Systems and methods for multi-color LED pixel units

Abstract

A micro multi-color LED device includes two or more LED structures for emitting a series of color lights. The two or more LED structures are vertically stacked to mix the lights emitted by the two or more LED structures vertically and / or horizontally and reflect them upward via some reflective structures. In some embodiments, each LED structure is connected to a pixel driver and / or a common electrode. The LED structures are bonded together by a bonding layer. In some embodiments, a planarization layer encloses each LED structure or the micro multi-color LED device. In some embodiments, one or more of a reflective layer, a refractive layer, a microlens, a spacer, and a reflector cup structure are implemented in the device to improve the LED light-emitting efficiency. A display panel including an array of micro tri-color LED devices has high resolution and high illumination brightness.

Description

[0001] Cross - reference to Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 863,559, filed on June 19, 2019, titled "Systems and Methods for Coaxial Multi - Color LED"; U.S. Provisional Patent Application No. 63 / 013,358, filed on April 21, 2020, titled "Light - Emitting Diode Chip Structures with Reflective Elements"; U.S. Provisional Patent Application No. 63 / 013,370, filed on April 21, 2020, titled "Light - Emitting Diode Chip Structures with Reflective Elements"; U.S. Provisional Patent Application No. 63 / 034,391, filed on June 3, 2020, titled "Systems and Methods for Multi - Color LED Pixel Unit with Vertical Light Emission"; and U.S. Provisional Patent Application No. 63 / 034,394, filed on June 3, 2020, titled "Systems and Methods for Multi - Color LED Pixel Unit with Horizontal Light Emission", each of which is incorporated herein by reference. Technical Field

[0003] The present disclosure generally relates to light - emitting diode (LED) display devices, and more particularly, to systems and manufacturing methods for LED semiconductor devices that emit different - colored light with high brightness and micron - scale pixel sizes. Background Art

[0004] With the development of mini-LED and micro-LED technologies in recent years, consumer devices and applications such as augmented reality (AR), virtual reality (VR), projection, head-up displays (HUDs), mobile device displays, wearable device displays, and in-vehicle displays require LED panels with improved resolution and brightness. For example, an AR display integrated within goggles and positioned close to the wearer's eyes can have a size as small as a fingernail while still requiring a clarity of HD (1280x720 pixels) or higher. Many electronic devices require a certain pixel size, a certain distance between adjacent pixels, a certain brightness, and a certain viewing angle of the LED panel. Generally, it is challenging to maintain both resolution and brightness requirements while attempting to achieve the maximum resolution and brightness on a small display. Conversely, in some cases, it is difficult to balance pixel size and brightness simultaneously because they have a roughly inverse relationship. For example, achieving high brightness per pixel results in low resolution. Or, achieving high resolution causes the brightness to decrease.

[0005] Generally, at least red, green, and blue are superimposed to reproduce a wide range of colors. In some cases, to include at least red, green, and blue within a pixel area, separate monochromatic LEDs are fabricated on different non-overlapping areas within the pixel area. The prior art faces the challenge of increasing the effective illumination area within each pixel when the distance between adjacent LEDs is determined. On the other hand, when the illumination area of a single LED is determined, it is a difficult task to further improve the overall resolution of the LED panel because LEDs of different colors must occupy their designated areas within a single pixel.

[0006] The combination of active matrix liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays with thin-film transistor (TFT) technology has become increasingly popular in today's commercial electronic devices. These displays are widely used in personal laptops, smartphones, and personal digital assistants. Millions of pixels together create an image on the display. The TFTs act as switches to individually turn each pixel on and off, making the pixel either bright or dark, allowing for convenient and efficient control of each pixel and the entire display.

[0007] However, traditional LCD displays have the disadvantage of low light efficiency, resulting in high power consumption and limited battery runtime. While active matrix organic light-emitting diode (AMOLED) display panels generally consume less power than LCD panels, AMOLED display panels are still the main power-consuming devices in battery-powered devices. To extend battery life, it is necessary to reduce the power consumption of the display panel.

[0008] Traditional inorganic semiconductor light-emitting diodes (LEDs) have shown excellent optical efficiency, which makes active matrix LED displays more desirable for battery-powered devices. A drive circuit and a light-emitting diode (LED) array are used to control millions of pixels to present an image on the display. Both monochromatic display panels and full-color display panels can be produced according to various manufacturing methods.

[0009] However, the integration of thousands or even millions of micro-LEDs with a pixel drive circuit array is challenging. Various manufacturing methods have been proposed. In one method, the control circuit is fabricated on one substrate and the LEDs are fabricated on a separate substrate. The LEDs are transferred to an intermediate substrate and the original substrate is removed. Then, the LEDs on the intermediate substrate are picked up and one or several are sequentially placed on the substrate with the control circuit. However, this manufacturing process is inefficient, expensive, and unreliable. In addition, there are no off-the-shelf production tools for large-scale transfer of micro-LEDs. Therefore, new tools must be developed.

[0010] In another method, the entire LED array with the original substrate is aligned with the control circuit and bonded to the control circuit using metal bonding. The substrate with the LEDs remains in the final product, which may cause optical crosstalk. Additionally, the thermal mismatch between the two different substrates generates stress at the bonding interface, which may lead to reliability issues. Moreover, compared with monochromatic display panels, multi-color display panels generally require more LEDs and the growth of different color LEDs on different substrate materials, making the traditional production process more complex and inefficient.

[0011] Display technologies are becoming increasingly popular in today's commercial electronic devices. These display panels are widely used in fixed large screens such as liquid crystal display televisions (LCD TVs) and organic light-emitting diode televisions (OLED TVs) and in portable electronic devices such as personal laptops, smartphones, tablets, and wearable electronic devices. The development direction of fixed large screen technology is to achieve a large viewing angle so as to adapt and enable multiple viewers to see the screen from various angles. For example, various liquid crystal materials such as super twisted nematic (STN) and film compensated super twisted nematic (FSTN) have been developed to achieve a large viewing angle for all pixel light sources in the display panel.

[0012] However, most portable electronic devices are designed mainly for a single user, and the screen orientation of these portable devices should be adjusted to the best viewing angle for the corresponding user rather than adapting to the large viewing angle of multiple viewers. For example, the appropriate viewing angle for the user can be perpendicular to the screen surface. In this case, compared with fixed large screens, most of the light emitted at a large viewing angle is wasted. Additionally, a large viewing angle raises privacy issues for the use of portable electronic devices in public areas.

[0013] In addition, in a conventional projection system based on a passive imaging device such as a liquid crystal display (LCD), a digital micromirror device (DMD), and a liquid crystal on silicon (LCOS), the passive imaging device itself does not emit light. Specifically, parallel light emitted from a light source is optically modulated, for example, a part of the light is emitted at a pixel level by an LCD panel or reflected at a pixel level by a DMD panel, and the conventional projection system projects an image. However, the part of the light that is not emitted or reflected is lost, which reduces the efficiency of the projection system. In addition, in order to provide parallel light, complex illumination optical components are required to collect the divergent light emitted by the light source. The illumination optical components not only make the system bulky but also introduce additional light loss into the system, which further affects the performance of the system. In a conventional projection system, usually less than 10% of the illumination light generated by the light source is used to form a projection image.

[0014] Light-emitting diodes (LEDs) made of semiconductor materials can be used in monochromatic or full-color displays. In a current display using LEDs, the LEDs are usually used as a light source to provide light that is optically modulated by, for example, an LCD or DMD panel. That is, the light emitted by the LEDs does not form an image by itself. Research has also been conducted on LED displays with an LED panel including a plurality of LED dies as an imaging device. In such an LED display, the LED panel is a self-emitting imaging device, where each pixel may include one LED die (monochromatic display) or multiple LED dies, each die representing a primary color (full-color display).

[0015] However, the light emitted by the LED dies is generated from spontaneous emission and is thus non-directional, resulting in a large divergence angle. The large divergence angle can cause various problems in a micro-LED display. On the one hand, due to the large divergence angle, only a small part of the light emitted by the micro-LEDs 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, causing light crosstalk between pixels, loss of clarity, and loss of contrast. Conventional solutions for reducing the large divergence angle may not effectively handle the overall light emitted by the micro-LEDs and will only utilize the central part of the light emitted by the micro-LEDs, leaving the rest of the light emitted at a more oblique angle unutilized.

[0016] In summary, there is a need to provide an LED structure for a display panel to address the above-mentioned drawbacks and other deficiencies, in particular. Summary of the Invention

[0017] There is a need to improve the design of multi - color LEDs, which improvement helps to solve the drawbacks such as those described above of conventional display systems. In particular, there is a need for an LED device structure that can simultaneously increase brightness and resolution while effectively maintaining low power consumption. Also needed is a display panel that reduces the viewing angle to better protect user privacy, and / or reduces light waste to lower power consumption, and reduces light interference between pixels to provide a better image.

[0018] The multi - color LED device described herein integrates at least three micro - LED structures, which three micro - LED structures are arranged in different layers to form a vertically stacked device structure, and separate electrodes are used to receive control currents. By arranging at least three LED structures along the same axis as disclosed herein, the system effectively improves the light illumination efficiency within a single pixel area and simultaneously increases the resolution of the LED panel.

[0019] Pitch refers to the distance between the centers of adjacent pixels on a display panel. In some embodiments, the pitch can vary from about 40 microns to about 20 microns, to about 10 microns, and / or preferably to about 5 microns or less. Many efforts have been made to reduce the pitch. When the pitch size is determined, the area of a single pixel is fixed.

[0020] The multi - color coaxial LED system described herein enables light of different colors to be mixed and emitted from a single pixel area without using additional area to accommodate LED structures of different colors. Thus, the occupied area of a single pixel is significantly reduced and the resolution of the micro - LED panel can be increased. At the same time, the concentration of different - colored light at the boundary of a single micro - LED device greatly increases the brightness within a single pixel area.

[0021] Compared to conventional manufacturing processes for micro - LED display chips that rely on inefficient pick - and - place processes or unreliable multi - substrate methods, the multi - color micro - LED manufacturing process disclosed herein effectively improves the efficiency and reliability of micro - LED device manufacturing. For example, the LED structures can be directly bonded to a substrate having pixel drivers without introducing an intermediate substrate, which simplifies the manufacturing steps and thus improves the reliability and performance of the LED chips. Additionally, no substrate for the micro - LED structures remains in the final multi - color device, so crosstalk and mismatch can be reduced. Additionally, planarization is applied to each LED structure within the multi - color micro - LED or to the entire multi - color micro - LED, allowing different LED structures and / or other layers to be directly bonded or formed together within the planarized layer with less disruption to existing structures.

[0022] The multicolor micro-LED devices described herein may include vertical emission and horizontal emission or any combination thereof, where vertical emission is, for example, light from individual stacked LED structures being emitted substantially vertically with respect to the surface of the substrate, and horizontal emission is, for example, light from individual stacked LED structures being emitted horizontally with respect to the surface of the substrate and then being reflected substantially vertically by some reflective structures. Since the vertically emitted light needs to pass through all the different layers within the multicolor micro-LED device, improved light propagation and light reflection for each layer are achieved. Compared with vertical emission, the light horizontally emitted from individual stacked LED structures does not need to pass through all the layers above a specific structure. Therefore, horizontal emission can have better light propagation efficiency and produce better light saliency.

[0023] Various embodiments include a display panel integrated with a microlens array. The display panel generally includes an array of pixel light sources (e.g., LEDs, OLEDs) electrically coupled to corresponding pixel driving circuits (e.g., FETs). The microlens array is aligned with the pixel light sources and reduces the divergence of the light generated by the pixel light sources. The display panel may also include integrated optical spacers to maintain the gap between the microlens and the pixel driving circuit.

[0024] The microlens array reduces the divergence angle of the light generated by the pixel light sources and the available viewing angle of the display panel. This in turn reduces power waste, increases brightness, and / or better protects user privacy in the common area.

[0025] A display panel integrated with a microlens array can be fabricated using various production methods, resulting in a wide variety of device designs. In one aspect, the microlens array is directly fabricated as a protrusion or mesa of a substrate with pixel light sources. In some aspects, techniques such as self-assembly, high-temperature reflow, gray-scale mask lithography, molding / imprinting / stamping, and dry etching pattern transfer can be used to fabricate the microlens array.

[0026] Other aspects include components, devices, systems, improvements, methods and processes including production methods, applications, and other technologies related to any of the above aspects.

[0027] Some exemplary embodiments include a reflector cup disposed on a semiconductor substrate and surrounding a light-emitting region, which is, for example, a region where light is emitted from a multi-color micro-LED device. The reflector cup can reduce the divergence of light emitted from the light-emitting region and suppress light crosstalk between adjacent pixel units. For example, the reflector cup can utilize light at an inclined angle, which is more efficient in collecting and converging the light, to achieve a display with higher brightness and higher power efficiency than conventional solutions. Additionally, the reflector cup can block the light emitted by the micro-LEDs in adjacent pixel units, which can effectively suppress the light crosstalk between pixels and improve the color contrast and clarity. The exemplary embodiments of the present disclosure can increase the projection brightness and contrast, and thus reduce the power consumption in projection applications. The exemplary embodiments of the present disclosure also improve the directivity of the light emission of the display, and thus provide better image quality for users and protect the privacy of users in direct-view applications. The exemplary embodiments of the present disclosure can provide multiple advantages. One advantage is that the exemplary embodiments of the present disclosure can suppress the light crosstalk between pixels and increase the brightness. The exemplary embodiments of the present disclosure can suppress the light crosstalk between pixels at a smaller pitch while increasing the brightness within a single pixel in a power-efficient manner.

[0028] In some exemplary embodiments, a single-pixel multi-color LED device can include one or more top electrodes integrated with the reflector cup. The top electrodes can be electrically connected to a top electrode layer. The top electrodes integrated with the reflector cup can make the structure of the single-pixel multi-color LED device more compact and simplify the manufacturing process. By adopting the top electrodes, the reflector cup can be used as a common P electrode or N electrode of the single-pixel multi-color LED device, and thus can provide a compact structure for the single-pixel multi-color LED device.

[0029] In some exemplary embodiments, in addition to the reflector cup, the micro-LED pixel unit may further include a microlens. The microlens may be aligned with the light-emitting region and reduce the divergence of the light emitted by the light source, reducing the available viewing angle of the single-pixel multi-color LED device. For example, the microlens may be coaxially aligned with the light-emitting region and be positioned on the light-emitting region and on top of the reflector cup. A portion of the light emitted by the light-emitting region may directly reach the microlens and pass through the microlens; another portion may reach the reflector cup and be reflected by the reflector cup, and then reach the microlens and pass through the microlens. Thus, the divergence of the light can be reduced, and the available viewing angle can be reduced to such an extent that a display and a panel using the single-pixel multi-color LED device can be seen by a user perpendicular to the surface of the display and the panel. In turn, power waste can be reduced and the brightness can be increased and / or better protect user privacy in a common area. In another example, the microlens may be coaxially aligned with the light-emitting region, be located on the light-emitting region and be surrounded by the reflector cup. A portion of the light emitted by the light-emitting region can directly reach the microlens and pass through the microlens; another portion of the light may reach the reflector cup and be reflected by the reflector cup, and then reach the microlens and pass through the microlens; the remaining light may reach the reflector cup and be reflected by the reflector cup without passing through the microlens. Thus, the divergence can be reduced, and the available viewing angle can be reduced to such an extent that a display and a panel using the single-pixel multi-color LED device can be seen by several users. This can also reduce power waste, increase the brightness and / or properly protect user privacy in a common area.

[0030] In some exemplary embodiments, the single-pixel multi-color LED device may further include a spacer. The spacer may be an optically transparent layer formed to provide a proper spacing between the microlens and the light-emitting region. For example, in the case where the microlens is disposed above the reflector cup, the spacer may be disposed between the microlens and the top of the reflector cup. Thus, the light emitted by the light-emitting region can pass through the spacer and then through the microlens. The spacer may also fill the region surrounded by the reflector cup to increase the refractive index of the medium surrounding the light-emitting region. Thus, the spacer can change the optical path of the light emitted by the light-emitting region. By adopting the microlens, the light extraction efficiency of the single-pixel multi-color LED device can be improved to further increase the brightness of, for example, a micro-LED display panel.

[0031] In some exemplary embodiments, a single-pixel multi-color LED device may include a stepped reflector cup. The stepped reflector cup may include a cavity surrounding a light-emitting region. The cavity may be formed by a plurality of inclined surfaces surrounding the light-emitting region. Sub-cavities may be formed by the plurality of inclined surfaces and may have different dimensions in a horizontal direction. The stepped reflector cup may be disposed on a semiconductor substrate. The stepped reflector cup may reduce the divergence of light emitted from the light-emitting region and suppress light crosstalk between adjacent pixel units. For example, the stepped reflector cup may utilize light at an inclined angle by reflecting the light in different reflection directions. In addition, the stepped reflector cup may block light emitted from the micro-LEDs in adjacent pixel units, which may effectively suppress inter-pixel light crosstalk and improve color contrast and sharpness. Exemplary embodiments of the present disclosure may increase projection brightness and contrast and thus reduce power consumption in projection applications. Exemplary embodiments of the present disclosure may also improve the directivity of light emission of the display and thus provide users with better image quality and protect user privacy in direct-view applications.

[0032] The multi-color micro-LED devices described herein may simultaneously increase brightness and resolution and are suitable for current display panels, particularly for high-definition AR devices and virtual reality (VR) glasses.

[0033] Some exemplary embodiments provide a multi-color micro-light-emitting diode (LED) pixel unit for a display panel, including: a first-color LED structure formed on an IC substrate, wherein the first-color LED structure includes a first light-emitting layer, and a first reflective structure is formed at the bottom of the first light-emitting layer; a first dielectric bonding layer having a planar top surface and covering the first-color LED structure; a second-color LED structure formed on the planar top surface of the first dielectric bonding layer, wherein the second-color LED structure includes a second light-emitting layer, and a second reflective structure is formed on the bottom of the second light-emitting layer; a second dielectric bonding layer having a planar top surface and covering the second-color LED structure; a top electrode layer covering the micro-LED pixel unit and being in electrical contact with the first-color LED structure and the second-color LED structure; and an IC substrate electrically connected to the first-color LED structure and the second LED structure.

[0034] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a first-color LED structure formed on an IC substrate, wherein the first-color LED structure includes a first light-emitting layer, and a first reflective structure is formed on the bottom of the first light-emitting layer; a first dielectric bonding layer having a planar top surface and covering the first-color LED structure; a second-color LED structure formed on the planar top surface of the first dielectric bonding layer, wherein the second-color LED structure includes a second light-emitting layer, and a second reflective structure is formed on the bottom of the second light-emitting layer; a second dielectric bonding layer having a planar top surface and covering the second-color LED structure; a third-color LED structure formed on the top surface of the second dielectric bonding layer, wherein the third-color LED structure includes a third light-emitting layer, and a third reflective structure is formed on the bottom of the third light-emitting layer; a third dielectric bonding layer having a planar top surface and covering the third-color LED structure; a top electrode layer covering the micro-LED pixel unit and being in electrical contact with the first-color LED structure, the second-color LED structure, and the third-color LED structure; and an IC substrate electrically connected to the first-color LED structure, the second-color LED structure, and the third-color LED structure.

[0035] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first dielectric bonding layer is transparent, and the second dielectric bonding layer is transparent.

[0036] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first reflective structure includes at least one first high-reflectivity layer, the second reflective structure includes at least one second high-reflectivity layer, and the third reflective structure includes at least one third high-reflectivity layer; the reflectivity of the first high-reflectivity layer, the second high-reflectivity layer, or the third high-reflectivity layer is higher than 60%.

[0037] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the material of the first high-reflectivity layer, the second high-reflectivity layer, or the third high-reflectivity layer is one or more metals selected from Rh, Al, Ag, and Au.

[0038] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first reflective structure includes at least two first high-reflectivity layers having different refractive indices; the second reflective structure includes at least two second high-reflectivity layers having different refractive indices; and the third reflective structure includes at least two third high-reflectivity layers having different refractive indices.

[0039] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first reflective structure further includes a first transparent layer on the first high-reflectivity layer; the second reflective structure further includes a second transparent layer on the second high-reflectivity layer; and, the third reflective structure further includes a second transparent layer on the third high-reflectivity layer.

[0040] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first transparent layer is selected from one or more of ITO and SiO2; the second transparent layer is selected from one or more of ITO and SiO2; and, the third transparent layer is selected from one or more of ITO and SiO2.

[0041] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first-color LED structure further includes a first bottom electrode conductive contact layer, the second-color LED structure further includes a second bottom electrode conductive contact layer, and the third-color LED structure further includes a third bottom electrode conductive contact layer; the first bottom electrode conductive contact layer is electrically connected to the IC substrate through a first contact via at the bottom of the first bottom electrode conductive contact layer; the second bottom electrode conductive contact layer is electrically connected to the IC substrate through a second contact via passing through the first dielectric bonding layer; and, the third bottom electrode conductive contact layer is electrically connected to the IC substrate through a third contact via passing through the second dielectric layer and the first dielectric bonding layer.

[0042] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first bottom electrode conductive contact layer is transparent, the second bottom electrode conductive contact layer is transparent, and the third bottom electrode conductive contact layer is transparent.

[0043] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a first extension portion extends from one side of the first light-emitting layer; a second extension portion extends from one side of the second light-emitting layer; a third extension portion extends from one side of the second light-emitting layer; and, a top contact via passes through the second dielectric bonding layer and the third dielectric bonding layer to connect the first extension portion, the second extension portion, and the third extension portion to the top electrode layer.

[0044] Some exemplary embodiments provide a micro-LED pixel unit, at least including: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate; and, a reflective optical isolation structure formed around the light-emitting region, wherein the top of the reflective optical isolation structure is higher than the top of the light-emitting region.

[0045] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a microlens is located above the top of the light-emitting region.

[0046] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the top of the reflective optical isolation structure is higher than the top of the microlens.

[0047] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the reflective optical isolation structure has a top opening, and the lateral area of the microlens is smaller than the lateral area of the top opening.

[0048] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the lateral dimension of the microlens is greater than the effective light-emitting area of the first color LED structure; the lateral dimension of the microlens is greater than the effective light-emitting area of the second color LED structure; and the lateral dimension of the microlens is greater than the effective light-emitting area of the third color LED structure.

[0049] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the lateral dimensions of the first color LED structure, the second color LED structure, and the third color LED structure are the same.

[0050] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first LED structure, the second LED structure, and the third LED structure have the same central axis.

[0051] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first dielectric bonding layer is transparent, the second dielectric bonding layer is transparent, and the third dielectric bonding layer is transparent.

[0052] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the thickness of the first reflective structure is 5 nm to 10 nm; the thickness of the second reflective structure is 5 nm to 10 nm; the thickness of the third reflective structure is 5 nm to 10 nm; the thickness of the first LED structure does not exceed 300 nm; the thickness of the second LED structure does not exceed 300 nm; and the thickness of the third LED structure does not exceed 300 nm.

[0053] Some exemplary embodiments provide a multi-color micro-LED pixel unit for a display panel, comprising: a first LED structure formed on an IC substrate and emitting a first color light; a first transparent dielectric bonding layer having a first planar top surface and covering the first LED structure; a second LED structure formed on the first planar top surface of the first transparent dielectric bonding layer and emitting a second color light; a second transparent dielectric bonding layer having a second planar top surface and covering the second LED structure; and a top electrode layer covering the multi-color micro-LED pixel unit and being in electrical contact with the first LED structure and the second LED structure; wherein the IC substrate is electrically connected to the first LED structure and the second LED structure.

[0054] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a first-color LED structure formed on an IC substrate; a first transparent dielectric bonding layer having a planar top surface and covering the first-color LED structure; a second-color LED structure formed on the planar top surface of the first transparent dielectric bonding layer; a second transparent dielectric bonding layer having a planar top surface and covering the second-color LED structure; a third-color LED structure formed on the planar top surface of the second transparent dielectric bonding layer; a third dielectric bonding layer having a planar top surface and covering the third-color LED structure; a top electrode layer covering the micro-LED pixel unit and being in electrical contact with the first-color LED structure, the second-color LED structure, and the third-color LED structure; and an IC substrate electrically connected to the first-color LED structure, the second LED structure, and the third LED structure.

[0055] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a first reflective structure is formed at the bottom of the first-color LED structure; a second reflective structure is formed at the bottom of the second-color LED structure; and a third reflective structure is formed at the bottom of the third-color LED structure.

[0056] Some exemplary embodiments provide a micro-LED pixel unit, comprising: an IC substrate; a light-emitting region formed on the IC substrate and including at least one LED structure and at least one dielectric bonding layer, wherein each dielectric bonding layer has a planar top surface covering the surface of each LED structure; a top electrode layer covering the micro-LED pixel unit and being in electrical contact with each color LED structure, wherein the IC substrate is electrically connected to each color LED structure; and a stepped light-reflecting cup structure having a cavity and surrounding the light-emitting region.

[0057] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate; a reflective optical isolation structure formed around the light-emitting region; and a refraction structure formed between the reflective optical isolation structure and the light-emitting region.

[0058] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate, the light-emitting region including at least one LED structure and at least one transparent dielectric bonding layer, wherein each transparent dielectric bonding layer has a planar top surface covering the surface of each LED structure; a top electrode layer covering the micro-LED pixel unit and in electrical contact with each color LED structure, wherein the IC substrate is electrically connected to each color LED structure; a stepped reflector cup structure formed around the light-emitting region; and a refractive structure formed between the stepped reflector cup structure and the light-emitting region.

[0059] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the reflector cup structure has a top opening, and the lateral area of the microlens is smaller than the lateral area of the top opening.

[0060] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate; a floating reflective optical isolation structure surrounding the light-emitting region, wherein the floating reflective optical isolation structure is positioned at a certain distance above the semiconductor substrate.

[0061] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate; a reflective optical isolation structure surrounding the light-emitting region; a top electrode layer covering the light-emitting region and electrically connected to the reflective optical isolation structure, wherein the top electrode layer is in electrical contact with the reflective optical isolation structure.

[0062] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the edge of the top electrode layer touches the reflective optical isolation structure.

[0063] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the light-emitting region includes: at least one LED structure and at least one dielectric bonding layer; a top electrode layer covering the micro-LED pixel unit and in electrical contact with each color LED structure, wherein the semiconductor substrate is electrically connected to each color LED structure.

[0064] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the reflective optical isolation structure is a floating reflective structure.

[0065] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the reflective optical isolation structure is a stepped reflector cup structure.

[0066] Some exemplary embodiments provide a micro-LED pixel unit, comprising at least: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate; a floating reflective optical isolation structure surrounding the light-emitting region, wherein the floating reflective optical isolation structure is located at a certain distance above the semiconductor substrate; and a top electrode layer formed on top of the light-emitting region, wherein the top electrode layer is in contact with the floating reflective optical isolation structure.

[0067] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the light-emitting region includes at least one LED structure and a bonding layer located at the bottom of each LED structure.

[0068] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first-color LED structure further includes a first bottom electrode conductive contact layer, and the second-color LED structure further includes a second bottom electrode conductive contact layer; the first bottom electrode conductive contact layer is electrically connected to the IC substrate through a first contact via located at the bottom of the first bottom electrode conductive contact layer; the second bottom electrode conductive contact layer is electrically connected to the IC substrate through a second contact via passing through the first dielectric bonding layer.

[0069] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate; a top electrode layer covering the light-emitting region and being in electrical contact with the light-emitting region; a reflecting cup structure formed around the light-emitting region, wherein the top electrode layer is electrically connected to the reflecting cup structure, and the semiconductor substrate is electrically connected to the reflecting cup structure; and a refraction structure formed between the reflecting cup structure and the light-emitting region.

[0070] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate, the light-emitting region including at least one LED structure and a bonding layer located at the bottom of each LED structure, wherein each LED structure includes a light-emitting layer and a bottom reflection structure located at the bottom of the light-emitting layer; a top electrode layer covering the micro-LED pixel unit and being in electrical contact with each color LED structure, wherein the semiconductor substrate is electrically connected to each color LED structure; a reflecting cup structure formed around the light-emitting region; and a refraction structure formed between the reflecting cup structure and the light-emitting region.

[0071] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate, the light-emitting region including at least one LED structure and a bonding layer located at the bottom of each LED structure, wherein the LED structure includes a light-emitting layer and a reflective structure located at the bottom of the light-emitting layer; a top electrode layer covering the LED structure pixel unit and electrically contacting each color LED structure, wherein the semiconductor substrate is electrically connected to each color LED structure; and a stepped light-reflecting cup structure surrounding the light-emitting region, light emitted from the sidewalls of the first light-emitting layer and the second light-emitting layer along a horizontal plane reaches the stepped light-reflecting cup structure and is reflected upward by the stepped light-reflecting cup structure, wherein the top of the stepped light-reflecting cup structure is higher than the top of the light-emitting region.

[0072] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate, the light-emitting region including at least one LED structure and a metal bonding layer located at the bottom of each LED structure, wherein the LED structure includes a light-emitting layer and a reflective structure located at the bottom of the light-emitting layer; a top electrode layer covering the micro-LED pixel unit and electrically contacting each color LED structure, wherein the semiconductor substrate is electrically connected to each color LED structure; and a floating light-reflecting cup structure surrounding the light-emitting region, wherein the floating light-reflecting cup structure is positioned at a certain distance from the semiconductor substrate, and light emitted from the sidewalls of the first light-emitting layer and the second light-emitting layer along a horizontal plane reaches the floating light-reflecting cup structure and is reflected upward through the floating light-reflecting cup structure.

[0073] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the bottom of the floating light-reflecting cup structure is higher than the top surface of the semiconductor substrate.

[0074] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the floating light-reflecting cup structure is a stepped light-reflecting cup structure.

[0075] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first LED structure is embedded in a first planarized transparent dielectric layer.

[0076] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first planarized transparent dielectric layer is composed of a solid inorganic material or a plastic material.

[0077] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the second LED structure is embedded in a second planarized transparent dielectric layer.

[0078] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the second planarized transparent dielectric layer is composed of a solid inorganic material or a plastic material.

[0079] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first transparent dielectric bonding layer is composed of a solid inorganic material or a plastic material.

[0080] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first LED structure includes a first bottom electrode conductive contact layer formed at the bottom of the first LED structure; the second LED structure includes a second bottom electrode conductive contact layer formed at the bottom of the second LED structure; the first bottom electrode conductive contact layer is electrically connected to the IC substrate through a first contact in a first via located at the bottom of the first bottom electrode conductive contact layer; and the second bottom electrode conductive contact layer is electrically connected to the IC substrate through a second contact in a second via passing through the first transparent dielectric bonding layer.

[0081] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first bottom electrode conductive contact layer is transparent, and the second bottom electrode conductive contact layer is transparent.

[0082] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first LED structure includes a first light-emitting layer; a first side portion extends from one side of the first light-emitting layer; the second LED structure includes a second light-emitting layer; a second side portion extends from one side of the second light-emitting layer; and a third contact in a third via passing through the second transparent dielectric bonding layer connects the first side portion and the second side portion to the top electrode layer.

[0083] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the optical isolation structure is formed around the micro-LED pixel unit.

[0084] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the optical isolation structure is a reflector cup.

[0085] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the lateral dimension of the first LED structure is the same as the lateral dimension of the second LED structure.

[0086] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first LED structure and the second LED structure have the same central axis.

[0087] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a first reflective layer is formed at the bottom of the first LED structure; a second reflective layer is formed at the bottom of the second LED structure.

[0088] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the thickness of the first reflective layer is 5 to 10 nm; the thickness of the second reflective layer is 5 to 10 nm; the thickness of the first LED structure is not greater than 300 nm; and the thickness of the second LED structure is not greater than 300 nm.

[0089] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a bonding metal layer is formed at the bottom of the first LED structure.

[0090] Some exemplary embodiments provide a micro-LED pixel unit, including: a first-color LED structure formed on an IC substrate, wherein the first-color LED structure includes a first light-emitting layer, and a first reflective structure is formed on the bottom of the first light-emitting layer; a first bonding metal layer is formed at the bottom of the first-color LED structure and configured to bond the IC substrate and the first-color LED structure; a second bonding metal layer is formed on the top of the first-color LED structure; a second-color LED structure is formed on the second bonding metal layer, wherein the second-color LED structure includes a second light-emitting layer, and a second reflective structure is formed on the bottom of the second light-emitting layer; a top electrode layer covering the first-color LED structure and the second-color LED structure and being in electrical contact with the first-color LED structure and the second-color LED structure, wherein the IC substrate is electrically connected to the first-color LED structure and the second-color LED structure; and a reflector cup surrounding the first-color LED structure and the second-color LED structure, and light emitted horizontally from the first light-emitting layer and the second light-emitting layer reaches the reflector cup and is reflected upward through the reflector cup.

[0091] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first reflective structure includes at least one first reflective layer, the second reflective structure includes at least one second reflective layer, and the reflectivity of the first reflective layer or the second reflective layer is higher than 60%.

[0092] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the material of the first reflective layer or the second reflective layer includes one or more of Rh, Al, Ag, or Au.

[0093] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first reflective structure includes two first reflective layers with different refractive indices, and wherein the second reflective structure includes two second reflective layers with different refractive indices.

[0094] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the two first reflective layers respectively include SiO2 and Ti3O5, and the two second reflective layers respectively include SiO2 and Ti3O5.

[0095] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first reflective structure further includes a first transparent layer on the first reflective layer, and the second reflective structure further includes a second transparent layer on the second reflective layer.

[0096] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first transparent layer includes one or more of indium tin oxide (ITO) or SiO2, and the second transparent layer includes one or more of ITO or SiO2.

[0097] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first-color LED structure further includes a first bottom conductive contact layer and a first top conductive contact layer, and the second-color LED structure further includes a second bottom conductive contact layer and a second top conductive contact layer; the first light-emitting layer is located between the first bottom conductive contact layer and the first top conductive contact layer, and the second light-emitting layer is located between the second bottom conductive contact layer and the second top conductive contact layer; the first bottom conductive contact layer is electrically connected to the IC substrate through a first contact via passing through the first reflective structure and the first bonding metal layer, and the second bottom conductive contact layer is electrically connected to the IC substrate through a second contact via; and the edge of the first top conductive contact layer contacts the top electrode layer, and the top surface of the second top conductive contact layer contacts the top electrode layer.

[0098] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the material of the reflector cup includes metal.

[0099] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a microlens is formed above the top electrode layer.

[0100] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a spacer is formed between the microlens and the top electrode layer.

[0101] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the material of the spacer includes silicon oxide.

[0102] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the lateral dimension of the microlens is greater than the lateral dimension of the effective light-emitting region of the first LED structure; the lateral dimension of the microlens is greater than the lateral dimension of the effective light-emitting region of the second LED structure.

[0103] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first-color LED structure and the second-color LED structure have the same lateral dimension.

[0104] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the first-color LED structure and the second-color LED structure have the same central axis.

[0105] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the thickness of at least one first reflective layer is in the range of 5 nm to 10 nm, and the thickness of at least one second reflective layer is in the range of 5 nm to 10 nm, and wherein the thickness of the first-color LED structure is not greater than 300 nm, and the thickness of the second-color LED structure is not greater than 300 nm.

[0106] Some exemplary embodiments provide a micro-LED pixel unit, including: an IC substrate; a light-emitting region formed on the IC substrate, including a plurality of color LED structures, the bottom of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light-emitting region, wherein each of the plurality of color LED structures includes a light-emitting layer and a reflective structure located at the bottom of the light-emitting layer; a top electrode layer covering each of the plurality of color LED structures and being in electrical contact with each of the plurality of color LED structures, wherein the IC substrate is electrically connected to each of the plurality of color LED structures; and a stepped reflector cup forming a cavity, surrounding the light-emitting region, and the light emitted horizontally along the sidewalls of the light-emitting layer of each of the plurality of color LED structures reaches the reflector cup and is reflected upward through the reflector cup.

[0107] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the inner sidewall of the cavity includes a plurality of inclined surfaces.

[0108] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the angles of the plurality of inclined surfaces with respect to the surface of the IC substrate become smaller from the bottom of the cavity to the top of the cavity.

[0109] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the sub-cavities formed by a plurality of inclined surfaces have different sizes in the horizontal direction.

[0110] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the inner sidewalls of the sub-cavities are not arranged in the same plane.

[0111] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the heights of the respective sub-cavities are different.

[0112] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the height of the sub-cavity located in the middle of the cavity is less than the heights of the other sub-cavities.

[0113] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the height of the sub-cavity located at the top of the cavity is greater than the height of the sub-cavity located at the bottom of the cavity.

[0114] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the plurality of color LED structures further include a top color LED structure.

[0115] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the top of the cavity is higher than the top of the top color LED structure.

[0116] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the cavity includes a plurality of sub-cavities, and each of the plurality of color LED structures is respectively located in a different sub-cavity among the plurality of sub-cavities.

[0117] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a transparent dielectric bonding layer covers at least one of the plurality of color LED structures, wherein the transparent dielectric bonding layer includes a solid inorganic material or a plastic material.

[0118] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the solid inorganic material includes one or more materials of SiO2, Al2O3, Si3N4, phosphosilicate glass (PSG), and borophosphosilicate glass (BPSG).

[0119] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the plastic material includes one or more polymers of SU-8, PermiNex, benzocyclobutene (BCB), and spin-on glass (SOG).

[0120] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, each of the plurality of color LED structures includes a bottom conductive contact layer and a top conductive contact layer, and a light-emitting layer is formed between the bottom conductive contact layer and the top conductive contact layer; and wherein, the bottom conductive contact layer is electrically connected to the IC substrate through a contact via passing through the reflective structure and the corresponding bonding metal layer, and the top surface of the top conductive contact layer of the top color LED structure contacts the top electrode layer, and the edge of the top conductive contact layer of the color LED structure below the top color LED structure contacts the top electrode layer.

[0121] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, an extension portion extends from one side of the light-emitting layer of the color LED structure below the top color LED structure, and the contact via connects the extension portion to the top electrode layer.

[0122] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the lateral dimension of the microlens is greater than the light-emitting dimension of each of the plurality of color LED structures.

[0123] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the plurality of color LED structures have the same central axis.

[0124] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the reflective structure includes a reflective layer, the thickness of the reflective layer is in the range of 5 nm to 10 nm, and the thickness of each of the plurality of color LED structures does not exceed 300 nm.

[0125] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the material of the top electrode layer is selected from the following materials: graphene, indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), and fluorine-doped tin oxide (FTO).

[0126] Some exemplary embodiments provide a micro-LED pixel unit, which includes: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate, including a plurality of color LED structures, the bottom of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light-emitting region, wherein each of the plurality of color LED structures includes a light-emitting layer and a reflective structure located at the bottom of the light-emitting layer; a top electrode layer covering and electrically contacting each of the plurality of color LED structures, wherein the semiconductor substrate is electrically connected to each of the plurality of color LED structures; a reflector cup surrounding the light-emitting region; and a refractive structure formed between the reflector cup and the light-emitting region.

[0127] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a microlens is formed on the top surface of the refractive structure.

[0128] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the lateral dimension of the microlens is not less than the lateral dimension of the light-emitting region.

[0129] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the reflector cup has a top opening region, and the lateral dimension of the microlens is smaller than the lateral dimension of the top opening region.

[0130] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a bottom dielectric layer is formed between the bottom of the reflector cup and the semiconductor substrate.

[0131] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a top conductive layer is formed on the top of the light-emitting region, and the top conductive layer is electrically connected to the reflector cup.

[0132] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the top conductive layer is in direct contact with the top or the bottom of the reflector cup.

[0133] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the top of the refractive structure is higher than the top of the reflector cup.

[0134] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the semiconductor substrate is an IC substrate.

[0135] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the reflector cup is a stepped reflector cup that forms a cavity surrounding the light-emitting region.

[0136] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the sub-cavities formed by a plurality of inclined surfaces have different sizes in the horizontal direction.

[0137] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, each of the plurality of color LED structures includes a corresponding extension portion extending from one side of the corresponding color LED structure, and the corresponding extension portion is electrically connected to the top electrode layer via a corresponding first contact via, and the bottom of each of the plurality of color LED structures is electrically connected to the semiconductor substrate via a corresponding second contact via.

[0138] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate, including a plurality of color LED structures, the bottom of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light-emitting region, wherein each of the plurality of color LED structures includes a light-emitting layer and a reflective structure located at the bottom of the light-emitting layer; a top electrode layer covering and electrically contacting each of the plurality of color LED structures, wherein the semiconductor substrate is electrically connected to each of the plurality of color LED structures; and a reflector cup surrounding the light-emitting region, light emitted horizontally from the sidewalls of the light-emitting layer of each of the plurality of color LED structures reaches the reflector cup and is reflected upward by the reflector cup, and the top of the reflector cup is higher than the top of the light-emitting region.

[0139] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a microlens is formed above the light-emitting region.

[0140] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the top of the reflector cup is higher than the top of the microlens.

[0141] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a refractive structure is formed between the bottom of the microlens and between the reflector cup and the light-emitting region.

[0142] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the bottom of the light-emitting region is electrically connected to the semiconductor substrate.

[0143] Some exemplary embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light-emitting region formed on the semiconductor substrate, including a plurality of color LED structures, the bottom of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light-emitting region, wherein each of the plurality of color LED structures includes a light-emitting layer and a reflective structure located at the bottom of the light-emitting layer; a top electrode layer covering and electrically contacting each of the plurality of color LED structures, wherein the semiconductor substrate is electrically connected to each of the plurality of color LED structures; and a floating reflector cup surrounding the light-emitting region, wherein the bottom of the floating reflector cup is located above the semiconductor substrate, and light emitted horizontally from the sidewalls of the light-emitting layer of each of the plurality of color LED structures reaches the suspended floating reflector cup and is reflected upward by the suspended floating reflector cup.

[0144] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the bottom of the floating reflector cup is higher than the top surface of the corresponding bonding metal layer at the bottom of one of the plurality of color LED structures.

[0145] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the floating reflector cup is stepped.

[0146] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the top of the floating reflector cup is higher than the top of the microlens.

[0147] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a refractive structure is formed between the bottom of the microlens and between the floating reflector cup and the light-emitting region.

[0148] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the floating reflector cup has a top opening region, and the lateral dimension of the microlens is smaller than the lateral dimension of the top opening region.

[0149] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, a bottom dielectric layer is formed between the floating reflector cup and the semiconductor substrate.

[0150] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the top electrode layer directly contacts the top or the bottom of the floating reflector cup.

[0151] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the stepped floating reflector cup forms a cavity surrounding the light-emitting region.

[0152] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the material of the floating reflector cup includes a metal.

[0153] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the reflective structure includes a reflective layer, and the reflective layer is respectively formed at the bottom of each of the plurality of color LED structures.

[0154] In some exemplary embodiments of the micro-LED pixel unit or any combination of the foregoing exemplary embodiments, the thickness of the reflective layer ranges from 5 nm to 10 nm, and the thickness of each of the plurality of color LED structures does not exceed 300 nm.

[0155] The compact design of the multicolor LED devices and systems disclosed herein utilizes the lateral overlap of the light-emitting LED structures, thereby improving the luminous efficiency, resolution, and overall performance of the LED display system. In addition, the fabrication of the multicolor LED display system can reliably and efficiently form the LED structure pattern without using or retaining additional substrates. In some cases, the design of the display devices and systems disclosed herein directly forms microlenses on top of the multicolor LED devices on the substrate by utilizing the conformity of the shape of the microlens material with the shape of the multicolor LED devices, thereby greatly reducing the steps of microlens fabrication and improving the efficiency of forming the display panel structure. Reducing the viewing angle and reducing light interference improve the luminous efficiency, resolution, and overall performance of the display system. Therefore, the implementation of the multicolor LED display system can meet the stringent display requirements for AR and VR, head-up displays, displays for mobile devices, displays for wearable devices, high-definition small projectors, and automotive displays compared to the use of conventional LEDs.

[0156] It should be noted that the various embodiments described above can be combined with any other embodiments described herein. The features and advantages described in the specification are not all-inclusive, and in particular, many additional features and advantages will be apparent to those of ordinary skill in the art in terms of the drawings, the specification, and the claims. In addition, it should be noted that the choice of language used in the specification is mainly for readability and guidance purposes and is not chosen to delimit or define the inventive subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0157] For the present disclosure to be more particularly understood, the present disclosure may be described in more detail by reference to the features of various embodiments, some of which are shown in the drawings. However, these drawings only show the relevant features of the present disclosure content and should not be considered restrictive, as the description may allow other effective features.

[0158] Figure 1AIs a top view of a single-pixel three-color LED device 100 according to some embodiments.

[0159] Figure 1B Is a cross-sectional view of a single-pixel three-color LED device 100 according to some embodiments along Figure 1A the main diagonal 102.

[0160] Figure 1C Is a cross-sectional view of a single-pixel three-color LED device 100 according to some embodiments along Figure 1A the main diagonal 150.

[0161] Figure 2A Is a cross-sectional view of a single-pixel three-color LED device 100 with planarization features according to some embodiments along Figure 1A the main diagonal 102.

[0162] Figure 2B Is a cross-sectional view of a single-pixel three-color LED device 100 with planarization features according to some embodiments along Figure 1A the main diagonal 150.

[0163] Figure 3A Is a cross-sectional view of a single-pixel three-color LED device 100 with planarization features according to some embodiments along Figure 1A the main diagonal 102.

[0164] Figure 3B Is a cross-sectional view of a single-pixel three-color LED device 100 with planarization features according to some embodiments along Figure 1A the main diagonal 150.

[0165] Figure 4A Is a top view of a single-pixel three-color LED device 400 with hierarchical planarization according to some embodiments.

[0166] Figure 4B Is a cross-sectional view of a single-pixel three-color LED device 400 with hierarchical planarization according to some embodiments along Figure 4A the main diagonal 402.

[0167] Figure 5 Is a cross-sectional view of a single-pixel three-color LED device 500 with a refractive structure according to some embodiments along Figure 1A the main diagonal 102.

[0168] Figure 6A Is a cross-sectional view of a single-pixel three-color LED device 600 with a microlens on a reflective structure according to some embodiments along Figure 1A the main diagonal 102.

[0169] Figure 6Bis a cross - sectional view along the Figure 1A diagonal 102 of a single - pixel three - color LED device 600 having a microlens within a region formed by a reflective structure, according to some embodiments.

[0170] Figure 6C is a method of manufacturing a display panel forming an integrated microlens array using top - down pattern transfer, according to some embodiments.

[0171] Figure 6D is a method of manufacturing a display panel forming an integrated microlens array using top - down pattern transfer, according to some embodiments.

[0172] Figure 7 is a cross - sectional view 700 along a diagonal such as 102 of three single - pixel three - color LED devices 710, 720, and 730 located on a substrate 104, according to some embodiments. Figure 1A diagonal such as 102.

[0173] Figure 8 is a cross - sectional view along a diagonal such as 402 of a single - pixel three - color LED device 800 having a stepped reflector cup, according to some embodiments. Figure 4A diagonal such as 402.

[0174] Figure 9 is a cross - sectional view along a diagonal such as 402 of a single - pixel three - color LED device 900 having a floating reflector cup, according to some embodiments. Figure 4A diagonal such as 402.

[0175] Figure 10A is a circuit diagram of a matrix of single - pixel three - color LED devices 1000, according to some embodiments.

[0176] Figure 10B is a circuit diagram of a matrix of single - pixel three - color LED devices 1000, according to some embodiments.

[0177] Figure 11 is a top - view of a micro - LED display panel 1100, according to some embodiments.

[0178] According to common practice, the various features illustrated in the drawings may not be drawn to scale. Thus, for clarity, the dimensions of the various features may be arbitrarily enlarged or reduced. Additionally, some of the drawings may not depict all of the components of a given system, method, or device. Finally, the same reference numerals may be used to represent similar features throughout the specification and the drawings. Detailed Description

[0179] This document describes many details in order to provide a thorough understanding of the example embodiments shown in the accompanying drawings. However, some embodiments can be practiced without many specific details, and the scope of the claims is limited only by those features and aspects specifically recited in the claims. In addition, well-known methods, components, and materials are not described in detail so as not to unnecessarily obscure the relevant aspects of the embodiments described herein.

[0180] In some embodiments, a single-pixel multicolor LED device includes two or more LED structures. In some embodiments, each LED structure includes at least one LED light-emitting layer that emits light of different colors. When two LED structures are present within a single-pixel multicolor LED device, light of two colors and the mixed colors of the two colors can be emitted from the single-pixel multicolor LED device. When three LED structures are present within a single-pixel multicolor LED device, light of three colors and the mixed colors of the three colors can be emitted from the single-pixel multicolor LED device.

[0181] In some embodiments, the light emitted from a single-pixel multicolor LED device exits from the sidewalls of each LED structure within the single-pixel multicolor LED device. In some embodiments, a reflective structure is provided around the single-pixel multicolor LED device to reflect the light exiting from the sidewalls of each LED structure upward. In some embodiments, the light emitted from a single-pixel multicolor LED device exits from the top surface of each LED structure within the single-pixel multicolor LED device. In some embodiments, the light emitted from a single-pixel multicolor LED device is a combination of the light exiting from the sidewalls and the top surface of each LED structure within the single-pixel multicolor LED device. For example, in a certain proportion, the light exiting from the sidewalls accounts for about 20% to 100% of the light emitted from the single-pixel multicolor LED device.

[0182] Figure 1A is a top view of a single-pixel three-color LED device 100 according to some embodiments.

[0183] Figure 1B is a cross-sectional view of a single-pixel three-color LED device 100 according to some embodiments along Figure 1A the diagonal 102 therein.

[0184] Figure 1C is a cross-sectional view of a single-pixel three-color LED device 100 according to some embodiments along Figure 1A the diagonal 150 therein.

[0185] Diagonals 102 and 150 each pass through the center of a single-pixel three-color LED device 100. Diagonals 102 and 150 are orthogonal to each other. In some embodiments, the three-color LED device 100 includes a substrate 104. For convenience, "upward" is used to denote away from the substrate 104, "downward" denotes toward the substrate 104, and other directional terms such as top, bottom, above, below, directly below, beneath, etc. are interpreted accordingly. The support substrate 104 is a substrate on which an array of respective drive circuits 106 is fabricated. In some embodiments, the drive circuits may also be located in one of the layers above the substrate 104, or above the micro three-color LED structure 100. Each drive circuit is a pixel driver 106. In some cases, the drive circuit 106 is a thin-film transistor pixel driver or a silicon CMOS pixel driver. In one embodiment, the substrate 104 is a Si substrate. In another embodiment, the support substrate 104 is a transparent substrate, such as a glass substrate. Examples of other substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. The drive circuits 106 form respective pixel drivers to control the operation of the respective single-pixel three-color LED devices 100. The circuits on the substrate 104 include contacts for each individual drive circuit 106 and ground contacts. As Figure 1A , 1B and as shown in 1C, each micro three-color LED structure 100 also has two types of contacts: P electrodes or anodes connected to the pixel driver 106, such as 108, 126, 152; and N electrodes or cathodes connected to ground (i.e., common electrodes), such as 116, 120, and 140.

[0186] In some embodiments, the N electrodes (or N electrode contact pads) and their connecting components, such as 116, 120, and 140, are made of materials such as graphene, ITO, aluminum-doped zinc oxide (AZO), or fluorine-doped tin oxide (FTO), or any combination of the above materials. In some embodiments, the N electrodes (or N electrode contact pads) and their connecting components, such as 116, 120, and 140, are made of non-transparent or transparent conductive materials, and in a preferred embodiment, are made of transparent conductive materials. In some embodiments, the P electrodes (or P electrode contact pads) and their connecting components, such as 126, 152, are made of materials such as graphene, ITO, AZO, or FTO, or any combination of the above materials. In some embodiments, the P electrodes (or P electrode contact pads) and their connecting components, such as 126, 152, are made of non-transparent or transparent conductive materials, and in a preferred embodiment, are made of transparent conductive materials. In some embodiments, the positions of the P electrodes (or P electrode contact pads) and their connecting components and the N electrodes (or N electrode contact pads) and their connecting components can be switched.

[0187] Although some features are described herein using the term "layer", it should be understood that these features are not limited to a single layer, but may include multiple sub-layers. In some cases, a "structure" may take the form of a "layer".

[0188] In some embodiments, three LED structures respectively including LED light-emitting layers 112, 130, and 136 form a stacked structure. For example, a green LED light-emitting layer 130 is formed on top of the red LED light-emitting layer 112, and a blue LED light-emitting layer 136 is formed on top of the green LED light-emitting layer 130.

[0189] Generally, an LED light-emitting layer includes a PN junction having a p-type region / layer and an n-type region / layer, and an active layer between the p-type region / layer and the n-type region / layer.

[0190] In some embodiments, as Figure 1A and 1B shown, the area of the bottom red LED light-emitting layer 112 is larger than the area of the middle green LED light-emitting layer 130. In some embodiments, the area of the middle green LED light-emitting layer 130 is larger than the area of the top blue LED light-emitting layer 136.

[0191] In some embodiments, the light emitted by the red LED light-emitting layer 112 can propagate horizontally toward the sidewall of the red LED light-emitting layer 112, and then be reflected upward by reflection elements such as 146 and / or 148 as described below, and be emitted at the top surface of the single-pixel three-color LED device 100. As described below, a reflection layer 109 is provided below the red LED light-emitting layer 112, and a reflection layer 115 is provided above the red LED light-emitting layer 112. The light emitted by the red LED light-emitting layer 112 is reflected between the two reflection layers 109 and 115 toward the sidewall of the red LED light-emitting layer 112.

[0192] In some embodiments, the light emitted by the green LED light-emitting layer 130 can propagate horizontally toward the sidewall of the green LED light-emitting layer 130, and then be reflected upward by reflection elements such as 146 and / or 148 as described below, and be emitted at the top surface of the single-pixel three-color LED device 100. As described below, a reflection layer 127 is provided below the green LED light-emitting layer 130, and a reflection layer 133 is provided above the green LED light-emitting layer 130. The light emitted from the green LED light-emitting layer 130 is reflected between the two reflection layers 127 and 133 toward the sidewall of the green LED light-emitting layer 130.

[0193] In some embodiments, the light emitted by the blue LED light-emitting layer 136 can propagate horizontally toward the sidewalls of the blue LED light-emitting layer 136, and then be reflected upward by reflection elements such as 146 and / or 148 as described below, and be emitted at the top surface of the single-pixel three-color LED device 100. As described below, a reflective layer 135 is provided below the blue LED light-emitting layer 136. The light emitted from the blue LED light-emitting layer 136 is reflected toward the sidewalls of the blue LED light-emitting layer 136 between the reflective layer 135 and the upper surface of the blue LED light-emitting layer 136.

[0194] In some embodiments, the light emitted by the red LED light-emitting layer 112 can propagate vertically through the green LED light-emitting layer 130, and then pass through the blue LED light-emitting layer 136 and be emitted from the three-color LED device 100. In some embodiments, the light emitted by the green LED light-emitting layer 130 can propagate through the blue LED light-emitting layer 136 to be emitted from the three-color LED device 100. In the case of vertical light transmission, in some preferred embodiments, top reflective layers such as 115 and 133 above each light-emitting layer are not included in the three-color LED device 100.

[0195] In some embodiments, the LED light-emitting layers such as 112, 130, and 136 include many sub-epitaxial layers with different compositions. Examples of LED epitaxial layers include III-V nitrides, III-V arsenides, III-V phosphides, and III-V antimonide epitaxial structures. Examples of micro-LEDs include GaN-based UV / blue / green micro-LEDs, AlInGaP-based red / orange micro-LEDs, and GaAs- or InP-based infrared (IR) micro-LEDs.

[0196] In some embodiments, each LED structure in the stacked LED structure can be separately controlled to generate its individual light. In some embodiments, the mixed light emitted from the top LED epitaxial layer can change the color of a single pixel within a small coverage area on the display panel due to the simultaneous operation of all the LED epitaxial layers in the three-color LED device 100.

[0197] In some embodiments, according to the design of the LED device 100, the colors of the light emitted by the respective LED structures included in the same device are not limited to red, green, and blue. For example, suitable colors can be selected from the range of different color lights with wavelengths from 380 nm to 700 nm within the visible light range. In some embodiments, the LED structures can also emit other color lights in the invisible range such as ultraviolet and infrared.

[0198] In some embodiments, when vertical light emission is combined with horizontal light emission, for example, the selection of the three colors can be red, green, and blue from bottom to top. In another embodiment, the selection of the three colors can be infrared, orange, and ultraviolet from bottom to top. In some embodiments, the wavelength of the light emitted by the LED structure on a certain layer of the device 100 is longer than the wavelength of the light emitted by the LED structure on the layer above the current layer. For example, the wavelength of the light emitted by the bottom LED light-emitting layer 112 is longer than the wavelength of the light emitted by the middle LED light-emitting layer 130, and the wavelength of the light emitted by the middle LED light-emitting layer 130 is longer than the wavelength of the light emitted by the top LED light-emitting layer 136.

[0199] In some embodiments, when in the case of horizontal light emission or when the portion of horizontal light emission is more than the portion of vertical light emission from the top surface of the LED device 100, each of the light-emitting layers 112, 130, and 136 in the LED light-emitting layer can be any suitable color of visible or invisible light. The advantage of horizontal light emission is that since the emitted light does not need to pass through other upper layers of the LED device 100 but directly exits from the edge or side wall of the current light-emitting layer, the light propagation loss can be reduced and the light-emitting efficiency can be improved. For example, compared with the vertical light-emitting LED device, the horizontal light-emitting LED device can increase the light propagation efficiency by 15%, 50%, 100%, 150%, or 200%. In some cases, the light propagation efficiency of the horizontal light-emitting LED device can be equal to or greater than 20%, 40%, or 60%.

[0200] In some embodiments, the bottom red LED light-emitting layer 112 is bonded to the substrate 104 through the metal bonding layer 108. The metal bonding layer 108 can be disposed on the substrate 104. In one method, the metal bonding layer 108 is grown on the substrate 104. In some embodiments, the metal bonding layer 108 is electrically connected to the driving circuit 106 on the substrate 104 and the red LED light-emitting layer 112 above the metal bonding layer 108, and serves as a P electrode. In some embodiments, the thickness of the metal bonding layer 108 is about 0.1 micrometer to 3 micrometers. In a preferred embodiment, the thickness of the metal bonding layer 108 is about 0.3 μm. The metal bonding layer 108 can include an ohmic contact layer and a metal bonding layer. In some cases, the metal bonding layer 108 includes two metal layers. One of the metal layers is deposited on the layer above the metal bonding layer within the LED device 100. The corresponding bonding metal layer is also deposited on the substrate 104. In some embodiments, the composition of the metal bonding layer 108 includes Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or a combination of the above. For example, if Au-Au bonding is selected, two layers of Au respectively require a Cr coating as an adhesion layer and a Pt coating as an anti-diffusion layer. The Pt coating is located between the Au layer and the Cr layer. The Cr layer and the Pt layer are located on the top and bottom of the two bonded Au layers. In some embodiments, when the thicknesses of the two Au layers are substantially the same, at high pressure and high temperature, the Au on the two layers diffuses into each other to bond the two layers together. Eutectic bonding, thermocompression bonding, and transient liquid phase (TLP) bonding are exemplary techniques that can be used.

[0201] In some embodiments, the metal bonding layer 108 can also be used as a reflector to reflect the light emitted from the LED structure above.

[0202] In some embodiments, a conductive layer 110 for electrode connection is formed at the bottom of the red LED light-emitting layer 112. In some embodiments, the conductive layer 110 can be an opaque metal layer that is opaque to the light emitted by the LED device 100. In some embodiments, the conductive layer 110 is a conductive transparent layer such as an indium tin oxide (ITO) layer that is transparent to the light emitted by the LED device 100, and is formed between the red LED light-emitting layer 112 and the metal bonding layer 108 to improve conductivity and light transmittance.

[0203] In Figures 1A to 1C Some embodiments not shown, the red LED structure has a P electrode contact pad 168 electrically connected to the red LED light-emitting layer 112. In some embodiments, the P electrode contact pad 168 is connected to the conductive layer 110. In some embodiments, a conductive layer 114 for electrode connection is formed on the top of the red LED light-emitting layer 112. In some embodiments, the conductive layer 114 can be as Figure 1CA metal layer or a conductive transparent layer, such as an ITO layer, for improving conductivity and light transmittance, is formed between the red LED light-emitting layer 112 and the N electrode contact pad 116. In some embodiments, the N electrode contact pad, such as 116, is made of graphene, ITO, AZO, or FTO, or any combination of the above materials.

[0204] In some embodiments, a reflective layer 109 is provided between the conductive layer 110 and the metal bonding layer 108 below the red LED light-emitting layer 112, and a reflective layer 115 is provided between the conductive layer 114 and the bonding layer 156 above the red LED light-emitting layer 112.

[0205] In some embodiments, the red LED light-emitting layer 112 has an extension portion 164 on one side thereof relative to other upper layers, as Figure 1C shown. In some embodiments, the extension portion 164 extends together with the conductive layers 110 and 114. In some embodiments, the extension portion 164 extends together with the reflective layer 109 and the metal bonding layer 108 at the bottom of the red LED light-emitting layer 112. In some embodiments, the red LED light-emitting layer 112 is connected to the N electrode contact pad 116 through an extension portion of the conductive layer 114 above the extension portion 164.

[0206] In one method, the red LED light-emitting layer 112 is grown on another separate substrate (referred to as an epitaxial substrate). After bonding, the epitaxial substrate is removed by, for example, a laser lift-off process or wet chemical etching, leaving behind Figure 1B and Figure 1C the structure shown in

[0207] In some embodiments, the red LED light-emitting layer 112 is used to form a red micro-LED. Examples of the red LED light-emitting layer include III-V nitrides, III-V arsenides, III-V phosphides, and III-V antimonide epitaxial structures. In some cases, the film within the red LED light-emitting layer 112 may include a layer of P-type GaP / P-type AlGaInP light-emitting layer / AlGaInP / N-type AlGaInP / N-type GaAs. In some embodiments, the P-type layer is typically doped with Mg, while the N-type layer is typically doped with Si. In some examples, the thickness of the red LED light-emitting layer is about 0.1 micrometer to 5 micrometers. In a preferred embodiment, the thickness of the red LED light-emitting layer is about 0.3 micrometers.

[0208] In some embodiments, the red LED structure includes a metal bonding layer 108, a reflective layer 109, a conductive layer 110, a red LED light-emitting layer 112, a conductive layer 114, a reflective layer 115, and an N electrode contact pad 116.

[0209] In some embodiments, the bonding layer 156 is used to bond the red LED structure and the green LED structure together. In some embodiments, the bonding layer 156 is opaque to the light emitted from the LED device 100. In some embodiments, the material and thickness of the bonding layer 156 are the same as those described above for the metal bonding layer 108. In some embodiments, the bonding layer 156 can also be used as a reflector to reflect the light emitted by the upper LED structure.

[0210] In some embodiments, when vertical propagation is used, the bonding layer 156 is transparent to the light emitted by the micro-LED 100. In some embodiments, the bonding layer 156 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 borophosphosilicate 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-on glass (SOG), or the bonding adhesive BCL-1200 from Micro Resist Company, or any combination of the above. In some embodiments, the transparent bonding layer can facilitate the light emitted by the layer below the bonding layer to pass through.

[0211] In some embodiments, as Figure 1A and Figure 1B shown, the green LED structure has a P electrode contact pad 126 electrically connected to the green LED light-emitting layer 130. In some embodiments, the P electrode contact pad 126 is connected to the conductive layer 128. In some embodiments, the conductive layer 128 for electrode connection is formed at the bottom of the green LED light-emitting layer 130. In some embodiments, as Figure 1A and 1B shown, the conductive layer 128 can be a conductive transparent layer such as an ITO layer or a metal layer for improving conductivity and light transmittance, formed between the green LED light-emitting layer 130 and the P electrode contact pad 126.

[0212] In some embodiments, relative to other upper layers, the conductive layer 128 has an extension portion 128-1 on one side of it, as Figure 1B shown. In some embodiments, the extension portion 128-1 extends together with all the layers below the conductive layer 128 within the LED device 100. In some embodiments, the green LED light-emitting layer 130 is electrically connected to the P electrode contact pad 126 through the extension portion 128-1 of the conductive layer 128. In some embodiments, the P electrode contact pad 126 is also electrically connected to the drive circuit 106 in the substrate 104.

[0213] In some embodiments, an insulating layer 174 made of a dielectric material, such as an SiO2 layer, is deposited on the surface of the LED device 100. The P electrode contact pad 126 extends from its contact with the driving circuit 106 to its contact with the conductive layer 128 through a via or a channel in the insulating layer 174. The P electrode contact pad 126 does not contact other layers within the LED device 100.

[0214] In some embodiments, a conductive layer 132 for electrode connection is formed on top of the green LED light-emitting layer 130. In some embodiments, the conductive layer 132 can be a conductive transparent layer, such as an ITO layer, or a metal layer, formed between the green LED light-emitting layer 130 and the N electrode contact pad 120 to improve conductivity and light transmittance. In some embodiments, the N electrode contact pad 120 is made of a transparent conductive material such as ITO. In some embodiments, the N electrode contact pad 120 is made of a material such as graphene, ITO, AZO, or FTO, or any combination thereof.

[0215] In some embodiments, as Figure 1C shown, the green LED structure has an N electrode contact pad 120 electrically connected to the green LED light-emitting layer 130. In some embodiments, the N electrode contact pad 120 is connected to the conductive layer 132. In some embodiments, the N electrode contact pad 120 of the green LED structure is also electrically connected to the N electrode contact pad 116 of the red LED structure.

[0216] As Figure 1C shown, in some embodiments, the green LED light-emitting layer 130 has an extension portion 166 on one side thereof. In some embodiments, the extension portion 166 extends together with the conductive layers 128 and 132 and all other layers below the conductive layer 128. In some embodiments, the extension portion 166 is electrically connected to the N electrode contact pad 120 through an extension portion of the conductive layer 132 above the extension portion 166.

[0217] In some embodiments, the lateral dimension of the green LED light-emitting layer 130 is smaller than the lateral dimension of the red LED light-emitting layer 112.

[0218] In some embodiments, a reflective layer 127 is provided between the conductive layer 128 and the bonding layer 156 below the green LED light-emitting layer 130, and a reflective layer 133 is provided between the conductive layer 132 and the bonding layer 160 above the green LED light-emitting layer 130.

[0219] In one method, the green LED light-emitting layer 130 is grown on another separate substrate (referred to as an epitaxial substrate). After bonding, the epitaxial substrate is removed by, for example, a laser lift-off process or a wet chemical etching process, leaving Figure 1B and Figure 1C the structure shown in

[0220] In some embodiments, the green LED light-emitting layer 130 is used to form green micro-LEDs. Examples of the green LED light-emitting layer include III-V nitride, III-V arsenide, III-V phosphide, and III-V antimonide epitaxial structures. In some cases, the film within the green LED light-emitting layer 130 may include a layer of P-type GaN / InGaN light-emitting layer / N-type GaN. In some embodiments, P-type is typically Mg-doped, while N-type is typically Si-doped. In some examples, the thickness of the green LED light-emitting layer is about 0.1 micrometer to 5 micrometers. In a preferred embodiment, the thickness of the green LED light-emitting layer is about 0.3 micrometers.

[0221] In some embodiments, the green LED structure includes a reflective layer 127, a conductive layer 128, a green LED light-emitting layer 130, a conductive layer 132, a reflective layer 133, a P electrode contact pad 126, and an N electrode contact pad 120.

[0222] In some embodiments, without including an extension of a portion below 128-1 such as 164, 166, and the conductive layer 128, a first LED structure, e.g., a red LED structure, and a second LED structure, e.g., the structure of a green LED, have the same central axis. In some embodiments, without including an extension of a portion below 128-1 such as 164, 166, and the conductive layer 128, the first LED structure and the second LED structure are aligned along the same central axis.

[0223] In some embodiments, the bonding layer 160 is used to bond the green LED structure and the blue LED structure together. In some embodiments, the bonding layer 156 is opaque to the light emitted by the LED device 100. In some embodiments, the material and thickness of the bonding layer 160 are the same as those described above for the metal bonding layer 108. In some embodiments, the bonding layer 160 can also be used as a reflector to reflect the light emitted by the upper LED structure.

[0224] In some embodiments, when vertical propagation is used, the bonding layer 160 is transparent to the light emitted by the LED device 100. In some embodiments, the bonding layer 160 is made of a dielectric material such as a solid inorganic material or a plastic material, the same as those described above for the bonding layer 156. In some embodiments, the transparent bonding layer can facilitate the light emitted by the layer below the bonding layer to pass through.

[0225] In some embodiments, as Figure 1A and Figure 1BAs shown, the blue LED structure has a P electrode contact pad 152 electrically connected to the blue LED light-emitting layer 136. In some embodiments, the P electrode contact pad 152 is connected to the conductive layer 134. In some embodiments, a conductive layer 134 for electrode connection is formed at the bottom of the blue LED light-emitting layer 136. In some embodiments, as Figure 1A and 1B shown, the conductive layer 134 can be a conductive transparent layer such as an ITO layer or a metal layer, formed between the blue LED light-emitting layer 136 and the P electrode contact pad 152 to improve conductivity and light transmittance.

[0226] In some embodiments, the conductive layer 134 has an extension portion 134-1 on one side thereof relative to other layers above, as Figure 1B shown. In some embodiments, the extension portion 134-1 extends together with all the layers below the conductive layer 134 within the LED device 100. In some embodiments, the blue LED light-emitting layer 136 is electrically connected to the P electrode contact pad 152 through the extension portion 134-1 of the conductive layer 134. In some embodiments, the P electrode contact pad 152 is also electrically connected to the driving circuit 106 in the substrate 104.

[0227] In some embodiments, an insulating layer 174 made of a dielectric material, such as an SiO2 layer, is deposited on the surface of the LED device 100. The P electrode contact pad 152 extends from its contact with the driving circuit 106 to its contact with the conductive layer 134 through a via or a channel in the insulating layer 174. The P electrode contact pad 152 does not contact other layers within the LED device 100.

[0228] In some embodiments, a conductive layer 138 for electrode connection is formed on the top of the blue LED light-emitting layer 136. In some embodiments, the conductive layer 138 can be a conductive transparent layer such as an ITO layer or a metal layer, formed between the blue LED light-emitting layer 136 and the N electrode contact pad 140 to improve conductivity and light transmittance. In some embodiments, the N electrode contact pad 140 is made of a transparent conductive material such as ITO. In some embodiments, the N electrode contact pad 140 is made of a material such as graphene, ITO, AZO, or FTO or any combination of the above materials. In some embodiments, the N electrode contact pads 116, 120, and 140 are all electrically connected together as a common N electrode. In some embodiments, the N electrode contact pads 116, 120, and 140 are formed as an integral element as a common N electrode.

[0229] In some embodiments, as Figure 1B shown, the blue LED structure has an N electrode contact pad 140 electrically connected to the blue LED light-emitting layer 136. In some embodiments, the N electrode contact pad 140 is connected to the conductive layer 138.

[0230] In some embodiments, the lateral dimension of the blue LED light-emitting layer 136 is smaller than the lateral dimension of the green LED light-emitting layer 130.

[0231] In some embodiments, a top electrode element such as the N electrode pad 140 is connected by an electrical connection element below an optical isolation structure such as 146, 148, 170, and 172. In some embodiments, the top electrode is connected by an electrical connection element embedded in the substrate 104. In one example, the top electrode 140 is connected by an electrical connection element located above the insulating layer 174 and below an optical isolation structure such as 146, 148, 170, and 172.

[0232] In some embodiments, a reflective layer 135 is provided between the conductive layer 134 and the bonding layer 160 below the blue LED light-emitting layer 136. In some embodiments, an optional reflective layer 139 ( Figures 1A - 1C not shown in the figure) is provided on top of the conductive layer 138 above the blue LED light-emitting layer 136.

[0233] In one method, the blue LED light-emitting layer 136 is grown on a separate substrate (referred to as an epitaxial substrate). After bonding, the epitaxial substrate is removed by, for example, a laser lift-off process or wet chemical etching, leaving Figure 1B and Figure 1C the structure shown in the figure.

[0234] In some embodiments, the blue LED light-emitting layer 136 is used to form a blue micro-LED. Examples of the blue LED light-emitting layer include III-V nitride, III-V arsenide, III-V phosphide, and III-V antimonide epitaxial structures. In some cases, the film within the blue LED light-emitting layer 136 may include a layer of P-type GaN / InGaN light-emitting layer / N-type GaN. In some embodiments, P-type is typically Mg-doped, while N-type is typically Si-doped. In some examples, the thickness of the blue LED light-emitting layer is about 0.1 micrometer to 5 micrometers. In a preferred embodiment, the thickness of the blue LED light-emitting layer is about 0.3 micrometers.

[0235] In some embodiments, the blue LED structure includes a reflective layer 135, a conductive layer 134, a blue LED light-emitting layer 136, a conductive layer 138, an optional reflective layer 139, a P electrode contact pad 152, and an N electrode contact pad 140.

[0236] In some embodiments, without including an extension of the lower portion such as 166 and 134-1 of the conductive layer 134, the second LED structure, e.g., the green LED structure and the third LED structure, e.g., the blue LED structure, have the same central axis. In some embodiments, without including an extension of the lower portion such as 166 and 134-1 of the conductive layer 134, the first LED structure and the second LED structure are aligned along the same central axis.

[0237] In some embodiments, the N electrode 140 covers the top of the three-color LED device 100. In some embodiments, the N electrode 140 is connected to the N electrode in an adjacent three-color LED device via some electrical connection components (not shown in Figures 1A - 1C ), serving as a common electrode.

[0238] In some embodiments, the thickness of each of the conductive layers 110, 114, 128, 132, 134, and 138 is about 0.01 micrometer to 1 micrometer. In some cases, before any bonding process for bonding to the next epitaxial layer, each of the conductive layers 110, 114, 128, 132, 134, and 138 is typically deposited on its respective corresponding epitaxial layer by a vapor deposition process, such as electron beam evaporation or sputter deposition. In some examples, the conductive layer is used to maintain good electrical conductivity of the electrode connection, and in some cases, is also used to improve the optical properties of the LED device, such as reflectivity or transmittance.

[0239] In some embodiments, above the bottom light-emitting layer 112 (and above the conductive layer 114), preferably above the reflective layer 115 and below the bonding layer 156, an additional dielectric layer such as a SiO2 layer is formed (not shown in Figures 1A - 1C ), electrically separating the N-type layer of the light-emitting layer 112 from the bonding layer 156. In some embodiments, the thickness of the additional dielectric layer is 20 nanometers to 2 micrometers. In a preferred embodiment, the thickness of the additional dielectric layer is about 100 nanometers. In some embodiments, above the intermediate light-emitting layer 130 (and above the conductive layer 132), preferably above the reflective layer 133 and below the bonding layer 160, an additional dielectric layer such as a SiO2 layer is formed (not shown in Figures 1A - 1C ), electrically separating the N-type layer of the light-emitting layer 130 from the bonding layer 160. In some embodiments, the thickness of the additional dielectric layer is 20 nanometers to 2 micrometers. In a preferred embodiment, the thickness of the additional dielectric layer is about 100 nanometers.

[0240] In some embodiments, to improve the luminous efficiency of the three-color LED device 100, optical isolation structures such as 146, 148, 170, and 172 are formed along the sidewalls of the three-color LED device 100 as further described hereinafter. In some embodiments, the optical isolation structures such as 146, 148, 170, and 172 are made of a dielectric material such as SiO2.

[0241] As shown in the top view in Figure 1A , in some embodiments, the three-color LED device 100 has a circular shape. In some embodiments, the optical isolation structures such as 146, 148, 170, and 172 are connected together and form a circular sidewall surrounding the three-color LED device 100. In some embodiments, the optical isolation structure forms a reflector cup as further described in detail hereinafter. In some embodiments, the three stacked LED structures within the three-color LED device 100 also have a circular shape. In some embodiments, the three-color LED device 100 may have other shapes, such as rectangular, square, triangular, trapezoidal, polygonal. In some embodiments, the optical isolation structures such as 146, 148, 170, and 172 are connected together and form sidewalls of other shapes such as rectangular, square, triangular, trapezoidal, polygonal surrounding the three-color LED device 100.

[0242] As Figure 1B and Figure 1C shown, in some embodiments, the red LED light-emitting layer 112, the green LED light-emitting layer 130, and the blue LED light-emitting layer 136 have inclined side surfaces. As used herein, an inclined side surface may refer to a surface that is not perpendicular to the top surface or the bottom surface of the corresponding LED light-emitting layer. In some embodiments, the angle between the inclined sidewall and the bottom surface of the corresponding LED light-emitting layer is less than 90 degrees. In some embodiments, the bonding layers 108, 156, and 160 also have inclined side surfaces. The inclined side surfaces can facilitate the connection of different connecting elements to each LED light-emitting layer, prevent the connection from being disconnected due to the abrupt corners of the connecting elements, and enhance the overall stability of the device.

[0243] In some embodiments, the light propagation efficiency of the multicolor LED device changes with the change in the angle of the inclined side surface of the LED light-emitting layer relative to the surface normal of the substrate 104. In some embodiments, the light propagation efficiency of the multicolor LED device increases as the angle of the inclined side surface of the LED light-emitting layer relative to the surface normal of the substrate 104 increases. For example, when the angle of the side surface of the LED light-emitting layer relative to the surface normal of the substrate 104 is ±5 degrees and when the optical isolation structures such as 146, 148, 170, and / or 172 are not the reflecting cups described below, the luminous efficiency of the multicolor LED device is 0.32%. For example, when the angle of the side surface of the LED light-emitting layer relative to the surface normal of the substrate 104 is ±15 degrees and when the optical isolation structures such as 146, 148, 170, and / or 172 are not the reflecting cups described below, the luminous efficiency of the multicolor LED device is 2.7%. For example, when the angle of the side surface of the LED light-emitting layer relative to the surface normal of the substrate 104 is at (e.g., when the light-emitting layer is inclined) or very close to ±90 degrees and when the optical isolation structures such as 146, 148, 170, and / or 172 are not the reflecting cups described below, the luminous efficiency of the multicolor LED device is equal to or very close to 56.4%.

[0244] In contrast, the implementation of the reflecting cup structure, which is described in further detail below, improves the light propagation efficiency of the multicolor LED device. For example, when the angle of the side surface of the LED light-emitting layer relative to the surface normal of the substrate 104 is ±5 degrees and when the optical isolation structures such as 146, 148, 170, and / or 172 are the reflecting cups described below, the luminous efficiency of the multicolor LED device is 0.65%, i.e., a 104.6% increase compared to the LED device without a reflecting cup. For example, when the angle of the side surface of the LED light-emitting layer relative to the surface normal of the substrate 104 is ±15 degrees and when the optical isolation structures such as 146, 148, 170, and / or 172 are the reflecting cups described below, the luminous efficiency of the multicolor LED device is 6.65%, i.e., a 144.4% increase compared to the LED device without a reflecting cup. For example, when the angle of the side surface of the LED light-emitting layer relative to the surface normal of the substrate 104 is at (e.g., when the light-emitting layer is inclined) or very close to ±90 degrees and when the optical isolation structures such as 146, 148, 170, and / or 172 are the reflecting cups described below, the luminous efficiency of the multicolor LED device is equal to or very close to 66.65%, i.e., an 18.4% increase compared to the LED device without a reflecting cup.

[0245] In some embodiments, a reflective layer is formed above and below each LED light-emitting layer to improve the light propagation efficiency. As Figure 1B and 1CAs shown, in some embodiments, a reflective layer 109 is formed between the bonding layer 108 and the red LED light-emitting layer 112. In some embodiments, in the presence of the conductive layer 110, the reflective layer 109 is formed between the bonding layer 108 and the conductive layer 110. In some embodiments, a reflective layer 115 is formed between the bonding layer 156 and the red LED light-emitting layer 112. In some embodiments, in the presence of the conductive layer 114, the reflective layer 115 is formed between the bonding layer 156 and the conductive layer 114.

[0246] In some embodiments, a reflective layer 127 is formed between the bonding layer 156 and the green LED light-emitting layer 130. In some embodiments, in the presence of the conductive layer 128, the reflective layer 127 is formed between the bonding layer 156 and the conductive layer 128. In some embodiments, a reflective layer 133 is formed between the bonding layer 160 and the green LED light-emitting layer 130. In some embodiments, in the presence of the conductive layer 132, the reflective layer 133 is formed between the bonding layer 160 and the conductive layer 132.

[0247] In some embodiments, a reflective layer 135 is formed between the bonding layer 160 and the blue LED light-emitting layer 136. In some embodiments, in the presence of the conductive layer 134, the reflective layer 135 is formed between the bonding layer 160 and the conductive layer 134. In some embodiments, an optional reflective layer 139 ( Figures 1B - 1C not shown) is formed between the N electrode pad 140 and the blue LED light-emitting layer 136 while still allowing the blue LED light-emitting layer 136 to be electrically connected to the N electrode pad 140, for example, through a conductive path. In some embodiments, in the presence of the conductive layer 138, the optional reflective layer 139 is formed between the N electrode pad 140 and the conductive layer 138 while still allowing the conductive layer 138 to be electrically connected to the N electrode pad 140, for example, through a conductive path.

[0248] In some embodiments, the materials of the reflective layers 109, 115, 127, 133, 135, and 139 have a high reflectivity, especially for the light emitted by the single-pixel three-color LED device 200. For example, the reflectivity of the reflective layers 109, 115, 127, 133, 135, and 139 is higher than 60%. In another example, the reflectivity of the reflective layers 109, 115, 127, 133, 135, and 139 is higher than 70%. In yet another example, the reflectivity of the reflective layers 109, 115, 127, 133, 135, and 139 is higher than 80%.

[0249] In some embodiments, the materials of the reflective layers 109, 115, 127, 133, 135, and 139 are one or more selected from the following metals: Rh, Al, Ag, and Au. In certain embodiments, any one of the reflective layers 109, 115, 127, 133, 135, and 139 may include at least two sub-layers having different refractive indices. Each sub-layer also has a high reflectivity such as higher than 60%, 70%, or 80%.

[0250] In some embodiments, each reflective layer, such as 109, 115, 127, 135, and 139, is coated on both sides of each light-emitting layer in the light-emitting layers such as 112, 130, and 136, or in the case of including a conductive layer, is coated on both sides of the conductive layers 110, 114, 128, 132, 134, and 138 before bonding. In some cases, the thickness of each of the reflective layers such as 109, 115, 127, 133, 135, and 139 is about 2 nanometers (nm) to 5 micrometers. In some embodiments, the thickness of each of the reflective layers such as 109, 115, 127, 133, 135, and 139 is equal to or less than 1 micrometer. In some preferred embodiments, the thickness of each layer in the reflective layers such as 109, 115, 127, 133, 135, and 139 is about 5 nanometers (nm) to 10 nm.

[0251] In some embodiments, any one of the reflective layers such as 109, 115, 127, 133, 135, and 139 includes a distributed Bragg reflector (DBR) structure. For example, any one of the reflective layers such as 109, 115, 127, 133, 135, and 139 is formed by multiple alternating layers or multiple layers of different materials having different refractive indices. In some cases, each layer boundary of the DBR structure results in partial reflection of light waves. The reflective layers such as 109, 115, 127, 133, 135, and 139 can be used to reflect some selected wavelengths. For example, the reflective layers 109 and 115 for red light, the reflective layers 127 and 133 for green light, and the reflective layers 135 and 139 for blue light. In some embodiments, any one of the reflective layers such as 109, 115, 127, 133, 135, and 139 is made of multiple layers, such as at least two layers of SiO2 and Ti3O5 respectively. By changing the thickness and number of the layers of SiO2 and Ti3O5 respectively, selective reflection or selective propagation of light of different wavelengths can be formed.

[0252] In some embodiments, any one of the reflective layers such as 109, 115, 127, 133, 135, and 139 further includes a transparent layer on one of the high-reflectivity sub-layers. For example, the transparent layer preferably formed on one or both sides of the reflective layers such as 109, 115, 127, 133, 135, and 139 is selected from one or more of ITO and SiO2.

[0253] In some embodiments, each of the reflective layers 109 and 115 for red LEDs includes multiple layers of Au or / and indium tin oxide (ITO).

[0254] In some embodiments, each of the reflective layers 109 and 115 for red LED structures has a low absorbance of light generated by different layers of the three-color LED device 100 (e.g., equal to or less than 25%). In some embodiments, each of the reflective layers 109 and 115 for red LED structures has a high reflectivity (e.g., equal to or greater than 75%) for light generated between the current two reflective layers 109 and 115, such as red light.

[0255] In one example, the following DBR structure shown in Table 1 is used to reflect green light from a green LED:

[0256] Table 1: DBR layer structure for the green LED reflective layer.

[0257]

[0258] In some embodiments, each of the reflective layers 127 and 133 for green LED structures has a low absorbance of light generated by different layers of the three-color LED device 100 (e.g., equal to or less than 25%). In some embodiments, each of the reflective layers 127 and 133 for green LED structures has a high reflectivity (e.g., equal to or greater than 75%) for light generated between the current two reflective layers 127 and 133, such as green light.

[0259] In one example, the following DBR structure shown in Table 2 is used to reflect blue light from a blue LED:

[0260] Table 2: DBR layer structure for the blue LED reflective layer.

[0261]

[0262] In some embodiments, each of the reflective layers 135 and optional 139 for the blue LED structure has a low absorbance (e.g., equal to or less than 25%) for light generated by different layers of the tri-color LED device 100. In some embodiments, the reflective layer 135 for the blue LED structure has a high reflectivity (e.g., equal to or greater than 75%) for light generated above the current reflective layer 135 or between the current reflective layer 135 and 139, such as blue light.

[0263] Figure 2A is a cross-sectional view of a single-pixel tri-color LED device 100 with planarization features along Figure 1A the diagonal 102 in. In some embodiments, the single-pixel tri-color LED device 100 has a structure similar to the single-pixel tri-color LED device 100 shown in Figure 1A , 1B and 1C, which adds a planarization layer 176 covering the single-pixel tri-color LED device 100.

[0264] Figure 2B is a cross-sectional view of a single-pixel tri-color LED device 100 with planarization features along Figure 1A the diagonal 150 in. In some embodiments, the single-pixel tri-color LED device 100 has a structure similar to the single-pixel tri-color LED device 100 shown in Figure 1A , 1B and 1C, which adds a planarization layer 176 covering the single-pixel tri-color LED device 100.

[0265] In some embodiments, a planarization layer such as 176 is transparent to the light emitted by the micro-LED 100. In some embodiments, the planarization layer 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 borophosphosilicate 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-on glass (SOG), or the bonding adhesive BCL-1200 from Micro Resist Company, or any combination thereof. In some embodiments, the planarization layer can facilitate the passage of the light emitted by the micro-LED 100.

[0266] In some embodiments, the planarization layer 176 has the same height as the optical isolation structures such as 146, 148, 170, and 172 with respect to the surface of the substrate 104. For example, the planarization layer 176 covers the entire single-pixel three-color LED device 100 and the sidewalls of the optical isolation structures. The planarization layer 176 is in the same plane as the top surface of the optical isolation structures.

[0267] Figure 3A is a cross-sectional view of a single-pixel three-color LED device 100 with planarization features along Figure 1A the diagonal 102 in FIG. In some embodiments, the single-pixel three-color LED device 100 has a structure similar to the single-pixel three-color LED device 100 shown in Figure 1A , 1B and 1C, with an added planarization layer 178 that covers the single-pixel three-color LED device 100.

[0268] Figure 3B is a cross-sectional view of a single-pixel three-color LED device 100 with planarization features along Figure 1A the diagonal 150 in FIG. In some embodiments, the single-pixel three-color LED device 100 has a structure similar to the single-pixel three-color LED device 100 shown in Figure 1A , 1B and 1C, with an added planarization layer 178 that covers the single-pixel three-color LED device 100.

[0269] In some embodiments, the planarization layer 178 has the same height as the top electrode element such as 140. The planarization layer 178 is in the same plane as the top surface of the top electrode element such as the N electrode pad 140. In some embodiments, the top electrode element such as 140 is exactly on top of the planarization layer 178. The planarization layer 178 is in the same plane as the bottom surface of the top electrode element such as the N electrode pad 140. For example, the planarization layer 178 covers the entire single-pixel three-color LED device 100 and a portion of the sidewalls of the optical isolation structures such as 146, 148, 170, and 172.

[0270] Different from being connected to the top electrode element such as the N electrode pad 140 as shown in Figures 1A - 1C through electrical connection elements under the optical isolation structures such as 146, 148, 170, and 172, in Figures 2A - 2B, in FIGS. 3A-3B, a top electrode element such as the N electrode pad 140 is connected by an electrical connection element at least on the sidewalls of the optical isolation structures such as 146, 148, 170, and 172. In some embodiments, the N electrode pad 140 is fixed or secured on the surface of the optical isolation structures such as 146, 148, 170, and 172 through the surface of the optical isolation structures such as 146, 148, 170, and 172. The top electrode structure can simplify the manufacturing process, especially with a planarized layer, making the single pixel three-color LED device 100 compact.

[0271] In some embodiments, the insulating layer can be deposited on each LED light-emitting layer and other layers such as the conductive layer and the reflective layer to achieve deposition on the single pixel multi-color LED device. Then a planarization process is performed to make the surface of the insulating layer embedded in the single pixel multi-color LED device flat. Via holes for electrical connection are also formed within each planarized layer. Compared with an insulating layer without planarization using other processes, the features and layers within the planarized LED structure are better protected and less vulnerable to external destructive forces. In addition, the planarized surface can provide light propagation efficiency by reducing deflection caused by an uneven surface.

[0272] In some embodiments, a three-color LED structure is formed by dry etching and wet etching, and the axes of the LED structures of different colors are vertically aligned with each other. In some embodiments, the LED structures of different colors share the same axis.

[0273] In some embodiments, each of the LED structures of different colors forms a pyramid shape or a shape with a trapezoidal cross-section. Each layer has a narrower width or a smaller area compared to the layer below it. In this case, the width or area is measured by the size of a plane parallel to the surface of the substrate 104.

[0274] In some embodiments, each of the multiple LED structures of different colors is bonded together by a bonding layer that only covers the area of the LED structure without an extended portion beyond the LED structure, and the entire multi-color LED device forms a pyramid (or inverted cone) shape or a shape with a trapezoidal cross-section (as shown in FIGS. 1-3). In some embodiments, for example, the lateral dimension of the bottom LED structure such as the red LED structure can be the longest, and the lateral dimension of the top LED structure such as the blue LED structure can be the shortest. The pyramid shape can be naturally formed from the bottom up when the layers within the LED device are etched and patterned. The pyramid-shaped structure can improve the electrical connection between individual LED structures and between the electrodes and simplify the manufacturing process. For example, the electrode connection elements in each layer are exposed in each layer for easy connection.

[0275] In some embodiments, a bottom layer such as the metal bonding layer 108 has a lateral dimension of about 1 micron to 500 microns. In a preferred embodiment, the lateral dimension of the metal bonding layer 108 at the bottom of the multicolor LED device is about 1.75 microns. In some embodiments, the vertical height of the multicolor LED device is about 1 micron to 500 microns. In a preferred embodiment, the vertical height of the multicolor LED device is about 1.9 microns. In a preferred embodiment, the lateral dimension of the conductive layer 138 at the top of the multicolor LED device is about 1.0 micron.

[0276] In some embodiments, the aspect ratio of the cross-section of the layers of the three-color LED device remains substantially the same with changes in the lateral dimension of the same layer. For example, when the lateral dimension of the patterned epitaxial layer is 5 microns, the thickness of the patterned epitaxial layer is less than 1 micron. In another example, with an increase in the lateral dimension of the same patterned epitaxial layer, the thickness of the patterned epitaxial layer increases correspondingly to maintain the same aspect ratio. In some embodiments, the aspect ratio of the cross-section of the epitaxial layer and other layers is less than 1 / 5 of the thickness / width.

[0277] The shape of the LED device is not limited. In some other embodiments, the cross-sectional shape of the three-color LED device can adopt other shapes, such as, for example, an inverted trapezoid, a semi-ellipse, a rectangle, a parallelogram, a triangle, or a hexagon, etc.

[0278] In some embodiments, the top conductive layer 138 above the third LED light-emitting layer 136 is patterned using photolithography and etching. In some cases, the etching method used to form the pattern is, for example, dry etching such as inductively coupled plasma (ICP) etching or wet etching with an ITO etching solution. In some embodiments, the same patterning method can be applied to all other conductive layers within the three-color LED device 100, including the conductive layers 110, 114, 128, 132, 134, and 138.

[0279] In some embodiments, the blue LED light-emitting layer 136 and the green LED light-emitting layer 130 are patterned using photolithography and etching. In some cases, the etching method used to form the pattern is dry etching, such as inductively coupled plasma (ICP) etching using C12 and BC13 etching gases.

[0280] In some embodiments, the bonding layers including 160 and 156 are patterned using photolithography and etching. In some cases, the etching method used to form the pattern is dry etching, such as inductively coupled plasma (ICP) etching using CF4 and O2 etching gases.

[0281] In some embodiments, the reflective layer including 109, 115, 127, 133, 135, and 139 is patterned using photolithography and etching. In some cases, the etching method used to pattern the reflective layer, particularly the DBR layer, is dry etching, for example, inductively coupled plasma (ICP) etching using CF4 and O2 etching gases or ion beam etching (IBE) using Ar gas.

[0282] In some embodiments, the red LED light-emitting layer 112 is patterned using photolithography and etching. In some cases, the etching method used to form the pattern is dry etching, for example, inductively coupled plasma (ICP) etching using C12 and HBr etching gases.

[0283] In some embodiments, the metal bonding layer 108 is patterned using photolithography and etching. In some cases, the etching method used to form the pattern is dry etching, for example, inductively coupled plasma (ICP) etching using C12 / BC13 / Ar etching gases or ion beam etching (IBE) using Ar gas.

[0284] In some embodiments, after each LED device structure in each LED device structure is patterned, an insulating layer such as 174, 176, 178 is deposited on the surface of each patterned LED structure including all the patterned layers, sidewalls, and the exposed substrate. In some embodiments, the insulating layer is made of SiO2 and / or Si3N4. In some embodiments, the insulating layer is made of TiO2. In some embodiments, an insulating layer having a composition similar to SiO2 is formed after curing a layer such as SOG at a high temperature. In some embodiments, the insulating layer is made of a material having a thermal coefficient similar to that of the layers below the insulating layer. Then, the surfaces of the insulating layers such as 176 and 178 are smoothed or planarized by related methods such as chemical mechanical polishing understood by those of ordinary skill in the art.

[0285] In some embodiments, the insulating layers such as 176 and 178 after planarization are patterned using photolithography and etching to expose the electrode contact regions. In some cases, the etching method used to form the pattern is dry etching, for example, inductively coupled plasma (ICP) etching using CF4 and O2.

[0286] In some embodiments, the P electrode or the anode metal pad is deposited at a suitable position on the patterned LED structure, such as on one side and / or in the vias within the planarized insulating layer, by vapor deposition or other deposition methods to electrically connect the red LED structure, the green LED structure, and the blue LED structure.

[0287] In some embodiments, a separate N electrode or cathode metal pad is deposited at a suitable location of the patterned LED structure, such as on one side / top and / or in vias within the planarized insulating layer, by vapor deposition or other deposition methods, to electrically connect the red LED structure, the green LED structure, and the blue LED structure.

[0288] Figure 4A is a top view of a single-pixel three-color LED device 400 with hierarchical planarization according to some embodiments.

[0289] Figure 4B is along a Figure 4A cross-sectional view of the diagonal 402 in a single-pixel three-color LED device 400 with hierarchical planarization according to some embodiments. The diagonal passes through the center of the single-pixel three-color LED device 400.

[0290] Compared with the embodiments depicted in FIGS. 1-3, Figures 4A - 4B the main difference in the embodiments herein is that each LED structure in the LED structures of different colors is embedded in a corresponding planarized insulating layer, and the planarized insulating layers with LED structures inside are bonded together via some bonding layers.

[0291] In some embodiments, the three-color LED device 400 includes a substrate 404. For convenience, "upward" is used to indicate away from the substrate 404, and "downward" indicates toward the substrate 404. Other directional terms such as top, bottom, above, below, directly below, underneath, etc. are also interpreted accordingly. The support substrate 404 is a substrate on which an array of respective drive circuits 406 is fabricated. In some embodiments, the drive circuits can also be located in one of the layers above the substrate 404, or above the micro three-color LED structure 400. Each drive circuit is a pixel driver 406. In certain cases, the drive circuit 406 is a thin-film transistor pixel driver or a silicon CMOS pixel driver. In one embodiment, the substrate 404 is a Si substrate. In another embodiment, the support substrate 404 is a transparent substrate, for example, a glass substrate. Examples of other substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. In some embodiments, the substrate 404 is about 700 microns thick. The drive circuits 406 form respective pixel drivers to control the operation of each single-pixel three-color LED device 400. The circuits on the substrate 404 include contacts for each individual drive circuit 406 and ground contacts. As Figure 4A and Figure 4BAs shown, each micro triple-color LED structure 400 also has two types of contacts: P electrodes or anodes such as 450 (or 408), 452 connected to the pixel driver and the merged portions 422, 424, and 426; and N electrodes or cathodes such as 440, 442, 444 connected to ground (i.e., the common electrode) and the merged portions 416, 418, and 420.

[0292] In some embodiments, the N electrodes (or N electrode contact pads) and their connecting components, such as 440, 442, 444 and the merged portions 416, 418, and 420, are made of materials such as graphene, ITO, aluminum-doped zinc oxide (AZO), or fluorine-doped tin oxide (FTO), or any combination of the above. In some embodiments, the N electrodes (or N electrode contact pads) and their connecting components, such as 440, 442, 444, and the merged portions 416, 418, and 420, are made of non-transparent or transparent conductive materials, and in a preferred embodiment, are made of transparent conductive materials. In some embodiments, the P electrodes (or P electrode contact pads) and their connecting components, such as 450, 452, and the merged portions 422, 424, and 426, are made of materials such as graphene, ITO, AZO, or FTO, or any combination of the above. In some embodiments, the P electrodes (or P electrode contact pads) and their connecting components, such as 450, 452 and the merged portions 422, 424, and 426, are made of non-transparent or transparent conductive materials, and in a preferred embodiment, are made of transparent conductive materials. In some embodiments, the positions of the P electrodes (or P electrode contact pads) and their connecting components and the N electrodes (or N electrode contact pads) and their connecting components can be switched.

[0293] Generally, the LED light-emitting layer includes a PN junction having a p-type region / layer and an n-type region / layer, and an active layer between the p-type region / layer and the n-type region / layer.

[0294] In some embodiments, the light emitted by the red LED light-emitting layer 412 can propagate horizontally toward the sidewalls of the red LED light-emitting layer 412, and then be reflected upward by reflection elements such as 446 and / or 448 as described below, and emitted at the top surface of the single-pixel triple-color LED device 400. As described below, a reflective layer 409 is provided below the red LED light-emitting layer 412, and a reflective layer 415 is provided above the red LED light-emitting layer 412. The light emitted by the red LED light-emitting layer 412 is reflected between the two reflective layers 409 and 415 toward the sidewalls of the red LED light-emitting layer 412.

[0295] In some embodiments, the light emitted by the green LED light-emitting layer 430 can propagate horizontally toward the sidewall of the green LED light-emitting layer 430, and then be reflected upward by reflection elements such as 446 and / or 448 as described below, and emitted at the top surface of the single-pixel tri-color LED device 400. As described below, a reflective layer 427 is provided below the green LED light-emitting layer 430, and a reflective layer 433 is provided above the green LED light-emitting layer 430. The light emitted from the green LED light-emitting layer 430 is reflected toward the sidewall of the green LED light-emitting layer 430 between the two reflective layers 427 and 433.

[0296] In some embodiments, the light emitted by the blue LED light-emitting layer 436 can propagate horizontally toward the sidewall of the blue LED light-emitting layer 436, and then be reflected upward by reflection elements such as 446 and / or 448 as described below, and emitted at the top surface of the single-pixel tri-color LED device 400. As described below, a reflective layer 435 is provided below the blue LED light-emitting layer 436. The light emitted from the blue LED light-emitting layer 436 is reflected toward the sidewall of the blue LED light-emitting layer 436 between the reflective layer 435 and the upper surface of the blue LED light-emitting layer 436.

[0297] In some embodiments, the light emitted by the red LED light-emitting layer 412 can propagate vertically through the green LED light-emitting layer 430, and then through the blue LED light-emitting layer 436 to be emitted from the tri-color LED device 400. In some embodiments, the light emitted by the green LED light-emitting layer 430 can propagate through the blue LED light-emitting layer 436 to be emitted from the tri-color LED device 400. In the case of vertical light propagation, in some preferred embodiments, the top reflective layers such as 415 and 433 above each light-emitting layer are not included in the tri-color LED device 400.

[0298] In some embodiments, the LED light-emitting layers such as 412, 430, and 436 include many sub-epitaxial layers with different compositions. Examples of LED epitaxial layers include III-V nitrides, III-V arsenides, III-V phosphides, and III-V antimonide epitaxial structures. Examples of micro-LEDs include GaN-based UV / blue / green micro-LEDs, AlInGaP-based red / orange micro-LEDs, and GaAs or InP-based infrared (IR) micro-LEDs.

[0299] In some embodiments, each LED structure in the stacked LED structure can be separately controlled to generate its individual light. In some embodiments, the mixed light emitted from the top LED epitaxial layer can change the color of a single pixel within a small coverage area on the display panel due to the simultaneous operation of all the LED epitaxial layers in the tri-color LED device 400.

[0300] In some embodiments, according to the design of the LED device 400, the colors of the light emitted by the respective LED structures included in the same device are not limited to red, green, and blue. For example, suitable colors can be selected from the range of different color lights with wavelengths from 380 nm to 700 nm within the visible light range. In some embodiments, the LED structures can also be implemented to emit other color lights from the invisible range such as ultraviolet and infrared.

[0301] In some embodiments, when vertical light emission is combined with horizontal light emission, for example, the selection of the three colors can be red, green, and blue from bottom to top. In another embodiment, the selection of the three colors can be infrared light, orange, and ultraviolet light from bottom to top. In some embodiments, the wavelength of the light emitted by the LED structure on one layer of the device 400 is longer than the wavelength of the light emitted by the LED structure on the layer above the current layer. For example, the wavelength of the light emitted by the bottom LED light-emitting layer 412 is longer than the wavelength of the light emitted by the middle LED light-emitting layer 430, and the wavelength of the light emitted by the middle LED light-emitting layer 430 is longer than the wavelength of the light emitted by the top LED light-emitting layer 436.

[0302] In some embodiments, when in the case of horizontal light emission or when the portion of horizontal light emission is more than the portion of vertical light emission from the top surface of the LED device 400, each of the light-emitting layers 412, 430, and 436 of the LED can be any suitable visible or invisible light color. The advantage of horizontal light emission is that since the emitted light does not need to pass through other upper layers of the LED device 400 but is directly emitted from the edge or side wall of the current light-emitting layer, the light propagation loss can be reduced and the light-emitting efficiency can be improved. For example, compared with a vertical light-emitting LED device, a horizontal light-emitting LED device can increase the light propagation efficiency by 15%, 50%, 100%, 150%, or 200%. In some cases, the light propagation efficiency of the horizontal light-emitting LED device can be equal to or greater than 20%, 40%, or 60%.

[0303] In some embodiments, the bottom red LED light-emitting layer 412 is bonded to the substrate 404 through the metal bonding layer 408. The metal bonding layer 408 can be disposed on the substrate 404. In one method, the metal bonding layer 408 grows on the substrate 404. In some embodiments, the metal bonding layer 408 is electrically connected to the driving circuit 406 on the substrate 404 and the red LED light-emitting layer 412 above the metal bonding layer 408, and serves as a P electrode. In some embodiments, the thickness of the metal bonding layer 408 is about 0.1 micrometer to 3 micrometers. In a preferred embodiment, the thickness of the metal bonding layer 408 is about 0.3 μm. The metal bonding layer 408 can include an ohmic contact layer and a metal bonding layer. In some cases, the metal bonding layer 408 includes two metal layers. One of the metal layers is deposited on the layer above the metal bonding layer within the LED device 400. The corresponding bonding metal layer is also deposited on the substrate 404. In some embodiments, the composition of the metal bonding layer 408 includes Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or a mixture of the above. For example, if Au-Au bonding is selected, two Au layers respectively require a Cr coating as an adhesive layer and a Pt coating as an anti-diffusion layer. The Pt coating is located between the Au layer and the Cr layer. The Cr layer and the Pt layer are located on the top and bottom of the two bonded Au layers. In some embodiments, when the thicknesses of the two Au layers are substantially the same, at high pressure and high temperature, the Au on the two layers diffuses into each other to bond the two layers together. Eutectic bonding, thermocompression bonding, and transient liquid phase (TLP) bonding are exemplary techniques that can be used.

[0304] In some embodiments, the metal bonding layer 408 can also be used as a reflector to reflect the light emitted from the LED structure above.

[0305] In some embodiments, a conductive layer 410 for electrode connection is formed at the bottom of the red LED light-emitting layer 412. In some embodiments, the conductive layer 410 is a conductive transparent layer such as an indium tin oxide (ITO) layer that is transparent to the light emitted by the LED device 400, and is formed between the red LED light-emitting layer 412 and the metal bonding layer 408 to improve conductivity and light transmittance. As shown in Figure 4A and not shown in Figure 4B In some embodiments, the red LED structure has a P electrode contact pad 450 electrically connected to the red LED light-emitting layer 412. In some embodiments, the P electrode contact pad 450 is connected to the conductive layer 410. In some embodiments, a conductive layer 414 for electrode connection is formed on the top of the red LED light-emitting layer 412. In some embodiments, the conductive layer 414 can be a conductive transparent layer such as an ITO layer, and is formed between the red LED light-emitting layer 412 and the N electrode contact pad 416 to improve conductivity and light transmittance.

[0306] In some embodiments, the red LED light-emitting layer 412 has an extension portion 464 on one side thereof relative to other upper layers. In some embodiments, the extension portion 464 extends together with the conductive layers 410 and 414. In some embodiments, the extension portion 464 is connected to the N electrode contact pad 416 through an extension portion of the conductive layer 414 above the extension portion 464.

[0307] In some embodiments, the reflective layer 409 is located between the conductive layer 410 and the metal bonding layer 408 below the red LED light-emitting layer 412, and the reflective layer 415 is located between the conductive layer 414 and the bonding layer 456 above the red LED light-emitting layer 412, and in one example, is located within the planarized insulating layer 454.

[0308] In one method, the red LED light-emitting layer 412 is grown on a separate substrate (referred to as an epitaxial substrate). After bonding, the epitaxial substrate is removed by, for example, a laser lift-off process or wet chemical etching, leaving Figure 4B the structure shown in

[0309] In some embodiments, the red LED light-emitting layer 412 is used to form a red micro-LED. Examples of the red LED light-emitting layer include III-V nitrides, III-V arsenides, III-V phosphides, and III-V antimonide epitaxial structures. In some cases, the film within the red LED light-emitting layer 412 may include layers of P-type GaP / P-type AlGaInP light-emitting layer / AlGaInP / N-type AlGaInP / N-type GaAs. In some embodiments, the P-type layer is typically doped with Mg, while the N-type layer is typically doped with Si. In some examples, the thickness of the red LED light-emitting layer is about 0.1 micrometer to 5 micrometers. In a preferred embodiment, the thickness of the red LED light-emitting layer is about 0.3 micrometers.

[0310] In some embodiments, the red LED structure includes a metal bonding layer 408, a reflective layer 409, a conductive layer 410, a red LED light-emitting layer 412, a conductive layer 414, a reflective layer 115, and an N electrode contact pad 416. In some embodiments, the red LED structure is formed within a planarized insulating layer 454, for example, within a silicon dioxide (SiO2) layer. In some embodiments, the planarized insulating layer 454 covers the entire red LED structure. In some embodiments, the entire red LED structure is embedded within the planarized insulating layer 454. In some embodiments, the surface of the planarized insulating layer 454 is smoothed or planarized by a chemical mechanical polishing method.

[0311] In some embodiments, a planarization layer such as 454 is transparent to the light emitted by the LED device 400. In some embodiments, the planarization layer 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 borophosphosilicate 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-on glass (SOG), or the bonding adhesive BCL-1200 from Micro Resist, or any combination thereof. In some embodiments, the planarization layer can facilitate the light emitted by the micro-LED 400 to pass through. In some embodiments, the planarization layers such as 454, 468, and 462 have the same composition as the bonding layers such as 456 and 460. In some embodiments, the planarization layers such as 454, 468, and 462 have a different composition from the bonding layers such as 456 and 460.

[0312] In some embodiments, vias or through-holes are formed in the planarized insulating layer 454 to accommodate the P electrode contact elements 422 and 424 for the green LED structure. The P electrode contact elements 422 and 424 are connected to the drive circuit 406.

[0313] In some embodiments, the bonding layer 456 is used to bond the red LED structure and the green LED structure together. In some embodiments, the bonding layer 456 is opaque to the light emitted by the LED device 400. In some embodiments, the material and thickness of the bonding layer 456 are the same as those described above for the metal bonding layer 408. In some embodiments, the bonding layer 456 can also be used as a reflector to reflect the light emitted by the upper LED structure.

[0314] In some embodiments, when vertical propagation is used, the bonding layer 456 is transparent to the light emitted by the micro-LED 400. In some embodiments, the bonding layer 456 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 borophosphosilicate 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-on glass (SOG), or the bonding adhesive BCL-1200 from Micro Resist, or any combination thereof. In some embodiments, the transparent bonding layer can facilitate the light emitted by the layer below the bonding layer to pass through.

[0315] In some embodiments, a conductive layer 428 for electrode connection is formed at the bottom of the green LED light-emitting layer 430. In some embodiments, the conductive layer 428 is a conductive transparent layer 428 such as an ITO layer, formed between the green LED light-emitting layer 430 and the bonding layer 456 to improve conductivity and light transmittance.

[0316] In some embodiments, as Figure 4A and Figure 4B shown, the green LED structure has a P electrode contact pad 426 electrically connected to the green LED light-emitting layer 430. In some embodiments, the P electrode contact pad is connected to the conductive layer 428. In some embodiments, the P electrode contact pad 426 is also connected to P electrode contact elements 422 and 424 in the planarized insulating layer 454 through a portion of the P electrode contact pad 426 within the bonding layer 456. In some embodiments, the P electrode contact element 422 has a cylindrical shape. In some embodiments, the P electrode contact element 424 has a funnel-shaped configuration with a narrow top side and a wide bottom side, the narrow top side matching the width of the component 422, and the funnel-shaped configuration for supporting the element 422 above it. In some embodiments, a conductive layer 432 for electrode connection is formed at the top of the green LED light-emitting layer 430. In some embodiments, the conductive layer 432 is a conductive transparent layer 432 such as an ITO layer, formed between the green LED light-emitting layer 430 and the N electrode contact pad 420 to improve conductivity and light transmittance. In some embodiments, in Figure 4A and Figure 4B both shown, the green LED structure has an N electrode contact pad 420 electrically connected to the green LED light-emitting layer 430. In some embodiments, the N electrode contact pad 420 is connected to the conductive layer 432. In some embodiments, the N electrode contact pad 420 of the green LED structure is also electrically connected to the N electrode contact pad 416 of the red LED structure through an N electrode contact element 418 within the transparent bonding layer 456. In some embodiments, vias or through-holes are formed within the bonding layer 456 to accommodate a portion of the N electrode contact element 418 and the P electrode contact pad 426.

[0317] In some embodiments, the green LED light-emitting layer 430 has an extension portion 466 on one side thereof relative to other layers above. In some embodiments, the extension portion 466 extends together with the conductive layers 428 and 432. In some embodiments, the extension portion 466 is connected to the N electrode contact pad 420 through an extension of the conductive layer 432 above the extension portion 466.

[0318] In some embodiments, the lateral dimension of the green LED light-emitting layer 430 is substantially the same as that of the red LED light-emitting layer 412, especially for the effective light-emitting area.

[0319] In some embodiments, the reflective layer 427 is below the green LED light-emitting layer 430, between the conductive layer 428 and the bonding layer 456, and the reflective layer 433 is above the green LED light-emitting layer 430, between the conductive layer 432 and the bonding layer 460. In one example, it is within the planarized insulating layer 458.

[0320] In one method, the green LED light-emitting layer 430 is grown on another separate substrate (referred to as an epitaxial substrate). After bonding, the epitaxial substrate is removed by, for example, a laser lift-off process or wet chemical etching, leaving Figure 4B the structure shown in

[0321] In some embodiments, the green LED light-emitting layer 430 is used to form green micro-LEDs. Examples of the green LED light-emitting layer include III-V nitrides, III-V arsenides, III-V phosphides, and III-V antimonide epitaxial structures. In some cases, the film within the green LED light-emitting layer 430 may include a layer of P-type GaN / InGaN light-emitting layer / N-type GaN. In some embodiments, P-type is typically Mg-doped, and N-type is typically Si-doped. In some examples, the thickness of the green LED light-emitting layer is about 0.1 micrometer to 5 micrometers. In a preferred embodiment, the thickness of the green LED light-emitting layer is about 0.3 micrometers.

[0322] In some embodiments, the green LED structure includes a reflective layer 427, a conductive layer 428, a green LED light-emitting layer 430, a conductive layer 432, a reflective layer 433, and an N electrode contact pad 420. In some embodiments, the green LED structure is formed within the planarized insulating layer 458. In some embodiments, the planarized insulating layer 458 covers the entire green LED structure and a portion of the P electrode contact pad 426. In some embodiments, the entire green LED structure is embedded within the planarized insulating layer 458. In some embodiments, the two surfaces of the planarized insulating layer 458 are smoothed or planarized by a chemical mechanical polishing method.

[0323] In some embodiments, without including extensions such as 464, 466, the first LED structure, e.g., a red LED structure, and the second LED structure, e.g., a green LED structure, have the same central axis. In some embodiments, without including extensions such as 464, 466, the first LED structure and the second LED structure are aligned along the same central axis.

[0324] In some embodiments, the bonding layer 460 is used to bond the green LED structure and the blue LED structure together. In some embodiments, the bonding layer 456 is opaque to the light emitted by the LED device 400. In some embodiments, the material and thickness of the bonding layer 460 are the same as those described above for the metal bonding layer 408. In some embodiments, the bonding layer 460 can also be used as a reflector to reflect the light emitted by the upper LED structure.

[0325] In some embodiments, when vertical propagation is used, the bonding layer 460 is transparent to the light emitted by the LED device 400. In some embodiments, the bonding layer 460 is made of a dielectric material such as a solid inorganic material or a plastic material, the same as the description of the bonding layer 456 above. In some embodiments, the transparent bonding layer can facilitate the light emitted by the layer below the bonding layer to pass through.

[0326] In some embodiments, a conductive layer 434 for electrode connection is formed at the bottom of the blue LED light-emitting layer 436. In some embodiments, the conductive layer 434 is a conductive transparent layer 434 such as an ITO layer, formed between the blue LED light-emitting layer 436 and the bonding layer 460 to improve conductivity and light transmittance. In some embodiments, as Figure 4A shown, but not shown in Figure 4B , the blue LED structure has a P electrode contact pad 452 electrically connected to the blue LED light-emitting layer 436. In some embodiments, the P electrode contact pad 452 is connected to the conductive layer 434. In some embodiments, the P electrode contact pad 452 is also connected to some P electrode contact elements similar to 422 and 424 within the planarized insulating layers 454 and 458 and within the transparent bonding layers 456 and 460 ( Figure 4A and 4B are not shown in either). Those P electrode contact elements are connected to the drive circuit 406.

[0327] In some embodiments, a conductive layer 438 for electrode connection is formed at the top of the blue LED light-emitting layer 436. In some embodiments, the conductive layer 438 is a conductive transparent layer 438 such as an ITO layer, formed between the blue LED light-emitting layer 436 and the N electrode 440 to improve conductivity and light transmittance. In some embodiments, as Figure 4B shown, the N electrode 440 has N electrode contact pads 442 and 444 electrically connected to the blue LED light-emitting layer 436 through the N electrode 440 and the conductive layer 438. In some embodiments, the N electrode 440 is also electrically connected to the N electrode contact pad 420 of the green LED structure. In some embodiments, the N electrode 440 is made of a material such as graphene, ITO, AZO, or FTO or any combination of the above.

[0328] In some embodiments, the lateral dimension of the blue LED light-emitting layer 436 is substantially the same as that of the green LED light-emitting layer 430, especially for the effective light-emitting area.

[0329] In some embodiments, a reflective layer 435 is provided between the conductive layer 434 and the bonding layer 460 below the blue LED light-emitting layer 436. In some embodiments, an optional reflective layer 439 ( Figure 4B not shown in the figure) is provided on top of the conductive layer 438 above the blue LED light-emitting layer 436.

[0330] In one method, the blue LED light-emitting layer 436 is grown on another separate substrate (referred to as an epitaxial substrate). After bonding, the epitaxial substrate is removed by, for example, laser lift-off process or wet chemical etching, leaving Figure 4B the structure shown in the figure.

[0331] In some embodiments, the blue LED light-emitting layer 436 is used to form a blue micro-LED. Examples of the blue LED light-emitting layer include III-V nitride, III-V arsenide, III-V phosphide, and III-V antimonide epitaxial structures. In some cases, the film within the blue LED light-emitting layer 436 may include a layer of P-type GaN / InGaN light-emitting layer / N-type GaN. In some embodiments, P-type is typically Mg-doped, while N-type is typically Si-doped. In some examples, the thickness of the blue LED light-emitting layer is about 0.1 micrometer to 5 micrometers. In a preferred embodiment, the thickness of the blue LED light-emitting layer is about 0.3 micrometers.

[0332] In some embodiments, the blue LED structure includes a reflective layer 435, a conductive layer 434, a blue LED light-emitting layer 436, a conductive layer 438, and an optional reflective layer 439. In some embodiments, the blue LED structure is formed within a planarized insulating layer 462. In some embodiments, the planarized insulating layer 462 covers the entire blue LED structure. In some embodiments, the entire blue LED structure is embedded within the planarized insulating layer 462. In some embodiments, the bottom surface of the planarized insulating layer 462 is smoothed or planarized by chemical mechanical polishing.

[0333] In some embodiments, vias or through-holes are formed within the planarized insulating layer 462 and the transparent bonding layer 460 to accommodate the portion of the N electrode 440 connected to the N electrode contact pad 420 of the green LED structure.

[0334] In some embodiments, the N electrode 440 covers the top of the planarized insulating layer 462. In some embodiments, the N electrode 440 covers the top of the three-color LED device 400. In some embodiments, the N electrode 440 is connected to the N electrodes of adjacent three-color LED devices (not shown in Figure 4A or 4B) via the N electrode contact pads 442 and 444, serving as a common electrode.

[0335] In some embodiments, the lateral dimension of the blue LED structure is substantially the same as that of the green LED structure. In some embodiments, without including an extension such as 466, the second LED structure, e.g., the green LED structure, and the third LED structure, e.g., the blue LED structure, have the same central axis. In some embodiments, without including an extension such as 466, the second LED structure and the third LED structure are aligned along the same central axis.

[0336] In some embodiments, the thickness of each of the conductive layers 410, 414, 428, 432, 434, and 438 is about 0.01 micrometer to 1 micrometer. In some cases, before any bonding process for bonding with the next epitaxial layer, each of the conductive layers 410, 414, 428, 432, 434, and 438 is typically deposited on its respective corresponding epitaxial layer by a vapor deposition process, such as electron beam evaporation or sputter deposition. In some examples, the conductive layers are used to maintain good electrical conductivity of the electrode connections, and in some cases, are also used to improve the optical characteristics of the LED device, such as reflectivity or transmittance.

[0337] In some embodiments, to improve the luminous efficiency of the three-color LED device 400, optical isolation structures such as 446 and 448 are formed along the sidewalls of the three-color LED device 400. In some embodiments, the optical isolation structures 446 and 448 are made of a dielectric material such as SiO2.

[0338] As Figure 4AAs shown in the top view, in some embodiments, the three-color LED device 400 has a circular shape. In some embodiments, optical isolation structures such as 446 and 448 are connected together and form a circular sidewall surrounding the three-color LED device 400. In some embodiments, the optical isolation structure forms a reflector cup which will be described in further detail below. In some embodiments, the three stacked LED structures within the three-color LED device 400 also have a circular shape. In some embodiments, the three-color LED device 400 can have other shapes, such as rectangular, square, triangular, trapezoidal, polygonal. In some embodiments, optical isolation structures such as 446 and 448 are connected together and form sidewalls surrounding the three-color LED device 400 in other shapes such as rectangular, square, triangular, trapezoidal, polygonal.

[0339] As Figure 4B shown, in some embodiments, the red LED light-emitting layer 412, the green LED light-emitting layer 430, and the blue LED light-emitting layer 436 have inclined side surfaces. As used herein, an inclined side surface can refer to a surface that is not perpendicular to the top or bottom surface of the corresponding LED light-emitting layer. In some embodiments, the angle between the inclined sidewall and the bottom surface of the corresponding LED light-emitting layer is less than 90 degrees. In some embodiments, the metal bonding layer 408 also has an inclined side surface. This inclined side surface can facilitate the connection of different connecting elements to each LED light-emitting layer, prevent the connecting elements from being disconnected due to the abrupt corners, and enhance the overall stability of the device.

[0340] In some embodiments, the light propagation efficiency of the multi-color LED device changes with the change of the angle of the inclined side surface of the LED light-emitting layer relative to the normal of the surface of the substrate 404. In some embodiments, the light propagation efficiency of the multi-color LED device increases with the increase of the angle of the inclined side surface of the LED light-emitting layer relative to the normal of the surface of the substrate 404. For example, when the angle of the side surface of the LED light-emitting layer relative to the normal of the surface of the substrate 404 is ±5 degrees, and when the optical isolation structures such as 446 and / or 448 are not the reflector cups described below, the light-emitting efficiency of the multi-color LED device is 0.32%. For example, when the angle of the side surface of the LED light-emitting layer relative to the normal of the surface of the substrate 404 is ±15 degrees and when the optical isolation structures such as 446 and / or 448 are not the reflector cups described below, the light-emitting efficiency of the multi-color LED device is 2.7%. For example, when the angle of the side surface of the LED light-emitting layer relative to the normal of the surface of the substrate 404 is at (e.g., when the light-emitting layer is inclined) or very close to ±90 degrees and when the optical isolation structures such as 446 and / or 448 are not the reflector cups described below, the light-emitting efficiency of the multi-color LED device is equal to or very close to 56.4%.

[0341] In contrast, the implementation of the reflector cup structure, as described in further detail below, improves the light propagation efficiency of the multicolor LED device. For example, when the angle of the side surface of the LED light-emitting layer with respect to the normal of the surface of the substrate 404 is ±5 degrees and when the optical isolation structures such as 446 and / or 448 are reflector cups as described below, the luminous efficiency of the multicolor LED device is 0.65%, that is, it is increased by 104.6% compared with the LED device without a reflector cup. For example, when the angle of the side surface of the LED light-emitting layer with respect to the normal of the surface of the substrate 404 is ±15 degrees and when the optical isolation structures such as 446 and / or 448 are reflector cups as described below, the luminous efficiency of the multicolor LED device is 6.65%, that is, it is increased by 144.4% compared with the LED device without a reflector cup. For example, when the angle of the side surface of the LED light-emitting layer with respect to the normal of the surface of the substrate 404 is at (e.g., when the light-emitting layer is tilted) or very close to ±90 degrees and when the optical isolation structures such as 446 and / or 448 are reflector cups as described below, the luminous efficiency of the multicolor LED device is equal to or very close to 66.65%, that is, it is increased by 18.4% compared with the LED device without a reflector cup.

[0342] In some embodiments, the sizes of the red LED light-emitting layer 412, the green LED light-emitting layer 430, and the blue LED light-emitting layer 436 are similar. For example, the surface areas of the red LED light-emitting layer 412, the green LED light-emitting layer 430, and the blue LED light-emitting layer 436 are substantially the same, especially for the effective light-emitting area.

[0343] In some embodiments, reflective layers are formed above and below each layer in the LED light-emitting layer to improve the light propagation efficiency. As Figure 4B shown, in some embodiments, a reflective layer 409 is formed between the bonding layer 408 and the red LED light-emitting layer 412. In some embodiments, in the presence of the conductive layer 410, the reflective layer 409 is formed between the bonding layer 408 and the conductive layer 410. In some embodiments, a reflective layer 415 is formed between the bonding layer 456 (or / and within the planarized insulating layer 454) and the red LED light-emitting layer 412. In some embodiments, in the presence of the conductive layer 414, the reflective layer 415 is formed between the bonding layer 456 (or / and within the planarized insulating layer 454) and the conductive layer 414.

[0344] In some embodiments, a reflective layer 427 is formed between the bonding layer 456 (or / and within the planarized insulating layer 458) and the green LED light-emitting layer 430. In some embodiments, in the presence of the conductive layer 428, the reflective layer 427 is formed between the bonding layer 456 (or / and within the planarized insulating layer 458) and the conductive layer 428. In some embodiments, a reflective layer 433 is formed between the bonding layer 460 (or / and within the planarized insulating layer 458) and the green LED light-emitting layer 430. In some embodiments, in the presence of the conductive layer 432, the reflective layer 433 is formed between the bonding layer 460 (or / and within the planarized insulating layer 458) and the conductive layer 432.

[0345] In some embodiments, a reflective layer 435 is formed between the bonding layer 460 (or / and within the planarized insulating layer 462) and the blue LED light-emitting layer 436. In some embodiments, in the presence of the conductive layer 434, the reflective layer 435 is formed between the bonding layer 460 (or / and within the planarized insulating layer 462) and the conductive layer 434. In some embodiments, an optional reflective layer 439 ( Figure 4B not shown in the figure) is formed between the N electrode pad 440 and the blue LED light-emitting layer 436 while still allowing the blue LED light-emitting layer 436 to be electrically connected to the N electrode pad 440 through a conductive path, for example. In some embodiments, in the presence of the conductive layer 438, the optional reflective layer 439 is formed between the N electrode pad 440 and the conductive layer 438 while still allowing the conductive layer 438 to be electrically connected to the N electrode pad 440 through a conductive path, for example.

[0346] In some embodiments, the material, composition, properties, and manufacturing process of the reflective layer are the same as those described above with respect to FIGS. 1-3.

[0347] In some embodiments, a three-color LED structure is formed by dry etching and wet etching, and the axes of the LED structures of different colors are vertically aligned with each other. In some embodiments, the LED structures of different colors share the same axis.

[0348] In some embodiments, each of the plurality of LED structures of different colors forms a pyramid shape or a trapezoidal cross-section shape within its respective planarized insulating structure. Each layer has a narrower width or a smaller area compared to the layer below it. In this case, the width or area is measured by the size of the plane parallel to the surface of the substrate 404. In some embodiments, especially when using a planarized layered structure, each LED structure among the LED structures of different colors has a substantially the same lateral dimension compared to other LED structures. When each LED structure among the LED structures has a substantially the same area, the light-emitting efficiency of the entire LED device is improved.

[0349] In some embodiments, particularly in the case of a layered structure without planarization, each LED structure in the LED structures of different colors is bonded together by a bonding layer that only covers the area of the LED structure without an extension beyond the LED structure area, and the entire multi-color LED device forms a pyramid (or inverted cone) shape or a trapezoidal cross-section shape (not shown in Figure 4B . In some embodiments, for example, the lateral dimension of the bottom LED structure of the red LED structure can be the longest, and the lateral dimension of the top LED structure of the blue LED structure can be the shortest, for example. The pyramid shape can be naturally formed from the bottom up when etching and patterning the respective layers within the LED device. The pyramid structure can improve the electrical connection between individual LED structures and between the electrodes and simplify the manufacturing process. For example, the electrode connection elements of each layer are exposed in each layer for easy connection.

[0350] In some embodiments, a bottom layer such as the metal bonding layer 408 has a lateral dimension of about 1 micron to 500 microns. In a preferred embodiment, the lateral dimension of the metal bonding layer 408 at the bottom of the multi-color LED device is about 2.0 microns. In some embodiments, the vertical height of the multi-color LED device is about 1 micron to 500 microns. In a preferred embodiment, the vertical height of the multi-color LED device is about 1.9 microns. In a preferred embodiment, the lateral dimension of the conductive layer 438 at the top of the multi-color LED device is about 1.0 micron.

[0351] In some embodiments, the aspect ratio of the cross-section of the layers in a three-color LED device remains substantially the same when the lateral dimension of the same layer changes. For example, when the lateral dimension of the patterned epitaxial layer is 5 microns, the thickness of the patterned epitaxial layer is less than 1 micron. In another example, when the lateral dimension of the same patterned epitaxial layer increases, the thickness of the same patterned epitaxial layer increases correspondingly to maintain the same aspect ratio. In some embodiments, the aspect ratio of the cross-section of the epitaxial layer and other layers is less than 1 / 5 of the thickness / width.

[0352] The shape of the LED device is not limited, and in some other embodiments, the cross-sectional shape of the three-color LED device can adopt other shapes, such as, for example, an inverted trapezoid, a semi-ellipse, a rectangle, a parallelogram, a triangle, or a hexagon, etc.

[0353] In some embodiments, a planarized insulating layer, such as 454, 458, and 462, is used to cover each LED structure of different colors, thereby simplifying the manufacturing process of a single-pixel three-color LED device and improving the luminous efficiency of a single-pixel three-color LED device. For example, each LED structure of different colors can first be independently formed in a corresponding planarized insulating layer to include a conductive layer, a reflective layer, and an electrode contact pad and their related connectors, and then each LED structure is bonded together through a corresponding bonding layer.

[0354] In contrast, in the process of manufacturing a directly stacked three-color LED device without a planarization feature, the LED structures of different colors are directly bonded together using some bonding layers, and a single pixel three-color LED device can be formed into a pyramid (or inverted cone) shape or a trapezoidal shape in cross section due to layer-by-layer patterning (and / or etching). Therefore, the effective light-emitting area for the LED structure at the bottom of the stack of the single pixel three-color LED device is the largest, while the effective light-emitting area for the LED structure at the top of the stack is the smallest. The non-uniformity of the light-emitting area between multiple LED structures in the LED device will reduce its luminous efficiency. Although it has a planarized layered structure, since each LED structure is manufactured in its own planarized insulating layer, the single pixel three-color LED device is not limited to the pyramid structure as described above. On the contrary, the effective light-emitting area of ​​different LED structures in a single pixel three-color LED device can be adjusted according to the design. In some cases, the horizontal effective light-emitting area of ​​different LED structures in a single pixel three-color LED device is substantially the same to improve the luminous efficiency and make it easier to electrically connect. In some cases, the planarized three-color LED structure can increase the luminous efficiency by at least 5%, at least 10%, or sometimes, at least 20%, compared to a similar three-color LED structure without planarization.

[0355] In some embodiments, when a corresponding epitaxial substrate is used to grow each layer of the LED light-emitting layer as described above, an insulating layer may be first deposited on the epitaxial substrate covering the corresponding LED light-emitting layer and each of the other layers such as the conductive layer and the reflective layer. Then, a planarization process is performed to make the surface of the insulating layer in which the corresponding LED structure is embedded flat. Vias for electrical connection are also formed in the planarized layer before bonding.

[0356] In another embodiment, the layers of the LED structure including the bonding layer can be formed directly on the planarized insulating layer with the formed LED structure already embedded therein, and then the planarized insulating layer is formed to cover the current LED structure. Before the next LED structure is formed over the current LED structure, vias for electrical connection are formed in the planarized layer.

[0357] Compared with some other processes that directly contact the top or bottom of the LED structure with a non-planarized insulating layer and bonding layer to form a device, the bonding layer can contact the planarized insulating layer without touching the LED structure. Therefore, the features and layers within each planarized LED structure are better protected and less vulnerable to external destructive forces. Additionally, the planarized surface can improve the light propagation efficiency by reducing the deflection caused by the uneven surface.

[0358] In some embodiments, the top conductive layer 438 above the third LED light-emitting layer 436 is patterned using photolithography and etching. In some cases, the etching method used to form the pattern is, for example, dry etching such as inductively coupled plasma (ICP) etching or wet etching with an ITO etching solution. In some embodiments, the same patterning method can be applied to all other conductive layers within the tricolor LED device 400, including layers 410, 414, 428, 432, 434, and 438.

[0359] In some embodiments, the blue LED light-emitting layer 436 and the green LED light-emitting layer 430 are patterned using photolithography and etching. In some cases, the etching method used to form the pattern is dry etching, for example, inductively coupled plasma (ICP) etching using C12 and BC13 etching gases.

[0360] In some embodiments, the bonding layers including 460 and 456 are patterned using photolithography and etching. In some cases, the etching method used to form the pattern is dry etching, for example, inductively coupled plasma (ICP) etching using CF4 and O2 etching gases.

[0361] In some embodiments, the reflective layers including 409, 415, 427, 433, 435, and 439 are patterned using photolithography and etching. In some cases, the etching method used to pattern the reflective layer, particularly the DBR layer, is dry etching, for example, inductively coupled plasma (ICP) etching using CF4 and O2 etching gases or ion beam etching (IBE) using Ar gas.

[0362] In some embodiments, the red LED light-emitting layer 412 is patterned using photolithography and etching. In some cases, the etching method used to form the pattern is dry etching, for example, inductively coupled plasma (ICP) etching using C12 and HBr etching gases.

[0363] In some embodiments, the metal bonding layer 408 is patterned using photolithography and etching. In some cases, the etching method used to form the pattern is dry etching, for example, inductively coupled plasma (ICP) etching using C12 / BC13 / Ar etching gas, or ion beam etching (IBE) using Ar gas.

[0364] In some embodiments, after each LED device structure in each of the LED device structures is patterned, an insulating layer such as 454, 458, 462 is deposited on the surface of each patterned LED structure including all the patterned layers, sidewalls, and the exposed substrate. In some embodiments, the insulating layer is made of SiO2 and / or Si3N4. In some embodiments, the insulating layer is made of TiO2. In some embodiments, an insulating layer having a composition similar to SiO2 is formed after curing a layer such as SOG at a high temperature. In some embodiments, the insulating layer is made of a material having a thermal coefficient similar to that of the layers below the insulating layer. Then, the surface of the insulating layer is smoothed or planarized by a related method such as chemical mechanical polishing understood by those of ordinary skill in the art.

[0365] In some embodiments, the planarized insulating layer is patterned using photolithography and etching to expose the electrode contact regions. In some cases, the etching method used to form the pattern is dry etching, for example, inductively coupled plasma (ICP) etching using CF4 and O2.

[0366] In some embodiments, the P electrode or the anode metal pad is deposited by vapor deposition or by other deposition methods at a suitable position of the patterned LED structure, such as on one side and / or in a via within the planarized insulating layer, to electrically connect the red LED structure, the green LED structure, and the blue LED structure.

[0367] In some embodiments, a separate N electrode or the cathode metal pad is deposited by vapor deposition or by other deposition methods at a suitable position of the patterned LED structure, such as on one side / top and / or in a via within the planarized insulating layer, to electrically connect the red LED structure, the green LED structure, and the blue LED structure.

[0368] Figure 5 is a cross-sectional view along the Figure 1A middle diagonal 102 of a single-pixel three-color LED device 500 having a refractive structure according to some embodiments. In some embodiments, although not all are shown in Figure 5As shown, the single-pixel three-color LED device 500 has a structure similar to any of the single-pixel three-color LED devices shown in FIGS. 1-4, but a refractive structure 502 formed above the top surface of the single-pixel three-color LED device is added to improve the light emission efficiency. The light emitted by the single-pixel three-color LED device is emitted through the top surface of the single-pixel three-color LED device without the refractive structure (light-emitting region). In some embodiments, the top surface of the refractive structure 502 is planarized. In some embodiments, the refractive structure 502 covers and contacts the exposed surface of a top electrode such as the N electrode 140. In some embodiments, the refractive structure 502 is directly formed on the surface of the planarized insulating layer 176. In some embodiments, the refractive structure 502 is the same as the planarized insulating layer 176 and is integrated with the planarized insulating layer 176.

[0369] In some embodiments, the refractive structure 502 is formed between the optical isolation structures of the reflector cups such as 146 and 148 and the top surface of the single-pixel three-color LED device without the refractive structure, that is, the light-emitting region. In some embodiments, the top surface of the refractive structure 502 is above the top of the optical isolation structure. In some embodiments, the top surface of the refractive structure 502 is at the same height as the top of the optical isolation structure or below the top of the optical isolation structure. In some embodiments, the top surface of the refractive structure is above a top electrode such as the N electrode 140. In some embodiments, the top surface of the refractive structure is at the same height as a top electrode such as the N electrode 140 or below the top electrode.

[0370] In some embodiments, the refractive structure 502 changes the optical path of the light emitted by the single-pixel three-color LED device by making the light emitted by the LED device more focused or more divergent according to design requirements.

[0371] In some embodiments, the refractive layer 502 is made of a dielectric material. In some embodiments, the dielectric material is transparent to the light emitted by the single-pixel three-color LED device, such as silicon oxide, silicon nitride, silicon carbide, titanium oxide, zirconium oxide, aluminum oxide, etc. In some embodiments, the dielectric material is selected from one or more polymers such as SU-8, photosensitive polyimide (PSPI), BCB, etc.

[0372] In some embodiments, the refractive layer 502 is directly formed above the planarized insulating layer. In some embodiments, the refractive layer 502 is formed by deposition, sputtering or other methods.

[0373] Figure 6A is a cross-sectional view along the Figure 1A diagonal 102 of a single-pixel three-color LED device 600 having a microlens on a reflective structure according to some embodiments.

[0374] Figure 6B is a cross-sectional view along the medium diagonal 102 of a single-pixel three-color LED device 600 having microlenses within a region formed by a reflective structure, according to some embodiments. Figure 1A In some embodiments, although not all shown in

[0375] it, the single-pixel three-color LED device 600 has a structure similar to any one of the single-pixel three-color LED devices shown in FIGS. 1-5, and a microlens 602 formed above the top surface of the single-pixel three-color LED device is added to improve the light-emitting efficiency. In the absence of such a microlens structure (light-emitting region), the light emitted by the single-pixel three-color LED device passes through the top surface of the single-pixel three-color LED device and is emitted. In some embodiments, the microlens 602 is directly formed on the surface of a planarized insulating layer 176. In some embodiments, the microlens 602 is directly formed on the surface of a refractive structure 502 as Figures 6A - 6B shown. In some embodiments, the microlens 602 covers and contacts the exposed surface of a top electrode such as the N electrode 140. Figure 5 In some embodiments, an optional spacer 604 is formed on top of the light-emitting region at the bottom of the microlens 602. In some embodiments, the top surface of the spacer 604 is planarized. In some embodiments, the spacer 604 is directly formed on the surface of a planarized insulating layer 176. In some embodiments, the spacer 604 is directly formed on the surface of a refractive structure 502 as

[0376] shown. In some embodiments, the spacer 604 is the same as the refractive structure 502 as Figure 5 shown and is integrated with the refractive structure 502. In some embodiments, the spacer 604 covers and contacts the exposed surface of a top electrode such as the N electrode 140. In some embodiments, the spacer 604 is integrated with the microlens 602. In some embodiments, the spacer 604 is the same as the planarized insulating layer 176 and is integrated with the planarized insulating layer 176. Figure 5 In some embodiments, the microlens 602 is formed between each optical isolation structure such as the reflective structures 146 and 148 or the light-reflecting cup and the top surface of the single-pixel three-color LED device where there is no microlens, i.e., the light-emitting region, between the optical isolation structures. In some embodiments, the top surface of the microlens 602 is located above the top of the optical isolation structure, as

[0377] shown in Figure 6AAs shown, when the top surface of the microlens 602 is above the top of the reflective structures such as 146 and 148, all the light emitted by the single-pixel tri-color LED device including the reflector cup can be substantially captured and focused by the microlens 602. In some embodiments, the top surface of the microlens 602 is at the same height as or below the top of the optical isolation structure as shown in Figure 6B When the top surface of the microlens 602 is at the same level as or below the top of the reflective structures such as 146 and 148, at least a part of the light emitted by the microlens 602 is further reflected by the reflective structures or the reflector cup defined within a certain area.

[0378] In some embodiments, the lateral dimension of the bottom of the microlens 602 is smaller than the lateral dimension of the light-emitting area. In some embodiments, the lateral dimension of the bottom of the microlens 602 is the same as or larger than the lateral dimension of the light-emitting area. In some embodiments, the lateral dimension of the bottom of the microlens 602 is smaller than the lateral dimension of the top surface area of the top light-emitting layer 136. In some embodiments, the lateral dimension of the bottom of the microlens 602 is the same as or larger than the lateral dimension of the top surface area of the top light-emitting layer 136.

[0379] In some embodiments, an optional spacer 604 is formed between the optical isolation structure of the reflector cup such as 146 and 148 and the top surface of the single-pixel tri-color LED device without a microlens and a spacer, i.e., the light-emitting area. In some embodiments, the top surface of the spacer 604 is above the top of the optical isolation structure. In some embodiments, the top surface of the spacer 604 is at the same height as or below the top of the optical isolation structure. In some embodiments, the top surface of the spacer 604 is above the top electrode such as the N electrode 140. In some embodiments, the top surface of the spacer 604 is at the same height as or below the top electrode such as the N electrode 140. In some embodiments, the lateral dimension of the bottom of the microlens 602 is smaller than the lateral dimension of the top surface of the spacer 604. In some embodiments, the lateral dimension of the bottom of the microlens 602 is the same as or larger than the lateral dimension of the top surface of the spacer 604.

[0380] In some embodiments, the microlens 602 changes the optical path of the light emitted by the single-pixel tri-color LED device by making the light more focused or more divergent according to design requirements.

[0381] In some embodiments, the spacer 604 extends the optical path of the light emitted by the single-pixel three-color LED device. In some embodiments, the spacer 604 changes the optical path of the light emitted by the single-pixel three-color LED device by making the light emitted by the single-pixel three-color LED device more focused or more divergent according to design requirements.

[0382] In some embodiments, the microlens 602 can be made of various materials that are transparent to light of each wavelength emitted by the single-pixel three-color LED device. Exemplary transparent materials for the microlens 602 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 602 is made of photoresist.

[0383] The spacer 604 is an optically transparent layer formed to maintain the position of the microlens 602 relative to a pixel light source such as a single-pixel three-color LED device below the microlens 602. The spacer 604 can be made of various materials that are transparent to light of each wavelength emitted by the pixel light source. For example, exemplary transparent materials for the spacer 604 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 spacer 604 is made of photoresist. In some embodiments, the spacer 604 and the microlens 602 have the same material. In some embodiments, the spacer 604 and the microlens 602 have different materials.

[0384] In some embodiments, the height of the microlens 602 is not greater than 2 microns. In some embodiments, the height of the microlens 602 is not greater than 1 micron. In some embodiments, the height of the microlens 602 is not greater than 0.5 micron. In some embodiments, the width of the microlens 602 is not greater than 4 microns. In some embodiments, the width of the microlens 602 is not greater than 3 microns. In some embodiments, the width of the microlens 602 is not greater than 2 microns. In some embodiments, the width of the microlens 602 is not greater than 1 micron. In some embodiments, the width-to-height ratio of the microlens 602 is greater than 2.

[0385] In some embodiments, the shape of the microlens 602 is generally hemispherical. In some embodiments, the central axis of the microlens 602 is aligned with or the same as the central axis of the lensless single-pixel three-color LED device.

[0386] For clarity, Figures 6A - 6BIn some embodiments, in a display panel, each pixel light source in a single pixel light source such as a three-color LED device corresponds to a microlens 602. It should be understood that a complete display panel includes an array of many individual pixels and many microlenses. Additionally, there may not be a one-to-one correspondence between the microlenses and the pixel light sources, nor between the pixel driving circuits (not shown) and the pixel light sources. The pixel light source may also be made of multiple individual light elements, for example, multiple single pixel LEDs connected in parallel. In some embodiments, one microlens 602 may cover multiple lensless single pixel three-color LED devices.

[0387] Each microlens 602 has a positive optical power and is configured to reduce the divergence or viewing angle of the light emitted by the corresponding pixel light source. In one example, the light beam emitted by the pixel light source has a relatively wide original divergence angle. In one embodiment, the original angle of the marginal rays of the light beam with respect to the vertical axis perpendicular to the substrate 104 is greater than 60 degrees. The light is bent by the microlens 602 such that the new marginal 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 the same. Examples of microlenses include spherical microlenses, aspherical microlenses, FRESNAL microlenses, and cylindrical microlenses.

[0388] The microlens 602 generally has a planar side and a curved side. In FIG. 6, the bottom of the microlens 602 is the planar side, and the top of the microlens 602 is the curved side. The typical shape of the base of each microlens 602 includes a circle, a square, a rectangle, and a hexagon. The individual microlenses in the microlens array of the display panel may be the same or different in terms of shape, curvature, optical power, size, base, spacing, etc. In some embodiments, the microlens 602 conforms to the shape of the single pixel three-color LED device. In one example, the shape of the base of the microlens 602 is the same as the shape of the single pixel three-color LED device, for example, Figures 6A - 6B in which they are both circular. In another example, the shape of the base of the microlens 602 is different from the shape of the single pixel three-color LED device. For example, the circular base of the microlens has the same width as the single pixel three-color LED but a smaller area because the base of the microlens is circular while the base of the single pixel three-color LED 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.

[0389] In some embodiments, when the microlens 602 is formed, the spacer layer 604 may be formed with the same process and the same material as the microlens 602. In some embodiments, measured from the bottom of the substrate 104, the height of the pixel light source is greater than, equal to, or less than the thickness of the spacer 604.

[0390] The thickness of the spacer 604 is designed to maintain an appropriate spacing between the microlens 604 and the pixel light source. As an example, for a spacer that maintains an optical spacing between the pixel light source and the microlens greater than the focal length of the microlens, an image of a single pixel is formed at a certain distance. As another example, for an optical spacer that maintains an optical spacing between the pixel light source and the microlens less than the focal length of the microlens, a reduced divergence / viewing angle is achieved. The amount of reduction in the divergence / viewing angle also depends in part on the thickness of the spacer 604 measured from the top surface of the pixel light source. In some embodiments, the thickness of the spacer 604 measured from the top surface of the pixel light source is no greater than 1 micron. In some embodiments, the thickness of the spacer 604 measured from the top surface of the pixel light source is no greater than 0.5 micron. In some embodiments, the thickness of the spacer 604 measured from the top surface of the pixel light source is no greater than 0.2 micron. In some embodiments, the thickness of the spacer 604 measured from the top surface of the pixel light source is approximately 1 micron.

[0391] In some embodiments, the brightness enhancement effect is achieved by integrating a microlens array onto the display panel. In some examples, due to the light condensing effect of the microlens, in the direction perpendicular to the surface of the display, the brightness with the microlens array is 4 times that without the microlens array. In alternative embodiments, the brightness enhancement factor can vary according to different designs of the microlens array and the optical spacer. For example, a factor greater than 8 can be achieved.

[0392] In some embodiments, a first method for manufacturing a microlens includes the steps of at least directly depositing a microlens material layer on top of the pixel light source and directly physically contacting the microlens material layer with the pixel light source. In some embodiments, the shape of the microlens material layer conforms to the shape of the pixel light source and forms a hemisphere on the pixel light source. In some embodiments, the top of the pixel light source is substantially flat, and the shape of the formed microlens 602 is substantially hemispherical. In some embodiments, the microlens material layer is directly deposited on the surface of the pixel light source by chemical vapor deposition (CVD) technology, such as on the planarized surface of a single pixel tri-color LED device. In some embodiments, the deposition parameters for the CVD process are: power of approximately 0 W to 1000 W, pressure of approximately 100 mTorr to 2000 mTorr, temperature of approximately 23 °C to 500 °C, gas flow of 0 to 3000 sccm (standard cubic centimeters per minute), and time of approximately 1 hour to 3 hours. In some embodiments, the material of the microlens material layer is a dielectric material such as silicon dioxide.

[0393] In some embodiments, the first method for manufacturing a microlens further includes the step of patterning a microlens material layer to expose the electrode region of the substrate. In some embodiments, the step of patterning the microlens material layer includes an etching step. In some embodiments, the etching step includes the step of forming a mask on the surface of the microlens material. The etching step further includes patterning the mask by a photolithography process to form an opening in the mask and expose the microlens material layer above the electrode region of the pixel light source. The etching step further includes the step of etching the portion of the microlens material layer exposed by the opening protected by the mask. In some embodiments, the exposed microlens material layer is etched by a wet etching method.

[0394] In some embodiments, the second method for manufacturing a microlens further includes, optionally, the step of forming a marker layer with alignment markers for aligning with the microlens material layer to be deposited in a subsequent step. For example, the formed marker layer aligns the units of the light-emitting pixels with the microlens material layer so that microlenses are formed at the centers of the pixel light sources. In some embodiments, the formed marker layer aligns the pixel light sources with the layer above them, particularly the microlens material layer, so that microlenses are formed on top of the pixel light sources.

[0395] The second method for manufacturing a microlens further includes the step of directly depositing a microlens material layer on top of at least one pixel light source. Figures 6C - 6D Further shown is a manufacturing method of a display panel integrated with a microlens array using a top-down pattern transfer according to some embodiments. In some embodiments, as Figure 6C shown, the microlens material layer 645 covers the top of the pixel light source 606M, and the top surface of the microlens material layer 645 is flat. In some embodiments, the microlens material layer 645 is deposited on top of the pixel light source array 606 by spin coating. In some embodiments, the material of the microlens material layer 645 is a photoresist. In some embodiments, the material of the microlens material layer 645 is a dielectric material such as silicon oxide.

[0396] The second method for manufacturing a microlens further includes top-down patterning of the microlens material layer to form at least one hemisphere in the microlens material layer as Figures 6C - 6D shown. In some embodiments, the patterning step does not need to penetrate through or etch to the bottom of the microlens material layer 645. In some embodiments, the hemispheres of the microlenses 620 are disposed above at least one pixel light source 606M.

[0397] In some embodiments, the step of top-down patterning the microlens material layer further includes a first step of depositing a mask layer 630 on the surface of the microlens material layer 645 as Figure 6C shown.

[0398] The step of top-down patterning the microlens material layer further includes a second step of patterning the mask layer 630 to form a hemispherical pattern in the mask layer 630. In some examples, the mask layer 630 is first patterned by a photolithography process and then by a reflow process. In some embodiments, the photosensitive polymer mask layer 630 is patterned into separate units 640, as shown by the dashed rectangular units in Figure 6C to prepare for the formation of the hemispherical pattern. As an example, the separate units 640 are patterned and formed by a photolithography process. The patterned photosensitive polymer mask layer 650 with the separate units 640 is then formed into a hemispherical pattern 660 by a high-temperature reflow process. In one method, the separate units 640 are formed into separate hemispherical patterns 660 by high-temperature reflow. In some embodiments, the hemispherical patterns 660 of one pixel are not in direct physical contact with the hemispherical patterns of adjacent pixels. In some embodiments, the hemispherical pattern 660 of one pixel only contacts the hemispherical pattern of an adjacent pixel at the bottom of the hemispherical pattern 660. The patterned photosensitive polymer mask layer 650 is heated to a temperature above the melting point of the polymer material for a certain period of time. After the polymer material melts into a liquefied state, the surface tension of the liquefied material will cause it to become a shape with a smooth curved surface. For a unit with a circular base of radius R, a hemispherical shape / pattern will be formed after the reflow process when the height of the unit is 2R / 3. Figure 6C FIG. shows a display panel integrated with an array of hemispherical patterns 660 after the high-temperature reflow process is completed. In some embodiments, the hemispherical pattern in the mask layer can be formed by other manufacturing methods, including the manufacturing methods for microlenses described in the first method for manufacturing microlenses. In some other embodiments, the hemispherical pattern in the mask layer can be formed using gray-scale mask lithography exposure. In some other embodiments, the hemispherical pattern in the mask layer can be formed via a molding / imprinting process.

[0399] The step of top-down patterning the microlens material layer further includes a third step of etching the microlens material layer 645 using the hemispherical pattern 660 as a mask to form hemispheres in the microlens material layer 645. In some examples, the etching of the microlens material layer 645 is performed by a photolithography process. In some examples, the etching of the microlens material layer 645 is a dry etching such as a plasma etching process 635 as shown in Figure 6C . In some embodiments, after the microlens material layer 645 is etched, the microlens material layer 645 is not etched through to expose the top surface of the pixel light source 606M, as shown in Figures 6C - 6D , so that the spacer 670 is formed on top of the pixel light source 606M or covers the top of the pixel light source 606M, as shown in Figure 6D .

[0400] The second method for manufacturing the microlens further includes a step of patterning the microlens material layer to expose the electrode region of the substrate (not shown in Figure 6D ). In some embodiments, the step of patterning the microlens material layer includes an etching step. In some embodiments, the etching step includes a step of forming a mask on the surface of the microlens material. The etching step further includes a step of patterning the mask by a photolithography process to form an opening in the mask, exposing the microlens material layer above the electrode region of the pixel light source. The etching step further includes a step of etching the exposed microlens material layer with the mask protection. In some embodiments, the exposed microlens material layer is etched by a wet etching method. In some embodiments, the opening for the electrode is provided outside the display array region.

[0401] As described above, Figures 6A to 6D illustrates various manufacturing methods for forming a display panel integrated with a microlens array. It should be understood that these are merely examples, and other manufacturing techniques may also be used.

[0402] Although the detailed description includes many details, these should not be construed as limiting the scope of the present invention, but merely as illustrating different examples and aspects of the present invention. It should be understood that the scope of the present invention includes other embodiments not discussed in detail above. For example, microlenses with bases of different shapes, such as square bases or other polygonal bases, may also be used.

[0403] Figure 7 is a cross-sectional view 700 along the Figure 1A diagonal line such as 102 of three single-pixel three-color LED devices 710, 720, and 730 located on the substrate 104 according to some embodiments. In some embodiments, although not all shown in Figure 7 , each of the single-pixel three-color LED devices 710, 720, and 730 has a structure similar to any of the single-pixel three-color LED devices shown in FIGS. 1-6. The cross-sectional view of the single-pixel three-color LED device 710 within the rectangle 750 is equivalent to the cross-sectional view shown in any of FIGS. 1-6 as described above.

[0404] In some embodiments, as shown in any of the embodiments in FIGS. 1-7, the single-pixel three-color LED device further includes one or more reflector cup structures, such as 702, 704, and 706. Reflective structures, such as 702, 704, and 706, surround the respective single-pixel three-color LED devices 710, 720, and 730. The reflector cup can be formed on the semiconductor substrate 104 and is configured to surround the light-emitting region where the light emitted by the single-pixel three-color LED is emitted. For example, as Figures 1A - 1C shown, according to the cross-sectional view along the direction of 102 in Figure 1B , and according toFigure 1C A cross-sectional view along the 150 direction, the reflector cup may include four reflector cup portions 146, 148, 170, and 172. In some embodiments, the reflector cup portions 146, 148, 170, and 172 may be formed on the semiconductor substrate 104 and positioned around the light-emitting region. In some embodiments, the reflector cup may isolate at least some or substantially all of the light emitted from the light-emitting region. For example, as shown in FIGS. IB-1C, when the height of the reflector cup is higher than the height of the light-emitting region, the reflector cup portions 146, 148, 170, and 172 may isolate at least some or substantially all of the light emitted from the light-emitting region. Thus, the reflector cup can suppress inter-pixel light crosstalk and improve the overall contrast of the LED display. The reflection in the reflector cup also increases the luminous efficiency and brightness by focusing the light emission in a specific direction.

[0405] In some embodiments, the height of the reflector cup can be greater than the height of the bottom LED structure such as the red LED structure, greater than the height of the middle LED structure such as the green LED structure, or greater than the height of the top LED structure such as the blue LED structure. In some embodiments, the total height of the reflector cup can be greater than the combined height of the bottom LED structure such as the red LED structure, the middle LED structure such as the green LED structure, and the top LED structure such as the blue LED structure. In some embodiments, the total height of the reflector cup can be greater than the height of a single-pixel tri-color LED device without planarizing the layers. In some embodiments, the height of the reflector cup is between 0.5 micrometers and 50 micrometers. In some embodiments, the height of the reflector cup is between 1 micrometer and 20 micrometers. In some embodiments, the height of the reflector cup is between 2 micrometers and 10 micrometers. In a preferred embodiment, the height of the reflector cup is about 2.5 micrometers, while the height of a single-pixel tri-color LED device without planarizing the layers is about 1.9 micrometers. However, in some embodiments, the reflector cup portions 146, 148, 170, and 172 can have different heights. In some embodiments, the cross-section of the reflector cup portion such as 146 or 148 is triangular. In some embodiments, the cross-section of the reflector cup portion such as 146 or 148 is a trapezoid with the bottom side longer than the top side. In some embodiments, the bottom width of the reflector cup portion such as 146 or 148 is between 0.3 micrometers and 50 micrometers. In some embodiments, the bottom width of the reflector cup portion such as 146 or 148 is between 0.5 micrometers and 25 micrometers. In a preferred embodiment, the bottom width of the reflector cup portion such as 146 or 148 is about 1 micrometer. In some embodiments, the distance from the nearest edge of the bottom of the reflector cup portion such as 146 or 148 to the nearest edge of the bottom of the single-pixel tri-color LED device is between 0.2 micrometers and 30 micrometers. In some embodiments, the distance from the nearest edge of the bottom of the reflector cup portion such as 146 or 148 to the nearest edge of the bottom of the single-pixel tri-color LED device is between 0.4 micrometers and 10 micrometers. In a preferred embodiment, the distance from the nearest edge of the bottom of the reflector cup portion such as 146 / 446 or 148 / 448 to the nearest edge of the bottom of the single-pixel tri-color LED device, such as Figure 4B the distance to the P electrode connection structure 422 shown is about 0.6 micrometers.

[0406] In some embodiments, the distance between the centers of adjacent reflector cup portions such as 146 / 446 and 148 / 448 in the single-pixel tri-color LED device is between 1 micrometer and 50 micrometers. In a preferred embodiment, the distance between the centers of adjacent reflector cup portions such as 146 and 148 in the single-pixel tri-color LED device is about 5 micrometers.

[0407] In some embodiments, a divergence angle of 0° can correspond to light propagation perpendicular to the top surface of the light-emitting region, and a divergence angle of 90° can correspond to light propagation parallel to the top surface of the light-emitting region. Changing the geometric shape of the reflector cup can control the divergence angle of the light emitted by the light-emitting region. Therefore, the reflector cup can reduce the divergence of the light emitted by the light-emitting region and enhance the brightness of the single-pixel multicolor LED device. In some embodiments, as Figures 1B - 1C shown, the side walls 146-1, 148-1, 170-1, and 172-1 of the reflector cup can be straight, curved, wavy, multi-line, or a combination thereof. In some embodiments, the steepness of the side walls of the reflector cup portions 146, 148, 170, and 172 can be designed to reduce the divergence of the light emitted by the light-emitting region. For example, the angle of the side walls of the reflector cup portions 146, 148, 170, and 172 relative to the vertical axis perpendicular to the substrate 104 can range from a minimum of 15 degrees to a maximum of 75 degrees. The angle of the side walls of the reflector cup portions 146, 148, 170, and 172 relative to the vertical axis perpendicular to the substrate 104 can range from a minimum of 5 degrees to a maximum of 60 degrees. In some preferred embodiments, the angle of the side walls of the reflector cup portions 146, 148, 170, and 172 relative to the vertical axis perpendicular to the substrate 104 can range from a minimum of 10 degrees to a maximum of 50 degrees. The reflector cup can also reflect some of the light emitted by the light-emitting region upward. For example, some of the light emitted by the light-emitting region can reach the reflector cup portions 146, 148, 170, and 172 and be reflected upward through them.

[0408] In some embodiments, the reflector cup can include metal. In some embodiments, the reflector cup can include a dielectric material such as silicon oxide. In some embodiments, the reflector cup can include a photosensitive dielectric material. In some embodiments, the photosensitive dielectric material can include SU-8, photosensitive polyimide (PSPI), or BCB. In other embodiments, the reflector cup can include a photoresist.

[0409] In some embodiments, the reflector cup can be manufactured by a combination of deposition, lithography, and etching processes. In some embodiments, the reflector cup can be manufactured by other suitable methods. In one method, PSPI is formed into the shape of a reflector cup through a lithography process. Then, a metal layer including one or more metals such as Pt, Rh, Al, Au, and Ag with a high reflectivity, a stacked DBR layer including a TiO2 / SiO2 layer, any other layer with total reflection characteristics including a multi-layer omnidirectional reflector (ODR), or a combination of the above is formed by vapor deposition on the entire surface of the multicolor LED device including the reflector cup as the reflective layer. Next, the reflective layer is masked by the photoresist in the reflector cup region while the reflective layer in another region is etched so that the light-emitting region is exposed.

[0410] In another method, an isolation layer including one or more of SiO2, silicon nitride, or SU8, which is thicker than the stacked LED structure, is deposited or spin-coated on the stacked LED structure. Then, using a photoresist as a mask, the isolation layer is etched and formed into a reflector cup shape. Next, a metal layer including one or more metals such as Pt, Rh, Al, Au, and Ag having a high reflectivity, a stacked DBR layer including a TiO2 / SiO2 layer, any other layer having a total reflection characteristic including a multilayer omnidirectional reflector (ODR), or a combination of the above is formed by vapor deposition on the entire surface of the multicolor LED device including the reflector cup as a reflective layer. Finally, the reflective layer is masked by the photoresist in the reflector cup region while the reflective layer in another region is etched so that the light-emitting region is exposed.

[0411] In some embodiments, as shown in FIGS. 2-6, the single-pixel three-color LED device further includes one or more top electrodes (e.g., top electrodes 140 / 440, 442, and 444) integrated with the reflector cup. The one or more top electrodes may be electrically connected to the top electrode (layer) 140 / 440. For example, as Figure 4B shown, electrodes 442 and 444 may be integrated with the reflector cup, e.g., reflector cup portions 446 and 448, respectively. Both of the two top electrodes 442 and 444 may extend toward the light-emitting region and be electrically connected to the top electrode (layer) 140 / 440. By adopting one or more top electrodes, the reflector cup can be used as a common P electrode or N electrode of the single-pixel three-color LED device. For example, when the top electrode (layer) 140 / 440 is electrically connected to the LED structure (e.g., the LED structure including the light-emitting layers 112 / 412, 130 / 430, and 136 / 436) and optionally, the top electrodes 442 and 444, the reflector cup can be used as a common P electrode or a common N electrode of the single-pixel three-color LED device.

[0412] In some embodiments, the reflector cup further includes one or more reflective coatings. The one or more reflective coatings may be disposed on one or more sidewalls of the reflector cup, e.g., on the sidewalls 146-1, 148-1, 170-1, and 172-1 of the reflector cup. The bottom of each layer of the one or more reflective coatings does not contact each LED structure such as a red LED structure, a green LED structure, and a blue LED structure. The one or more reflective coatings can reflect the light emitted from the light-emitting region, thus improving the brightness and luminous efficacy of the micro-LED panel or display. For example, the light emitted from the light-emitting region can reach the one or more reflective coatings and can be reflected upward through them.

[0413] The one or more reflective coatings, together with the reflector cup, can utilize the reflection direction and / or reflection intensity of the light emitted by the light-emitting region. For example, the side walls 146-1, 148-1, 170-1, and 172-1 of the reflector cup are inclined at a certain angle, so the one or more reflective coatings disposed on the side walls 146-1, 148-1, 170-1, and 172-1 of the reflector cup are inclined at the same angle as the side walls 146-1, 148-1, 170-1, and 172-1 of the reflector cup. When the light emitted by the light-emitting region reaches the one or more reflective coatings, the light emitted by the light-emitting region is reflected by the one or more reflective coatings according to the angles of the side walls 1461-1, 148-1, 170-1, and 172-1 of the reflector cup.

[0414] The material of the one or more reflective coatings can be highly reflective, having a reflectivity greater than 60%, 70%, or 80%, so that most of the light emitted by the light-emitting region can be reflected. In some embodiments, the one or more reflective coatings may include one or more metal conductive materials having a high reflectivity. In these embodiments, the one or more metal conductive materials may include one or more of aluminum, gold, or silver. In some other embodiments, the one or more reflective coatings can be multilayered. More specifically, the one or more reflective coatings may include one or more stacked reflective material layers and one or more dielectric material layers. For example, the one or more reflective coatings may include a reflective material layer and a 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, and the metal layers may include one or more of TiAu, CrAl, or TiWAg.

[0415] In some embodiments, the one or more reflective coatings may be multilayer omnidirectional reflectors (ODRs), including 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, AI2O3, or TiO2. The one or more reflective coatings may further include a dielectric material layer, a TCO, and a DBR. In other embodiments, the one or more reflective coatings may include one or more metal conductive materials having a high reflectivity. In these embodiments, the one or more metal conductive materials may include one or more of aluminum, gold, or silver. In some embodiments, the reflective coating may have the same composition, structure, and manufacturing process as the reflective layers such as 109, 115, 127, 133 above and below the light-emitting layer as described above.

[0416] In some embodiments, the one or more reflective coatings may be conductive, and then, the one or more reflective coatings may also perform the function of making electrical contact with a single-pixel multicolor LED device. For example, the top electrode (layer) 140 may be electrically connected to the one or more reflective coatings. Again, for example, one or more reflective coatings may be electrically connected to the one or more transparent electrode contact layers 114, 132, and 138. The one or more reflective coatings may be patterned so as not to block the light emitted from the light-emitting region. Then, the one or more reflective coatings may also be used as a common electrode for the LED structure within a single-pixel multicolor LED device and / or a common electrode for the LEDs on a display panel.

[0417] In some embodiments, a top conductive layer for connecting to an electrode is formed on the top of the multicolor LED device, and the top conductive layer is electrically connected to the reflector cup. In some embodiments, the top conductive layer is in direct contact with the top or the bottom of the reflector cup.

[0418] In some embodiments, a bottom dielectric layer is formed between the bottom of the reflector cup and the semiconductor substrate.

[0419] In some embodiments, the one or more reflective coatings may be manufactured by one or more of electron beam deposition or sputtering processes.

[0420] In some embodiments, the reflector cup may have the shape of a stepped structure. Figure 8 is along a single-pixel three-color LED device 800 having a stepped reflector cup according to some embodiments Figure 4AA cross-sectional view of a diagonal line such as 402 therein. In some embodiments, although not all are shown in Figure 8 As shown in, the single-pixel three-color LED device 800 has a structure similar to any of the single-pixel three-color LED devices shown in FIGS. 1-7 having light cup portions such as 146, 148, 170, and 172, and has a stepped light cup. The stepped light cup can be formed on the semiconductor substrate 104 / 404 and positioned around the light-emitting region. For example, as Figure 8 shown, according to the cross-sectional view of the diagonal line such as 402 in Figure 4A the stepped light cup may include two stepped light cup portions 846 and 848. The stepped light cup portions 846 and 848 can be formed on the semiconductor substrate 104 / 404 and positioned around the light-emitting region. In some embodiments, the stepped light cup can isolate at least some or substantially all of the light emitted by the light-emitting region. For example, as Figure 8 shown, in the case where the height of the stepped light cup is higher than the height of the light-emitting region, the stepped light cup portions 846 and 848 can isolate at least some or substantially all of the light emitted by the light-emitting region. Therefore, the stepped light cup can suppress inter-pixel light crosstalk and improve the overall contrast of the LED display.

[0421] In some embodiments, the stepped light cup includes one or more stepped structures such as 846-1, 846-2, 846-3, 848-1, 848-2, and 848-3. In some embodiments, the height of each step of the light cup can be the same as the height of the LED structure at the same vertical level. For example, the stepped structures 846-1 and 848-1 each have the same height as the bottom LED structure. The stepped structures 846-2 and 848-2 each have the same height as the middle LED structure. The stepped structures 846-3 and 848-3 each have the same height as the top LED structure. However, in some embodiments, the stepped light cup portions 846 and 848 can have the same or different heights. The stepped light cup can also reflect the light emitted by the light-emitting region upward. For example, according to the design, some of the light emitted by the light-emitting region can reach the stepped light cup portions 846 and 848 and be reflected upward through them in different patterns for each LED structure within the single-pixel multi-color LED device. For example, each step can adjust the focus in a different pattern for the emitted (especially horizontal) light. For example, focusing the red light of the light beam from the LED device more centrally and the blue light more peripherally. Therefore, it can reduce the divergence of the light emitted by the light-emitting region and enhance the brightness of the single-pixel multi-color LED device.

[0422] In some embodiments, the stepped reflector cup structure may include or form a cavity surrounding the light-emitting region. The cavity may include a region that is surrounded by the stepped reflector cup and is above the semiconductor substrate 404. The cavity may include an inner sidewall, and the inner sidewall may include a plurality of inclined surfaces. For example, as Figure 8 shown, the stepped reflector cup may include or surround a cavity, and the cavity may include a region between the stepped reflector cup portions 846 and 848 and above the semiconductor substrate 404. The light-emitting region may be positioned within the cavity and surrounded by the stepped reflector cup portions 846 and 848.

[0423] In some embodiments, the top of the cavity is higher than the top of the light-emitting region. For example, the top of the cavity included in the stepped reflector cup (e.g., stepped reflector cup portions 846 and 848) is higher than the top of the light-emitting region. In some embodiments, the cavity may include an inner sidewall, and the inner sidewall may include a plurality of inclined surfaces (e.g., inclined surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S). In some embodiments, the inclination angles of the plurality of inclined surfaces (relative to the surface of the substrate 404) increase from the bottom to the top of the cavity. For example, as Figure 8 shown, the angles of the inclined surfaces 846-1S, 846-2S, and 846-3S are respectively represented as the inclination angles α, β, and γ. The inclination angles of the inclined surfaces 846-1S, 846-2S, and 846-3S may be the same as the inclination angles of the inclined surfaces 848-1S, 848-2S, and 848-3S, respectively. In some embodiments, the inclination angles α, β, and γ remain the same or increase from the bottom to the top of the cavity. In some preferred embodiments, the inclination angles α, β, and γ may gradually decrease from the bottom to the top of the cavity, so that the light emitted by the LED device can be more divergent towards the upper part of the LED device. However, in some embodiments, the inclination angles α, β, and γ may be any angles according to the design. In some embodiments, the cavity may be filled with a silicon-containing material, such as silicon oxide, and this filling may improve optical refraction, increase light transmittance, and / or enhance ultraviolet and heat aging resistance. In some embodiments, the cavity may be empty or vacuum. In some embodiments, the inclined surfaces (e.g., inclined surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S) may be straight, curved, wavy, multi-line, or a combination thereof.

[0424] In some embodiments, the cavity may include a plurality of sub-cavities. The sub-cavities may be formed or surrounded by respective inclined surfaces and may have different sizes in the horizontal direction. For example, there may be as Figure 8The three sub-cavities shown. The sub-cavity at the bottom of the cavity may include an area surrounded or defined by the semiconductor substrate 104 / 404, the inclined surfaces 846-1S and 848-1S, and the bottom of the bonding layer 156 / 456. The sub-cavity in the middle of the cavity may include an area surrounded or defined by the bottom of the bonding layer 156 / 456, the inclined surfaces 846-2S and 848-2S, and the bottom of the bonding layer 160 / 460. The sub-cavity at the top of the cavity may include an area surrounded or defined by the bottom of the bonding layer 160 / 460, the inclined surfaces 846-3S and 848-3S, and the top electrode layer 140 / 440 (or the open top at the top of the stepped structures 846-3 and 848-3). In some embodiments, the inclined surfaces of the sub-cavities are not arranged in the same plane. For example, as Figure 8 shown, each sub-cavity may be formed or surrounded by a plurality of inclined surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S and have different dimensions in the horizontal direction. In some embodiments, the inclined surfaces 846-1S, 846-2S, and 846-3S may not be arranged in the same plane, and the inclined surfaces 848-1S, 848-2S, and 848-3S may not be arranged in the same plane. For example, the inclined surfaces 846-1S, 846-2S, and 846-3S are arranged staggeredly in the vertical direction in different planes.

[0425] In some embodiments, the heights of the sub-cavities may be different. For example, the height of the sub-cavity in the middle of the cavity may be less than the heights of the other sub-cavities. The height of the sub-cavity at the top of the cavity may be greater than the height of the sub-cavity at the bottom of the cavity. Also in some embodiments, each color LED structure is located in a different one of the sub-cavities. For example, the bottom red LED structure is located in the sub-cavity at the bottom of the cavity, the top blue LED structure is located in the sub-cavity at the top of the cavity, and the middle green LED structure is located in the sub-cavity in the middle of the cavity. In some embodiments, the sub-cavities may be filled with a silicon-containing material, such as silicon oxide, which can improve optical refraction, increase light transmittance, and / or enhance ultraviolet and heat aging resistance. In some embodiments, the materials of the sub-cavities may be different. For example, the sub-cavity at the top of the cavity may be filled with silicon oxide, and the sub-cavity at the bottom of the cavity may be filled with epoxy methylsilane. In some embodiments, the sub-cavities may be empty or vacuum.

[0426] In some embodiments, the stepped reflector cup may include metal. In some embodiments, the stepped reflector cup may include a dielectric material such as silica. In some embodiments, the stepped reflector cup may include a photosensitive dielectric material. In some embodiments, the photosensitive dielectric material may include SU-8 or photosensitive polyimide (PSPI). In other embodiments, the stepped reflector cup may include a photoresist. In some embodiments, the manufacturing process of the stepped reflector cup is similar to that described above with reference to the reflector cup.

[0427] In some embodiments, the single-pixel multi-color LED device 800 further includes one or more reflective coatings. The one or more reflective coatings may be disposed on one or more inclined surfaces of the stepped reflector cup, for example, on the inclined surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S. The bottom of each layer of the one or more reflective coatings does not contact the respective LED structures, such as the red LED structure, the green LED structure, and the blue LED structure. The one or more reflective coatings may reflect the light emitted from the light-emitting region, thereby enhancing the brightness and luminous efficacy of the micro-LED panel or display. For example, the light emitted from the light-emitting region may reach the one or more reflective coatings and may be reflected upward through them.

[0428] The one or more reflective coatings together with the stepped reflector cup may utilize the reflection direction and / or reflection intensity of the light emitted by the light-emitting region. For example, the tilt angles α, β, and γ corresponding to the inclined surfaces 846-1S, 846-2S, and 846-3S may become smaller from the bottom to the top of the cavity, so that the one or more reflective coatings disposed on the inclined surfaces 846-1S, 846-2S, and 846-3S are tilted at the same tilt angles as the inclined surfaces 846-1S, 846-2S, and 846-3S. When the light emitted from the light-emitting region reaches the one or more reflective coatings, the light emitted from the light-emitting region is reflected by the one or more reflective coatings at the tilt angles α, β, and γ. The tilt angles α, β, and γ may become larger, the same, or smaller, or the tilt angles α, β, and γ may be otherwise selected according to a specific design.

[0429] The material of the one or more reflective coatings may be highly reflective, having a reflectivity greater than 60%, 70%, or 80%, and may reflect most of the light emitted from the light-emitting region. In some embodiments, the material of the one or more reflective coatings is similar to that described above with reference to the reflector cup. In some embodiments, the materials of the one or more reflective coatings disposed on each inclined surface may be different. For example, the material of the reflective coating disposed on the inclined surface 846-1S may be different from the materials of the reflective coatings disposed on the inclined surfaces 846-2S and 846-3S, respectively.

[0430] In some embodiments, one or more of the reflective coatings may be fabricated by one or more of electron beam deposition or sputtering processes. In some embodiments, each of the one or more stepped structures such as 846-1, 846-2, 846-3, 848-1, 848-2, and 848-3 is formed layer by layer in a multi-step process. For example, stepped structures such as 846-1 and 848-1 are formed in the same step before or after the formation of the planarized layer 454. Stepped structures such as 846-2 and 848-2 are formed in the same step before or after the formation of the planarized layer 458. Stepped structures such as 846-3 and 848-3 are formed in the same step before or after the formation of the planarized layer 462. In some embodiments, particularly when layer-by-layer planarization is involved in the process of forming a single-pixel tri-color LED device, the stepped structures are formed as a result of layer-by-layer processing and misalignment of the bonding of different planarized layers including the LED structure. In some embodiments, as a result of layer-by-layer processing and misalignment of the bonding of different planarized layers including the LED structure, there may be gaps (not shown in Figure 8 ) between different stepped structures such as 846-1, 846-2, and 846-3.

[0431] In some embodiments, the reflector cup may have a floating structure. Figure 9 is a cross-sectional view along the Figure 4A diagonal such as 402 of a single-pixel tri-color LED device 900 having a floating reflector cup according to some embodiments. In some embodiments, although not all shown in Figure 9 , the single-pixel tri-color LED device 900 has a structure similar to any of the single-pixel tri-color LED devices shown in FIGS. 1-8 and has floating reflector cup portions such as 946 and 948.

[0432] In some embodiments, the floating reflector cup may surround the light-emitting region, and the bottom of the reflector cup does not directly contact the semiconductor substrate 104 / 404. For example, as Figure 9 shown, the reflector cup portions 946 and 948 surround the light-emitting region, and the bottoms of the reflector cup portions 946 and 948 do not directly contact the semiconductor substrate 104. For example, there is a gap between the bottom of the reflector cup and the substrate 104 / 404. In some embodiments, this gap is filled with a planarized insulating layer 454. In some embodiments, the light emitted by the light-emitting region may reach the reflector cup and be reflected upward through the reflector cup. For example, as Figure 9 shown, the light emitted by the light-emitting region, including the light emitted from the sidewalls and / or the top of the LED structure, may reach the reflector cup portions 946 and 948 and be reflected upward through them. Therefore, it can reduce the divergence of the light emitted by the light-emitting region and enhance the brightness of the single-pixel multi-color LED device.

[0433] In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 104 / 404 can be adjusted according to design requirements. In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 104 / 404 can be adjusted during the production process of the single-pixel multicolor LED device and the display panel. When the production of the single-pixel multicolor LED device 900 is completed, this distance is fixed and non-adjustable. In other embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 104 / 404 can be specifically selected during the design process and fixed after the production of the single-pixel multicolor LED device 900 and the display panel. In some embodiments, the distance between the bottom of the reflector cup such as components 946 and 948 and the top surface of the substrate 404 can be the same as or smaller than the distance between the top surface of the bonding layer 408 at the bottom of the light-emitting layer 412 and the top surface of the substrate 404. In some embodiments, the distance between the bottom of the reflector cup such as components 946 and 948 and the top surface of the substrate 404 can be greater than the distance between the top surface of the bonding layer 408 at the bottom of the light-emitting layer 412 and the top surface of the substrate 404. By adjusting the gap of the floating reflector cup, specific light from certain parts of the single-pixel multicolor LED device 900 can be not reflected or isolated, which can make the light more focused at the selected parts of the device 900.

[0434] In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 can be less than 0.5 micrometers. In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 can be less than 1 micrometer. In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 140 can be less than 2 micrometers. In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 can be less than 5 micrometers. In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 can be less than 10 micrometers. In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 can be less than 20 micrometers. In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 can be less than 50 micrometers. In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 can be less than 75 micrometers. In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 can be less than 100 micrometers. Generally, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 is determined by the height at the bottom of the light-emitting layer such as the thickness of the metal bonding layer. In a preferred embodiment, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 is not greater than 20 micrometers.

[0435] In some embodiments, the reflector cup can isolate at least some of the light emitted from the light-emitting region. For example, as Figure 9 shown, when the height of the reflector cup is higher than the height of the light-emitting region, the reflector cup portions 946 and 948 can isolate at least some of the light emitted from the light-emitting region. Thus, the reflector cup can suppress inter-pixel light crosstalk and improve the overall contrast of the LED display. The floating reflector cup has the same or similar components, shape, and manufacturing process (except for position and orientation) as the reflector cup described above.

[0436] FIGS. 1-9 illustrate only a single-pixel multicolor LED device according to some embodiments. In other embodiments, the reflector cup can be of a different shape when viewed from a top view or a side view. That is, the sidewall of the reflector cup surrounding the light-emitting region can be circular, triangular, square, rectangular, pentagonal, hexagonal, and octagonal. The sidewall of the reflector cup can surround one light-emitting region or one single-pixel multicolor LED device, or can surround a group of light-emitting regions or a group of single-pixel multicolor LED devices. For example, the sidewall of the reflector cup can surround two or more light-emitting regions arranged in the same plane or two or more single-pixel multicolor LED devices arranged in the same plane.

[0437] An array of single-pixel multicolor LED devices can be utilized, and each single-pixel multicolor LED device can include a reflector cup. When viewed from a top view or a plan view, each reflector cup can have a different shape. For example, the reflector cup of the first single-pixel multicolor LED device can be circular, and the reflector cup of an adjacent single-pixel multicolor LED device can be square. Additionally, the reflector cups can be electrically isolated from each other. The reflector cups can also be isolated if a buffer space is provided between adjacent reflector cups or if the material of the reflector cup may not extend all the way to the interface with an adjacent reflector cup. Alternatively, the reflective coating formed on the sidewall of the reflector cup can simply extend to cover the gap region between adjacent reflector cups. In another embodiment, the reflector cups can be electrically connected to each other through a common electrode such as a top electrode.

[0438] For those skilled in the art, various other obvious modifications, changes, and variations can be made in the arrangement, operation, and details of the methods and apparatuses of the present invention disclosed herein without departing from the spirit and scope of the present invention as defined in the appended claims. Therefore, the scope of the present invention should be determined by the appended claims and their legal equivalents.

[0439] Further embodiments also include various subsets that include the above-described embodiments shown in FIGS. 1-9 combined or otherwise rearranged in various other embodiments.

[0440] Various design aspects of a single-pixel multi-color LED device, such as the dimensions of the layers (e.g., the width, length, height, and cross-sectional area of each layer), the dimensions of the electrodes, the size, shape, spacing, and arrangement of the two or more LED structural layers, the bonding layer, the reflective layer, and the conductive layer, and the configuration among the integrated circuit, the pixel driver, and the electrical connection are selected (e.g., optimized using a cost or performance function) to obtain the desired LED characteristics. The LED characteristics changed based on the above design aspects include, for example, size, material, cost, manufacturing efficiency, luminous efficiency, power consumption, directivity, luminous intensity, luminous flux, color, spectrum, and spatial radiation pattern.

[0441] Figure 10A is a circuit diagram of a 1000 matrix of single-pixel three-color LED devices 1000 according to some embodiments. Figure 10A The circuit in includes three pixel drivers 1002, 1004, and 1006 and three three-color LED devices 1008, 1010, and 1012.

[0442] In some embodiments, the display panel includes a plurality of pixels such as millions of pixels, and each pixel includes a three-color LED device structure. In some embodiments, the LED device structure can be a micro-LED. Micro-LEDs typically have a lateral dimension of 50 micrometers (μm) or less, and can have a lateral dimension of less than 10 μm or even only a few μm.

[0443] In some embodiments, a pixel driver such as 1002 includes a plurality of transistors and capacitors ( Figure 10A not shown in ). The transistors include a driving transistor connected to a power supply and a control transistor configured to have its gate connected to a scan signal bus. The capacitors include a storage capacitor that is used to maintain the gate voltage of the driving transistor during the scan signal setting of other pixels.

[0444] In this example, each of the three three-color LED devices, such as 1008, has its own integrated circuit (IC) pixel driver 1002. The three-color LED device 1008 for a single pixel can be regarded as three separate LEDs connected in parallel with different colors. For example, the red LED 1018, the green LED 1016, and the blue LED 1014 within the same three-color LED device 1008 are connected to the same IC pixel driver 1002 through a common P electrode pad or anode.

[0445] In some embodiments, the respective red LEDs, green LEDs, and blue LEDs within the same three-color LED device 1008 are connected to separate N electrode pads or cathodes.

[0446] In some embodiments, all of the red LEDs, such as 1018, 1024, and 1030, from different tri-color LED devices are connected to the same common N electrode 1036. All of the green LEDs, such as 1016, 1022, and 1028, from different tri-color LED devices are connected to the same common N electrode 1034. All of the blue LEDs, such as 1014, 1020, and 1026, from different tri-color LED devices are connected to the same common N electrode 1032. The use of common electrodes simplifies the manufacturing process and reduces the area of the LED device, especially the area occupied by the electrodes.

[0447] In some embodiments, the connections of the P electrode and the N electrode can be switched and interchanged ( Figure 10A not shown in). For example, the red LED 1018, the green LED 1016, and the blue LED 1014 within the same tri-color LED device 1008 are connected to a shared N electrode pad or cathode. The red, green, and blue LEDs within the same tri-color LED device 1008 are connected to separate P electrode pads or anodes. All of the red LEDs, such as 1018, 1024, and 1030, from different tri-color LED devices are connected to the same common N electrode 1036.

[0448] Figure 10B is a circuit diagram of a matrix of single-pixel tri-color LED devices 1000 according to some embodiments. Figure 10B Similar to Figure 10A , except that in this example, each LED structure, such as 1008, in each of the three tri-color LED devices has its own integrated circuit (IC) pixel driver 1002. For example, within the same tri-color LED device 1008, the red LED 1018, the green LED 1016, and the blue LED 1014 are respectively connected to different IC pixel drivers 1002-1, 1002-2, and 1002-3 via separate P electrode pads or anodes. As can be observed from FIGS. 1-9, this type of P electrode connection is shown in some embodiments.

[0449] In addition, in some embodiments as shown in Figure 10B , all LEDs of different colors from different tri-color LED devices are connected to the same common N electrode 1032.

[0450] In some embodiments, the connections of the P electrode and the N electrode can be switched and interchanged ( Figure 10B(not shown in the figure). For example, in the same three-color LED device 1008, the red LED 1018, the green LED 1016, and the blue LED 1014 are respectively connected to different N electrode pads or cathodes. All the LEDs of different colors of different three-color LED devices are connected to the same common P electrode 1032.

[0451] Figure 11 is a top view of a micro-LED display panel 1100 according to some embodiments. The display panel 1100 includes a data interface 1110, a control module 1120, and a pixel region 1150. The data interface 1110 receives data defining an image to be displayed. The source and format of this data will vary according to the application. The control module 1120 receives the input data and converts it into a form suitable for driving the pixels in the display panel. The control module 1120 may include: digital logic and / or a state machine to convert from the received format to a format suitable for the pixel region 1140; shift registers or other types of buffers and memories to store and transmit data; digital-to-analog converters and level converters; and a scan controller including a clock circuit.

[0452] The pixel region 1150 includes a pixel array. The pixels include micro-LEDs such as multi-color LEDs 1134 integrated with pixel drivers as described above. In some embodiments, the top of the multi-color LED array is covered with an array of microlenses ( Figure 11 (not shown separately in the LED 1134 in the figure). In some embodiments, an array of optical isolation structures such as a reflective structure or a reflector cup ( Figure 11 (not shown separately in the LED 1134 in the figure) is formed around the multi-color LED array. In this example, the display panel 1100 is a color RGB display panel. It includes red, green, and blue pixels. Within each pixel, the three-color LED 1134 is controlled by a pixel driver. According to the previously shown embodiments, the pixel is in contact with a power supply voltage (not shown), in contact with ground through a ground pad 1136, and also in contact with control signals. Although not shown in Figure 11 (the figure), the P electrode of the three-color LED 1134 and the output terminal of the driving transistor are located within the LED 1134. The LED current drive signal connection (between the P electrode of the LED and the output terminal of the pixel driver), the ground connection (between the n electrode and the system ground), the power supply voltage Vdd connection (between the source of the pixel driver and the system Vdd), and the control signal connection to the gate of the pixel driver are made according to various embodiments.

[0453] Figure 11 are only representative drawings. Other designs will be obvious. For example, the colors do not have to be red, green, and blue. They also do not have to be arranged in rows or stripes. As an example, in addition to Figure 11In addition to the square matrix arrangement of pixels shown, a hexagonal matrix arrangement of pixels can also be used to form the display panel 1100.

[0454] In some applications, a fully programmable rectangular pixel array is not necessary. Other designs of display panels and displays with various shapes can also be formed using the device structures described herein. One class of examples is special applications, including signage and automotive. For example, multiple pixels can be arranged in a star or spiral shape to form a display panel, and different patterns on the display panel can be generated by turning on and off the LEDs. Another specialized example is automotive headlights and smart lighting, where certain pixels are grouped together to form various lighting shapes, and each group of LED pixels can be turned on or off or otherwise adjusted by individual pixel drivers.

[0455] Even the lateral arrangement of the devices within each pixel can vary. In FIGS. 1-9, the LEDs and pixel drivers are arranged vertically, i.e., each LED is located on top of the corresponding pixel driving circuit. Other arrangements are possible. For example, the pixel driving circuit can also be located "behind", "in front of", or "next to" the LED.

[0456] Different types of display panels can be manufactured. For example, the resolution of the display panel can generally be in the range of 8×8 to 3840x2160. Common display resolutions include QVGA with a resolution of 320x240 and an aspect ratio of 4:3, XGA with a resolution of 1024x768 and an aspect ratio of 4:3, D with a resolution of 1280x720 and an aspect ratio of 16:9, FHD with a resolution of 1920×1080 and an aspect ratio of 16:9, UHD with a resolution of 3840x2160 and an aspect ratio of 16:9, and 4K with a resolution of 4096×2160. There can also be a wide variety of pixel sizes, ranging from sub-microns and below to 10 mm and above. The size of the overall display area can also vary widely, ranging from a diagonal as small as a few tens of microns or less to hundreds of inches or more.

[0457] Different applications will also have different requirements for optical brightness and viewing angle. Example applications include direct-view displays, light engines for home / office projectors and portable electronic products such as smartphones, laptops, wearable electronic devices, AR and VR glasses, and retinal projection. The power consumption can vary from as low as a few milliwatts for retinal projectors to up to the kilowatt level for large-screen outdoor displays, projectors, and smart automotive headlights. In terms of frame rate, due to the fast response (nanosecond level) of inorganic LEDs, the frame rate can be as high as the KHz level, or even the MHz level for small resolutions.

[0458] Additional embodiments also include various subsets that combine and otherwise re-arrange the embodiments shown in FIGS. 1-11 in various other embodiments. For example, multi-color LED pixel devices / cells with and without a reflective layer, with and without a planarized layer, with and without a cup structure including various shapes and positioning types, with and without a refractive layer, with and without microlenses, with and without spacers, and with and without different electrode connection structures.

[0459] Although the detailed description contains many details, these should not be construed as limiting the scope of the invention, but merely as illustrating different examples and aspects of the invention. It should be understood that the scope of the invention includes other embodiments not discussed in detail above. For example, the above methods can be applied to the integration of functional devices other than LEDs and OLEDs and control circuits 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 devices, and distributed feedback lasers (DFBs). Examples of other control circuits include current drivers, voltage drivers, transimpedance amplifiers, and logic circuits.

[0460] The foregoing description of the disclosed embodiments is provided to enable the making or use of the embodiments described herein and their variations. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can 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 rather to embrace the widest scope consistent with the following claims and the principles and novel features disclosed herein.

[0461] The features of the present invention can be implemented by using a computer program product or with the aid of a computer program product, the computer program product being a storage medium (plural media) or a computer-readable storage medium (plural media), in or on which instructions are stored that can be used to program a processing system to perform any of the features presented herein. The storage medium may include, but is not limited to, high-speed random access memory, such as DRAM, SRAM, DDRRAM, or other random access solid-state memory 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 optionally includes one or more storage devices located remotely from the CPU. The memory or optionally the non-volatile memory device within the memory includes a non-transitory computer-readable storage medium.

[0462] Features of the present invention stored on any machine-readable medium (media) may be embodied in software and / or firmware for controlling the hardware of a processing system and enabling the processing system to utilize the results of the present invention to interact with other entities. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0463] It should be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0464] The terms used herein are for the purpose of describing particular embodiments only and are 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 as well, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It should also be understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups.

[0465] As used herein, the term "if" may be interpreted to mean "in the case that", "when", or "in response to detecting", depending on the context, that the stated precondition is true. Similarly, the phrases "if it is determined that [the stated precondition is true]" or "if [the stated precondition is true]" or "when [the stated precondition is true]" may be interpreted to mean, depending on the context, "when it is determined", "in response to determining", "in accordance with determining", "when detecting", or "in response to detecting", that the stated precondition is true.

[0466] The foregoing description has been presented for purposes of illustration with reference to specific embodiments. However, the above illustrative discussion is not intended to be exhaustive or to limit the claims to the precise forms disclosed. Many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of practical application and operation, such that others skilled in the art may implement them.

Claims

1. A micro light-emitting diode (LED) pixel unit, comprising: A first-color LED structure formed on an IC substrate, wherein the first-color LED structure includes a first light-emitting layer and a first reflection structure, and the first reflection structure includes a first bottom reflection structure formed at the bottom of the first light-emitting layer and a first top reflection layer formed at the top of the first light-emitting layer; A first bonding metal layer formed at the bottom of the first-color LED structure, configured to bond the IC substrate and the first-color LED structure; A second bonding metal layer formed at the top of the first-color LED structure; A second-color LED structure formed on the second bonding metal layer, wherein the second-color LED structure includes a second light-emitting layer and a second reflection structure, and the second reflection structure includes a second bottom reflection structure formed at the bottom of the second light-emitting layer and a second top reflection layer formed at the top of the second light-emitting layer; A top electrode layer covering the first-color LED structure and the second-color LED structure and being in electrical contact with the first-color LED structure and the second-color LED structure, wherein the first-color LED structure is also electrically connected to a first driving circuit and the second-color LED structure is also electrically connected to a second driving circuit; And A reflector cup surrounding the first-color LED structure and the second-color LED structure, and light emitted horizontally from the first light-emitting layer and the second light-emitting layer reaches the reflector cup and is reflected upward by the reflector cup. Wherein, the light emitted from the first light-emitting layer propagates in a substantially horizontal direction between the first bottom reflection structure and the first top reflection layer before reaching the reflection cup and being reflected upward by the reflection cup, and the light emitted from the second light-emitting layer propagates in a substantially horizontal direction between the second bottom reflection structure and the second top reflection layer before reaching the reflection cup and being reflected upward by the reflection cup.

2. The micro-LED pixel unit according to claim 1, wherein, The first reflection structure includes at least one first reflection layer, the second reflection structure includes at least one second reflection layer, and the reflectivity of the first reflection layer or the second reflection layer is higher than 60%.

3. The micro-LED pixel unit according to claim 2, wherein The material of the first reflection layer or the second reflection layer includes one or more of Rh, Al, Ag, or Au.

4. The micro-LED pixel unit according to claim 2, wherein, The first reflection structure includes two first reflection layers with different refractive indexes, and wherein, the second reflection structure includes two second reflection layers with different refractive indexes.

5. The micro-LED pixel unit according to claim 4, wherein, The two first reflection layers respectively include SiO2 and Ti3O5, and the two second reflection layers respectively include SiO2 and Ti3O5.

6. The micro-LED pixel unit according to claim 2, wherein, The first reflection structure further includes a first transparent layer on the first reflection layer, and the second reflection structure further includes a second transparent layer on the second reflection layer.

7. The micro-LED pixel unit according to claim 6, wherein, The first transparent layer includes one or more of indium tin oxide (ITO) or SiO2, and the second transparent layer includes one or more of ITO or SiO2.

8. The micro-LED pixel unit according to claim 1, wherein The first-color LED structure further includes a first bottom conductive contact layer and a first top conductive contact layer, and the second-color LED structure further includes a second bottom conductive contact layer and a second top conductive contact layer; Wherein, the first light-emitting layer is located between the first bottom conductive contact layer and the first top conductive contact layer, and the second light-emitting layer is located between the second bottom conductive contact layer and the second top conductive contact layer; Wherein, the first bottom conductive contact layer is electrically connected to the IC substrate through the first reflective structure and the first bonding metal layer by a first contact via, and the second bottom conductive contact layer is electrically connected to the IC substrate through a second contact via; and Wherein, the edge of the first top conductive contact layer contacts the top electrode layer, and the top surface of the second top conductive contact layer contacts the top electrode layer.

9. The micro-LED pixel unit according to claim 1, wherein, The material of the reflector cup includes metal.

10. The micro-LED pixel unit according to claim 1, further comprising a microlens formed above the top electrode layer.

11. The micro-LED pixel unit according to claim 10, further comprising a spacer formed between the microlens and the top electrode layer.

12. The micro-LED pixel unit according to claim 11, wherein, The material of the spacer includes silicon oxide.

13. The micro-LED pixel unit according to claim 10, wherein, The lateral dimension of the microlens is greater than the lateral dimension of the effective light-emitting area of the first-color LED structure; the lateral dimension of the microlens is greater than the lateral dimension of the effective light-emitting area of the second-color LED structure.

14. The micro-LED pixel unit according to claim 1, wherein, The first-color LED structure and the second-color LED structure have the same lateral dimension.

15. The micro-LED pixel unit according to claim 1, wherein, The first-color LED structure and the second-color LED structure have the same central axis.

16. The micro-LED pixel unit according to claim 2, wherein, The thickness of the at least one first reflective layer is in the range of 5 nm to 10 nm, and the thickness of the at least one second reflective layer is in the range of 5 nm to 10 nm. Wherein, the thickness of the first-color LED structure is not greater than 300 nm, and the thickness of the second-color LED structure is not greater than 300 nm.

17. A multicolor micro-light-emitting diode (LED) pixel device for a display panel, comprising: A first LED structure formed on an IC substrate, emitting light of a first color, wherein the first LED structure includes a first bottom reflective structure formed at the bottom of the first light-emitting layer of the first LED structure and a first top reflective layer formed on top of the first light-emitting layer; A first transparent dielectric bonding layer having a first planar top surface, covering the first LED structure; A second LED structure formed on the first planar top surface of the first transparent dielectric bonding layer, emitting light of a second color, wherein the second LED structure includes a second bottom reflective structure formed at the bottom of the second light-emitting layer of the second LED structure and a second top reflective layer formed on top of the second light-emitting layer; A second transparent dielectric bonding layer having a second planar top surface, covering the second LED structure; A top electrode layer, covering the multicolor micro-LED pixel device and being in electrical contact with the first LED structure and the second LED structure; And A reflector cup surrounds the first LED structure and the second LED structure, wherein the light emitted from the first light-emitting layer propagates in a substantially horizontal direction between a first bottom reflective layer and a first top reflective layer before reaching the reflector cup and being reflected upward by the reflector cup, and the light emitted from the second light-emitting layer propagates in a substantially horizontal direction between a second bottom reflective layer and a second top reflective layer before reaching the reflector cup and being reflected upward by the reflector cup; Wherein, the first LED structure is also electrically connected to a first driving circuit and the second LED structure is also electrically connected to a second driving circuit.

18. The multi-color micro-LED pixel device according to claim 17, wherein, The first LED structure is embedded in a first planarized transparent dielectric layer.

19. The multi-color micro-LED pixel device according to claim 17, wherein, The second LED structure is embedded in a second planarized transparent dielectric layer.

20. The multi-color micro-LED pixel device according to claim 17, wherein, The first transparent dielectric bonding layer is composed of a solid inorganic material or a plastic material.

21. The multi-color micro-LED pixel device according to claim 20, wherein, The solid inorganic material is composed of one or more materials selected from SiO2, Al2O3, Si3N4, phosphosilicate glass (PSG), and borophosphosilicate glass (BPSG).

22. The multi-color micro-LED pixel device according to claim 20, wherein, The plastic material is one or more polymers selected from SU-8, PermiNex, benzocyclobutene (BCB), and spin-on glass (SOG).

23. The multicolor micro-LED pixel device according to claim 17, wherein, The first LED structure includes a first bottom electrode layer formed at the bottom of the first LED structure, The second LED structure includes a second bottom electrode layer formed at the bottom of the second LED structure; The first bottom electrode layer is electrically connected to the IC substrate through a first contact in a first via located at the bottom of the first bottom electrode layer; And The second bottom electrode layer is electrically connected to the IC substrate through a second contact in a second via passing through the first transparent dielectric bonding layer.

24. The multi-color micro-LED pixel device according to claim 23, wherein, The first bottom electrode layer is transparent and the second bottom electrode layer is transparent.

25. The multicolor micro-LED pixel device according to claim 17, wherein, The first LED structure includes a first light-emitting layer; A first side extends from one side of the first light-emitting layer; The second LED structure includes a second light-emitting layer; A second side extends from one side of the second light-emitting layer; And A third contact in a third via passes through the second transparent dielectric bonding layer to connect the first side and the second side to the top electrode layer.

26. The multi-color micro-LED pixel device according to claim 17, wherein, An optical isolation structure is formed around the multicolor micro-LED pixel device.

27. The multi-color micro-LED pixel device according to claim 26, wherein, The optical isolation structure is a reflector cup.

28. The multi-color micro-LED pixel device according to claim 26, wherein, The material of the reflector cup is metal.

29. The multicolor micro-LED pixel device according to claim 17, wherein, A microlens is formed above the top electrode layer.

30. The multi-color micro-LED pixel device according to claim 29, wherein, A spacer is formed between the microlens and the top electrode layer.

31. The multi-color micro-LED pixel device according to claim 30, wherein, The spacer is composed of silicon oxide.

32. The multi-color micro-LED pixel device according to claim 29, wherein, The lateral dimension of the microlens is larger than the effective light-emitting area of the first LED structure; the lateral dimension of the microlens is larger than the effective light-emitting area of the second LED structure.

33. The multi-color micro-LED pixel device according to claim 17, wherein, The lateral dimensions of the first LED structure and the second LED structure are the same.

34. The multi-color micro-LED pixel device according to claim 17, wherein, The first LED structure and the second LED structure have the same central axis.

35. The multi-color micro-LED pixel device according to claim 17, wherein, A first reflective layer is formed at the bottom of the first LED structure; a second reflective layer is formed at the bottom of the second LED structure.

36. The multicolor micro-LED pixel device according to claim 35, wherein the thickness of the first reflective layer is 5 to 10 nm; the thickness of the second reflective layer is 5 to 10 nm; the thickness of the first LED structure does not exceed 300 nm; and the thickness of the second LED structure does not exceed 300 nm.

37. The multi-color micro-LED pixel device according to claim 17, wherein, A bonding metal layer is formed at the bottom of the first LED structure.

38. The multi-color micro-LED pixel device according to claim 17, wherein, The material of the top electrode layer is selected from the following materials: graphene, indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), and fluorine-doped tin oxide (FTO).

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