GaN-based miniature LED display unit and preparation method thereof

Abstract

The invention discloses a GaN-based miniature LED display unit and a preparation method thereof. The GaN-based miniature LED display unit structurally comprises a substrate, a GaN-based composite buffer layer, an N-type GaN layer, a mask layer containing a micropore array, a hexagonal close-packed N-type GaN hexagonal island structure, a quantum well prepared on the N-type GaN hexagonal island, a carrier regulation and control layer, a P-type In < x > Ga < 1-x > N layer and the like which are sequentially arranged from bottom to top. A light-emitting structure of the micro LED display unit is formed by the hexagonal close-packed N-type GaN hexagonal islands and the quantum wells, adverse effects caused by etching damage can be avoided by taking an independent mesa structure as a unit, the fringe effect of each light-emitting unit is effectively inhibited, and the brightness is improved; the light-emitting units are arranged on the basis of hexagonal close packing, the area of the epitaxial wafer can be effectively utilized to the maximum extent, and economic benefits are maximized. The structure effectively inhibits the negative influence of the traditional GaN-based micro LED preparation process on the lighting effect, and has important significance for the development of a GaN-based micro LED display.

Description

Technical Field

[0001] The invention relates to a GaN-based micro LED display unit and a preparation method thereof, and belongs to the fields of semiconductor epitaxial growth, GaN-based LEDs, etc. Background Art

[0002] Micro light-emitting diode (LED) display technology has the advantages of low energy consumption, long life and good color rendering. It has broad application prospects in high-definition display fields of various sizes and shapes such as large displays, consumer electronics, car displays, virtual reality, augmented reality and wearable displays. It is the next-generation display technology that international research institutions and enterprises focus on. How to achieve full-color display is one of the challenges facing micro light-emitting diode display technology. This is mainly because under the existing technical conditions, it is still difficult to achieve monolithic integration of red, green and blue primary color micro LED display units. With the development of semiconductor solid-state light sources, solid-state light sources based on III-nitride GaN-based LED display units have become the mainstream light sources for lighting, display backlighting, and screen display, and are gradually developing into fields such as optical communications and micro LED displays.

[0003] At present, high-efficiency solid-state visible light sources are mainly nitride-based blue-green LEDs and phosphide-based red LEDs. When the emission wavelength of AlInGaP-based materials is modulated from red to yellow, its band gap gradually transitions from direct band gap to indirect band gap, resulting in a rapid decrease in efficiency. This physical property seriously restricts its development and application as a short-wavelength light source. Moreover, AlInGaP-based LEDs have strong surface recombination, and the etching damage produced when preparing micro-LEDs will further aggravate the surface recombination, leading to serious non-radiative recombination; it is reported that when the LED chip size is reduced to 262μm, its external quantum efficiency is less than 6%, and when the size is further reduced to 32μm, the external quantum efficiency is less than 1%; there are even reports showing that 50×50μm 2 The external quantum efficiency of a chip of this size is less than 0.12%, which seriously restricts the application of AlInGaP-based LEDs as red light sources in the field of micro-LED displays. The low luminous efficiency of InGaN-based LEDs in the long-wavelength band is due to the difficulty in epitaxial growth of InGaN with a high In component, but this can be solved through technology, and certain progress has been made. On the other hand, the non-radiative recombination caused by etching damage in InGaN-based LEDs is relatively small, and its luminous wavelength can cover the entire visible light band. It is most likely to be used in fields such as micro-LED displays and high-speed visible light communications, but the efficiency in the red light band is currently low. Therefore, designing solutions to the problems of epitaxial growth of InGaN films with a high In component and non-radiative recombination caused by etching damage has become an important research topic.

[0004] At the same time, displays are developing in the direction of higher resolution and smaller size, aiming to achieve more delicate and realistic picture display. The current process for preparing small-sized and high-density light-emitting units still has problems such as low yield, high manufacturing cost and difficult driving circuit design. Therefore, large display panel manufacturers have begun to solve this problem by changing the sub-light-emitting arrangement structure and reducing the number of sub-light-emitting units, namely sub-light-emitting unit rendering technology. Sub-light-emitting unit rendering technology is to map multi-primary color light-emitting units with different shapes and arrangements through mathematical algorithms, and convert the sub-light-emitting unit data of the original light-emitting arrangement into the sub-light-emitting unit data of the target light-emitting arrangement, and use the continuity of the numerical values ​​between the light-emitting units and the borrowing between adjacent sub-light-emitting units to achieve the display effect equivalent to the traditional RGB strip arrangement, thereby improving the PPI and display effect of the image. Summary of the invention

[0005] The main reason for the difficulty in applying nitride micro-LEDs is that it is difficult to design a high-density micro-LED dot matrix structure, and when preparing the micro-LED structure, quantum well etching damage is easily generated, which leads to serious non-radiative recombination and reduces the light efficiency. The GaN-based micro-LED display unit provided by the present invention is specially designed to adopt a hexagonal close-packed N-type GaN hexagonal island structure to address the etching damage problem generated when preparing the micro-LED structure, fundamentally avoiding the damage of etching to the multi-quantum well, improving the radiative recombination efficiency of the nitride micro-LED, and arranging the light-emitting units based on hexagonal close packing to maximize the area of ​​the epitaxial wafer. The unique light-emitting unit structure helps to design pixel rendering technology, realize delicate and realistic picture display, and maximize economic benefits.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a GaN-based micro LED display unit, which includes a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a microhole array, a hexagonally close-packed N-type GaN hexagonal island array 105, a quantum well array 106 on the N-type GaN hexagonal island, a carrier regulation layer 107 and a P-type In x Ga 1-x N layer 108.

[0008] The hexagonally close-packed N-type GaN hexagonal island array 105 is selectively epitaxially grown on a mask layer 104 containing a microhole array and is composed of independent N-type GaN hexagonal island structures. When the top of this structure ends with a table, it is an N-type GaN hexagonal pyramid, and when the top ends with a pyramid structure, it is an N-type GaN hexagonal pyramid.

[0009] When the N-type GaN hexagonal island array 105 is in the structure of an N-type GaN hexagonal prism, the quantum well array 106, the carrier regulation layer 107, and the P-type In x Ga 1-x N layer 108 is an epitaxial structure grown on the top surface of the tabletop of the N-type GaN hexagonal prism; when the N-type GaN hexagonal island array 105 is in the structure of an N-type GaN hexagonal pyramid, the quantum well array 106, the carrier regulation layer 107, and the P-type In x Ga 1-x N layer 108 is an epitaxial structure grown on the six side surfaces of the N-type GaN hexagonal pyramid.

[0010] Preferably, the substrate 101 is one of a (111)-plane Si substrate or a (002) sapphire substrate.

[0011] Preferably, when the substrate 101 is a (111)-plane Si substrate, the GaN-based composite buffer layer 102 sequentially includes an AlN thin film with a thickness of 10 - 50 nm, 5 - 30 periods of an Al y1 Ga (1-y1) N / GaN superlattice with a single-period thickness of 5 - 15 nm, 10 - 20 periods of an In y2 Ga (1-y2) N / GaN superlattice with a single-period thickness of 5 - 10 nm, and a GaN thin film with a thickness of 1 - 3 μm; when the substrate 101 is a (002) sapphire substrate, the GaN-based composite buffer layer 102 sequentially includes an AlN thin film with a thickness of 3 - 10 nm, 10 - 30 periods of an In y3 Ga (1-y3) N / GaN superlattice, and a GaN thin film with a thickness of 1 - 3 μm. Among them, 0.05 < y1 < 0.2, 0.05 < y2 < 0.15, 0.03 < y3 < 0.10. When setting the GaN-based composite buffer layer, by growing an AlN layer and an Al y1 Ga (1-y1) N / GaN superlattice with very small lattice mismatch and thermal mismatch with GaN and AlGaN on the substrate, it can play a better role in stress release, and then obtain a high-quality GaN thin film, providing a better bottom substrate for subsequent epitaxial growth.

[0012] Preferably, the N-type GaN layer 103 is formed by doping Si elements into GaN, and the doping concentration of Si elements is 5×10 17 cm -3 ~5×10 19 cm -3 , and its electron concentration is less than 1.5 times the doping concentration of Si elements.

[0013] The mask layer 104 containing the micropore array is formed by etching a 5 to 50 nm thick SiO2, SiN or hBN dielectric film on the N-type GaN layer 103 from top to bottom through process technology, exposing the underlying N-type GaN layer 103 in the micropores; the diameter of the micropores is between 0.5 and 5 μm, and the micropores are arranged in a densely packed form with the centers of the micropores. The center of any micropore is equidistant from the centers of the six adjacent micropores, and the distance is between 5 and 50 μm, which can be adjusted according to actual needs.

[0014] Preferably, the hexagonal close-packed N-type GaN hexagonal island array 105 is a hexagonal island N-type GaN array structure obtained by secondary epitaxial growth in the form of selective epitaxy by one of MOCVD, HVPE, and MBE techniques on the basis of preparing a mask layer 104 containing a microhole array, wherein the bottom surface of the island is a regular hexagon, and the diameter of the circumscribed circle is 3 to 40 μm; wherein the top view of any N-type GaN hexagonal island is a regular hexagon, and any two N-type GaN hexagonal islands do not contact each other. The adjacent bottom sides of any two adjacent N-type GaN hexagonal islands are parallel and the two ends are aligned.

[0015] Preferably, the N-type GaN hexagonal islands in the hexagonal close-packed N-type GaN hexagonal island array 105 are either regular hexagonal pyramids or regular hexagonal prisms; when the N-type GaN hexagonal islands are regular hexagonal pyramids, the six side faces are the (10-11) crystal plane or the (10-12) crystal plane of GaN, and at this time, the hexagonal close-packed quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is epitaxially grown on the inclined surface; when the N-type GaN hexagonal island is a regular hexagonal pyramid, the top surface is the (0002) crystal plane of GaN, and the six side surfaces are the (10-11) crystal plane or (10-12) crystal plane of GaN. At this time, the hexagonal close-packed quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is epitaxially grown on the top surface. The light-emitting units are arranged based on hexagonal close packing (close packing), which can effectively utilize the area of ​​the epitaxial wafer to the greatest extent. At the same time, the table structure is set to fundamentally avoid the damage of etching to the multi-quantum well, improve the radiation recombination efficiency of the nitride micro-LED, and the table structure is conducive to releasing the underlying stress, improving the crystal quality of the entire structure of the LED, and then weakening the influence of defects and polarization on carriers, and improving the luminous efficiency of the LED.

[0016] Preferably, the boundary of the hexagonally closely packed N-type GaN hexagonal island array is a rectangle and has row and column characteristics. In the odd-numbered rows of the N-type GaN hexagonal island array, red light, blue light, green light, and white light GaN-based micro-LED display units are repeatedly arranged in sequence starting from the first display unit in the row. In the even-numbered rows of the N-type GaN hexagonal island array, green light, white light, red light, and blue light GaN-based micro-LED display units are repeatedly arranged in sequence starting from the first display unit in the row. In specific applications, a mapping algorithm is designed to convert traditional sub-light-emitting unit data into hexagonally closely packed light-emitting unit data, and the continuity of the numerical values ​​between the light-emitting units and the borrowing between adjacent sub-light-emitting units are utilized to achieve the same display effect as the traditional RGBW strip-arranged LED while greatly reducing the number of LEDs required, thereby achieving a higher PPI per unit area and maximizing economic benefits.

[0017] Preferably, the red light GaN-based micro LED display unit is above the N-type GaN hexagonal island, and includes 1 pair of blue quantum wells, 1 pair of red quantum wells, 1 pair of blue quantum wells, and 1 pair of red quantum wells from bottom to top; the green light GaN-based micro LED display unit is above the N-type GaN hexagonal island, and includes 1 pair of blue quantum wells and 2 pairs of green quantum wells from bottom to top; the blue light GaN-based micro LED display unit is above the N-type GaN hexagonal island, and includes 1 to 2 pairs of blue light quantum wells from bottom to top; the white light GaN-based micro LED display unit is above the N-type GaN hexagonal island, and includes 1 pair of green quantum wells, 2 pairs of red quantum wells, 1 pair of green quantum wells, and 1 pair of blue quantum wells from bottom to top. Since the red quantum well efficiency of GaN-based micro LED is the lowest, a specific structure is designed to use the blue quantum well to perform secondary excitation on the red quantum well to increase the red light efficiency and brightness. Since the efficiency of the green quantum well is slightly higher than that of the red quantum well, the green light can be regulated by adding a blue quantum well, thereby improving the luminous efficiency of the green light GaN-based micro-LED display unit.

[0018] Preferably, the carrier regulation layer 107 is one of an electron blocking layer and a hole injection layer. The electron blocking layer is an Al2O3 layer with 2 to 8 cycles and a single cycle thickness of less than 10 nm. y4 Ga (1-y4) N / GaN superlattice, where the molar composition y4 is between 0.1 and 0.6 and Al y4 Ga (1-y4) The hole injection layer is P-doped with an overall thickness of less than 30nm Al y5 Ga (1-y5) N / In y6 Ga (1-y6) N / GaN superlattice, Mg doping concentration is 5×10 17 cm -3 ~1×1019 cm -3 The hole concentration is not higher than 1×10 18 cm -3 By setting an electron blocking layer with a wider bandgap or a highly P-doped hole injection layer, the carriers in the active area, i.e., the multiple quantum wells, are restricted, thereby increasing the overlap of the hole and electron wave functions in the multiple quantum wells and achieving a higher radiation recombination efficiency.

[0019] Preferably, the P-type In x Ga 1-x The thickness of the N layer 108 is between 50 and 200 nm, and the molar composition x is between 0 and 0.15. When x=0, it is GaN. The Mg element doping concentration is 2×10 19 cm -3 ~5×10 19 cm -3 The hole concentration is not less than 1×10 18 cm -3 ; Among them, P type In x Ga 1-x In the 5-30 nm thickness region on the upper surface of the N layer 108, the doping concentration of the Mg element is not less than 1×10 20 cm -3 , the hole concentration is not less than 5×10 18 cm -3 .

[0020] On the other hand, the present invention provides a method for preparing the GaN-based micro LED display unit.

[0021] The method for preparing the GaN-based micro LED display unit can be used to prepare a structure including a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a microhole array, a hexagonally closely packed N-type GaN hexagonal island array 105, a quantum well array 106 on the N-type GaN hexagonal island, a carrier regulation layer 107 and a P-type In x Ga 1-x N layer 108; wherein the hexagonally closely packed N-type GaN hexagonal island array 105 is epitaxially grown on the mask layer 104 containing the microhole array, and is composed of independent N-type GaN hexagonal island structures. When the top of this structure ends with a table, it is an N-type GaN hexagonal pyramid, and when the top ends with a pyramid structure, it is an N-type GaN hexagonal pyramid; when the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal pyramid structure, the quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is an epitaxial structure grown on top of an N-type GaN hexagonal table. The method for preparing the LED display unit includes the following steps: a) using a (111) Si substrate or a (002) sapphire substrate to grow a GaN-based composite buffer layer 102 based on an epitaxial growth technique; b) continuing to epitaxially grow an N-type GaN layer 103 on the GaN-based composite buffer layer 102; c) preparing a dielectric layer (one of SiO2, SiN or hBN) on the N-type GaN layer 103, and using micro-machining technology to process a micro-hole array on the dielectric layer to expose the N-type GaN layer 103 below, thereby forming a mask layer 104 containing the micro-hole array; d) using the selective epitaxial growth technology to perform selective epitaxy using the micropores, and then controlling the temperature, V / III ratio, reaction chamber pressure and carrier gas, and reactant source achieve lateral epitaxy to form a hexagonally closely packed N-type GaN hexagonal island array 105; e) during the epitaxial growth process, the supply of Ga source is stopped, the flow rate of N source is reduced, and the N-type GaN hexagonal island array 105 is subjected to in-situ annealing treatment to decompose the N-type GaN hexagonal island in-situ to form an N-type GaN hexagonal pyramid structure; f) epitaxially growing the quantum well array 106, the carrier control layer 107 and the P-type In layer on the N-type GaN hexagonal structure using epitaxial growth technology x Ga 1-x N layer 108 completes the preparation of the epitaxial structure of the LED display unit.

[0022] The method for preparing the GaN-based micro LED display unit can be used to prepare a structure including a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a microhole array, a hexagonally closely packed N-type GaN hexagonal island array 105, a quantum well array 106 on the N-type GaN hexagonal island, a carrier regulation layer 107 and a P-type In x Ga 1-x N layer 108; wherein the hexagonally closely packed N-type GaN hexagonal island array 105 is epitaxially grown on the mask layer 104 containing the microhole array, and is composed of independent N-type GaN hexagonal island structures. When the top of this structure ends with a table, it is an N-type GaN hexagonal pyramid, and when the top ends with a pyramid structure, it is an N-type GaN hexagonal pyramid; when the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal pyramid structure, the quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is an epitaxial structure grown on the six sides of an N-type GaN hexagonal pyramid. The method for preparing the LED display unit includes the following steps: a) using a (111) Si substrate or a (002) sapphire substrate to grow a GaN-based composite buffer layer 102 based on an epitaxial growth technique; b) continuing to epitaxially grow an N-type GaN layer 103 on the GaN-based composite buffer layer 102; c) preparing a dielectric layer (one of SiO2, SiN or hBN) on the N-type GaN layer 103, and using micro-machining technology to process a micro-hole array on the dielectric layer to expose the N-type GaN layer 103 below, thereby forming a mask layer 104 containing the micro-hole array; d) using the selective epitaxial growth technology to perform selective epitaxy using the micropores, and then controlling the temperature, V / III ratio, reaction chamber pressure and carrier gas, and reactant source realize lateral epitaxy to form a hexagonally closely packed N-type GaN hexagonal island array 105, i.e., an N-type GaN hexagonal pyramid array; e) epitaxially growing the quantum well array 106, the carrier regulation layer 107 and the P-type In layer on the six sides of the N-type GaN hexagonal island using epitaxial growth technology x Ga 1-x N layer 108 completes the preparation of the epitaxial structure of the LED display unit.

[0023] Beneficial effects:

[0024] The present invention proposes a GaN-based micro-LED display unit. The design adopts micropore selective epitaxy technology to naturally form a GaN hexagonal island structure with high symmetry, thereby realizing the regular and controllable growth of the island surface layer structure. The full structure of Micro-LED is prepared on the inclined surface of GaN hexagonal island, which fundamentally avoids the damage of etching to the multi-quantum well, thereby improving the radiation recombination efficiency of nitride Micro-LED. In addition, the island structure helps to release the stress between layers during epitaxial growth, improves the crystal quality of the full structure of Micro-LED, weakens the influence of defects and polarization on carriers, and improves the luminous efficiency of Micro-LED.

[0025] In order to solve the quality problem of epitaxially grown GaN crystals caused by the lack of a suitable substrate, a GaN-based composite buffer layer is set up, and an AlN layer with very small lattice mismatch and thermal mismatch with GaN and AlGaN is grown on the substrate. y1 Ga (1-y1)N / GaN superlattice can play a good role in stress release, thereby obtaining high-quality GaN film and providing a good underlying substrate for subsequent epitaxial growth. Setting an electron blocking layer with a wider bandgap width or a high P-doped hole injection layer can achieve the restriction of carriers in the active area, i.e., the multiple quantum wells, so that the overlap of hole and electron wave functions in the multiple quantum wells increases, achieving higher radiation recombination efficiency, and further solving the problem of the decrease of internal quantum efficiency with the increase of injection current density.

[0026] At the same time, this patent uses hexagonal close packing (close packing) as the basis for arranging the light-emitting units, making the most of the area of ​​the epitaxial wafer. And the unique hexagonal display unit structure helps to design a mapping algorithm to convert the traditional sub-light-emitting unit data into hexagonal close-packed sub-light-emitting unit data, and utilizes the continuity of the values ​​between the light-emitting units and the borrowing between adjacent sub-light-emitting units to achieve the same display effect as the traditional RGBW strip arrangement LED while greatly reducing the number of LEDs required, thereby achieving a higher PPI per unit area, achieving a more delicate and realistic display effect, and having a wide range of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Exemplary embodiments are shown in the referenced drawings. The embodiments and drawings disclosed herein are to be considered illustrative rather than restrictive.

[0028] Figure 1 1 is a schematic cross-sectional view and a schematic top view of a GaN-based micro LED display unit when the N-type GaN hexagonal island array ends with a table in one embodiment of the present invention, in which: 101 is a substrate, 102 is a GaN-based composite buffer layer, 103 is an N-type GaN layer, 104 is a mask layer containing a microhole array, 105 is a hexagonally closely packed N-type GaN hexagonal island array, 106 is a quantum well array, 107 is a carrier control layer, 108 is a P-type In x Ga 1-x N layers. The numbers in the single hexagon in the top view schematic diagram represent the number of rows and columns of the display unit from left to right.

[0029] Figure 2 1 is a schematic cross-sectional view and a schematic top view of a GaN-based micro LED display unit when the N-type GaN hexagonal island array ends with a pyramid in one embodiment of the present invention, in which: 101 is a substrate, 102 is a GaN-based composite buffer layer, 103 is an N-type GaN layer, 104 is a mask layer containing a microhole array, 105 is a hexagonally closely packed N-type GaN hexagonal island array, 106 is a quantum well array, 107 is a carrier control layer, 108 is a P-type In x Ga 1-x N layers. The numbers in the single hexagon in the top view schematic diagram represent the number of rows and columns of the display unit from left to right. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0032] Embodiment 1:

[0033] Specific application structure such as Figure 1 The present invention comprises a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a microhole array, a hexagonally close-packed N-type GaN hexagonal island array 105, a quantum well array 106 on the N-type GaN hexagonal island, a carrier control layer 107 and a P-type In x Ga 1-x N layer 108; wherein the hexagonal close-packed N-type GaN hexagonal island array 105 is epitaxially grown on the mask layer 104 containing the microhole array and is composed of independent N-type GaN hexagonal pyramids; the quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is an epitaxial structure grown on top of the N-type GaN hexagonal mesas.

[0034] The specific application parameters and preparation method of the structure of Example 1 are as follows:

[0035] A (111) Si substrate was selected. A 40nm thick AlN film, a 20-period AlN film with a single period thickness of 7nm, and a 20-period AlN film were sequentially placed on the Si substrate from bottom to top. y1 Ga (1-y1) N / GaN superlattice, 15 periods with a single period thickness of 7nm In y2 Ga (1-y2) The N / GaN superlattice and the 2 μm thick GaN film act as the GaN-based composite buffer layer 102; at the same time, y1=0.1 and y2=0.7 are controlled. The doping concentration in GaN is 9×10 17 cm-3 The Si element is doped, and the electron concentration is controlled to be less than 1.5 times the Si element doping concentration to form the N-type GaN layer 103.

[0036] A 30nm thick SiO2 is disposed on the N-type GaN layer 103, and a micropore array is etched from top to bottom through process technology, exposing the underlying N-type GaN layer 103 in the micropores; the diameter of the micropores is controlled at 1μm, and the micropores are arranged in a densely packed form with the center of any micropore being equidistant from the center of the adjacent six micropores, with a distance of 25μm, thereby forming a mask layer 104 containing a micropore array.

[0037] A hexagonally closely packed N-type GaN hexagonal island array 105 is arranged in the microholes, and the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal pyramid structure.

[0038] In the odd-numbered rows of the N-type GaN hexagonal island array, red, blue, green, and white GaN-based micro LED display units are sequentially arranged starting from the first display unit in the row. In the even-numbered rows of the N-type GaN hexagonal island array, green, white, red, and blue GaN-based micro LED display units are sequentially arranged starting from the first display unit in the row.

[0039] On the quantum well, 5 periods of Al2O3 with a thickness of 10 nm per period are arranged. y4 Ga (1-y4) N / GaN superlattice, where the molar composition y4 is 0.3, and Al y4 Ga (1-y4) N has a negative correlation with the thickness and acts as a carrier regulation layer.

[0040] A 150nm P-type In layer is placed above the carrier control layer. x Ga 1-x The N layer 108 has a molar composition x of 0.07 and a Mg element doping concentration of 2.5×10 19 cm -3 , whose hole concentration is 1×10 18 cm -3 ; Among them, P type In x Ga 1-x In the 20 nm thick region on the upper surface of the N layer 108, the doping concentration of Mg element is 1×10 20 cm -3 , and its hole concentration is 5×10 18 cm -3 .

[0041] The preparation method of this example comprises the following steps: a) using a (111)-surface Si substrate and growing a GaN-based composite buffer layer 102 based on an epitaxial growth technique; b) continuing to epitaxially grow an N-type GaN layer 103 on the GaN-based composite buffer layer 102; c) preparing a dielectric layer on the N-type GaN layer 103, and using micromachining technology to process a microhole array on the dielectric layer to expose the N-type GaN layer 103 below, thereby forming a mask layer 104 containing the microhole array; d) using the selective epitaxial growth technology to perform selective epitaxy using the micropores, and then controlling the temperature, V / III ratio, reaction chamber pressure and carrier gas, and reactant source achieve lateral epitaxy to form a hexagonally closely packed N-type GaN hexagonal island array 105; e) During the epitaxial growth process, the supply of Ga source is stopped and the flow of N source is reduced to achieve the N-type GaN hexagonal island array. 105 performs in-situ annealing to decompose the N-type GaN hexagonal islands in-situ to form an N-type GaN hexagonal pyramid structure; f) epitaxially growing the quantum well array 106, the carrier control layer 107 and the P-type In layer on the N-type GaN hexagonal structure using epitaxial growth technology x Ga 1-x N layer 108 completes the preparation of the epitaxial structure of the LED display unit.

[0042] Embodiment 2:

[0043] Specific application structure such as Figure 2 The present invention comprises a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a microhole array, a hexagonally close-packed N-type GaN hexagonal island array 105, a quantum well array 106 on the N-type GaN hexagonal island, a carrier control layer 107 and a P-type In x Ga 1-x N layer 108; wherein the hexagonal close-packed N-type GaN hexagonal island array 105 is epitaxially grown on the mask layer 104 containing the microhole array and is composed of independent N-type GaN hexagonal pyramids; the quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is an epitaxial structure grown on the six sides of an N-type GaN hexagonal pyramid;

[0044] The specific application parameters and preparation method of the structure of Example 2 are as follows:

[0045] A (002) sapphire substrate is selected. A 5nm thick AlN film, a 20-period In film with a single period thickness of 7nm, and a 20-period In film are sequentially arranged from bottom to top on the (002) sapphire substrate. y3 Ga (1-y3)The N / GaN superlattice and the 2 μm thick GaN film act as the GaN-based composite buffer layer 102; at the same time, y3=0.07 is controlled. The doping concentration in GaN is 7×10 18 cm -3 The Si element is doped, and the electron concentration is controlled to be less than 1.5 times the Si element doping concentration to form the N-type GaN layer 103.

[0046] A 25 nm thick hBN is disposed on the N-type GaN layer 103, and a micropore array is etched from top to bottom through process technology, exposing the underlying N-type GaN layer 103 in the micropores; the diameter of the micropores is controlled at 2 μm, and the micropores are arranged in a densely packed form with the center of any micropore being equidistant from the center of the adjacent six micropores, with a distance of 30 μm, thereby forming a mask layer 104 containing a micropore array.

[0047] A hexagonally closely packed N-type GaN hexagonal island array 105 is arranged in the microholes, and the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal pyramid array.

[0048] In the odd-numbered rows of the N-type GaN hexagonal island array, red, blue, green, and white GaN-based micro LED display units are sequentially arranged starting from the first display unit in the row. In the even-numbered rows of the N-type GaN hexagonal island array, green, white, red, and blue GaN-based micro LED display units are sequentially arranged starting from the first display unit in the row.

[0049] Six periods of Al2O3 with a thickness of 5 nm per period are arranged on the quantum well. y4 Ga (1-y4) N / GaN superlattice, where the molar composition y4 is 0.4, and Al y4 Ga (1-y4) It is negatively correlated with the thickness of N. It acts as a carrier regulation layer.

[0050] A 150nm P-type In layer is placed above the carrier control layer. x Ga 1-x N layer 108, the molar composition x is 0.1, and the Mg element doping concentration is 3×10 19 cm -3 , and its hole concentration is 1.5×10 18 cm -3 ; Among them, P type In x Ga 1-x In the 15 nm thick region on the upper surface of the N layer 108, the doping concentration of the Mg element is 1.8×10 20 cm -3 , and its hole concentration is 7×10 18 cm -3 .

[0051] The preparation method of this example comprises the following steps: a) using a (002) sapphire substrate and growing a GaN-based composite buffer layer 102 based on an epitaxial growth technique; b) continuing to epitaxially grow an N-type GaN layer 103 on the GaN-based composite buffer layer 102; c) preparing a dielectric layer on the N-type GaN layer 103, and using micromachining technology to process a microhole array on the dielectric layer to expose the N-type GaN layer 103 below, thereby forming a mask layer 104 containing the microhole array; d) using the selective epitaxial growth technology to perform selective epitaxy using the micropores, and then controlling the epitaxial growth temperature, V / III ratio, reaction chamber pressure and carrier gas, and reactant source to achieve lateral epitaxy, thereby forming a hexagonally closely packed N-type GaN hexagonal island array 105, i.e., an N-type GaN hexagonal pyramid array; e) epitaxially growing the quantum well array 106, the carrier regulation layer 107 and the P-type In layer on the six sides of the N-type GaN hexagonal island using epitaxial growth technology x Ga 1-x N layer 108 completes the preparation of the epitaxial structure of the LED display unit.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A GaN-based micro LED display unit, characterized in that: The film comprises a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a microhole array, a hexagonally close-packed N-type GaN hexagonal island array 105, a quantum well array 106 on the N-type GaN hexagonal island, a carrier control layer 107 and a P-type In x Ga 1-x N layer 108. Among them, the hexagonal close-packed N-type GaN hexagonal island array 105 is epitaxially grown on the mask layer 104 containing the microhole array, and is composed of independent N-type GaN hexagonal island structures. When the top of this structure ends with a table, it is an N-type GaN hexagonal pyramid, and when the top ends with a pyramid structure, it is an N-type GaN hexagonal pyramid; when the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal pyramid structure, the quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is an epitaxial structure grown on the top of the N-type GaN hexagonal pyramid. When the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal pyramid structure, the quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is an epitaxial structure grown on the six sides of an N-type GaN hexagonal pyramid.

2. A GaN-based micro LED display unit according to claim 1, characterized in that: The substrate 101 is a (111) Si substrate or a (002) sapphire substrate; when the substrate 101 is a (111) Si substrate, the GaN-based composite buffer layer 102 includes, from bottom to top, a 10-50 nm thick AlN film, a single period of 5-30 cycles with a thickness of 5-15 nm, and a GaN-based composite buffer layer 102. y1 Ga (1-y1) N / GaN superlattice, 10 to 20 periods of In with a single period thickness of 5 to 10 nm y2 Ga (1-y2) N / GaN superlattice and 1 to 3 μm thick GaN film; when the substrate 101 is a (002) sapphire substrate, the GaN-based composite buffer layer 102 includes, from bottom to top, a 3 to 10 nm thick AlN film, 10 to 30 cycles of a single cycle thickness of 5 to 10 nm thick In y3 Ga (1-y3) N / GaN superlattice and 1-3μm thick GaN film; among them, 0.05 <y1<0.2,0.05<y2<0.15,0.03<y3<0.10。 3. A GaN-based micro-LED display unit according to claim 1, characterized in that: The mask layer 104 containing the micro-hole array is formed by etching a dielectric film of SiO2, SiN or hBN with a thickness of 5 to 50 nm on the N-type GaN layer 103, and then etching the micro-hole array from top to bottom through a process technology, so that the N-type GaN layer 103 below is exposed in the micro-holes; The diameter of the micropores is between 0.5 and 5 μm, and the micropores are arranged in a densely packed form at the center. The distance between the center of any micropore and the centers of the six adjacent micropores is equal, and the distance is between 5 and 50 μm, which can be adjusted according to actual needs.

4. A GaN-based micro LED display unit according to claim 1, characterized in that: The hexagonal close-packed N-type GaN hexagonal island array 105 is a hexagonal N-type GaN array structure obtained by secondary epitaxial growth in the form of selective epitaxy by using one of MOCVD, HVPE, and MBE technologies on the basis of preparing a mask layer 104 containing a microhole array. The bottom surface of the island is a regular hexagon, and the diameter of the circumscribed circle is 3 to 40 μm; wherein, the top view of any N-type GaN hexagonal island is a regular hexagon, and any two N-type GaN hexagonal islands do not contact each other. The adjacent bottom sides of any two adjacent N-type GaN hexagonal islands are parallel and the two ends are aligned.

5. A GaN-based micro LED display unit according to claim 1, characterized in that: The N-type GaN hexagonal islands in the hexagonal close-packed N-type GaN hexagonal island array 105 are either regular hexagonal pyramids or regular hexagonal prisms. When the N-type GaN hexagonal islands are regular hexagonal pyramids, the six side faces are the (10-11) crystal plane or the (10-12) crystal plane of GaN. At this time, the hexagonal close-packed quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is epitaxially grown on the inclined surface; when the N-type GaN hexagonal island is a regular hexagonal pyramid, the top surface is the (0002) crystal plane of GaN, and the six side surfaces are the (10-11) crystal plane or (10-12) crystal plane of GaN. At this time, the hexagonal close-packed quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is epitaxially grown on the top surface.

6. A GaN-based micro-LED display unit according to claim 1, characterized in that: The boundary of the hexagonally packed N-type GaN hexagonal island array is rectangular and has row and column characteristics. In the odd-numbered rows of the N-type GaN hexagonal island array, red, blue, green, and white GaN-based micro-LED display units are repeatedly arranged in sequence starting from the first display unit in the row. In the even-numbered rows of the N-type GaN hexagonal island array, green, white, red, and blue GaN-based micro-LED display units are repeatedly arranged in sequence starting from the first display unit in the row. Among them, the red light GaN-based micro LED display unit is above the N-type GaN hexagonal island, and includes 1 pair of blue quantum wells, 1 pair of red quantum wells, 1 pair of blue quantum wells, and 1 pair of red quantum wells from bottom to top; the green light GaN-based micro LED display unit is above the N-type GaN hexagonal island, and includes 1 pair of blue quantum wells and 2 pairs of green quantum wells from bottom to top; the blue light GaN-based micro LED display unit is above the N-type GaN hexagonal island, and includes 1 to 2 pairs of blue quantum wells from bottom to top; the white light GaN-based micro LED display unit is above the N-type GaN hexagonal island, and includes 1 pair of green quantum wells, 2 pairs of red quantum wells, 1 pair of green quantum wells, and 1 pair of blue quantum wells from bottom to top.

7. A GaN-based micro LED display unit according to claim 1, characterized in that: The carrier regulation layer 107 is one of an electron blocking layer and a hole injection layer; wherein the electron blocking layer is an Al2O3 layer with 2 to 8 cycles and a single cycle thickness of less than 10 nm. y4 Ga (1-y4) N / GaN superlattice, where the molar composition y4 is between 0.1 and 0.6 and Al y4 Ga (1-y4) The hole injection layer is P-doped with an overall thickness of less than 30nm Al y5 Ga (1-y5) N / In y6 Ga (1-y6) N / GaN superlattice, Mg doping concentration is 5×10 17 cm -3 ~1×10 19 cm -3 The hole concentration is not higher than 1×10 18 cm -3 .

8. A GaN-based micro LED display unit according to claim 1, characterized in that: P-type In x Ga 1-x The thickness of the N layer 108 is between 50 and 200 nm, and the molar composition x is between 0 and 0.

15. When x=0, it is GaN. The Mg element doping concentration is 2×10 19 cm -3 ~5×10 19 cm -3 The hole concentration is not less than 1×10 18 cm -3 ; Among them, P type In x Ga 1-x In the 5-30 nm thickness region on the upper surface of the N layer 108, the doping concentration of the Mg element is not less than 1×10 20 cm -3 , the hole concentration is not less than 5×10 18 cm -3 .

9. A method for preparing a GaN-based micro LED display unit, characterized in that: The structure includes a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a microhole array, a hexagonally close-packed N-type GaN hexagonal island array 105, a quantum well array 106 on the N-type GaN hexagonal island, a carrier control layer 107 and a P-type In x Ga 1-x N layer 108; wherein the hexagonally closely packed N-type GaN hexagonal island array 105 is epitaxially grown on the mask layer 104 containing the microhole array, and is composed of independent N-type GaN hexagonal island structures. When the top of this structure ends with a table, it is an N-type GaN hexagonal pyramid, and when the top ends with a pyramid structure, it is an N-type GaN hexagonal pyramid; when the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal pyramid structure, the quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is an epitaxial structure grown on top of an N-type GaN hexagonal table; The preparation method of the LED display unit comprises the following steps: a) using a (111) Si substrate or a (002) sapphire substrate to grow a GaN-based composite buffer layer 102 based on an epitaxial growth technique; b) continuing to epitaxially grow an N-type GaN layer 103 on the GaN-based composite buffer layer 102; c) preparing a dielectric layer (one of SiO2, SiN or hBN) on the N-type GaN layer 103, and using micro-machining technology to process a micro-hole array on the dielectric layer to expose the N-type GaN layer 103 below, thereby forming a mask layer 104 containing the micro-hole array; d) using the selective epitaxial growth technology to perform selective epitaxy using the micropores, and then achieving lateral epitaxy by controlling the epitaxial growth temperature, V / III ratio, reaction chamber pressure and carrier gas, and reactant source to form a hexagonally closely packed N-type GaN hexagonal island array 105; e) during the epitaxial growth process, the supply of Ga source is stopped, the flow rate of N source is reduced, and the N-type GaN hexagonal island array 105 is subjected to in-situ annealing treatment to decompose the N-type GaN hexagonal island in-situ to form an N-type GaN hexagonal pyramid structure; f) epitaxially growing the quantum well array 106, the carrier control layer 107 and the P-type In layer on the N-type GaN hexagonal structure using epitaxial growth technology x Ga 1-x N layer 108 completes the preparation of the epitaxial structure of the LED display unit.

10. A method for preparing a GaN-based micro LED display unit, characterized in that: The structure includes a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a microhole array, a hexagonally close-packed N-type GaN hexagonal island array 105, a quantum well array 106 on the N-type GaN hexagonal island, a carrier control layer 107 and a P-type In x Ga 1-x N layer 108; wherein the hexagonally closely packed N-type GaN hexagonal island array 105 is epitaxially grown on the mask layer 104 containing the microhole array, and is composed of independent N-type GaN hexagonal island structures. When the top of this structure ends with a table, it is an N-type GaN hexagonal pyramid, and when the top ends with a pyramid structure, it is an N-type GaN hexagonal pyramid; when the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal pyramid structure, the quantum well array 106, the carrier control layer 107 and the P-type In x Ga 1-x The N layer 108 is an epitaxial structure grown on the six sides of an N-type GaN hexagonal pyramid; The preparation method of the LED display unit comprises the following steps: a) using a (111) Si substrate or a (002) sapphire substrate to grow a GaN-based composite buffer layer 102 based on an epitaxial growth technique; b) continuing to epitaxially grow an N-type GaN layer 103 on the GaN-based composite buffer layer 102; c) preparing a dielectric layer (one of SiO2, SiN or hBN) on the N-type GaN layer 103, and using micro-machining technology to process a micro-hole array on the dielectric layer to expose the N-type GaN layer 103 below, thereby forming a mask layer 104 containing the micro-hole array; d) using the selective epitaxial growth technology to perform selective epitaxy using the micropores, and then controlling the epitaxial growth temperature, V / III ratio, reaction chamber pressure and carrier gas, and reactant source to achieve lateral epitaxy, thereby forming a hexagonally closely packed N-type GaN hexagonal island array 105, i.e., an N-type GaN hexagonal pyramid array; e) epitaxially growing the quantum well array 106, the carrier regulation layer 107 and the P-type In layer on the six sides of the N-type GaN hexagonal island using epitaxial growth technology x Ga 1-x N layer 108 completes the preparation of the epitaxial structure of the LED display unit.

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