Miniature LED light-emitting structure, miniature light-emitting device and manufacturing method

Abstract

The invention discloses a miniature LED light-emitting structure, a miniature light-emitting device and a manufacturing method. The miniature LED light-emitting structure comprises a semiconductor transition layer, and a first semiconductor layer is formed on one side of the semiconductor transition layer. A plurality of discrete light-emitting step structures are formed on one side, deviating from the semiconductor transition layer, of the first semiconductor layer, and non-light-emitting regions are formed among the light-emitting step structures; the non-light-emitting area is provided with a filling layer, a refraction layer is arranged between the filling layer and the first semiconductor layer, and the refractive index of the first semiconductor layer is lower than that of the refraction layer and higher than that of the filling layer. According to the invention, the refraction layer with high refractive index is arranged in the channel between the light-emitting step structures, the light which is transversely propagated in the first semiconductor layer can be introduced into the refraction layer, the generation of transverse light is reduced, the light introduced into the refraction layer is totally reflected at the interface between the refraction layer and the filling layer, the effect similar to the optical fiber effect is formed, and the light-emitting efficiency is improved. The capability of light transmission to the side surface is effectively reduced, the modulation transfer function value is improved, and the contrast effect is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor light-emitting technology, specifically to a micro LED light-emitting structure, a micro light-emitting device, and a fabrication method. Background Technology

[0002] Micro-LED, also known as mLED or μLED, is an electroluminescent device composed of a micrometer-scale array of semiconductor light-emitting units that converts electrical energy into light energy. Micro-LED chips possess extremely high research and application value due to their disruptive advantages such as high brightness, high resolution, low power consumption, long lifespan, and lightweight design.

[0003] Currently, in the structure used in micro LED products, the light emitted by the light-emitting layer can easily pass through the non-light-emitting area between the light-emitting mesa, resulting in a poor contrast between the ideal light-emitting area and the adjacent non-light-emitting area. Summary of the Invention

[0004] This application provides a micro LED light-emitting structure, a micro light-emitting device, and a fabrication method to solve the problems of poor contrast and low modulation transfer function values ​​in related technologies.

[0005] To address the aforementioned technical problems, this application provides a micro LED light-emitting structure, which includes a semiconductor transition layer. A first semiconductor layer is disposed on one side surface of the semiconductor transition layer. Multiple discrete light-emitting step structures are formed on the side of the first semiconductor layer away from the semiconductor transition layer, and non-light-emitting regions are formed between the light-emitting step structures. A filling layer is disposed in the non-light-emitting regions, and a refractive layer is disposed between the filling layer and the first semiconductor layer. The refractive index of the first semiconductor layer is lower than that of the refractive layer and higher than that of the filling layer.

[0006] Furthermore, the filling layer is an underfill layer, and the refractive layer is a TiO2 layer.

[0007] Furthermore, the light absorption rate of the refractive layer is 20%-90%.

[0008] Furthermore, the cross-section of the refractive layer is one of a circle, an ellipse, or a polygon.

[0009] Furthermore, the light-emitting step structure is frustoconical, and the end face with the smaller diameter of the light-emitting step structure is far away from the semiconductor transition layer.

[0010] Furthermore, the light-emitting step structure includes a light-emitting layer, the distance between the side of the light-emitting layer away from the first semiconductor layer and the semiconductor transition layer is L1, and the distance between the side of the refractive layer away from the first semiconductor layer and the semiconductor transition layer is L2, where L1 < L2.

[0011] Furthermore, the array of light-emitting step structures is distributed such that the refractive layer is disposed in the area enclosed between four adjacent light-emitting step structures.

[0012] Furthermore, the filling layer covers the non-light-emitting area.

[0013] Furthermore, the thickness of the semiconductor transition layer is 0.5μm to 5μm, and the height of the light-emitting step structure is 0.5μm to 2.5μm.

[0014] To address the aforementioned technical problems, this application also provides a micro light-emitting device, including a micro LED light-emitting structure.

[0015] A method for fabricating a micro LED light-emitting structure is also provided, comprising the following steps: Take an epitaxial wafer with a sapphire or silicon substrate and clean the surface of the epitaxial wafer to remove contaminants; The epitaxial wafer includes a semiconductor transition layer, a first semiconductor layer, a light-emitting layer, and a second semiconductor layer stacked sequentially on one side of the substrate. Discrete light-emitting step structures are etched on the surface of the epitaxial wafer; A bottom-filling adhesive is deposited in the channels formed between the luminescent stepped structures; Open pores in the bottom filler adhesive and deposit a refractive layer; Another layer of underfill adhesive is deposited to cover the refractive layer; Remove the substrate.

[0016] Furthermore, it also includes preparing an electrode layer on the surface of the light-emitting stepped structure.

[0017] The beneficial effects of the micro LED light-emitting structure and micro light-emitting device in the embodiments of this application are: By setting a high-refractive-index refractive layer in the channel between the light-emitting step structures, the light that propagates laterally in the semiconductor transition layer at a large angle can be introduced into the refractive layer with a higher refractive index between the light-emitting mesa, effectively suppressing the lateral propagation of light between the light-emitting mesa and reducing the generation of lateral light. At the same time, the light introduced into the refractive layer undergoes total internal reflection at the interface between the refractive layer and the filling layer, forming an effect similar to the "fiber optic effect". This prevents the light from being transmitted to the adjacent light-emitting step structure through the filling layer, effectively reducing the ability of light to propagate to the side, thereby improving the modulation transfer function (MTF) value and enhancing the contrast. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the embodiments will be briefly introduced. Obviously, the accompanying drawings described below are only one embodiment of the present invention.

[0019] Figure 1 This is a cross-sectional view of a micro LED light-emitting structure in the prior art; Figure 2 This is a diagram showing the light transmission path in a micro LED light-emitting structure in the prior art, where the dashed lines represent the light transmission path; Figure 3 This is a top view of a micro LED light-emitting structure in the prior art; Figure 4 This is a cross-sectional view of the micro LED light-emitting structure provided in the embodiment of the present invention; Figure 5 This is a diagram showing the light transmission path in the micro LED light-emitting structure provided in this embodiment of the invention, wherein the dashed line represents the light transmission path; Figure 6 This is a top view of the micro LED light-emitting structure provided in the embodiment of the present invention; Figure 7 This is another cross-sectional view of the micro LED light-emitting structure provided in the embodiment of the present invention.

[0020] The annotations in the attached figures are explained as follows: 1. Semiconductor transition layer; 2. First semiconductor layer; 3. Light-emitting step structure; 4. Filling layer; 5. Refractive layer; 31. Light-emitting layer. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0022] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0023] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0024] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0025] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0026] In the prior art, the design of micro LED light-emitting structures is described in the following reference. Figure 1 and Figure 3 In this micro LED light-emitting structure, a portion of the large-angle incident light emitted from the light-emitting layer of the self-emissive mesa enters the semiconductor transition layer and the first semiconductor layer. Because the refractive indices of these two layers are greater than the refractive index of the filler layer in the channel between the light-emitting mesa, the light undergoes total internal reflection at the interface S of the first semiconductor layer and the filler layer. After total internal reflection, the light propagates laterally into one or more adjacent pixels (see...). Figure 2 (The dashed line represents the path of light transmission), resulting in a decrease in contrast. Specifically, the first semiconductor layer (usually a GaN layer) in the mesa has a refractive index of 2.15~2.4 in the visible light range, while the refractive index of the filler layer in the channel is around 1.5. When large-angle incident light enters the surface GaN, it will undergo total internal reflection at the GaN bottom filler surface.

[0027] Based on this, this application provides a micro LED light-emitting structure and a micro light-emitting device. In this application, the crosstalk phenomenon caused by the lateral propagation of light in the first semiconductor layer is not easily generated between the various light-emitting mesa of the micro light-emitting structure. Therefore, the micro LED light-emitting structure and micro light-emitting device of this application have good MTF value and contrast, and the display effect is better.

[0028] Before explaining this application, the definitions and test methods for refractive index and absorbance will be explained in detail: Refractive index is the ratio of the speed of light in a vacuum to the speed of light in a medium. The test method is to fabricate a thin film material of the target thickness on a silicon wafer with a thickness of more than 0.5 mm, and use an ellipsometry to measure the thickness and refractive index of the target film layer. Film formation methods such as CVD (Chemical Vapor Deposition), PVD (Physical Vapor Deposition), evaporation, coating, and ALD (Atomic Layer Deposition) can be used. Absorbance refers to the reduction in light intensity due to absorption when light passes through a solution or solid. This application uses visible light as an example to compare the absorbance of various structures. The testing method involves fabricating a thin film material of the target thickness (using methods such as CVD / PVD / evaporation / coating / ALD, etc.) on a double-sided polished transparent glass slide with a thickness of 0.2~1mm, using the same glass slide as a control group. Specifically, the method includes: 1. Placing the film layer to be tested vertically in front of the spectrophotometer before incident light and testing the reflectance and transmittance across the entire wavelength range. 100% - reflectance - transmittance gives the full-wavelength absorptivity of the material at that thickness. 2. Placing the control group glass slide vertically in front of the spectrophotometer before incident light and testing the reflectance and transmittance across the entire wavelength range. 100% - reflectance - transmittance gives the full-wavelength absorptivity of the stripped slide. 3. ab at the target wavelength range is the absorptivity of the material of that thickness for a specific wavelength range.

[0029] For details, please refer to Figure 4 and Figure 5 The micro LED light-emitting structure of this application embodiment mainly includes a semiconductor transition layer 1, a first semiconductor layer 2 stacked on one side of the semiconductor transition layer 1, and a light-emitting step structure 3.

[0030] The semiconductor transition layer 1 is generally an undoped semiconductor layer, specifically an undoped gallium nitride layer, i.e., UGaN. UGaN has high light transmittance and good heat dissipation, and its thickness can be flexibly configured in the range of 0.5μm to 5μm. A stacked micro-LED light-emitting structure is set on one side of the semiconductor transition layer 1. This stacked micro-LED light-emitting structure generally includes a first semiconductor layer (i.e., the first semiconductor layer 2 in this embodiment), a light-emitting layer 31, and a second semiconductor layer. Multiple discrete light-emitting step structures 3 (i.e., light-emitting mesa) are formed from the surface of the second semiconductor layer to the first semiconductor layer. The first semiconductor layer is formed by doping the semiconductor transition layer 1 with ions.

[0031] Specifically, the first semiconductor layer (i.e., the first semiconductor layer 2 in this embodiment) can be either an N-type first semiconductor layer or a P-type first semiconductor layer, more specifically, it can be an N-type gallium nitride layer or an N-type gallium arsenide layer. The light-emitting layer 31 can be a quantum well layer, for example, an indium gallium nitride quantum well layer, or an indium gallium nitride / gallium nitride multi-quantum well layer. The second semiconductor layer can be either a P-type first semiconductor layer or an N-type first semiconductor layer, more specifically, it can be a P-type gallium nitride layer or a P-type gallium arsenide layer.

[0032] In this embodiment, a filling layer 4 (including but not limited to conventional underfill adhesive) is provided in the non-light-emitting area (i.e., the channel between pixels) formed between the light-emitting step structures 3, and a high-refractive-index refractive layer 5 is provided between the filling layer 4 and the first semiconductor layer 2.

[0033] The refractive index of the refractive layer 5 should be higher than that of the first semiconductor layer 2, and also higher than that of the filling layer 4. Light emitted from the light-emitting step structure 3 enters the first semiconductor layer 2. Some small-angle incident light passes through the first semiconductor layer 2 and exits through the semiconductor transition layer 1. Some large-angle incident light is reflected at the interface of the semiconductor transition layer 1 in the non-light-emitting area and then propagates towards the first semiconductor layer 2. When the light reaches the interface between the first semiconductor layer and the refractive layer (S′ in the diagram), because the refractive index of the refractive layer 5 is higher than that of the first semiconductor layer 2, total internal reflection does not occur at this interface. The light then passes through the first semiconductor layer 2 and enters the refractive layer 5. In other words, the lateral transmission direction of the large-angle incident light is changed, and it enters the "longitudinal channel" where the refractive layer 5 is located. Furthermore, when light entering the refractive layer 5 is incident on the interface between the refractive layer and the filling layer (represented by H in the figure), because the refractive index of the filling layer 4 is lower than that of the refractive layer 5, the light undergoes total internal reflection at this interface and will not penetrate laterally into another light-emitting step structure 3. This avoids the problem of light propagating laterally into adjacent pixels, thereby increasing the modulation transfer function (MTF) value and narrowing the field of view.

[0034] In this application, since the light-emitting step structure 3 emits light while the non-light-emitting area between the light-emitting step structures 3 does not emit light, the light emitted by the light-emitting step structure 3 passes through the semiconductor transition layer 1 and is received by the human eye or other devices. The combined effect of the light-emitting step structure 3 and the non-light-emitting area ensures that the micro LED light-emitting structure can display images. Because a refractive layer 5 and a filling layer 4 are provided in the non-light-emitting area, the lateral transmission direction of the light emitted by the light-emitting step structure 3 after being incident at a large angle into the first semiconductor layer 2 and the semiconductor transition layer 1 is changed by total internal reflection. The light enters the refractive layer 5 with a higher refractive index, and the lateral propagation changes from lateral to longitudinal propagation. Combined with the design of different refractive indices between the refractive layer 5 and the filling layer 4, the light entering the refractive layer 5 will undergo total internal reflection at the refractive layer-filling layer interface and will not enter the adjacent light-emitting step structure 3 from the side, effectively reducing the ability of light to propagate to the side.

[0035] More specifically, see Figure 5 Part of the light emitted from the light-emitting stepped structure 3 exits through the first semiconductor layer 2 and the semiconductor transition layer 1, while the other part of the emitted light enters the first semiconductor layer 2 at a large angle (e.g., Figure 5 The light ray m), after being reflected by the side of the semiconductor transition layer 1 away from the first semiconductor layer 2, does not undergo total internal reflection at the GaN (first semiconductor layer 2)-fill layer interface. The lateral light propagation direction is changed, and the longitudinal light ray p enters the refractive layer 5. The light ray p undergoes total internal reflection at the refractive layer-fill layer interface and propagates in the refractive layer 5 in the direction of light ray n. With such a light propagation path, the light can be prevented from entering the adjacent light-emitting step structure 3.

[0036] Compared to existing technologies, the intensity and path length of light propagating laterally in the first semiconductor layer 2 and the semiconductor transition layer 1 are reduced to a certain extent. This is beneficial for improving the contrast and narrowing the field of view of the micro LED light-emitting structure and micro light-emitting device, ultimately achieving the effect of improving MTF and contrast.

[0037] It is important to note that higher contrast is not always better. Specifically, while increased contrast is beneficial for display quality in low-light environments, excessively high contrast is not eye-friendly and can easily cause eye fatigue. Therefore, in this embodiment, to ensure that the contrast of the micro-LED light-emitting structure is within a suitable range and does not easily cause eye fatigue for the viewer, the refractive index of the refractive layer 5 is preferably 0.1-0.5 higher than that of the first semiconductor layer 2. This ensures that the contrast of the micro-LED light-emitting structure is within a suitable range and does not easily cause eye fatigue for the viewer.

[0038] In some embodiments, the refractive layer 5 has light absorption properties. After some light rays are incident on the first semiconductor layer 2 and the semiconductor transition layer 1 at a large angle, the propagation direction changes at the interface between the refractive layer and the first semiconductor layer, and enters the refractive layer 5 "vertically". Some light rays are absorbed by the refractive layer 5, which reduces the light crosstalk phenomenon in the non-light-emitting area and improves the display contrast and MTF value.

[0039] It should be noted that, referring to the aforementioned description that "higher contrast is not always better", in order to reduce eye fatigue for viewers, in this embodiment, the light absorption rate of the refractive layer 5 is preferably designed to be 20%-90%, which can reduce eye fatigue for viewers while ensuring that the micro-LED light-emitting structure has good contrast. In some embodiments, the refractive layer 5 is designed with a relatively regular shape, at least to ensure that the interface between the refractive layer 5 and the filling layer 4 is a regular plane or curved surface, so that the light entering the refractive layer 5 will undergo total internal reflection when it is incident on the interface between the refractive layer 5 and the filling layer 4, and will not continue to propagate laterally.

[0040] Preferably, the cross-section of the refractive layer 5 is designed to be circular, elliptical, or polygonal. The most suitable cross-sectional shape is circular, meaning the refractive layer 5 is designed as a cylinder and evenly distributed in the central region of the channels between pixels.

[0041] It is understandable that the outer contour of the interface of the refractive layer 5 should be as close as possible to the periphery of the light-emitting step structure 3, and the cross-sectional area of ​​the filling layer 4 between them should be as small as possible.

[0042] In some embodiments, the cross-sectional area of ​​the light-emitting step structure 3 gradually decreases from the proximal end near the first semiconductor layer 2 to the distal end. It can be designed as a frustum-shaped structure or a trapezoidal shape, and the end face of the light-emitting step structure 3 with the smaller diameter is farther from the semiconductor transition layer 1. This shape design of the light-emitting step structure 3 is beneficial for increasing the light-emitting area.

[0043] In this application, there are no special requirements for the height of the light-emitting step structure 3, as long as it meets the purpose of this application. In some embodiments, the height of the light-emitting step structure 3 can be set to 0.5μm~2.5μm, and the specific height can be flexibly selected and configured within this range according to actual needs.

[0044] In this application, the height of the light-emitting layer 31 within the light-emitting step structure 3 is limited as follows: In this design, the height of the light-emitting layer 31 relative to the semiconductor transition layer 1 is less than the height of the refractive layer 5 relative to the semiconductor transition layer 1. Specifically, the distance between the side of the light-emitting layer 31 facing away from the first semiconductor layer 2 and the semiconductor transition layer 1 is set to L1, and the distance between the side of the refractive layer 5 facing away from the first semiconductor layer 2 and the semiconductor transition layer 1 is set to L2, with L1 < L2. In this way, most of the light emitted from the side of the light-emitting stepped structure 3 will preferentially enter the filling layer 4 between the refractive layer 5 and the light-emitting stepped structure 3, and then enter the high-refractive-index refractive layer 5 under the condition of refractive index difference. That is to say, the light emitted from the side of the light-emitting stepped structure 3 will enter the refractive layer 5, some of the light will be absorbed by the refractive layer 5, and the other part will pass through the first semiconductor layer 2 and the semiconductor transition layer 1 after the emission angle is changed by the refractive layer 5. This process will change the large angle of the light emitted from the side of the light-emitting stepped structure 3 into a small angle, and since the light is emitted from the semiconductor transition layer 1, the emission angle of the light passing through the refractive layer 5 is small, which can play a role in narrowing the field of view. At the same time, this height difference design allows the refractive layer 5 to better enhance the contrast and display effect of the light-emitting diode.

[0045] It should also be noted that, in actual use, displays with different contrast ratios can be made by controlling the thickness of the refractive layer 5, depending on the different display scenarios.

[0046] In some embodiments, see Figure 6 The light-emitting step structures 3 are arranged in an array on one side of the first semiconductor layer 2, and the refractive layer 5 is also arranged in an array. Specifically, the refractive layer 5 is set in the area enclosed between every four light-emitting step structures 3, rather than being distributed between every two adjacent light-emitting step structures 3, because there is not enough channel space between two adjacent light-emitting step structures 3 to set the refractive layer 5. Therefore, only the filling layer 4 is set in the channel between two adjacent light-emitting step structures 3 in the same row or column. The filling layer 4 is set between the four rectangularly distributed light-emitting step structures 3, and the refractive layer 5 is set in the filling layer 4, ensuring that the refractive layer 5 is in contact with the surface of the first semiconductor layer on the bottom wall of the channel. This can also improve the contrast and enhance the MTF.

[0047] In this embodiment, the filler layer 4 is an adhesive layer that covers the non-light-emitting area and the periphery between the light-emitting step structures 3. Specifically, when the filler layer 4 fills the non-light-emitting area, its surface should be flush with the side of the light-emitting step structure 3 away from the first semiconductor layer 2. The side of the refractive layer 5 away from the first semiconductor layer 2 is close to the surface of the filler layer 4.

[0048] It should be further noted that the light-emitting step structure 3 in this embodiment can be composed of one or more pre-defined visual elements, including but not limited to common graphic symbols such as numbers, letters, icons, or brand logos. This design enables the light-emitting device of the final product of the optical chip structure to be suitable for specific scenarios requiring static pattern display, such as public information and advertising display, medical and scientific visualization, or fixed display of facility floor plans and sensor warning status on monitoring panels. It can significantly reduce power consumption and improve brightness performance while ensuring display effect.

[0049] It should be noted that the visual elements in different luminous step structures 3 can be the same or different in shape, and the specific choice should be made flexibly according to the actual needs.

[0050] In this embodiment, the filling layer 4 includes, but is not limited to, a base filler layer of a suitable type, with a refractive index generally set at around 1.5. The refractive layer 5 is a TiO2 layer with a refractive index > 2, which is much higher than the refractive index of the filling layer 4, so that good total internal reflection conditions can be formed at the interface between the two.

[0051] In some embodiments, see Figure 7 The micro LED light-emitting structure may also include at least one electrode (a in the figure), each electrode corresponds to a light-emitting step structure 3, the electrode is disposed on the surface of the second semiconductor layer in the corresponding light-emitting step structure 3 (the side of the second semiconductor layer away from the light-emitting layer 31), and is electrically connected to the second semiconductor layer.

[0052] In some embodiments, in the light-emitting step structure 3, for each electrode, a current diffusion layer may be provided between the electrode and the second semiconductor layer in the corresponding light-emitting step structure 3. The purpose of this is that the current diffusion layer can extend and distribute the current injected from the electrode to the second semiconductor layer in the light-emitting step structure 3 corresponding to the electrode, thereby improving the luminous efficiency of the light-emitting layer 31 in the light-emitting step structure 3.

[0053] The micro-light-emitting device of this embodiment includes a micro-LED light-emitting structure. Specifically, the micro-light-emitting device may include a driver chip and a micro-LED light-emitting structure, with the driver chip bonded to an electrode on the surface of the second semiconductor layer disposed in the light-emitting step structure 3 of the micro-LED light-emitting structure. Other devices, such as microlenses or color-shifting structures, may also be disposed on the side of the semiconductor transition layer 1 away from the first semiconductor layer 2 to achieve other corresponding functional effects.

[0054] In this embodiment, the first semiconductor layer 2 is GaN, with a refractive index of 2.15~2.4 in the visible light range, which is lower than the refractive index of the refractive layer 5.

[0055] The micro LED light-emitting structure in this embodiment was prepared using the following method: S1. Take an epitaxial wafer with a sapphire or silicon substrate and clean the surface of the epitaxial wafer to remove contaminants. The epitaxial wafer includes a semiconductor transition layer, a first semiconductor layer, a light-emitting layer, and a second semiconductor layer that are sequentially stacked on one side of the substrate. S2. Deposit an oxide layer on the surface of the second semiconductor layer as a hard mask, and further prepare multiple separate light-emitting step structures on the epitaxial wafer by etching. S3. Deposit bottom filler adhesive in the channels formed between the light-emitting step structures; S4. Create pores in the bottom filler adhesive and deposit high refractive index material TiO2 to form a refractive layer; S5. Deposit another layer of underfill adhesive to cover the refractive layer; S6. Deposit an insulating material on the surface of the epitaxial wafer to form an insulating layer. The insulating layer may be one of SiO2, Al2O3, etc. S7. An opening is etched using photoresist at the location of the insulating layer corresponding to the second semiconductor layer, and a conductive metal layer is deposited to form a current spreading layer. The current spreading layer is made of at least one material layer selected from metal materials such as titanium (Ti), gold (Au), platinum (Pt), nickel (Ni) and aluminum (Al). S7. Deposit another layer of insulating material on the surface of the epitaxial wafer. Then, use photoresist to etch an opening at the location of the corresponding current spreading layer and deposit a metal layer to form an electrode. S8. The substrate is peeled off to obtain the optical chip structure.

[0056] In some embodiments, a micro-light-emitting device is further fabricated based on the optical chip structure, as detailed below: S9. A bonding substrate is placed on the electrode surface of the optical chip structure, wherein the bonding substrate uses a combination of metals such as Ti / Al / Cr / Pt / Au. S10. Deposit metal (In, Sn, etc.) on the surface of the bonding underlayer, or apply ACF conductive adhesive to form a bonding layer; S11. Bond the bonding layer to the electrodes of the driving substrate (i.e., the driving chip) one by one to form a micro light-emitting device.

[0057] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0058] The foregoing has provided a detailed description of a micro LED light-emitting structure, micro light-emitting device, and fabrication method provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A micro LED light-emitting structure, characterized in that, include: A semiconductor transition layer, wherein a first semiconductor layer is disposed on one side surface of the semiconductor transition layer; The first semiconductor layer has multiple discrete light-emitting step structures formed on the side away from the semiconductor transition layer. The light-emitting step structure includes the first semiconductor layer, the light-emitting layer and the second semiconductor layer stacked sequentially along the direction away from the semiconductor transition layer. Non-light-emitting areas are formed between the light-emitting step structures. A filling layer is provided in the non-light-emitting areas. A refractive layer is provided between the filling layer and the first semiconductor layer. The refractive index of the first semiconductor layer is lower than that of the refractive layer and higher than that of the filling layer.

2. The micro LED light-emitting structure according to claim 1, characterized in that: The filling layer is a bottom filler layer, and the refractive layer is a TiO2 layer.

3. A micro LED light-emitting structure according to claim 1 or 2, characterized in that: The light absorption rate of the refractive layer is 20%-90%.

4. The micro LED light-emitting structure according to claim 1, characterized in that: The refractive layer is a columnar structure with a circular, elliptical, or polygonal cross-section.

5. A micro LED light-emitting structure according to claim 1, characterized in that: The light-emitting step structure is frustoconical, and the end face with the smaller diameter of the light-emitting step structure is far away from the semiconductor transition layer.

6. The micro LED light-emitting structure according to claim 1, characterized in that: The light-emitting step structure is provided with a light-emitting layer. The distance between the side of the light-emitting layer away from the first semiconductor layer and the semiconductor transition layer is L1, and the distance between the side of the refractive layer away from the first semiconductor layer and the semiconductor transition layer is L2, where L1 < L2.

7. The micro LED light-emitting structure according to claim 1, characterized in that: The array of light-emitting step structures is distributed such that the refractive layer is disposed in the area enclosed between four adjacent light-emitting step structures.

8. A micro LED light-emitting structure according to claim 7, characterized in that: The filling layer covers the non-light-emitting area.

9. A micro LED light-emitting structure according to claim 1, characterized in that: The thickness of the semiconductor transition layer is 0.5μm to 5μm, and the height of the light-emitting step structure is 0.5μm to 2.5μm.

10. A miniature light-emitting device, characterized in that: Includes the micro LED light-emitting structure as described in any one of claims 1 to 9.

11. A method for fabricating a micro LED light-emitting structure, characterized in that, Includes the following steps: Take an epitaxial wafer with a sapphire or silicon substrate and clean the surface of the epitaxial wafer to remove contaminants; The epitaxial wafer includes a semiconductor transition layer, a first semiconductor layer, a light-emitting layer, and a second semiconductor layer stacked sequentially on one side of the substrate. Discrete light-emitting step structures are etched on the surface of the epitaxial wafer; A bottom-filling adhesive is deposited in the channels formed between the luminescent stepped structures; Open pores in the bottom filler adhesive and deposit a refractive layer; Another layer of underfill adhesive is deposited to cover the refractive layer; Remove the substrate.

12. The method for fabricating a micro LED light-emitting structure according to claim 11, characterized in that: It also includes preparing an electrode layer on the surface of the light-emitting stepped structure.

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