Micro-LED block, preparation method thereof and display device

Abstract

The invention discloses a Micro-LED (Light Emitting Diode) block, a preparation method thereof and a display device, the Micro-LED block comprises a substrate and a plurality of Micro-LED units arranged on the substrate at intervals, the plurality of Micro-LED units distributed at intervals have thickness difference, and the thickness difference between different Micro-LED units is 5-200 nm. According to the invention, the transfer efficiency and luminous efficiency of the Micro-LED can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of LED devices, and in particular to a Micro-LED block and a preparation method thereof, and a display device. Background Art

[0002] Micro-LED refers to the technology that uses LED light-emitting units with a size of 1μm to 60μm to form a display array. Micro-LED has the characteristics of high resolution, low power consumption, high brightness, high contrast, high color saturation, fast response speed, thin thickness, and long life. Its power consumption can be as low as 10% of LCD and 50% of OLED. It is the next generation display technology expected by the industry. Moreover, Micro-LED has a wide range of applications, including wearable devices, ultra-large indoor display screens, head-mounted displays, head-up displays, taillights, wireless optical communications, AR / VR, projectors and other fields.

[0003] Since the Micro-LEDs that make up the display array are small in size and large in number, it is necessary to transfer millions or even tens of millions of chips correctly and efficiently to the circuit substrate through mass transfer. After the performance test, it is difficult to locate and replace a single defective chip. In addition, the luminous efficiency of the Micro-LED pixel unit needs to be further improved. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a Micro-LED block and a preparation method thereof, wherein the Micro-LED block has high transfer efficiency and high luminous efficiency.

[0005] The technical problem to be solved by the present invention is to provide a display device with high luminous efficiency.

[0006] In order to solve the above problems, the present invention discloses a Micro-LED block, including a substrate and a plurality of Micro-LED units distributed at intervals arranged on the substrate, wherein the plurality of Micro-LED units distributed at intervals have a thickness difference, and the thickness difference between different Micro-LED units is 5nm to 200nm.

[0007] As an improvement of the above technical solution, it includes a substrate and three spaced-apart Micro-LED units arranged on the substrate, wherein the three Micro-LED units are distributed along a straight line and have increasing or decreasing thicknesses, and the thickness difference between different Micro-LED units is 5nm to 200nm.

[0008] As an improvement of the above technical solution, the cross-section of the Micro-LED unit is a hexagon, the side length of the hexagon is 1.5 μm to 25 μm, and the distance between adjacent Micro-LED units is 1 μm to 100 μm.

[0009] As an improvement of the above technical solution, the Micro-LED unit includes an N-type semiconductor layer, an active layer, a P-type semiconductor layer, an N-electrode and a P-electrode, the N-electrode is arranged on the N-type semiconductor layer, and the P-electrode is arranged on the P-type semiconductor layer; the thickness difference of the P-type semiconductor layer of different Micro-LED units in the same Micro-LED block is 5nm to 200nm;

[0010] The N-type semiconductor layer includes a first N-type semiconductor layer and a second N-type semiconductor layer sequentially arranged on a substrate, a plurality of the second N-type semiconductor layers are isolated from each other, and a cross section of the second N-type semiconductor layer is a hexagon.

[0011] As an improvement of the above technical solution, a transparent conductive layer is provided on the P-type semiconductor layer of the Micro-LED unit, and an insulating layer is provided on the P-type semiconductor layer, on the first N-type semiconductor layer, and on the side wall of the P-type semiconductor layer extending to the first N-type semiconductor layer;

[0012] A P extension line is provided on the insulating layer on one side of the Micro-LED unit, and the P extension line is used to connect the P electrodes of multiple Micro-LED units in a Micro-LED block.

[0013] Correspondingly, the present invention also discloses a method for preparing a Micro-LED block, which is used to prepare the above-mentioned Micro-LED block, comprising the following steps:

[0014] providing a substrate;

[0015] A plurality of Micro-LED units with thickness differences are formed on the substrate; the thickness difference between different Micro-LED units is 5nm to 200nm.

[0016] As an improvement of the above technical solution, the following steps are used to form a plurality of Micro-LED units with thickness differences:

[0017] The same process is used to form multiple epitaxial structures with the same thickness. The epitaxial structure includes an N-type semiconductor layer, an active layer and a P-type semiconductor layer. The P-type semiconductor layers of different epitaxial structures are etched separately to obtain the required thickness. The thickness difference of the P-type semiconductor layer of different Micro-LED units is 5nm to 200nm.

[0018] As an improvement of the above technical solution, the following steps are adopted to form the Micro-LED unit:

[0019] growing a first N-type semiconductor layer on the substrate;

[0020] Growing an isolation layer on the first N-type semiconductor layer, wherein the thickness of the isolation layer is 5 nm to 500 nm, the isolation layer has a plurality of hollow portions exposing the first N-type semiconductor layer, the size of the hollow portions is 3 μm to 50 μm, and the distance between adjacent hollow portions is 1 μm to 100 μm;

[0021] A second N-type semiconductor layer, an active layer and a P-type semiconductor layer are grown in the hollow portion.

[0022] As an improvement of the above technical solution, the following steps are adopted to prepare the epitaxial structure: the temperature is controlled at 650°C to 850°C, the pressure is 50 torr to 200 torr, and the carrier gas and MO source are introduced, the carrier gas is N2 and / or H2, the flow rate of N2 is 5SLM to 20SLM, the flow rate of H2 is 0 to 10SLM, and the flow rate of N source in MO source is 20SLM to 50SLM.

[0023] Correspondingly, the present invention also discloses a display device, comprising the above-mentioned Micro-LED block.

[0024] The implementation of the present invention has the following beneficial effects:

[0025] 1. The Micro-LED block of the present invention includes a plurality of Micro-LED units distributed at intervals. When the Micro-LED block is transferred to a circuit substrate, a plurality of Micro-LED units in the Micro-LED block can be transferred at one time. Compared with conventional mass transfer, the operation is simple, the transfer rate is fast, and the transfer yield is high.

[0026] 2. The Micro-LED block of the present invention includes multiple Micro-LED units with different thicknesses, which can reduce the spacing between the multiple Micro-LED units, reduce the area of ​​the Micro-LED block and increase the pixel density of the Micro-LED block. In addition, Micro-LED units of different thicknesses can produce a three-dimensional light-emitting effect and a more uniform color mixing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of the structure of the Micro-LED block provided by the present invention;

[0028] Figure 2 is a top view of the Micro-LED block provided by the present invention;

[0029] Figure 3 is a partial structural schematic diagram of a display device provided by an embodiment of the present invention;

[0030] Figure 4 It is a schematic diagram of a partial structure of a display device provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in further detail below.

[0032] See also Figure 1 and Figure 2 The present invention provides a Micro-LED block, including a substrate 1 and a plurality of Micro-LED units 2 arranged on the substrate 1 and spaced apart from each other. The plurality of Micro-LED units 2 have a thickness difference, and the thickness difference between different Micro-LED units 2 is 5nm to 500nm.

[0033] The Micro-LED block of the present invention includes a plurality of Micro-LED units distributed at intervals. When the Micro-LED block is transferred to the circuit substrate, the multiple Micro-LED units in the Micro-LED block can be transferred at one time. Compared with the conventional mass transfer, the operation is simple, the transfer rate is fast, and the transfer yield is high. Moreover, the Micro-LED block of the present invention includes a plurality of Micro-LED units with different thicknesses, which can reduce the spacing between the plurality of Micro-LED units, reduce the area of ​​the Micro-LED block and increase the pixel density of the Micro-LED block, and the Micro-LED units of different thicknesses can produce a three-dimensional luminous effect and a more uniform color mixing effect.

[0034] In a preferred embodiment, the Micro-LED block includes a substrate 1 and three Micro-LED units 2 distributed at intervals on the substrate 1, the thickness of the three Micro-LED units 2 increases or decreases, and the thickness difference between adjacent Micro-LED units 2 is 5nm to 200nm, exemplarily 10nm, 50nm, 100nm, 150nm or 180nm, but not limited to this, that is, three Micro-LED units 2 distributed at intervals form a Micro-LED block, and the three Micro-LED units 2 with increasing or decreasing thickness can significantly improve the luminous efficiency. In particular, when preparing a display device, a quantum dot layer can also be set on the Micro-LED block, and the three Micro-LED units 2 with thickness difference cooperate with quantum dot units of different colors in the quantum dot layer to achieve high color gamut display.

[0035] Optionally, the cross section of the Micro-LED unit 2 is rectangular, pentagonal, hexagonal, octagonal, etc. The closer the shape of the cross section of the Micro-LED unit 2 is to a circle, the fuller the light type. In a preferred embodiment, the cross section of the Micro-LED unit 2 is a hexagon, and the side length of the hexagon is 1.5μm to 25μm. If the side length of the hexagon is less than 1.5μm, the preparation of the Micro-LED unit is difficult; if the side length of the hexagon is greater than 25μm, it will cause the area of ​​the Micro-LED block to increase, which is not conducive to the demand for miniaturization of display devices. Exemplarily, the side length of the hexagon is 5μm, 10μm, 12μm, 15μm or 20μm, but not limited to this. The distance between adjacent Micro-LED units 2 is 1μm to 100μm. If the distance between adjacent Micro-LED units is less than 1μm, it is not conducive to the heat dissipation of the Micro-LED unit; if the distance between adjacent Micro-LED units is greater than 100μm, the area of ​​the Micro-LED block will increase. Exemplarily, the distance between adjacent Micro-LED units 2 is 10 μm, 20 μm, 40 μm, 60 μm or 80 μm, but not limited thereto. Compared with conventional rectangular Micro-LED units, the cross-section of the Micro-LED unit 2 of the present invention is hexagonal, and the cross-section shape of the Micro-LED unit 2 is closer to a circle, which can improve the fullness of the light type. In addition, the stable phase of conventional semiconductor III-nitride (In-N, Ga-N, Al-N) materials is a hexagonal wurtzite structure, so high-quality Micro-LED units with hexagonal cross-sections can be grown.

[0036] It can be understood that the Micro-LED unit 2 includes an N-type semiconductor layer 21, an active layer 22, a P-type semiconductor layer 23, an N-electrode 24 and a P-electrode 25, the N-electrode 24 is arranged on the N-type semiconductor layer 21, and the P-electrode 25 is arranged on the P-type semiconductor layer 23. In a preferred embodiment, the N-semiconductor layer 21 includes a first N-type semiconductor layer 211 and a second N-type semiconductor layer 212 sequentially arranged on the substrate 1, the plurality of second N-type semiconductor layers 212 are isolated from each other, and the cross section of the second N-type semiconductor layer 212 is a hexagon.

[0037] Specifically, a transparent conductive layer 26 is provided on the P-type semiconductor layer 23 of the Micro-LED unit 2, and an insulating layer 27 is provided on the P-type semiconductor layer 23, on the first N-type semiconductor layer 211, and on the sidewalls of the P-type semiconductor layer 23 extending to the first N-type semiconductor layer 211. The material of the transparent conductive layer is one or more of ITO, CTO, and AZO, and the material of the insulating layer is SiO2, SiN x, Al2O3 or more. A P extension line 28 is provided on the insulating layer on one side of the Micro-LED unit. The P extension line 28 is used to connect the P electrodes of multiple Micro-LED units in a Micro-LED block, so as to facilitate full testing of each Micro-LED block.

[0038] Accordingly, the present invention also provides a method for preparing a Micro-LED block, which is used to prepare the above-mentioned Micro-LED block, comprising the following steps:

[0039] S1. Provide a substrate.

[0040] S2. Form a plurality of Micro-LED units with thickness differences on a substrate, wherein the Micro-LED units include an N-type semiconductor layer, an active layer, and a P-type semiconductor layer stacked in sequence.

[0041] In a preferred embodiment, the following steps are used to form a plurality of Micro-LED units with a thickness difference: a plurality of epitaxial structures with the same thickness are formed by the same process, the epitaxial structure includes an N-type semiconductor layer, an active layer and a P-type semiconductor layer, and the P-type semiconductor layer is etched to obtain the desired thickness by photolithography, development, etching and other processes. Specifically, the thickness difference of the P-type semiconductor layer of adjacent Micro-LED units is 5nm to 200nm. In other words, a plurality of Micro-LED units can be prepared at the same time, and finally the Micro-LED unit with a thickness difference is obtained by etching the P-type semiconductor layer, and the preparation efficiency is high.

[0042] In a preferred embodiment, the preparation of the N-type semiconductor layer comprises the following steps:

[0043] S21 . Growing a first N-type semiconductor layer on a substrate.

[0044] S22, growing an isolation layer on the first N-type semiconductor layer, the isolation layer having an array of hollow portions. Specifically, the isolation layer may be made of SiO2, SiN x , Al2O3. The thickness of the isolation layer is 5nm to 500nm, exemplarily 50nm, 100nm, 200nm, 300nm or 400nm, but not limited thereto. The isolation layer is used to achieve the simultaneous growth of multiple Micro-LED units. After the growth of the Micro-LED units is completed, the isolation layer is removed to obtain multiple Micro-LED units spaced apart from each other.

[0045] In a preferred embodiment, the size of the hollow portion is 3μm to 50μm, and the hollow portion can be a rectangle, pentagon, hexagon, octagon, etc. Specifically, the size of the hollow portion is the diameter of the circumscribed circle of the hollow portion, and the cross-sectional shape of the Micro-LED unit is defined by the shape of the hollow portion. Preferably, the shape of the hollow portion is a hexagon. Exemplarily, the size of the hollow portion is 5μm, 10μm, 20μm, 30μm or 40μm, but not limited to this. If the size of the hollow portion is less than 3μm, it increases the difficulty of growing the chip epitaxial structure therein; if the size of the hollow portion is greater than 50μm, it will increase the area of ​​the Micro-LED block, resulting in an increase in the area of ​​the display device made thereof. The distance between adjacent hollow parts is 1μm to 100μm, and is exemplarily 10μm, 20μm, 40μm, 60μm or 80μm, but not limited thereto. If the distance between adjacent hollow parts is less than 1μm, it is not conducive to the heat dissipation of the Micro-LED unit; if the distance between adjacent hollow parts is greater than 100μm, the area of ​​the Micro-LED block will increase. The size of the hollow part defines the size of each Micro-LED unit, and the distance between adjacent hollow parts defines the distance between two adjacent Micro-LED units. By defining the size of the hollow part and the distance between adjacent hollow parts, the size of the obtained Micro-LED block is small and the luminous efficiency is high.

[0046] S23, growing a second N-type semiconductor layer, an active layer and a P-type semiconductor layer in the hollow portion.

[0047] The N-type semiconductor layer can be an N-type GaN layer, an N-type AlGaN layer, etc., the active layer can be an InGaN / GaN superlattice layer, an InGaN / AlGaN superlattice layer, etc., and the P-type semiconductor layer can be a P-type GaN layer, a P-type AlGaN layer, etc., which are not specifically limited here. In a preferred embodiment, the following steps are adopted for preparation: the temperature is controlled to be 650°C to 850°C, the pressure is 50torr to 200torr, a carrier gas and an MO source are introduced, N2 and H2 are used as carrier gases, the flow rate of N2 is 5SLM to 20SLM, the flow rate of H2 is 0 to 10SLM, and the flow rate of N source in the MO source is 20SLM to 50SLM. Under this condition, 3D growth can be formed without polymerization, and the stable phase of conventional semiconductor III-nitride (In-N, Ga-N, Al-N) materials is a hexagonal wurtzite structure, so under this condition, a high-quality epitaxial layer with a hexagonal cross section can be grown.

[0048] S3. Form an N electrode and a P electrode on the N-type semiconductor layer and the P-type semiconductor layer respectively to obtain a Micro-LED block.

[0049] In a preferred embodiment, the method further includes performing a full test on the Micro-LED blocks, marking the defective blocks, and obtaining the required Micro-LED blocks after cutting.

[0050] Correspondingly, such as Figure 3 As shown, the present invention also provides a display device, including the above-mentioned Micro-LED blocks. Specifically, multiple Micro-LED blocks that meet the performance requirements after full testing are transferred to a circuit substrate and arranged according to actual needs, and the electrodes of the Micro-LED units are electrically connected to the circuits laid on the circuit substrate, and packaged to obtain a display device. In a preferred embodiment, Figure 4 As shown, color conversion can also be achieved by setting different quantum dot layers above the Micro-LED unit.

[0051] The present invention will be further described below with specific embodiments:

[0052] Example 1

[0053] The present embodiment provides a Micro-LED block, including a substrate and three Micro-LED units. The three Micro-LED units are spaced apart in a straight line. The cross-sectional shape of each Micro-LED unit is rectangular with a size of 20μm×20μm. The thicknesses of the three Micro-LED units are 460nm, 455nm and 465nm, respectively, and the spacing is 1μm.

[0054] Example 2

[0055] The present embodiment provides a Micro-LED block, including a substrate and three Micro-LED units. The three Micro-LED units are spaced apart in a straight line. The cross-sectional shape of each Micro-LED unit is rectangular with a size of 20μm×20μm. The thicknesses of the three Micro-LED units are 460nm, 455nm and 450nm, respectively, and the spacing is 40μm.

[0056] Example 3

[0057] The present embodiment provides a Micro-LED block, including a substrate and three Micro-LED units. The three Micro-LED units are spaced apart in a straight line. The cross-sectional shape of each Micro-LED unit is a hexagon with a side length of 20 μm. The thicknesses of the three Micro-LED units are 460 nm, 455 nm and 450 nm, respectively, and the spacing is 40 μm.

[0058] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A Micro-LED block, characterized in that: It includes a substrate and a plurality of Micro-LED units distributed at intervals on the substrate, wherein the plurality of Micro-LED units distributed at intervals have a thickness difference, and the thickness difference between different Micro-LED units is 5nm to 200nm.

2. The Micro-LED block according to claim 1, wherein: It includes a substrate and three spaced-apart Micro-LED units arranged on the substrate, wherein the three Micro-LED units are distributed along a straight line and have increasing or decreasing thicknesses, and the thickness difference between different Micro-LED units is 5nm to 200nm.

3. The Micro-LED block according to claim 1, wherein: The cross section of the Micro-LED unit is a hexagon, the side length of the hexagon is 1.5 μm to 25 μm, and the distance between adjacent Micro-LED units is 1 μm to 100 μm.

4. The Micro-LED block according to claim 1, wherein: The Micro-LED unit includes an N-type semiconductor layer, an active layer, a P-type semiconductor layer, an N-electrode and a P-electrode, wherein the N-electrode is disposed on the N-type semiconductor layer, and the P-electrode is disposed on the P-type semiconductor layer; the thickness difference of the P-type semiconductor layer of different Micro-LED units in the same Micro-LED block is 5nm to 200nm; The N-type semiconductor layer includes a first N-type semiconductor layer and a second N-type semiconductor layer sequentially arranged on a substrate, a plurality of the second N-type semiconductor layers are isolated from each other, and a cross section of the second N-type semiconductor layer is a hexagon.

5. The Micro-LED block according to claim 4, wherein: A transparent conductive layer is provided on the P-type semiconductor layer of the Micro-LED unit, and an insulating layer is provided on the P-type semiconductor layer, on the first N-type semiconductor layer, and on the side wall of the P-type semiconductor layer extending to the first N-type semiconductor layer; A P extension line is provided on the insulating layer on one side of the Micro-LED unit, and the P extension line is used to connect the P electrodes of multiple Micro-LED units in a Micro-LED block.

6. A method for preparing a Micro-LED block, for preparing the Micro-LED block according to any one of claims 1 to 5, characterized in that: The following steps are involved: providing a substrate; A plurality of Micro-LED units with thickness differences are formed on the substrate; the thickness difference between different Micro-LED units is 5nm to 200nm.

7. The method for preparing a Micro-LED block according to claim 6, wherein: The following steps are used to form a plurality of Micro-LED units with different thicknesses: The same process is used to form multiple epitaxial structures with the same thickness. The epitaxial structure includes an N-type semiconductor layer, an active layer and a P-type semiconductor layer. The P-type semiconductor layers of different epitaxial structures are etched separately to obtain the required thickness. The thickness difference of the P-type semiconductor layer of different Micro-LED units is 5nm to 200nm.

8. The method for preparing a Micro-LED block according to claim 6, wherein: The Micro-LED unit is formed by the following steps: growing a first N-type semiconductor layer on the substrate; Growing an isolation layer on the first N-type semiconductor layer, wherein the thickness of the isolation layer is 5 nm to 500 nm, the isolation layer has a plurality of hollow portions exposing the first N-type semiconductor layer, the size of the hollow portions is 3 μm to 50 μm, and the distance between adjacent hollow portions is 1 μm to 100 μm; A second N-type semiconductor layer, an active layer and a P-type semiconductor layer are grown in the hollow portion.

9. The method for preparing a Micro-LED block according to claim 8, wherein: The epitaxial structure is prepared by the following steps: controlling the temperature to 650°C to 850°C, the pressure to 50 torr to 200 torr, introducing a carrier gas and an MO source, the carrier gas being N2 and / or H2, the flow rate of N2 being 5SLM to 20SLM, the flow rate of H2 being 0 to 10SLM, and the flow rate of the N source in the MO source being 20SLM to 50SLM.

10. A display device, characterized in that: It comprises the Micro-LED block as claimed in any one of claims 1 to 5.

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