阅读说明：本技术 一种减小光学串扰的新型Micro-LED显示阵列及其制备方法 (Novel Micro-LED display array capable of reducing optical crosstalk and preparation method thereof ) 是由 寇建权 于 2020-12-15 设计创作，主要内容包括：本发明的目的是针对当前Micro-LED显示中存在的不足,提出一种减小光学串扰的新型Micro-LED显示阵列。该方案将当前主流的Micro-LED显示阵列中的各个Micro-LED的间隔处做成粗糙表面,使得在GaN层和蓝宝石(sapphire)衬底之间的通道内部传播的光通过粗糙表面透出,从而抑制其在通道内传播并进一步影响相邻的Micro-LED,提高每个像素点色彩的纯洁性,进而提高显示阵列的对比度和可靠性,减少芯片成本。(The invention aims to provide a novel Micro-LED display array capable of reducing optical crosstalk aiming at the defects in the current Micro-LED display. According to the scheme, the interval of each Micro-LED in the current mainstream Micro-LED display array is made into a rough surface, so that light propagating inside a channel between a GaN layer and a sapphire (sapphire) substrate is transmitted out through the rough surface, propagation in the channel is inhibited, adjacent Micro-LEDs are further influenced, the purity of the color of each pixel point is improved, the contrast and the reliability of the display array are further improved, and the chip cost is reduced.)

1. A novel Micro-LED display array for reducing optical crosstalk, comprising: the LED chip comprises a sapphire substrate (1), an intrinsic GaN buffer layer (2), an n-GaN layer (3), an InGaN/GaN multi-quantum well layer (4), a p-type electronic barrier layer (5), a p-GaN layer (6), a current expansion layer (7), a Micro-LED p-type ohmic electrode (8) and a Micro-LED n-type ohmic electrode (9), wherein the bottommost layer is the sapphire substrate 1, the intrinsic GaN buffer layer (2) is arranged next, the intrinsic GaN buffer layer (2) is sequentially covered with the n-GaN layer (3), the InGaN/GaN multi-quantum well layer (4), the p-type electronic barrier layer (5), the p-GaN layer (6), the current expansion layer (7) and the Micro-LED p-type ohmic electrode (8), and the Micro-LED n-type ohmic electrode (9) is positioned at one corner of the n-GaN layer (3); the side wall of a device at one side of the Micro-LED p-type ohmic electrode (8) is of an inclined side wall structure; the interval between each Micro-LED device is 20-100 mu m, and the exposed nGaN surface at intervals is of a patterned surface structure.

2. The novel Micro-LED display array for reducing optical crosstalk of claim 1, wherein: the sapphire substrate (1) is one of sapphire, SiC, Si, AlN, GaN or quartz glass, and the substrate (1) is divided into a polar plane [0001] substrate, a semipolar plane [11-22] substrate or a nonpolar plane [1-100] substrate along the difference of the epitaxial growth direction;

the material of the current spreading layer (7) is one of ITO, Ni/Au, zinc oxide, graphene, aluminum or metal nanowires;

the Micro-LED p-type ohmic electrode (8) is made of one of Ni/Au, Cr/Au, Pt/Au or Ni/Al;

the Micro-LED n-type ohmic electrode (9) is made of one of Al/Au, Cr/Au or Ti/Al/Ti/Au.

3. A novel Micro-LED display array with reduced optical crosstalk according to claims 1-2, wherein: the inclined angle of the inclined side wall of the Micro-LED device is 10-85 degrees.

4. A novel Micro-LED display array with reduced optical crosstalk according to claims 1-3, wherein: the height of the coarse patterned surface is 20nm-2000 nm.

5. A novel Micro-LED display array capable of reducing optical crosstalk is prepared by the following steps:

firstly, baking a substrate at 1250-1350 ℃ in an MOCVD reaction furnace, removing foreign matters on the surface of the substrate, and then respectively growing an intrinsic GaN buffer layer (2), an n-GaN layer (3), an InGaN/GaN multi-quantum well layer (4), a p-type electronic barrier layer (5) and a p-GaN layer (6);

secondly, evaporating and plating a current expansion layer on the substrate grown in the first step, wherein the material is ITO;

thirdly, exposing the substrate obtained in the second step to the n-GaN layer (3) through photoetching and etching according to the array distribution of the devices, realizing mutual isolation of the devices and enabling the side walls to form side walls with a certain inclination angle;

fourthly, forming the surface of the conical or hemispherical GaN buffer layer (2) in the exposed n-GaN layer (3) region through a nanosphere lithography technology, a holographic lithography or nanoimprint lithography technology and an etching technology;

and fifthly, respectively photoetching and evaporating a p-type ohmic electrode (8) of a single Micro-LED device and a Micro-LED n-type ohmic electrode (9) of the whole chip unit.

Technical Field

The invention relates to the field of semiconductor photoelectricity, in particular to a novel Micro-LED display array for reducing optical crosstalk and a preparation method thereof.

Background

Currently, for smart phones, tablet computers and television displays, Liquid Crystal Display (LCD) and Organic Light Emitting Diode (OLED) display are two mainstream display technologies. Both techniques have their advantages and disadvantages. The main advantages of the LCD are long lifespan, high brightness, and low cost, and the unique advantage of the OLED is that it is easily implemented to be ultra-thin, thereby implementing flexible display. However, LCDs have two drawbacks to overcome: contrast and flexibility are limited. On the other hand, the main challenges of OLEDs are their lifetime of use and high cost. And the display technology based on the Mini-LED and the Micro-LED gradually attracts wide attention, and the Micro-LED as a new generation display technology has higher brightness, better luminous efficiency and lower power consumption compared with the existing OLED and LCD technologies. In 2017, in 5 months, apples have started the development of a new generation of display technology. In 2018, 2 months, samsung released a Micro LED television on CES 2018.

Nowadays, ill-nitride semiconductors have found good application in the fields of lighting technology and power electronics. Nitride LEDs have become the primary lighting system choice for many residential, commercial, and industrial indoor and outdoor lighting systems due to their unprecedented high luminous efficiency combined with their long life and reliability. Nitride based LEDs can cover the uv to green spectral range very well. The Micro-LED technology as a new generation display technology mainly realizes full-color display through two methods, one is to manufacture red, green and blue Micro-LED devices based on the principle of three primary colors for combination, the other is to realize full-color display based on a color conversion material, and through the scheme of the color conversion material, the Micro-LED technology needs blue light or a deep ultraviolet LED to activate quantum dots or fluorescent powder of the color conversion material for realizing full-color display. And blue or deep ultraviolet LEDs based on III-nitride semiconductors have again become a focus of research.

However, a problem to be solved still exists in the Micro-LED full-color display technology based on the color conversion material: optical crosstalk (cross-talk). When the entire array addresses individual pixels through the addition of specific circuitry, adjacent pixels and regions will also experience some interference. These problems can cause malfunction of the display array, and in implementing display applications, can also reduce image fidelity and color contrast, as well as cause data transmission defects and reduce signal-to-noise ratio in optical communications. A common method for reducing crosstalk (cross-talk) is to integrate a hemispherical microlens array into the Micro-LED array, where each microlens is coupled to a single Micro-LED pixel, and the microlenses can effectively collimate the diverging light emitted by the Micro-LEDs, thereby reducing optical crosstalk between different pixel points. Secondly, a window for QD ejection and a barrier wall for reducing crosstalk are fabricated by a simple photolithography method, and divergent light of a single pixel is absorbed by the barrier wall to be confined in the window. In the method, the surfaces with specific shapes are formed by roughening at intervals of different Micro-LED pixel points, so that divergent light of the pixel points is projected out through the rough surfaces, the influence of each independent pixel on each other is reduced, optical crosstalk among different pixels is greatly reduced, more accurate control of display colors and higher color contrast are achieved, and the manufacturing cost of a display chip is reduced.

Disclosure of Invention

The invention aims to provide a novel Micro-LED display array capable of reducing optical crosstalk aiming at the defects in the current Micro-LED display. According to the scheme, the interval of each Micro-LED in the current mainstream Micro-LED display array is made into a rough surface, so that light propagating inside a channel between a GaN layer and a sapphire (sapphire) substrate is transmitted out through the rough surface, propagation in the channel is reduced, adjacent Micro-LEDs are further influenced, the purity of the color of each pixel point is improved, the contrast and the reliability of the display array are further improved, and the chip cost is reduced.

The technical scheme adopted by the invention for solving the technical problem is as follows:

a novel Micro-LED display array capable of reducing optical crosstalk comprises a sapphire substrate 1, an intrinsic GaN buffer layer 2, an n-GaN layer 3, an InGaN/GaN multi-quantum well layer 4, a p-type electronic barrier layer 5, a p-GaN layer 6, a current expansion layer 7, a Micro-LED p-type ohmic electrode 8 and a Micro-LED n-type ohmic electrode 9, wherein the sapphire substrate 1 is arranged at the bottommost layer, the intrinsic GaN buffer layer 2 is arranged next, the n-GaN layer 3, the InGaN/GaN multi-quantum well layer 4, the p-type electronic barrier layer 5, the p-GaN layer 6, the current expansion layer 7 and the Micro-LED p-type ohmic electrode 8 are sequentially covered on the intrinsic GaN buffer layer 2, and the Micro-LED n-type ohmic electrode 9 is positioned at one corner of the n-GaN layer 3; the side wall of the device at one side of the Micro-LED p-type ohmic electrode 8 is of an inclined side wall structure; the interval between each Micro-LED device is 20-100 mu m, and the exposed nGaN surface at intervals is of a patterned surface structure.

Further, the sapphire substrate 1 is one of sapphire, SiC, Si, AlN, GaN or quartz glass, and the substrate 1 is divided into a polar plane [0001] substrate, a semipolar plane [11-22] substrate or a nonpolar plane [1-100] substrate along the difference of the epitaxial growth direction;

the material of the current expansion layer 7 is one of ITO, Ni/Au, zinc oxide, graphene, aluminum or metal nanowires;

the Micro-LED p-type ohmic electrode 8 is made of one of Ni/Au, Cr/Au, Pt/Au or Ni/Al;

the Micro-LED n-type ohmic electrode 9 is made of one of Al/Au, Cr/Au or Ti/Al/Ti/Au;

further, the inclined angle of the inclined side wall of the Micro-LED device is 10-85 degrees.

Further, the height of the coarse patterned surface is 20nm-2000 nm.

A preparation method of a novel Micro-LED display array capable of reducing optical crosstalk comprises the following steps:

firstly, baking a substrate at 1250-1350 ℃ in an MOCVD reaction furnace, removing foreign matters on the surface of the substrate, and then respectively growing an intrinsic GaN buffer layer 2, an n-GaN layer 3, an InGaN/GaN multi-quantum well layer 4, a p-type electronic barrier layer 5 and a p-GaN layer 6;

secondly, evaporating and plating a current expansion layer on the substrate grown in the first step, wherein the material is ITO;

thirdly, exposing the substrate obtained in the second step to the n-GaN layer 3 through photoetching and etching according to the array distribution of the devices, realizing mutual isolation of the devices and enabling the side walls to form side walls with a certain inclination angle;

fourthly, obtaining the surface of the conical or hemispherical GaN buffer layer 2 in the exposed n-GaN layer 3 area through a nanosphere photoetching technology, a holographic photoetching or nanoimprint photoetching technology and an etching technology;

and fifthly, respectively photoetching and evaporating a p-type ohmic electrode 8 of a single Micro-LED device and a Micro-LED n-type ohmic electrode 9 of the whole chip unit.

Thus, the novel Micro-LED display array capable of reducing optical crosstalk is prepared.

Compared with the prior art, the invention has the following advantages:

the device of the invention is to carry out pattern roughening on the surface between single pixels in the current mainstream Micro-LED array, and form a hemispherical or conical surface on an n-GaN layer through roughening, so that light in a channel between a sapphire substrate and the n-GaN can be transmitted out by means of the roughened pattern surface, and the principle of transmission out is to change the incident angle of the light at an interface, so that the light which can realize total reflection at the interface can not meet the condition of total reflection any more and then is transmitted out. This correspondingly reduces the effect between adjacent Micro-LED emissive pixels, i.e., reduces optical cross talk (crosstalk).

The invention has the beneficial effects that:

1. according to the novel Micro-LED display array capable of reducing optical crosstalk, the hemispherical or conical rough surface is manufactured on the surface of the n-GaN layer between the gaps of the single device, so that light in a channel between the sapphire substrate and the n-GaN can be transmitted out through the rough surface before reaching the adjacent device, the optical crosstalk between single Micro-LED pixel points is greatly reduced, the crosstalk ratio is reduced by 50% -80% compared with that of a device without the rough surface, the color display of the single pixel point is accurately controlled, and the image fidelity and the color contrast are improved.

2. In addition, in order to avoid the influence of crosstalk, the traditional device controls the distance between the devices as much as possible and is not suitable for being overlarge, but the optical crosstalk is reduced by adopting the rough surface, so that the distance between adjacent Micro-LED pixel points can be shortened, the Micro-LED display pitch is further reduced, and the PPI (pixel density) and the display resolution are improved.

3. The novel Micro-LED display array capable of reducing optical crosstalk adopts the inclined side wall structure, improves the light extraction efficiency of the device, is easier to operate compared with a common device for improving light extraction by a vapor deposition metal reflector, has strong repeatability, and reduces the production cost and the consumed time by about 20-40%.

Drawings

The invention will be further described with reference to the accompanying drawings.

FIG. 1 is a schematic view of an initial substrate structure of the present invention.

FIG. 2 is a schematic diagram of a vapor deposition current spreading layer according to the present invention.

Fig. 3 is a schematic view of the exposure of an n-GaN mesa by photolithography and etching in the present invention.

FIG. 4 is a schematic diagram of the rough surface formed by nanosphere lithography, holographic lithography, and etching in the present invention.

FIG. 5 is a schematic diagram of evaporation of p-type and n-type ohmic electrodes in the present invention.

Fig. 6 is a schematic three-dimensional structure of the present invention.

Fig. 7 is a layout of devices according to the present invention.

Fig. 8 is a cross comparison of whether the device has a rough surface at different tilt angles obtained by FDTD simulation software.

Wherein, 1-a substrate; 2-an intrinsic GaN buffer layer; a 3-n-GaN layer; 4-InGaN/GaN multi-quantum well layer; a 5-P-type electron blocking layer; a 6-p-GaN layer; 7-a current spreading layer; 8-Micro-LED p-type ohmic electrode; 9-Micro-LED n-type ohmic electrode

Detailed Description

The present invention is further described with reference to the following examples and drawings, but the scope of the claims of the present application is not limited thereto.

Fig. 5 is a schematic structural view of the array device, and the complete Micro-LED device sequentially comprises, along the epitaxial growth direction: the GaN-based light-emitting diode comprises a substrate 1, an intrinsic GaN buffer layer 2, an N-GaN layer 3, an InGaN/GaN multi-quantum well layer 4, a P-type electronic barrier layer 5, a P-GaN layer 6, a current expansion layer 7, a P-type ohmic electrode 8 and an N-type ohmic electrode 9.

FIG. 2 shows the deposition of a current spreading layer on the initial substrate of FIG. 1.

FIG. 3 shows that the devices are isolated from each other and the sidewalls are formed into sidewalls with a certain inclination angle by exposing to the n-GaN layer according to the array distribution of the devices on the substrate of FIG. 2 through photolithography and etching;

FIG. 4 shows that a tapered or hemispherical GaN layer surface is formed on the exposed n-GaN layer region on the substrate of FIG. 3 by nanosphere lithography, holographic lithography or nanoimprint lithography, and etching;

FIG. 5 shows that the p-type ohmic electrode of a single Micro-LED device and the n-type ohmic electrode of the whole chip unit are respectively etched and evaporated in FIG. 4;

the realization of the invention is based on the basic design idea of the Micro-LED array, the pattern roughening is carried out on the spacing surface between the Micro-LED pixels in the traditional Micro-LED array, and the hemispherical or conical surface is formed on the upper side of the exposed n-GaN layer through the roughening, so that the optical crosstalk displayed by the Micro-LED is reduced, and the color purity and the contrast are improved.

The theoretical mechanism is as follows: a hemispherical or conical surface is manufactured at a gap between Micro-LED pixel points, when light in a channel between an n-GaN layer and a sapphire substrate reaches the upper surface of the n-GaN, the incident angle formed by the light in the channel and the hemispherical or conical surface is very small and is far smaller than the critical angle of total reflection between two media, so that the light in the channel can be transmitted out at the rough surface of the n-GaN layer of the gap, and the influence on adjacent devices is not influenced by continuous reflection and propagation in the channel.

If a conventional display array without roughening between the pitches is used, since there is no surface with a specific shape, a part of light inside the channel has an incident angle larger than a critical angle at the interface of the n-GaN layer, and therefore cannot penetrate out to continue to propagate and affect the adjacent devices.

A novel Micro-LED display array capable of reducing optical crosstalk comprises a Micro-LED device, wherein the bottommost layer of the Micro-LED device is a sapphire substrate, an intrinsic GaN buffer layer is arranged on the sapphire substrate, an n-GaN layer covers the intrinsic GaN buffer layer, an InGaN/GaN multi-quantum well layer, a p-type electronic barrier layer, a p-GaN layer and a current expansion layer are sequentially arranged on the upper portion of the upper layer of the n-GaN layer from bottom to top, a p-type ohmic electrode covers the outer side of the upper surface of the current expansion layer, and the area of the p-type ohmic electrode is 5-10% of that of the current expansion layer; an n-type ohmic electrode is arranged on one corner surface of the n-GaN layer of the whole array, and the area of the n-type ohmic electrode is approximately 0.01-0.04 mm²；

In array arrangement, the interval between each Micro-LED device is 40-80 μm;

the substrate is sapphire, SiC, Si, AlN, GaN or quartz glass; the difference of the substrate along the epitaxial growth direction can be classified into a polar plane [0001] substrate, a semipolar plane [11-22] substrate, or a nonpolar plane [1-100] substrate.

The current expansion layer can be made of ITO, Ni/Au, zinc oxide, graphene, aluminum or metal nanowires, and the thickness of the current expansion layer is 10-100 nm.

The side wall of the Micro-LED device is slightly inclined inwards, and the inclination angle is 10-85 degrees.

The shape of the rough surface can be semi-circle, ellipse and cone, the radius of the cross section is 200 nm-2 μm, and the height is 200 nm-2 μm.

The p-type ohmic electrode of the Micro-LED device is made of Ni/Au, Cr/Au, Pt/Au or Ni/Al, and the n-type ohmic electrode is made of Al/Au, Cr/Au or Ti/Al/Ti/Au.

Example 1

A novel Micro-LED display array for reducing optical crosstalk is formed by arranging a plurality of Micro-LEDs.

The Micro-LED device sequentially comprises the following components along the epitaxial growth direction: the substrate 1 and the intrinsic GaN buffer layer 2 are 1.5 mu m thick; an n-GaN layer 3 with a thickness of 3 μm; an InGaN/GaN multi-quantum well layer 4 with a thickness of 50 nm; a p-type electron blocking layer 5 with a thickness of 20 nm; a p-GaN layer 6 with a thickness of 500 nm; a current spreading layer 7 with a thickness of 20 nm; a p-type ohmic electrode 8 and an n-type ohmic electrode 9, wherein the p-type ohmic electrode 8 is positioned in the center of the current spreading layer 7, has a width of 0.5 μm and a thickness of 200 nm; the n-type ohmic electrode 9 was positioned at one corner of the exposed portion of the n-GaN lower layer, and had a side length of 0.5 μm and a thickness of 200 nm.

The preparation method of the novel Micro-LED display array capable of reducing the optical crosstalk comprises the following steps:

firstly, baking a substrate at 1250-1350 ℃ in an MOCVD reaction furnace, removing foreign matters on the surface of the substrate, and then respectively growing an intrinsic GaN buffer layer 2, an n-GaN layer 3, a pair of InGaN/GaN multi-quantum well layers 4, a pair of p-type electronic barrier layers 5 and a pair of p-GaN layers 6;

secondly, evaporating a current expansion layer 7 on the substrate grown in the first step, wherein the material is ITO and the thickness is 20 nm;

thirdly, exposing the substrate obtained in the second step to the n-GaN layer 3 through photoetching and etching according to the array distribution of the devices, realizing mutual isolation of the devices, wherein the distance between the adjacent devices is 40nm, and forming a side wall with an inclination angle of 50 degrees by controlling the ICP speed in the etching process;

and fourthly, obtaining the surface of the hemispherical GaN layer in the exposed n-GaN layer 3 region through a nanosphere photoetching technology, a holographic photoetching or nanoimprint photoetching technology and an etching technology, wherein the spherical radius is 0.5 mu m.

Fifthly, respectively photoetching and evaporating a p-type ohmic electrode 8 of a single Micro-LED device and an n-type ohmic electrode 9 of the whole chip unit;

the novel Micro-LED display array of the present invention with reduced optical crosstalk is thus made.

Example 2

A novel Micro-LED display array for reducing optical crosstalk is formed by arranging a plurality of Micro-LEDs.

The Micro-LED device sequentially comprises the following components along the epitaxial growth direction: the substrate 1 and the intrinsic GaN buffer layer 2 are 1.5 mu m thick; an n-GaN layer 3 with a thickness of 3 μm; an InGaN/GaN multi-quantum well layer 4 with a thickness of 50 nm; a p-type electron blocking layer 5 with a thickness of 20 nm; a p-GaN layer 6 with a thickness of 500 nm; a current spreading layer 7 with a thickness of 20 nm; a p-type ohmic electrode 8 and an n-type ohmic electrode 9, wherein the p-type ohmic electrode 9 is positioned in the center of the current spreading layer 7, has a width of 0.5 μm and a thickness of 200 nm; the n-type ohmic electrode 10 was positioned at one corner of the exposed portion of the n-GaN lower layer, with a side length of 0.5 μm and a thickness of 200 nm.

The preparation method of the novel Micro-LED display array capable of reducing the optical crosstalk comprises the following steps:

firstly, baking a substrate at 1250-1350 ℃ in an MOCVD reaction furnace, removing foreign matters on the surface of the substrate, and then respectively growing an intrinsic GaN buffer layer 2, an n-GaN layer 3, a pair of InGaN/GaN multi-quantum well layers 4, a pair of p-type electronic barrier layers 5 and a pair of p-GaN layers 6;

secondly, evaporating a current expansion layer 7 on the substrate grown in the first step, wherein the material is ITO and the thickness is 20 nm;

thirdly, exposing the substrate obtained in the second step to the n-GaN layer 3 through photoetching and etching according to the array distribution of the devices, realizing mutual isolation of the devices, wherein the distance between the adjacent devices is 40nm, and forming a side wall with an inclination angle of 50 degrees by controlling the ICP speed in the etching process;

and fourthly, obtaining the surface of the conical GaN layer in the exposed n-GaN layer 3 region by a nanosphere photoetching technology, a holographic photoetching or nano-imprinting photoetching technology and an etching technology, wherein the radius of the bottom surface is 0.5 mu m, and the height is 1 mu m.

Fifthly, respectively photoetching and evaporating a p-type ohmic electrode 8 of a single Micro-LED device and an n-type ohmic electrode 9 of the whole chip unit;

the novel Micro-LED display array of the present invention with reduced optical crosstalk is thus made.

The above examples are only preferred embodiments of the present invention, it should be noted that: it will be apparent to those skilled in the art that the patterned rough surface and equivalent substitutions can be made without departing from the spirit of the invention, and those technical solutions obtained by patterning the rough surface and equivalent substitutions according to the claims of the present invention are all within the scope of the present invention.

The invention is not the best known technology.