Miniature light-emitting structure, miniature light-emitting device and preparation method of miniature light-emitting structure

Abstract

The invention provides a micro light-emitting structure, a micro light-emitting device and a preparation method of the micro light-emitting structure. The miniature light-emitting structure comprises a plurality of light-emitting units, and each light-emitting unit comprises a first semiconductor layer, a light-emitting layer and a second semiconductor layer which are stacked; the plurality of nano grating units are arranged in an array, the plurality of nano grating units are arranged on the side, away from the light emitting layer, of the first semiconductor layer, and the grating period between every two adjacent nano grating units is smaller than the wavelength of light emitted by the light emitting unit; each nano grating unit comprises a plurality of first grating layers and second grating layers which are alternately stacked in the direction away from the first semiconductor layer, the first grating layer is arranged at one end, facing the first semiconductor layer, of each nano grating unit, and the first grating layers and the second grating layers are made of non-metal dielectric materials; the refractive index of the first grating layer is smaller than that of the second grating layer.

Description

Technical Field

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

[0002] Micro LED is a next-generation display technology that utilizes micrometer-scale (typically <100μm) LED chips as pixel units. Each pixel unit can emit light independently. It has attracted widespread attention due to its superior brightness, contrast, energy efficiency, and lifespan, and has broad application prospects in high-end markets and AR / VR (augmented reality / virtual reality) near-eye displays. The linear polarization characteristics of the light source, as a key functional extension, open up entirely new application paths for display backlighting, 3D (three-dimensional) imaging, and information encryption.

[0003] However, Micro LEDs suffer from degraded electrical performance and a tradeoff between high polarization characteristics and process compatibility when emitting linearly polarized light. Summary of the Invention

[0004] This application provides a micro-light-emitting structure, including: Multiple light-emitting units, each of which includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer stacked together; The array comprises multiple nanograting units disposed on the side of the first semiconductor layer away from the light-emitting layer. The grating period between two adjacent nanograting units is less than the wavelength of the light emitted by the light-emitting unit. Each nanograting unit includes multiple alternating layers of a first grating layer and a second grating layer disposed in a direction away from the first semiconductor layer. The end of each nanograting unit facing the first semiconductor layer is the first grating layer. The materials of the first grating layer and the second grating layer are non-metallic dielectric materials, and the refractive index of the first grating layer is less than the refractive index of the second grating layer.

[0005] The non-metallic dielectric material includes silicon, titanium dioxide, silicon nitride, or silicon oxide.

[0006] The number of layers in the first grating layer is equal to the number of layers in the second grating layer, and the number of layers in the first grating layer is greater than or equal to 5 and less than or equal to 7.

[0007] The micro-light-emitting structure further includes: An anode electrode is disposed on the side of the second semiconductor layer opposite to the light-emitting layer. A common cathode electrode is disposed between two adjacent light-emitting units, and a connection is formed between the first semiconductor layers of the two adjacent light-emitting units. The common cathode electrode is disposed on one side of the first semiconductor layer and electrically connected to the first semiconductor layer.

[0008] The anode electrode is located away from the surface of the second semiconductor layer, and is at the same horizontal position as the common cathode electrode, which is located away from the surface of the first semiconductor layer.

[0009] The thicknesses of the first grating layer and the second grating layer are respectively greater than or equal to 20 nm and less than or equal to 150 nm; The thickness of each nanograting unit is greater than or equal to 0.5 μm and less than or equal to 2 μm.

[0010] Wherein, the grating period is greater than or equal to 50nm and less than or equal to 150nm; The linewidth of each of the nanograting units is greater than or equal to 10 nm and less than or equal to 100 nm; The duty cycle of the plurality of nanograting units is greater than or equal to 0.2 and less than or equal to 0.8.

[0011] This application also provides a miniature light-emitting device, including: Drive substrate; A bonding layer is disposed on one side of the driving substrate; As described in any of the preceding micro-light-emitting structures, the driving substrate is bonded to the micro-light-emitting structure via the bonding layer.

[0012] This application also provides a method for preparing a micro-luminescent structure, including: Provide epitaxial stack; According to a preset pixel pattern, the epitaxial stack is etched to obtain multiple light-emitting units, each of which includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer stacked together. On the side of the first semiconductor layer away from the light-emitting layer, a non-metallic dielectric material is prepared, and the non-metallic dielectric material is etched to obtain a plurality of arrayed nanograting units. The plurality of light-emitting units and the plurality of nanograting units constitute a micro-light-emitting structure. The grating period between two adjacent nanograting units is smaller than the wavelength of the light emitted by the light-emitting unit. Each nanograting unit includes a first grating layer and a second grating layer that are alternately stacked in a direction away from the first semiconductor layer. The end of each nanograting unit facing the first semiconductor layer is the first grating layer. The materials of the first grating layer and the second grating layer are non-metallic dielectric materials, and the refractive index of the first grating layer is smaller than the refractive index of the second grating layer.

[0013] In this process, a non-metallic dielectric material is prepared on the side of the first semiconductor layer opposite to the light-emitting layer, and the non-metallic dielectric material is etched, including: On the side of the first semiconductor layer away from the light-emitting layer, a first non-metallic dielectric material layer and a second non-metallic dielectric material layer are sequentially prepared until the number of the first non-metallic dielectric material layer and the second non-metallic dielectric material layer reaches a preset number of layers, wherein the number of the first non-metallic dielectric material layer is equal to the number of the second non-metallic dielectric material layer, and the refractive index of the first non-metallic dielectric material layer is less than the refractive index of the second non-metallic dielectric material layer. According to a preset grating pattern, the first non-metallic dielectric material layer and the second non-metallic dielectric material layer are etched so that the etched first non-metallic dielectric material layer forms the first grating layer arranged in an array, and the etched second non-metallic dielectric material layer forms the second grating layer arranged in an array.

[0014] The step of etching the epitaxial stack according to a preset pixel pattern to obtain multiple light-emitting units further includes: An anode electrode is formed on the side of the second semiconductor layer opposite to the light-emitting layer; A common cathode electrode is formed between two adjacent light-emitting units, and the common cathode electrode is electrically connected to the first semiconductor layer of the two adjacent light-emitting units.

[0015] Compared with the prior art, the technical solution of this application has the following beneficial effects: This application discloses a micro-light-emitting structure, a micro-light-emitting device, and a method for fabricating the micro-light-emitting structure. The nano-grating units are fabricated using non-metallic dielectric materials to prepare the first and second grating layers. This avoids the electrical damage caused by metallic impurities to the core functional layers such as the first semiconductor layer and the light-emitting layer, solving the problem of electrical performance degradation when Micro-LEDs emit linearly polarized light. The grating period between two adjacent nano-grating units is smaller than the wavelength of the light emitted by the light-emitting unit, satisfying the subwavelength structural characteristics. This ensures that multiple nano-grating units do not generate high-order diffraction, retaining only the 0th order transmitted / reflected light. Simultaneously, by alternately stacking multiple layers of the first and second grating layers with different refractive indices in a direction away from the first semiconductor layer, the structural birefringence effect under the equivalent medium theory is utilized. This allows for efficient transmission of linearly polarized light perpendicular to the arrangement direction of the multiple nano-grating units, while linearly polarized light parallel to the arrangement direction is reflected, achieving a high polarization extinction ratio and ensuring high polarization characteristics. The non-metallic dielectric materials selected are all process-compatible materials commonly used in the Micro-LED manufacturing field. Furthermore, the fabrication of the nanograting units can be achieved through existing mature deposition processes such as magnetron sputtering and plasma-enhanced chemical vapor deposition, as well as photolithography and etching processes. This is highly compatible with the existing Micro-LED manufacturing process and does not require the introduction of additional complex or special processes, thus ensuring process compatibility. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the micro-light-emitting structure provided in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the micro light-emitting device provided in the embodiments of this application; Figure 3 This is a schematic flowchart of the method for preparing the micro-luminescent structure provided in the embodiments of this application; Figure 4 This is a schematic diagram of the epitaxial stack structure provided in the embodiments of this application; Figure 5 This is a schematic diagram of etching an epitaxial stack to obtain multiple light-emitting units, provided in an embodiment of this application. Figure 6 This is a schematic diagram of the preparation of non-metallic dielectric materials provided in the embodiments of this application; Figure 7 This is a schematic diagram of multiple nanograting units arranged in an array obtained by etching a non-metallic dielectric material, as provided in an embodiment of this application. Detailed Implementation

[0018] The embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. It should be particularly noted that the following embodiments are only used to illustrate the embodiments of this application and do not limit the scope of the embodiments of this application. Similarly, the following embodiments are only some embodiments of the embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the embodiments of this application.

[0019] In the embodiments of this application, 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. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0020] When describing the structure of a component, when referring to a layer or region as being located on or above another layer or region, it can mean that it is directly above another layer or region, or that it contains other layers or regions between itself and another layer or region. Furthermore, if the component is flipped, the layer or region will be located below or beneath another layer or region. Additionally, the features, structures, or characteristics described below can be combined in any suitable manner in one or more embodiments.

[0021] Furthermore, the directional terms mentioned in the embodiments of this application, such as [up], [down], [front], [back], [left], [right], [inner], [outer], [side], etc., are only for reference to the accompanying drawings. Therefore, the directional terms used are for illustrating and understanding the embodiments of this application, and not for limiting the embodiments of this application. In the various drawings, structurally similar units are represented by the same reference numerals. For clarity, the various parts in the drawings are not drawn to scale. In addition, some related parts may not be shown in the drawings.

[0022] Existing LEDs epitaxially grown on c-plane sapphire substrates are generally considered unpolarized light sources with extremely low polarization extinction ratios (ER), making them difficult to meet application requirements. Integrating linearly polarized optical structures on the surface of Micro LEDs can improve ER. These structures act as mode selection layers to extract transverse magnetic wave (TM) modes, enabling linearly polarized light emission.

[0023] In recent years, with the development of nanolithography technology, subwavelength metal wire grating structures have become an ideal choice for manufacturing thin-film polarizers due to their compactness, planarity, and excellent performance such as high extinction ratio, high transmittance, and wide incident angle range. However, with the miniaturization of Micro LEDs, the risk of metal contamination introduced by nanometal wire grating structures during the manufacturing process has become increasingly serious in its impact on the electrical performance of Micro LEDs. Using dielectric materials can avoid this problem, but designing and manufacturing nanopolarization gratings with high polarization characteristics and process integration compatibility is challenging.

[0024] The following detailed description is based on specific embodiments. It should be noted that the embodiments of this application can be presented in various forms, and some examples will be described below.

[0025] Please see Figure 1 , Figure 1 This is a schematic diagram of the micro-light-emitting structure provided in the embodiments of this application, as shown below. Figure 1 As shown, the micro-light-emitting structure 100 includes: a plurality of light-emitting units 110, each of the light-emitting units 110 including a first semiconductor layer 111, a light-emitting layer 112, and a second semiconductor layer 113 stacked together; and a plurality of nanograting units 120 arranged in an array, the plurality of nanograting units 120 being disposed on the side of the first semiconductor layer 111 away from the light-emitting layer 112, wherein the grating period between two adjacent nanograting units 120 is less than the wavelength of the light emitted by the light-emitting unit 110, each nanograting unit 120 including a first grating layer 121 and a second grating layer 122 alternately stacked in a direction away from the first semiconductor layer 111, the end of each nanograting unit 120 facing the first semiconductor layer 111 being the first grating layer 121, the material of the first grating layer 121 and the second grating layer 122 being a non-metallic dielectric material, and the refractive index of the first grating layer 121 being less than the refractive index of the second grating layer 122.

[0026] Among them, the micro-light-emitting structure is a device structure with miniaturized size, capable of electro-optical conversion and outputting specific light signals. It needs to integrate a core light-emitting module and functional auxiliary modules to meet specific light emission requirements. In this embodiment, the micro-light-emitting structure uses multiple light-emitting units as the light-emitting core, combined with stacked nanograting units to achieve linearly polarized light emission. It is a core functional structure suitable for high-end displays, near-eye displays, and other scenarios.

[0027] In this structure, the light-emitting unit is a basic functional unit capable of independently converting electrical energy into light energy. It is a core component of semiconductor light-emitting devices, and each unit can emit light individually or in conjunction with other units. In this embodiment, multiple light-emitting units work together to provide a stable light source. Each unit has a complete carrier transport and photon generation structure, providing a foundation for the polarization modulation of the subsequent nanograting unit.

[0028] The first semiconductor layer, the light-emitting layer, and the second semiconductor layer constitute the core functional layer combination of the semiconductor light-emitting device. The semiconductor layers are divided into N-type (providing electrons) and P-type (providing holes) layers, used for carrier transport and supply. The light-emitting layer is the key region for electron-hole recombination and photon release. In this embodiment, the first semiconductor layer is an N-GaN layer, the second semiconductor layer is a P-GaN layer, and the light-emitting layer is a multi-quantum-well layer. Each light-emitting unit includes a stacked first semiconductor layer, a light-emitting layer, and a second semiconductor layer, allowing electrons to migrate directionally from the first semiconductor layer and holes from the second semiconductor layer to the light-emitting layer, respectively. Efficient recombination in the light-emitting layer generates unpolarized light, providing a sufficient and stable light source for polarization filtering of the nanograting unit.

[0029] Among them, the nanograting unit is an optical control element based on a periodic nanoscale geometric structure. Utilizing the diffraction, interference, or equivalent medium effect of light, it can selectively control the polarization state and propagation direction of incident light. Its structural parameters determine its optical performance. In this embodiment, the nanograting unit separates the unpolarized light emitted by the light-emitting unit, allowing only linearly polarized light in a specific direction to pass through. Multiple nanograting units arranged in an array amplify the birefringence effect of the structure through synergistic action, effectively improving the polarization extinction ratio and ensuring that the purity of the output linearly polarized light meets application requirements. Multiple nanograting units are disposed on the side of the first semiconductor layer away from the light-emitting layer, allowing light generated by the light-emitting layer to directly incident on the nanograting unit, minimizing the occurrence of large-angle emission without polarization modulation and increasing the output ratio of polarized light. Figure 1 In this structure, multiple layers of first grating 121 and multiple layers of second grating 122 are alternately stacked to form a nanograting unit 120. Multiple nanograting units 120 are arranged in a horizontal direction to form an array.

[0030] In this context, the grating period is the center-to-center distance between two adjacent grating structural units in the nanograting. The relative magnitude of the grating period and the incident light wavelength directly affects whether the grating produces higher-order diffraction, thus influencing the optical control effect. The grating period between two adjacent nanograting units 120 is smaller than the wavelength of the light emitted by the light-emitting unit 110. When the grating period is much smaller than the incident light wavelength, the nanograting unit does not produce higher-order diffraction, retaining only the 0th-order transmitted / reflected light. In this case, the nanograting unit can be considered a homogeneous anisotropic medium, enabling efficient polarization selection. In this embodiment, a uniform grating period ensures that the polarization control direction of multiple nanograting units is consistent, while a period smaller than the emitted light wavelength satisfies subwavelength characteristics, avoiding the decrease in polarized light purity caused by higher-order diffraction and ensuring the stability of polarization selection.

[0031] The equivalent medium theory states that when the period of a grating structure is much smaller than the wavelength, the periodic structure can be considered a homogeneous anisotropic medium. The equivalent refractive index of a homogeneous anisotropic medium is determined by the fill factor and the material's refractive index. According to the equivalent medium theory, the equivalent refractive index of polarization states parallel and perpendicular to the grating can be approximately given by the following expression:

[0032]

[0033] Where nTE and nTM are the refractive indices of the TE and TM waves, respectively, and f is the filling ratio factor of material 1. Structural birefringence can achieve a higher birefringence than natural birefringence and is easier to integrate, giving it advantages in practical applications.

[0034] Each nanograting unit includes a first grating layer 121 and a second grating layer 122 that are stacked alternately in a direction away from the first semiconductor layer. The combination of multiple dielectric layers can generate a structural birefringence effect through the difference in refractive index of different dielectrics. Compared with a single dielectric layer, the equivalent refractive index can be more flexibly controlled, thereby improving polarization selectivity.

[0035] In this embodiment, the end of each nanograting unit facing the first semiconductor layer is designated as the first grating layer, which is disposed on the side facing the first semiconductor layer. A second grating layer is disposed on the side of the first grating layer facing away from the first semiconductor layer. The arrangement of the grating layers must match the incident direction of the light and the optical properties of the medium to optimize the transmission efficiency of the target polarized light and the reflection efficiency of the non-target polarized light. In this embodiment, the arrangement order, combined with the refractive index difference between the first and second grating layers, ensures that light rays with polarization directions perpendicular to the grating arrangement can be transmitted smoothly, while light rays in parallel directions are reflected, thus ensuring the directional output of linearly polarized light.

[0036] Non-metallic dielectric materials are functional materials with good optical stability and process compatibility. Compared with metallic materials, non-metallic dielectric materials do not introduce metal contamination and are highly compatible with existing semiconductor processes such as magnetron sputtering and photolithography. Common materials include silicon, titanium dioxide, silicon nitride, or silicon oxide. In this embodiment, a non-metallic dielectric material is selected to avoid the problem of Micro-LED electrical performance degradation caused by existing metal wire grid structures, while reducing the integration difficulty with existing manufacturing processes.

[0037] In this embodiment, the refractive index of the first grating layer is lower than that of the second grating layer. In a double-dielectric-layer grating, the greater the difference in refractive index, the more significant the birefringence effect and the stronger the ability to separate light of different polarization states. In this embodiment, the refractive index of the first grating layer is lower than that of the second grating layer, resulting in significant differences in the equivalent refractive index of multiple nanograting units parallel to the grating direction, while their equivalent refractive indices are similar in the perpendicular direction. This enables efficient filtering of light with specific polarization directions and improves the polarization extinction ratio.

[0038] In some embodiments, the non-metallic dielectric material includes silicon, titanium dioxide, silicon nitride, or silicon oxide.

[0039] The non-metallic dielectric materials include silicon, titanium dioxide, silicon nitride, or silicon oxide. Silicon, titanium dioxide, silicon nitride, or silicon oxide possess excellent optical properties, exhibiting high transmittance within the common emission wavelength range of Micro-LEDs and stable refractive index characteristics. They also demonstrate strong process compatibility, being highly compatible with existing semiconductor thin-film deposition processes such as magnetron sputtering and plasma-enhanced chemical vapor deposition, as well as micro / nano fabrication processes like photolithography and etching, eliminating the need for additional special process development. Furthermore, silicon, titanium dioxide, silicon nitride, or silicon oxide exhibits good chemical stability, making them less prone to chemical reactions with the core semiconductor layer of Micro-LEDs and preventing the introduction of impurities. In this application, the non-metallic dielectric materials can be flexibly combined according to actual polarization performance requirements, avoiding the contamination risks associated with metallic materials while achieving the desired refractive index differences through material combinations.

[0040] For example, in the micro light-emitting structure, the first grating layer of each nanograting unit is made of silicon oxide and the second grating layer is made of silicon nitride, wherein the refractive index of silicon oxide is about 1.46 and the refractive index of silicon nitride is about 2.0.

[0041] In some embodiments, the number of layers in the first grating layer is equal to the number of layers in the second grating layer, wherein the number of layers in the first grating layer is greater than or equal to 5 and less than or equal to 7.

[0042] The polarization modulation effect of the nanograting is positively correlated with the number of layers. Within a certain range, the more grating layers there are, the more significant the birefringence effect and the higher the polarization extinction ratio. However, as the number of layers increases, the requirements for the uniformity control of multilayer film deposition and the alignment accuracy of photolithography and etching will increase simultaneously, leading to increased process complexity and manufacturing costs. Furthermore, stress accumulation in the film layers may cause structural cracking, affecting device reliability. In this embodiment, multiple nanograting unit arrays are disposed on the side of the first semiconductor layer away from the light-emitting layer. They need to be close to the light-emitting core region to reduce the escape of unmodulated light. A grating layer number greater than or equal to 5 and less than or equal to 7 is the optimal balance choice. This allows for the amplification of the birefringence effect through multilayer stacking, meeting the high polarization characteristic requirements, without causing a significant increase in process difficulty or a decrease in film stability due to an excessive number of layers. Simultaneously, it adapts to the miniaturization size limitations of Micro-LEDs, avoiding excessive thickness of the nanograting units that could affect integration compatibility with other structures.

[0043] In some implementations, such as Figure 1 As shown, the micro-light-emitting structure 100 further includes: Anode electrode 130, wherein the anode electrode 130 is disposed on the side of the second semiconductor layer 113 opposite to the light-emitting layer 112; A common cathode electrode 140 is disposed between two adjacent light-emitting units 110, and a connection is formed between the first semiconductor layers 111 of the two adjacent light-emitting units 110. The common cathode electrode 140 is disposed on one side of the first semiconductor layer 111 and electrically connected to the first semiconductor layer 111.

[0044] The anode electrode is the core electrode component responsible for injecting holes. It must possess high conductivity, good ohmic contact and adhesion to the semiconductor layer, and be made of a single metal or a multi-layer metal composite structure. This allows for the efficient injection of holes from the external circuit into the P-type semiconductor layer, providing the necessary conditions for electron-hole recombination and light emission. In this embodiment, the anode electrode is adapted to the second semiconductor layer and is a key component for transporting holes to the light-emitting layer.

[0045] In this embodiment, the electrode layout of the semiconductor light-emitting device must avoid obstructing the light emission path, maintain the structural integrity of the core functional layer, and shorten the carrier transport distance. The anode electrode is located on the side of the second semiconductor layer away from the light-emitting layer. This side of the second semiconductor layer away from the light-emitting layer is far from the light emission side of the nanograting unit. This position avoids obstructing the emission of polarized light modulated by the nanograting unit and allows direct contact with the P-GaN layer, shortening the hole transport path from the electrode to the light-emitting layer, reducing carrier loss, and preventing structural interference between the electrode and the nanograting unit.

[0046] The common cathode electrode is a shared electrode used for unified electron collection, which can reduce the number of electrodes, simplify the device structure, reduce the space occupied, and improve the working consistency of multiple units. In this embodiment, the common cathode electrode corresponds to the first semiconductor layer, which can centrally collect electrons from multiple light-emitting units and export them to external circuits, adapting to the needs of multi-pixel display scenarios.

[0047] In micro-LEDs and other micro-devices, the light-emitting units are densely arranged, and the gaps between adjacent units provide the optimal space for electrode layout, avoiding the electrodes occupying the light-emitting area or the mounting space for the nanograting. In this embodiment, the common cathode electrode is placed between two adjacent light-emitting units, so that the common cathode electrode does not need to occupy the device surface or internal core area. This ensures the dense arrangement of multiple light-emitting units, reserves sufficient space for the setting of the nanograting unit, and facilitates the deposition and patterning of electrodes in subsequent processes.

[0048] Figure 1 In the process, the first semiconductor layer 111 of two adjacent light-emitting units 110 is not completely etched, and an opening is formed between the two adjacent light-emitting units 110, in which the common cathode electrode 140 is disposed.

[0049] The common cathode electrode is electrically connected to the first semiconductor layer of two adjacent light-emitting units. The first semiconductor layer is an N-GaN layer. This electrical connection allows electrons from two adjacent light-emitting units to flow out through the same common cathode electrode. This achieves a simplified design with one common cathode corresponding to two light-emitting units, while also ensuring the stability of electron transmission and avoiding uneven light emission or electrical abnormalities caused by poor contact.

[0050] In some implementations, such as Figure 1 As shown, the anode electrode 130 is away from the surface of the second semiconductor layer 113, and is at the same horizontal position as the common cathode electrode 140, which is away from the surface of the first semiconductor layer 111.

[0051] In order to facilitate the subsequent bonding of the micro-light-emitting structure to the driving substrate to form a micro-light-emitting device, the surface of the anode semiconductor layer and the surface of the common cathode electrode are set on the same horizontal plane. This not only facilitates bonding, but also reasonably distributes stress and avoids the micro-light-emitting device from cracking due to stress imbalance.

[0052] In some implementations, such as Figure 1As shown, when the micro-light-emitting structure 100 is working, the anode electrode 130 receives current; the current flows sequentially through the second semiconductor layer 113, the light-emitting layer 112, and the first semiconductor layer 111, and flows out through the common cathode electrode 140, so that the light-emitting layer 112 emits light of a preset color. The direction of the light is towards the plurality of nano-grating units 120. The light includes first linearly polarized light with a polarization direction perpendicular to the grating arrangement direction and second linearly polarized light with a polarization direction parallel to the grating arrangement direction; the plurality of nano-grating units 120 transmit the first linearly polarized light and reflect the second linearly polarized light.

[0053] In this process, light emission is essentially a process of carrier injection, recombination, and photon release. The anode electrode acts as the hole injection end, and the common cathode electrode acts as the electron collection end. The current path is consistent with the carrier transport path. In this embodiment, the current received by the anode electrode actually corresponds to the holes injected by the external circuit. The holes migrate to the light-emitting layer through the second semiconductor layer, while the electrons in the first semiconductor layer migrate to the light-emitting layer under the action of the electric field. Electrons and holes recombine in the light-emitting layer and release energy, which is output in the form of photons. The common cathode electrode is electrically connected to the first semiconductor layer of two adjacent light-emitting units, collecting electrons and leading them to the external circuit, forming a complete current loop.

[0054] The light emitted by the LED epitaxially grown on the c-plane sapphire substrate is unpolarized light, which is essentially a mixed light containing all polarization directions. In this embodiment, the first linearly polarized light with a polarization direction perpendicular to the grating arrangement direction and the second linearly polarized light with a polarization direction parallel to the grating arrangement direction are decomposed into two orthogonal basic polarization states.

[0055] When light is incident on multiple nanograting units, based on the equivalent medium theory and structural birefringence effect, the equivalent refractive index of the second linearly polarized light (TE wave) parallel to the grating arrangement direction is significantly different from that of the vertical direction, causing it to be reflected by the grating, while the first linearly polarized light (TM wave) perpendicular to the grating arrangement direction can be transmitted efficiently, thus realizing the directional output of linearly polarized light.

[0056] For example, when the micro-light-emitting structure is working, the anode electrode receives a 20mA driving current input from an external circuit. This current flows sequentially through the second semiconductor layer, the light-emitting layer, and the first semiconductor layer, and flows out through the common cathode electrode disposed between two adjacent light-emitting units. Electrons and holes recombine efficiently in the multi-quantum-well layer, causing the light-emitting layer to emit blue light of a preset color. The blue light propagates toward multiple nano-grating units disposed on the side of the N-GaN layer away from the multi-quantum-well layer. As unpolarized light, the blue light includes first linearly polarized light with a polarization direction perpendicular to the grating arrangement direction, and second linearly polarized light with a polarization direction parallel to the grating arrangement direction. Under the effect of structural birefringence, the multiple nano-grating units efficiently transmit the first linearly polarized light in the vertical direction and reflect the second linearly polarized light in the horizontal direction, ultimately outputting high-purity vertically linearly polarized blue light.

[0057] In some embodiments, the thicknesses of the first grating layer 121 and the second grating layer 122 are greater than or equal to 20 nm and less than or equal to 150 nm, respectively. The thickness of each nanograting unit 120 is greater than or equal to 0.5 μm and less than or equal to 2 μm.

[0058] The thickness of a single layer of the nanograting directly affects the phase delay effect of light. It needs to match the incident light wavelength to meet the quarter-wavelength condition: n*d=λ / 4, that is, the product of the refractive index of the medium (n) and the layer thickness (d) is equal to one-quarter of the incident light wavelength (λ). At this time, the transverse electric wave (TE wave) and the transverse magnetic wave (TM wave) can generate an effective phase difference and enhance the birefringence effect of the structure. At the same time, the thickness of the grating layer needs to be adapted to the precise control capability of the existing deposition process. When the thickness is less than 20nm, the optical modulation effect is weak, it is difficult to form a sufficient birefringence effect, and the polarization separation effect is poor. When the thickness is greater than 150nm, the difficulty of controlling the uniformity of the film increases dramatically, and the film is prone to cracking and peeling due to stress accumulation. It also increases the precision requirements of subsequent photolithography etching. In this application, the thicknesses of the first grating layer and the second grating layer are greater than or equal to 20 nm and less than or equal to 150 nm, respectively. This thickness range is adapted to the quarter-wavelength requirement of common Micro-LED emission wavelengths. For example, silicon oxide has a refractive index of 1.46, and the thickness corresponding to the quarter-wavelength of 450 nm blue light is about 77 nm, which is completely within the range of greater than or equal to 20 nm and less than or equal to 150 nm. This provides the necessary phase basis for polarization control and ensures the quality of film preparation and process compatibility.

[0059] In some embodiments, the grating period is greater than or equal to 50 nm and less than or equal to 150 nm; The linewidth of each nanograting unit 120 is greater than or equal to 10 nm and less than or equal to 100 nm; The duty cycle of the plurality of nanograting units 120 is greater than or equal to 0.2 and less than or equal to 0.8.

[0060] Among them, the polarization modulation performance of the nanograting depends on the grating period being much smaller than the incident light wavelength (Λ). The subwavelength characteristics of the grating (λ) are such that when the period meets the condition, the grating does not produce higher-order diffraction and only retains the 0th-order transmitted / reflected light. In this case, the grating can be regarded as a homogeneous anisotropic medium according to the equivalent medium theory, achieving efficient polarization selection. If the period is greater than 150 nm, it is difficult to meet the subwavelength condition for common emission wavelengths of Micro-LEDs, and higher-order diffraction is likely to occur, leading to a decrease in the purity of polarized light. If the period is less than 50 nm, existing nanolithography processes cannot achieve precise patterning, and the grating structure is prone to insufficient mechanical stability due to its small size. In this application, the grating period is greater than or equal to 50 nm and less than or equal to 150 nm, ensuring subwavelength characteristics while matching the capabilities of existing micro-nano fabrication processes.

[0061] The linewidth, being the physical width of the nanograting unit, directly affects the grating's fill ratio and structural stability. If the linewidth is too small, the grating strips lack mechanical strength, making them prone to breakage and collapse during deposition, etching, or subsequent processes, and hindering the formation of a uniform nanostructure. Conversely, if the linewidth is too large, the duty cycle exceeds a reasonable range, compressing the grating gap space, making it difficult to clean residual impurities after etching, and affecting the flexibility of equivalent refractive index control. In this application, the linewidth of each nanograting unit is greater than or equal to 10 nm and less than or equal to 100 nm. This linewidth range is compatible with a grating period greater than or equal to 50 nm and less than or equal to 150 nm, allowing for flexible combinations to achieve a reasonable duty cycle. This ensures the mechanical integrity of the grating structure and optimizes the grating's response to different polarization directions through linewidth adjustment, thereby enhancing the polarization filtering effect.

[0062] The duty cycle, calculated as linewidth / grating period, directly determines the equivalent refractive index of the homogeneous anisotropic medium. The difference in equivalent refractive index parallel to and perpendicular to the grating direction needs to be achieved through the coordinated design of the duty cycle and the medium's refractive index. When the duty cycle is less than 0.2, the proportion of grating strips is too low, the structural birefringence effect is weak, and the polarization separation capability is insufficient. When the duty cycle is greater than 0.8, the grating gap is too small, making it difficult to precisely control the pattern during the etching process, and impurities remaining in the gap can easily affect light transmission. At the same time, the space for adjusting the equivalent refractive index is compressed. In this application, the duty cycles of multiple nanograting units are greater than or equal to 0.2 and less than or equal to 0.8. This duty cycle range is adapted to a period of greater than or equal to 50 nm and less than or equal to 150 nm, and a linewidth of greater than or equal to 10 nm and less than or equal to 100 nm. This allows for flexible adjustment of the difference in equivalent refractive index parallel to and perpendicular to the grating direction, ensuring that the structural birefringence effect meets the requirements for a high polarization extinction ratio, while also being compatible with the process precision of existing photolithography etching.

[0063] As can be seen from the above, in the micro-light-emitting structure provided in this application embodiment, the first and second grating layers of the nanograting units are prepared using non-metallic dielectric materials, which avoids the electrical damage of the first semiconductor layer, the light-emitting layer, and other core functional layers caused by metallic impurities, and solves the problem of electrical performance degradation when Micro-LED emits linearly polarized light. The grating period between two adjacent nanograting units is smaller than the wavelength of the light emitted by the light-emitting unit, satisfying the subwavelength structural characteristics, so that multiple nanograting units do not generate high-order diffraction and only retain the 0th order transmitted / reflected light. At the same time, by stacking the first and second grating layers with different refractive indices alternately in multiple layers in the direction away from the first semiconductor layer, the structural birefringence effect under the equivalent medium theory is used to allow the efficient transmission of linearly polarized light perpendicular to the arrangement direction of multiple nanograting units and the reflection of linearly polarized light parallel to the arrangement direction of multiple nanograting units, achieving a high polarization extinction ratio and ensuring high polarization characteristics. The non-metallic dielectric materials selected are all process-compatible materials commonly used in the Micro-LED manufacturing field. Furthermore, the fabrication of the nanograting units can be achieved through existing mature deposition processes such as magnetron sputtering and plasma-enhanced chemical vapor deposition, as well as photolithography and etching processes. This is highly compatible with the existing Micro-LED manufacturing process and does not require the introduction of additional complex or special processes, thus ensuring process compatibility.

[0064] In some embodiments, a miniature light-emitting device is also provided, see [link to relevant documentation]. Figure 2 , Figure 2 This is a schematic diagram of the structure of the micro light-emitting device provided in the embodiments of this application, as shown below. Figure 2 As shown, the micro light-emitting device 1 includes: Drive substrate 200; A bonding layer 300 is disposed on one side of the driving substrate 200; As described in any of the preceding micro-light-emitting structures 100, the driving substrate 200 is bonded to the micro-light-emitting structure 100 via the bonding layer 300.

[0065] Among them, the driving substrate is the basic component that carries the driving circuit, transmits electrical signals, and provides mechanical support for the functional structure. Types include silicon-based driving substrates, glass-based TFT (thin film transistor) driving substrates, flexible driving substrates, etc. It can output precise driving signals through integrated circuit arrays to control the lighting, extinguishing, and brightness adjustment of each light-emitting unit. At the same time, it must have good mechanical stability, electrical insulation, and process compatibility.

[0066] The bonding layer serves as a transition layer for mechanically fixing and electrically connecting two independent structures. The material must be selected based on the bonding process and application requirements; common options include metal bonding materials, solder-based materials, or insulating bonding materials. Requirements include strong adhesion, low interfacial impedance, good thermal stability, and compatibility with upstream and downstream processes. In this application, the bonding layer connects the driving substrate and the micro-light-emitting structure, ensuring both mechanical reliability between the two and low-loss transmission of electrical signals from the driving substrate to the micro-light-emitting structure, while avoiding interference with the light emission path and polarization modulation effect of the micro-light-emitting structure.

[0067] In this embodiment, the driving substrate is bonded to the micro-light-emitting structure via a bonding layer. Bonding is a key technology in semiconductor packaging and system integration. Through processes such as hot pressing, ultrasonication, and eutectic bonding, the bonding layer undergoes physical or chemical reactions to achieve a tight bond between the two structures, meeting both mechanical strength requirements and ensuring reliable electrical connections. In this embodiment, the driving substrate is bonded to the micro-light-emitting structure via a bonding layer, integrating the circuitry of the driving substrate with the linearly polarized light emission function of the micro-light-emitting structure. This allows the electrical signals from the driving substrate to be directly transmitted through the bonding layer to the anode and common cathode electrodes of the micro-light-emitting structure, controlling the coordinated operation of the light emission of the light-emitting unit and the polarization modulation of the nanograting. Furthermore, the bonding process is compatible with existing Micro-LED packaging processes, eliminating the need for specialized equipment and ensuring the feasibility of device integration.

[0068] It should be noted that the micro light-emitting device provided in this application embodiment, due to the micro light-emitting structure provided in this application embodiment, can achieve the beneficial effects that any micro light-emitting structure provided in this application embodiment can achieve, as detailed in the preceding embodiments, and will not be repeated here.

[0069] For example, the aforementioned micro-light-emitting device can be an electronic device such as an optical projector or a head-up display (HUD), or any device with a display screen such as a smartphone, smartwatch, laptop, tablet, dashcam, navigator, or head-mounted device.

[0070] Please see Figure 3 , Figure 3 This is a schematic flowchart illustrating the fabrication method of the micro-light-emitting structure provided in this application embodiment. This embodiment uses the formation of a micro-light-emitting device of any of the above embodiments as an example to illustrate the fabrication method. The specific process of fabricating the micro-light-emitting device can be as follows: Step S31: Provide an epitaxial stack.

[0071] For example, see Figure 4 , Figure 4 This is a schematic diagram of the epitaxial stack structure provided in an embodiment of this application. For example... Figure 4As shown, the epitaxial stack includes a first semiconductor layer 111, a light-emitting layer 112, and a second semiconductor layer 113.

[0072] Step S32: According to the preset pixel pattern, the epitaxial stack is etched to obtain multiple light-emitting units, each of which includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer stacked together.

[0073] For example, see Figure 5 , Figure 5 This is a schematic diagram illustrating the etching of an epitaxial stack to obtain multiple light-emitting units, as provided in an embodiment of this application. Figure 5 As shown, the epitaxial stack is etched to obtain multiple light-emitting units, each of which has a stepped structure.

[0074] Step S33: On the side of the first semiconductor layer away from the light-emitting layer, a non-metallic dielectric material is prepared, and the non-metallic dielectric material is etched to obtain a plurality of arrayed nanograting units. The plurality of light-emitting units and the plurality of nanograting units constitute a micro light-emitting structure. The grating period between two adjacent nanograting units is smaller than the wavelength of the light emitted by the light-emitting unit. Each nanograting unit includes a first grating layer and a second grating layer that are alternately stacked in a direction away from the first semiconductor layer. The end of each nanograting unit facing the first semiconductor layer is the first grating layer. The materials of the first grating layer and the second grating layer are non-metallic dielectric materials, and the refractive index of the first grating layer is smaller than the refractive index of the second grating layer.

[0075] In some embodiments, a non-metallic dielectric material is prepared on the side of the first semiconductor layer opposite to the light-emitting layer, and the non-metallic dielectric material is etched, including: On the side of the first semiconductor layer away from the light-emitting layer, a first non-metallic dielectric material layer and a second non-metallic dielectric material layer are sequentially prepared until the number of the first non-metallic dielectric material layer and the second non-metallic dielectric material layer reaches a preset number of layers, wherein the number of the first non-metallic dielectric material layer is equal to the number of the second non-metallic dielectric material layer, and the refractive index of the first non-metallic dielectric material layer is less than the refractive index of the second non-metallic dielectric material layer. According to a preset grating pattern, the first non-metallic dielectric material layer and the second non-metallic dielectric material layer are etched so that the etched first non-metallic dielectric material layer forms the first grating layer arranged in an array, and the etched second non-metallic dielectric material layer forms the second grating layer arranged in an array.

[0076] For example, see Figure 6 , Figure 6This is a schematic diagram illustrating the preparation of non-metallic dielectric materials according to an embodiment of this application. Figure 6 As shown, on the side of the first semiconductor layer 111 facing away from the light-emitting layer 112, a first non-metallic dielectric material layer 123 and a second non-metallic dielectric material layer 124 are sequentially stacked, for a total of four first non-metallic dielectric material layers 123 and four second non-metallic dielectric material layers 124. The refractive index of the first non-metallic dielectric material layer 123 is less than that of the second non-metallic dielectric material layer 124. When preparing the non-metallic dielectric material, magnetron sputtering is preferred, as it produces films with better uniformity. The magnetron sputtering acceleration voltage is greater than or equal to 300 V and less than or equal to 800 V, the gas pressure is greater than or equal to 1 Pa and less than or equal to 10 Pa, the current density is greater than or equal to 4 mA / cm² and less than or equal to 60 mA / cm², and the power density is greater than or equal to 1 W / cm². Plasma-enhanced chemical vapor deposition is the second preferred method.

[0077] For example, see Figure 7 , Figure 7 This is a schematic diagram illustrating the process of etching a non-metallic dielectric material to obtain an array of multiple nanograting units, as provided in an embodiment of this application. Figure 7 As shown, the first non-metallic dielectric material layer 123 and the second non-metallic dielectric material layer 124 are etched to obtain the first grating layer 121 and the second grating layer 122, thereby obtaining a plurality of nanograting units 120 arranged in an array. During the etching of the first non-metallic dielectric material layer 123 and the second non-metallic dielectric material layer 124, the etching chamber gas pressure is greater than or equal to 1 and less than or equal to 10 mTorr, the etching gas combination is CF4+Ar, the radio frequency power is greater than or equal to 50 and less than or equal to 200 W, the bias radio frequency power is greater than or equal to 5 and less than or equal to 50 W, and the stop time is calculated according to the etching rate.

[0078] In some embodiments, after etching the epitaxial stack according to a preset pixel pattern to obtain multiple light-emitting units, the method further includes: An anode electrode is formed on the side of the second semiconductor layer opposite to the light-emitting layer; A common cathode electrode is formed between two adjacent light-emitting units, and the common cathode electrode is electrically connected to the first semiconductor layer of the two adjacent light-emitting units.

[0079] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A micro-luminescent structure, characterized in that, include: Multiple light-emitting units, each of which includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer stacked together; The array comprises multiple nanograting units disposed on the side of the first semiconductor layer away from the light-emitting layer. The grating period between two adjacent nanograting units is less than the wavelength of the light emitted by the light-emitting unit. Each nanograting unit includes multiple alternating layers of a first grating layer and a second grating layer disposed in a direction away from the first semiconductor layer. The end of each nanograting unit facing the first semiconductor layer is the first grating layer. The materials of the first grating layer and the second grating layer are non-metallic dielectric materials, and the refractive index of the first grating layer is less than the refractive index of the second grating layer.

2. The micro-light-emitting structure as described in claim 1, characterized in that, The non-metallic dielectric material includes silicon, titanium dioxide, silicon nitride, or silicon oxide.

3. The micro-light-emitting structure as described in claim 1, characterized in that, The number of layers in the first grating layer is equal to the number of layers in the second grating layer, and the number of layers in the first grating layer is greater than or equal to 5 and less than or equal to 7.

4. The micro-light-emitting structure as described in claim 1, characterized in that, The micro-luminescent structure also includes: An anode electrode is disposed on the side of the second semiconductor layer opposite to the light-emitting layer. A common cathode electrode is disposed between two adjacent light-emitting units, and a connection is formed between the first semiconductor layers of the two adjacent light-emitting units. The common cathode electrode is disposed on one side of the first semiconductor layer and electrically connected to the first semiconductor layer.

5. The micro-light-emitting structure as described in claim 4, characterized in that, The anode electrode is located away from the surface of the second semiconductor layer, and is at the same horizontal position as the common cathode electrode, which is located away from the surface of the first semiconductor layer.

6. The micro-light-emitting structure as described in claim 1, characterized in that: The thicknesses of the first grating layer and the second grating layer are respectively greater than or equal to 20 nm and less than or equal to 150 nm; The thickness of each nanograting unit is greater than or equal to 0.5 μm and less than or equal to 2 μm.

7. The micro-light-emitting structure as described in claim 1, characterized in that: The grating period is greater than or equal to 50 nm and less than or equal to 150 nm; The linewidth of each of the nanograting units is greater than or equal to 10 nm and less than or equal to 100 nm; The duty cycle of the plurality of nanograting units is greater than or equal to 0.2 and less than or equal to 0.

8.

8. A miniature light-emitting device, characterized in that, include: Drive substrate; A bonding layer is disposed on one side of the driving substrate; The micro-light-emitting structure as described in any one of claims 1-7, wherein the driving substrate is bonded to the micro-light-emitting structure via the bonding layer.

9. A method for preparing a micro-luminescent structure, characterized in that, include: Provide epitaxial stack; According to a preset pixel pattern, the epitaxial stack is etched to obtain multiple light-emitting units, each of which includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer stacked together. On the side of the first semiconductor layer away from the light-emitting layer, a non-metallic dielectric material is prepared, and the non-metallic dielectric material is etched to obtain a plurality of arrayed nanograting units. The plurality of light-emitting units and the plurality of nanograting units constitute a micro-light-emitting structure. The grating period between two adjacent nanograting units is smaller than the wavelength of the light emitted by the light-emitting unit. Each nanograting unit includes a first grating layer and a second grating layer that are alternately stacked in a direction away from the first semiconductor layer. The end of each nanograting unit facing the first semiconductor layer is the first grating layer. The materials of the first grating layer and the second grating layer are non-metallic dielectric materials, and the refractive index of the first grating layer is smaller than the refractive index of the second grating layer.

10. The method for preparing the micro-luminescent structure as described in claim 9, characterized in that, On the side of the first semiconductor layer opposite to the light-emitting layer, a non-metallic dielectric material is prepared, and the non-metallic dielectric material is etched, including: On the side of the first semiconductor layer away from the light-emitting layer, a first non-metallic dielectric material layer and a second non-metallic dielectric material layer are sequentially prepared until the number of the first non-metallic dielectric material layer and the second non-metallic dielectric material layer reaches a preset number of layers, wherein the number of the first non-metallic dielectric material layer is equal to the number of the second non-metallic dielectric material layer, and the refractive index of the first non-metallic dielectric material layer is less than the refractive index of the second non-metallic dielectric material layer. According to a preset grating pattern, the first non-metallic dielectric material layer and the second non-metallic dielectric material layer are etched so that the etched first non-metallic dielectric material layer forms the first grating layer arranged in an array, and the etched second non-metallic dielectric material layer forms the second grating layer arranged in an array.

11. The method for preparing the micro-luminescent structure as described in claim 9, characterized in that, After etching the epitaxial stack according to a preset pixel pattern to obtain multiple light-emitting units, the method further includes: An anode electrode is formed on the side of the second semiconductor layer opposite to the light-emitting layer; A common cathode electrode is formed between two adjacent light-emitting units, and the common cathode electrode is electrically connected to the first semiconductor layer of the two adjacent light-emitting units.

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