Micro-LED devices

Abstract

This application relates to the semiconductor field, specifically to a Micro-LED device. By setting the sidewalls of the mesa structure to be inclined at an angle of less than 90° to the substrate, it facilitates dielectric film deposition, thereby forming a multilayer optical anti-reflection layer composed of different materials on the sidewall surface. This achieves sidewall light emission enhancement, ultimately improving the quantum efficiency of the Micro-LED device, while also achieving sidewall passivation. Simultaneously, by limiting the refractive index difference between two adjacent optical anti-reflection layers and placing a fluorescence conversion layer within the optical interference cavity they form, the fluorescence conversion layer can effectively absorb photons from inside the Micro-LED device and re-emit them as more easily emitted directional light, thereby improving light extraction efficiency. This structure not only helps to control the angular distribution and spectral structure of the emitted light but also enhances fluorescence conversion efficiency through the resonance enhancement effect of the optical interference cavity, achieving stronger light emission energy and better color consistency.

Description

Technical Field

[0001] This application relates to the semiconductor field, and more specifically, to a Micro-LED device. Background Technology

[0002] Light-emitting diodes (LEDs) typically offer higher efficiency and durability, more compact size, and greater design flexibility. When the size of an LED is reduced to below 50μm, it is called a micro-LED. Micro-LEDs, with their many superior characteristics, can be widely used in products such as panel displays, flexible displays, transparent displays, and micro-projectors.

[0003] However, the development of Micro-LEDs in current technology is severely constrained by low luminous efficiency, making improving light extraction efficiency a key research direction. Currently, several common methods for improving light extraction efficiency have significant drawbacks: high cost and extreme dependence on process precision and technology. These methods are quite effective on large-size LEDs, but their effectiveness on Micro-LEDs is very limited. This is because, compared to ordinary LEDs, the sidewall area of ​​Micro-LEDs is much larger, and simply performing anti-reflection treatment on the mesa structure is far from sufficient to meet the needs of improving overall light extraction efficiency.

[0004] In existing technologies, most methods for handling sidewall light emission involve depositing a metal reflective layer to reflect all the light emitted from the sidewall back into the chip. While this method has some effect on improving top light emission, it is extremely detrimental to improving overall light extraction efficiency. The light reflected back by the metal reflective layer cannot be emitted directly from the top; instead, it undergoes multiple reflections within the chip and is ultimately consumed as heat. This not only hinders the improvement of light extraction efficiency but also negatively impacts internal quantum efficiency due to the increased chip temperature.

[0005] Furthermore, many current methods for improving overall light extraction efficiency do not specifically address the effective processing of sidewall light extraction. Examples include patterned substrates, surface plasmon resonance (SPR), and photonic crystal micro / nano structures. Patterned substrate fabrication is complex and costly, and requires extremely stringent etching processes; photonic crystal fabrication is not only complex but also demands extremely high precision; SPR's characteristics are significantly affected by the surrounding environment, potentially impacting device stability and reliability, and its fabrication process is also complex and costly. Summary of the Invention

[0006] The purpose of this invention is to provide a Micro-LED device that can improve the external quantum efficiency and luminous performance of Micro-LED devices.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a Micro-LED device having a Micro-LED device body with a mesa structure and a dielectric film deposited on the sidewall of the mesa structure, wherein the angle between the sidewall and the substrate of the Micro-LED device body is less than 90°, and the dielectric film includes several stacked optical anti-reflection layers;

[0008] The Micro-LED device further includes a fluorescence conversion layer formed between two adjacent optical antireflection layers. The refractive index difference between some of the two adjacent optical antireflection layers is ≥0.5. One of the adjacent optical antireflection layers has a refractive index ≥2.0, and the other has a refractive index ≤1.5. The two adjacent optical antireflection layers constitute an optical interference cavity, and the fluorescence conversion layer is located within the optical interference cavity. Further, the optical thickness of each of the two adjacent optical antireflection layers forming the optical interference cavity is 1 / 4 of the target wavelength.

[0009] Furthermore, the fluorescence conversion layer comprises europium-doped yttrium aluminum garnet nanoparticles.

[0010] Furthermore, the refractive index of several stacked optical antireflection layers decreases layer by layer in the direction of light emission from the inside to the outside of the Micro-LED device, forming a refractive index gradient structure.

[0011] Furthermore, the Micro-LED device also includes a phosphor layer forming the top light-emitting surface of the Micro-LED device body, the phosphor layer being made of the same material as the phosphor conversion layer.

[0012] Furthermore, the included angle is greater than or equal to 30°.

[0013] Furthermore, the thickness of each optical antireflection layer ranges from 5 to 500 nm.

[0014] Furthermore, the number of optical antireflection layers is greater than 1 and less than 20, and the material of each optical antireflection layer is selected from at least one of SiO2, TiO2, Al2O3, MgF2, ZnO, and Si3N4.

[0015] Furthermore, several stacked optical antireflective layers are sequentially deposited on the sidewalls using an atomic layer deposition method.

[0016] Furthermore, the substrate includes a heterogeneous substrate or a GaN homogeneous substrate.

[0017] The beneficial effects of this invention are as follows: The Micro-LED device of this application sets the sidewalls of the mesa structure as inclined sidewalls with an angle of less than 90° with the substrate to facilitate the deposition of dielectric films, thereby forming a multilayer optical anti-reflection layer composed of different materials on the sidewall surface. This achieves sidewall light transmission enhancement, ultimately improving the quantum efficiency of the Micro-LED device, while also achieving sidewall passivation. Simultaneously, by limiting the refractive index difference between two adjacent optical anti-reflection layers and placing a fluorescence conversion layer within the optical interference cavity they form, the fluorescence conversion layer can effectively absorb photons from inside the Micro-LED device and re-emit them as more easily emitted directional light, thereby improving light extraction efficiency. This structure not only helps to control the angular distribution and spectral structure of the emitted light but also enhances the fluorescence conversion efficiency through the resonance enhancement effect of the optical interference cavity, achieving stronger light emission energy and better color consistency. Therefore, it comprehensively utilizes the synergistic effect of interference enhancement, fluorescence conversion, and optical control, significantly improving the external quantum efficiency and luminous performance of the Micro-LED device.

[0018] Furthermore, compared to existing technologies such as patterned substrate materials, which suffer from low utilization and excessive waste, this application can reasonably control the amount of material used and reduce waste by depositing the dielectric film on the sidewalls. Moreover, since the dielectric film is deposited directly on the sidewalls, there is no need for complex multi-step etching operations, which reduces process steps, simplifies the preparation process, and improves production efficiency.

[0019] Based on this, a phosphor layer is formed on the top light-emitting surface of the Micro-LED device body. The phosphor conversion layer and the phosphor layer can use the same materials and processes to ensure consistent and uniform color conversion of the emitted light, which can effectively eliminate spectral inhomogeneity caused by local color conversion. Furthermore, through the joint action of the phosphor layer and the phosphor conversion layer, photons are re-emitted in their respective regions. Combined with the optical interference cavity formed by stacked optical anti-reflection layers, not only is the original light extraction efficiency improved, angle control and cavity resonance enhancement effect maintained, but the wavelength uniformity of the device is also improved.

[0020] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a Micro-LED device according to an embodiment of this application;

[0022] Figure 2 A comparison of transmittance between unstructured sidewalls and sidewalls with the designed multilayer dielectric film structure added (λ=450nm).

[0023] Figure 3 A comparison of transmittance between unstructured sidewalls and sidewalls with the designed multilayer dielectric film structure (incident light half-cone angle of 40°).

[0024] Figure 4 This is a comparison chart of the light extraction efficiency of sidewalls with different structures. Detailed Implementation

[0025] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly 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 or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Micro-LEDs used in micro-displays and ultra-high-speed visible light communication are typically smaller than 10 μm. However, as the size of Micro-LEDs is gradually miniaturized to the micrometer level, due to sidewall defects caused by dry etching, the external quantum efficiency of Micro-LED chips is less than 10%, and the peak external quantum efficiency corresponds to a high current density. This often means high power consumption and high self-heating, which is extremely detrimental to the application of Micro-LED devices in displays. The purpose of this application is to improve the light extraction efficiency of Micro-LEDs, thereby ultimately improving their external quantum efficiency.

[0030] Figure 1 A structure for a Micro-LED device that improves light extraction efficiency to achieve enhanced external quantum efficiency is shown. The Micro-LED device includes a Micro-LED device body with a mesa structure and a dielectric film 9 deposited on the sidewalls of the mesa structure. The Micro-LED device body is the core light-emitting structure, typically comprising a substrate 1 and a Micro-LED epitaxial wafer formed on the substrate 1. The upper half of the sidewall of the Micro-LED epitaxial wafer is etched to form the mesa structure. The angle between the sidewall and the substrate 1 is less than 90°, for example, 30°, 50°, 70°, or 80°. The dielectric film 9 comprises several stacked optical antireflection layers. The substrate 1 includes a heterojunction substrate 1 (such as sapphire) or a GaN homojunction substrate 11. The Micro-LED epitaxial wafer, from bottom to top, includes: an n-GaN layer 2, an MQWs active region 3, a p-GaN layer 4, and an ITO layer 5. Metal electrodes 6, solder joints 7, and solder joints 8 are formed on the ITO layer 5 and the n-GaN layer 2, respectively.

[0031] This Micro-LED device uses a mesa structure with a sidewall that is tilted at an angle of less than 90° to the substrate 1 to facilitate the deposition of the dielectric film 9. This allows for the formation of a multilayer optical anti-reflection layer composed of different materials on the sidewall surface, thereby enhancing the light transmission of the sidewall and ultimately improving the quantum efficiency of the Micro-LED device. It also achieves the effect of sidewall passivation.

[0032] Furthermore, compared to existing technologies such as patterned substrate 1, which suffer from low utilization and excessive waste, this embodiment achieves reasonable control of material usage and reduces waste by depositing the dielectric film 9 on the sidewall. Moreover, since the dielectric film 9 is directly deposited on the sidewall, there is no need for complex multi-step etching operations, which reduces process steps, simplifies the preparation process, and improves production efficiency.

[0033] In this embodiment, the Micro-LED device further includes a fluorescence conversion layer (not shown) forming between two adjacent optical antireflection layers. The refractive index difference between some of the two adjacent optical antireflection layers is ≥0.5. One of the two adjacent optical antireflection layers is made of a material with a refractive index ≥2.0, such as TiO2, ZnO, or HfO2, while the other optical antireflection layer is made of a material with a refractive index ≤1.5, such as SiO2, MgF2, or AlF3. The two adjacent optical antireflection layers constitute an optical interference cavity, and the fluorescence conversion layer is located within the optical interference cavity.

[0034] In this embodiment, by limiting the refractive index difference between two adjacent optical antireflection layers and placing a fluorescence conversion layer within the optical interference cavity they form, the fluorescence conversion layer can effectively absorb photons from inside the Micro-LED device and re-emit them as more easily emitted directional light, thereby improving light extraction efficiency. This structure not only helps to control the angular distribution and spectral structure of the emitted light but also enhances fluorescence conversion efficiency through the resonance enhancement effect of the optical interference cavity, achieving stronger emitted light energy and better color consistency. Therefore, it comprehensively utilizes the synergistic effect of interference enhancement, fluorescence conversion, and optical control, significantly improving the external quantum efficiency and luminous performance of the Micro-LED device.

[0035] Based on this, in one embodiment, the Micro-LED device further includes a phosphor layer formed on the top light-emitting surface of the Micro-LED device body. The phosphor layer is made of the same material as the phosphor conversion layer, and the fabrication process of the phosphor layer is the same as that of the phosphor conversion layer. By forming a phosphor layer on the top light-emitting surface of the Micro-LED device body, and by using the same material and process for both the surface phosphor conversion layer and the phosphor layer, consistent and uniform color conversion of the emitted light can be ensured, effectively eliminating spectral inhomogeneity caused by local color conversion. Furthermore, through the combined action of the phosphor layer and the phosphor conversion layer, photons are re-emitted in their respective regions. Combined with the optical interference cavity formed by stacked optical antireflection layers, not only is the original light extraction efficiency improvement, angle control, and optical interference cavity resonance enhancement effect maintained, but the wavelength uniformity of the device is also improved.

[0036] In this embodiment, the optical thickness of each of the two adjacent antireflection layers forming the optical interference cavity is 1 / 4 of the target wavelength. By setting the target wavelength, an optical interference cavity with high selectivity and strong directional enhancement is constructed, thus solving the problem of weak reflection control of the antireflection film.

[0037] Specifically, the optical antireflection layers forming the two adjacent layers of the optical interference cavity are formed by alternating stacks of high-refractive-index and low-refractive-index materials, wherein the refractive index difference between adjacent layers is greater than or equal to 0.5, the refractive index of the high-refractive-index material is greater than or equal to 2.0, and the refractive index of the low-refractive-index material is less than or equal to 1.5. The optical thickness of each optical antireflection layer satisfies the following formula:

[0038] ;

[0039] in, Indicates the first The refractive index of the layer material, For its thickness, The target wavelength to be enhanced (usually the dominant wavelength of the light emitted by the fluorescent conversion layer).

[0040] By setting a λ / 4 thickness structure, an optical interference reflection interface is formed between adjacent optical antireflection layers, which can generate an interference standing wave distribution at the target wavelength, thereby constructing a microcavity structure, which is the optical interference cavity. Furthermore, since the fluorescence conversion layer is located within this optical interference cavity, it can be precisely aligned with the standing wave peak position within the optical interference cavity, achieving the emission enhancement effect (Purcell effect) and effectively improving the directional emission capability of the fluorescence conversion layer.

[0041] It should be noted that, in multiple experiments, the inventors discovered that if only the refractive index difference between two adjacent layers is limited to "greater than or equal to 0.5" and the λ / 4 thickness structure is not specified, the following problems will occur in some cases: 1. The interference between the reflection and transmission of incident light by the film layer is no longer destructive, and reflection cannot be effectively suppressed and transmission enhanced, resulting in a decrease in overall light extraction efficiency; 2. Since the standing wave conditions corresponding to different thicknesses are different, the interference bandwidth will be difficult to control if the structure is not λ / 4, which may lead to a decrease in the selectivity of the optical cavity, fluctuations in fluorescence conversion efficiency or excitation efficiency, and thus a weakening of spectral directionality; 3. In a structure with alternating stacks of multiple high / low refractive index optical antireflection layers, if the λ / 4 condition is not met between two adjacent layers, the overall optical path matching of the dielectric film will be disrupted, resulting in a decrease in energy coupling efficiency, leading to "no gain from superposition" or even "local enhancement and overall interference" phenomena; 4. Since the fluorescence conversion layer is embedded in the optical interference cavity, if it is not λ / 4... The structure forms a stable standing wave field distribution in this region, and the fluorescent material cannot be accurately placed at the peak position of the standing wave, which seriously affects the emission efficiency; 5. The non-λ / 4 thickness structure of the film layer does not have high selectivity in response to wavelength, which will make it difficult to match the emission wavelength of Micro-LED devices, making the improvement of anti-reflection and light extraction efficiency unstable and not universal.

[0042] To address the aforementioned issues, the inventors initially struggled to pinpoint the specific reasons for the performance instability. They attempted adjustments from multiple dimensions, including material impurities, film stress, and sidewall tilt angle, but the results remained unsatisfactory. For instance, they tried selecting optical antireflection layer materials with a large difference between high and low refractive indices, hoping to achieve interference antireflection and enhanced luminescence using a conventional refractive index difference design. However, repeated experiments revealed that even with a refractive index difference greater than or equal to 0.5, the fluorescence conversion efficiency, directional emission capability, and overall antireflection effect of the film system remained unstable and uncontrollable. Finally, in one experiment, the inventors attempted to adjust adjacent antireflection layers to an optical thickness of λ / 4 at the target wavelength, discovering a significant improvement in both light extraction efficiency and fluorescence emission performance.

[0043] However, in micro-LEDs and other miniaturized structures, a λ / 4 optical thickness design is generally not used as a conventional approach, mainly because controlling the thickness of the film stacking is difficult and the standing wave position is hard to precisely align with the fluorescence conversion layer, making this structure less widely accepted. However, in this embodiment, this technical obstacle is successfully overcome by combining sidewall tilt angle control with the ALD process.

[0044] In an alternative embodiment, the fluorescence conversion layer employs a red fluorescent material, including but not limited to europium-doped (Eu) material. 3+ Yttrium aluminum garnet (YAG:Eu) nanoparticles are used to convert the excitation light emitted by the Micro-LED chip into red-band emission light. In other embodiments, other conversion materials, such as yellow conversion materials, can also be used, depending on the actual needs. The fluorescence conversion layer and fluorescence layer can be formed between adjacent optical antireflection layers and on the top light-emitting surface of the Micro-LED device body through atomic layer deposition, solution self-assembly, or spin coating, respectively. The thickness can be controlled between 5 and 50 nm to ensure the alignment of the standing wave peaks.

[0045] The refractive index of several stacked antireflective layers decreases progressively from the inside of the Micro-LED device towards the outside light emission direction, forming a refractive index gradient structure. This arrangement helps to gradually mitigate the abrupt change in refractive index between high-refractive-index materials (such as GaN) and air, significantly reducing interface reflection loss and improving overall light extraction efficiency. Simultaneously, it expands the effective transmission angle, reduces the total internal reflection trapping effect, and increases the probability of photons emitted from the fluorescence conversion layer being emitted outwards. Furthermore, the refractive index gradient structure enhances the interference matching effect between film layers, stabilizes the standing wave distribution, and improves the directional light emission and emission enhancement effect of the optical cavity, thereby achieving high-efficiency, wide-band light emission control.

[0046] To ensure the optical performance of the cavity structure, several stacked antireflective layers are sequentially deposited on the sidewalls using atomic layer deposition (ALD). In this embodiment, since the sidewalls are not perpendicular to the substrate 1, the use of atomic layer deposition can achieve excellent film uniformity and multilayer stacking quality, thereby ensuring that the optical thickness of each optical film precisely meets the interference design requirements and improving light extraction efficiency.

[0047] In other embodiments, the optical antireflection layer can also be deposited by using methods such as plasma-enhanced chemical vapor deposition (PECVD), inductively coupled plasma chemical vapor deposition (ICPCVD), or magnetron sputtering.

[0048] It should be noted that during the research and development process, the inventors initially attempted not to set an angle, that is, the sidewalls of the Micro-LED device were perpendicular to the substrate 1 (with an included angle of 90°). However, after repeated experiments and analysis, the inventors discovered that in the actual manufacturing process, if the sidewalls are a vertical structure, the following technical problems are likely to occur:

[0049] First, during the subsequent deposition of optical antireflection layers on the vertical sidewalls, especially when using highly directional processes such as optical antireflection layer deposition (ALD) or evaporation, the thickness of the sidewall film layer may be uneven, or even deposition blind zones may appear, resulting in defects in the optical antireflection layer structure and seriously affecting the integrity of the optical interference structure and the interference enhancement effect.

[0050] Secondly, the emitted photons are prone to total internal reflection in the sidewall region due to excessive reflection angle, which can trap them inside the chip and affect the directionality of light emission and the light emission efficiency of the sidewall.

[0051] Furthermore, in the design of fluorescence conversion structures, if the sidewall angle is too small (i.e., the included angle is less than 30°), structural shading effects or difficulties in exposing the fluorescence region will occur, which is not conducive to the uniform deposition of the fluorescence conversion layer or subsequent patterning processing. Moreover, during the fabrication of the device mesa structure, an included angle of less than 30° is also not conducive to the precise control of the etching process.

[0052] Based on the above problems, the inventors further optimized the design and discovered through multiple experiments that when the angle between the sidewall of the mesa structure and the substrate 1 is set to less than 90° but not less than 30°, the deposition uniformity and adhesion of the dielectric film 9 on the sidewall can be effectively improved, avoiding problems such as film layer voids or uneven thickness. Furthermore, this angle design helps improve the photon emission path and angle matching, increasing light extraction efficiency, while also enhancing the deposition stability and process compatibility of the fluorescence conversion layer. Especially when using atomic layer deposition (ALD) directional deposition technology, an appropriate sidewall tilt angle can significantly reduce the deposition shadowing effect, improve film layer continuity and the integrity of the optical cavity structure, and ensure the effective realization of the interference enhancement function. Therefore, the sidewall angle is preferably greater than or equal to 30° to balance optical performance and process feasibility.

[0053] In one alternative embodiment, the thickness of each optical antireflection layer ranges from 5 to 500 nm, for example, 50 nm, 200 nm, 350 nm, or 500 nm. Antireflection is achieved while the sidewalls are passivated; by designing the film system, optimal antireflection can be achieved to obtain higher light extraction efficiency.

[0054] In other embodiments, the number of optical antireflection layers can be other than 1 layer and less than 20 layers. The material of each optical antireflection layer can be selected from, but is not limited to, at least one of SiO2, TiO2, Al2O3, MgF2, ZnO, and Si3N4.

[0055] In one application, such as Figure 1 In the illustrated Micro-LED device, the dielectric film 9 includes three optical anti-reflection layers, extending from the inside of the Micro-LED device outwards in the light-emitting direction. These three optical anti-reflection layers are a 16nm thick Si3N4 layer, a 110nm thick TiO2 layer, and an 87nm thick SiO2 layer, respectively. In another application, the dielectric film 9 includes eight optical anti-reflection layers, extending from the inside of the Micro-LED device outwards in the light-emitting direction. These eight optical anti-reflection layers are a 55.5nm thick Si3N4 layer, a 16nm thick SiO2 layer, a 10.5nm thick TiO2 layer, a 20nm thick SiO2 layer, a 40nm thick TiO2 layer, a 5.5nm thick Si3N4 layer, a 34.5nm thick TiO2 layer, and a 74nm thick SiO2 layer.

[0056] To verify the Micro-LED device, the verification was carried out using dielectric film 9 with 3 layers and 8 layers of optical anti-reflection layer as examples. Figure 2 The graph shows a comparison of transmittance between the sidewalls without structure and the sidewalls with the dielectric film 9 structure added. Figure 3 The graph shows a comparison of transmittance (λ=450nm) between the unstructured sidewalls and the sidewalls with the designed dielectric film 9 structure added (λ=450nm). Figure 2 and Figure 3 The data shown are from FDTD simulations, comparing the sidewall transmittance at 450 nm wavelength before and after adding different numbers of optical antireflective layers. Figure 2 As can be seen, by adding the designed dielectric membrane 9, more angles can achieve a transmittance of over 99.5%, which is 18% higher than the initial structure. Figure 3 The graph shows a comparison of average transmittance when the incident light half-cone angle is 40°. It can be seen that with the addition of the designed dielectric film 9, the average transmittance at the center wavelength of 450nm reaches 34.6%, which is 1.23 times that of the unstructured version. This demonstrates that the addition of dielectric film 9 significantly optimizes light transmission within a 25° range, allowing more light generated in the Micro-LED quantum well to be emitted, thereby improving the light extraction efficiency and external quantum efficiency of the Micro-LED device.

[0057] Furthermore, Figure 4 A comparison diagram of the light extraction efficiency of sidewalls with different structures is shown. As can be seen from the figure, the light extraction efficiency of the sidewalls with 3 optical antireflection layers and 8 optical antireflection layers is 1.13 times and 1.26 times that of the unstructured sidewalls, respectively. It can be seen that the Micro-LED device with dielectric film 9 can greatly improve the light extraction efficiency of the sidewalls.

[0058] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A Micro-LED device, characterized in that, include: The Micro-LED device comprises a mesa structure and a dielectric film deposited on the sidewall of the mesa structure. The angle between the sidewall and the substrate of the Micro-LED device is less than 90°. The dielectric film includes several stacked optical anti-reflection layers. The Micro-LED device also includes a fluorescence conversion layer formed between two adjacent optical anti-reflection layers. The refractive index difference between some of the two adjacent optical anti-reflection layers is ≥0.

5. The refractive index of one of the two adjacent optical anti-reflection layers is ≥2.0, and the refractive index of the other optical anti-reflection layer is ≤1.

5. The two adjacent optical anti-reflection layers constitute an optical interference cavity. The fluorescence conversion layer is located in the optical interference cavity. The Micro-LED device also includes a fluorescence layer formed on the top light-emitting surface of the Micro-LED device body. The material of the fluorescence layer is the same as that of the fluorescence conversion layer.

2. The Micro-LED device as described in claim 1, characterized in that, The optical thickness of each of the two adjacent optical anti-reflection layers forming the optical interference cavity is 1 / 4 of the target wavelength.

3. The Micro-LED device as described in claim 1, characterized in that, The fluorescence conversion layer comprises europium-doped yttrium aluminum garnet nanoparticles.

4. The Micro-LED device as described in claim 1, characterized in that, The refractive index of several stacked optical anti-reflection layers decreases layer by layer from the inside of the Micro-LED device to the outside light emission direction, forming a refractive index gradient structure.

5. The Micro-LED device as described in claim 1, characterized in that, The included angle is greater than or equal to 30°.

6. The Micro-LED device as described in claim 1, characterized in that, The thickness of each optical antireflective layer ranges from 5 to 500 nm.

7. The Micro-LED device as described in claim 1, characterized in that, The number of optical antireflective layers is greater than 1 and less than 20, and the material of each optical antireflective layer is selected from at least one of SiO2, TiO2, Al2O3, MgF2, ZnO, and Si3N4.

8. The Micro-LED device according to any one of claims 1 to 7, characterized in that, Several stacked optical antireflective layers are sequentially deposited on the sidewalls using an atomic layer deposition method.

9. The Micro-LED device as described in claim 1, characterized in that, The substrate includes a heterogeneous substrate or a GaN homogeneous substrate.

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