A GaN-based micro LED display unit and a preparation method thereof

Abstract

The application discloses a GaN-based micro-LED display unit and a preparation method thereof, and the structure comprises, from bottom to top, 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 layer and a P-type InGaN layer. x Ga 1‑x N layer. The hexagonal close-packed N-type GaN hexagonal island and the quantum well constitute a light-emitting structure of the micro-LED display unit, the independent mesa structure can avoid the adverse effects caused by etching damage, effectively suppress the edge effect of each light-emitting unit and improve the brightness, and the light-emitting units are arranged on the basis of the hexagonal close packing, so that the area of the epitaxial wafer can be effectively utilized to the maximum extent and the economic benefits can be maximized. The structure effectively suppresses the negative influence of the traditional GaN-based micro-LED preparation process on the light efficiency, and has important significance for the development of the GaN-based micro-LED display.

Description

Technical Field

[0001] This invention relates to a GaN-based micro LED display unit and its fabrication method, belonging to the fields of semiconductor epitaxial growth and GaN-based LEDs. Background Technology

[0002] Miniature light-emitting diode (LED) display technology boasts advantages such as low power consumption, long lifespan, and excellent color rendering. It holds broad application prospects in high-definition displays of various sizes and shapes, including large displays, consumer electronics, automotive displays, virtual reality, augmented reality, and wearable displays. It is a next-generation display technology that international research institutions and companies are focusing on. Achieving full-color display is one of the challenges facing miniature LED display technology, primarily because under current technological conditions, it is still difficult to achieve monolithic integration of red, green, and blue primary color miniature LED display units. With the development of semiconductor solid-state light sources, solid-state light sources based on GaN (Group III nitride) LED display units have become the mainstream light source for lighting, display backlighting, and screen displays, and are gradually expanding into fields such as optical communication and miniature LED displays.

[0003] Currently, high-efficiency solid-state visible light sources mainly consist of GaN-based blue-green LEDs and AlInGaP-based red LEDs. When the emission wavelength of AlInGaP-based materials is modulated from red to yellow light, its bandgap gradually transitions from a direct bandgap to an indirect bandgap, leading to a rapid decrease in efficiency. This physical property severely restricts its development and application as a short-wavelength light source. Furthermore, AlInGaP-based LEDs exhibit strong surface recombination, and etching damage during the fabrication of micro-LEDs further exacerbates surface recombination, resulting in severe non-radiative recombination. Reports indicate that when the LED chip size is reduced to 262 μm, its external quantum efficiency is less than 6%, and when the size is further reduced to 32 μm, the external quantum efficiency is less than 1%. There are even reports showing that 50×50 μm... 2 The external quantum efficiency of AlInGaP-based LEDs is less than 0.12%, a phenomenon that severely restricts their application as red light sources in micro-LED displays. The low luminous efficacy of long-wavelength InGaN-based LEDs is due to the difficulty in epitaxial growth of high-In-content InGaN, but this can be addressed technologically, and some progress has been made. On the other hand, InGaN-based LEDs have relatively low non-radiative recombination due to etching damage, and their emission wavelengths can cover the entire visible light spectrum, making them most promising for applications in micro-LED displays and high-speed visible light communication; however, their efficiency in the red light band is currently low. Therefore, designing solutions to the problems of epitaxial growth of high-In-content InGaN thin films and non-radiative recombination due to etching damage has become an important research topic.

[0004] At the same time, the display is developing towards higher resolution and smaller size, aiming to achieve more delicate and real picture display. The current process prepares small size high density light emitting unit, there are still low yield, high manufacturing cost and driving circuit design difficulties and other problems. Therefore, large display panel manufacturers begin to solve this problem by changing the sub-light arrangement structure and reducing the number of sub-light, that is, sub-light unit rendering technology. The sub-light unit rendering technology is to map the multiple base color light emitting units with different shapes and arrangements, convert the original light emitting arrangement sub-light unit data into the target light emitting arrangement sub-light unit data, and realize the equivalent display effect of traditional RGB strip arrangement by using the continuity of the numerical value between the light emitting units and the borrowing between the adjacent sub-light units, improve the PPI and display effect of the image. SUMMARY

[0005] The most important reason for the difficulty of application of nitride micro-LED is the difficulty of designing high-density micro-LED dot matrix structure, and when preparing the micro-LED structure, quantum well etching damage is easy to occur, which further causes serious non-radiative recombination, thereby reducing the light efficiency. The GaN-based micro-LED display unit provided by the application is particularly designed to adopt a hexagonal island structure of N-type GaN in a hexagonal close packing for the etching damage problem generated when preparing the micro-LED structure, thereby fundamentally avoiding the damage of etching to the multi-quantum well, improving the radiative recombination efficiency of the nitride micro-LED, arranging the light emitting units on the basis of the hexagonal close packing, and maximizing the use of the area of the epitaxial wafer. In addition, the unique light emitting unit structure is helpful for designing pixel rendering technology, realizing delicate and real picture display, and maximizing economic benefits.

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

[0007] In one aspect, the application provides a GaN-based micro-LED display unit, which comprises, from bottom to top, a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a micro-pore array, a hexagonal 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 hexagonal close-packed N-type GaN hexagonal island array 105 is a structure composed of independent N-type GaN hexagonal island structures, which is grown by selective epitaxy on the mask layer 104 containing the micro-pore array. When the top of the structure ends with a mesa, it is an N-type GaN hexagonal prism. When the top of the structure ends with a pyramid structure, it is an N-type GaN hexagonal pyramid.

[0009] The N-type GaN hexagonal island array 105 is a N-type GaN hexagonal platform structure, 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 of the N-type GaN hexagonal platform; the N-type GaN hexagonal island array 105 is a N-type GaN hexagonal pyramid structure, 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 sides of the N-type GaN hexagonal pyramid.

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

[0011] Preferably, when the substrate 101 is a (111) surface Si substrate, the GaN-based composite buffer layer 102 comprises, from bottom to top, 10-50 nm thick AlN film, 5-30 periods of single period thickness of 5-15 nm thick Al y1 Ga (1-y1) N / GaN superlattice, 10-20 periods of single period thickness of 5-10 nm thick In y2 Ga (1-y2) N / GaN superlattice and 1-3 μm thick GaN film; when the substrate 101 is a (002) sapphire substrate, the GaN-based composite buffer layer 102 comprises, from bottom to top, 3-10 nm thick AlN film, 10-30 periods of single period thickness of 5-10 nm thick In y3 Ga (1-y3) N / GaN superlattice and 1-3 μm thick GaN film. Wherein, 0.05 < y1 < 0.2, 0.05 < y2 < 0.15, 0.03 < y3 < 0.10. When the GaN-based composite buffer layer is set, by growing AlN layer and Al y1 Ga (1-y1) N / GaN superlattice with very small lattice mismatch and thermal mismatch with GaN and AlGaN on the substrate, a better stress release effect can be achieved, and a high-quality GaN film is obtained, providing a better bottom layer substrate for subsequent epitaxial growth.

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

[0013] The mask layer 104 containing the micropore array is a micropore array etched from top to bottom by a process after a 5-50 nm thick dielectric film of SiO2, SiN or hBN is plated on the N-type GaN layer 103, and the N-type GaN layer 103 under the micropores is exposed; wherein the diameter of the micropores is between 0.5-5 μm, and the micropores are arranged in a close-packed form with the center of the micropores, and the distance between the center of any micropore and the center of the adjacent six micropores is equal, and the distance is between 5-50 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 array structure of N-type GaN obtained by secondary epitaxial growth in a selected area epitaxy form by one of MOCVD, HVPE and MBE on the basis of the preparation of the mask layer 104 containing the micropore array, and the bottom surface of the island is a regular hexagon, and the diameter of the circumscribed circle is 3-40 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 edges of any two adjacent N-type GaN hexagonal islands are parallel and aligned at both ends.

[0015] Preferably, the N-type GaN hexagonal island in the hexagonal close-packed N-type GaN hexagonal island array 105 is one of a regular hexagonal pyramid and a regular hexagonal platform; when the N-type GaN hexagonal island is a regular hexagonal pyramid, the six side surfaces are (10-11) crystal planes or (10-12) crystal planes of GaN, and at this time, the hexagonal close-packed quantum well array 106, the carrier regulation layer 107 and the P-type In x Ga 1-x N layer 108 are all epitaxially grown on the inclined surface; when the N-type GaN hexagonal island is a regular hexagonal platform, the top surface is a (0002) crystal plane of GaN, and the six side surfaces are (10-11) crystal planes or (10-12) crystal planes of GaN, and at this time, the hexagonal close-packed quantum well array 106, the carrier regulation layer 107 and the P-type In x Ga 1-x N layer 108 are all epitaxially grown on the top surface. The light emitting units are arranged based on the hexagonal close packing (close packing), which can effectively utilize the area of the epitaxial wafer to the greatest extent. At the same time, the platform structure is provided, which fundamentally avoids the damage of etching to the multiple quantum wells, improves the radiation recombination efficiency of the nitride micro-LED, and the platform structure is beneficial to releasing the stress of the bottom layer, improving the crystal quality of the prepared LED full structure, and then weakening the influence of defects and polarization on the carriers, and improving the light emitting efficiency of the LED.

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

[0017] Preferably, the red GaN-based micro-LED display unit is above the N-type GaN hexagonal island and includes, from bottom to top, 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. The green GaN-based micro-LED display unit is above the N-type GaN hexagonal island and includes, from bottom to top, 1 pair of blue quantum wells and 2 pairs of green quantum wells. The blue GaN-based micro-LED display unit is above the N-type GaN hexagonal island and includes, from bottom to top, 1-2 pairs of blue quantum wells. The white GaN-based micro-LED display unit is above the N-type GaN hexagonal island and includes, from bottom to top, 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. Since the red quantum well of the GaN-based micro-LED has the lowest efficiency, a specific structure is designed to use the blue quantum well to excite the red quantum well twice, thereby increasing the red light efficiency and brightness. Since the green quantum well has a slightly higher efficiency than the red quantum well, the addition of the blue quantum well can adjust the green light, thereby improving the light efficiency of the green GaN-based micro-LED display unit.

[0018] Preferably, the carrier regulation layer 107 is one of an electron blocking layer or a hole injection layer. The electron blocking layer is an Al y4 Ga (1-y4) N / GaN superlattice with a molar composition y4 of 0.1-0.6 and a negative correlation with the thickness of Al y4 Ga (1-y4) N; and the hole injection layer is a P-doped Al y5 Ga (1-y5) N / In y6 Ga (1-y6) N / GaN superlattice with a Mg element doping concentration of 5×10 17 cm -3 ~1×1019 cm -3 Between these values, the hole concentration is no higher than 1×10⁻⁶. 18 cm -3 By setting an electron blocking layer with a wider bandgap or a hole injection layer with high p-doping, the carriers in the active region, i.e., the multiple quantum wells, can be confined, thereby increasing the overlap of the hole and electron wave functions in the multiple quantum wells and achieving higher radiative 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 × 10⁻⁶. 19 cm -3 ~5×10 19 cm -3 Between these points, the hole concentration is not less than 1×10 18 cm -3 ; among which P-type In x Ga 1-x Within a 5–30 nm thick region on the upper surface of the N-layer 108, the Mg doping concentration is not less than 1 × 10⁻⁶. 20 cm -3 Its hole concentration is not less than 5×10 18 cm -3 .

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

[0021] The method for fabricating the GaN-based micro-LED display unit can be used to fabricate a structure comprising, from bottom to top, a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a micro-pore array, a hexagonal close-packed N-type GaN hexagonal island array 105, a quantum well array 106 on the N-type GaN hexagonal islands, 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 selected-region epitaxially grown on the mask layer 104 containing a microporous array, and is composed of independent N-type GaN hexagonal island structures. When the top of this structure ends with a mesa, it is an N-type GaN hexagonal frustum; when the top ends with a pyramidal structure, it is an N-type GaN hexagonal pyramid. When the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal frustum 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 the hexagonal facet of an N-type GaN. The fabrication method of this LED display unit includes the following steps:

[0022] a) Using a (111) Si substrate or a (002) sapphire substrate, a GaN-based composite buffer layer 102 is grown based on epitaxial growth technology;

[0023] b) Continue epitaxial growth of an N-type GaN layer 103 on the GaN-based composite buffer layer 102;

[0024] c) Prepare a dielectric layer (one of SiO2, SiN or hBN) on the N-type GaN layer 103, and use microfabrication technology to fabricate a micro-hole array on the dielectric layer to expose the underlying N-type GaN layer 103, forming a mask layer 104 containing the micro-hole array.

[0025] d) Selective epitaxy is performed using the aforementioned micropores, followed by controlling the epitaxial growth temperature,

[0026] The V / III ratio, reaction chamber pressure, carrier gas, and reactant source enable lateral epitaxy to form a hexagonal close-packed N-type GaN hexagonal island array 105;

[0027] 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 to decompose the N-type GaN hexagonal islands in-situ and form an N-type GaN hexagonal frustum structure.

[0028] f) Using epitaxial growth techniques, continue to epitaxially grow the quantum well array 106, the carrier control layer 107, and the P-type In on the N-type GaN hexagonal structure. x Ga 1-x The N-layer 108 is used to complete the epitaxial structure fabrication of this LED display unit.

[0029] The method for fabricating the GaN-based micro-LED display unit can be used to fabricate a structure comprising, from bottom to top, a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a micro-pore array, a hexagonal close-packed N-type GaN hexagonal island array 105, a quantum well array 106 on the N-type GaN hexagonal islands, 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 selected-region epitaxially grown on the mask layer 104 containing a microporous array, and is composed of independent N-type GaN hexagonal island structures. When the top of this structure ends with a mesa, it is an N-type GaN hexagonal frustum; when the top ends with a pyramidal structure, it is an N-type GaN hexagonal pyramid. When the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal pyramidal structure, the quantum well array 106, the carrier control layer 107, and the P-type In x Ga1-x N layer 108 is an epitaxial structure grown on the six sides of N-type GaN hexagonal pyramid; the preparation method of the LED display unit comprises the following steps:

[0030] a) using a (111) surface Si substrate or a (002) sapphire substrate, growing a GaN-based composite buffer layer 102 based on epitaxial growth technology;

[0031] b) continuing to epitaxially grow an N-type GaN layer 103 on the GaN-based composite buffer layer 102;

[0032] c) preparing a layer of dielectric layer (one of SiO2, SiN or hBN) on the N-type GaN layer 103, using micro-processing technology to process a micro-hole array on the dielectric layer to expose the underlying N-type GaN layer 103, and forming a mask layer 104 containing the micro-hole array;

[0033] d) using selective epitaxy growth technology to perform selective epitaxy using the above micro-holes, and then by controlling the temperature of epitaxial growth,

[0034] V / III ratio, reaction chamber pressure and carrier gas and reactant source to realize lateral epitaxy to form a hexagonal close-packed N-type GaN hexagonal island array 105, i.e. an N-type GaN hexagonal pyramid array;

[0035] e) using epitaxial growth technology to continue to epitaxially grow a quantum well array 106, a carrier regulation layer 107 and a P-type In x Ga 1-x N layer 108 on the six sides of the N-type GaN hexagonal island, completing the preparation of the epitaxial structure of the LED display unit.

[0036] Advantages:

[0037] The application provides a GaN-based micro-LED display unit. The micro-hole selective epitaxy technology is adopted in the design, a GaN hexagonal island structure with high symmetry is naturally formed, and then the regular and controllable growth of the island surface layer structure is realized. The Micro-LED full structure is prepared on the GaN hexagonal island inclined surface, which fundamentally avoids the damage of etching to the multi-quantum well, and then the radiation recombination efficiency of the nitride Micro-LED is improved. Moreover, the island structure is helpful for the release of stress between layers during epitaxial growth, improves the crystal quality of the prepared Micro-LED full structure, weakens the influence of defects and polarization on carriers, and improves the light-emitting efficiency of the Micro-LED.

[0038] In order to solve the problem of epitaxial growth of GaN crystal quality caused by the lack of a suitable substrate, a GaN-based composite buffer layer is arranged, an AlN layer with very small lattice mismatch and thermal mismatch with GaN and AlGaN is grown on the substrate, and then an AlGaN layer is grown on the AlN layer, so that the GaN layer grown on the AlGaN layer has a very small lattice mismatch and thermal mismatch with the AlGaN layer, thereby improving the quality of the GaN layer. y1 Ga(1-y1) The N / GaN superlattice can effectively relieve stress, thereby obtaining high-quality GaN thin films and providing a good substrate for subsequent epitaxial growth. By setting up an electron blocking layer with a wider bandgap or a highly p-doped hole injection layer, carriers in the active region (multiple quantum wells) are confined, increasing the overlap of hole and electron wave functions and achieving higher radiative recombination efficiency. This further addresses the problem of decreased internal quantum efficiency with increasing injection current density.

[0039] This patent utilizes a hexagonal close-packed arrangement of light-emitting units to maximize the use of the epitaxial wafer area. Furthermore, the unique hexagonal display unit structure facilitates the design of mapping algorithms to convert traditional sub-light-emitting unit data into hexagonal close-packed sub-light-emitting unit data. By leveraging the continuity of values ​​between light-emitting units and the borrowing between adjacent sub-light-emitting units, it achieves the same display effect as traditional RGBW strip-arranged LEDs while significantly reducing the number of LEDs required. This results in a higher PPI per unit area, achieving a more delicate and realistic display effect, and has broad application scenarios. Attached Figure Description

[0040] Exemplary embodiments are illustrated in the accompanying drawings. The embodiments and drawings disclosed herein should be considered illustrative rather than restrictive.

[0041] Figure 1 This is a cross-sectional view and a top view of a GaN-based micro-LED display unit when the N-type GaN hexagonal island array ends at a mesa, according to one embodiment of the present invention. In the figures: 101 is the substrate, 102 is the GaN-based composite buffer layer, 103 is the N-type GaN layer, 104 is the mask layer containing a micro-hole array, 105 is the hexagonal close-packed N-type GaN hexagonal island array, 106 is the quantum well array, 107 is the carrier control layer, and 108 is the P-type In... x Ga 1-x N layers. In the top-view diagram, the numbers in a single hexagon represent the row and column numbers of that display unit from left to right.

[0042] Figure 2 This is a cross-sectional view and a top view of a GaN-based micro-LED display unit when the N-type GaN hexagonal island array ends in a pyramid shape, according to one embodiment of the present invention. In the figures: 101 is the substrate, 102 is the GaN-based composite buffer layer, 103 is the N-type GaN layer, 104 is the mask layer containing a micro-pore array, 105 is the hexagonal close-packed N-type GaN hexagonal island array, 106 is the quantum well array, 107 is the carrier control layer, and 108 is the P-type In... x Ga 1-xN layer. The numbers in a single hexagon in the schematic top view represent the row number and the column number of the display unit from left to right. DETAILED DESCRIPTION

[0043] The application will be further described below with reference to the drawings. The following examples are only used to more clearly illustrate the technical solutions of the application, and cannot be used to limit the protection scope of the application.

[0044] In the description of the application, it should be understood that the terms “center”, “longitudinal”, “transverse”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer” and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application. In the description of the application, unless otherwise specified, the meaning of “a plurality of” is two or more.

[0045] Example 1:

[0046] The specific application structure is as follows Figure 1 , including a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a micropore array, a hexagonal 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, arranged in order from bottom to top; wherein the hexagonal close-packed N-type GaN hexagonal island array 105 is a regionally selective epitaxial growth on the mask layer 104 containing a micropore array, and is composed of N-type GaN hexagonal pyramids independent of each other; the quantum well array 106, the carrier regulation layer 107, and the P-type In x Ga 1-x N layer 108 are epitaxial structures grown on the top of the N-type GaN hexagonal pyramid.

[0047] The specific application parameters and preparation method of the structure of example 1 are as follows:

[0048] A (111) surface Si substrate is selected. A 40 nm thick AlN film, 20 periods of a single period of 7 nm thick Al y1 Ga (1-y1) N / GaN superlattice, 15 periods of a single period of 7 nm thick In y2 Ga (1-y2)An N / GaN superlattice and a 2 μm thick GaN film serve as the GaN-based composite buffer layer 102; y1 = 0.1 and y2 = 0.7 are controlled simultaneously. The GaN doping concentration is 9 × 10⁻⁶. 17 cm -3 The Si element is controlled to have an electron concentration less than 1.5 times the Si element doping concentration to form an N-type GaN layer 103.

[0049] A 30nm thick SiO2 layer is formed on an N-type GaN layer 103. A micro-hole array is etched from top to bottom using a process technology, exposing the underlying N-type GaN layer 103 in the micro-holes. The diameter of the micro-holes is controlled at 1μm, and they are arranged in a close-packed manner with the center of each micro-hole in mind. The center of any micro-hole is equidistant from the center of the six adjacent micro-holes, with a distance of 25μm, forming a mask layer 104 containing the micro-hole array.

[0050] A hexagonal close-packed N-type GaN hexagonal island array 105 is set in the aforementioned micropores, and the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal frustum structure.

[0051] 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 arranged sequentially, starting from the first display unit in that 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 arranged sequentially, starting from the first display unit in that row.

[0052] Five Al atoms, each with a thickness of 10 nm, were placed on the aforementioned quantum well. y4 Ga (1-y4) N / GaN superlattice, wherein the molar composition y4 is 0.3, and Al y4 Ga (1-y4) The thickness of N is negatively correlated, acting as a carrier regulation layer.

[0053] A 150nm P-type In layer is placed above the aforementioned carrier modulation layer. x Ga 1-x The N-layer is 108, with a molar composition x of 0.07 and a Mg doping concentration of 2.5 × 10⁸. 19 cm -3 Its hole concentration is 1×10 18 cm -3 ; among which P-type In x Ga 1-x Within a 20 nm thick region on the upper surface of the N-layer 108, the Mg doping concentration is 1 × 10⁻⁶. 20 cm -3 Its hole concentration is 5×10 18 cm -3 .

[0054] The preparation method of this example comprises the following steps:

[0055] a) using a (111) Si substrate, growing a GaN-based composite buffer layer 102 based on epitaxial growth technology;

[0056] b) continuing epitaxial growth of an N-type GaN layer 103 on the GaN-based composite buffer layer 102;

[0057] c) preparing a dielectric layer on the N-type GaN layer 103, using micro-processing technology to process a micro-hole array on the dielectric layer, exposing the underlying N-type GaN layer 103, and forming a mask layer 104 containing the micro-hole array;

[0058] d) using selective epitaxial growth technology to perform selective epitaxy using the above micro-holes, and then achieving lateral epitaxy by controlling the temperature of epitaxial growth,

[0059] the V / III ratio, the reaction chamber pressure, and the carrier gas and reactant source to form a hexagonally packed N-type GaN hexagonal island array 105;

[0060] e) during epitaxial growth, stopping the supply of Ga source, reducing the flow of N source, and performing in-situ annealing treatment on the N-type GaN hexagonal island array

[0061] 105 to cause in-situ decomposition of the N-type GaN hexagonal island to form an N-type GaN hexagonal pyramid structure;

[0062] f) using epitaxial growth technology to continue epitaxial growth of a quantum well array 106, a carrier regulation layer 107, and a P-type In x Ga 1-x N layer 108 on the N-type GaN hexagonal pyramid structure, completing the epitaxial structure preparation of this LED display unit.

[0063] Example 2:

[0064] The specific application structure is as Figure 2 follows: a substrate 101, a GaN-based composite buffer layer 102, an N-type GaN layer 103, a mask layer 104 containing a micro-hole array, a hexagonally 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 arranged in order from bottom to top; wherein the hexagonally packed N-type GaN hexagonal island array 105 is selectively epitaxially grown on the mask layer 104 containing the micro-hole array and is composed of independent N-type GaN hexagonal pyramids; the quantum well array 106, the carrier regulation layer 107, and the P-type In x Ga 1-xThe N-type GaN layer 108 is an epitaxial structure grown on six sides of an N-type GaN hexagonal prism;

[0065] The specific application parameters and preparation method of the example 2 structure are as follows:

[0066] A (002) sapphire substrate is selected. A 5 nm thick AlN film, 20 periods of a single period 7 nm thick In y3 Ga (1-y3) N / GaN superlattice and a 2 pm thick GaN film are sequentially arranged above the (002) sapphire substrate from bottom to top, serving as a GaN-based composite buffer layer 102; meanwhile, y3 = 0.07 is controlled. 18 cm -3 A Si element with a concentration of 7 x 10 19 cm -3 is doped in the GaN, and the electron concentration is controlled to be less than 1.5 times the Si element doping concentration, forming an N-type GaN layer 103.

[0067] A 25 nm thick hBN is arranged on the N-type GaN layer 103, and a micropore array is etched from top to bottom by a process technique, and the lower N-type GaN layer 103 is exposed in the micropores; wherein the diameter of the micropores is controlled to be 2 pm, and the micropores are arranged in a close-packed form with the center of the micropores, and the distance between the center of any micropore and the center of the adjacent six micropores is 30 pm, forming a mask layer 104 containing a micropore array.

[0068] A hexagonal close-packed N-type GaN hexagonal island array 105 is arranged in the above micropores, and the N-type GaN hexagonal island array 105 is an N-type GaN hexagonal prism array.

[0069] The odd rows of the N-type GaN hexagonal island array are sequentially arranged with red, blue, green, and white GaN-based micro-LED display units starting from the first display unit of the row. The even rows of the N-type GaN hexagonal island array are sequentially arranged with green, white, red, and blue GaN-based micro-LED display units starting from the first display unit of the row.

[0070] A 6-period, single-period 5 nm thick Al y4 Ga (1-y4) N / GaN superlattice is arranged on the above quantum well, wherein the molar component y4 is 0.4, and the thickness of the Al y4 Ga (1-y4) N is in a negative correlation relationship. It serves as a carrier regulation layer.

[0071] A 150 nm P-type In x Ga 1-x N layer 108 is arranged above the above carrier regulation layer, the molar component x is 0.1, and the Mg element doping concentration is 3 x 10 19 cm -3hole concentration of 1.5 x 1018cm-3 18 cm -3 -3; wherein the Mg element doping concentration in the 15 nm thickness region on the upper surface of the P-type In x Ga 1-x N layer 108 is 1.8 x 1018cm-3, and the hole concentration is 7 x 1018cm-3 20 cm -3 -3. 18 cm -3 -3.

[0072] The preparation method of this example includes the following steps:

[0073] a) using a (002) sapphire substrate, growing a GaN-based composite buffer layer 102 based on epitaxial growth technology;

[0074] b) continuing to epitaxially grow a N-type GaN layer 103 on the GaN-based composite buffer layer 102;

[0075] c) preparing a dielectric layer on the N-type GaN layer 103, using micro-processing technology to process a micro-hole array on the dielectric layer, exposing the underlying N-type GaN layer 103, and forming a mask layer 104 containing the micro-hole array;

[0076] d) using selective epitaxial growth technology to perform selective epitaxy using the above micro-holes, 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 packed N-type GaN hexagonal island array 105, i.e., a N-type GaN hexagonal pyramid array;

[0077] e) using epitaxial growth technology to continue epitaxial growth of a quantum well array 106, a carrier regulation layer 107, and a P-type In x Ga 1-x N layer 108 on the six sides of the N-type GaN hexagonal island, to complete the epitaxial structure preparation of this LED display unit.

[0078] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A GaN-based micro-LED display unit, characterized in that: The application relates to a GaN-based quantum well structure, which comprises, from bottom to top, a substrate (101), a GaN-based composite buffer layer (102), an N-type GaN layer (103), a mask layer (104) containing a micro-pore array, a hexagonal island array (105) of N-type GaN in a hexagonal close-packed structure, 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 substrate (101) is one of a (111) Si substrate or a (002) sapphire substrate; when the substrate (101) is the (111) Si substrate, the GaN-based composite buffer layer (102) comprises, from bottom to top, 10-50nm-thick AlN film, 5-30 periods of Al y1 Ga (1-y1) N / GaN superlattice with a single period thickness of 5-15nm, 10-20 periods of In y2 Ga (1-y2) N / GaN superlattice with a single period thickness of 5-10nm and 1-3mu.m-thick GaN film; when the substrate (101) is the (002) sapphire substrate, the GaN-based composite buffer layer (102) comprises, from bottom to top, 3-10nm-thick AlN film, 10-30 periods of In y3 Ga (1-y3) N / GaN superlattice with a single period thickness of 5-10nm and 1-3mu.m-thick GaN film. Wherein, 0.05 < y1 < 0.2, 0.05 < y2 < 0.15, 0.03 < y3 < 0.10; the hexagonal island array (105) of N-type GaN in hexagonal close packing is grown by selective epitaxy on the mask layer (104) containing micro-hole array, and is composed of N-type GaN hexagonal island structure independent of each other, which is N-type GaN hexagonal platform when the top ends in platform, and is N-type GaN hexagonal pyramid when the top ends in pyramid; when the N-type GaN hexagonal island array (105) is N-type GaN hexagonal platform structure, 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 of the platform of N-type GaN hexagonal platform; when the N-type GaN hexagonal island array (105) is N-type GaN hexagonal pyramid structure, 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 sides of N-type GaN hexagonal pyramid; the thickness of the P-type In x Ga 1-x N layer (108) is between 50-200 nm, the molar component x is 0-0.15, when x = 0, it is GaN; the Mg element doping concentration is 2×10 19 cm -3 -5×10 19 cm -3 , and the hole concentration is not less than 1×10 18 cm -3 ; wherein the Mg element doping concentration in the 5-30 nm thickness area on the surface of the P-type In x Ga 1-x N layer (108) is not less than 1×10 20 cm -3 , and the hole concentration is not less than 5×10 18 cm -3 . 2.The GaN-based micro-LED display unit of claim 1, wherein: The mask layer (104) containing the micropore array is a micropore array etched from top to bottom by a process after a 5-50 nm thick dielectric film of SiO2, SiN or hBN is plated on the N-type GaN layer (103), and the N-type GaN layer (103) under the micropores is exposed; wherein the diameter of the micropores is between 0.5-5 μm, and the micropores are arranged in a close-packed form with the center of each micropore, and the distance between the center of any micropore and the center of any adjacent micropore is between 5-50 μm. 3.The GaN-based micro-LED display unit of claim 1, wherein: The hexagonal close-packed N-type GaN hexagonal island array (105) is a hexagonal island-shaped N-type GaN array structure obtained by secondary epitaxial growth in a selected area by one of MOCVD, HVPE and MBE based on the preparation of the mask layer (104) containing the micropore array, and the bottom surface of the island is a regular hexagon with an inscribed circle diameter of 3-40 μm; wherein the top view of any N-type GaN hexagonal island is a regular hexagon, and any two N-type GaN hexagonal islands are not in contact, and the adjacent bottom edges of any two adjacent N-type GaN hexagonal islands are parallel and aligned at both ends. 4.The GaN-based micro-LED display unit of claim 1, wherein: The N-type GaN hexagonal island in the hexagonal array (105) of N-type GaN hexagonal islands in hexagonal close packing is one of a regular hexagonal pyramid or a regular hexagonal frustum; when the N-type GaN hexagonal island is a regular hexagonal pyramid, the six side faces are all (10-11) crystal faces or (10-12) crystal faces of GaN, at this time, the hexagonal close-packed quantum well array (106), the carrier regulation layer (107) and the P-type In x Ga 1-x N layer (108) are all epitaxially grown on the inclined surface; when the N-type GaN hexagonal island is a regular hexagonal frustum, the top face is a (0002) crystal face of GaN, and the six side faces are all (10-11) crystal faces or (10-12) crystal faces of GaN, at this time, the hexagonal close-packed quantum well array (106), the carrier regulation layer (107) and the P-type In x Ga 1-x N layer (108) are all epitaxially grown on the top face. 5.The GaN-based micro-LED display unit of claim 1, wherein: The boundary of the hexagonal close-packed N-type GaN hexagonal island array is rectangular and has a row-column feature; in the odd rows of the N-type GaN hexagonal island array, red, blue, green and white GaN-based micro-LED display units are arranged in sequence from the first display unit in the row; in the even rows of the N-type GaN hexagonal island array, green, white, red and blue GaN-based micro-LED display units are arranged in sequence from the first display unit in the row; wherein the red 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 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 GaN-based micro-LED display unit is above the N-type GaN hexagonal island and includes 1-2 pairs of blue quantum wells from bottom to top; and the white 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.

6. The GaN-based micro-LED display unit of claim 1, wherein: The carrier modulation layer (107) is one of an electron blocking layer or a hole injection layer; wherein the electron blocking layer is an Al y4 Ga (1-y4) N / GaN superlattice with a molar composition y4 between 0.1 and 0.6 and in negative correlation with the thickness of Al y4 Ga (1-y4) N; and the hole injection layer is a P-doped Al y5 Ga (1-y5) N / In y6 Ga (1-y6) N / GaN superlattice with a Mg element doping concentration between 5x10 17 cm -3 and 1x10 19 cm -3 , and a hole concentration not higher than 1x10 18 cm -3 .

7. A method for fabricating a GaN-based micro LED display unit as described in claim 1, characterized in that: The structure comprises, from bottom to top, a substrate (101), a GaN-based composite buffer layer (102), an N-type GaN layer (103), a mask layer containing a micropore array (104), a hexagonal close-packed N-type GaN hexagonal island array (105), a quantum well array on the N-type GaN hexagonal island (106), a carrier regulation 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 grown by selective epitaxy on the mask layer containing a micropore array (104) and is composed of independent N-type GaN hexagonal island structures, the N-type GaN hexagonal island array (105) is an N-type GaN hexagonal platform structure, the quantum well array (106), the carrier regulation layer (107), and the P-type In x Ga 1-x N layer (108) are epitaxial structures grown on the top of the N-type GaN hexagonal platform. The preparation method of the LED display unit comprises the following steps: a) using a (111) Si substrate or a (002) sapphire substrate, growing a GaN-based composite buffer layer (102) based on epitaxial growth technology; 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), the dielectric layer being one of SiO2, SiN or hBN, and using a micro-processing technology to process a micropore array on the dielectric layer to expose the underlying N-type GaN layer (103) and form a mask layer (104) containing the micropore array; d) using the above-mentioned micro-holes to perform selective epitaxy by using selective epitaxial growth technology, and then realizing lateral epitaxy by controlling the temperature, V / III ratio, reaction chamber pressure and carrier gas and reactant source of epitaxial growth, to form a hexagonal island array (105) of N-type GaN in hexagonal close packing; e) during epitaxial growth, stopping the supply of Ga source, reducing the flow of N source, and performing in-situ annealing treatment on the N-type GaN hexagonal island array (105) to decompose the N-type GaN hexagonal island in-situ, to form a N-type GaN hexagonal pyramid structure; f) continue to epitaxially grow quantum well array (106), carrier modulation layer (107) and P-type In x Ga 1-x N layer (108) on the N-type GaN hexagonal prism structure using epitaxial growth technique, and complete the epitaxial structure preparation of the LED display unit.

8. A method for fabricating a GaN-based micro LED display unit as described in claim 1, characterized in that: The structure comprises, from bottom to top, a substrate (101), a GaN-based composite buffer layer (102), an N-type GaN layer (103), a mask layer containing a micropore array (104), a hexagonal close-packed N-type GaN hexagonal island array (105), a quantum well array on the N-type GaN hexagonal island (106), a carrier regulation 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 grown by selective epitaxy on the mask layer containing a micropore array (104) and is composed of N-type GaN hexagonal island structures independent of each other, the N-type GaN hexagonal island array (105) is an N-type GaN hexagonal pyramid structure, the quantum well array (106), the carrier regulation layer (107), and the P-type In x Ga 1-x N layer (108) are epitaxial structures grown on the six side surfaces of the N-type GaN hexagonal pyramid. The preparation method of the LED display unit comprises the following steps: a) using a (111) surface Si substrate or a (002) sapphire substrate, growing a GaN-based composite buffer layer (102) based on epitaxial growth technology; 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), the dielectric layer being one of SiO2, SiN or hBN, using micro-processing technology to process a micro-hole array on the dielectric layer to expose the underlying N-type GaN layer (103), to form a mask layer (104) containing the micro-hole array; d) using the above-mentioned micro-holes to perform selective epitaxy by using selective epitaxial growth technology, and then realizing lateral epitaxy by controlling the temperature, V / III ratio, reaction chamber pressure and carrier gas and reactant source of epitaxial growth, to form a hexagonal island array (105) of N-type GaN in hexagonal close packing; e) continue to epitaxially grow quantum well array (106), carrier modulation layer (107) and P-type In x Ga 1-x N layer (108) on the six side faces of the N-type GaN hexagonal island using epitaxial growth technique, complete the epitaxial structure preparation of this LED display unit.

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