A GaN-based light emitting diode epitaxial structure and a preparation method thereof

Abstract

The application provides a GaN-based light-emitting diode epitaxial structure and a preparation method thereof, wherein a Zn source is introduced as a surface activator during the growth of a P-type AlGaN electron blocking layer, a P-type AlGaN electron blocking layer structure with a gradient distribution of Zn concentration along the direction of the P-type AlGaN electron blocking layer is constructed, and specifically, through the core role of the Zn surface activator and the innovative design of the gradient distribution of the Zn concentration, the valence band Ev is smoothly and non-peaked along the whole process, and the hole injection is smooth along the whole process under the premise of ensuring that the conduction band Ec is smoothly and non-peaked and the strong electron blocking capability is not lost.

Description

Technical Field

[0001] This invention relates to the field of LED technology, and in particular to a GaN-based light-emitting diode epitaxial structure and its fabrication method. Background Technology

[0002] GaN-based third-generation semiconductor materials, with their core properties such as wide direct bandgap, high electron mobility, high breakdown field strength, excellent chemical stability, and radiation resistance, have become the core foundational materials for blue LEDs, green LEDs, and semiconductor lasers. They are widely used in core sectors of the national economy, including general lighting, new display backlighting, automotive lighting, plant factories, UV curing, and special lighting. As the global LED industry continues to upgrade towards higher luminous efficiency, higher power density, higher reliability, and lower energy consumption, increasingly stringent requirements are being placed on the core performance characteristics of LED devices, such as internal quantum efficiency, efficiency stability under high current (efficiency droop suppression), forward drive voltage, and long-term operating life.

[0003] In the epitaxial stacked structure of GaN-based LEDs, the p-type AlGaN electron blocking layer (EBL) is the core functional layer that determines the overall performance of the device. Its core role is reflected in two key dimensions: First, by utilizing the conduction band difference between AlGaN and GaN materials, a high-barrier electron blocking structure is constructed to restrict the leakage of electrons from the multiple quantum well (MQW) active region to the p-type layer, reducing non-radiative recombination losses caused by electron leakage. Second, as a hole transport channel, it provides a low-resistance transport path for holes injected from the p-type layer into the MQW active region. The hole injection efficiency and transport characteristics directly determine the carrier injection balance in the active region, which is the core bottleneck determining the quantum efficiency and luminous performance of the LED. Therefore, the band structure design, material crystal quality, and doping control technology of the p-type AlGaN electron blocking layer are the core research directions for the iteration of GaN-based LED technology.

[0004] The current mainstream P-type AlGaN electron blocking layer structure with uniform Al composition has inherent technical defects that cannot be overcome, which has become a core industry pain point restricting breakthroughs in LED performance. Specifically, these defects are manifested in the following aspects: 1. Abrupt polarization at the interface leads to an excessively high hole injection barrier, resulting in severely insufficient hole injection efficiency. The abrupt change in Al composition between the uniformly Al-composed EBL and the GaN barrier in the MQW active region causes a sharp distortion of the polarization electric field at the interface, forming an upward-sharp barrier of 120–180 meV in the valence band. Since holes have a large effective mass and a much lower mobility than electrons, this peak barrier severely hinders hole injection from the p-type layer into the MQW active region. This leads to a severe imbalance in electron-hole carrier injection within the active region, resulting in a significant decrease in radiative recombination efficiency, becoming the core bottleneck limiting the improvement of quantum efficiency in LEDs.

[0005] 2. Inherent defects in the growth characteristics of Al atoms lead to poor crystal quality and low controllability of high-Al-content AlGaN. The surface diffusion coefficient of Al atoms is much lower than that of Ga atoms. During the high-temperature growth process of metal-organic chemical vapor deposition (MOCVD), the thermal desorption effect of Al atoms is significant, resulting in low Al atom lattice incorporation efficiency and difficulty in accurately controlling the uniformity of Al composition. In particular, high-Al-content AlGaN materials are prone to crystal defects such as dislocations, stacking faults, and point defects. These defects not only weaken the electron blocking ability of EBL, but also act as non-radiative recombination centers, further reducing the luminous efficiency and long-term operational reliability of the device.

[0006] 3. A vicious cycle exists between electron blocking and hole transport that cannot be optimized synergistically. To improve the blocking capability for electrons leaking from the active region, the Al content of the EBL needs to be increased to increase the conduction band level. However, increasing the Al content will further exacerbate the valence band peak barrier and deteriorate hole injection performance. At the same time, in high Al content AlGaN materials, the acceptor activation energy of the P-type dopant Mg is significantly increased, and the activation rate is greatly reduced, resulting in extremely low hole concentration in the EBL. This also increases the heterojunction contact resistance between the EBL and the P-type GaN layer, increasing the device's forward drive voltage, ultimately forming an irreversible vicious cycle of "improved electron blocking capability - deteriorated hole injection performance".

[0007] To address the aforementioned shortcomings, the industry has proposed several improvement schemes, such as using an EBL structure with a gradient Al composition and introducing step-by-step doping control in the EBL. Some publicly disclosed technologies attempt to incorporate Zn elements into the barrier layer of the MQW active region to control carrier distribution. However, all existing schemes have significant technical limitations: while the gradient Al composition scheme can alleviate interface polarization abrupt changes to some extent, it cannot solve the fundamental problems of low Al atom incorporation efficiency and poor crystal quality; the scheme of incorporating Zn into the MQW active region introduces additional impurity energy levels and non-radiative recombination centers in the luminescent core region, which in turn damages the device's internal quantum efficiency and long-term operational reliability; none of the existing schemes can fundamentally solve the three core pain points of blocked hole injection, poor AlGaN crystal quality, and the inability to synergistically optimize electron blocking and hole transport. Ultimately, this leads to increased non-radiative recombination in GaN-based LED devices under high current operating conditions, resulting in severe efficiency droop (the phenomenon of decreased luminous efficiency of LEDs under high current conditions), which cannot meet the industrial upgrading requirements of high-efficiency and high-power LEDs. Summary of the Invention

[0008] Based on this, the purpose of this invention is to provide a GaN-based light-emitting diode epitaxial structure and its fabrication method, aiming to develop a P-type AlGaN electron blocking layer structure that can simultaneously achieve improved hole injection efficiency, optimized AlGaN crystal quality, and enhanced electron blocking capability.

[0009] According to an embodiment of the present invention, a GaN-based light-emitting diode epitaxial structure includes a P-type AlGaN electron blocking layer, wherein the P-type AlGaN electron blocking layer is sequentially divided into a first region, a second region and a third region along the epitaxial growth direction, the P-type AlGaN electron blocking layer is a P-type doped AlGaN material layer, and a Zn source is introduced into the P-type AlGaN electron blocking layer during the metal-organic chemical vapor deposition growth process. The Al composition increases linearly in the first, second, and third regions, forming an arched peak in the second region. Simultaneously, the Zn concentration gradient increases in the first, second, and third regions. The molar percentage of Al in the p-type AlGaN electron blocking layer is 5%–25%, and the Zn concentration is 1 × 10⁻⁶. 16 cm -3 ~5×10 18 cm -3 ; Zn acts as a surface activator to regulate the surface diffusion ability and lattice incorporation efficiency of Al atoms, while simultaneously regulating the conduction band and valence band structure of the P-type AlGaN electron blocking layer to eliminate the hole injection spike barrier.

[0010] Preferably, the GaN-based light-emitting diode epitaxial structure further includes a substrate, a buffer layer, a three-dimensional growth layer, an unintentionally doped GaN layer, an N-type GaN layer, a stress relief layer, a multi-quantum-well active region, a P-type GaN layer, and a P-type ohmic contact layer. The buffer layer, the three-dimensional growth layer, the unintentionally doped GaN layer, the N-type GaN layer, the stress relief layer, the multi-quantum well active region, the P-type AlGaN electron blocking layer, the P-type GaN layer, and the P-type ohmic contact layer are sequentially epitaxially grown on the substrate.

[0011] Preferably, the molar percentage of Al component in the first region is 5% to 12%, the molar percentage of Al component in the second region is 12% to 20%, and the molar percentage of Al component in the third region is 18% to 25%. In addition, the Zn concentration in the first region is 1×10⁻⁶. 16 cm -3 ~2×10 17 cm -3 The Zn concentration in the second region is 3 × 10⁻⁶. 17 cm -3 ~7×10 17 cm -3 The Zn concentration in the third region is 8 × 10⁻⁶. 17 cm -3 ~5×1018 cm -3 .

[0012] Preferably, during the growth of the P-type AlGaN electron blocking layer, the flux of the Zn source is 1 sccm to 200 sccm.

[0013] Preferably, in the p-type AlGaN electron blocking layer, the p-type dopant is Mg, and the Mg doping concentration is 1×10⁻⁶. 18 cm -3 ~5×10 19 cm -3 .

[0014] Preferably, the thickness of the P-type AlGaN electron blocking layer is 5 nm to 25 nm.

[0015] According to an embodiment of the present invention, a method for fabricating a GaN-based light-emitting diode epitaxial structure is provided, which is used to fabricate the aforementioned GaN-based light-emitting diode epitaxial structure. The fabrication method includes: A p-type AlGaN electron blocking layer was grown with a Zn source continuously introduced throughout the growth process. By adjusting the flux of the Zn source, the concentration of Zn in the grown p-type AlGaN electron blocking layer was made to be 1 × 10⁻⁶. 16 cm -3 ~5×10 18 cm -3 Furthermore, in the growth direction of the P-type AlGaN electron blocking layer, the Zn concentration gradient is controlled to increase gradually, and the Al composition increases linearly. The Zn source acts as a surface activator to regulate the surface diffusion and lattice incorporation of Al atoms, while simultaneously regulating the band structure to eliminate the hole injection spike barrier.

[0016] Preferably, the preparation method further includes: A substrate required for growth is provided, and the substrate is subjected to high-temperature annealing and nitriding treatment to form a stable substrate surface; On the treated substrate, a buffer layer, a three-dimensional growth layer, an unintentionally doped GaN layer, an N-type GaN layer, a stress relief layer, a multi-quantum well active region, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type ohmic contact layer are sequentially grown by metal-organic chemical vapor deposition.

[0017] Preferably, the growth temperature of the P-type AlGaN electron blocking layer is 850℃~1100℃, the growth pressure is 150 torr~250 torr, and the Zn source flux is gradually increased during the growth process. The initial flux is 1 sccm~100 sccm, and the flux is increased to 100 sccm~200 sccm before the end of the growth process to achieve a Zn concentration gradient distribution.

[0018] Preferably, during the growth of the P-type AlGaN electron blocking layer, trimethylaluminum, trimethylgallium, and ammonia are simultaneously introduced as reaction sources, and magnesium pyrocene is introduced as a P-type doping source. The molar percentage of Al was controlled to be 5%–25%, and the doping concentration of Mg was controlled to be 1 × 10⁻⁶. 18 cm -3 ~5×10 19 cm -3 The thickness of the grown P-type AlGaN electron blocking layer is 5nm~25nm.

[0019] This invention provides a GaN-based light-emitting diode epitaxial structure and its fabrication method. By introducing a Zn source as a surface activator throughout the growth process of the P-type AlGaN electron blocking layer, a P-type AlGaN electron blocking layer structure with a gradient distribution of Zn concentration along the direction of the P-type AlGaN electron blocking layer is constructed, which has the following beneficial effects: 1. Completely eliminates the hole injection peak barrier at the MQW / EBL interface, significantly improving hole injection efficiency. By controlling the gradient distribution of Zn concentration in conjunction with the controllable regulation of Al components, a smooth transition of the valence band Ev is achieved, completely eliminating the interface peak barrier. This reduces the hole injection barrier by 80meV~120meV, significantly improving hole injection efficiency by 35%~50%, fundamentally solving the core pain points of blocked and low injection efficiency in traditional structures. 2. Significantly improves Al atom lattice incorporation efficiency, greatly enhancing the crystallinity of high-Al content AlGaN materials. The Zn source introduced throughout the process acts as a core surface activator: Zn atoms preferentially adsorb onto the AlGaN growth surface to form a quasi-monoatom layer, reducing the Al atom surface diffusion barrier by 30meV~80meV, increasing the Al atom surface diffusion coefficient by 30%~80%, and improving the lattice incorporation efficiency by 1.5 to 3 times; simultaneously, Zn surface adsorption alters the Al atom adsorption / desorption balance, suppressing thermal desorption of Al atoms at high temperatures, achieving uniform and controllable Al composition growth under the same TMAl source flow rate, avoiding the problems of Al composition fluctuation and poor crystallinity in traditional EBL growth, significantly reducing the dislocation density and surface defects of AlGaN materials, and realizing the stable growth of high-quality, high-Al content AlGaN materials; 3. Balancing strong electron blocking capability with efficient hole transport characteristics, reducing device operating voltage. Through stable and controllable Al composition design, the conduction band Ec of the EBL is ensured to rise smoothly overall, maintaining or even enhancing the blocking capability for electrons leaking from the active region, avoiding nonradiative recombination losses caused by electron overflow; at the same time, the high Zn concentration on the side of the EBL near the P-type GaN layer can effectively assist the acceptor activation of the P-type dopant Mg, increasing the hole concentration by 20%~30%, and reducing the valence band discontinuity and contact resistance of the EBL / P-type GaN heterointerface through polarization electric field modulation, ultimately achieving a reduction of approximately 0.15V in the device's forward operating voltage, achieving synergistic optimization of electron blocking and hole transport; 4. The overall optoelectronic performance of the device is significantly improved, and the efficiency droop effect is significantly suppressed. Based on the optimization of the above-mentioned structural and material properties, the optoelectronic performance of the LED device prepared by this invention achieves a comprehensive breakthrough: under a standard operating current of 20mA, the light output power of the device is increased by 28%; under a high current operating condition of 100mA, the light output power is increased by 32%; the device efficiency droop is reduced by 45% at 100mA current, and in high-power applications, the efficiency droop can be reduced to 52% at 350mA current; the peak wall penetration efficiency (WPE) of the device is increased by about 18%. Overall, it achieves excellent device performance with high luminous efficiency, low driving voltage, and low efficiency droop. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the epitaxial structure of a GaN-based light-emitting diode in an embodiment of the present invention.

[0021] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0023] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] Please see Figure 1 This is a schematic diagram of the epitaxial structure of a GaN-based light-emitting diode in an embodiment of the present invention, including a substrate 1, and a buffer layer 2, a three-dimensional growth layer 3, an unintentionally doped GaN layer 4, an N-type GaN layer 5, a stress relief layer 6, a multi-quantum well active region 7, a P-type AlGaN electron blocking layer 8, a P-type GaN layer 9, and a P-type ohmic contact layer 10, which are epitaxially grown sequentially on the substrate 1.

[0026] Specifically, substrate 1 is a patterned sapphire substrate (PSS), silicon substrate, or silicon carbide substrate, with a thickness of 200 μm to 1000 μm; buffer layer 2 is an AlN buffer layer, GaN buffer layer, or AlGaN buffer layer, with a thickness of 5 nm to 15 nm; the thickness of three-dimensional growth layer 3 is 500 nm to 1000 nm; the thickness of unintentionally doped GaN layer 4 is 1000 nm to 2000 nm; the thickness of N-type GaN layer 5 is 2000 nm to 4000 nm; and the stress relief layer 6 is an N-type AlGaN layer with a thickness of 100 nm to 2000 nm. 00nm; The multi-quantum-well active region 7 is composed of alternating stacked InGaN quantum well layers and GaN or AlGaN quantum barrier layers. In the embodiments of the present invention, the thickness of a single InGaN quantum well layer is 2nm~4nm, the thickness of a single GaN or AlGaN quantum barrier layer is 8nm~12nm, and the number of quantum well periods is 5~9; the thickness of the P-type AlGaN electron blocking layer 8 is 5nm~25nm; the thickness of the P-type GaN layer 9 is 100nm~200nm; and the thickness of the P-type ohmic contact layer 10 is 2nm~100nm.

[0027] It should be noted that the P-type AlGaN electron blocking layer 8 is divided into a first region 81, a second region 82 and a third region 83 along the epitaxial growth direction. The P-type AlGaN electron blocking layer 8 is a P-type doped AlGaN material layer, and a Zn source is introduced into the P-type AlGaN electron blocking layer 8 during the metal-organic chemical vapor deposition growth process. The Al composition in the first region 81, the second region 82, and the third region 83 increases linearly, forming an arched peak in the second region 82. Simultaneously, the Zn concentration gradient in the first region 81, the second region 82, and the third region 83 increases progressively. The molar percentage of Al in the p-type AlGaN electron blocking layer 8 is 5%–25%, and the Zn concentration is 1 × 10⁻⁶. 16 cm -3 ~5×10 18 cm -3 It should be noted that the molar percentage of Al component in the first region 81 is 5% to 12%, the molar percentage of Al component in the second region 82 is 12% to 20%, and the molar percentage of Al component in the third region 83 is 18% to 25%. In addition, the Zn concentration in the first region 81 is 1×10⁻⁶. 16 cm -3 ~2×10 17 cm -3 The Zn concentration in the second region 82 is 3 × 10⁻⁶. 17 cm -3 ~7×10 17 cm -3 The Zn concentration in the third region 83 is 8 × 10⁻⁶. 17 cm -3 ~5×10 18 cm -3 Among them, Zn forms a quasi-monolayer surface cover at a low to medium concentration (coverage rate 10%~30%), which significantly reduces the adsorption potential energy barrier of Al atoms (30meV~80meV), increases the surface diffusion coefficient by 1.5 times to 3 times, thereby achieving an Al incorporation rate increase of 15%~25% without increasing the TMAl flow rate, and forming a unique arched Al composition distribution, solving the problem of poor crystal quality of AlGaN with high Al composition; Understandably, the first region 81 (near the multi-quantum-well active region 7) has a low Al composition and low Zn concentration, achieving a smooth transition of the interface barrier between the multi-quantum-well active region 7 and the P-type AlGaN electron blocking layer 8; the second region 82 has an arched Al peak and a moderate Zn concentration, serving as the core functional region for Zn surface activators; the third region 83 (near the P-type GaN layer 9) has a high Al composition and a high Zn concentration, achieving strong electron blocking and Mg activation assistance. Zn, acting as a surface activator, regulates the surface diffusion ability and lattice incorporation efficiency of Al atoms, while simultaneously controlling the conduction and valence band structures of the p-type AlGaN electron blocking layer 8 to eliminate hole injection spike barriers. Specifically, the Al and Zn gradients work synergistically to eliminate interfacial spike barriers while ensuring no loss of electron blocking ability, and optimize the polarization electric field distribution. In this embodiment, the continuous gradient introduction of the Zn source increases the diffusion coefficient of Al atoms on the growth surface by 30% to 80%, improves the lattice incorporation efficiency of Al atoms by 1.5 to 3 times, and suppresses thermal desorption of Al atoms, achieving uniform and controllable growth of the Al composition in the p-type AlGaN electron blocking layer 8. Furthermore, through the surface activation effect and concentration gradient control of the Zn source, the valence band structure of the p-type AlGaN electron blocking layer 8 is optimized, eliminating valence band spike barriers, reducing the hole injection barrier by 80 meV to 120 meV, and improving the hole injection efficiency by 35% to 50%.

[0028] It should be noted that during the growth of the p-type AlGaN electron blocking layer 8, the flux of the Zn source is 1 sccm to 200 sccm; in the p-type AlGaN electron blocking layer 8, the p-type dopant is Mg, and the Mg doping concentration is 1 × 10⁻⁶. 18 cm -3 ~5×10 19 cm -3 .

[0029] In the embodiments of the present invention, the source materials include: trimethylgallium (TMGa), trimethylindium (TMIn), ammonia (NH3) as a group V source, silane (SiH4) as a Si donor source, diethylzinc (DEZn) or dimethylzinc (DMZn) as a Zn source, and dicyclopentadienylmagnesium (CP2Mg) as a Mg acceptor source.

[0030] This invention also provides a method for fabricating a GaN-based light-emitting diode epitaxial structure, the method comprising: S1 provides a substrate required for growth and performs high-temperature annealing and nitriding treatment on the substrate to form a stable substrate surface.

[0031] Specifically, a patterned sapphire substrate (PSS), silicon substrate, or silicon carbide substrate is selected as the growth substrate, with the substrate orientation being the (0001) plane. The substrate is placed on a graphite base in the MOCVD reaction chamber, and the rotation speed of the graphite base is set to 500 r / min to 800 r / min. First, H2 is introduced as a carrier gas, and the pressure in the reaction chamber is adjusted to 200 torr to 500 torr. At the same time, the temperature is raised to 1050℃ to 1150℃ for in-situ annealing for 5 to 10 minutes to remove contaminants from the substrate surface and form a stable surface structure.

[0032] S2, depositing a buffer layer on the substrate.

[0033] Specifically, a buffer layer is deposited on the aforementioned substrate using metal-organic chemical vapor deposition (MOCVD). The specific process parameters are as follows: Growth pressure in the reaction chamber: 50 torr ~ 200 torr; Graphite base rotation speed: 500 r / min ~ 1000 r / min; NH3 (ammonia) flow rate: 20 slm~70 slm, as a nitrogen (N) source; TMGa (trimethylgallium) flow rate: 20 sccm~150 sccm, used as a Ga (gallium) source; TMAl (trimethylaluminum) flow rate: 20 sccm~120 sccm, as an Al (aluminum) source (optional, for AlGaN buffer layer); Growth temperature: 950℃~1050℃; An AlN buffer layer, GaN buffer layer, or AlGaN buffer layer with a thickness of 5 nm to 15 nm is deposited on the substrate. The AlN buffer layer helps to reduce the lattice mismatch between the epitaxial layer and the substrate, reducing the dislocation density to 10-1. 8 cm -2 ~10 9 cm -2 Magnitude.

[0034] S3, depositing a three-dimensional growth layer on the buffer layer.

[0035] Specifically, NH3 (ammonia) gas is introduced into the buffer layer at a flow rate of 10 slm to 60 slm as the N source, and TMGa gas is introduced at a flow rate of 200 sccm to 500 sccm as the Ga source. The temperature of the reaction chamber is raised to 1000℃ to 1090℃, the pressure is controlled at 200 torr to 500 torr, and the rotation speed of the graphite base is controlled at 500 r / min to 1000 r / min.

[0036] First, a GaN nucleation layer (20nm~50nm thick) is grown, then transitioning to a three-dimensional island growth mode to grow a GaN three-dimensional island growth layer (i.e., a three-dimensional growth layer). The nucleation density and surface roughness of the three-dimensional island growth layer are controlled by adjusting the V / III ratio (molar ratio of ammonia to TMGa) within the range of 1000~5000. Ultimately, the thickness of the three-dimensional island growth layer is controlled to be 500nm~1000nm, and the surface RMS roughness is less than 2nm (AFM 5×5μm). 2 ).

[0037] S4, depositing an unintentionally doped GaN layer on a three-dimensional growth layer.

[0038] It should be noted that the temperature of the reaction chamber is raised to 1100℃~1200℃, the pressure is controlled at 150 torr~250 torr, and the rotation speed of the graphite base is controlled at 800 r / min~1200 r / min. NH3 is introduced at a flow rate of 40 slm~90 slm as the N source, and TMGa is introduced at a flow rate of 300 sccm~1000 sccm as the Ga source.

[0039] High-temperature growth conditions are used to promote surface atomic migration, achieving a two-dimensional layered growth mode (step-flow growth mode). A two-dimensional merged GaN layer (i.e., an unintentionally doped GaN layer) is grown, with its thickness controlled to be 1000 nm~2000 nm. After merging, the surface RMS roughness should be less than 1 nm (AFM 10 × 10 μm). 2 The dislocation density decreased to 10. 7 cm -2 ~10 8 cm -2 Magnitude.

[0040] S5, depositing an N-type GaN layer on an unintentionally doped GaN layer.

[0041] Specifically, the temperature of the reaction chamber is reduced to 1050℃~1100℃, the pressure is controlled at 150 torr~250 torr, and the rotation speed of the graphite base is controlled at 800 r / min~1200 r / min. NH3 is introduced at a flow rate of 30 slm~80 slm as the N source, and TMGa is introduced at a flow rate of 200 sccm~500 sccm as the Ga source.

[0042] SiH4 (silane) was introduced as an N-type dopant, with a SiH4 flow rate of 50 sccm to 200 sccm, and the Si doping concentration was 5 × 10⁻⁶. 18 atoms / cm 3 ~2×10 19 atoms / cm 3 A Si-doped N-type GaN layer was grown, and the thickness of the N-type GaN layer was controlled to be 2000 nm to 4000 nm.

[0043] Understandably, the N-type GaN layer serves as the main epitaxial layer that provides electrons. During the growth of the N-type GaN layer, SiH4 is introduced to provide Si elements. Si is a tetravalent element, while Ga in the N-type GaN layer is a trivalent element. When Si atoms replace Ga atoms, they will provide electrons, thus forming the electron-providing N-type GaN layer.

[0044] S6, a stress-relieving layer is deposited on an N-type GaN layer.

[0045] Specifically, the temperature of the reaction chamber is reduced to 1000℃~1050℃, and the pressure is controlled at 150 torr~250 torr. The rotation speed of the graphite base is controlled at 800 r / min~1200 r / min. NH3 is introduced at a flow rate of 30 slm~80 slm as the N source, TMGa is introduced at a flow rate of 150 sccm~400 sccm as the Ga source, and TMAl is introduced at a flow rate of 30 sccm~80 sccm as the Al source.

[0046] SiH4 is introduced as an N-type dopant, and the Si doping concentration is 2 × 10⁻⁶. 18 cm -3 ~5×10 18 cm -3 N-type Al grows 0.1-0.2 The GaN layer (i.e., the stress relief layer) has a thickness of 100nm~200nm. This layer is used to alleviate lattice mismatch stress and also acts as an electron spreading layer to promote electron injection into the active region.

[0047] S7, depositing a multi-quantum-well active region on the stress-relief layer.

[0048] Specifically, N alternating quantum well light-emitting layers (MQWs) are deposited, the temperature of the reaction chamber is reduced to 750℃~850℃, the pressure is controlled at 200 torr~300 torr, and the rotation speed of the graphite substrate is controlled at 500r / min~1000r / min.

[0049] Alternating stacking of InGaN quantum well layers and GaN or AlGaN quantum barrier layers. Specific parameters are as follows: InGaN quantum well layer: The In source is TMIn, the flux is 100sccm~300sccm, the In composition is 10%~22%, the growth temperature is 750℃~800℃, and the thickness is 2nm~4nm; GaN quantum barrier layer: growth temperature is 850℃~900℃, and thickness is 10nm~16nm; AlGaN quantum barrier layer (optional): Al composition of 5%~15%, thickness of 8nm~12nm; Quantum well period number: 5≤N≤9, where N is a positive integer.

[0050] S8, depositing a P-type AlGaN electron blocking layer on the multi-quantum-well active region.

[0051] Specifically, a Zn source is continuously supplied throughout the process, and a gradient distribution of Zn concentration is achieved through linear flow rate control. The specific process parameters are as follows: Growth pressure in the reaction chamber: 150 torr ~ 200 torr; Growth temperature: 850℃~1100℃; NH3 flow rate: 40 slm~80 slm; TMGa flow rate: 60 sccm~200 sccm; TMAl flow rate: 30 sccm~200 sccm, with the molar percentage of Al component stably controlled between 5% and 25%; Zn source: Diethylzinc (DEZn) or dimethylzinc (DMZn) was selected, and the flux was increased linearly with the growth process. The initial flux was 1 sccm to 100 sccm, and the flux was increased to 100 sccm to 200 sccm before the end of growth. Through flux control, the overall Zn concentration in the completed p-type AlGaN electron blocking layer was made to be 1 × 10⁻⁶. 16 cm -3 ~5×10 18 cm -3 Furthermore, a gradient distribution is formed along the epitaxial growth direction of the P-type AlGaN electron blocking layer: the Zn concentration is low on the side closer to the multi-quantum-well active region and high on the side closer to the subsequently grown P-type GaN layer. Cp2Mg (magnesium pyrocene) flow rate: 50 sccm~300 sccm, Mg doping concentration stably controlled at 1×10 18 cm -3 ~5×10 19 cm -3 ; Deposition thickness: 5nm~25nm.

[0052] The core mechanism of Zn surface activator: During the entire growth process of the p-type AlGaN electron blocking layer, Zn atoms preferentially adsorb onto the AlGaN growth surface, forming a quasi-monoatom layer. Zn surface adsorption can reduce the surface diffusion barrier of Al atoms by 30 meV~80 meV, increasing the diffusion coefficient of Al atoms on the growth surface by 30%~80% and the lattice incorporation efficiency by 1.5 times~3 times. Simultaneously, it suppresses the thermal desorption of Al atoms at high temperatures, achieving uniform and controllable growth of Al composition under the same TMAl flow rate, and avoiding abrupt polarization field changes caused by fluctuations in Al composition.

[0053] Meanwhile, the concentration gradient distribution of Zn can synergistically regulate the conduction band and valence band structure of the P-type AlGaN electron blocking layer, eliminating the hole injection peak barrier of 80meV~120meV at the interface between the multi-quantum well active region and the P-type AlGaN electron blocking layer, thereby improving the hole injection efficiency by 35%~50% and fundamentally suppressing the efficiency droop phenomenon of LEDs. The high-concentration Zn can also help increase the activation rate of Mg acceptors by 20%~30%, reduce the valence band discontinuity at the heterojunction between the P-type AlGaN electron blocking layer and the P-type GaN layer, and further optimize the continuous hole injection.

[0054] In this embodiment of the invention, the P-type AlGaN electron blocking layer is sequentially divided into a first region, a second region, and a third region along the epitaxial growth direction using the above method. The molar percentage of Al component in the first region is 5% to 12%, the molar percentage of Al component in the second region is 12% to 20%, and the molar percentage of Al component in the third region is 18% to 25%. In addition, the Zn concentration in the second region is 3 × 10⁻⁶. 17 cm -3 ~7×10 17 cm -3 .

[0055] S9, depositing a P-type GaN layer on a P-type AlGaN electron blocking layer.

[0056] Specifically, the process parameters for growing the p-type GaN layer are as follows: Reaction chamber growth pressure: 150 torr ~ 250 torr; Growth temperature: 920℃~970℃; NH3 flow rate: 40 slm~90 slm; TMGa flow rate: 300 sccm~800 sccm; Cp2Mg flow rate: 200 sccm~500 sccm, Mg concentration: 1×10 19 atoms / cm 3 ~5×10 19 atoms / cm 3 ; Deposition thickness: 100nm~200nm; Work function adjustment: A small amount of TMAl can be pre-introduced before the P-type GaN layer deposition to form a gradient interface. This allows for the growth of a highly doped P-type GaN current-spreading layer, serving as the main hole injection layer and the P-electrode contact layer.

[0057] S10, depositing a P-type ohmic contact layer on a P-type GaN layer.

[0058] The present invention will be further described below with reference to specific embodiments: Example 1 Embodiment 1 of this invention proposes a GaN-based light-emitting diode epitaxial structure. In this structure, the p-type AlGaN electron blocking layer is sequentially divided into a first region, a second region, and a third region along the epitaxial growth direction. The molar percentage of Al in the first region is 8%, the molar percentage of Al in the second region is 16% (forming an arched peak), and the molar percentage of Al in the third region is 22%. The Zn concentration in the first region is 5 × 10⁻⁶. 16 cm-3 The Zn concentration in the second region is 5 × 10⁻⁶. 17 cm -3 The Zn concentration in the third region is 2 × 10⁻⁶. 18 cm -3 The thicknesses of the first region, the second region, and the third region are 4nm, 5nm, and 6nm, respectively, with a total thickness of 15nm.

[0059] The method for fabricating the GaN-based light-emitting diode epitaxial structure proposed in Embodiment 1 of this invention includes the following steps: S1. A patterned sapphire substrate (PSS) is provided, with the substrate orientation being (0001) and a thickness of 430 μm. The substrate is placed on a graphite substrate in the MOCVD reaction chamber, and the rotation speed of the graphite substrate is set to 600 r / min. H2 is introduced as a carrier gas, the pressure in the reaction chamber is adjusted to 300 torr, the temperature is raised to 1100℃, and in-situ annealing is performed for 8 minutes.

[0060] S2, depositing an AlN buffer layer on the substrate. The reaction chamber growth pressure is 100 torr, the graphite substrate rotation speed is 800 r / min, the NH3 flow rate is 40 slm, the TMAl flow rate is 60 sccm, the growth temperature is 1000℃, and the deposition thickness is 10 nm.

[0061] S3, a three-dimensional growth layer was deposited on the buffer layer. The NH3 flow rate was 30 slm, the TMGa flow rate was 350 sccm, the temperature was increased to 1050℃, the pressure was controlled at 300 torr, and the graphite substrate rotation speed was 800 r / min. First, a GaN nucleation layer (35 nm thick) was grown, then transitioned to a three-dimensional island growth mode, with the V / III ratio controlled at 3000, resulting in a three-dimensional growth layer with a thickness of 800 nm and a surface RMS roughness of 1.2 nm.

[0062] S4. An unintentionally doped GaN layer was deposited on the three-dimensional growth layer. The temperature was increased to 1150℃, the pressure was controlled at 200 torr, the graphite substrate rotation speed was 1000 r / min, the NH3 flow rate was 60 slm, and the TMGa flow rate was 600 sccm. Through a high-temperature step-flow growth mode, an unintentionally doped GaN layer with a thickness of 1500 nm was grown, with a surface RMS roughness of 0.6 nm and a dislocation density reduced to 5 × 10⁻⁶. 7 cm -3 .

[0063] S5, depositing an N-type GaN layer on an unintentionally doped GaN layer. The temperature was lowered to 1080℃, the pressure controlled at 200 torr, the graphite substrate rotation speed at 1000 r / min, the NH3 flow rate at 50 slm, and the TMGa flow rate at 350 sccm. SiH4 was introduced as the N-type dopant, with a Si doping concentration of 1 × 10⁻⁶. 19 atoms / cm 3 An N-type GaN layer with a thickness of 3000 nm was grown.

[0064] S6. Deposit a stress-relieving layer on the N-type GaN layer. The temperature is lowered to 1020℃, the pressure is controlled at 200 torr, the graphite substrate rotation speed is 1000 r / min, the NH3 flow rate is 50 slm, the TMGa flow rate is 280 sccm, and the TMAl flow rate is 50 sccm. SiH4 is introduced as the N-type dopant, with a Si doping concentration of 3.5 × 10⁻⁶. 18 atoms / cm 3 N-type Al grows 0.15 Ga 0.85 The N-stress relief layer has a thickness of 150 nm.

[0065] S7, depositing multi-quantum-well active regions on the stress-relief layer. The temperature was lowered to 780℃, the pressure controlled at 250 torr, and the graphite substrate rotation speed at 800 r / min. Alternating stacking of InGaN quantum well layers and GaN quantum barrier layers was performed: the InGaN quantum well layer had an In composition of 15%, a growth temperature of 780℃, and a thickness of 3 nm; the GaN quantum barrier layer had a growth temperature of 880℃ and a thickness of 12 nm; the number of quantum well periods was 7.

[0066] S8, a p-type AlGaN electron blocking layer is deposited on the multi-quantum-well active region. Specifically, DEZn is continuously introduced as the Zn source throughout the process, and the gradient distribution of Zn concentration is achieved by linearly controlling the flow rate. First stage (first region growth): Reaction chamber pressure 170 torr, temperature 900℃, NH3 flow rate 60 slm, TMGa flow rate 120 sccm, TMAl flow rate 45 sccm, Cp2Mg flow rate 150 sccm, DEZn flow rate 10 sccm. Growth time 2 min, forming the first region, Al molar percentage 8%, Zn concentration 5 × 10⁻⁶. 16 cm -3 The thickness is 4nm.

[0067] Second stage (second region growth): Maintain pressure of 170 torr, increase temperature to 980℃, increase TMAl flow rate to 110 sccm, increase DEZn flow rate to 60 sccm, and Cp2Mg flow rate to 250 sccm. Growth time is 2.5 min, forming the second region, with the Al molar percentage reaching a peak of 16% and the Zn concentration at 5 × 10⁻⁶. 17 cm -3 The thickness is 5nm.

[0068] Third stage (third region growth): TMAl flow rate was adjusted to 80 sccm, DEZn flow rate increased to 150 sccm, and Cp2Mg flow rate increased to 400 sccm. Growth time was 2.5 min, forming the third region. The molar percentage of Al was 22%, and the Zn concentration was 2 × 10⁻⁶. 18 cm -3 The thickness is 6nm.

[0069] The final P-type AlGaN electron blocking layer has a total thickness of 15 nm. The Al composition in the three regions is distributed in an arch shape, with the second region forming the Al peak. The Zn concentration in the three regions increases in a gradient.

[0070] During the aforementioned growth process, Zn atoms preferentially adsorb onto the AlGaN growth surface, forming a quasi-monoatom layer with a coverage rate of 20%. Zn surface adsorption lowers the surface diffusion barrier of Al atoms by approximately 50 meV, increasing the diffusion coefficient of Al atoms on the growth surface by 55% and doubling the lattice incorporation efficiency. Simultaneously, it suppresses thermal desorption of Al atoms at high temperatures, achieving uniform and controllable growth of the Al composition. Furthermore, the Zn concentration gradient distribution synergistically regulates the conduction and valence band structures of the P-type AlGaN electron blocking layer, eliminating the approximately 100 meV hole injection spike barrier at the interface between the multi-quantum-well active region and the P-type AlGaN electron blocking layer, thus improving the hole injection efficiency by 42%. The high-concentration Zn also helps increase the activation rate of Mg acceptors by 25% and reduces the valence band discontinuity at the heterojunction interface between the P-type AlGaN electron blocking layer and the P-type GaN layer.

[0071] S9, depositing a p-type GaN layer on a p-type AlGaN electron-blocking layer. The reaction chamber pressure was 200 torr, the temperature was 950℃, the NH3 flow rate was 60 slm, the TMGa flow rate was 500 sccm, the Cp2Mg flow rate was 350 sccm, and the Mg concentration was 3 × 10⁻⁶. 19 atoms / cm 3 The deposition thickness is 150 nm.

[0072] S10, depositing a p-type ohmic contact layer on a p-type GaN layer. The reaction chamber temperature was 880℃, the pressure was 150 torr, the NH3 flow rate was 60 slm, the TMGa flow rate was 350 sccm, the Cp2Mg flow rate was 700 sccm, and the Mg concentration was 8 × 10⁻⁶. 19 atoms / cm 3 A heavily doped P-type GaN ohmic contact layer with a thickness of 30 nm was grown.

[0073] The aforementioned epitaxial wafer was fabricated into a 300μm × 300μm LED chip using standard LED chip manufacturing processes. The photoelectric performance was measured on an integrating sphere testing system at room temperature (25℃) in continuous wave mode. Test results showed that with an injection current of 20mA, the external quantum efficiency (EQE) of the LED chip was 48.2%, the forward voltage was 3.08V, the emission wavelength was 450nm, and the full width at half maximum (FWHM) was 14.0nm. With an injection current of 100mA, the EQE was 37.5%, and the efficiency droop was only 22.2%. At a reverse bias of -5V, the leakage current was 0.12μA. These performance indicators significantly outperform existing technologies, verifying the significant technical effect of the synergistic optimization of the regional arched Al composition distribution and Zn gradient doping in Embodiment 3 of this invention.

[0074] Example 2 The epitaxial structure of a GaN-based light-emitting diode proposed in Embodiment 2 of this invention maintains the same layered structure and material system for each layer as in Embodiment 1. The only difference is that the Zn concentration in each region of the P-type AlGaN electron blocking layer is reduced by an order of magnitude to verify the effect of the lower limit of Zn concentration on the surface activation effect.

[0075] Specifically, the Zn concentration in the first region is 1×10⁻⁶. 16 cm -3 The Zn concentration in the second region is 3 × 10⁻⁶. 17 cm -3 The Zn concentration in the third region is 7 × 10⁻⁶. 17 cm -3 The Al composition and thickness of the first region, the second region, and the third region are consistent with those of Example 1.

[0076] In the preparation method, steps S1 to S7 and S9 to S10 are consistent with those in Example 1. The flow rate of the Zn source DEZn in step S8 is adjusted accordingly: 5 sccm in the first stage, 30 sccm in the second stage, and 50 sccm in the third stage.

[0077] The prepared epitaxial wafer was tested under the same chip fabrication process and testing conditions as in Example 1. The test results showed that: at an injection current of 20mA, the LED chip had an EQE of 43.5%, a forward voltage of 3.18V, an emission wavelength of 450nm, and an FWHM of 15.5nm; at an injection current of 100mA, the EQE was 31.2%, and the efficiency droop was 28.3%; at a reverse bias of -5V, the leakage current was 0.22μA.

[0078] Compared to Example 1, Example 2 showed a 4.7 percentage point decrease in EQE, a 6.1 percentage point increase in droop efficiency, a 0.10 V increase in forward voltage, and a 0.10 μA increase in leakage current. These results indicate that when the Zn concentration is below the preferred range of this invention, the surface activation effect of Zn is insufficient, the reduction in the surface diffusion barrier of Al atoms is inadequate, resulting in limited improvement in Al incorporation efficiency, insignificant improvement in the crystal quality of the P-type AlGaN electron blocking layer, and weakened elimination of the hole injection barrier, thereby limiting the LED luminous efficiency and droop suppression capability.

[0079] Example 3 The epitaxial structure of a GaN-based light-emitting diode proposed in Embodiment 3 of this invention maintains the same layered structure and material system for each layer as in Embodiment 1. The only difference is that the Zn concentration in each region of the P-type AlGaN electron blocking layer is increased overall to verify whether excessively high Zn concentration causes lattice distortion or self-compensation effect.

[0080] Specifically, the Zn concentration in the first region is 1×10⁻⁶. 17 cm -3 The Zn concentration in the second region is 7 × 10⁻⁶. 17 cm -3 The Zn concentration in the third region is 5 × 10⁻⁶. 18 cm -3 The Al composition and thickness of the first region, the second region, and the third region are consistent with those of Example 1.

[0081] In the preparation method, steps S1 to S7 and S9 to S10 are consistent with those in Example 1. The flow rate of the Zn source DEZn in step S8 is adjusted accordingly: 20 sccm in the first stage, 100 sccm in the second stage, and 200 sccm in the third stage.

[0082] The prepared epitaxial wafer was tested under the same chip fabrication process and testing conditions as in Example 1. The test results showed that: at an injection current of 20mA, the LED chip had an EQE of 44.8%, a forward voltage of 3.12V, an emission wavelength of 450nm, and an FWHM of 15.0nm; at an injection current of 100mA, the EQE was 33.5%, and the efficiency droop was 25.2%; at a reverse bias of -5V, the leakage current was 0.28μA.

[0083] Compared to Example 1, Example 3 showed a 3.4 percentage point decrease in EQE, a 3.0 percentage point increase in efficiency droop, a 0.04 V increase in forward voltage, and a 0.16 μA increase in leakage current. These results indicate that while surface activation is enhanced when the Zn concentration exceeds the preferred range of this invention, excessively high Zn concentrations introduce additional lattice stress, and the Zn concentration in the third region reaches 5 × 10⁻⁶. 18 cm -3 A certain Zn self-compensation effect occurs, partially offsetting the activation effect of Mg acceptors, resulting in a lower increase in hole injection efficiency compared to Example 1. This demonstrates that there is an optimal range for Zn concentration, and it is not a monotonically increasing relationship.

[0084] Example 4 The epitaxial structure of a GaN-based light-emitting diode proposed in Embodiment 4 of this invention maintains the same layered structure, material system of each layer, and Zn concentration gradient distribution as in Embodiment 1. The only difference is that the distribution of Al component in the P-type AlGaN electron blocking layer changes from an arched peak to a linear increase, in order to verify the necessity of the arched Al peak in the second region.

[0085] Specifically, the molar percentage of Al component in the first region is 8%, the molar percentage of Al component in the second region is 12% (without arched peaks), and the molar percentage of Al component in the third region is 20%; the Zn concentration and thickness in the first region, the second region, and the third region are consistent with those in Example 1.

[0086] In the preparation method, steps S1 to S7 and S9 to S10 are consistent with those in Example 1. In step S8, the TMA1 flow rate is not increased in the second stage, remaining close to that in the first stage (45 sccm), and is increased to 75 sccm in the third stage.

[0087] The prepared epitaxial wafer was tested under the same chip fabrication process and testing conditions as in Example 1. The test results showed that: at an injection current of 20mA, the LED chip had an EQE of 42.0%, a forward voltage of 3.20V, an emission wavelength of 450nm, and an FWHM of 16.2nm; at an injection current of 100mA, the EQE was 29.4%, and the efficiency droop was 30.0%; at a reverse bias of -5V, the leakage current was 0.35μA.

[0088] Compared to Example 1, Example 4 showed a 6.2 percentage point decrease in EQE, a 7.8 percentage point increase in efficiency droop, a 0.12 V increase in forward voltage, and a 0.23 μA increase in leakage current. These results indicate that when the Al composition in the second region lacks an arched peak, the electron blocking layer's ability to block electrons in the peak region is insufficient. Simultaneously, the concentration of the Zn surfactant in the peak region does not optimally match the Al peak value, leading to a weakened hole injection barrier elimination effect, increased electron overflow under high current, and a significant deterioration in efficiency droop. This demonstrates that the arched Al peak in the second region is a key feature of this invention for achieving synergistic optimization of electron blocking capability and hole injection efficiency.

[0089] Example 5 The epitaxial structure of a GaN-based light-emitting diode proposed in Embodiment 5 of this invention maintains the same layered structure, material system of each layer, and arched distribution of Al composition as Embodiment 1. The only difference is that the Zn concentration in the P-type AlGaN electron blocking layer is uniformly distributed (non-gradient) in three regions to verify the necessity of Zn gradient distribution.

[0090] Specifically, the Zn concentration in the first region, the second region, and the third region is all 5 × 10⁻⁶. 17 cm -3 The Al composition and thickness of the first region, the second region, and the third region are consistent with those of Example 1.

[0091] In the preparation method, steps S1 to S7 and S9 to S10 are consistent with those in Example 1. In step S8, the DEZn flow rate is kept constant at 60 sccm throughout the process, and the Zn concentration remains uniform during the growth of the three regions.

[0092] The prepared epitaxial wafer was tested under the same chip fabrication process and testing conditions as in Example 1. The test results showed that: at an injection current of 20mA, the LED chip had an EQE of 40.5%, a forward voltage of 3.25V, an emission wavelength of 450nm, and an FWHM of 16.8nm; at an injection current of 100mA, the EQE was 26.4%, and the efficiency droop was 34.8%; at a reverse bias of -5V, the leakage current was 0.45μA.

[0093] Compared to Example 1, Example 5 showed a 7.7 percentage point decrease in EQE, a 12.6 percentage point increase in efficiency droop, a 0.17 V increase in forward voltage, and a 0.33 μA increase in leakage current. These results indicate that when the Zn concentration is uniformly distributed, the Zn concentration in the first region is excessively high (5 × 10⁻⁶). 17 cm -3 vs 5×10 of Example 1 16 cm -3 Introducing unnecessary defect states affects the crystal quality of the interface between the multi-quantum-well active region and the electron blocking layer; simultaneously, the Zn concentration in the third region is too low (5×10⁻⁶). 17 cm -3 vs 2×10 of Example 1 18 cm -3 The insufficient activation effect of Mg as the host cell leads to a failure to effectively reduce the valence band discontinuity at the interface between the p-type AlGaN electron blocking layer and the p-type GaN layer. The uniform Zn concentration prevents the functional specialization of the three regions, resulting in the failure of coordinated band structure modulation and extremely limited performance improvement.

[0094] Comparative Example 1 Comparative Example 1 provides a GaN-based light-emitting diode epitaxial structure employing a conventional P-type AlGaN electron blocking layer for performance comparison with Examples 1 to 5.

[0095] The epitaxial structure of Comparative Example 1 includes: a substrate, a buffer layer, a three-dimensional growth layer, an unintentionally doped GaN layer, an N-type GaN layer, a stress relief layer, a multi-quantum-well active region, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type ohmic contact layer. The materials, thicknesses, and fabrication process parameters of the substrate to the stress relief layer, the multi-quantum-well active region, the P-type GaN layer, and the P-type ohmic contact layer are consistent with those of Example 1.

[0096] The only difference is that the P-type AlGaN electron blocking layer is a single-layer structure, the Al composition is uniformly distributed with a molar percentage of 15%, there is no Zn doping, and the Mg doping concentration is 3 × 10⁻⁶. 19 atoms / cm 3 The thickness is 15nm.

[0097] The specific steps for preparing the p-type AlGaN electron blocking layer are as follows: The reaction chamber temperature was lowered to 920℃, the pressure was controlled at 180 torr, the graphite substrate rotation speed was 800 r / min, the NH3 flow rate was 60 slm, the TMGa flow rate was 120 sccm, the TMAl flow rate was 70 sccm, and the Cp2Mg flow rate was 300 sccm. The growth time was 6 min, forming a monolayer of p-type Al. 0.15 Ga 0.85 N electron blocking layer.

[0098] The prepared epitaxial wafer was tested under the same chip fabrication process and testing conditions as in Example 1. The test results showed that: at an injection current of 20mA, the LED chip had an EQE of 38.0%, a forward voltage of 3.30V, an emission wavelength of 450nm, and an FWHM of 18.2nm; at an injection current of 100mA, the EQE was 22.0%, and the efficiency droop was 42.1%; at a reverse bias of -5V, the leakage current was 0.80μA.

[0099] Please refer to Table 1, which is a performance comparison table between each embodiment and the comparative example.

[0100] Table 1

[0101] Based on the data in Table 1, we can find that: (1) Compared with Comparative Example 1, Example 1 (the optimal solution of the present invention) shows that EQE is improved by 26.8%, efficiency droop is reduced by 47.3%, forward voltage is reduced by 6.7%, leakage current is reduced by 85%, and FWHM is narrowed by 23.1%. This verifies that the present invention achieves significant technical effects in improving luminescence efficiency, suppressing efficiency decay, reducing operating voltage, and improving crystal quality through the synergistic optimization of the three-region arched Al composition distribution and Zn gradient doping.

[0102] (2) Comparing Examples 1, 2, and 3, it can be seen that there is an optimal range for Zn concentration. In Example 2, the Zn concentration is too low, resulting in insufficient surface activation; in Example 3, the Zn concentration is too high, introducing additional lattice stress and a self-compensation effect. Neither of these can achieve the optimal performance of Example 1, proving that the preferred first region of the present invention is 5×10 16 cm -3 Second area 5×10 17 cm -3 Third region 2×10 18 cm -3 The Zn concentration gradient distribution is an optimized technical solution.

[0103] (3) Comparing Example 1 and Example 4, it can be seen that the arched Al peak in the second region is a key feature of the present invention. After removing the arched peak, both the electron blocking ability and the hole injection efficiency decreased significantly, and the efficiency droop deteriorated from 22.2% to 30.0%.

[0104] (4) Comparing Example 1 and Example 5, it can be seen that the Zn gradient distribution is the core condition for realizing the functional division of the three regions. Uniform Zn doping cannot achieve the synergistic optimization of the band structure. The functions of each region interfere with each other, and the efficiency droop only improves from 42.1% in Comparative Example 1 to 34.8%, which is a very limited improvement.

[0105] As can be seen from the above, this invention achieves a comprehensive improvement in epitaxial crystal quality, carrier injection efficiency, and luminescence efficiency through the three-region structure design of the P-type AlGaN electron blocking layer, the arched distribution of Al components, and the synergistic effect of gradient doping of Zn surface activator. It has significant technological advancements and industrial application value.

[0106] In summary, the GaN-based light-emitting diode epitaxial structure and its fabrication method in the embodiments of the present invention, by introducing a Zn source as a surface activator throughout the growth process of the P-type AlGaN electron blocking layer, constructs a P-type AlGaN electron blocking layer structure with a gradient distribution of Zn concentration along the direction of the P-type AlGaN electron blocking layer. Specifically, through the core role of the Zn surface activator and the innovative design of the Zn concentration gradient distribution, while ensuring a smooth rise in the conduction band Ec and no loss of strong electron blocking capability, the valence band Ev is smooth throughout without spikes, and hole injection is unimpeded throughout.

[0107] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A GaN-based light-emitting diode epitaxial structure, characterized in that, It includes a P-type AlGaN electron blocking layer, which is divided into a first region, a second region and a third region along the epitaxial growth direction. The P-type AlGaN electron blocking layer is an AlGaN material layer doped with a P-type dopant, and a Zn source is introduced into the P-type AlGaN electron blocking layer during the metal-organic chemical vapor deposition growth process. The Al composition increases linearly in the first, second, and third regions, forming an arched peak in the second region. Simultaneously, the Zn concentration gradient increases in the first, second, and third regions. The molar percentage of Al in the p-type AlGaN electron blocking layer is 5%–25%, and the Zn concentration is 1 × 10⁻⁶. 16 cm -3 ~5×10 18 cm -3 ; Zn acts as a surface activator to regulate the surface diffusion ability and lattice incorporation efficiency of Al atoms, while simultaneously regulating the conduction band and valence band structure of the P-type AlGaN electron blocking layer to eliminate the hole injection spike barrier.

2. The GaN-based light-emitting diode epitaxial structure according to claim 1, characterized in that, The epitaxial structure of the GaN-based light-emitting diode also includes a substrate, a buffer layer, a three-dimensional growth layer, an unintentionally doped GaN layer, an N-type GaN layer, a stress relief layer, a multi-quantum-well active region, a P-type GaN layer, and a P-type ohmic contact layer. The buffer layer, the three-dimensional growth layer, the unintentionally doped GaN layer, the N-type GaN layer, the stress relief layer, the multi-quantum well active region, the P-type AlGaN electron blocking layer, the P-type GaN layer, and the P-type ohmic contact layer are sequentially epitaxially grown on the substrate.

3. The GaN-based light-emitting diode epitaxial structure according to claim 2, characterized in that, The molar percentage of Al component in the first region is 5%–12%, the molar percentage of Al component in the second region is 12%–20%, and the molar percentage of Al component in the third region is 18%–25%. In addition, the Zn concentration in the first region is 1×10⁻⁶. 16 cm -3 ~2×10 17 cm -3 The Zn concentration in the second region is 3 × 10⁻⁶. 17 cm -3 ~7×10 17 cm -3 The Zn concentration in the third region is 8 × 10⁻⁶. 17 cm -3 ~5×10 18 cm -3 .

4. The GaN-based light-emitting diode epitaxial structure according to claim 3, characterized in that, During the growth of the P-type AlGaN electron blocking layer, the flux of the Zn source is 1 sccm to 200 sccm.

5. The GaN-based light-emitting diode epitaxial structure according to claim 4, characterized in that, In the p-type AlGaN electron blocking layer, the p-type dopant is Mg, and the Mg doping concentration is 1×10⁻⁶. 18 cm -3 ~5×10 19 cm -3 .

6. The GaN-based light-emitting diode epitaxial structure according to claim 5, characterized in that, The thickness of the P-type AlGaN electron blocking layer is 5 nm to 25 nm.

7. A method for fabricating a GaN-based light-emitting diode epitaxial structure, characterized in that, The method for preparing the GaN-based light-emitting diode epitaxial structure according to any one of claims 1-6 includes: A p-type AlGaN electron blocking layer was grown with a Zn source continuously introduced throughout the growth process. By adjusting the flux of the Zn source, the concentration of Zn in the grown p-type AlGaN electron blocking layer was made to be 1 × 10⁻⁶. 16 cm -3 ~5×10 18 cm -3 Furthermore, in the growth direction of the P-type AlGaN electron blocking layer, the Zn concentration gradient is controlled to increase gradually, and the Al composition increases linearly. The Zn source acts as a surface activator to regulate the surface diffusion and lattice incorporation of Al atoms, while simultaneously regulating the band structure to eliminate the hole injection spike barrier.

8. The method for fabricating a GaN-based light-emitting diode epitaxial structure according to claim 7, characterized in that, The preparation method further includes: A substrate required for growth is provided, and the substrate is subjected to high-temperature annealing and nitriding treatment to form a stable substrate surface; On the treated substrate, a buffer layer, a three-dimensional growth layer, an unintentionally doped GaN layer, an N-type GaN layer, a stress relief layer, a multi-quantum well active region, a P-type AlGaN electron blocking layer, a P-type GaN layer, and a P-type ohmic contact layer are sequentially grown by metal-organic chemical vapor deposition.

9. The method for fabricating a GaN-based light-emitting diode epitaxial structure according to claim 8, characterized in that, The growth temperature of the P-type AlGaN electron blocking layer is 850℃~1100℃, the growth pressure is 150 torr~250 torr, and the Zn source flux is gradually increased during the growth process. The initial flux is 1 sccm~100 sccm, and the flux is increased to 100 sccm~200 sccm before the end of the growth to achieve a Zn concentration gradient distribution.

10. The method for fabricating a GaN-based light-emitting diode epitaxial structure according to claim 9, characterized in that, During the growth of the P-type AlGaN electron blocking layer, trimethylaluminum, trimethylgallium, and ammonia are simultaneously introduced as reaction sources, and magnesium pyrocene is introduced as a P-type doping source. The molar percentage of Al was controlled to be 5%–25%, and the doping concentration of Mg was controlled to be 1 × 10⁻⁶. 18 cm -3 ~5×10 19 cm -3 The thickness of the grown P-type AlGaN electron blocking layer is 5nm~25nm.

Images