Ingan-based red light LED epitaxial thin film structure having folded quantum well layer

Abstract

An InGaN-based red light LED epitaxial thin film structure having a folded quantum well layer, aiming to solve the problems of material matching, process complexity, optical attenuation and the like in the existing red light LED technology. By means of the specially designed folded quantum well layer, stress release layer, and porous structure, the emission wavelength of a red light LED is significantly improved to the range of 600 nm to 620 nm, the whole epitaxial barrier crystal quality is improved, and the stress is effectively released. In addition, by optimizing the structure and parameters of the epitaxial layer, the light-emitting efficiency and stability of the LED are further improved. The InGaN-based red light LED epitaxial thin film structure having a folded quantum well layer provides an innovative technical solution for the development of red light LEDs, and has important application value and development potential.

Description

InGaN-based red light LED epitaxial film structure with folded quantum well layer

[0001] The present application claims priority to the Chinese patent application No. 2024108153174, filed on June 24, 2024, with the State Intellectual Property Office, and entitled "InGaN-based red light LED epitaxial film structure with folded quantum well layer", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of semiconductor optoelectronic technology, and particularly to an InGaN-based red light LED epitaxial film structure with folded quantum well layer. BACKGROUND

[0003] The core epitaxial material of red light LED in the current market is mainly GaAs, which plays an important role in LED manufacturing. However, with the rapid development and wide application of micro-LED technology in various application fields, some problems have begun to surface. In particular, the compatibility problem between GaAs material and GaN material widely used in blue-green LED is gradually becoming a key factor restricting the further development of the industry.

[0004] This problem not only reflects the differences in physical and chemical properties between the two materials, but also reflects the insurmountable gap in process integration and performance matching. At the same time, the manufacturing process of GaAs material is quite complex, involving multiple precise process steps, which undoubtedly increases production costs and affects product yield. The decline in yield not only means waste of resources, but also affects the profitability of enterprises.

[0005] In addition, the light attenuation problem of GaAs on small-size LED chips also cannot be ignored. Although researchers and engineers have tried various methods to solve this problem, so far they have not found an economical and efficient solution. The existence of this problem not only affects the performance and service life of LED products, but also limits the further development of LED technology to some extent.

[0006] Under such circumstances, InGaN-based red light epitaxial technology has begun to attract widespread attention in the industry. This technology is considered to be a possible alternative to GaAs and a core technology for the next generation of red light LEDs. Its main advantage is that it is expected to improve the uniformity of materials and devices, thereby improving production efficiency. However, this technology is not without challenges.

[0007] The epitaxy technology of InGaN-based red LEDs is limited by the physical properties of the material. Especially when trying to achieve high In doping concentrations, the quality of the crystal is often affected, and the carrier band is distorted. These problems not only affect the performance of the LED, but also increase the difficulty and cost of manufacturing.

[0008] Therefore, in order to promote the development of InGaN-based red LED epitaxy technology, researchers are working to improve the overall crystalline quality of GaN epitaxy and find effective ways to release internal stress in the material. These efforts not only concern the performance and production cost of LED products, but also are the key to promoting the development of the entire LED industry. It can be said that solving these problems has become the primary task of developing InGaN-based red LED epitaxial thin film layers. SUMMARY

[0009] The purpose of the present application is to provide an InGaN-based red LED epitaxial thin film structure with a folded quantum well layer to solve the above technical problems. The present application further increases the emission wavelength of the LED thin film layer by special folded quantum well layer design, and realizes red light emission.

[0010] The technical solution of the present application is as follows:

[0011] An InGaN-based red LED epitaxial thin film structure with a folded quantum well layer, comprising:

[0012] a sapphire patterned substrate;

[0013] a composite buffer layer disposed on the sapphire patterned substrate;

[0014] a uGaN (un-doped gallium nitride) layer disposed on the composite buffer layer;

[0015] a stress release and porous structure generation layer disposed on the uGaN layer, comprising a multi-layer structure of u-InGaN (un-doped Si indium gallium nitride) / H2etching / GaN, for releasing stress and forming a porous structure;

[0016] a GaN cap layer disposed on the stress release and porous structure generation layer;

[0017] a N-type GaN layer cyclic structure disposed on the GaN cap layer, formed with a concave-convex surface by low-temperature growth;

[0018] a third stress release layer disposed on the N-type GaN layer cyclic structure;

[0019] The folding quantum well layer, provided on the third stress release layer, is a cyclic structure of InN layer, quantum well and quantum well barrier, the cycle number is controlled in 5-20, the thickness of the InN layer is controlled in 0.5-1.0 nm, the quantum well is InGaN with the thickness controlled in 2-3 nm, the doping concentration of In is controlled in 30%-35%, the quantum well barrier includes Barrier1 and Barrier2, wherein Barrier1 is AlGaN with the thickness controlled in 1-2 nm, the doping concentration of Al is controlled in 20%-25%, and Barrier2 is GaN with the thickness controlled in 2-3 nm;

[0020] The LT-PGaN (low temperature P-type gallium nitride) layer, the electron blocking layer (EBL), the HT-PGaN (high temperature P-type gallium nitride) layer and the P-type contact layer (P-Contact layer) are sequentially provided on the folding quantum well layer.

[0021] The folding quantum well layer is designed to control the light emitting peak wavelength of the LED in the red light band of 600-620 nm.

[0022] The composite buffer layer includes the AlN material composite buffer layer and the low temperature GaN material composite buffer layer which are sequentially provided.

[0023] In the growth process of the stress release and porous structure generation layer, the H2 etching is used to etch the surface layer and the shallow layer InN material to form the micro-pore structure.

[0024] The cyclic structure of the N-type GaN layer includes the N-type GaN layer doped with Si and the N-type InGaN layer doped with Si, the cycle number is controlled in 10-15; wherein the thickness of each layer of the N-type GaN layer doped with Si is controlled in 0.05-0.1 um, and the Si doping concentration is controlled in 1.0E19-1.5E19 atoms / cm 3 ; the thickness of each layer of the N-type InGaN layer doped with Si is controlled in 0.1-0.2 um, and the Si doping concentration is controlled in 1.0E19-1.5E19 atoms / cm 3 .

[0025] The InGaN-based red light LED epitaxial film structure with the folding quantum well layer has the light emitting peak wavelength controlled in the red light band of 600-620 nm.

[0026] The preparation method of the InGaN-based red light LED epitaxial film structure with the folded quantum well layer comprises specific growth steps, material selection and parameter control; the growth steps comprise the sequential growth of a composite buffer layer, a uGaN layer, a stress release and porous structure generation layer, a GaN cap layer, an N-GaN layer cycle structure, a third stress release layer, a multi-quantum well light emitting layer, an LT-PGaN layer, an EBL, an HT-PGaN layer and a P-Contact layer; by adjusting the fine parameters, the light emitting peak wavelength of the LED chip is controlled in the red light band of 600nm-620nm.

[0027] In the application, the design of the folded quantum well layer is a key innovation point, and by specific growth steps and parameter control, the red light band is realized: the design of the stress release and porous structure generation layer improves the overall barrier crystal quality of GaN epitaxy and releases the stress; the N-type GaN layer cycle structure adopts a low-temperature growth mode, further releases the stress and forms a concave-convex surface; the multi-quantum well light emitting layer comprises a fine structure of Well and Barrier, and an InN layer for increasing the effective In doping concentration of Well; the design of the LT-PGaN layer, the EBL layer, the HT-PGaN layer and the P-Contact layer optimizes the electron blocking and hole injection effect.

[0028] The application has the beneficial effects that: by the design of the folded quantum well layer, the light emitting wavelength and the light emitting efficiency of the InGaN-based red light LED are effectively improved; at the same time, by the special design of the stress release and porous structure generation layer, the overall barrier crystal quality of GaN epitaxy is effectively improved and the stress is released; in addition, the structure of the application also has good repeatability and stability. BRIEF DESCRIPTION OF DRAWINGS

[0029] Fig. 1 is a structural schematic diagram of a complete epitaxial barrier crystal of the application.

[0030] Fig. 2 is a schematic diagram of a u-InGaN / H2etching / GaN multilayer structure.

[0031] Fig. 3 is a TEM characterization diagram after the actual design of the u-InGaN / H2etching / GaN multilayer structure with 20 loops of cycle number is completed.

[0032] Fig. 4 shows the influence of the u-InGaN / H2etching / GaN multilayer porous structure on the light emitting wavelength of the LED structure.

[0033] Fig. 5 is a schematic diagram of an N-type GaN layer cycle structure.

[0034] Fig. 6 shows the fine structure of the multi-quantum well layer and the specific parameters.

[0035] Figure 7 is a real growth folded quantum well morphology characterization of the present application.

[0036] Figure 8 shows a PL spectrum with a peak wavelength of 616 nm and a red light emission during EL point measurement. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present application are described below in detail with reference to the accompanying drawings, so as to explain the technical solutions of the present application.

[0038] EMBODIMENT

[0039] The present application provides an InGaN-based red LED epitaxial film structure with a folded quantum well layer (as shown in Figure 1), which effectively solves the problems existing in the current red LED technology through special structural design, and realizes high-efficiency and high-quality red light emission.

[0040] The specific implementation steps are as follows:

[0041] Preparation of substrate 1: Select a sapphire patterned substrate as the substrate. This substrate has good thermal stability and mechanical strength, and is suitable for LED epitaxial growth.

[0042] Growth of composite buffer layer 2: First, a layer of AlN material composite buffer layer is grown on the substrate using PVD evaporation technology, with a thickness controlled between 15-30 nm. This layer is mainly used to relieve the lattice mismatch between the substrate and the subsequent epitaxial layer. Next, a low-temperature GaN material composite buffer layer is grown on the AlN buffer layer using MOCVD technology, with a thickness of 10-30 nm and a growth temperature maintained at 700-850°C. This step helps to further improve the bonding quality of the epitaxial layer and the substrate.

[0043] Growth of uGaN layer 3: A non-doped GaN layer is grown above the composite buffer layer. This layer first fills in the substrate pattern height through a 3D roughening layer, and then grows a cover layer to make the GaN thin film surface flat, with a total thickness controlled between 2.5-3.5 μm.

[0044] Stress release and porous structure generation layer 4 growth: Above the flat uGaN layer, a first set of stress release and porous structure generation layers are grown. The detailed structure is u-InGaN / H2etching / GaN, with InGaN thickness ranging from 2-6 nm, a 150-300 second pause layer is set after InGaN growth is completed, and the atmosphere is switched to 50% N2 / 50% H2, using H2etching to etch the surface and subsurface InN material to form micro-porous structures, followed by a layer of GaN (2-4 nm) to separate the InGaN and enlarge the size of the porous cavities formed by H2etching, with a growth temperature set to 850-950°C, and an InGaN layer growth temperature set to 720-780°C. This step can be repeated 5-20 times to further enhance the stress release effect. Figure 2 shows a schematic diagram of the u-InGaN / H2etching / GaN multilayer structure, this special structure of micro-porous structure formed by H2etching helps to release the stress in the epitaxial layer; Figure 3 is a TEM characterization diagram after the u-InGaN / H2etching / GaN multilayer structure is grown with an actual design of 20 loops, an initial design value of u-InGaN (4.5 nm), and an initial design value of GaN (2.0 nm). The average thickness of the u-InGaN single layer is 4.5 nm, and the average thickness of the GaN layer is 2.2 nm. Compared with the initial design value, the relative thickness of the u-InGaN layer is thinner, and the GaN is relatively thicker, which is mainly caused by the corrosion of InN in the u-InGaN layer by the H2etching layer, but the micro-porous morphology cannot be clearly presented under this characterization accuracy. In order to prove that the u-InGaN / H2etching / GaN multilayer porous structure designed in this scheme has an effect on the LED structure light emitting wavelength, the u-InGaN / H2etching / GaN multilayer porous structure is removed and grown, as shown in Figure 4(a), it can be clearly seen that the peak wavelength WLP after removing the u-InGaN / H2etching / GaN multilayer porous layer is about 550 nm, and the light emitting color is obviously yellow, but the peak wavelength WLP with the u-InGaN / H2etching / GaN multilayer porous layer structure is about 600 nm, and the light emitting color is red, as shown in Figure 4(b). 2 etching / GaN multilayer structure. The average thickness of the u-InGaN single layer is 4.5 nm, and the average thickness of the GaN layer is 2.2 nm. Compared with the initial design value, the relative thickness of the u-InGaN layer is thinner, and the GaN is relatively thicker, which is mainly caused by the corrosion of InN in the u-InGaN layer by the H2etching layer, but the micro-porous morphology cannot be clearly presented under this characterization accuracy. In order to prove that the u-InGaN / H2etching / GaN multilayer porous structure designed in this scheme has an effect on the LED structure light emitting wavelength, the u-InGaN / H2etching / GaN multilayer porous structure is removed and grown, as shown in Figure 4(a), it can be clearly seen that the peak wavelength WLP after removing the u-InGaN / H2etching / GaN multilayer porous layer is about 550 nm, and the light emitting color is obviously yellow, but the peak wavelength WLP with the u-InGaN / H2etching / GaN multilayer porous layer structure is about 600 nm, and the light emitting color is red, as shown in Figure 4(b).

[0045] uGaN cap layer 5 growth: After the stress release layer and porous layer cycle structure growth is completed, a uGaN cap layer with a thickness of 0.2-0.5 μm is grown to isolate the doping of the upper structure layer.

[0046] N-type GaN layer cycle structure 6 growth: on the flat uGaN surface layer, grow the N-type GaN layer cycle structure. This structure is all Si-doped N-type GaN layer, using low-temperature growth method to further release stress and form a concave-convex surface, to provide a substrate for the subsequent folding quantum well layer. Among them, the cycle structure is GaN(Si) / InGaN(Si), the single cycle thickness is controlled in 0.15-0.3 μm, the In doping concentration is controlled in 5E18-2E19 atoms / cm 3 , the cycle number is controlled in 10-15, the Si doping concentration is in 1.0E19-1.5E19 atoms / cm 3 , the overall N-type GaN layer cycle structure thickness is controlled in 1.5-3.0 μm range, the overall growth temperature is controlled in 850℃ to 950℃; its structure is shown in Figure 5.

[0047] Superlattice structure 7 growth: grow a layer of low Si-doped (1.0 E19-2.0E19 atoms / cm 3 ) n-GaN as Barrier and low In (5.0 E18-2.0E19 atoms / cm 3 ) and Si-doped (doping concentration 1.0 E19-2.0E19 atoms / cm 3 ) n-InGaN as Well superlattice structure as the third stress release layer on the N-type GaN cycle structure layer, the overall thickness range is 0.5-1.0 μm.

[0048] Folded quantum well layer 8 growth: After the growth of the folded quantum well layer, the folded quantum well layer fine structure and specific parameters are shown in FIG. 6. The folded quantum well structure is designed to increase the effective In doping concentration of the Well. The folded quantum well layer is a cyclic structure of InN layer, quantum well, and quantum well barrier. In this embodiment, the number of cycles is controlled to be 5, the thickness of the InN layer is controlled to be 0.5 nm, the thickness of the quantum well is controlled to be 2-3 nm of InGaN, and the In doping concentration is controlled to be 35%. The quantum well barrier includes Barrier 1 and Barrier 2. Barrier 1 is AlGaN with a thickness of 1-2 nm and an Al doping concentration of 25%, and Barrier 2 is GaN with a thickness of 2-3 nm. The InN layer can increase the effective In doping concentration in the InGaN quantum well. The actual growth morphology of the folded quantum well in this embodiment is shown in FIG. 7. As shown in part (a) of FIG. 7, the actual Well average is 2.36 nm = (23+20+24+22+29) Å / 5, and the actual Barrier thickness average is 3.84 nm = (47+34+43+35+33) Å / 5. There are some differences between the two characterization values and the design values. In addition to the characterization error fluctuations, there are also differences caused by the actual thickness of the folded quantum well and the thickness when grown on a flat C crystal surface. Part (b) of FIG. 7 shows a folded multi-quantum well TEM structure under a wide viewing angle.

[0049] Subsequent layer structure growth: After the growth of the multi-quantum well layer, a low-temperature PGaN layer 9, an electron blocking layer EBL 10, a high-temperature PGaN layer 11, and a PGaN contact layer 12 are sequentially grown. These layer structures help improve the light-emitting efficiency and stability of the LED. Among them, the low-temperature P-type GaN layer (LT-PGaN) has a thickness ranging from 15-30 nm, a Mg doping concentration of 5E19-1E21 atoms / cm 3 , an In doping concentration of 1E18-1E19 atoms / cm 3 , and an Al doping concentration of 1E18-5E18 atoms / cm 3 ; the electron blocking layer EBL has a thickness of 20-40 nm, and the Al doping is gradually changed from 1E21 atoms / cm 3 to 1E19 atoms / cm 3 ; the high-temperature P-type GaN layer (HT-PGaN) has a thickness of 15-30 nm, a Mg doping concentration of 1E20-1E21 atoms / cm 3 ; and the PGaN contact layer (P-Contact layer) with high Mg component has a thickness of 5-10 nm, a Mg doping concentration of 1E21-2E21 atoms / cm3 The N-type GaN layer cycle structure electrode is etched by ICP to make an interface, and ITO transparent conductive film 13 is evaporated above the PGaN contact layer, and the thickness can be controlled in the range of 30-110nm;

[0050] Electrode fabrication and testing: finally, the process layer structure of LED chip electrode (p-PAD1201, n-PAD601) is fabricated, and point measurement is carried out. By adjusting the fine parameters, the peak wavelength of the InGaN-based red light LED of the application can be controlled in the red light band of 600nm-620nm, and excellent photoelectric performance is shown. As shown in Figure 8, the PL spectrum with a peak wavelength of 616nm and the red light emission during EL point measurement.

[0051] In summary, by special folding quantum well layer design and optimization of other epitaxial layer structure, high efficiency and high quality red light emission is successfully realized. This technical scheme provides a new idea and method for the development of red light LED, and has important application value and development prospect.

Claims

1. An InGaN-based red LED epitaxial thin film structure with a folded quantum well layer, characterized in that, include: Sapphire patterned substrate; A composite buffer layer is disposed on the patterned sapphire substrate; A uGaN layer is disposed on the composite buffer layer; A stress relief and porous structure generation layer is disposed on the uGaN layer, which includes a multilayer structure of u-InGaN / H2etching / GaN for stress relief and formation of a porous structure; A GaN capping layer is disposed on the stress relief and porous structure generation layer; An N-type GaN layer loop structure is disposed on the GaN capping layer, and an uneven surface is formed by low-temperature growth. A third stress relief layer is disposed on the N-type GaN layer loop structure; A folded quantum well layer is disposed on the third stress relief layer. It is a cyclic structure of an InN layer, a quantum well, and a quantum well barrier, with the number of cycles controlled between 5 and 20. The thickness of the InN layer is controlled between 0.5 and 1.0 nm. The quantum well is InGaN with a thickness controlled between 2 and 3 nm and the In doping concentration is controlled between 30% and 35%. The quantum well barrier includes Barrier 1 and Barrier 2, wherein Barrier 1 is AlGaN with a thickness controlled between 1 and 2 nm and the Al doping concentration is controlled between 20% and 25%, and Barrier 2 is GaN with a thickness controlled between 2 and 3 nm. An LT-pGaN layer, an EBL, an HT-pGaN layer, and a P-type contact layer are sequentially disposed on the folded quantum well layer; The design of the folded quantum well layer enables the LED's peak emission wavelength to be controlled within the red light band of the 600nm~620nm range.

2. The InGaN-based red LED epitaxial thin film structure with a folded quantum well layer according to claim 1, characterized in that, The composite buffer layer comprises an AlN material composite buffer layer and a low-temperature GaN material composite buffer layer arranged sequentially.

3. The InGaN-based red LED epitaxial thin film structure with a folded quantum well layer according to claim 1, characterized in that, The stress relief and porous structure generation layer comprises 5-20 layers of u-InGaN / H2etching / GaN structure.

4. The InGaN-based red LED epitaxial thin film structure with a folded quantum well layer according to claim 1, characterized in that, The N-type GaN layer cycling structure includes a Si-doped N-type GaN layer and a Si-doped N-type InGaN layer, with the number of cycles controlled between 10 and 15.

5. The InGaN-based red LED epitaxial thin film structure with a folded quantum well layer according to claim 4, characterized in that, The thickness of each Si-doped N-type GaN layer is controlled at 0.05-0.1 μm, and the Si doping concentration is controlled at 1.0E19-1.5E19 atoms / cm². 3 .

6. The InGaN-based red LED epitaxial thin film structure with a folded quantum well layer according to claim 4, characterized in that, The thickness of each Si-doped N-type InGaN layer is controlled at 0.1-0.2 μm, and the Si doping concentration is controlled at 1.0E19-1.5E19 atoms / cm². 3 .

7. The InGaN-based red LED epitaxial thin film structure with a folded quantum well layer according to claim 1, characterized in that, Its emission peak wavelength is controlled in the red light band within the range of 600nm to 620nm.

8. The application of the InGaN-based red LED epitaxial thin film structure with a folded quantum well layer according to any one of claims 1-7 in the field of semiconductor optoelectronic technology.

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