Display device for improving light extraction efficiency and method of manufacturing same

Abstract

The invention provides a display device for improving light extraction efficiency and a preparation method thereof, and belongs to the technical field of photoelectron manufacturing. The display device comprises a light-emitting block, a flat layer, a metal electrode layer and a hyperbolic metamaterial layer, the light-emitting block is located on the surface of the metal electrode layer, the flat layer is located on the surface of the metal electrode layer and covers the light-emitting block, and the hyperbolic metamaterial layer is located on the flat layer and covers the light-emitting block. The orthographic projection of the light-emitting block on the surface of the metal electrode layer is located in the orthographic projection of the hyperbolic metamaterial layer on the surface of the metal electrode layer; the hyperbolic metamaterial layer comprises a plurality of hafnium dioxide layers and a plurality of zirconium dioxide layers which are alternately stacked. According to the embodiment of the invention, evanescent waves formed by total internal reflection can be collected, and the light extraction efficiency of the display device is improved.

Description

Technical Field

[0001] This disclosure relates to the field of optoelectronic manufacturing technology, and in particular to a display device with improved light extraction efficiency and a method for its fabrication. Background Technology

[0002] A micro light-emitting diode (Micro LED) is a light-emitting diode with an extremely small side length. Because the refractive index of LED materials is much higher than that of air, according to Snell's law, the critical angle for light at the interface inside the LED chip is very small. When light travels from an optically denser medium to an optically less dense medium, and the angle of incidence exceeds the critical angle, the light cannot be refracted but undergoes total internal reflection, being entirely reflected back to the original medium, ultimately absorbed by the material and converted into heat. During this total internal reflection, an evanescent wave is generated at the interface on the optically less dense side.

[0003] When LED chip size shrinks to below 5 micrometers, most light hits the sidewalls of the LED chip more frequently, drastically amplifying the loss effect of total internal reflection, resulting in over 70% of photons being lost inside the chip. Related technologies involve placing microlenses on the light-emitting surface of the LED chip, using these microlenses to change the light path angle, allowing more light to escape at angles less than the critical angle, thereby improving light extraction efficiency.

[0004] However, even with microlenses, it is impossible to collect evanescent waves formed by total internal reflection, so 60% to 70% of the light still cannot be effectively extracted. Summary of the Invention

[0005] This disclosure provides a display device and its fabrication method for improving light extraction efficiency, which can collect evanescent waves formed by total internal reflection and improve the light extraction efficiency of light-emitting diodes. The technical solution is as follows:

[0006] On one hand, this disclosure provides a display device comprising: a light-emitting block, a planarization layer, a metal electrode layer, and a hyperbolic metamaterial layer; the light-emitting block is located on the metal electrode layer, the planarization layer is located on the metal electrode layer and covers the light-emitting block, the hyperbolic metamaterial layer is located on the planarization layer, and the orthographic projection of the light-emitting block on the surface of the metal electrode layer is located within the orthographic projection of the hyperbolic metamaterial layer on the surface of the metal electrode layer; the hyperbolic metamaterial layer comprises alternating layers of hafnium dioxide and zirconium dioxide.

[0007] In one implementation of this disclosure, the thickness of the hafnium dioxide layer is 5 nm to 15 nm, and the thickness of the zirconium dioxide layer is 10 nm to 20 nm; the number of hafnium dioxide layers is 150 to 250, and the number of zirconium dioxide layers is 150 to 250.

[0008] In another implementation of this disclosure, the surface of the flat layer away from the metal electrode layer is provided with a hemispherical protrusion, the orthographic projection of the light-emitting block on the surface of the metal electrode layer is located within the orthographic projection of the hemispherical protrusion on the surface of the metal electrode layer, and the hyperbolic metamaterial layer covers the outer wall surface of the hemispherical protrusion.

[0009] In another implementation of this disclosure, the radius of curvature of the hemispherical protrusion is 1 μm to 2 μm, and the height of the hemispherical protrusion is 400 nm to 600 nm.

[0010] In another implementation of this disclosure, the surface of the metal electrode layer has an arcuate groove, and the surface of the light-emitting block near the metal electrode layer is in contact with the groove surface of the arcuate groove.

[0011] In another implementation of this disclosure, the outer wall surface of the hemispherical protrusion and the groove surface of the arcuate groove form a confocal resonant cavity.

[0012] In another implementation of this disclosure, the radius of curvature of the arcuate groove is 50 μm to 60 μm.

[0013] In another implementation of this disclosure, the thickness uniformity of the hyperbolic metamaterial layer is greater than or equal to 98%.

[0014] On the other hand, embodiments of this disclosure also provide a method for fabricating a light-emitting diode (LED), the method comprising: forming an epitaxial layer on a temporary substrate, the surface of the epitaxial layer having bumps, the surface of the bumps away from the temporary substrate being an arc surface; forming a metal electrode layer on the surface of the epitaxial layer, such that the metal electrode layer covers the bumps; bonding the surface of the metal electrode layer away from the epitaxial layer to a substrate, and removing the temporary substrate; etching the epitaxial layer to form a light-emitting block, the light-emitting block including the bumps; forming a planarization layer on the surface of the metal electrode layer, such that the planarization layer covers the light-emitting block; etching the planarization layer to form a hemispherical protrusion on the surface of the planarization layer; forming a hyperbolic metamaterial layer on the surface of the hemispherical protrusion, wherein the orthographic projection of the light-emitting block on the surface of the metal electrode layer lies within the orthographic projection of the hyperbolic metamaterial layer on the surface of the metal electrode layer, the hyperbolic metamaterial layer comprising alternating layers of hafnium dioxide and zirconium dioxide.

[0015] In another implementation of this disclosure, forming a hyperbolic metamaterial layer on the surface of the hemispherical protrusion includes: controlling the substrate to tilt by 30° in a reaction chamber and controlling the substrate to rotate about a central axis perpendicular to the substrate, and forming the hyperbolic metamaterial layer using atomic layer deposition technology.

[0016] The beneficial effects of the technical solutions provided in this disclosure include at least the following:

[0017] The light-emitting diode provided in this embodiment of the present disclosure has a hyperbolic metamaterial layer disposed on a planar layer, and the orthographic projection of the light-emitting block on the surface of the metal electrode layer is located within the orthographic projection of the hyperbolic metamaterial layer on the surface of the metal electrode layer, so that the hyperbolic metamaterial layer can completely cover the light-emitting block, allowing most of the light emitted by the light-emitting block to be directed to the hyperbolic metamaterial layer.

[0018] Among them, the hyperbolic metamaterial layer, through its unique hyperbolic dispersion properties, can couple with the high wave vector component of evanescent waves, converting them into propagable radiation waves. This overcomes the limitation of total internal reflection, extracting previously trapped photons to the outside of the chip and significantly improving light extraction efficiency. Furthermore, the negative refraction effect of the hyperbolic metamaterial can change the direction of light propagation, twisting laterally propagating light into a more easily emitted vertical direction (perpendicular to the surface of the light-emitting diode), effectively enhancing the directional focusing ability of light and further improving the overall luminous efficiency.

[0019] Meanwhile, the hyperbolic metamaterial layer is composed of alternating layers of hafnium dioxide and zirconium dioxide, both of which are high-refractive-index media with a certain difference in refractive index. This alternating stacking creates extreme anisotropy, with a negative dielectric constant along the stacking direction and a positive dielectric constant parallel to the layers, satisfying the necessary condition for hyperbolic dispersion and thus efficiently supporting the conversion between evanescent and propagating waves. Furthermore, hafnium dioxide and zirconium dioxide exhibit extremely low absorption loss in the visible light band. As metamaterial media layers, they can reduce energy attenuation during light propagation, ensuring that more photons are effectively extracted rather than absorbed by the material. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this disclosure, 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 disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure;

[0022] Figure 2 This is a flowchart of a method for fabricating a light-emitting diode according to an embodiment of this disclosure;

[0023] Figure 3 This is a fabrication state diagram of a light-emitting diode provided in an embodiment of this disclosure;

[0024] Figure 4 This is a fabrication state diagram of a light-emitting diode provided in an embodiment of this disclosure;

[0025] Figure 5 This is a fabrication state diagram of a light-emitting diode provided in an embodiment of this disclosure;

[0026] Figure 6 This is a fabrication state diagram of a light-emitting diode provided in an embodiment of this disclosure;

[0027] Figure 7 This is a fabrication state diagram of a light-emitting diode provided in an embodiment of this disclosure.

[0028] The markings in the diagram are explained as follows:

[0029] 10. Substrate; 11. Temporary substrate;

[0030] 20. Light-emitting block; 200. Epitaxial layer; 201. Bump;

[0031] 30. Flat layer; 31. Hemispherical protrusion;

[0032] 40. Metal electrode layer; 41. Arc-shaped groove;

[0033] 50. Hyperbolic metamaterial layer; 51. Hafnium dioxide layer; 52. Zirconia layer. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0035] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” “third,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” “right,” “top,” and “bottom,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0036] Figure 1 This is a schematic diagram of the structure of a light-emitting diode provided in an embodiment of this disclosure. For example... Figure 1As shown, the light-emitting diode includes: a light-emitting block 20, a planarization layer 30, a metal electrode layer 40, and a hyperbolic metamaterial layer 50.

[0037] like Figure 1 As shown, the light-emitting block 20 is located on the surface of the metal electrode layer 40, the planarization layer 30 is located on the surface of the metal electrode layer 40 and covers the light-emitting block 20, the hyperbolic metamaterial layer 50 is located on the planarization layer 30, and the orthographic projection of the light-emitting block 20 on the surface of the metal electrode layer 40 is located within the orthographic projection of the hyperbolic metamaterial layer 50 on the surface of the metal electrode layer 40.

[0038] The hyperbolic metamaterial layer 50 includes alternating layers of hafnium dioxide 51 and zirconium dioxide 52.

[0039] The light-emitting diode provided in this embodiment of the present disclosure has a hyperbolic metamaterial layer 50 disposed on the planarization layer 30, and the orthographic projection of the light-emitting block 20 on the surface of the metal electrode layer 40 is located within the orthographic projection of the hyperbolic metamaterial layer 50 on the surface of the metal electrode layer 40, so that the hyperbolic metamaterial layer 50 can completely cover the light-emitting block 20, and most of the light emitted by the light-emitting block 20 can be directed to the hyperbolic metamaterial layer 50.

[0040] Among them, the hyperbolic metamaterial layer 50, through its unique hyperbolic dispersion properties, can couple with the high wave vector component of evanescent waves, converting them into propagable radiation waves. This overcomes the total internal reflection limitation, extracting previously trapped photons to the outside of the chip and significantly improving light extraction efficiency. Furthermore, the negative refraction effect of the hyperbolic metamaterial can change the direction of light propagation, twisting laterally propagating light into a more easily emitted vertical direction (perpendicular to the surface of the light-emitting diode), effectively enhancing the directional focusing ability of light and further improving the overall luminous efficiency.

[0041] Meanwhile, the hyperbolic metamaterial layer 50 is composed of alternating layers of hafnium dioxide and zirconium dioxide, both of which are high-refractive-index media with a certain difference in refractive index. This alternating stacking creates extreme anisotropy, with a negative dielectric constant along the stacking direction and a positive dielectric constant parallel to the layers, satisfying the necessary conditions for hyperbolic dispersion and thus efficiently supporting the conversion between evanescent and propagating waves. Furthermore, hafnium dioxide and zirconium dioxide exhibit extremely low absorption loss in the visible light band. As metamaterial media layers, they can reduce energy attenuation during light propagation, ensuring that more photons are effectively extracted rather than absorbed by the material.

[0042] Optionally, the thickness of the hafnium dioxide layer 51 is 5 nm to 15 nm, and the thickness of the zirconium dioxide layer 52 is 10 nm to 20 nm.

[0043] Optionally, the number of hafnium dioxide layers 51 is 150 to 250, and the number of zirconium dioxide layers 52 is 150 to 250.

[0044] When the size of the light-emitting diode is miniaturized to below 5 μm, the evanescent wave wavelength formed by total internal reflection is extremely short. The thickness of the HfO2 and ZrO2 layers is much smaller than the wavelength of visible light (400 nm to 700 nm), meeting the requirements of the subwavelength scale. This ultrathin layer design enables the equivalent optical response of the hyperbolic metamaterial to be precisely matched with the high wave vector component of the evanescent wave, ensuring that the evanescent wave energy is efficiently coupled into the metamaterial's interior, avoiding wave vector mismatch or energy scattering loss due to excessive thickness.

[0045] The HfO2 layer is thinner than the ZrO2 layer, with the thickness difference controlled within a reasonable range. This maintains the gradient contrast of refractive indices between the layers (HfO2 and ZrO2 have similar refractive indices but slight differences) and further optimizes the anisotropy of the overall dielectric constant through thickness adjustment (the dielectric constant is negative in the direction perpendicular to the layer and positive in the direction parallel to the layer). This design enhances the intensity of hyperbolic dispersion, making the metamaterial more likely to capture and convert evanescent waves, while avoiding structural instability or optical performance degradation caused by thickness imbalance.

[0046] In the example selection, the thickness of the hafnium dioxide layer 51 is 10 nm, and the thickness of the zirconium dioxide layer 52 is 15 nm.

[0047] The multilayer film, consisting of 150 to 250 layers each of hafnium dioxide and zirconium dioxide, has a total thickness of approximately 3 μm to 7 μm. This design achieves significant hyperbolic dispersion through sufficient interfacial accumulation, ensuring efficient capture of evanescent waves. Simultaneously, it avoids stress accumulation, increased interfacial defects, or increased processing difficulty caused by excessive layer count. The uniform, alternating stacking structure guarantees a high degree of spatial consistency in optical anisotropy, thereby achieving stable negative refraction and light extraction effects, providing a reliable high-efficiency solution for micro-LEDs.

[0048] Optionally, such as Figure 1 As shown, the surface of the planar layer 30 away from the metal electrode layer 40 is provided with a hemispherical protrusion 31. The orthographic projection of the light-emitting block 20 on the surface of the metal electrode layer 40 is located within the orthographic projection of the hemispherical protrusion 31 on the surface of the metal electrode layer 40. The hyperbolic metamaterial layer 50 covers the outer wall surface of the hemispherical protrusion 31.

[0049] In the above implementation, the hemispherical protrusion 31 is equivalent to a microlens. Its curved structure can change the optical path angle, allowing more light to be emitted from the chip at a angle less than the critical angle, thus reducing the total internal reflection loss of the sidewalls.

[0050] The hyperbolic metamaterial layer 50 precisely covers the raised outer wall surface, seamlessly connecting with the light guided by the microlens. The hyperbolic dispersion properties of the hyperbolic metamaterial layer 50 can capture evanescent waves that the raised surface cannot fully extract and convert them into propagable radiation waves; at the same time, the negative refraction effect further twists the lateral light into a vertical or near-vertical direction, enhancing the directional focusing ability of the light.

[0051] Meanwhile, the hemispherical protrusions 31 increase the contact area between light and the hyperbolic metamaterial layer 50, enabling the hyperbolic metamaterial layer 50 to act more efficiently on light that is originally easily lost. The combination of the two optimizes the initial optical path through microlenses and solves the evanescent wave problem through hyperbolic metamaterials, which can effectively improve the light extraction efficiency and light output uniformity.

[0052] Optionally, the radius of curvature of the hemispherical protrusion 31 is 1 μm to 2 μm, and the height of the hemispherical protrusion 31 is 400 nm to 600 nm.

[0053] The curvature radius and height of the protrusion are in the transition range from subwavelength to micro-nano. This not only guides lateral light to converge to the outer wall of the protrusion through the curved surface, but also ensures that the light field interacts fully with the protrusion surface. This provides more efficient preprocessing for the subsequent capture of evanescent waves in the hyperbolic metamaterial layer 50 and reduces light field dissipation.

[0054] Furthermore, the small radius of curvature (1μm to 2μm) gives the hemispherical protrusion 31 sufficient curvature to change the direction of light propagation and reduce the probability of total internal reflection; while the height of 400nm to 600nm ensures sufficient geometric thickness to change the light path.

[0055] Optionally, such as Figure 1 As shown, the surface of the metal electrode layer 40 has an arc groove 41, and the surface of the light-emitting block 20 near the metal electrode layer 40 is in contact with the groove surface of the arc groove 41.

[0056] In this embodiment, the curved structure of the arc groove 41 can refract the light emitted by the light-emitting block 20 toward the metal electrode layer 40 to the groove wall or above, so that the lateral light that might have caused total internal reflection changes the propagation angle, and more light is emitted out of the chip under the condition of less than the critical angle, reducing the side wall light loss and improving the light extraction efficiency.

[0057] The curved groove surface of the arc groove 41 is closely fitted with the light-emitting block 20, so that the light field generated by the light-emitting block 20 is more concentrated and transitioned to the hemispherical protrusion 31 and the hyperbolic metamaterial layer 50 covering it, reducing the scattering or leakage of light at the interface, and ensuring that the rear hemispherical protrusion 31 and the hyperbolic metamaterial layer 50 can more efficiently control the light path and further capture evanescent waves or directional emitted light.

[0058] Furthermore, the arc-shaped groove 41 can optimize the contact area and electron transport path between the metal electrode layer 40 and the light-emitting block 20, making the current distribution more uniform and reducing local overheating. At the same time, the adhesion between the groove surface and the light-emitting block 20 increases the stability of the interface bonding, which helps heat to be conducted more efficiently through the metal electrode layer 40 to the external heat dissipation structure, alleviating the problem of heat accumulation under small size.

[0059] Optionally, the outer wall surface of the hemispherical protrusion 31 and the groove surface of the arc groove 41 form a confocal resonant cavity.

[0060] In the above implementation, the confocal resonant cavity formed by the outer wall of the hemispherical protrusion 31 and the groove surface of the arcuate groove 41 causes the light emitted by the light-emitting block 20 to gradually converge towards the confocal point after multiple coordinated reflections within the cavity by the metal electrode layer 40. Ultimately, the light can be emitted in a directional manner.

[0061] In addition to reflecting light, the metal electrode layer 40 also has a certain thermal conductivity. The arc groove structure 41 can increase the contact area between the light-emitting block 20 and the metal electrode layer 40, assist the heat dissipation of the light-emitting block 20, and alleviate the efficiency decay caused by high temperature.

[0062] Meanwhile, the sealed characteristics of the confocal resonant cavity can reduce the erosion of the surface of the light-emitting block 20 by external dust and moisture, and extend the device life; the arc-shaped confocal resonant cavity has better mechanical stability and can reduce the risk of film cracking caused by packaging stress.

[0063] Optionally, the cross-sectional shape of the confocal resonant cavity is circular or elliptical.

[0064] The cross-sectional shape of the confocal resonant cavity refers to the shape of the cross-section of the confocal resonant cavity in the direction perpendicular to the surface of the metal electrode layer 40.

[0065] For example, when the cross-sectional shape of the confocal resonator is circular, the symmetry is maximized, and the optical path evolution in all directions is completely consistent.

[0066] This type of confocal resonant cavity ensures that light emitted from the light-emitting block 20 in any direction, after being reflected by the metal electrode layer 40 within the circular cavity, converges along a symmetrical path towards the common focal point. Because the reflection trajectories of light rays at each angle are symmetrical, the final angular distribution of the emitted light is highly uniform.

[0067] Meanwhile, the circular structure only requires a single radius of curvature to define the cavity shape, without having to consider the difference between the major and minor axes, which reduces the processing complexity of the arc groove 41 and the arc surface of the flat layer 30, making it more suitable for the consistency requirements in mass production.

[0068] For example, when the cross-section of the confocal resonant cavity is elliptical, by adjusting the ratio of the major and minor axes of the ellipse (e.g., the major axis corresponds to the horizontal direction and the minor axis corresponds to the vertical direction), the light can be reflected more times in a specific direction (e.g., the direction of the major axis), thereby forming a higher concentration of light intensity in that direction.

[0069] Optionally, the radius of curvature of the groove surface of the arc groove 41 is 50 μm to 60 μm.

[0070] As an example, the radius of curvature of the groove surface of the arc groove 41 is 55 μm.

[0071] From the perspective of optical path guidance, the radius of curvature is set within the above range, which enables the arc groove 41 to gently and effectively refract the light emitted by the light-emitting block 20 towards the metal electrode layer 40, smoothly guiding the light that would normally be directed toward the sidewall to a more favorable direction for emission, reducing total internal reflection of the sidewall, and preventing excessive distortion of light due to excessive curvature.

[0072] In terms of manufacturing process, a curvature radius of 50μm to 60μm facilitates processing and manufacturing, ensuring the forming accuracy and surface quality of the arc groove 41, and reducing processing difficulty and cost. For the bonding of the light-emitting block 20 and the groove surface, this curvature radius allows for a tighter and more uniform bonding between the two surfaces, enhancing the light field coupling effect, reducing light scattering and leakage at the bonding interface, ensuring that subsequent optical structures can function more efficiently, and improving the overall light extraction efficiency.

[0073] Optionally, the thickness uniformity of the hyperbolic metamaterial layer 50 is greater than or equal to 98%.

[0074] Among them, the thickness deviation is controlled within 2% to ensure that the optical properties (such as dielectric constant and refractive index) of the hyperbolic metamaterial layer 50 are highly consistent, so that the conversion efficiency of evanescent wave to propagating wave remains stable and the light extraction capability is avoided due to thickness differences in local areas.

[0075] Secondly, the uniform thickness distribution ensures that the negative refraction effect plays a uniform role on the entire surface of the hemispherical protrusion 31, accurately and consistently adjusting the side light to a vertical or near-vertical emission direction, enhancing the directional focusing ability of the light, and improving the overall light efficiency and light emission uniformity.

[0076] Furthermore, high uniformity reduces light scattering or absorption losses caused by fluctuations in local optical performance, allowing more photons to effectively overcome the total internal reflection limitation and escape from the chip, maximizing light extraction efficiency.

[0077] Optionally, the planarization layer 30 includes at least one of a silicon oxide layer, a titanium oxide layer, and an aluminum oxide layer.

[0078] For example, the planarization layer 30 may be a silicon oxide layer.

[0079] Optionally, the planarization layer 30 includes a plurality of alternating layers of first material and a plurality of layers of second material, the first material layers and the second material layers having different refractive indices.

[0080] In this embodiment of the disclosure, the planarization layer 30 is constructed by alternating layers of a first material layer and a second material layer to form a distributed Bragg reflector (DBR).

[0081] For example, one of the first material layer and the second material layer is a TiO2 layer, and the other of the first material layer and the second material layer is a SiO2 layer.

[0082] In this process, DBR uses two materials with significantly different refractive indices stacked periodically to form a strong reflection band by utilizing the principle of light interference. When light shines from the light-emitting block 20 onto the planarization layer 30, light of a specific wavelength is coherently enhanced after multiple reflections at the interlayer interface, achieving a reflectivity of over 95%. This significantly reduces the disordered leakage of light energy outside the cavity and improves light extraction efficiency.

[0083] Furthermore, the DBR's reflection band is wavelength selective, which can accurately reflect the main emission band of the light-emitting block 20 while transmitting other stray wavelengths. This not only enhances the directional output of effective light but also suppresses interference from non-target wavelengths, thus optimizing the spectral purity of the emitted light.

[0084] Optionally, the number of layers in both the first and second material layers can be 1 to 20.

[0085] For example, when the number of layers of the first material layer is 1 to 5, the DBR layer is suitable for scenarios with low reflectivity requirements, where the reflectivity is about 90%.

[0086] For example, when the number of layers in the first material layer is 10 to 20, the reflectivity of the DBR layer can reach more than 95%, which is suitable for high-efficiency LEDs.

[0087] Optionally, the thickness of the first material layer is 100 nm to 110 nm. The thickness of the second material layer is 60 nm to 64 nm.

[0088] Optionally, the light-emitting block 20 includes a first semiconductor layer, a multi-quantum well layer, and a second semiconductor layer stacked sequentially.

[0089] In this embodiment of the present disclosure, one of the first semiconductor layer and the second semiconductor layer is a p-type layer, and the other of the first semiconductor layer and the second semiconductor layer is an n-type layer.

[0090] As an example, the first semiconductor layer is a p-type layer and the second semiconductor layer is an n-type layer.

[0091] Optionally, the first semiconductor layer is an indium-doped p-type AlInP layer. The thickness of the p-type AlInP layer can be from 0.5 μm to 3 μm.

[0092] Optionally, the multiple quantum well layer includes alternating AlGaInP quantum well layers and AlGaInP quantum barrier layers. The Al content in the AlGaInP quantum well layers and AlGaInP quantum barrier layers is different. The multiple quantum well layer may include 3 to 8 alternating stacked AlGaInP quantum well layers and AlGaInP quantum barrier layers.

[0093] As an example, in an embodiment of this disclosure, the multi-quantum-well layer includes five alternating stacked AlGaInP quantum-well layers and AlGaInP quantum-barrier layers.

[0094] Optionally, the thickness of the multi-quantum well layer can be from 150 nm to 200 nm.

[0095] Optionally, the second semiconductor layer is an n-type AlGaInP layer. The thickness of the n-type AlGaInP layer can be from 0.5 μm to 3 μm.

[0096] Optionally, such as Figure 1 As shown, the light-emitting diode also includes a substrate 10, and a metal electrode layer 40 is located on the substrate 10.

[0097] For example, substrate 10 is a sapphire substrate. Sapphire substrates have high light transmittance, meaning substrate 10 is a transparent substrate. Furthermore, sapphire material is relatively hard and chemically stable, giving the light-emitting diode good luminous effect and stability.

[0098] Optionally, the metal electrode layer 40 may include at least one of the following: AuBe layer, Au layer, Ti layer, Ni layer, and Pt layer.

[0099] For example, the metal electrode layer 40 includes an Au layer, an AuGe layer and a Pt layer sequentially stacked on the surface of the substrate 10.

[0100] The last metal layer of the metal electrode layer 40 is set as a Pt layer, which covers the AuGe layer. This effectively prevents Ge elements from diffusing upwards during annealing, thus ensuring the total amount of elements diffusing into the semiconductor and allowing the metal electrode layer 40 to achieve a better ohmic contact effect.

[0101] Optionally, the thickness of the Au layer is 80 to 150 angstroms. The Au layer has good conductivity, which can improve the ohmic contact effect between the metal electrode layer 40 and the light-emitting block 20.

[0102] For example, the thickness of the Au layer is 100 angstroms.

[0103] Optionally, the thickness of the AuGe layer is between 800 and 1500 angstroms. The AuGe layer also has good conductivity, which can reduce the amount of Au metal used, thereby reducing the fabrication cost of the electrode.

[0104] For example, the thickness of the AuGe layer is 1000 angstroms.

[0105] Optionally, the thickness of the Pt layer is 450 to 600 angstroms. Setting the last metal layer of the electrode as a Pt layer, allowing the Pt layer to cover the AuGe layer, can ensure the AuGe layer.

[0106] For example, the thickness of the Pt layer is 500 angstroms.

[0107] Figure 2 This is a flowchart illustrating a method for fabricating a light-emitting diode according to an embodiment of this disclosure. Figure 2 As shown, the preparation method includes:

[0108] S11: An epitaxial layer 200 is formed on a temporary substrate 11.

[0109] For example, the epitaxial layer 200 may include a first semiconductor layer, a multiple quantum well layer and a second semiconductor layer sequentially stacked on the temporary substrate 11.

[0110] The first semiconductor layer has a first conductivity type, the second semiconductor layer has a second conductivity type different from the first conductivity type, and the multiple quantum well layer is used to generate light through electron-hole recombination.

[0111] In this process, one of the first semiconductor layer and the second semiconductor layer is a p-type layer, and the other of the first semiconductor layer and the second semiconductor layer is an n-type layer.

[0112] As an example, the first semiconductor layer is a p-type layer and the second semiconductor layer is an n-type layer.

[0113] For example, the first semiconductor layer is an indium-doped p-type AlInP layer. The thickness of the p-type AlInP layer can be from 0.5 μm to 3 μm.

[0114] For example, the second semiconductor layer may be an n-type AlGaInP layer. The thickness of the n-type AlGaInP layer may be from 0.5 μm to 3 μm.

[0115] Optionally, the multiple quantum well layer includes alternating AlGaInP quantum well layers and AlGaInP quantum barrier layers. The Al content in the AlGaInP quantum well layers and AlGaInP quantum barrier layers is different. The multiple quantum well layer may include 3 to 8 alternating stacked AlGaInP quantum well layers and AlGaInP quantum barrier layers.

[0116] As an example, in an embodiment of this disclosure, the multi-quantum-well layer includes five alternating stacked AlGaInP quantum-well layers and AlGaInP quantum-barrier layers.

[0117] Optionally, the thickness of the multi-quantum well layer can be from 150 nm to 200 nm.

[0118] In step S11, after forming the epitaxial layer 200 on the temporary substrate 11, the epitaxial layer 200 can be etched to form a plurality of bumps 201 on the epitaxial layer 200.

[0119] like Figure 3 As shown, the surface of the epitaxial layer 200 has bumps 201, and the surface of the bumps 201 away from the temporary substrate 11 is an arc surface.

[0120] S12: A metal electrode layer 40 is formed on the surface of the epitaxial layer 200, so that the metal electrode layer 40 covers the bump 201.

[0121] like Figure 3 As shown, the metal electrode layer 40 covers the epitaxial layer 200, and an arcuate groove 41 is formed in the area where the metal electrode layer 40 contacts the bump 201.

[0122] For example, the metal electrode layer 40 includes an Au layer, an AuGe layer, and a Pt layer sequentially stacked on the surface of the epitaxial layer 200.

[0123] For example, the thickness of the AuBe layer is between 800 angstroms and 1200 angstroms. As an example, the thickness of the AuBe layer is 1000 angstroms.

[0124] For example, the thickness of the Au layer is between 800 angstroms and 1200 angstroms. As an example, the thickness of the Au layer is 900 angstroms.

[0125] For example, the thickness of the Ti layer is 300 to 700 angstroms. As an example, the thickness of the Ti layer is 500 angstroms.

[0126] For example, the thickness of the Ni layer is between 2000 angstroms and 4000 angstroms. As an example, the thickness of the Ni layer is 3000 angstroms.

[0127] S13: Bond the surface of the metal electrode layer 40 away from the epitaxial layer 200 to the substrate 10, and remove the temporary substrate 11.

[0128] like Figure 4 As shown, the surface of the metal electrode layer 40 away from the epitaxial layer 200 is firmly bonded to the substrate 10 by means of eutectic bonding, adhesive bonding or other methods, and then the temporary substrate 11 is removed by laser lift-off or other techniques.

[0129] S14: Etch epitaxial layer 200 to form light-emitting block 20.

[0130] like Figure 5 As shown, after etching the epitaxial layer 200, the area where the bump 201 is located is retained to form a light-emitting block 20 including the bump 201.

[0131] For example, such as Figure 5 As shown, the portion of the light-emitting block 20 located on the metal electrode layer 40 is trapezoidal in shape.

[0132] like Figure 5As shown, before step S15, the method further includes etching the metal electrode layer 40 to form an isolation trench exposing the substrate 10, thereby obtaining a plurality of pixel units arranged at intervals.

[0133] S15: A planarization layer 30 is formed on the surface of the metal electrode layer 40, so that the planarization layer 30 covers the light-emitting block 20.

[0134] like Figure 6 As shown, the planarization layer 30 covers the light-emitting block 20 and the metal electrode layer 40.

[0135] Optionally, the planarization layer 30 includes at least one of a silicon oxide layer, a titanium oxide layer, and an aluminum oxide layer.

[0136] For example, the planarization layer 30 may be a silicon oxide layer.

[0137] S16: Etch planarization layer 30 to form hemispherical protrusions 31 on the surface of planarization layer 30.

[0138] like Figure 6 As shown, the surface of the planar layer 30 away from the metal electrode layer 40 is provided with a hemispherical protrusion 31. The orthographic projection of the light-emitting block 20 on the surface of the metal electrode layer 40 is located within the orthographic projection of the hemispherical protrusion 31 on the surface of the metal electrode layer 40. The hyperbolic metamaterial layer 50 covers the outer wall surface of the hemispherical protrusion 31.

[0139] Among them, the hemispherical protrusion 31 is equivalent to a microlens. Its curved structure can change the optical path angle, allowing more light to be emitted from the chip at a angle less than the critical angle, thus reducing the total internal reflection loss of the sidewalls.

[0140] Optionally, the radius of curvature of the hemispherical protrusion 31 is 1 μm to 2 μm, and the height of the hemispherical protrusion 31 is 400 nm to 600 nm.

[0141] Optionally, the outer wall surface of the hemispherical protrusion 31 and the groove surface of the arc groove 41 form a confocal resonant cavity.

[0142] In the above implementation, the confocal resonant cavity formed by the outer wall of the hemispherical protrusion 31 and the groove surface of the arcuate groove 41 causes the light emitted by the light-emitting block 20 to gradually converge towards the confocal point after multiple coordinated reflections within the cavity by the metal electrode layer 40. Ultimately, the light can be emitted in a directional manner.

[0143] S17: A hyperbolic metamaterial layer 50 is formed on the surface of the hemispherical protrusion 31.

[0144] like Figure 7 As shown, the orthographic projection of the light-emitting block 20 on the surface of the metal electrode layer 40 lies within the orthographic projection of the hyperbolic metamaterial layer 50 on the surface of the metal electrode layer 40.

[0145] The hyperbolic metamaterial layer 50 includes multiple hafnium dioxide layers 51 and multiple zirconium dioxide layers 52 stacked alternately.

[0146] Optionally, the thickness of the hafnium dioxide layer 51 is 5 nm to 15 nm, and the thickness of the zirconium dioxide layer 52 is 10 nm to 20 nm.

[0147] Optionally, the number of hafnium dioxide layers 51 is 150 to 250, and the number of zirconium dioxide layers 52 is 150 to 250.

[0148] Specifically, step S17 may include: controlling the substrate 10 to tilt by 30° in the reaction chamber and controlling the substrate 10 to rotate around a central axis perpendicular to the substrate 10, and forming a hyperbolic metamaterial layer 50 using atomic layer deposition technology.

[0149] An atomic layer deposition process with substrate 10 tilted at 30° and rotated around a vertical central axis is employed, and surface coverage uniformity >98% is achieved through dual dynamic control.

[0150] The 30° tilt angle changes the incident path of the reaction precursor gas to the surface of the substrate 10, making it easier for the gas flow to penetrate the curved surface of the hemispherical protrusion 31.

[0151] Simultaneously, continuous rotation ensures that all points on the surface of substrate 10 are uniformly exposed to airflow at different angles during deposition, eliminating local deposition differences caused by fixed tilt and averaging precursor transport differences in all directions. Through the synergistic effect of these two factors, the self-limiting reaction characteristics of ALD combined with precise process control ensure that the thickness deviation of the hyperbolic metamaterial layer 50 on the curved surface is less than 2%, achieving uniform coverage with atomic-level precision. Ultimately, this provides efficient and stable light extraction performance for the micro-LED chip.

[0152] Finally, the substrate 10 can be invisibly cut and scratched, which can effectively reduce the loss of brightness. Then, the light-emitting diode is tested.

[0153] The above description is merely an optional embodiment of this disclosure and is not intended to limit this disclosure. The data therein represents only illustrative examples. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A display device, characterized in that, The display device includes: a light-emitting block (20), a planarization layer (30), a metal electrode layer (40), and a hyperbolic metamaterial layer (50); The light-emitting block (20) is located on the metal electrode layer (40), the planarization layer (30) is located on the metal electrode layer (40) and covers the light-emitting block (20), the hyperbolic metamaterial layer (50) is located on the planarization layer (30), and the orthographic projection of the light-emitting block (20) on the surface of the metal electrode layer (40) is located within the orthographic projection of the hyperbolic metamaterial layer (50) on the surface of the metal electrode layer (40); The hyperbolic metamaterial layer (50) comprises alternating layers of hafnium dioxide (51) and zirconium dioxide (52).

2. The display device according to claim 1, characterized in that, The thickness of the hafnium dioxide layer (51) is 5 nm to 15 nm, and the thickness of the zirconium dioxide layer (52) is 10 nm to 20 nm. The number of hafnium dioxide layers (51) is 150 to 250, and the number of zirconium dioxide layers (52) is 150 to 250.

3. The display device according to claim 1, characterized in that, The surface of the flat layer (30) away from the metal electrode layer (40) is provided with a hemispherical protrusion (31), the orthographic projection of the light-emitting block (20) on the surface of the metal electrode layer (40) is located within the orthographic projection of the hemispherical protrusion (31) on the surface of the metal electrode layer (40), and the hyperbolic metamaterial layer (50) covers the outer wall surface of the hemispherical protrusion (31).

4. The display device according to claim 3, characterized in that, The radius of curvature of the hemispherical protrusion (31) is 1 μm to 2 μm, and the height of the hemispherical protrusion (31) is 400 nm to 600 nm.

5. The display device according to claim 3, characterized in that, The surface of the metal electrode layer (40) has an arc groove (41), and the surface of the light-emitting block (20) near the metal electrode layer (40) is in contact with the groove surface of the arc groove (41).

6. The display device according to claim 5, characterized in that, The outer wall of the hemispherical protrusion (31) and the groove surface of the arc groove (41) form a confocal resonant cavity.

7. The display device according to claim 6, characterized in that, The radius of curvature of the arc-shaped groove (41) is 50 μm to 60 μm.

8. The display device according to any one of claims 1 to 7, characterized in that, The thickness uniformity of the hyperbolic metamaterial layer (50) is greater than or equal to 98%.

9. A method for manufacturing a display device, characterized in that, The preparation method includes: An epitaxial layer is formed on a temporary substrate, the surface of the epitaxial layer having bumps, and the surface of the bumps away from the temporary substrate being an arc surface; A metal electrode layer is formed on the surface of the epitaxial layer, so that the metal electrode layer covers the bump; The surface of the metal electrode layer away from the epitaxial layer is bonded to the substrate, and the temporary substrate is removed; The epitaxial layer is etched to form a light-emitting block, the light-emitting block including the bump; A planarization layer is formed on the surface of the metal electrode layer, so that the planarization layer covers the light-emitting block; The planarization layer is etched to form hemispherical protrusions on the surface of the planarization layer; A hyperbolic metamaterial layer is formed on the surface of the hemispherical protrusion. The orthographic projection of the light-emitting block on the surface of the metal electrode layer is located within the orthographic projection of the hyperbolic metamaterial layer on the surface of the metal electrode layer. The hyperbolic metamaterial layer includes alternating layers of hafnium dioxide and zirconium dioxide.

10. The preparation method according to claim 9, characterized in that, Forming a hyperbolic metamaterial layer on the surface of the hemispherical protrusion includes: The substrate is tilted at 30° in the reaction chamber and rotated about a central axis perpendicular to the substrate to form the hyperbolic metamaterial layer using atomic layer deposition technology.

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