CN119300570B - Micro-LED structure with double emergent directions and preparation method thereof - Google Patents

Abstract

This invention discloses a dual-emission Micro-LED structure and its fabrication method. The structure includes an N-type GaN layer with a non-polar upward crystal plane, a mask layer, N-type In _x Ga _1-x N triangular islands, a quantum well layer, a P-type layer, electrodes, and other functional layers. This invention utilizes selected area epitaxy combined with lateral epitaxy to obtain highly symmetrical N-type In _x Ga _1-x N triangular islands, and grows LED epitaxial layers on the two symmetrical bevels of the triangular islands to form a dual-emission Micro-LED structure, which can serve as the basic display unit for near-eye naked-eye 3D displays. Simultaneously, growing independent epitaxial LED structures on the bevels of the triangular islands avoids the adverse effects of etching damage to the quantum well and P-type layer caused by traditional microfabrication techniques, effectively suppressing the edge effect of each light-emitting unit and improving luminous efficiency. Arranging the light-emitting units in a close-packed configuration maximizes the utilization of the epitaxial wafer area, thus maximizing economic benefits.

Description

Micro-LED structure with double emergent directions and preparation method thereof

Technical Field

The invention relates to a Micro-LED structure with double emergent directions and a preparation method thereof, belonging to the fields of semiconductor light-emitting devices, micro LED displays and the like.

Background

The Micro light emitting diode (Micro-LED) display technology has wide application prospect due to the advantages of low energy consumption, long service life, good color rendering property and the like, and particularly has wide application prospect in the high-definition display fields of various sizes and shapes such as large-scale displays, consumer electronics, vehicle-mounted displays, virtual Reality (VR), augmented Reality (AR), wearable displays and the like. The current mainstream naked eye three-dimensional (3D) technology utilizes a specific algorithm to interactively arrange images, and then realizes the naked eye 3D effect through a parallax barrier arranged between a display backlight source and a liquid crystal panel, but the problem that the brightness is reduced and the resolution of a screen is reduced due to the fact that a backlight module is blocked by the parallax barrier exists. In the near-eye and naked-eye 3D field, the screen resolution seriously affects the picture display quality due to the limitation of the distance between the device and the observer and the area of the light-emitting panel. Researchers have developed a variety of techniques for increasing resolution, such as increasing pixel density by time multiplexing, using Micro-LEDs for small-scale high resolution displays. The PPI of the screen is improved through Micro-LEDs, and further, the realization of high-resolution near-to-eye 3D display is a popular research direction. Therefore, micro-LED display technology has become one of the next generation display technologies of great interest to internationally related research institutions and enterprises. However, how to realize a 3D full-color display is one of the main challenges facing Micro-LED display technology. This is mainly due to the fact that under the prior art conditions, it is also difficult to realize monolithic integration of red, green and blue three primary colors Micro-LEDs.

Currently, high-efficiency solid-state visible light sources are mainly nitride GaN-based blue-green LEDs and phosphide AlInGaP-based red LEDs. When the light emission wavelength of AlInGaP-based materials is modulated from red to yellow, their bandgap gradually transitions from a direct bandgap to an indirect bandgap, resulting in a rapid decrease in efficiency. This physical property severely constrains its development and application as a short wavelength light source. In addition, alInGaP-based LEDs have a strong surface recombination, which is further exacerbated by etching damage that occurs during the fabrication of Micro-LEDs, resulting in severe non-radiative recombination. Research shows that when the size of the LED chip is reduced to 262 mu m, the external quantum efficiency is smaller than 6%, when the size is further reduced to 32 mu m, the external quantum efficiency is smaller than 1%, and even the reported chip with the size of 50 multiplied by 50 mu m ² has the external quantum efficiency smaller than 0.12%. This phenomenon severely restricts the application of AlInGaP-based LEDs as red light sources in the Micro-LED display field. The low light efficiency of the long-band InGaN-based LED is due to the difficulty In epitaxial growth of InGaN with high In composition, but the problem can be solved by technical means and has been advanced to some extent. On the other hand, the InGaN-based LED has relatively smaller non-radiative recombination caused by etching damage, and the light-emitting wavelength of the InGaN-based LED can cover the whole visible light wave band, so the InGaN-based LED is most hopefully applied to the fields of Micro-LED display, high-speed visible light communication and the like, and the efficiency of the red light wave band is low at present. Therefore, it is an important research topic to solve the problem of epitaxial growth of InGaN thin films with high In composition and the problem of non-radiative recombination caused by etching damage.

Disclosure of Invention

In near-to-eye naked eye 3D display, the most main reason for the difficulty in Micro-LED application is that the high-density Micro-LED lattice structure capable of realizing the 3D visual effect is difficult to design, and when the Micro-LED structure is prepared, quantum well etching damage is easy to occur, so that severe non-radiative recombination is caused, and the light efficiency is reduced. The Micro-LED structure with the double emitting directions is characterized In that a Micro-LED structure with independent In _xGa_1-x N triangle island structures is further epitaxially grown according to the etching damage problem generated when the Micro-LED structure is manufactured, damage of etching to multiple quantum wells is fundamentally avoided, radiation recombination efficiency of nitride Micro-LEDs is improved, light emitting units are arranged on the basis of close packing, the area of an epitaxial wafer is utilized to the greatest extent, meanwhile, the unique Micro-LED structure with the double emitting directions emits light rays with two different directions when working, the structure can be further designed to enable the light rays with the two directions to enter left eyes and right eyes respectively to generate parallax effect, a 3D display effect is achieved, meanwhile, the structure is convenient for achieving design of a 3D display algorithm, fine and real near-eye naked eye 3D picture display is achieved, and economic benefits are maximized.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

On one hand, the invention provides a Micro-LED structure with double emergent directions, which comprises an N-type GaN layer 101 with an upward crystal face of a nonpolar face, a mask layer 102 containing a micropore array, an N-type In _xGa_1-x N triangular island 103 with an In component of 0-0.35, a strain regulating layer 104, a quantum well layer 105, a carrier regulating layer 106, a P-type In _yGa_1-y N layer 107 with an In component of y, a PL electrode 108 and a PR electrode 109 which have good ohmic contact with the P-type In _yGa_1-y N layer 107, and an N electrode 1010 which has good ohmic contact with the N-type GaN layer 101, wherein the N-type GaN layer 101 is sequentially arranged from bottom to top.

The bottom of the N-type In _xGa_1-x N triangular island 103 is obtained by epitaxial growth upwards from micropores of the mask layer 102, the bottom comprises two laterally symmetrical triangular inclined planes and a triangular side surface perpendicular to the bottom surface, the strain regulating layer 104, the quantum well layer 105, the carrier regulating layer 106, the P-type In _yGa_1-y N layer 107 and the PL electrode 108 (or the PR electrode 109) are all laterally symmetrically arranged on the inclined planes of the N-type In _xGa_1-x N triangular island 103, parameters of the same structure are identical, and the left-side strain regulating layer 104, the quantum well layer 105, the carrier regulating layer 106, the P-type In _yGa_1-y N layer 107, the PL electrode 108 and the N electrode 1010 and the left-side N-type In _xGa_1-x N triangular island inclined planes form a Micro-LED structure L, and the right-side strain regulating layer 104, the quantum well layer 105, the carrier regulating layer 106, the P-type In _yGa_1-y N layer 107, the PR electrode 109 and the right-side N-type In _xGa_1-x N triangular island inclined planes form a Micro-LED structure R. The N electrode 1010 may be positioned on top of or on the bottom of the GaN layer 101 whose upward crystal plane is a nonpolar plane, respectively, and establish a good ohmic contact. When the N electrode 1010 is arranged at the top, the N electrode 1010 is positioned In front of two inclined planes of the In _xGa_1-x N triangular island, the N electrode 1010 is In non-contact with the N-type In _xGa_1-x N triangular island 103, and when the N electrode 1010 is arranged at the bottom, the N electrode covers the bottom of the whole N-type GaN layer 101 with the upward crystal face being a nonpolar plane.

Preferably, the mask layer 102 containing the micropore array is a micropore array which is prepared by etching one dielectric film of SiO ₂, siN or hBN with the thickness of 5-50 nm on the N-type GaN layer 101 from top to bottom through a process technology, the lower N-type GaN layer 101 is exposed in micropores, the diameters of the micropores are 0.5-5 mu m, the micropores are arranged in a close-packed mode at the centers of the micropores, the distances between the centers of any micropores and the centers of the adjacent 6 micropores are equal, and the micropores are adjustable according to actual needs.

Preferably, the GaN layer 101 with the upward crystal face being a nonpolar plane and the N-type In _xGa_1-x N triangular island 103 have the upward crystal face being a (11-20) plane at the same time, and at the moment, the crystal faces of the left and right inclined planes are simultaneously one of {1-101} or {1-102} crystal face groups, and since the crystal face {1-101} or {1-102} is a lower potential energy plane, a regular triangular island can be formed, and the upper layer structure can be grown In a regular and controllable manner, in addition, the GaN layer 101 with the upward crystal face being a nonpolar plane and the crystal face upward of the N-type In _xGa_1-x N triangular island 103 can also be simultaneously (1-100) planes, at the moment, the crystal faces of the left and right inclined planes are simultaneously {20-21} crystal face groups, and the side of the N-type In _xGa_1-x N triangular island 103 perpendicular to the bottom face is a (000-1) plane. The light-emitting units are arranged by using the close packing as a base, so that the area of the epitaxial wafer can be effectively utilized to the greatest extent. The mesa structure is arranged, so that the damage of etching to the multiple quantum wells is fundamentally avoided, the radiation recombination efficiency of the nitride Micro-LED is improved, the mesa structure is beneficial to releasing the bottom layer stress, the crystal quality of the whole structure of the LED is improved, the influence of defects and polarization on current carriers is further weakened, and the luminous efficiency of the LED is improved. Meanwhile, the Micro-LED structure with unique double emergent directions can emit light rays in two different directions when in operation, and the structure can be further designed to enable the light rays in the two directions to enter left and right eyes respectively to generate parallax effect, so that 3D display effect is realized; meanwhile, the structure is convenient for realizing the design of a 3D display algorithm, so that the fine and real near-to-eye naked eye 3D picture display is realized, and the economic benefit is maximized.

Preferably, when the diameter of the micropores of the mask layer 102 is not greater than 1.5 μm, the diameter of the circumscribed circle of the N-type In _xGa_1-x N triangular island 103 In the plane is adjusted to be 5-20 μm as required, because when the micropores are smaller, regular islands are easy to form, and the size of the islands can be controlled as required, and when the diameter of the micropores of the mask layer 102 is greater than 1.5 μm, the diameter of the circumscribed circle of the N-type In _xGa_1-x N triangular island 103 In the plane is 3-4 times the diameter of the micropores, but is not more than 15 μm at maximum. When the micropores are large, the islands are liable to be irregular, thus defining the size of the islands.

Preferably, the strain regulating layer 104 covers the whole left and right inclined planes of the N-type In _xGa_1-x N triangular island 103, But not at the edge In the middle of the N-type In _xGa_1-x N triangle island 103; when the molar component x of the N-type In _xGa_1-x N triangular island is less than or equal to 0.05, the strain regulating layer 104 is a 1-3 period GaN/Al _x1Ga_1-x1 N/GaN composite layer from bottom to top, wherein the thickness of Al _x1Ga_1-x1 N is smaller than 3nm, x1<0.15, namely when x is smaller, the stress of In _xGa_1-x N is smaller, in-plane stress In a certain c direction can be compensated only by introducing AlGaN with a lower component, when the molar component x of the N-type In _xGa_1-x N triangular island is less than 0.05< x <0.15, the strain regulating layer 104 is a 1-3 period GaN/Al _x1Ga_1-x1N/GaN/In_xGa_1-x N composite layer, wherein the molar component x of the In _xGa_1-x N is the molar component of the N-type In _xGa_1-x N triangular island, and the thickness of Al _x1Ga_1-x1 N is controlled to be smaller than 2nm, wherein the lattice mismatch value of GaN and Al _x1Ga_1-x1 N In the c direction is delta ₁＝-0.03915×x1;In_xGa_1-x N and the lattice mismatch value of delta ₂ = 0.09797 x In the c direction, and the lattice mismatch value of GaN and the lattice mismatch value of In _x1Ga_1-x1 N In the c direction is 3438N is equal to that the total quantum well quality of the LED is improved by adjusting the molar component x 1-3 to the molar component x and the molar component x 2N from bottom to top, thereby the quantum well is achieved.

Preferably, the left and right groups of quantum wells are symmetrically covered on the top of the strain regulating layer 104, have the same area and are not connected with each other, the shape of the two groups of quantum wells is consistent with that of the inclined plane of the GaN three-dimensional triangular island 103, when the light emitting wavelength of the quantum wells is red light, green light and blue light respectively, the number of pairs of quantum wells is 1-2 pairs, 2-4 pairs and 3-5 pairs, the layer structure of the quantum wells is In _x2Ga_1-x2N/GaN/Al_x3Ga_1-x3 N/GaN, as the lattice mismatch value of In _x2Ga_1-x2 N and GaN In the c direction is delta ₃＝0.09797×x2;Al_x3Ga_1-x3 N and the lattice mismatch value of GaN In the c direction is delta ₄ = -0.03915 x3, the lattice mismatch value of In _x2Ga_1-x2 N and Al _x3Ga_1-x3 N In the c direction is equal to that of GaN by adjusting molar components x2 and x3, namely, the thickness of In _x2Ga_1-x2 N is 2-4 nm, the total thickness of two layers of GaN and Al _x3Ga_1-x3 N is not more than 6nm, further better stress is released, and the radiation recombination efficiency of the quantum wells is improved.

Preferably, the carrier regulating layer 106 is one of an electron blocking layer and a hole injection layer, wherein the electron blocking layer is an Al _y1Ga_(1-y1) N/GaN superlattice with a single period of 2-8 periods and a thickness of less than 8nm, wherein the molar component y1 is between 0.1 and 0.6 and is in negative correlation with the thickness of Al _y1Ga_(1-y1) N, the hole injection layer is an Al _y2Ga_(1-y2)N/In_y3Ga_(1-y3) N/GaN superlattice with P doping and an overall thickness of less than 30nm, the doping concentration of Mg element is between 5 multiplied by 10 ¹⁷cm^-3～1×10¹⁹cm^-3, and the hole concentration is not higher than 1 multiplied by 10 ¹⁸cm^-3. By arranging the electron blocking layer or the high P doped hole injection layer with wider forbidden bandwidth, the limitation of carriers in an active region, namely the multi-quantum well is realized, so that the overlapping of hole and electron wave functions in the multi-quantum well is increased, and higher radiation recombination efficiency is realized.

Preferably, the thickness of the P-type In _yGa_1-y N layer 107 is 50-200 nm, the molar component y is 0-0.15, gaN is adopted when y=0, the doping concentration of Mg element is 2×10 ¹⁹cm^-3～5×10¹⁹cm^-3, the hole concentration is not lower than 1×10 ¹⁸cm^-3, wherein the doping concentration of Mg element is not lower than 1×10 ²⁰cm^-3 In the region of 5-30 nm thickness on the upper surface of the P-type In _yGa_1-y N layer 107, and the hole concentration is not lower than 5×10 ¹⁸cm^-3.

On the other hand, the invention provides a preparation method of the Micro-LED structure with double emergent directions.

The preparation method of the Micro-LED structure with double emergent directions can be used for preparing an N-type GaN layer 101 with an upward crystal face of a nonpolar face, a mask layer 102 containing a micropore array, an N-type In _xGa_1-x N triangular island 103 with an In component of 0-0.35, a strain regulating layer 104, a quantum well layer 105, a carrier regulating layer 106, a P-type In _yGa_1-y N layer 107 with an In component of y, which are sequentially arranged from bottom to top, A PL electrode 108 and a PR electrode 109 having good ohmic contact with the P-type In _yGa_1-y N layer 107, and an N electrode 1010 having good ohmic contact with the N-type GaN layer 101. The bottom of the N-type In _xGa_1-x N triangular island 103 is obtained by epitaxial growth upwards from the micropores of the mask layer 102, and comprises two bilaterally symmetrical triangular inclined planes and one triangular side surface perpendicular to the bottom surface except the bottom, wherein a strain regulating layer 104, a quantum well layer 105, a carrier regulating layer 106, a P-type In _yGa_1-y N layer 107 and a PL electrode 108 (or PR electrode 109) are all bilaterally symmetrically arranged on the inclined planes of the N-type In _xGa_1-x N triangular island 103, and parameters of the same structure are completely the same, a strain regulating layer 104 on the left side, the quantum well layer 105, the carrier regulating layer 106, the P-type In _yGa_1-y N layer 107, the PL electrode 108, the N electrode 1010 and the left N-type In _xGa_1-x N triangle island inclined plane form a Micro-LED structure L, the strain regulating layer 104, the quantum well layer 105, the carrier regulating layer 106, the P-type InyGa1-yN layer 107, the right side, PR electrode 109, N electrode 1010 and right N-type In _xGa_1-x N triangle island slope form Micro-LED structure R. The N electrode 1010 is arranged on top of the N-type GaN layer 101 with the upward crystal face being a nonpolar face and positioned In front of two inclined planes of the In _xGa_1-x N triangular island, and the N electrode 1010 is In non-contact with the N-type In _xGa_1-x N triangular island 103. The preparation method of the Micro-LED structure comprises the following steps:

a) Preparing a nonpolar N-type GaN template as an N-type GaN layer 101 with nonpolar upward crystal face, or epitaxially growing an N-type GaN film with nonpolar upward crystal face on a sapphire, si or SiC substrate as N-type GaN film

A GaN layer 101;

b) Preparing a non-metal compound dielectric layer on the N-type GaN layer 101 with the upward crystal face being a nonpolar face, and processing a micropore structure on the dielectric layer by using a micromachining technology to form a mask layer 102 containing a micropore array, so as to expose the underlying N-type GaN layer 101;

c) The selective epitaxy is carried out by using the micropore by using the selective epitaxy growth technology, and then the temperature of the epitaxy growth is controlled,

The V/III ratio, the pressure of the reaction chamber and the flow of the carrier gas and the reactant source realize lateral epitaxy, and the In component is formed to be more than or equal to 0 and less than or equal to x

N-type In _xGa_1-x N triangle island 103 of 0.35;

d) The strain regulating layer 104 is epitaxially grown on the basis of the N-type In _xGa_1-x N triangular island 103, and the micro-processing technology is combined, so that the strain regulating layer 104 covers the left and right inclined planes of the whole N-type In _xGa_1-x N triangular island 103 but does not cover the N-type In _xGa_1-

_x The edge in the middle of the N triangle island 103;

e) Epitaxially growing a quantum well layer 105 on the strain regulating layer 104, so that the quantum well is symmetrically covered on the top of the strain regulating layer 104;

f) Epitaxially growing a carrier regulating layer 106 on the quantum well layer 105 and covering the quantum well layer 105;

g) Epitaxially growing a P-type In _yGa_1-y N layer 107 on the carrier regulating layer 106 and covering the carrier regulating layer 106;

h) And etching the corresponding position of the N electrode 1010 on the mask layer 102 by using a standard micromachining technology to leak the N-type GaN layer 101 on the lower layer, and completing the preparation of the Micro-LED structure by selecting one of the techniques of evaporation coating and magnetron sputtering to complete the PL electrode 108, the PR electrode 109 and the N electrode 1010.

The preparation method of the Micro-LED structure with double emergent directions can be used for preparing an N-type GaN layer 101 with an upward crystal face of a nonpolar face, a mask layer 102 containing a micropore array, an N-type In _xGa_1-x N triangular island 103 with an In component of 0-0.35, a strain regulating layer 104, a quantum well layer 105, a carrier regulating layer 106, a P-type In _yGa_1-y N layer 107 with an In component of y, which are sequentially arranged from bottom to top, A PL electrode 108 and a PR electrode 109 having good ohmic contact with the P-type In _yGa_1-y N layer 107, and an N electrode 1010 having good ohmic contact with the N-type GaN layer 101. The bottom of the N-type In _xGa_1-x N triangular island 103 is obtained by epitaxial growth upwards from the micropores of the mask layer 102, and comprises two bilaterally symmetrical triangular inclined planes and one triangular side surface perpendicular to the bottom surface except the bottom, wherein a strain regulating layer 104, a quantum well layer 105, a carrier regulating layer 106, a P-type In _yGa_1-y N layer 107 and a PL electrode 108 (or PR electrode 109) are all bilaterally symmetrically arranged on the inclined planes of the N-type In _xGa_1-x N triangular island 103, and parameters of the same structure are completely the same, a strain regulating layer 104 on the left side, The quantum well layer 105, the carrier regulating layer 106, the P-type In _yGa_1-y N layer 107, the PL electrode 108, the N electrode 1010 and the left N-type In _xGa_1-x N triangle island inclined plane form a Micro-LED structure L, the strain regulating layer 104, the quantum well layer 105, the carrier regulating layer 106, the P-type In _yGa_1-y N layer 107, the right side, PR electrode 109, N electrode 1010 and right N-type In _xGa_1-x N triangle island slope form Micro-LED structure R. the N electrode 1010 is disposed at the bottom of the GaN layer 101 with an upward crystal plane being a nonpolar plane, and directly covers the bottom of the entire N-type GaN layer 101. The preparation method of the Micro-LED structure comprises the following steps:

a) Preparing a nonpolar N-type GaN template as an N-type GaN layer 101 with nonpolar upward crystal face, or epitaxially growing an N-type GaN film with nonpolar upward crystal face on a sapphire, si or SiC substrate as N-type GaN film

A GaN layer 101;

b) Preparing a non-metal compound dielectric layer on the N-type GaN layer 101 with the upward crystal face being a nonpolar face, and processing a micropore structure on the dielectric layer by using a micromachining technology to form a mask layer 102 containing a micropore array, so as to expose the underlying N-type GaN layer 101;

c) The selective epitaxy is carried out by using the micropore by using the selective epitaxy growth technology, and then the temperature of the epitaxy growth is controlled,

The V/III ratio, the pressure of the reaction chamber and the flow of the carrier gas and the reactant source realize lateral epitaxy, and the In component is formed to be more than or equal to 0 and less than or equal to x

N-type In _xGa_1-x N triangle island 103 of 0.35;

d) The strain regulating layer 104 is epitaxially grown on the basis of the N-type In _xGa_1-x N triangular island 103, and the micro-processing technology is combined, so that the strain regulating layer 104 covers the left and right inclined planes of the whole N-type In _xGa_1-x N triangular island 103 but does not cover the N-type In _xGa_1-

_x The edge in the middle of the N triangle island 103;

e) Epitaxially growing a quantum well layer 105 on the strain regulating layer 104, so that the quantum well is symmetrically covered on the top of the strain regulating layer 104;

f) Epitaxially growing a carrier regulating layer 106 on the quantum well layer 105 and covering the quantum well layer 105;

g) Epitaxially growing a P-type In _yGa_1-y N layer 107 on the carrier regulating layer 106 and covering the carrier regulating layer 106;

h) The preparation of the PL electrode 108 and the PR electrode 109 is completed by selecting one technique of evaporation coating and magnetron sputtering;

i) And (3) peeling off the structure above the N-type GaN layer 101 by using a peeling process, and preparing an N electrode 1010 at the original bottom of the N-type GaN layer 101 by using one of evaporation coating and magnetron sputtering to finish the preparation of the Micro-LED structure.

The beneficial effects are that:

The invention provides a Micro-LED structure with double emergent directions and a preparation method thereof. The design adopts micropore selective epitaxy technology to grow N-type In _xGa_1-x N with a lower potential energy surface, and a triangular island structure with high symmetry is naturally formed, so that regular controllable growth of an island surface layer structure is realized. And the independent Micro-LED full structure is prepared on the In _xGa_1-x N triangle island inclined plane, so that the damage of etching to the multiple quantum wells is fundamentally avoided, and the radiation recombination efficiency of the nitride Micro-LED is further improved. And the triangular island structure is favorable for releasing stress between layers during epitaxial growth, so that the crystal quality of the whole structure for preparing the Micro-LED is improved, the influence of defects and polarization on carriers is weakened, and the light-emitting efficiency of the Micro-LED is improved.

Meanwhile, in order to relieve a series of adverse effects (such as defects generated by stress release) caused by larger lattice mismatch between an In _xGa_1-x N quantum well and GaN, a strain regulating layer and a quantum well structure with special design are arranged before the quantum well is grown, and the strain opposite to InGaN is generated by introducing an AlGaN layer with specific molar components so as to offset the strain of the InGaN. The principle is as follows, firstly according to the formula

The lattice mismatch values were calculated, where Δ is the lattice mismatch value, c _GaN is the c-axis lattice constant of GaN at 5.185 angstroms, and c _n represents the c-axis lattice constants of Al _x1Ga_1-x1 N and In _xGa_1-x N. Wherein the calculation formula of c _n is as follows:

c_n＝b×c_{AlN Or (b) InN}+(1-b)c_GaN

Wherein b is x, x1, x2 or x3, c _{AlN Or (b) InN} is the c-axis lattice constant of AlN or InN, which are 4.982 angstroms and 5.693 angstroms respectively. The lattice mismatch value of Al _x1Ga_1-x1 N and GaN in the c direction is delta ₁＝-0.03915×x1;In_xGa_1-x N, the lattice mismatch value of GaN in the c direction is delta ₂＝0.09797×x;In_x2Ga_1-x2 N, the lattice mismatch value of GaN in the c direction is delta ₃＝0.09797×x2;Al_x3Ga_1-x3 N, and the lattice mismatch value of GaN in the c direction is delta ₄ = -0.03915 x3. By adjusting the molar components x, x1, x2 and x3, the lattice mismatch values of Al _x1Ga_1-x1 N and In _xGa_1-x N In the c direction are equal to those of GaN, and the lattice mismatch values of In _x2Ga_1-x2 N and Al _x3Ga_1-x3 N In the c direction are equal to those of GaN (such as delta ₁＝-△₂、△₃＝-△₄), namely that x1=2.5xx+ -0.05 and x3=2.5x2+ -0.05 are satisfied, at the moment, alGaN can generate strain with opposite directions and values close to those of InGaN so as to offset the strain of InGaN, inhibit defects generated by excessive strain of InGaN, further obtain high-quality quantum wells, and improve the light efficiency of the whole Micro-LED.

The electron blocking layer or the high P doped hole injection layer with wider forbidden bandwidth is arranged, so that the limitation of carriers in an active region, namely the multi-quantum well is realized, the overlapping of the holes and the electron wave functions in the multi-quantum well is increased, the higher radiation recombination efficiency is realized, and the problem of the reduction of internal quantum efficiency caused by the increase of injection current density is further solved.

Meanwhile, the invention arranges the light-emitting units on the basis of close packing, thereby effectively utilizing the area of the epitaxial wafer to the greatest extent. The Micro-LED structure with the two emergent directions which are symmetrical in nature can emit light rays in two different directions when in operation, the structure can be further designed to enable the light rays in the two directions to enter left eyes and right eyes respectively to generate parallax effect so as to achieve 3D display effect, meanwhile, the structure is convenient to achieve the design of a 3D display algorithm, and the structure has great advantages in the field of near-eye naked eye 3D display. Meanwhile, depending on the Micro-LED micron-level size, PPI higher in unit area can be realized, fine and real pictures can be easily realized, and the method has wide application scenes.

Drawings

Exemplary embodiments are illustrated in referenced figures. The embodiments and figures disclosed herein are to be regarded as illustrative rather than restrictive.

Fig. 1 is a schematic cross-sectional view of a Micro-LED structure with dual emission directions when an N electrode is disposed on top of an N-type GaN layer with an upward crystal plane being a nonpolar plane.

Fig. 2 is a schematic top view of a Micro-LED structure with dual emission directions when an N electrode is disposed on top of an N-type GaN layer with an upward crystal plane being a nonpolar plane.

Fig. 3 is a schematic cross-sectional view of a Micro-LED structure with dual emission directions when an N electrode is disposed at the bottom of an N-type GaN layer with an upward crystal plane being a nonpolar plane.

Fig. 4 is a schematic top view of a Micro-LED structure with dual emission directions when an N electrode is disposed at the bottom of an N-type GaN layer with an upward crystal plane being a nonpolar plane.

In the figure, 101 is an N-type GaN layer with an upward crystal face as a nonpolar face, 102 is a mask layer containing a micropore array, 103 is an N-type In _xGa_1-x N triangular island, 104 is a strain regulating layer, 105 is a quantum well layer, 106 is a carrier regulating layer, 107 is a P-type In _yGa_1-y N layer, 108 is a PL electrode, 109 is a PR electrode, and 1010 is an N electrode.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and are not intended to limit the scope of the present invention.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.

Example 1:

The cross-sectional schematic view of example 1 is shown In FIG. 1, and the schematic top view is shown In FIG. 2, and comprises an N-type GaN layer 101 with a nonpolar upward crystal face, a mask layer 102 containing a micropore array, an N-type In _xGa_1-x N triangular island 103, a strain regulating layer 104, a quantum well layer 105, a carrier regulating layer 106, a P-type In _yGa_1-y N layer 107, and a mask layer, A PL electrode 108 and a PR electrode 109 having good ohmic contact with the P-type In _yGa_1-y N layer 107, and an N electrode 1010 having good ohmic contact with the N-type GaN layer 101. The bottom of the N-type In _xGa_1-x N triangular island 103 is obtained by epitaxial growth upwards from the micropores of the mask layer 102, and comprises two bilaterally symmetrical triangular inclined planes and one triangular side surface perpendicular to the bottom surface except the bottom, wherein a strain regulating layer 104, a quantum well layer 105, a carrier regulating layer 106, a P-type In _yGa_1-y N layer 107 and a PL electrode 108 (or PR electrode 109) are all bilaterally symmetrically arranged on the inclined planes of the N-type In _xGa_1-x N triangular island 103, and parameters of the same structure are completely the same, a strain regulating layer 104 on the left side, The quantum well layer 105, the carrier regulating layer 106, the P-type In _yGa_1-y N layer 107, the PL electrode 108, the N electrode 1010 and the left N-type In _xGa_1-x N triangle island inclined plane form a Micro-LED structure L, the strain regulating layer 104, the quantum well layer 105, the carrier regulating layer 106, the P-type In _yGa_1-y N layer 107, the right side, PR electrode 109, N electrode 1010 and right N-type In _xGa_1-x N triangle island slope form Micro-LED structure R. The N electrode 1010 is arranged on top of the N-type GaN layer 101 with the upward crystal face being a nonpolar face and positioned In front of two inclined planes of the In _xGa_{1- x} N triangular island, and the N electrode 1010 is In non-contact with the N-type In _xGa_1-x N triangular island 103.

Example 1 specific parameters and preparation method are as follows:

an N-type GaN template having an upward crystal plane of nonpolar planes (11-20) is used as the N-type GaN layer 101. A layer of SiO ₂ with the thickness of 25nm is covered on the N-type GaN layer 101 as a nonmetallic compound dielectric layer, a micropore array is arranged in the nonmetallic compound dielectric layer, the N-type GaN layer 101 at the lower layer is exposed in micropores, wherein the diameter of the micropores is 1.5 mu m, the micropores are arranged in a close-packed mode, and the distance between the center of any micropore and the centers of the 6 adjacent micropores is 25 mu m.

An N-type In _xGa_1-x N triangular island 103 with an In component of x=0.05 is formed at the micropore position, the diameter of an external circle of the N-type In _xGa_1-x N triangular island 103 In the plane is 15 mu m, crystal faces upwards of the GaN layer 101 and the N-type In _xGa_1-x N triangular island 103 are simultaneously (11-20) planes, at the moment, crystal faces of the left inclined plane and the right inclined plane are simultaneously {1-101} crystal face groups, and a side face of the N-type In _xGa_1-x N triangular island 103 perpendicular to the bottom face is a (000-1) plane.

A 2-period bottom-up GaN/Al _x1Ga_1-x1 N/GaN composite layer is disposed on the symmetrical inclined plane of the N-type In _xGa_1-x N triangle island 103, wherein the thickness of Al _x1Ga_1-x1 N is 2.5nm, x1=0.1, and AlGaN with a lower composition is introduced to compensate for a certain In-plane stress In the c direction and serves as a strain regulating layer 104. The strain regulating layer 104 covers the left and right inclined planes of the whole N-type In _xGa_1-x N triangular island 103, but does not cover the edge In the middle of the N-type In _xGa_1-x N triangular island 103.

The two groups of quantum wells are symmetrically covered on the top of the strain regulating layer 104, the areas are the same and are not connected, the shape of the quantum wells is consistent with the inclined plane of the GaN three-dimensional triangular island 103, when the light emitting wavelength of the quantum wells is red light, green light and blue light respectively, the pairs of the quantum wells are 2 pairs, 3 pairs and 4 pairs, the layer structure of the quantum wells is In _x2Ga_1-x2N/GaN/Al_x3Ga_1-x3 N/GaN, wherein x2 = 0.2, x3 = 0.5, the thickness of In _x2Ga_1-x2 N is 3nm, and the total thickness of the two layers of GaN and Al _x3Ga_1-x3 N is 5nm.

A 6-period, single-period thickness 8nm Al _y1Ga_(1-y1) N/GaN superlattice was provided on the quantum well layer 105, with a molar composition y1 of 0.4, serving as a carrier regulating layer.

The method comprises the steps of arranging a P-type In _yGa_1-y N layer 107 with the thickness of 100nm and the molar component y of 0.1 on a carrier regulating layer, regulating the doping concentration of Mg element to be 3 multiplied by 10 ¹⁹cm^-3, and the hole concentration to be 1.5 multiplied by 10 ¹⁸cm^-3, wherein In a20 nm thickness area on the upper surface of the P-type In _yGa_1-y N layer 107, the doping concentration of Mg element is 1.5 multiplied by 10 ²⁰cm^-3, and the hole concentration is 5 multiplied by 10 ¹⁸cm^-3.

The specific preparation flow of this example structure is as follows:

a) Preparing an N-type GaN template with an upward crystal face being a nonpolar face (11-20) as an N-type GaN layer 101;

b) Preparing a non-metal compound dielectric layer on the N-type GaN layer 101, and processing a micropore structure on the dielectric layer by using a micromachining technology to form a mask layer 102 containing a micropore array, so as to expose the underlying N-type GaN layer 101;

c) The selective epitaxy is carried out by using the micropore by using the selective epitaxy growth technology, and then the temperature of the epitaxy growth is controlled,

The V/III ratio, the reaction chamber pressure and the flow of the carrier gas and reactant source achieve lateral epitaxy to form an In composition of x=0.05

N-type In _xGa_1-x N triangular islands 103;

d) The strain regulating layer 104 is epitaxially grown on the basis of the N-type In _xGa_1-x N triangular island 103, and the micro-processing technology is combined, so that the strain regulating layer 104 covers the left and right inclined planes of the whole N-type In _xGa_1-x N triangular island 103 but does not cover the N-type In _xGa_1-

_x The edge in the middle of the N triangle island 103;

e) Epitaxially growing a quantum well layer 105 on the strain regulating layer 104, so that the quantum well is symmetrically covered on the top of the strain regulating layer 104;

f) Epitaxially growing a carrier regulating layer 106 on the quantum well layer 105 and covering the quantum well layer 105;

g) Epitaxially growing a P-type In _yGa_1-y N layer 107 on the carrier regulating layer 106 and covering the carrier regulating layer 106;

h) And etching the corresponding position of the N electrode 1010 on the mask layer 102 by using a standard micromachining technology to leak the N-type GaN layer 101 on the lower layer, and completing the preparation of the Micro-LED structure by selecting one of the techniques of evaporation coating and magnetron sputtering to complete the PL electrode 108, the PR electrode 109 and the N electrode 1010.

Example 2:

The cross-sectional schematic diagram of example 2 is shown In FIG. 3, and the schematic plan view is shown In FIG. 4, and the cross-sectional schematic diagram comprises an N-type GaN layer 101 with an upward crystal face of a nonpolar face, a mask layer 102 containing a micropore array, an N-type In _xGa_1-x N triangular island 103, a strain regulating layer 104, a quantum well layer 105, a carrier regulating layer 106, a P-type In _yGa_1-y N layer 107 with an In component of y, which are sequentially arranged from bottom to top, A PL electrode 108 and a PR electrode 109 having good ohmic contact with the P-type In _yGa_{1- y} N layer 107, and an N electrode 1010 having good ohmic contact with the N-type GaN layer 101. The bottom of the N-type In _xGa_1-x N triangular island 103 is obtained by epitaxial growth upwards from the micropores of the mask layer 102, and comprises two bilaterally symmetrical triangular inclined planes and one triangular side surface perpendicular to the bottom surface except the bottom, wherein a strain regulating layer 104, a quantum well layer 105, a carrier regulating layer 106, a P-type In _yGa_1-y N layer 107 and a PL electrode 108 (or PR electrode 109) are all bilaterally symmetrically arranged on the inclined planes of the N-type In _xGa_1-x N triangular island 103, and parameters of the same structure are completely the same, a strain regulating layer 104 on the left side, The quantum well layer 105, the carrier regulating layer 106, the P-type In _yGa_1-y N layer 107, the PL electrode 108, the N electrode 1010 and the left N-type In _xGa_1-x N triangle island inclined plane form a Micro-LED structure L, the strain regulating layer 104, the quantum well layer 105, the carrier regulating layer 106, the P-type In _yGa_1-y N layer 107, the right side, PR electrode 109, N electrode 1010 and right N-type In _xGa_1-x N triangle island slope form Micro-LED structure R. the N electrode 1010 is disposed at the bottom of the GaN layer 101 with an upward crystal plane being a nonpolar plane, and directly covers the bottom of the entire N-type GaN layer 101.

Example 2 specific parameters and preparation method are as follows:

An N-type GaN thin film having an upward crystal plane (11-20) as a nonpolar plane grown on a sapphire substrate is used as the N-type GaN layer 101. An hBN layer with the thickness of 15nm is arranged on the N-type GaN layer 101 as a nonmetallic compound medium layer, a micropore array is arranged in the nonmetallic compound medium layer, the N-type GaN layer 101 on the lower layer is exposed in micropores, wherein the diameter of the micropores is 2 mu m, the micropores are arranged in a close-packed mode at the centers of the micropores, and the distance between the centers of any micropores and the centers of the 6 adjacent micropores is 20 mu m.

And forming an N-type In _xGa_1-x N triangular island 103 with an In component of x=0.15 at the center of the micropore, wherein the diameter of an external circle of the N-type In _xGa_{1- x} N triangular island 103 In the plane is 10 mu m, crystal faces upwards of the nonpolar plane GaN layer 101 and the N-type In _xGa_1-x N triangular island 103 are simultaneously (11-20) planes, at the moment, the crystal faces of the left inclined plane and the right inclined plane are simultaneously {1-102} crystal face groups, and the side faces of the N-type In _xGa_1-x N triangular island 103 vertical to the bottom face are both (000-1) planes.

A 3-cycle bottom-up GaN/Al _x1Ga_1-x1N/GaN/In_xGa_1-x N composite layer was provided on the symmetrical slope of the N-type In _xGa_1-x N delta island 103, where the molar fraction x of In _xGa_1-x N is the molar fraction of the N-type In _xGa_1-x N delta island, the thickness of Al _x1Ga_1-x1 N was 1.5nm, x=0.16, x1=0.4, serving as the strain regulating layer 104. The strain regulating layer 104 covers the left and right inclined planes of the whole N-type In _xGa_1-x N triangular island 103, but does not cover the edge In the middle of the N-type In _xGa_1-x N triangular island 103.

The two groups of quantum wells are symmetrically covered on the top of the strain regulating layer 104, the areas are the same and are not connected, the shape of the quantum wells is consistent with the inclined plane of the GaN three-dimensional triangular island 103, when the light emitting wavelength of the quantum wells is red light, green light and blue light respectively, the number of pairs of quantum wells is 1 pair, 4 pairs and 3 pairs, the layer structure of the quantum wells is In _x2Ga_1-x2N/GaN/Al_x3Ga_1-x3 N/GaN, wherein x2 = 0.18, x3 = 0.45, the thickness of In _x2Ga_1-x2 N is 2nm, and the total thickness of the two layers of GaN and Al _x3Ga_1-x3 N is not more than 6nm.

An Al _y2Ga_(1-y2)N/In_y3Ga_(1-y3) N/GaN superlattice with a thickness of 25nm is provided on the quantum well layer 105, doped so that Mg element doping concentration is 5×10 ¹⁸cm^-3 and hole concentration is 7×10 ¹⁷cm^-3 to serve as a carrier regulating layer.

And setting an Al _y2Ga_(1-y2)N/In_y3Ga_(1-y3) N/GaN superlattice with the overall thickness of P doping being smaller than 30nm on the carrier regulating layer, controlling the doping concentration of Mg element of the carrier regulating layer to be 6 multiplied by 10 ¹⁸cm^-3, and taking the hole concentration of the carrier regulating layer as 1 multiplied by 10 ¹⁸cm^-3 as the carrier regulating layer.

The method comprises the steps of arranging a P-type In _yGa_1-y N layer 107 with the thickness of 90nm and the molar component y of 0.08 on a carrier regulating layer, regulating the doping concentration of Mg element to be 3 multiplied by 10 ¹⁹cm^-3 and the hole concentration to be 2 multiplied by 10 ¹⁸cm^-3, wherein In a 25nm thickness area on the upper surface of the P-type In _yGa_1-y N layer 107, the doping concentration of Mg element is 2 multiplied by 10 ²⁰cm^-3 and the hole concentration to be 6 multiplied by 10 ¹⁸cm^-3.

The specific preparation flow of this example structure is as follows:

a) Epitaxially growing an N-type GaN film with an upward crystal face of a nonpolar face (11-20) on a sapphire substrate to serve as an N-type GaN layer 101;

b) Preparing a non-metal compound dielectric layer on the N-type GaN layer 101, and processing a micropore structure on the dielectric layer by using a micromachining technology to form a mask layer 102 containing a micropore array, so as to expose the underlying N-type GaN layer 101;

c) The selective epitaxy is carried out by using the micropore by using the selective epitaxy growth technology, and then the temperature of the epitaxy growth is controlled,

The V/III ratio, the pressure of the reaction chamber and the flow of the carrier gas and the reactant source realize lateral epitaxy, and the formed In component is

N-type In _xGa_1-x N triangle islands 103 with x=0.15;

d) Epitaxially growing a strain regulating layer 104 on the basis of an N-type In _xGa_1-x N triangular island 103, and combining a micro-processing technology to ensure that the strain regulating layer 104 covers the left and right inclined planes of the whole N-type In _xGa_1-x N triangular island 103 but does not cover the edge In the middle of the N-type In _xGa_1-x N triangular island 103;

e) Epitaxially growing a quantum well layer 105 on the strain regulating layer 104, so that the quantum well is symmetrically covered on the top of the strain regulating layer 104;

f) Epitaxially growing a carrier regulating layer 106 on the quantum well layer 105 and covering the quantum well layer 105;

g) Epitaxially growing a P-type In _yGa_1-y N layer 107 on the carrier regulating layer 106 and covering the carrier regulating layer 106;

h) The preparation of the PL electrode 108 and the PR electrode 109 is completed by selecting one technique of evaporation coating and magnetron sputtering;

i) And (3) peeling off the structure above the N-type GaN layer 101 by using a peeling process, and preparing an N electrode 1010 at the original bottom of the N-type GaN layer 101 by using one of evaporation coating and magnetron sputtering to finish the preparation of the Micro-LED structure.

The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and variations could be made by those skilled in the art without departing from the technical principles of the present invention, and such modifications and variations should also be regarded as being within the scope of the invention.

Claims (6)

1. A Micro-LED structure with dual emission directions, characterized in that: it comprises, from bottom to top, an N-type GaN layer (101) with an upward-facing non-polar crystal plane, a mask layer (102) containing a micropore array, an N-type In _x Ga _1-x N-triangular island (103) with an In composition of 0≤x≤0.35, a strain control layer (104), a quantum well layer (105), a carrier control layer (106), a P-type In _y Ga _1-y N-layer (107) with an In composition of y, a PL electrode (108) and a PR electrode (109) having good ohmic contact with the P-type In _y Ga _1-y N-layer (107), and an N electrode (1010) having good ohmic contact with the N-type GaN layer (101); wherein, the N-type In _x Ga _1-x The N-type triangular island (103) is epitaxially grown from the micropores of the mask layer (102) at the bottom, and includes two left-right symmetrical triangular bevels and a triangular side perpendicular to the bottom surface, except for the bottom. The strain control layer (104) covers the two left and right bevels of the entire N-type In _x Ga _1-x N triangular island (103), but does not cover the middle edge of the N-type In _x Ga _1-x N triangular island (103). When the molar composition x of the N-type In _x Ga _1-x N triangular island is ≤0.05, the strain control layer (104) is a 1-3 period bottom-up GaN/Al _x1 Ga _1-x1 N/GaN composite layer, where the thickness of Al _x1 Ga _1-x1 N is less than 3 nm and x1 < 0.15. When the molar composition of the N-type In _x Ga _1-x N triangular island is 0.05 < x < 0.15, the strain control layer (104) is a 1-3 period bottom-up GaN/Al _x1 Ga _{A 1-x1} N/GaN/ _{InxGa 1-x} N composite layer is formed, wherein the molar composition x of _{InxGa 1-x} N is the same as the molar composition of the N-type _{InxGa 1-x} N triangular island. The thickness of _{Alx1Ga 1-x1} N is less than 2 nm, and x1 = 2.5 × x ± 0.05. The strain control layer (104), quantum well layer (105), carrier control layer (106), P-type _{InyGa 1 -y} N layer (107), PL electrode (108) or PR electrode (109) are symmetrically arranged on the inclined surface of the N-type _{InxGa 1-x} N triangular island (103), and the parameters of the same structure are exactly the same. The strain control layer (104), quantum well layer (105), carrier control layer (106), P-type _{InyGa 1-y} N layer (107), PL electrode (108), and N electrode (1010) on the left side are the same as those on the left side of the N-type _{InxGa 1-x N} triangular island. The N-type triangular island slope forms the Micro-LED structure L; the strain control layer (104), quantum well layer (105), carrier control layer (106), P-type In _y Ga _1-y N layer (107), PR electrode (109), N electrode (1010) on the right side and the N-type In _x Ga _1-x N triangular island slope on the right side form the Micro-LED structure R; the two sets of quantum wells on the left and right sides symmetrically cover the top of the strain control layer (104), with the same area and not connected to each other, and their shape is consistent with the slope of the N-type In _x Ga _1-x N triangular island (103); when the quantum well emission wavelengths are red, green and blue light respectively, the number of quantum well pairs is 1~2 pairs, 2~4 pairs and 3~5 pairs respectively; the layer structure of the quantum well is In _x2 Ga _1-x2 N/GaN/Al _x3 Ga _1-x3 N/GaN, where x3=2.5×x2±0.05, and In _x2 Ga _1-x2 The thickness of N is 2-4 nm, and the total thickness of the two GaN layers and _{Alx3Ga1 -x3N} does not exceed 6 nm; the carrier control layer (106) is either an electron blocking layer or a hole injection layer; the electron blocking layer is an _{Aly1Ga (1-y1)} N/GaN superlattice with 2-8 periods and a single period thickness of less than 8 nm, wherein the molar composition y1 is between 0.1 and 0.6 and is negatively correlated with the thickness of _{Aly1Ga (1-y1)} N; the hole injection layer is an _{Aly2Ga (1-y2)} N/ _{Iny3Ga (1-y3)} N/GaN superlattice with an overall thickness of less than 30 nm and a Mg doping concentration between 5× ^{10¹⁷ cm⁻³} and 1× ^{10¹⁹ cm⁻³} , and its hole concentration is not higher than 1× ^10¹⁸ cm⁻³ ^. The N electrode (1010) is located at the top or bottom of the GaN layer (101) with the upward crystal plane being non-polar and establishes a good ohmic contact. When the N electrode (1010) is located at the top, it is located in front of the two inclined faces of the In _x Ga _1-x N triangular island, and the N electrode (1010) has no contact with the N-type In _x Ga _1-x N triangular island (103). When the N electrode (1010) is located at the bottom, the N electrode covers the bottom of the entire N-type GaN layer (101) with the upward crystal plane being non-polar. 2. The Micro-LED structure with dual emission directions as described in claim 1, characterized in that: the mask layer (102) containing the micro-hole array is formed by etching a micro-hole array from top to bottom through a process technology after a dielectric film of _SiO2 , SiN or hBN with a thickness of 5~50 nm is prepared on an N-type GaN layer (101), with the lower N-type GaN layer (101) exposed in the micro-holes; the diameter of the micro-holes is between 0.5~5 μm, and they are arranged in a close-packed form with the center of the micro-holes, the center of any micro-hole is equal to the center of the six adjacent micro-holes, and the distance is adjustable according to actual needs. 3. A Micro-LED structure with dual emission directions as described in claim 1, characterized in that: the upward-facing crystal planes of the N-type GaN layer (101) and the N-type In _x Ga _1-x N-triangular island (103) are simultaneously (11-20) planes, and the crystal planes of the left and right inclined surfaces are simultaneously one of the {1-101} or {1-102} crystal plane families; in addition, the upward-facing crystal planes of the N-type GaN layer (101) and the N-type In _x Ga _1-x N-triangular island (103) can also be simultaneously (1-100) planes, and the crystal planes of the left and right inclined surfaces are simultaneously the {20-21} crystal plane family; the side of the N-type In _x Ga _1-x N-triangular island (103) perpendicular to the bottom surface is a (000-1) plane; when the micropore diameter of the mask layer (102) is not greater than 1.5 μm, the N-type In _x Ga _1-x The diameter of the circumscribed circle of the N-type In _x Ga _1-x N-type triangular island (103) in the plane is between 5 and 20 μm, which can be adjusted as needed. When the diameter of the micropores in the mask layer (102) is greater than 1.5 μm, the diameter of the circumscribed circle of the N-type In x Ga 1-x N-type triangular island (103) in the plane is 3 to 4 times the diameter of the micropores, but the maximum is no more than 15 μm. 4. A Micro-LED structure with dual emission directions as described in claim 1, characterized in that: the thickness of the P-type _{InyGa1 -yN} layer (107) is between 50 and 200 nm, the molar composition y is 0 to 0.15, and when y=0 it is GaN; the Mg element doping concentration is between 2×10 ^{19 cm⁻³} and 5×10 ^{19 cm⁻³} , and its hole concentration is not less than 1×10 ^{18 cm⁻³} ; wherein in the 5 to 30 nm thickness region on the upper surface of the P-type _{InyGa1 -yN} layer (107), the Mg element doping concentration is not less than 1×10 ^{20 cm⁻³} , and its hole concentration is not less than 5×10 ^{18 cm⁻³} . 5. A method for fabricating a Micro-LED structure with dual emission directions, characterized in that: the Micro-LED structure comprises, from bottom to top, an N-type GaN layer (101) with an upward-facing non-polar crystal plane, a mask layer (102) containing a micropore array, an N-type In _x Ga _1-x N-triangular island (103) with an In composition of 0≤x≤0.35, a strain control layer (104), a quantum well layer (105), a carrier control layer (106), a P-type In _y Ga _1-y N-layer (107) with an In composition of y, a PL electrode (108) and a PR electrode (109) having good ohmic contact with the P-type In _y Ga 1- _y N-layer (107), and an N electrode (1010) having good ohmic contact with the N-type GaN layer (101); wherein, the N-type In _x Ga _1-x The N-type triangular island (103) is epitaxially grown from the micropores of the mask layer (102) at the bottom. Besides the bottom, it comprises two symmetrical triangular bevels and a triangular side face perpendicular to the bottom. Furthermore, the strain control layer (104), quantum well layer (105), carrier control layer (106), P-type _{InyGa1 -y} N-layer (107), PL electrode (108), or PR electrode (109) are all symmetrically arranged on the bevels of the N-type _{InxGa1 -x} N-type triangular island (103), and the parameters of the same structure are completely identical. The strain control layer (104), quantum well layer (105), carrier control layer (106), P-type _{InyGa1 -y} N-layer (107), PL electrode (108), and N electrode (1010) on the left side are identical to those on the left side of the N-type _{InxGa1 -x} N-type triangular island (103). The N-type triangular island slope forms a Micro-LED structure L; the strain control layer (104), quantum well layer (105), carrier control layer (106), P-type In _y Ga _1-y N layer (107), PR electrode (109), N electrode (1010) and the N-type In _x Ga _1-x N triangular island slope on the right side form a Micro-LED structure R; the N electrode (1010) is disposed on top of the N-type GaN layer (101) with the upward crystal plane being non-polar, located in front of the two slopes of the In _x Ga _1-x N triangular island, and the N electrode (1010) has no contact with the N-type In _x Ga _1-x N triangular island (103); The fabrication method of this Micro-LED structure includes the following steps: a) Prepare a non-polar N-type GaN template as an N-type GaN layer (101) with the upward crystal plane being non-polar, or epitaxially grow an N-type GaN thin film with the upward crystal plane being non-polar on a sapphire, Si or SiC substrate as an N-type GaN layer (101). b) A non-metallic compound dielectric layer is prepared on the N-type GaN layer (101) with the upward crystal plane being non-polar. Micro-fabrication technology is used to process a micro-pore structure on the dielectric layer to form a mask layer (102) containing a micro-pore array, exposing the underlying N-type GaN layer (101). c) Selective epitaxy is performed using the micropores described above. Lateral epitaxy is then achieved by controlling the epitaxial growth temperature, V/III ratio, reaction chamber pressure, carrier gas, and reactant source flow rate to form N-type In _x Ga _1-x N triangular islands (103) with an In composition of 0≤x≤0.35. d) An epitaxial strain control layer (104) is grown on the basis of the N-type In _x Ga _1-x N triangular island (103). By combining microfabrication technology, the strain control layer (104) covers the two inclined surfaces of the entire N-type In _x Ga _1-x N triangular island (103), but does not cover the edge in the middle of the N-type In _x Ga _1-x N triangular island (103). e) Epitaxially grow a quantum well layer (105) on the strain control layer (104) so that the quantum well symmetrically covers the top of the strain control layer (104); f) Epitaxially grow a carrier control layer (106) on the quantum well layer (105) and cover it with the quantum well layer (105); g) Epitaxially grow a P-type In _y Ga _1-y N layer (107) on the carrier control layer (106) and cover it with the carrier control layer (106); h) Using standard microfabrication techniques, the corresponding positions of the N electrode (1010) on the mask layer (102) are etched to expose the underlying N-type GaN layer (101); the PL electrode (108), PR electrode (109) and N electrode (1010) are completed by selecting one of the evaporation coating and magnetron sputtering techniques to complete the fabrication of this Micro-LED structure. 6. A method for fabricating a Micro-LED structure with dual emission directions, characterized in that: the Micro-LED structure comprises, from bottom to top, an N-type GaN layer (101) with an upward-facing non-polar crystal plane, a mask layer (102) containing a micropore array, an N-type In _x Ga _1-x N-triangular island (103) with an In composition of 0≤x≤0.35, a strain control layer (104), a quantum well layer (105), a carrier control layer (106), a P-type In _y Ga _1-y N-layer (107) with an In composition of y, a PL electrode (108) and a PR electrode (109) having good ohmic contact with the P-type In _y Ga 1- _y N-layer (107), and an N electrode (1010) having good ohmic contact with the N-type GaN layer (101); wherein, the N-type In _x Ga _1-x The N-type triangular island (103) is epitaxially grown from the micropores of the mask layer (102) at the bottom. Besides the bottom, it comprises two symmetrical triangular bevels and a triangular side face perpendicular to the bottom. Furthermore, the strain control layer (104), quantum well layer (105), carrier control layer (106), P-type _{InyGa1 -y} N-layer (107), PL electrode (108), or PR electrode (109) are all symmetrically arranged on the bevels of the N-type _{InxGa1 -x} N-type triangular island (103), and the parameters of the same structure are completely identical. The strain control layer (104), quantum well layer (105), carrier control layer (106), P-type _{InyGa1 -y} N-layer (107), PL electrode (108), and N electrode (1010) on the left side are identical to those on the left side of the N-type _{InxGa1 -x} N-type triangular island (103). The N-type triangular island slope forms the Micro-LED structure L; the strain control layer (104), quantum well layer (105), carrier control layer (106), P-type In _y Ga _1-y N layer (107), PR electrode (109), N electrode (1010) and the N-type In _x Ga _1-x N triangular island slope on the right side form the Micro-LED structure R; the N electrode (1010) is disposed at the bottom of the GaN layer (101) with the upward crystal plane being non-polar, directly covering the bottom of the entire N-type GaN layer (101); The fabrication method of this Micro-LED structure includes the following steps: a) Prepare a non-polar N-type GaN template as an N-type GaN layer (101) with the upward crystal plane being non-polar, or epitaxially grow an N-type GaN thin film with the upward crystal plane being non-polar on a sapphire, Si or SiC substrate as an N-type GaN layer (101). b) A non-metallic compound dielectric layer is prepared on the N-type GaN layer (101) with the upward crystal plane being non-polar. Micro-fabrication technology is used to process a micro-pore structure on the dielectric layer to form a mask layer (102) containing a micro-pore array, exposing the underlying N-type GaN layer (101). c) Selective epitaxy is performed using the micropores described above. Lateral epitaxy is then achieved by controlling the epitaxial growth temperature, V/III ratio, reaction chamber pressure, carrier gas, and reactant source flow rate to form N-type In _x Ga _1-x N triangular islands (103) with an In composition of 0≤x≤0.35. d) An epitaxial strain control layer (104) is grown on the basis of the N-type In _x Ga _1-x N triangular island (103). By combining microfabrication technology, the strain control layer (104) covers the two inclined surfaces of the entire N-type In _x Ga _1-x N triangular island (103), but does not cover the edge in the middle of the N-type In _x Ga _1-x N triangular island (103). e) Epitaxially grow a quantum well layer (105) on the strain control layer (104) so that the quantum well symmetrically covers the top of the strain control layer (104); f) Epitaxially grow a carrier control layer (106) on the quantum well layer (105) and cover it with the quantum well layer (105); g) Epitaxially grow a P-type _{InyGa1 -} yN layer (107) on the carrier control layer (106) and cover it with the carrier control layer (106); h) The PL electrode (108) and PR electrode (109) are prepared by selecting one of the following techniques: evaporation coating or magnetron sputtering; i) The structure above the N-type GaN layer (101) is peeled off using a stripping process, and an N-electrode (1010) is prepared on the original bottom of the N-type GaN layer (101) by selecting one of the following techniques: evaporation coating or magnetron sputtering, to complete the preparation of this Micro-LED structure.