Light emitting element for display and LED display device having the same

Abstract

A light emitting element according to an embodiment includes: a first light emitting stack, a second light emitting stack, and a third light emitting stack, each of the first light emitting stack, the second light emitting stack, and the third light emitting stack including a first-conductivity-type semiconductor layer, a second-conductivity-type semiconductor layer, and an active layer disposed between the first-conductivity-type semiconductor layer and the second-conductivity-type semiconductor layer; a first lower contact electrode ohmic-contacting the first light emitting stack; a second lower contact electrode ohmic-contacting a second-conductivity-type semiconductor layer of the second light emitting stack; and a third lower contact electrode ohmic-contacting a second-conductivity-type semiconductor layer of the third light emitting stack, wherein the second light emitting stack is disposed between the first light emitting stack and the third light emitting stack, the first lower contact electrode is disposed between the first light emitting stack and the second light emitting stack, the second lower contact electrode and the third lower contact electrode are disposed between the second light emitting stack and the third light emitting stack, the first lower contact electrode, the second lower contact electrode, and the third lower contact electrode include a transparent conductive oxide layer, and a thickness of the second lower contact electrode or the third lower contact electrode is greater than a thickness of the first lower contact electrode.

Description

Technical Field

[0001] This disclosure relates to a light-emitting element for display and an LED display device having the same. Background Technology

[0002] Light-emitting diodes (LEDs), as inorganic light sources, are widely used in various fields such as display devices, vehicle lighting, and general lighting. LEDs have advantages such as long lifespan, low power consumption, and fast response speed, and are therefore rapidly replacing existing light sources.

[0003] In addition, existing light-emitting diodes (LEDs) are mainly used as backlight sources in display devices. However, LED displays that utilize LEDs to directly display images are currently under development.

[0004] Display devices typically utilize a mixture of blue, green, and red to achieve a variety of colors. To realize diverse images, a display device includes multiple pixels, each pixel having blue, green, and red sub-pixels. The color of a specific pixel is determined by the colors of these sub-pixels, and the image is realized through the combination of these pixels.

[0005] LEDs can emit a variety of colors of light depending on their material, so a display device can be provided by arranging individual LED chips that emit blue, green, and red light on a two-dimensional plane. However, if an LED chip is arranged for each sub-pixel, the number of LED chips increases, thus requiring a lot of time in the mounting process.

[0006] Because subpixels are arranged on a two-dimensional plane, the area occupied by a single pixel, including blue, green, and red subpixels, is relatively wider. Therefore, in order to arrange subpixels within a limited area, the area of ​​each LED chip needs to be reduced. However, reducing the size of the LED chip makes it more difficult to mount the LED chip, which in turn leads to a reduction in the light-emitting area and a decrease in luminous intensity.

[0007] Furthermore, display devices capable of displaying multiple colors require consistently high-quality white light. Existing TVs use a 3:6:1 RGB mixing ratio to achieve the standard white light of the D65. That is, the intensity of red is relatively higher than that of blue, and the intensity of green is relatively the highest. However, because the blue LEDs in currently used LED chips typically have a relatively higher intensity than other LEDs, there is a problem in matching the RGB mixing ratio in display devices using LED chips. Summary of the Invention

[0008] The technical problem this disclosure aims to solve is to provide a display device that can increase the area of ​​each sub-pixel within a limited pixel area.

[0009] Another technical problem that this disclosure aims to solve is to provide a display device that can shorten the mounting process time.

[0010] Another technical problem that this disclosure aims to solve is to provide a display device that can easily control the RGB mixing ratio.

[0011] A light-emitting element according to an embodiment of the present disclosure includes: a first light-emitting stack, a second light-emitting stack, and a third light-emitting stack. Each of the first, second, and third light-emitting stacks includes a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer disposed between the first and second conductive semiconductor layers; a first lower contact electrode, ohmically contacting the first light-emitting stack; a second lower contact electrode, ohmically contacting the second conductive semiconductor layer of the second light-emitting stack; and a third lower contact electrode, ohmically contacting the second conductive semiconductor layer of the third light-emitting stack. The second light-emitting stack is disposed between the first and third light-emitting stacks, the first lower contact electrode is disposed between the first and second light-emitting stacks, and the second and third lower contact electrodes are disposed between the second and third light-emitting stacks. The first, second, and third lower contact electrodes each include a transparent conductive oxide layer, and the thickness of the second or third lower contact electrode is greater than the thickness of the first lower contact electrode.

[0012] A display device according to an embodiment of the present disclosure includes: a display substrate; and a plurality of light-emitting elements disposed on the display substrate, wherein the light-emitting elements are the light-emitting elements described above. Attached Figure Description

[0013] Figure 1a This is a schematic perspective view illustrating a light-emitting element according to an embodiment of the present disclosure.

[0014] Figure 1b yes Figure 1a A schematic plan view of the light-emitting element.

[0015] Figure 1c and Figure 1d They are along Figure 1b A schematic cross-sectional view obtained by cutting lines AA′ and BB′.

[0016] Figure 2 This is a schematic cross-sectional view of a light-emitting stacked structure according to an embodiment of the present disclosure.

[0017] Figure 3a , Figure 4a , Figure 5a , Figure 6a , Figure 7a and Figure 8a This indicates manufacturing according to an exemplary embodiment. Figure 1a A plan view of the process of the light-emitting element.

[0018] Figure 3b , Figure 4b , Figure 5b , Figure 6b , Figure 7b and Figure 8b According to the exemplary embodiments, along Figure 3a , Figure 4a , Figure 5a , Figure 6a , Figure 7a and Figure 8a The cross-sectional view of line AA′ corresponding to the plan view shown.

[0019] Figure 3c , Figure 4c , Figure 5c , Figure 6c , Figure 7c and Figure 8c According to the exemplary embodiments, along Figure 3a , Figure 4a , Figure 5a , Figure 6a , Figure 7a and Figure 8a The cross-sectional view of the corresponding plan view along line BB′ is shown.

[0020] Figure 9 , Figure 10 , Figure 11 , Figure 12 and Figure 13 This is an illustrative representation according to an exemplary embodiment. Figure 1a A cross-sectional view of the manufacturing process of the light-emitting element.

[0021] Figure 14 , Figure 15 , Figure 16a and Figure 16b This is a schematic cross-sectional view illustrating the manufacturing process of a light-emitting package according to an embodiment of the present disclosure.

[0022] Figure 17 This is a schematic cross-sectional view used to illustrate a display device according to an embodiment of the present disclosure.

[0023] Figure 18 This is a schematic cross-sectional view used to illustrate a light-emitting package according to yet another embodiment of the present disclosure.

[0024] Figure 19This is a schematic cross-sectional view of a light-emitting stacked structure according to yet another embodiment of the present disclosure. Detailed Implementation

[0025] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. To fully convey the ideas of the present disclosure to those skilled in the art, the following embodiments are provided as examples. Therefore, the present disclosure is not limited to the embodiments described below, but can be embodied in other forms. Furthermore, in the drawings, the width, length, thickness, etc., of the constituent elements may be exaggerated for ease of explanation. Also, when described as one constituent element being "above" or "on top of" another constituent element, this includes not only cases where each part is "directly" located above or on top of other parts, but also cases where another constituent element is sandwiched between each constituent element and another constituent element. Throughout the specification, the same reference numerals denote the same constituent elements.

[0026] A light-emitting element according to an embodiment of the present disclosure includes: a first light-emitting stack, a second light-emitting stack, and a third light-emitting stack. Each of the first, second, and third light-emitting stacks includes a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer disposed between the first and second conductive semiconductor layers; a first lower contact electrode, ohmically contacting the first light-emitting stack; a second lower contact electrode, ohmically contacting the second conductive semiconductor layer of the second light-emitting stack; and a third lower contact electrode, ohmically contacting the second conductive semiconductor layer of the third light-emitting stack. The second light-emitting stack is disposed between the first and third light-emitting stacks, the first lower contact electrode is disposed between the first and second light-emitting stacks, and the second and third lower contact electrodes are disposed between the second and third light-emitting stacks. The first, second, and third lower contact electrodes each include a transparent conductive oxide layer, and the thickness of the second or third lower contact electrode is greater than the thickness of the first lower contact electrode.

[0027] Since the first to third light-emitting stacks overlap each other, the area of ​​each sub-pixel can be increased within a limited pixel area without increasing the pixel area. Furthermore, since the light-emitting element includes the first to third light-emitting stacks, the total number of light-emitting elements used in the display can be reduced compared to existing light-emitting elements, thus shortening the light-emitting element mounting process time.

[0028] Furthermore, since the second lower contact electrode and the third lower contact electrode are arranged in the path of the light emitted from the second light-emitting stack, it is possible to prevent the light emitted from the third light-emitting stack from being lost due to the lower contact electrodes. Furthermore, by forming the second lower contact electrode or the third lower contact electrode to be relatively thicker than the first lower contact electrode, it is possible to selectively reduce the luminous intensity of the light emitted from the second light-emitting stack.

[0029] Furthermore, the first, second, and third light-emitting stacks can be configured to emit red, blue, and green light, respectively. By emitting blue light from the second light-emitting stack and green light from the third light-emitting stack, the intensity of the green light can be increased, thereby easily providing an RGB mixing ratio suitable for the display device.

[0030] In one embodiment, the thickness of the second lower contact electrode may be greater than the thickness of the third lower contact electrode.

[0031] In one embodiment, the second lower contact electrode or the third lower contact electrode may include a lower layer that has been heat-treated for ohmic contact with the second conductive semiconductor layer and an upper layer disposed on the heat-treated lower layer that has not been heat-treated. Furthermore, the thickness of the upper layer that has not been heat-treated may be greater than the thickness of the lower layer that has been heat-treated.

[0032] By utilizing a heat-treated lower layer to achieve good ohmic contact while employing an upper layer formed without heat treatment, the luminous intensity of light emitted from the second light-emitting stack can be effectively reduced.

[0033] The first lower contact electrode to the third lower contact electrode may include an ITO-based transparent conductive oxide layer, for example, ITO or ITZO.

[0034] In addition, the first lower contact electrode can make ohmic contact with the second conductive semiconductor layer of the first light-emitting stack.

[0035] The light-emitting element may further include: a first connecting electrode electrically connected to the first light-emitting stack; a second connecting electrode electrically connected to the second light-emitting stack; a third connecting electrode electrically connected to the third light-emitting stack; and a fourth connecting electrode electrically connected together with the first light-emitting stack, the second light-emitting stack, and the third light-emitting stack.

[0036] Furthermore, the fourth connecting electrode can be electrically connected to the first conductive semiconductor layer of the first to third light-emitting stacks, and the first conductive semiconductor layer may include an n-type semiconductor layer. Accordingly, a light-emitting element with a common n-structure can be provided.

[0037] The light-emitting element may further include a protective layer surrounding at least a portion of the first to fourth connecting electrodes. The protective layer may include an epoxy molding compound or a polyimide film, and the upper surface of the protective layer may be substantially parallel to the upper surfaces of the first to fourth connecting electrodes.

[0038] The light-emitting element may also include a substrate arranged adjacent to the third light-emitting stack.

[0039] Furthermore, the light-emitting element may also include: a first adhesive layer, which bonds the first light-emitting stack and the second light-emitting stack; and a second adhesive layer, which bonds the second light-emitting stack and the third light-emitting stack.

[0040] A display device according to an embodiment of the present disclosure includes: a display substrate; and a plurality of light-emitting elements disposed on the display substrate, wherein the light-emitting elements include: a first light-emitting stack, a second light-emitting stack, and a third light-emitting stack, each of the first light-emitting stack, the second light-emitting stack, and the third light-emitting stack including a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer; a first lower contact electrode, ohmicly contacting the first light-emitting stack; a second lower contact electrode, ohmicly contacting the second conductive semiconductor layer of the second light-emitting stack; and a third lower contact electrode. The first lower contact electrode is ohmically contacted with the second conductive semiconductor layer of the third light-emitting stack, wherein the second light-emitting stack is disposed between the first light-emitting stack and the third light-emitting stack, the first lower contact electrode is disposed between the first light-emitting stack and the second light-emitting stack, the second lower contact electrode and the third lower contact electrode are disposed between the second light-emitting stack and the third light-emitting stack, the first lower contact electrode, the second lower contact electrode and the third lower contact electrode include a transparent conductive oxide layer, and at least one of the second lower contact electrode and the third lower contact electrode is thicker than the first lower contact electrode.

[0041] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this description, the light-emitting stack structure, light-emitting element, or light-emitting package may include a micro LED, as is known in the art, with a light-emitting area of ​​10000 μm. 2 Below. As another embodiment, the microLED has a size of 4000 μm² or less, and further has a size of 2500 μm. 2 The following is the luminous area.

[0042] Figure 1aThis is a schematic perspective view illustrating a light-emitting element according to an embodiment of the present disclosure. Figure 1b yes Figure 1a A schematic plan view of the light-emitting element. Figure 1c and Figure 1d Each along Figure 1b A schematic cross-sectional view obtained by cutting lines AA′ and BB′.

[0043] Reference Figure 1a as well as Figure 1b The light-emitting element 100 may include: a light-emitting stacked structure; a first connecting electrode 20ce, a second connecting electrode 30ce, a third connecting electrode 40ce, and a fourth connecting electrode 50ce, formed on the light-emitting stacked structure; and a protective layer 90 surrounding the connecting electrodes 20ce, 30ce, 40ce, and 50ce. An array of light-emitting elements 100 may be formed on the substrate 11, and... Figure 1a The light-emitting element 100 shown in the example illustrates a light-emitting element unified from the array, and therefore can be named a light-emitting element. The formation and unification of the light-emitting element 100 will be described in detail below. In several embodiments, the light-emitting element 100, including a light-emitting stack structure, can be additionally processed to form a light-emitting package, which will also be described in detail below.

[0044] Reference Figure 1a as well as Figure 1d The light-emitting element 100 according to the illustrated embodiment includes a light-emitting stack structure, which may include a first LED sub-unit, a second LED sub-unit, and a third LED sub-unit disposed on a substrate. The first LED sub-unit may include a first light-emitting stack 20, the second LED sub-unit may include a second light-emitting stack 30, and the third LED sub-unit may include a third light-emitting stack 40. Three light-emitting stacks 20, 30, and 40 are shown for the light-emitting stack structure, but this disclosure is not limited to a specific number of light-emitting stacks. For example, in some embodiments, the light-emitting stack structure may include two or more light-emitting stacks. Here, a light-emitting stack structure comprising three light-emitting stacks 20, 30, and 40 according to one embodiment will be described.

[0045] The substrate 11 may include a light-transmitting insulating material for transmitting light. However, in some embodiments, the substrate 11 may be formed as translucent or partially transparent so that only a specific wavelength of light or only a portion of a specific wavelength of light is transmitted. The substrate 11 may be a growth substrate capable of epitaxially growing the third light-emitting stack 40, for example, it may be a sapphire substrate. However, the substrate 11 is not limited to a sapphire substrate and may include a variety of other transparent insulating materials. For example, the substrate 11 may include glass, quartz, silicon, organic polymers, or organic-inorganic composite materials, such as silicon carbide (SiC), gallium nitride (GaN), indium gallium nitride (InGaN), aluminum gallium nitride (AlGaN), aluminum nitride (AlN), gallium oxide (Ga2O3), or a silicon substrate. Furthermore, the substrate 11 may include bumps and depressions on its upper surface, for example, it may be a patterned sapphire substrate. Including bumps and depressions on the upper surface can improve the extraction efficiency of light generated in the third light-emitting stack 40 in contact with the substrate 11. The unevenness of the substrate 11 can be used to selectively increase the luminous intensity of the third light-emitting stack 40 compared to the first light-emitting stack 20 and the second light-emitting stack 30. Alternatively, as another embodiment, the substrate 11 can be removed. As described below, by removing the substrate 11, the direction angle of light emitted from the first light-emitting stack to the third light-emitting stacks 20, 30, and 40 can be reduced.

[0046] The first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 are configured to emit light toward the substrate 11. Therefore, light emitted from the first light-emitting stack 20 can pass through the second light-emitting stack 30 and the third light-emitting stack 40. According to one embodiment, the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 can emit light with different peak wavelengths. In one embodiment, the light-emitting stack farther from the substrate 11 emits a longer wavelength of light than the closer light-emitting stack, thereby reducing light loss. In another embodiment, in order to adjust the color mixing ratio of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40, the second light-emitting stack 30 can emit a shorter wavelength of light than the third light-emitting stack 40. Accordingly, the luminous intensity of the second light-emitting stack 30 can be reduced, and the luminous intensity of the third light-emitting stack 40 can be increased; therefore, the luminous intensity ratio of the light emitted from the first, second, and third light-emitting stacks can be significantly changed. For example, the first light-emitting stack 20 can be configured to emit red light, the second light-emitting stack 30 to emit blue light, and the third light-emitting stack 40 to emit green light. Accordingly, the intensity of blue light can be relatively reduced, and the intensity of green light can be relatively increased, thus easily adjusting the ratio of red, green, and blue light intensities to approximately 3:6:1. Furthermore, the light-emitting areas of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 can be approximately 10000 μm. 2 Furthermore, it can be up to 4000μm. 2 Furthermore, it can be further improved to 2500μm. 2 Furthermore, the closer to the substrate 11, the larger the light-emitting area can be. The intensity of green light emission is further increased by arranging the third light-emitting stack 40 that emits green light as close as possible to the substrate 11.

[0047] The first light-emitting stack 20 includes a first conductive semiconductor layer 21, an active layer 23, and a second conductive semiconductor layer 25. According to one embodiment, the first light-emitting stack 20 may include, for example, a red-light-emitting semiconductor material such as AlGaAs, GaAsP, AlGaInP, and GaP, but is not limited thereto.

[0048] The first upper contact electrode 21n is disposed on the first conductive semiconductor layer 21 and can form an ohmic contact with the first conductive semiconductor layer 21. The first lower contact electrode 25p can be disposed below the second conductive semiconductor layer 25. According to one embodiment, a portion of the first conductive semiconductor layer 21 can be patterned and recessed, and the first upper contact electrode 21n is disposed in the recessed region of the first conductive semiconductor layer 21 to increase the degree of ohmic contact. The first upper contact electrode 21n can have a single-layer structure or a multi-layer structure, and can include Al, Ti, Cr, Ni, Au, Ag, Sn, W, Cu or alloys thereof, such as Au-Te alloy or Au-Ge alloy, but is not limited thereto. In one embodiment, the first upper contact electrode 21n can have a thickness of about 100 nm and can include a metal with high reflectivity to increase luminous efficiency downward toward the substrate 11.

[0049] The second light-emitting stack 30 includes a first conductive semiconductor layer 31, an active layer 33, and a second conductive semiconductor layer 35. According to one embodiment, the second light-emitting stack 30 may include a blue-light-emitting semiconductor material such as GaN, InGaN, or ZnSe, but is not limited thereto. A second lower contact electrode 35p is disposed below the second conductive semiconductor layer 35 of the second light-emitting stack 30.

[0050] The third light-emitting stack 40 includes a first conductive semiconductor layer 41, an active layer 43, and a second conductive semiconductor layer 45. According to one embodiment, the third light-emitting stack 40 may include a green-light-emitting semiconductor material such as GaN, InGaN, GaP, AlGaInP, or AlGaP. A third lower contact electrode 45p is disposed on the second conductive semiconductor layer 45 of the third light-emitting stack 40.

[0051] According to one embodiment, each of the first conductive semiconductor layers 21, 31, 41 and the second conductive semiconductor layers 25, 35, 45 of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 has a single-layer structure or a multi-layer structure. In some embodiments, a superlattice layer may be included. Furthermore, the active layers 23, 33, 43 of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 may have a single quantum well structure or a multi-quantum well structure.

[0052] Each of the first lower contact electrode 25p, the second lower contact electrode 35p, and the third lower contact electrode 45p may include a transparent conductive material that transmits light. For example, the lower contact electrodes 25p, 35p, and 45p may include transparent conductive oxides (TCOs), such as SnO, InO2, ZnO, ITO, ITZO, etc., but are not limited to these.

[0053] Compared to red and green light, the position, material, and thickness of the lower contact electrodes 25p, 35p, and 45p can be selected to reduce the luminous intensity of blue light. For example, as shown in the figure, the second lower contact electrode 35p and the third lower contact electrode 45p can be arranged in the light emission path of blue light. However, the lower contact electrodes 25p, 35p, and 45p are not arranged in the light emission path of green light. That is, the third lower contact electrode 45p, which makes an ohmic contact with the third light-emitting stack 40, is arranged between the second light-emitting stack 30 and the third light-emitting stack 40.

[0054] Furthermore, the second lower contact electrode 35p or the third lower contact electrode 45p can be formed using a material that absorbs light and loses light, such as an ITO-based conductive oxide layer like ITO or ITZO. Generally, the shorter the wavelength of ITO, the greater the light loss due to increased thickness. Therefore, increasing the thickness of the second lower contact electrode 35p or the third lower contact electrode 45p arranged in the blue light emission path can reduce the blue light transmittance without affecting the red light transmittance. For example, when the first lower contact electrode 25p is also an ITO-based transparent conductive oxide layer, the thickness of the second lower contact electrode 35p or the third lower contact electrode 45p can be greater than the thickness of the first lower contact electrode 25p. Furthermore, the thickness of the second lower contact electrode 35p can be greater than the thickness of the third lower contact electrode 45p.

[0055] Furthermore, the heat treatment temperature of the transparent electrode affects the light transmittance. Therefore, to increase the transmittance of red light, the heat treatment temperature of the first lower contact electrode 25p can be relatively higher than that of the second lower contact electrode 35p or the third lower contact electrode 45p. For example, the first lower contact electrode 25p can be heat-treated at a temperature above 500°C, while the second lower contact electrode 35p and the third lower contact electrode 45p can be heat-treated at a temperature below 400°C.

[0056] Table 1 below schematically shows the transmittance based on the thickness of ITO and the heat treatment temperature.

[0057] Table 1

[0058]

[0059] Referring to Table 1, under the same heat treatment conditions, according to and The thickness variation confirmed that the transmittance change for red light at a wavelength of 625 nm was relatively smaller than that for blue light at a wavelength of 450 nm. Furthermore, it was confirmed that at heat treatment temperatures above 500°C, generally higher transmittance was observed for all wavelengths, while at temperatures below 400°C, generally lower transmittance was observed for all wavelengths. Additionally, for ITO without heat treatment, a thicker thickness confirmed that the transmittance for blue light at 450 nm was relatively lower.

[0060] Therefore, to reduce the luminous intensity of blue light, the thickness of the lower contact electrodes 35p and / or 45p arranged in the luminous path of blue light can be increased, and the heat treatment temperature can be lowered. Additionally, to prevent a decrease in the luminous intensity of red light, the lower contact electrode 25p can be heat-treated at a relatively high temperature (especially above 400°C).

[0061] A first adhesive layer 61 is disposed between the first light-emitting stack 20 and the second light-emitting stack 30, and a second adhesive layer 63 is disposed between the second light-emitting stack 30 and the third light-emitting stack 40. The first adhesive layer 61 and the second adhesive layer 63 may comprise a non-conductive material that transmits light. For example, the first adhesive layer 61 and the second adhesive layer 63 may comprise an optically transparent adhesive (OCA), which may include epoxy resin, polyimide, SU8, spin-coated glass (SOG), benzocyclobutene (BCB), and is not limited thereto.

[0062] According to the illustrated embodiment, the first insulating layer 81 and the second insulating layer 83 are disposed on at least a portion of the sides of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40. At least one of the first insulating layer 81 and the second insulating layer 83 may comprise a variety of organic or inorganic insulating materials, such as polyimide, SiO2, or SiN. x Al2O3, etc. For example, at least one of the first insulating layer 81 and the second insulating layer 83 may include a distributed Bragg reflector (DBR). As another embodiment, at least one of the first insulating layer 81 and the second insulating layer 83 may include a black organic polymer. In several embodiments, an electrically floating metal reflective layer is disposed on the first insulating layer 81 and the second insulating layer 83 to reflect light emitted from the light-emitting stacks 20, 30, and 40 toward the substrate 11 side. In several embodiments, at least one of the first insulating layer 81 and the second insulating layer 83 may have a single-layer structure or a multilayer structure formed by two or more insulating layers having different refractive indices.

[0063] According to one embodiment, each of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 can be driven independently. More specifically, a common voltage can be applied to one of the first and second conductive semiconductor layers of each light-emitting stack, and a separate light-emitting signal can be applied to the other of the first and second conductive semiconductor layers of each light-emitting stack. For example, according to an embodiment of this disclosure, the first conductive semiconductor layers 21, 31, and 41 of each light-emitting stack can be n-type, and the second conductive semiconductor layers 25, 35, and 45 can be p-type. In this case, the third light-emitting stack 40 can have the opposite stacking sequence to the first light-emitting stack 20 and the second light-emitting stack 30, whereby the p-type semiconductor layer 45 is disposed on top of the active layer 43, thereby simplifying the manufacturing process. Hereinafter, according to the illustrated embodiment, the first and second conductive semiconductor layers can be replaced with n-type and p-type, respectively. Furthermore, n-type and p-type can be interchanged.

[0064] Each of the first lower contact electrode 25p, the second lower contact electrode 35p, and the third lower contact electrode 45p, which are respectively connected to the p-type semiconductor layers 25, 35, and 45 of the light-emitting stack, can be electrically connected to the first connecting electrode 20ce, the second connecting electrode 30ce, and the third connecting electrode 40ce, thereby receiving the corresponding light-emitting signal. Furthermore, the n-type semiconductor layers 21, 31, and 41 of the light-emitting stack are commonly electrically connected to the fourth connecting electrode 50ce. Accordingly, the light-emitting element 100 can have a common n-type light-emitting stack structure in which the n-type semiconductor layers 21, 31, and 41 of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 are commonly connected, and can be driven independently of each other. Because it has a common n-type light-emitting stack structure, the voltage sources applied to the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 can be different from each other.

[0065] The light-emitting element 100 according to the illustrated embodiment has a common n-type structure, but this disclosure is not limited thereto. For example, in some exemplary embodiments, the first conductivity semiconductor layers 21, 31, and 41 of each light-emitting stack can be p-type, and the second conductivity semiconductor layers 25, 35, and 45 of each light-emitting stack can be n-type, thus forming a common p-type light-emitting stack structure. Furthermore, in some embodiments, the stacking sequence of the various light-emitting stacks is not limited to the stacking sequence shown in the drawings, but can be varied. Hereinafter, a light-emitting element 100 according to an embodiment of this disclosure will be described with reference to a common n-type light-emitting stack structure.

[0066] According to the illustrated embodiment, the light-emitting element 100 includes a first pad 20pd, a second pad 30pd, a third pad 40pd, and a fourth pad 50pd. The first pad 20pd is electrically connected to a first lower contact electrode 25p through a first contact hole 20CH defined by a first insulating layer 81. A first connecting electrode 20ce is electrically connected to the first pad 20pd through a first through hole 20ct defined by a second insulating layer 83. The second pad 30pd is electrically connected to a second lower contact electrode 35p through a second contact hole 30CH defined by the first insulating layer 81. The second connecting electrode 30ce is electrically connected to the second pad 30pd through a second through hole 30ct defined by the second insulating layer 83.

[0067] The third pad 40pd is electrically connected to the third lower contact electrode 45p through a third contact hole 40CH defined by the first insulating layer 81. The third connecting electrode 40ce is electrically connected to the third pad 40pd through a third through hole 40ct defined by the second insulating layer 83. The fourth pad 50pd is connected to the first conductive semiconductor layers 21, 31, and 41 of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 through a first sub-contact hole 50CHa, a second sub-contact hole 50CHb, and a third sub-contact hole 50CHc defined on the first conductive semiconductor layers 21, 31, and 41 of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40. In particular, the first sub-contact hole 50CHa can expose the first upper contact electrode 21n, and the fourth pad 50pd can be connected to the first upper contact electrode 21n through the first sub-contact hole 50CHa. In this way, the fourth pad 50pd can be electrically connected to the first conductive semiconductor layers 21, 31, and 41 through sub-contact holes 50CHa, 50CHb, and 50CHc, thereby simplifying the manufacturing process of the light-emitting element 100. The fourth connecting electrode 50ce can be electrically connected to the fourth pad 50pd through the fourth through hole 50ct defined by the second insulating layer 83.

[0068] In this embodiment, although it is shown and described that the connecting electrodes 20ce, 30ce, 40ce, and 50ce are in direct contact with the pads 20pd, 30pd, 40pd, and 50pd respectively, the connecting electrodes 20ce, 30ce, 40ce, and 50ce may not be directly connected to the pads 20pd, 30pd, 40pd, and 50pd, but instead have connectors sandwiched in them.

[0069] The first pad 20pd, the second pad 30pd, the third pad 40pd, and the fourth pad 50pd are spaced apart from and insulated from each other. According to one embodiment, the first pad 20pd, the second pad 30pd, the third pad 40pd, and the fourth pad 50pd may respectively cover at least a portion of the side surfaces of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40. This facilitates the dissipation of heat generated from the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40.

[0070] According to the illustrated embodiment, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may have a substantially elongated shape projecting upward from the substrate 11. The connecting electrodes 20ce, 30ce, 40ce, and 50ce may include, but are not limited to, metals such as Cu, Ni, Ti, Sb, Zn, Mo, Co, Sn, Ag, or alloys thereof. For example, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may include two or more metals or multiple different metal layers to reduce stress from the elongated shape of the connecting electrodes 20ce, 30ce, 40ce, and 50ce. In another embodiment, when the connecting electrodes 20ce, 30ce, 40ce, and 50ce comprise Cu, additional metal may be deposited or plated to suppress Cu oxidation. In some embodiments, when the connecting electrodes 20ce, 30ce, 40ce, and 50ce comprise Cu / Ni / Sn, Cu may prevent Sn from penetrating into the light-emitting stack structure. In some embodiments, the connecting electrodes 20ce, 30ce, 40ce, and 50ce may include a seed layer for forming a metal layer during the metal plating process, as will be described later.

[0071] As shown in the figure, each of the connecting electrodes 20ce, 30ce, 40ce, and 50ce can have a substantially flat upper surface, thus facilitating the electrical connection between the external lines or electrodes described later and the light-emitting stack structure. According to one embodiment of this disclosure, when the light-emitting element 100 includes a surface area of ​​less than about 10,000 μm, as is known in the art... 2 (Or in other embodiments, approximately less than 4000 μm) 2 Or approximately less than 2500μm 2When constructing a micro LED, the connecting electrodes 20ce, 30ce, 40ce, and 50ce can overlap with a portion of at least one of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40, as shown in the figure. More specifically, the connecting electrodes 20ce, 30ce, 40ce, and 50ce can overlap with at least one step formed on the side of the light-emitting stack structure. As described above, since the area of ​​the lower surface of the connecting electrodes is larger than the area of ​​the upper surface, a larger contact area can be formed between the connecting electrodes 20ce, 30ce, 40ce, and 50ce and the light-emitting stack structure. Accordingly, the connecting electrodes 20ce, 30ce, 40ce, and 50ce can be formed more stably on the light-emitting stack structure. For example, the lengths L1, L2, L3, and L4 of the outward-facing side of the connecting electrodes 20ce, 30ce, 40ce, and 50ce can be different from the lengths L1′, L2′, L3′, and L4′ of the side facing the center of the light-emitting element 100. More specifically, the length of the outer side of the connecting electrode can be greater than the length of the other side facing the center of the light-emitting element 100. For example, the difference between the lengths (L and L′) of the two opposing surfaces can be greater than the thickness (or height) of one of the light-emitting stacks 20, 30, and 40. In this way, the structure of the light-emitting element 100 can be enhanced to have a larger contact area between the connecting electrodes 20ce, 30ce, 40ce, and 50ce and the light-emitting stack structure. Furthermore, since the connecting electrodes 20ce, 30ce, 40ce, and 50ce can overlap with at least one step formed on the side of the light-emitting stack structure, heat generated from the light-emitting stack structure can be more effectively dissipated to the outside.

[0072] According to an exemplary embodiment, the difference between the length L1, L2, L3, or L4 of the outer side of the connecting electrode and the length L1′, L2′, L3′, and L4′ of the other side facing the center of the light-emitting element 100 can be approximately 3 μm. In this case, the light-emitting stack structure can be formed relatively thin; specifically, the first light-emitting stack 20 can have a thickness of approximately 1 μm, the second light-emitting stack 30 can have a thickness of approximately 0.7 μm, the third light-emitting stack 40 can have a thickness of approximately 0.7 μm, and the first adhesive layer and the second adhesive layer can each have a thickness of approximately 0.2 μm to 0.3 μm, but are not limited thereto. According to another embodiment, the difference between the length L1, L2, L3, or L4 of the outer side of the connecting electrode and the length L1′, L2′, L3′, and L4′ of the other side facing the center of the light-emitting element 100 can be approximately 10 μm to 16 μm. At this point, the light-emitting stack structure is formed to have a relatively thick and more stable structure. In particular, the first light-emitting stack 20 can have a thickness of about 4 μm to about 5 μm, the second light-emitting stack 30 can have a thickness of about 3 μm, the third light-emitting stack 40 can have a thickness of about 3 μm, and the thicknesses of the first adhesive layer and the second adhesive layer can each be about 3 μm, but are not limited thereto. According to yet another embodiment, the difference between the length L1, L2, L3 or L4 of the outer side of the connecting electrode and the length L1′, L2′, L3′ and L4′ of the other side facing the center of the light-emitting element 100 can be about 25% of the longest side length. However, the concept of this disclosure is not limited to a specific difference in length between the opposing surfaces of the connecting electrodes, and the difference in length between the opposing surfaces of the connecting electrodes can be varied.

[0073] In some exemplary embodiments, at least one of the connecting electrodes 20ce, 30ce, 40ce, and 50ce may overlap with the side of each of the light-emitting stacks 20, 30, and 40, thus effectively dissipating heat generated internally from the light-emitting stacks 20, 30, and 40 to the outside. Furthermore, when the connecting electrodes 20ce, 30ce, 40ce, and 50ce comprise a reflective material such as metal, they can reflect light emitted from at least one of the light-emitting stacks 20, 30, and 40, thereby improving luminous efficiency.

[0074] Typically, during manufacturing, an array of multiple light-emitting elements is formed on a substrate. The substrate is cut along dicing lines to individualize (separate) the individual light-emitting elements. These elements can then be transferred to another substrate or strip using various transfer techniques for additional processing, such as encapsulation. In this case, when the light-emitting element includes connecting electrodes such as metal bumps or pillars protruding outwards from the light-emitting structure, various problems may occur during subsequent processes (e.g., transfer steps) due to the structure of the light-emitting element exposing these connecting electrodes. Furthermore, when the light-emitting element includes components with a diameter of approximately less than 10,000 μm, depending on the application, various problems may arise. 2 Or approximately less than 4000μm 2 Or approximately less than 2500μm 2 When dealing with miniature LEDs with a large surface area, the processing of the light-emitting element becomes more difficult due to its small size.

[0075] For example, when the connecting electrode has a substantially long shape, such as a rod, it becomes difficult to transfer the light-emitting element using existing vacuum methods because the light-emitting element cannot have sufficient adsorption area due to the protruding structure of the connecting electrode. Furthermore, the exposed connecting electrode is directly affected by stress during subsequent processes, such as when the connecting electrode comes into contact with the manufacturing apparatus, which may damage the structure of the light-emitting element. As another example, when transferring the light-emitting element by attaching adhesive tape to the upper surface of the light-emitting element (e.g., the surface opposite to the substrate), the contact area between the light-emitting element and the adhesive tape may be limited to the upper end surface of the connecting electrode. In this case, unlike when the adhesive tape is attached to the lower surface of the light-emitting element (e.g., the substrate), the adhesion of the light-emitting element to the adhesive tape may be weakened, and the light-emitting element may undesirably detach from the adhesive tape during transfer. As yet another example, when transferring the light-emitting element using existing pick and place methods, the ejector pin directly contacts a portion of the light-emitting element arranged between the connecting pins, which may damage the upper structure of the light-emitting structure. In particular, the ejector pin may strike the center of the light-emitting element, which may cause physical damage to the upper light-emitting stack of the light-emitting element.

[0076] According to one embodiment of this disclosure, the protective layer 90 may be formed on the light-emitting stack structure. More specifically, as shown in the attached... Figure 1aAs shown, a protective layer 90 is formed between the connecting electrodes 20ce, 30ce, 40ce, and 50ce and at least covers the sides of the light-emitting stack structure. According to the illustrated embodiment, the protective layer 90 may expose the sides of the substrate 11, the first insulating layer 81, the second insulating layer 83, and the third light-emitting stack 40. The protective layer 90 is formed substantially parallel to the upper surfaces of the connecting electrodes 20ce, 30ce, 40ce, and 50ce and may include epoxy molding compound (EMC), which can be formed in various colors such as black, white, or transparent. However, this disclosure is not limited thereto. For example, in some embodiments, the protective layer 90 may include polyimide (PID), where, when the PID is applied to the light-emitting stack structure, it is provided as a dry film rather than a liquid form to increase flatness. In some embodiments, the protective layer 90 may include a photosensitive material. In this way, the protective layer 90 not only protects the light-emitting structure from external impacts that may be applied during subsequent processes but also provides sufficient contact area to the light-emitting element 100 to facilitate processing during subsequent transfer steps. In addition, the protective layer 90 prevents light leakage from the side of the light-emitting element 100, thereby preventing or at least suppressing interference from light emitted from adjacent light-emitting elements 100.

[0077] Figure 2 This is a schematic cross-sectional view of a light-emitting stacked structure according to an embodiment of the present disclosure. The light-emitting stacked structure according to the illustrated embodiment is substantially the same as the light-emitting stacked structure including the aforementioned light-emitting element 100, therefore, to avoid repetition, the description of the configuration forming the substantially identical light-emitting stacked structure will be omitted.

[0078] Reference Figure 2 According to an embodiment of this disclosure, the first lower contact electrode 25p, the second lower contact electrode 35p, and the third lower contact electrode 45p can be respectively connected to the light-emitting signal line S. R S G S B The first conductive semiconductor layer 21 of the first light-emitting stack 20, the first conductive semiconductor layer 31 of the second light-emitting stack 30, and the first conductive semiconductor layer 41 of the third light-emitting stack 40 can be connected to a common line S. C Public Line S C It can be connected to the first conductive semiconductor layer 21 of the first light-emitting stack 20 through the first upper contact electrode 21n.

[0079] The first to third lower contact electrodes 25p, 35p, and 45p can be formed using an ITO-based transparent conductive oxide layer such as ITO or ITZO. Furthermore, to reduce the intensity of blue light emission, the second lower contact electrode 35p or the third lower contact electrode 45p can be thicker than the first lower contact electrode 25p. In particular, the second lower contact electrode 35p can be thicker than both the first lower contact electrode 25p and the third lower contact electrode 45p.

[0080] Furthermore, one embodiment of this disclosure employs a common n-structure, allowing different voltages to be applied to the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40. For example, compared to the second and third light-emitting stacks 30 and 40, which emit blue and green light, respectively, the first light-emitting stack 20, which emits red light, can be applied a relatively lower voltage. Therefore, voltage sources suitable for each light-emitting stack can be used independently, thereby reducing power loss. In the exemplary embodiment shown, the light-emitting signal line S is used... R S G S B Along with the common line Sc, the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 can be controlled independently to selectively emit light.

[0081] Figure 2 A light-emitting stack structure with a common n-structure is shown, but this disclosure is not limited thereto. For example, in some exemplary embodiments, the common line Sc is electrically connected to the lower contact electrode 25p of the first light-emitting stack 20, the lower contact electrode 35p of the second light-emitting stack 30, and the lower contact electrode 45p of the third light-emitting stack 40, and the light-emitting signal line S... R S G S B They can be electrically connected to the first conductive semiconductor layer 21 of the first light-emitting stack 20, the first conductive semiconductor layer 31 of the second light-emitting stack 30, and the first conductive semiconductor layer 41 of the third light-emitting stack 40, respectively.

[0082] According to an embodiment of the present disclosure, a light-emitting stack structure displays a variety of colors of light based on the operating states of each light-emitting stack 20, 30, 40. In contrast, conventional light-emitting elements display a variety of colors of light through a combination of multiple light-emitting units that emit monochromatic light. More specifically, conventional light-emitting elements typically include light-emitting units spaced apart on a two-dimensional plane and emitting different colors of light (e.g., red, green, and blue) to achieve a full-color display device. In this way, a large area is occupied based on conventional light-emitting units. However, the light-emitting stack structure according to an embodiment of the present disclosure can stack multiple light-emitting stacks 20, 30, 40 to emit light of different colors from each other, thus providing a high level of integration and achieving full color with a smaller area compared to conventional light-emitting devices.

[0083] Furthermore, when the light-emitting element 100 is mounted onto another substrate for manufacturing a display device, the number of components to be mounted may be significantly reduced compared to existing light-emitting elements. In this way, especially when hundreds of thousands or millions of pixels are formed in a display device, the manufacturing of display devices using the light-emitting element 100 can be substantially simplified.

[0084] According to exemplary embodiments, the light-emitting stack structure may further include various additional components to improve the purity and efficiency of the light emitted therefrom. For example, in some exemplary embodiments, wavelength-passing filters may be arranged between the light-emitting stacks. In several embodiments, to achieve a balance in light brightness between the light-emitting stacks, unevenness may be formed on the light-emitting surface of at least one of the light-emitting stacks. For example, to increase the intensity of green light so that the RGB light intensity mixing ratio is close to 3:6:1, unevenness may be formed on the surface of the substrate 11.

[0085] Hereinafter, a method for forming a light-emitting element 100 according to an embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0086] Figure 3a , Figure 4a , Figure 5a , Figure 6a , Figure 7a and Figure 8a This indicates manufacturing according to an exemplary embodiment. Figure 1a A plan view of the process of the light-emitting element. Figure 3b , Figure 4b , Figure 5b , Figure 6b , Figure 7b and Figure 8b According to the exemplary embodiments, along Figure 3a , Figure 4a , Figure 5a , Figure 6a , Figure 7a and Figure 8a The cross-sectional view of line AA′ corresponding to the plan view shown. Figure 3c , Figure 4c , Figure 5c , Figure 6c , Figure 7c and Figure 8c According to the exemplary embodiments, along Figure 3a , Figure 4a , Figure 5a , Figure 6a , Figure 7a and Figure 8a The cross-sectional view of the BB′ line corresponding to the plan view shown. Figure 9 , Figure 10 , Figure 11 , Figure 12 and Figure 13 This is an illustrative representation according to an exemplary embodiment. Figure 1a A cross-sectional view of the manufacturing process of the light-emitting element.

[0087] Re-reference Figure 2The first conductive semiconductor layer 41, the third active layer 43, and the second conductive semiconductor layer 45 of the third light-emitting stack 40 can be sequentially grown on the substrate, for example, by metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). The third lower contact electrode 45p can be formed on the third p-type semiconductor layer 45, for example, by physical vapor deposition or chemical vapor deposition, and can include transparent conductive oxides (TCOs) such as SnO, InO2, ZnO, ITO, and ITZO. When the third light-emitting stack 40 emits green light according to an embodiment of the present disclosure, the substrate 11 can include Al2O3 (e.g., a sapphire substrate), and the third lower contact electrode 45p can include transparent conductive oxides (TCOs) such as tin oxide. The first light-emitting stack 20 and the second light-emitting stack 30 can be similarly formed by sequentially growing the first conductive semiconductor layer, the active layer, and the second conductive semiconductor layer on a temporary substrate, respectively. The lower contact electrodes, including transparent conductive oxide (TCO), can be formed on the second conductive semiconductor layer, for example, by physical vapor deposition or chemical vapor deposition. Furthermore, the first light-emitting stack 20 and the second light-emitting stack 30 are bonded together by placing the first adhesive layer 61 between them, and at least one of the temporary substrates of the first light-emitting stack 20 and the second light-emitting stack 30 can be removed by laser lift-off, chemical process, or mechanical process. Moreover, the first light-emitting stack 20 and the second light-emitting stack 30 are bonded together with the third light-emitting stack 40 by placing the second adhesive layer 63 in the middle, and the remaining temporary substrates of the first light-emitting stack 20 and the second light-emitting stack 30 can be removed by laser lift-off, chemical process, or mechanical process.

[0088] Reference Figure 3a , Figure 3b and Figure 3c Various portions of each of the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 can be patterned by an etching process to expose a first conductive semiconductor layer 21, a first lower contact electrode 25p, a first conductive semiconductor layer 31, a second lower contact electrode 35p, a third lower contact electrode 45p, and a portion of the first conductive semiconductor layer 41. According to the illustrated embodiment, the first light-emitting stack 20 has the smallest area among the light-emitting stacks 20, 30, and 40. On the other hand, the third light-emitting stack 40 can have the largest area among the light-emitting stacks 20, 30, and 40, thus enabling a relative increase in the luminous intensity of the third light-emitting stack 40. However, the concept of this disclosure is not particularly limited to the relative dimensions of the light-emitting stacks 20, 30, and 40.

[0089] Reference Figure 4a , Figure 4b and Figure 4c A portion of the upper surface of the first conductive semiconductor layer 21 of the first light-emitting stack 20 can be patterned by wet etching to form the first upper contact electrode 21n. As described above, the first upper contact electrode 21n is formed to a thickness of about 100 nm in the recessed region of the first conductive semiconductor layer 21, thereby improving the ohmic contact between them, for example.

[0090] Reference Figure 5a , Figure 5b as well as Figure 5c The first insulating layer 81 can be formed to cover the light-emitting stack 20, 30, and 40, and a portion of the first insulating layer 81 can be removed to form the first contact hole 20CH, the second contact hole 30CH, the third contact hole 40CH, and the fourth contact hole 50CH. The first contact hole 20CH is defined on the first lower contact electrode 25p, exposing a portion of the first lower contact electrode 25p. The second contact hole 30CH can be defined on the second lower contact electrode 35p, exposing a portion of the second lower contact electrode 35p. The third contact hole 40CH can be defined on the third lower contact electrode 45p, exposing a portion of the third lower contact electrode 45p.

[0091] The fourth contact hole 50CH provides a pathway for allowing electrical connection to the first conductive semiconductor layer 21 of the first light-emitting stack 20, the first conductive semiconductor layer 31 of the second light-emitting stack 30, and the first conductive semiconductor layer 41 of the third light-emitting stack 40. The fourth contact hole 50CH may include a first sub-contact hole 50CHa, a second sub-contact hole 50CHb, and a third sub-contact hole 50CHc. The first sub-contact hole 50CHa may be defined on the first conductive semiconductor layer 21, exposing a portion of the first upper contact electrode 21n; the second sub-contact hole 50CHb may be defined on the first conductive semiconductor layer 31, exposing a portion of the first conductive semiconductor layer 31; and the third sub-contact hole 50CHc may be defined on the first conductive semiconductor layer 41, exposing a portion of the first conductive semiconductor layer 41.

[0092] Reference Figure 6a , Figure 6b and Figure 6c The first pad 20pd, the second pad 30pd, the third pad 40pd, and the fourth pad 50pd are formed on a first insulating layer 81 having a first contact hole 20CH, a second contact hole 30CH, a third contact hole 40CH, and a fourth contact hole 50CH. The first pad 20pd, the second pad 30pd, the third pad 40pd, and the fourth pad 50pd can be formed, for example, by substantially forming a conductive layer on the front surface of the substrate and patterning the conductive layer using a photolithography process.

[0093] The first pad 20pd is formed to overlap with the area where the first contact hole 20CH is formed, thereby connecting to the first lower contact electrode 25p through the first contact hole 20CH. The second pad 30pd is formed to overlap with the area where the second contact hole 30CH is formed, thereby connecting to the second lower contact electrode 35p through the second contact hole 30CH. The third pad 40pd can be formed to overlap with the area where the third contact hole 40CH is formed, thereby connecting to the third lower contact electrode 45p through the third contact hole 40CH. The fourth pad 50pd is formed to overlap with the area where the fourth contact hole 50CH is formed, especially with the areas where the first sub-contact hole 50CHa, the second sub-contact hole 50CHb, and the third sub-contact hole 50CHc are formed, thereby being electrically connected to the first conductive semiconductor layer 21 of the first light-emitting stack 20, the first conductive semiconductor layer 31 of the second light-emitting stack 30, and the first conductive semiconductor layer 41 of the third light-emitting stack 40.

[0094] Reference Figure 7a , Figure 7b and Figure 7c A second insulating layer 83 may be formed on the first insulating layer 81. The second insulating layer 83 may include silicon oxide and / or silicon nitride. However, this disclosure is not limited thereto; in several embodiments, the first insulating layer 81 and the second insulating layer 83 may include inorganic materials. Subsequently, the second insulating layer 83 may be patterned to form a first through-hole 20ct, a second through-hole 30ct, a third through-hole 40ct, and a fourth through-hole 50ct exposing the first pad 20pd, the second pad 30pd, the third pad 40pd, and the fourth pad 50pd.

[0095] A first through-hole 20ct formed on the first pad 20pd exposes a portion of the first pad 20pd. A second through-hole 30ct formed on the second pad 30pd exposes a portion of the second pad 30pd. A third through-hole 40ct formed on the third pad 40pd exposes a portion of the third pad 40pd. A fourth through-hole 50ct formed on the fourth pad 50pd exposes a portion of the fourth pad 50pd. In the illustrated exemplary embodiment, the first through-hole 20ct, the second through-hole 30ct, the third through-hole 40ct, and the fourth through-hole 50ct can be defined respectively within the regions where the first pad 20pd, the second pad 30pd, the third pad 40pd, and the fourth pad 50pd are formed.

[0096] Reference Figure 8a , Figure 8b and Figure 8cA first connecting electrode 20ce, a second connecting electrode 30ce, a third connecting electrode 40ce, and a fourth connecting electrode 50ce are formed on a second insulating layer 83 having a first through hole 20ct, a second through hole 30ct, a third through hole 40ct, and a fourth through hole 50ct. The first connecting electrode 20ce is formed to overlap with the area having the first through hole 20ct, thereby allowing it to be connected to the first pad 20pd through the first through hole 20ct. The second connecting electrode 30ce is formed to overlap with the area having the second through hole 30ct, thereby allowing it to be connected to the second pad 30pd through the second through hole 30ct. The third connecting electrode 40ce is formed to overlap with the area having the third through hole 40ct, thereby allowing it to be connected to the third pad 40pd through the third through hole 40ct. The fourth connecting electrode 50ce is formed to overlap with the area having the fourth through hole 50ct, thereby allowing it to be connected to the fourth pad 50pd through the fourth through hole 50ct.

[0097] The first connecting electrode 20ce, the second connecting electrode 30ce, the third connecting electrode 40ce, and the fourth connecting electrode 50ce are spaced apart from each other and can be formed on the light-emitting stack structure. The first connecting electrode 20ce, the second connecting electrode 30ce, the third connecting electrode 40ce, and the fourth connecting electrode 50ce are electrically connected to the first pad 20pd, the second pad 30pd, the third pad 40pd, and the fourth pad 50pd, respectively, so that external signals can be transmitted to each of the light-emitting stack components 20, 30, and 40.

[0098] The methods for forming the first connecting electrode 20ce, the second connecting electrode 30ce, the third connecting electrode 40ce, and the fourth connecting electrode 50ce are not particularly limited. For example, according to one embodiment of this disclosure, a seed layer is deposited as a conductive surface on a light-emitting stack structure, and a photoresist pattern can be formed in such a way that the seed layer is exposed at the locations where the connecting electrodes will be formed. According to one embodiment, the seed layer can be deposited to approximately The thickness is [not limited to this]. Subsequently, the seed layer can be plated with metals such as Cu, Ni, Ti, Sb, Zn, Mo, Co, Sn, Ag, or alloys thereof, and the photoresist pattern remaining between the connecting electrodes, as well as the seed layer, can be removed. In some exemplary embodiments, to prevent or at least suppress oxidation of the gold-plated metal, additional metal is deposited or plated onto the plating metal (e.g., the connecting electrode) using methods such as electroless nickel immersion gold (ENIG). In several embodiments, the seed layer may be retained at each connecting electrode.

[0099] According to the exemplary embodiments shown, the respective connecting electrodes 20ce, 30ce, 40ce, and 50ce may have substantially elongated shapes to be located away from the substrate 11. In another exemplary embodiment, to reduce stress from the elongated shapes of the connecting electrodes 20ce, 30ce, 40ce, and 50ce, the connecting electrodes 20ce, 30ce, and 40ce may comprise two or more metals or multiple different metal layers. However, this disclosure is not limited to the specific shapes of the connecting electrodes 20ce, 30ce, 40ce, and 50ce; in several embodiments, the connecting electrodes may have various shapes.

[0100] As shown in the figure, to facilitate electrical connections between the light-emitting stack structure and external lines or electrodes, each connecting electrode 20ce, 30ce, 40ce, and 50ce can have a substantially flat upper surface. The connecting electrodes 20ce, 30ce, 40ce, and 50ce can overlap with at least one step formed on the side of the light-emitting stack structure. In this way, the lower surface of the connecting electrodes can have a greater width than the upper surface, and a larger contact area is provided between the connecting electrodes 20ce, 30ce, 40ce, and 50ce and the light-emitting stack structure, thereby giving the light-emitting element 100 a more stable structure capable of withstanding various subsequent processes along with the protective layer 90. In this case, the length L of the outward-facing side of the connecting electrodes 20ce, 30ce, 40ce, and 50ce can differ from the length L' of the other surface facing the center of the light-emitting element 100. For example, the length difference between the two opposing surfaces of the connecting electrodes can be 3 to 16 μm, but is not limited to this.

[0101] Additionally, a protective layer 90 is disposed between the connecting electrodes 20ce, 30ce, 40ce, and 50ce. The protective layer 90 can be formed by a polishing process to be substantially parallel to the upper surfaces of the connecting electrodes 20ce, 30ce, 40ce, and 50ce. According to one embodiment, the protective layer 90 may include a black epoxy molding compound (EMC), but is not limited thereto. For example, in several embodiments, the protective layer 90 may include a photosensitive polyimide film (PID). In this way, the protective layer 90 not only protects the light-emitting structure from external impacts that may be applied during subsequent processes, but also provides sufficient contact area for the light-emitting element 100 to facilitate processing during subsequent transfer steps. Furthermore, the protective layer 90 prevents light leakage to the sides of the light-emitting element 100, thereby preventing, or at least suppressing, interference from light emitted from adjacent light-emitting elements 100.

[0102] Figure 9This example illustrates a plurality of light-emitting elements 100 arranged on a substrate 11, which undergo a single-process separation to separate each light-emitting element 100. (Refer to...) Figure 10 According to one embodiment of this disclosure, laser beams are irradiated between the light-emitting stacked structures, thereby forming separation paths that locally separate the light-emitting stacked structures. (See also...) Figure 11 A separation path can be added within the substrate 11 using a stealth laser. The stealth laser can travel from... Figure 10 The laser beam is irradiated from the opposite direction to the surface being irradiated.

[0103] Reference Figure 12 To individual light-emitting elements 100 while the substrate 11 is attached to the first bonding layer 95, various methods known in the art are used to cut or separate it. For example, the substrate 11 is cut by dicing lines formed thereon, or separated by applying mechanical force, for example, along a separation path formed during the laser irradiation process. The first bonding layer 95 may be an adhesive tape, but this disclosure is not limited thereto as long as the first bonding layer 95 can stably adhere to and separate the light-emitting elements 100 in subsequent processes. Although the first bonding layer 95 is described above as being attached to the substrate after the laser irradiation step, in some exemplary embodiments, the first bonding layer 95 may be attached to the substrate 11 before the laser irradiation step.

[0104] Reference Figure 13 After the substrate 11 is separated into individual light-emitting elements 100, the first bonding layer 95 can be expanded, thereby allowing the light-emitting elements 100 to be spatially separated from each other.

[0105] Figure 14 , Figure 15 , Figure 16a and Figure 16b This is a schematic cross-sectional view illustrating a manufacturing process of a light-emitting package according to an embodiment of the present disclosure. The light-emitting element 100 according to an embodiment of the present disclosure can be transferred and packaged using various methods known in the art. Hereinafter, an example will be described of transferring the light-emitting element 100 by attaching a second adhesive layer 13 to a substrate 11 using a carrier substrate 11c; however, the present disclosure is not limited to any particular transfer method.

[0106] Reference Figure 14According to one embodiment of this disclosure, the unified light-emitting element 100 can be arranged such that a second adhesive layer 13 is placed in the middle and transferred onto a carrier substrate 11c. In this case, when the light-emitting element includes connecting electrodes protruding outward from the light-emitting stack structure, various problems may occur in subsequent processes (especially the transfer process) due to the non-uniform structure, as described above. Furthermore, when the light-emitting element includes electrodes with a diameter of approximately less than 10000 μm, depending on its application,... 2 Or approximately less than 4000μm 2 Or approximately less than 2500μm 2 When dealing with miniature LEDs with a large surface area, the handling of the light-emitting element becomes more difficult due to the small form factor. However, providing a light-emitting element 100 according to an exemplary embodiment, with a protective layer 90 arranged between the connecting electrodes 20ce, 30ce, 40ce, and 50ce, not only makes the handling of the light-emitting element 100 easier during subsequent processes such as transfer printing and encapsulation, but also protects the light-emitting structure from external impacts and prevents light interference between adjacent light-emitting elements 100.

[0107] The carrier substrate 11c is not particularly limited as long as it can stably mount the light-emitting element 100 to the second adhesive layer 13. The second adhesive layer 13 may be tape, but this disclosure is not limited thereto as long as it can stably attach the light-emitting element 100 to the carrier substrate 11c and allow for separation of the light-emitting element 100 during subsequent processes. In several embodiments, Figure 13 The light-emitting element 100 can be directly transferred to the circuit board 11p instead of being transferred to a separate carrier substrate 11c.

[0108] The light-emitting element 100 can be mounted on the circuit board 11p. According to one embodiment, the circuit board 11p may include an upper circuit electrode 11pa, a lower circuit electrode 11pc, and an intermediate circuit electrode 11pb that are electrically connected to each other. The upper circuit electrode 11pa may correspond to the first connecting electrode 20ce, the second connecting electrode 30ce, the third connecting electrode 40ce, and the fourth connecting electrode 50ce, respectively. In an exemplary embodiment, the upper circuit electrode 11pa is surface-treated by ENIG and locally melted at high temperature, thereby facilitating the electrical connection to the connecting electrodes of the light-emitting element 100.

[0109] According to an exemplary embodiment, the spacing P of the upper circuit electrodes of the circuit board 11p to be mounted to the final target device (e.g., a display device) can be preferably considered (refer to...). Figure 16b The light-emitting elements 100 are spaced apart from each other on the carrier substrate at a desired spacing.

[0110] According to one embodiment of this disclosure, the first connecting electrode 20ce, the second connecting electrode 30ce, the third connecting electrode 40ce, and the fourth connecting electrode 50ce of each light-emitting element 100 can be bonded to the upper circuit electrode 11pa of the circuit substrate 11p by, for example, anisotropic conductive film (ACF). When the light-emitting element 100 is bonded to the circuit substrate by ACF bonding, which can be performed at a lower temperature compared to other bonding methods, the light-emitting element 100 can be prevented from being exposed to high temperatures during bonding. However, this disclosure is not limited to a particular bonding method. For example, in some exemplary embodiments, the light-emitting element 100 can be bonded to the circuit substrate 11p using anisotropic conductive paste (ACP), solder, ball grid array (BGA), or micro-bumps including at least one of Cu and Sn. At this time, the upper surfaces of the connecting electrodes 20ce, 30ce, 40ce, and 50ce and the protective layer 90 are substantially parallel to each other through polishing processes, etc., which increases the adhesion of the light-emitting element 100 to the anisotropic conductive adhesive film, thereby forming a more stable structure when bonded to the circuit board 11p.

[0111] Reference Figure 15 An injection-molded layer 91 is formed between the light-emitting elements 100. According to one embodiment, the injection-molded layer 91 can reflect or absorb light emitted from the light-emitting elements 100, thereby blocking light. The injection-molded layer 91 is particularly parallel to the upper surface (i.e., the light-emitting surface) of the light-emitting elements 100, thereby reducing the pointing angle of light emitted from the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40. For example, the injection-molded layer 91 can cover the side surface of the substrate 11 and can be parallel to the upper surface of the substrate 11. Therefore, the injection-molded layer 91 can prevent light from emitting from the side surface of the substrate 11, thereby reducing the pointing angle. In particular, since the light-emitting surface is limited to the upper surface of the substrate 11, the pointing angles of light from the first light-emitting stack 20, the second light-emitting stack 30, and the third light-emitting stack 40 are substantially the same. In another embodiment, the injection-molded layer 91 can cover the upper surface of the light-emitting elements 100. The injection-molded layer 91 is arranged on the upper surface of the light-emitting element 100 with a relatively thin thickness to transmit light emitted from the light-emitting element 100 and to prevent light incident from the outside from being reflected from the light-emitting element 100. The injection-molded layer 91, together with the protective layer 90 formed on the light-emitting element 100, strengthens its structure, thereby providing additional protection for the light-emitting package.

[0112] In exemplary embodiments, injection molding layer 91 may comprise an organic or inorganic polymer. In several embodiments, injection molding layer 91 may additionally comprise a filler such as silica or alumina. In exemplary embodiments, injection molding layer 91 may comprise the same material as protective layer 90. Injection molding layer 91 may be formed by a variety of methods known in the art, such as lamination, metal plating, and / or printing methods. For example, injection molding layer 91 may be formed by a vacuum lamination process in which an organic polymer sheet is disposed on light-emitting element 100 and subjected to high temperature and high pressure in a vacuum, providing a substantially flat upper surface of the light-emitting package to improve light uniformity. Injection molding layer 91 may be partially removed by a grinding process or a full etching process to expose the upper surface of light-emitting element 100.

[0113] In several embodiments, the substrate 11 may be removed from the light-emitting element 100 before the injection molding layer 91 is formed. In this case, the injection molding layer 91 may cover the side surface of the first conductive semiconductor layer 41 and expose the upper surface of the first conductive semiconductor layer 41.

[0114] Reference Figure 16a as well as Figure 16b The light-emitting element 100 arranged on the circuit board 11p can be cut into the desired configuration and formed into a light-emitting package 110. Figure 16b This includes four light-emitting elements 100 (2×2) arranged on the circuit board 11p. However, this disclosure is not limited to a specific number of light-emitting elements formed on the light-emitting package 110. For example, in some embodiments, the light-emitting package 110 may include more than one light-emitting element 100 formed on the circuit board 11p. Furthermore, this disclosure is not limited to a specific arrangement of more than one light-emitting element 100 within the light-emitting package 110; for example, more than one light-emitting element 100 within the light-emitting package 110 may be arranged in an n×m arrangement. Here, n and m are positive integers. According to one embodiment, the circuit board 11p may include scan lines and data lines for independently driving each light-emitting element 100 contained in the light-emitting package 110.

[0115] Figure 17 This is a schematic cross-sectional view used to illustrate a display device according to an embodiment of the present disclosure.

[0116] Reference Figure 17The display device may include a display substrate 11b and a light-emitting package 110. The light-emitting package 110 may be mounted onto the display substrate 11b of a final device (e.g., a display device). The display substrate 11b may include target electrodes 11s corresponding to the lower circuit electrodes 11pc of the light-emitting package 110. The display device according to this disclosure may include a plurality of pixels, and each light-emitting element 100 may be arranged to correspond to each pixel. More specifically, each light-emitting stack of the light-emitting element 100 according to this disclosure may correspond to each sub-pixel of a pixel. The light-emitting element 100 includes vertically stacked light-emitting stacks 20, 30, and 40, so the number of elements to be transferred to each sub-pixel can be substantially reduced compared to the number of existing light-emitting elements. Furthermore, since the lengths of the opposing surfaces of the connecting electrodes are different from each other, the connecting electrodes can be stably formed in the light-emitting stack structure, thereby strengthening the internal structure. In addition, since the light-emitting element 100 according to several embodiments includes a protective layer 90 between the connecting electrodes, the light-emitting element 100 can be protected from external impacts.

[0117] In this embodiment, although the case of the light-emitting package 110 being mounted on the display substrate 11b is described, the process of manufacturing the light-emitting package 110 can be omitted, and the injection molding layer 91 can be formed by directly mounting the light-emitting element 100 onto the display substrate 11b.

[0118] Figure 18 This is a schematic cross-sectional view used to illustrate a light-emitting package according to yet another embodiment of the present disclosure.

[0119] Reference Figure 18 The light-emitting package according to this embodiment is generally similar to the previously referenced one. Figure 15 , Figure 16a and Figure 16b The light-emitting package described differs in that the light-emitting element 200 does not include the substrate 11. The substrate 11 is removed from the light-emitting element 100, thereby exposing the first conductive semiconductor layer 41. The light-emitting element 200 emits light through the upper surface of the first conductive semiconductor layer 41; therefore, the upper surface of the first conductive semiconductor layer 41 becomes the light-emitting surface. An injection molding layer 91 covers the side surfaces of the first conductive semiconductor layer 41 and exposes its upper surface.

[0120] Figure 19 This is a schematic cross-sectional view of a light-emitting stacked structure according to yet another embodiment of the present disclosure.

[0121] Reference Figure 19 According to this embodiment, the light-emitting stacked structure and the reference Figure 2Compared to the described light-emitting stacked structure, the difference lies in that the second lower contact electrode 135p includes a lower layer 135a and an upper layer 135b. Both the lower layer 135a and the upper layer 135b can be formed using an ITO-based transparent conductive oxide layer. However, the lower layer 135a undergoes heat treatment at a temperature above 300°C to make an ohmic contact with the second conductive semiconductor layer 35, while the upper layer 135b can be formed without heat treatment. In one embodiment, the lower layer 135a can be heat-treated at a temperature below 400°C to reduce the transmittance of blue light. Referring to Table 1, it can be seen that the greater the thickness of the ITO, the lower its transmittance for short wavelengths, and the lower the transmittance without heat treatment when the thickness is relatively thicker. Therefore, if the second lower contact electrode 135p is formed thicker without heat treatment, the transmittance of blue light can be significantly reduced. However, since the second lower contact electrode 135p needs to make an ohmic contact with the second conductive semiconductor layer 35, heat treatment cannot be ruled out. Therefore, this disclosure forms the lower layer 135a, which makes an ohmic contact with the second conductive semiconductor layer 35, and the upper layer 135b, which increases the thickness, separately, thus providing a second lower contact electrode 135p that can further reduce overall transmittance while making an ohmic contact with the second conductive semiconductor layer 35. In particular, the lower layer 135a is formed for ohmic contact, and the upper layer 135b is formed to increase the overall thickness; the upper layer 135b can be thicker than the lower layer 135a.

[0122] In this embodiment, the second lower contact electrode 135p is described as including a heat-treated lower layer 135a and an upper layer 135b formed without heat treatment. However, the third lower contact electrode 45p may replace the second lower contact electrode 135p or be formed together with the second lower contact electrode 135p to include a heat-treated lower layer for ohmic contact and an upper layer formed without heat treatment.

[0123] While exemplary embodiments and implementations have been described in this specification, other embodiments and modifications will become apparent from this description. Therefore, this disclosure is not limited to these embodiments, but includes a wider scope and various modifications and equivalent configurations that will be apparent to those skilled in the art.

Claims

1. A light-emitting element, characterized in that, include: The first light-emitting stack, the second light-emitting stack, and the third light-emitting stack, each of the first light-emitting stack, the second light-emitting stack, and the third light-emitting stack includes a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer. The first lower contact electrode is in ohmic contact with the first light-emitting stack; The second lower contact electrode is in ohmic contact with the second light-emitting stack; The third lower contact electrode is in ohmic contact with the third light-emitting stack; The first connecting electrode is electrically connected to the first light-emitting stack; The second connecting electrode is electrically connected to the second light-emitting stack; as well as The third connecting electrode is electrically connected to the third light-emitting stack. The second light-emitting stack is disposed between the first light-emitting stack and the third light-emitting stack. The first lower contact electrode is disposed between the first light-emitting stack and the second light-emitting stack. The second lower contact electrode is disposed between the second light-emitting stack and the third light-emitting stack. The first lower contact electrode, the second lower contact electrode, and the third lower contact electrode each include a transparent conductive oxide layer. The thickness of the second lower contact electrode or the third lower contact electrode is greater than the thickness of the first lower contact electrode. The first light-emitting stack, the second light-emitting stack, and the third light-emitting stack are electrically connected to circuit electrodes arranged on the upper surface of the circuit board through the first connecting electrode, the second connecting electrode, and the third connecting electrode, respectively. Each of the first connecting electrode, the second connecting electrode, and the third connecting electrode includes a first surface facing the upper surface of the circuit board and a second surface facing the first surface, wherein the area of ​​the second surface is larger than the area of ​​the first surface.

2. The light-emitting element according to claim 1, characterized in that, The first light-emitting stack is configured to emit red light, the second light-emitting stack is configured to emit blue light, and the third light-emitting stack is configured to emit green light.

3. The light-emitting element according to claim 1, characterized in that, The thickness of the second lower contact electrode is greater than the thickness of the third lower contact electrode.

4. The light-emitting element according to claim 1, characterized in that, The second lower contact electrode or the third lower contact electrode includes a lower layer that has been heat-treated for ohmic contact with the corresponding second conductivity semiconductor layer and an upper layer that has not been heat-treated and disposed on the heat-treated lower layer.

5. The light-emitting element according to claim 4, characterized in that, The upper layer that has not undergone heat treatment is thicker than the lower layer that has undergone heat treatment.

6. The light-emitting element according to claim 1, characterized in that, The first lower contact electrode to the third lower contact electrode comprise an ITO-based transparent conductive oxide layer.

7. The light-emitting element according to claim 1, characterized in that, The first lower contact electrode makes ohmic contact with the second conductive semiconductor layer of the first light-emitting stack.

8. The light-emitting element according to claim 1, characterized in that, Also includes: The fourth connecting electrode is electrically connected to the first light-emitting stack, the second light-emitting stack, and the third light-emitting stack.

9. The light-emitting element according to claim 8, characterized in that, The fourth connecting electrode is electrically connected to the first conductive semiconductor layer of the first light-emitting stack to the third light-emitting stack. The first conductive semiconductor layer includes an n-type semiconductor layer.

10. The light-emitting element according to claim 8, characterized in that, Also includes: A protective layer surrounds at least a portion of the first connecting electrode to the fourth connecting electrode.

11. The light-emitting element according to claim 10, characterized in that, The protective layer includes epoxy molding compound or polyimide film. The upper surface of the protective layer is parallel to the upper surfaces of the first connecting electrode to the fourth connecting electrode.

12. The light-emitting element according to claim 1, characterized in that, Also includes: The substrate is arranged adjacent to the third light-emitting stack.

13. The light-emitting element according to claim 1, characterized in that, Also includes: A first adhesive layer bonds the first light-emitting stack and the second light-emitting stack. as well as The second adhesive layer bonds the second light-emitting stack and the third light-emitting stack.

14. A display device, characterized in that, include: A circuit board, including an upper surface and circuit electrodes disposed on the upper surface; A first light-emitting stack, a second light-emitting stack, and a third light-emitting stack are disposed on the upper surface of the circuit substrate and electrically connected to the circuit electrodes, and each of the first light-emitting stack, the second light-emitting stack, and the third light-emitting stack includes a first conductive semiconductor layer, a second conductive semiconductor layer, and an active layer disposed between the first conductive semiconductor layer and the second conductive semiconductor layer. The first lower contact electrode is in ohmic contact with the first light-emitting stack; The second lower contact electrode is in ohmic contact with the second light-emitting stack; The third lower contact electrode is in ohmic contact with the third light-emitting stack; The first connecting electrode is electrically connected to the first light-emitting stack; The second connecting electrode is electrically connected to the second light-emitting stack; as well as The third connecting electrode is electrically connected to the third light-emitting stack. The second light-emitting stack is disposed between the first light-emitting stack and the third light-emitting stack. The first lower contact electrode is disposed between the first light-emitting stack and the second light-emitting stack. The second lower contact electrode is disposed between the second light-emitting stack and the third light-emitting stack. The first lower contact electrode, the second lower contact electrode, and the third lower contact electrode each include a transparent conductive oxide layer. The second lower contact electrode or the third lower contact electrode is thicker than the first lower contact electrode. The first light-emitting stack, the second light-emitting stack, and the third light-emitting stack are electrically connected to the circuit electrodes of the circuit board through the first connecting electrode, the second connecting electrode, and the third connecting electrode, respectively. Each of the first connecting electrode, the second connecting electrode, and the third connecting electrode includes a first surface facing the upper surface of the circuit board and a second surface facing the first surface, wherein the area of ​​the second surface is larger than the area of ​​the first surface.

15. The display device according to claim 14, characterized in that, The second lower contact electrode is thicker than the third lower contact electrode.

16. The display device according to claim 14, characterized in that, The second lower contact electrode or the third lower contact electrode includes a lower layer that has been heat-treated for ohmic contact with the second conductive semiconductor layer and an upper layer disposed on the heat-treated lower layer but not heat-treated.

17. The display device according to claim 16, characterized in that, The upper layer that has not undergone heat treatment is thicker than the lower layer that has undergone heat treatment.

18. The display device according to claim 14, characterized in that, The first lower contact electrode to the third lower contact electrode comprise an ITO-based transparent conductive oxide layer.

19. The display device according to claim 14, characterized in that, The first lower contact electrode makes ohmic contact with the second conductive semiconductor layer of the first light-emitting stack.

20. The display device according to claim 14, characterized in that, Also includes: The fourth connecting electrode is electrically connected to the first light-emitting stack, the second light-emitting stack, and the third light-emitting stack.

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