A micro-led device based on a ga n homogeneous substrate and a design method and application thereof

Abstract

The application relates to the technical field of optoelectronic device design and manufacturing, in particular to a Micro-LED device based on a GaN homogeneous substrate and a design method and application thereof. The device comprises a GaN homogeneous substrate and a driving substrate; the GaN homogeneous substrate comprises a circular truncated cone structure, an active light-emitting structure is arranged at the small end face of the circular truncated cone structure, and the included angle between the sidewall of the circular truncated cone structure and the large end face thereof is limited to 80-87 degrees; the collimation regulation and control of a light beam are realized by using the total reflection effect of the sidewall; electrodes are arranged on the GaN homogeneous substrate and the active light-emitting structure, and the GaN homogeneous substrate is connected to the driving substrate in an inverted manner through the electrodes. By optimizing the sidewall inclination angle and height of the circular truncated cone structure, the light beam emitted by the active light-emitting structure is subjected to multiple total reflections in the circular truncated cone structure, the divergence angle of the outgoing light beam is significantly reduced, and the effect of greatly improving the light collimation property of the device is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optoelectronic device design, in particular to a Micro-LED device based on GaN homogeneous substrate and a design method and application thereof. BACKGROUND

[0002] Micro light emitting diode (Micro-LED) technology is regarded as the core direction of the next generation of display technology due to its excellent characteristics such as high brightness, high efficiency, long service life and fast response, and is gradually applied to augmented reality, virtual reality, wearable devices and vehicle-mounted displays and other fields. However, the Micro-LED device prepared by traditional heterogeneous substrate (such as sapphire) has problems such as high lattice defect density, insulation characteristics and heat dissipation bottleneck, which not only limits the internal quantum efficiency and reliability of the device, but also makes it difficult to achieve efficient beam regulation. In addition, with the miniaturization of Micro-LED devices, their light emission behavior presents a typical Lambertian distribution, resulting in serious beam divergence and increased inter-pixel optical crosstalk, which becomes a core bottleneck restricting their application in high-precision optical systems.

[0003] At present, the main methods to reduce the light emission angle of Micro-LED include microlens, photonic crystal, side wall reflection layer, etc. However, these methods all have obvious limitations. Although the integrated microlens array can collimate the divergent light, reduce the light emission angle and reduce optical crosstalk, the integrated process is complex, and the microlens structure size needs to be much larger than the Micro-LED chip size, which limits the miniaturization of the pixel arrangement period and is not conducive to the manufacture of high-resolution display devices. The photonic crystal needs to be etched in the multi-quantum well layer, which will introduce more quantum well defects and reduce the internal quantum efficiency. Moreover, when the shallow etched photonic crystal uses the grating characteristics to reduce the light emission angle, the Micro-LED will still emit light at a large angle due to the multiple diffraction directions of the grating. The side wall reflection layer has strict requirements on the side wall angle of the Micro-LED. Only when the angle between the side wall and the vertical direction is large enough (about 60°), can a good collimation effect be achieved. However, a too large side wall angle is difficult to achieve in the process. In the prior art, although a simple photolithography method can be used to manufacture a window for QD injection and a blocking wall for reducing crosstalk, it is limited to single pixel divergent light and reduces crosstalk, but the effect is limited. Therefore, there is an urgent need to provide a new type of Micro-LED device to simultaneously solve the industry problems of light emission divergence and pixel crosstalk existing in the existing Micro-LED device. SUMMARY

[0004] The purpose of the present application is to provide a Micro-LED device based on GaN homogeneous substrate and a design method thereof, to solve the industry problems of light emission divergence and pixel crosstalk existing in the existing Micro-LED device.

[0005] To achieve the above object, the application provides the following technical scheme: a Micro-LED device based on GaN homogeneous substrate, comprising a GaN homogeneous substrate and a driving substrate;

[0006] The GaN homogeneous substrate comprises a circular truncated cone structure in the shape of a circular truncated cone, a source light-emitting structure is arranged on a small end surface of the circular truncated cone structure, the height of the circular truncated cone structure is any value in the range of 25 μm-100 μm, and the included angle between the sidewall of the circular truncated cone structure and the large end surface thereof is any value in the range of 80°-87°, so as to realize collimation regulation and control of a light beam by using the total reflection effect of the sidewall of the circular truncated cone structure.

[0007] Electrodes are arranged on the GaN homogeneous substrate and the source light-emitting structure, and the GaN homogeneous substrate is connected to the driving substrate in a flip-chip manner through the electrodes.

[0008] Further, the height of the circular truncated cone structure is proportional to the thickness of the GaN homogeneous substrate.

[0009] Further, the thickness of the GaN homogeneous substrate is any value in the range of 30 μm-500 μm.

[0010] Further, the source light-emitting structure is in the shape of a circular truncated cone as a whole with the circular truncated cone structure.

[0011] Further, the source light-emitting structure comprises, in sequence, a buffer layer, a quantum well, an AlGaN layer, a p-GaN layer and a transparent conductive layer arranged in a stacked manner, and the buffer layer is attached to the circular truncated cone structure.

[0012] Further, the electrodes comprise a p-electrode and an n-electrode, the p-electrode is arranged on the source light-emitting structure, the n-electrode is arranged on the GaN homogeneous substrate, and the n-electrode and the p-electrode are both located on the same side of the GaN homogeneous substrate.

[0013] The application further provides a design method of the above Micro-LED device, characterized by comprising the following steps:

[0014] S1, creating a simulation model by using simulation software, the simulation model comprising a GaN homogeneous substrate, a source light-emitting structure and a light intensity distribution receiver, the light intensity distribution receiver being located on the side of the GaN homogeneous substrate far from the source light-emitting structure, and the light intensity distribution receiver being used for receiving light intensity;

[0015] S2, setting the height and sidewall inclination angle of the circular truncated cone structure of the GaN homogeneous substrate as optimization design variables, and setting the light-emitting divergence angle of the GaN homogeneous substrate as an optimization target, and performing optimization simulation;

[0016] S3, determining the geometric parameters of the frustum structure according to the optimization result, so as to prepare the Micro-LED device according to the geometric parameters of the frustum structure.

[0017] Further, in step S2, the optimization target is to optimize the light-emitting divergence angle of the GaN homogeneous substrate to within ± 15°.

[0018] Further, in step S2, during the optimization process, the light beam wavelength is set to 450 nm or 436 nm, and the background medium is set to air.

[0019] The application also provides an application of the above Micro-LED device in a micro display device, an AR device or a VR device.

[0020] The Micro-LED device based on the GaN homogeneous substrate provided by the application constructs a frustum structure on the GaN homogeneous substrate, and optimizes the side wall inclination angle and height of the frustum structure, so that the light beam emitted by the active light-emitting structure undergoes multiple total reflections in the frustum structure, the included angle between the light beam and the optical axis gradually decreases each time the light beam undergoes total reflection, and after multiple total reflections, the divergence angle of the outgoing light beam is significantly reduced, thereby achieving the effect of greatly improving the light collimation of the Micro-LED device without additional optical elements.

[0021] The GaN homogeneous substrate has excellent structural integrity and consistency, and has extremely low dislocation density and high crystal quality, so that the side wall of the frustum structure is smooth and flat, which helps to ensure the efficiency and stability of the total reflection process and improve the light beam collimation effect and light escape rate of the Micro-LED device. At the same time, most of the light that should originally be leaked from the side wall can be "bound" and directed to the light-emitting surface for output, effectively solving the problems of side wall light leakage and pixel crosstalk of the traditional Micro-LED device. In addition, the frustum structure can homogenize the light, improve the brightness distribution uniformity of the light-emitting surface, and make the Micro-LED device suitable for micro display scenarios with high uniformity requirements.

[0022] Compared with a heterogeneous substrate such as sapphire, in the Micro-LED device based on the GaN homogeneous substrate provided in the application, the GaN homogeneous substrate has sufficient physical thickness, can provide longitudinal space for constructing a large-scale circular table structure, and can further directly construct a circular table structure with an ideal depth-width ratio inside the chip, and can also avoid the lattice and thermal mismatch problems of the heterogeneous substrate. The thick GaN homogeneous substrate has excellent mechanical integrity, can effectively inhibit the generation and expansion of cracks when etching the tapered sidewall, and can ensure the edge integrity and optical quality of the complex three-dimensional structure. Moreover, the processing process has low energy consumption and small tool wear, and is highly compatible with the existing semiconductor batch manufacturing process. In addition, because the thickness of the GaN homogeneous substrate is sufficient, the self-supporting tapered structure can be realized without additional substrate transfer or bonding steps, which simplifies the process flow, reduces the manufacturing cost, and improves the yield from the root cause.

[0023] The above description is only a summary of the technical scheme of the application. In order to more clearly understand the technical means of the application and can be implemented according to the content of the specification, the following will be described in detail with the preferred embodiments of the application and with the help of the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The structure schematic diagram of the Micro-LED device based on the GaN homogeneous substrate shown in an embodiment of the application;

[0025] Figure 2 The structure schematic diagram of the GaN homogeneous substrate constructed by software shown in an embodiment of the application;

[0026] Figure 3 The propagation path schematic diagram of the light in the Micro-LED device simulated by software shown in embodiment 1 of the application;

[0027] Figure 4 The light beam divergence angle comparison diagram of the Micro-LED device simulated by software shown in embodiment 1 of the application;

[0028] Figure 5 The light ray illuminance distribution diagram of the Micro-LED device shown in embodiment 1 of the application;

[0029] Figure 6 The two-dimensional Cartesian coordinate light intensity profile diagram of the Micro-LED device shown in embodiment 1 of the application;

[0030] Figure 7 The two-dimensional polar coordinate light intensity profile diagram of the Micro-LED device shown in embodiment 1 of the application;

[0031] Figure 8 The two-dimensional Cartesian coordinate light intensity profile diagram of the Micro-LED device arranged in an array shown in embodiment 1 of the application;

[0032] Figure 9 Figure 1 is a two-dimensional polar coordinate light intensity profile of the Micro-LED device shown in Embodiment 1 of the present application arranged in an array.

[0033] Reference signs:

[0034] 1, GaN homogenous substrate; 2, active light-emitting structure; 21, buffer layer; 22, quantum well; 23, AlGaN layer; 24, p-GaN layer; 25, transparent conductive layer; 3, driving substrate; 4, electrode; 5, light path; 6, receiver. DETAILED DESCRIPTION

[0035] The technical solutions of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0036] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0037] In addition, the terms "first", "second", "third" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance. In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0039] The Micro-LED device based on GaN homogenous substrate shown in a preferred embodiment of the present application, as shown in Figure 1, is arranged in an array. Figure 1As shown, the Micro-LED device includes a GaN homogeneous substrate 1 and a driving substrate 3. Among them, the GaN homogeneous substrate 1 is provided with a source light-emitting structure 2. The GaN homogeneous substrate includes a circular truncated cone structure in the shape of a circular truncated cone, that is, one end of the GaN homogeneous substrate 1 gradually shrinks to form a circular truncated cone structure. The circular truncated cone structure is used as a waveguide structure, which can make the light output after multiple total reflections inside the circular truncated cone structure, and has excellent beam shaping and collimation functions. The source light-emitting structure 2 is arranged on the small end face of the circular truncated cone structure, so that the light beam emitted by the source light-emitting structure 2 can directly enter the circular truncated cone structure and be output after being regulated by the circular truncated cone structure. Among them, the small end face of the circular truncated cone structure is the light entrance face, and the large end face is the light exit face, that is, the end face of the circular truncated cone structure close to the source light-emitting structure 2 is the light entrance face, and the end face away from the source light-emitting structure 2 is the light exit face. Based on the optical principle and actual application requirements, the height of the circular truncated cone structure is set to any value in the range of 25 μm-100 μm, and the side wall inclination angle of the circular truncated cone structure, that is, the included angle between the side wall of the circular truncated cone and its large end face, is limited in the range of 80°-87°, such as 80°, 81.2°, 84.3°, 86.8°, 87°, etc., so that the light beam can occur multiple total reflections inside the circular truncated cone structure. In each total reflection process, the light exit divergence angle (or the light beam divergence angle), that is, the included angle between the light beam and the optical axis, gradually decreases. After multiple total reflections, the divergence angle of the emitted light beam is significantly reduced. By reasonably controlling the height and side wall inclination angle of the circular truncated cone structure, the side wall total reflection effect is fully utilized to accurately collimate and regulate the light beam, thereby compressing the light exit divergence angle of the Micro-LED device to within ±15°, and significantly improving the light extraction efficiency and uniformity. The GaN homogeneous substrate 1 and the source light-emitting structure 2 are both provided with electrodes 4, so that the GaN homogeneous substrate 1 can be flip-chip connected to the driving substrate 3 through the electrodes 4 to realize the electrical connection and signal transmission between the GaN homogeneous substrate 1 and the driving substrate 3. By connecting the GaN homogeneous substrate 1 and the driving substrate 3 through the flip-chip connection mode, the signal transmission path can be shortened, the connection reliability can be improved, and thus the performance and stability of the entire Micro-LED device can be further improved. This design takes advantage of the geometric characteristics of the circular truncated cone structure, without the need for additional optical elements, to achieve the effect of high collimation of the emitted light beam, effectively simplifying the structure of the optical system, reducing the manufacturing cost, and improving the stability and reliability of the system.

[0040] Compared with a gallium nitride epitaxial layer with a thickness of only a few microns on a heterogeneous substrate such as sapphire, the GaN homogeneous substrate 1 in the embodiment is a single crystal material with a thickness of several hundred microns. This sufficient physical thickness enables the GaN homogeneous substrate 1 to have excellent three-dimensional structural freedom, provides a key longitudinal space for constructing a large-scale waveguide structure, and makes it possible to directly form a waveguide structure with an ideal aspect ratio inside the chip. In addition, the GaN homogeneous substrate 1 has moderate hardness, and can be micro-processed with high precision by using mainstream dry etching technology or wet etching technology, and has high processing feasibility. At this time, a large-scale circular truncated cone structure, i.e., a circular truncated cone structure with a large height, can also "trap" and guide most of the light that should have leaked from the side wall to the light output surface by total reflection, thereby fundamentally physically suppressing light crosstalk between pixels.

[0041] In one embodiment, to ensure the coordination of the circular truncated cone structure and the overall structure of the substrate and the stability of the circular truncated cone structure, the height of the circular truncated cone structure can be reasonably designed according to the thickness of the GaN homogeneous substrate 1. The height of the circular truncated cone structure is proportional to the thickness of the GaN homogeneous substrate, i.e., as the thickness of the GaN homogeneous substrate 1 increases, to optimize the collimation of the Micro-LED device, reduce its beam divergence angle, and reduce light crosstalk between pixels, the height of the circular truncated cone structure can also be increased accordingly. Further preferably, the height of the circular truncated cone structure is set to be not less than 5% of the thickness of the GaN homogeneous substrate 1, to ensure that it has sufficient height to achieve multiple total reflections. Through this design, the total reflection effect can be effectively used to adjust the divergence angle of the light beam and reduce the loss of brightness caused by beam divergence. In the embodiment and other embodiments, the thickness of the GaN homogeneous substrate 1 is preferably limited to the range of 30 μm-500 μm, such as 30 μm, 70 μm, 200 μm, 500 μm, etc., for stable and efficient transmission of optical signals and to provide an ideal physical basis for constructing a waveguide structure with excellent performance. In addition, in some embodiments, the height of the circular truncated cone structure is preferably limited to the range of 25 μm-100 μm, such as 30 μm, 48 μm, 67 μm, 100 μm, etc. When the light beam propagates inside the circular truncated cone structure with this height range, enough times of total reflection phenomenon can occur.

[0042] In one embodiment, the active light-emitting structure 2 is frustoconical as a whole with the frustoconical structure. Specifically, the active light-emitting structure 2 is equal to the corresponding angle and proportional to the corresponding side of the frustoconical structure, so that the included angle between the side wall of the active light-emitting structure 2 and its large end face is the same as that of the frustoconical structure. Moreover, the diameter of the large end face of the active light-emitting structure 2 is set to be the same as that of the small end face of the frustoconical structure, and the two are aligned and attached, which helps to ensure the continuity of the propagation path of the light beam when it propagates from the active light-emitting structure 2 to the frustoconical structure, and at the same time ensures that the light beam emitted by the active light-emitting structure 2 is transmitted to the inside of the frustoconical structure as much as possible with the maximum efficiency and the minimum loss during the propagation process, further improving the light extraction efficiency of the Micro-LED device. In this embodiment and other embodiments, the active light-emitting structure 2 sequentially includes a buffer layer 21, a quantum well 22, an AlGaN layer 23, a p-GaN layer 24, and a transparent conductive layer 25 which are stacked, wherein the buffer layer is attached to the frustoconical structure. The buffer layer 21 is used to reduce defects caused by lattice mismatch. The quantum well 22 serves to generate light and form the required light radiation area. The AlGaN layer 23 is used to adjust the energy band structure of the quantum well 22, further optimizing the light-emitting efficiency. The p-GaN layer 24 serves as a current injection layer for providing current to the quantum well 22 area. The transparent conductive layer 25 is used to provide good electrical contact while ensuring effective light transmission. The electrode 4 includes a p-electrode and an n-electrode. The p-electrode is disposed on the transparent conductive layer 25 of the active light-emitting structure 2 and is responsible for providing positive current to the active area. The n-electrode is disposed on the GaN homogeneous substrate 1, and the n-electrode and the p-electrode are located on the same side of the GaN homogeneous substrate and are responsible for providing negative current from the GaN substrate to the active area. This structure design enables the GaN homogeneous substrate 1 to be flip-chip connected to the driving substrate 3 through the electrode 4 to form a complete Micro-LED device. The flip-chip connection effectively reduces the thermal expansion difference of the materials, improves the mechanical strength and stability of the device. In addition, the flip-chip structure can also optimize the light output direction, improve the light beam collimation effect, and further improve the performance and reliability of the display device.

[0043] The application also provides a design method of the above Micro-LED device. The design method comprises the following steps:

[0044] S1, creating a simulation model using simulation software, the simulation model comprising a GaN homogeneous substrate, an active light-emitting structure, and a light intensity distribution receiver located on the side of the GaN homogeneous substrate away from the active light-emitting structure, the light intensity distribution receiver being used to receive light intensity;

[0045] S2, setting the height and side wall inclination angle of the frustoconical structure of the GaN homogeneous substrate as optimization design variables, and setting the light emission divergence angle of the GaN homogeneous substrate as an optimization target to perform optimization simulation;

[0046] S3. Determine the geometric parameters of the frustum structure based on the optimization results, so as to fabricate the Micro-LED device based on the geometric parameters of the frustum structure.

[0047] In step S1, the optical simulation software LightTools is used to model and construct the GaN homogeneous substrate 1 and the active light-emitting structure 2. Since the non-frustum structure on the GaN homogeneous substrate 1 has a relatively small impact on the overall optical performance, and its impact is negligible compared to a large-scale frustum structure, this non-frustum structure can be simplified during optical simulation, thereby reducing design complexity and improving simulation efficiency. Figure 2 As shown, a three-dimensional model of a GaN homogeneous substrate 1 including a frustum structure is established. In this embodiment and other embodiments, the geometric parameters of the frustum structure include the size of the small end face, the height h, and the sidewall tilt angle θ, etc. These geometric parameters directly determine the collimation effect, divergence angle, and intensity distribution of the light beam, thus affecting the final optical performance. For example, the height h and the sidewall tilt angle θ of the frustum structure together determine the light path 5, that is, the propagation direction and path of the light beam, enabling the light to be effectively collimated and reducing optical crosstalk. The intensity distribution receiver 6 is located on one side of the small end face of the frustum structure, that is, directly above the light-emitting surface of the frustum structure. The receiver 6 is used to record the far-field intensity distribution, beam divergence angle (FWHM), and spatial uniformity of the constructed GaN homogeneous substrate 1, providing comprehensive data support for subsequent analysis.

[0048] In step S2, ray tracing analysis is performed on the constructed GaN homogeneous substrate 1. In this embodiment and other embodiments, during the ray tracing analysis, the ray tracing wavelength is set to the characteristic emission wavelength of the Micro-LED device, such as 450nm or 436nm, and the background medium is set to air to simulate the actual working environment. Simultaneously, the active light-emitting structure 2 of the Micro-LED device is set as the light source, and its emission characteristics are set to follow the Lambertian distribution law, thus accurately reflecting the emission characteristics of the active region. When running the Monte Carlo ray tracing simulation, the propagation behavior of a large number of light rays within the frustum structure is tracked, and the distribution of the emitted light field after multiple reflections through the sidewalls is analyzed. By analyzing the data from receiver 6, the collimation effect and light extraction efficiency, such as the degree of divergence angle compression, are quantitatively evaluated; the system tracks the propagation path and behavior of a large number of light rays inside the frustum structure. By deeply analyzing the distribution of the emitted light field after multiple reflections through the sidewalls, the control effect of the frustum structure on light can be intuitively understood. By carefully analyzing the data recorded by receiver 6, the collimation effect and light extraction efficiency of the beam can be quantitatively evaluated. The degree of divergence angle compression is one of the important indicators for measuring the collimation effect.

[0049] In the present embodiment and other embodiments, in order to explore the optimal combination of geometric parameters of the circular truncated cone structure, the side wall inclination angle or the height of the circular truncated cone structure can be used as the optimization design variable, and a systematic analysis can be performed through parameter scanning and optimization algorithms. By changing the values of these parameters, the optical performance of the circular truncated cone structure under different geometric parameters can be simulated, the influence of each parameter on the light collimation effect can be comprehensively studied, and finally a set of circular truncated cone structure parameters that can minimize the light divergence angle and optimize the spatial uniformity can be determined. The above simulation principle is mainly based on geometric optics and total reflection theory. In the circular truncated cone structure, when the light rays undergo multiple total reflections in the side wall, the propagation direction of the light rays will gradually change, and the angle between the light rays and the optical axis will also gradually decrease, thereby achieving the collimation effect of the light beam. The non-sequential ray tracing function in the LightTools software can accurately simulate the propagation process of light rays in complex structures, providing a reliable technical means for verifying the collimation effect of the circular truncated cone structure.

[0050] The present application also provides applications of the above-mentioned Micro-LED device, including its applications in micro-projection, near-eye display systems, etc., specifically, applications in micro-display devices, AR devices, or VR devices. When the Micro-LED device based on the GaN homogeneous substrate is applied to the lighting system, the light spot emitted by the active light-emitting structure 2 can be converted into a high-uniformity rectangular collimated light spot required by the display chip, greatly improving the energy utilization rate of the entire optical system. Specifically, the light rays enter the large-scale circular truncated cone structure from the light entrance surface of the circular truncated cone structure, and after experiencing multiple total reflections between the side walls of the circular truncated cone structure, the light rays exit from the bottom surface, i.e., the light exit surface of the circular truncated cone structure, forming a uniform rectangular light spot. Specifically, the light rays enter the large-scale circular truncated cone structure from the entrance surface, and after multiple total reflections in the side wall, the light rays exit from the bottom surface, forming a uniform rectangular light spot. Since the GaN homogeneous substrate 1 has extremely low dislocation density, high crystal quality, and sufficient physical thickness, a large-scale circular truncated cone structure with flat side walls and low optical loss can be directly etched on the chip level. The high-quality side wall ensures the efficiency and stability of the total reflection process, significantly improves the beam shaping effect and light energy utilization efficiency, and effectively solves the common problems of side wall light leakage and pixel crosstalk in traditional Micro-LED devices.

[0051] Embodiment 1

[0052] S1. Using simulation software, create a GaN homogeneous substrate 1, and gradually taper one end of the GaN homogeneous substrate 1 to form a frustum structure. The diameter of the small end face of this frustum structure is set to 5 μm. Create a circular light spot with a diameter of 5 μm on the small end face of the frustum structure to replace the active light-emitting structure 2, and set it to be a Lambertian light source with a wavelength of 436 nm and a power of 1 W, with the emission angle limited to ±60°. Place a rectangular receiver 6 with dimensions of 400 μm × 400 μm on the side of the GaN homogeneous substrate 1 away from the circular light spot, at a distance of 200 μm from the GaN homogeneous substrate 1, to monitor the illuminance and energy distribution of the emitted light.

[0053] S2, such as Figure 3 As shown, simulation software was used to simulate the light-emitting collimation effect of GaN homogeneous substrate 1. During the simulation, the height and sidewall tilt angle of the frustum structure were used as variables to optimize its geometric parameters, thereby optimizing the light-emitting divergence angle and achieving beam collimation. Furthermore, the collimation evaluation function was used as the objective during the optimization process to concentrate the emitted light rays along the normal direction, thus achieving the optimal collimation effect. The collimation effect achieved at different sidewall tilt angles at each preset height, i.e., the corresponding light-emitting divergence angle, is shown in the results. Figure 4 As shown.

[0054] S3. Optimize the geometric parameters of the frustum structure to obtain the optimal light divergence angle, so as to fabricate Micro-LED devices based on the geometric parameters of the frustum structure.

[0055] Depend on Figure 4 It can be seen that, under different preset heights, the sidewall tilt angle corresponding to the optimal collimation effect of the Micro-LED device is 83.7°. Under the same sidewall tilt angle, the beam collimation effect of the Micro-LED device gradually improves with the increase of the height of the frustum structure. By comparing the collimation effects of Micro-LED devices corresponding to frustum structures with different geometric parameters, it can be seen that when the height of the frustum structure is 90μm and the sidewall tilt angle is 83.7°, the collimation effect of the corresponding Micro-LED device reaches its optimum, and its beam divergence angle can be controlled within ±10°, significantly better than other parameter combinations. Furthermore, from... Figure 4 It can be observed that when the side wall inclination angle of the frustum structure is within the range of 80° to 85°, the collimation angle of the corresponding Micro-LED device at the same preset height fluctuates within ±5°. This indicates that the outer frustum structure has a certain tolerance for process errors, which in turn shows that the Micro-LED device has good process feasibility.

[0056] Further verification is made on the light uniformization effect of the Micro-LED device corresponding to the circular truncated cone structure with a height of 90 μm and a side wall inclination angle of 83.7°, and the verification result is shown in Figure 5 、 Figure 6 、 Figure 7 .

[0057] As shown in Figure 5 , according to the two-dimensional illumination distribution on the receiving surface of the planar receiver 6, it can be known that the single Micro-LED device forms a specific illumination distribution on the rectangular receiver 6, and the energy is concentrated to a certain extent, and the spot shape is good. Moreover, according to the total power received on the receiving surface of the rectangular receiver 6, which is 0.99994 W, it is calculated that the light extraction efficiency is 99.994%. As shown in Figure 6 、 Figure 7 , it can be directly seen from the figure that the collimation effect of the single Micro-LED device is excellent, and the light intensity distribution presents a sharp peak state, and the light extraction divergence angle of the single Micro-LED device is within ±10°. It is further illustrated that the Micro-LED device performs excellently in beam collimation control and has good practical application potential.

[0058] The Micro-LED device corresponding to the circular truncated cone structure with a height of 90 μm and a side wall inclination angle of 83.7° is expanded to an 8×8 array structure to simulate the optical performance of the actual micro display unit. A rectangular receiver 6 with a size of 300 μm×300 μm is arranged at the same position directly above the array light emitting surface, light tracing simulation is performed, and the far field light intensity distribution is analyzed, and the analysis result is shown in Figure 8 、 Figure 9 .

[0059] According to the total energy received on the receiving surface of the rectangular receiver 6, which is 64.991 W, and the total energy of the 64 circular light sources, which is 64 W, it is calculated that the light extraction efficiency of the array is 99.987%, which is highly consistent with the light extraction efficiency value of 99.994% of the single Micro-LED device, which illustrates that after the expansion of the Micro-LED device array, the optical performance still has high stability, and the array of multiple Micro-LED devices does not cause energy diffusion or morphological distortion. As shown in Figure 8 、 Figure 9 , it can be directly seen from the figure that the collimation effect of the array is excellent, and the light intensity distribution presents a sharp peak state, and the light extraction divergence angle of the array is ±14.427°. This illustrates that the Micro-LED device based on the GaN homogeneous substrate proposed in the embodiment still maintains good collimation effect in array integration, can effectively suppress sidelobe light emission and improve axial light intensity, and meets the optical requirements of high directivity and low crosstalk of the micro display system.

[0060] Based on the optimization result, the geometric parameters of the circular truncated cone structure are determined, and then the Micro-LED device is prepared according to the parameters. In the actual preparation process, in order to meet the diversified actual use requirements, the Micro-LED device can be arranged into an array form according to a specific rule.

[0061] The technical features of the above embodiments can be combined arbitrarily. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, but as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the description.

[0062] The above embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the patent of the present application should be subject to the appended claims.

Claims

1. A Micro-LED device based on a GaN homogeneous substrate, characterized in that, Including GaN homogeneous substrate and driving substrate; The GaN homogeneous substrate includes a frustum-shaped structure, with an active light-emitting structure disposed on the small end face of the frustum structure. The height of the frustum structure is any value between 25μm and 100μm, and the angle between the sidewall of the frustum structure and its large end face is any value between 80° and 87°, so as to achieve collimation and control of the light beam by utilizing the total internal reflection effect of the sidewall of the frustum structure. Electrodes are provided on both the GaN homogeneous substrate and the active light-emitting structure, and the GaN homogeneous substrate is flip-chip connected to the driving substrate through the electrodes.

2. The Micro-LED device as described in claim 1, characterized in that, The height of the frustum structure is proportional to the thickness of the GaN homogeneous substrate.

3. The Micro-LED device as described in claim 1, characterized in that, The thickness of the GaN homogeneous substrate is any value between 30 μm and 500 μm.

4. The Micro-LED device as described in claim 3, characterized in that, The active light-emitting structure and the frustum structure together form a frustum shape.

5. The Micro-LED device as described in claim 3, characterized in that, The active light-emitting structure comprises, in sequence, a buffer layer, a quantum well, an AlGaN layer, a p-GaN layer, and a transparent conductive layer, wherein the buffer layer is attached to the frustum structure.

6. The Micro-LED device as described in claim 5, characterized in that, The electrode includes a p electrode and an n electrode. The p electrode is disposed on the active light-emitting structure, and the n electrode is disposed on the GaN homogeneous substrate. The n electrode and the p electrode are both located on the same side of the GaN homogeneous substrate.

7. The design method of the Micro-LED device according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Use simulation software to create a simulation model. The simulation model includes a GaN homogeneous substrate, an active light-emitting structure, and a light intensity distribution receiver. The light intensity distribution receiver is located on the GaN homogeneous substrate on the side away from the active light-emitting structure. The light intensity distribution receiver is used to receive light intensity. S2. Set the height and sidewall tilt angle of the frustum structure of the GaN homogeneous substrate as optimization design variables, and perform optimization simulation with the light emission divergence angle of the GaN homogeneous substrate as the optimization target. S3. Determine the geometric parameters of the frustum structure based on the optimization results, so as to fabricate the Micro-LED device based on the geometric parameters of the frustum structure.

8. The design method as described in claim 7, characterized in that, In step S2, the optimization objective is to optimize the light emission divergence angle of the GaN homogeneous substrate to within ±15°.

9. The design method as described in claim 7, characterized in that, In step S2, during the optimization process, the beam wavelength is set to 450nm or 436nm, and the background medium is set to air.

10. The application of the Micro-LED device according to any one of claims 1-6 in a micro-display device, AR device or VR device.

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