MicroLED chip and micro display device

Abstract

The invention provides a Micro LED chip and a micro display device. A light-emitting table top of a Micro LED comprises a first-type semiconductor layer, a light-emitting layer and a second-type semiconductor layer, wherein the first-type semiconductor layer, the light-emitting layer and the second-type semiconductor layer are sequentially stacked from bottom to top. The light-emitting layer comprises a plurality of stacked quantum barrier layers and quantum well layers; the surface of the quantum well layer is provided with a plurality of nanometer protrusions. The light-emitting layer comprising the quantum barrier layer and the quantum well layer which are repeatedly stacked is adopted, the surface of the quantum well layer is provided with a plurality of nanometer protrusions, and the adverse effect of side wall damage on the Micro LED can be effectively restrained.

Description

Technical Field

[0001] This application relates to the field of semiconductors, and particularly to a MicroLED chip and a microdisplay device. Background Art

[0002] In recent years, with the continuous development of MicroLED (Micro Light Emitting Diode Display) technology, more and more electronic devices have started to use MicroLED technology, bringing great convenience to people's lives.

[0003] In MicroLED technology, MicroLED chips have the advantages of high luminous efficiency, adjustable emission wavelength, and low operating voltage. However, with the reduction of MicroLED size, serious size effects have emerged, seriously affecting the efficiency and performance of MicroLEDs. The main reasons are as follows: The preparation of the MicroLED light-emitting mesa is mainly through physical / chemical etching methods. During the etching process using these methods, it is inevitable to damage the sidewalls of the light-emitting mesa, destroying the crystal structure around the sidewalls, resulting in the formation of a large number of defects in these areas, bringing serious non-radiative recombination and current leakage. In particular, the smaller the size of the light-emitting mesa, the more serious the sidewall effect, because the proportion of the sidewalls in the smaller-sized light-emitting mesa is higher, and coupled with the lateral diffusion of current in the light-emitting layer, it causes the serious defect of a large recombination rate on the sidewalls of the light-emitting mesa. Summary of the Invention

[0004] The problem solved by this application is how to improve the size effect and sidewall non-radiative recombination defects of MicroLEDs in MicroLED chips as the size decreases.

[0005] To solve the above problems, this application provides a MicroLED chip, characterized in that the light-emitting mesa of the MicroLED includes: a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer stacked in sequence from bottom to top; the light-emitting layer includes: multiple stacked quantum barrier layers and quantum well layers; the surface of the quantum well layer has multiple nanobumps.

[0006] Optionally, at least some of the adjacent nanobumps are separated from each other.

[0007] Optionally, in the quantum well layer, the bottoms of adjacent nanobumps do not have a continuous layer.

[0008] Optionally, in the quantum well layer, the bottoms of adjacent nanobumps have a continuous layer.

[0009] Optionally, the height of the nano-protrusions ranges from 4 to 8 nm, and the diameter of the nano-protrusions ranges from 200 to 300 nm.

[0010] Optionally, the sidewall of the nano-protrusion has an arc or a straight line.

[0011] Optionally, the quantum barrier layers and the quantum well layers exist in pairs; or, the number of the quantum barrier layers is at least one more than that of the quantum well layers.

[0012] Optionally, the bottommost layer and the topmost layer of the light-emitting layer are quantum barrier layers.

[0013] Optionally, the quantum well layers and the quantum barrier layers are alternately stacked.

[0014] Optionally, an insertion layer is further provided between the quantum well layer and the quantum barrier layer.

[0015] Optionally, the quantum barrier layers and the quantum well layers have different brightness and darkness under TEM scanning, forming a stacked layer with alternating brightness and darkness.

[0016] Optionally, multiple nano-protrusions are presented in the quantum well layer.

[0017] Optionally, the thickness of the quantum well layer is less than that of the quantum barrier layer; under dark-field TEM scanning, the brightness of the quantum well layer is higher than that of the quantum barrier layer; under bright-field TEM scanning, the brightness of the quantum well layer is lower than that of the quantum barrier layer.

[0018] Optionally, the thickness of the quantum barrier layer ranges from 5 nm to 25 nm.

[0019] Optionally, in the quantum well layer, at least some of the nano-protrusions are located at an intermediate position between the sidewalls of the light-emitting mesa and are separated from the sidewalls of the light-emitting mesa.

[0020] Optionally, the mismatch rate between the lattice constant of the nano-protrusion material and the lattice constant of the quantum barrier layer material is greater than a preset value.

[0021] Optionally, the preset value is greater than or equal to 15%.

[0022] Optionally, multiple nano-protrusions are uniformly distributed in the quantum well layer.

[0023] Optionally, the light-emitting mesa generates one or a mixture of red light, blue light, and green light.

[0024] Optionally, the material of the quantum barrier layer is AlGa 1-x In x P, x is close to or equal to 0.5, and close means the error does not exceed plus or minus 0.02. The material of the quantum well layer is AlGa1-y In y P and y are between 0.55 and 0.8; the material of the quantum barrier layer is GaN, and the material of the quantum well layer is In x Ga 1-x N, and x is between 0.2 and 0.35.

[0025] Optionally, the width range of the light-emitting mesa is between 1 μm and 10 μm.

[0026] Optionally, the MicroLED chip further includes:

[0027] A top conductive layer electrically connected to the second-type semiconductor layer;

[0028] A bottom conductive layer electrically connected to the first-type semiconductor layer;

[0029] A driving chip electrically connected to the bottom conductive layer.

[0030] Correspondingly, a MicroLED microdisplay device includes the MicroLED chip of the display panel combination structure described in any one of the above;

[0031] A circuit board electrically connected to the MicroLED chip to transmit signals between the MicroLED chip and the outside world.

[0032] Compared with the prior art, the technical solution of the present application has the following advantages:

[0033] In the technical solution of the present application, a light-emitting layer including repeatedly stacked quantum barrier layers and quantum well layers is adopted. The surface of the quantum well layer has multiple nano-protrusions, which can effectively suppress the adverse effects of sidewall damage on MicroLEDs. When the size of MicroLEDs is further reduced, the size effect of MicroLEDs is reduced, the light-emitting efficiency of small-size MicroLEDs is improved, and the limitation of further reducing the size of MicroLEDs under existing conditions is broken through. Moreover, due to the adoption of the quantum well layer, the nano-protrusions are restricted in three dimensions and have higher light-emitting efficiency and temperature stability. In addition, the local states of the quantum well layer can greatly reduce the lateral diffusion of current in the light-emitting layer, thereby reducing the defect of large sidewall recombination rate of the light-emitting mesa and improving the performance of the MicroLED chip. Description of the Drawings

[0034] The following, by describing the specific embodiments of the present invention in detail in conjunction with the drawings, will make the technical solutions and other beneficial effects of the present invention obvious

[0035] Figure 1 It is a schematic cross-sectional view of a light-emitting mesa in a MicroLED;

[0036] Figure 2 is an enlarged cross-sectional view of a light-emitting layer provided by an embodiment of the present application;

[0037] Figure 3 is a top view of a quantum well layer provided by an embodiment of the present application;

[0038] Reference numerals: 100 - light-emitting mesa, 110 - first-type semiconductor layer, 120 - light-emitting layer, 121b - quantum barrier layer, 121d - quantum well layer, qd - nano bump, qdc

[0039] —first-type nano bump, qdd - second-type nano bump, 130 - second-type semiconductor layer, 140 - sidewall. Detailed implementation manners

[0040] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0041] The disclosure of the present application provides many different implementation manners or examples for implementing different structures of the present application. To simplify the disclosure of the present application, components and settings of specific examples are described in the present application. Of course, they are only examples and are not intended to limit the present application. In addition, the present application may repeat reference numerals and / or reference letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between various implementation manners and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those skilled in the art can be aware of the application of other processes and / or the use of other materials.

[0042] Generally, terms can be understood at least in part according to the usage of the present application. For example, the term "one or more" used in the present application can be understood at least in part according to the present application and can be used to describe any component, structure or feature in the singular form, or can be used to describe a combination of components, structures or features in the plural form. Similarly, terms such as "a", "an" or "the" can also be understood at least in part according to the present application to convey singular usage or convey plural usage. In addition, the term "based on..." can be understood as not necessarily intended to convey a set of exclusive factors, but can instead allow, at least in part according to the present application, the existence of additional factors that do not necessarily have to be explicitly described.

[0043] It should be readily understood that the meanings of "on", "above", and "over" in this application should be interpreted in the broadest sense, such that "on" not only means "directly on something", but also means "on something" including intermediate components or layers therebetween, and "above" or "over" something not only means the meaning of "above" or "over" something, but also includes the meaning of "above" or "over" something without intermediate components or layers therebetween.

[0044] In addition, for ease of description, spatial relative terms such as "below", "beneath", "lower", "above", "upper", etc. may be used in this application to describe the relationship of one element or component to another element or component shown in the drawings. In addition to the orientation described in the figures, the spatial relative terms are also intended to cover different orientations of the device during use or operation. The device may be oriented otherwise rotated 90° or in other orientations, and the spatial relative descriptive terms used in this application may be interpreted accordingly in the same manner.

[0045] The term "layer" as used in this application refers to a portion of material including a region having a certain thickness. The layer may extend over the entire underlying or overlying structure, or may have an extent less than the extent of the underlying or overlying structure. In addition, the layer may be a region of a homogeneous or inhomogeneous continuous structure, the thickness of which is less than the thickness of the continuous structure. For example, the layer may be located between the top and bottom surfaces of the continuous structure or between any pair of horizontal planes therebetween. The layer may extend horizontally, vertically, and / or along a conical surface. The substrate may be a layer, may include one or more layers therein, and / or may have one or more layers thereon, above, and / or below it. A layer may include multiple layers. For example, a semiconductor layer may include one or more doped or undoped semiconductor layers and may have the same or different materials.

[0046] Please refer to Figure 1 , a schematic cross-sectional view of a light-emitting mesa in a microLED chip of an embodiment, the light-emitting mesa 100 in the microLED including:

[0047] A first-type semiconductor 110, a light-emitting layer 120 is disposed on the first-type semiconductor 110, and a second-type semiconductor layer 130 is disposed on a side of the light-emitting layer 120 away from the first-type semiconductor 110, forming a sequential arrangement of the first-type semiconductor 110, the light-emitting layer 120, and the second-type semiconductor layer 130 from bottom to top, and a sidewall 140 is disposed outside the three.

[0048] Generally, physical or chemical methods can be used to etch the epitaxial layer to form the light-emitting mesa 100. During the etching process, it is inevitable to damage the sidewalls 140 disposed outside the first-type semiconductor layer 110, the light-emitting layer 120, and the second-type semiconductor layer 130, that is, a large number of crystal structures of the sidewalls 140 are damaged, and a large number of defects are formed in these regions. The defects of the sidewalls 140 will cause serious non-radiative recombination, and the current of the light-emitting layer is also likely to diffuse out from the positions of the defects, resulting in current leakage problems.

[0049] In addition, since the smaller the size of the light-emitting mesa in the MicroLED, the larger the relative area of the sidewalls 140, the higher the proportion of the sidewalls 140, the more serious the non-radiative recombination and current leakage problems caused by the damage of the sidewalls 140, and the more serious the size effect of the LED.

[0050] To solve the above technical problems, the present application provides a MicroLED chip. The light-emitting mesa of the MicroLED includes: a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer stacked in sequence from bottom to top; the light-emitting layer includes: a plurality of stacked quantum barrier layers and quantum well layers; the surface of the quantum well layer has a plurality of nano-protrusions.

[0051] By using a light-emitting layer including a plurality of stacked quantum barrier layers and quantum well layers, and the surface of the quantum well layer has a plurality of nano-protrusions, it can effectively suppress the adverse effects brought by sidewall damage to the MicroLED. When the size of the MicroLED is further reduced, the size effect of the MicroLED is reduced, the light-emitting efficiency of the small-size MicroLED is improved, and the limitation of further reducing the size of the MicroLED under the existing conditions is broken through. And, due to the use of the quantum well layer, the nano-protrusions are restricted in three dimensions and have higher light-emitting efficiency and temperature stability. In addition, the local states of the quantum well layer can greatly reduce the lateral diffusion of current in the light-emitting layer, thereby reducing the defect of the large recombination rate of the sidewalls of the light-emitting mesa and improving the performance of the MicroLED chip.

[0052] To make the above objects, features, and advantages of the present application more obvious and understandable, the following detailed description of the specific embodiments of the present application will be given with reference to the accompanying drawings.

[0053] As Figure 2 shown, the light-emitting layer 120 includes repeatedly and alternately stacked quantum barrier layers 121b and quantum well layers 121d, and the quantum barrier layer 121b serves as the topmost and bottommost layers of the light-emitting layer 120, that is, the quantum barrier layer 121b is adjacent to the first-type semiconductor layer 110 and the second-type semiconductor layer 130. Further, in other examples, there is also an insertion layer between the quantum well layer and the quantum barrier layer. The material composition of the insertion layer is selected from group III-V.

[0054] In some embodiments, the quantum barrier layer 121b and the quantum well layer 121d exist in pairs to form the light-emitting stack 121. Alternatively, a quantum well layer 121d is disposed between two quantum barrier layers 121b, and the light-emitting stack 121 can also be formed. The light-emitting layer 120 can be formed by combining the same or different types of light-emitting stacks 121 according to actual needs, which is not limited herein.

[0055] Exemplarily, when the light-emitting layer 120 employs paired quantum barrier layers 121b and quantum well layers 121d, the quantum barrier layer 121b has at least one more layer than the quantum well layer 121d, that is, the quantum barrier layer 121b has one or more layers more than the quantum well layer 121d, such that the topmost and bottommost layers of the light-emitting layer 120 are quantum barrier layers 121b.

[0056] In some embodiments, the thickness of the quantum well layer is less than the thickness of the quantum barrier layer.

[0057] In some embodiments, the quantum well layer 121d and the quantum barrier layer 121b have different brightnesses under a TEM (Transmission Electron Microscope), forming a stack with alternating bright and dark regions. Under dark-field TEM scanning, the brightness of the quantum well layer 121d is higher than that of the quantum barrier layer 121b; under bright-field TEM scanning, the brightness of the quantum well layer 121d is lower than that of the quantum barrier layer 121b. Multiple nano-protrusions can be presented in the quantum well layer regardless of bright-field or dark-field conditions. In some embodiments, the surface of the quantum well layer 121d can have multiple nano-protrusions qd, the quantum well layer 121d can also present multiple nano-protrusions qd, or the surface and the interior of the quantum well layer 121d can simultaneously have multiple nano-protrusions qd, which is not limited herein.

[0058] Exemplarily, the surface of the quantum well layer 121d has nano-protrusions qd, and the nano-protrusions qd are limited in all three dimensions, thus having higher luminous efficiency and temperature stability; moreover, it can effectively reduce non-radiative recombination caused by damage to the sidewall 140, effectively suppress the lateral diffusion of current to reduce current leakage, is beneficial to suppressing the reduction of the external quantum efficiency and the socket efficiency caused by sidewall 140 damage, and is beneficial to breaking through the limitation of the LED size effect.

[0059] In some embodiments, referring to Figure 2 , adjacent nano-protrusions qd can be separated from each other, that is, there is a gap between adjacent nano-protrusions qd, or some nano-protrusions qd are separated and some are not separated, which is not limited herein.

[0060] Exemplarily, at least some adjacent nanobumps qd are separated from each other, which can not only expose the surface of the quantum barrier layer 121b in the gaps between adjacent nanobumps qd, but also effectively ensure the confinement between adjacent nanobumps qd, form the local states of the quantum well layer 121d, avoid the current flowing between adjacent nanobumps qd, greatly reduce the lateral diffusion of the current in the quantum well layer 121d, and improve the luminescence performance.

[0061] In some embodiments, multiple nanobumps qd may be uniformly or non-uniformly distributed on the surface of the quantum well layer 121d, or may be uniformly or non-uniformly distributed in the quantum well layer 121d, which is not limited herein.

[0062] Exemplarily, multiple nanobumps qd are uniformly distributed on the surface of the quantum well layer 121d, which can effectively ensure the luminescence uniformity and ensure the luminescence effect.

[0063] In some embodiments, the density of the nanobumps qd is uniform or non-uniform, which is not limited herein.

[0064] Exemplarily, the nanobumps qd adopt a uniform density to improve the color purity and brightness, enhance the color reproducibility, reduce the light scattering and reflection, and improve the stability and consistency.

[0065] In some embodiments, the bottoms of adjacent nanobumps qd may or may not have a continuous layer, which is not limited herein.

[0066] Exemplarily, the bottoms of adjacent nanobumps dq may be an integral layer structure formed by connecting with the same material as the nanobumps dq, that is, the bottoms of adjacent nanobumps qd have a continuous layer; the bottoms of adjacent nanobumps dq may also be blocky without being connected by the same material as the nanobumps dq between the bottoms of adjacent nanobumps dq, that is, the bottoms of adjacent nanobumps qd have a discontinuous layer.

[0067] In some embodiments, the shapes of the nanobumps qd may be the same or different, as long as the same functions can be achieved, which is not limited herein.

[0068] Exemplarily, the shape of the nanobumps qd may be spherical, quasi-spherical, frustum-shaped or other shapes, and one of them may be adopted, or a combination may be used.

[0069] In some embodiments, the side walls of the nanobumps qd may have one or a combination of arcs and straight lines, which is not limited herein.

[0070] In some embodiments, the lattice constant of the nanobump QD material is related to the composition ratio of the nanobump QD material, that is, by adjusting the composition ratio of the nanobump QD material, an appropriate mismatch rate is achieved between the lattice constant of the nanobump QD material and the lattice constant of the quantum barrier layer 121b material. Preferably, the mismatch rate between the lattice constant of the nanobump material and the lattice constant of the quantum barrier layer material is greater than a preset value, and the preset value is preferably greater than or equal to 15%.

[0071] In some embodiments, the material of the quantum barrier layer is (AlGa) 1-x In x P, x is close to or equal to 0.5. Preferably, "close to" means the error does not exceed plus or minus 0.02 to reduce lattice mismatch. The material of the quantum well layer is (AlGa) 1-y In y P, y is between 0.55 and 0.8; the material of the nanobump is GaN, and the material of the quantum well layer is In x Ga 1-x N, x is between 0.2 and 0.35. The materials of the quantum barrier layer and the quantum well layer are set appropriately to reduce lattice matching. It should be noted that (AlGa) 1-x In x P, with parentheses added here, meaning that Al and Ga are taken as a whole.

[0072] Exemplarily, when the epitaxial layer corresponding to the red light is generated by the light-emitting layer 120, the material of the quantum barrier layer 121b is AlGaInP, and the material of the quantum well layer 121d is AlGaInP; by adjusting the component ratios of Al, Ga, and In in the quantum well layer 121d according to the above y, an appropriate mismatch rate is achieved between the lattice constants of the quantum well layer and the nanobump QD material and the lattice constant of the quantum barrier layer 121b material. Preferably, the mismatch rate between the lattice constant of the nanobump material and the lattice constant of the quantum barrier layer material is greater than a preset value, and the preset value is preferably greater than or equal to 15%.

[0073] When the epitaxial layer corresponding to the blue or green light is generated by the light-emitting layer 120, the material of the quantum barrier layer 121b is GaN, and the material of the quantum well layer 121d is InGaN; by adjusting the component ratios of Ga and In in the quantum well layer 121d according to the above x, an appropriate mismatch rate is achieved between the lattice constants of the quantum well layer 121d and the nanobump QD material and the lattice constant of the quantum barrier layer 121b material. Preferably, the mismatch rate between the lattice constant of the nanobump material and the lattice constant of the quantum barrier layer material is greater than a preset value, and the preset value is preferably greater than or equal to 15%.

[0074] In some embodiments, the lattice mismatch rate between the lattice constants of the quantum well layer 121d and the nanobump qd material is greater than a preset value, so as to introduce a large stress during the growth of the quantum well layer 121d on the quantum barrier layer 121b, thereby spontaneously forming nanobumps qd by the layer-island (Stranski-Krastanov, S-K) growth mode.

[0075] For example, the preset value is greater than or equal to 15%. The preset value is appropriately sized. On the one hand, it can introduce an appropriate amount of stress to form nanobumps qd. On the other hand, it can also control the mismatch rate between the nanobumps qd and the quantum barrier layer 121b to avoid the formation of structural defects.

[0076] In some embodiments, the material of the nanobumps qd affects the wavelength of the light generated by the nanobumps qd and the wavelength of the light generated by the epitaxial layer. That is, by adjusting the composition ratio of the nanobumps qd material, the wavelength of the light generated by the epitaxial layer can also be adjusted. For example, an increase in the Al / Ga ratio in the composition of the nanobumps qd increases its bandgap width and shortens the wavelength; conversely, a decrease in the Al / Ga ratio decreases its bandgap width and shortens the wavelength.

[0077] In some embodiments, the diameter of the nanobumps qd is related to the wavelength of the light generated by the epitaxial layer. That is, by adjusting the diameter of the nanobumps qd, the wavelength of the light generated by the epitaxial layer can be adjusted. For example, when the light-emitting layer 120 emits red light, the diameter range of the nanobumps qd is between 200 nm and 300 nm; the wavelength of the generated red light is between 610 and 650 nm.

[0078] When the light-emitting layer 120fa emits blue or green light, the diameter of the nanobumps qd is in the range of 10 nm to 200 nm. The thickness of the quantum barrier layer 121b can be adjusted as needed to optimize the voltage and luminous efficiency of the entire device. For example, the wavelength range of blue light is between 450 and 490 nm, and the wavelength range of green light is between 510 and 550 nm.

[0079] It should be noted that the quantum barrier layer 121b needs to have an appropriate thickness. An appropriate thickness can not only effectively ensure that the nanobumps qd are confined in the direction perpendicular to the surface of the quantum barrier layer 121b, but also ensure structural relaxation and reduce the generation of structural defects. Preferably, the thickness range of the quantum barrier layer 121b is between 5 nm and 25 nm. In some embodiments, the thickness of the quantum barrier layer 121b can be less than, equal to, or greater than the thickness of the quantum well layer 121d, which is not limited here. The thickness of the quantum barrier layer 121b can be adjusted as needed to optimize the voltage and luminous efficiency of the entire device.

[0080] In some embodiments, the thickness of the light-emitting layer 120 ranges from 10 to 600 nm. The light-emitting layer 120 includes a plurality of quantum barrier layers 121b and a plurality of quantum well layers 121d. The thickness of each quantum barrier layer 121b may be the same or different, and the thickness of each quantum well layer 121d may be the same or different.

[0081] In some embodiments, the thickness of the quantum well layer 121d is greater than or equal to the height of the nano-protrusion qd. There may be an extremely thin quantum well layer thickness at the bottom of qd.

[0082] In some embodiments, the quantum barrier layer 121b is located in the gaps and on the surfaces of the nano-protrusions qd of the quantum well layer 121d.

[0083] In some embodiments, the height of the nano-protrusions qd within the same quantum well layer 121d may be the same or different. The height of the nano-protrusions qd ranges between 2 nm and 8 nm.

[0084] Exemplarily, when the light-emitting layer 120 emits red light, the height of the nano-protrusions qd ranges between 4 nm and 8 nm; when the light-emitting layer 120 emits blue or green light, the height of the nano-protrusions qd ranges between 2 nm and 6 nm.

[0085] Reference Figure 3 , in the quantum well layer 121d, at least some of the nano-protrusions qd may be located at the intermediate position between the sidewalls 140 of the light-emitting mesa, separated from the sidewalls 140 of the light-emitting mesa, forming a complete nano-protrusion structure, denoted as the first type of nano-protrusion qdc. The nano-protrusions qd may also be located on the sidewalls 140 of the light-emitting mesa, forming the second type of nano-protrusion qdd, which is not limited herein.

[0086] It should be noted that during the process of etching the LED epitaxial layer by physical or chemical methods to form the light-emitting mesa, it is inevitable to cause damage to the sidewalls 140 disposed outside the first type of semiconductor layer 110, the light-emitting layer 120, and the second type of semiconductor layer 130. Therefore, the edge position of the sidewalls 140 of the light-emitting mesa will be affected by the damage to the sidewalls 140, that is, affected by the etching process, resulting in an incomplete second type of nano-protrusion qdd with defective problems; while the intermediate position between the sidewalls 140 of the light-emitting mesa is not affected by the etching process, and the first type of nano-protrusion qdc with a complete structure has no defects.

[0087] It can be seen that the first type of nano bump qdc located at the middle position between the side walls 140 of the light-emitting mesa has a complete structure and no defects. Therefore, the non-radiative recombination rate is low and the lateral current diffusion range is limited, which can effectively ensure the external quantum efficiency (EQE) and the wall-plug efficiency (WPE). When the size of the MicroLED is further reduced, the defect of the large recombination rate of the side wall 140 of the light-emitting mesa is reduced, thereby reducing the size effect of the MicroLED and improving the light-emitting efficiency of the small-size MicroLED, breaking through the limitation of further reducing the size of the MicroLED under the existing conditions.

[0088] It should be noted that although the epitaxial growth method is used as an example for the growth of nano bumps in the embodiments of the present application, the nano bumps obtained by using the chemical solution growth method, the electric field confinement method or other methods are also within the protection scope of the present application.

[0089] In the embodiments of the present application, the chemical vapor deposition method or the molecular beam epitaxy method in the epitaxial growth method is used to grow nano bumps. The above methods are prior arts and will not be described in detail herein.

[0090] In some embodiments, the nano bump qd can be a quantum dot, or other nano structures can be used, as long as the function of the nano bump qd can be realized, which is not limited herein.

[0091] The nano bump is a semiconductor nano structure in which excitons are confined in three spatial dimensions. The nano bump will generate light with a preset frequency under a preset electric field, and the frequency of the light generated by the quantum dot is related to the size, structure and material of the quantum dot.

[0092] The nano bump is confined in three spatial dimensions, which can effectively provide the probability of radiative recombination. Therefore, the nano bump has higher light-emitting efficiency and temperature stability; moreover, the local state property of the nano bump can also greatly reduce the lateral diffusion of current to provide current density and reduce the probability of current leakage.

[0093] The confinement for forming the nano bump can be formed by at least one of an electrostatic potential, a semiconductor material interface and a semiconductor material surface; among them, the electrostatic potential can be formed by reasons such as an external electrode, material doping, and structural strain.

[0094] Please refer to again Figure 1 , in a MicroLED chip of the present invention, it includes:

[0095] The light-emitting mesa 100 of a MicroLED, where the light-emitting mesa 100 includes a first-type semiconductor layer 110, a light-emitting layer 120, and a second-type semiconductor layer 130 stacked in sequence from bottom to top;

[0096] In some embodiments, the light-emitting mesa 100 can generate one or a mixture of red light, blue light, and green light, which is not limited herein.

[0097] In some embodiments, Figure 1 In the cross-sectional structure of the light-emitting mesa shown where the sidewall is vertical, of course, the sidewalls of the cross-sectional structure of the light-emitting mesa in other embodiments of the present invention can also be inclined. In some embodiments, the inclination angle of the sidewall of the light-emitting mesa 100 is within a certain range, that is, the angle between the sidewall and the second-type semiconductor layer 130. The inclination angle of the sidewall can be less than 90°, or can be less than 90° and greater than 60°, which is not limited herein. For example, the cross-section of the light-emitting mesa 100 is a regular trapezoid or an inverted trapezoid. The shape of the light-emitting mesa 100 can be a conical structure without a pointed top, or can be a mesa structure with a flat top surface, or other three-dimensional mesa shapes, which is not limited herein. The regular trapezoidal light-emitting mesa makes the light more convergent when emitted upward, and the inverted trapezoidal light-emitting mesa increases the light-emitting area of a single pixel while keeping the pixel area unchanged when the light is emitted upward.

[0098] In some embodiments, the width range of the light-emitting mesa 100 is from 1 μm to 10 μm.

[0099] In some embodiments, the thickness or height range of the light-emitting mesa 100 is from 1 μm to 5 μm.

[0100] In some embodiments, the first-type semiconductor layer 110 and the second-type semiconductor layer 130 have different conductivity types to respectively provide different carriers.

[0101] Specifically, the first-type semiconductor layer 110 is an N-type doped semiconductor layer, and the second-type semiconductor layer 130 is a P-type doped semiconductor layer; in some other embodiments, the first-type semiconductor layer 110 can also be a P-type doped semiconductor layer, and the second-type semiconductor layer 130 can also be an N-type doped semiconductor layer.

[0102] In some embodiments, the material of the first-type semiconductor layer 110 can be one or more of p-GaAs, p-GaP, p-AlInP, p-GaN, p-InGaN, or p-AlGaN. The material of the second-type semiconductor layer 130 can be one or more of n-GaAs, n-AlInP, n-GaInP, n-AlGaAs, n-AlGaInP, n-GaN, n-InGaN, or n-AlGaN.

[0103] In some embodiments, the materials of the first-type semiconductor layer 110 and the second-type semiconductor layer 130 may be related to the wavelength of the light generated by the epitaxial layer. When the light-emitting layer 120 generates red light, at least one of the first-type semiconductor layer 110 and the second-type semiconductor layer 130 may be an AlGaInP layer; when the light-emitting layer 120 generates blue light or green light, the materials of the first-type semiconductor layer 110 and the second-type semiconductor layer 130 are at least one of GaN, InGaN, and AlGaN.

[0104] In some embodiments, the thickness of the first-type semiconductor layer 110 is the same as or different from the thickness of the second-type semiconductor layer 130.

[0105] Specifically, the thickness of the first-type semiconductor layer 110 may be greater than, less than, or equal to the thickness of the second-type semiconductor layer 130.

[0106] The thickness of at least one of the first-type semiconductor layer 110 and the second-type semiconductor layer 130 ranges from 100 nm to 1000 nm.

[0107] In some embodiments, at least one of the first-type semiconductor layer 110 and the second-type semiconductor layer 130 is a III-V compound semiconductor. With an appropriate thickness of the semiconductor layer, on the one hand, it can form a good contact with the light-emitting layer 120, which is beneficial to ensuring the formation of a good ohmic contact. On the other hand, it can also effectively ensure the formation of a good epitaxial layer, which is beneficial to the formation of subsequent processes.

[0108] In the above embodiments, the light-emitting layer 120 has been described in detail, so it will not be elaborated here.

[0109] In some embodiments, the thickness of the light-emitting layer 120 is the same as or different from the thickness of the first-type semiconductor layer 110 and the thickness of the second-type semiconductor layer 130, respectively.

[0110] Specifically, the thickness of the light-emitting layer 120 may be greater than, less than, or equal to the thickness of the first-type semiconductor layer 110; the thickness of the light-emitting layer 120 may be greater than, less than, or equal to the thickness of the second-type semiconductor layer 130.

[0111] In some embodiments, the MicroLED chip further includes:

[0112] The top conductive layer is electrically connected to the second-type semiconductor layer 130,

[0113] The bottom conductive layer is electrically connected to the first-type semiconductor layer 110;

[0114] The driving chip is electrically connected to the bottom conductive layer.

[0115] Specifically, a driving chip, a bottom conductive layer, a first-type semiconductor layer 110, a light-emitting layer 120, a second-type semiconductor layer 130, and a top conductive layer are stacked in sequence from bottom to top.

[0116] In some embodiments, the top conductive layer can be transparent.

[0117] Specifically, the material of the top conductive layer can be

[0118] one or a combination of more of TCO (Transparent Conductive Oxide) thin film, ITO (Indium Tin Oxide) thin film,

[0119] AZO (Antimony doped Zinc Oxide) thin film, ATO (Antimony doped Tin Oxide) thin film, FTO (Fluorine doped Tin Oxide) thin film.

[0120] In some embodiments, the thickness range of the top conductive layer is not greater than 1 micron, preferably 50 - 1000 nm.

[0121] In some embodiments, the top conductive layer can be deposited by chemical vapor deposition methods known in the art to deposit the top conductive layer, or other methods can also be used, which are not limited herein.

[0122] In some embodiments, the bottom conductive layer can be an opaque conductive metal layer to the light emitted by the light-emitting mesa 100, or a transparent conductive layer that improves conductivity and light transmittance.

[0123] Specifically, when the bottom conductive layer uses a conductive metal layer, the material can be one or more conductive metals, including but not limited to one or a combination of titanium, gold, or aluminum.

[0124] When the bottom conductive layer uses a transparent conductive layer, the material can be

[0125] TCO (Transparent Conductive Oxide) thin film, ITO (Indium Tin Oxide) thin film,

[0126] One or a combination of more than one of AZO (Antimony-doped Zinc Oxide) thin films, ATO (Antimony-doped Tin Oxide) thin films, and FTO (Fluorine-doped Tin Oxide) thin films.

[0127] In some embodiments, the thickness of the bottom conductive layer ranges from not greater than 1 micron. Preferably, it is 50 - 1000 nm.

[0128] In some embodiments, physical deposition methods such as physical vapor deposition or magnetron sputtering can be used to deposit the bottom conductive layer of the top conductive layer 202, or other methods can also be used, which are not limited herein.

[0129] In some embodiments, the driving chip 203 can be one of a CMOS (Complementary Metal Oxide Semiconductor) driving circuit, a TFT (Thin Film Transistor) driving circuit, a circuit of III-V compound semiconductors, or an integrated circuit (IC) board.

[0130] It is not limited herein.

[0131] In some embodiments, the width of the light-emitting mesa ranges from 1 μm to 10 μm. The size ranges of the length and width of the MicroLED chip are determined by the size of the driving backplane. Optionally, the length of the microLED chip is not greater than 2 cm, and the width is not greater than 2 cm. Preferably, the length of the microLED chip is not greater than 1 cm, and the width is not greater than 1 cm.

[0132] An embodiment of the present invention also protects a MicroLED microdisplay device, which includes the MicroLED chip in the above embodiment; and a circuit board, which is electrically connected to the above MicroLED chip to transmit signals between the microLED chip and the outside. In some embodiments, the circuit board can be a flexible circuit board, a rigid circuit board, or a combination of both, which is not limited herein. In some embodiments, there is an electrical connection between the circuit board and the driving chip, and the driving chip can obtain signals such as image data from the outside through the circuit board, so as to control the light-emitting mesa 100 to emit light or not.

[0133] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application shall be subject to the scope defined by the claims.

Claims

1. A Micro LED chip, characterized in that, The light-emitting mesa of the Micro LED includes: a first-type semiconductor layer, a light-emitting layer, and a second-type semiconductor layer stacked in sequence from bottom to top; the light-emitting layer includes: multiple stacked quantum barrier layers and quantum well layers; the surface of the quantum well layer has multiple nano-protrusions.

2. The Micro LED chip according to claim 1, wherein, At least some of the adjacent nano-protrusions are separated from each other.

3. The Micro LED chip according to claim 1, characterized in that, In the quantum well layer, there is no continuous layer at the bottom of adjacent nano-protrusions.

4. The Micro LED chip according to claim 1, characterized in that, In the quantum well layer, there is a continuous layer at the bottom of adjacent nano-protrusions.

5. The Micro LED chip according to claim 1, wherein, The height range of the nano-protrusions is between 4 - 8 nm, and the diameter range of the nano-protrusions is between 200 - 300 nm.

6. The Micro LED chip according to claim 1, wherein, The side wall of the nano-protrusion has an arc or a straight line.

7. The Micro LED chip according to claim 1, wherein The quantum barrier layers and the quantum well layers exist in pairs; or, the number of quantum barrier layers is at least one more than that of the quantum well layers.

8. The Micro LED chip according to claim 7, characterized in that, The bottommost layer and the topmost layer of the light-emitting layer are quantum barrier layers.

9. The Micro LED chip according to claim 7, characterized in that, The quantum well layers and the quantum barrier layers are alternately stacked.

10. The Micro LED chip according to claim 9, wherein, There is also an insertion layer between the quantum well layer and the quantum barrier layer.

11. The Micro LED chip according to claim 1, characterized in that, The quantum barrier layers and the quantum well layers have different brightness and darkness under TEM scanning, forming a stacked layer with alternating light and darkness.

12. The Micro LED chip according to claim 11, wherein, The thickness of the quantum well layer is less than that of the quantum barrier layer; under dark-field TEM scanning, the brightness of the quantum well layer is higher than that of the quantum barrier layer; under bright-field TEM scanning, the brightness of the quantum well layer is lower than that of the quantum barrier layer.

13. The Micro LED chip according to claim 1, characterized in that, In the quantum well layer, at least some of the nano-protrusions are located at the middle position between the side walls of the light-emitting mesa and are separated from the side walls of the light-emitting mesa.

14. The Micro LED chip according to claim 1, wherein The mismatch rate between the lattice constant of the material of the nano-protrusion and the lattice constant of the material of the quantum barrier layer is greater than a preset value.

15. The Micro LED chip according to claim 14, wherein The preset value is greater than or equal to 15%.

16. The Micro LED chip according to claim 1, wherein Multiple nano-protrusions are evenly distributed in the quantum well layer.

17. The Micro LED chip according to claim 1, characterized in that, The light-emitting mesa generates one or more mixtures of red light, blue light, and green light.

18. The Micro LED chip according to claim 1, characterized in that, The material of the quantum barrier layer is AlGa 1- x In x P, x is close to or equal to 0.5, where "close to" means the error does not exceed plus or minus 0.02; the material of the quantum well layer is AlGa 1- y In y P, y is between 0.55 and 0.8; the material of the quantum barrier layer is GaN, and the material of the quantum well layer is In x Ga 1-x N, x is between 0.2 and 0.

35.

19. The Micro LED chip according to claim 1, wherein, The width range of the light-emitting mesa is between 1 μm - 10 μm; the thickness range of the quantum barrier layer is between 5 nm - 25 nm.

20. The Micro LED chip according to claim 1, wherein It also includes: A top conductive layer electrically connected to the second-type semiconductor layer; A bottom conductive layer electrically connected to the first-type semiconductor layer; A driving chip electrically connected to the bottom conductive layer.

21. A Micro LED microdisplay device, characterized in that, It includes: The Micro LED chip as described in claim 1; A circuit board electrically connected to the Micro LED chip to achieve signal transmission between the Micro LED chip and the outside.

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