Monochromatic miniature LED pixel with high reflectivity

Abstract

Described herein is a monochromatic micro LED pixel comprising: an LED structure emitting light of a first color, where the LED structure is formed on a substrate; the top conductive structure is located above the LED structure and surrounds the periphery of a light emitting area of the LED structure, and a first reflecting layer is arranged on the side wall of the top conductive structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of light emitting diode (LED) display devices, and in particular to a monochromatic micro-LED pixel with high reflectivity. BACKGROUND

[0002] Light emitting diodes (LEDs) are widely used in lighting, backlighting, and display applications. The advantages of using LEDs as pixels include high brightness, low operating voltage, low power consumption, large volume, long life, impact resistance, and stable performance. In recent years, with the development of Mini-LED and micro-LED technology, consumer devices and applications such as augmented reality (AR), virtual reality (VR), projection, heads-up display (HUD), mobile device display, wearable device display, and automotive display require LED panels with higher resolution and brightness. For example, an AR display integrated in goggles and close to the wearer's eyes can only have the size of a fingernail, but still requires high-definition resolution (1280 x 720 pixels) or higher. Many electronic devices have specific requirements for the pixel size, distance between adjacent pixels, brightness, and viewing angle of the LED panel. In general, it is challenging to meet both resolution and brightness requirements when trying to achieve the highest resolution and brightness on a small-sized display. Conversely, in some cases, pixel size and brightness are difficult to balance at the same time because they can have roughly opposite relationships. For example, obtaining high brightness for each pixel can result in reduced resolution. Similarly, obtaining high resolution can reduce brightness.

[0003] The light emitted by the LED chip is generated by spontaneous emission, and therefore has no directionality, resulting in a large divergence angle. The large divergence angle can cause various problems in micro-LED displays. On the one hand, due to the large divergence angle, only a small portion of the light emitted by the micro-LED can be utilized. This can significantly reduce the efficiency and brightness of the micro-LED display system. On the other hand, due to the large divergence angle, the light emitted by one micro-LED pixel can illuminate its adjacent pixels, resulting in inter-pixel light crosstalk, loss of clarity, and loss of contrast. Figure 1 Conventional solutions to reduce large divergence are shown to reduce light loss, thereby reducing power consumption and light interference between pixels. As shown in Figure 1 The light isolation structure 110 surrounds each micro-LED pixel. However, these individual light isolation structures occupy a large chip area, increase the process difficulty, and are not conducive to the miniaturization of the micro-LED pixel unit.

[0004] Therefore, there is a need to provide an LED structure for a display panel to address the above-mentioned shortcomings and other issues. SUMMARY

[0005] There is therefore a need for an improved monochromatic LED design to address the shortcomings of conventional display systems. In particular, there is a need for an LED device structure that can improve brightness and resolution while effectively maintaining low power consumption.

[0006] The monochromatic micro-LED pixel described herein can include a high-reflectivity structure to improve internal reflectivity of emitted light while facilitating a narrow beam width, thereby being suitable for modern display panels, particularly for high-definition AR devices and virtual reality (VR) glasses, while improving brightness and resolution.

[0007] Some example embodiments provide a monochromatic micro-LED pixel comprising: an LED structure emitting a first color light, the LED structure being formed on a substrate; and a conductive structure surrounding the LED structure, a sidewall of the conductive structure being provided with a first reflective layer.

[0008] In some example embodiments of the monochromatic micro-LED pixel and any combination of the foregoing example embodiments, further comprising a bottom reflective layer formed between the LED structure and the substrate.

[0009] In some example embodiments of the monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the first reflective layer and the bottom reflective layer comprise one or more of a metal layer, a DBR layer, a multilayer omnidirectional reflector (ODR).

[0010] In some example embodiments of the monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the DBR layer is a conductive DBR or a dielectric DBR.

[0011] In some example embodiments of the monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the first reflective layer is one or more reflective coatings.

[0012] In some example embodiments of the monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the LED structure comprises a lower conductive layer, an upper conductive layer, and an LED light-emitting layer between the lower conductive layer and the upper conductive layer.

[0013] In some example embodiments of the monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the conductive structure is connected to the upper conductive layer of the LED structure.

[0014] In some example embodiments of the monochromatic micro-LED pixel and any combination of the foregoing example embodiments, a lower end of the conductive structure is located on the substrate; an upper end of the conductive structure reaches a position no lower than a top surface of the LED structure.

[0015] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, further comprising a micro-lens over the LED structure.

[0016] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the LED structure is embedded within an insulating dielectric.

[0017] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, an upper end of the electrically conductive structure reaches a top surface of the insulating dielectric or a bottom of the micro-lens.

[0018] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, an upper end of the top electrically conductive structure is higher than a bottom of the micro-lens.

[0019] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the LED structure emits red light, green light, or blue light.

[0020] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, a shape of a cross-section of the LED structure comprises a circle, a square, a rectangle, and a hexagon, and a shape of a cross-section of the first reflective layer is similar to or different from the shape of the LED structure.

[0021] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, a shape of a cross-section of the LED structure is a circle; and

[0022] a shape of a cross-section of the first reflective layer is an annulus around the LED structure or a rectangular annulus around the LED structure.

[0023] Some example embodiments provide a monochromatic micro-LED pixel, comprising: an LED structure emitting a first color light, wherein the LED structure is formed on a substrate; and a top electrically conductive structure located above the LED structure and surrounding a periphery of a light emitting area of the LED structure, wherein a first reflective layer is disposed on a sidewall of the top electrically conductive structure.

[0024] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the LED structure comprises a lower electrically conductive layer, an extension layer, and a micro-tiled structure between the lower electrically conductive layer and the extension layer.

[0025] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the micro-mesa structure has an inverted-trapezoidal cross-sectional shape, and the micro-mesa structure includes a first-type epitaxial layer, a multi-quantum well layer, and a second-type epitaxial layer, the multi-quantum well layer being between the first-type epitaxial layer and the second-type epitaxial layer.

[0026] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the LED structure includes a passivation layer for electrically isolating the lower conductive layer from the first-type epitaxial layer, the multi-quantum well layer, and the second-type epitaxial layer.

[0027] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the passivation layer covers a bottom surface of the first-type epitaxial layer, side surfaces of the first-type epitaxial layer, the multi-quantum well layer, and the second-type epitaxial layer, and a top surface of the insulating medium between adjacent micro-mesa structures, forms an opening in the passivation layer on the bottom surface of the first-type epitaxial layer, and forms the lower conductive layer at the opening.

[0028] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the LED structure includes a second reflective layer formed on a surface of the passivation layer and the lower conductive layer away from the micro-mesa structure.

[0029] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the monochromatic micro-LED pixel further includes a gap between the reflective layers of adjacent micro-mesa structures.

[0030] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the first reflective layer and / or the second reflective layer includes one or more of a metal layer, a DBR layer, and a multilayer omnidirectional reflector (ODR).

[0031] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the DBR layer is a conductive DBR or a dielectric DBR.

[0032] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the first reflective layer and / or the second reflective layer is one or more reflective coatings.

[0033] In some example embodiments of a monochromatic micro-LED pixel and any combination of the foregoing example embodiments, the top conductive structure is connected to an extension layer of the LED structure.

[0034] In some example embodiments of a monochrome micro-LED pixel and any combination of the foregoing example embodiments, a lower end of the conductive structure is on the extended layer of the LED structure.

[0035] In some example embodiments of a monochrome micro-LED pixel and any combination of the foregoing example embodiments, the top conductive structure is a mesh electrode; wherein the mesh frame of the mesh electrode is the conductive part that serves as the electrode, the hollow area between the mesh frame is the light-transmitting part, and the LED structure is located below the hollow area.

[0036] In some example embodiments of a monochrome micro-LED pixel and any combination of the foregoing example embodiments, a height of the top conductive structure is in a range of 0.2 pm to 5.0 pm.

[0037] In some example embodiments of a monochrome micro-LED pixel and any combination of the foregoing example embodiments, a material of the top conductive structure comprises: ITO, FTO, Al, Au, Ag, Cr, Ti, Pt, Cu.

[0038] In some example embodiments of a monochrome micro-LED pixel and any combination of the foregoing example embodiments, further comprising a microlens above the LED structure.

[0039] In some example embodiments of a monochrome micro-LED pixel and any combination of the foregoing example embodiments, an upper end of the top conductive structure reaches a bottom of the microlens; or

[0040] The upper end of the top conductive structure is higher than the bottom of the microlens.

[0041] In some example embodiments of a monochrome micro-LED pixel and any combination of the foregoing example embodiments, the LED structure emits red light, green light, or blue light.

[0042] In some example embodiments of a monochrome micro-LED pixel and any combination of the foregoing example embodiments, the LED structure is embedded within an insulating dielectric.

[0043] In some example embodiments of a monochrome micro-LED pixel and any combination of the foregoing example embodiments, a shape of a horizontal cross-section of the LED structure comprises a circle, a square, a rectangle, and a hexagon, and the first reflective layer is similar or different in shape to the LED structure in the horizontal cross-section.

[0044] In some example embodiments of a monochrome micro-LED pixel and any combination of the foregoing example embodiments, the shape of the horizontal cross-section of the LED structure is a circle; and the shape of the horizontal cross-section of the first reflective layer is an annular shape around the LED structure or a rectangular annular shape around the LED structure.

[0045] Some exemplary embodiments also provide a monochromatic micro-LED structure, including: a plurality of LED structures emitting a first color light, wherein the plurality of LED structures are formed on a substrate; and a top conductive structure located above the plurality of LED structures and surrounding the periphery of the light-emitting area of ​​the plurality of LED structures, wherein a first reflective layer is disposed on the sidewall of the top conductive structure.

[0046] In some exemplary embodiments of monochrome micro LED pixels and any combination of the aforementioned exemplary embodiments, the top conductive structure is a grid electrode, wherein the grid frame of the grid electrode is a conductive portion serving as an electrode, the hollow area between the grid frames is a light-transmitting portion, and the plurality of LED structures are located below the hollow area.

[0047] Some exemplary embodiments also provide a monochrome micro-LED pixel array, including a plurality of monochrome micro-LED pixels as described in any one of the embodiments of the present invention.

[0048] Other aspects include components, equipment, systems, improvements, methods, and processes, including manufacturing methods, applications, and other technologies related to any of the foregoing.

[0049] Note that the various embodiments described above can be combined with any other embodiments described herein, and the features and advantages described in the specification are not exhaustive. In particular, many additional features and advantages will be apparent to those skilled in the art from the drawings, specification, and claims. Furthermore, it should be noted that the language used in the specification has been chosen primarily for readability and instruction purposes and may not have been chosen to depict or limit the subject matter of the invention. Attached Figure Description

[0050] To gain a more detailed understanding of this disclosure, reference can be made to the features of the various embodiments, some of which are illustrated in the accompanying drawings. However, the accompanying drawings only illustrate relevant features of this disclosure and should not be considered limiting, as the description may cover other valid features.

[0051] Figure 1 A conventional solution for reducing large divergence angles is shown.

[0052] Figure 2A A schematic top view of a monochrome micro-LED pixel with high reflectivity according to an embodiment of the present invention is shown.

[0053] Figure 2B An embodiment of the present invention is shown as follows. Figure 2A The diagram shows a schematic cross-sectional view of a monochrome micro-LED pixel along line AA.

[0054] Figure 3 A schematic top view of the top electrode of a monochrome micro LED pixel according to an embodiment of the present invention is shown.

[0055] Figure 4 A schematic top view of a monochrome micro-LED pixel with high reflectivity according to another embodiment of the present invention is shown.

[0056] Figure 5A A schematic top view of a monochrome micro-LED pixel with high reflectivity according to an embodiment of the present invention is shown.

[0057] Figure 5B An embodiment of the present invention is shown as follows. Figure 5A The diagram shows a schematic cross-sectional view of a monochrome micro-LED pixel along line AA.

[0058] Figure 6 A schematic top view of the top electrode of a monochrome micro LED pixel according to an embodiment of the present invention is shown.

[0059] Figure 7 A schematic top view of a monochrome micro-LED pixel with high reflectivity according to another embodiment of the present invention is shown.

[0060] Figure 8A A schematic top view of four LED structures sharing a single top conductive structure is shown according to an embodiment of the present invention.

[0061] Figure 8B An embodiment of the present invention is shown as follows. Figure 8A The diagram shows a schematic cross-sectional view of the structure along line AA.

[0062] Figure 9A A schematic top view of a monochrome micro-LED pixel array with high reflectivity according to an embodiment of the present invention is shown.

[0063] Figure 9B An embodiment of the present invention is shown as follows. Figure 9A The diagram shows a schematic cross-sectional view of a monochrome micro-LED pixel along line AA.

[0064] By convention, features shown in the accompanying drawings may not be drawn to scale. Therefore, for clarity, the dimensions of various features may be arbitrarily enlarged or reduced. Furthermore, some drawings may not depict all components of a particular system, method, or apparatus. Finally, the same reference numerals may be used to denote the same features throughout the specification and the accompanying drawings. Detailed Implementation

[0065] This document describes numerous details to provide a thorough understanding of the exemplary embodiments illustrated in the accompanying drawings. However, some embodiments may be practiced without many specific details, and the scope of the claims is limited only to those features and aspects specifically recited in the claims. Furthermore, well-known processes, components, and materials have not been described exhaustively so as not to unnecessarily obscure relevant aspects of the embodiments described herein.

[0066] In some embodiments, a single monochrome LED pixel includes an LED structure. In some embodiments, the LED structure includes at least an LED light-emitting layer that emits different colors of light, i.e., the LED light-emitting layer can emit red, green, blue, or other colors of light.

[0067] Figure 2A A schematic top view of a monochrome micro-LED pixel with high reflectivity according to an embodiment of the present invention is shown. Figure 2B An embodiment of the present invention is shown as follows. Figure 2A The diagram shows a schematic cross-sectional view of a monochrome micro-LED pixel along line AA. Figure 2B As shown, the monochrome micro LED pixel includes a substrate 210, an LED structure 220, a conductive structure 250, and a microlens 260.

[0068] For convenience, "above" is used to indicate away from substrate 210, "below" indicates towards substrate 210, and other directional terms such as top, bottom, above, below, and under are interpreted accordingly. Support substrate 210 is a substrate on which a single array of driving circuits is fabricated. In some embodiments, the driving circuits may also be located in one of the layers above substrate 210. Each driving circuit is a pixel driver. In some instances, the driving circuit is a thin-film transistor pixel driver or a silicon complementary metal-oxide-semiconductor CMOS pixel driver. In one embodiment, substrate 210 is a Si substrate. In another embodiment, support substrate 210 is a transparent substrate, such as a glass substrate. Other example substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. The driving circuits form individual pixel drivers to control the operation of individual monochrome micro-LED pixels. The circuitry on substrate 210 includes contacts 211 for each individual driving circuit and a ground contact.

[0069] In some embodiments, the LED structure 220 may include a lower conductive layer 221, an upper conductive layer 222, and an LED light-emitting layer 223 located between the lower conductive layer 221 and the upper conductive layer 222. Those skilled in the art should understand that the LED light-emitting layer 223 in the LED structure 220 may be a red light-emitting layer, a green light-emitting layer, a blue light-emitting layer, or a light-emitting layer of any other color. In some embodiments, the LED structure 220 may further include an upper connection portion 224 located between the upper conductive layer 222 and the LED light-emitting layer 223 and electrically connected to both the upper conductive layer 222 and the LED light-emitting layer 223. The upper connection portion 224 is made of a metal, including one or more of Al, Au, Rh, Ag, Cr, Ti, Pt, Sn, Cu, AuSn, TiW, etc.

[0070] In some embodiments, the LED light-emitting layer 223 may include a first semiconductor epitaxial layer of a first conductivity type, a second semiconductor epitaxial layer of a second conductivity type, and an intermediate light-emitting layer. The light-emitting layer may be, but is not limited to, a multi-quantum-well layer. The first conductivity type may be N-type, and the second conductivity type may be P-type; or the first conductivity type may be P-type, and the second conductivity type may be N-type. The N-type semiconductor epitaxial layer in each of the three color light-emitting layers includes, but is not limited to, N-type Si-doped GaN, Si-doped Al GaN, Si-doped Al Ga InP, Si-doped GaAs, or Si-doped Al InP; the P-type semiconductor epitaxial layer includes, but is not limited to, Mg-doped GaN, Mg-doped Al GaN, Mg-doped InGaN, Mg-doped InAl GaN, Mg-doped Al InP, Mg-doped Al Ga InP, Mg-doped GaP, or C-doped GaP. The quantum well layer includes, but is not limited to, InGaN / GaN cycling and InGaP / Al Ga InP cycling.

[0071] In some embodiments, the upper and lower conductive layers may be metal layers or conductive transparent layers, such as ITO, FTO, or copper layers, formed to improve conductivity and transparency. In another embodiment, the lower conductive layer 221 may be a metal layer to form part of the metal bonding layer 270.

[0072] Although some features are described in this paper using the term "layer," it should be understood that these features are not limited to a single layer but may include multiple sub-layers.

[0073] In some embodiments, the LED structure 220 is bonded to the substrate 210 via a metal bonding layer 270. The metal bonding layer 270 may be disposed on the substrate 210. In one method, the metal bonding layer 270 is grown on the substrate 210. In some embodiments, the metal bonding layer 270 electrically connects the contacts 211 on the substrate 210 and the LED structure 220 above the metal bonding layer 270, acting as a p-electrode. In some embodiments, the thickness of the metal bonding layer 270 is approximately 0.1 μm to approximately 3 μm. In a preferred embodiment, the thickness of the metal bonding layer 270 is approximately 0.3 μm. The metal bonding layer 270 may include an ohmic contact layer and a metal bonding layer. In some instances, two metal layers are included in the metal bonding layer 270. One of the metal layers is deposited at the bottom of the LED structure 220. A corresponding bonding metal layer is also deposited on the substrate 210. In some embodiments, the composition of the metal bonding layer 270 includes Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or mixtures thereof. For example, if Au-Au bonding is chosen, the two Au layers require a Cr coating as an adhesive layer and a Pt coating as an anti-diffusion layer, respectively. The Pt coating is located between the Au layer and the Cr layer. The Cr and Pt layers are located at the top and bottom of the two bonded Au layers. In some embodiments, when the two Au layers are approximately the same thickness, mutual diffusion of Au on the two layers will bond the two layers together under high pressure and high temperature. Eutectic bonding, hot-press bonding, and transient liquid phase (TLP) bonding are example techniques that can be used.

[0074] In some embodiments, the metal bonding layer 270 may also function as a reflector to reflect light emitted from the LED structure above. In some embodiments, the metal bonding layer 270 may include a reflective layer. Furthermore, the reflective layer may include stacked reflective sublayers.

[0075] In some embodiments, the LED structure 220 may be embedded within an insulating dielectric 280. The insulating dielectric 280 is transparent to light emitted from the LED structure 220. In some embodiments, the insulating dielectric 280 is made of a dielectric material such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, SiCN, HfO2, Ta2O5, TiO2, ZrO2, La2O3, MgO, phosphosilicate glass (PSG), borosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes polymers such as SU-8, PermiNex, benzocyclobutene (BCB), or transparent plastics (resins) including spin-coated glass (SOG), or bonding adhesives such as Micro Resist BCL-1200, or any combination thereof. In some embodiments, the insulating dielectric 280 may facilitate the transmission of light emitted from the LED structure.

[0076] like Figures 2A-2B As shown, the conductive structure 250 is located around the LED structure 220. In some embodiments, the conductive structure 250 can serve as a common electrode to connect with the upper conductive layer 222 of the LED structure 220. The conductive structure 250 can be positioned on the substrate 210, but is not directly electrically connected to the substrate 210. The conductive structure 250 can electrically connect the upper conductive layer 222 of the LED structure 220 to the negative terminal of an external power supply. In some embodiments, the conductive structure 250 can also be referred to as a top electrode or an N-electrode.

[0077] However, those skilled in the art should recognize that the N and P electrodes of an LED structure are interchangeable. For example, a conductive structure can serve as a common P electrode connected to the P-type epitaxial layer of each LED structure, while the corresponding N-type epitaxial layer of the LED structure is connected to a metal bonding layer.

[0078] In some embodiments, such as Figure 3 As shown, the top electrode 310 may also include a current spreading layer. The upper conductive layer 222 may be formed on the LED light-emitting layer 223 and extend over the entire surface of the array of multiple monochromatic micro-LED pixels below the bottom of the microlens. The current spreading layer may be formed on the upper conductive layer 222 and have better conductivity than the upper conductive layer 222. The current spreading layer does not cover the light-emitting area of ​​each micro-LED pixel.

[0079] The upper conductive layer can be flat, or it can have an upward or downward slope due to the height difference between the conductive structure and the LED light-emitting layer. For example, when forming the upper conductive layer, if the height of the conductive structure is the same as the height of the LED light-emitting layer, the upper conductive layer is substantially flat; if the height of the conductive structure is higher than the height of the LED light-emitting layer, the upper conductive layer includes a slope rising from the edge of the LED light-emitting layer to the conductive structure; if the height of the conductive structure is lower than the height of the LED light-emitting layer, the upper conductive layer includes a slope descending from the edge of the LED light-emitting layer to the conductive structure. Those skilled in the art will understand that any shape of the upper conductive layer can be designed according to the specific requirements of the micro-LED pixels, and these all fall within the scope of protection of this invention.

[0080] In some embodiments, the lower end of the conductive structure 250 is located on the substrate 210; and the upper end of the conductive structure 250 can reach a position not lower than the top surface of the LED structure; preferably, the upper end of the conductive structure 250 can reach the top surface of the insulating medium 280 or the bottom of the microlens or directly reach the bottom of the top pad. In other embodiments of the present invention, the upper end of the top conductive structure 250 can be higher than the bottom of the microlens 260.

[0081] Those skilled in the art should understand that the layout, size, and connection method of the conductive structure 250 and the top pad are not limited to... Figures 2A-2B The embodiments shown in Figures 1 and 3 can be modified according to actual needs, such as adjusting the shape and size of the conductive structure, and all such modifications fall within the protection scope of this invention.

[0082] In some embodiments, such as Figures 2A-2B As shown, a reflective layer 251 is disposed on the sidewall of the conductive structure 250. In some embodiments, the conductive structure 250 substantially surrounds the LED structure 220, such that light emitted from the LED structure 220 toward the conductive structure is reflected by the reflective layer 251 and emitted at the top surface of a single LED pixel.

[0083] In some embodiments, the conductive structure 250 with the reflective layer 251 can be fabricated by a combination of deposition, photolithography, and etching processes. In some embodiments, the conductive structure 250 with the reflective layer 251 can be fabricated by other suitable methods.

[0084] In some embodiments, the reflective layer 251 may be a metal layer with high reflectivity comprising one or more metals such as Pt, Rh, Al, Au and Ag, a stacked DBR layer comprising TiO2 / SiO2 layers, or any other layer with total reflection characteristics comprising a multilayer omnidirectional reflector (ODR), or a combination thereof.

[0085] In some embodiments, the reflective layer 251 may be one or more reflective coatings. These one or more reflective coatings may be disposed on the sidewalls of the conductive structure 250. The bottom of each of the one or more reflective coatings does not contact the corresponding LED structure. These one or more reflective coatings can reflect light emitted from the light-emitting area and thus enhance the brightness and luminous efficiency of the micro-LED panel or display. For example, light emitted from the light-emitting area can reach the one or more reflective coatings and can be reflected upwards by them.

[0086] One or more reflective coatings may be made of materials with a high reflectivity greater than 60%, 70%, or 80%, so that most of the light emitted from the luminescent region can be reflected. In some embodiments, the one or more reflective coatings may comprise one or more metallic conductive materials with high reflectivity. In these embodiments, the one or more metallic conductive materials may comprise one or more of aluminum, gold, or silver. In other embodiments, the one or more reflective coatings may be multilayered. More specifically, the one or more reflective coatings may comprise a stack of one or more reflective material layers and one or more dielectric material layers. For example, the one or more reflective coatings may comprise one reflective material layer and one dielectric material layer. In other embodiments, the one or more reflective coatings may comprise two reflective material layers and a dielectric material layer located between the two reflective material layers. However, in some other embodiments, the one or more reflective coatings may comprise two dielectric material layers and a reflective material layer located between the two dielectric material layers. In some embodiments, the multilayer structure may comprise two or more metal layers, which may comprise one or more of TiAu, CrAl, or TiWAg.

[0087] In some embodiments, the one or more reflective coatings may be multilayer omnidirectional reflectors (ODRs) comprising a metal layer and a transparent conductive oxide (TCO) layer. For example, the multilayer structure may include a dielectric material layer, a metal layer, and a TCO layer. In some embodiments, the one or more reflective coatings may include two or more dielectric material layers alternately arranged to form a distributed Bragg reflector (DBR). For example, the one or more reflective coatings may include a dielectric material layer, a metal layer, and a transparent dielectric layer. The transparent dielectric layer may include one or more of SiO2, Si3N4, Al2O3, or TiO2. The one or more reflective coatings may also include a dielectric material layer, a TCO, and a DBR. In other embodiments, the one or more reflective coatings may include one or more highly reflective metallic conductive materials. In these embodiments, the one or more metallic conductive materials may include one or more of aluminum, gold, or silver.

[0088] In some embodiments, the reflective layer 251 may be a conductive reflective layer or a dielectric reflective layer.

[0089] A highly reflective reflective layer 251 on the sidewall of the conductive structure 250 allows for high WPE and narrow beam width.

[0090] In some embodiments, a microlens 260 is formed on the top surface of the LED structure 220.

[0091] In some embodiments, the microlens 260 alters the light path emitted from a single microLED pixel by making the light emitted from the LED device more focused or more diffuse, depending on design requirements.

[0092] In some embodiments, the microlens 260 may be made of a variety of materials that are transparent at the wavelength emitted by a single microLED pixel. Example transparent materials for the microlens 260 include polymers, dielectrics, and semiconductors. In some embodiments, the dielectric material includes one or more materials, such as silicon oxide, silicon nitride, silicon carbide, titanium oxide, zirconium oxide, aluminum oxide, etc. In some embodiments, the microlens 260 is made of photoresist.

[0093] In some embodiments, the microlens 260 is typically hemispherical in shape. In some embodiments, the central axis of the microlens 260 is aligned with or the same as the central axis of a single microLED pixel without a lens.

[0094] It should be understood that a full display panel comprises an array of many individual pixels and many microlenses. Furthermore, it need not be a one-to-one correspondence between microlenses and pixel light sources, nor between pixel driving circuitry (not shown) and pixel light sources. Pixel light sources can also be made of multiple individual light elements, such as multiple single-pixel LEDs connected in parallel. In some embodiments, a microlens 260 can cover several lensless individual LED pixels.

[0095] Individual microlenses 260 have positive optical power and are positioned to reduce the divergence or viewing angle of light emitted from their respective pixel light sources. In one example, the beam emitted from the pixel light source has a fairly wide initial divergence angle. In one embodiment, the initial angle of the edge rays of the beam relative to a vertical axis orthogonal to the substrate 210 is greater than 60 degrees. The light is bent by the microlenses 260, such that the new edge rays now have a reduced divergence angle. In one embodiment, the reduced angle is less than 30 degrees. The microlenses in the microlens array are typically identical. Examples of microlenses include spherical microlenses, aspherical microlenses, Fresnel microlenses, and cylindrical microlenses.

[0096] Microlenses 260 typically have a flat side and a curved side. Figure 2BIn this configuration, the bottom of the microlens 260 is flat, and the top of the microlens 260 is curved. Typical shapes of the base of each microlens 260 include circular, square, rectangular, and hexagonal. Individual microlenses in the microlens array of the display panel may be the same or different in shape, curvature, optical power, size, base, and spacing. In some embodiments, the microlens 260 conforms to the shape of a single LED pixel. In one example, the shape of the base of the microlens 260 is the same as the shape of a single LED pixel. In another example, the shape of the base of the microlens 260 is different from the shape of a single LED pixel; for example, the circular base of the microlens has the same width as a single LED pixel, but its area is smaller because the microlens base is circular while the base of the single LED pixel is square. In some embodiments, the area of ​​the microlens base is smaller than the area of ​​the pixel light source. In some embodiments, the area of ​​the microlens base is the same as or larger than the area of ​​the pixel light source.

[0097] In some embodiments, brightness enhancement is achieved by integrating a microlens array onto the display panel. In some examples, due to the light-concentrating effect of the microlenses, the brightness with the microlens array is four times that without the microlens array in the direction perpendicular to the display surface. In alternative embodiments, the brightness enhancement factor can vary depending on the design of the microlens array and optical spacers. For example, a factor greater than 8 can be achieved.

[0098] Microlenses can be manufactured using various methods, including deposition, patterning, and etching.

[0099] In some embodiments, such as Figure 2A As shown, typical cross-sectional shapes of LED structures include circles, squares, rectangles, and hexagons. In some embodiments, the reflective layer 251 on the sidewall of the conductive structure 250 conforms to the shape of the LED structure. In one example, the cross-sectional shape of the LED structure is circular, and the cross-sectional shape of the reflective layer 251 is a ring surrounding the LED structure. In another example, the cross-sectional shape of the LED structure is different from the shape of the reflective layer 251; for example, the cross-sectional shape of the LED structure is circular, but the cross-sectional shape of the reflective layer 251 is a rectangular ring surrounding the LED structure, such as... Figure 4 As shown.

[0100] Figure 5A A schematic top view of a monochrome micro-LED pixel with high reflectivity according to an embodiment of the present invention is shown. Figure 5B An embodiment of the present invention is shown as follows. Figure 5A The schematic cross-sectional view of the monochrome micro LED pixel along line AA is shown below. Figure 5BAs shown, the monochrome micro LED pixel includes a substrate 510, an LED structure 520, a top conductive structure 550, and a microlens 560.

[0101] The support substrate 510 is a substrate on which the various driving circuit arrays are fabricated. In some embodiments, the driving circuits may also be located in one of the layers above the substrate 510. Each driving circuit is a pixel driver. In some instances, the driving circuit is a thin-film transistor pixel driver or a silicon complementary metal-oxide-semiconductor CMOS pixel driver. In one embodiment, the substrate 510 is a Si substrate. In another embodiment, the support substrate 510 is a transparent substrate, such as a glass substrate. Other example substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. The driving circuits form the individual pixel drivers to control the operation of each monochrome MicroLED pixel. The circuitry on the substrate 510 includes contacts 511 to each driving circuit and a ground contact.

[0102] In some embodiments, the LED structure 520 may include a lower conductive layer 530, an extension layer 540, and a micromesa structure located between the lower conductive layer 530 and the extension layer 540. In some embodiments, the micromesa structure may include a first type epitaxial layer 521, a multiple quantum well layer 523, and a second type epitaxial layer 522, from bottom to top. Those skilled in the art will understand that the micromesa structure in the LED structure 520 can emit red, green, blue, or any other color of light.

[0103] In some embodiments, the extended layer 540 may be made of the same material as the second type epitaxial layer 522, and the thickness of the layer 540 may be between 0.2 μm and 3.0 μm, while the thickness of the second type epitaxial layer 522 may be between 0.2 μm and 2.0 μm.

[0104] In some embodiments, the lower conductive layer 530 may be a metal layer or a conductive transparent layer, such as an ITO, FTO, or copper layer, formed to improve conductivity and transparency. In another embodiment, the lower conductive layer 530 may be a metal layer to form part of the metal bonding layer 570.

[0105] In some embodiments, such as Figure 5B As shown, the cross-sectional shape of the micro-mesa structure is an inverted trapezoid, meaning that the upper area of ​​the micro-mesa structure is larger than the bottom area.

[0106] In some embodiments, the LED structure 520 may further include a passivation layer 524. The passivation layer 524 may cover the bottom surface of the first type epitaxial layer 521, the sides of the first type epitaxial layer 521, the multiple quantum well layer 523, the second type epitaxial layer 522, and the top surface of the insulating medium 581 between adjacent micromesa structures. An opening exists in the passivation layer 524 on the bottom surface of the first type epitaxial layer 521. The lower conductive layer 530 may be formed in the opening. In this embodiment, the passivation layer 524 primarily serves as an electrical isolation layer, and the first passivation material layer may be an alumina (Al2O3) film formed using an atomic layer deposition process with better step coverage. The passivation layer 524 provides electrical isolation between the lower conductive layer 530 and the first type epitaxial layer 521, the multiple quantum well layer 523, and the second type epitaxial layer 522.

[0107] In some embodiments, the LED structure 520 may further include a reflective layer 590 formed on the surface of the passivation layer 524 and the lower conductive layer 530 away from the micromesa structure.

[0108] In some embodiments, the reflective layer 590 may be a metal layer with high reflectivity, comprising one or more metals such as Pt, Rh, Al, Au and Ag, a stacked DBR layer including TiO2 / SiO2 layers, or any other layer with total reflection properties including a multilayer omnidirectional reflector (ODR), or a combination thereof.

[0109] In some embodiments, the reflective layer 590 may be one or more reflective coatings. These one or more reflective coatings can reflect light emitted from the light-emitting area and thus enhance the brightness and luminous efficacy of the micro-LED panel or display. For example, light emitted from the light-emitting area can reach one or more reflective coatings and be reflected upwards through them.

[0110] Since the reflective layer can be made of conductive material, there is a gap 591 between the reflective layers of adjacent micro-mesa structures, thus avoiding short circuits between adjacent micro-mesa structures.

[0111] In some embodiments, the LED structure 520 is bonded to the substrate 510 via a combination of an oxide bonding layer 571 and a metal bonding layer 570. In some embodiments, the metal bonding layer 570 electrically connects a contact 511 on the substrate 510 and the LED structure 520 above the metal bonding layer 570, functioning similarly to a P-electrode. The metal bonding layer 570 may include an ohmic contact layer and a metal bonding layer. In some instances, two metal layers are included in the metal bonding layer 570, with two oxide bonding layers surrounding the two metal layers. One metal layer is deposited at the bottom of the LED structure 520; the corresponding bonding metal layer is deposited on the bonding surface of the substrate 510. On the bonding surface, the surface of the metal bonding layer is flush with the surface of the oxide bonding layer. In some embodiments, the composition of the metal bonding layer 570 includes Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or mixtures thereof. For example, if Au-Au bonding is chosen, each Au layer requires a Cr coating as an adhesive layer and a Pt coating as an anti-diffusion layer. The Pt coating is located between the Au and Cr layers. The Cr and Pt layers are located at the top and bottom of the two bonded Au layers. In some embodiments, when the two Au layers are of approximately the same thickness, mutual diffusion of Au on both layers under high pressure and high temperature will bond the two layers together. Eutectic bonding, thermocompression bonding, and transient liquid phase (TLP) bonding are example techniques that can be used. The oxide bonding layer 571 can be composed of SiO2; for this structure, bonding is achieved through oxide-oxide bonding and metal-metal bonding.

[0112] In some embodiments, the insulating dielectric 581 may fill the spaces between the LED structures 520. In some embodiments, the insulating dielectric 581 is made of a dielectric material such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, phosphosilicate glass (PSG), or borosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes polymers such as SU-8, PermiNex, benzocyclobutene (BCB), or transparent plastics (resins) including spin-coated glass (SOG) or bonding adhesive Micro Resist BCL-1200, or any combination thereof.

[0113] like Figures 5A-5BAs shown, the top conductive structure 550 is located above the LED structure 520 and surrounds the periphery of the light-emitting area of ​​the LED structure 520. In some embodiments, the top conductive structure 550 can serve as a common electrode and be connected to the extension layer 540 of the LED structure 520. The top conductive structure 550 can electrically connect the extension layer 540 of the LED structure 520 to the negative terminal of an external power supply. In some embodiments, the top conductive structure 550 can also be referred to as a top electrode or an N-electrode.

[0114] In some embodiments, such as Figure 6 As shown, the top electrode 610 can be a grid electrode. That is, the grid frame is the conductive part used as an electrode, and the hollow area between the grid frames is the light-transmitting part. Each LED structure 520 is located below the hollow area between the grid frames so that the light emitted by the LED can be emitted from the hollow area. The material of the top electrode 310 may include: ITO, FTO, Al, Au, Ag, Cr, Ti, Pt, Cu.

[0115] In some embodiments, the lower end of the top conductive structure 550 is located on the extension layer 540; and the upper end of the top conductive structure 550 can reach the bottom of the microlens 560. The height of the top conductive structure 550 is in the range of 0.1 μm to 5.0 μm. In other embodiments of the invention, the upper end of the top conductive structure 550 can be higher than the bottom of the microlens 560.

[0116] Those skilled in the art should understand that the shape, size, and connection method of the top conductive structure 550 are not limited to... Figures 5A-5B The embodiments shown in 6 can be modified according to actual requirements, such as adjusting the shape and size of the top conductive structure 550, and these modifications all fall within the protection scope of this invention.

[0117] In some embodiments, such as Figures 5A-5B As shown, a reflective layer 551 is provided on the sidewall of the top conductive structure 550. In some embodiments, the top conductive structure 550 substantially surrounds the LED structure 520, such that light emitted from the LED structure 520 toward the top conductive structure 550 is reflected by the reflective layer 551 and emitted on the top surface of a single LED pixel.

[0118] In some embodiments, the top conductive structure 550 having the reflective layer 551 can be fabricated by a combination of deposition, photolithography, and etching processes. In some embodiments, the top conductive structure 550 with the reflective layer 551 can be fabricated by other suitable methods.

[0119] In some embodiments, the reflective layer 551 may be a metal layer with high reflectivity, comprising one or more metals such as Pt, Rh, Al, Au and Ag, a stacked DBR layer including TiO2 / SiO2 layers, or any other layer with total reflection characteristics including a multilayer omnidirectional reflector (ODR), or a combination thereof.

[0120] In some embodiments, the reflective layer 551 may be one or more reflective coatings. These one or more reflective coatings may be disposed on the sidewalls of the top conductive structure 550. These one or more reflective coatings may reflect light emitted from the light-emitting area and thus enhance the brightness and luminous efficacy of the micro-LED panel or display. For example, light emitted from the light-emitting area may reach the one or more reflective coatings and may be reflected upwards by them.

[0121] The material of the one or more reflective coatings can have a high reflectivity of greater than 60%, 70%, or 80%, so that most of the light emitted from the luminescent region can be reflected. In some embodiments, the one or more reflective coatings may include one or more metallic conductive materials with high reflectivity. In these embodiments, the one or more metallic conductive materials may include one or more of aluminum, gold, or silver. In other embodiments, the one or more reflective coatings may be multilayered. More specifically, the one or more reflective coatings may include a stack of one or more reflective material layers and one or more dielectric material layers. For example, the one or more reflective coatings may include one reflective material layer and one dielectric material layer. In other embodiments, the one or more reflective coatings may include two reflective material layers and a dielectric material layer located between the two reflective material layers. However, in some other embodiments, the one or more reflective coatings may include two dielectric material layers and a reflective material layer located between the two dielectric material layers. In some embodiments, the multilayer structure may include two or more metal layers, which may include one or more of TiAu, CrAl, or TiWAg.

[0122] In some embodiments, the one or more reflective coatings may be multilayer omnidirectional reflectors (ODRs) comprising a metal layer and a transparent conductive oxide (TCO) layer. For example, the multilayer structure may include a dielectric material layer, a metal layer, and a TCO layer. In some embodiments, the one or more reflective coatings may include two or more dielectric material layers alternately arranged to form a distributed Bragg reflector (DBR). For example, the one or more reflective coatings may include a dielectric material layer, a metal layer, and a transparent dielectric layer. The transparent dielectric layer may include SiO or Si3N. 42The reflective coating may contain one or more of Al2O3 or TiO2. The one or more reflective coatings may further include a dielectric material layer, TCO, and DBR. In other embodiments, the one or more reflective coatings may include one or more highly reflective metallic conductive materials. In these embodiments, the one or more metallic conductive materials may include one or more of aluminum, gold, or silver.

[0123] In some embodiments, the reflective layer 551 may be a conductive reflective layer or a dielectric reflective layer.

[0124] On the sidewall of the top conductive structure 550, a highly reflective reflective layer 551 allows for high WPE and narrow beam width.

[0125] In some embodiments, a microlens 560 is formed on the top surface of the LED structure 520.

[0126] In some embodiments, the microlens 560 alters the light path emitted from a single microLED pixel by making the light emitted from the LED device more focused or more diffuse, depending on design requirements.

[0127] In some embodiments, the microlens 560 may be made of a variety of materials that are transparent at the wavelength emitted by a single microLED pixel. Example transparent materials for the microlens 560 include polymers, dielectrics, and semiconductors. In some embodiments, the dielectric material includes one or more materials, such as silicon oxide, silicon nitride, silicon carbide, titanium oxide, zirconium oxide, aluminum oxide, etc. In some embodiments, the microlens 560 is made of photoresist.

[0128] In some embodiments, the microlens 560 is typically hemispherical in shape, and in some embodiments, the central axis of the microlens 560 is aligned with or the same as the central axis of a single microLED pixel without a lens.

[0129] It should be understood that a full display panel comprises an array of many individual pixels and many microlenses. Furthermore, there is not necessarily a one-to-one correspondence between microlenses and pixel light sources, nor is there necessarily a one-to-one correspondence between pixel driving circuitry (not shown) and pixel light sources. Pixel light sources can also be made of multiple individual light elements, such as multiple single-pixel LEDs connected in parallel. In some embodiments, a microlens 560 can cover several lensless individual LED pixels.

[0130] Individual microlenses 560 have positive optical power and are positioned to reduce the divergence or viewing angle of light emitted from their respective pixel light sources. In one example, the beam emitted from the pixel light source has a fairly wide initial divergence angle. In one embodiment, the initial angle of the edge rays of the beam relative to a vertical axis orthogonal to the substrate 510 is greater than 60 degrees. The light is bent by the microlenses 560, such that the new edge rays now have a reduced divergence angle. In one embodiment, the reduced angle is less than 30 degrees. The microlenses in the microlens array are typically identical. Examples of microlenses include spherical microlenses, aspherical microlenses, Fresnel microlenses, and cylindrical microlenses.

[0131] Microlenses 560 typically have a flat side and a curved side. Figure 5B In this configuration, the bottom of microlens 560 is flat, and the top of microlens 560 is curved. Typical shapes of the base of each microlens 560 include circular, square, rectangular, and hexagonal. Individual microlenses in the microlens array of the display panel may be the same or different in shape, curvature, optical power, size, base, and spacing. In some embodiments, the shape of the microlens 560 conforms to that of a single LED pixel. In one example, the shape of the base of the microlens 560 is the same as that of a single LED pixel. In another example, the shape of the base of the microlens 560 is different from that of a single LED pixel; for example, the circular base of the microlens has the same width as that of a single LED pixel, but its area is smaller because the microlens base is circular while the base of the single LED pixel is square. In some embodiments, the area of ​​the microlens base is smaller than the area of ​​the pixel light source. In some embodiments, the area of ​​the microlens base is the same as or larger than the area of ​​the pixel light source.

[0132] In some embodiments, brightness enhancement is achieved by integrating a microlens array onto the display panel. In some examples, due to the light-focusing effect of the microlenses, the brightness with the microlens array is four times that without the microlens array in the direction perpendicular to the display surface. In other embodiments, the brightness enhancement factor varies depending on the design of the microlens array and the optical spacing. For example, the brightness enhancement factor can reach a value greater than 8.

[0133] The microlenses can be manufactured using various methods, including deposition, patterning, etching, and other steps.

[0134] In some embodiments, such as Figure 5AAs shown, typical cross-sectional shapes of LED structures include circles, squares, rectangles, and hexagons. In some embodiments, the reflective layer 551 on the sidewall of the top conductive structure 550 conforms to the shape of the LED structure. In one example, the LED structure is circular in cross-section, and the reflective layer 551 is a ring around the LED structure in cross-section. In another example, the shape of the LED structure in cross-section differs from the shape of the reflective layer 551; for example, the LED structure is circular in cross-section, but the reflective layer 551 is a rectangular ring around the LED structure in cross-section. Figure 7 As shown.

[0135] In some embodiments, multiple LED structures may share a single top conductive structure. For example, Figure 8A A schematic diagram of four LED structures sharing a top conductive structure according to an embodiment of the present invention is shown. Figure 8B An embodiment of the present invention is shown as follows. Figure 8A The diagram shows a cross-sectional view of the structure along line AA.

[0136] like Figures 8A-8B As shown, the top conductive structure 850 is located above and surrounds the four LED structures 820. In some embodiments, the top conductive structure 850 can be used as a common electrode to connect the extension layer 840 of the four LED structures 820 to the negative terminal of an external power supply. In some embodiments, the top conductive structure 850 may also be referred to as a top electrode or an N-electrode.

[0137] In some embodiments, such as Figure 8A As shown, the top conductive structure 850 can be a grid electrode. That is, the top conductive structure 850 can be a rectangular frame surrounding four LED structures 820. The four LED structures 820 are located below the hollow region in the frame so that light emitted by the LEDs can be emitted from the hollow region.

[0138] In some embodiments, the lower end of the top conductive structure 850 is located on the extension layer 840; and the upper end of the top conductive structure 850 can reach the bottom of the microlens 860. The height of the top conductive structure 850 is in the range of 0.2 μm to 5.0 μm. In other embodiments of the invention, the upper end of the top conductive structure 850 may be higher than the bottom of the microlens 860.

[0139] Those skilled in the art should understand that the shape, size, and connection method of the top conductive structure 850 are not limited to... Figures 8A-8BThe embodiments shown are applicable, and modifications can be made according to actual requirements, such as adjusting the shape and size of the top conductive structure 850, and all such modifications fall within the scope of protection of this invention.

[0140] In some embodiments, such as Figures 8A-8B As shown, a reflective layer 851 is provided on the sidewall of the top conductive structure 850. In some embodiments, the top conductive structure 850 substantially surrounds four LED structures 820, such that light emitted from the LED structures 820 toward the top conductive structure 850 is reflected by the reflective layer 851 and emitted onto the top surface of a single LED pixel.

[0141] The reflective layer 851 is similar to the reflective layer 551 described above, so it will not be described again.

[0142] Those skilled in the art should understand that Figure 8A and Figure 8B The embodiments shown are merely exemplary, and a top conductive structure mesh can surround more or fewer LED structures. For example, a top conductive structure mesh can surround two, three, five, six, seven, eight, or more LED structures.

[0143] In some embodiments of the present invention, multiple LED pixels can form an array. For example, Figure 9A A top view schematic diagram of a monochromatic micro-LED pixel array with high reflectivity is shown according to an embodiment of the present invention. Figure 9B An embodiment of the present invention is shown. Figure 9A The diagram shows a schematic cross-sectional view of a monochrome micro-LED pixel along line AA.

[0144] like Figure 9A and 9B As shown, a top conductive structure mesh can surround four LED pixels.

[0145] Those skilled in the art will understand that a monochrome micro-LED pixel according to embodiments of the present invention can comprise any number of LED structures having the same or different colors. For example, a monochrome micro-LED pixel can comprise four, five, or six LED structures.

[0146] Each microLED chip has a size not exceeding 1 centimeter (cm), and preferably not exceeding 20 micrometers (μm). The microLED structures are formed in an array within the microLED chips, with resolutions of 720*480, 640*480, 1920*1080, 1280*720, 2k, or 4k. The diameter of the microLED structures is in the nanometer range, for example, from 20nm to 100nm.

[0147] The microLED chip includes an integrated circuit (IC) backplane and a microLED array. The microLED array includes multiple microLEDs. Each microLED can form at least a portion of a pixel element on the microLED chip.

[0148] In some embodiments, the IC backplane can be electrically connected to each microLED of the microLED array via separate metal interconnects. In some embodiments, each microLED can be electrically controlled individually by the IC backplane. In some embodiments, the IC backplane can be electrically connected to the electrodes of the microLED chip via metal interconnects. In some embodiments, a dielectric layer can be formed in the gaps between the microLEDs. In some embodiments, the dielectric layer can also be formed in the gaps between interconnects.

[0149] In some embodiments, each microLED in the microLED array may include a micromesa structure. In some embodiments, the micromesa structure may include, from bottom to top, a first type epitaxial layer, a light-emitting layer, and a second type epitaxial layer. That is, of the three layers, the first type epitaxial layer is closest to the IC backplane; the light-emitting layer is located on top of the first type epitaxial layer and further away from the IC backplane; the second type epitaxial layer is located on top of the light-emitting layer and farthest from the IC backplane. In some embodiments, the light-emitting layer is formed by a plurality of stacked quantum well layers, particularly supercrystalline stacked quantum well layers. Preferably, the supercrystalline stacked quantum well layers include multiple pairs of quantum blocking layers stacked with quantum well layers. In some embodiments, the first type epitaxial layer is a semiconductor material having a first conductivity type and includes a plurality of semiconductor layers. The main material of the first type epitaxial layer may be, but is not limited to, Ga, N, As, P, In, Al, and other base materials. Furthermore, the first type epitaxial layer may include, from top to bottom, a waveguide layer, a confinement layer, a transition layer, and a window layer; in addition, an ohmic contact layer may be formed below the window layer. In some embodiments, the second type epitaxial layer is a semiconductor material having a second conductivity type and includes a plurality of semiconductor layers. The host material of the second type of epitaxial layer may be, but is not limited to, base materials such as Ga, N, As, P, In, or Al. Furthermore, the first type of epitaxial layer may consist of, from top to bottom, a confinement layer and a waveguide layer; additionally, in some embodiments, an ohmic contact layer may be, but is not limited to, formed on the confinement layer.

[0150] In some embodiments, a top conductive layer may be formed on the top surface of the microLED array. In some embodiments, the top conductive layer may be shared by all microLEDs in the microLED array. In some embodiments, the light-emitting layer may include at least one quantum well layer. In some embodiments, the microLED array may include a single-layer microLED structure. In some embodiments, the microLED array may include a vertically stacked multilayer microLED structure.

[0151] In some embodiments, the micro-LED array may include blue micro-LEDs. In some embodiments, the spacing of the micro-LED array, i.e. the minimum center-to-center distance between micro-LEDs, may be in the range of about 2 μm to about 50 μm. In some embodiments, the number of pixels in the micro-LED chip may be in the range of several thousand to more than several million.

[0152] While the detailed description contains numerous details, these should not be construed as limiting the scope of the invention but merely as illustrating different examples and aspects of it. It should be understood that the scope of the invention includes other embodiments not discussed in detail above. For example, the methods described above can be applied to the integration of functional devices other than LEDs and OLEDs with control circuitry other than pixel drivers. Examples of non-LED devices include vertical-cavity surface-emitting lasers (VCSELs), photodetectors, microelectromechanical systems (MEMS), silicon photonics devices, power electronics, and distributed feedback lasers (DFBs). Examples of other control circuitry include current drivers, voltage drivers, transimpedance amplifiers, and logic circuits.

[0153] The foregoing description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the embodiments described herein and variations thereof. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit or scope of the subject matter disclosed herein. Therefore, this disclosure is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.

[0154] The features of this invention can be implemented, used, or with the aid of a computer program product, such as a storage medium (media) or a computer-readable storage medium (media) on which / therein instructions are stored, said storage medium being usable for programming a processing system to perform any of the features presented herein, said storage medium may include, but is not limited to, high-speed operating memory, such as DRAM, SRAM, DDRRAM, or other random access solid-state storage devices, and may include non-volatile memory, such as one or more disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid-state storage devices. The memory may optionally include one or more storage devices located remotely from the CPU(one or more). Non-volatile storage devices within the memory, or alternatively within the memory, include non-transitory computer-readable storage media.

[0155] The features of the invention can be stored on any machine-readable medium (media) and can be incorporated into software and / or firmware for controlling the hardware of a processing system, and for enabling the processing system to interact with other mechanisms using the results of the invention. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0156] Understandably, although the terms "first," "second," etc., may be used in this document to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0157] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the claims. As used in the description of the embodiments and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It will also be understood that the term “and / or” as used herein refers to and covers any and all possible combinations of one or more of the associated listed items. It will be further understood that the term “comprising,” when used in this specification, specifies the presence of the stated feature, integer, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0158] As used herein, the term "if" can be interpreted as meaning "when" or "in response to determination" or "according to determination" or "in response to detection" the conditional precedent is true, depending on the context. Similarly, the phrase "if determination [the conditional precedent is true]" or "if [the conditional precedent is true]" or "when [the conditional precedent is true]" can be interpreted as meaning "in determination" or "in response to determination" or "according to determination" or "in response to detection" the conditional precedent is true, depending on the context.

[0159] For ease of explanation, the above description is illustrated in conjunction with specific embodiments. However, the above illustrative discussion is not intended to be exhaustive, nor is it intended to limit the claims to the precise forms disclosed. Many modifications and variations can be made based on the above teachings. These embodiments were chosen and described in order to best explain the operating principles and practical applications, thereby enabling others skilled in the art to understand them.

Claims

1. A monochromatic micro-LED pixel, comprising: an LED structure emitting light of a first color, wherein the LED structure is formed on a substrate; and a top conductive structure located above the LED structure and surrounding a periphery of a light emitting area of the LED structure, wherein a first reflective layer is disposed on sidewalls of the top conductive structure. The LED structure comprises a lower conductive layer, an extension layer, and a micro-mesa structure between the lower conductive layer and the extension layer.

2. The monochrome micro-LED pixel of claim 1, wherein, The micro-mesa structure has an inverted-trapezoidal cross-sectional shape, and comprises a first-type epitaxial layer, a multi-quantum well layer, and a second-type epitaxial layer, the multi-quantum well layer being between the first-type epitaxial layer and the second-type epitaxial layer.

3. The monochrome micro-LED pixel of claim 2, wherein, The LED structure comprises a passivation layer for electrically isolating the lower conductive layer from the first-type epitaxial layer, the multi-quantum well layer, and the second-type epitaxial layer.

4. The monochrome micro-LED pixel of claim 3, wherein, The passivation layer covers a bottom surface of the first-type epitaxial layer, side surfaces of the first-type epitaxial layer, the multi-quantum well layer, and the second-type epitaxial layer, and a top surface of an insulating medium between adjacent micro-mesa structures, 5. The monochrome micro-LED pixel of claim 4, wherein, wherein an opening is formed in the passivation layer on the bottom surface of the first-type epitaxial layer, and the lower conductive layer is formed at the opening. The LED structure comprises a second reflective layer formed on a surface of the passivation layer and the lower conductive layer away from the micro-mesa structure.

6. The monochrome micro-LED pixel of claim 4, wherein, Further comprising a gap between the reflective layers of adjacent micro-mesa structures.

7. The monochrome micro-LED pixel of claim 6, wherein, The first reflective layer and / or the second reflective layer comprises one or more of a metal layer, a DBR layer, and a multi-layer omnidirectional reflector (ODR).

8. The monochrome micro-LED pixel of claim 6, wherein, The DBR layer is a conductive DBR or a dielectric DBR.

9. The monochrome micro-LED pixel of claim 8, wherein, The first reflective layer and / or the second reflective layer is one or more reflective coatings.

10. The monochrome micro-LED pixel of claim 6, wherein, The top conductive structure is connected to the extension layer of the LED structure.

11. The monochrome micro-LED pixel of claim 2, wherein, A lower end of the conductive structure is located on the extension layer of the LED structure.

12. The monochrome micro-LED pixel of claim 2, wherein, The top conductive structure is a mesh electrode.

13. The monochrome micro-LED pixel of claim 1, wherein, The mesh frame of the mesh electrode is a conductive part serving as an electrode, the hollow area between the mesh frames is a light-transmitting part, and the LED structure is located below the hollow area. The height of the top conductive structure is in a range of 0.2 μm to 5.0 μm.

14. The monochrome micro-LED pixel of claim 1, wherein, The material of the top conductive structure comprises ITO, FTO, Al, Au, Ag, Cr, Ti, Pt, and Cu.

15. The monochrome micro-LED pixel of claim 1, wherein, Further comprising a microlens above the LED structure.

16. The monochrome micro-LED pixel of claim 1, wherein, An upper end of the top conductive structure reaches a bottom of the microlens; or 17. The monochrome micro-LED pixel of claim 10, wherein, The upper end of the top conductive structure is higher than the bottom of the microlens. The LED structure emits red light, green light, or blue light.

18. The monochrome micro-LED pixel of claim 1, wherein, The LED structure is embedded in an insulating dielectric medium.

19. The monochrome micro-LED pixel of claim 1, wherein, The shape of a horizontal cross-section of the LED structure comprises a circle, a square, a rectangle, and a hexagon, and the shape of the horizontal cross-section of the first reflective layer is similar to or different from the shape of the LED structure.

20. The monochrome micro-LED pixel of claim 1, wherein, The shape of the horizontal cross-section of the LED structure is a circle; and 21. The monochrome micro-LED pixel of claim 1, wherein, The shape of the horizontal cross-section of the first reflective layer is an annular shape surrounding the LED structure or a rectangular annular shape surrounding the LED structure.

22. A monochromatic micro-LED structure, comprising: a plurality of LED structures emitting light of a first color, wherein the plurality of LED structures are formed on a substrate; and ​ A top conductive structure is located above the plurality of LED structures and surrounds a periphery of a light emitting area of the plurality of LED structures, and a first reflective layer is disposed on sidewalls of the top conductive structure.

23. The monochrome micro-LED structure of claim 21, wherein, The top conductive structure is a mesh electrode, wherein a mesh frame of the mesh electrode is a conductive part serving as an electrode, a hollow area between the mesh frames is a light-transmitting part, and the plurality of LED structures are located below the hollow area.

24. A monochromatic micro-LED pixel array comprising a plurality of monochromatic micro-LED pixels according to any one of claims 1-22.

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