System and method for multi-color LED pixel unit

Abstract

A micro multi-color LED device includes two or more LED structures for emitting a series of color light. The two or more LED structures are vertically stacked to mix the light emitted by the two or more LED structures vertically and / or horizontally and reflect upward via some reflective structures. In some embodiments, each LED structure is connected with 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 light reflecting 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, titled “Systems and Methods for Coaxial Multi-Color LED,” filed June 19, 2019; U.S. Provisional Patent Application No. 63 / 013,358, titled “Light-Emitting Diode Chip Structures with Reflective Elements,” filed April 21, 2020; U.S. Provisional Patent Application No. 63 / 013,370, titled “Light-Emitting Diode Chip Structures with Reflective Elements,” filed April 21, 2020; U.S. Provisional Patent Application No. 63 / 034,391, titled “Systems and Methods for Multi-Color LED Pixel Unit with Vertical Light Emission,” filed June 3, 2020; and U.S. Provisional Patent Application No. 63 / 034,394, titled “Systems and Methods for Multi-Color LED Pixel Unit with Horizontal Light Emission,” filed June 3, 2020, each of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates generally to light-emitting diode (LED) display devices, and more particularly, to systems and methods of manufacturing LED semiconductor devices for emitting different colors of light with high luminance and micron-scale pixel size. BACKGROUND

[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, heads-up display (HUD), mobile device displays, wearable device displays, and automotive displays require LED panels with improved resolution and brightness. For example, an AR display integrated within goggles and positioned close to a wearer’s eyes can have a size as small as a fingernail while still requiring a HD (1280 x 720 pixels) or higher definition. 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 simultaneously maintain resolution and brightness requirements when trying to achieve 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 roughly inverse relationships. For example, obtaining high brightness for each pixel results in low resolution. Or, obtaining high resolution results in low brightness.

[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, independent 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 individual LED illumination area is determined, it is a difficult task to further increase the overall resolution of the LED panel because LEDs of different colors must occupy their designated areas within a single pixel.

[0006] Active matrix liquid crystal displays (LCDs) and organic light emitting diode (OLED) displays, in combination with thin film transistor (TFT) technology, are becoming increasingly popular in today’s commercial electronic devices. These displays are widely used in personal notebook computers, smart phones, and personal digital assistants. Millions of pixels together create an image on the display. TFTs act as switches to individually turn on and off each pixel, making the pixel either bright or dark, allowing each pixel and the entire display to be conveniently and efficiently controlled.

[0007] However, conventional LCD displays have the disadvantage of low light efficiency, resulting in high power consumption and limited battery run time. While active matrix organic light emitting diode (AMOLED) display panels generally consume less power than LCD panels, the AMOLED display panel is still the major power consuming device in a battery-powered device. To extend the battery life, it is desirable to reduce the power consumption of the display panel.

[0008] Conventional inorganic semiconductor light emitting diodes (LEDs) have demonstrated excellent light efficiency, which makes active matrix LED displays more desirable for battery-powered devices. A driving circuit and an array of light emitting diodes (LEDs) are used to control millions of pixels to render images on a display. Both monochrome 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 an array of pixel driving circuits 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. Furthermore, there is no existing production tool for mass transfer of micro-LEDs. Therefore, new tools have to 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 can cause optical cross-talk. In addition, thermal mismatch between the two different substrates creates stress at the bonding interface, which can cause reliability issues. Furthermore, a multi-color display panel typically requires more LEDs compared to a monochrome display panel, and different colors of LEDs grown on different substrate materials, making the conventional production process more complicated and inefficient.

[0011] Display technology has become increasingly popular in today's commercial electronic devices. These display panels are widely used in both stationary large screens such as liquid crystal display televisions (LCD TVs) and organic light emitting diode televisions (OLED TVs) and portable electronic devices such as personal laptops, smartphones, tablets, and wearable electronic devices. The development direction of stationary large screen technology is to achieve a large viewing angle so as to accommodate 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 of all pixel light sources in a display panel.

[0012] However, most portable electronic devices are designed primarily for a single user, and the screen orientation of these portable devices should be adjusted for the best viewing angle for the corresponding user rather than a large viewing angle to accommodate multiple viewers. For example, the appropriate viewing angle for a user can be perpendicular to the screen surface. In this case, a large portion of the light emitted at a large viewing angle is wasted compared to a stationary large screen. In addition, a large viewing angle raises privacy issues for using a portable electronic device in a public area.

[0013] Additionally, in conventional projection systems based on passive imaging devices such as liquid crystal display (LCD), digital mirror device (DMD), and liquid crystal on silicon (LCOS), the passive imaging device itself does not emit light. Specifically, a conventional projection system projects an image by optically modulating parallel light emitted from a light source, for example, by an LCD panel to emit or by a DMD panel to reflect a portion of light at a pixel level. However, the portion of light that is not emitted or reflected is lost, which reduces the efficiency of the projection system. Furthermore, to provide the parallel light, a complex illumination optical component is needed to collect the divergent light emitted from the light source. The illumination optical component not only makes the system bulky, but also introduces additional light loss into the system, which further affects the performance of the system. In a conventional projection system, typically less than 10% of the illumination light generated by the light source is used to form the projected image.

[0014] Light emitting diodes (LEDs) made of semiconductor materials can be used in monochrome or full color displays. In current displays employing LEDs, the LEDs are typically used as light sources to provide light that is optically modulated by, for example, an LCD or DMD panel. That is, the light emitted by the LEDs themselves does not form an image. LED displays including LED panels with multiple LED dies as the imaging devices have also been investigated. In such LED displays, the LED panel is a self-emissive imaging device, where each pixel can include one LED die (monochrome display) or multiple LED dies, each die representing one primary color (full color display).

[0015] However, the light emitted by the LED dies is generated from self-emission and thus is non-directional, resulting in a large divergence angle. The large divergence angle can cause various problems for micro-LED displays. On one hand, due to the large divergence angle, only a small portion of the light emitted by a micro-LED can be utilized. This can greatly 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 neighboring pixels, causing light cross-talk between pixels, loss of sharpness, and loss of contrast. Conventional solutions to reduce the large divergence angle can not effectively handle the overall light emitted by the micro-LED, and can only utilize the central portion of the light emitted by the micro-LED, such that the remaining portion of the light emitted at more oblique angles is not utilized.

[0016] In view of the foregoing, there exists a need to provide an LED structure for a display panel to address, at least partly, the aforementioned disadvantages and other deficiencies. SUMMARY

[0017] There is a need to improve the design of multi-color LEDs that improve and help address the shortcomings of conventional display systems such as those described above. In particular, there is a need for LED device structures that can simultaneously improve brightness and resolution, yet effectively maintain low power consumption. There is also a need for display panels that reduce viewing angles to better protect user privacy, and / or reduce light waste to lower power consumption, and reduce light interference between pixels to provide better images.

[0018] The multi-color LED devices described herein integrate at least three micro-LED structures arranged in different layers forming a vertically stacked device structure and utilize separate electrodes to receive control current. By arranging at least three LED structures to be aligned along the same axis as disclosed herein, the system effectively improves light illumination efficiency within a single pixel area and simultaneously improves 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 lower. Much effort has been made to reduce the pitch. When the pitch size is determined, the individual pixel area is fixed.

[0020] The multi-color coaxial LED system described herein makes it possible to emit light mixed by different colors from a single pixel area without using additional area to accommodate LED structures with different colors. As a result, the footprint of a single pixel is significantly reduced and the resolution of the micro-LED panel can be improved. At the same time, the concentration of different color light at one micro-LED device boundary greatly improves 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 on a substrate with pixel drivers without the need to introduce an intermediate substrate, which simplifies the manufacturing steps and thus improves the reliability and performance of the LED chip. In addition, no substrate for the micro-LED structures is retained in the final multi-color device, thus reducing crosstalk and mismatch. In addition, 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 planarization layer with less damage to existing structures.

[0022] The multicolor micro-LED devices described herein can include vertical light emission, e.g., light from the individual LED structures of the stack being emitted generally vertically with respect to the surface of the substrate, and horizontal light emission, e.g., light from the individual LED structures of the stack being emitted horizontally with respect to the surface of the substrate and then being reflected generally vertically by some reflective structure, or any combination thereof. 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 the individual layers are achieved. Compared to the vertical light emission, the light emitted horizontally from the individual LED structures of the stack does not need to pass through all the layers above a particular structure. Thus, the horizontal light emission can have better light propagation efficiency and produce better light conspicuity.

[0023] Various embodiments include display panels that integrate a microlens array. The display panel generally includes an array of pixel light sources (e.g., LEDs, OLEDs) electrically coupled to corresponding pixel drive circuitry (e.g., FETs). The microlens array is aligned with the pixel light sources and reduces the divergence of light produced by the pixel light sources. The display panel can also include integrated optical spacers to maintain a gap between the microlenses and the pixel drive circuitry.

[0024] The microlens array reduces the divergence angle of light produced 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 public areas.

[0025] The display panel that integrates the microlens array can be manufactured using a variety of production methods, resulting in a variety of device designs. In one aspect, the microlens array is fabricated directly as a protrusion or mesa of the substrate with the 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 including production methods and processes, applications, and other technology related to any of the above.

[0027] Some example embodiments include a light reflecting cup disposed on a semiconductor substrate and surrounding a light emitting region, e.g., a region from which light is emitted from a multi-color micro-LED device. The light reflecting cup can reduce the divergence of light emitted from the light emitting region and suppress light cross-talk between adjacent pixel cells. For example, the light reflecting cup can utilize light at an oblique angle, which is more efficient in collecting and converging the light to achieve higher brightness and higher power efficiency of the display than conventional solutions. In addition, the light reflecting cup can block light emitted from micro-LEDs in adjacent pixel cells, which can effectively suppress inter-pixel light cross-talk and improve color contrast and clarity. Example embodiments of the present disclosure can improve projection brightness and contrast, thus reducing power consumption in projection applications. Example embodiments of the present disclosure also improve the directionality of light emission from the display, thus providing better image quality for users and protecting the privacy of users in direct view applications. Example embodiments of the present disclosure can provide multiple advantages. One advantage is that example embodiments of the present disclosure can suppress inter-pixel light cross-talk and improve brightness. Example embodiments of the present disclosure can suppress inter-pixel light cross-talk at smaller pitches while improving brightness within a single pixel in a power efficient manner.

[0028] In some example embodiments, a single pixel multi-color LED device can include one or more top electrodes integrated with the light reflecting cup. The top electrodes can be electrically connected with a top electrode layer. The top electrodes integrated with the light reflecting cup can make the single pixel multi-color LED device structure more compact and simplify the manufacturing process. By employing the top electrodes, the light reflecting cup can be used as a common P-electrode or N-electrode for 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 example embodiments, in addition to the reflective cup, the micro-LED pixel unit can also include a micro-lens. The micro-lens can 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 micro-lens can be coaxially aligned with the light emitting region and positioned on top of the light emitting region and the reflective cup. A portion of the light emitted by the light emitting region can directly reach the micro-lens and pass through the micro-lens; another portion can reach the reflective cup and be reflected by the reflective cup, and then reach the micro-lens and pass through the micro-lens. Thus, the divergence of the light can be reduced, and the available viewing angle can be reduced to the extent that the display and panel using the single pixel multi-color LED device can be seen by one user perpendicular to the surface of the display and panel. In turn, power waste can be reduced and brightness and / or better protection of user privacy in public areas can be improved. In another example, the micro-lens can be coaxially aligned with the light emitting region, positioned on the light emitting region and surrounded by the reflective cup. A portion of the light emitted by the light emitting region can directly reach the micro-lens and pass through the micro-lens; another portion of the light can reach the reflective cup and be reflected by the reflective cup, and then reach the micro-lens and pass through the micro-lens; the remaining light can reach the reflective cup and be reflected by the reflective cup without passing through the micro-lens. Thus, the divergence can be reduced, and the available viewing angle can be reduced to the extent that the display and panel using the single pixel multi-color LED device can be seen by several users. This can also reduce power waste, increase brightness and / or properly protect user privacy in public areas.

[0030] In some example embodiments, the single pixel multi-color LED device can also include a spacer. The spacer can be an optically transparent layer formed to provide proper spacing between the micro-lens and the light emitting region. For example, in the case where the micro-lens is disposed above the reflective cup, the spacer can be disposed between the micro-lens and the top of the reflective cup. Thus, the light emitted by the light emitting region can pass through the spacer and then pass through the micro-lens. The spacer can also fill the area surrounded by the reflective 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 employing the micro-lens, the light extraction efficiency of the single pixel multi-color LED device can be improved to further improve the brightness of, for example, a micro-LED display panel.

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

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

[0033] Some example 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, a bottom of the first light emitting layer forming a first reflective structure; 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 a 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 electrically contacting the first color LED structure and the second color LED structure; and the IC substrate electrically connected to the first color LED structure and the second LED structure.

[0034] Some example embodiments provide a micro-LED pixel unit, comprising: a first color LED structure formed on an IC substrate, wherein the first color LED structure comprises a first light emitting layer, a first reflective structure is formed on a 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 comprises a second light emitting layer, and a second reflective structure is formed on a 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 comprises a third light emitting layer, a third reflective structure is formed on a 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 electrically contacting the first color LED structure, the second color LED structure, and the third color LED structure; and the IC substrate electrically connected with the first color LED structure, the second color LED structure, and the third color LED structure.

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

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

[0037] In some example embodiments of the micro-LED pixel unit or any combination of the foregoing example 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 example embodiments of the micro-LED pixel unit or any combination of the foregoing example embodiments, the first reflective structure comprises at least two first high-reflectivity layers having different refractive indices; the second reflective structure comprises at least two second high-reflectivity layers having different refractive indices; and the third reflective structure comprises at least two third high-reflectivity layers having different refractive indices.

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

[0040] In some example embodiments of the micro-LED pixel cell or any combination of the foregoing example 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 example embodiments of the micro-LED pixel cell or any combination of the foregoing example embodiments, the first color LED structure further comprises a first bottom electrode conductive contact layer, the second color LED structure further comprises a second bottom electrode conductive contact layer, and the third color LED structure further comprises 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 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 through the second dielectric layer and the first dielectric bonding layer.

[0042] In some example embodiments of the micro-LED pixel cell or any combination of the foregoing example 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 example embodiments of the micro-LED pixel cell or any combination of the foregoing example embodiments, a first extension extends from a side of the first light emitting layer; a second extension extends from a side of the second light emitting layer; a third extension extends from a side of the second light emitting layer; and the top contact via connects the first extension, the second extension, and the third extension to the top electrode layer through the second dielectric bonding layer and the third dielectric bonding layer.

[0044] Some example embodiments provide a micro-LED pixel cell comprising at least: 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 a top of the reflective optical isolation structure is higher than a top of the light emitting region.

[0045] In some example embodiments of the micro-LED pixel cell or any combination of the foregoing example embodiments, the micro-lens is located above the top of the light emitting region.

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

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

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

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

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

[0051] In some example embodiments of the micro LED pixel unit, or any combination of the foregoing example 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 example embodiments of the micro LED pixel unit, or any combination of the foregoing example embodiments, a thickness of the first reflective structure is 5 nm to 10 nm; a thickness of the second reflective structure is 5 nm to 10 nm; a thickness of the third reflective structure is 5 nm to 10 nm; a thickness of the first LED structure is no more than 300 nm; a thickness of the second LED structure is no more than 300 nm; and, a thickness of the third LED structure is no more than 300 nm.

[0053] Some example embodiments provide a multi-color micro-LED pixel cell for a display panel, comprising: a first LED structure formed on an IC substrate to emit 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 to emit 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 cell and electrically contacting 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 example embodiments provide a micro-LED pixel cell, 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 cell and electrically contacting the first color LED structure, the second color LED structure, and the third color LED structure; and the IC substrate electrically connected to the first color LED structure, the second LED structure, and the third LED structure.

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

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

[0057] Some example embodiments provide a micro-LED pixel cell, 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 refractive structure formed between the reflective optical isolation structure and the light emitting region.

[0058] Some example embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light emitting region formed on the semiconductor substrate, the light emitting region comprising 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 a surface of each LED structure; a top electrode layer covering the micro-LED pixel unit and electrically contacting each color LED structure, wherein the IC substrate is electrically connected with each color LED structure; a stepped light reflecting cup structure formed around the light emitting region; and a refractive structure formed between the stepped light reflecting cup structure and the light emitting region.

[0059] In some example embodiments of the micro-LED pixel unit or any combination of the foregoing example embodiments, the light reflecting cup structure has a top opening, and a lateral area of the micro-lens is less than a lateral area of the top opening.

[0060] Some example 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 around the light emitting region, wherein the floating reflective optical isolation structure is positioned at a distance above the semiconductor substrate.

[0061] Some example 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 around the light emitting region; a top electrode layer covering the light emitting region and electrically connected with the reflective optical isolation structure, wherein the top electrode layer electrically contacts the reflective optical isolation structure.

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

[0063] In some example embodiments of the micro-LED pixel unit or any combination of the foregoing example embodiments, the light emitting region comprises: at least one LED structure and at least one dielectric bonding 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 with each color LED structure.

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

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

[0066] Some example 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 located at a distance above the semiconductor substrate; 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 example embodiments of the micro-LED pixel unit or any combination of the aforementioned example embodiments, the light emitting region comprises at least one LED structure and a bonding layer located at the bottom of each LED structure.

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

[0069] Some example 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 electrically contacting the light emitting region; a reflective cup structure formed around the light emitting region, wherein the top electrode layer is electrically connected with the reflective cup structure, and the semiconductor substrate is electrically connected with the reflective cup structure; and a refractive structure formed between the reflective cup structure and the light emitting region.

[0070] Some example embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light emitting region formed on the semiconductor substrate, the light emitting region comprising at least one LED structure and a bonding layer located at the bottom of each LED structure, wherein each LED structure comprises a light emitting layer and a bottom 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 with each color LED structure; a reflective cup structure formed around the light emitting region; and a refractive structure formed between the reflective cup structure and the light emitting region.

[0071] Some example embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light emitting region formed on the semiconductor substrate, the light emitting region comprising at least one LED structure and a bonding layer at the bottom of each LED structure, wherein the LED structure comprises a light emitting layer and a reflective structure 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 stepped light cup structure surrounding the light emitting region, wherein the top of the stepped light cup structure is higher than the top of the light emitting region.

[0072] Some example embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light emitting region formed on the semiconductor substrate, the light emitting region comprising at least one LED structure and a metal bonding layer at the bottom of each LED structure, wherein the LED structure comprises a light emitting layer and a reflective structure 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 cup structure surrounding the light emitting region, wherein the floating light cup structure is positioned at a distance from the semiconductor substrate, and light emitted from the sidewalls of the first and second light emitting layers along a horizontal plane reaches the floating light cup structure and is reflected upward by the floating light cup structure.

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

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

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

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

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

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

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

[0080] In some example embodiments of the micro-LED pixel unit, or any combination of the foregoing example embodiments, the first LED structure includes a first bottom electrode conductive contact layer formed at a bottom of the first LED structure; the second LED structure includes a second bottom electrode conductive contact layer formed at a 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 a 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 through the first transparent dielectric bonding layer.

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

[0082] In some example embodiments of the micro-LED pixel unit, or any combination of the foregoing example embodiments, the first LED structure includes a first light emitting layer; a first side portion extends from a side of the first light emitting layer; the second LED structure includes a second light emitting layer; a second side portion extends from a side of the second light emitting layer; and a third contact in a third via 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 example embodiments of the micro-LED pixel unit, or any combination of the foregoing example embodiments, the optical isolation structure is formed around the micro-LED pixel unit.

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

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

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

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

[0088] In some example embodiments of the micro LED pixel unit or any combination of the foregoing example embodiments, the thickness of the first reflective layer is 5-10 nm; the thickness of the second reflective layer is 5-10 nm; the thickness of the first LED structure is no more than 300 nm; and the thickness of the second LED structure is no more than 300 nm.

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

[0090] Some example embodiments provide a micro light LED pixel unit, comprising: a first color LED structure formed on an IC substrate, wherein the first color LED structure comprises a first light emitting layer, 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 is configured to bond the IC substrate and the first color LED structure; a second bonding metal layer is 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 comprises 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 and electrically contacting 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 light reflecting cup surrounding the first color LED structure and the second color LED structure, light emitted from the first light emitting layer and the second light emitting layer in a horizontal direction reaches the light reflecting cup and is reflected upward by the light reflecting cup.

[0091] In some example embodiments of the micro LED pixel unit or any combination of the foregoing example embodiments, the first reflective structure comprises at least one first reflective layer, the second reflective structure comprises 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 example embodiments of the micro LED pixel unit or any combination of the foregoing example embodiments, the material of the first reflective layer or the second reflective layer comprises one or more of Rh, Al, Ag, or Au.

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

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

[0095] In some example embodiments of the micro-LED pixel unit, or any combination of the foregoing example 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 example embodiments of the micro-LED pixel unit, or any combination of the foregoing example 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 example embodiments of the micro-LED pixel unit, or any combination of the foregoing example 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 between the first bottom conductive contact layer and the first top conductive contact layer, and the second light-emitting layer is between the second bottom conductive contact layer and the second top conductive contact layer; the first bottom conductive contact layer is electrically connected with the IC substrate through a first contact via hole passing through the first reflective structure and the first bonding metal layer, and the second bottom conductive contact layer is electrically connected with the IC substrate through a second contact via hole; and an edge of the first top conductive contact layer is in contact with the top electrode layer, and a top surface of the second top conductive contact layer is in contact with the top electrode layer.

[0098] In some example embodiments of the micro-LED pixel unit, or any combination of the foregoing example embodiments, a material of the light-reflecting cup includes a metal.

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

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

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

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

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

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

[0105] In some example embodiments of the micro LED pixel unit, or any combination of the foregoing example embodiments, 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, and wherein the thickness of the first color LED structure is no greater than 300 nm, and the thickness of the second color LED structure is no greater than 300 nm.

[0106] Some example embodiments provide a micro LED pixel unit, comprising: an IC substrate; a light emitting area formed on the IC substrate, comprising a plurality of color LED structures, a bottom of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light emitting area, wherein each of the plurality of color LED structures comprises 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 IC substrate is electrically connected to each of the plurality of color LED structures; and a stepped light cup forming a cavity, surrounding the light emitting area, a sidewall of the light emitting layer of each of the plurality of color LED structures emitting light in a horizontal direction to the light cup and being reflected upward by the light cup.

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

[0108] In some example embodiments of the micro LED pixel unit, or any combination of the foregoing example embodiments, the angle of the plurality of inclined surfaces relative to the surface of the IC substrate decreases from the bottom of the cavity to the top of the cavity.

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

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

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

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

[0113] In some example embodiments of the micro LED pixel unit, or any combination of the aforementioned example 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 example embodiments of the micro LED pixel unit, or any combination of the aforementioned example embodiments, the plurality of color LED structures further comprises a top color LED structure.

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

[0116] In some example embodiments of the micro LED pixel unit, or any combination of the aforementioned example embodiments, the cavity comprises a plurality of sub-cavities, and each of the plurality of color LED structures is respectively located within a different one of the plurality of sub-cavities.

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

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

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

[0120] In some example embodiments of the micro LED pixel unit, or any combination of the foregoing example 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 a top surface of the top conductive contact layer of the top color LED structure is in contact with the top electrode layer, and an edge of the top conductive contact layer of the color LED structure underneath the top color LED structure is in contact with the top electrode layer.

[0121] In some example embodiments of the micro LED pixel unit, or any combination of the foregoing example embodiments, an extension is extended from a side of the light emitting layer of the color LED structure underneath the top color LED structure, and the contact via connects the extension to the top electrode layer.

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

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

[0124] In some example embodiments of the micro LED pixel unit, or any combination of the foregoing example embodiments, the reflective structure includes a reflective layer, a thickness of the reflective layer is in a range of 5 nm to 10 nm, and a thickness of each of the plurality of color LED structures is no more than 300 nm.

[0125] In some example embodiments of the micro LED pixel unit, or any combination of the foregoing example embodiments, a 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 example embodiments provide a micro-LED pixel unit, comprising: a semiconductor substrate; a light emitting region formed on the semiconductor substrate, comprising a plurality of color LED structures, a 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 comprises a light emitting layer and a reflective structure at a 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 reflective cup surrounding the light emitting region; and a refractive structure formed between the reflective cup and the light emitting region.

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

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

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

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

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

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

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

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

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

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

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

[0138] Some example 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, a 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 a 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 reflective cup surrounding the light emitting region, light emitted from a sidewall of the light emitting layer of each of the plurality of color LED structures in a horizontal direction reaching the reflective cup and being reflected upward by the reflective cup, a top of the reflective cup being higher than a top of the light emitting region.

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

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

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

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

[0143] Some example 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, a bottom of each of the plurality of color LED structures 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 at a 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 reflective cup surrounding the light emitting region, wherein a bottom of the floating reflective cup is above the semiconductor substrate, light emitted from a sidewall of the light emitting layer of each of the plurality of color LED structures in a horizontal direction reaches the suspended floating reflective cup and is reflected upward by the suspended floating reflective cup.

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

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

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

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

[0148] In some example embodiments of the micro-LED pixel unit or any combination of the foregoing example embodiments, the floating reflective cup has a top open area, a lateral dimension of the microlens is smaller than a lateral dimension of the top open area.

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

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

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

[0152] In some example embodiments of the micro LED pixel unit, or any combination of the foregoing example embodiments, the material of the floating reflective cup comprises a metal.

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

[0154] In some example embodiments of the micro LED pixel unit, or any combination of the foregoing example embodiments, 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 is no more than 300 nm.

[0155] The compact design of the multi-color LED devices and systems disclosed herein utilizes the lateral overlap of the light-emitting LED structures, thereby improving the light-emitting efficiency, resolution, and overall performance of the LED display system. Furthermore, the manufacturing of the multi-color LED display system can reliably and efficiently form the LED structure pattern without using or preserving additional substrates. In some cases, the design of the display devices and systems disclosed herein greatly reduces the steps of micro-lens manufacturing and improves the efficiency of display panel structure formation by utilizing the consistency of the shape of the micro-lens material with the shape of the multi-color LED device to form the micro-lens directly on top of the multi-color LED device on the substrate. The reduced viewing angle and reduced light interference improve the light-emitting efficiency, resolution, and overall performance of the display system. Therefore, the implementation of the multi-color 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 using conventional LEDs.

[0156] It is noted that the various embodiments described above can be combined with any of the other embodiments described herein. The features and advantages described in the specification are not all inclusive, and particularly, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it is noted that the language used in the specification has been principally selected for readability and instructional purposes and can not have been selected to delineate or circumscribe the inventive subject matter. BRIEF DESCRIPTION OF DRAWINGS

[0157] So that the disclosure can be more readily understood, the present disclosure will be described in greater detail below with reference to the various embodiments, some of which are illustrated in the accompanying drawings. These drawings are for illustration only and are not exclusive, as the description can allow for other effective features.

[0158] FIG. 1Ais a top view of a single-pixel tri-color LED device 100 according to some embodiments.

[0159] FIG. 1B is a cross-sectional view of the single-pixel tri-color LED device 100 along diagonal line 102 in FIG. 1A

[0160] FIG. 1C is a cross-sectional view of the single-pixel tri-color LED device 100 along diagonal line 150 in FIG. 1A

[0161] FIG. 2A is a cross-sectional view of the single-pixel tri-color LED device 100 with planarization features along diagonal line 102 in FIG. 1A

[0162] FIG. 2B is a cross-sectional view of the single-pixel tri-color LED device 100 with planarization features along diagonal line 150 in FIG. 1A

[0163] FIG. 3A is a cross-sectional view of the single-pixel tri-color LED device 100 with planarization features along diagonal line 102 in FIG. 1A

[0164] FIG. 3B is a cross-sectional view of the single-pixel tri-color LED device 100 with planarization features along diagonal line 150 in FIG. 1A

[0165] FIG. 4A is a top view of a single-pixel tri-color LED device 400 with layered planarization according to some embodiments.

[0166] FIG. 4B is a cross-sectional view of the single-pixel tri-color LED device 400 with layered planarization along diagonal line 402 in FIG. 4A

[0167] FIG. 5 is a cross-sectional view of the single-pixel tri-color LED device 500 with refractive structures along diagonal line 102 in FIG. 1A

[0168] FIG. 6A is a cross-sectional view of the single-pixel tri-color LED device 600 with microlenses on reflective structures along diagonal line 102 in FIG. 1A

[0169] FIG. 6B ​​​​​​​​​is a cross-sectional view along a diagonal line 102 of a single-pixel tri-color LED device 600 having microlenses within regions formed by reflective structures, according to some embodiments. FIG. 1A is a cross-sectional view along a diagonal line 102 of a single-pixel tri-color LED device 600 having microlenses within regions formed by reflective structures, according to some embodiments.

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

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

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

[0173] FIG. 8 is a cross-sectional view along a diagonal line such as 402 of a single-pixel tri-color LED device 800 having stepped light cups, according to some embodiments. FIG. 4A is a cross-sectional view along a diagonal line such as 402 of a single-pixel tri-color LED device 800 having stepped light cups, according to some embodiments.

[0174] FIG. 9 is a cross-sectional view along a diagonal line such as 402 of a single-pixel tri-color LED device 900 having floating light cups, according to some embodiments. FIG. 4A is a cross-sectional view along a diagonal line such as 402 of a single-pixel tri-color LED device 900 having floating light cups, according to some embodiments.

[0175] FIG. 10A is a circuit diagram of a single-pixel tri-color LED device 1000 matrix, according to some embodiments.

[0176] FIG. 10B is a circuit diagram of a single-pixel tri-color LED device 1000 matrix, according to some embodiments.

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

[0178] In accordance with common practice the various features illustrated in the drawings can not be drawn to scale. Therefore, the dimensions of the various features can be arbitrarily expanded or reduced for the clarity of presentation. In addition, some of the drawings can not depict all of the components of a given system, method or device. Finally, like reference numerals can be used to denote like features throughout the specification and figures. DETAILED DESCRIPTION

[0179] Many details are described herein in order to provide a thorough understanding of the example embodiments shown in the figures. However, many embodiments can be practiced without many of the specific details, and the scope of the claims is not limited to the embodiments with the specific details. Additionally, well-known methods, components, and materials are not described in detail in order to avoid unnecessarily obscuring the relevant aspects of the examples herein.

[0180] In some embodiments, a single-pixel multi-color 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 a different color. When there are two LED structures within a single-pixel multi-color LED device, light of two colors and a mix of the two colors can be emitted from the single-pixel multi-color LED device. When there are three LED structures within a single-pixel multi-color LED device, light of three colors and a mix of the three colors can be emitted from the single-pixel multi-color LED device.

[0181] In some embodiments, light emitted from a single-pixel multi-color LED device is emitted from the sidewalls of each LED structure within the single-pixel multi-color LED device. In some embodiments, a reflective structure is provided around the single-pixel multi-color LED device to reflect light emitted from the sidewalls of each LED structure upward. In some embodiments, light emitted from a single-pixel multi-color LED device is emitted from the top surface of each LED structure within the single-pixel multi-color LED device. In some embodiments, light emitted from a single-pixel multi-color LED device is a combination of light emitted from the sidewalls and the top surface of each LED structure within the single-pixel multi-color LED device, e.g., in a ratio where light emitted from the sidewalls accounts for about 20% to 100% of the light emitted from the single-pixel multi-color LED device.

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

[0183] FIG. 1B is a cross-sectional view of the single-pixel tri-color LED device 100 along diagonal line 102 in FIG. 1A .

[0184] FIG. 1C is a cross-sectional view of the single-pixel tri-color LED device 100 along diagonal line 150 in FIG. 1A .

[0185] Diagonals 102 and 150 each pass through the center of the individual pixel tri-color LED device 100. Diagonals 102 and 150 are orthogonal to each other. In some embodiments, the tri-color LED device 100 includes a substrate 104. For convenience, "up" is used to mean away from the substrate 104, "down" to mean toward the substrate 104, and other directional terms such as top, bottom, above, below, directly below, underneath, and the like are interpreted accordingly. The support substrate 104 is a substrate on which an array of individual drive circuits 106 are fabricated. In some embodiments, the drive circuits can also be located in one of the layers above the substrate 104, or above the micro tri-color LED structure 100. Each drive circuit is a pixel driver 106. In some cases, the drive circuits 106 are thin film transistor pixel drivers or silicon CMOS pixel drivers. 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 individual pixel drivers to control the operation of individual single pixel tri-color LED devices 100. The circuitry on the substrate 104 includes contacts for each individual drive circuit 106 as well as a ground contact. As shown in FIGS. 1A, 1B, and 1C, each micro tri-color LED structure 100 also has two types of contacts: P-electrodes or anodes, such as 108, 126, 152, connected to the pixel drivers 106; and N-electrodes or cathodes, such as 116, 120, and 140, connected to ground (i.e., the common electrode). FIG. 1A 、 1B and 1C, each micro tri-color LED structure 100 also has two types of contacts: P-electrodes or anodes, such as 108, 126, 152, connected to the pixel drivers 106; and N-electrodes or cathodes, 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 a material 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 116, 120, and 140, are made of a non-transparent or transparent conductive material, in preferred embodiments, a transparent conductive material. In some embodiments, the P-electrodes (or P-electrode contact pads) and their connecting components, such as 126, 152, are made of a material 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 126, 152, are made of a non-transparent or transparent conductive material, in preferred embodiments, a transparent conductive material. In some embodiments, the locations of the P-electrodes (or P-electrode contact pads) and their connecting components, such as 126, 152, and the N-electrodes (or N-electrode contact pads) and their connecting components, such as 116, 120, and 140, can be switched.

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

[0188] In some embodiments, the three LED structures including LED light emitting layers 112, 130 and 136, respectively, form a stacked structure, for example, the green LED light emitting layer 130 is formed on top of the red LED light emitting layer 112, and the 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 with 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 shown in FIGS. 1A and IB, the area of the bottom red LED light emitting layer 112 is greater 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 greater than the area of the top blue LED light emitting layer 136. FIG. 1A and 1B In some embodiments, as shown in FIGS. 1A and IB, the area of the bottom red LED light emitting layer 112 is greater 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 greater 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 towards the sidewall of the red LED light emitting layer 112, then be reflected upwards by a reflective element such as 146 and / or 148 as described below, and be emitted at the top surface of the single-pixel tri-color LED device 100. As described below, a reflective layer 109 is provided below the red LED light emitting layer 112, and a reflective 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 reflective layers 109 and 115 towards 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 towards the sidewall of the green LED light emitting layer 130, then be reflected upwards by a reflective element such as 146 and / or 148 as described below, and be emitted at the top surface of the single-pixel tri-color LED device 100. As described below, a reflective layer 127 is provided below the green LED light emitting layer 130, and a reflective layer 133 is provided above the green LED light emitting layer 130. The light emitted by the green LED light emitting layer 130 is reflected between the two reflective layers 127 and 133 towards the sidewall of the green LED light emitting layer 130.

[0193] In some embodiments, light emitted from 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 upwards by reflective elements such as 146 and / or 148 as described below, and emitted at the top surface of the single-pixel tri-color LED device 100. As described below, a reflective layer 135 is provided below the blue LED light-emitting layer 136. 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, light emitted from the red LED light-emitting layer 112 can propagate vertically through the green LED light-emitting layer 130 and then through the blue LED light-emitting layer 136 before being emitted from the tri-color LED device 100. In some embodiments, light emitted from the green LED light-emitting layer 130 can propagate through the blue LED light-emitting layer 136 to be emitted from the tri-color LED device 100. In the case of vertical light transmission, in some preferred embodiments, top reflective layers above each light-emitting layer, such as 115 and 133, are not included in the tri-color LED device 100.

[0195] In some embodiments, the LED light-emitting layer, such as 112, 130, and 136, comprises a plurality of sub-epitaxial layers with different compositions. Examples of LED epitaxial layers include III-V nitride, III-V arsenide, III-V phosphide, and III-V antimonide epitaxial structures. Examples of microLEDs include GaN-based UV / blue / green microLEDs, AlInGaP-based red / orange microLEDs, and GaAs or InP-based infrared (IR) microLEDs.

[0196] In some embodiments, each LED structure in the stacked LED structure can be controlled individually to produce its own 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 LED epitaxial layers in the tri-color LED device 100.

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

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

[0199] In some embodiments, when the light emission is horizontal or when the horizontally emitting portion exceeds the vertically emitting portion from the top surface of the LED device 100, each of the LED light-emitting layers 112, 130, and 136 can be any suitable visible or invisible 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 100 but exits directly from the edge or sidewall of the current light-emitting layer, light propagation loss can be reduced, and luminous efficiency can be improved. For example, compared to vertically emitting LED devices, horizontally emitting LED devices can improve light propagation efficiency by 15%, 50%, 100%, 150%, or 200%. In some cases, the light propagation efficiency of horizontally emitting LED devices 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 via a metal bonding layer 108. The metal bonding layer 108 may 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, serving as a P-electrode. In some embodiments, the thickness of the metal bonding layer 108 is approximately 0.1 micrometers to 3 micrometers. In a preferred embodiment, the thickness of the metal bonding layer 108 is approximately 0.3 micrometers. The metal bonding layer 108 may 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 a layer above the metal bonding layer within the LED device 100. A 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 combinations thereof. For example, if Au-Au bonding is selected, the two Au layers require a Cr coating as an adhesive layer and a Pt coating as an anti-diffusion layer, respectively. The Pt coating is located between the Au layer and the Cr layer. The Cr layer and the Pt layer are located at the top and bottom of the two bonded Au layers. In some embodiments, when the two Au layers are of approximately the same thickness, the Au on the two layers diffuses into each other under high pressure and high temperature, bonding 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 may also be used as a reflector to reflect 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 may be an opaque metal layer that is opaque to the light emitted by the LED device 100. In some embodiments, the conductive layer 110 may be a conductive transparent layer, such as an indium tin oxide (ITO) layer, that is transparent to the light emitted by the LED device 100, formed between the red LED light-emitting layer 112 and the metal bonding layer 108 to improve conductivity and light transmittance.

[0203] exist FIG. 1A-1C In 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 top of the red LED light-emitting layer 112. In some embodiments, the conductive layer 114 may be as follows: FIG. 1CA metal layer or conductive transparent layer, such as an ITO layer, shown for improving conductivity and light transmission, 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 under the red LED light emitting layer 112, and a reflective layer 115 is provided between the conductive layer 114 and the bonding layer 156 over the red LED light emitting layer 112.

[0205] In some embodiments, the red LED light emitting layer 112 has an extension 164 on one side thereof relative to the other layers above, as shown. FIG. 1C In some embodiments, the extension 164 extends with the conductive layers 110 and 114. In some embodiments, the extension 164 extends 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 of the conductive layer 114 over the extension 164.

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

[0207] In some embodiments, the red LED light emitting layer 112 is used to form a red micro-LED. Examples of red LED light emitting layers include III-V nitride, III-V arsenide, III-V phosphide, and III-V antimonide epitaxial structures. In some cases, the films within the red LED light emitting layer 112 can 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 layers are typically Mg-doped, while the N-type layers are typically Si-doped. In some examples, the red LED light emitting layer has a thickness of about 0.1 microns to 5 microns. In one preferred embodiment, the red LED light emitting layer has a thickness of about 0.3 microns.

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

[0209] In some embodiments, bonding layer 156 is used to bond the red LED structure and the green LED structure together. In some embodiments, bonding layer 156 is opaque to light emitted from LED device 100. In some embodiments, the material and thickness of bonding layer 156 are the same as described above for metallic bonding layer 108. In some embodiments, bonding layer 156 may also be used as a reflector to reflect 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 microLED 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 borosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes polymers such as SU-8, PermiNex, benzocyclobutene (BCB), or transparent plastics (resins) including spin-coated glass (SOG), or Micro Resist's bonding adhesive BCL-1200, or any combination thereof. In some embodiments, the transparent bonding layer may facilitate the passage of light emitted from layers beneath the bonding layer.

[0211] In some embodiments, such as FIG. 1A and FIG. 1B As 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 a conductive layer 128. In some embodiments, the conductive layer 128 for electrode connection is formed on the bottom of the green LED light-emitting layer 130. In some embodiments, such as FIG. 1A and 1B As shown, the conductive layer 128 may be a conductive transparent layer or a metal layer, such as an ITO layer, used to improve conductivity and light transmittance, and is formed between the green LED light-emitting layer 130 and the P electrode contact pad 126.

[0212] In some embodiments, the conductive layer 128 has an extension 128-1 on one side relative to the other layers above, such as FIG. 1B As shown. In some embodiments, the extension 128-1 extends together with all 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 via the extension 128-1 of the conductive layer 128. In some embodiments, the P-electrode contact pad 126 is also electrically connected to the driving circuit 106 in the substrate 104.

[0213] In some embodiments, an insulating layer 174 made of a dielectric material, such as a Si02layer, 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 tunnel 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 the 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 shown in FIG. 1C , 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 with the conductive layer 132. In some embodiments, the N-electrode contact pad 120 of the green LED structure is also electrically connected with the N-electrode contact pad 116 of the red LED structure.

[0216] As shown in FIG. 1C , in some embodiments, the green LED light emitting layer 130 has an extension 166 on one side thereof. In some embodiments, the extension 166 extends with the conductive layers 128 and 132 and all other layers under the conductive layer 128. In some embodiments, the extension 166 is electrically connected to the N-electrode contact pad 120 through the extension of the conductive layer 132 above the extension 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 under 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, known as an epitaxial substrate. The epitaxial substrate is removed after bonding by, for example, a laser lift-off process or a wet chemical etch, leaving behind FIG. 1B and FIG. 1C the structure shown in

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

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

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

[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 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 LED structure above.

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

[0225] In some embodiments, as FIG. 1A and FIG. 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 a 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, such as FIG. 1A and 1B As 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 134-1 on one side relative to the other layers above it, such as FIG. 1B As shown. In some embodiments, the extension 134-1 extends together with all 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 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 a SiO2 layer, is deposited on the surface of the LED device 100. A P-electrode contact pad 152 extends from its contact with the drive circuit 106 to its contact with the conductive layer 134 through vias or channels within 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 top of the blue LED light-emitting layer 136. In some embodiments, the conductive layer 138 may 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 thereof. 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 a single integral element as a common N-electrode.

[0229] In some embodiments, such as FIG. 1B As 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, the top electrode element such as the N-electrode pad 140 is connected through an electrical connection element under the optical isolation structure such as 146, 148, 170 and 172. In some embodiments, the top electrode is connected through an electrical connection element embedded in the substrate 104. In one example, the top electrode 140 is connected through an electrical connection element located above the insulating layer 174, under the 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 under the blue LED light emitting layer 136. In some embodiments, a reflective layer 139 (not shown in FIG. 1) is provided on top of the conductive layer 138 over the blue LED light emitting layer 136. FIG. 1A-1C

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

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

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

[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 the adjacent three-color LED device (not shown in FIG. 1) via some electrical connecting elements, as a common electrode. FIG. 1A-1C

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

[0239] In some embodiments, an additional dielectric layer such as a SiO2layer (not shown in FIG. 1) is formed above the bottom light emitting layer 112 (and above the conductive layer 114), preferably above the reflective layer 115, below the bonding layer 156, to electrically separate the N-type layer of the light emitting layer 112 from the bonding layer 156. In some embodiments, the additional dielectric layer has a thickness of 20 nanometers to 2 microns. In one preferred embodiment, the additional dielectric layer has a thickness of about 100 nanometers. FIG. 1A-1C In some embodiments, an additional dielectric layer such as a SiO2layer (not shown in FIG. 1) is formed above the intermediate light emitting layer 130 (and above the conductive layer 132), preferably above the reflective layer 133, below the bonding layer 160, to electrically separate the N-type layer of the light emitting layer 130 from the bonding layer 160. In some embodiments, the additional dielectric layer has a thickness of 20 nanometers to 2 microns. In one preferred embodiment, the additional dielectric layer has a thickness of about 100 nanometers. FIG. 1A-1C

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

[0241] As in FIG. 1A As shown in the top view, in some embodiments, the tri-color LED device 100 has a circular shape. In some embodiments, optical isolation structures such as 146, 148, 170, and 172 are integrated and form a circular sidewall surrounding the tri-color LED device 100. In some embodiments, the optical isolation structures form a reflector cup, which is described in further detail below. In some embodiments, the three stacked LED structures within the tri-color LED device 100 are also circular. In some embodiments, the tri-color LED device 100 may have other shapes, such as rectangular, square, triangular, trapezoidal, or polygonal. In some embodiments, optical isolation structures such as 146, 148, 170, and 172 are integrated and form a sidewall surrounding the tri-color LED device 100 in other shapes such as rectangular, square, triangular, trapezoidal, or polygonal.

[0242] like FIG. 1B and FIG. 1C As 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 can refer to a surface that is not perpendicular to the top or bottom surface of the respective LED light-emitting layer. In some embodiments, the angle between the inclined sidewall and the bottom surface of the respective LED light-emitting layer is less than 90 degrees. In some embodiments, bonding layers 108, 156, and 160 also have inclined side surfaces. The inclined side surfaces facilitate the connection of different connecting elements to each LED light-emitting layer, prevent the connection from breaking due to abrupt angles, and enhance the overall stability of the device.

[0243] In some embodiments, the light propagation efficiency of the multi-color LED device varies with the angle of the tilted 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 multi-color LED device increases with the increase of the angle of the tilted side surface of the LED light emitting layer relative to the normal of the surface of the substrate 104. 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 104 is ±5 degrees and when the optical isolation structure such as 146, 148, 170, and / or 172 is not a light reflecting cup as described below, the light emission 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 104 is ±15 degrees and when the optical isolation structure such as 146, 148, 170, and / or 172 is not a light reflecting cup as described below, the light emission 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 104 is at (e.g., when the light emitting layer is tilted) or very close to ±90 degrees and when the optical isolation structure such as 146, 148, 170, and / or 172 is not a light reflecting cup as described below, the light emission efficiency of the multi-color LED device is equal to or very close to 56.4%.

[0244] In contrast, the implementation of the light reflecting cup structure as described in further detail below improves the light propagation efficiency of the multi-color LED device. 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 104 is ±5 degrees and when the optical isolation structure such as 146, 148, 170, and / or 172 is a light reflecting cup as described below, the light emission efficiency of the multi-color LED device is 0.65%, i.e., an increase of 104.6% compared to the LED device without the light reflecting cup. 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 104 is ±15 degrees and when the optical isolation structure such as 146, 148, 170, and / or 172 is a light reflecting cup as described below, the light emission efficiency of the multi-color LED device is 6.65%, i.e., an increase of 144.4% compared to the LED device without the light reflecting cup. 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 104 is at (e.g., when the light emitting layer is tilted) or very close to ±90 degrees and when the optical isolation structure such as 146, 148, 170, and / or 172 is a light reflecting cup as described below, the light emission efficiency of the multi-color LED device is equal to or very close to 66.65%, i.e., an increase of 18.4% compared to the LED device without the light 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 FIG. 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, the reflective layer 109 is formed between the bonding layer 108 and the conductive layer 110 in the presence of 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 the presence of the conductive layer 114. In some embodiments, the reflective layer 115 is formed between the bonding layer 156 and the conductive layer 114 in the presence of 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, if a conductive layer 128 is present, 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, if a conductive layer 132 is present, 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, if a conductive layer 134 is present, the reflective layer 135 is formed between the bonding layer 160 and the conductive layer 134. In some embodiments, an optional reflective layer 139 is formed between the N-electrode pad 140 and the blue LED light-emitting layer 136. FIG. 1B-1C (Not shown in the image), while still allowing the blue LED emitting layer 136 to be electrically connected to the N electrode pad 140, for example, via a conductive path. In some embodiments, in the presence of the conductive layer 138, an 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, via a conductive path.

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

[0249] In some embodiments, the material of the reflective layers 109, 115, 127, 133, 135, and 139 is 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 can include at least two sub-layers with 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, such as 112, 130, and 136, or, in the case of a conductive layer, 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 of 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 a plurality of layers of different materials with different refractive indices or a plurality of layers of alternating layers. In some cases, each layer boundary of the DBR structure causes 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 a plurality of layers, for example, at least two layers of Si02and Ti3O5, respectively. By changing the thickness and number of layers of Si02and Ti3O5, respectively, selective reflection or selective propagation of light of different wavelengths can be formed.

[0252] In some embodiments, any of the reflective layers such as 109, 115, 127, 133, 135, and 139 further include a transparent layer on one of the high reflectivity sub-layers. For example, the transparent layer formed on either or both sides of any of the reflective layers such as 109, 115, 127, 133, 135, and 139 is preferably selected from one or more of ITO and Si02.

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

[0254] In some embodiments, each of the reflective layers 109 and 115 for the red 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, each of the reflective layers 109 and 115 for the red LED structure has a high reflectance (e.g., equal to or greater than 75%) for light generated between the current two reflective layers 109 and 115, e.g., 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 green LED reflective layers.

[0257]

[0258]

[0259] In some embodiments, each of the reflective layers 127 and 133 for the green 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, each of the reflective layers 127 and 133 for the green LED structure has a high reflectance (e.g., equal to or greater than 75%) for light generated between the current two reflective layers 127 and 133, e.g., green light.

[0260] In one example, the following DBR structure shown in Table 2 is used to reflect blue light from a blue LED:

[0261] Table 2: DBR layer structure for blue LED reflective layers.

[0262]

[0263] In some embodiments, each layer of the reflective layers 135 and optionally 139 for the blue light LED structure has a low absorbance (e.g., equal to or less than 25%) of light generated by different layers of the tri-color LED device 100. In some embodiments, the reflective layer 135 for the blue light LED structure has a high reflectivity (e.g., equal to or greater than 75%) of light generated above the current reflective layer 135 or between the current reflective layers 135 and 139, such as blue light.

[0264] FIG. 2A is a cross-sectional view along diagonal line 102 in FIG. 1A of a single-pixel tri-color LED device 100 having planarization features according to some embodiments. In some embodiments, the single-pixel tri-color LED device 100 has a similar structure as the single-pixel tri-color LED device 100 shown in FIGS. 1A-1C with the addition of a planarization layer 176 covering the single-pixel tri-color LED device 100. FIG. 1A FIG. 1A 1B is a cross-sectional view along diagonal line 102 in FIG. 1A of a single-pixel tri-color LED device 100 having planarization features according to some embodiments. In some embodiments, the single-pixel tri-color LED device 100 has a similar structure as the single-pixel tri-color LED device 100 shown in FIGS. 1A-1C with the addition of a planarization layer 176 covering the single-pixel tri-color LED device 100.

[0265] FIG. 2B is a cross-sectional view along diagonal line 102 in FIG. 1A of a single-pixel tri-color LED device 100 having planarization features according to some embodiments. In some embodiments, the single-pixel tri-color LED device 100 has a similar structure as the single-pixel tri-color LED device 100 shown in FIGS. 1A-1C with the addition of a planarization layer 176 covering the single-pixel tri-color LED device 100. FIG. 1A FIG. 1A 1B is a cross-sectional view along diagonal line 102 in FIG. 1A of a single-pixel tri-color LED device 100 having planarization features according to some embodiments. In some embodiments, the single-pixel tri-color LED device 100 has a similar structure as the single-pixel tri-color LED device 100 shown in FIGS. 1A-1C with the addition of a planarization layer 176 covering the single-pixel tri-color LED device 100.

[0266] In some embodiments, the planarization layer such as 176 is transparent to 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 of the above. In some embodiments, the plastic material includes a polymer such as SU-8, PermiNex, benzocyclobutene (BCB), or a transparent plastic (resin) including spin-on glass (SOG), or a bonding adhesive BCL-1200 by Micro Resist Technology, or any combination of the above. In some embodiments, the planarization layer can facilitate light emitted by the micro-LED 100 to pass through.

[0267] ​​​​In some embodiments, the planarization layer 176 has the same height as the optical isolation structures, e.g., 146, 148, 170, and 172, relative to the surface of the substrate 104. For example, the planarization layer 176 covers the entire single-pixel tri-color LED device 100 and the sidewalls of the optical isolation structures. The planarization layer 176 is on the same plane as the top surface of the optical isolation structures.

[0268] FIG. 3A is a cross-sectional view along diagonal line 102 of the single-pixel tri-color LED device 100 having planarization features according to some embodiments. In some embodiments, the single-pixel tri-color LED device 100 has a similar structure as the single-pixel tri-color LED device 100 shown in FIGS. 1A, 1B, 1C, which adds a planarization layer 176 covering the single-pixel tri-color LED device 100. FIG. 1A FIG. 1A 1B and 1C, which adds a planarization layer 178 covering the single-pixel tri-color LED device 100.

[0269] FIG. 3B is a cross-sectional view along diagonal line 102 of the single-pixel tri-color LED device 100 having planarization features according to some embodiments. In some embodiments, the single-pixel tri-color LED device 100 has a similar structure as the single-pixel tri-color LED device 100 shown in FIGS. 1A, 1B, 1C, which adds a planarization layer 176 covering the single-pixel tri-color LED device 100. FIG. 1A FIG. 1A 1B and 1C, which adds a planarization layer 178 covering the single-pixel tri-color LED device 100.

[0270] In some embodiments, the planarization layer 178 has the same height as the top electrode element, e.g., 140. The planarization layer 178 is on the same plane as the top surface of the top electrode element, such as the N-pad 140. In some embodiments, the top electrode element, such as 140, is right on top of the planarization layer 178. The planarization layer 178 is on the same plane as the bottom surface of the top electrode element, such as the N-pad 140. For example, the planarization layer 178 covers the entire single-pixel tri-color LED device 100 and a portion of the optical isolation structure sidewalls, such as 146, 148, 170, and 172.

[0271] The top electrode element, such as the N-pad 140, is connected by an electrical connection element, such as 146, 148, 170, and 172, under the optical isolation structure, as shown in FIGS. 1A, 1B, 1C, which is different from FIG. 1A-1C FIG. 2A-2B ​​​​​In FIGS. 3A-3B, the top electrode elements such as the N-electrode pad 140 are connected through electrical connection elements on at least the sidewalls of the optical isolation structures such as 146, 148, 170, and 172. In some embodiments, the N-electrode pad 140 is secured or fixed on 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 planarized layers, making the individual pixel tri-color LED device 100 compact.

[0272] In some embodiments, the insulating layer can be deposited on each LED light emitting layer and other layers such as conductive layers and reflective layers to achieve deposition on the individual pixel multi-color LED device. A planarization process is then performed to make the surface of the insulating layer embedded in the individual pixel multi-color LED device flat. Vias for electrical connections are also formed within each planarized layer. Compared to using other processes without planarizing the insulating layer, the features and layers within the planarized LED structure are better protected and less susceptible to external damaging forces. In addition, the planarized surface can provide light propagation efficiency by reducing deflection caused by uneven surfaces.

[0273] In some embodiments, the tri-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.

[0274] 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 underneath it. In this case, the width or area is measured by the dimension of the plane parallel to the surface of the substrate 104.

[0275] In some embodiments, each of the plurality of LED structures of different colors is bonded together by a bonding layer that only covers the area of the LED structure without extending beyond the area of 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, 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 naturally form from the bottom up as each layer within the LED device is etched and patterned. The pyramid-shaped structure can improve electrical connections between individual LED structures and with electrodes, and simplify the manufacturing process. For example, the electrode connection elements in each layer are exposed in each layer for ease of connection.

[0276] In some embodiments, the bottom layer such as the metal bonding layer 108 has a lateral dimension of about 1 micron to 500 microns. In one 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 implementations, the vertical height of the multicolor LED device is about 1 micron to 500 microns. In one preferred embodiment, the vertical height of the multicolor LED device is about 1.9 microns. In one preferred embodiment, the lateral dimension of the conductive layer 138 at the top of the multicolor LED device is about 1.0 micron.

[0277] In some embodiments, the aspect ratio of the layers of the tricolor LED device remains substantially the same with variations in the lateral dimension of the same layer. For example, where the lateral dimension of the patterned epitaxial layer is 5 microns, the thickness of the patterned epitaxial layer is less than one micron. In another example, where the lateral dimension of the same patterned epitaxial layer increases, the thickness of the patterned epitaxial layer increases accordingly 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.

[0278] The shape of the LED device is not limited, and in some other embodiments, the cross-sectional shape of the tricolor LED device can take other shapes, for example, an inverted trapezoid, a half-ellipse, a rectangle, a parallelogram, a triangle, or a hexagon, etc.

[0279] 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 a dry etching, for example, an inductively coupled plasma (ICP) etching or a 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 100, including the conductive layers 110, 114, 128, 132, 134, and 138.

[0280] 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 a dry etching, for example, an inductively coupled plasma (ICP) etching with C12 and BC13 etching gases.

[0281] 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 a dry etching, for example, an inductively coupled plasma (ICP) etching with CF4 and O2 etching gases.

[0282] In some embodiments, the reflective layers including 109, 115, 127, 133, 135, and 139 are patterned using photolithography and etching. In some cases, the etching method used to form the pattern for the reflective layers, particularly the DBR layers, is dry etching, for example, inductively coupled plasma (ICP) etching with CF4and O2etching gases or ion beam etching (IBE) with Ar gas.

[0283] 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 with C12and HBr etching gases.

[0284] 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 with C12 / BC13 / Ar etching gases or ion beam etching (IBE) with Ar gas.

[0285] In some embodiments, after each LED device structure is patterned, an insulating layer such as 174, 176, 178 is deposited on the surface of the patterned LED structure including all the patterned layers, sidewalls, and exposed substrate. In some embodiments, the insulating layer is made of SiO2and / or Si3N4. In some embodiments, the insulating layer is made of TiO2. In some embodiments, the insulating layer with similar composition as SiO2is formed after curing a layer such as SOG at high temperature. In some embodiments, the insulating layer is made of a material with similar thermal coefficient as the thermal coefficient of the layers underneath the insulating layer. The surface of the insulating layer such as 176 and 178 is then smoothed or planarized by relevant methods such as chemical mechanical polishing, which are understood by those of ordinary skill in the art.

[0286] In some embodiments, the insulating layer such as 176 and 178 after planarization is patterned using photolithography and etching to expose the electrode contact areas. In some cases, the etching method used to form the pattern is dry etching, for example, inductively coupled plasma (ICP) etching with CF4and O2.

[0287] In some embodiments, the P-electrode or anode metal pads are deposited in suitable locations of the patterned LED structure, such as on one side and / or vias in the planarized insulating layer, using vapor deposition or by other deposition methods, to electrically connect the red LED structure, the green LED structure, and the blue LED structure.

[0288] In some embodiments, separate N-electrodes or cathode metal pads are deposited in suitable locations of the patterned LED structure, such as on one side / top and / or in vias within the planarized insulating layers, using vapor deposition or by other deposition methods, to electrically connect the red, green, and blue LED structures.

[0289] FIG. 4A is a top view of a layered planarized single-pixel tri-color LED device 400 according to some embodiments.

[0290] FIG. 4B is a cross-sectional view along diagonal line 402 of the layered planarized single-pixel tri-color LED device 400 according to some embodiments. The diagonal line passes through the center of the single-pixel tri-color LED device 400. FIG. 4A

[0291] Compared to the embodiments depicted in FIGS. 1-3, FIG. 4A-4B The main difference of the embodiment in FIG. 4 is that each of the LED structures of different colors is embedded in a respective planarized insulating layer, and the planarized insulating layers with the LED structures inside are bonded together via some bonding layers.

[0292] In some embodiments, the tri-color LED device 400 includes a substrate 404. For convenience, “upward” is used to mean away from the substrate 404, and “downward” means toward the substrate 404, with other directional terms such as top, bottom, above, below, directly below, underneath, and the like interpreted accordingly. The support substrate 404 is a substrate on which an array of individual driving circuits 406 are fabricated. In some embodiments, the driving circuits can also be located in one of the layers above the substrate 404, or above the micro tri-color LED structure 400. Each driving circuit is a pixel driver 406. In some cases, the driving 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 driving circuits 406 form individual pixel drivers to control the operation of individual single-pixel tri-color LED devices 400. The circuitry on the substrate 404 includes contacts for each individual driving circuit 406 as well as a ground contact. As FIG. 4A and FIG. 4B ​As shown, each micro tri-color LED structure 400 also has two types of contacts: P-electrodes or anodes such as 450 (or 408), 452 and merged portions 422, 424 and 426 connected to the pixel driver; and N-electrodes or cathodes such as 440, 442, 444 and merged portions 416, 418 and 420 connected to ground (i.e., the common electrode).

[0293] In some embodiments, the N-electrodes (or N-electrode contact pads) and their connecting components, such as 440, 442, 444 and merged portions 416, 418 and 420, are made of a material 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 merged portions 416, 418 and 420, are made of a non-transparent or transparent conductive material, in a preferred embodiment, a transparent conductive material. In some embodiments, the P-electrodes (or P-electrode contact pads) and their connecting components, such as 450, 452 and merged portions 422, 424 and 426, are made of a material 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 merged portions 422, 424 and 426, are made of a non-transparent or transparent conductive material, in a preferred embodiment, a transparent conductive material. 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.

[0294] Generally, an LED light emitting layer includes a PN junction with 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.

[0295] In some embodiments, the light emitted by the red LED light emitting layer 412 can propagate horizontally towards the sidewall of the red LED light emitting layer 412, then be reflected upwards by a reflective element such as 446 and / or 448 as described below, and be emitted at the top surface of the single-pixel tri-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 towards the sidewall of the red LED light emitting layer 412.

[0296] In some embodiments, light emitted by the green LED light emitting layer 430 can propagate horizontally towards the sidewall of the green LED light emitting layer 430, then be reflected upwards by reflective elements such as 446 and / or 448 as described below, and be 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. Light emitted from the green LED light emitting layer 430 is reflected between the two reflective layers 427 and 433 towards the sidewall of the green LED light emitting layer 430.

[0297] In some embodiments, light emitted by the blue LED light emitting layer 436 can propagate horizontally towards the sidewall of the blue LED light emitting layer 436, then be reflected upwards by reflective elements such as 446 and / or 448 as described below, and be 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. Light emitted from the blue LED light emitting layer 436 is reflected between the reflective layer 435 and the upper surface of the blue LED light emitting layer 436 towards the sidewall of the blue LED light emitting layer 436.

[0298] In some embodiments, light emitted by the red LED light emitting layer 412 can propagate vertically through the green LED light emitting layer 430, then through the blue LED light emitting layer 436 to be emitted from the tri-color LED device 400. In some embodiments, 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.

[0299] In some embodiments, the LED light emitting layers such as 412, 430, and 436 include a number of sub-epitaxial layers with different compositions. Examples of LED epitaxial layers include III-V nitride, III-V arsenide, III-V phosphide, 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.

[0300] In some embodiments, each LED structure in the stacked LED structure can be controlled individually to produce its individual light. In some embodiments, the mixed light emitted by the top LED epitaxial layer can be changed in color of a single pixel in a small footprint on a display panel due to the simultaneous operation of all the LED epitaxial layers in the tri-color LED device 400.

[0301] In some embodiments, the colors of light emitted by the LED structures included in the same device are not limited to red, green, and blue, depending on the design of the LED device 400. For example, suitable colors can be selected from a range of different colors of light in the visible range from 380 nm to 700 nm wavelengths. In some embodiments, the LED structures can also be implemented to emit other colors of light from non-visible ranges such as ultraviolet and infrared.

[0302] In some embodiments, when the vertical light emission is combined with the horizontal light emission, the selection of the three colors can be red, green, and blue from the bottom to the top, for example. In another embodiment, the selection of the three colors can be infrared, orange, and ultraviolet from the bottom to the top. In some embodiments, the LED structures on one layer of the device 400 emit light at a longer wavelength than the LED structures on the layer above the current layer. For example, the bottom LED light-emitting layer 412 emits light at a longer wavelength than the middle LED light-emitting layer 430, which emits light at a longer wavelength than the top LED light-emitting layer 436.

[0303] In some embodiments, each of the LED light-emitting layers 412, 430, and 436 can be any suitable color of visible or non-visible light when the horizontal light emission is present or when the portion of the horizontal light emission is greater than the portion of the vertical light emission from the top surface of the LED device 400. The advantage of the horizontal light emission is that the light emission efficiency can be improved because the emitted light does not need to travel through other upper layers of the LED device 400 but is emitted directly from the edge or sidewall of the current light-emitting layer. For example, the horizontal light emission LED device can improve the light emission efficiency by 15%, 50%, 100%, 150%, or 200% compared to the vertical light emission LED device. In some cases, the light emission efficiency of the horizontal light emission LED device can be equal to or greater than 20%, 40%, or 60%.

[0304] In some embodiments, the bottom red LED light-emitting layer 412 is bonded to the substrate 404 via a metal bonding layer 408. The metal bonding layer 408 may be disposed on the substrate 404. In one method, the metal bonding layer 408 is grown 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, serving as a P-electrode. In some embodiments, the thickness of the metal bonding layer 408 is approximately 0.1 micrometers to 3 micrometers. In a preferred embodiment, the thickness of the metal bonding layer 408 is approximately 0.3 micrometers. The metal bonding layer 408 may 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 above the metal bonding layer within the LED device 400. A 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 thereof. For example, if Au-Au bonding is selected, the two Au layers require a Cr coating as a binder layer and a Pt coating as an anti-diffusion layer, respectively. The Pt coating is located between the Au layer and the Cr layer. The Cr layer and the Pt layer are located on top and bottom of the two bonded Au layers. In some embodiments, when the two Au layers are of approximately the same thickness, the Au on the two layers diffuses into each other under high pressure and high temperature, bonding the two layers together. Eutectic bonding, thermocompression bonding, and transient liquid phase (TLP) bonding are exemplary techniques that can be used.

[0305] In some embodiments, the metal bonding layer 408 may also be used as a reflector to reflect light emitted from the LED structure above.

[0306] 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. FIG. 4A As shown in FIG. 4B In some embodiments not shown, 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 top of the red LED light-emitting layer 412. In some embodiments, the conductive layer 414 may be a conductive transparent layer such as an ITO layer, formed between the red LED light-emitting layer 412 and the N-electrode contact pad 416 to improve conductivity and light transmittance.

[0307] In some embodiments, the red LED light emitting layer 412 has an extension 464 on one side thereof relative to other layers above. In some embodiments, the extension 464 extends with the conductive layers 410 and 414. In some embodiments, the extension 464 is connected to the N-electrode contact pad 416 through an extension of the conductive layer 414 above the extension 464.

[0308] In some embodiments, a reflective layer 409 is located between the conductive layer 410 and the metal bonding layer 408 below the red LED light emitting layer 412, a 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, within the planarized insulating layer 454.

[0309] In one method, the red LED light emitting layer 412 is grown on a separate substrate, referred to as an epitaxial substrate. The epitaxial substrate is removed after bonding by, for example, a laser lift-off process or wet chemical etching, leaving the structure shown in FIG. 4B. FIG. 4B

[0310] In some embodiments, the red LED light emitting layer 412 is used to form a red micro-LED. Examples of red LED light emitting layers include III-V nitride, III-V arsenide, III-V phosphide, and III-V antimonide epitaxial structures. In some cases, the films within the red LED light emitting layer 412 can include layers of P-type GaP / P-type AlGalnP light emitting layer / AlGalnP / N-type AlGalnP / N-type GaAs. In some embodiments, the P-type layers are typically Mg-doped, while the N-type layers are typically Si-doped. In some examples, the red LED light emitting layer has a thickness of about 0.1 microns to 5 microns. In one preferred embodiment, the red LED light emitting layer has a thickness of about 0.3 microns.

[0311] In some embodiments, the red LED structure includes the metal bonding layer 408, the reflective layer 409, the conductive layer 410, the red LED light emitting layer 412, the conductive layer 414, the reflective layer 115, and the N-electrode contact pad 416. In some embodiments, the red LED structure is formed within a planarized insulating layer 454, for example, 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 process.

[0312] ​In some embodiments, the 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, AI2O3, Si3N4, phosphosilicate glass (PSG), or borophosphosilicate glass (BPSG), or any combination of the above. In some embodiments, the plastic material includes a polymer such as SU-8, PermiNex, benzocyclobutene (BCB), or a transparent plastic (resin) including spin-on glass (SOG), or Micro Resist’s bonding adhesive BCL-1200, or any combination of the above. In some embodiments, the planarization layer can facilitate the light emitted by the micro-LED 400 to pass through. In some embodiments, the planarization layer, such as 454, 468, and 462, has the same composition as the bonding layer, such as 456 and 460. In some embodiments, the planarization layer, such as 454, 468, and 462, has a different composition than the bonding layer, such as 456 and 460.

[0313] In some embodiments, vias or through-holes are formed within 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 driving circuit 406.

[0314] 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 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 LED structure above.

[0315] In some embodiments, the bonding layer 456 is transparent to the light emitted by the micro-LED 400 when using vertical propagation. 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, AI2O3, Si3N4, phosphosilicate glass (PSG), or borophosphosilicate glass (BPSG), or any combination of the above. In some embodiments, the plastic material includes a polymer such as SU-8, PermiNex, benzocyclobutene (BCB), or a transparent plastic (resin) including spin-on glass (SOG), or Micro Resist’s bonding adhesive BCL-1200, or any combination of the above. In some embodiments, the transparent bonding layer can facilitate the light emitted by the layers below the bonding layer to pass through.

[0316] 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.

[0317] In some embodiments, as shown in FIG. 4A and FIG. 4B , 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 the P electrode contact elements 422 and 424 within the planarized insulating layer 454 through the portion of the P electrode contact pad 426 within the bonding layer 456. In some embodiments, the P electrode contact element 422 is in a cylindrical shape. In some embodiments, the P electrode contact element 424 is in a funnel shape with a narrow top side matching the width of the element 422 and a wide bottom side for supporting the element 422 above it. In some embodiments, the top of the green LED light emitting layer 430 forms a conductive layer 432 for electrode connection. 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, the conductive layer 432 is formed to extend over the green LED light emitting layer 430 and the N electrode contact pad 420. FIG. 4A and FIG. 4B In some embodiments, as shown in

[0318] In some embodiments, the green LED light emitting layer 430 has an extension 466 on one side thereof relative to other layers above it. In some embodiments, the extension 466 extends with the conductive layers 428 and 432. In some embodiments, the extension 466 is connected to the N electrode contact pad 420 through the extension of the conductive layer 432 above the extension 466.

[0319] 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.

[0320] 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, within the planarized insulating layer 458.

[0321] In one method, the green LED light emitting layer 430 is grown on another separate substrate, referred to as an epitaxial substrate. The epitaxial substrate is removed after bonding by, for example, a laser lift-off process or wet chemical etching, leaving the green LED light emitting layer 430 on the substrate 402. FIG. 4B The structure shown in FIG. 4B.

[0322] In some embodiments, the green LED light emitting layer 430 is used to form a green micro-LED. Examples of green LED light emitting layers include III-V nitride, III-V arsenide, III-V phosphide, and III-V antimonide epitaxial structures. In some cases, the films within the green LED light emitting layer 430 can include layers of P-type GaN / InGaN light emitting layer / N-type GaN. In some embodiments, the P-type is typically Mg-doped, while the N-type is typically Si-doped. In some examples, the green LED light emitting layer has a thickness of about 0.1 microns to 5 microns. In one preferred embodiment, the green LED light emitting layer has a thickness of about 0.3 microns.

[0323] In some embodiments, the green LED structure includes the reflective layer 427, the conductive layer 428, the green LED light emitting layer 430, the conductive layer 432, the reflective layer 433, and the 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, both surfaces of the planarized insulating layer 458 are smoothed or planarized by a chemical mechanical polishing method.

[0324] In some embodiments, the first LED structure, e.g., the red LED structure, and the second LED structure, e.g., the green LED structure, have the same central axis without including extensions such as 464, 466. In some embodiments, the first LED structure and the second LED structure are aligned along the same central axis without including extensions such as 464, 466.

[0325] In some embodiments, bonding layer 460 is used to bond the green LED structure and the blue LED structure together. In some embodiments, bonding layer 456 is opaque to light emitted by LED device 400. In some embodiments, the material and thickness of bonding layer 460 are the same as described above for metal bonding layer 408. In some embodiments, bonding layer 460 may also function as a reflector to reflect light emitted by the LED structure above.

[0326] In some embodiments, when vertical propagation is used, the bonding layer 460 is transparent to 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, as described above for the bonding layer 456. In some embodiments, a transparent bonding layer can facilitate the passage of light emitted from layers beneath the bonding layer.

[0327] 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, such as FIG. 4A As shown, but FIG. 4B Not shown, 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 a number of P-electrode contact elements similar to 422 and 424 within the planarized insulating layers 454 and 458 and the transparent bonding layers 456 and 460. FIG. 4A and 4B (None are shown in the image). Those P-electrode contact elements are connected to the drive circuit 406.

[0328] In some embodiments, a conductive layer 438 for electrode connection is formed on 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, such as FIG. 4B As shown, the N electrode 440 has N electrode contact pads 442 and 444 electrically connected to the blue LED light-emitting layer 436 via 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 thereof.

[0329] In some embodiments, the lateral dimension of the blue LED light emitting layer 436 is substantially the same as the lateral dimension of the green LED light emitting layer 430, particularly for the effective light emitting area.

[0330] In some embodiments, a reflective layer 435 is provided between the blue LED light emitting layer 436 and the conductive layer 434, below the blue LED light emitting layer 436. FIG. 4B An optional reflective layer 439 is provided on top of the conductive layer 438, above the blue LED light emitting layer 436 (not shown in FIG. 4).

[0331] In one method, the blue LED light emitting layer 436 is grown on another separate substrate, referred to as an epitaxial substrate. The epitaxial substrate is removed after bonding by, for example, a laser lift-off process or wet chemical etching, leaving the structure shown in FIG. 4. FIG. 4B

[0332] In some embodiments, the blue LED light emitting layer 436 is used to form a blue micro-LED. Examples of blue LED light emitting layers include III-V nitride, III-V arsenide, III-V phosphide, and III-V antimonide epitaxial structures. In some cases, the films within the blue LED light emitting layer 436 can include layers of P-type GaN / InGaN light emitting layer / N-type GaN. In some embodiments, the P-type is typically Mg-doped, while the N-type is typically Si-doped. In some examples, the thickness of the blue LED light emitting layer is about 0.1 microns to 5 microns. In one preferred embodiment, the thickness of the blue LED light emitting layer is about 0.3 microns.

[0333] In some embodiments, the blue LED structure includes the reflective layer 435, the conductive layer 434, the blue LED light emitting layer 436, the conductive layer 438, and the optional reflective layer 439. In some embodiments, the blue LED structure is formed within the 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 a chemical mechanical polishing process.

[0334] In some embodiments, vias or through-holes are formed within the planarized insulating layer 462 and the transparent bonding layer 460 to accommodate portions of the N-electrode 440 connecting to the green LED structure N-electrode contact pad 420.

[0335] ​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 tricolor LED device 400. In some embodiments, the N-electrode 440 is connected to the N-electrode of the adjacent tricolor LED device via the N-electrode contact pads 442 and 444 (not shown in FIG. 4B), as a common electrode. FIG. 4A

[0336] In some embodiments, the lateral dimension of the blue LED structure is substantially the same as the lateral dimension of the green LED structure. In some embodiments, 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 without including the extension such as 466. In some embodiments, the second LED structure and the third LED structure are aligned along the same central axis without including the extension such as 466.

[0337] In some embodiments, each of the conductive layers 410, 414, 428, 432, 434, and 438 has a thickness of about 0.01 microns to 1 micron. In some cases, each of the conductive layers 410, 414, 428, 432, 434, and 438 is typically deposited on the respective corresponding epitaxial layer by a vapor deposition process, such as electron beam evaporation or sputter deposition, before any bonding process is performed to bond with the next epitaxial layer. In some examples, the conductive layers are used to maintain good electrical conductivity of the electrode connections, while in some cases, also used to improve optical properties of the LED device, such as reflectivity or transmittance.

[0338] In some embodiments, to improve the light emission efficiency of the tricolor LED device 400, optical isolation structures such as 446 and 448 are formed along the sidewalls of the tricolor LED device 400. In some embodiments, the optical isolation structures 446 and 448 are made of a dielectric material such as SiO2.

[0339] As FIG. 4A ​As shown in the top view, in some embodiments, the tri-color LED device 400 has a circular shape. In some embodiments, optical isolation structures such as 446 and 448 are integrally connected and form a circular sidewall surrounding the tri-color LED device 400. In some embodiments, the optical isolation structures form a reflector cup, which is described in further detail below. In some embodiments, the three stacked LED structures within the tri-color LED device 400 are also circular in shape. In some embodiments, the tri-color LED device 400 may have other shapes, such as rectangles, squares, triangles, trapezoids, and polygons. In some embodiments, optical isolation structures such as 446 and 448 are integrally connected and form a sidewall surrounding the tri-color LED device 400 in other shapes such as rectangles, squares, triangles, trapezoids, and polygons.

[0340] like FIG. 4B As 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 respective LED light-emitting layer. In some embodiments, the angle between the inclined sidewall and the bottom surface of the respective LED light-emitting layer is less than 90 degrees. In some embodiments, the metal bonding layer 408 also has inclined side surfaces. These inclined side surfaces facilitate the connection of different connecting elements to the respective LED light-emitting layers, prevent the connection from breaking due to abrupt angles, and enhance the overall stability of the device.

[0341] In some embodiments, the light propagation efficiency of the multicolor LED device changes with the angle of the tilted side surface of the LED light-emitting layer relative to the normal of the substrate 404 surface. In some embodiments, the light propagation efficiency of the multicolor LED device increases with the increase of the angle of the tilted side surface of the LED light-emitting layer relative to the normal of the substrate 404 surface. For example, when the angle of the side surface of the LED light-emitting layer relative to the normal of the substrate 404 surface is ±5 degrees, and when the optical isolation structure such as 446 and / or 448 is not a reflector cup as 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 404 is ±15 degrees, and when the optical isolation structure such as 446 and / or 448 is not a reflector cup as described below, the luminous efficiency of the multicolor LED device is 2.7%. For example, when the angle between the side surface of the LED light-emitting layer and the normal to the surface of the substrate 404 is (e.g., when the light-emitting layer is tilted) or very close to ±90 degrees and when the optical isolation structure such as 446 and / or 448 is not a reflector cup as described below, the luminous efficiency of the multicolor LED device is equal to or very close to 56.4%.

[0342] In contrast, the implementation of the reflector structure, as described in further detail below, improves the light propagation efficiency of the multicolor LED device. For example, when the angle between the side surface of the LED light-emitting layer and the normal to the surface of the substrate 404 is ±5 degrees and when the optical isolation structure, such as 446 and / or 448, is the reflector as described below, the luminous efficiency of the multicolor LED device is 0.65%, which is an increase of 104.6% compared to an LED device without a reflector. For example, when the angle between the side surface of the LED light-emitting layer and the normal to the surface of the substrate 404 is ±15 degrees and when the optical isolation structure, such as 446 and / or 448, is the reflector as described below, the luminous efficiency of the multicolor LED device is 6.65%, which is an increase of 144.4% compared to an LED device without a reflector. For example, when the angle between the side surface of the LED light-emitting layer and the normal to the surface of the substrate 404 is (e.g., when the light-emitting layer is tilted) or very close to ±90 degrees and when the optical isolation structure such as 446 and / or 448 is a reflector cup as described below, the luminous efficiency of the multicolor LED device is equal to or very close to 66.65%, that is, an increase of 18.4% compared to an LED device without a reflector cup.

[0343] 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 in terms of the effective light-emitting area.

[0344] In some embodiments, reflective layers are formed above and below each layer of the LED light-emitting layer to improve light propagation efficiency. For example... FIG. 4B As 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, when a conductive layer 410 is present, 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 (and / and within the planarized insulating layer 454) and the red LED light-emitting layer 412. In some embodiments, when a conductive layer 414 is present, the reflective layer 415 is formed between the bonding layer 456 (and / and within the planarized insulating layer 454) and the conductive layer 414.

[0345] 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.

[0346] 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 (not shown in FIG. 4) 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, for example, through a conductive path. 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, for example, through a conductive path. FIG. 4B

[0347] In some embodiments, the materials, compositions, properties, and fabrication processes of the reflective layers are the same as described above with respect to FIGS. 1-3.

[0348] In some embodiments, the three-color LED structure is formed by dry etching and wet etching, with the axes of the different color LED structures vertically aligned with each other. In some embodiments, the different color LED structures share the same axis.

[0349] In some embodiments, each of the plurality of different color LED structures 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 underneath it. In this case, the width or area is measured by the dimension of the plane parallel to the surface of the substrate 404. In some embodiments, particularly when using planarized layered structures, each of the different color LED structures has substantially the same lateral dimension compared to the other LED structures. When each of the LED structures has substantially the same area, the light emitting efficiency of the entire LED device is improved.​

[0350] In some embodiments, particularly in the case of layered structures without planarization, each of the LED structures of different colors are bonded together by the bonding layer covering only the LED structure area without extending beyond the LED structure area, the entire multi-color LED device forms a pyramid (or inverted cone) shape or a trapezoidal shape (not shown in FIG. 4B In some embodiments, the lateral dimension of the bottom LED structure, e.g., the red LED structure, can be the longest, and the lateral dimension of the top LED structure, e.g., the blue LED structure, can be the shortest. The pyramid shape can be naturally formed from the bottom up when each layer is etched and patterned within the LED device. The pyramid structure can improve the electronic connection between the individual LED structures and with the electrodes, and simplify the manufacturing process. For example, the electrode connection elements of each layer are exposed in each layer to facilitate the connection.

[0351] In some embodiments, the bottom layer such as the metal bonding layer 408 has a lateral dimension of about 1 micron to 500 microns. In one 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 one preferred embodiment, the vertical height of the multi-color LED device is about 1.9 microns. In one preferred embodiment, the lateral dimension of the conductive layer 438 at the top of the multi-color LED device is about 1.0 micron.

[0352] In some embodiments, the aspect ratio of the cross-section of a layer in a three-color LED device remains substantially the same in the case of a change in the lateral dimension of the same layer. For example, in the case of a patterned epitaxial layer having a lateral dimension of 5 microns, the thickness of the patterned epitaxial layer is less than one micron. In another example, in the case of an increase in the lateral dimension of the same patterned epitaxial layer, the thickness of the same patterned epitaxial layer is increased accordingly to maintain the same aspect ratio. In some embodiments, the aspect ratio of the cross-section of an epitaxial layer and other layers is less than 1 / 5 of the thickness / width.

[0353] 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 take other shapes, e.g., an inverted trapezoid, a semi-ellipse, a rectangle, a parallelogram, a triangle, or a hexagon, etc.

[0354] In some embodiments, the use of planarized insulating layers, such as 454, 458, and 462, to cover each of the LED structures of different colors simplifies the manufacturing process of the single-pixel tri-color LED device and improves the light emission efficiency of the single-pixel tri-color LED device. For example, each of the LED structures of different colors can first be independently formed to include the conductive layer, the reflective layer, and the electrode contact pad, and their associated connections within the corresponding planarized insulating layer, and then the individual LED structures are bonded together through the corresponding bonding layer.

[0355] In contrast, in the process of manufacturing a directly stacked tri-color LED device without planarization features, the LED structures of different colors are directly bonded together using some bonding layers, and the single-pixel tri-color LED device can be formed with a pyramid (or inverted cone) shape or a trapezoidal shape in cross-section due to the layer-by-layer patterning (and / or etching). As a result, the bottom of the stack of the single-pixel tri-color LED device has the largest effective light emission area for the LED structures, while the top of the stack has the smallest effective light emission area for the LED structures. The non-uniformity of the light emission area among the multiple LED structures within the LED device can reduce its light emission efficiency. Although having planarized sub-layers, the single-pixel tri-color LED device is not limited to the pyramid structure as described above because each LED structure is manufactured within its own planarized insulating layer. Instead, the effective light emission area of the different LED structures within the single-pixel tri-color LED device can be adjusted according to the design. In some cases, the horizontal effective light emission areas of the different LED structures within the single-pixel tri-color LED device are substantially the same to improve the light emission efficiency and to facilitate the electrical connections. In some cases, the planarized tri-color LED structure can improve the light emission efficiency by at least 5%, at least 10%, or sometimes, at least 20% compared to a similar tri-color LED structure without planarization.

[0356] In some embodiments, when each layer in the LED light emission layer as described above is grown using a corresponding epitaxial substrate, an insulating layer can first be deposited on each of the epitaxial substrate covering the corresponding LED light emission layer and other layers such as the conductive layer and the reflective layer. Then a planarization process is performed to flatten the surface of the insulating layer with the corresponding LED structure embedded therein. The via for electrical connection is also formed within the planarized layer before the bonding.

[0357] In another embodiment, the layers including the bonding layer can be directly formed on the planarized insulating layer that has already embedded the formed LED structure, and then the planarized insulating layer is formed to cover the current LED structure. The via for electrical connection is formed within the planarized layer before the next LED structure is formed on top of the current LED structure.

[0358] In contrast to some other processes that contact the top or bottom of the LED structure directly with the insulating layer, the bonding layer can be in contact with the planarized insulating layer without touching the LED structure. Thus, the features and layers within each planarized LED structure are better protected and less susceptible to external damaging forces. In addition, the planarized surface can improve light propagation efficiency by reducing deflection caused by uneven surfaces.

[0359] 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 a dry etching such as inductively coupled plasma (ICP) etching or a wet etching with ITO etching solution. In some embodiments, the same patterning method can be applied to all other conductive layers within the three-color LED device 400, including layers 410, 414, 428, 432, 434, and 438.

[0360] 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 a dry etching such as inductively coupled plasma (ICP) etching with C12 and BCl3 etching gases.

[0361] 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 a dry etching such as inductively coupled plasma (ICP) etching with CF4 and O2 etching gases.

[0362] 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 form the pattern for the reflective layers, especially the DBR layers, is a dry etching such as inductively coupled plasma (ICP) etching with CF4 and O2 etching gases or ion beam etching (IBE) with Ar gas.

[0363] 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 a dry etching such as inductively coupled plasma (ICP) etching with C12 and HBr etching gases.

[0364] 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, such as inductively coupled plasma (ICP) etching using C12 / BC13 / Ar etching gases, or ion beam etching (IBE) using Ar gas.

[0365] In some embodiments, after each LED device structure in each LED device structure is patterned, an insulating layer such as 454, 458, or 462 is deposited on the surface of each patterned LED structure, including all patterned layers, sidewalls, and 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 a layer such as SOG is cured 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 it. The surface of the insulating layer is then smoothed or planarized by methods such as chemical mechanical polishing, as understood by those skilled in the art.

[0366] In some embodiments, the planarized insulating layer is patterned using photolithography and etching to expose the electrode contact areas. 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.

[0367] In some embodiments, the P-electrode or anode metal pad is deposited at appropriate locations on the patterned LED structure, such as on one side within a planarized insulating layer and / or in a via, using vapor deposition or other deposition methods, to electrically connect the red LED structure, the green LED structure, and the blue LED structure.

[0368] In some embodiments, individual N-electrodes or cathode metal pads are deposited using vapor deposition or other deposition methods at appropriate locations on the patterned LED structure, such as on one side / top and / or in vias within a planarized insulating layer, to electrically connect the red LED structure, green LED structure, and blue LED structure.

[0369] FIG. 5 It is a single-pixel tri-color LED device 500 with a refractive structure according to some embodiments. FIG. 1A A cross-sectional view of the middle diagonal 102. In some embodiments, although not all FIG. 5As shown in FIG. 5, the single-pixel tri-color LED device 500 has a similar structure as any of the single-pixel tri-color LED devices shown in FIGS. 1-4, but with a refractive structure 502 formed over the top surface of the single-pixel tri-color LED device to improve the light emission efficiency. The light emitted by the single-pixel tri-color LED device is emitted through the top surface of the single-pixel tri-color LED device without the refractive structure (light emission area). 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 the top electrode such as the N-electrode 140. In some embodiments, the refractive structure 502 is formed directly on the surface of the planarized insulating layer 176. In some embodiments, the refractive structure 502 is the same as and integrated with the planarized insulating layer 176.

[0370] In some embodiments, the refractive structure 502 is formed between the optical isolation structure such as the reflective cup 146 and 148 and the top surface of the single-pixel tri-color LED device without the refractive structure, i.e., the light emission area. 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 or below the top of the optical isolation structure. In some embodiments, the top surface of the refractive structure is above the top electrode such as the N-electrode 140. In some embodiments, the top surface of the refractive structure is at the same height as or below the top electrode such as the N-electrode 140.

[0371] In some embodiments, the refractive structure 502 changes the light path of the light emitted by the single-pixel tri-color LED device by focusing the light emitted by the LED device more or less.

[0372] 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 tri-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.

[0373] In some embodiments, the refractive layer 502 is formed directly over the planarized insulating layer. In some embodiments, the refractive layer 502 is formed by deposition, sputtering, or other methods.

[0374] FIG. 6A is a cross-sectional view along diagonal line 102 of a single-pixel tri-color LED device 600 with a microlens on a reflective structure according to some embodiments. FIG. 1A is a cross-sectional view along diagonal line 102 of a single-pixel tri-color LED device 600 with a microlens on a reflective structure according to some embodiments. is a cross-sectional view along diagonal line 102 of a single-pixel tri-color LED device 600 with a microlens on a reflective structure according to some embodiments.

[0375] FIG. 6B It is according to some embodiments a single-pixel tri-color LED device 600 having microlenses in a region formed by a reflective structure along its edge. FIG. 1A Cross-sectional view of the middle diagonal 102.

[0376] In some embodiments, although not all of them FIG. 6A-6B As shown, however, the single-pixel tri-color LED device 600 has a structure similar to any of the single-pixel tri-color LED devices shown in Figures 1-5, and adds a microlens 602 formed above the top surface of the single-pixel tri-color LED device to improve luminous efficiency. Without this microlens structure (light-emitting region), the light emitted by the single-pixel tri-color LED device passes through the top surface of the single-pixel tri-color LED device. In some embodiments, the microlens 602 is formed directly on the surface of the planarized insulating layer 176. In some embodiments, the microlens 602 is formed directly on, such as... FIG. 5 The refractive structure 502 shown is on the surface. In some embodiments, the microlens 602 covers and contacts the exposed surface of the top electrode, such as the N electrode 140.

[0377] 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 formed directly on the surface of the planarized insulating layer 176. In some embodiments, the spacer 604 is formed directly on, such as... FIG. 5 On the surface of the refractive structure 502 shown. In some embodiments, the spacer 604 and as shown FIG. 5 The refractive structure 502 shown is identical and integrated with it. In some embodiments, the spacer 604 covers and contacts the exposed surface of the 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 identical to and integrated with the planarized insulating layer 176.

[0378] In some embodiments, microlens 602 is formed between each optical isolation structure of a reflective structure or reflector cup, such as 146 and 148, and the top surface of a single-pixel tri-color LED device that does not have a microlens, i.e., a light-emitting region, between the optical isolation structures. In some embodiments, the top surface of microlens 602 is located above the top of the optical isolation structure, such as... FIG. 6Aas shown. When the top surface of the microlens 602 is above the top of the reflective structure such as 146 and 148, substantially all of the light emitted by the single-pixel tri-color LED device including the reflective cup can be 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. When the top surface of the microlens 602 is at the same level as or below the top of the reflective structure such as 146 and 148, at least a portion of the light emitted by the microlens 602 is further reflected by the reflective structure or the reflective cup confined within a certain area. FIG. 6B

[0379] 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.

[0380] In some embodiments, an optional spacer 604 is formed between the optical isolation structure such as 146 and 148 of the reflective cup and the top surface of the single-pixel tri-color LED device without microlens and 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.

[0381] 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 emitted by the single-pixel tri-color LED device more focused or more divergent as needed by the design.

[0382] ​In some embodiments, the spacer 604 lengthens the optical path of the light emitted by the single-pixel tri-color LED device. In some embodiments, the spacer 604 changes the optical path of the light emitted by the single-pixel tri-color LED device by making the light emitted by the single-pixel tri-color LED device more focused or more divergent, as desired by the design.

[0383] In some embodiments, the microlens 602 can be made of various materials that are transparent to the light of each wavelength emitted by the single-pixel tri-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, and the like. In some embodiments, the microlens 602 is made of photoresist.

[0384] The spacer 604 is an optically transparent layer formed to maintain the position of the microlens 602 relative to the pixel light source, such as the single-pixel tri-color LED device, underneath the microlens 602. The spacer 604 can be made of various materials that are transparent to the 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, and the like. 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.

[0385] In some embodiments, the height of the microlens 602 is no greater than 2 microns. In some embodiments, the height of the microlens 602 is no greater than 1 micron. In some embodiments, the height of the microlens 602 is no greater than 0.5 microns. In some embodiments, the width of the microlens 602 is no greater than 4 microns. In some embodiments, the width of the microlens 602 is no greater than 3 microns. In some embodiments, the width of the microlens 602 is no greater than 2 microns. In some embodiments, the width of the microlens 602 is no greater than 1 micron. In some embodiments, the width-to-height ratio of the microlens 602 is greater than 2.

[0386] In some embodiments, the shape of the microlens 602 is approximately hemispherical. In some embodiments, the central axis of the microlens 602 is aligned with or the same as the central axis of the single-pixel tri-color LED device without a lens.

[0387] For clarity, FIG. 6A-6BIt is shown that in some embodiments, in a display panel, each of the single-pixel light sources, such as single-pixel tri-color LED devices, corresponds to one microlens 602. It should be understood that a complete display panel includes an array of many individual pixels and many microlenses. In addition, the one-to-one correspondence between the microlenses and the pixel light sources, and between the pixel driving circuit (not shown) and the pixel light sources, can not be necessary. The pixel light source can also be made of multiple individual light elements, for example, multiple single-pixel LEDs connected in parallel. In some embodiments, one microlens 602 can cover multiple single-pixel tri-color LED devices without lenses.

[0388] Each microlens 602 has 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 fairly wide original divergence angle. In one embodiment, the original angle of the edge rays of the light beam relative to the vertical axis normal to the substrate 104 is greater than 60 degrees. The light is bent by the microlens 602 so that the new edge rays now have a reduced divergence angle. In one embodiment, the reduced angle is less than 30 degrees. The microlenses in the microlens array are typically identical. Examples of microlenses include spherical microlenses, aspherical microlenses, FRESNAL (Fresnel) microlenses, and cylindrical microlenses.

[0389] The microlens 602 typically 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. Typical shapes of the base of each microlens 602 include circular, square, rectangular, and hexagonal. The individual microlenses in the microlens array of a display panel can be identical or different in shape, curvature, optical power, size, base, spacing, etc. In some embodiments, the microlens 602 conforms to the shape of the single-pixel tri-color LED device. In one example, the shape of the base of the microlens 602 is identical to the shape of the single-pixel tri-color LED device, for example, in FIG. 6A-6B , 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 tri-color LED device, for example, the circular base of the microlens has the same width as the single-pixel tri-color LED, but a smaller area because the base of the microlens is circular while the base of the single-pixel tri-color LED is square. In some embodiments, the base of the microlens has a smaller area than the pixel light source. In some embodiments, the base of the microlens has the same or larger area than the pixel light source.

[0390] In some embodiments, the spacer layer 604 can be formed of the same material as the microlens 602 in the same process where the microlens 602 is formed. In some embodiments, the height of the pixel light source is greater than, equal to, or less than the thickness of the spacer 604 as measured from the bottom of the substrate 104.

[0391] The thickness of the spacer 604 is designed to maintain an appropriate spacing between the microlens 604 and the pixel light source. As one example, for a spacer that maintains an optical spacing between the pixel light source and the microlens that is greater than the focal length of the microlens, an image of a single pixel is formed at a distance. As another example, for an optical spacer that maintains an optical spacing between the pixel light source and the microlens that is less than the focal length of the microlens, a reduced divergence / angle of view is achieved. The amount of reduction in divergence / angle of view 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.

[0392] 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 focusing effect of the microlens, the brightness with the microlens array is 4 times the brightness without the microlens array in a direction perpendicular to the surface of the display. In alternative embodiments, the brightness enhancement factor can vary depending on the different designs of the microlens array and the optical spacer. For example, a factor greater than 8 can be achieved.

[0393] In some embodiments, a first method for fabricating a microlens includes a step of directly depositing a microlens material layer on top of the pixel light source and bringing the microlens material layer into direct physical contact 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, such as the planarized surface of a single pixel tri-color LED device, by a chemical vapor deposition (CVD) technique. In some embodiments, the deposition parameters for the CVD process are: power of about 0 W to 1000 W, pressure of about 100 mTorr to 2000 mTorr, temperature of about 23 °C to 500 °C, gas flow of about 0 to 3000 seem (standard cubic centimeter per minute), and time of about 1 hour to 3 hours. In some embodiments, the material of the microlens material layer is a dielectric material such as silicon dioxide.

[0394] In some embodiments, the first method for manufacturing a microlens further includes the step of patterning a microlens material layer to expose an electrode region of a 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 using 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 using a wet etching method.

[0395] In some embodiments, a second method for manufacturing a microlens may further include an optional step of forming a marker layer with markings for alignment with a microlens material layer deposited in subsequent steps. For example, the formed marker layer aligns the units of the luminescent pixels with the microlens material layer to form a microlens at the center of the pixel light source. In some embodiments, the formed marker layer aligns the pixel light source with layers above it, particularly the microlens material layer, to form a microlens on top of the pixel light source.

[0396] A second method for manufacturing microlenses also includes the step of directly depositing a layer of microlens material on top of at least one pixel light source. FIG. 6C-6D Further illustrated is a method for manufacturing a display panel with an integrated microlens array using top-down pattern transfer, according to some embodiments. In some embodiments, such as FIG. 6C As shown, a 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 by spin-coating onto the top of the pixel light source array 606. In some embodiments, the material of the microlens material layer 645 is photoresist. In some embodiments, the material of the microlens material layer 645 is a dielectric material such as silicon oxide.

[0397] A second method for manufacturing microlenses also includes top-down patterning of microlens material layers, thereby... FIG. 6C-6D The step of forming at least one hemisphere in the microlens material layer is illustrated. In some embodiments, the patterning step does not need to penetrate or etch to the bottom of the microlens material layer 645. In some embodiments, the hemisphere of the microlens 620 is positioned above at least one pixel light source 606M.

[0398] In some embodiments, the step of patterning the microlens material layer from top to bottom further includes, for example, FIG. 6C The first step shown is depositing a mask layer 630 on the surface of the microlens material layer 645.

[0399] The step of top-down patterning the microlens material layer also 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 a reflow process. In some embodiments, the photosensitive polymer mask layer 630 is patterned into discrete units 640, as shown in dashed outline square units in FIG. 6C FIG. 6B. As an example, the discrete units 640 are patterned and formed by a photolithography process. The patterned photosensitive polymer mask layer 650 with the discrete units 640 is then shaped into a hemispherical pattern 660 by a high-temperature reflow process. In one approach, the discrete units 640 are shaped into discrete hemispherical patterns 660 by a high-temperature reflow process. In some embodiments, a hemispherical pattern 660 of one pixel is not in direct physical contact with the hemispherical pattern of an adjacent pixel. In some embodiments, a hemispherical pattern 660 of one pixel is only in contact with 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 liquid state, the surface tension of the liquid material causes it to take the shape of a smooth curved surface. For a unit with a circular base with a radius R, the hemispherical shape / pattern will be formed after the reflow process when the height of the unit is 2R / 3. FIG. 6C A display panel with an array of hemispherical patterns 660 integrated is shown after the high-temperature reflow process is completed. In some embodiments, the hemispherical patterns in the mask layer can be formed by other manufacturing methods, including the manufacturing methods for microlenses described in the first approach for manufacturing microlenses. In some other embodiments, the hemispherical patterns in the mask layer can be formed using grayscale mask photolithography exposure. In some other embodiments, the hemispherical patterns in the mask layer can be formed via a molding / imprinting process.

[0400] The step of top-down patterning the microlens material layer also includes a third step of etching the microlens material layer 645 using the hemispherical patterns 660 as a mask to form hemispheres in the microlens material layer 645. In some examples, the microlens material layer 645 is etched by a photolithography process. In some examples, the microlens material layer 645 is etched by a dry etching process such as a plasma etching process 635, as shown in FIG. 6D. FIG. 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 FIG. 6E, so that a spacer 670 is formed on top of or covering the top of the pixel light source 606M, as shown in FIG. 6F. FIG. 6C-6D 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 FIG. 6E, so that a spacer 670 is formed on top of or covering the top of the pixel light source 606M, as shown in FIG. 6F. FIG. 6D 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 FIG. 6E, so that a spacer 670 is formed on top of or covering the top of the pixel light source 606M, as shown in FIG. 6F.

[0401] The second method for fabricating the microlens further includes a step of patterning the microlens material layer to expose the electrode region of the substrate (not shown in FIG. 6D 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 openings in the mask to expose 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 openings for the electrodes are provided outside the display array region.

[0402] As described above, FIG. 6A to 6D Various fabrication methods are shown to form a display panel integrated with a microlens array. It should be understood that these are merely examples, and other fabrication techniques can also be used.

[0403] While the detailed description contains many specifics, these should not be construed as limiting the scope of the application but merely as illustrating different examples and aspects of the application. It should be appreciated that the scope of the application includes other embodiments not discussed in detail above. For example, microlenses having different shaped bases can also be used, such as square bases or other polygonal bases.

[0404] FIG. 7 is a cross-sectional view of three single-pixel tri-color LED devices 710, 720, and 730 on a substrate 104 along a diagonal of FIG. 1A such as 102 in some embodiments, although not all are shown in FIG. 7 each of the single-pixel tri-color LED devices 710, 720, and 730 has a similar structure as any of the single-pixel tri-color LED devices shown in Figures 1-6. The cross-sectional view of the single-pixel tri-color LED device 710 within the rectangle 750 is equivalent to the cross-sectional view shown in any of Figures 1-6 as described above.

[0405] In some embodiments, as shown in any of Figures 1-7, the single-pixel tri-color LED devices further include one or more light-reflecting cup structures, such as 702, 704, and 706. The light-reflecting structures, such as 702, 704, and 706, surround the respective single-pixel tri-color LED devices 710, 720, and 730. The light-reflecting cups can be formed on the semiconductor substrate 104 and provided to surround the light-emitting regions where the light emitted by the single-pixel tri-color LED is emitted. For example, as shown in FIG. 1A-1C along the direction of 102 in FIG. 1B and according toFIG. 1C In cross-section along direction 150, the reflective cup can include four reflective cup portions 146, 148, 170, and 172. In some embodiments, the reflective cup portions 146, 148, 170, and 172 can be formed on the semiconductor substrate 104 and positioned around the light emitting region. In some embodiments, the reflective cup can isolate at least some or substantially all of the light emitted by the light emitting region. For example, as shown in FIGS. IB-1C, when the height of the reflective cup is higher than the height of the light emitting region, the reflective cup portions 146, 148, 170, and 172 can isolate at least some or substantially all of the light emitted from the light emitting region. Thus, the reflective cup can suppress inter-pixel light crosstalk and improve the overall contrast of the LED display. The reflection in the reflective cup also increases the light emitting efficiency and brightness by focusing the light emission into a certain specific direction.

[0406] In some embodiments, the height of the reflector cup can be greater than the height of a bottom LED structure such as the red LED structure, greater than the height of a middle LED structure such as the green LED structure, or greater than the height of a 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 a bottom LED structure such as the red LED structure, a middle LED structure such as the green LED structure, and a 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 microns and 50 microns. In some embodiments, the height of the reflector cup is between 1 micron and 20 microns. In some embodiments, the height of the reflector cup is between 2 microns and 10 microns. In a preferred embodiment, the height of the reflector cup is approximately 2.5 microns, while the height of a single pixel tri-color LED device without planarizing the layers is approximately 1.9 microns. However, in some embodiments, the reflector cup portions 146, 148, 170, and 172 can have different heights. In some embodiments, the cross-section of a reflector cup portion such as 146 or 148 is triangular. In some embodiments, the cross-section of a reflector cup portion such as 146 or 148 is a trapezoid with a longer base than a top. In some embodiments, the base width of a reflector cup portion such as 146 or 148 is between 0.3 microns and 50 microns. In some embodiments, the base width of a reflector cup portion such as 146 or 148 is between 0.5 microns and 25 microns. In a preferred embodiment, the base width of a reflector cup portion such as 146 or 148 is approximately 1 micron. In some embodiments, the distance from the nearest edge of the base of a reflector cup portion such as 146 or 148 to the nearest edge of the base of a single pixel tri-color LED device is between 0.2 microns and 30 microns. In some embodiments, the distance from the nearest edge of the base of a reflector cup portion such as 146 or 148 to the nearest edge of the base of a single pixel tri-color LED device is between 0.4 microns and 10 microns. In a preferred embodiment, the distance from the nearest edge of the base of a reflector cup portion such as 146 / 446 or 148 / 448 to the nearest edge of the base of a single pixel tri-color LED device, as shown in P-electrode connection structure 422, is approximately 0.6 microns. FIG. 4B

[0407] In some embodiments, the distance between the centers of adjacent reflector cup portions such as 146 / 446 and 148 / 448 in a single pixel tri-color LED device is between 1 micron and 50 microns. In a preferred embodiment, the distance between the centers of adjacent reflector cup portions such as 146 and 148 in a single pixel tri-color LED device is approximately 5 microns.

[0408] ​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 geometry 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 a single pixel multicolor LED device. In some embodiments, such as FIG. 1B-1C The sidewalls 146-1, 148-1, 170-1, and 172-1 of the reflector cups shown can be straight, curved, wavy, multi-lined, or a combination thereof. In some embodiments, the steepness of the sidewalls of the reflector cup portions 146, 148, 170, and 172 can be designed to reduce the divergence of light emitted from the light-emitting area. For example, the angle of the sidewalls 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 sidewalls 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 sidewalls 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 cups can also reflect some of the light emitted from the light-emitting area upwards. For example, some of the light emitted by the light-emitting area can reach reflector cups 146, 148, 170 and 172 and be reflected upwards through them.

[0409] In some embodiments, the reflector may include a metal. In some embodiments, the reflector may include a dielectric material such as silicon oxide. In some embodiments, the reflector may include a photosensitive dielectric material. In some embodiments, the photosensitive dielectric material may include SU-8, photosensitive polyimide (PSPI), or BCB. In other embodiments, the reflector may include photoresist.

[0410] In some embodiments, the reflector cup can be manufactured by a combination of deposition, photolithography, and etching processes. In some embodiments, the reflector cup can be manufactured by other suitable methods. In one method, PSPI forms the reflector cup shape using a photolithography process. Then, a metal layer with high reflectivity, including one or more metals such as Pt, Rh, Al, Au, and Ag, a stacked DBR layer including TiO2 / SiO2 layers, any other layer with total reflectivity including a multilayer omnidirectional reflector (ODR), or a combination thereof, is formed by vapor deposition on the entire surface of the multicolor LED device, which includes the reflector cup as a reflective layer. Next, the reflective layer is masked by photoresist in one region of the reflector cup, while the reflective layer in another region is etched to expose the light-emitting area.

[0411] In another method, an isolation layer comprising one or more of SiO2, silicon nitride or SU8 is deposited or spin-coated on the stacked LED structure, which is thicker than the stacked LED structure. Then, using photoresist as a mask, the isolation layer is etched and formed into a light-reflecting cup shape. Next, a metal layer comprising one or more metals such as Pt, Rh, Al, Au and Ag, a stacked DBR layer comprising TiO2 / SiO2 layers, any other layer with total reflection properties including a multilayer omnidirectional reflector (ODR), or a combination of the above, with high reflectivity, is formed on the entire surface of the multicolor LED device including the light-reflecting cup as a reflective layer by vapor deposition. Finally, the reflective layer is masked by the photoresist in the light-reflecting cup area, while the reflective layer on the other area is etched so that the light-emitting area is exposed.

[0412] In some embodiments, as shown in FIGS. 2-6, the single-pixel tri-color LED device further comprises one or more top electrodes (e.g., top electrodes 140 / 440, 442 and 444) integrated with the light-reflecting cup. The one or more top electrodes can be electrically connected with the top electrode (layer) 140 / 440. For example, as shown, the electrodes 442 and 444 can be integrated with the light-reflecting cup, e.g., light-reflecting cup portions 446 and 448, respectively. Both top electrodes 442 and 444 can extend towards the light-emitting area and be electrically connected with the top electrode (layer) 140 / 440. By employing one or more top electrodes, the light-reflecting cup can be used as a common P-electrode or N-electrode for the single-pixel tri-color LED device. For example, when the top electrode (layer) 140 / 440 is electrically connected with the LED structure (e.g., the LED structure comprising the light-emitting layer 112 / 412, 130 / 430 and 136 / 436) and, optionally, the top electrodes 442 and 444, the light-reflecting cup can be used as a common P-electrode or a common N-electrode for the single-pixel tri-color LED device. FIG. 4B

[0413] In some embodiments, the light-reflecting cup further comprises one or more reflective coatings. The one or more reflective coatings can be disposed on one or more sidewalls of the light-reflecting cup, e.g., on sidewalls 146-1, 148-1, 170-1 and 172-1 of the light-reflecting cup. The bottom of each of the one or more reflective coatings does not contact the respective LED structure, e.g., the red LED structure, the green LED structure and the blue LED structure. The one or more reflective coatings can reflect the light emitted by the light-emitting area, thus improving the brightness and light-emitting efficiency of the micro-LED panel or display. For example, the light emitted by the light-emitting area can reach the one or more reflective coatings and can be reflected upwards by them.

[0414] ​The one or more reflective coatings, together with the light cup, can exploit the direction and / or intensity of reflection of light emitted by the light emitting region. For example, the sidewalls 146-1, 148-1, 170-1, and 172-1 of the light cup are tilted at an angle, and thus the one or more reflective coatings disposed on the sidewalls 146-1, 148-1, 170-1, and 172-1 of the light cup are tilted at the same angle as the sidewalls 146-1, 148-1, 170-1, and 172-1 of the light cup. When 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 angle of the sidewalls 146-1, 148-1, 170-1, and 172-1 of the light cup.

[0415] The one or more reflective coatings can be highly reflective, having a reflectivity greater than 60%, 70%, or 80%, and thus can reflect a large portion of the light emitted by the light emitting region. In some embodiments, the one or more reflective coatings can include one or more metallic conductive materials having a high reflectivity. In these embodiments, the one or more metallic conductive materials can include one or more of aluminum, gold, or silver. In other embodiments, the one or more reflective coatings can be multilayered. More specifically, the one or more reflective coatings can include one or more layers of a reflective material and one or more layers of a dielectric material stacked together. For example, the one or more reflective coatings can include one layer of a reflective material and one layer of a dielectric material. In other embodiments, the one or more reflective coatings can include two layers of a reflective material and one layer of a dielectric material disposed between the two layers of the reflective material. In some other embodiments, however, the one or more reflective coatings can include two layers of a dielectric material and one layer of a reflective material disposed between the two layers of the dielectric material. In some embodiments, the multilayer structure can include two or more metallic layers, which can include one or more of TiAu, CrAl, or TiWAg.

[0416] In some embodiments, the one or more reflective coatings can be a multilayer omnidirectional reflector (ODR) including a metal layer and a transparent conductive oxide (TCO) layer. For example, the multilayer structure can include a dielectric material layer, a metal layer, and a TCO layer. In some embodiments, the one or more reflective coatings can include two or more dielectric material layers, alternatingly disposed to form a distributed Bragg reflector (DBR). For example, the one or more reflective coatings can include a dielectric material layer, a metal layer, and a transparent dielectric layer. The transparent dielectric layer can include one or more of SiO2, Si3N4, AI2O3, or TiO2. The one or more reflective coatings can further include a dielectric material layer, a TCO, and a DBR. In other embodiments, the one or more reflective coatings can include one or more metal conductive materials having high reflectivity. In these embodiments, the one or more metal conductive materials can include one or more of aluminum, gold, or silver. In some embodiments, the reflective coatings can have the same composition, structure, and fabrication process as the reflective layers above and below the light emitting layer such as 109, 115, 127, 133 as described above.

[0417] In some embodiments, the one or more reflective coatings can be electrically conductive, and then the one or more reflective coatings can also perform the function of making electrical contact with the single pixel multicolor LED device. For example, the top electrode (layer) 140 can be electrically connected with the one or more reflective coatings. For another example, the one or more reflective coatings can be electrically connected with the one or more transparent electrode contact layers 114, 132, and 138. The one or more reflective coatings can be patterned to not block the light emitted by the light emitting area. Then, the one or more reflective coatings can also serve as a common electrode for the LED structure within the single pixel multicolor LED device and / or a common electrode for the LEDs on the display panel.

[0418] In some embodiments, a top conductive layer for connection with an electrode is formed on top of the multicolor LED device, and the top conductive layer is in electrical contact with the light reflecting cup. In some embodiments, the top conductive layer is in direct contact with the top of the light reflecting cup or the bottom of the light reflecting cup.

[0419] In some embodiments, a bottom dielectric layer is formed between the bottom of the light reflecting cup and the semiconductor substrate.

[0420] In some embodiments, the one or more reflective coatings can be fabricated by one or more of an e-beam deposition or a sputtering process.

[0421] In some embodiments, the light reflecting cup can have a shape of a stepped structure. FIG. 8 is a cross-sectional view of a single pixel tricolor LED device 800 having a stepped light reflecting cup according to some embodiments. FIG. 4Aa cross-sectional view along a diagonal of 402. In some embodiments, although not all, the cross-sectional view along a diagonal of 402 is taken along a diagonal of 402 FIG. 8 As shown in FIG. 8, a single pixel multi-color LED device 800 has a similar structure as any one of the single pixel multi-color LED devices shown in FIGS. 1-7 with reflective cups such as 146, 148, 170, and 172, and has a stepped reflective cup. The stepped reflective cup can be formed on the semiconductor substrate 104 / 404 and positioned around the light emitting region. For example, as shown in FIG. 8, the stepped reflective cup can include two stepped reflective cup portions 846 and 848. The stepped reflective 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 reflective cup can isolate at least some or substantially all of the light emitted by the light emitting region. For example, as shown in FIG. 8, in the case where the height of the stepped reflective cup is higher than the height of the light emitting region, the stepped reflective cup portions 846 and 848 can isolate at least some or substantially all of the light emitted by the light emitting region. Thus, the stepped reflective cup can suppress inter-pixel light crosstalk and improve the overall contrast of the LED display. FIG. 8 As shown in FIG. 8, a single pixel multi-color LED device 800 has a similar structure as any one of the single pixel multi-color LED devices shown in FIGS. 1-7 with reflective cups such as 146, 148, 170, and 172, and has a stepped reflective cup. The stepped reflective cup can be formed on the semiconductor substrate 104 / 404 and positioned around the light emitting region. For example, as shown in FIG. 8, the stepped reflective cup can include two stepped reflective cup portions 846 and 848. The stepped reflective 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 reflective cup can isolate at least some or substantially all of the light emitted by the light emitting region. For example, as shown in FIG. 8, in the case where the height of the stepped reflective cup is higher than the height of the light emitting region, the stepped reflective cup portions 846 and 848 can isolate at least some or substantially all of the light emitted by the light emitting region. Thus, the stepped reflective cup can suppress inter-pixel light crosstalk and improve the overall contrast of the LED display. FIG. 4A As shown in FIG. 8, a single pixel multi-color LED device 800 has a similar structure as any one of the single pixel multi-color LED devices shown in FIGS. 1-7 with reflective cups such as 146, 148, 170, and 172, and has a stepped reflective cup. The stepped reflective cup can be formed on the semiconductor substrate 104 / 404 and positioned around the light emitting region. For example, as shown in FIG. 8, the stepped reflective cup can include two stepped reflective cup portions 846 and 848. The stepped reflective 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 reflective cup can isolate at least some or substantially all of the light emitted by the light emitting region. For example, as shown in FIG. 8, in the case where the height of the stepped reflective cup is higher than the height of the light emitting region, the stepped reflective cup portions 846 and 848 can isolate at least some or substantially all of the light emitted by the light emitting region. Thus, the stepped reflective cup can suppress inter-pixel light crosstalk and improve the overall contrast of the LED display. FIG. 8 As shown in FIG. 8, a single pixel multi-color LED device 800 has a similar structure as any one of the single pixel multi-color LED devices shown in FIGS. 1-7 with reflective cups such as 146, 148, 170, and 172, and has a stepped reflective cup. The stepped reflective cup can be formed on the semiconductor substrate 104 / 404 and positioned around the light emitting region. For example, as shown in FIG. 8, the stepped reflective cup can include two stepped reflective cup portions 846 and 848. The stepped reflective 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 reflective cup can isolate at least some or substantially all of the light emitted by the light emitting region. For example, as shown in FIG. 8, in the case where the height of the stepped reflective cup is higher than the height of the light emitting region, the stepped reflective cup portions 846 and 848 can isolate at least some or substantially all of the light emitted by the light emitting region. Thus, the stepped reflective cup can suppress inter-pixel light crosstalk and improve the overall contrast of the LED display.

[0422] As shown in FIG. 8, a single pixel multi-color LED device 800 has a similar structure as any one of the single pixel multi-color LED devices shown in FIGS. 1-7 with reflective cups such as 146, 148, 170, and 172, and has a stepped reflective cup. The stepped reflective cup can be formed on the semiconductor substrate 104 / 404 and positioned around the light emitting region. For example, as shown in FIG. 8, the stepped reflective cup can include two stepped reflective cup portions 846 and 848. The stepped reflective 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 reflective cup can isolate at least some or substantially all of the light emitted by the light emitting region. For example, as shown in FIG. 8, in the case where the height of the stepped reflective cup is higher than the height of the light emitting region, the stepped reflective cup portions 846 and 848 can isolate at least some or substantially all of the light emitted by the light emitting region. Thus, the stepped reflective cup can suppress inter-pixel light crosstalk and improve the overall contrast of the LED display.

[0423] In some embodiments, the stepped reflector cup structure can include or form a cavity around the light emitting region. The cavity can include a region surrounded by the stepped reflector cup and above the semiconductor substrate 404. The cavity can include an inner sidewall, which can include a plurality of inclined surfaces. For example, as shown in FIG. 8A, the stepped reflector cup can include a cavity or surround a cavity, which can include a region between the stepped reflector cup portions 846 and 848 and above the semiconductor substrate 404. The light emitting region can be positioned in the cavity and surrounded by the stepped reflector cup portions 846 and 848. FIG. 8

[0424] 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., the stepped reflector cup portions 846 and 848) is higher than the top of the light emitting region. In some embodiments, the cavity can include an inner sidewall, and the inner sidewall can include a plurality of inclined surfaces (e.g., the inclined surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S). In some embodiments, the inclined 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 shown in FIG. 8A, the angles of the inclined surfaces 846-1S, 846-2S, 846-3S are denoted as the inclined angles a, b, and g, respectively. The inclined angles of the inclined surfaces 846-1S, 846-2S, and 846-3S can be the same as the inclined angles of the inclined surfaces 848-1S, 848-2S, and 848-3S, respectively. In some embodiments, the inclined angles a, b, and g remain the same or increase from the bottom to the top of the cavity. In some preferred embodiments, the inclined angles a, b, and g can gradually decrease from the bottom to the top of the cavity, thus the light emitted by the LED device can be more divergent towards the upper portion of the LED device. However, in some embodiments, the inclined angles a, b, and g can be any angles according to the design. In some embodiments, the cavity can be filled with a silicon-containing material, such as silicon oxide, which can improve optical refraction, increase light transmittance, and / or enhance ultraviolet aging resistance and heat aging resistance. In some embodiments, the cavity can be empty or vacuumed. In some embodiments, the inclined surfaces (e.g., the inclined surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S) can be straight, curved, wavy, multi-linear, or a combination thereof. FIG. 8

[0425] In some embodiments, the cavity can include a plurality of sub-cavities. The sub-cavities can be formed by or surround individual inclined surfaces and can have different sizes in the horizontal direction. For example, as shown in FIG. 8A, there can be a plurality of sub-cavities 846-1C, 846-2C, 846-3C, 848-1C, 848-2C, and 848-3C formed by the inclined surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S, respectively. The sub-cavities 846-1C, 846-2C, 846-3C, 848-1C, 848-2C, and 848-3C can have different sizes in the horizontal direction. For example, the sub-cavities 846-1C, 846-2C, 846-3C can have a size of L1, L2, and L3, respectively, and the sub-cavities 848-1C, 848-2C, 848-3C can have a size of L1, L2, and L3, respectively. FIG. 8 ​​The three sub-cavities are shown. The sub-cavity at the bottom of the cavity can include an area surrounded or defined by the bottom of 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 can 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 can 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 of the stepped structure 846-3 and 848-3 at the top). In some embodiments, the inclined surfaces of the sub-cavities are not arranged in the same plane. For example, as shown, each sub-cavity can 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 sizes in the horizontal direction. In some embodiments, the inclined surfaces 846-1S, 846-2S, and 846-3S can not be arranged in the same plane, and the inclined surfaces 848-1S, 848-2S, and 848-3S can not be arranged in the same plane. For example, the inclined surfaces 846-1S, 846-2S, and 846-3S are arranged in different planes and staggered in the vertical direction. FIG. 8

[0426] In some embodiments, the heights of the sub-cavities can be different. For example, the height of the sub-cavity in the middle of the cavity can be smaller than the heights of the other sub-cavities. The height of the sub-cavity at the top of the cavity can be greater than the height of the sub-cavity at the bottom of the cavity. 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, and the top blue LED structure is located in the sub-cavity at the top of the cavity. The middle green LED structure is located in the sub-cavity in the middle of the cavity. In some embodiments, the sub-cavities can be filled with a silicon-containing material, such as silicon oxide, which can improve optical refraction, increase light transmittance, and / or enhance ultraviolet aging resistance and heat aging resistance. In some embodiments, the materials of the sub-cavities can be different. For example, the sub-cavity at the top of the cavity can be filled with silicon oxide, and the sub-cavity at the bottom of the cavity can be filled with epoxy methyl silicon. In some embodiments, the sub-cavities can be empty or vacuumed.

[0427] ​In some embodiments, the stepped light cup can comprise metal. In some embodiments, the stepped light cup can comprise a dielectric material such as silicon dioxide. In some embodiments, the stepped light cup can comprise a photosensitive dielectric material. In some embodiments, the photosensitive dielectric material can comprise SU-8 or photosensitive polyimide (PSPI). In other embodiments, the stepped light cup can comprise photoresist. In some embodiments, the manufacturing process of the stepped light cup is similar to that described above with reference to the light cup.

[0428] In some embodiments, the single-pixel multi-color LED device 800 further comprises one or more reflective coatings. The one or more reflective coatings can be disposed on one or more of the inclined surfaces of the stepped light cup, for example, on the inclined surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S. The bottom of each of the one or more reflective coatings does not contact the respective LED structure, for example, the red LED structure, the green LED structure, and the blue LED structure. The one or more reflective coatings can reflect the light emitted by the light emitting region, thus enhancing the brightness and light emitting efficiency of the micro-LED panel or display. For example, the light emitted by the light emitting region can reach the one or more reflective coatings and can be reflected upward by them.

[0429] The one or more reflective coatings together with the stepped light cup can utilize the reflection direction and / or reflection intensity of the light emitted by the light emitting region. For example, the inclined angles a, b, and g corresponding to the inclined surfaces 846-1S, 846-2S, and 846-3S can become smaller and smaller from the bottom to the top of the cavity, and thus the one or more reflective coatings disposed on the inclined surfaces 846-1S, 846-2S, and 846-3S are inclined at the same inclined angles as the inclined surfaces 846-1S, 846-2S, and 846-3S. 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 at the inclined angles a, b, and g. The inclined angles a, b, and g can become larger, the same, or smaller, or the inclined angles a, b, and g can be otherwise selected according to a particular design.

[0430] The material of the one or more reflective coatings can be highly reflective, having a reflectivity greater than 60%, 70%, or 80%, and can reflect a large portion of the light emitted by 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 light cup. In some embodiments, the material of the one or more reflective coatings disposed on each inclined surface can be different. For example, the material of the reflective coating disposed on the inclined surface 846-1S can be different from the material of the reflective coatings disposed on the inclined surfaces 846-2S and 846-3S, respectively.

[0431] In some embodiments, one or more of the reflective coatings can be fabricated by one or more of an e-beam deposition or sputtering process. 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 planarized layer 454. Stepped structures such as 846-2 and 848-2 are formed in the same step before or after the formation of planarized layer 458. Stepped structures such as 846-3 and 848-3 are formed in the same step before or after the formation of 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 bonding of different planarized layers including LED structures. In some embodiments, as a result of layer-by-layer processing and misalignment of bonding of different planarized layers including LED structures, there can be gaps (not shown in FIGS. 8A-8C) between different stepped structures such as 846-1, 846-2, and 846-3. FIG. 8

[0432] In some embodiments, the light reflecting cup can have a floating structure. FIG. 9 is a cross-sectional view along a diagonal line such as 402 in FIG. 9A-9C of a single-pixel tri-color LED device 900 having floating light reflecting cups according to some embodiments. In some embodiments, although not all are shown in FIGS. 9A-9C, the single-pixel tri-color LED device 900 has a similar structure as any one of the single-pixel tri-color LED devices shown in FIGS. 1-8, and has floating light reflecting cup portions such as 946 and 948. FIG. 4A FIG. 9 In some embodiments, the light reflecting cup can have a floating structure.

[0433] In some embodiments, the floating light reflecting cup can surround the light emitting area, and the bottom of the light reflecting cup does not directly contact the semiconductor substrate 104 / 404. For example, as shown in FIGS. 9A-9C, the light reflecting cup portions 946 and 948 surround the light emitting area, and the bottom of the light reflecting cup portions 946 and 948 does not directly contact the semiconductor substrate 104, e.g., there is a gap between the bottom of the light reflecting cup and the substrate 104 / 404. In some embodiments, the gap is filled by the planarized insulating layer 454. In some embodiments, the light emitted by the light emitting area can reach the light reflecting cup and be reflected upward by the light reflecting cup. For example, as shown in FIGS. 9A-9C, the light emitted by the light emitting area, including the light emitted by the sidewalls and / or the top of the LED structure, can reach the light reflecting cup portions 946 and 948 and be reflected upward by them. Thus, it can reduce the divergence of the light emitted by the light emitting area, enhance the brightness of the single-pixel multi-color LED device. FIG. 9 FIG. 9 In some embodiments, the light reflecting cup can have a floating structure.​​​

[0434] 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 as needed for design. 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 of the single-pixel multicolor LED device and display panel. When the production of the single-pixel multicolor LED device 900 is complete, the distance is fixed and cannot be adjusted. 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 display panel. In some embodiments, the distance between the bottom of the reflector cup and the top surface of the substrate 404, such as components 946 and 948, can be the same or less 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 and the top surface of the substrate 404, such as components 946 and 948, 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, certain light from certain parts of the single-pixel multicolor LED device 900 can not be reflected or isolated, which can make the light more focused at selected parts of the device 900.

[0435] 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 microns. 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 micron. 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 microns. 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 microns. 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 microns. 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 microns. 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 microns. 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 microns. 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 microns. In general, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 is determined by the height of the light emitting layer bottom, such as the thickness of the metal bonding layer. In preferred embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 404 is no greater than 20 microns.

[0436] In some embodiments, the reflector can isolate at least some of the light emitted by the light-emitting area. For example, such as FIG. 9 As shown, when the height of the reflector cup is higher than the height of the light-emitting area, reflector cup portions 946 and 948 can isolate at least some of the light emitted by the light-emitting area. Therefore, 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 composition, shape, and manufacturing process as the reflector cup described above (except for position and orientation).

[0437] Figures 1-9 illustrate only a single-pixel multicolor LED device according to some embodiments. In other embodiments, the reflector cup can have different shapes when viewed from a top or side view. That is, the sidewalls of the reflector cup surrounding the light-emitting area can be circular, triangular, square, rectangular, pentagonal, hexagonal, and octagonal. The sidewalls of the reflector cup can surround a light-emitting area or a single-pixel multicolor LED device, or they can surround a group of light-emitting areas or a group of single-pixel multicolor LED devices. For example, the sidewalls of the reflector cup can surround two or more light-emitting areas or two or more single-pixel multicolor LED devices arranged in the same plane.

[0438] An array of single-pixel multicolor LED devices can be used, each of which may include a reflector cup. Each reflector cup may have a different shape when viewed from a top view or a plan view. For example, the reflector cup of the first single-pixel multicolor LED device may be round, and the reflector cups of adjacent single-pixel multicolor LED devices may be square. Additionally, the reflector cups may be electrically isolated from each other. Reflector cups may also be isolated if a buffer space is provided between adjacent reflector cups, or if the material of the reflector cups may not extend all the way to the boundary with adjacent reflector cups. Alternatively, a reflective coating formed on the sidewalls of the reflector cups may simply extend to cover the gap area between adjacent reflector cups. In another embodiment, the reflector cups may be electrically connected to each other via a common electrode, such as a top electrode.

[0439] Various other modifications, alterations, and variations will be apparent to those skilled in the art regarding the arrangement, operation, and details of the methods and apparatus of the invention disclosed herein, without departing from the spirit and scope of the invention as defined in the appended claims. Therefore, the scope of the invention should be determined by the appended claims and their legal equivalents.

[0440] Other embodiments include various subsets that combine or otherwise rearrange the embodiments shown in Figures 1-9 in various other embodiments.

[0441] Various design aspects of a single-pixel multicolor LED device, such as layer dimensions (e.g., width, length, height, and cross-sectional area of ​​each layer), electrode dimensions, the size, shape, spacing, and arrangement of the two or more LED structure layers, bonding layers, reflective layers, and conductive layers, as well as the configuration between the integrated circuit, pixel driver, and electrical connections, are selected (e.g., optimized using cost or performance functions) to obtain the desired LED characteristics. LED characteristics altered based on the aforementioned design aspects include, for example, size, material, cost, manufacturing efficiency, luminous efficacy, power consumption, directivity, luminous intensity, luminous flux, color, spectrum, and spatial radiation pattern.

[0442] FIG. 10A This is a circuit diagram of a 1000-matrix matrix of single-pixel tri-color LED devices according to some embodiments. FIG. 10A The circuitry includes three pixel drivers 1002, 1004 and 1006 and three tri-color LED devices 1008, 1010 and 1012.

[0443] In some embodiments, the display panel includes multiple pixels, such as millions of pixels, and each pixel includes a tri-color LED device structure. In some embodiments, the LED device structure may be a micro-LED. Micro-LEDs typically have a lateral dimension of 50 micrometers (μm) or less, and may have a lateral dimension of less than 10 μm or even only a few μm.

[0444] In some embodiments, such as 1002, the pixel driver includes a plurality of transistors and capacitors. FIG. 10A (Not shown in the image). The transistor includes a drive transistor connected to a power supply and a control transistor configured with its gate connected to a scan signal bus. The capacitor includes a storage capacitor used to maintain the gate voltage of the drive transistor while the scan signal sets other pixels.

[0445] In this example, each of the three tri-color LED devices, such as 1008, has its own integrated circuit (IC) pixel driver 1002. The tri-color LED device 1008 for a single pixel can be considered as three separate LEDs connected in parallel with different colors. For example, the red LED 1018, green LED 1016, and blue LED 1014 within the same tri-color LED device 1008 are connected to the same IC pixel driver 1002 via a common P-electrode pad or anode.

[0446] In some embodiments, each red LED, green LED, and blue LED within the same tri-color LED device 1008 is connected to a separate N-electrode pad or cathode.

[0447] In some embodiments, all red LEDs from different tri-color LED devices, such as 1018, 1024, and 1030, are connected to the same common N-electrode 1036. All green LEDs from different tri-color LED devices, such as 1016, 1022, and 1028, are connected to the same common N-electrode 1034. All blue LEDs from different tri-color LED devices, such as 1014, 1020, and 1026, are connected to the same common N-electrode 1032. The use of a common electrode simplifies the manufacturing process and reduces the area of ​​the LED device, especially the area occupied by the electrodes.

[0448] In some embodiments, the connections of the P electrode and the N electrode can be switched and interchanged. FIG. 10A (Not shown in the image). For example, red LEDs 1018, green LEDs 1016, and blue LEDs 1014 within the same tri-color LED device 1008 are connected to a shared N-electrode pad or cathode. Red LEDs, green LEDs, and blue LEDs within the same tri-color LED device 1008 are connected to separate P-electrode pads or anodes. All red LEDs from different tri-color LED devices, such as 1018, 1024, and 1030, are connected to the same common N-electrode 1036.

[0449] FIG. 10B This is a circuit diagram of a 1000-matrix matrix of single-pixel tri-color LED devices according to some embodiments. FIG. 10B Similar to FIG. 10A The difference lies in that, in this example, each LED structure in each of the three tri-color LED devices, such as 1008, has its own integrated circuit (IC) pixel driver 1002. For example, within the same tri-color LED device 1008, the red LED 1018, green LED 1016, and blue LED 1014 are connected to different IC pixel drivers 1002-1, 1002-2, and 1002-3 respectively via separate P-electrode pads or anodes. This type of P-electrode connection is shown in some embodiments, as can be observed from Figures 1-9.

[0450] In addition, in such FIG. 10B In some of the embodiments shown, all LEDs of different colors from different tri-color LED devices are connected to the same common N electrode 1032.

[0451] In some embodiments, the connections of the P electrode and the N electrode can be switched and interchanged. FIG. 10B(Not shown in the image). For example, within the same tri-color LED device 1008, the red LED 1018, green LED 1016, and blue LED 1014 are connected to different N-electrode pads or cathodes. All LEDs of different colors in different tri-color LED devices are connected to the same common P-electrode 1032.

[0452] FIG. 11 This 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 area 1150. The data interface 1110 receives data defining the image to be displayed. The source and format of this data will vary depending on the application. The control module 1120 receives 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 area 1140; shift registers or other types of buffers and memories to store and transfer data; digital-to-analog converters and level converters; and a scan controller including clock circuitry.

[0453] Pixel region 1150 includes a pixel array. Pixels include microLEDs such as multicolor LEDs 1134 integrated with, for example, a pixel driver as described above. In some embodiments, the top of the multicolor LED array is covered by an array of microlenses. FIG. 11 (Not shown separately in LED1134). In some embodiments, an array of multicolor LEDs is formed around it with a reflective structure or a reflector cup (not shown separately in LED1134). FIG. 11 An array of optically isolated structures (not shown separately in LED1134). In this example, 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 embodiment, the pixel is in contact with a power supply voltage (not shown), ground via ground pad 1136, and also with a control signal. Although in FIG. 11 As not shown, the P electrode of the tri-color LED 1134 and the output of the driving transistor are located within the LED 1134. LED current drive signal connections (between the P electrode of the LED and the output of the pixel driver), ground connections (between the n electrode and system ground), power supply voltage Vdd connections (between the source of the pixel driver and system Vdd), and control signal connections to the pixel driver gate are made according to various embodiments.

[0454] FIG. 11 This is just a representative illustration. Other designs will be obvious. For example, the colors don't have to be red, green, and blue. Nor do they have to be arranged in rows or bars. As an example, besides FIG. 11In addition to the square matrix arrangement of pixels shown, the hexagonal matrix arrangement of pixels can also be used to form the display panel 1100.

[0455] In some applications, a fully programmable rectangular pixel array is not necessary. Other designs for display panels and displays with various shapes can also be formed using the device structures described herein. One class of examples is specialized applications, including signage and automobiles. For instance, 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 the LEDs on and off. Another specialized example is automotive headlights and intelligent 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 via individual pixel drivers.

[0456] Even the lateral arrangement of the devices within each pixel can be varied. In Figures 1-9, the LEDs and pixel drivers are arranged vertically, meaning each LED is located on top of its corresponding pixel driver circuit. Other arrangements are also possible. For example, the pixel driver circuit could also be located "behind," "in front of," or "beside" the LEDs.

[0457] Different types of display panels can be manufactured. For example, the resolution of display panels typically ranges from 8×8 to 3840x2160. Common display resolutions include QVGA (320x240 with a 4:3 aspect ratio), XGA (1024x768 with a 4:3 aspect ratio), D (1280x720 with a 16:9 aspect ratio), FHD (1920×1080 with a 16:9 aspect ratio), UHD (3840x2160 with a 16:9 aspect ratio), and 4K (4096×2160). A wide variety of pixel sizes are also available, ranging from submicron and below to 10mm and above. The overall display area size can also vary widely, from diagonally small to tens of micrometers or smaller to hundreds of inches or larger.

[0458] Different applications will also have different requirements for optical brightness and viewing angle. Example applications include direct-view displays for home / office projectors and portable electronics such as light engines for smartphones, laptops, wearable electronics, AR and VR glasses, and retinal projection. Power consumption can vary from as low as a few milliwatts for retinal projectors to up to kilowatts for large-screen outdoor displays, projectors, and smart car headlights. In terms of frame rate, due to the fast response (nanosecond level) of inorganic LEDs, frame rates can reach the kHz level, or even the MHz level for low resolutions.

[0459] Other embodiments include various subsets of the embodiments shown in Figures 1-11 that are combined and rearranged in various other embodiments, such as having and not having a reflective layer, having and not having a planarized layer, having and not having a reflector cup structure including various shapes and positioning types, having and not having a refractive layer, having and not having a microlens, having and not having spacers, and having and not having multicolor LED pixel devices / units with different electrode connection structures.

[0460] While 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 methods described above can be applied to the integration of non-LED and OLED functional devices with control circuitry that is not pixel-driven. Examples of non-LED devices include vertical-cavity surface-emitting lasers (VCSELs), photodetectors, microelectromechanical systems (MEMS), silicon photonic devices, power electronic devices, and distributed feedback lasers (DFBs). Examples of other control circuitry include current drivers, voltage drivers, transimpedance amplifiers, and logic circuits.

[0461] The foregoing description of the disclosed embodiments is provided to enable making or using the embodiments and variations thereof described herein. 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 is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.

[0462] The features of this invention can be implemented using a computer program product or with the aid of a computer program product, such as a storage medium (of various media) or a computer-readable storage medium (of various media), wherein instructions are stored thereon or thereon, which 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 memory devices. The memory may optionally include one or more storage devices located remotely from the CPU. The non-volatile memory devices within the memory, or optionally within the memory, include non-transitory computer-readable storage media.

[0463] Features of the invention, stored on any machine-readable medium (of various kinds), can be contained in software and / or firmware for controlling the hardware of a processing system and enabling the processing system to interact with other entities using the results of the invention. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0464] It should be understood that although this document may use terms such as “firstly” and “secondly” to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0465] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the claims. As used in the description of the embodiments and the appended claims, the singular forms “a,” “an,” and “this” are intended to include multiple 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 includes any and all possible combinations of one or more of the associated listed items. It should also be understood that the terms “comprising” and / or “including”, when used in this specification, specify the presence of said 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.

[0466] As used herein, the term "if" can be interpreted as meaning, depending on the context, that the prerequisite of a statement is true "in the case of," "when," or "in response to detection." Similarly, the phrases "if it is determined that [the prerequisite of that statement is true]," "if [the prerequisite of the statement is true]," or "when [the prerequisite of the statement is true]" can be interpreted as meaning, depending on the context, that the stated prerequisite is true "when determined," "in response to determined," "according to determined," "when detected," or "in response to detection."

[0467] The foregoing description, used for illustration, has been described with reference to specific embodiments. However, the illustrative discussion above is not intended to be exhaustive or to limit the claims to the precise forms disclosed. Many modifications and variations can be made in light of the foregoing teachings. The embodiments were chosen and described in order to best explain the principles of practical application and operation, thereby enabling others skilled in the art to implement them.

Claims

1. A micro-LED pixel unit, comprising a semiconductor substrate; a light emitting region formed on the semiconductor substrate, comprising a plurality of color LED structures, a bottom of each of the plurality of color LED structures connected to a corresponding bonding metal layer in the light emitting region, wherein each of the plurality of color LED structures comprises a light emitting layer and a reflective structure at a bottom of the light emitting layer, wherein the plurality of color LED comprises a first color LED structure and a second color LED structure, wherein the first color LED structure comprises a first light emitting layer, a first bottom reflective layer formed at a bottom of the first light emitting layer, and a first top reflective layer formed at a top of the first light emitting layer, and wherein the second color LED structure comprises a second light emitting layer, a second bottom reflective layer formed at a bottom of the second light emitting layer, and a second top reflective layer formed at a top of the second 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 reflective cup surrounding the light emitting region, wherein a bottom of the floating reflective cup is above the semiconductor substrate, and sidewalls of the light emitting layer of each of the plurality of color LED structures emit light in a horizontal direction to the suspended floating reflective cup and are reflected upward by the suspended floating reflective cup; wherein: light emitted by the first light emitting layer propagates approximately in a horizontal direction between the first bottom reflective layer and the first top reflective layer before reaching the reflective cup and being reflected upward by the reflective cup; light emitted by the second light emitting layer propagates approximately in a horizontal direction between the second bottom reflective layer and the second top reflective layer before reaching the reflective cup and being reflected upward by the reflective cup.

2. The micro-LED pixel unit of claim 1, wherein, the bottom of the floating reflective cup is higher than a top surface of the corresponding bonding metal layer of a bottom of one of the plurality of color LED structures.

3. The micro-LED pixel unit of claim 1, wherein, the floating reflective cup is stepped.

4. The micro-LED pixel unit of claim 3, further comprising a microlens formed above the light emitting region.

5. The micro-LED pixel unit of claim 4, wherein, a top of the floating reflective cup is higher than a top of the microlens.

6. The micro-LED pixel unit of claim 4, further comprising a refractive structure at a bottom of the microlens, the refractive structure formed between the floating reflective cup and the light emitting region.

7. The micro-LED pixel unit of claim 4, wherein, a lateral dimension of the microlens is not less than a lateral dimension of the light emitting region.

8. The micro-LED pixel unit of claim 4, wherein, the floating reflective cup has a top open area, and a lateral dimension of the microlens is less than a lateral dimension of the top open area.

9. The micro-LED pixel unit of claim 3, further comprising a bottom dielectric layer formed between the floating reflective cup and the semiconductor substrate.

10. The micro-LED pixel unit of claim 1, wherein, the top electrode layer directly contacts a top of the floating reflective cup or a bottom of the floating reflective cup.

11. The micro-LED pixel unit of claim 10, wherein, Each of the plurality of color LED structures includes a bottom conductive contact layer and a top conductive contact layer, the light emitting layer being formed between the bottom conductive contact layer and the top conductive contact layer; wherein the bottom conductive contact layer is electrically connected with the semiconductor substrate through a contact via hole passing through the reflective structure and the corresponding bonding metal layer, and a top surface of the top conductive contact layer of a top color LED structure is in contact with the top electrode layer, and edges of the top conductive contact layer of color LED structures under the top color LED structure are in contact with the top electrode layer.

12. The micro-LED pixel unit of claim 1, wherein, The semiconductor substrate is an IC substrate.

13. The micro-LED pixel unit of claim 3, wherein, The stepped floating reflective cup forms a cavity around the light emitting region.

14. The micro-LED pixel unit of claim 13, wherein, Inner sidewalls of the cavity include a plurality of inclined surfaces.

15. The micro-LED pixel unit of claim 14, wherein, Angles of the plurality of inclined surfaces with respect to a surface of the semiconductor substrate become smaller and smaller from a bottom of the cavity to a top of the cavity.

16. The micro-LED pixel unit of claim 14, wherein, Sub-cavities formed by the plurality of inclined surfaces have different sizes in a horizontal direction.

17. The micro-LED pixel unit of claim 16, wherein, Inner sidewalls of the sub-cavities are not positioned in the same plane.

18. The micro-LED pixel unit of claim 17, wherein, The sub-cavities have different heights.

19. The micro-LED pixel unit of claim 16, wherein, A height of a sub-cavity located in a middle of the cavity is smaller than heights of other sub-cavities.

20. The micro-LED pixel unit of claim 16, wherein, A height of a sub-cavity located at a top of the cavity is greater than heights of sub-cavities located at a bottom of the cavity.

21. The micro-LED pixel unit of claim 13, wherein, The plurality of color LED structures further includes a top color LED structure.

22. The micro-LED pixel unit of claim 21, wherein, A top of the cavity is higher than a top of the top color LED structure.

23. The micro-LED pixel unit of claim 13, wherein, The cavity includes a plurality of sub-cavities, each of the plurality of color LED structures is located in a different sub-cavity of the plurality of sub-cavities, respectively.

24. The micro-LED pixel unit of claim 1, wherein, A material of the floating reflective cup includes metal.

25. The micro-LED pixel unit of claim 1, wherein, Each of the plurality of color LED structures includes a corresponding extension part extending from a side of the corresponding color LED structure, the corresponding extension part is electrically connected with the top electrode layer via a corresponding first contact via hole, and a bottom of each of the plurality of color LED structures is electrically connected with the semiconductor substrate via a corresponding second contact via hole.

26. The micro-LED pixel unit of claim 1, wherein, The plurality of color LED structures have the same central axis.

27. The micro-LED pixel unit of claim 1, wherein, The reflective structure includes a reflective layer formed at a bottom of each of the plurality of color LED structures, respectively.

28. The micro-LED pixel unit of claim 27, wherein, A thickness of the reflective layer is in a range of 5nm to 10nm, and a thickness of each of the plurality of color LED structures is no more than 300nm.

29. The micro-LED pixel unit of claim 1, wherein, A material of the top electrode layer includes one or more of graphene, indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), or fluorine-doped tin oxide (FTO).

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