Miniature light-emitting element display device

Abstract

The invention provides a micro light-emitting element display device which comprises a plurality of micro light-emitting elements. Each micro light-emitting element comprises a first light-emitting layer and a second light-emitting layer. The first light emitting layer includes a first epitaxial structure for emitting light of a first wavelength. The second light-emitting layer is arranged on the first light-emitting layer in a bonding and stacking mode through a metal layer. The second light-emitting layer comprises a second epitaxial structure and a third epitaxial structure, the second epitaxial structure is used for emitting light of a second wavelength, and the third epitaxial structure is used for emitting light of a third wavelength. The second epitaxial structure and the third epitaxial structure are nanopillar arrays made of the same epitaxial material. The third wavelength is greater than the second wavelength. The second wavelength and the third wavelength are both smaller than the first wavelength, and the sum of orthographic projection areas of the second epitaxial structure and the third epitaxial structure is smaller than the orthographic projection area of the first epitaxial structure.

Description

TECHNICAL FIELD

[0001] The present application relates to a display device, and more particularly to a micro light emitting element display device. BACKGROUND

[0002] With the progress of display technology, display devices are developed not only in the direction of large size, but also in the direction of small size. For example, the head-mounted display (HMD) devices, such as virtual reality (VR) display devices, augmented reality (AR) display devices, or mixed reality (MR) display devices, adopt small-size display panels. In addition, in addition to the HMD devices, the AR display devices can also be applied to head-up displays (HUDs), which also adopt small-size display panels. In addition, projectors or micro projectors also adopt small-size display panels.

[0003] Small-size display panels need high resolution and full color, and in particular, wearable devices also need to consider thin and light design. In order to meet the requirements of full color and high resolution, the red sub-pixels, green sub-pixels and blue sub-pixels are arranged in a vertical stack in the conventional way. However, due to the need to sacrifice the light emitting area or occupy the very limited space between the pixels, it is difficult to design the wiring of the three-color stack in the limited pixel space under the requirement of higher and higher resolution. SUMMARY

[0004] The present application is directed to a micro light emitting element display device which can maintain large light emitting area and high spatial resolution, and can improve light emitting efficiency and reduce the influence of alignment tolerance in vertical stacking.

[0005] An embodiment of the present application provides a micro light emitting element display device, comprising a plurality of micro light emitting elements, wherein each micro light emitting element comprises a first light emitting layer and a second light emitting layer. The first light emitting layer comprises a first epitaxial structure for emitting light of a first wavelength. The second light emitting layer is bonded and stacked on the first light emitting layer by a metal layer. The second light emitting layer comprises a second epitaxial structure for emitting light of a second wavelength and a third epitaxial structure for emitting light of a third wavelength. The second epitaxial structure and the third epitaxial structure are nanorod arrays of the same epitaxial material. The third wavelength is greater than the second wavelength, and both the second wavelength and the third wavelength are less than the first wavelength. The sum of the projected areas of the second epitaxial structure and the third epitaxial structure is less than the projected area of the first epitaxial structure.

[0006] An embodiment of the present application provides a micro light emitting element display device, comprising a first light emitting layer, a second light emitting layer and a wavelength conversion structure. The first light emitting layer comprises a first epitaxial structure having a first portion and a second portion, both of which emit light of a first wavelength. The second light emitting layer is stacked on the first light emitting layer and comprises a second epitaxial structure which is bonded to the first portion by a metal layer and emits light of a second wavelength. The wavelength conversion structure is stacked on the second portion and is configured to convert the light of the first wavelength emitted by the second portion into light of a third wavelength. The second epitaxial structure has a smaller area of orthographic projection than the first portion. In some embodiments, the first portion and the second portion of the first epitaxial structure are electrically independent and are configured to be driven by different signals, respectively, and both of which emit light of the first wavelength.

[0007] In the micro light emitting element display device of the embodiment of the present application, the first light emitting layer and the second light emitting layer are stacked, and the second light emitting layer can emit light of two different wavelengths, so that the spatial resolution of the display pixels can be improved, and the space occupied by the circuit traces can be reduced, and the light emitting area can be increased. In addition, in the micro light emitting element of the embodiment of the present application, the sum of the areas of orthographic projection of the second epitaxial structure and the third epitaxial structure is smaller than the area of orthographic projection of the first epitaxial structure, or the area of orthographic projection of the second epitaxial structure is smaller than the area of orthographic projection of the first portion, so that the sub-pixels in the second light emitting layer only cover part of the sub-pixels in the first light emitting layer, and the light emitting efficiency can be improved. Furthermore, in the micro light emitting element display device of the embodiment of the present application, the first light emitting layer and the second light emitting layer are connected by bonding with the metal layer, so that the second epitaxial structure and the third epitaxial structure can be disposed on the first light emitting layer in a single process step. Compared with defining the epitaxial regions by two times of photolithography for respectively manufacturing the second epitaxial structure and the third epitaxial structure, the step of alignment can be reduced, so that the influence of the alignment tolerance on the vertical stacking can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0008] FIG. 1A FIG. 1 is a cross-sectional schematic view of a micro light emitting element according to an embodiment of the present application;

[0009] FIG. 1B FIG. 2 is a partial cross-sectional schematic view showing a nanorod array of the second epitaxial structure in the micro light emitting element of FIG. 1; FIG. 1A

[0010] FIG. 1C FIG. 3 is a partial cross-sectional schematic view showing a nanorod array of the third epitaxial structure in the micro light emitting element of FIG. 1; FIG. 1A

[0011] FIG. 1D FIG. 4 is a cross-sectional schematic view of a micro light emitting element according to another embodiment of the present application;

[0012] FIG. 2A ​​A top view schematic diagram of a micro light emitting element of another embodiment of the present application;

[0013] FIG. 2B A top view schematic diagram of a micro light emitting element of another embodiment of the present application; FIG. 2A A cross-sectional schematic diagram of the micro light emitting element of claim 1 along the line A-A';

[0014] FIG. 2C A top view schematic diagram of a micro light emitting element of another embodiment of the present application; FIG. 2A A cross-sectional schematic diagram of the micro light emitting element of claim 1 along the line B-B';

[0015] FIG. 3A A top view schematic diagram of a micro light emitting element of another embodiment of the present application;

[0016] FIG. 3B A top view schematic diagram of a micro light emitting element of another embodiment of the present application; FIG. 3A A cross-sectional schematic diagram of the micro light emitting element of claim 1 along the line A-A';

[0017] FIG. 4A A top view schematic diagram of a micro light emitting element of another embodiment of the present application;

[0018] FIG. 4B A partial cross-sectional schematic diagram showing a nanorod array of a first epitaxial structure and a nanorod array of a second epitaxial structure in claim 1; FIG. 1A

[0019] FIG. 5A A top view schematic diagram of a micro light emitting element of another embodiment of the present application;

[0020] FIG. 5B A top view schematic diagram of a micro light emitting element of another embodiment of the present application; FIG. 5A A cross-sectional schematic diagram of the micro light emitting element of claim 1 along the line A-A';

[0021] FIG. 6A A top view schematic diagram of a micro light emitting element of another embodiment of the present application;

[0022] FIG. 6B A top view schematic diagram of a micro light emitting element of another embodiment of the present application; FIG. 6A A cross-sectional schematic diagram of the micro light emitting element of claim 1 along the line A-A';

[0023] FIG. 7 A partial top view schematic diagram of a micro light emitting element display device of an embodiment of the present application;

[0024] FIG. 8 A flowchart of a manufacturing method of a micro light emitting element of an embodiment of the present application;

[0025] FIG. 9 A flowchart of a manufacturing method of a micro light emitting element of another embodiment of the present application. DETAILED DESCRIPTION

[0026] ​Reference will now be made in detail embodiments of the application, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or similar parts.

[0027] FIG. 1A A cross-sectional view of a micro light emitting element of an embodiment of the present application, FIG. 1B is a partial cross-sectional view showing a nanorod array of a second epitaxial structure in FIG. 1A , and FIG. 1C is a partial cross-sectional view showing a nanorod array of a third epitaxial structure in FIG. 1A . Please refer to FIG. 1A , FIG. 1B and FIG. 1C , the micro light emitting element 100 of the embodiment is disposed on a substrate 110, and includes a first light emitting layer 200 and a second light emitting layer 300. The first light emitting layer 200 includes a first epitaxial structure 210 for emitting light of a first wavelength, such as red light. The second light emitting layer 300 is bonded and stacked on the first light emitting layer 200 by a metal layer 400. The second light emitting layer 300 includes a second epitaxial structure 310 for emitting light of a second wavelength, such as blue light, and a third epitaxial structure 320 for emitting light of a third wavelength, such as green light, the third wavelength being greater than the second wavelength. The second epitaxial structure 310 and the third epitaxial structure 320 are nanorod arrays of the same epitaxial material. For example, the second epitaxial structure 310 includes a plurality of nanorods 312 arranged in an array, such as a two-dimensional array, and the third epitaxial structure 320 includes a plurality of nanorods 322 arranged in an array, such as a two-dimensional array. In the embodiment, the nanorods 312 and the nanorods 322 are upright on the first epitaxial structure 210.

[0028] In the present embodiment, the second epitaxial structure 310 and the third epitaxial structure 320 are made of, for example, indium gallium nitride (InGaN) or gallium nitride (GaN), and the indium concentration of the second epitaxial structure 310 is greater than that of the third epitaxial structure 320. This can be achieved by adjusting the indium concentration of different regions in the process. The higher the indium concentration of a region, the greater the diameter of the nanorods formed in the region. Therefore, in the present embodiment, the diameter of a single nanorod in the nanorod array of the second epitaxial structure 310 (i.e. the diameter D1 of the nanorod 312) is greater than the diameter of a single nanorod in the nanorod array of the third epitaxial structure 320 (i.e. the diameter D2 of the nanorod 322). Furthermore, the smaller the diameter of a nanorod, the longer the wavelength of the light emitted by the nanorod. Therefore, the third wavelength (i.e. the wavelength of the light emitted by the third epitaxial structure 320) is greater than the second wavelength (i.e. the wavelength of the light emitted by the second epitaxial structure 310). In addition, in the present embodiment, the first wavelength (i.e. the wavelength of the light emitted by the first epitaxial structure 210) is greater than the third wavelength. That is, both the second wavelength and the third wavelength are less than the first wavelength. In an embodiment, the light of the first wavelength is red light, the light of the second wavelength is blue light, and the light of the third wavelength is green light. In the present embodiment, the first epitaxial structure 210 can have a nanorod array, or can be a continuous film layer.

[0029] In the present embodiment, the sum of the orthographic projection areas of the second epitaxial structure 310 and the third epitaxial structure 320 is less than the orthographic projection area of the first epitaxial structure 210. Here or elsewhere in the specification, "orthographic projection" and "orthographic projection area" refer to, for example, the orthographic projection and the orthographic projection area on the substrate 110. That is, the sum of the orthographic projection areas of the second epitaxial structure 310 and the third epitaxial structure 320 on the substrate 110 is less than the orthographic projection area of the first epitaxial structure 210 on the substrate 110. The light-exit surface 212 exposed by the first light-emitting layer 200 is not shielded by the second epitaxial structure 310 and the third epitaxial structure 320, and can emit light with high efficiency.

[0030] In the micro light emitting element 100 of the present embodiment, since the first light emitting layer 200 and the second light emitting layer 300 are stacked, and the second light emitting layer 300 can emit light of two different wavelengths, when the micro light emitting element 100 is used as a display pixel, the spatial resolution of the display pixel can be improved, and the space occupied by the circuit traces can be reduced, thereby increasing the light emitting area, especially in the horizontal direction. In the present embodiment, in order to enable the second light emitting layer 300 to be stably stacked on the first light emitting layer 200, the area of the orthographic projection of the first light emitting layer 200 must be sufficient to simultaneously support the second epitaxial structure 310 and the third epitaxial structure 320. When the second epitaxial structure 310 is a blue light emitting diode and the third epitaxial structure 320 is a green light emitting diode, both have similar light emitting efficiencies, and the areas of the orthographic projections of the second epitaxial structure 310 and the third epitaxial structure 320 are similar, then both of them at most occupy 1 / 2 of the area of the orthographic projection of the first epitaxial structure 210, that is, the area of the orthographic projection of the second epitaxial structure 310 is less than 1 / 2 of the area of the orthographic projection of the first epitaxial structure 210, and the area of the orthographic projection of the third epitaxial structure 320 is less than 1 / 2 of the area of the orthographic projection of the first epitaxial structure 210. In addition, in the micro light emitting element 100 of the present embodiment, the sum of the areas of the orthographic projections of the second epitaxial structure 310 and the third epitaxial structure 320 is less than the area of the orthographic projection of the first epitaxial structure 210, so the sub-pixels in the second light emitting layer 300 only cover part of the sub-pixels in the first light emitting layer 200, thereby improving the light emitting efficiency. In some embodiments, the first epitaxial structure 210 is a red light emitting diode, the second epitaxial structure 310 is a blue light emitting diode, and the third epitaxial structure 320 is a green light emitting diode. In order to enable the first epitaxial structure 210 with lower light emitting efficiency to emit light sufficient to achieve white balance with the second epitaxial structure 310 and the third epitaxial structure 320, the exposed light emitting area of the first epitaxial structure 210 is more than 2 times that of the second epitaxial structure 310 or the third epitaxial structure 320, that is, the sum of the areas of the orthographic projections of the second epitaxial structure 310 and the third epitaxial structure 320 is less than 1 / 2 of the area of the orthographic projection of the first epitaxial structure 210. Furthermore, in the micro light emitting element 100 of the present embodiment, the first light emitting layer 200 and the second light emitting layer 300 are connected by bonding with the metal layer 400, which can simultaneously place the second epitaxial structure 310 and the third epitaxial structure 320 on the first light emitting layer 200 in a single process step. Compared with defining the epitaxial region by performing lithography twice to respectively fabricate the second epitaxial structure 310 and the third epitaxial structure 320, this method can reduce the step of alignment, thereby reducing the influence of the alignment tolerance on vertical stacking.

[0031] In this embodiment, the thickness T1 of the first light-emitting layer 200 or the thickness T2 of the second light-emitting layer 300 falls within the range of 1 micrometer to 2 micrometers. Furthermore, in this embodiment, a metal layer 400 is disposed in the region where the second epitaxial structure 310 or the third epitaxial structure 320 is bonded to the first epitaxial structure 210, exposing a portion of the light-emitting surface 212 of the first epitaxial structure 210. The metal layer 400 also serves as a reflective layer to reflect light of the first wavelength to the light-emitting surface 212 for emission.

[0032] FIG. 1D This is a cross-sectional schematic diagram of a micro light-emitting element according to another embodiment of the present invention. Please refer to... FIG. 1D The micro light-emitting element 100c in this embodiment is similar to FIG. 1A The micro light-emitting element 100, and the main differences between the two are described below. FIG. 1A In the micro light-emitting element 100, the first epitaxial structure 210 is divided into two separate parts located below the second epitaxial structure 310 and the third epitaxial structure 320, respectively. FIG. 1D In the micro light-emitting element 100c, the first epitaxial structure 210c is a single piece connected together, and the second epitaxial structure 310 and the third epitaxial structure 320 are disposed on it.

[0033] FIG. 2A This is a top view schematic diagram of a micro light-emitting element according to another embodiment of the present invention. FIG. 2B for FIG. 2A A schematic diagram of a cross-section of a micro-light-emitting element along line A-A', while FIG. 2C for FIG. 2A A schematic diagram of the cross-section of the miniature light-emitting element along line B-B'. Please refer to... FIG. 2A to FIG. 2C In this embodiment, the micro light-emitting element 100a and FIG. 1AThe micro light emitting element 100a is similar to the micro light emitting element 100, and the main difference between the two is described as follows. In the micro light emitting element 100a of the present embodiment, the first epitaxial structure 210a has a conductive via 2141 for electrically connecting the external pad 1121 (e.g., a positive electrode) of the substrate 110 to the side 211 of the first epitaxial structure 210 close to the second light emitting layer 300 in the vertical direction. Specifically, the first epitaxial structure 210a includes a first-type semiconductor layer 213, an active layer 215, and a second-type semiconductor layer 217 stacked in sequence, the second epitaxial structure 310 includes a second-type semiconductor layer 317, an active layer 315, and a first-type semiconductor layer 313 stacked in sequence, and the third epitaxial structure 320 includes a second-type semiconductor layer 327, an active layer 325, and a first-type semiconductor layer 323 stacked in sequence. In the present embodiment, the first type is N-type, and the second type is P-type. However, in other embodiments, the first type can be P-type, and the second type can be N-type. In addition, in the present embodiment, the active layers 215, 315, and 325 are, for example, quantum well layers or multiple quantum well layers, which can respectively emit light of a first wavelength, light of a second wavelength, and light of a third wavelength. In an embodiment not shown, the active layer 315 of the second epitaxial structure 310 and the active layer 325 of the third epitaxial structure 320 include a plurality of non-epitaxial media. The material of the non-epitaxial media is, for example, silicon dioxide, silicon nitride, or metal oxide, and the non-epitaxial media are a plurality of insulating patterns. The non-epitaxial media are separated from each other to disperse indium and control the degree of aggregation of indium in the active layer, thereby adjusting the color of light emitted by the active layer 315 or the active layer 325. The horizontal distance between any two adjacent non-epitaxial media is less than 100 nanometers. The two adjacent non-epitaxial media in the active layer 315 have a first pitch, the two adjacent non-epitaxial media in the active layer 325 have a second pitch, and the second pitch is greater than the first pitch, so that the active layer 315 emits blue light of a shorter wavelength, and the active layer 325 emits green light of a longer wavelength.

[0034] In the present embodiment, the lower side of the first-type semiconductor layer 213 is electrically connected to an external pad 1123, which is a negative electrode, and the external pad 1121 (a positive electrode) is electrically connected to the second-type semiconductor layer 217 via the conductive via 2141, which includes a conductive material filled in a through hole, such as a metal (other conductive vias in the present specification also include a conductive material filled in a through hole). Therefore, when a forward voltage is applied to the external pad 1121 and the external pad 1123, the active layer 215 can emit light of a first wavelength.

[0035] On the other hand, the first light emitting layer 200a can have a conductive via 2142 electrically connecting the external contact pad 1122 (e.g., a negative electrode) on the substrate 110 and the second light emitting layer 300 in the vertical direction. The conductive via 2142 is electrically connected to the external contact pad 1122 and the first type semiconductor layer 313 through the trace layer 302, and is electrically connected to the external contact pad 1122 and the first type semiconductor layer 323. In addition, the first light emitting layer 200a can have a conductive via 2143 electrically connecting the external contact pad 1124 (e.g., a positive electrode) and the second type semiconductor layer 317. When a forward voltage is applied between the external contact pad 1124 and the external contact pad 1122, the active layer 315 can emit light of the second wavelength. In this embodiment, the orthogonal projection of the conductive via 2142 at least partially overlaps the orthogonal projection of the external contact pad 1122.

[0036] In addition, the first light emitting layer 200a can have a conductive via 2144 electrically connecting the external contact pad 1125 (e.g., a positive electrode) and the second type semiconductor layer 327. When a forward voltage is applied between the external contact pad 1125 and the external contact pad 1122, the active layer 325 can emit light of the third wavelength.

[0037] In this embodiment, the external contact pads 1121, 1122, 1123, 1124, 1125 are located in the substrate 110, which is, for example, a silicon substrate. However, in other embodiments, the substrate 110 can also be a glass substrate, a plastic substrate, or a substrate made of other materials.

[0038] In this embodiment, the top of conductive via 2141 is connected to the top of the second type semiconductor layer 217 via metal layer 410, the top of conductive via 2143 is connected to the bottom of the second type semiconductor layer 317 via metal layer 420, and the top of conductive via 2143 is connected to the bottom of the second type semiconductor layer 327 via metal layer 430. An insulating layer 440 is provided between metal layers 410 and 420, and the insulating layer 440 is also located between metal layers 410 and 430. Metal layers 410, 420, and 430 and insulating layer 440 form a metal layer 400a that bonds the first light-emitting layer 200a and the second light-emitting layer 300. In this embodiment, conductive vias 2142, 2143, and 2144 penetrate the insulating layer 220 of the first light-emitting layer 200a in a vertical direction. In this embodiment, the position of the conductive via 2141 in the orthographic projection direction at least partially overlaps with the position of the external pad 1121 in the orthographic projection direction. In some embodiments, the position of the conductive via 2142 in the orthographic projection direction at least partially overlaps with the position of the external pad 1122 in the orthographic projection direction. This allows the two to be directly soldered after alignment when making electrical connections, without needing to rely on horizontal circuitry for connection, thus saving space for horizontal circuitry and further reducing the spacing between pixels.

[0039] FIG. 3A This is a top view schematic diagram of a micro light-emitting element according to another embodiment of the present invention. FIG. 3B for FIG. 3A A schematic diagram of the cross-section of the miniature light-emitting element along line A-A'. Please refer to... FIG. 3A and FIG. 3B In this embodiment, the micro light-emitting element 100b and FIG. 2A to FIG. 2C Similar to the micro-light-emitting element 100a, the main differences between the two are as follows. In the micro-light-emitting element 100b of this embodiment, the first epitaxial structure 210b has a conductive via 2141b for electrically connecting the external pad 1122b and the second light-emitting layer 300b in the vertical direction. Specifically, the first epitaxial structure 210b has a second type semiconductor layer 217, an active layer 215, and a first type semiconductor layer 213 stacked in sequence; the second epitaxial structure 310b has a first type semiconductor layer 313, an active layer 315, and a second type semiconductor layer 317 stacked in sequence; and the third epitaxial structure 320b has a first type semiconductor layer 323, an active layer 325, and a second type semiconductor layer 327 stacked in sequence. The conductive via 2141b connects the external pad 1122b (e.g., a negative electrode) to the first type semiconductor layer 213, the first type semiconductor layer 313, and the first type semiconductor layer 323 via a metal layer 400b. In other words, the metal layer 400b bonds the first epitaxial structure 210b and the second epitaxial structure 310b, and also bonds the first epitaxial structure 210b and the third epitaxial structure 320b.

[0040] On the other hand, the second-type semiconductor layer 217 is electrically connected to the external pad 1121b (e.g., a positive electrode) on the lower side. When a forward voltage is applied between the external pad 1121b and the external pad 1122b, the active layer 215 can emit light of the first wavelength.

[0041] In the present embodiment, the second epitaxial structure 310b has a conductive via 2143b for electrically connecting the external pad 1124b (e.g., a positive electrode) on the substrate 110 to the side of the second epitaxial structure 310b away from the first light-emitting layer 200b in the vertical direction. In the present embodiment, the conductive via 2143b is electrically connected to the external pad 1124b on the substrate 110 by the conductive via 2145b of the first epitaxial structure 210b, the conductive via 2143b also penetrates the first epitaxial structure 210b, and the top of the conductive via 2143b is electrically connected to the second-type semiconductor layer 317. When a forward voltage is applied between the external pad 1124b and the external pad 1122b, the active layer 315 can emit light of the second wavelength.

[0042] In the present embodiment, the third epitaxial structure 320b has a conductive via 2144b for electrically connecting the external pad 1125b (e.g., a positive electrode) on the substrate 110 to the side of the third epitaxial structure 320b away from the first light-emitting layer 200b in the vertical direction. In the present embodiment, the conductive via 2144b is electrically connected to the external pad 1125b on the substrate 110 by the conductive via 2146b of the first epitaxial structure 210b, the conductive via 2144b also penetrates the first epitaxial structure 210b, and the top of the conductive via 2144b is electrically connected to the second-type semiconductor layer 327. When a forward voltage is applied between the external pad 1125b and the external pad 1122b, the active layer 325 can emit light of the third wavelength.

[0043] In the present embodiment, the first epitaxial structure 210b has a portion (e.g., the lower half of FIG. 3A and the right half of FIG. 3B ) above which the second epitaxial structure 310b and the third epitaxial structure 320b are not disposed, so that the light of the first wavelength emitted by this portion of the first epitaxial structure 210b is not blocked by the second epitaxial structure 310b and the third epitaxial structure 320b, and thus has good light-emitting efficiency.

[0044] FIG. 4A A cross-sectional schematic view of a micro light-emitting element according to another embodiment of the present application is shown in FIG. 10D. As shown in FIG. 10D, the micro light-emitting element 100d according to the present embodiment is similar to the micro light-emitting element 100c shown in FIG. 10C, and thus the same components are denoted by the same reference numerals, and a detailed description thereof will not be provided. FIG. 4A FIG. 1A ​The micro light emitting element 100d of the present embodiment includes a first light emitting layer 200d, a second light emitting layer 300d, and a wavelength conversion structure 120. The first light emitting layer 200d includes a first epitaxial structure 210d having a first portion P1 and a second portion P2, both of which emit light of a first wavelength. In the present embodiment, the first portion P1 and the second portion P2 of the first epitaxial structure 210d are electrically independent of each other. The second light emitting layer 300d is disposed on the first light emitting layer 200d in a stacked manner, and includes a second epitaxial structure 310d bonded to the first portion P1 by a metal layer 400, which emits light of a second wavelength. The wavelength conversion structure 120 is disposed on the second portion P2 in a stacked manner, and is configured to convert the light of the first wavelength emitted by the second portion P2 into light of a third wavelength. In the present embodiment, the light of the first wavelength is, for example, blue light, the light of the second wavelength is, for example, green light, and the light of the third wavelength is, for example, red light. In the present embodiment, the wavelength conversion structure 120 is, for example, a quantum dot layer or a fluorescent layer, wherein the fluorescent layer can be a potassium fluorosilicate (KSF) fluorescent powder layer or a fluorescent powder layer of other material, and the quantum dot layer or the fluorescent layer can convert the light of the first wavelength into the light of the third wavelength.

[0045] In the present embodiment, the sum of the areas of the orthographic projections of the second epitaxial structure 310d and the wavelength conversion structure 120 is less than the area of the orthographic projection of the first epitaxial structure 210d (including the first portion P1 and the second portion P2). That is, the sum of the areas of the orthographic projections of the second epitaxial structure 310d and the wavelength conversion structure 120 on the substrate 110 is less than the area of the orthographic projection of the first epitaxial structure 210d (including the first portion P1 and the second portion P2) on the substrate 110. In an embodiment, the area of the orthographic projection of the second epitaxial structure 310d is less than the area of the orthographic projection of the first portion P1.

[0046] In the present embodiment, the first epitaxial structure 210d and the second epitaxial structure 310d are solid chips of the same epitaxial material. In some embodiments, the first epitaxial structure 210d and the second epitaxial structure 310d are nanorod arrays of the same epitaxial material, as shown in FIG. 1C. FIG. 4B As shown in FIG. 1C, the nanorod array 310d of the first epitaxial structure and the nanorod array 210d of the second epitaxial structure are stacked in the manner shown in the figure and are bonded by the metal layer 400. For example, the first epitaxial structure 210d includes a plurality of nanorods 216 arranged in an array (e.g., a two-dimensional array), and the second epitaxial structure 310d includes a plurality of nanorods 312d arranged in an array (e.g., a two-dimensional array). In the present embodiment, the nanorods 216 are upright on the substrate 110, and the nanorods 312d are upright on the metal layer 400.

[0047] In this embodiment, the materials of the first epitaxial structure 210d and the second epitaxial structure 310d are, for example, indium gallium nitride (InGaN) or gallium nitride (GaN), and the indium concentration of the first epitaxial structure 210d is greater than that of the second epitaxial structure 310d. The higher the indium concentration, the larger the diameter of the formed nanopillars. Therefore, in this embodiment, the diameter of a single nanopillar in the nanopillar array of the first epitaxial structure 210d (i.e., the diameter D1 of nanopillar 216) is greater than the diameter of a single nanopillar in the nanopillar array of the second epitaxial structure 310d (i.e., the diameter D2 of nanopillar 312d). Furthermore, the smaller the diameter of the nanopillar, the longer the wavelength of the emitted light. Therefore, the second wavelength (i.e., the wavelength of the light emitted by the second epitaxial structure 310d) is greater than the first wavelength (i.e., the wavelength of the light emitted by the first epitaxial structure 210d).

[0048] In some embodiments, the material of the first epitaxial structure 210d includes (Al) x Ga 1-x ) 1-y In y P, which stands for aluminum gallium indium phosphide, where 1 ≥ x ≥ 0 and 1 > y > 0. The second epitaxial structure 310d includes multiple nanopillars 312d arranged in an array (e.g., a two-dimensional array). The material of the second epitaxial structure 310d is, for example, indium gallium nitride (InGaN) or gallium nitride (GaN).

[0049] In the micro-light-emitting element 100d of this embodiment, the sum of the projected areas of the second epitaxial structure 310d and the wavelength conversion structure 120 is smaller than the projected area of ​​the first epitaxial structure 210d. Therefore, when the micro-light-emitting element 100d is used as a display pixel, the sub-pixels in the second light-emitting layer 300d and the sub-pixels in the wavelength conversion structure 120 only cover a portion of the sub-pixels in the first light-emitting layer 200d, thus improving luminous efficiency. In some embodiments, the projected area of ​​the second epitaxial structure 310d is smaller than the projected area of ​​the first portion P1. The light-emitting surface 212 exposed by the first portion P1 is not blocked by the second epitaxial structure 310d, resulting in higher light emission efficiency. Furthermore, in the micro-light-emitting element 100d of this embodiment, the first light-emitting layer 200d and the second light-emitting layer 300d are connected by bonding with a metal layer 400, thus reducing the impact of alignment tolerances during vertical stacking.

[0050] In this embodiment, the thickness T1 of the first epitaxial structure 210d falls within the range of 1 micrometer to 2 micrometers. In this embodiment, the thickness T2 of the second epitaxial structure 300d falls within the range of 1 micrometer to 2 micrometers. Furthermore, in this embodiment, a metal layer 400 is disposed in the region where the second epitaxial structure 300d and the first epitaxial structure 210d are bonded, exposing the light-emitting surface 212 of the first epitaxial structure 210d to reflect light of the first wavelength to the light-emitting surface 212 for emission.

[0051] FIG. 5A This is a top view schematic diagram of a micro light-emitting element according to another embodiment of the present invention. FIG. 5B for FIG. 5A A schematic diagram of the cross-section of the miniature light-emitting element along line A-A'. Please refer to... FIG. 5A and FIG. 5B In this embodiment, the micro light-emitting element 100e and FIG. 4A Similar to the micro-light-emitting element 100d, the main differences between the two are as follows. In the micro-light-emitting element 100e of this embodiment, the first light-emitting layer 200e has a conductive via 2141e for electrically connecting the external pad 1121e of the substrate 110 to the side of the first epitaxial structure 210d near the second light-emitting layer 300d in the vertical direction. For example, the external pad 1121e is electrically connected to the first type semiconductor layer 213d of the first epitaxial structure 210d, for example, by means of a metal layer 400. The external pad 1123e is electrically connected to the lower side of the second type semiconductor layer 217d of the second portion P2 of the first epitaxial structure 210d. When a forward voltage is applied to external pads 1123e and 1121e, the active layer 215d of the second portion P2 of the first epitaxial structure 210d emits light of a first wavelength. This second wavelength light, after illuminating the wavelength conversion structure 120 above, is converted into light of a third wavelength. The lower side of the second-type semiconductor layer 217d of the first portion P1 of the first epitaxial structure 210d is electrically connected to external pad 1122e. When a forward voltage is applied to external pads 1122e and 1121e, the active layer 215d of the first portion P1 of the first epitaxial structure 210d emits light of the first wavelength.

[0052] On the other hand, the conductive via 2141e is also electrically connected to the first type semiconductor layer 313d of the second epitaxial structure 310d via the metal layer 400. Furthermore, the first light-emitting layer 200e also has a conductive via 2142e for electrically connecting another external pad 1125e on the substrate 110 to the second light-emitting layer 300d in the vertical direction. For example, the conductive via 2142e is electrically connected to the second type semiconductor layer 317d of the second epitaxial structure 310d via the wiring layer 302e. Moreover, the conductive via 2141e is electrically connected to the external pad 1125e and the second type semiconductor layer 317d. When a forward voltage is applied to the external pad 1125e and the external pad 1121e, the active layer 315d of the second epitaxial structure 310d emits light of a second wavelength. In this embodiment, conductive vias 2141e and 2142e are insulating layers 220 that penetrate the first light-emitting layer 200e, and conductive vias 2141e and 2142e are disposed on the side of the first portion P1 or the second portion P2. In this embodiment, the projected area of ​​the wavelength conversion structure 120 covers the projected area of ​​the second portion P2.

[0053] FIG. 6A This is a top view schematic diagram of a micro light-emitting element according to another embodiment of the present invention. FIG. 6B for FIG. 6A A schematic diagram of the cross-section of the miniature light-emitting element along line A-A'. Please refer to... FIG. 6A and FIG. 6B In this embodiment, the micro light-emitting element 100f and FIG. 5A and FIG. 5B Similar to the micro-light-emitting element 100e, the main differences between the two are as follows. In the micro-light-emitting element 100f of this embodiment, the first epitaxial structure 210f of the first light-emitting layer 200f has a conductive via 2141f for electrically connecting the external pad 1121f to the side of the first epitaxial structure 210f near the second light-emitting layer 300f in the vertical direction, for example, electrically connecting the external pad 1121f to the first type semiconductor layer 213d of the first epitaxial structure 210f. In this embodiment, the first epitaxial structure 210f has a conductive via 2142f for electrically connecting the external pad 1125f to the second epitaxial structure 310f, for example, electrically connecting the external pad 1125f to the second type semiconductor layer 317d of the second epitaxial structure 310f. On the other hand, the conductive via 2141f is also electrically connected to the first type semiconductor layer 313d of the second epitaxial structure 310f via a wiring layer 302f. When a forward voltage is applied to the external pads 1125f and 1121f, the active layer 315d of the second epitaxial structure 310f emits light of a second wavelength.

[0054] FIG. 7This is a partial top view schematic diagram of a micro light-emitting element display device according to an embodiment of the present invention. Please refer to... FIG. 7 In this embodiment, the micro-light-emitting element display device 60 includes a plurality of micro-light-emitting elements 100a, and the spacing I1 between adjacent micro-light-emitting elements 100a is smaller than the size of the micro-light-emitting element 100a (e.g., the width W1 of the micro-light-emitting element 100a). Furthermore, in this embodiment, a barrier 50 is provided between adjacent micro-light-emitting elements 100a to reduce light crosstalk, wherein the barrier 50 can be formed of a light-absorbing material or a reflective material. Additionally, in this embodiment, adjacent micro-light-emitting elements 100a may share a portion of the conductive via and a portion of the external pad, for example, sharing the conductive via 2142 and the external pad 1122 connected to it (e.g., ...). FIG. 2B (As shown). In some embodiments, conductive vias 2143 and 2144 are disposed on the side of the first portion P1 or the second portion P2 of the first epitaxial structure 210. A plurality of micro-light-emitting elements 100a arranged in an array can form a pixel array of the micro-light-emitting element display device 60, that is, each micro-light-emitting element 100a is a pixel. In other embodiments, the number of micro-light-emitting elements 100, 100b to 100f described in the other embodiments above can also be multiple, arranged in an array to form a pixel array of the micro-light-emitting element display device 60. In some embodiments, a single micro-light-emitting element 100a occupies more than or equal to 70% of the area of ​​its corresponding pixel in the orthographic projection direction.

[0055] FIG. 8 This is a flowchart illustrating a method for manufacturing a micro light-emitting element according to an embodiment of the present invention. Please refer to... FIG. 8 The method for manufacturing the micro light-emitting element in this embodiment can be used to manufacture... FIG. 1A to FIG. 1D The various embodiments of the micro light-emitting elements 100, 100a to 100c, and the following mainly focuses on the manufacturing process. FIG. 2A to FIG. 2C The following description uses a micro-light-emitting element 100a as an example. The manufacturing method of the micro-light-emitting element in this embodiment includes the following steps. First, step S110 is performed, which is a wafer bonding process, where a first light-emitting layer 200a is disposed on a substrate 110, wherein the substrate 110 is, for example, a circuit substrate, and the first light-emitting layer 200a includes a first type semiconductor layer 213, an active layer 215, and a second type semiconductor layer 217. This wafer bonding process can be performed by metal bonding, which can reduce the impact of alignment errors. Next, step S120 is performed, which is an array process, where the first light-emitting layer 200a is defined into a pixel array, for example, defining a pixel array such as... FIG. 2BThe first epitaxial structure 210a is then executed. Next, step S130, a bonding process, is performed to form conductive lines on the first light-emitting layer 200a, such as forming conductive vias 2141, 2142, 2143, 2144, or wiring layers. Then, step S140, a wafer bonding process, is performed to deposit the second light-emitting layer 300 on the first light-emitting layer 200a, for example, by bonding the first light-emitting layer 200a and the second light-emitting layer 300 with a metal layer 400a. Metal bonding reduces the impact of alignment errors. After this, step S150, an array process, is performed to divide the second light-emitting layer 300 into multiple epitaxial structures at the positions corresponding to display pixels, thereby defining a pixel array, such as... FIG. 2B The second epitaxial structure 310 and the third epitaxial structure 320 are respectively, and the second light-emitting layer 300 includes two regions (i.e., the region of the second epitaxial structure 310 and the region of the third epitaxial structure 320) that emit light of two different wavelengths respectively. Then, step S160 is performed, which is a connection process, forming conductive lines between the first light-emitting layer 200a and the second light-emitting layer 300, for example, forming a conductive line between the first light-emitting layer 200a and the second light-emitting layer 300. FIG. 2B The wiring layer 302, or forming a layer like FIG. 3B Conductive vias 2143b and 2144b.

[0056] FIG. 9 This is a flowchart illustrating a method for manufacturing a micro light-emitting element according to another embodiment of the present invention. Please refer to... FIG. 9 The method for manufacturing the micro light-emitting element in this embodiment can be used to manufacture... FIG. 4A to FIG. 6B The various embodiments of the micro light-emitting elements 100d to 100f, and the following mainly focuses on the manufacturing of FIG. 5A and FIG. 5B The method of manufacturing the micro light-emitting element 100e in this embodiment will be described using steps S110 to S140 as an example. FIG. 8 The embodiments are similar and will not be repeated here. Instead, the following description focuses on different steps S170 and S180. In step S170, a connection process is performed to define the pixel array (e.g., as shown in the image) of the second light-emitting layer 300d. FIG. 5B The second epitaxial structure 310d), and a conductive line is formed between the first light-emitting layer 200e and the second light-emitting layer 300d (e.g., as shown in the image). FIG. 5B (The trace layer 302e or conductive vias 2141e, 2142e). Then, step S180 is performed, which is a wavelength conversion structure process, in which the wavelength conversion structure 120 is disposed on the first light-emitting layer 200e.

[0057] In summary, in the micro light emitting element display device of the embodiment of the present application, because the first light emitting layer and the second light emitting layer are stacked, and the second light emitting layer can emit light of two different wavelengths, the spatial resolution of the display pixels can be improved, and the space occupied by the circuit traces can be reduced, and the light emitting area can be increased. In addition, in the micro light emitting element display device of the embodiment of the present application, the sum of the orthographic projection areas of the second epitaxial structure and the third epitaxial structure is less than the orthographic projection area of the first epitaxial structure, or the orthographic projection area of the second epitaxial structure is less than the orthographic projection area of the first part, so that the sub-pixels in the second light emitting layer only cover part of the sub-pixels in the first light emitting layer, and the light emitting efficiency can be improved. Furthermore, in the micro light emitting element display device of the embodiment of the present application, the metal layer can be used to simultaneously arrange the second epitaxial structure and the third epitaxial structure on the first light emitting layer in a single process step. Compared with defining the epitaxial area by performing two times of photolithography to manufacture the second epitaxial structure and the third epitaxial structure respectively, the alignment step can be reduced, and the first light emitting layer and the second light emitting layer are connected by bonding, so that the influence of the alignment tolerance during vertical stacking can be reduced.

[0058] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A miniature light-emitting element display device, characterized in that, It includes multiple micro-light-emitting elements, wherein each micro-light-emitting element includes: A first light-emitting layer, including a first epitaxial structure, for emitting light of a first wavelength; and A second light-emitting layer is stacked on the first light-emitting layer by metal layer bonding, and the second light-emitting layer includes: A second epitaxial structure is used to emit light of a second wavelength; and The third epitaxial structure is used to emit light of a third wavelength. Wherein, the second epitaxial structure and the third epitaxial structure are nanopillar arrays of the same epitaxial material, the third wavelength is greater than the second wavelength, and both the second wavelength and the third wavelength are less than the first wavelength, and the sum of the projected areas of the second epitaxial structure and the third epitaxial structure is less than the projected area of ​​the first epitaxial structure.

2. The micro light-emitting element display device according to claim 1, characterized in that, The indium concentration of the second epitaxial structure is greater than that of the third epitaxial structure, and the diameter of a single nanopillar in the nanopillar array of the second epitaxial structure is greater than that of a single nanopillar in the nanopillar array of the third epitaxial structure.

3. The micro light-emitting element display device according to claim 1, characterized in that, The projected area of ​​the second epitaxial structure is less than 1 / 2 times the projected area of ​​the first epitaxial structure, and the projected area of ​​the third epitaxial structure is less than 1 / 2 times the projected area of ​​the first epitaxial structure.

4. The micro light-emitting element display device according to claim 1, characterized in that, It also includes a substrate disposed on a side away from the first light-emitting layer, wherein the first epitaxial structure of the first light-emitting layer has a conductive via for electrically connecting an external pad on the substrate to the side of the first epitaxial structure near the second light-emitting layer in the vertical direction.

5. The micro light-emitting element display device according to claim 4, characterized in that, The orthographic projection of the conductive via at least partially overlaps with the orthographic projection of the external pad.

6. The micro light-emitting element display device according to claim 4, characterized in that, The first light-emitting layer has another conductive via for electrically connecting another external pad on the substrate to the second light-emitting layer in the vertical direction.

7. The micro light-emitting element display device according to claim 6, characterized in that, The orthographic projection of the conductive via at least partially overlaps with the orthographic projection of the external pad.

8. The micro light-emitting element display device according to claim 4, characterized in that, The second epitaxial structure has another conductive via for electrically connecting another external pad on the substrate in the vertical direction to the side of the second epitaxial structure away from the first light-emitting layer.

9. The micro light-emitting element display device according to claim 8, characterized in that, The conductive via of the second epitaxial structure is electrically connected to another external pad on the substrate via the conductive via of the first epitaxial structure.

10. The micro light-emitting element display device according to claim 1, characterized in that, The third epitaxial structure has another conductive via for electrically connecting another external pad on the substrate in the vertical direction to the side of the third epitaxial structure away from the first light-emitting layer.

11. The micro light-emitting element display device according to claim 10, characterized in that, The third epitaxial structure's additional conductive via is electrically connected to another external pad on the substrate via the first epitaxial structure's conductive via.

12. The micro light-emitting element display device according to claim 1, characterized in that, The metal layer is disposed in the region where the second epitaxial structure or the third epitaxial structure is bonded to the first epitaxial structure, exposing a portion of the light-emitting surface of the first epitaxial structure.

13. A miniature light-emitting element display device, characterized in that, include: The first light-emitting layer includes a first epitaxial structure having a first portion and a second portion, both of which emit light of a first wavelength; A second light-emitting layer is stacked on the first light-emitting layer. The second light-emitting layer includes a second epitaxial structure bonded to the first portion by a metal layer and emits light of a second wavelength. as well as A wavelength conversion structure, stacked on the second part, is used to convert light of the first wavelength emitted by the second part into light of the third wavelength. The projected area of ​​the second extensional structure is smaller than the projected area of ​​the first part.

14. The micro light-emitting element display device according to claim 13, characterized in that, It also includes a substrate disposed on a side away from the first light-emitting layer, wherein the first light-emitting layer has conductive vias for electrically connecting the external pads of the substrate to the side of the first epitaxial structure near the second light-emitting layer in the vertical direction.

15. The micro light-emitting element display device according to claim 14, characterized in that, The first light-emitting layer has another conductive via for electrically connecting another external pad on the substrate to the second light-emitting layer in the vertical direction.

16. The micro light-emitting element display device according to claim 15, characterized in that, The conductive via and the other conductive via are disposed on the side of the first portion or the second portion.

17. The micro light-emitting element display device according to claim 13, characterized in that, The projected area of ​​the wavelength conversion structure covers the projected area of ​​the second part.

18. The micro light-emitting element display device according to claim 13, characterized in that, The first portion and the second portion of the first epitaxial structure are electrically independent of each other.

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