A micro-LED and its preparation method

Abstract

The present invention discloses a micro-LED and a preparation method thereof, which is applied to red light micro-LED and relates to the field of diode technology. The micro-LED includes a substrate; a red light epitaxial preparation layer, an N-type Indium substrate are sequentially provided on the substrate. b Ga 1‑b N / GaN layer, light-emitting layer, electron blocking layer, P-type In f Ga 1‑f N layer and contact layer; a waveguide layer is provided between the light-emitting layer and the electron blocking layer, and the waveguide layer is In e Ga 1‑e The present invention can solve the technical problem in the prior art that impurities in the epitaxial layer diffuse into the light-emitting layer, resulting in low luminous efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of diodes, and in particular to a micro-LED and a preparation method thereof. Background Art

[0002] With the continuous development of social productivity and science and technology, the application of virtual reality (VR) and augmented reality (AR) technologies in various fields is becoming increasingly widespread. Consequently, the demand for these technologies across various industries is also growing. Due to the small size, high integration, and self-luminescence of micro-LED chips, they offer significant advantages in terms of brightness, resolution, contrast, energy consumption, lifespan, response speed, and thermal stability in VR and AR displays. Micro-LED is a display technology that uses self-luminous micron-sized LEDs as light-emitting pixel units, which are assembled onto a driver panel to form a high-density LED array. Therefore, as the demand for VR and AR technologies continues to grow, micro-LEDs will play an increasingly important role in these technologies.

[0003] Currently, the more common main material of micro-LED is AlGaInN material. AlGaInN system micro-LED has good thermal stability and will not be affected by changes in temperature. However, in order to improve the effective doping of P-type gallium nitride, AlGaInN system micro-LED adopts low-temperature growth. The C impurity concentration of low-temperature grown P-type gallium nitride is relatively high, and atoms such as C and Mg in P-type gallium nitride will diffuse into the light-emitting layer, reducing the crystal quality of the quantum well in the light-emitting layer, resulting in a decrease in the internal quantum efficiency, thereby affecting the electron-hole recombination efficiency of the light-emitting layer and reducing the luminous efficiency of the micro-LED.

[0004] Therefore, existing AlGaInN system micro-LEDs generally have a technical problem in which impurities in the epitaxial layer diffuse into the light-emitting layer, resulting in low luminous efficiency. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a micro-LED and a preparation method thereof, aiming to solve the technical problem in the existing technology that impurities in the epitaxial layer diffuse into the light-emitting layer, resulting in low luminous efficiency.

[0006] One aspect of the present invention is to provide a micro-LED, which is applied to red light micro-LEDs. The micro-LED includes:

[0007] substrate;

[0008] On the substrate, a red light epitaxial preparation layer, an N-type In b Ga 1-b N / GaN layer, light-emitting layer, electron blocking layer, P-type In f Ga 1-f N layer and contact layer;

[0009] A waveguide layer is provided between the light emitting layer and the electron blocking layer. The waveguide layer is In e Ga 1-e N thin film layer, wherein the In composition e is 0.01-0.1.

[0010] Compared with the prior art, the present invention has the following advantages: a waveguide layer is provided between the light-emitting layer and the electron blocking layer through the micro-LED provided by the present invention, and the waveguide layer is In e Ga 1-e The N thin film layer can block the C, Mg, Al and other atoms in the subsequent epitaxial layer from diffusing into the light-emitting layer, thereby improving the radiation recombination efficiency of electrons and holes in the light-emitting layer and improving the luminous efficiency of micro-LEDs. At the same time, the waveguide layer can block the N-type In b Ga 1-b The electrons in the N / GaN layer overflow into the P-type In f Ga 1-f The N layer reduces carrier leakage, further improving the efficiency of electron-hole radiative recombination, and further enhancing the luminous efficiency of micro-LEDs. This solves the common technical problem of impurities in the epitaxial layer diffusing into the light-emitting layer, resulting in low luminous efficiency. In addition, the patterned composite substrate facilitates the growth of the epitaxial layer, effectively reducing the threading dislocation density and improving the crystal quality of the epitaxial layer.

[0011] According to one aspect of the above technical solution, the thickness of the waveguide layer is 5-10 nm.

[0012] According to one aspect of the above technical solution, the N-type In b Ga 1-b The N / GaN layer is a periodic superlattice structure, in which In b Ga 1-b The thickness of the N thin film layer is 1-5 nm, the component b of In is 0.01-0.1, and the thickness of the GaN thin film layer is 10-50 nm.

[0013] According to one aspect of the above technical solution, the P-type In f Ga 1-f The thickness of the N layer is 100-200 nm, wherein the In composition f is 0.01-0.1.

[0014] According to one aspect of the above technical solution, the light emitting layer is a multi-quantum well layer structure, including several periods of In c Ga 1-c N well layer and In d Ga 1-d N barrier layer, where In c Ga 1-c The thickness of the N-well layer is 1-5 nm, the In composition c is 0.3-0.5, and In d Ga 1-d The thickness of the N barrier layer is 5-15 nm, and the In composition d is 0.01-0.1.

[0015] According to one aspect of the above technical solution, a mask layer is provided on the substrate, and the mask layer is etched into a specific pattern by nanoimprinting or photolithography to form a patterned composite substrate.

[0016] According to one aspect of the above technical solution, the red light epitaxial preparation layer is In a Ga 1-a N thin film layer, wherein the thickness of the red light epitaxial preparation layer is 100-2000nm, and the In component a is 0-0.2.

[0017] According to one aspect of the above technical solution, the contact layer is doped with In g Ga 1-g N thin film layer, the doped In g Ga 1-g The thickness of the N thin film layer is 5-30 nm, and the In composition g is 0.01-0.1.

[0018] Another aspect of the present invention is to provide a method for preparing a micro-LED, the method comprising:

[0019] providing a substrate;

[0020] growing a mask layer on the substrate to form a patterned composite substrate;

[0021] On the patterned composite substrate, a red epitaxial preparation layer, an N-type In layer and a b Ga 1-b N / GaN layer, light-emitting layer, electron blocking layer, P-type In f Ga 1-f N layer and contact layer;

[0022] A waveguide layer is epitaxially grown between the light-emitting layer and the electron blocking layer, wherein the waveguide layer is In e Ga 1- e N thin film layer, wherein the In composition e is 0.01-0.1.

[0023] Further description, the step of growing the waveguide layer includes:

[0024] The temperature is set between 800-100℃, triethylgallium, trimethylindium and ammonia are introduced into the reaction chamber, wherein nitrogen and hydrogen are used as carrier gases, and In2O3 with a thickness of 5-10nm is epitaxially grown on the light-emitting layer. e Ga 1-e N thin film layer, wherein the In composition e is 0.01-0.1. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0026] Figure 1 Schematic diagram of the structure of the micro-LED in the first embodiment of the present invention;

[0027] Figure 2 Flowchart of a method for preparing micro-LEDs according to a second embodiment of the present invention;

[0028] Component symbol description in the attached figure:

[0029] Substrate 100, mask layer 110, red light epitaxial preparation layer 200, N-type In b Ga 1-b N / GaN layer 300, light emitting layer 400, waveguide layer 500, electron blocking layer 600, P-type In f Ga 1-f N layer 700 and contact layer 800 . DETAILED DESCRIPTION

[0030] To make the objectives, features, and advantages of the present invention more readily apparent, the following detailed description of specific embodiments of the present invention is provided in conjunction with the accompanying drawings. The accompanying drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0031] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an element centered thereon. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an element centered thereon. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used herein are for illustrative purposes only and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0032] In the present invention, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixed," and the like should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances. The term "and / or" as used herein includes any and all combinations of one or more of the relevant listed items.

[0033] Example 1

[0034] See also Figure 1 , shown is a micro-LED provided by the first embodiment of the present invention, which is applied to red micro-LEDs. The micro-LED includes a substrate 100, also known as a supporting substrate. Substrate 100 is primarily the foundation for epitaxial layer growth, used to support and secure subsequent epitaxial layers. The selection of substrate 100 must strictly match the characteristics of the epitaxial layer, otherwise it will affect the growth of the epitaxial layer and the quality of the micro-LED. The choice of substrate 100 also determines the subsequent epitaxial layer growth technology, chip processing technology, and LED packaging technology. In this embodiment, the material of substrate 100 can be sapphire, silicon carbide, silicon, gallium oxide, gallium nitride, etc.

[0035] Among them, a mask layer 110 is provided on the substrate 100, and the mask layer 110 is etched into a specific pattern by nanoimprinting or photolithography to form a patterned composite substrate, which is conducive to the growth of the subsequent epitaxial layer, can effectively reduce the threading dislocation density, and improve the crystal quality of the subsequent epitaxial layer. The mask layer 110 is grown on the substrate 100 by the PECVD method. SiO2 or SiN x Thin film layer, plasma enhanced chemical vapor deposition (PECVD) is to use microwave or radio frequency to ionize the gas containing the atoms of the film components, forming plasma locally. The plasma chemical activity is very strong and it is easy to react to deposit the desired thin film on the substrate. Specifically, silane (SiH4), oxygen (O2) or ammonia (NH3) gas is introduced into the PECVD reaction chamber to deposit a layer of SiO2 or SiN with a thickness of 1000-3000nm on the substrate 100. x Thin film layer, the deposited SiO2 or SiN x Spin-coat a layer of photoresist with a thickness of 1000-3000nm on the film layer, and use nanoimprint technology or photolithography technology to coat SiO2 or SiN xThe thin film layer is made into a specific pattern. Among them, nanoimprint technology is to transfer the pattern on the silicon master to the soft template by imprinting, and then continue to transfer the pattern on the soft template to the photoresist by imprinting. Photolithography technology is to transfer the pattern on the photoresist plate to the photoresist through ultraviolet light irradiation.

[0036] In addition, the SiO2 or SiN x The thin film layer is etched by ICP (Inductively Coupled Plasma). Inductively Coupled Plasma (ICP) etching is a process in which the etching gas glow discharge generates a high-density plasma under the action of an electric field, which physically bombards and chemically reacts with the material to be etched to selectively remove the area to be removed. Specifically, the etching gas boron trichloride (BCl3) is introduced into the reaction chamber, and SiO2 or SiN is etched by ICP. x The thin film layer is etched into a specific pattern to make SiO2 or SiN x The thin film layer has several periodically arranged epitaxial growth regions, among which the unetched SiO2 or SiN x The width of the thin film layer is 100-3000nm, and the periodically arranged SiO2 or SiN is etched x The width of the thin film layer is 10-100 nm and the thickness is 100-3000 nm.

[0037] Among them, a red epitaxial preparation layer 200, an N-type In b Ga 1-b N / GaN layer 300, light emitting layer 400, electron blocking layer 600, P-type In f Ga 1-f N layer 700 and contact layer 800. Red light epitaxial preparation layer 200 is In a Ga 1-a N thin film layer, due to the large lattice mismatch between micro-LED and GaN-based epitaxial layer, in the epitaxial growth of N-type In b Ga 1-b The red light epitaxial preparation layer 200 is pre-grown on the N / GaN layer 300, which can reduce the N-type In b Ga 1-b The lattice mismatch between the N / GaN layer 300 and the substrate 100 facilitates the subsequent growth of N-type In b Ga 1-b N / GaN layer 300, to avoid N-type In b Ga 1-b The N / GaN layer 300 is directly deposited on the substrate 100, which has a large lattice mismatch, resulting in the N-type In b Ga 1-bA large number of lattice defects and dislocations appear at the interface between the N / GaN layer 300 and the substrate 100, resulting in N-type In b Ga 1-b The crystal quality of the N / GaN layer 300 is degraded, and even the performance of the micro-LED is affected.

[0038] Specifically, the patterned composite substrate is transferred to an MOCVD (metal organic chemical vapor deposition) reaction chamber. Metal organic chemical vapor deposition (MOCVD) uses organic compounds of Group III and Group II elements and hydrides of Group V and VI elements as crystal growth source materials, and performs vapor phase epitaxy on substrate 100 by thermal decomposition reaction to grow thin-layer single crystal materials of various Group III-V, Group II-VI compound semiconductors and their multicomponent solid solutions. The temperature is heated to between 800-1200°C, the pressure is adjusted to between 100-500 Torr, and trimethylgallium ((CH3)3Ga), trimethylindium (In(CH3)3) and ammonia (NH3) are introduced. Nitrogen (N2) and hydrogen (H2) are used as carrier gases to epitaxially grow In2O3 with a thickness of 100-2000nm. a Ga 1-a The N thin film layer serves as the red light epitaxial preparation layer 200 , wherein the In composition a is 0-0.2.

[0039] Among them, N-type In is provided on the red light epitaxial preparation layer 200. b Ga 1-b N / GaN layer 300, N-type In b Ga 1-b The N / GaN layer 300 is used to provide electrons. It has excess electrons. b Ga 1-b The electrons in the N / GaN layer 300 migrate to the light-emitting layer 400, so that the electrons and holes can be radiatively recombinated in the light-emitting layer 400, thereby achieving the light-emitting effect of the micro-LED. b Ga 1- b The N / GaN layer 300 is a periodic superlattice structure, and several In b Ga 1-b The periodic structure formed by the N thin film layer / GaN thin film layer has a period number of 10-30. Specifically, trimethyl gallium ((CH3)3Ga), silane (SiH4) and ammonia (NH3) are introduced, and nitrogen (N2) and hydrogen (H2) are used as carrier gases. At a temperature between 1000-1200℃ and a pressure between 100-300Torr, epitaxial growth is performed to form N-type In b Ga 1-b N / GaN layer 300, wherein In b Ga 1-bThe thickness of the N thin film layer is 1-5 nm, the component b of In is 0.01-0.1, and the thickness of the GaN thin film layer is 10-50 nm.

[0040] In addition, in N-type In b Ga 1-b The light emitting layer 400 is provided on the N / GaN layer 300. The light emitting layer 400 is a multi-quantum well structure including several periods of In c Ga 1-c N well layer and In d Ga 1-d N barrier layer, the number of cycles is 1-10, specifically, triethylgallium (Ga(C2H5)3), trimethylindium (In(CH3)3) and ammonia (NH3) are introduced into the reaction chamber, nitrogen (N2) is used as a carrier gas, the temperature is adjusted to between 700-800℃, the pressure is adjusted to between 100-300Torr, and In2O3 with a thickness of 1-5nm is epitaxially grown. c Ga 1-c The N well layer has an In component c of 0.3-0.5. In addition, triethylgallium (Ga(C2H5)3), trimethylindium (In(CH3)3) and ammonia (NH3) are introduced into the reaction chamber. Nitrogen (N2) and hydrogen (H2) are used as carrier gases. The temperature is set to between 700-900°C and the pressure is set to between 100-300 Torr. In is epitaxially grown to a thickness of 5-15nm. d Ga 1-d The N barrier layer has an In composition d of 0.01-0.1. b Ga 1-b The N / GaN layer 300 has excess electrons, and the N-type In b Ga 1-b The electrons in the N / GaN layer 300 migrate to the light emitting layer 400, and the P-type In f Ga 1-f The N layer 700 has extra holes, and the P-type In f Ga 1-f The holes in the N layer 700 migrate to the light-emitting layer 400 to realize electron-hole radiative recombination in the multi-quantum well structure of the light-emitting layer 400, thereby realizing the light-emitting effect of the micro-LED.

[0041] In this embodiment, a waveguide layer 500 is provided on the light emitting layer 400. The waveguide layer 500 is In e Ga 1-eN thin film layer, since the C, Mg, Al and other atoms in the subsequent epitaxial layer will diffuse into the multi-quantum well layer of the light-emitting layer 400, the internal quantum efficiency in the multi-quantum well layer will be reduced, that is, the radiation recombination efficiency of electrons and holes in the multi-quantum well layer will be reduced. The setting of the waveguide layer 500 will block the C, Mg, Al and other atoms in the subsequent epitaxial layer from diffusing into the multi-quantum well layer of the light-emitting layer 400, thereby improving the radiation recombination efficiency of electrons and holes in the multi-quantum well layer, thereby improving the luminous efficiency of the micro-LED. At the same time, since the electron migration rate is faster than the hole migration rate, the N-type In b Ga 1-b Electrons in the N / GaN layer 300 easily flow to the P-type In f Ga 1- f N layer 700 overflows, and the P-type In f Ga 1-f The N layer 700 undergoes electron-hole recombination, which reduces the efficiency of electron-hole radiation recombination in the multi-quantum well layer, thereby reducing the luminous efficiency of the micro-LED. The waveguide layer 500 can prevent the N-type In b Ga 1-b The electrons in the N / GaN layer 300 overflow into the P-type In f Ga 1-f The N layer 700 reduces carrier leakage, further improves the electron-hole radiation recombination efficiency, and further improves the luminous efficiency of the micro-LED.

[0042] Specifically, the temperature is adjusted to between 800-1000°C, triethylgallium (Ga(C2H5)3), trimethylindium (In(CH3)3) and ammonia (NH3) are introduced into the reaction chamber, wherein nitrogen (N2) and hydrogen (H2) are used as carrier gases to epitaxially grow In2O3 with a thickness of 5-10 nm on the light-emitting layer 400. e Ga 1-e N thin film layer, wherein the In composition e is 0.01-0.1.

[0043] The electron blocking layer 600 is provided on the waveguide layer 500. The electron blocking layer 600 is an AlGaN thin film layer, which is used to block the N-type In b Ga 1-b The electrons in the N / GaN layer 300 are directed to the P-type In f Ga 1-fThe N layer 700 overflows, specifically, by setting the temperature to between 700-800°C and the pressure to between 100-300 Torr, and introducing trimethylaluminum (C3H9Al), triethylgallium (Ga(C2H5)3) and ammonia (NH3) into the reaction chamber, and epitaxially growing an AlGaN thin film layer with a thickness of 10-30nm on the waveguide layer 500. Similarly, the electron migration rate is faster than the hole migration rate, and the N-type In b Ga 1-b The electrons in the N / GaN layer 300 easily overflow to the P-type InfGa1-fN layer 700. f Ga 1-f The N layer 700 undergoes electron-hole non-radiative recombination, and the electron blocking layer 600 further prevents the N-type In b Ga 1-b The electrons in the N / GaN layer 300 overflow into the P-type In f Ga 1-f N layer 700, reducing N-type In b Ga 1-b The leakage of electrons in the N / GaN layer 300 further improves the radiative recombination efficiency of electrons and holes in the multi-quantum wells, thereby improving the luminous efficiency of the micro-LED.

[0044] In addition, a P-type In f Ga 1-f N layer 700, P type In f Ga 1-f The N layer 700 is used to provide holes, and it has excess holes. f Ga 1-f The holes in the N layer 700 migrate to the light-emitting layer 400, and the electrons and holes realize radiative recombination in the multi-quantum wells of the light-emitting layer 400, thereby realizing the light-emitting effect of the micro-LED. f Ga 1-f The N layer 700 is grown in two stages: first, low temperature and low pressure growth, and then high temperature and high pressure growth. f Ga 1-f The N layer 700 reduces internal defects in the crystal, improves crystal quality, and thus improves the performance of the micro-LED. Specifically, first, magnesium cyclopentadienyl (Mg(C5H5)2), triethyl gallium (Ga(C2H5)3), and ammonia (NH3) are introduced into the reaction chamber, with nitrogen (N2) and hydrogen (H2) as carrier gases. The temperature is heated to between 700-900°C, and the pressure is adjusted to between 100-300 Torr. P-type Indium ions are then grown epitaxially. f Ga 1-fN layer 700, then, the temperature is heated to between 900-1100 ° C, the pressure is adjusted to between 200-500 Torr, and a two-stage epitaxial growth is performed to form a P-type In layer with a thickness of 100-200 nm. f Ga 1-f The N layer 700 has an In composition f of 0.01-0.1.

[0045] Naturally, in P-type In f Ga 1-f A contact layer 800 is provided on the N layer 700. The contact layer 800 is doped with In g Ga 1-g The N thin film layer is used to form an ohmic contact when bonding with the chip electrode, effectively reducing voltage and increasing brightness. Specifically, the temperature is set to between 800-1000°C and the pressure is adjusted to between 100-400 Torr. Magnesium cyclopentadienyl (Mg(C5H5)2), triethylgallium (Ga(C2H5)3) and ammonia (NH3) are introduced into the reaction chamber. The carrier gas is nitrogen (N2) and hydrogen (H2). Epitaxial growth forms a 5-30nm thick In doped layer. g Ga 1-g The N thin film layer has an In component g of 0.01-0.1, wherein the amount of the dopant bismuth magnesium (Mg(C5H5)2) introduced is P-type In f Ga 1-f 5-20 times the amount of the dopant bismuth magnesium (Mg(C5H5)2) introduced into the N layer 700.

[0046] It should be noted that when an electric field is applied across the micro-LED, the N-type In b Ga 1-b The N / GaN layer 300 serves as the cathode, and the P-type In f Ga 1-f The N layer 700 serves as the positive electrode, and the N-type In b Ga 1-b The electrons in the N / GaN layer 300 are directed to the positive electrode P-type In f Ga 1-f N layer 700 direction migration, P type In f Ga 1-f The holes in the N layer 700 flow to the negative electrode N-type In b Ga 1-b The electrons migrate in the direction of the N / GaN layer 300, and the electrons and holes migrated on both sides merge in the light-emitting layer 400. In the multi-quantum well layer of the light-emitting layer 400, the electrons and holes undergo radiative recombination, thus forming the micro-LED luminescence effect. f Ga 1-fThe C, Mg, Al atoms in the N layer 700 will diffuse into the multi-quantum well layer of the light-emitting layer 400, resulting in a decrease in the internal quantum efficiency of the multi-quantum well layer, that is, a decrease in the radiation recombination efficiency of electrons and holes in the multi-quantum well layer. A waveguide layer 500 is provided between the light-emitting layer 400 and the electron blocking layer 600 to block the P-type In f Ga 1-f The C, Mg, Al atoms in the N layer 700 diffuse into the multi-quantum well layer of the light-emitting layer 400, thereby increasing the radiation recombination efficiency of electrons and holes in the multi-quantum well layer, thereby increasing the luminous efficiency of the micro-LED. b Ga 1-b Electrons in the N / GaN layer 300 easily flow to the P-type In f Ga 1-f N layer 700 overflows, and the P-type In f Ga 1-f The N layer 700 undergoes non-radiative recombination of electron holes, which reduces the efficiency of radiative recombination of electron holes in the multi-quantum well layer, thereby reducing the luminous efficiency of the micro-LED. The waveguide layer 500 can prevent the N-type In b Ga 1-b The electrons in the N / GaN layer 300 overflow into the P-type In f Ga 1-f The N layer 700 reduces the leakage of carriers, further improves the efficiency of electron-hole radiation recombination, and further improves the luminous efficiency of the micro-LED. The external quantum efficiency of the micro-LED epitaxial structure in this embodiment is 8A / cm 2 At a current density of about 10%, it is improved compared to the traditional epitaxial structure.

[0047] Compared with the prior art, the micro-LED provided in this embodiment has the following advantages: a waveguide layer is provided between the light-emitting layer and the electron blocking layer. e Ga 1-e The N thin film layer can block the C, Mg, Al and other atoms in the subsequent epitaxial layer from diffusing into the light-emitting layer, thereby improving the radiation recombination efficiency of electrons and holes in the light-emitting layer and improving the luminous efficiency of micro-LEDs. At the same time, the waveguide layer can block the N-type In b Ga 1-b N / GaN electrons overflow to P-type In f Ga 1-fThe N layer reduces carrier leakage, further improving the efficiency of electron-hole radiative recombination, and further enhancing the luminous efficiency of micro-LEDs. This solves the common technical problem of impurities in the epitaxial layer diffusing into the light-emitting layer, resulting in low luminous efficiency. In addition, the patterned composite substrate facilitates the growth of the epitaxial layer, effectively reducing the threading dislocation density and improving the crystal quality of the epitaxial layer.

[0048] Example 2

[0049] See also Figure 2 , which shows a method for preparing a micro-LED provided by a second embodiment of the present invention, the method comprising steps S10-S13:

[0050] Step S10, providing a substrate;

[0051] The substrate serves as the base for epitaxial layer growth, supporting and securing subsequent epitaxial layers. The choice of substrate must be highly compatible with the epitaxial layer's characteristics; otherwise, it will affect epitaxial layer growth and the quality of the micro-LED. The choice of substrate determines the subsequent epitaxial layer growth technology, chip processing technology, and LED packaging technology. In this embodiment, the substrate material can be sapphire, silicon carbide, silicon, gallium oxide, gallium nitride, etc.

[0052] Step S11, growing a mask layer on the substrate to form a patterned composite substrate;

[0053] Among them, forming a patterned composite substrate on the substrate is conducive to the growth of the subsequent epitaxial layer, can effectively reduce the threading dislocation density, and improve the crystal quality of the subsequent epitaxial layer.

[0054] Specifically, silane (SiH4), oxygen (O2) or ammonia (NH3) gas is introduced into the PECVD reaction chamber to deposit a layer of SiO2 or SiN with a thickness of 1000-3000nm on the substrate. x The thin film layer acts as a mask layer. Plasma-enhanced chemical vapor deposition (PECVD) uses microwaves or radio frequency to ionize the gas containing the atoms of the film components, forming a plasma locally. The plasma is highly chemically active and easily reacts, depositing the desired thin film on the substrate.

[0055] Secondly, the SiO2 or SiN deposited on the substrate x A layer of photoresist is spin-coated on the film layer. The thickness of the photoresist is 1000-3000nm. SiO2 or SiN xThe thin film layer is made into a specific pattern. Among them, nanoimprint technology is to transfer the pattern on the silicon master to the soft template by imprinting, and then continue to transfer the pattern on the soft template to the photoresist by imprinting. Photolithography technology is to transfer the pattern on the photoresist plate to the photoresist through ultraviolet light irradiation.

[0056] Finally, the etching gas boron trichloride (BCl3) is introduced into the reaction chamber, and the SiO2 or SiN with an epitaxial width of 100-3000nm is etched by ICP (inductively coupled plasma). x The thin film layer is etched into a specific pattern to make SiO2 or SiN x The thin film layer has several periodically arranged epitaxial growth regions, periodically arranged SiO2 or SiN x The film layer has a width of 10-100nm and a thickness of 100-3000nm. Inductively coupled plasma (ICP) etching uses an electric field to generate a high-density plasma through glow discharge of an etching gas. This plasma physically bombards and chemically reacts with the material to be etched, selectively removing the desired area.

[0057] Step S12, sequentially growing a red epitaxial preparation layer, an N-type In layer, and a b Ga 1-b N / GaN layer, light-emitting layer, electron blocking layer, P-type In f Ga 1-f N layer and contact layer;

[0058] Among them, a red light epitaxial preparation layer is epitaxially grown on a patterned composite substrate, and an N-type In b Ga 1-b The N / GaN layer is pre-grown with a red epitaxial preparation layer, which can reduce the size of the N-type In b Ga 1-b The lattice mismatch between the N / GaN layer and the substrate reduces the N-type In b Ga 1-b During the epitaxial growth of the N / GaN layer, the crystal defects and dislocations caused by the large lattice mismatch increase the N-type In b Ga 1-b The crystal quality of the epitaxial growth of the N / GaN layer is improved, thereby improving the performance of micro-LEDs.

[0059] Specifically, the temperature is set to between 800-1200 ° C and the pressure is set to between 100-500 Torr. Trimethyl gallium ((CH3)3Ga), trimethyl indium (In(CH3)3) and ammonia (NH3) are introduced. Nitrogen (N2) and hydrogen (H2) are used as carrier gases to epitaxially grow In2O3 with a thickness of 100-2000 nm on the patterned composite substrate. aGa 1-a The N thin film layer serves as a preparation layer for red light epitaxy, wherein the In component a is 0-0.2.

[0060] In addition, a Ga 1-a N-type In epitaxial growth on N red light epitaxial preparation layer b Ga 1-b N / GaN layer, N-type In b Ga 1-b The N / GaN layer is used to provide electrons, and it has excess electrons. b Ga 1-b The electrons in the N / GaN layer migrate to the light-emitting layer, so that the electrons and holes can be radiatively recombinated in the light-emitting layer, thus achieving the light-emitting effect of the micro-LED. b Ga 1-b The N / GaN layer is a periodic superlattice structure consisting of 10-30 In b Ga 1-b A periodic structure formed by N thin film layer / GaN thin film layer.

[0061] Specifically, trimethylgallium ((CH3)3Ga), silane (SiH4) and ammonia (NH3) are introduced into the reaction chamber, nitrogen (N2) and hydrogen (H2) are used as carrier gases, the growth temperature is between 1000-1200℃, the pressure is between 100-300Torr, and the In a Ga 1-a N-type In epitaxial growth is formed on the N red light epitaxial preparation layer. b Ga 1-b N / GaN layer, where In b Ga 1-b The thickness of the N thin film layer is 1-5 nm, the component b of In is 0.01-0.1, and the thickness of the GaN thin film layer is 10-50 nm.

[0062] Among them, the light-emitting layer is epitaxially grown on the N-type InbGa1-bN / GaN layer, and the light-emitting layer is a multi-quantum well structure, including several periodic In c Ga 1-c N well layer and In d Ga 1-d N barrier layer, the period number is 1-10. b Ga 1-b The electrons in the N / GaN layer migrate to the light-emitting layer, and the P-type In f Ga 1-f The holes in the N layer migrate to the light-emitting layer to realize electron-hole radiative recombination in the multi-quantum well structure of the light-emitting layer, thereby realizing the luminescence effect of the micro-LED.

[0063] Specifically, triethylgallium (Ga(C2H5)3), trimethylindium (In(CH3)3) and ammonia (NH3) are introduced into the reaction chamber, and nitrogen (N2) is used as a carrier gas. The temperature is adjusted to between 700-800°C and the pressure is adjusted to between 100-300 Torr. Indium with a thickness of 1-5 nm is epitaxially grown. c Ga 1-c In the N well layer, the In component c is 0.3-0.5; in addition, triethylgallium (Ga(C2H5)3), trimethylindium (In(CH3)3) and ammonia (NH3) are introduced into the reaction chamber, with nitrogen (N2) and hydrogen (H2) as carrier gases. The temperature is set to between 700-900℃ and the pressure is set to between 100-300Torr to epitaxially grow In with a thickness of 5-15nm. d Ga 1-d In the N barrier layer, the In composition d is 0.01-0.1.

[0064] In addition, the electron blocking layer is an AlGaN thin film layer, which is used to block N-type In b Ga 1-b The electrons in the N / GaN layer move to the P-type In f Ga 1-f N layer overflow. It should be noted that the electron migration rate is faster than the hole migration rate. b Ga 1-b The electrons in the N / GaN layer easily move to the P-type In f Ga 1-f N layer overflow, in P type In f Ga 1-f Electron-hole non-radiative recombination occurs in the N layer, and the AlGaN electron blocking layer will block the N-type In b Ga 1-b The electrons in the N / GaN layer overflow into the P-type In f Ga 1-f N layer, reducing N-type In b Ga 1-b The leakage of electrons in the N / GaN layer causes non-radiative recombination, which improves the radiative recombination efficiency of electrons and holes in the multi-quantum wells, thereby improving the luminous efficiency of the micro-LED.

[0065] Specifically, the temperature is heated to between 700-800°C, the pressure is adjusted to between 100-300 Torr, trimethylaluminum (C3H9Al), triethylgallium (Ga(C2H5)3) and ammonia (NH3) are introduced into the reaction chamber to epitaxially grow an AlGaN thin film layer with a thickness of 10-30nm.

[0066] Naturally, P-type In is epitaxially grown on the AlGaN electron blocking layer.f Ga 1-f N layer, P type In f Ga 1-f The N layer is used to provide holes, and it has extra holes. f Ga 1-f The holes in the N layer migrate to the light-emitting layer, and the electrons and holes realize radiative recombination in the multi-quantum wells of the light-emitting layer, thereby realizing the luminous effect of the micro-LED. f Ga 1-f The N layer is grown in two stages: low temperature and low pressure, and high temperature and high pressure. The two-stage growth is beneficial to reducing internal defects in the crystal, improving crystal quality, and thus improving the performance of micro-LEDs.

[0067] Specifically, magnesium cyclopentadienyl (Mg(C5H5)2), triethyl gallium (Ga(C2H5)3) and ammonia (NH3) are introduced into the reaction chamber, and nitrogen (N2) and hydrogen (H2) are used as carrier gases. First, the temperature is heated to between 700-900°C and the pressure is adjusted to between 100-300 Torr. Second, the temperature is heated to between 900-1100°C and the pressure is adjusted to between 200-500 Torr. A P-type In layer with a thickness of 100-200 nm is epitaxially grown on the AlGaN electron blocking layer. f Ga 1-f N layer, wherein the In composition f is 0.01-0.1.

[0068] Among them, in P-type In f Ga 1-f A contact layer is grown epitaxially on the N layer, and the contact layer is doped with In g Ga 1-g The N thin film layer is used to form an ohmic contact when bonding with the chip electrode, effectively reducing voltage and increasing brightness.

[0069] Specifically, the temperature is set to between 800-1000 ° C, the pressure is adjusted to between 100-400 Torr, and bismuth magnesium (Mg (C5H5) 2), triethyl gallium (Ga (C2H5) 3) and ammonia (NH3) are introduced into the reaction chamber, and the carrier gas is nitrogen (N2) and hydrogen (H2). f Ga 1-f Epitaxial growth of 5-30nm doped In layers is formed on the N layer. g Ga 1-g The N thin film layer has an In component g of 0.01-0.1, wherein the amount of the dopant bismuth magnesium (Mg(C5H5)2) introduced is P-type In f Ga 1-f 5-20 times the amount of the N-layer dopant magnesium cyclopentadienyl (Mg(C5H5)2) introduced.

[0070] It should be noted that when an electric field is applied to both ends of the micro-LED, the N-type In b Ga 1-b The N / GaN layer serves as the negative electrode, and the P-type In f Ga 1-f The N layer is used as the positive electrode, and the N-type In b Ga 1-b The electrons in the N / GaN layer flow to the positive electrode P-type In f Ga 1-f Migration in the N-layer direction, P-type In f Ga 1-f The holes in the N layer flow to the negative electrode N-type In b Ga 1-b The electrons and holes migrate in the direction of the N / GaN layer, and the electrons and holes migrated on both sides converge in the light-emitting layer. In the multi-quantum well layer of the light-emitting layer, the electrons and holes undergo radiative recombination, thereby forming a micro-LED luminescence effect.

[0071] Step S13, epitaxially growing a waveguide layer between the light-emitting layer and the electron blocking layer, wherein the waveguide layer is In e Ga 1-e N thin film layer, wherein the In composition e is 0.01-0.1.

[0072] Among them, a waveguide layer is epitaxially grown between the light-emitting layer and the electron blocking layer. The waveguide layer is In e Ga 1-e In the N thin film layer, since the C, Mg, Al and other atoms in the subsequent epitaxial layer will diffuse into the multi-quantum well layer of the light-emitting layer, the C, Mg, Al and other atoms in the epitaxial layer will recombine with electron holes, resulting in a decrease in the radiation recombination efficiency of electrons and holes in the multi-quantum well layer. The setting of the waveguide layer will prevent the C, Mg, Al and other atoms in the subsequent epitaxial layer from diffusing into the multi-quantum well layer of the light-emitting layer, thereby improving the radiation recombination efficiency of electrons and holes in the multi-quantum well layer, thereby improving the luminous efficiency of micro-LEDs. At the same time, since the electron migration rate is faster than the hole migration rate, the N-type In b Ga 1-b The electrons in the N / GaN layer easily move to the P-type In f Ga 1-f N layer overflow, in P type In f Ga 1-f The non-radiative recombination of electrons and holes occurs in the N layer, which reduces the efficiency of radiative recombination of electrons and holes in the multi-quantum well layer. The waveguide layer can prevent the N-type In b Ga 1-b The electrons in the N / GaN layer overflow into the P-type In f Ga 1-fThe N layer reduces the leakage of carriers, further improves the efficiency of electron-hole radiation recombination, and further improves the luminous efficiency of the micro-LED. In this embodiment, the external quantum efficiency of the micro-LED epitaxial structure is 8A / cm 2 At a current density of about 10%, it is improved compared to the traditional epitaxial structure.

[0073] Specifically, the temperature is adjusted to between 800-1000 ° C, triethyl gallium (Ga(C2H5)3), trimethyl indium (In(CH3)3) and ammonia (NH3) are introduced into the reaction chamber, wherein nitrogen (N2) and hydrogen (H2) are used as carrier gases to epitaxially grow In2O3 with a thickness of 5-10nm on the light-emitting layer. e Ga 1-e N thin film layer, wherein the In composition e is 0.01-0.1.

[0074] Compared with the prior art, the micro-LED preparation method provided in this embodiment has the following advantages: through the micro-LED preparation method provided by the present invention, an epitaxial growth waveguide layer is provided between the light-emitting layer and the electron blocking layer, and the waveguide layer is In e Ga 1-e The N thin film layer can block the C, Mg, Al and other atoms in the subsequent epitaxial layer from diffusing into the light-emitting layer, preventing the C, Mg, Al and other atoms in the epitaxial layer from recombining with electron holes, thereby improving the radiation recombination efficiency of electrons and holes in the light-emitting layer and improving the luminous efficiency of micro-LEDs. At the same time, the waveguide layer can block the N-type In b Ga 1-b The electrons in the N / GaN layer overflow into the P-type In f Ga 1-f The N layer reduces carrier leakage, further improving the efficiency of electron-hole radiative recombination, and further enhancing the luminous efficiency of micro-LEDs. This solves the common technical problem of impurities in the epitaxial layer diffusing into the light-emitting layer, resulting in low luminous efficiency. In addition, the patterned composite substrate facilitates the growth of the epitaxial layer, effectively reducing the threading dislocation density and improving the crystal quality of the epitaxial layer.

[0075] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0076] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A micro-LED, applied to red light micro-LED, characterized in that: The micro-LED includes: substrate; On the substrate, a red light epitaxial preparation layer, an N-type In b Ga 1-b N / GaN layer, light-emitting layer, electron blocking layer, P-type In f Ga 1-f N layer and contact layer; A waveguide layer is provided between the light emitting layer and the electron blocking layer. The waveguide layer is In e Ga 1-e N thin film layer, wherein the In component e is 0.01-0.1 and the thickness is 5-10nm, The light emitting layer is a multi-quantum well layer structure, including several periods of In c Ga 1-c N well layer and In d Ga 1-d N barrier layer, where In c Ga 1-c The thickness of the N-well layer is 1-5 nm, the In composition c is 0.3-0.5, and In d Ga 1-d The thickness of the N barrier layer is 5-15 nm, and the In composition d is 0.01-0.

1.

2. The micro-LED according to claim 1, wherein The thickness of the waveguide layer is 5-10 nm.

3. The micro-LED according to claim 1, wherein The N-type In b Ga 1-b The N / GaN layer is a periodic superlattice structure, in which In b Ga 1-b The thickness of the N thin film layer is 1-5 nm, the component b of In is 0.01-0.1, and the thickness of the GaN thin film layer is 10-50 nm.

4. The micro-LED according to claim 1, wherein The P-type In f Ga 1-f The thickness of the N layer is 100-200 nm, wherein the In composition f is 0.01-0.

1.

5. The micro-LED according to claim 1, wherein A mask layer is provided on the substrate, and the mask layer is etched into a specific pattern by nano-imprinting or photolithography to form a patterned composite substrate.

6. The micro-LED according to claim 1, wherein The red light epitaxial preparation layer is In a Ga 1-a N thin film layer, wherein the thickness of the red light epitaxial preparation layer is 100-2000nm, and the In component a is 0-0.

2.

7. The micro-LED according to claim 1, wherein The contact layer is doped with In g Ga 1-g N thin film layer, In composition g is 0.01-0.

1.

8. A method for preparing micro-LED, characterized in that: The preparation method is used to prepare the micro-LED according to claims 1 to 7, and the preparation method comprises: providing a substrate; growing a mask layer on the substrate to form a patterned composite substrate; On the patterned composite substrate, a red epitaxial preparation layer, an N-type In layer and a b Ga 1-b N / GaN layer, light-emitting layer, electron blocking layer, P-type In f Ga 1-f N layer and contact layer, the light emitting layer is a multi-quantum well layer structure, including several periods of In c Ga 1-c N well layer and In d Ga 1-d N barrier layer, where In c Ga 1-c The thickness of the N-well layer is 1-5 nm, the In composition c is 0.3-0.5, and In d Ga 1-d The thickness of the N barrier layer is 5-15 nm, and the In composition d is 0.01-0.1; A waveguide layer is epitaxially grown between the light-emitting layer and the electron blocking layer, wherein the waveguide layer is In e Ga 1-e N thin film layer, wherein the In component e is 0.01-0.1 and the thickness is 5-10 nm.

9. The method for preparing a micro-LED according to claim 8, wherein: The step of growing the waveguide layer comprises: The temperature is set between 800-100℃, triethylgallium, trimethylindium and ammonia are introduced into the reaction chamber, wherein nitrogen and hydrogen are used as carrier gases, and In2O3 with a thickness of 5-10nm is epitaxially grown on the light-emitting layer. e Ga 1-e N thin film layer, wherein the In composition e is 0.01-0.1.

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