the substrate 100 , wherein the quantum dot layer 400 at least includes a plurality of quantum dots 410 distributed on the side surface 301 .

[0040] In the embodiment of the present invention, the quantum dot layer 400 is composed of nanoparticles with three dimensions in the nanometer range (1nm-100nm), and is formed on the side 301 of the light-emitting platform 300 with high density (High density, <910cm -2 ), small size, highly uniform size and shape (size fluctuation is less than 10%); the quantum dots 410 distributed on the side 301 of the light-emitting platform 300 in the present invention are grown in a homogeneous structure epitaxially with the quantum well layer material on the light-emitting platform 300, which can achieve atomic layer level precision etching damage repair. It is known to those skilled in the art that, according to the different quantum well layer materials, the preparation material of the quantum dot layer 400 can be selected to be the same homogeneous material as the quantum well layer material to achieve homogeneous epitaxy. The material of the quantum dot 410 can be AlGaN, InGaN or GaN, and the growth method of the quantum dot 410 can be a molecular beam epitaxy (MBE) in-situ thermal evaporation method.

[0041] According to an embodiment of the present invention, before growing the quantum dot layer 400 on the surface of the light emitting stage 300 away from the substrate 100, the method further includes: performing GaN material decomposition on the p-GaN layer on the surface of the light emitting stage 300, and the specific steps include:

[0042] S10: In the vacuum growth chamber, organic matter and water molecules on the surface of the light-emitting platform 300 are evaporated and removed at a first temperature.

[0043] S20: Raising the temperature to a second temperature to decompose the GaN material of the p-GaN layer on the surface of the light-emitting stage 300, and removing the decomposed Ga atoms and N atoms.

[0044] Since the second temperature is significantly higher than the first temperature, GaN material may appear during the temperature rise process. The decomposition trend of such GaN material is uncontrollable, resulting in an increase in the density of the NRC on the side surface 301 of the light-emitting stage 300 instead of a decrease, and failure to effectively repair the damage. Therefore, after step S10, the method of heating the vacuum growth chamber to the second temperature includes:

[0045] S11: During the heating process to the second temperature, N source is continuously introduced into the vacuum growth chamber to prevent the GaN material from decomposing during the heating process, and the introduction of N source is stopped after the heating is completed. After completing this step, S420 is then performed in a stable temperature environment to decompose the GaN material to achieve damage repair.

[0046] In some embodiments, the material of the quantum dot 410 is MGaN, wherein M is Al or In. In step S400, the quantum dot layer 400 is grown on a surface of the light emitting stage 300 away from the substrate 100. The method includes:

[0047] S410: Growing an MGaN single crystal film 500 on the surface of the light-emitting platform 300 away from the substrate 100 in an island / layered growth mode. After the MGaN single crystal film 500 is grown to a preset thickness, the MGaN single crystal film 500 undergoes energy relaxation to form an MGaN wetting layer 510 on the surface of the light-emitting platform 300 and an MGaN quantum dot layer 400 attached to the surface of the MGaN wetting layer 510 away from the light-emitting platform 300. The MGaN quantum dot layer 400 includes a plurality of MGaN quantum dots 410.

[0048] In the present invention, the material of the quantum dot 410 is AlGaN for exemplary description. Specifically, the GaN-based LED epitaxial wafer with the light-emitting stage 300 prepared in step S320 is transferred to the MBE growth chamber. First, 1*10 -10 The temperature of the sample is raised to a first temperature at a rate of 5°C / s in a Torr ultravacuum, and evaporated at this temperature for a period of time to remove organic matter and water molecules on the surface of the sample. The first temperature is 150-250°C, and the evaporation time is 15-25 min. For example, the first temperature is 150°C, 180°C, 200°C, 220°C, and 250°C, and the evaporation time is 25 min, 23 min, 20 min, 18 min, and 15 min.

[0049] Then, the sample temperature is raised to the second temperature at a rate of 10°C / s, and the N source is turned on during the heating process, and the N source is continuously introduced into the vacuum growth chamber so that the growth chamber is filled with N atoms to prevent the GaN material from decomposing during the heating process. The second temperature is 650-1000°C, for example, the second temperature is 650, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 850, 880°C, 900°C, 920°C, 940°C, 960°C, 980°C, 1000°C. In the present invention, 900°C is used for exemplary description.

[0050] When the sample temperature rises to the second temperature (900°C), the N source is turned off, and the sample is kept at the second temperature for a certain period of time to decompose the GaN material of the p-GaN layer on the surface of the light-emitting stage 300, and remove the decomposed Ga atoms and N atoms. For example, after decomposing at 900°C for 3 to 5 minutes, the GaN material on the side 301 of the light-emitting stage 300 will be decomposed into Ga atoms and N atoms at a rate of 10 to 15 nm / min, and then removed by the high vacuum pump equipped in the growth chamber. After the decomposition process, the density of the etching damage sites on the surface of the light-emitting stage 300 will be greatly reduced.

[0051] After the thermal decomposition process is completed, the baffles of the Al source, Ga source, and N source are opened again, and the Al source, Ga source, and N source are continuously introduced into the vacuum growth chamber. The temperature and speed of the Al source, Ga source, and N source introduced into the vacuum growth chamber are controlled, and the atomic stoichiometry of Al atoms, Ga atoms, and N atoms is controlled to grow Al on the surface of the light-emitting platform 300. x Ga 1-x N single crystal film 500, x is 0.05 to 0.4. For example, the atomic ratio of the released Al source and the N source is controlled to be 2:10, and the atomic ratio of the released Ga source and the N source is 1:1. Since the volume of Al atoms is smaller than that of Ga atoms, Al atoms and Ga atoms will form Al with N atoms at a molecular ratio of 2:8. 0.2 Ga 0.8 N single crystal film 500, similarly, Al x Ga 1-x N, x is 0.05 to 0.4 other single crystal thin film 500. The structure of the finished product is as follows Figure 2 (a) shown.

[0052] Since there is a certain difference in lattice constants between AlGaN and GaN, when AlGaN grows on the surface of the light-emitting platform 300, it will follow the island / layer growth mode (Stranski-Krastanov). When the thickness of the AlGaN single crystal film 500 reaches a certain value, due to stress release, the surface layer of the AlGaN single crystal film 500 will undergo energy relaxation. Finally, the AlGaN single crystal film 500 will form an AlGaN wetting layer 510 on the surface of the light-emitting platform 300 after energy relaxation, and an AlGaN quantum dot layer 400 attached to the surface of the AlGaN wetting layer 510 away from the light-emitting platform 300. The diameter of the AlGaN quantum dot 410 in the direction parallel to the side 301 is less than 20nm, and the height of the AlGaN quantum dot 410 in the direction perpendicular to the side 301 is less than 10nm; the thickness of the AlGaN wetting layer 510 in the direction perpendicular to the side 301 is 10 to 20nm. The structure after formation is as follows Figure 1 (b) as shown.

[0053] It should be noted that the material of the quantum dot 410 can also be an InGaN system, and its growth method can refer to the growth method of the AlGaN quantum dot 410, and InGaN is grown on the surface of the light-emitting platform 300. x Ga 1-x N single crystal film 500, x is 0.05-0.4; after energy relaxation, the InGaN single crystal film 500 forms an InGaN wetting layer 510 on the surface of the light-emitting table and an InGaN quantum dot layer 400 attached to the surface of the InGaN wetting layer 510 away from the light-emitting table 300, thereby repairing the etching damage of the InGaN-based red light LED and improving the brightness at a lower growth temperature, which will not be repeated here.

[0054] Furthermore, in some embodiments, the quantum dot 410 is GaN, and in step S400, the quantum dot layer 400 is grown on a surface of the light emitting stage 300 away from the substrate 100, and the method includes:

[0055] S510 : Ga droplets 600 are formed on the surface of the light emitting stage 300 away from the substrate 100 , and a GaN quantum dot layer 400 is formed on the surface of the light emitting stage 300 away from the substrate 100 after irradiation in a nitrogen atomic atmosphere. The GaN quantum dot layer 400 includes a plurality of GaN quantum dots 410 .

[0056] Specifically, the GaN-based LED epitaxial wafer with the light-emitting stage 300 prepared in step S320 is transferred to the MBE growth chamber, and firstly, 1*10 -10The temperature of the sample is raised to a first temperature at a rate of 5°C / s in a Torr ultravacuum, and evaporated at this temperature for a period of time to remove organic matter and water molecules on the surface of the sample. The first temperature is 150-250°C, and the evaporation time is 15-25 min. For example, the first temperature is 150°C, 180°C, 200°C, 220°C, and 250°C, and the evaporation time is 25 min, 23 min, 20 min, 18 min, and 15 min.

[0057] Then, the sample temperature is raised to the second temperature at a rate of 10°C / s, and the N source is turned on during the heating process, and the N source is continuously introduced into the vacuum growth chamber so that the growth chamber is filled with N atoms to prevent the GaN material from decomposing during the heating process. The second temperature is 650-1000°C, for example, 650-1000°C, for example, the second temperature is 650, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 850, 880°C, 900°C, 920°C, 940°C, 960°C, 980°C, 1000°C. In the present invention, 700°C is used for exemplary description.

[0058] When the sample temperature rises to the second temperature (700°C), the N source is turned off, and the sample is kept at the second temperature for a certain period of time to decompose the GaN material on the p-GaN layer on the surface of the light-emitting stage 300, and remove the decomposed Ga atoms and N atoms. For example, after decomposing at 700°C for 3 to 5 minutes, the GaN material on the side 301 of the light-emitting stage 300 will decompose into Ga atoms and N atoms at a rate of 10 to 15 nm / min, and then be removed by the high vacuum pump equipped in the growth chamber. After the decomposition process, the density of etching damage sites on the Mesa surface will be greatly reduced.

[0059] After the thermal decomposition process is completed, the baffle of the Ga source is opened, and the Ga source is continuously introduced into the vacuum growth chamber. After 1 to 2 minutes, the Ga source is closed, and a Ga atomic layer with a thickness of 10 to 20 nm is deposited on the surface of the light-emitting platform 300. The Ga source baffle is closed, and the introduction of the Ga source into the vacuum growth chamber is stopped; the temperature is maintained at 700° C. for 60 to 90 seconds. During this process, the Ga atoms adsorbed on the surface of the light-emitting platform 300 will follow the law of molecular dynamics, migrate and partially desorb on the surface of the light-emitting platform 300, thereby forming Ga droplets 600 on the surface of the light-emitting platform 300, as shown in FIG. Figure 3 (a) shown.

[0060] After the Ga droplets 600 are formed, the baffle of the N source is opened, and N atoms are continuously introduced into the vacuum growth chamber. The light-emitting table 300 with the Ga droplets 600 is irradiated in a nitrogen atomic atmosphere for 10 to 20 minutes, and GaN quantum dots 410 are formed on the surface of the light-emitting table 300 away from the substrate 100. The diameter of the GaN quantum dots 410 in the direction parallel to the side surface 301 is 20 to 30 nm, and the height of the GaN quantum dots 410 in the direction perpendicular to the side surface 301 is 40 to 50 nm.

[0061] In the present invention, by forming a quantum dot layer 400 on the surface of the light-emitting platform 300, especially on the side surface 301, the regrowth repair of the etching damage site can be achieved. The structure after growing GaN quantum dots 410 is as follows: Figure 3 (b) as shown.

[0062] S500: growing an insulating layer 700 on the surface of the non-doped GaN layer 200 away from the substrate 100. The material of the insulating layer 700 may be silicon nitride or silicon oxide. The insulating layer 700 may be grown by plasma enhanced chemical vapor deposition (PECVD). The thickness of the insulating layer 700 in the direction perpendicular to the substrate 100 is at least greater than the thickness of the light emitting stage 300 in the direction perpendicular to the substrate 100. Preferably, the thickness of the insulating layer 700 in the direction perpendicular to the substrate 100 is 2-3 μm.

[0063] S600: At least part of the insulating layer 700 and the quantum dot layer 400 on the table 302 of the light-emitting stage 300 is removed to form a first via hole 710 exposing the P-type semiconductor layer 330. The first via hole 710 can be formed above the light-emitting stage 300 by processes such as coating photoresist, exposure, development, etching, degumming, and cleaning. The shape and size of the first via hole 710 are determined according to the shape and size of the light-emitting stage 300. For example, the cross-sectional shape of the first via hole 710 in the direction parallel to the substrate 100 is circular or square, and the size of the first via hole 710 can be 60-80% of the size of the light-emitting stage 300.

[0064] S700: grow a first electrode layer 800 on the table 302 of the light-emitting table 300, the first electrode layer 800 contacts the P-type semiconductor layer 330 through the first via hole, and the surface of the first electrode layer 800 on the side away from the substrate 100 is flush with the surface of the insulating layer 700 on the side away from the substrate 100. The first electrode layer 800 is deposited in the first via hole 710 using a photolithography process and an electron beam evaporation process, wherein the first electrode layer 800 may include one or more layers of metal, for example, the first electrode layer 800 includes a Ni layer / Au layer / Sn layer sequentially deposited on the surface of the light-emitting table 300, with thicknesses of 30nm, 500nm and 300nm, respectively. The present invention does not limit the coverage area of ​​the first electrode layer 800 on the table 302 of the light-emitting table 300. In some embodiments, the first electrode layer 800 may be disposed in the first via hole 710. The structure of the prepared LED chip whose quantum dot material is AlGaN is as follows Figure 4 As shown in (a), the structure of the LED chip with GaN quantum dot material after preparation is as follows Figure 5 As shown in (a).

[0065] S800 : providing a driving backplane 900 , on which a plurality of spaced metal contacts 910 are disposed, and bonding the first electrode layer 800 to the metal contacts 910 of the driving backplane 900 .

[0066] The driving backplane 900 may be a CMOS backplane, and a pixel circuit for driving the LED chip to emit light is disposed on the driving backplane 900. In some embodiments, electron beam evaporation or magnetron sputtering may be used to deposit a bonding metal layer, and its material includes but is not limited to at least one of Cr, Pt, Ti, Ni and Ag. For example, the bonding metal layer is a Ti layer, and a metal contact 910 is formed on the bonding metal layer by a photolithography process, and the metal contact 910 is arranged one-to-one with the first electrode layer 800 (first via 710). The structure prepared in step S800 is aligned with the IC driving board with a driving circuit and bonded by laser assisted bonding (LAB) technology. The laser wavelength is 1024nm, and the laser spot is shaped into a rectangle to eliminate thermal damage during the bonding process. It can achieve precise bonding in a low temperature environment, avoid thermal stress introduced by the thermal expansion coefficient, and improve the bonding strength. The structure of the LED chip whose quantum dot material is AlGaN after bonding is as follows Figure 4 As shown in (b), the structure of the LED chip with GaN quantum dot material after bonding is as follows Figure 5 As shown in (b).

[0067] S900: peeling off the substrate 100 from the bonded structure.

[0068] In some embodiments, the substrate 100 is a sapphire substrate 100, and the substrate 100 can be stripped by a laser lift-off process (LLO), and the laser wavelength is 355nm, 265nm or 248nm. In other embodiments, the substrate 100 is a silicon substrate 100, and the substrate 100 can be stripped by a wet etching method. In other embodiments, the substrate 100 is an n-type doped silicon carbide substrate 100, and the substrate 100 can be stripped by a wet etching method or by inductively coupled plasma etching (ICP-RIE). In other embodiments, the substrate 100 is an n-type doped gallium nitride substrate 100, and the substrate 100 can be stripped by inductively coupled plasma etching (ICP-RIE).

[0069] S1000: After peeling off the substrate 100, the non-doped GaN layer 200 is spin-coated on the surface of the side away from the light-emitting table 300 by spin coating with a hydrochloric acid solution, so as to remove and clean the Ga residue 520 generated on the surface of the side of the non-doped GaN layer 200 close to the light-emitting table 300. The hydrochloric acid solution is highly selective for the nitride layer, so it will not cause surface damage to the AlGaN / GaN below. The hydrochloric acid solution can effectively remove the Ga residue 520 generated on the surface of the non-doped GaN layer 200 when forming the quantum dot layer 400 in step S400, so as to avoid the residual Ga atoms causing leakage of the LED chip, thereby affecting the LED display effect. The hydrochloric acid solution can be made of concentrated hydrochloric acid and water in a volume ratio of 1:1 to 1:10. After removing the Ga residue 520 after spin coating, it is washed with deionized water. The structure of the prepared LED chip whose quantum dot material is AlGaN is as follows Figure 4 As shown in (c), the structure of the LED chip after the quantum dot material is GaN is as follows Figure 5 As shown in (c).

[0070] S1100: removing at least part of the non-doped GaN layer 200 on the light-emitting stage 300 away from the table 302, and forming a second via hole 720 exposing the N-type semiconductor layer 310. The second via hole 720 can be formed below the light-emitting stage 300 by processes such as coating photoresist, exposure, development, etching, degumming, and cleaning. The shape and size of the second via hole 720 are determined according to the shape and size of the light-emitting stage 300. For example, the cross-sectional shape of the second via hole 720 in the direction parallel to the substrate 100 is circular or square, and the size of the second via hole 720 can be 60-80% of the size of the light-emitting stage 300.

[0071] S1200: Form a second electrode layer 1000 on the side surface of the non-doped GaN layer 200 away from the light-emitting stage 300 and in the second via hole 720. The second electrode layer 1000 is deposited on the side surface of the non-doped GaN layer 200 away from the light-emitting stage 300 and in the second via hole 720 using a photolithography process and a magnetron sputtering process, wherein the second electrode layer 1000 is made of ITO material, and the thickness of the second electrode layer 1000 on the side surface of the non-doped GaN layer 200 away from the light-emitting stage 300 is 1.8 to 2 μm. Then, rapid annealing is performed in an oxygen atmosphere at 550°C for 5 minutes to improve the conductivity of ITO. The structure of the prepared LED chip whose quantum dot material is AlGaN is as follows Figure 6 As shown in (a), the structure of the LED chip with GaN quantum dot material after preparation is as follows Figure 7 As shown in (a).

[0072] S1300: grow a reflective layer 1100 on the surface of the second electrode layer 1000 away from the non-doped GaN layer 200, remove at least part of the reflective layer 1100 corresponding to the light-emitting stage 300, and form a transmission hole 1110. In some embodiments, electron beam evaporation or magnetron sputtering can be used to deposit a reflective layer 1100 with a thickness of 100 to 300 nm to improve the light extraction efficiency of the LED chip. The material of the reflective layer 1100 can be silver or aluminum metal. A light-transmitting hole is formed on the reflective layer 1100 by a photolithography process, and the orthographic projection of the light-transmitting hole on the substrate 100 at least covers the orthographic projection of the light-emitting stage 300 on the substrate 100. The light-transmitting hole is beneficial to improving the light transmittance and improving the display effect. The structure of the LED chip whose quantum dot material is AlGaN after preparation is as follows Figure 6 As shown in (b), the structure of the LED chip with GaN quantum dot material after preparation is as follows Figure 7 As shown in (b).

[0073] It should be noted that the above materials and values ​​are set only to facilitate those skilled in the art to fully implement this embodiment, and they can be adjusted accordingly according to actual needs. Those skilled in the art should know that any obvious conventional material replacement and value change are within the protection scope of this embodiment.

[0074] Based on the same inventive concept, another aspect of the present invention further provides an LED chip, which is prepared by any of the above methods. The LED chip in the present invention can be a micro light emitting diode (Micro Light Emitting Diode Display, Micro LED) chip, and can also be a nano light emitting diode (Nano-Pixel Light-Emitting Display, Nano LED) chip.

[0075] Based on the same inventive concept, another aspect of the present invention further provides a display device, comprising an LED chip prepared by any of the above methods. The display device can be any product or component with a display function, such as a mobile phone, a tablet computer, a wearable device, a car display, a television, a monitor, a laptop computer, a digital photo frame, a navigator, etc.

[0076] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0077] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0078] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing an LED chip, characterized in that: The method comprises: providing a substrate; growing a non-doped GaN layer on the substrate; Forming an epitaxial layer on a surface of the non-doped GaN layer away from the substrate, and etching the epitaxial layer to form a plurality of light-emitting platforms spaced apart from each other, wherein the light-emitting platforms include a platform away from the substrate and a side surface connected to the platform; Growing a quantum dot layer on a surface of the light-emitting platform away from the substrate, wherein the quantum dot layer at least includes a plurality of quantum dots distributed on the side surface; Growing a first electrode layer on the surface of the light-emitting platform; The substrate is peeled off and a second electrode layer is grown on a side of the epitaxial layer away from the mesa.

2. The method for preparing an LED chip according to claim 1, characterized in that: An epitaxial layer is formed on a surface of the non-doped GaN layer away from the substrate, and the epitaxial layer is etched to form a plurality of light-emitting stages arranged at intervals, the method comprising: An N-type semiconductor layer, a quantum well light-emitting layer, and a P-type semiconductor layer are sequentially grown on a surface of the non-doped GaN layer away from the substrate to form the epitaxial layer; The epitaxial layer is etched to form the light-emitting platform, and the side surface is arranged at an angle with the substrate, and the angle ranges from 70° to 90°.

3. The method for preparing an LED chip according to claim 2, characterized in that: The material of the substrate includes any one of sapphire, silicon, gallium nitride, gallium oxide or silicon carbide; The thickness of the non-doped GaN layer is 1 to 5 μm; The N-type semiconductor layer is an n-GaN layer, and the thickness of the N-type semiconductor layer is 1 to 2 μm; The quantum well light-emitting layer is an InGaN multi-quantum well layer, and the total thickness of the quantum well light-emitting layer is 100-200 nm; The P-type semiconductor layer comprises an electron blocking layer and a P-GaN layer which are sequentially grown on a surface of the quantum well light-emitting layer away from the substrate, and the total thickness of the P-type semiconductor layer is 50-150 nm.

4. The method for preparing an LED chip according to claim 1, characterized in that: Before growing the quantum dot layer on the surface of the light emitting platform away from the substrate, the method further comprises: The p-GaN layer on the surface of the light-emitting platform is subjected to GaN material decomposition, and the specific steps include: In a vacuum growth chamber, evaporating and removing organic matter and water molecules on the surface of the light-emitting platform at a first temperature; The temperature is raised to a second temperature to decompose the GaN material of the p-GaN layer on the surface of the light-emitting platform, and the decomposed Ga atoms and N atoms are removed.

5. The method for preparing an LED chip according to claim 4, characterized in that: The first temperature is 150-250°C, and the evaporation time is 15-25 minutes; the second temperature is 650-1000°C; The method of heating the vacuum growth chamber to a second temperature includes: The temperature in the growth chamber is raised to a second temperature, and an N source is continuously introduced into the vacuum growth chamber during the heating process to prevent the GaN material from decomposing during the heating process. After the heating is completed, the introduction of the N source is stopped.

6. The method for preparing an LED chip according to claim 4, characterized in that: The material of the quantum dots is MGaN, wherein M is Al or In, and a quantum dot layer is grown on a surface of the light-emitting platform away from the substrate, and the method comprises: An MGaN single crystal film is grown on a surface of the light emitting platform away from the substrate in an island / layered growth mode. After the MGaN single crystal film is grown to a preset thickness, the MGaN single crystal film forms an MGaN infiltration layer on the surface of the light emitting platform after energy relaxation, and an MGaN quantum dot layer attached to the surface of the MGaN infiltration layer away from the light emitting platform, wherein the MGaN quantum dot layer includes a plurality of MGaN quantum dots.

7. The method for preparing an LED chip according to claim 6, characterized in that: The method comprises: after the GaN material in the p-GaN layer on the surface of the light-emitting platform is decomposed for a preset time, continuously introducing an M source, a Ga source, and an N source into the vacuum growth chamber at a second temperature, controlling the atomic stoichiometry, and growing an MGaN single crystal thin film on the surface of the light-emitting platform. x Ga 1-x N single crystal film, x is 0.05-0.4; the preset thickness of the MGaN single crystal film is 25-30 nm; M is Al or In; The diameter of the MGaN quantum dot in a direction parallel to the side surface is less than 20 nm, and the height of the MGaN quantum dot in a direction perpendicular to the side surface is less than 10 nm; the thickness of the MGaN wetting layer in a direction perpendicular to the side surface is 10-20 nm.

8. The method for preparing an LED chip according to claim 4, characterized in that: The quantum dots are GaN, and a quantum dot layer is grown on a surface of the light-emitting platform away from the substrate, and the method includes: Ga droplets are formed on the surface of the light emitting platform away from the substrate, and after irradiation in a nitrogen atomic atmosphere, a GaN quantum dot layer is formed on the surface of the light emitting platform away from the substrate, wherein the GaN quantum dot layer includes a plurality of GaN quantum dots.

9. The method for preparing an LED chip according to claim 8, characterized in that: A GaN quantum dot layer is grown on a surface of the light emitting platform away from the substrate, the method comprising: After the GaN material in the p-GaN layer on the surface of the light-emitting platform is decomposed for a preset time, a Ga source is continuously introduced into the vacuum growth chamber at a second temperature, and a Ga atomic layer is deposited on the surface of the light-emitting platform after a certain period of time; Stop introducing the Ga source, and maintain the second temperature for a preset time, so that the Ga atomic layer forms Ga droplets; Continue to introduce N source into the vacuum growth chamber, and form the GaN quantum dots after irradiation in a nitrogen atomic atmosphere; the diameter of the GaN quantum dots in a direction parallel to the side surface is 20 to 30 nm, and the height of the GaN quantum dots in a direction perpendicular to the side surface is 40 to 50 nm.

10. The method for preparing an LED chip according to claim 2, characterized in that: The step of growing a first electrode layer on the surface of the light-emitting platform comprises: Growing an insulating layer on a surface of the non-doped GaN layer away from the substrate, wherein the thickness of the insulating layer in a direction perpendicular to the substrate is 2-3 μm; removing at least a portion of the insulating layer and the quantum dot layer on the surface of the light-emitting platform to form a first via hole exposing the P-type semiconductor layer; The first electrode layer is grown on the surface of the light-emitting platform, the first electrode layer contacts the P-type semiconductor layer through the first via hole, and the surface of the first electrode layer away from the substrate is flush with the surface of the insulating layer away from the substrate.

11. The method for preparing an LED chip according to claim 1, characterized in that: The method further comprises: Providing a driving backplane, wherein a plurality of metal contacts arranged at intervals are arranged on the driving backplane; The first electrode layer is bonded to the metal contacts of the driving backplane.

12. The method for preparing an LED chip according to claim 1, characterized in that: The method further comprises: After the substrate is peeled off, a hydrochloric acid solution is used to spin-coat the surface of the non-doped GaN layer away from the light-emitting platform to remove and clean Ga residues generated on the surface of the non-doped GaN layer close to the light-emitting platform.

13. The method for preparing an LED chip according to claim 2, characterized in that: The step of peeling off the substrate and growing a second electrode layer on a side of the epitaxial layer away from the mesa comprises: After peeling off the substrate, at least a portion of the non-doped GaN layer on a surface of the light-emitting platform away from the platform is removed to form a second via hole exposing the N-type semiconductor layer. A second electrode layer is grown on a surface of the non-doped GaN layer away from the mesa, and the second electrode layer is in contact with the N-type semiconductor layer through the second via hole.

14. The method for preparing an LED chip according to claim 1, characterized in that: A reflective layer is grown on a surface of the second electrode layer away from the non-doped GaN layer, and at least a portion of the reflective layer corresponding to the light-emitting stage is removed to form a transmission hole.

15. An LED chip, characterized in that: It is prepared by the method according to any one of claims 1 to 13.

16. A display device, characterized in that: The invention comprises an LED chip prepared by the method according to any one of claims 1 to 13.

Images