System and method for multi-color LED pixel unit

Abstract

To provide an LED structure for display panels.SOLUTION: A micro multi-color LED device includes two or more LED structures for emitting a range of colors. The two or more LED structures are vertically stacked to combine light from the two more LED structures vertically and / or horizontally and reflected upward via some reflective structures. In some embodiments, each LED structure is connected to a pixel drive circuit and / or a common electrode. The LED structures are bonded together through bonding layers. In some embodiments, planarization layers enclose each of the LED structures or the micro multi-color LED device. In some embodiments, one or more of reflective layers, refractive layers, micro-lenses, spacers, and reflective cup structures are implemented in the device to improve the LED emission efficiency. A display panel comprising an array of micro tri-color LED devices has a high resolution and a high illumination brightness.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] Related Applications

[0001] This application is a joint venture between U.S. Provisional Patent Application No. 62 / 863,559, filed June 19, 2019, entitled "Systems and Methods for Coaxial Multi-Color LEDs," U.S. Provisional Patent Application No. 63 / 013,358, filed April 21, 2020, entitled "Light-Emitting Diode Chip Structures with Reflective Elements," U.S. Provisional Patent Application No. 63 / 013,370, filed April 21, 2020, entitled "Light-Emitting Diode Chip Structures with Reflective Elements," U.S. Provisional Patent Application No. 63 / 034,391, filed June 3, 2020, entitled "Systems and Methods for Multi-Color LED Pixel Unit with Vertical Light Emission," and U.S. Provisional Patent Application No. 63 / 034,391, filed June 3, 2020, entitled "Systems and Methods for Multi-Color LED Pixel Unit with Horizontal Light Emission," This application claims priority to U.S. Provisional Patent Application No. 63 / 034,394, entitled "Radio-Absorption and Emission of Polymeric Materials," each of which is incorporated herein by reference.

[0002] Technical Field This disclosure relates generally to light emitting diode (LED) display devices, and more particularly to systems and methods for making LED semiconductor devices that emit different colors with high brightness and micrometer-scale pixel sizes. [Background technology]

[0003] background

[0003] With the recent development of small LED and micro LED technology, consumer devices and applications such as augmented reality (AR), virtual reality (VR), projection, head-up display (HUD), mobile device display, wearable device display, and automotive display require LED panels with improved resolution and brightness. For example, an AR display integrated in goggles and located close to the wearer's eyes may be as small as a fingernail while still requiring HD definition (1280x720 pixels) or more. Many electronic devices require a specific pixel size, adjacent pixel distance, brightness, and viewing angle for an LED panel. In many cases, maintaining both the resolution and brightness requirements is a challenge when trying to achieve maximum resolution and brightness with a small display. Conversely, in some cases, pixel size and brightness may have a roughly inverse relationship, making it difficult to balance them simultaneously. For example, getting high brightness for each pixel may result in low resolution. Alternatively, getting high resolution may result in reduced brightness.

[0004]

[0004] Generally, at least red, green, and blue colors are overlapped to reproduce a wide range of colors. In some cases, separate monochromatic LEDs are fabricated in different non-overlapping zones in a pixel area to include at least red, green, and blue colors in the pixel area. Existing technologies face the challenge of improving the effective illumination area in each pixel when the distance between adjacent LEDs is fixed. On the other hand, when one LED illumination area is fixed, it can be a difficult task to further improve the overall resolution of the LED panel, because LEDs with different colors need to occupy their designated zones in one pixel.

[0005]

[0005] Active matrix liquid crystal displays (LCD) and organic light emitting diode (OLED) displays combined with thin film transistor (TFT) technology are becoming increasingly popular in today's commercial electronic devices. These displays are widely used in laptop personal computers, smart phones, and personal digital assistants. Millions of pixels work together to create an image on the display. TFTs turn each pixel on and off individually, acting as a switch to brighten or darken the pixel, allowing convenient and efficient control of each pixel and the entire display.

[0006]

[0006] However, conventional LCD displays suffer from low light efficiency, resulting in high power consumption and limited battery operating time. Although active matrix organic light emitting diode (AMOLED) display panels generally consume less power than LCD panels, AMOLED display panels are still large power consumers in battery-operated devices. It is desirable to reduce the power consumption of display panels to extend battery life.

[0007]

[0007] Conventional inorganic semiconductor light emitting diodes (LEDs) have demonstrated excellent light efficiency, making active matrix LED displays more desirable for battery-operated electronic devices. An array of driver circuits and light emitting diodes (LEDs) are used to control millions of pixels to display images on a display. Both monochrome and full-color display panels can be manufactured according to a wide variety of fabrication methods.

[0008]

[0008] However, integrating thousands or even millions of micro-LEDs with a pixel driving circuit array is quite difficult. Various fabrication methods have been proposed. In one approach, the control circuitry 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. The LEDs on the intermediate substrate are then picked and placed, one or a few at a time, onto the substrate with the control circuitry. However, this fabrication process is inefficient, costly, and unreliable. In addition, there are no existing manufacturing tools to transfer micro-LEDs in large quantities. Therefore, new tools need to be developed.

[0009]

[0009] In another approach, the entire LED array with the original substrate is aligned to the control circuit and bonded to the control circuit using metal bonding. The substrate on which the LEDs are fabricated remains in the final product and can cause optical crosstalk. In addition, thermal mismatch between two different substrates can cause stress at the bonding interface, resulting in reliability issues. In addition, multi-color display panels usually require more LEDs and LEDs of different colors to be grown on different substrate materials compared to monochromatic display panels, thus making the traditional manufacturing process more complex and inefficient.

[0010]

[0010] Display technology is becoming more and more popular in today's commercial electronic devices. These display panels are widely used in 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 laptop personal computers, smartphones, tablets, and wearable electronic devices. Most of the development of stationary large screens is directed at achieving a high viewing angle to accommodate and allow many audiences to view the screen from various angles. For example, various liquid crystal materials such as super twisted nematic (STN) and compensation film super twisted nematic (FSTN) have been developed to achieve a large viewing angle for each and every pixel light source of the display panel.

[0011]

[0011] However, most portable electronic devices are designed primarily for a single user, and the orientation of the screen of these portable devices should be adjusted to the best viewing angle for the corresponding user, rather than a large viewing angle that would accommodate multiple audiences. For example, the viewing angle suitable for one user may be perpendicular to the screen surface. In this case, compared to a stationary large surface, the light emitted at a large viewing angle is largely wasted. Furthermore, a large viewing angle raises privacy concerns for portable electronic devices used in public areas.

[0012]

[0012] In addition, in conventional projection systems based on passive imager devices such as liquid crystal displays (LCDs), digital monitor devices (DMDs), and liquid crystal on silicon (LCOS), the passive imager devices themselves do not emit light. Specifically, conventional projection systems project images by optically modulating collimated light emitted from an imager, i.e., by either transmitting a portion of the light at a pixel level, for example, by an LCD panel, or reflecting a portion of the light, for example, by a DMD panel. However, the portion of the light that is not transmitted or reflected is lost, reducing the efficiency of the projection system. In addition, to provide collimated light, complex illumination optics are used to collect the divergent light emitted from the light source. The illumination optics not only makes the system bulky, but also introduces additional optical losses into the system, further affecting the performance of the system. In conventional projection systems, typically less than 10% of the illumination light generated by the light source is used to form the projected image.

[0013]

[0013] Light emitting diodes (LEDs) made of semiconductor materials can be used in monochrome or full color displays. In current displays utilizing LEDs, the LEDs are typically used as light sources that provide light that is optically modulated by, for example, an LCD or DMD panel. That is, the light emitted by the LED does not form an image by itself. LED displays that use an LED panel containing multiple LED dies as an imager device have also been investigated. In such LED displays, the LED panel is a self-emitting imager device, and each pixel can include one LED die (monochrome display) or multiple LED dies, each representing one of the primary colors (full color display).

[0014]

[0014] However, the light emitted by the LED die is generated from spontaneous emission, and therefore is not directional and has a large divergence angle. The large divergence angle can cause various problems for the micro-LED display. On the one hand, due to the large divergence angle, only a small portion of the light emitted by the micro-LED can be utilized. This can significantly reduce the efficiency and brightness of the micro-LED display system. On the other hand, due to the large divergence angle, the light emitted by one micro-LED pixel can illuminate its neighboring pixels, resulting in optical crosstalk between pixels, loss of sharpness, and loss of contrast. Conventional solutions to reduce the large divergence angle may not deal with the light emitted from the micro-LED as a whole efficiently, and only the central part of the light emitted from the micro-LED can be utilized, while the remaining part of the light emitted at more oblique angles remains unused. Summary of the Invention [Problem to be solved by the invention]

[0015]

[0015] It would therefore be desirable to provide an LED structure for a display panel that specifically addresses the above-mentioned shortcomings.

[0016] overview

[0016] Improved multicolor LEDs are needed to help improve and address the shortcomings of conventional display systems such as those mentioned above. In particular, LED device structures are needed that can simultaneously improve brightness and resolution while efficiently maintaining low power consumption. And display panels with narrow viewing angles to better protect user privacy and / or reduced light waste to lower power consumption, and reduced light interference between pixels while providing better images are also needed. [Means for solving the problem]

[0017]

[0017] The multi-color LED device described herein integrates at least three LED structures that are vertically stacked by arranging them in different layers of the device structure and utilize separate electrodes for receiving control current. By arranging at least three LED structures aligned along one axis as disclosed herein, the system effectively enhances the light illumination efficiency within one pixel area and at the same time improves the resolution of the LED panel.

[0018]

[0018] Pitch refers to the center-to-center distance of adjacent pixels on a display panel. In some embodiments, the pitch can vary from about 20 μm, from about 10 μm, and / or preferably from about 5 μm or less to about 40 μm. Much effort has been put into pitch reduction. When the pitch specification is determined, the area of ​​one pixel is fixed.

[0019]

[0019] The multi-color coaxial LED system described herein allows light with different color combinations to be emitted from one pixel area without using additional area to accommodate LED structures with different colors. Therefore, the footprint of one pixel is greatly reduced and the resolution of the micro LED panel can be improved. Meanwhile, the concentration of different color lights from the boundary of one micro LED device greatly enhances the brightness within one pixel area.

[0020]

[0020] Compared with the conventional fabrication process of micro-LED display chips that rely on inefficient pick-and-place processes or unreliable multiple substrate approaches, the multi-color micro-LED fabrication process disclosed herein effectively increases the efficiency and reliability of micro-LED device fabrication. For example, the LED structure can be directly bonded to a substrate with pixel driving circuits without introducing an intermediate substrate, thereby simplifying the fabrication steps and thus enhancing the reliability and performance of the LED chip. In addition, the lack of a substrate in the micro-LED structure can be continued to the final multi-color device, thereby reducing crosstalk and misalignment. In addition, polarized light is applied to either the LED structures in the multi-color micro-LEDs or the entire multi-color micro-LEDs, thereby allowing different LED structures and / or other layers to be directly bonded or formed together with less disruption to existing structures in the planarized layer.

[0021]

[0021] The multicolor micro LED device described herein can include vertical emission, for example, light from each of the stacked LED structures is emitted approximately vertically to the surface of the substrate, and also includes horizontal emission, for example, light from each of the stacked LED structures is emitted horizontally to the surface of the substrate and then reflected approximately vertically by some reflecting structure or any combination thereof. Since the vertically emitted light passes through all of the different layers in the multicolor micro LED device, various layers are implemented to improve light transmission and light reflection. Compared to vertical emission, the vertically emitted light from each of the stacked LED structures does not need to pass through all the layers above a particular structure. Therefore, horizontal emission can have better light transmission efficiency and improve light discrimination.

[0022]

[0022] Various embodiments include a display panel with an integrated microlens array. A display panel typically includes an array of pixel light sources (e.g., LEDs, OLEDs) electrically coupled to corresponding pixel drive circuits (e.g., FETs). An array of microlenses is aligned with the pixel light sources and positioned to reduce divergence of the light generated by the pixel light sources. The display panel may also include integrated optical spacers that maintain the positioning between the microlenses and the pixel drive circuits.

[0023]

[0023] The microlens array reduces the divergence angle of the light generated by the pixel light sources and the usable viewing angle of the display panel, which reduces power waste, increases brightness, and / or better protects user privacy in public areas.

[0024]

[0024] The display panel integrated with the microlens array can be fabricated using a wide variety of manufacturing methods, resulting in a wide variety of device designs.In one aspect, the microlens array is fabricated directly as a mesa or protrusion on the substrate that has the pixel light source.In some aspects, self-assembly, high temperature reflow, grayscale mask photolithography, molding / imprinting / punching, and dry etching pattern transfer are techniques that can be used to fabricate the microlens array.

[0025]

[0025] Other aspects include components, devices, systems, improvements, methods, and processes, including manufacturing methods, applications, and other techniques related to any of the above.

[0026]

[0026] Some exemplary embodiments include a reflector cup disposed on a semiconductor substrate and surrounding a light-emitting region, for example, a region where light is emitted from a multicolor micro-LED device. The reflector cup can reduce the divergence of light emitted from the light-emitting region and suppress optical crosstalk between adjacent pixel units. For example, the reflector cup can utilize light at an oblique angle, which is more efficient in collecting and converting this light into a brighter and more power-efficient display than conventional solutions. In addition, the reflector cup can block light emitted from the micro-LEDs of adjacent pixel units, thereby effectively suppressing inter-pixel optical crosstalk and enhancing color contrast and sharpness. The exemplary embodiments of the present disclosure can improve the brightness and contrast of the projection, thus reducing power consumption in projection applications. The exemplary embodiments of the present disclosure can also improve the light emission directionality of the display, thus providing better image quality and protecting user privacy in direct-view applications. The exemplary embodiments of the present disclosure can provide multiple advantages. One advantage is that the exemplary embodiments of the present disclosure can suppress inter-pixel optical crosstalk and increase brightness. Exemplary embodiments of the present disclosure can suppress inter-pixel optical crosstalk at smaller pitches while power-efficiently increasing luminance within a single pixel.

[0027]

[0027] In some exemplary embodiments, the single pixel multicolor LED device may include one or more top electrodes integrated with a reflective cup. The top electrodes may be electrically connected to the top electrode layer. The top electrode integration with the reflective cup may make the single pixel multicolor LED device structure more compact and simplify the fabrication process. By adopting the top electrodes, the reflective cup may perform as the common P or N electrode of the single pixel multicolor LED device, thus providing a compact structure of the single pixel multicolor LED device.

[0028]

[0028] In some exemplary embodiments, the micro LED pixel unit may include a micro lens in addition to the reflector cup. The micro lens may be aligned with the light emitting area and may reduce the divergence of the light emission from the light source and may be positioned to reduce the usable viewing angle from the single pixel multi-color LED device. For example, the micro lens may be aligned coaxially with the light emitting area and positioned on the light emitting area and above the reflector cup. A portion of the light emitted from the light emitting area may reach the micro lens directly and transmit through the micro lens, and another portion of the light emitted from the light emitting center may reach the reflector cup and be reflected by the reflector cup, and then reach the micro lens and transmit through the micro lens. Thus, the divergence may be reduced and the usable viewing angle may be reduced to the extent that the displays and panels using the single pixel multi-color LED device may be viewed by one user perpendicular to the surface of the displays and panels. This may reduce power waste, increase brightness, and / or better protect user privacy in public areas. In another example, the micro lens may be aligned coaxially with the light emitting area and positioned above the light emission and surrounded by the reflector cup. A portion of the light emitted from the light-emitting area can reach the microlens directly and be transmitted through the microlens, another portion of the light emitted from the light-emitting center can reach the reflective cup and be reflected by the reflective cup, then reach the microlens and be transmitted through the microlens, and the remaining portion of the light emitted from the light-emitting center can reach the reflective cup without being transmitted through the microlens and be reflected by the reflective cup. Thus, the divergence can be reduced and the available viewing angle can be reduced to the extent that displays and panels using single pixel multicolor LED devices can be viewed by several users. This can reduce power waste, increase brightness, and / or appropriately protect user privacy in public areas.

[0029]

[0029] In some exemplary embodiments, the single pixel multicolor LED device may further include a spacer. The spacer may be an optically transparent layer formed to provide a suitable spacing between the microlens and the light-emitting region. For example, the spacer may be disposed between the microlens and the top of the reflecting cup when the microlens is disposed on the reflecting cup. Thus, the light emitted from the light-emitting region may transmit through the spacer and then through the microlens. The spacer may also fill the area surrounded by the reflecting cup to increase the refractive index of the medium surrounding the light-emitting region. Thus, the spacer may change the optical path of the light emitted from the light-emitting region. By employing the microlens, the light extraction efficiency of the single pixel multicolor LED device may be increased to further enhance the brightness of, for example, a micro LED display panel.

[0030]

[0030] In some exemplary embodiments, the single pixel multi-color LED device may include a stepped cup. The stepped reflective cup may include a cavity surrounding the light emitting region. The cavity may be formed by a plurality of inclined surfaces surrounding the light emitting region. The plurality of inclined surfaces may form a sub-cavity, and the sub-cavity may have different dimensions in the horizontal direction. The stepped reflective cup may be disposed on a semiconductor substrate. The stepped reflective cup may reduce the divergence of light emitted from the light emitting region and suppress the optical crosstalk between adjacent pixel units. For example, the stepped reflective cup may utilize light at an oblique angle by reflecting it in different reflection directions. In addition, the stepped reflective cup may block the light emitted from the micro LEDs of the adjacent pixel units, thereby effectively suppressing the inter-pixel optical crosstalk and enhancing the color contrast and sharpness. The exemplary embodiments of the present disclosure may improve the brightness and contrast of the projection, and thus reduce the power consumption in the projection application. Exemplary embodiments of the present disclosure may also improve the light emission directionality of the display, thus providing better image quality and protecting user privacy in direct viewing applications.

[0031]

[0031] The multi-color micro-LED devices described herein can simultaneously improve brightness and resolution, making them suitable for modern display panels, especially for high-definition AR devices and virtual reality (VR) glasses.

[0032]

[0032] Some exemplary embodiments provide a multi-color micro-light emitting diode (LED) pixel unit of a display panel, the multi-color micro-LED pixel unit including: a first color LED structure formed on an IC substrate, the first color LED structure including a first light emitting layer and a first reflective structure formed on an underside of the first light emitting layer; a first dielectric bonding layer having a flat top surface covering the first color LED structure; a second color LED structure formed on the flat top surface of the first dielectric bonding layer, the second color LED structure including a second light emitting layer and a second reflective structure formed on an underside of the second light emitting layer; a second dielectric bonding layer having a flat top surface covering the second color LED structure; an upper electrode layer covering the micro-LED pixel unit and in electrical contact with the first color LED structure and the second color LED structure; and an IC substrate electrically connected to the first color LED structure and the second LED structure.

[0033] Some exemplary embodiments are micro-LED pixel units, comprising: a first color LED structure formed on an IC substrate, the first color LED structure including a first light emitting layer and a first reflecting structure formed below the first light emitting layer; a first dielectric bonding layer having a flat top surface covering the first color LED structure; a second color LED structure formed on the flat top surface of the first dielectric bonding layer, the second color LED structure including a second light emitting layer and a second reflecting structure formed below the second light emitting layer; a second dielectric bonding layer having a flat top surface covering the second color LED structure; a third color LED structure formed on a lower surface of the third color LED structure, the third color LED structure including a third light emitting layer, and a third reflective structure formed on a lower surface of the third light emitting layer; a third dielectric bonding layer having a flat upper surface covering the third color LED structure; an upper electrode layer covering the micro-LED pixel unit and in electrical contact with the first color LED structure, the second color LED structure, and the third color LED structure; and an IC substrate electrically connected to the first color LED structure, the second color LED structure, and the third color LED structure.

[0034] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first dielectric bonding layer is transparent and the second dielectric bonding layer is transparent.

[0035]

[0035] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the first reflective structure includes at least one first high-reflectivity layer, the second reflective structure includes at least one second high-reflectivity layer, and the third reflective structure includes at least one third high-reflectivity layer, and the reflectivities of the first high-reflectivity layer, the second high-reflectivity layer, and the third high-reflectivity layer are greater than 60%.

[0036]

[0036] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the material of the first high reflectivity layer, the second high reflectivity layer, or the third high reflectivity layer is a metal selected from one or more of Rh, Al, Ag, or Au.

[0037]

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

[0038]

[0038] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first reflective structure further includes a first transparent layer on the first high-reflectivity layer, the second reflective structure further includes a second transparent layer on the second high-reflectivity layer, and the third reflective structure further includes a second transparent layer on the third high-reflectivity layer.

[0039]

[0039] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, 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.

[0040]

[0040] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first color LED structure further includes a first bottom electrode conductive contact layer, the second color LED structure further includes a second bottom electrode conductive contact layer, and the third color LED structure further includes a third bottom electrode conductive contact layer, the first bottom electrode conductive contact layer is electrically connected to the IC substrate by 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 by 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 by a third contact via through the second dielectric layer and the first dielectric bonding layer.

[0041]

[0041] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the first lower electrode conductive contact layer is transparent, the second lower electrode conductive contact layer is transparent, and the third lower electrode conductive contact layer is transparent.

[0042]

[0042] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro LED pixel unit, a first extension extends from one side of the first light-emitting layer, a second extension extends from one side of the second light-emitting layer, and a third extension extends from one side of the second light-emitting layer, and an upper contact via connects the first extension, the second extension, and the third extension to the upper electrode layer through the second dielectric bonding layer and the third dielectric bonding layer.

[0043]

[0043] Some illustrative embodiments provide a micro-LED pixel unit including at least a light-emitting region formed on a 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.

[0044] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, a micro-lens is located on top of the light-emitting area.

[0045]

[0045] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the top of the reflective optical isolation structure is higher than the top of the micro-lens.

[0046]

[0046] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the reflective optical isolation structure has an upper opening, and the lateral area of ​​the micro-lens is less than the lateral area of ​​the upper opening.

[0047]

[0047] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the lateral dimension of the micro-lens is larger than the active light-emitting area of ​​the first color LED structure, the lateral dimension of the micro-lens is larger than the active light-emitting area of ​​the second color LED structure, and the lateral dimension of the micro-lens is larger than the active light-emitting area of ​​the third color LED structure.

[0048]

[0048] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the lateral dimensions of the first color LED structure, the second color LED structure, and the third color LED structure are the same.

[0049]

[0049] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first LED structure, the second LED structure, and the third LED structure have the same central axis.

[0050]

[0050] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the first dielectric bonding layer is transparent, the second dielectric bonding layer is transparent, and the third dielectric bonding layer is transparent.

[0051]

[0051] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro LED pixel unit, the thickness of the first reflective structure is 5 nm to 10 nm, the thickness of the second reflective structure is 5 nm to 10 nm, the thickness of the third reflective structure is 5 nm to 10 nm, the thickness of the first LED structure is 300 nm or less, the thickness of the second LED structure is 300 nm or less, and the thickness of the third LED structure is 300 nm or less.

[0052]

[0052] Some exemplary embodiments provide a multi-color micro-LED pixel unit for a display panel, comprising: a first LED structure emitting a first color formed on an IC substrate; a first transparent dielectric bonding layer having a first flat upper surface covering the first LED structure; a second LED structure emitting a second color formed on the first flat upper surface of the first transparent dielectric bonding layer; a second transparent dielectric bonding layer having a second flat upper surface covering the second LED structure; and an upper electrode layer covering the multi-color micro-LED pixel unit and in electrical contact with the first LED structure and the second LED structure, wherein the IC substrate is electrically connected to the first LED structure and the second LED structure.

[0053]

[0053] Some exemplary embodiments provide a micro-LED pixel unit including a first color LED structure formed on an IC substrate, a first transparent dielectric bonding layer having a flat top surface covering the first color LED structure, a second color LED structure formed on the first flat top surface of the first transparent dielectric bonding layer, a second transparent dielectric bonding layer having a flat top surface covering the second color LED structure, a third color LED structure formed on the flat top surface of the second transparent dielectric bonding layer, a third dielectric bonding layer having a flat top surface covering the third color LED structure, an upper electrode layer covering the micro-LED pixel unit and in electrical contact with the first color LED structure, the second color LED structure, and the third color LED structure, and an IC substrate electrically connected to the first color LED structure, the second color LED structure, and the third color LED structure.

[0054]

[0054] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro LED pixel unit, a first reflective structure is formed on the bottom of the first color LED structure, a second reflective structure is formed on the bottom of the second color LED structure, and a third reflective structure is formed on the bottom of the third color LED structure.

[0055]

[0055] Some exemplary embodiments provide a micro-LED pixel unit comprising an IC substrate, a light-emitting region formed on the IC substrate and including at least one LED structure and at least one dielectric bonding layer, each dielectric bonding layer having a flat upper surface covering a surface of every LED structure, a top electrode layer covering the micro-LED pixel unit and in electrical contact with every color LED structure, the IC substrate being electrically connected to every color LED structure, and a stepped reflective cup structure having a cavity surrounding the light-emitting region.

[0056]

[0056] Some illustrative embodiments provide a micro-LED pixel unit including 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.

[0057]

[0057] Some exemplary embodiments provide a micro-LED pixel unit including a semiconductor substrate; a light-emitting region formed on the semiconductor substrate and including at least one LED structure and at least one transparent dielectric bonding layer, each transparent dielectric bonding layer having a flat upper surface covering a surface of every LED structure; an upper electrode layer covering the micro-LED pixel unit and in electrical contact with every color LED structure, the IC substrate being electrically connected to every color LED structure; a stepped reflective cup structure formed around the light-emitting region; and a refractive structure formed between the stepped reflective cup structure and the light-emitting region.

[0058]

[0058] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the reflective cup structure has an upper opening, and the lateral area of ​​the micro-lens is less than the lateral area of ​​the upper opening.

[0059]

[0059] Some illustrative embodiments provide a micro-LED pixel unit including a semiconductor substrate, a light-emitting region formed on the semiconductor substrate, and a floating reflective optical isolation structure surrounding the light-emitting region, the floating reflective optical isolation structure being positioned at a distance above the semiconductor substrate.

[0060]

[0060] Some illustrative embodiments provide a micro-LED pixel unit including a semiconductor substrate, a light-emitting region formed on the semiconductor substrate, a reflective optical isolation structure surrounding the light-emitting region, and an upper electrode layer covering the light-emitting region and electrically connecting to the reflective optical isolation structure, the upper electrode layer being in electrical contact with the reflective optical isolation structure.

[0061]

[0061] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, an edge of the top electrode layer contacts the reflective optical isolation structure.

[0062]

[0062] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the light-emitting region includes at least one LED structure and at least one dielectric bonding layer, an upper electrode layer covers the micro-LED pixel unit and is in electrical contact with all of the color LED structures, and a semiconductor substrate is electrically connected to all of the color LED structures.

[0063]

[0063] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the reflective optical isolation structure is a floating reflective structure.

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

[0065]

[0065] Some illustrative embodiments provide a micro-LED pixel unit including at least a semiconductor substrate, a light-emitting region formed on the semiconductor substrate, a floating reflective optical isolation structure surrounding the light-emitting region, the floating reflective optical isolation structure being positioned at a distance above the semiconductor substrate, and an upper electrode layer formed on top of the light-emitting region, the upper electrode layer being in contact with the floating reflective optical isolation structure.

[0066]

[0066] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the light emitting region includes at least one LED structure and a bonding layer underneath each LED structure.

[0067]

[0067] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first color LED structure further includes a first bottom electrode conductive contact layer, the second color LED structure further includes a second bottom electrode conductive contact layer, the first bottom electrode conductive contact layer is electrically connected to the IC substrate by a first contact via at the bottom of the first bottom electrode conductive contact layer, and the second bottom electrode conductive contact layer is electrically connected to the IC substrate by a second contact via through the first dielectric bonding layer.

[0068]

[0068] Some exemplary embodiments provide a micro-LED pixel unit including a semiconductor substrate, a light-emitting region formed on the semiconductor substrate, an upper electrode layer covering the light-emitting region and in electrical contact with the light-emitting region, a reflective cup structure formed around the light-emitting region, wherein the upper electrode layer is electrically connected to the reflective cup structure and the semiconductor substrate is electrically connected to the reflective cup structure, and a refractive structure formed between the reflective cup structure and the light-emitting region.

[0069]

[0069] Some exemplary embodiments provide a micro-LED pixel unit comprising a semiconductor substrate; a light-emitting region formed on the semiconductor substrate, the light-emitting region including at least one LED structure and a bonding layer beneath every LED structure, each LED structure including a light-emitting layer and a lower reflective structure beneath the light-emitting layer; an upper electrode layer covering the micro-LED pixel unit and in electrical contact with every color LED structure, the semiconductor substrate being electrically connected to every 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.

[0070]

[0070] Some exemplary embodiments provide a micro LED pixel unit including a semiconductor substrate, a light emitting region formed on the semiconductor substrate, the light emitting region including at least one LED structure and a bonding layer beneath every LED structure, the LED structure including a light emitting layer and a reflective structure beneath the light emitting layer, an upper electrode layer covering the LED structure pixel unit and in electrical contact with every color LED structure, the semiconductor substrate being electrically connected to every color LED structure, and a stair-like reflective cup structure formed around the light emitting region, the light emitted along a horizontal level from sidewalls of the first light emitting layer and the second light emitting layer reaches the stair-like reflective cup structure and is reflected upward by the stair-like reflective cup structure, the top of the stair-like reflective cup structure being higher than the top of the light emitting region.

[0071]

[0071] Some exemplary embodiments provide a micro-LED pixel unit including a semiconductor substrate; a light-emitting region formed on the semiconductor substrate, the light-emitting region including at least one LED structure and a metal bonding layer underneath every LED structure, the LED structure including a light-emitting layer and a reflective structure underneath the light-emitting layer; an upper electrode layer covering the micro-LED pixel unit and in electrical contact with every color LED structure, the semiconductor substrate being electrically connected to every color LED structure; and a floating reflective cup structure surrounding the light-emitting region, the floating reflective cup structure being positioned at a distance above the semiconductor substrate, wherein light emitted along a horizontal level from sidewalls of the first light-emitting layer and the second light-emitting layer reaches the floating reflective cup and is reflected upwards by the floating reflective cup.

[0072]

[0072] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the bottom of the floating reflective cup structure is higher than the top surface of the semiconductor substrate.

[0073]

[0073] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the floating reflector cup structure is a stepped reflector cup structure.

[0074]

[0074] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first LED structure is embedded in a first flat transparent dielectric layer.

[0075]

[0075] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first flat transparent dielectric layer is composed of a solid inorganic material or a plastic material.

[0076] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the second LED structure is embedded in a second flat transparent dielectric layer.

[0077]

[0077] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the second flat transparent dielectric layer is composed of a solid inorganic material or a plastic material.

[0078]

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

[0079]

[0079] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first LED structure includes a first bottom electrode conductive contact layer formed on a bottom of the first LED structure, the second LED structure includes a second bottom electrode conductive contact layer formed on a bottom of the second LED structure, the first bottom electrode conductive contact layer is electrically connected to the IC substrate by a first contact in a first via at the bottom of the first bottom electrode conductive contact layer, and the second bottom electrode conductive contact layer is electrically connected to the IC substrate by a second contact in a second via through the first transparent dielectric bonding layer.

[0080]

[0080] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first bottom electrode conductive contact layer is transparent and the second bottom electrode conductive contact layer is transparent.

[0081]

[0081] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first LED structure includes a first light-emitting layer with a first side extending from one side of the first light-emitting layer, the second LED structure includes a second light-emitting layer with a second side extending from one side of the second light-emitting layer, and a third contact in a third via connects the first side and the second side to the upper electrode layer through a second transparent dielectric bonding layer.

[0082]

[0082] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, an optical isolation structure is formed around the micro-LED pixel unit.

[0083]

[0083] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the optical isolation structure is a reflective cup.

[0084]

[0084] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the lateral dimension of the first LED structure is the same as the lateral dimension of the second LED structure.

[0085]

[0085] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first LED structure and the second LED structure have the same central axis.

[0086]

[0086] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, a first reflective layer is formed on the bottom of the first LED structure and a second reflective layer is formed on the bottom of the second LED structure.

[0087]

[0087] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the thickness of the first reflective layer is 5 nm to 10 nm, the thickness of the second reflective layer is 5 nm to 10 nm, the thickness of the first LED structure is 300 nm or less, and the thickness of the second LED structure is 300 nm or less.

[0088]

[0088] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, a bonding metal layer is formed on the bottom of the first LED structure.

[0089]

[0089] Some exemplary embodiments are a micro-light LED pixel unit including a first color LED structure formed on an IC substrate, the first color LED structure including a first light emitting layer and a first reflective structure formed on an underside of the first light emitting layer, a first bonding metal layer formed on an underside of the first color LED structure and configured to bond the IC substrate and the first color LED structure, a second bonding metal layer formed on an upper side of the first color LED structure, and a second color LED structure formed on the second bonding metal layer, the second color LED structure including a second light emitting layer and a second reflective structure. The present invention provides a micro-light LED pixel unit, comprising: a second color LED structure formed under the second light-emitting layer; an upper electrode layer covering the first color LED structure and the second color LED structure and in electrical contact with the first color LED structure and the second color LED structure, the upper electrode layer being electrically connected to the IC substrate; and a reflective cup surrounding the first color LED structure and the second color LED structure, wherein horizontal light emitted from the first light-emitting layer and the second light-emitting layer reaches the reflective cup and is reflected upward by the reflective cup.

[0090]

[0090] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro LED pixel unit, the first reflective structure includes at least one first reflective layer, the second reflective structure includes at least one second reflective layer, and the reflectivity of the first reflective layer or the second reflective layer is greater than 60%.

[0091]

[0091] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the material of the first reflective layer or the second reflective layer includes one or more of Rh, Al, Ag, or Au.

[0092]

[0092] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the first reflective structure includes two first reflective layers, the reflectivities of the two first reflective layers are different, and the second reflective structure includes two second reflective layers, the reflectivities of the two second reflective layers are different.

[0093]

[0093] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the two first reflective layers include SiO2 and Ti3O5, respectively, and the two second reflective layers include SiO2 and Ti3O5, respectively.

[0094]

[0094] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, 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.

[0095]

[0095] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, 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.

[0096]

[0096] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first color LED structure further includes a first lower conductive contact layer and a first upper conductive contact layer, the second color LED structure further includes a second lower conductive contact layer and a second upper conductive contact layer, the first light emitting layer is between the first lower conductive contact layer and the first upper conductive contact layer, the second light emitting layer is between the second lower conductive contact layer and the second upper conductive contact layer, the first lower conductive contact layer is electrically connected to the IC substrate through the first reflective structure and electrically connected to the first bonding metal layer through the first contact via, the second lower conductive contact layer is electrically connected to the IC substrate through the second contact via, an edge of the first upper conductive contact layer contacts the upper electrode layer, and an upper surface of the second upper conductive contact layer contacts the upper electrode layer.

[0097]

[0097] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the material of the reflective cup includes a metal.

[0098]

[0098] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, a micro-lens is formed on the top electrode layer.

[0099]

[0101] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, a spacer is formed between the micro-lens and the top electrode layer.

[0100]

[0100] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the material of the spacer includes silicon oxide.

[0101]

[0101] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the lateral dimensions of the micro-lens are larger than the lateral dimensions of the active light-emitting area of ​​the first LED structure, and the lateral dimensions of the micro-lens are larger than the lateral dimensions of the active light-emitting area of ​​the second LED structure.

[0102]

[0102] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the first color LED structure and the second color LED structure have the same lateral dimension.

[0103]

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

[0104]

[0104] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro LED pixel unit, the thickness of the at least one first reflective layer is in the range of 5 nm to 10 nm, the thickness of the at least one second reflective layer is in the range of 5 nm to 10 nm, the thickness of the first color LED structure is 300 nm or less, and the thickness of the second color LED structure is 300 nm or less.

[0105]

[0105] Some exemplary embodiments provide a micro-LED pixel unit including an IC substrate, a light-emitting region formed on the IC substrate and including a plurality of color LED structures, a lower portion of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light-emitting region, each of the plurality of color LED structures including a light-emitting layer and a reflective structure at a lower portion of the light-emitting layer, an upper electrode layer covering each of the plurality of color LED structures and in electrical contact with each of the plurality of color LED structures, the IC substrate being electrically connected to each of the plurality of color LED structures, and a stepped reflective cup forming a cavity and surrounding the light-emitting region, wherein light emitted horizontally from a sidewall of the light-emitting layer of each of the plurality of color LED structures reaches the reflective cup and is reflected upward by the reflective cup.

[0106]

[0106] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the inner sidewall of the cavity includes a plurality of sloping surfaces.

[0107]

[0107] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the angle of the multiple inclined surfaces with respect to the surface of the IC substrate decreases from the bottom to the top of the cavity.

[0108]

[0108] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the sub-cavities formed by the multiple inclined surfaces have different dimensions in the horizontal direction.

[0109]

[0109] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the inner sidewalls of the sub-cavities are not disposed in the same plane.

[0110]

[0110] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the heights of the sub-cavities are different.

[0111]

[0111] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the height of the sub-cavity in the middle of the cavity is less than the height of the other sub-cavities.

[0112]

[0112] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the height of the sub-cavity at the top of the cavity is greater than the height of the sub-cavity at the bottom of the cavity.

[0113]

[0113] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the multiple color LED structure further includes a top color LED structure.

[0114]

[0114] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the top of the cavity is higher than the top of the upper color LED structure.

[0115]

[0115] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the cavity includes a plurality of sub-cavities, and each of the plurality of color LED structures is within a respective different one of the sub-cavities.

[0116]

[0116] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, a transparent dielectric bonding layer covers at least one of the multiple color LED structures, and the transparent dielectric bonding layer comprises a solid inorganic material or a plastic material.

[0117]

[0117] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the solid inorganic material includes one or more materials selected from the group consisting of SiO2, Al2O3, Si3N4, phosphosilicate glass (PSG), and boron phosphosilicate glass (BPSG).

[0118]

[0118] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the plastic material includes one or more polymers selected from the group consisting of SU-8, PermiNex, benzocyclobutene (BCB), and spin-on glass (SOG).

[0119]

[0119] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, each of the multiple color LED structures includes a lower conductive contact layer and an upper conductive contact layer, an emitting layer is formed between the lower conductive contact layer and the upper conductive contact layer, the lower conductive contact layer is electrically connected to the IC substrate through the reflective structure and electrically connected to the corresponding bonding metal layer through the contact via, an upper surface of the upper conductive contact layer of the upper color LED structure contacts the upper electrode layer, and an edge of the upper conductive contact layer of the color LED structure below the upper color LED structure contacts the upper electrode layer.

[0120]

[0120] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro LED pixel unit, an extension extends from one side of the light emitting layer of the color LED structure below the upper color LED structure, and a contact via connects the extension to the upper electrode layer.

[0121]

[0121] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the lateral dimension of the micro-lens is larger than the light-emitting dimension of each of the multiple color LED structures.

[0122]

[0122] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the multiple color LED structures have the same central axis.

[0123]

[0123] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro LED pixel unit, the reflective structure includes a reflective layer, the thickness of the reflective layer is in the range of 5 nm to 10 nm, and the thickness of each of the multiple color LED structures is 300 nm or less.

[0124]

[0124] In some exemplary embodiments or any combination of the above exemplary embodiments of the micro-LED pixel unit, the material of the upper electrode layer is selected from the group consisting of graphene, indium tin oxide (ITO), aluminum doped zinc oxide (AZO), or fluorine doped tin oxide (FTO).

[0125]

[0125] Some exemplary embodiments provide a micro-LED pixel unit including a semiconductor substrate, a light-emitting region formed on the semiconductor substrate and including a plurality of color LED structures, a lower portion of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light-emitting region, each of the plurality of color LED structures including a light-emitting layer and a reflective structure at a lower portion of the light-emitting layer, an upper electrode layer covering each of the plurality of color LED structures and in electrical contact with each of the plurality of color LED structures, the semiconductor substrate being 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.

[0126]

[0126] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, a micro-lens is formed on the top surface of the refractive structure.

[0127]

[0127] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the lateral dimension of the micro-lens is greater than or equal to the lateral dimension of the light-emitting area.

[0128]

[0128] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the reflector cup has an upper opening area, and the lateral dimension of the micro-lens is less than the lateral dimension of the upper opening area.

[0129]

[0129] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, a bottom dielectric layer is formed between the reflective cup and the semiconductor substrate.

[0130]

[0130] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the micro-LED pixel unit further includes an upper conductive layer formed on the top of the light-emitting area, the upper conductive layer being electrically connected to the reflective cup.

[0131]

[0131] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the top conductive layer is in direct contact with the top of the reflective cup and the bottom of the reflective cup.

[0132]

[0132] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the top of the refractive structure is higher than the top of the reflective cup.

[0133]

[0133] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the semiconductor substrate is an IC substrate.

[0134]

[0134] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the reflector cup is a stepped reflector cup that forms a cavity surrounding the light-emitting area.

[0135]

[0135] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the sub-cavities formed by the multiple inclined surfaces have different dimensions in the horizontal direction.

[0136]

[0136] In some exemplary embodiments or any combination of the preceding exemplary embodiments of the micro-LED pixel unit, each of the plurality of color LED structures includes an extension extending from one side of each of the color LED structures, each of the extensions being electrically connected to the upper electrode layer via a respective first contact via, and a lower portion of each of the plurality of color LED structures being electrically connected to the semiconductor substrate via a respective second contact via.

[0137]

[0137] Some exemplary embodiments provide a micro-LED pixel unit including a semiconductor substrate; a light-emitting region formed on the semiconductor substrate and including a plurality of color LED structures, a lower portion of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light-emitting region, each of the plurality of color LED structures including a light-emitting layer and a reflective structure at a lower portion of the light-emitting layer; an upper electrode layer covering each of the plurality of color LED structures and in electrical contact with each of the plurality of color LED structures, the semiconductor substrate being electrically connected to each of the plurality of color LED structures; and a reflective cup surrounding the light-emitting region, wherein light emitted horizontally from a sidewall of the light-emitting layer of each of the plurality of color LED structures reaches the reflective cup and is reflected upward by the reflective cup, the upper portion of the reflective cup being higher than the upper portion of the light-emitting region.

[0138]

[0138] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, a micro-lens is formed above the light-emitting area.

[0139]

[0139] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the top of the reflective cup is higher than the top of the micro-lens.

[0140]

[0140] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, a refractive structure is formed at the bottom of the micro-lens, between the reflective cup and the light-emitting area.

[0141]

[0141] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the bottom of the light-emitting region is electrically connected with the semiconductor substrate.

[0142]

[0142] Some exemplary embodiments provide a micro-LED pixel unit including a semiconductor substrate; a light-emitting region formed on the semiconductor substrate and including a plurality of color LED structures, a lower portion of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light-emitting region, each of the plurality of color LED structures including a light-emitting layer and a reflective structure at a lower portion of the light-emitting layer; an upper electrode layer covering each of the plurality of color LED structures and in electrical contact with each of the plurality of color LED structures, the semiconductor substrate being electrically connected to each of the plurality of color LED structures; and a floating reflective cup surrounding the light-emitting region, a lower portion of the floating reflective cup being on the semiconductor substrate, light emitted horizontally from a sidewall of the light-emitting layer of each of the plurality of color LED structures reaching the suspended floating reflective cup and being reflected upward by the floating reflective cup.

[0143]

[0143] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the bottom of the floating reflector cup is higher than the top surface of the corresponding bonding metal layer under one of the multiple color LED structures.

[0144]

[0144] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the floating reflector cup is stepped.

[0145]

[0145] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the top of the floating reflector cup is higher than the top of the micro-lens.

[0146]

[0146] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, a refractive structure is formed at the bottom of the micro-lens, between the floating reflector cup and the light-emitting area.

[0147]

[0147] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the floating reflector cup has an upper opening area, and the lateral dimension of the micro-lens is less than the lateral dimension of the upper opening area.

[0148]

[0148] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, a bottom dielectric layer is formed between the floating reflector cup and the semiconductor substrate.

[0149]

[0149] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the top conductive layer directly contacts the top of the floating reflector cup or the bottom of the floating reflector cup.

[0150]

[0150] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the stepped floating reflector cup forms a cavity surrounding the light emitting area.

[0151]

[0151] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the material of the floating reflector cup includes a metal.

[0152]

[0152] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the reflective structures include a reflective layer formed underneath each of the multiple color LED structures, respectively.

[0153]

[0153] In some exemplary embodiments or any combination of the previous exemplary embodiments of the micro-LED pixel unit, the thickness of the reflective layer is in the range of 5 nm to 10 nm, and the thickness of each of the multiple color LED structures is 300 nm or less.

[0154]

[0154] The compact design of the multi-color LED device and system disclosed herein utilizes the lateral overlap of the light-emitting LED structure, thereby improving the luminous efficiency, resolution, and overall performance of the LED display system. Furthermore, the fabrication of the multi-color LED display system can reliably and efficiently form the LED structure pattern without using or holding an additional substrate. In some cases, the design of the display device and system disclosed herein utilizes the direct formation of the microlenses on top of the multi-color LED device on the substrate by utilizing the conformity of the shape of the microlens material to the shape of the multi-color LED device, thereby greatly reducing the microlens fabrication steps and improving the efficiency of the display panel structure formation. The reduction of the viewing angle and the reduction of the light interference improve the luminous efficiency, resolution, and overall performance of the display system. Thus, the implementation of the multi-color LED display system can meet the stringent display requirements of AR and VR, HUD, mobile device display, wearable device display, high-definition miniature projector, and automotive display, compared to the use of traditional LEDs.

[0155]

[0155] It should be noted that the various embodiments described above can be combined with any other embodiments described herein. The features and advantages described herein are not all-inclusive, and many additional features and advantages will be apparent to those skilled in the art in view of the drawings, the specification, and the claims. Furthermore, it should be noted that the terms used in this specification are primarily selected for ease of reading and instructional purposes, and may not be selected to delineate or limit the scope of the present invention.

[0156] BRIEF DESCRIPTION OF THE DRAWINGS

[0156] In order that the present disclosure may be understood in more detail, a more particular description may be made by referring to the features of various embodiments, some of which are illustrated in the accompanying drawings. However, the accompanying drawings merely illustrate the relevant features of the present disclosure and should therefore be considered as illustrative rather than limiting, and other useful features may be recognized. [Brief description of the drawings]

[0157] [Figure 1A]

[0157] FIG. 1 is a top view of a single pixel tri-color LED device 100 according to some embodiments. [Figure 1B]

[0158] 1B is a cross-sectional view of a single pixel tri-color LED device 100 along diagonal 102 of FIG. 1A according to some embodiments. [Figure 1C]

[0159] 1B is a cross-sectional view of a single pixel tri-color LED device 100 along diagonal 150 of FIG. 1A according to some embodiments. [Figure 2A]

[0160] 1B is a cross-sectional view of a single pixel tri-color LED device 100 along a diagonal 102 of FIG. 1A with planarization according to some embodiments. [Figure 2B]

[0161] 1B is a cross-sectional view of a single pixel tri-color LED device 100 along the diagonal 150 of FIG. 1A with planarization according to some embodiments. [Figure 3A]

[0162] 1B is a cross-sectional view of a single pixel tri-color LED device 100 with planarization along diagonal 102 of FIG. 1A with planarization according to some embodiments. [Figure 3B]

[0163] 1B is a cross-sectional view of a single pixel tri-color LED device 100 along the diagonal 150 of FIG. 1A with planarization according to some embodiments. [Figure 4A]

[0164] FIG. 4 is a top view of a single pixel tri-color LED device 400 with layered planarization according to some embodiments. [Figure 4B]

[0165] 4B is a cross-sectional view of a single pixel tri-color LED device 400 along diagonal 402 of FIG. 4A with layered planarization according to some embodiments. [Diagram 5]

[0166] 1B is a cross-sectional view of a single pixel tri-color LED device 500 along the diagonal 102 of FIG. 1A with a refractive structure according to some embodiments. [Figure 6A]

[0167] 1B is a cross-sectional view of a single pixel tri-color LED device 600 along diagonal 102 of FIG. 1A with a microlens over a reflective structure according to some embodiments. [Figure 6B]

[0168] 1B is a cross-sectional view of a single pixel tri-color LED device 600 along diagonal 102 of FIG. 1A with microlenses in the area formed by the reflective structure according to some embodiments. [Figure 6C]

[0169] 1 illustrates a fabrication method for forming a display panel integrated with a microlens array using top-down pattern transfer according to some embodiments. [Figure 6D]

[0170] 1 illustrates a fabrication method for forming a display panel integrated with a microlens array using top-down pattern transfer according to some embodiments. [Figure 7]

[0171] 1A is a cross-sectional view 700 of three single pixel tri-color LED devices 710, 720, and 730 along a diagonal such as 102 in FIG. 1A on a substrate 104 according to some embodiments. [Figure 8]

[0172] 8 is a cross-sectional view of a single pixel tri-color LED device 800 with a stepped reflector cup taken along a diagonal such as 402 in FIG. 4A according to some embodiments. [Figure 9]

[0173] FIG. 4B is a cross-sectional view of a single pixel tri-color LED device 900 with a floating reflector cup taken along a diagonal such as 402 in FIG. 4A according to some embodiments. [Figure 10A]

[0174] FIG. 10 is a circuit diagram illustrating a matrix of single pixel tri-color LED devices 1000 according to some embodiments. [Figure 10B]

[0175] FIG. 10 is a circuit diagram illustrating a matrix of single pixel tri-color LED devices 1000 according to some embodiments. [Figure 11]

[0176] FIG. 11 is a top view of a micro-LED display panel 1100 according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0158]

[0177] According to common practice, the various features illustrated in the figures are not drawn to scale. Thus, dimensions of the various features may be arbitrarily expanded or reduced for clarity. In addition, some of the figures may not depict all of the components of a given system, method, or device. Finally, like reference numerals may be used to denote like features throughout the specification and figures.

[0159] Detailed Description

[0178] Numerous details are described herein to provide a thorough understanding of the example embodiments illustrated in the accompanying drawings. However, some embodiments may be practiced without many of the specific details, and the claims are limited only by the features and aspects specifically recited in the claims. Moreover, well-known processes, components, and materials have not been described in extensive detail so as not to unnecessarily obscure relevant aspects of the embodiments described herein.

[0160]

[0179] In some embodiments, the single pixel multicolor LED device includes two or more LED structures. In some embodiments, each of the LED structures includes at least one LED light emitting layer that emits a distinct color. When two LED structures are in the single pixel multicolor LED device, two colors and combinations of the two colors can be emitted from the single pixel multicolor LED device. When three LED structures are in the single pixel multicolor LED device, three colors and combinations of the three colors can be emitted from the single pixel multicolor LED device.

[0161]

[0180] In some embodiments, the light emitted from the single pixel multicolor LED device is emitted from the sidewalls of each of the LED structures in the single pixel multicolor LED device. In some embodiments, a reflecting structure is positioned to surround the single pixel multicolor LED device and directs the light from the sidewalls of each of the LED structures upward. In some embodiments, the light emitted from the single pixel multicolor LED device is emitted from the top surface of each of the LED structures in the single pixel multicolor LED device. In some embodiments, the light emitted from the single pixel multicolor LED device is emitted from a combination of the sidewalls and the top surface of each of the LED structures in the single pixel multicolor LED device in a specific ratio, for example, where the light from the sidewalls accounts for about 20% to 100% of the light from the single pixel multicolor LED device.

[0162]

[0181] FIG. 1A is a top view of a single pixel tri-color LED device 100 according to some embodiments.

[0163]

[0182] FIG. 1B is a cross-sectional view of a single pixel tri-color LED device 100 along diagonal 102 of FIG. 1A according to some embodiments.

[0164]

[0183] FIG. 1C is a cross-sectional view of a single pixel tri-color LED device 100 along diagonal 150 of FIG. 1A according to some embodiments.

[0165]

[0184] Each of the diagonals 102 and 150 passes through the center of the single pixel tri-color LED device 100. The 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" means away from the substrate 104, and "down" means toward the substrate 104, and other directional terms such as above, below, above, below, below, below, etc. are interpreted accordingly. The support substrate 104 is a substrate on which an array of individual drive circuits 106 is fabricated. In some embodiments, the drive circuits may be located on the substrate 104 or in one of the layers above the miniature tri-color LED structure 100. Each drive circuit is a pixel drive circuit 106. In some cases, the drive circuits 106 are thin film transistor pixel drive circuits or silicon CMOS pixel drive circuits. 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. Other example substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. The drive circuits 106 form individual pixel drive circuits that control the operation of the individual single pixel tri-color LED devices 100. The circuitry on the substrate 104 includes contacts to each individual drive circuit 106, as well as a ground contact. As shown in both Figures 1A, 1B, and 1C, each miniature tri-color LED structure 100 also has two types of contacts: a P-electrode or anode, such as 108, 126, 152, which is connected to the pixel drive circuit 106, and an N-electrode or cathode, such as 116, 120, and 140, which is connected to ground (i.e., common electrode).

[0166]

[0185] In some embodiments, the N-electrodes (or N-electrode contact pads) such as 116, 120, and 140 and their connections are made of a material such as graphene, ITO, aluminum doped zinc oxide (AZO), fluorine doped tin oxide (FTO), or any combination thereof. In some embodiments, the N-electrodes (or N-electrode contact pads) such as 116, 120, and 140 and their connections are made of a non-transparent or transparent conductive material, and in preferred embodiments, a transparent conductive material. In some embodiments, the P-electrodes (or P-electrode contact pads) such as 126, 152 and their connections are made of a material such as graphene, ITO, AZO, FTO, or any combination thereof. In some embodiments, the P-electrodes (or P-electrode contact pads) such as 126, 152 and their connections are made of a non-transparent or transparent conductive material, and in preferred embodiments, a transparent conductive material. In some embodiments, the locations of the P electrode (or P electrode contact pad) and its connections and the N electrode (or N electrode contact pad) and its connections may be swapped.

[0167]

[0186] Although some features are described herein using the term "layer," it should be understood that such features are not limited to one layer, but may include multiple sublayers. In some cases, a "structure" may take the form of a "layer."

[0168]

[0187] In some embodiments, the three LED structures including LED light-emitting layers 112, 130, and 136 are each formed in a stacked structure, for example, green LED light-emitting layer 130 is formed on red LED light-emitting layer 112, and blue LED light-emitting layer 136 is formed on green LED light-emitting layer 130.

[0169]

[0188] Generally, an LED light emitting layer includes a PN junction having a p-type region / layer and an n-type region / layer, and an active layer between the p-type region / layer and the n-type region / layer.

[0170]

[0189] 1A and 1B, the area of ​​the bottom red LED light-emitting layer 112 is larger than the area of ​​the middle green LED light-emitting layer 130. In some embodiments, the area of ​​the middle green LED light-emitting layer 130 is larger than the area of ​​the top blue LED light-emitting layer 136.

[0171]

[0190] In some embodiments, the light emitted from the red LED light emitting layer 112 may propagate horizontally towards the sidewalls of the red LED light emitting layer 112 and then is reflected upward by reflective elements such as 146 and / or 148 as described below and emitted from the top surface of the single pixel tri-color LED device 100. As described below, a reflective layer 109 is positioned below the red LED light emitting layer 112 and a reflective layer 115 is positioned above the red LED light emitting layer 112. The light emitted from the red LED light emitting layer 112 is reflected between the two reflective layers 109 and 115 towards the sidewalls of the red LED light emitting layer 112.

[0172]

[0191] In some embodiments, the light emitted from the green LED light-emitting layer 130 may propagate horizontally towards the sidewalls of the green LED light-emitting layer 130 and then is reflected upward by reflective elements such as 146 and / or 148 as described below and emitted from the top surface of the single pixel tri-color LED device 100. As described below, a reflective layer 127 is positioned below the green LED light-emitting layer 130 and a reflective layer 133 is positioned above the green LED light-emitting layer 130. The light emitted from the green LED light-emitting layer 130 is reflected between the two reflective layers 127 and 133 towards the sidewalls of the green LED light-emitting layer 130.

[0173]

[0192] In some embodiments, light emitted from blue LED light emitting layer 136 may propagate horizontally toward the sidewalls of blue LED light emitting layer 136 and then be reflected upward by reflective elements such as 146 and / or 148 as described below and emitted from the top surface of single pixel tri-color LED device 100. As described below, a reflective layer 135 is positioned below blue LED light emitting layer 136. Light emitted from blue LED light emitting layer 136 is reflected between reflective layer 135 and the top surface of blue LED light emitting layer 136 toward the sidewalls of blue LED light emitting layer 136.

[0174]

[0193] In some embodiments, light emitted from red LED light emitting layer 112 may propagate vertically through green LED light emitting layer 130 and then blue LED light emitting layer 136 and is emitted from the tri-color LED device 100. In some embodiments, light emitted from green LED light emitting layer 130 may propagate through blue LED light emitting layer 136 and is emitted from the tri-color LED device 100. For vertical light transmission, in some embodiments, a top reflective layer above each light emitting layer such as 115 and 133 is preferably not included in the tri-color LED device 100.

[0175]

[0194] In some embodiments, LED light emitting layers such as 112, 130, and 136 include many epitaxial sublayers 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.

[0176]

[0195] In some embodiments, each of the stacked LED structures can be individually controlled to generate its individual light. In some embodiments, the combined light of the top LED epitaxial layer resulting from the operation of all the LED epitaxial layers in the tri-color LED device 100 can change the color of one pixel on a display panel within a small footprint.

[0177]

[0196] In some embodiments, depending on the design of the LED device 100, the colors emitted by the LED structures included in the same device are not limited to red, green, and blue. For example, suitable colors can be selected from a range of different colors in the visible color range from 380 nm to 700 nm wavelength. In some embodiments, LED structures can be implemented that emit other colors from the non-visible range, such as ultraviolet and infrared.

[0178]

[0197] In some embodiments, when vertical light emission is combined with horizontal light emission, for example, the three color selection can be red, green, and blue from bottom to top. In another embodiment, the three color selection can be infrared, orange, and ultraviolet from bottom to top. In some embodiments, the wavelength of light from the LED structures on one layer of the device 100 is longer than the LED structures on the layer above the current layer. For example, the wavelength of light from the bottom LED light emitting layer 112 is longer than the wavelength of light from the middle LED light emitting layer 130, which is longer than the wavelength of light from the top LED light emitting layer 136.

[0179]

[0198] In some embodiments, in the case of horizontal light emission or when the portion of horizontal light emission is greater than the portion of vertical light emission 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 the emitted light does not need to pass through other upper layers of the LED device 100, but directly exits from the edge or sidewall of the current light-emitting layer, so that lower light transmission loss and higher light emission efficiency can be achieved. For example, compared to a vertical light-emitting LED device, a horizontal light-emitting LED device may obtain a light transmission efficiency of 15%, 50%, 100%, 150%, or 200%. In some cases, the light transmission efficiency from a horizontal light-emitting LED device can be 20%, 40%, or 60% or more.

[0180]

[0199] In some embodiments, the lower red LED light emitting layer 112 is bonded to the substrate 104 through the metal bonding layer 108. The metal bonding layer 108 may be disposed on the substrate 104. In one approach, the metal bonding layer 108 is grown on the substrate 104. In some embodiments, the metal bonding layer 108 is electrically connected to both the driving circuitry 106 on the substrate 104 and the red LED light emitting layer 112 on the metal bonding layer 108, and acts as a P electrode. In some embodiments, the thickness of the metal bonding layer 108 is about 0.1 μm to about 3 μm. In a preferred embodiment, the thickness of the metal bonding layer 108 is about 0.3 μm. The metal bonding layer 108 may include an ohmic contact layer and a metal bonding layer. In some cases, two metal layers are included in the metal bonding layer 108. One of the metal layers is deposited on a layer above the metal bonding layer in the LED device 100. The other bonding metal layer is also deposited on the substrate 104. In some embodiments, the composition of the metal bonding layer 108 includes Au-Au bonding, Au-Sn bonding, Au-In bonding, Ti-Ti bonding, Cu-Cu bonding, or a mixture thereof. For example, if Au-Au bonding is selected, two layers of Au each require a Cr coating as an adhesion layer and a Pt coating as an anti-diffusion layer. And the Pt coating is between the Au layer and the Cr layer. The Cr layer and the Pt layer are positioned on the top and bottom of the two bonded Au layers. In some embodiments, if the thickness of the two Au layers is approximately the same, the interdiffusion of Au on both layers will bond the two layers together under high pressure and high temperature. Eutectic bonding, thermocompression bonding, and transient liquid phase (TLP) bonding are examples of techniques that may be used.

[0181]

[0200] In some embodiments, the metal bonding layer 108 can also be used as a reflector to reflect light emitted from the LED structure above.

[0182]

[0201] In some embodiments, a conductive layer 110 for electrode connection is formed under the red LED light emitting layer 112. In some embodiments, the conductive layer 110 can be a non-transparent metal layer that does not transmit the light emitted from the LED device 100. In some embodiments, the conductive layer 110 is a conductive transparent layer that transmits the light emitted from the LED device 100, such as an indium tin oxide (ITO) layer formed between the red LED light emitting layer 112 and the metal bonding layer 108 to improve electrical conductivity and transparency.

[0183]

[0202] In some embodiments not shown in FIGS. 1A-1C, the red LED structure has a P electrode contact pad 168 electrically connected to the red LED light emitting layer 112. In some embodiments, the P electrode contact pad 168 is connected to the conductive layer 110. In some embodiments, a conductive layer 114 for electrode connection is formed on the red LED light emitting layer 112. In some embodiments, the conductive layer 114 can be a metal layer or a conductive transparent layer such as an ITO layer formed between the red LED light emitting layer 112 and the N electrode contact pad 116 as shown in FIG. 1C to improve conductivity and transparency. In some embodiments, the N electrode contact pad such as 116 is made of a material such as graphene, ITO, AZO, FTO, or any combination thereof.

[0184]

[0203] In some embodiments, reflective layer 109 is positioned below red LED light emitting layer 112 between conductive layer 110 and metal bonding layer 108, and reflective layer 115 is positioned above red LED light emitting layer 112 between conductive layer 114 and bonding layer 156.

[0185]

[0204] 1C , on one side of the red LED light emitting layer 112. 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 below the red LED light emitting layer 112 and the metal bonding layer 108. 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 above the extension 164.

[0186]

[0205] In one approach, the red LED light emitting layer 112 is grown on a separate substrate (called an epitaxial substrate). Then, after bonding, the epitaxial substrate is removed, for example, by a laser lift-off process or chemical wet etching, leaving the structure shown in Figures 1B and 1C.

[0187]

[0206] In some embodiments, the red LED light emitting layer 112 is for forming 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 thin films in 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 and the N-type layers are typically Si doped. In some examples, the thickness of the red LED light emitting layer is about 0.1 μm to about 5 μm. In a preferred embodiment, the thickness of the red LED light emitting layer is about 0.3 μm.

[0188]

[0207] In some embodiments, the red LED structure includes a metal bonding layer 108 , a reflective layer 109 , a conductive layer 110 , a red LED light emitting layer 112 , a conductive layer 114 , a reflective layer 115 , and an N-electrode contact pad 116 .

[0189]

[0208] In some embodiments, a bonding layer 156 is used to bond the red and green LED structures together. In some embodiments, the bonding layer 156 is opaque to the light emitted from the LED device 100. In some embodiments, the material and thickness of the bonding layer 156 is the same as that described above for the metal bonding layer 108. In some embodiments, the bonding layer 156 can also be used as a reflector to reflect light emitted from the LED structure above.

[0190]

[0209] In some embodiments, when vertical transmission is used, the bonding layer 156 transmits the light emitted from the micro-LED 100. In some embodiments, the bonding layer 156 is made of a dielectric material, such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, phosphosilicate glass (PSG), boron phosphosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes a polymer, such as SU-8, PermiNex, benzocyclobutene (BCB), transparent plastics (resins) including spin-on glass (SOG), bonding adhesive Micro Resist BCL-1200, or any combination thereof. In some embodiments, the transparent bonding layer can facilitate the transmission of light emitted from the layer below the bonding layer.

[0191]

[0210] In some embodiments, as shown in both Figures 1A and 1B, 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 under the green LED light emitting layer 130. In some embodiments, the conductive layer 128 can be a metal layer or a conductive transparent layer such as an ITO layer formed between the green LED light emitting layer 130 and the P electrode contact pad 126 to improve conductivity and transparency, as shown in Figures 1A and 1B.

[0192]

[0211] 1B, the conductive layer 128 has an extension 128-1 on one side of the conductive layer 128 relative to the layers above. In some embodiments, the extension 128-1 extends with all layers below the conductive layer 128 in the LED device 100. In some embodiments, the green LED light-emitting layer 130 is electrically connected to the P electrode contact pad 126 through the extension 128-1 of the conductive layer 128. In some embodiments, the P electrode contact pad 126 is also electrically connected to the drive circuitry 106 of the substrate 104.

[0193]

[0212] 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. The P electrode contact pad 126 extends from the contact with the drive circuit 106 through a via or passage in the insulating layer 174 to the contact with the conductive layer 128. The P electrode contact pad 126 does not contact any other layers in the LED device 100.

[0194]

[0213] 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 metal layer or a conductive transparent layer such as an ITO layer formed between the green LED light-emitting layer 130 and the N-electrode contact pad 120 to improve conductivity and transparency. 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, FTO, or any combination thereof.

[0195]

[0214] 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 to the conductive layer 132. In some embodiments, the N-electrode contact pad 120 of the green LED structure is also electrically connected to the N-electrode contact pad 116 of the red LED structure.

[0196]

[0215] 1C , in some embodiments, green LED light-emitting layer 130 has an extension 166 on one side of green LED light-emitting layer 130. In some embodiments, extension 166 extends with conductive layers 128 and 132 and all other layers below conductive layer 128. In some embodiments, extension 166 is electrically connected to N-electrode contact pad 120 through an extension of conductive layer 132 above extension 166.

[0197]

[0216] In some embodiments, the lateral dimensions of green LED light emitting layer 130 are smaller than the lateral dimensions of red LED light emitting layer 112 .

[0198]

[0217] In some embodiments, reflective layer 127 is positioned below green LED light-emitting layer 130 between conductive layer 128 and bonding layer 156, and reflective layer 133 is positioned above green LED light-emitting layer 130 between conductive layer 132 and bonding layer 160.

[0199]

[0218] In one approach, the green LED light emitting layer 130 is grown on a separate substrate (called an epitaxial substrate). Then, after bonding, the epitaxial substrate is removed, for example, by a laser lift-off process or chemical wet etching, leaving the structure shown in Figures 1B and 1C.

[0200]

[0219] In some embodiments, the green LED light emitting layer 130 is for forming 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 thin film in the green LED light emitting layer 130 can include a layer of P-type GaN / InGaN light emitting layer / N-type GaN. In some embodiments, the P-type is typically Mg doped, and the N-type is typically Si doped. In some examples, the thickness of the green LED light emitting layer is about 0.1 μm to about 5 μm. In a preferred embodiment, the thickness of the green LED light emitting layer is about 0.3 μm.

[0201]

[0220] In some embodiments, the green LED structure includes a reflective layer 127 , a conductive layer 128 , a green LED light emitting layer 130 , a conductive layer 132 , a reflective layer 133 , a P electrode contact pad 126 , and an N electrode contact pad 120 .

[0202]

[0221] In some embodiments, the first LED structure, e.g., a red LED structure, and the second LED structure, e.g., a green LED structure, have the same central axis when extensions such as 164, 166, and portion 128-1 under conductive layer 128 are excluded. In some embodiments, the first LED structure and the second LED structure are aligned along the same central axis when extensions such as 164, 166, and portion 128-1 under conductive layer 128 are excluded.

[0203]

[0222] In some embodiments, a bonding layer 160 is used to bond the green and blue LED structures together. In some embodiments, the bonding layer 156 is opaque to the light emitted from the LED device 100. In some embodiments, the material and thickness of the bonding layer 160 is the same as that described above for the metal bonding layer 108. In some embodiments, the bonding layer 160 can also be used as a reflector to reflect light emitted from the LED structure above.

[0204]

[0223] In some embodiments, when vertical transmission is used, bonding layer 160 transmits light emitted from LED device 100. In some embodiments, bonding layer 160 is made of a dielectric material, such as the same solid inorganic or plastic materials described above for bonding layer 156. In some embodiments, a transparent bonding layer can facilitate the transmission of light emitted from layers below the bonding layer.

[0205]

[0224] In some embodiments, as shown in both Figures 1A and 1B, the blue LED structure has a P electrode contact pad 152 electrically connected to the blue LED light emitting layer 136. In some embodiments, the P electrode contact pad 152 is connected to the conductive layer 134. In some embodiments, the conductive layer 134 for electrode connection is formed under the blue LED light emitting layer 136. In some embodiments, the conductive layer 134 can be a metal layer or a conductive transparent layer such as an ITO layer formed between the blue LED light emitting layer 136 and the P electrode contact pad 152 to improve conductivity and transparency, as shown in Figures 1A and 1B.

[0206]

[0225] 1B, the conductive layer 134 has an extension 134-1 on one side of the conductive layer 134 relative to the layers above. In some embodiments, the extension 134-1 extends with all layers below the conductive layer 134 in 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 drive circuitry 106 of the substrate 104.

[0207]

[0226] 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. The P electrode contact pad 152 extends from the contact with the drive circuit 106 through a via or passage in the insulating layer 174 to the contact with the conductive layer 134. The P electrode contact pad 152 does not contact any other layers in the LED device 100.

[0208]

[0227] 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 can be a conductive transparent layer, such as a metal layer or an ITO layer, formed between the blue LED light emitting layer 136 and the N-electrode contact pad 140 to improve conductivity and transparency. 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, 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 integrally formed as a common N-electrode.

[0209]

[0228] 1B, 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.

[0210]

[0229] In some embodiments, the lateral dimensions of blue LED light emitting layer 136 are smaller than the lateral dimensions of green LED light emitting layer 130 .

[0211]

[0230] In some embodiments, the top electrode elements, such as N-electrode pad 140, are connected through electrical connections underneath the optical isolation structures, such as 146, 148, 170, and 172. In some embodiments, the top electrodes are connected through electrical connections built into the substrate 104. In one example, the top electrode 140 is connected through electrical connection elements, such as 146, 148, 170, and 172, that are on top of the insulating layer 174 and underneath the optical isolation structures.

[0212]

[0231] In some embodiments, a reflective layer 135 is positioned below blue LED light emitting layer 136, between conductive layer 134 and bonding layer 160. In some embodiments, an optional reflective layer 139 (not shown in FIGS. 1A-1C ) is positioned on top of conductive layer 138 and above blue LED light emitting layer 136.

[0213]

[0232] In one approach, the blue LED light emitting layer 136 is grown on a separate substrate (called an epitaxial substrate). Then, after bonding, the epitaxial substrate is removed, for example, by a laser lift-off process or chemical wet etching, leaving the structure shown in Figures 1B and 1C.

[0214]

[0233] In some embodiments, the blue LED light emitting layer 136 is for forming 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 thin film in the blue LED light emitting layer 136 can include a layer of P-type GaN / InGaN light emitting layer / N-type GaN. In some embodiments, the P-type is typically Mg doped and the N-type is typically Si doped. In some examples, the thickness of the blue LED light emitting layer is about 0.1 μm to about 5 μm. In a preferred embodiment, the thickness of the blue LED light emitting layer is about 0.3 μm.

[0215]

[0234] 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 .

[0216]

[0235] 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 when extensions such as 166 and portion 134-1 below the conductive layer 134 are excluded. In some embodiments, the first LED structure and the second LED structure are aligned along the same central axis when extensions such as 166 and portion 134-1 below the conductive layer 134 are excluded.

[0217]

[0236] In some embodiments, the N-electrode 140 covers the top of the tri-color LED device 100. In some embodiments, the N-electrode 140 connects to the N-electrode of an adjacent tri-color LED device (not shown in FIGS. 1A-1C) through some electrical connection components, and thus functions as a common electrode.

[0218]

[0237] In some embodiments, each of the conductive layers 110, 114, 128, 132, 134, and 138 has a thickness of about 0.01 μm to about 1 μm. In some cases, each of the conductive layers 110, 114, 128, 132, 134, and 138 is commonly deposited on each corresponding epitaxial layer by evaporation, such as electron beam evaporation or sputtering deposition, prior to any bonding process with the next epitaxial layer. In some examples, the conductive layers are used to maintain good electrical conductivity for electrode connections while in some cases improving the optical properties of the LED device, such as reflectivity or transparency.

[0219]

[0238] In some embodiments, an additional dielectric layer such as a SiO2 layer (not shown in FIGS. 1A-1C) is formed on the lower light emitting layer 112 (and on the conductive layer 114), preferably on the reflective layer 115 and below the bonding layer 156, to electrically isolate the N-type layer of the light emitting layer 112 from the bonding layer 156. In some embodiments, the thickness of the additional dielectric layer is 20 nm to 2 μm. In a preferred embodiment, the thickness of the additional dielectric layer is about 100 nm. In some embodiments, an additional dielectric layer such as a SiO2 layer (not shown in FIGS. 1A-1C) is formed on the middle light emitting layer 130 (and on the conductive layer 132), preferably on the reflective layer 133 and below the bonding layer 160, to electrically isolate the N-type layer of the light emitting layer 130 from the bonding layer 160. In some embodiments, the thickness of the additional dielectric layer is 20 nm to 2 μm. In a preferred embodiment, the thickness of the additional dielectric layer is about 100 nm.

[0220]

[0239] In some embodiments, optical isolation structures, such as 146, 148, 170, and 172, described further below, are formed along the sidewalls of the tri-color LED device 100 to improve the light emission efficiency from the tri-color LED device 100. In some embodiments, the optical isolation structures, such as 146, 148, 170, and 172, are made from a dielectric material, such as SiO2.

[0221]

[0240] As shown from a top view in FIG. 1A, in some embodiments, the tri-color LED device 100 has a circular shape. In some embodiments, the optical isolation structures such as 146, 148, 170, and 172 are connected together and formed as a circular sidewall around the tri-color LED device 100. In some embodiments, the optical isolation structures are formed as reflector cups, as described in more detail below. In some embodiments, the three stacked LED structures in the tri-color LED device 100 are also circular. In some embodiments, the tri-color LED device 100 can be other shapes, such as rectangular, square, triangular, trapezoidal, polygonal, etc. In some embodiments, the optical isolation structures such as 146, 148, 170, and 172 are connected together and formed as a sidewall around the tri-color LED device 100 having other shapes, such as rectangular, square, triangular, trapezoidal, polygonal, etc.

[0222]

[0241] As shown in FIG. 1B and FIG. 1C, in some embodiments, red LED light-emitting layer 112, green LED light-emitting layer 130, and blue LED light-emitting layer 136 have angled sides. As used herein, angled sides may refer to surfaces that are not perpendicular to the top or bottom surface of each LED light-emitting layer. In some embodiments, the angle between the angled sidewall and the bottom surface of each LED light-emitting layer is less than 90 degrees. In some embodiments, bonding layers 108, 156, and 160 also have angled sides. The angled sides may enhance easy connection of different connectors to the LED light-emitting layers and may prevent separation of those connectors due to the sharp angles, enhancing the overall stability of the device.

[0223]

[0242] In some embodiments, the light transmission efficiency of the multicolor LED device changes as the angle of the oblique side of the LED light emitting layer with respect to the normal to the surface of the substrate 104 changes. In some embodiments, the light transmission efficiency of the multicolor LED device increases as the angle of the oblique side of the LED light emitting layer with respect to the normal to the surface of the substrate 104 increases. For example, if the angle of the side of the LED light emitting layer with respect to the normal to the surface of the substrate 104 is ±5 degrees and the optical isolation structures such as 146, 148, 170, and / or 172 are not reflector cups as described below, the light transmission efficiency of the multicolor LED device is 0.32%. For example, if the angle of the side of the LED light emitting layer with respect to the normal to the surface of the substrate 104 is ±15 degrees and the optical isolation structures such as 146, 148, 170, and / or 172 are not reflector cups as described below, the light transmission efficiency of the multicolor LED device is 2.7%. For example, if the angle of the side of the LED light-emitting layer relative to the normal to the surface of the substrate 104 is ±90 degrees (e.g., the light-emitting layer is tilted) or very close to ±90 degrees and the optical isolation structures such as 146, 148, 170, and / or 172 are not reflective cups as described below, the light transmission efficiency of the multi-color LED device is equal to or very close to 56.4%.

[0224]

[0243] In contrast, embodiments of reflective cup structures, described in more detail below, improve the light transmission efficiency of the multicolor LED device. For example, when the angle of the LED light emitting layer side relative to the normal to the surface of the substrate 104 is ±5 degrees and the optical isolation structures such as 146, 148, 170, and / or 172 are reflective cups as described below, the light transmission efficiency of the multicolor LED device is 0.65%, which is a 104.6% increase over an LED device without a reflective cup. For example, when the angle of the LED light emitting layer side relative to the normal to the surface of the substrate 104 is ±15 degrees and the optical isolation structures such as 146, 148, 170, and / or 172 are reflective cups as described below, the light transmission efficiency of the multicolor LED device is 6.65%, which is a 144.4% increase over an LED device without a reflective cup. For example, when the angle of the side of the LED light-emitting layer relative to the normal to the surface of the substrate 104 is ±90 degrees (e.g., the light-emitting layer is tilted) or very close to ±90 degrees and the optical isolation structures such as 146, 148, 170, and / or 172 are reflective cups as described below, the light transmission efficiency of the multi-color LED device is equal to or very close to 66.65%, which is an 18.4% increase compared to an LED device without a reflective cup.

[0225]

[0244] In some embodiments, a reflective layer is formed above and below each LED light emitting layer to improve light transmission efficiency. As shown in both FIG. 1B and FIG. 1C, in some embodiments, reflective layer 109 is formed between bonding layer 108 and red LED light emitting layer 112. In some embodiments, if conductive layer 110 is present, reflective layer 109 is formed between bonding layer 108 and conductive layer 110. In some embodiments, reflective layer 115 is formed between bonding layer 156 and red LED light emitting layer 112. In some embodiments, if conductive layer 114 is present, reflective layer 115 is formed between bonding layer 156 and conductive layer 114.

[0226]

[0245] 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 the 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 the conductive layer 132 is present, the reflective layer 133 is formed between the bonding layer 160 and the conductive layer 132.

[0227]

[0246] 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 the 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 (not shown in FIGS. 1B and 1C ) is formed between the N electrode pad 140 and the blue LED light emitting layer 136, while still allowing the blue LED light emitting layer 136 to be electrically connected to the N electrode pad 140, for example, through a conductive path. In some embodiments, if the conductive layer 138 is present, the optional reflective layer 139 is formed between the N electrode pad 140 and the conductive layer 138, while still allowing the conductive layer 138 to be electrically connected to the N electrode pad 140, for example, through a conductive path.

[0228]

[0247] In some embodiments, the materials of the reflective layers 109, 115, 127, 133, 135, and 139 have a high reflectivity, especially for the light emitted by the single pixel tri-color LED device 200. For example, the reflectivity of the reflective layers 109, 115, 127, 133, 135, and 139 is greater than 60%. In another example, the reflectivity of the reflective layers 109, 115, 127, 133, 135, and 139 is greater than 70%. In yet another example, the reflectivity of the reflective layers 109, 115, 127, 133, 135, and 139 is greater than 80%.

[0229]

[0248] In some embodiments, the material of the reflective layers 109, 115, 127, 133, 135, and 139 is a metal selected from one or more of Rh, Al, Ag, and Au. In some embodiments, any one of the reflective layers 109, 115, 127, 133, 135, and 139 can include at least two sublayers with different refractive indices. Each sublayer also has a high reflectivity, such as greater than 60%, greater than 70%, or greater than 80%.

[0230]

[0249] In some embodiments, each of the reflective layers such as 109, 115, 127, 133, 135, and 139 is deposited on both sides of the emissive layers such as 112, 130, and 136, or the conductive layers 110, 114, 128, 132, 134, and 138 if a conductive layer is included prior to bonding. In some cases, each of the reflective layers such as 109, 115, 127, 133, 135, and 139 has a thickness of about 2 nanometers (nm) to about 5 μm. In some embodiments, each of the reflective layers such as 109, 115, 127, 133, 135, and 139 has a thickness of 1 μm or less. In some preferred embodiments, each of the reflective layers such as 109, 115, 127, 133, 135, and 139 has a thickness of about 5 nanometers (nm) to 10 nm.

[0231]

[0250] 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 from multiple layers of alternating materials with different refractive indices or multiple layers of different materials with different refractive indices. In some cases, each layer boundary of the DBR structure causes partial reflection of the light wave. The reflective layers such as 109, 115, 127, 133, 135, and 139 can be used to reflect several selected wavelengths, for example, the reflective layers 109 and 115 are used to reflect red light, the reflective layers 127 and 133 are used to reflect green light, and the reflective layers 135 and 139 are used to reflect blue light. In some embodiments, any one of the reflective layers such as 109, 115, 127, 133, 135, and 139 is made of multiple layers, for example at least two layers of SiO2 and Ti3O5, respectively. By varying the thickness and number of SiO2 and Ti3O5 layers, respectively, selective reflection or transmission of different wavelengths of light can be formed.

[0232]

[0251] In some embodiments, any one of the reflective layers such as 109, 115, 127, 133, 135, and 139 further comprises a transparent layer on one of the high reflectance sublayers. For example, the transparent layer, preferably formed on one side of the reflective layer such as 109, 115, 127, 133, 135, and 139, is selected from one or more of ITO and SiO2.

[0233]

[0252] In some embodiments, each reflective layer 109 and 115 of the red light LEDs includes multiple layers of Au and / or indium tin oxide (ITO).

[0234]

[0253] In some embodiments, each reflective layer 109 and 115 of the red light LED structure has a low absorptivity (e.g., 25% or less) for light generated by a different layer of the tri-color LED device 100. In some embodiments, each reflective layer 109 and 115 of the red light LED structure has a high reflectivity (e.g., 75% or more) for light generated between the current two reflective layers 109 and 115, e.g., red light.

[0235]

[0254] In one example, the following DBR structure shown in Table 1 is used to reflect green light from a green light LED.

[0236] [Table 1]

[0237]

[0256] In some embodiments, each of the reflective layers 127 and 133 of the green light LED structure has a low absorptivity (e.g., 25% or less) for light generated by different layers of the tri-color LED device 100. In some embodiments, each of the reflective layers 127 and 133 of the green light LED structure has a high reflectivity (e.g., 75% or more) for light generated between the current two reflective layers 127 and 133, e.g., green light.

[0238]

[0257] In one example, the following DBR structure shown in Table 2 is used to reflect blue light from a blue light LED.

[0239] [Table 2]

[0240]

[0259] In some embodiments, the reflective layers 135 and optionally 139 of the blue light LED structure each have a low absorptivity (e.g., 25% or less) for light generated by different layers of the tri-color LED device 100. In some embodiments, the reflective layer 135 of the blue light LED structure has a high reflectivity (e.g., 75% or more) for light generated above the current reflective layer 135 or between the current reflective layers 135 and 139, e.g., blue light.

[0241]

[0260] 2A is a cross-sectional view of the single pixel tri-color LED device 100 along the diagonal 102 of FIG. 1A with planarization, according to some embodiments. In some embodiments, the single pixel tri-color LED device 100 has a similar structure to the single pixel tri-color LED device 100 shown in FIGS. 1A, 1B, and 1C, but with the addition of a planarization layer 176 covering the single pixel tri-color LED device 100.

[0242]

[0261] 2B is a cross-sectional view of the single pixel tri-color LED device 100 along the diagonal 150 of FIG. 1A with planarization, according to some embodiments. In some embodiments, the single pixel tri-color LED device 100 has a similar structure to the single pixel tri-color LED device 100 shown in FIGS. 1A, 1B, and 1C, but with the addition of a planarization layer 176 covering the single pixel tri-color LED device 100.

[0243]

[0262] In some embodiments, the planar layer, such as 176, is transparent to the light emitted from the micro-LEDs 100. In some embodiments, the planar 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), boron phosphosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes a polymer, such as SU-8, PermiNex, benzocyclobutene (BCB), transparent plastics (resins) including spin-on glass (SOG), bonding adhesive Micro Resist BCL-1200, or any combination thereof. In some embodiments, the planar layer can facilitate the transmission of light emitted from the micro-LEDs 100.

[0244]

[0263] In some embodiments, the planar 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 planar layer 176 covers the entire single pixel tri-color LED device 100 and the sidewalls of the optical isolation structures. The planar layer 176 is in the same plane as the top surface of the optical isolation structures.

[0245]

[0264] 3A is a cross-sectional view of a single pixel tri-color LED device 100 along the diagonal 102 of FIG. 1A with planarization, according to some embodiments. In some embodiments, the single pixel tri-color LED device 100 has a similar structure to the single pixel tri-color LED device 100 shown in FIGS. 1A, 1B, and 1C, but with the addition of a planarization layer 178 covering the single pixel tri-color LED device 100.

[0246]

[0265] 3B is a cross-sectional view of the single pixel tri-color LED device 100 along the diagonal 150 of FIG. 1A with planarization, according to some embodiments. In some embodiments, the single pixel tri-color LED device 100 has a similar structure to the single pixel tri-color LED device 100 shown in FIGS. 1A, 1B, and 1C, but with the addition of a planarization layer 178 covering the single pixel tri-color LED device 100.

[0247]

[0266] In some embodiments, the planar layer 178 has the same height as the top electrode elements, e.g., 140. The planar layer 178 is coplanar with the top surfaces of the top electrode elements, such as N-electrode pad 140. In some embodiments, the top electrode elements, e.g., 140, are directly above the planar layer 178. The planar layer 178 is coplanar with the bottom surfaces of the top electrode elements, such as N-electrode pad 140. For example, the planar layer 178 covers the entire single pixel tri-color LED device 100 as well as portions of the sidewalls of the optical isolation structures, e.g., 146, 148, 170, and 172.

[0248]

[0267] Unlike the electrode connections shown in Figures 1A-1C where the top electrode elements such as N electrode pad 140 are connected through electrical connections under the optical isolation structures such as 146, 148, 170, and 172, in Figures 2A-2B and 3A-3B, the top electrode elements such as N electrode pad 140 are connected through electrical connections 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 fixed through or on the surface of the optical isolation structures such as 146, 148, 170, and 172. The top electrode structure can make the single pixel tri-color LED device 100 compact, particularly in the fabrication process using a planar layer.

[0249]

[0268] In some embodiments, an insulating layer can be deposited on the LED light emitting layer of the single pixel multicolor LED device and other layers such as conductive and reflective layers. A planarization process then follows to flatten the surface of the insulating layer that embeds the single pixel multicolor LED device. Vias for electrical connections are also formed in the planar layer. Compared to some other processes that do not have a planar insulating layer, the features and layers in the planar LED structure are better protected and less susceptible to external destructive forces. In addition, the planarized surface can improve light transmission efficiency by reducing deflection from non-planar surfaces.

[0250]

[0269] In some embodiments, through dry etching and wet etching, a tri-color LED structure is formed, and the axes of the LED structures of different colors are aligned perpendicular to each other. In some embodiments, the LED structures of different colors share the same axis.

[0251]

[0270] In some embodiments, each of the different color LED structures is shaped like a pyramid or has a trapezoidal cross section. Each layer has a narrow width or area compared to the layer below, where the width or area is measured by a dimension in a plane parallel to the surface of the substrate 104.

[0252]

[0271] In some embodiments, each LED structure of a different color is bonded together by a bonding layer that covers only the area of ​​the LED structure with no extension beyond the area of ​​the LED structure, and the entire multicolor LED device forms a pyramid (or inverted cone)-like shape or a trapezoidal cross-sectional shape (as shown in Figures 1-3). 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-like shape can be formed naturally as each layer in the LED device is etched and patterned from bottom to top. The pyramid-like structure can improve the electronic connection between the individual LED structures and to the electrodes, simplifying the fabrication process. For example, electrode connections are exposed at each layer for easy connection.

[0253]

[0272] In some embodiments, the lower layer, such as the metal bonding layer 108, has a lateral dimension of about 1 μm to about 500 μm. In a preferred embodiment, the lateral dimension of the metal bonding layer 108 at the bottom of the multicolor LED device is about 1.75 μm. In some embodiments, the vertical height of the multicolor LED device is about 1 μm to about 500 μm. In a preferred embodiment, the vertical height of the multicolor LED device is about 1.9 μm. In a preferred embodiment, the lateral dimension of the conductive layer 138 at the top of the multicolor LED device is about 1.0 μm.

[0254]

[0273] In some embodiments, the cross-sectional aspect ratio of the layers of the tri-color LED device remains approximately the same when the lateral dimensions of the same layer are changed. For example, if the lateral dimension of the patterned epitaxial layer is 5 μm, the thickness of the patterned epitaxial layer is less than 1 μm. In another example, if the lateral dimension of the same patterned epitaxial layer is increased, the thickness of the patterned epitaxial layer is increased accordingly to maintain the same aspect ratio. In some embodiments, the cross-sectional aspect ratio of the epitaxial layer and other layers is less than 1 / 5 in thickness / width.

[0255]

[0274] The shape of the LED device is not limited, and in some other embodiments, the cross-sectional shape of the tri-color LED device can take other shapes, such as an inverted trapezoid, a semi-ellipse, a rectangle, a parallelogram, a triangle, or a hexagon.

[0256]

[0275] 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 pattern is dry etching, such as inductively coupled plasma (ICP) etching, or wet etching using an ITO etching solution. In some embodiments, the same patterning method can be applied to all other conductive layers, including conductive layers 110, 114, 128, 132, 134, and 138 in the three-color LED device 100.

[0257]

[0276] 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 for patterning is dry etching, such as inductively coupled plasma (ICP) etching, using Cl2 and BCl3 etching gases.

[0258]

[0277] In some embodiments, the bonding layers, including 160 and 156, are patterned using photolithography and etching. In some cases, the etching method used for patterning is dry etching, such as inductively coupled plasma (ICP) etching, using CF4 and O2 etching gases.

[0259]

[0278] 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 pattern the reflective layers, particularly the DBR layers, is dry etching, such as inductively coupled plasma (ICP) etching with CF4 and O2 etching gases, or ion beam etching (IBE) with Ar gas.

[0260]

[0279] In some embodiments, the red LED light emitting layer 112 is patterned using photolithography and etching. In some cases, the etching method used for patterning is dry etching, such as inductively coupled plasma (ICP) etching, using Cl2 and HBr etching gases.

[0261]

[0280] In some embodiments, the metal bonding layer 108 is patterned using photolithography and etching. In some cases, the etching method used for patterning is dry etching using Cl2 / BCl3 / Ar etching gas, such as inductively coupled plasma (ICP) etching or ion beam etching (IBE) using Ar gas.

[0262]

[0281] 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 of the 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, the insulating layer is formed using a composition similar to SiO2 after curing a layer such as SOG at high temperature. In some embodiments, the insulating layer is made of a material that has a similar thermal coefficient as the layer below the insulating layer. The surfaces of the insulating layers such as 176 and 178 are then smoothed or planarized by a suitable method understood by one of ordinary skill in the art, such as chemical mechanical polishing.

[0263]

[0282] In some embodiments, after planarization, insulating layers such as 176 and 178 are patterned using photolithography and etching to expose electrode contact areas. In some cases, the etching method used for patterning is dry etching using CF4 and O2, e.g., inductively coupled plasma (ICP) etching.

[0264]

[0283] In some embodiments, P-electrode or anode metal pads are deposited by evaporation or other deposition methods on one side of the planar insulating layer and / or in suitable locations of the patterned LED structures, such as in vias in the planar insulating layer, to electrically connect to the red, green, and blue LED structures.

[0265]

[0284] In some embodiments, separate N-electrode or cathode metal pads are evaporated or otherwise deposited at suitable locations of the patterned LED structures, such as on one side / top of the planar insulating layer and / or in vias in the planar insulating layer, to electrically connect to the red, green, and blue LED structures.

[0266]

[0285] FIG. 4A is a top view of a single pixel tri-color LED device 400 using layered planarization according to some embodiments.

[0267]

[0286] 4B is a cross-sectional view of a single pixel tri-color LED device 400 along the diagonal 402 of FIG. 4A with layered planarization according to some embodiments. The diagonal passes through the center of the single pixel tri-color LED device 400.

[0268]

[0287] Compared to the embodiment shown in Figures 1-3, the main difference in the embodiment of Figures 4A and 4B is that each LED structure of a different color is embedded within a respective planar insulating layer, and the planar insulating layers with the LED structures therein are then bonded together via several bonding layers.

[0269]

[0288] In some embodiments, the tri-color LED device 400 includes a substrate 404. For convenience, "up" means away from the substrate 404, and "down" means toward the substrate 404, and other directional terms such as above, below, above, below, below, below, etc. are interpreted accordingly. The support substrate 404 is a substrate on which an array of individual drive circuits 406 is fabricated. In some embodiments, the drive circuits may be located on the substrate 404 or in one of the layers above the miniature tri-color LED structure 400. Each drive circuit is a pixel drive circuit 406. In some cases, the drive circuits 406 are thin film transistor pixel drive circuits or silicon CMOS pixel drive circuits. In one embodiment, the substrate 404 is a Si substrate. In another embodiment, the support substrate 404 is a transparent substrate, such as a glass substrate. Other example substrates include GaAs, GaP, InP, SiC, ZnO, and sapphire substrates. In some embodiments, the substrate 404 is about 700 μm thick. The drive circuits 406 form individual pixel drive circuits that control the operation of the individual single pixel tri-color LED devices 400. The circuitry on the substrate 404 includes contacts to each individual drive circuit 406, as well as a ground contact. As shown in both Figures 4A and 4B, each miniature tri-color LED structure 400 also has two types of contacts: a P-electrode or anode, such as 450 (or 408), 452, and coupling sections 422, 424, and 426, which are connected to the pixel drive circuit, and an N-electrode or cathode, such as 440, 442, 444, and coupling sections 416, 418, and 420, which are connected to ground (i.e., the common electrode).

[0270]

[0289] In some embodiments, the N-electrodes (or N-electrode contact pads) such as 440, 442, 444 and bonding sections 416, 418, and 420 and their connections are made of materials such as graphene, ITO, aluminum doped zinc oxide (AZO), fluorine doped tin oxide (FTO), or any combination thereof. In some embodiments, the N-electrodes (or N-electrode contact pads) such as 440, 442, 444 and bonding sections 416, 418, and 420 and their connections are made of non-transparent or transparent conductive materials, and in preferred embodiments are made of transparent conductive materials. In some embodiments, the P-electrodes (or P-electrode contact pads) such as 450, 452 and bonding sections 422, 424, and 426 and their connections are made of materials such as graphene, ITO, AZO, FTO, or any combination thereof. In some embodiments, the P electrodes (or P electrode contact pads) and their connections, such as 450, 452 and bonding sections 422, 424, and 426, are made of a non-transparent or transparent conductive material, and in preferred embodiments are made of a transparent conductive material. In some embodiments, the locations of the P electrodes (or P electrode contact pads) and their connections and the N electrodes (or N electrode contact pads) and their connections can be interchanged.

[0271]

[0290] Generally, an LED light emitting layer includes a PN junction having a p-type region / layer and an n-type region / layer, and an active layer between the p-type region / layer and the n-type region / layer.

[0272]

[0291] In some embodiments, the light emitted from the red LED light emitting layer 412 may propagate horizontally towards the sidewalls of the red LED light emitting layer 412 and then is reflected upwards by reflective elements such as 446 and / or 448 as described below and emitted from the top surface of the single pixel tri-color LED device 400. As described below, a reflective layer 409 is positioned below the red LED light emitting layer 412 and a reflective layer 415 is positioned above the red LED light emitting layer 412. The light emitted from the red LED light emitting layer 412 is reflected between the two reflective layers 409 and 415 towards the sidewalls of the red LED light emitting layer 412.

[0273]

[0292] In some embodiments, the light emitted from the green LED light emitting layer 430 may propagate horizontally towards the sidewalls of the green LED light emitting layer 430 and then is reflected upwards by reflective elements such as 446 and / or 448 as described below and emitted from the top surface of the single pixel tri-color LED device 400. As described below, a reflective layer 427 is positioned below the green LED light emitting layer 430 and a reflective layer 433 is positioned above the green LED light emitting layer 430. The light emitted from the green LED light emitting layer 430 is reflected between the two reflective layers 427 and 433 towards the sidewalls of the green LED light emitting layer 430.

[0274]

[0293] In some embodiments, light emitted from blue LED light emitting layer 436 may propagate horizontally toward the sidewalls of blue LED light emitting layer 436 and then be reflected upward by reflective elements such as 446 and / or 448 as described below and emitted from the top surface of single pixel tri-color LED device 400. A reflective layer 435 is positioned below blue LED light emitting layer 436 as described below. Light emitted from blue LED light emitting layer 436 is reflected between reflective layer 435 and the top surface of blue LED light emitting layer 436 toward the sidewalls of blue LED light emitting layer 436.

[0275]

[0294] In some embodiments, light emitted from the red LED light emitting layer 412 may propagate vertically through the green LED light emitting layer 430 and then the blue LED light emitting layer 436 and is emitted from the tri-color LED device 400. In some embodiments, light emitted from the green LED light emitting layer 430 may propagate through the blue LED light emitting layer 436 and is emitted from the tri-color LED device 400. For vertical light transmission, in some embodiments, a top reflective layer above each light emitting layer such as 415 and 433 is preferably not included in the tri-color LED device 400.

[0276]

[0295] In some embodiments, LED light emitting layers such as 412, 430, and 436 include many epitaxial sublayers 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.

[0277]

[0296] In some embodiments, each of the stacked LED structures can be individually controlled to generate its individual light. In some embodiments, the combined light of the top LED epitaxial layer resulting from the operation of all the LED epitaxial layers in the tri-color LED device 400 can change the color of one pixel on a display panel in a small footprint.

[0278]

[0297] In some embodiments, depending on the design of the LED device 400, the colors emitted by the LED structures included in the same device are not limited to red, green, and blue. For example, suitable colors can be selected from a range of different colors in the visible color range from 380 nm to 700 nm wavelength. In some embodiments, LED structures can be implemented that emit other colors from the non-visible range, such as ultraviolet and infrared.

[0279]

[0298] In some embodiments, when vertical light emission is combined with horizontal light emission, for example, the three color choices can be red, green, and blue from bottom to top. In another embodiment, the three color choices can be infrared, orange, and ultraviolet from bottom to top. In some embodiments, the wavelength of light from the LED structures on one layer of device 400 is longer than the LED structures on the layer above the current layer. For example, the wavelength of light from bottom LED light emitting layer 412 is longer than the wavelength of light from middle LED light emitting layer 430, which is longer than the wavelength of light from top LED light emitting layer 436.

[0280]

[0299] In some embodiments, in the case of horizontal light emission or when the portion of horizontal light emission is greater than the portion of vertical light emission from the top surface of the LED device 400, each of the LED light-emitting layers 412, 430, and 436 can be any suitable visible or invisible color. The advantage of horizontal light emission is that the emitted light does not need to pass through other upper layers of the LED device 400, but directly exits from the edge or sidewall of the current light-emitting layer, so that lower light transmission loss and higher light emission efficiency can be achieved. For example, compared to a vertical light-emitting LED device, a horizontal light-emitting LED device may obtain a light transmission efficiency of 15%, 50%, 100%, 150%, or 200%. In some cases, the light transmission efficiency from a horizontal light-emitting LED device can be 20%, 40%, or 60% or more.

[0281]

[0300] In some embodiments, the lower red LED light emitting layer 412 is bonded to the substrate 404 through a metal bonding layer 408. The metal bonding layer 408 may be disposed on the substrate 404. In one approach, the metal bonding layer 408 is grown on the substrate 404. In some embodiments, the metal bonding layer 408 is electrically connected to both the driving circuitry 406 on the substrate 404 and the red LED light emitting layer 412 on the metal bonding layer 408, and acts as a P electrode. In some embodiments, the thickness of the metal bonding layer 408 is about 0.1 μm to about 3 μm. In a preferred embodiment, the thickness of the metal bonding layer 408 is about 0.3 μm. The metal bonding layer 408 may include an ohmic contact layer and a metal bonding layer. In some cases, two metal layers are included in the metal bonding layer 408. One of the metal layers is deposited on a layer above the metal bonding layer in the LED device 400. The other 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, two layers of Au each require a Cr coating as an adhesion layer and a Pt coating as an anti-diffusion layer. And the Pt coating is between the Au layer and the Cr layer. The Cr layer and the Pt layer are positioned on the top and bottom of the two bonded Au layers. In some embodiments, if the thickness of the two Au layers is approximately the same, the interdiffusion of Au on both layers will bond the two layers together under high pressure and high temperature. Eutectic bonding, thermocompression bonding, and transient liquid phase (TLP) bonding are examples of techniques that may be used.

[0282]

[0301] In some embodiments, the metal bonding layer 408 can also be used as a reflector to reflect light emitted from the LED structure above.

[0283]

[0302] In some embodiments, a conductive layer 410 for electrode connection is formed on the bottom of the red LED light emitting layer 412. In some embodiments, the conductive layer 410 is a conductive transparent layer 410 that transmits light emitted from the LED device 400, such as an indium tin oxide (ITO) layer, formed between the red LED light emitting layer 412 and the metal bonding layer 408 to improve conductivity and transparency. In some embodiments, as shown in FIG. 4A and not shown in FIG. 4B, the red LED structure has a P electrode contact pad 450 electrically connected to the red LED light emitting layer 412. In some embodiments, the P electrode contact pad 450 is connected to the conductive layer 410. In some embodiments, a conductive layer 414 for electrode connection is formed on the top of the red LED light emitting layer 412. In some embodiments, the conductive layer 414 is a conductive transparent layer 414, 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 transparency.

[0284]

[0303] In some embodiments, the red LED light emitting layer 412 has an extension 464 to the layer above on one side of the red LED light emitting layer 412. 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.

[0285]

[0304] In some embodiments, a reflective layer 409 is positioned below the red LED light emitting layer 412 between the conductive layer 410 and the metal bonding layer 408, and a reflective layer 415 is positioned above the red LED light emitting layer 412 between the conductive layer 414 and the bonding layer 456, in one example within the planar insulating layer 454.

[0286]

[0305] In one approach, the red LED light emitting layers 412 are grown on a separate substrate (called an epitaxial substrate). Then, after bonding, the epitaxial substrate is removed, for example, by a laser lift-off process or chemical wet etching, leaving the structure shown in FIG. 4B.

[0287]

[0306] In some embodiments, the red LED light emitting layer 412 is for forming 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 thin films in the red LED light emitting layer 412 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 and the N-type layers are typically Si doped. In some examples, the thickness of the red LED light emitting layer is about 0.1 μm to about 5 μm. In a preferred embodiment, the thickness of the red LED light emitting layer is about 0.3 μm.

[0288]

[0307] In some embodiments, the red LED structure includes a metal bonding layer 408, a reflective layer 409, a conductive layer 410, a red LED light emitting layer 412, a conductive layer 414, a reflective layer 415, and an N-electrode contact pad 416. In some embodiments, the red LED structure is formed in a planar insulating layer 454, such as a silicon dioxide (SiO2) layer. In some embodiments, the planar insulating layer 454 covers the entire red LED structure. In some embodiments, the entire red LED structure is embedded in the planar insulating layer 454. In some embodiments, the surface of the planar insulating layer 454 is smoothed or planarized by a chemical mechanical polishing method.

[0289]

[0308] In some embodiments, the planar layer, such as 454, transmits the light emitted from the micro-LEDs 400. In some embodiments, the planar 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), boron phosphosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes a polymer, such as SU-8, PermiNex, benzocyclobutene (BCB), transparent plastics (resins) including spin-on glass (SOG), bonding adhesive Micro Resist BCL-1200, or any combination thereof. In some embodiments, the planar layer can facilitate the transmission of light emitted from the micro-LEDs 400. In some embodiments, the planar layers, such as 454, 468, and 462, have the same composition as the bonding layers, such as 456 and 460. In some embodiments, planar layers such as 454 , 468 , and 462 have a different composition than bonding layers such as 456 and 460 .

[0290]

[0309] In some embodiments, vias or through-holes are formed in the planar insulating layer 454 to accommodate the P electrode contact components 422 and 424 of the green LED structure. The P electrode contact components 422 and 424 are connected to the drive circuitry 406.

[0291]

[0310] In some embodiments, a bonding layer 456 is used to bond the red and green LED structures together. In some embodiments, the bonding layer 456 is opaque to the light emitted from the LED device 400. In some embodiments, the material and thickness of the bonding layer 456 is the same as that described above for the metal bonding layer 408. In some embodiments, the bonding layer 456 can also be used as a reflector to reflect light emitted from the LED structure above.

[0292]

[0311] In some embodiments, when vertical transmission is used, the bonding layer 456 transmits the light emitted from the micro-LEDs 400. In some embodiments, the bonding layer 456 is made of a dielectric material, such as a solid inorganic material or a plastic material. In some embodiments, the solid inorganic material includes SiO2, Al2O3, Si3N4, phosphosilicate glass (PSG), boron phosphosilicate glass (BPSG), or any combination thereof. In some embodiments, the plastic material includes a polymer, such as SU-8, PermiNex, benzocyclobutene (BCB), transparent plastics (resins) including spin-on glass (SOG), bonding adhesive Micro Resist BCL-1200, or any combination thereof. In some embodiments, the transparent bonding layer can facilitate the transmission of light emitted from the layer below the bonding layer.

[0293]

[0312] In some embodiments, a conductive layer 428 for electrode connection is formed under 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 transparency.

[0294]

[0313] As shown in FIGS. 4A and 4B, in some embodiments, 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 426 is connected to a conductive layer 428. In some embodiments, the P electrode contact pad 426 also connects to the P electrode contact elements 422 and 424 in the planar insulating layer 454 through a portion of the P electrode contact pad 426 in the bonding layer 456. In some embodiments, the P electrode contact element 422 can be cylindrical. In some embodiments, the P electrode contact element 424 has a funnel-like shape with a narrow upper side and a wide lower side that match the width of the element 422, and this shape is for supporting the element 422 above. In some embodiments, a conductive layer 432 for electrode connection is formed on top of the green LED light emitting layer 430. In some embodiments, the conductive layer 432 is a conductive transparent layer 432, such as an ITO layer, formed between the green LED light emitting layer 430 and the N electrode contact pad 420 to improve conductivity and transparency. 4A and 4B , the green LED structure has an N-electrode contact pad 420 electrically connected to the green LED light emitting layer 430. In some embodiments, the N-electrode contact pad 420 is connected to the conductive layer 432. In some embodiments, the N-electrode contact pad 420 of the green LED structure is also electrically connected to the N-electrode contact pad 416 of the red LED structure through an N-electrode contact component 418 in the transparent bonding layer 456. In some embodiments, a via or through-hole is formed in the bonding layer 456 to accommodate the P-electrode contact pad 426 and a portion of the N-electrode contact component 418.

[0295]

[0314] In some embodiments, green LED light emitting layer 430 has an extension 466 to the layer above on one side of green LED light emitting layer 430. In some embodiments, extension 466 extends with conductive layers 428 and 432. In some embodiments, extension 466 is connected to N-electrode contact pad 420 through an extension of conductive layer 432 above extension 466.

[0296]

[0315] In some embodiments, the lateral dimensions of the green LED light emitting layer 430 are approximately the same as the lateral dimensions of the red LED light emitting layer 412, particularly with respect to the effective light emitting area.

[0297]

[0316] In some embodiments, reflective layer 427 is positioned below green LED light-emitting layer 430 between conductive layer 428 and bonding layer 456, and reflective layer 433 is positioned above green LED light-emitting layer 430 between conductive layer 432 and bonding layer 460, in one example within planar insulating layer 458.

[0298]

[0317] In one approach, the green LED light emitting layer 430 is grown on a separate substrate (called an epitaxial substrate). Then, after bonding, the epitaxial substrate is removed, for example, by a laser lift-off process or chemical wet etching, leaving the structure shown in FIG. 4B.

[0299]

[0318] In some embodiments, the green LED light emitting layer 430 is for forming 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 thin film in the green LED light emitting layer 430 can include a layer of P-type GaN / InGaN light emitting layer / N-type GaN. In some embodiments, the P-type is typically Mg doped, and the N-type is typically Si doped. In some examples, the thickness of the green LED light emitting layer is about 0.1 μm to about 5 μm. In a preferred embodiment, the thickness of the green LED light emitting layer is about 0.3 μm.

[0300]

[0319] In some embodiments, the green LED structure includes reflective layer 427, conductive layer 428, green LED light emitting layer 430, conductive layer 432, reflective layer 433, and N electrode contact pad 420. In some embodiments, the green LED structure is formed within a planar insulating layer 458. In some embodiments, planar insulating layer 458 covers the entire green LED structure and a portion of P electrode contact pad 426. In some embodiments, the entire green LED structure is embedded within planar insulating layer 458. In some embodiments, both sides of planar insulating layer 458 are smoothed or planarized by chemical mechanical polishing.

[0301]

[0320] In some embodiments, the lateral dimensions of the green LED structure are approximately the same as the lateral dimensions of the red LED structure. 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 when extensions such as 464 and 466 are excluded. In some embodiments, the first LED structure and the second LED structure are aligned along the same central axis when extensions such as 464 and 466 are excluded.

[0302]

[0321] In some embodiments, a bonding layer 460 is used to bond the green and blue LED structures together. In some embodiments, the bonding layer 456 is opaque to the light emitted from the LED device 400. In some embodiments, the material and thickness of the bonding layer 460 is the same as that described above for the metal bonding layer 408. In some embodiments, the bonding layer 460 can also be used as a reflector to reflect light emitted from the LED structure above.

[0303]

[0322] In some embodiments, when vertical transmission is used, bonding layer 460 transmits light emitted from LED device 400. In some embodiments, bonding layer 460 is made of a dielectric material, such as the same solid inorganic or plastic materials described above for bonding layer 456. In some embodiments, a transparent bonding layer can facilitate the transmission of light emitted from layers below the bonding layer.

[0304]

[0323] In some embodiments, a conductive layer 434 for electrode connection is formed under 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 transparency. In some embodiments, as shown in FIG. 4A and not shown in FIG. 4B, the blue LED structure has a P electrode contact pad 452 electrically connected to the blue LED light emitting layer 436. In some embodiments, the P electrode contact pad 452 is connected to the conductive layer 434. In some embodiments, the P electrode contact pad 452 is also connected to some P electrode contact components (not shown in FIG. 4A and FIG. 4B) in the planar insulating layers 454 and 458 and in the transparent bonding layers 456 and 460, as well as 422 and 424. These P electrode contact components are connected to the driving circuit 406.

[0305]

[0324] 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 can be 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 transparency. In some embodiments, as shown in FIG. 4B, the N-electrode 440 has N-electrode contact pads 442 and 444 electrically connected to the blue LED light emitting layer 436 through the N-electrode 440 and the conductive layer 438. In some embodiments, the N-electrode 440 is also electrically connected to the N-electrode contact pad 420 of the green LED structure. In some embodiments, the N-electrode 440 is made of materials such as graphene, ITO, AZO, FTO, or any combination thereof.

[0306]

[0325] In some embodiments, the lateral dimensions of blue LED light emitting layer 436 are approximately the same as the lateral dimensions of green LED light emitting layer 430, particularly with respect to effective light emitting area.

[0307]

[0326] In some embodiments, a reflective layer 435 is positioned below the blue LED light emitting layer 436, between the conductive layer 434 and the bonding layer 460. In some embodiments, an optional reflective layer 439 (not shown in FIG. 4B ) is positioned on top of the conductive layer 438 and above the blue LED light emitting layer 436.

[0308]

[0327] In one approach, the blue LED light emitting layer 436 is grown on a separate substrate (called an epitaxial substrate). Then, after bonding, the epitaxial substrate is removed, for example, by a laser lift-off process or chemical wet etching, leaving the structure shown in FIG. 4B.

[0309]

[0328] In some embodiments, the blue LED light emitting layer 436 is for forming 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 thin film in the blue LED light emitting layer 436 can include a layer of P-type GaN / InGaN light emitting layer / N-type GaN. In some embodiments, the P-type is typically Mg doped, and the N-type is typically Si doped. In some examples, the thickness of the blue LED light emitting layer is about 0.1 μm to about 5 μm. In a preferred embodiment, the thickness of the blue LED light emitting layer is about 0.3 μm.

[0310]

[0329] In some embodiments, the blue LED structure includes a reflective layer 435, a conductive layer 434, a blue LED light emitting layer 436, a conductive layer 438, and an optional reflective layer 439. In some embodiments, the blue LED structure is formed in a planar insulating layer 462. In some embodiments, the planar insulating layer 462 covers the entire blue LED structure. In some embodiments, the entire blue LED structure is embedded in the planar insulating layer 462. In some embodiments, the bottom surface of the planar insulating layer 462 is smoothed or planarized by chemical mechanical polishing.

[0311]

[0330] In some embodiments, a via or through-hole is formed in the planar insulating layer 462 and the transparent bonding layer 460 to accommodate a portion of the N-electrode 440 and connect it to the N-electrode contact pad 420 of the green LED structure.

[0312]

[0331] In some embodiments, the N-electrode 440 covers the top of the planar insulating layer 462. In some embodiments, the N-electrode 440 covers the top of the tri-color LED device 400. In some embodiments, the N-electrode 440 connects to N-electrodes in adjacent tri-color LED devices (not shown in FIGS. 4A and 4B) via N-electrode contact pads 442 and 444, and thus functions as a common electrode.

[0313]

[0332] In some embodiments, the lateral dimensions of the blue LED structure are approximately the same as the lateral dimensions 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 when the extensions, such as 466, are excluded. In some embodiments, the second LED structure and the third LED structure are aligned along the same central axis when the extensions, such as 466, are excluded.

[0314]

[0333] In some embodiments, each of the conductive layers 410, 414, 428, 432, 434, and 438 has a thickness of about 0.01 μm to about 1 μm. In some cases, each of the conductive layers 410, 414, 428, 432, 434, and 438 is commonly deposited on each corresponding epitaxial layer by evaporation, such as electron beam evaporation or sputtering deposition, prior to any bonding process with the next epitaxial layer. In some examples, the conductive layers are used to maintain good electrical conductivity for electrode connections while in some cases improving the optical properties of the LED device, such as reflectivity or transparency.

[0315]

[0334] In some embodiments, to improve the light emission efficiency from the tri-color LED device 400, optical isolation structures such as 446 and 448 are formed along the sidewalls of the tri-color LED device 400. In some embodiments, the optical isolation structures 446 and 448 are made of a dielectric material such as SiO2.

[0316]

[0335] As shown from a top view in FIG. 4A, in some embodiments, the tri-color LED device 400 has a circular shape. In some embodiments, the optical isolation structures, such as 446 and 448, are connected together and formed as a circular sidewall around the tri-color LED device 400. In some embodiments, the optical isolation structures are formed as reflector cups, as described in more detail below. In some embodiments, the three stacked LED structures in the tri-color LED device 400 are also circular. In some embodiments, the tri-color LED device 400 can be other shapes, such as rectangular, square, triangular, trapezoidal, polygonal, etc. In some embodiments, the optical isolation structures, such as 446 and 448, are connected together and formed as a sidewall around the tri-color LED device 400 having other shapes, such as rectangular, square, triangular, trapezoidal, polygonal, etc.

[0317]

[0336] As shown in FIG. 4B, 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 angled sides. As used herein, angled sides may refer to surfaces that are not perpendicular to the top or bottom surface of each LED light-emitting layer. In some embodiments, the angle between the angled sidewall and the bottom surface of each LED light-emitting layer is less than 90 degrees. In some embodiments, the metal bonding layer 408 also has angled sides. The angled sides may enhance easy connection of different connectors to the LED light-emitting layers and may prevent separation of those connectors due to the sharp angles, increasing the overall stability of the device.

[0318]

[0337] In some embodiments, the light transmission efficiency of the multicolor LED device changes as the angle of the slanted side of the LED light emitting layer with respect to the normal to the surface of the substrate 404 changes. In some embodiments, the light transmission efficiency of the multicolor LED device increases as the angle of the slanted side of the LED light emitting layer with respect to the normal to the surface of the substrate 404 increases. For example, if the angle of the side of the LED light emitting layer with respect to the normal to the surface of the substrate 404 is ±5 degrees and the optical isolation structures such as 446 and / or 448 are not reflector cups as described below, the light transmission efficiency of the multicolor LED device is 0.32%. For example, if the angle of the side of the LED light emitting layer with respect to the normal to the surface of the substrate 404 is ±15 degrees and the optical isolation structures such as 446 and / or 448 are not reflector cups as described below, the light transmission efficiency of the multicolor LED device is 2.7%. For example, if the angle of the side of the LED light-emitting layer relative to the normal to the surface of the substrate 404 is ±90 degrees (e.g., the light-emitting layer is tilted) or very close to ±90 degrees and the optical isolation structures such as 446 and / or 448 are not reflective cups as described below, the light transmission efficiency of the multi-color LED device is equal to or very close to 56.4%.

[0319]

[0338] In contrast, embodiments of the reflector cup structure, described in more detail below, improve the light transmission efficiency of the multicolor LED device. For example, when the angle of the LED light emitting layer side relative to the normal to the surface of the substrate 404 is ±5 degrees and the optical isolation structures such as 446 and / or 448 are reflector cups as described below, the light transmission efficiency of the multicolor LED device is 0.65%, which is a 104.6% increase compared to an LED device without a reflector cup. For example, when the angle of the LED light emitting layer side relative to the normal to the surface of the substrate 404 is ±15 degrees and the optical isolation structures such as 446 and / or 448 are reflector cups as described below, the light transmission efficiency of the multicolor LED device is 6.65%, which is a 144.4% increase compared to an LED device without a reflector cup. For example, if the angle of the side of the LED light-emitting layer relative to the normal to the surface of the substrate 404 is ±90 degrees (e.g., the light-emitting layer is tilted) or very close to ±90 degrees and the optical isolation structures such as 446 and / or 448 are reflective cups as described below, the light transmission efficiency of the multi-color LED device is equal to or very close to 66.65%, which is an 18.4% increase compared to an LED device without a reflective cup.

[0320]

[0339] 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 are similar in size. 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 approximately the same, particularly with respect to effective light emitting area.

[0321]

[0340] In some embodiments, a reflective layer is formed above and below each LED light emitting layer to improve light transmission efficiency. As shown in FIG. 4B, 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, if 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 / or in the planar insulating layer 454) and the red LED light emitting layer 412. In some embodiments, if a conductive layer 414 is present, the reflective layer 415 is formed between the bonding layer 456 (and / or in the planar insulating layer 454) and the conductive layer 414.

[0322]

[0341] In some embodiments, a reflective layer 427 is formed between bonding layer 456 (and / or in planar insulating layer 458) and green LED light emitting layer 430. In some embodiments, if conductive layer 428 is present, reflective layer 427 is formed between bonding layer 456 (and / or in planar insulating layer 458) and conductive layer 428. In some embodiments, a reflective layer 433 is formed between bonding layer 460 (and / or in planar insulating layer 458) and green LED light emitting layer 430. In some embodiments, if conductive layer 432 is present, reflective layer 433 is formed between bonding layer 460 (and / or in planar insulating layer 458) and conductive layer 432.

[0323]

[0342] In some embodiments, a reflective layer 435 is formed between the bonding layer 460 (and / or in the planar insulating layer 462) and the blue LED light emitting layer 436. In some embodiments, if the conductive layer 434 is present, the reflective layer 435 is formed between the bonding layer 460 (and / or in the planar insulating layer 462) and the conductive layer 434. In some embodiments, an optional reflective layer 439 (not shown in FIG. 4B ) 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, if the conductive layer 438 is present, 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.

[0324]

[0343] In some embodiments, the materials, composition, properties, and fabrication of the reflective layer are the same as those described above with respect to FIGS.

[0325]

[0344] In some embodiments, through dry etching and wet etching, a tri-color LED structure is formed, and the axes of the LED structures of different colors are aligned perpendicular to each other. In some embodiments, the LED structures of different colors share the same axis.

[0326]

[0345] In some embodiments, each LED structure of a different color has a pyramid-like shape or a trapezoidal cross-section within its respective flat insulating structure. Each layer has a narrow width or small area compared to the layer below, where the width or area is measured by a dimension in a plane parallel to the surface of the substrate 404. In some embodiments, particularly when a flat layered structure is used, each LED structure of a different color has approximately the same lateral dimension compared to the other LED structures. When each LED structure has approximately the same area, the efficiency of light emission from the entire LED device is improved.

[0327]

[0346] In some embodiments, especially when a flat layered structure is not used and each LED structure of different colors is bonded together by a bonding layer that covers only the area of ​​the LED structure and does not extend beyond the area of ​​the LED structure, the entire multicolor LED device forms a pyramid (or inverted cone)-like shape or a trapezoidal cross-sectional shape (not shown in FIG. 4B). In some embodiments, the lateral dimension of the lower LED structure, e.g., the red LED structure, can be the longest, and the lateral dimension of the upper LED structure, e.g., the blue LED structure, can be the shortest. The pyramid-like shape can be formed naturally when each layer in the LED device is etched and patterned from bottom to top. The pyramid-like structure can improve the electronic connection between the individual LED structures and to the electrodes and simplify the fabrication process. For example, the electrode connection is exposed at each layer for easy connection.

[0328]

[0347] In some embodiments, the lower layers, such as the metal bonding layer 408, have lateral dimensions of about 1 μm to about 500 μm. In a preferred embodiment, the lateral dimension of the metal bonding layer 408 at the bottom of the multicolor LED device is about 2.0 μm. In some embodiments, the vertical height of the multicolor LED device is about 1 μm to about 500 μm. In a preferred embodiment, the vertical height of the multicolor LED device is about 1.9 μm. In a preferred embodiment, the lateral dimension of the conductive layer 438 at the top of the multicolor LED device is about 1.0 μm.

[0329]

[0348] In some embodiments, the cross-sectional aspect ratio of the layers of the tri-color LED device remains approximately the same when the lateral dimensions of the same layer are changed. For example, if the lateral dimension of the patterned epitaxial layer is 5 μm, the thickness of the patterned epitaxial layer is less than 1 μm. In another example, if the lateral dimension of the same patterned epitaxial layer is increased, the thickness of the patterned epitaxial layer is increased accordingly to maintain the same aspect ratio. In some embodiments, the cross-sectional aspect ratio of the epitaxial layer and other layers is less than 1 / 5 in thickness / width.

[0330]

[0349] The shape of the LED device is not limited, and in some other embodiments, the cross-sectional shape of the tri-color LED device can take other shapes, such as an inverted trapezoid, a semi-ellipse, a rectangle, a parallelogram, a triangle, or a hexagon.

[0331]

[0350] In some embodiments, the fabrication process of the single pixel tri-color LED device is simplified and the luminous efficiency of the single pixel tri-color LED device is improved when using a planar insulating layer such as 454, 458, and 462 covering each of the different color LED structures. For example, each of the different color LED structures itself, including the conductive layer, the reflective layer, and the electrode contact pads and their associated connections within the planar insulating layer, can be formed first, and then the LED structures are bonded together using respective bonding layers.

[0332]

[0351] In contrast, in the process of making a direct stacked tri-color LED device without planarization, where the LED structures of different colors are directly bonded together using several bonding layers, the single pixel tri-color LED device can be shaped like a pyramid (or an inverted cone) or a trapezoidal cross-section as a result of the layer-by-layer patterning (and / or etching). Thus, the effective light-emitting area of ​​the LED structure at the bottom of the stack of the single pixel tri-color LED device is the largest, while the effective light-emitting area of ​​the LED structure at the top of the stack is the smallest. The unevenness of the light-emitting area between the multiple LED structures in the LED device may reduce its light-emitting efficiency. On the other hand, when using a planar layered structure, the single pixel tri-color LED device is not limited to a pyramidal structure as described above, since each LED structure is fabricated in its own planar insulating layer. Instead, the effective light-emitting areas of the different LED structures in the single pixel tri-color LED device can be adjusted according to design. In some cases, the horizontal effective light-emitting areas of the different LED structures in the single pixel tri-color LED device are approximately the same, improving the light-emitting efficiency and ease of electrical connection. In some cases, the planarized tri-color LED structure can improve luminous efficiency by at least 5%, at least 10%, or sometimes at least 20%, compared to a simpler tri-color LED structure without planarization.

[0333]

[0352] In some embodiments, when each epitaxial substrate is used to grow each LED light emitting layer as described above, an insulating layer covering the corresponding LED light emitting layer and other layers such as conductive and reflective layers can be first deposited on each epitaxial substrate. A planarization process then follows to planarize the surface of the insulating layer with each LED structure embedded therein. Vias for electrical connection are also formed in the planarization layer before bonding.

[0334]

[0353] In some embodiments, the layers of the LED structure, including the bonding layer, can be formed directly on the planar insulating layer that already has the formed LED structure embedded in it, and then the planar insulating layer is formed over the current LED structure, and vias for electrical connection are also formed in the planar layer before the next LED structure is formed over the current LED structure.

[0335]

[0354] Compared to some other processes that do not use a planar insulating layer, in which the bonding layer directly contacts the top or bottom of the LED structure to form a device, the bonding layer can contact the planar insulating layer without touching the LED structure. Therefore, the features and layers within each of the planarized LED structures are better protected and less susceptible to external destructive forces. In addition, the planarized surface can improve light transmission efficiency by reducing deflection from non-planar surfaces.

[0336]

[0355] 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 pattern is dry etching, such as inductively coupled plasma (ICP) etching, or wet etching using an ITO etching solution. In some embodiments, the same patterning method can be applied to all other conductive layers, including conductive layers 410, 414, 428, 432, 434, and 438 in the three-color LED device 400.

[0337]

[0356] 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 for patterning is dry etching, such as inductively coupled plasma (ICP) etching, using Cl2 and BCl3 etching gases.

[0338]

[0357] In some embodiments, the bonding layer including 460 and 456 is patterned using photolithography and etching. In some cases, the etching method used for patterning is dry etching, such as inductively coupled plasma (ICP) etching, using CF4 and O2 etching gases.

[0339]

[0358] In some embodiments, the reflective layers, including 409, 415, 427, 433, 435, and 439, are patterned using photolithography and etching. In some cases, the etching method used to pattern the reflective layers, especially the DBR layers, is dry etching, such as inductively coupled plasma (ICP) etching with CF4 and O2 etching gases, or ion beam etching (IBE) with Ar gas.

[0340]

[0359] In some embodiments, the red LED light emitting layer 412 is patterned using photolithography and etching. In some cases, the etching method used for patterning is dry etching, such as inductively coupled plasma (ICP) etching, using Cl2 and HBr etching gases.

[0341]

[0360] In some embodiments, the metal bonding layer 408 is patterned using photolithography and etching. In some cases, the etching method used for patterning is dry etching using Cl2 / BCl3 / Ar etching gas, such as inductively coupled plasma (ICP) etching or ion beam etching (IBE) using Ar gas.

[0342]

[0361] In some embodiments, after each LED device structure is patterned, an insulating layer such as 454, 458, 462 is deposited on the surface of the patterned LED structure, including all of the 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, the insulating layer is formed using a composition similar to SiO2 after curing a layer such as SOG at high temperature. In some embodiments, the insulating layer is made of a material that has a similar thermal coefficient as the layer below the insulating layer. The surface of the insulating layer is then smoothed or planarized by a suitable method understood by one of ordinary skill in the art, such as chemical mechanical polishing.

[0343]

[0362] In some embodiments, after planarization, the insulating layer is patterned using photolithography and etching to expose the electrode contact areas. In some cases, the etching method used for patterning is dry etching using CF4 and O2, e.g., inductively coupled plasma (ICP) etching.

[0344]

[0363] In some embodiments, P-electrode or anode metal pads are deposited by evaporation or other deposition methods on one side of the planar insulating layer and / or in suitable locations of the patterned LED structures, such as in vias in the planar insulating layer, to electrically connect to the red, green, and blue LED structures.

[0345]

[0364] In some embodiments, separate N-electrode or cathode metal pads are evaporated or otherwise deposited at suitable locations of the patterned LED structures, such as on one side / top of the planar insulating layer and / or in vias in the planar insulating layer, to electrically connect to the red, green, and blue LED structures.

[0346]

[0365] FIG. 5 is a cross-sectional view of a single pixel tri-color LED device 500 along the diagonal 102 of FIG. 1A with a refractive structure according to some embodiments. In some embodiments, not all of which are shown in FIG. 5, the single pixel tri-color LED device 500 has a structure similar to any one of the single pixel tri-color LED devices shown in FIGS. 1-4, but with the addition of a refractive structure 502 formed on the top surface of the single pixel tri-color LED device to improve light emitting efficiency. Light emitted from the single pixel tri-color LED device is emitted through the top surface (light emitting area) of the single pixel tri-color LED device without the refractive structure. 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 planar insulating layer 176. In some embodiments, the refractive structure 502 is the same as the planar insulating layer 176 and is integrated with the planar insulating layer 176.

[0347]

[0366] In some embodiments, the refractive structure 502 is formed between an optical isolation structure, e.g., a reflector cup such as 146 and 148, and a top surface, i.e., light emitting area, of a single pixel tri-color LED device that does not have a refractive structure. 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 the same 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 N-electrode 140. In some embodiments, the top surface of the refractive structure is the same as or below the top electrode, such as N-electrode 140.

[0348]

[0367] In some embodiments, the refractive structure 502 alters the light path emitted from the single pixel tri-color LED device by converging or diverging the light emitted from the LED device according to design needs.

[0349]

[0368] In some embodiments, the refractive layer 502 is made of a dielectric material. In some embodiments, the dielectric material, such as silicon oxide, silicon nitride, silicon carbide, titanium oxide, zirconium oxide, aluminum oxide, etc., transmits the light emitted by the single pixel tri-color LED device. In some embodiments, the dielectric material is selected from one or more polymers, such as SU-8, photosensitive polyimide (PSPI), BCB, etc.

[0350]

[0369] In some embodiments, the refractive layer 502 is formed directly on the planar insulating layer, hi some embodiments, the refractive layer 502 is formed by deposition, sputtering, or other methods.

[0351]

[0370] FIG. 6A is a cross-sectional view of a single pixel tri-color LED device 600 along diagonal 102 of FIG. 1A with a microlens over a reflective structure according to some embodiments.

[0352]

[0371] FIG. 6B is a cross-sectional view of a single pixel tri-color LED device 600 along diagonal 102 of FIG. 1A with microlenses in the area formed by the reflective structure according to some embodiments.

[0353]

[0372] In some embodiments, not all of which are shown in FIGS. 6A and 6B, the single pixel tri-color LED device 600 has a structure similar to any one of the single pixel tri-color LED devices shown in FIGS. 1-5, but with the addition of microlenses 602 formed on the top surface of the single pixel tri-color LED device to improve light emitting efficiency. Light emitted from the single pixel tri-color LED device is emitted through the top surface (light emitting area) of the single pixel tri-color LED device without the microlens structure. In some embodiments, the microlenses 602 are formed directly on the surface of the flat insulating layer 176. In some embodiments, the microlenses 602 are formed directly on the surface of the refractive structure 502, as shown in FIG. 5. In some embodiments, the microlenses 602 cover and contact the exposed surface of the top electrode, such as the N-electrode 140.

[0354]

[0373] In some embodiments, optional spacers 604 are formed above the light emitting area under the microlenses 602. In some embodiments, the top surface of the spacers 604 is planarized. In some embodiments, the spacers 604 are formed directly on the surface of the planar insulating layer 176. In some embodiments, the spacers 604 are formed directly on the surface of the refractive structure 502 as shown in FIG. 5. In some embodiments, the spacers 604 are the same as the refractive structure 502 shown in FIG. 5 and are integrated therewith. In some embodiments, the spacers 604 cover and contact the exposed surface of the top electrode, such as the N-electrode 140. In some embodiments, the spacers 604 are integrated with the microlenses 602. In some embodiments, the spacers 604 are the same as the planar insulating layer 176 and are integrated therewith.

[0355]

[0374] In some embodiments, the microlens 602 is formed on the top surface, i.e., light emitting area, of the single pixel tri-color LED device between the optical isolation structures, e.g., between the reflecting structures or reflecting cups such as 146 and 148, between the optical isolation structures without the microlens. In some embodiments, the top surface of the microlens 602 is above the top of the optical isolation structures, as shown in FIG. 6A. When the top surface of the microlens 602 is above the top of the reflecting structures such as 146 and 148, substantially all of the light emitted from the single pixel tri-color LED device including the reflecting cup can be captured and focused by the microlens 602. In some embodiments, the top surface of the microlens 602 is at the same level as or below the top of the optical isolation structures, as shown in FIG. 6B. When the top surface of the microlens 602 is lower than or at the same level as the top of the reflecting structures such as 146 and 148, at least a portion of the light emitted from the microlens 602 is further reflected by the reflecting structures or reflecting cups and confined to a specific area.

[0356]

[0375] In some embodiments, the lateral dimension of the bottom of the microlenses 602 is smaller than the lateral dimension of the light emitting area. In some embodiments, the lateral dimension of the bottom of the microlenses 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 microlenses 602 is smaller than the top surface area of ​​the upper light emitting layer 136. In some embodiments, the lateral dimension of the bottom of the microlenses 602 is the same as or larger than the top surface area of ​​the upper light emitting layer 136.

[0357]

[0376] In some embodiments, optional spacers 604 are formed on the top surface, i.e., light emitting area, of the single pixel tri-color LED device without microlenses and spacers between the optical isolation structures, e.g., between the reflector cups such as 146 and 148. In some embodiments, the top surface of the spacer 604 is above the top of the optical isolation structures. In some embodiments, the top surface of the spacer 604 is the same as or below the top of the optical isolation structures. 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 the same as or below the top electrode, such as the N-electrode 140. In some embodiments, the lateral dimension of the bottom of the microlenses 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 microlenses 602 is the same as or larger than the lateral dimension of the top surface of the spacer 604.

[0358]

[0377] In some embodiments, the microlenses 602 modify the light path emitted from the single pixel tri-color LED device by converging or diverging the light emitted from the LED device according to design needs.

[0359]

[0378] In some embodiments, the spacer 604 expands the light path emitted from the single pixel tri-color LED device, hi some embodiments, the spacer 604 modifies the light path emitted from the single pixel tri-color LED device by converging or diverging the light emitted from the LED device according to design needs.

[0360]

[0379] In some embodiments, the microlenses 602 can be made from a wide variety of materials that are transparent to the wavelengths emitted by the single pixel tri-color LED device. Example transparent materials for the microlenses 602 include polymers, dielectrics, and semiconductors. In some embodiments, the dielectric material includes one or more of silicon oxide, silicon nitride, silicon carbide, titanium oxide, zirconium oxide, aluminum oxide, and the like. In some embodiments, the microlenses 602 are made from photoresist.

[0361]

[0380] The spacer 604 is an optional transparent layer formed to maintain the position of the microlens 602 relative to an underlying pixel light source, such as a single pixel tri-color LED device. The spacer 604 can be made from a wide variety of materials that are transparent to the wavelengths emitted by the pixel light source. Examples of transparent materials for the spacer 604 include polymers, dielectrics, and semiconductors. In some embodiments, the dielectric material includes one or more of 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.

[0362]

[0381] In some embodiments, the height of the microlenses 602 is 2 μm or less. In some embodiments, the height of the microlenses 602 is 1 μm or less. In some embodiments, the height of the microlenses 602 is 0.5 μm or less. In some embodiments, the height of the microlenses 602 is 4 μm or less. In some embodiments, the height of the microlenses 602 is 3 μm or less. In some embodiments, the height of the microlenses 602 is 2 μm or less. In some embodiments, the height of the microlenses 602 is 1 μm or less. In some embodiments, the ratio of the width to the height of the microlenses 602 is greater than 2.

[0363]

[0382] In some embodiments, the shape of the microlens 602 is generally hemispherical. In some embodiments, the central axis of the microlens 602 is aligned with or is the same as the central axis of the lensless single pixel tri-color LED device.

[0364]

[0383] For clarity, Figures 6A and 6B show that in some embodiments, in a display panel, each single pixel light source, such as a tri-color LED device, corresponds to one microlens 602. It should be understood that a full display panel includes an array of many individual pixels and many microlenses. In addition, there need not be a one-to-one correspondence between the microlenses and the pixel light sources, nor between the pixel driving circuit (not shown) and the pixel light sources. A pixel light source can also be made of multiple individual light elements, for example, single pixel LEDs connected in parallel. In some embodiments, one microlens 602 can cover several lensless single pixel tri-color LED devices.

[0365]

[0384] Each microlens 602 has a positive refractive power and is positioned to reduce the divergence or viewing angle of the light emitted from the corresponding pixel light source. In one example, the light beam emitted from the pixel light source has a fairly wide original divergence angle. In one embodiment, the original angle of the edge ray of the light beam with respect to the normal axis perpendicular to the substrate 104 is more than 60 degrees. The light is bent by the microlens 602, so that the new edge ray now has a reduced divergence angle. In one embodiment, the reduced angle is less than 30 degrees. The microlenses in the microlens array are typically the same. Examples of microlenses include spherical microlenses, aspherical microlenses, Fresnal microlenses, and cylindrical microlenses.

[0366]

[0385] The microlenses 602 typically have a flat surface and a curved surface. In FIG. 6, the bottom of the microlenses 602 is a flat surface, and the top of the microlenses 602 is a curved surface. Typical shapes of the base of each microlens 602 include a circle, a square, a rectangle, and a hexagon. The individual microlenses in the microlens array of the display panel may have the same or different shapes, curvatures, optical powers, sizes, bases, and spacings. In some embodiments, the microlenses 602 conform to the shape of a single pixel tri-color LED device. In one example, the shape of the base of the microlenses 602 is the same as that of the single pixel tri-color LED structure, e.g., in FIG. 6A and FIG. 6B, both are circular. In another example, the shape of the base of the microlenses 602 is not the same as that of the single pixel tri-color LED device, e.g., the circular base of the microlenses has the same width as the single pixel tri-color LED, but has a smaller area because the base of the microlenses is circular and the base of the single pixel tri-color LED is square. In some embodiments, the area of ​​the microlens base is smaller than the area of ​​the pixel light source, hi some embodiments, the area of ​​the microlens base is the same as or larger than the area of ​​the pixel light source.

[0367]

[0386] In some embodiments where the microlenses 602 are formed, the spacer layer 604 can be formed in the same process using the same materials along with the microlenses 602. In some embodiments, the height of the pixel light source is greater than, the same as, or less than the thickness of the spacer 604 measured from the bottom of the substrate 104.

[0368]

[0387] The thickness of the spacer 604 is designed to maintain an appropriate spacing between the microlens 604 and the pixel light source. As an example, for a spacer that maintains an optical spacing between the pixel light source and the microlens that is greater than the focal length of the microlens, an image of a single pixel is formed at a particular 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 reduction in divergence / field of view is achieved. The amount of reduction in divergence / field 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 1 μm or less. In some embodiments, the thickness of the spacer 604 measured from the top surface of the pixel light source is 0.5 μm or less. In some embodiments, the thickness of the spacer 604 measured from the top surface of the pixel light source is 0.2 μm or less. In some embodiments, the thickness of the spacer 604 measured from the top surface of the pixel light source is about 1 μm.

[0369]

[0388] In some embodiments, the brightness enhancement effect is achieved through the integration of a microlens array into the display panel. In some examples, the brightness with the microlens array is four times that without the microlens array in the direction perpendicular to the display surface due to the focusing effect of the microlenses. In alternative embodiments, the brightness enhancement factor can vary according to different designs of the microlens array and the optical spacer. For example, a factor of more than 8 can be achieved.

[0370]

[0389] In some embodiments, a first method of making microlenses includes depositing a microlens material layer directly on at least the top of the pixel light source and in 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 generally flat and the shape of the formed microlenses 602 is generally hemispherical. In some embodiments, the microlens material layer is deposited by chemical vapor deposition (CVD) directly on the surface of the pixel light source, such as the planarized surface of a single pixel tri-color LED device. In some embodiments, the deposition parameters of the CVD process are as follows: power is about 0 W to about 1000 W, pressure is about 100 mTorr to about 2000 mTorr, temperature is about 23° C. to about 500° C., gas flow is about 0 sccm (standard cubic centimeters per minute) to about 3000 sccm, and time is about 1 hour to about 3 hours. In some embodiments, the material of the microlens material layer is a dielectric material such as silicon dioxide.

[0371]

[0390] In some embodiments, the first method of making microlenses further comprises patterning the microlens material layer, thereby exposing the electrode areas of the substrate. In some embodiments, the patterning the microlens material layer comprises an etching step. In some embodiments, the etching step comprises forming a mask on the surface of the microlens material. The etching step also comprises patterning the mask via a photolithography process, thereby forming openings in the mask and exposing the microlens material layer above the electrode areas of the pixel light sources. The etching step further comprises etching the portions of the microlens material layer exposed by the openings while the mask is protected. In some embodiments, the exposed microlens material layer is etched by a wet etching method.

[0372]

[0391] In some embodiments, the second method of making microlenses also includes an optional step of forming a mark layer having marks for aligning a microlens material layer deposited in a later step. For example, the mark layer is formed to align a unit of light-emitting pixels to the microlens material layer to form a microlens at the center of the pixel light source. In some embodiments, the mark layer is formed to align a pixel light source to a layer above the pixel light source, particularly the microlens material layer, to form a microlens on top of the pixel light source.

[0373]

[0392] The second method of fabricating the microlenses further includes depositing a microlens material layer directly on at least one pixel light source. Figures 6C and 6D further illustrate a fabrication method of forming a display panel with an integrated microlens array using top-down pattern transfer according to some embodiments. In some embodiments, the microlens material layer 645 covers the top of the pixel light source 606M as shown in Figure 6C, and the top surface of the microlens material layer 645 is flat. In some embodiments, the microlens material layer 645 is deposited on top of the pixel light source array 606 by spin coating. In some embodiments, the material of the microlens material layer 645 is a photoresist. In some embodiments, the material of the microlens material layer 645 is a dielectric material such as silicon oxide.

[0374]

[0393] A second method of fabricating a microlens further includes patterning the microlens material layer from top to bottom, thereby forming at least one hemisphere in the microlens material layer, as shown in Figures 6C and 6D. In some embodiments, the patterning is performed without etching through or to the bottom of the microlens material layer 645. In some embodiments, the hemisphere of the microlens 620 is disposed above at least one pixel light source 606M.

[0375]

[0394] In some embodiments, patterning the microlens material layer from top to bottom further comprises a first step of depositing a mask layer 630 on the surface of the microlens material layer 645, as shown in Figure 6C.

[0376]

[0395] The step of patterning the microlens material layer from top to bottom 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 patterned by a reflow process. In some embodiments, the photosensitive polymer mask layer 630 is patterned into isolated cells 640 to prepare for the formation of a hemispherical pattern, as shown by the dotted rectangular cells in FIG. 6C. As an example, the isolated cells 640 are patterned and formed through a photolithography process. The patterned photosensitive polymer mask layer 650 with isolated cells 640 is then formed into a hemispherical pattern 660 using a high-temperature reflow process. In one approach, the isolated cells 640 are formed into the isolated hemispherical pattern 660 through high-temperature reflow. In some embodiments, the isolated hemispherical pattern 660 of one pixel does not directly physically contact the hemispherical pattern of an adjacent pixel. In some embodiments, the hemispherical pattern 660 of one pixel only contacts the hemispherical pattern of the 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 time. After the polymer material melts to a liquefied state, the surface tension of the liquefied material results in a shape with a smooth surface curvature. For a cell with a round base of radius R, a hemispherical shape / pattern is formed after the reflow process when the cell height is 2R / 3. FIG. 6C shows a display panel integrated with an array of hemispherical patterns 660 after the high temperature reflow process. In some embodiments, the hemispherical pattern in the mask layer can also be formed by other fabrication methods, including the microlens fabrication method described in the first method of fabricating microlenses. In some other embodiments, the hemispherical pattern in the mask layer can be formed using a grayscale mask photolithography exposure. In some other embodiments, the hemispherical pattern in the mask layer can be formed via a molding / imprinting process.

[0377]

[0396] The step of patterning the microlens material layer from top to bottom further includes a third step of using the hemisphere pattern 660 as a mask to etch the microlens material layer 645 to form hemispheres in the microlens material layer 645. In some examples, etching the microlens material layer 645 is by a photolithography process. In some examples, etching the microlens material layer 645 is by dry etching, such as a plasma etching process 635, as shown in FIG. 6C. In some embodiments, after the microlens material layer 645 is etched, the microlens material layer 645 is not etched until it exposes the top surface of the pixel light source 606M, as shown in FIG. 6C and FIG. 6D, so that the spacer 670 is formed on the top of the pixel light source 606M, or the spacer 670 covers the top of the pixel light source 606M, as shown in FIG. 6D.

[0378]

[0397] The second method of making the microlenses further includes patterning the microlens material layer, thereby exposing the electrode area (not shown in FIG. 6D) of the substrate. In some embodiments, the patterning the microlens material layer includes etching. In some embodiments, the etching includes forming a mask on the surface of the microlens material. The etching also includes patterning the mask through a photolithography process, thereby forming an opening in the mask and exposing the microlens material layer above the electrode area of ​​the pixel light source. The etching further includes etching the exposed microlens material layer while the mask is protected. In some embodiments, the exposed microlens material layer is etched by a wet etching method. In some embodiments, the opening of the electrode is positioned outside the display array area.

[0379]

[0398] As mentioned above, Figures 6A-6D show various fabrication methods for forming a display panel with an integrated microlens array, it should be understood that these are merely examples and other fabrication techniques may be used.

[0380]

[0399] Although the detailed description contains many details, these should not be interpreted 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 described in detail above. For example, it is also possible to use microlenses with bases of different shapes, such as square bases or other polygonal bases.

[0381]

[0400] Figure 7 is a cross-sectional view 700 of three single pixel tri-color LED devices 710, 720, and 730 along a diagonal such as 102 in Figure 1A on a substrate 104, according to some embodiments. In some embodiments, although not all are shown in Figure 7, each of the single pixel tri-color LED devices 710, 720, and 730 has a structure similar to any one 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 a rectangle 750 is equivalent to the cross-sectional view shown in any of Figures 1-16 described above.

[0382]

[0401] In some embodiments, as shown in any of the embodiments of Figures 1-7, the single pixel tri-color LED device further comprises one or more reflective cup structures, such as 702, 704, and 706. The reflective structures, such as 702, 704, and 706, surround each of the single pixel tri-color LED devices 710, 720, and 730. The reflective cups may be formed on the semiconductor substrate 104 and positioned around the light emitting area from which the light from the single pixel tri-color LED device is emitted. For example, as shown in Figures 1A-1C, from the cross-sectional view along the 102 direction in Figure 1B and the cross-sectional view along the 150 direction in Figure 1C, the reflective cup may include four reflective cup portions 146, 148, 170, and 172. In some embodiments, the reflective cup portions 146, 148, 170, and 172 may be formed on the semiconductor substrate 104 and positioned around the light emitting area. In some embodiments, the reflector cup can separate at least some or substantially all of the light emitted from the light emitting area. For example, as shown in Figures 1B and 1C, when the height of the reflector cup is greater than the height of the light emitting area, the reflector cup portions 146, 148, 170, and 172 can separate at least some or substantially all of the light emitted from the light emitting area. Thus, the reflector cup can suppress inter-pixel optical crosstalk and improve the overall contrast of the LED display. Reflection from the reflector cup also increases luminous efficiency and brightness by focusing the light emission in a particular direction.

[0383]

[0402] In some embodiments, the height of the reflective cup may be greater than the height of the bottom LED structure, such as a red LED structure, greater than the height of the middle LED structure, such as a green LED structure, or greater than the height of the top LED structure, such as a blue LED structure. In some embodiments, the total height of the reflective cup may be greater than the combined height of the bottom LED structure, such as a red LED structure, the middle LED structure, such as a green LED structure, and the top LED structure, such as a blue LED structure. In some embodiments, the total height of the reflective cup may be greater than the height of a single pixel tri-color LED device without a planar layer. In some embodiments, the height of the reflective cup is between 0.5 μm and 50 μm. In some embodiments, the height of the reflective cup is between 1 μm and 20 μm. In some embodiments, the height of the reflective cup is between 2 μm and 10 μm. In some embodiments, the height of the reflective cup is about 2.5 μm, while the height of the single pixel tri-color LED device without a planar layer is about 1.9 μm. Additionally, in some embodiments, the reflective cup portions 146, 148, 170, and 172 may have different heights. In some embodiments, the cross section of the reflective cup portion such as 146 or 148 is triangular. In some embodiments, the cross section of the reflective cup portion such as 146 or 148 is trapezoidal with the base longer than the top. In some embodiments, the width of the bottom of the reflective cup portion such as 146 or 148 is between 0.3 μm and 50 μm. In some embodiments, the width of the bottom of the reflective cup portion such as 146 or 148 is between 0.5 μm and 25 μm. In a preferred embodiment, the width of the bottom of the reflective cup portion such as 146 or 148 is about 1 μm. In some embodiments, the distance of the bottom closest edge of the reflective cup portion such as 146 or 148 to the bottom closest edge of the single pixel tri-color LED device is between 0.2 μm and 30 μm. In some embodiments, the distance of the bottom closest edge of the reflective cup portion such as 146 or 148 to the bottom closest edge of the single pixel tri-color LED device is between 0.4 μm and 10 μm. In a preferred embodiment, the distance of the bottom nearest edge of a reflective cup portion such as 146 / 446 or 148 / 448 to the bottom nearest edge of a single pixel tri-color LED device such as p-electrode connection structure 422 as shown in FIG. 4B is about 0.6 μm.

[0384]

[0403] In some embodiments, the center-to-center distance between adjacent reflector cup portions, such as 146 / 446 and 148 / 448 of the single pixel tri-color LED device, is between 1 μm and 50 μm. In a preferred embodiment, the center-to-center distance between adjacent reflector cup portions, such as 146 and 148 of the single pixel tri-color LED device, is about 5 μm.

[0385]

[0404] In some embodiments, a divergence angle of 0° may correspond to light propagating perpendicular to the top surface of the light emitting region, and a divergence angle of 90° may correspond to light propagating parallel to the top surface of the light emitting region. By modifying the geometry of the reflector cup, the divergence angle of the light emitted from the light emitting region can be controlled. Thus, the reflector cup can reduce the divergence of the light emitted from the light emitting region and increase the brightness of the single pixel multi-color LED device. In some embodiments, the sidewalls 146-1, 148-1, 170-1, and 172-1 of the reflector cup can be straight, curved, wavy, multi-lined, or combinations thereof, as shown in FIG. 1B and FIG. 1C. 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 the light emitted from the light emitting region. For example, the angle of the sidewalls of the reflective cup portions 146, 148, 170, and 172 with respect to a vertical axis perpendicular to the substrate 104 may be at least 15 degrees and at most 75 degrees. The angle of the sidewalls of the reflective cup portions 146, 148, 170, and 172 with respect to a vertical axis perpendicular to the substrate 104 may be at least 5 degrees and at most 60 degrees. In some preferred embodiments, the angle of the sidewalls of the reflective cup portions 146, 148, 170, and 172 with respect to a vertical axis perpendicular to the substrate 104 may be at least 10 degrees and at most 50 degrees. The reflective cups can also reflect some of the light emitted from the light emitting area upward. For example, some of the light emitted from the light emitting area may reach the reflective cup portions 146, 148, 170, and 172 and be reflected upward by the reflective cup portions 146, 148, 170, and 172.

[0386]

[0405] In some embodiments, the reflector cup may include a metal. In some embodiments, the reflector cup may include a dielectric material, such as silicon oxide. In some embodiments, the reflector cup 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 cup may include a photoresist.

[0387]

[0406] In some embodiments, the reflector cup can be made by a combination of deposition, photolithography, and etching processes. In some embodiments, the reflector cup can be made by other suitable methods. In one approach, the PSPI is formed into a reflector cup shape by 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 a TiO2 / SiO2 layer, any other layer with total reflectivity including a multi-layer omnidirectional reflector (ODR), or a combination thereof is deposited by evaporation on the entire surface of the multi-color LED device including the reflector cup as a reflector layer. Then, the reflector layer in the reflector cup area is shaped by photoresist, while the reflector layer in other areas is etched, thereby exposing the light-emitting area.

[0388]

[0407] In another approach, a separation layer including one or more of SiO2, silicon nitride, or SU8, which is thicker than the stacked LED structure, is deposited or spun onto the stacked LED structure. Then, using photoresist as a mask, the separation layer is etched and formed into a reflective cup shape. Next, 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 layer, any other layer with total reflectivity including a multi-layer omnidirectional reflector (ODR), or a combination thereof is deposited by evaporation on the entire surface of the multi-color LED device including the reflective cup as a reflective layer. Finally, the reflective layer in the reflective cup area is shaped by photoresist, while the reflective layer in other areas is etched, thereby exposing the light-emitting area.

[0389]

[0408] In some embodiments, as shown in Figures 2-6, the single pixel tri-color LED device further includes one or more top electrodes (e.g., top electrodes 140 / 440, 442, and 444) integrated with the reflective cup. The one or more top electrodes may be electrically connected to the top electrode (layer) 140 / 440. For example, as shown in Figure 4B, electrodes 442 and 444 may be integrated with the reflective cup, e.g., reflective cup portions 446 and 448, respectively. Both top electrodes 442 and 444 may extend toward the light-emitting area and be electrically connected to the top electrode (layer) 140 / 440. The reflective cup may be implemented as a common P-electrode or N-electrode of the single pixel tri-color LED device employing one or more top electrodes. For example, when the top electrode (layer) 140 / 440 is electrically connected to each LED structure (e.g., an LED structure including light-emitting layers 112 / 412, 130 / 430, and 136 / 436) and optionally the top electrodes 442 and 444, the reflector cup can act as a common P or N electrode of a single pixel tri-color LED device.

[0390]

[0409] In some embodiments, the reflector cup further includes one or more reflective coatings. The one or more reflective coatings may be deposited on one or more sidewalls of the reflector cup, for example, sidewalls 146-1, 148-1, 170-1, and 172-1 of the reflector cup. The bottom of each of the one or more reflective coatings does not contact each LED structure, for example, red, green, and blue LED structures. The one or more reflective coatings may reflect light emitted from the light-emitting region, thus increasing the brightness and luminance effectiveness of the micro-LED panel or display. For example, light emitted from the light-emitting region may reach the one or more reflective coatings and be reflected upward by the one or more reflective coatings.

[0391]

[0410] The one or more reflective coatings together with the reflective cup can utilize the reflection direction and / or reflection intensity of the light emitted from the light-emitting region. For example, the sidewalls 146-1, 148-1, 170-1, and 172-1 of the reflective cup can be inclined at a certain angle, and therefore the one or more reflective coatings deposited on the sidewalls 146-1, 148-1, 170-1, and 172-1 of the reflective cup are also inclined at the same angle as the sidewalls 146-1, 148-1, 170-1, and 172-1 of the reflective cup. When the light emitted from the light-emitting region reaches the one or more reflective coatings, the light emitted from the light-emitting region is reflected by the one or more reflective coatings according to the angles of the sidewalls 146-1, 148-1, 170-1, and 172-1 of the reflective cup.

[0392]

[0411] The material of the reflective coating(s) may be highly reflective, having a reflectance of more than 60%, more than 70%, or more than 80%, and thus may reflect most of the light emitted from the light-emitting region. In some embodiments, the reflective coating(s) may include one or more metallic conductive materials having a high reflectance. In these embodiments, the metallic conductive materials may include one or more of aluminum, gold, or silver. In some other embodiments, the reflective coating(s) may be multi-layered. More specifically, the reflective coating(s) may include a stack of one or more reflective material layers and one or more dielectric material layers. For example, the reflective coating(s) may include one reflective material layer and one dielectric material layer. In other embodiments, the reflective coating(s) may include two reflective material layers and one dielectric material layer located between the two reflective material layers. In yet some other embodiments, the one or more reflective coatings may include two dielectric layers and a reflective layer located between the two dielectric layers, hi some embodiments, the multi-layer structure may include two or more metal layers, which may include one or more of TiAu, CrAl, or TiWAg.

[0393]

[0412] In some embodiments, the one or more reflective coatings may be a multi-layer omnidirectional reflector (ODR) including a metal and a transparent conductive oxide (TCO) layer. For example, the multi-layer structure may include a dielectric material layer, a metal layer, and a TCO layer. In some embodiments, the one or more reflective coatings may include two or more dielectric material layers alternately deposited to form a distributed Bragg reflector (DBR). For example, the one or more reflective coatings may include a dielectric material layer, a metal layer, and a transparent dielectric layer. The transparent dielectric layer may include one or more of SiO2, Si3N4, Al2O3, or TiO2. The one or more reflective coatings may further include a dielectric material layer, a TCO, and a DBR. In other embodiments, the one or more reflective coatings may include one or more metallic conductive materials having high reflectivity. In these embodiments, the one or more metallic conductive materials may 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 such as 109, 115, 127, 133, and 135 above and below the emissive layer, as described above.

[0394]

[0413] In some embodiments, the reflective coating(s) can be electrically conductive, in which case the reflective coating(s) can also function as electrical contacts to the single pixel multicolor LED device. For example, the top electrode (layer) 140 can be electrically connected to the reflective coating(s). In another example, the reflective coating(s) can be electrically connected to the transparent electrode contact layer(s) 114, 132, and 138. The reflective coating(s) can be patterned so as not to block light emitted from the light emitting region. In that case, the reflective coating(s) can also function as a common electrode for the LED structure in the single pixel multicolor LED device and / or the LEDs on the display panel.

[0395]

[0414] In some embodiments, a top conductive layer that connects to the electrodes is formed on the top of the multi-color LED device, and the top conductive layer is electrically connected to the reflective cup. In some embodiments, the top conductive layer is in direct contact with the top of the reflective cup or the bottom of the reflective cup.

[0396]

[0415] In some embodiments, a bottom dielectric layer is formed between the bottom of the reflective cup and the semiconductor substrate.

[0397]

[0416] In some embodiments, one or more of the reflective coatings may be produced by one or more of an electron beam deposition or sputtering process.

[0398]

[0417] In some embodiments, the reflector cup can have a shape of a stair-like structure. FIG. 8 is a cross-sectional view of a single pixel tri-color LED device 800 having a stepped reflector cup along a diagonal such as 402 in FIG. 4A according to some embodiments. In some embodiments, not all of which are shown in FIG. 8, the single pixel tri-color LED device 800 has a structure similar to any one of the single pixel tri-color LED devices shown in FIGS. 1-7, but has reflector cup portions such as 146, 148, 170, and 172, having a stepped reflector cup. The stepped reflector cup can be formed on the semiconductor substrate 104 / 404 and positioned around the light-emitting area. For example, as shown in FIG. 8, from a cross-sectional view along a diagonal such as 402 in FIG. 4A, the stepped reflector cup can include two stepped reflector cup portions 846 and 848. The stepped reflector cup portions 846 and 848 can be formed on the semiconductor substrate 104 / 404 and positioned around the light-emitting area. In some embodiments, the stepped reflector cup can separate at least some or substantially all of the light emitted from the light emitting area. For example, as shown in FIG. 8, when the height of the stepped reflector cup is greater than the height of the light emitting area, the stepped reflector cup portions 846 and 848 can separate at least some or substantially all of the light emitted from the light emitting area. Thus, the stepped reflector cup can suppress inter-pixel optical crosstalk and improve the overall contrast of the LED display.

[0399]

[0418] In some embodiments, the stepped reflector cup includes one or more step structures, such as 846-1, 846-2, 846-3, 848-1, 848-2, and 848-3. In some embodiments, the height of each step of the reflector cup can be the same as the height of the LED structure at the same vertical level. For example, the step structures 846-1 and 848-1 each have the same height as the bottom LED structure. The step structures 846-2 and 848-2 each have the same height as the middle LED structure. The step structures 846-3 and 848-3 each have the same height as the top LED structure. Additionally, in some embodiments, the stepped reflector cup portions 846 and 848 can have the same or different heights. The stepped reflector cup can also reflect some of the light emitted from the light emitting region upwards. For example, some of the light emitted from the light emitting region may reach the stepped reflector cup portions 846 and 848 and be reflected upward by the stepped reflector cup portions 846 and 848 for each LED structure in the single pixel multi-color LED device in different patterns according to the design. For example, each step may adjust the convergence of the emitted light (especially horizontally) in different patterns. For example, the red light of the light beam from the LED device may be more focused in the center and the blue light may be more focused on the edge. Thus, the divergence of the light emitted from the light emitting region may be reduced and the brightness of the single pixel multi-color LED device may be increased.

[0400]

[0419] In some embodiments, the stepped reflector cup structure may include or form a cavity that surrounds the light emitting region. The cavity may include an area above the semiconductor substrate 404 that is surrounded by the stepped reflector cup. The cavity may include an inner sidewall, which may include a plurality of sloping surfaces. For example, as shown in FIG. 8, the stepped reflector cup may include or surround a cavity that is between stepped reflector cup portions 846 and 848 and may include an area above the semiconductor substrate 404. The light emitting region may be positioned within the cavity and may be surrounded by the stepped reflector cup portions 846 and 848.

[0401]

[0420] In some embodiments, the top of the cavity is higher than the top of the light-emitting area. For example, the top of the cavity in a stepped reflector cup (e.g., stepped reflector cup portions 846 and 848) is higher than the top of the light-emitting area. In some embodiments, the cavity can include an inner sidewall, and the inner sidewall can include multiple sloped surfaces (e.g., sloped surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S). In some embodiments, the slope angle (relative to the surface of the substrate 404) of the multiple sloped surfaces from bottom to top of the cavity is large. For example, as shown in FIG. 8, the angles of the sloped surfaces 846-1S, 846-2S, and 846-3S are indicated as slope angles α, β, and γ, respectively. The inclination angles of the inclined surfaces 846-1S, 846-2S, and 846-3S may be the same as the inclination angles of the inclined surfaces 848-1S, 848-2S, and 848-3S, respectively. In some embodiments, the inclination angles α, β, and γ remain the same from the bottom to the top of the cavity, or increase from the bottom to the top. In some preferred embodiments, the inclination angles α, β, and γ may decrease from the bottom to the top of the cavity, and thus the light emitted from the LED device may diverge more toward the upper part of the LED device. In further embodiments, the inclination angles α, β, and γ may be any angle according to the design. In some embodiments, the cavity may be filled with a material including silicon, such as silicon oxide, and the filling may improve the optical refraction, increase the transparency, and / or increase the UV aging and heat aging resistance. In some embodiments, the cavity may be empty or vacuum. In some embodiments, the inclined surfaces (eg, inclined surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S) can be straight, curved, wavy, multi-line, or a combination thereof.

[0402]

[0421] In some embodiments, the cavity may include multiple sub-cavities. The sub-cavities may be formed or bounded by each of the sloping surfaces and may have different dimensions in the horizontal direction. For example, there may be three sub-cavities as shown in FIG. 8. The sub-cavities at the bottom of the cavity may include areas bounded or limited by the semiconductor substrate 104 / 404, the sloping surfaces 846-1S and 848-1S, and the bottom of the bonding layer 156 / 456. The sub-cavities in the middle of the cavity may include areas bounded or limited by the bottom of the bonding layer 156 / 456, the sloping surfaces 846-2S and 848-2S, and the bottom of the bonding layer 160 / 460. The sub-cavity at the top of the cavity may include an area surrounded or limited by the bottom of the bonding layer 160 / 460, the inclined surfaces 846-3S and 848-3S, and the top of the electrode layer 140 / 440 (or the top of the opening at the top of the staircase structure 846-3 and 848-3). In some embodiments, the inclined surfaces of the sub-cavity are not arranged in the same plane. For example, as shown in FIG. 8, the sub-cavity may be formed or surrounded by multiple inclined surfaces 846-1S, 846-2S, 846-3S, 848-1S, 848-2S, and 848-3S and may have different dimensions in the horizontal direction. In some embodiments, the inclined surfaces 846-1S, 846-2S, and 846-3S may not be arranged in the same plane, and the inclined surfaces 848-1S, 848-2S, and 848-3S may not be arranged in the same plane. For example, the inclined surfaces 846-1S, 846-2S, and 846-3S are staggered in different planes in the vertical direction.

[0403]

[0422] In some embodiments, the heights of the subcavities may be different. For example, the height of a subcavity in the middle of the cavity may be lower than the height of the other subcavities. The height of a subcavity at the top of the cavity may be higher than the height of a subcavity at the bottom of the cavity. Furthermore, in some embodiments, each color LED structure is in a different subcavity of the subcavity. For example, a lower red LED structure is in a subcavity at the bottom of the cavity, and an upper blue LED structure is in a subcavity at the top of the cavity. A middle green LED structure is in a subcavity in the middle of the cavity. In some embodiments, the subcavities may be filled with a material including silicon, e.g., silicon oxide, which may improve optical refraction, increase transparency, and / or enhance UV and heat aging resistance. In some embodiments, the materials of the subcavities may be different. For example, the material of the sub-cavity at the top of the cavity may be filled with silicon oxide and the material of the sub-cavity at the bottom of the cavity may be filled with epoxymethylsilicone, hi some embodiments, the sub-cavities may be empty or vacuum.

[0404]

[0423] In some embodiments, the stepped reflector cup may include a metal. In some embodiments, the stepped reflector cup may include a dielectric material such as silicon dioxide. In some embodiments, the stepped reflector cup may include a photosensitive dielectric material. In some embodiments, the photosensitive dielectric material may include SU-8 or photosensitive polyimide (PSPI). In other embodiments, the stepped reflector cup may include a photoresist. In some embodiments, the fabrication process for the stepped reflector cup is similar to that described above with reference to the reflector cup.

[0405]

[0424] In some embodiments, the single pixel multicolor LED device 800 further includes one or more reflective coatings. The one or more reflective coatings may be deposited on one or more sloping surfaces of the stepped reflector cup, for example, sloping 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 each LED structure, for example, red, green, and blue LED structures. The one or more reflective coatings may reflect light emitted from the light-emitting region, thus enhancing the brightness and luminance effectiveness of the micro-LED panel or display. For example, light emitted from the light-emitting region may reach the one or more reflective coatings and be reflected upward by the one or more reflective coatings.

[0406]

[0425] The one or more reflective coatings can utilize the reflection direction and / or reflection intensity of the light emitted from the light-emitting region together with the stepped reflector cup. For example, the inclination angles α, β, and γ of the inclined surfaces 846-1S, 846-2S, and 846-3S, respectively, can be smaller from the bottom to the top of the cavity, and thus the one or more reflective coatings deposited on the inclined surfaces 846-1S, 846-2S, and 846-3S are inclined at the same angle as the inclined surfaces 846-1S, 846-2S, and 846-3S. When the light emitted from the light-emitting region reaches the one or more reflective coatings, the light emitted from the light-emitting region is reflected by the one or more reflective coatings according to the inclination angles α, β, and γ. The inclination angles α, β, and γ can be larger, remain the same, or smaller, or the inclination angles α, β, and γ are otherwise selected according to a specific design.

[0407]

[0426] The material of the reflective coating(s) may be highly reflective, having a reflectivity of more than 60%, more than 70%, or more than 80%, and thus may reflect most of the light emitted from the light emitting region. In some embodiments, the material of the reflective coating(s) may be similarly described with reference to the reflective cup. In some embodiments, the material of the reflective coating(s) deposited on each inclined surface may be different. For example, the material of the reflective coating deposited on the inclined surface 846-1S may be different from the material of the reflective coating deposited on each of the inclined surfaces 846-2S and 846-3S.

[0408]

[0427] In some embodiments, one or more of the reflective coatings can be produced by one or more of e-beam deposition or sputtering processes. In some embodiments, each of the one or more staircase 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, the staircase structures, such as 846-1 and 848-1, are formed in the same step before or after the planar layer 454 is formed. The staircase structures, such as 846-2 and 848-2, are formed in the same step before or after the planar layer 458 is formed. The staircase structures, such as 846-3 and 848-3, are formed in the same step before or after the planar layer 462 is formed. In some embodiments, the staircase structures are formed as a result of layer-by-layer processes and rearrangements of junctions of different planar layers that comprise the LED structures, especially when layer-by-layer planarization is involved in the process of forming a single pixel tri-color LED device. In some embodiments, there may be gaps (not shown in FIG. 8) between different step structures such as 846-1, 846-2, and 846-3 as a result of layer-by-layer processing and rearrangement of junctions of different planar layers that comprise the LED structure.

[0409]

[0428] In some embodiments, the reflector cup can have a floating structure. Figure 9 is a cross-sectional view of a single pixel tri-color LED device 900 with a floating reflector cup taken along a diagonal line such as 402 in Figure 4A according to some embodiments. In some embodiments, not all of which are shown in Figure 9, the single pixel tri-color LED device 900 has a structure similar to any one of the single pixel tri-color LED devices shown in Figures 1-8, but has floating reflector cup portions such as 946 and 948.

[0410]

[0429] In some embodiments, the floating reflector cup may surround the light emitting region, and the bottom of the reflector cup may not directly contact the semiconductor substrate 104 / 404. For example, as shown in FIG. 9, the reflector cup portions 946 and 948 may surround the light emitting region, and the bottom of the reflector cup portions 946 and 948 may not directly contact the semiconductor substrate 104, e.g., there may be a gap between the bottom of the reflector cup and the substrate 104 / 404. In some embodiments, the gap is filled with a planar insulating layer 454. In some embodiments, light emitted from the light emitting region may reach the reflector cup and may be reflected upward by the reflector cup. For example, as shown in FIG. 9, light emitted from the light emitting region, including light emitted from the sidewalls and / or top of the LED structure, may reach the reflector cup portions 946 and 948 and may be reflected upward by the reflector cup portions 946 and 948. Thus, the divergence of the light emitted from the light emitting region may be reduced, and the brightness of the single pixel multi-color LED device may be increased.

[0411]

[0430] In some embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 104 / 404 can be adjusted according to design needs. 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 manufacturing process of the single pixel multicolor LED device and the display panel. When the manufacturing of the single pixel multicolor LED device 900 is completed, this distance is fixed and not adjustable. In other embodiments, the distance between the bottom of the reflector cup and the top surface of the semiconductor substrate 104 / 404 can be specifically selected during the design process and is fixed after the manufacturing of the single pixel multicolor LED device 900 and the display panel. In some embodiments, the distance between the bottom of the reflector cup, such as portions 946 and 948, to the top surface of the substrate 404 can be equal to or less than the distance between the top surface of the bonding layer 408 at the bottom of the light emitting layer 412 to the top surface of the substrate 404. In some embodiments, the distance between the bottom of the reflective cups, such as portions 946 and 948, to the top surface of the substrate 404 can be greater than the distance between the top surface of the bonding layer 408 below the light emitting layer 412 to the top surface of the substrate 404. By adjusting the gap of the floating reflective cups, certain light from certain portions of the single pixel multi-color LED device 900 is not reflected or separated, allowing the light to be better focused on selected portions of the device 900.

[0412]

[0431] In some embodiments, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 404 can be less than 0.5 μm. In some embodiments, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 404 can be less than 1 μm. In some embodiments, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 140 can be less than 2 μm. In some embodiments, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 404 can be less than 5 μm. In some embodiments, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 404 can be less than 10 μm. In some embodiments, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 404 can be less than 20 μm. In some embodiments, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 404 can be less than 50 μm. In some embodiments, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 404 can be less than 75 μm. In some embodiments, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 404 can be less than 100 μm. In general, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 404 depends on the height of the bottom of the light emitting layer, such as the thickness of the metal bonding layer. In a preferred embodiment, the distance between the bottom of the reflective cup and the top surface of the semiconductor substrate 404 is 20 μm or less.

[0413]

[0432] In some embodiments, the reflector cup can separate at least some of the light emitted from the light emitting area. For example, as shown in FIG. 9, when the height of the reflector cup is greater than the height of the light emitting area, the reflector cup portions 946 and 948 can separate at least some of the light emitted from the light emitting area. Thus, the reflector cup can suppress inter-pixel optical crosstalk and improve the overall contrast of the LED display. The floating reflector cup has the same or similar composition, shape, and fabrication process (except for the position and location) as the reflector cup described above.

[0414]

[0433] 1-9 show only a single pixel multicolor LED device according to some embodiments. In other embodiments, the reflector cup can be of different shapes when viewed from a top view or a side view. That is, the sidewall of the reflector cup surrounding the light emitting area can be circular, triangular, square, rectangular, pentagonal, hexagonal, and octagonal. The sidewall of the reflector cup can surround one light emitting area or one single pixel multicolor LED device or a group of light emitting areas or a group of single pixel multicolor LED devices. For example, the sidewall of the reflector cup can surround two or more light emitting areas or single pixel multicolor LED devices arranged in the same plane.

[0415]

[0434] An array of single pixel multicolor LED devices may be utilized, each of which may include a reflective cup. Each reflective cup may have a different shape when viewed from a top or side view. For example, the reflective cup of a first single pixel multicolor LED device may be circular, while the reflective cup of an adjacent single pixel multicolor LED device may be square. In addition, the reflective cups may be electrically isolated from each other. The reflective cups may also be separated if a buffer space is provided between adjacent reflective cups or the material of the reflective cup may not extend all the way to the boundary with the adjacent reflective cups. Alternatively, a reflective coating formed on the sidewall of the reflective cup may simply extend to cover the gap area between adjacent reflective cups. In another embodiment, the reflective cups may be electrically connected to each other by a common electrode, such as a top electrode.

[0416]

[0435] Various other modifications, changes and variations which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the method and apparatus of the present invention disclosed herein without departing from the spirit and scope of the invention as defined in the appended claims. Accordingly, the scope of the present invention should be determined by the appended claims and their legal equivalents.

[0417]

[0436] Further embodiments include various subsets of the above embodiments, including the embodiments shown in Figures 1-9, combined or otherwise reconfigured with various other embodiments.

[0418]

[0437] Various design aspects of single pixel multicolor LED devices, such as layer dimensions (e.g., width, length, height, and cross-sectional area of ​​each layer), electrode dimensions, size, shape, spacing, and arrangement of the two or more LED structural layers, bonding layers, reflective layers, and conductive layers, as well as the configuration between the integrated circuits, pixel driving circuits, and electrical connections, are selected (e.g., optimized using cost or performance functions) to obtain desired LED characteristics, such as size, materials, cost, fabrication efficiency, luminous efficiency, power consumption, directivity, luminance intensity, luminance flux, color, spectrum, and spatial radiation pattern.

[0419]

[0438] Figure 10A is a circuit diagram illustrating a matrix of single pixel tri-color LED devices 1000 according to some embodiments. The circuit of Figure 10A includes three pixel drive circuits 1002, 1004, and 1006 and three tri-color LED devices 1008, 1010, and 1012.

[0420]

[0439] In some embodiments, the display panel includes a plurality of pixels, such as millions of pixels, each pixel including a tri-color LED device structure. In some embodiments, the LED device structure can be a micro-LED. Micro-LEDs typically have lateral dimensions of 50 micrometers (μm) or less, and can have lateral dimensions of less than 10 μm, or even only a few μm.

[0421]

[0440] In some embodiments, a pixel drive circuit, e.g., 1002, includes several transistors and capacitors (not shown in FIG. 10A). The transistors include a drive transistor connected to a voltage supply and a control transistor configured with a gate connected to a scan signal bus line. The capacitor includes a reservoir capacitor used to maintain the gate voltage of the drive transistor while the scan signal is setting other pixels.

[0422]

[0441] In this example, each of the three tri-color LED devices, e.g., 1008, has its own integrated circuit (IC) pixel drive circuit 1002. The single pixel tri-color LED device 1008 can be viewed as three individual LEDs of different colors connected in parallel. For example, a red LED 1018, a green LED 1016, and a blue LED 1014 in the same tri-color LED device 1008 are connected to the same IC pixel drive circuit 1002 via a shared P electrode pad or anode.

[0423]

[0442] In some embodiments, each of the red, green, and blue LEDs in the same tri-color LED device 1008 are connected to separate N-electrode pads or cathodes.

[0424]

[0443] In some embodiments, all red LEDs from different tri-color LED devices, e.g., 1018, 1024, and 1030, are connected to the same common N-electrode 1036. All green LEDs from different tri-color LED devices, e.g., 1016, 1022, and 1028, are connected to the same common N-electrode 1034. All blue LEDs from different tri-color LED devices, e.g., 1014, 1020, and 1026, are connected to the same common N-electrode 1032. The use of a common electrode simplifies the fabrication process and reduces the area of ​​the LED device, especially the footprint of the electrodes.

[0425]

[0444] In some embodiments, the connections of the P and N electrodes can be switched and interchanged (not shown in FIG. 10A ). For example, the red LED 1018, the green LED 1016, and the blue LED 1014 in the same tri-color LED device 1008 are connected to a shared N electrode pad or cathode. Each of the red LEDs, green LEDs, and blue LEDs in the same tri-color LED device 1008 are connected to a separate P electrode pad or anode. All the red LEDs, e.g., 1018, 1024, and 1030, from different tri-color LED devices are connected to the same common N electrode 1036.

[0426]

[0445] FIG 10B is a circuit diagram showing a matrix of single pixel tri-color LED devices 1000 according to some embodiments. FIG 10B is similar to FIG 10A, but in this example, each of the three tri-color LED devices, e.g., each LED structure in 1008, has its own integrated circuit (IC) pixel drive circuit 1002. For example, a red LED 1018, a green LED 1016, and a blue LED 1014 in the same tri-color LED device 1008 are connected to different IC pixel drive circuits 1002-1, 1002-2, and 1002-3, respectively, via separate P electrode pads or anodes. As can be seen from FIGS. 1-9, this type of P electrode connection is shown in some embodiments.

[0427]

[0446] In addition, in some embodiments, such as that shown in FIG. 10B, all of the different color LEDs from different tri-color LED devices are connected to the same common N-electrode 1032.

[0428]

[0447] In some embodiments, the connections of the P and N electrodes can be switched and interchanged (not shown in FIG. 10B). For example, the red LED 1018, the green LED 1016, and the blue LED 1014 in the same tri-color LED device 1008 are each connected to a shared N electrode pad or cathode. All of the different color LEDs from different tri-color LED devices are connected to the same common P electrode 1032.

[0429]

[0448] 11 is a top view of a micro-LED display panel 1100 according to some embodiments. The display panel 1100 includes a data interface 1110, a control module 1120, and a pixel area 1150. The data interface 1110 receives data defining an image to be displayed. The source and format of this data can vary depending on the application. The control module 1120 receives the input data and converts it into a form suitable for driving pixels of the display panel. The control module 1120 may include digital logic and / or state machines to convert the received format into a format suitable for the pixel area 1140, a scan controller including shift registers or other types of buffers and memories to store and transfer data, digital-to-analog converters and level shifters, and clock circuits.

[0430]

[0449] The pixel area 1150 includes an array of pixels. The pixels include micro LEDs, such as multi-color LEDs 1134 integrated with pixel drive circuitry, as described above. In some embodiments, a micro lens (not shown separately from the LEDs 1134 in FIG. 11) covers the top of the array of multi-color LEDs. In some embodiments, an array of optical isolation structures, such as reflective structures or reflective cups (not shown separately from the LEDs 1134 in FIG. 11), is formed around the array of multi-color LEDs. In this example, the display panel 1100 is a color RGB display panel. It includes red, green, and blue pixels. Within each pixel, the three-color LEDs 1134 are controlled by pixel drive circuitry. The pixels communicate with a supply voltage (not shown) and ground via a ground pad 1136, as well as with control signals, according to the previously illustrated embodiment. Although not shown in FIG. 11, the p-electrode of the tri-color LED 1134 and the output of the drive transistor are positioned within the LED 1134. The LED current drive signal connections (between the LED's p-electrode and the output of the pixel drive circuit), the ground connection (between the n-electrode and system ground), the supply voltage Vdd connection (between the source of the pixel drive circuit and system Vdd), and the control signal connection to the gate of the pixel drive circuit may be made according to various embodiments.

[0431]

[0450] FIG. 11 is a representative diagram only. Other designs will be apparent. For example, the colors need not be red, green, and blue. Nor need they be arranged in columns or stripes. As an example, away from the square matrix arrangement of pixels shown in FIG. 11, a hexagonal matrix arrangement of pixels can be used to form the display panel 1100.

[0432]

[0451] In some applications, a fully programmable rectangular array of pixels is not necessary. Other designs of display panels with a wide variety of shapes and displays can also be formed using the device structures described herein. One class of examples is specialized applications including signs and automobiles. For example, multiple pixels can be arranged in a star or spiral shape to form a display panel, and different patterns can be generated on the display panel by turning LEDs on and off. Another specialized example is automobile headlights and smart lighting, where certain pixels are grouped together to form various lighting shapes, and each group of LEDs can be turned on and off or otherwise adjusted by individual pixel drive circuits.

[0433]

[0452] Even the lateral arrangement of the devices within each pixel can be varied. In Figures 1-9, the LEDs and pixel drive circuits are arranged vertically, i.e., each LED is located on top of its corresponding pixel drive circuit. Other arrangements are possible. For example, the pixel drive circuit can be located "behind," "in front," or "to the side" of the LEDs.

[0434]

[0453] Different types of display panels can be made. For example, the resolution of a display panel can typically range from 8x8 to 3840x2160. Common display resolutions include QVGA with a resolution of 320x240 and an aspect ratio of 4:3, XGA with a resolution of 1024x768 and an aspect ratio of 4:3, D with a resolution of 1280x720 and an aspect ratio of 16:9, FHD with a resolution of 1920x1080 and an aspect ratio of 16:9, UHD with a resolution of 3840x2160 and an aspect ratio of 16:9, and 4K with a resolution of 4096x2160. There can also be a wide variety of pixel sizes ranging from submicron to over 100mm. The size of the total display area can also vary widely, from as little as a diagonal of tens of microns or less to over hundreds of inches.

[0435]

[0454] Different applications also have different requirements for optical brightness and viewing angle. Example applications include direct view display screens, home / office projectors and portable electronics such as smartphones, laptops, wearable electronics, AR and VR glasses, as well as light engines for retinal projection. Power consumption can vary from a few milliwatts for retinal projectors to several kilowatts for large screen outdoor displays, projectors, and smart car headlights. In terms of frame rate, due to the fast response (nanoseconds) of inorganic LEDs, the frame rate can be KHz or even MHz at low resolution.

[0436]

[0455] Further embodiments also include various subsets of the above embodiments, including the embodiments of Figures 1-11 combined or otherwise reconfigured with various embodiments, such as multi-color LED pixel devices / units with and without reflective layers, with and without planar layers, with and without reflective cup structures including various shapes and types of positioning, with and without reflective layers, with and without microlenses, with and without spacers, and with different electrode connection structures.

[0437]

[0456] Although the detailed description includes many details, these should not be interpreted as limitations on the scope of the present invention, but merely as illustrative of different examples and aspects of the present invention. It should be understood that the scope of the present invention includes other embodiments not described in detail above. For example, the above-described techniques can also be applied to the integration of functional devices other than LEDs and OLEDs with control circuits other than pixel drive circuits. 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 circuits include current drive circuits, voltage drive circuits, transimpedance amplifiers, and logic circuits.

[0438]

[0457] The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the embodiments described herein and variations thereof. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit or scope of the subject matter disclosed herein. Thus, the present 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.

[0439]

[0458] Features of the present invention may be implemented in, using, or with the aid of a computer program product, such as a storage medium or computer-readable storage medium having instructions stored thereon that can be used to program a processing system to perform any of the features presented herein. The storage medium may include high-speed random access memory, such as, but not limited to, DRAM, SRAM, DDR RAM, or other random access solid-state memory devices, and may include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid-state storage devices. The memory optionally includes one or more storage devices located remotely from the CPU. The memory, or alternatively, the non-volatile memory devices within the memory, include non-transitory computer-readable storage media.

[0440]

[0459] When stored on any machine-readable medium, features of the present invention may be embodied in software and / or firmware to control the hardware of a processing system and to enable the processing system to utilize the results of the present invention and interact with other mechanisms. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0441]

[0460] Although the terms "first," "second," etc. may be used herein to describe various elements, it will be understood that these elements are not to be limited by these terms. These terms are used only to distinguish one element from another.

[0442]

[0461] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the claims. When used in the description of the embodiments and in the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and / or," when used herein, refers to and includes any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms "comprise" and / or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0443]

[0462] As used herein, the term "if" may be interpreted to mean "when" a stated precondition is true or "being" true or "in response to determining" that it is true or "according to determining" that it is true or "in response to detecting" that it is true, depending on the context. Similarly, the phrase "if it is determined [that the stated precondition is true]" or "if [the stated precondition is true]" or "when [the stated precondition is true]" may be interpreted to mean "when" a stated precondition is true or "in response to determining" that it is true or "according to determining" that it is true or "when" it is detected as true or "in response to detecting" that it is true, depending on the context.

[0444]

[0463] The above description, for purposes of illustration, has been set forth with reference to specific embodiments. However, the above exemplary discussion is not intended to be exhaustive or to limit the scope of the claims to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of operation and practical application, thereby enabling others skilled in the art to do so.

Claims

1. A micro light emitting diode (LED) pixel unit, comprising: A first color LED structure formed on an IC substrate, the first color LED structure including a first light emitting layer, and a first reflecting structure formed below the first light emitting layer; a first bonding metal layer formed under the first color LED structure and configured to bond the IC substrate and the first color LED structure; a second bonding metal layer formed on the first color LED structure; a second color LED structure formed on the second bonding metal layer, the second color LED structure including a second light emitting layer, and a second reflective structure formed below the second light emitting layer; an upper electrode layer covering the first color LED structure and the second color LED structure 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; a reflector cup surrounding the first color LED structure and the second color LED structure, wherein horizontal light emitted from the first light emitting layer and the second light emitting layer reaches the reflector cup and is reflected upward by the reflector cup; A micro LED pixel unit including:

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

3. 3. The micro-LED pixel unit of claim 2, wherein a material of the first reflective layer or the second reflective layer comprises one or more of Rh, Al, Ag, or Au.

4. 3. The micro-LED pixel unit of claim 2, wherein the first reflective structure includes two first reflective layers, the reflectivities of the two first reflective layers being different, and the second reflective structure includes two second reflective layers, the reflectivities of the two second reflective layers being different.

5. The two first reflective layers are made of SiO ２ and Ti ３ O ５ and the two second reflective layers each include SiO ２ and Ti ３ O ５ 5. The micro-LED pixel unit of claim 4, each comprising:

6. 3. The micro-LED pixel unit of claim 2, wherein the first reflective structure further comprises a first transparent layer on the first reflective layer, and the second reflective structure further comprises a second transparent layer on the second reflective layer.

7. The first transparent layer is made of indium tin oxide (ITO) or SiO ２ and the second transparent layer is one or more of ITO or SiO ２ The micro-LED pixel unit of claim 6 , comprising one or more of:

8. the first color LED structure further includes a first lower conductive contact layer and a first upper conductive contact layer, and the second color LED structure further includes a second lower conductive contact layer and a second upper 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 lower conductive contact layer is electrically connected to the IC substrate through the first reflective structure and electrically connected to the first bonding metal layer through a first contact via, the second lower conductive contact layer is electrically connected to the IC substrate through a second contact via; 10. The micro-LED pixel unit of claim 1, wherein an edge of the first top conductive contact layer contacts the top electrode layer and a top surface of the second top conductive contact layer contacts the top electrode layer.

9. The micro-LED pixel unit of claim 1 , wherein the material of the reflective cup comprises a metal.

10. 10. The micro-LED pixel unit of claim 1, further comprising a micro-lens formed on the top electrode layer.

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

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

13. 11. The micro-LED pixel unit of claim 10, wherein a lateral dimension of the micro-lens is larger than a lateral dimension of an active light-emitting area of ​​the first LED structure, and a lateral dimension of the micro-lens is larger than a lateral dimension of an active light-emitting area of ​​the second LED structure.

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

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

16. 3. The micro-LED pixel unit of claim 2, wherein a thickness of the at least one first reflective layer is in the range of 5 nm to 10 nm, a thickness of the at least one second reflective layer is in the range of 5 nm to 10 nm, a thickness of the first color LED structure is 300 nm or less, and a thickness of the second color LED structure is 300 nm or less.

17. A micro LED pixel unit, An IC substrate; a light-emitting region formed on the IC substrate, the light-emitting region including a plurality of color LED structures, a lower portion of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light-emitting region, and each of the plurality of color LED structures including a light-emitting layer and a reflecting structure at a lower portion of the light-emitting layer; an upper electrode layer covering each of the plurality of color LED structures and electrically contacting each of the plurality of color LED structures, the IC substrate being electrically connected to each of the plurality of color LED structures; a stepped reflector cup forming a cavity and surrounding the light emitting region, wherein light emitted horizontally from a sidewall of the light emitting layer of each of the plurality of color LED structures reaches the stepped reflector cup and is reflected upward by the stepped reflector cup; A micro LED pixel unit including:

18. 20. The micro-LED pixel unit of claim 17, wherein an inner sidewall of the cavity comprises a plurality of sloped surfaces.

19. 20. The micro-LED pixel unit of claim 18, wherein the angle of the sloped surfaces relative to a surface of the IC substrate decreases from the bottom to the top of the cavity.

20. 20. The micro-LED pixel unit of claim 18, wherein sub-cavities formed by the plurality of slanted surfaces have different dimensions in the horizontal direction.

21. The micro-LED pixel unit of claim 20 , wherein inner sidewalls of the sub-cavities are not coplanar.

22. The micro-LED pixel unit of claim 20 , wherein the sub-cavities have different heights.

23. 21. The micro-LED pixel unit of claim 20, wherein a height of a sub-cavity in the middle of the cavity is less than a height of other sub-cavities.

24. 21. The micro-LED pixel unit of claim 20, wherein a height of a sub-cavity at an upper portion of the cavity is greater than a height of a sub-cavity at a lower portion of the cavity.

25. 20. The micro-LED pixel unit of claim 17, wherein the plurality of color LED structures further comprises a top color LED structure.

26. 26. The micro-LED pixel unit of claim 25, wherein a top of the cavity is higher than a top of the upper color LED structure.

27. 20. The micro-LED pixel unit of claim 17, wherein the cavity includes a plurality of sub-cavities, and each of the plurality of color LED structures is within a respective different one of the sub-cavities.

28. 20. The micro-LED pixel unit of claim 17, further comprising a transparent dielectric bonding layer covering at least one of the plurality of color LED structures, the transparent dielectric bonding layer comprising a solid inorganic material or a plastic material.

29. The solid inorganic material is SiO ２ , Al ２ O ３ , Si ３ N ４ 30. The micro-LED pixel unit of claim 28, comprising one or more materials selected from the group consisting of: polyphosphosilicate glass (PSG), and borophosphosilicate glass (BPSG).

30. 30. The micro-LED pixel unit of claim 28, wherein the plastic material comprises one or more polymers selected from the group consisting of SU-8, PermiNex, benzocyclobutene (BCB), and spin-on glass (SOG).

31. Each of the plurality of color LED structures includes a lower conductive contact layer and an upper conductive contact layer, and the light emitting layer is formed between the lower conductive contact layer and the upper conductive contact layer; the lower conductive contact layer is electrically connected to the IC substrate through the reflective structure and electrically connected to the corresponding bonding metal layer through a contact via; 26. The micro-LED pixel unit of claim 25, wherein a top surface of the upper conductive contact layer of the upper color LED structure contacts the upper electrode layer, and an edge of the upper conductive contact layer of a color LED structure below the upper color LED structure contacts the upper electrode layer.

32. 26. The micro-LED pixel unit of claim 25, wherein an extension extends from one side of the light emitting layer of a color LED structure below the upper color LED structure, and a contact via connects the extension to the upper electrode layer.

33. The micro-LED pixel unit of claim 17 , wherein the material of the reflective cup comprises a metal.

34. 20. The micro-LED pixel unit of claim 17, further comprising a micro-lens formed on the top electrode layer.

35. 20. The micro-LED pixel unit of claim 18, further comprising a spacer formed between the micro-lens and the top electrode layer.

36. 20. The micro-LED pixel unit of claim 19, wherein the material of the spacer comprises silicon oxide.

37. 20. The micro-LED pixel unit of claim 18, wherein a lateral dimension of the micro-lens is greater than an emitting dimension of each of the plurality of color LED structures.

38. 20. The micro-LED pixel unit of claim 17, wherein said multiple color LED structures have the same central axis.

39. 20. The micro-LED pixel unit of claim 17, wherein the reflective structure includes a reflective layer, the thickness of the reflective layer being in the range of 5 nm to 10 nm, and the thickness of each of the plurality of color LED structures is 300 nm or less.

40. 20. The micro-LED pixel unit of claim 17, wherein the material of the top electrode layer is selected from the group consisting of graphene, indium tin oxide (ITO), aluminum doped zinc oxide (AZO), or fluorine doped tin oxide (FTO).

41. A micro LED pixel unit, A semiconductor substrate; a light emitting region formed on the semiconductor substrate, the light emitting region including a plurality of color LED structures, a bottom portion of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light emitting region, and each of the plurality of color LED structures including a light emitting layer and a reflective structure at a bottom portion of the light emitting layer; an upper electrode layer covering each of the plurality of color LED structures and electrically contacting each of the plurality of color LED structures, the semiconductor substrate being electrically connected to each of the plurality of color LED structures; a reflector cup surrounding the light emitting area; a refractive structure formed between the reflector cup and the light emitting area; A micro LED pixel unit including:

42. 42. The micro-LED pixel unit of claim 41, further comprising a micro-lens formed on a top surface of the refractive structure.

43. 43. The micro-LED pixel unit of claim 42, wherein a lateral dimension of the micro-lens is equal to or greater than a lateral dimension of the light-emitting area.

44. 43. The micro-LED pixel unit of claim 42, wherein the reflective cup has an upper opening area, and a lateral dimension of the micro-lens is less than a lateral dimension of the upper opening area.

45. 42. The micro-LED pixel unit of claim 41, further comprising a lower dielectric layer formed between a lower portion of the reflective cup and the semiconductor substrate.

46. 42. The micro-LED pixel unit of claim 41, further comprising: a top conductive layer formed on top of the light emitting region, the top conductive layer being electrically connected to the reflective cup.

47. 47. The micro-LED pixel unit of claim 46, wherein the top conductive layer is in direct contact with a top of the reflective cup and a bottom of the reflective cup.

48. 42. The micro-LED pixel unit of claim 41, wherein a top of the refractive structure is higher than a top of the reflective cup.

49. Each of the plurality of color LED structures includes a lower conductive contact layer and an upper conductive contact layer, and the light emitting layer is formed between the lower conductive contact layer and the upper conductive contact layer; the lower conductive contact layer is electrically connected to the semiconductor substrate through the reflective structure and electrically connected to the corresponding bonding metal layer through a contact via; 42. The micro-LED pixel unit of claim 41 , wherein a top surface of the upper conductive contact layer of an upper color LED structure contacts the upper electrode layer, and an edge of the upper conductive contact layer of a color LED structure below the upper color LED structure contacts the upper electrode layer.

50. 42. The micro-LED pixel unit of claim 41, wherein the semiconductor substrate is an IC substrate.

51. 42. The micro-LED pixel unit of claim 41, wherein the reflector cup is a stepped reflector cup that forms a cavity surrounding the light emitting area.

52. 52. The micro-LED pixel unit of claim 51, wherein an inner sidewall of the cavity comprises a plurality of sloped surfaces.

53. 53. The micro-LED pixel unit of claim 52, wherein an angle of the plurality of slopes relative to a surface of the semiconductor substrate decreases from the bottom to the top of the cavity.

54. 53. The micro-LED pixel unit of claim 52, wherein sub-cavities formed by the plurality of slanted surfaces have different dimensions in the horizontal direction.

55. 55. The micro-LED pixel unit of claim 54, wherein inner sidewalls of the sub-cavities are not coplanar.

56. 55. The micro-LED pixel unit of claim 54, wherein the sub-cavities have different heights.

57. 55. The micro-LED pixel unit of claim 54, wherein a height of a sub-cavity in the middle of the cavity is less than a height of other sub-cavities.

58. 55. The micro-LED pixel unit of claim 54, wherein a height of a sub-cavity at an upper portion of the cavity is greater than a height of the sub-cavity at a lower portion of the cavity.

59. 42. The micro-LED pixel unit of claim 41, wherein the plurality of color LED structures further comprises a top color LED structure.

60. 60. The micro-LED pixel unit of claim 59, wherein a top of the cavity is higher than a top of the upper color LED structure.

61. 52. The micro-LED pixel unit of claim 51, wherein the cavity includes a plurality of sub-cavities, and each of the plurality of color LED structures is within a respective different one of the sub-cavities.

62. 42. The micro-LED pixel unit of claim 41, wherein the material of the reflective cup comprises a metal.

63. 60. The micro-LED pixel unit of claim 59, wherein an extension extends from one side of the light emitting layer of a color LED structure below the upper color LED structure, and a contact via connects the extension to the upper electrode layer.

64. 42. The micro-LED pixel unit of claim 41, wherein said multiple color LED structures have the same central axis.

65. 42. The micro-LED pixel unit of claim 41, wherein the reflective structure includes a reflective layer, the reflective layer having a thickness in the range of 5 nm to 10 nm, and each of the plurality of color LED structures has a thickness of 300 nm or less.

66. 42. The micro-LED pixel unit of claim 41, wherein the material of the top electrode layer is selected from the group consisting of graphene, indium tin oxide (ITO), aluminum doped zinc oxide (AZO), or fluorine doped tin oxide (FTO).

67. 42. The micro-LED pixel unit of claim 41 , wherein each of the plurality of color LED structures includes a respective extension extending from one side of the respective color LED structure, each of the extensions being electrically connected to the upper electrode layer through a first contact via, and the lower portion of each of the plurality of color LED structures being electrically connected to the semiconductor substrate through a respective second contact via.

68. A micro LED pixel unit, A semiconductor substrate; a light emitting region formed on the semiconductor substrate, the light emitting region including a plurality of color LED structures, a bottom portion of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light emitting region, and each of the plurality of color LED structures including a light emitting layer and a reflective structure at a bottom portion of the light emitting layer; an upper electrode layer covering each of the plurality of color LED structures and electrically contacting each of the plurality of color LED structures, the semiconductor substrate being electrically connected to each of the plurality of color LED structures; a reflector cup surrounding the light emitting region, wherein light emitted horizontally from a sidewall of the light emitting layer of each of the plurality of color LED structures reaches the reflector cup and is reflected upward by the reflector cup, and an upper portion of the reflector cup is higher than an upper portion of the light emitting region; A micro LED pixel unit including:

69. 69. The micro-LED pixel unit of claim 68, further comprising a micro-lens formed over the light emitting region.

70. 70. The micro-LED pixel unit of claim 69, wherein the top of the reflective cup is higher than the top of the micro-lens.

71. 70. The micro-LED pixel unit of claim 69, further comprising a refractive structure formed below the micro-lens between the reflective cup and the light emitting area.

72. 70. The micro-LED pixel unit of claim 69, wherein a lateral dimension of the microlens is equal to or greater than a lateral dimension of the light-emitting area.

73. 70. The micro-LED pixel unit of claim 69, wherein the reflective cup has an upper opening area, and a lateral dimension of the micro-lens is less than a lateral dimension of the upper opening area.

74. 69. The micro-LED pixel unit of claim 68, further comprising a lower dielectric layer formed between the reflective cup and the semiconductor substrate.

75. 69. The micro-LED pixel unit of claim 68, further comprising: a top conductive layer formed on top of the light emitting area, the top conductive layer being electrically connected to the reflective cup.

76. Each of the plurality of color LED structures includes a lower conductive contact layer and an upper conductive contact layer, and the light emitting layer is formed between the lower conductive contact layer and the upper conductive contact layer; the lower conductive contact layer is electrically connected to the semiconductor substrate through the reflective structure and electrically connected to the corresponding bonding metal layer through a contact via; 69. The micro-LED pixel unit of claim 68, wherein a top surface of the upper conductive contact layer of an upper color LED structure contacts the upper electrode layer, and an edge of the upper conductive contact layer of a color LED structure below the upper color LED structure contacts the upper electrode layer.

77. 69. The micro-LED pixel unit of claim 68, wherein a bottom portion of the light emitting region is electrically connected to the semiconductor substrate.

78. 69. The micro-LED pixel unit of claim 68, wherein the semiconductor substrate is an IC substrate.

79. 69. The micro-LED pixel unit of claim 68, wherein the reflector cup is a stepped reflector cup that forms a cavity surrounding the light emitting area.

80. 80. The micro-LED pixel unit of claim 79, wherein an inner sidewall of the cavity comprises a plurality of sloped surfaces.

81. 81. The micro-LED pixel unit of claim 80, wherein an angle of the plurality of slopes relative to a surface of the semiconductor substrate decreases from the bottom to the top of the cavity.

82. 81. The micro-LED pixel unit of claim 80, wherein sub-cavities formed by the plurality of slanted surfaces have different dimensions in the horizontal direction.

83. 83. The micro-LED pixel unit of claim 82, wherein the inner sidewalls of the sub-cavities are not coplanar.

84. 83. The micro-LED pixel unit of claim 82, wherein the sub-cavities have different heights.

85. 83. The micro-LED pixel unit of claim 82, wherein a height of a sub-cavity in the middle of the cavity is less than a height of other sub-cavities.

86. 83. The micro-LED pixel unit of claim 82, wherein a height of the sub-cavity at an upper portion of the cavity is greater than a height of the sub-cavity at a lower portion of the cavity.

87. 80. The micro-LED pixel unit of claim 79, wherein the plurality of color LED structures further comprises a top color LED structure.

88. 88. The micro-LED pixel unit of claim 87, wherein a top of the cavity is higher than a top of the upper color LED structure.

89. 80. The micro-LED pixel unit of claim 79, wherein the cavity includes a plurality of sub-cavities, and each of the plurality of color LED structures is within a respective different one of the sub-cavities.

90. 69. The micro-LED pixel unit of claim 68, wherein the material of the reflective cup comprises a metal.

91. 88. The micro-LED pixel unit of claim 87, wherein an extension extends from one side of the light emitting layer of a color LED structure below the upper color LED structure, and a contact via connects the extension to the upper electrode layer.

92. 69. The micro-LED pixel unit of claim 68, wherein said multiple color LED structures have the same central axis.

93. 69. The micro-LED pixel unit of claim 68, wherein the reflective structure includes a reflective layer, the reflective layer having a thickness in the range of 5 nm to 10 nm, and each of the plurality of color LED structures has a thickness of 300 nm or less.

94. 69. The micro-LED pixel unit of claim 68, wherein a material of the top electrode layer comprises one or more of graphene, indium tin oxide (ITO), aluminum doped zinc oxide (AZO), or fluorine doped tin oxide (FTO).

95. A micro LED pixel unit, A semiconductor substrate; a light emitting region formed on the semiconductor substrate, the light emitting region including a plurality of color LED structures, a bottom portion of each of the plurality of color LED structures being connected to a corresponding bonding metal layer in the light emitting region, and each of the plurality of color LED structures including a light emitting layer and a reflective structure at a bottom portion of the light emitting layer; an upper electrode layer covering each of the plurality of color LED structures and electrically contacting each of the plurality of color LED structures, the semiconductor substrate being electrically connected to each of the plurality of color LED structures; a floating reflector cup surrounding the light emitting region, a bottom of the floating reflector cup being above the semiconductor substrate, and light emitted horizontally from a sidewall of the light emitting layer of each of the plurality of color LED structures reaches the suspended floating reflector cup and is reflected upward by the floating reflector cup; A micro LED pixel unit including:

96. 96. The micro-LED pixel unit of claim 95, wherein the bottom of the floating reflector cup is higher than a top surface of the corresponding bonding metal layer at a bottom of one of the multiple color LED structures.

97. 96. The micro-LED pixel unit of claim 95, wherein the floating reflector cup is stepped.

98. 98. The micro-LED pixel unit of claim 97, further comprising a micro-lens formed over the light emitting region.

99. 100. The micro-LED pixel unit of claim 98, wherein a top of the floating reflector cup is higher than a top of the micro-lens.

100. 100. The micro-LED pixel unit of claim 98, further comprising a refractive structure formed below the micro-lens between the floating reflective cup and the light-emitting area.

101. 99. The micro-LED pixel unit of claim 98, wherein a lateral dimension of the microlens is greater than or equal to a lateral dimension of the light-emitting area.

102. 100. The micro-LED pixel unit of claim 98, wherein the floating reflector cup has an upper opening area, and a lateral dimension of the micro-lens is less than a lateral dimension of the upper opening area.

103. 98. The micro-LED pixel unit of claim 97, further comprising a lower dielectric layer formed between the floating reflective cup and the semiconductor substrate.

104. 96. The micro-LED pixel unit of claim 95, wherein the top conductive layer directly contacts a top of the floating reflector cup or the bottom of the floating reflector cup.

105. Each of the plurality of color LED structures includes a lower conductive contact layer and an upper conductive contact layer, and the light emitting layer is formed between the lower conductive contact layer and the upper conductive contact layer; the lower conductive contact layer is electrically connected to the semiconductor substrate through the reflective structure and electrically connected to the corresponding bonding metal layer through a contact via; 105. The micro-LED pixel unit of claim 104, wherein a top surface of the upper conductive contact layer of an upper color LED structure contacts the upper electrode layer, and an edge of the upper conductive contact layer of a color LED structure below the upper color LED structure contacts the upper electrode layer.

106. 96. The micro-LED pixel unit of claim 95, wherein the semiconductor substrate is an IC substrate.

107. 98. The micro-LED pixel unit of claim 97, wherein the stepped floating reflector cup forms a cavity surrounding the light emitting area.

108. 108. The micro-LED pixel unit of claim 107, wherein an inner sidewall of the cavity comprises a plurality of sloped surfaces.

109. 109. The micro-LED pixel unit of claim 108, wherein an angle of the plurality of sloping surfaces relative to a surface of the semiconductor substrate decreases from the bottom to the top of the cavity.

110. 109. The micro-LED pixel unit of claim 108, wherein sub-cavities formed by the plurality of slanted surfaces have different dimensions in the horizontal direction.

111. 111. The micro-LED pixel unit of claim 110, wherein the inner sidewalls of the sub-cavities are not coplanar.

112. 111. The micro-LED pixel unit of claim 110, wherein the sub-cavities have different heights.

113. 111. The micro-LED pixel unit of claim 110, wherein a height of a sub-cavity in the middle of the cavity is less than a height of other sub-cavities.

114. 111. The micro-LED pixel unit of claim 110, wherein a height of the sub-cavity at an upper portion of the cavity is greater than a height of the sub-cavity at a lower portion of the cavity.

115. 108. The micro-LED pixel unit of claim 107, wherein the plurality of color LED structures further comprises a top color LED structure.

116. 116. The micro-LED pixel unit of claim 115, wherein a top of the cavity is higher than a top of the upper color LED structure.

117. 108. The micro-LED pixel unit of claim 107, wherein the cavity includes a plurality of sub-cavities, and each of the plurality of color LED structures is within a respective different one of the sub-cavities.

118. 96. The micro-LED pixel unit of claim 95, wherein a material of the floating reflector cup comprises a metal.

119. 96. The micro-LED pixel unit of claim 95, wherein each of the plurality of color LED structures includes an extension extending from one side of the respective color LED structure, the extension being electrically connected to the upper electrode layer through a respective first contact via, and the lower portion of each of the plurality of color LED structures being electrically connected to the semiconductor substrate through a respective second contact via.

120. 96. The micro-LED pixel unit of claim 95, wherein said multiple color LED structures have the same central axis.

121. 96. The micro-LED pixel unit of claim 95, wherein the reflective structures respectively comprise a reflective layer formed on the bottom of each of the plurality of color LED structures.

122. 122. The micro-LED pixel unit of claim 121, wherein the thickness of the reflective layer is in the range of 5 nm to 10 nm, and the thickness of each of the multiple color LED structures is 300 nm or less.

123. 96. The micro-LED pixel unit of claim 95, wherein a material of the top electrode layer comprises one or more of graphene, indium tin oxide (ITO), aluminum doped zinc oxide (AZO), or fluorine doped tin oxide (FTO).

124. 1. A multi-color micro light emitting diode (LED) pixel device for a display panel, comprising: a first LED structure formed on the IC substrate and emitting a first color; a first transparent dielectric bonding layer having a first planar upper surface overlying the first LED structure; a second LED structure emitting a second color formed on the first planar upper surface of the first transparent dielectric bonding layer; a second transparent dielectric bonding layer having a second planar upper surface overlying the second LED structure; a top electrode layer covering the multi-color micro-LED pixel device and in electrical contact with the first LED structure and the second LED structure; Including, The IC substrate is electrically connected to the first LED structure and the second LED structure, forming a multi-color micro-LED pixel device.

125. 125. The multi-color micro-LED pixel device of claim 124, wherein the first LED structure is embedded in a first planar transparent dielectric layer.

126. 125. The multi-color micro-LED pixel device of claim 124, wherein the second LED structure is embedded in a second planar transparent dielectric layer.

127. 125. The multi-color micro-LED pixel device of claim 124, wherein the first transparent dielectric bonding layer is composed of a solid inorganic material or a plastic material.

128. The solid inorganic material is SiO ２ , Al ２ O ３ , Si ３ N ４ 128. The multi-color micro-LED pixel device of claim 127, wherein the pixel device is comprised of one or more materials selected from the group consisting of: phosphosilicate glass (PSG), and borophosphosilicate glass (BPSG).

129. 128. The multi-color micro-LED pixel device of claim 127, wherein the plastic material is one or more polymers selected from the group consisting of SU-8, PermiNex, benzocyclobutene (BCB), and spin-on glass (SOG).

130. the first LED structure includes a first lower electrode layer formed on a lower portion of the first LED structure; the second LED structure includes a second lower electrode layer formed on a lower portion of the second LED structure; the first bottom electrode layer is electrically connected to the IC substrate by a first contact in a first via at a bottom of the first bottom electrode layer; 125. The multi-color micro-LED pixel device of claim 124, wherein the second bottom electrode layer is electrically connected to the IC substrate by a second contact in a second via through the first transparent dielectric bonding layer.

131. 131. The multi-color micro-LED pixel device of claim 130, wherein the first bottom electrode layer is transparent and the second bottom electrode layer is transparent.

132. the first LED structure includes a first light emitting layer; a first side extending from one side of the first light-emitting layer; the second LED structure includes a second light emitting layer; a second side extending from one side of the second light-emitting layer; 125. The multi-color micro-LED pixel device of claim 124, wherein a third contact in a third via connects the first side and the second side to the top electrode layer through the second transparent dielectric bonding layer.

133. 125. The multi-color micro-LED pixel device of claim 124, wherein an optical isolation structure is formed around the periphery of the multi-color micro-LED pixel device.

134. 134. The multi-color micro-LED pixel device of claim 133, wherein the optical isolation structure is a reflective cup.

135. 134. The multi-color micro-LED pixel device of claim 133, wherein the material of the reflective cup is metal.

136. 125. The multi-color micro-LED pixel device of claim 124, wherein a micro-lens is formed over the top electrode layer.

137. 137. The multi-color micro-LED pixel device of claim 136, wherein a spacer is formed between the microlens and the top electrode layer.

138. 138. The multi-color micro-LED pixel device of claim 137, wherein said spacers are comprised of silicon oxide.

139. 137. The multi-color micro-LED pixel device of claim 136, wherein a lateral dimension of the microlens is larger than a lateral dimension of an active light-emitting area of ​​the first LED structure and a lateral dimension of the microlens is larger than a lateral dimension of an active light-emitting area of ​​the second LED structure.

140. 125. The multicolor micro-LED pixel device of claim 124, wherein a lateral dimension of the first LED structure is the same as a lateral dimension of the second LED structure.

141. 125. The multi-color micro-LED pixel device of claim 124, wherein the first LED structure and the second LED structure have the same central axis.

142. 125. The multi-color micro-LED pixel device of claim 124, wherein a first reflective layer is formed underneath the first LED structure and a second reflective layer is formed underneath the second LED structure.

143. the first reflective layer has a thickness of 5 nm to 10 nm; the second reflective layer has a thickness of 5 nm to 10 nm; the thickness of the first LED structure is less than or equal to 300 nm; 143. The multicolor micro-LED pixel device of claim 142, wherein the second LED structure has a thickness of 300 nm or less.

144. 125. The multicolor micro-LED pixel device of claim 124, wherein a bonding metal layer is formed underneath the first LED structure.

145. 125. The multi-color micro-LED pixel device of claim 124, wherein the material of the top electrode layer is selected from the group consisting of graphene, indium tin oxide (ITO), aluminum doped zinc oxide (AZO), and fluorine doped tin oxide (FTO).

Images