AlGaN-based deep ultraviolet light emitting diode and preparation method thereof

Abstract

The invention provides an aluminum gallium nitride-based deep ultraviolet light-emitting diode and a preparation method thereof, which can be applied to the technical field of semiconductor optoelectronic devices. The structure of the aluminum-gallium-nitrogen-based deep ultraviolet light emitting diode comprises a sapphire substrate, an aluminum nitride buffer layer, an n-type aluminum-gallium-nitrogen layer, a multi-quantum well layer, an electron barrier layer, a p-type aluminum-gallium-nitrogen layer, a p-type gallium nitride contact layer and a metal electrode which are sequentially arranged, and table wall micro-nano reflection structures are arranged in the p-type aluminum-gallium-nitrogen layer and the p-type gallium nitride contact layer. The table wall micro-nano reflection structure comprises a plurality of table wall micro-nano reflection units which are distributed in an array mode, and the table wall micro-nano reflection structure is obtained through chaos-Jaya algorithm optimization and used for improving the light extraction efficiency of the deep ultraviolet light emitting diode.

Description

Technical Field

[0001] The present invention relates to the technical field of light-emitting diode packaging structures, and more particularly to an aluminum gallium nitride-based deep ultraviolet light-emitting diode and a preparation method thereof. Background Art

[0002] Since the 21st century, numerous large-scale public health incidents have highlighted unprecedented public health and safety challenges, significantly increasing the demand for safe and environmentally friendly semiconductor ultraviolet (UV) light sources, particularly deep-UV light-emitting diodes (DUV-LEDs) based on aluminum gallium nitride (AlGaN). In addition to addressing public health and safety needs, DUV-LEDs have also been widely used in industrial manufacturing, such as rapid curing of printing inks, high-precision UV lithography, liquid crystal display panel processing, and deep purification of drinking water. They are also used in modern agriculture to promote plant growth and monitor growth status. In addition, given the unique "sun-blind" characteristics of ultraviolet light in the deep ultraviolet (UVC) band, DUV-LEDs have also attracted increasing research interest and attention in wireless optical communications, missile warning systems, and other defense science and technology fields in recent years.

[0003] Currently, the major obstacle to the large-scale deployment of AlGaN-based DUV-LEDs is achieving high-efficiency power output, primarily due to their low intrinsic external quantum efficiency (EQE). The EQE of an LED is determined by both the internal quantum efficiency (IQE) and the light extraction efficiency (LEE). Although IQE has been increased to over 80% through optimized epitaxial growth techniques and active region structure design, the LEE of DUV-LEDs remains relatively low. The main reasons for the low light extraction efficiency of traditional flip-chip DUV-LEDs include: the significant refractive index difference between the light-emitting interface and air, which reduces the light escape angle; optical losses caused by the high UV absorption of p-type GaN; and the increased proportion of transverse magnetic (TM) polarized light in the high-aluminum-content AlGaN quantum wells (QWs). To address these issues, researchers have proposed methods for patterning p-type GaN surfaces. Existing research has shown that micron-scale patterning on p-type GaN surfaces can significantly improve LEE. However, there is currently a lack of systematic research on subwavelength, nanometer-scale patterned p-type GaN layers for DUV-LEDs. Furthermore, existing research has primarily focused on improving overall LEE, while few strategies have been reported for enhancing LEEs for light with different polarization modes, particularly those for TM-polarized light in DUV-LEDs. Summary of the Invention

[0004] (1) Technical issues to be resolved

[0005] To solve at least one of the above problems, the present invention provides an aluminum gallium nitride-based deep ultraviolet light-emitting diode and a preparation method thereof. The reflective structure is optimized by an artificial intelligence (AI)-assisted inverse design method, and a new p-type gallium nitride (p-GaN) surface terrace micro-nano reflective structure is introduced. This structure further improves the light extraction efficiency by enhancing the scattering effect.

[0006] (2) Technical solution

[0007] In response to the above technical problems, embodiments of the present invention provide an AlGaN-based deep ultraviolet light-emitting diode and a method for manufacturing the same.

[0008] According to a first aspect of the present invention, there is provided an aluminum gallium nitride-based deep ultraviolet light-emitting diode, comprising: a sapphire substrate; an aluminum nitride buffer layer located on the surface of the sapphire substrate; an n-type aluminum gallium nitride layer located on the side of the aluminum nitride buffer layer away from the sapphire substrate; a multi-quantum well layer located on the side of the n-type aluminum gallium nitride layer away from the sapphire substrate; an electron blocking layer located on the side of the multi-quantum well layer away from the sapphire substrate; a p-type aluminum gallium nitride layer located on the side of the electron blocking layer away from the sapphire substrate; a p-type gallium nitride contact layer located on the side of the p-type aluminum gallium nitride layer away from the sapphire substrate; a metal electrode located on the side of the p-type gallium nitride contact layer away from the sapphire substrate; and a table wall micro-nano reflective structure arranged in the p-type aluminum gallium nitride layer and the p-type gallium nitride contact layer, the table wall micro-nano reflective structure comprising a plurality of table wall micro-nano reflective units distributed in an array, the table wall micro-nano reflective structure being obtained by optimizing the chaos-Jaya algorithm and being used to improve the light extraction efficiency of the deep ultraviolet light-emitting diode.

[0009] In some exemplary embodiments, the micro-nano reflection unit on the wall is a composite structure composed of a cylinder and a truncated cone, wherein the parameters of the micro-nano reflection unit on the wall include a period p, a height h, a top diameter d1 of the structure, and a bottom diameter d2 of the structure; and a metal aluminum layer is deposited between adjacent micro-nano reflection units on the wall as a reflective material.

[0010] In some exemplary embodiments, the period p is 650 nm ± 65 nm; the height h is 85.0 nm ± 8.5 nm; the structure top diameter d1 is 450 nm ± 45 nm; and the structure bottom diameter d2 is 300 nm ± 30 nm.

[0011] In some exemplary embodiments, the method of optimizing the parameters of the micro-nano reflection structure of the table wall using the chaos-Jaya algorithm includes: randomly generating initial particles as the first generation of individuals within a preset parameter range, and the particles represent various combinations of the parameters of the micro-nano reflection structure of the table wall; simulating and calculating the fitness function value of each particle through the time-domain finite difference method; sorting the fitness function values ​​of all particles, and selecting the particle with the highest fitness function value as the representative particle of the current generation; feeding back the fitness function value of the representative particle to the chaos-Jaya algorithm, and adjusting the current position and speed of the particle to generate a particle group for the next generation; repeating the above iterative process until the preset convergence criteria are met or the maximum number of iterations is reached, wherein the preset parameters include height h, period p, structure top diameter d1, and structure bottom diameter d2.

[0012] In some exemplary embodiments, the doping element of the n-type aluminum gallium nitride layer is silicon, and the doping concentration of silicon is 1.3×10 19 cm -3 ~1.7×10 19 cm -3; The thickness of the n-type aluminum gallium nitride layer is 2.0μm±0.2μm.

[0013] In some exemplary embodiments, the multi-quantum well layer is composed of alternately grown aluminum gallium nitride barrier layers and aluminum gallium nitride well layers, wherein the thickness of the multi-quantum well layer is 100nm±10nm; the molar fraction of the aluminum component in the aluminum gallium nitride barrier layer is 56%±5%; and the molar fraction of the aluminum component in the aluminum gallium nitride well layer is 40%±4%.

[0014] In some exemplary embodiments, the material of the electron blocking layer is p-type aluminum gallium nitride, the molar fraction of the aluminum component in the electron blocking layer is 45%, and the doping element of the p-type aluminum gallium nitride is magnesium; the thickness of the electron blocking layer is 30nm±3nm.

[0015] In some exemplary embodiments, the doping element of the p-type AlGaN layer is magnesium, and the doping concentration of magnesium is 0.8×10 16 cm -3 ~1.2×10 16 cm -3 ; The thickness of the p-type aluminum gallium nitride layer is 70nm±7nm.

[0016] In some exemplary embodiments, the doping element of the p-type gallium nitride contact layer is magnesium, and the doping concentration of magnesium is 0.8×10 18 cm -3 ~1.2×10 18 cm -3 ; The thickness of the p-type gallium nitride contact layer is 100nm±10nm.

[0017] According to a second aspect of the present invention, a method for preparing an aluminum gallium nitride-based deep ultraviolet light-emitting diode is provided, comprising: obtaining a sapphire substrate; sequentially epitaxially growing an aluminum nitride buffer layer, an n-type aluminum gallium nitride layer, a multi-quantum well layer, an electron blocking layer, a p-type aluminum gallium nitride layer, and a p-type gallium nitride contact layer on the sapphire substrate, the layer being located on a side of the p-type aluminum gallium nitride layer away from the sapphire substrate; using electron beam lithography and inductively coupled plasma etching technology to etch a table wall micro-nano reflective structure in the p-type aluminum gallium nitride layer and the p-type gallium nitride contact layer, the table wall micro-nano reflective structure comprising a plurality of array-distributed table wall micro-nano reflective units, the table wall micro-nano reflective structure being obtained by optimizing the chaos-Jaya algorithm and being used to improve the light extraction efficiency of the deep ultraviolet light-emitting diode; depositing a metal aluminum layer as a reflective material between adjacent table wall micro-nano reflective units; and preparing a metal electrode on the metal aluminum.

[0018] (3) Beneficial effects

[0019] It can be seen from the above technical solutions that the AlGaN-based deep ultraviolet light-emitting diode and its preparation method provided by the embodiments of the present invention have at least the following beneficial effects:

[0020] (1) By designing a micro-nano reflective structure on the platform wall and optimizing it using the Chaos-Jaya (C-Jaya) algorithm combined with three-dimensional electromagnetic simulation software based on the finite-difference time-domain method, the optimal parameters of the micro-nano reflective structure on the platform wall were obtained. Experimental preparation and luminescence characterization results show that the LEE of flip-chip AlGaN DUV-LEDs increased by more than 200%. Compared with the traditional structure (LEE of 3.1%) and the structure with the introduction of an aluminum reflective layer (LEE of 5.8%), the LED with the optimal micro-nano reflective structure on the platform wall achieved an LEE of 16.54%, an increase of 442% and 185%, respectively.

[0021] (2) Compared with traditional metal reflective surfaces, the micro-nano reflective structure on the wall provides a more flexible and finely adjustable structural design space. The structure is defined by the height h, period p, and top / bottom width (d1 / d2). By adjusting these parameters, the propagation path of light within the device can be precisely controlled, significantly increasing the probability of deep ultraviolet light escaping into the air, thereby better meeting the light output requirements of different application scenarios.

[0022] (3) Considering process tolerances during the fabrication process, such as reduced or increased bottom diameters, and reduced structural depth due to insufficient etching, a three-dimensional electromagnetic simulation software based on the finite-difference time-domain method was used for analysis. When the degree of disorder of the structural parameters was controlled below 10%, the LEE decreased by no more than 4.8%. This indicates that the structure has a certain degree of fault tolerance during the actual fabrication process, reducing process difficulty and cost.

[0023] (4) Analysis of LED emission angles under different reflective structures shows that, while the extraction of Class I and Class III radiation light is lower for the proposed LED with a micro-nano reflective structure on the wall than for an LED with a metal reflective layer, the extraction intensity of Class II radiation light (22° to 158°, which is difficult to emit directly without control) is significantly enhanced. This characteristic enables the structure to more effectively improve the light extraction efficiency of LEDs and meet the light distribution requirements of different application scenarios.

[0024] (5) The luminescence performance of the AlGaN-based DUV-LED with the micro-nano reflective structure was characterized and analyzed using room-temperature photoluminescence (RTPL). Spectral test results showed that the peak wavelength of the measured sample was 278 nm, which was basically consistent with the target wavelength of 280 nm, indicating that the prepared LED epitaxial wafer met the expected design specifications. At the same time, the radiation intensity of the LED with the micro-nano reflective structure at the peak wavelength proposed in this invention was 2.11 times that of the LED with the Al reflective layer, further verifying the effectiveness of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above contents and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0026] Figure 1 The following schematically shows a structural diagram of an aluminum gallium nitride-based deep ultraviolet light-emitting diode according to an embodiment of the present invention;

[0027] Figure 2 A flow chart schematically illustrates a method for preparing an AlGaN-based deep ultraviolet light-emitting diode according to an embodiment of the present invention;

[0028] Figure 3 A schematic diagram showing a comparison between the AlGaN-based deep ultraviolet light-emitting diode structure according to an embodiment of the present invention and a conventional structure;

[0029] Figure 4 Schematically shows a schematic diagram of a single iteration result in a reverse design process according to an embodiment of the present invention;

[0030] Figure 5 Schematically showing the light extraction efficiency analysis results of an AlGaN-based deep ultraviolet light-emitting diode under different tolerances according to an embodiment of the present invention;

[0031] Figure 6 Schematic diagram showing the comparison of LED light emission angles between the micro-nano reflective structure on the wall and the traditional reflective structure;

[0032] Figure 7 A schematic diagram of the process for preparing the micro-nano reflective structure of the table wall according to an embodiment of the present invention is shown;

[0033] Figure 8 A schematic diagram of a micro-nano reflective structure of a table wall according to an embodiment of the present invention is shown;

[0034] Figure 9 The schematic diagram shows the spectrum results of LED epitaxial wafer samples with Al reflective layer and micro-nano reflective structure of the platform wall obtained by using a room temperature photoluminescence testing system.

[0035] Reference numerals:

[0036] 1-sapphire substrate; 2-aluminum nitride buffer layer; 3-n-type aluminum gallium nitride layer; 4-multi-quantum well layer; 5-electron blocking layer; 6-p-type aluminum gallium nitride layer; 7-p-type gallium nitride contact layer; 8-metal electrode; 9-metal aluminum layer. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0038] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise," "include," etc. used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0039] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0040] When expressions such as "at least one of A, B, and C, etc." are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0041] Figure 1 The figure schematically shows a structural diagram of an AlGaN-based deep ultraviolet light-emitting diode according to an embodiment of the present invention.

[0042] like Figure 1As shown, an AlGaN-based deep ultraviolet light-emitting diode according to an embodiment of the present invention includes a sapphire substrate 1; an AlGaN buffer layer 2 located on the surface of the sapphire substrate 1; an n-type AlGaN layer 3 located on the side of the AlGaN buffer layer 2 away from the sapphire substrate 1; a multi-quantum well layer 4 located on the side of the n-type AlGaN layer 3 away from the sapphire substrate 1; an electron blocking layer 5 located on the side of the multi-quantum well layer 4 away from the sapphire substrate 1; a p-type AlGaN layer 6 located on the side of the electron blocking layer 5 away from the sapphire substrate 1; a p-type GaN contact layer 7 located on the side of the p-type AlGaN layer 6 away from the sapphire substrate 1; a metal electrode 8 located on the side of the p-type GaN contact layer 7 away from the sapphire substrate 1; and a terrace micro-nano reflective structure disposed between the p-type AlGaN layer 6 and the p-type GaN contact layer 7. The terrace micro-nano reflective structure includes a plurality of terrace micro-nano reflective units distributed in an array. The terrace micro-nano reflective structure is optimized using a Chaos-Jaya (C-Jaya) algorithm to improve the light extraction efficiency of the deep ultraviolet light-emitting diode.

[0043] The Jaya optimization algorithm is a meta-heuristic algorithm based on the principle of "seeking benefits and avoiding harm". Its core idea is to search for the global optimal solution by continuously approaching the current optimal solution and moving away from the worst solution in an iterative process. The algorithm formula uses random numbers to dynamically adjust the search direction. It does not require setting complex algorithm parameters or relying on gradient information. Therefore, it has the characteristics of simple structure, strong adaptability and easy implementation. It is suitable for continuous optimization problems and has demonstrated efficient solution capabilities in engineering design, power system scheduling and mechanical optimization.

[0044] The C-Jaya algorithm is an efficient meta-heuristic algorithm improved based on the Jaya optimization algorithm. By introducing chaotic mapping to replace the traditional random number generation strategy and combining it with an adaptive parameter adjustment mechanism, it significantly enhances the global search capability and convergence speed. At the same time, it uses a hybrid strategy to balance exploration and exploitation, making it more robust and accurate in complex nonlinear optimization problems. It is particularly suitable for scenarios with high dimensions, multi-modal functions, or those that are sensitive to the initial solution.

[0045] In an embodiment of the present invention, the micro-nano reflective unit on the wall is a composite structure composed of a cylinder and a truncated cone, wherein the parameters affecting the micro-nano reflective unit on the wall of the aluminum gallium nitride-based deep ultraviolet light-emitting diode include period p, height h, structure top diameter d1 and structure bottom diameter d2; and a metal aluminum layer 9 is deposited between adjacent micro-nano reflective units as a reflective material.

[0046] In the embodiment of the present invention, the period p is 650nm±65nm; the height h is 85.0nm±8.5nm; the diameter of the top of the structure is 450nm±45nm; the diameter of the bottom of the structure It is 300nm±30nm.

[0047] Optionally, the doping element of the n-type aluminum gallium nitride layer 3 is silicon, and the doping concentration of silicon is 1.3×10 19 cm -3 ~1.7×10 19 cm -3 ; The thickness of the n-type aluminum gallium nitride layer 3 is 2.0μm±0.2μm.

[0048] Optionally, the multi-quantum well layer 4 is composed of alternately grown aluminum gallium nitride barrier layers and aluminum gallium nitride potential well layers, wherein the thickness of the multi-quantum well layer 4 is 100nm±10nm; the molar fraction of the aluminum component in the aluminum gallium nitride barrier layer is 56%±5%; and the molar fraction of the aluminum component in the aluminum gallium nitride potential well layer is 40%±4%.

[0049] Optionally, the material of the electron blocking layer 5 is p-type aluminum gallium nitride, the molar fraction of the aluminum component in the electron blocking layer 5 is 45%, and the doping element of the p-type aluminum gallium nitride is magnesium; the thickness of the electron blocking layer 5 is 30nm±3nm.

[0050] Optionally, the doping element of the p-type aluminum gallium nitride layer 6 is magnesium, and the doping concentration of magnesium is 0.8×10 16 cm -3 ~1.2×10 16 cm -3 ; The thickness of the p-type aluminum gallium nitride layer 6 is 70nm±7nm.

[0051] Optionally, the doping element of the p-type gallium nitride contact layer 7 is magnesium, and the doping concentration of magnesium is 0.8×10 18 cm -3 -1.2×10 18 cm -3 ; The thickness of the p-type gallium nitride contact layer 7 is 100nm±10nm.

[0052] In some exemplary embodiments, the method of optimizing the parameters of the micro-nano reflective structure of the table wall using the Chaos-Jaya algorithm includes: randomly generating initial particles as the first generation of individuals within a preset parameter range, and the particles represent various combinations of the parameters of the micro-nano reflective structure of the table wall; simulating and calculating the fitness function value of each particle by the time-domain finite difference method; sorting the fitness function values ​​of all particles, and selecting the particle with the highest fitness function value as the representative particle of the current generation; feeding the fitness function value of the representative particle back to the Chaos-Jaya algorithm, and adjusting the current position and speed of the particle to generate a particle group for the next generation; repeating the above iterative process until the preset convergence standard is met or the maximum number of iterations is reached, wherein the preset parameters include height h, period p, and structure top diameter. and the bottom diameter of the structure .

[0053] Specifically, a DUV-LEDs emission characteristic model is first established. The model is established by first obtaining the polarization characteristics of the light radiated from the active region, then establishing a compact equivalent replacement model, and finally introducing a light source with an adjustable polarization ratio into the active region. The light source is modeled as a planar emitter that radiates light with an angle-dependent intensity variation. Perturbation theory ( Perturbation theory is an important method used in solid-state physics to calculate the band structure and optical properties of crystals. In light propagating in a specific direction, both the transverse electric polarization component TE and the transverse magnetic polarization component TM exist. The polarization characteristics during propagation are described by introducing the s-polarization component and the p-polarization component, whose directionality is accurately characterized by the azimuth angle φ and the spatial angle θ. The electric field of the s-polarization component (-sinφ, -cosφ, 0) is defined as perpendicular to the direction of light propagation and the plane determined by the c-axis, while the p-polarization component (-cosθcosφ, -cosθsinφ, sinθ) is characterized by an electric field orientation perpendicular to the s-polarization direction. Based on the hexagonal symmetry principle and the theoretical framework under the biaxial stress assumption, the polarization characteristics of light along the propagation direction can be derived from the polarization characteristics of spontaneously emitted radiation:

[0054]

[0055] in, is the reflection coefficient under s-polarization, is the reflection coefficient under p polarization, is the reflection coefficient in TE mode, is the reflection coefficient in TM mode.

[0056] In the embodiments of the present invention, three-dimensional electromagnetic simulation software based on the finite-difference time-domain method is used to further study the light extraction behavior of radiated light with different polarization characteristics in AlGaN-based DUV-LEDs. By defining a specific electromagnetic field distribution and propagation characteristics, a plane wave source is used to simulate the incident electromagnetic wave with actual lateral uniformity. When the plane wave radiates energy at a specific elevation angle θ, the light extraction factor α in that direction is defined. θ is the energy collected on the substrate side P export With the plane wave source input energy P source Ratio:

[0057]

[0058] The ratio of the radiation energy corresponding to each spatial angle to the total energy of the light source is defined as the light output factor corresponding to the angle The weight factor , the normalized space volume corresponding to the angle The normalized spatial volume containing all light source angles The ratio is determined as follows:

[0059]

[0060] Will Its corresponding weight factor After multiplication and integration, we can get the light extraction efficiency LEE:

[0061]

[0062] When the ratio of TE and TM polarization modes in the DUV-LED spontaneous emission light changes, α θ The corresponding angle weight factors will be adjusted dynamically accordingly. Specifically including p: cos 2 θ polarization source, s:1 polarization source and p:sin 2 Schematic diagram of spontaneous emission from a θ-polarized source. The corresponding LEE calculation formulas are as follows:

[0063]

[0064]

[0065]

[0066] in, represents p:cos 2 LEE of the θ-polarized source, represents the LEE of s:1 polarization source, Indicates p:sin 2 LEE of θ polarized source, n represents the minimum refractive index value, is the angular transmission factor corresponding to the kth minimum refractive index. The distribution of the weighting factor of the spontaneous emission light at different spatial angles changes with different polarization ratios, with the 50% optical power cutoff angles being 34°, 62°, and 70°, respectively. Therefore, the angular weighting factor varies with angle and depends on the polarization composition of the emitted light.

[0067] In order to improve the light extraction efficiency of AlGaN-based DUV-LEDs, the present invention proposes a micro-nano reflective structure on the wall that combines the C-Jaya algorithm with three-dimensional electromagnetic simulation software based on the finite-difference time-domain method. The structure first randomly generates a large number of initial particles as the first generation of individuals within a preset parameter range. These particles represent various combinations of structural parameters, and then the fitness function value of each particle is calculated by simulation using the finite-difference time-domain method. Next, the fitness function values ​​of all particles are sorted, and the optimal particle with the highest fitness function value is selected as the representative of the current generation. The fitness value is fed back to the C-Jaya algorithm to adjust the current position and velocity of the particle, thereby generating a particle swarm for the next generation. The iterative process continues until the preset convergence criteria are met or the maximum number of iterations is reached.

[0068] Figure 2 The flowchart of a method for preparing an AlGaN-based deep ultraviolet light-emitting diode according to an embodiment of the present invention is schematically shown.

[0069] like Figure 2 As shown, a method for preparing an AlGaN-based deep ultraviolet light-emitting diode according to an embodiment of the present invention includes steps S110 to S150.

[0070] In step S110 , a sapphire substrate 1 is obtained.

[0071] In step S120, an aluminum nitride buffer layer 2, an n-type aluminum gallium nitride layer 3, a multi-quantum well layer 4, an electron blocking layer 5, a p-type aluminum gallium nitride layer 6, and a p-type gallium nitride contact layer 7 are epitaxially grown in sequence on the sapphire substrate 1, and are located on the side of the p-type aluminum gallium nitride layer 6 away from the sapphire substrate 1.

[0072] In step S130, electron beam lithography and inductively coupled plasma etching technology are used to etch the table wall micro-nano reflective structure on the p-type aluminum gallium nitride layer 6 and the p-type gallium nitride contact layer 7. The table wall micro-nano reflective structure includes a plurality of array-distributed table wall micro-nano reflective units. The table wall micro-nano reflective structure is obtained by optimizing the chaos-Jaya algorithm to improve the light extraction efficiency of the deep ultraviolet light-emitting diode.

[0073] In step S140 , a metal aluminum layer 9 is deposited between adjacent micro-nano reflective units on the wall as a reflective material.

[0074] In step S150, a metal electrode 8 is prepared on the metal aluminum. Optionally, the material of the metal electrode 8 may include gold, copper, aluminum, etc. Preferably, the material of the metal electrode 8 is gold.

[0075] For example, the 3D finite-difference time-domain method is used to simulate and analyze the LEE of a flip-chip AlGaN-based DUV-LED. First, the overall device layout is constructed. From top to bottom, the traditional LED device consists of: 2μm sapphire substrate 1, 1μm AlN buffer layer, 2μm n-AlGaN layer, 100nm MQWs layer, 30nm electron blocking layer 5, 70nm p-AlGaN layer, and 100nm p-GaN contact layer. Figure 3 In part (a), a 30nm GaN buffer layer and a 70nm aluminum reflective layer can be introduced into the LED epitaxial structure to enhance light reflection, see Figure 3 (b) in the figure. The LED configuration of the micro-nano reflective structure on the wall proposed in the embodiment of the present invention is shown in FIG. Figure 3 In (c), each unit of the reflective structure is defined by a height h, a period p, and a ratio (d1 / d2) of a structure top diameter d1 to a structure bottom diameter d2, and metallic aluminum is deposited between adjacent structural units as a reflective material.

[0076] The device is set to a single-period unit structure laterally, Bloch boundary conditions are added to the lateral boundaries, the light source is set to a single wavelength of 280 nm, and is placed in the center of the MQWs area in the center of the epitaxial wafer, a non-uniform grid is set with a minimum grid size of 5 nm, perfect matching layers are set on the upper and lower surfaces of the simulation model, and a power monitor is set, and its position is 50 nm above the sapphire substrate 1.

[0077] The C-Jaya intelligent optimization algorithm is used to reversely design the micro-nano reflective structure of the AlGaN-based DUV-LEDs platform. Figure 4 This figure schematically illustrates the results of a single iteration of the reverse design process according to an embodiment of the present invention. The LEE value of the traditional device structure is represented by a solid rectangle, the LEE value of the device with an aluminum reflective layer is represented by a solid triangle, the LEE value of each particle in the current iteration is represented by a hollow circle, and the optimal LEE value accumulated during the current iteration is marked with a solid diamond. As the number of iterations increases, the algorithm gradually approaches the optimal solution.

[0078] After multiple rounds of iteration, the optimal LEE and its corresponding parameters of the micro-nano reflective structure on the wall were finally obtained: the structural period p is about 650nm, which has a significant impact on the interference and diffraction effects of light; the structural height h is about 85nm, which determines the propagation path of light in the nanostructure and the number of reflections; the diameters of the top and bottom of the structure are and The wavelengths of the nanostructures are 450nm and 300nm, respectively, defining the shape and size of the nanostructures. The LED using this optimal structure achieved an LEE of 16.54%, an improvement of 442% and 185% compared to the conventional structure (3.1%) and the structure with an aluminum reflective layer (5.8%).

[0079] Figure 5 The figure schematically shows the light extraction efficiency analysis results of the AlGaN-based deep ultraviolet light-emitting diode under different tolerances according to an embodiment of the present invention.

[0080] like Figure 5 As shown in (a), the process tolerances during the fabrication process are mainly: reduced bottom diameter, increased bottom diameter, and reduced structure depth due to insufficient etching, which are defined as deviation types A, B, and C, respectively. Using 3D electromagnetic simulation software based on the finite-difference time-domain method, the ratio of the structural deviation amplitude to the standard structural parameter value is used as a measure of structural disorder. The effects of different types of deviations on LEE are analyzed. The analysis results are shown in Figure 5 (b) in the equation is given by Figure 5 As shown in (b), when the degree of disorder in the structural parameters is controlled below 10%, the LEE decreases by no more than 4.8%. In addition, due to the coupling between the structural parameters and the optical cavity effect, the LEE variation trend with increasing structural disorder is not a monotonic decrease.

[0081] Figure 6 A schematic diagram shows the comparison of LED light-emitting angles of the micro-nano reflective structure on the wall and the traditional reflective structure.

[0082] like Figure 6 As shown, a traditional non-reflective structure, a 100nmp-GaN / 75nmpAlGaN reflective layer structure, a 30nmp-GaN / 100nmp-AlGaN / Al reflective layer structure, and a micro-nano reflective structure on the wall proposed by the present invention are set; type I radiation light (0°~22°): is easier to be emitted directly from the top surface; type II radiation light (22°~158°): is difficult to be emitted directly without regulation; type III radiation light (68°~180°): is more likely to be redirected and emitted through reflection. Figure 6 It can be seen that in the LED with the micro-nano reflective structure on the table wall according to the embodiment of the present invention, although the amount of Class I and Class III radiation light extracted is lower than that of the LED with the metal reflective layer structure, the extraction intensity of Class II radiation light is significantly enhanced, effectively improving the light extraction efficiency of the LED. In the LED with the nanoscale reflective structure on the table wall, although the amount of Class I and Class III radiation light extracted is lower than that of the LED with the metal reflective layer structure, the extraction intensity of Class II radiation light is significantly enhanced. This enhancement is mainly due to the fact that the proposed reflective structure regulates the propagation path of light through scattering and cavity effects, allowing more radiation light to be redirected and emitted from the sapphire surface, thereby more effectively improving the light extraction efficiency of the LED.

[0083] The micro-nano reflective structure of the mesa wall proposed in the present invention is prepared by using metal organic chemical vapor deposition to perform epitaxial growth on a sapphire substrate 1, including a 2 μm Si doped n-AlGaN layer with a doping concentration of 1.5×10 19 cm -3 , Al content is 56% of the barrier layer and 40% of the well layer in the MQWs active region, 30nmMg doped electron barrier layer 5, Al content is 45%, 70nmMg doped p-AlGaN layer, doping concentration is 1×10 16 cm -3 , and a 100nmMg-doped p-GaN layer with a doping concentration of 1×10 18 cm -3 .

[0084] Figure 7 The schematic diagram of the process of preparing the micro-nano reflective structure of the table wall according to an embodiment of the present invention is shown schematically.

[0085] like Figure 7 As shown in the figure, the micro-nano reflective structure on the p-type side of the mesa composed of p-GaN and p-AlGaN layers was prepared by electron beam lithography (EBL) and inductively coupled plasma (ICP) etching. The main steps include: cleaning and drying the epitaxial wafer, spin coating 0.4μm thick negative resist AR-N7520.17, pre-baking at 85℃ for 1min, and using 400℃ Exposure measurement for EBL, 85℃ post-bake for 90s, development, and ICP etching was performed on the GaN and p-AlGaN layers, and 400nm Al was evaporated by electron beam to make a reflective layer. The preparation results are shown in Figure 8 .

[0086] The luminescence performance of an AlGaN-based DUV-LED incorporating a micro-nano reflective structure on the stage wall was characterized and analyzed using room-temperature photoluminescence (RTPL). The testing process is as follows: Laser light with a wavelength of 266 nm is applied to the sample surface at a 45° angle of incidence, stimulating electron transitions in the active region and inducing spontaneous emission. The excited light propagates within the LED, is collected by optical components, and then focused onto the entrance slit of a spectrometer. After dispersion by a grating, the light is received by a photomultiplier tube and converted into an electrical signal, ultimately yielding the sample's photoluminescence spectrum. By adjusting the position of the displacement stage, the LED's optical response can be measured and captured at different laser incidence positions.

[0087] Figure 9The schematic diagram shows the spectrum results of LED epitaxial wafer samples with Al reflective layer and micro-nano reflective structure of the platform wall obtained by using a room temperature photoluminescence testing system.

[0088] Depend on Figure 9 Spectral test results show that the peak wavelength of the measured sample is 278nm, which is basically consistent with the target wavelength of 280nm, indicating that the prepared LED epitaxial wafer meets the expected design specifications. In addition, the radiation intensity at the peak wavelength of the LED with the micro-nano reflective structure on the table wall according to the embodiment of the present invention is 2.11 times that of the LED with an Al reflective layer, indicating that the proposed micro-nano reflective structure on the table wall effectively improves the light output intensity of the LED.

[0089] It will be understood by those skilled in the art that the features described in the various embodiments of the present invention may be combined and / or coupled in various ways, even if such combinations or couplings are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention may be combined and / or coupled in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or couplings fall within the scope of the present invention.

Claims

1. An aluminum gallium nitride-based deep ultraviolet light-emitting diode, characterized in that: include: Sapphire substrate; an aluminum nitride buffer layer, located on the surface of the sapphire substrate; An n-type aluminum gallium nitride layer is located on a side of the aluminum nitride buffer layer away from the sapphire substrate; a multi-quantum well layer, located on a side of the n-type aluminum gallium nitride layer away from the sapphire substrate; an electron blocking layer, located on a side of the multi-quantum well layer away from the sapphire substrate; A p-type aluminum gallium nitride layer is located on a side of the electron blocking layer away from the sapphire substrate; A p-type gallium nitride contact layer is located on a side of the p-type aluminum gallium nitride layer away from the sapphire substrate; a metal electrode, located on a side of the p-type gallium nitride contact layer away from the sapphire substrate; as well as The micro-nano reflective structure of the table wall is arranged in the p-type aluminum gallium nitride layer and the p-type gallium nitride contact layer. The micro-nano reflective structure of the table wall includes a plurality of micro-nano reflective units distributed in an array. The micro-nano reflective structure of the table wall is obtained by optimizing the chaos-Jaya algorithm and is used to improve the light extraction efficiency of the deep ultraviolet light-emitting diode.

2. The AlGaN-based deep ultraviolet light-emitting diode according to claim 1, characterized in that: The micro-nano reflective unit on the wall is a composite structure composed of a cylinder and a truncated cone, wherein the parameters of the micro-nano reflective unit on the wall include period p, height h, structure top diameter d1 and structure bottom diameter d2; and a metal aluminum layer is deposited between adjacent micro-nano reflective units on the wall as a reflective material.

3. The AlGaN-based deep ultraviolet light-emitting diode according to claim 2, characterized in that: The period p is 650nm±65nm; The height h is 85.0 nm ± 8.5 nm; The top diameter d1 of the structure is 450nm±45nm; The bottom diameter d2 of the structure is 300nm±30nm.

4. The AlGaN-based deep ultraviolet light-emitting diode according to claim 1, characterized in that: The method of optimizing the parameters of the micro-nano reflective structure of the platform wall using the Chaos-Jaya algorithm includes: Randomly generating initial particles as the first generation of individuals within a preset parameter range, wherein the particles represent multiple combinations of parameters of the micro-nano reflective structure of the platform wall; The fitness function value of each particle is calculated by simulation using the finite difference time domain method; Sorting the fitness function values ​​of all particles and selecting the particle with the highest fitness function value as the representative particle of the current generation; Feeding the fitness function value of the representative particle back into the Chaos-Jaya algorithm, and adjusting the current position and velocity of the particle to generate a particle swarm for the next generation; Repeat the above iterative process until the preset convergence criteria are met or the maximum number of iterations is reached. The preset parameters include height h, period p, structure top diameter and the structure bottom diameter d2.

5. The AlGaN-based deep ultraviolet light-emitting diode according to claim 1, characterized in that: The doping element of the n-type aluminum gallium nitride layer is silicon, and the doping concentration of silicon is 1.3×10 19 cm -3 ~1.7×10 19 cm -3 ; The thickness of the n-type aluminum gallium nitride layer is 2.0 μm±0.2 μm.

6. The AlGaN-based deep ultraviolet light-emitting diode according to claim 1, characterized in that: The multi-quantum well layer is composed of an aluminum gallium nitride barrier layer and an aluminum gallium nitride well layer that are grown alternately. Wherein, the thickness of the multi-quantum well layer is 100nm±10nm; The molar fraction of the aluminum component in the aluminum gallium nitride barrier layer is 56%±5%; The molar fraction of the aluminum component in the aluminum gallium nitrogen potential well layer is 40%±4%.

7. The AlGaN-based deep ultraviolet light-emitting diode according to claim 1, characterized in that: The material of the electron blocking layer is p-type aluminum gallium nitride, the molar fraction of the aluminum component in the electron blocking layer is 45%, and the doping element of the p-type aluminum gallium nitride is magnesium; The thickness of the electron blocking layer is 30 nm±3 nm.

8. The AlGaN-based deep ultraviolet light-emitting diode according to claim 1, characterized in that: The doping element of the p-type aluminum gallium nitride layer is magnesium, and the doping concentration of magnesium is 0.8×10 16 cm -3 ~1.2×10 16 cm -3 ; The thickness of the p-type aluminum gallium nitride layer is 70nm±7nm.

9. The AlGaN-based deep ultraviolet light-emitting diode according to claim 1, characterized in that: The doping element of the p-type gallium nitride contact layer is magnesium, and the doping concentration of magnesium is 0.8×10 18 cm -3 ~1.2×10 18 cm -3 ; The thickness of the p-type gallium nitride contact layer is 100 nm±10 nm.

10. A method for preparing an aluminum gallium nitride-based deep ultraviolet light-emitting diode, characterized in that: include: Obtaining a sapphire substrate; Epitaxially growing an aluminum nitride buffer layer, an n-type aluminum gallium nitride layer, a multi-quantum well layer, an electron blocking layer, a p-type aluminum gallium nitride layer, and a p-type gallium nitride contact layer on the sapphire substrate, the layer being located on a side of the p-type aluminum gallium nitride layer away from the sapphire substrate; Using electron beam lithography and inductively coupled plasma etching technology, etching the platform wall micro-nano reflective structure on the p-type aluminum gallium nitride layer and the p-type gallium nitride contact layer, the platform wall micro-nano reflective structure includes a plurality of platform wall micro-nano reflective units distributed in an array, and the platform wall micro-nano reflective structure is obtained by chaos-Jaya algorithm optimization to improve the light extraction efficiency of the deep ultraviolet light-emitting diode; A metal aluminum layer is deposited between adjacent micro-nano reflective units on the wall as a reflective material; A metal electrode is prepared on the metal aluminum.

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