Multiwavelength light-emitting device and method for manufacturing the same

Abstract

A light-emitting element according to one embodiment comprises a short-wavelength emitting part; a long-wavelength emitting part; and a coupling layer that combines the short-wavelength emitting part and the long-wavelength emitting part, wherein the short-wavelength emitting part and the long-wavelength emitting part each comprise a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, wherein the active layer of the long-wavelength emitting part contains more indium (In) than the active layer of the short-wavelength emitting part, and the short-wavelength emitting part emits light with a shorter wavelength than the long-wavelength emitting part.

Description

Technology Field

[0001] The present disclosure relates to a multi-wavelength light-emitting device, and more specifically, to a light-emitting device capable of emitting light of multiple wavelengths without a phosphor. Background Technology

[0002] Light-emitting diodes (LEDs) are used as inorganic light sources in various fields, such as display devices, automotive lamps, and general lighting. Due to their advantages of long lifespan, low power consumption, and fast response speed, LEDs are rapidly replacing conventional light sources.

[0003] FIG. 1 is a schematic cross-sectional view illustrating a white light-emitting element according to the prior art.

[0004] Referring to FIG. 1, a white light-emitting device according to the prior art includes lead electrodes (11a, 11b), a housing (13), a light-emitting diode chip (15), a bonding wire (17), and a wavelength converter (19).

[0005] The light-emitting diode chip (15) can emit blue light. For example, the light-emitting diode chip (15) can emit light in the wavelength range of 430 to 470 nm.

[0006] The wavelength converter (19) may be formed from a resin containing, for example, a yellow phosphor. As the yellow phosphor, YAG-based (Yttrium aluminum garnet-based) or silicate-based phosphors are mainly used. The wavelength converter (19) is placed in the path of light emitted from the light-emitting diode chip (15).

[0007] The light-emitting diode chip (15) is electrically connected to lead electrodes (11a, 11b). For example, a bonding wire (17) can electrically connect one electrode of the light-emitting diode chip (15) to the lead electrode (11b), and the other electrode of the light-emitting diode chip (15) can be bonded to the lead electrode (11a) through a conductive material such as a conductive paste.

[0008] White light-emitting devices according to conventional technology generally realize white light at the package level. That is, blue light emitted from a blue light-emitting diode chip and yellow light emitted from a yellow phosphor are mixed to emit white light externally.

[0009] Figure 1 illustrates a typical white light-emitting device, but various packages may be provided, which generally include a phosphor.

[0010] White light-emitting devices according to conventional technology have the problem of complex manufacturing processes and high production costs because they include a phosphor in addition to a light-emitting diode chip. Furthermore, the resin in which the phosphor is dispersed is susceptible to heat and has problems such as degradation over time. The problem to be solved

[0011] The problem that the present disclosure aims to solve is to provide a light-emitting element capable of realizing light of multiple wavelengths, such as white light, without using a phosphor.

[0012] Another problem that the present disclosure aims to solve is to provide a light-emitting device capable of realizing multiple wavelengths of light at the wafer level or chip level. means of solving the problem

[0013] A light-emitting element according to one embodiment of the present disclosure comprises: a short-wavelength emitting part; a long-wavelength emitting part; and a coupling layer that combines the short-wavelength emitting part and the long-wavelength emitting part, wherein the short-wavelength emitting part and the long-wavelength emitting part each comprise a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, wherein the active layer of the long-wavelength emitting part contains more indium (In) than the active layer of the short-wavelength emitting part, and the short-wavelength emitting part emits light with a shorter wavelength than the long-wavelength emitting part.

[0014] A method for manufacturing a light-emitting device according to one embodiment comprises forming a first LED stack on a first substrate, forming a second LED stack on a second substrate, combining the first LED stack and the second LED stack using a bonding layer, and removing the first substrate or the second substrate, wherein the first and second LED stacks each comprise a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, and the first LED stack is configured to emit light of a shorter wavelength than the second LED stack. Brief explanation of the drawing

[0015] FIG. 1 is a schematic cross-sectional view illustrating a white light-emitting element according to the prior art. FIG. 2 is a schematic cross-sectional view for explaining a light-emitting element according to one embodiment of the present disclosure. FIG. 3 is a schematic cross-sectional view for explaining a light-emitting element according to one embodiment of the present disclosure. FIG. 4 is a schematic cross-sectional view for explaining a light-emitting element according to one embodiment of the present disclosure. FIG. 5 is a schematic cross-sectional view for explaining a light-emitting element according to one embodiment of the present disclosure. FIG. 6 is a schematic cross-sectional view for explaining a light-emitting element according to one embodiment of the present disclosure. FIG. 7 is a schematic cross-sectional view for explaining a light-emitting element according to one embodiment of the present disclosure. FIG. 8 is a schematic plan view for explaining a light-emitting element according to one embodiment of the present disclosure. FIG. 9A is a schematic cross-sectional view taken along the cut line A-A' of FIG. 8. FIG. 9B is a schematic cross-sectional view taken along the cut line B-B' of FIG. 8. FIG. 10 is a schematic plan view for illustrating a light-emitting element according to another embodiment of the present disclosure. FIG. 11A is a schematic cross-sectional view taken along the cut line C-C' of FIG. 10. FIG. 11B is a schematic cross-sectional view taken along the cut line D-D' of FIG. 10. FIGS. 12A and FIG. 12B are schematic cross-sectional views for illustrating a light-emitting element according to another embodiment of the present disclosure. FIGS. 13A and FIGS. 13B are schematic cross-sectional views for illustrating a light-emitting element according to another embodiment of the present disclosure. FIG. 14 is a schematic plan view for illustrating a light-emitting element according to another embodiment of the present disclosure. FIG. 15A is a schematic cross-sectional view taken along the cut line E-E' of FIG. 14. FIG. 15B is a schematic cross-sectional view taken along the cut line F-F' of FIG. 14. Figure 16 is a schematic circuit diagram of the light-emitting element of Figure 14. FIGS. 17 to 19 are schematic circuit diagrams for illustrating light-emitting elements according to some embodiments of the present disclosure. Specific details for implementing the invention

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings. The embodiments described below are provided as examples to ensure that the concept of the present disclosure is sufficiently conveyed to those skilled in the art to which the present disclosure pertains. Accordingly, the present disclosure is not limited to the embodiments described below and may be embodied in other forms. Furthermore, in the drawings, the width, length, thickness, etc., of components may be exaggerated for convenience. Also, when one component is described as being "above" or "on" another component, this includes not only cases where each part is "immediately above" or "immediately on" another part, but also cases where another component is interposed between each component and another component. Throughout the specification, the same reference numerals indicate the same components.

[0017] A light-emitting element according to one embodiment of the present disclosure comprises: a short-wavelength emitting part; a long-wavelength emitting part; and a coupling layer that combines the short-wavelength emitting part and the long-wavelength emitting part, wherein the short-wavelength emitting part and the long-wavelength emitting part each comprise a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, wherein the active layer of the long-wavelength emitting part contains more indium (In) than the active layer of the short-wavelength emitting part, and the short-wavelength emitting part emits light with a shorter wavelength than the long-wavelength emitting part.

[0018] By combining a short-wavelength emitting part and a long-wavelength emitting part, it is possible to provide a light-emitting element capable of emitting light of multiple wavelengths, such as white light, without a phosphor.

[0019] The light-emitting element may further include a substrate disposed on the side of the short-wavelength light-emitting part or the long-wavelength light-emitting part.

[0020] In one embodiment, the short-wavelength emitting part may emit blue light, and the long-wavelength emitting part may emit yellow light. In another embodiment, the short-wavelength emitting part may emit ultraviolet light.

[0021] The light emitted from the long-wavelength light-emitting unit can be emitted to the outside through the short-wavelength light-emitting unit. Accordingly, light loss can be reduced.

[0022] The bonding layer may be an insulating layer or a transparent electrode.

[0023] The light-emitting element may further include a first bonding pad electrically connected in common to the short-wavelength light-emitting part and the long-wavelength light-emitting part; and a second bonding pad and a third bonding pad electrically connected to the short-wavelength light-emitting part and the long-wavelength light-emitting part, respectively.

[0024] The light-emitting element can be flip-bonded using the first to third bonding pads.

[0025] In one embodiment, the first bonding pad is electrically connected in common to the first conductive semiconductor layers of the short-wavelength emitting part and the long-wavelength emitting part, the second bonding pad is electrically connected to the second conductive semiconductor layer of the short-wavelength emitting part, and the third bonding pad is electrically connected to the second conductive semiconductor layer of the long-wavelength emitting part.

[0026] Furthermore, the light-emitting element may further include buried vias that electrically connect the first to third bonding pads to the first conductivity type semiconductor layer and the second conductivity type semiconductor layer.

[0027] The light-emitting element may further include a planarization layer, the buried vias penetrate the planarization layer, and the first to third bonding pads may be disposed on the planarization layer.

[0028] In another embodiment, the first bonding pad is electrically connected in common to the second conductivity semiconductor layers of the short wavelength emitting part and the long wavelength emitting part, the second bonding pad is electrically connected to the second conductivity semiconductor layer of the short wavelength emitting part, and the third bonding pad is electrically connected to the second conductivity semiconductor layer of the long wavelength emitting part.

[0029] In one embodiment, the short-wavelength emitting unit and the long-wavelength emitting unit may be driven independently. In another embodiment, the short-wavelength emitting unit and the long-wavelength emitting unit may be driven together.

[0030] The light-emitting element may further include a substrate; and a plurality of light-emitting cells disposed on the substrate, wherein each light-emitting cell may include the short-wavelength light-emitting part, the long-wavelength light-emitting part, and the bonding layer.

[0031] Furthermore, the light-emitting element may further include connectors that electrically connect the plurality of light-emitting cells.

[0032] In one embodiment, the plurality of light-emitting cells can be connected in series and parallel to each other.

[0033] A method for manufacturing a light-emitting device according to one embodiment comprises forming a first LED stack on a first substrate, forming a second LED stack on a second substrate, combining the first LED stack and the second LED stack using a bonding layer, and removing the first substrate or the second substrate, wherein the first and second LED stacks each comprise a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, and the first LED stack is configured to emit light of a shorter wavelength than the second LED stack.

[0034] In one embodiment, the first LED stack may be configured to emit blue light, and the second LED stack may be configured to emit yellow light.

[0035] The above method for manufacturing a light-emitting device may further include forming a first transparent electrode and a second transparent electrode on the first LED stack and the second LED stack, respectively, before bonding the first LED stack and the second LED stack.

[0036] The above method for manufacturing a light-emitting device may further include forming a lower p-electrode pad on the first transparent electrode.

[0037] Additionally, the method for manufacturing the light-emitting device may further include, before bonding the first LED stack and the second LED stack, patterning the first transparent electrode and the first LED stack to expose the first conductive semiconductor layer of the first LED stack, and forming a lower n electrode on the exposed first conductive semiconductor layer.

[0038] The above method for manufacturing a light-emitting device may further include forming an upper p-electrode pad on the second transparent electrode.

[0039] Embodiments of the present disclosure will be described in detail below with reference to the drawings.

[0040] FIG. 2 is a schematic cross-sectional view for explaining a light-emitting element according to one embodiment of the present disclosure.

[0041] Referring to FIG. 2, the light-emitting element according to the present embodiment includes a short-wavelength light-emitting part (BL), a long-wavelength light-emitting part (YL), and an insulating layer (50). The short-wavelength light-emitting part (BL) includes a first LED stack (20) and may further include a first transparent electrode (29). The long-wavelength light-emitting part (YL) includes a second LED stack (30) and may further include a second transparent electrode (39).

[0042] The first LED stack (20) may include a first conductivity semiconductor layer (23), an active layer (25), and a second conductivity semiconductor layer (27). The first conductivity semiconductor layer (23), the active layer (25), and the second conductivity semiconductor layer (27) may each be a gallium nitride-based semiconductor layer. The first and second conductivity semiconductor layers (23, 27) may each be a single layer or a multilayer. The active layer (25) may have a multi-quantum well structure, and, for example, the material and thickness may be selected to emit light in the wavelength range of 365 nm to 460 nm.

[0043] The second LED stack (30) may include a first conductivity semiconductor layer (33), an active layer (35), and a second conductivity semiconductor layer (37). The first conductivity semiconductor layer (33), the active layer (35), and the second conductivity semiconductor layer (37) may each be a gallium nitride-based semiconductor layer. The first and second conductivity semiconductor layers (33, 37) may each be a single layer or a multilayer. The active layer (35) may have a multi-quantum well structure, and, for example, the material and thickness may be selected to emit light in the wavelength range of 500 nm to 600 nm. The well layer of the active layer (35) may contain more indium (In) than the well layer of the active layer (25). The first conductivity semiconductor layer (23, 33) of each LED stack (20, 30) is an n-type semiconductor layer, and the second conductivity semiconductor layer (27, 37) is a p-type semiconductor layer.

[0044] The first transparent electrode (29) contacts the second conductive semiconductor layer (27) of the first LED stack (20). The first transparent electrode (29) can be formed using a transparent conductive oxide (TCO) or a metal layer. Examples of transparent conductive oxide layers include SnO2, InO2, ITO, ZnO, IZO, etc. The first transparent electrode (29) transmits light generated in the first LED stack (20) or the second LED stack (30).

[0045] The second transparent electrode (39) contacts the second conductive semiconductor layer (37) of the second LED stack (30). The second transparent electrode (39) can be formed using a transparent conductive oxide (TCO) or a metal layer. Examples of transparent conductive oxide layers include SnO2, InO2, ITO, ZnO, IZO, etc. The second transparent electrode (39) transmits light generated in the first LED stack or the second LED stack (30).

[0046] An insulating layer (50) is placed between a short-wavelength emitting part (BL) and a long-wavelength emitting part (YL). The insulating layer (50) can combine the short-wavelength emitting part (BL) and the long-wavelength emitting part (YL). For example, the insulating layer (50) can combine the first transparent electrode (29) and the second transparent electrode (39).

[0047] The insulating layer (50) may be formed as a transparent organic layer or a transparent inorganic layer. Examples of the organic layer include SU8, poly(methylmethacrylate): PMMA, polyimide, parylene, benzocyclobutene (BCB), etc., and examples of the inorganic layer include Al2O3, SiO2, SiNx, etc. Additionally, the insulating layer (50) may be formed of spin-on-glass (SOG).

[0048] In one embodiment, as illustrated in FIG. 3, the light-emitting element may further include a first substrate (21). The first substrate (21) may be disposed on the side of the short-wavelength light-emitting part (BL). The first substrate (21) may be a substrate that can be used to grow the first LED stack (20), such as a sapphire substrate, a SiC substrate, or a GaN substrate. In one embodiment, the first substrate (21) may be a flat sapphire substrate, but may also be a patterned sapphire substrate. Light generated from the short-wavelength light-emitting part (BL) and the long-wavelength light-emitting part (YL) may be emitted to the outside through the first substrate (21), and thus, the first substrate (21) may be a transparent substrate that transmits light generated from the short-wavelength light-emitting part (BL) and the long-wavelength light-emitting part (YL). However, the present disclosure is not limited thereto, and light generated from the short-wavelength emitting part (BL) and the long-wavelength emitting part (YL) may be emitted to the opposite side of the first substrate (21). In this case, the first substrate (21) may be an opaque substrate.

[0049] In another embodiment, as illustrated in FIG. 4, the light-emitting element may further include a second substrate (31). The second substrate (31) may be positioned on the side of the long-wavelength light-emitting part (YL). The second substrate (31) may be a substrate that can be used to grow the second LED stack (30), such as a sapphire substrate, a SiC substrate, or a GaN substrate. In one embodiment, the second substrate (31) may be a flat sapphire substrate, but may also be a patterned sapphire substrate. Light generated from the short-wavelength light-emitting part (BL) and the long-wavelength light-emitting part (YL) may be emitted to the outside through the second substrate (31), and thus, the second substrate (31) may be a transparent substrate that transmits light generated from the short-wavelength light-emitting part (BL) and the long-wavelength light-emitting part (YL). However, the present disclosure is not limited thereto, and light generated from the short-wavelength emitting part (BL) and the long-wavelength emitting part (YL) may be emitted to the opposite side of the second substrate (31). In this case, the second substrate (31) may be an opaque substrate.

[0050] A light-emitting element can be formed, for example, by growing a first conductive semiconductor layer (23, 33), an active layer (25, 35), and a second conductive semiconductor layer (27, 37) on a first substrate (21) and a second substrate (31), respectively, and then forming a first transparent electrode (29) and a second transparent electrode (39) on the second conductive semiconductor layers (27, 37), respectively, and then bonding the first transparent electrode (29) and the second transparent electrode (39) to face each other using an insulating layer (50). After that, a light-emitting element as shown in FIG. 3 can be manufactured by separating the second substrate (31), or a light-emitting element as shown in FIG. 4 can be manufactured by separating the first substrate (21). Both the first substrate (21) and the second substrate (31) may be removed, and another substrate may be attached.

[0051] Before bonding, the first LED stack (20) or the second LED stack (30) may be patterned, and additional electrode pads may also be formed on the first transparent electrode (29) or the second transparent electrode (39).

[0052] FIG. 5 is a schematic cross-sectional view for explaining a light-emitting element according to one embodiment of the present disclosure.

[0053] Referring to FIG. 5, the light-emitting element according to the present embodiment is generally similar to the light-emitting element of FIG. 4, but differs in that the insulating layer (50) combines the first transparent electrode (29) and the first conductive semiconductor layer (33). The active layer (35) is located on the first conductive semiconductor layer (33), and the second conductive semiconductor layer (37) is located on the active layer (35). The second transparent electrode (39) may be located on the second conductive semiconductor layer (37).

[0054] In this embodiment, light generated in the second LED stack (30) can be emitted through the first substrate (21), and in this case, there is no need for the light to travel through the second transparent electrode (39). Therefore, a reflective metal layer may be disposed on the second conductive semiconductor layer (37) instead of or in addition to the second transparent electrode (39).

[0055] A light-emitting element according to the present embodiment can be manufactured, for example, by transferring a second LED stack (30) and a second transparent electrode (39) grown on a second substrate (31) to a temporary substrate, separating the second substrate (31) first, and then combining the second LED stack (30) and the first LED stack (20). The temporary substrate can be separated after the second LED stack (30) and the first LED stack (20) are combined, and accordingly, a light-emitting element can be provided in which the second transparent electrode (39) is far from the insulating layer (50).

[0056] In this embodiment, a light-emitting element is described in which the first substrate (21) remains and the second substrate (31) is removed; however, through a similar process, as shown in FIG. 6, the second substrate (31) may remain and the first substrate (21) may be removed. In the embodiment of FIG. 6, the second transparent electrode (39) will be transparent to light generated from the first LED stack (20) or the second LED stack (30). Also, in the embodiment of FIG. 6, when light generated from the first LED stack (20) and the second LED stack (30) is emitted to the outside through the second substrate (31), a reflective metal layer may be disposed on the second conductive semiconductor layer (27) instead of or in addition to the first transparent electrode (29).

[0057] FIG. 7 is a schematic cross-sectional view for explaining a light-emitting element according to one embodiment of the present disclosure.

[0058] Referring to FIG. 7, the light-emitting element according to the present embodiment is generally similar to the light-emitting element described with reference to FIG. 2, but differs in that the short-wavelength light-emitting part (BL) and the long-wavelength light-emitting part (YL) are combined by a transparent electrode (59) instead of an insulating layer (50). For example, the transparent electrode (59) of FIG. 7 can be formed by directly bonding the first transparent electrode (29) and the second transparent electrode (39) of FIG. 3.

[0059] The transparent electrode (59) is electrically connected in common to the second conductivity semiconductor layers (27, 37), and thus the second conductivity semiconductor layer (27) of the first LED stack (20) and the second conductivity semiconductor layer (37) of the second LED stack (30) are electrically connected to each other.

[0060] Meanwhile, in the present embodiment, the first substrate (21) may be placed on the side of the first conductive semiconductor layer (23), and the second substrate (31) may be placed on the side of the first conductive semiconductor layer (33).

[0061] Above, a stacked structure of various light-emitting elements in which a short-wavelength emitting part (BL) and a long-wavelength emitting part (YL) are combined by an insulating layer (50) or a transparent electrode layer (59) has been described. The present invention is not limited to these light-emitting elements, and various other light-emitting elements may also be possible. Meanwhile, at least two electrodes may be arranged to supply external power to the short-wavelength emitting part (BL) and the long-wavelength emitting part (YL). Below, light-emitting elements of various structures in which three or four electrodes are formed will be described in detail.

[0062] FIG. 8 is a schematic plan view for explaining a light-emitting element (100) according to one embodiment of the present disclosure, FIG. 9A is a schematic cross-sectional view taken along the cut line A-A' of FIG. 8, and FIG. 9B is a schematic cross-sectional view taken along the cut line B-B' of FIG. 8.

[0063] For convenience of explanation, the bonding pads (67a, 67b, 67c) are shown and described as being positioned on the top, but the light-emitting element may be flip-bonded on a circuit board or lead frame, in which case the bonding pads (67a, 67b, 67c) are positioned on the bottom.

[0064] Referring to FIGS. 8, FIGS. 9A, and FIGS. 9B, the light-emitting element (100) may include a first LED stack (20), a second LED stack (30), a first transparent electrode (29), a second transparent electrode (39), a lower p-electrode pad (47), an upper p-electrode pad (57), an insulating layer (50), a flattening layer (61), a sidewall insulating layer (63), embedded vias (65a, 65b, 65c, 65d), and first to third bonding pads (67a, 67b, 67c).

[0065] Furthermore, the light-emitting element (100) may include through holes (H1, H2) penetrating the second LED stack (30), a through hole (H3) partially penetrating the second LED stack (30), and a through hole (H4) located on the second LED stack (30).

[0066] The basic layer structure of the short-wavelength emitting part (BL) and the long-wavelength emitting part (YL) of the light-emitting element (100) is similar to that described with reference to FIG. 5, but a lower p-electrode pad (47) and an upper p-electrode pad (57) may be added on the first transparent electrode (29) and the second transparent electrode (39), respectively.

[0067] As illustrated in FIGS. 9A and 9B, embodiments of the present disclosure have first and second LED stacks (20, 30) stacked vertically. A first LED stack (20) is placed on a substrate (21), and a second LED stack (30) is bonded to the first LED stack (20). Before the second LED stack (30) is bonded, a lower p-electrode pad (47) may be formed on a first transparent electrode (29). The lower p-electrode pad (47) may be formed, for example, using a lift-off technique. The lower p-electrode pad (47) may be formed from a metal layer. The lower p-electrode pad (47) may be formed from, for example, Cr / Au / Ti, but is not specifically limited thereto. The lower p-electrode pad (47) may be omitted.

[0068] Meanwhile, the second LED stack (30) can be bonded to the first LED stack (20) using an insulating layer (50) after being grown on the second substrate using temporary bonding debonding (TBDB) technology. The second transparent electrode (39) may be formed before bonding or after bonding.

[0069] The upper p-electrode pad (57) may be partially formed on the second transparent electrode (39). The upper p-electrode pad (57) may be formed of a metal layer, and the material is not particularly limited. The upper p-electrode pad (57) may also be formed of the same material as the lower p-electrode pad (47). The upper p-electrode pad (57) may be positioned so as not to overlap with the lower p-electrode pad (47).

[0070] The planarization layer (61) may cover the second transparent electrode (39) and the upper p-electrode pad (57). The planarization layer (61) may have a flat upper surface. The planarization layer (61) is placed in the upper region of the second conductive semiconductor layer (37). The side of the planarization layer (61) may be parallel to the second conductive semiconductor layer (37), but is not limited thereto, and may be recessed inward from the edge of the second LED stack (30) as shown in FIGS. 9A and 9B. Additionally, the side of the planarization layer (61) may be parallel to the side of the second transparent electrode (39). The planarization layer (61) may be patterned by a photolithography and etching process, and at this time, the second transparent electrode (39) may also be patterned together. Accordingly, the second conductive semiconductor layer (37) may be exposed around the planarization layer (61). The flattening layer (61) can be formed of an aluminum oxide film, a silicon oxide film, or a silicon nitride film.

[0071] Through holes (H1, H2, H3, H4) can be formed to provide electrical paths to the short-wavelength emitting part (BL) and the long-wavelength emitting part (YL). The through holes (H1, H2, H3, H4) are spaced apart from each other. Since the through holes (H1, H2, H3, H4) have different depths, they can be formed using different processes.

[0072] The through hole (H1) can penetrate the flattening layer (61), the second transparent electrode (39), the second LED stack (30), the insulating layer (50), the first transparent electrode (29), the second conductive semiconductor layer (27), and the active layer (25), and can expose the first conductive semiconductor layer (23). The through hole (H2) can penetrate the flattening layer (61), the second transparent electrode (39), the second LED stack (30), and the insulating layer (50) to expose the lower p-electrode pad (47). The through hole (H3) can penetrate the flattening layer (61), the second transparent electrode (39), the second conductive semiconductor layer (37), and the active layer (35) to expose the first conductive semiconductor layer (23). The through hole (H4) can penetrate the flattening layer (61) to expose the upper p-electrode pad (57).

[0073] The sidewall insulating layer (63) covers the sidewalls of the through holes (H1, H2, H3, H4) and has openings that expose the bottoms of the through holes. The sidewall insulating layer (63) can be formed, for example, using chemical vapor deposition or atomic layer deposition technology, and can be formed, for example, from Al2O3, SiO2, Si3N4, etc. After the through holes (H1, H2, H3, H4) are formed, the sidewall insulating layer (63) can be formed to cover the flattening layer (61) and the interior of the through holes (H1, H2, H3, H4), and then, the sidewall insulating layer formed on the bottoms of the through holes can be removed through blanket etching to form openings that expose the bottom surfaces.

[0074] The buried vias (65a, 65b, 65c, 65d) can each fill the through holes (H1, H2, H3, H4). The buried vias (65a, 65b, 65c) are insulated from the inner walls of the through holes (H1, H2, H3) by the sidewall red layer (63), thus preventing an electrical short circuit.

[0075] The buried via (65a) is electrically connected to the first conductive semiconductor layer (23) of the first LED stack (20). The buried via (65b) is electrically connected to the lower p-electrode pad (47) and can be electrically connected to the second conductive semiconductor layer (27) through the lower p-electrode pad (47) and the first transparent electrode (29). The buried via (65c) is electrically connected to the first conductive semiconductor layer (33) of the second LED stack (30), and the buried via (65d) can be electrically connected to the upper p-electrode pad (57).

[0076] The buried vias (65a, 65b, 65c, 65d) can be formed using chemical mechanical polishing technology. For example, the buried vias (65a, 65b, 65c, 65d) can be formed by forming a seed layer and filling the through holes (H1, H2, H3, H4) with a conductive material such as Cu using plating technology, and then removing the metal layers on the flattening layer (61) using chemical mechanical polishing technology. As illustrated in FIGS. 9A and 9B, the buried vias (65a, 65b, 65c) may have a relatively wider width at the entrance of the through holes (H1, H2, H3) than at the bottom surface, thereby strengthening the electrical connection. Meanwhile, the buried via (65d) may have a columnar shape in which the top surface and the bottom surface are generally the same size.

[0077] The buried vias (65a, 65b, 65c, 65d) can be formed together through the same process. Accordingly, the upper surface of the buried vias (65a, 65b, 65c, 65d) can be generally parallel to the flattening layer (61).

[0078] Bonding pads (67a, 67b, 67c) may be disposed on each region of the planarization layer (61). The first bonding pad (67a) is electrically connected to the buried via (65a) and may also extend laterally to be electrically connected to the buried via (65c). Accordingly, the first conductive semiconductor layer (23) of the first LED stack (20) and the first conductive semiconductor layer (33) of the second LED stack (30) may be electrically connected in common. The first bonding pad (67a) may cover the buried vias (65a, 65c) (see FIG. 8).

[0079] The second bonding pad (67b) is electrically connected to the buried via (65b). The second bonding pad (67b) can cover the buried via (65b). The third bonding pad (67c) is electrically connected to the buried via (65d). The third bonding pad (67c) can cover the buried via (65d).

[0080] In this embodiment, the first to third bonding pads (67a, 67b, 67c) are all disposed on the flattening layer (61). The first to third bonding pads (67a, 67b, 67c) can be formed together in the same process, and thus, their upper surface heights can be the same.

[0081] In the present embodiment, when bonding the light-emitting element (100) to a circuit board or the like, the first to third bonding pads (67a, 67b, 67c) may be bonded to pads on the circuit board by a bonding material such as solder paste. Alternatively, bumps may be additionally formed on the first to third bonding pads (67a, 67b, 67c), and the light-emitting element (100) may be bonded to the circuit board using the bumps.

[0082] The light-emitting element (100) according to the present embodiment can emit short-wavelength light of ultraviolet or blue light using the first LED stack (20), and emit long-wavelength light of green or yellow light using the second LED stack (30). The light-emitting element (100) can realize mixed-color light by combining long-wavelength light and short-wavelength light, and, for example, can realize white light by combining blue light and yellow light.

[0083] Furthermore, by electrically connecting the first conductivity semiconductor layer (23) of the first LED stack (20) and the first conductivity semiconductor layer (33) of the second LED stack (30) in common, the first conductivity semiconductor layers (23, 33) can be electrically connected to a single first bonding pad (67a). Thus, the first LED stack (20) and the second LED stack (30) can be driven independently using three bonding pads. Moreover, the buried vias (65a, 65b) electrically connected to the first conductivity semiconductor layer (23) and the second conductivity semiconductor layer (27) of the first LED stack (20) are arranged diagonally within the light-emitting element (100). Additionally, buried vias (65c, 65d) electrically connected to the first conductivity semiconductor layer (33) and the second conductivity semiconductor layer (37) of the second LED stack (30) are arranged diagonally within the light-emitting element (100). By arranging the buried vias (65a, 65b) connected to the first LED stack (20) and the buried vias (65c, 65d) electrically connected to the second LED stack (30) diagonally, current distribution within the first LED stack (20) and the second LED stack (30) can be helped, and accordingly, the light-emitting efficiency can be increased.

[0084] In the present embodiment, the first conductive semiconductor layer (23) of the first LED stack (20) and the first conductive semiconductor layer (33) of the second LED stack (30) are electrically connected in common, but are not limited thereto. For example, the second conductive semiconductor layer (27) of the first LED stack (20) and the second conductive semiconductor layer (37) of the second LED stack (30) may be electrically connected in common. For example, the first bonding pad (67a) may be separated and placed on the buried vias (65a, 65c) respectively, and the second bonding pad (67b) and the third bonding pad (67c) may be connected to each other so that the second conductive semiconductor layer (27) of the first LED stack (20) and the second conductive semiconductor layer (37) of the second LED stack (30) may be electrically connected in common.

[0085] In another embodiment, the second conductive semiconductor layer (27) of the first LED stack (20) and the second conductive semiconductor layer (37) of the second LED stack (30) may be electrically connected to a single bonding pad. In this case, the first LED stack (20) and the second LED stack (30) can be driven simultaneously using two bonding pads.

[0086] FIG. 10 is a schematic plan view for illustrating a light-emitting element (200) according to another embodiment of the present disclosure, FIG. 11A is a schematic cross-sectional view taken along the cut line C-C' of FIG. 10, and FIG. 11B is a schematic cross-sectional view taken along the cut line D-D' of FIG. 10.

[0087] Referring to FIGS. 10, FIGS. 11A, and FIGS. 11B, the light-emitting element (200) according to the present embodiment is generally similar to the light-emitting element (100) described with reference to FIGS. 8, FIGS. 9A, and FIGS. 9B, but differs in that the first LED stack (20) is patterned and further includes a lower n electrode pad (47a).

[0088] That is, the first transparent electrode (29), the second conductive semiconductor layer (27), and the active layer (25) are patterned so that the first conductive semiconductor layer (23) is exposed. The lower n electrode pad (47a) can be formed on the exposed first conductive semiconductor layer (23). The lower n electrode pad (47a) can be formed of a material layer that makes ohmic contact with the first conductive semiconductor layer (23), such as Cr / Au / Ti.

[0089] Meanwhile, the lower p electrode pad (47b) may be placed on the first transparent electrode (29). The upper surface height of the lower p electrode pad (47b) may be generally similar to the upper surface height of the lower n electrode pad (47a).

[0090] The through hole (H1) may expose the lower n electrode pad (47a) instead of the first conductive semiconductor layer (23). Since the upper surface height of the lower n electrode pad (47a) is generally similar to the upper surface height of the lower p electrode pad (47b), the through holes (H1, H2) can be formed together in the same process.

[0091] In the present embodiment, patterning the first LED stack (20) can be performed before combining the first LED stack (20) and the second LED stack (30) using an insulating layer (50). Accordingly, the insulating layer (50) can cover the exposed first conductive semiconductor layer (20) and, together with the upper surface of the first transparent electrode (29), the side of the first transparent electrode (29), the second conductive semiconductor layer (27), and the active layer (25).

[0092] In this embodiment, the first LED stack (20) is described as being patterned, but the second LED stack (30) may also be patterned so that the first conductive semiconductor layer (33) is exposed, and an upper n-electrode pad may be formed on the exposed first conductive semiconductor layer (33). Additionally, an upper p-electrode pad (57b) is placed on the second transparent electrode (39). The upper surface height of the upper p-electrode pad (57b) and the upper surface height of the upper n-electrode pad formed on the first conductive semiconductor layer (33) may be formed to be generally similar, and thus, through holes (H3, H4) may be formed together in the same process.

[0093] FIGS. 12A and FIGS. 12B are schematic cross-sectional views for illustrating a light-emitting element (300) according to another embodiment of the present disclosure.

[0094] Referring to FIGS. 12A and FIGS. 12B, the light-emitting element (300) according to the present embodiment is generally similar to the light-emitting element (100) described with reference to FIGS. 8, FIGS. 9A, and FIGS. 9B, but differs in that the second transparent electrode (39) is positioned on the side of the insulating layer (50), and the first conductive semiconductor layer (33) is positioned far away from the insulating layer (50). That is, the stacking order of the first LED stack (20), the second LED stack (30), the first transparent electrode (29), and the second transparent electrode (39) placed on the first substrate (21) is similar to the light-emitting element described earlier with reference to FIG. 3, and a detailed description thereof is omitted.

[0095] The flattening layer (161) covers the first conductive semiconductor layer (33). The flattening layer (161) may be formed of an aluminum oxide film, a silicon oxide film, or a silicon nitride film. As described with reference to FIGS. 8, 9A, and 9B, the flattening layer (161) may be recessed to expose the edge of the first conductive semiconductor layer (33).

[0096] In this embodiment, the through hole (H1) may expose the first conductive semiconductor layer (23). In another embodiment, as described with reference to FIG. 10, the first LED stack (20) may be patterned and formed on the first conductive semiconductor layer (23) with the lower n electrode pad exposed, and the through hole (H1) may expose the lower n electrode pad.

[0097] The through hole (H2) may expose the first transparent electrode (29). In another embodiment, as described with reference to FIG. 8 or FIG. 10, a lower p-electrode pad may be placed on the first transparent electrode (29), and the through hole (H2) may expose the lower p-electrode pad.

[0098] The through hole (H3) can expose the first conductive semiconductor layer (33). An upper n-electrode pad may be added on the first conductive semiconductor layer (33), and the through hole (H3) may expose the upper n-electrode pad. The through hole (H4) penetrates the flattening layer (161) and the second LED stack (30), and can expose the second transparent electrode (39).

[0099] The side wall insulating layer (63) can cover the inner walls of the through holes (H1, H2, H3, H4) and expose the bottom surface. Additionally, as previously described, embedded vias (65a, 65b, 65c, 65d) are formed within the through holes (H1, H2, H3, H4), and bonding pads (67a, 67b, 67c) can be placed on the flattening layer (161) to cover the embedded vias (65a, 65b, 65c, 65d).

[0100] According to the present embodiment, the first bonding pad (67a) electrically connects the buried vias (65a, 65c), and thus the first conductive semiconductor layers (23, 33) of the first LED stack (20) and the second LED stack (30) are electrically connected in common. Meanwhile, the second bonding pad (67b) can be electrically connected to the second conductive semiconductor layer (27) through the buried via (65b) and the first transparent electrode (29), and the third bonding pad (67c) can be electrically connected to the second conductive semiconductor layer (37) through the buried via (65d) and the second transparent electrode (39). In another embodiment, the second conductivity semiconductor layers (27, 37) of the first LED stack (20) and the second LED stack (30) may be electrically connected in common, and the first conductivity semiconductor layers (23, 33) may be electrically separated. In yet another embodiment, the first conductivity semiconductor layers (23, 33) of the first LED stack (20) and the second LED stack (30) are electrically connected in common, and the second conductivity semiconductor layers (27, 37) are also electrically connected in common.

[0101] FIGS. 13A and FIGS. 13B are schematic cross-sectional views for illustrating a light-emitting element (400) according to another embodiment of the present disclosure.

[0102] Referring to FIG. 13A and FIG. 13B, the light-emitting element (400) according to the present embodiment includes a transparent electrode (59) that combines a first LED stack (20) and a second LED stack (30). That is, the first LED stack (20) and the second LED stack (30) are bonded by the transparent electrode (59). The transparent electrode (59) is electrically connected in common to the first conductive semiconductor layer (27) of the first LED stack (20) and the second conductive semiconductor layer (37) of the second LED stack (30).

[0103] The through hole (H1) exposes the transparent electrode (59), the through hole (H2) exposes the first conductive semiconductor layer (23), and the through hole (H3) exposes the first conductive semiconductor layer (33). In this embodiment, the light-emitting element (400) may have three through holes (H1, H2, H3), and the fourth through hole (H4) may be omitted.

[0104] As previously described, a sidewall insulating layer (63) is formed, embedded vias (165a, 165b, 165c) are formed within the through holes (H1, H2, H3), and bonding pads (167a, 167b, 167c) can be formed on the flattening layer (161).

[0105] In this embodiment, the first bonding pad (167a) can be electrically connected in common to the second conductive semiconductor layers (27, 37) through a transparent electrode (59), and the second and third bonding pads (167b, 167c) can be electrically connected to the first conductive semiconductor layer (23) and the first conductive semiconductor layer (33), respectively.

[0106] FIG. 14 is a schematic plan view for explaining a light-emitting element (500) according to another embodiment of the present disclosure, FIG. 15A is a schematic cross-sectional view taken along the cut line E-E' of FIG. 14, and FIG. 15B is a schematic cross-sectional view taken along the cut line F-F' of FIG. 14. Meanwhile, FIG. 16 is a schematic circuit diagram of the light-emitting element of FIG. 14.

[0107] Referring to FIGS. 14, FIGS. 15A, and FIGS. 15B, the light-emitting element (500) according to the present embodiment is generally similar to the light-emitting element (100) described with reference to FIGS. 8, FIGS. 9A, and FIGS. 9B, but differs in that it has a plurality of light-emitting cells (C1, C2). Since the layer structure of each light-emitting cell (C1, C2) is generally similar to that of the light-emitting element (100), a detailed description thereof is omitted.

[0108] The light-emitting cells (C1, C2) are spaced apart from each other on the substrate (21). After bonding the first LED stack (20) and the second LED stack (30) using an insulating layer (50), the second transparent electrode (39), the second LED stack (30), the insulating layer (50), the first transparent electrode (29), and the first LED stack (20) can be etched in sequence to form the light-emitting cells (C1, C2) that are spaced apart from each other.

[0109] The flattening layer (261) can cover the substrate (21) within the separation region between the light-emitting cells (C1, C2) together with the light-emitting cells (C1, C2). The upper surface of the flattening layer (261) can be flat.

[0110] Through holes (H1, H2, H3, H4) and a sidewall insulating layer (63) are formed in each of the light-emitting cells (C1, C2) as described with reference to FIGS. 8, 9A, and 9B, and embedded vias (265a, 265b, 265c, 265d) are formed within the through holes (H1, H2, H3, H4).

[0111] Additionally, as described with reference to FIGS. 8, 9A, and 9B, buried vias (265a, 265b) electrically connected to the first conductivity semiconductor layer (23) and the second conductivity semiconductor layer (27) of the first LED stack (20) are arranged diagonally within each light-emitting cell (C1, C2). Additionally, buried vias (265c, 265d) electrically connected to the first conductivity semiconductor layer (33) and the second conductivity semiconductor layer (37) of the second LED stack (30) are arranged diagonally within each light-emitting cell (C1, C2). By arranging the buried vias (265a, 265b) connected to the first LED stack (20) and the buried vias (265c, 265d) electrically connected to the second LED stack (30) in a diagonal direction, current distribution within the first LED stack (20) and the second LED stack (30) can be helped, and accordingly, the luminous efficiency can be increased.

[0112] Subsequently, connectors (267e, 267f) may be formed together with bonding pads (267a, 267b, 267c). The bonding pad (267a) may be placed on the second light-emitting cell (C2) and may be electrically connected to the first conductive semiconductor layers (23, 33) through buried vias (265a, 265c) within the second light-emitting cell (C2).

[0113] The bonding pad (267b) and the bonding pad (267c) can be placed on the first light-emitting cell (C1) and can be electrically connected to the buried vias (265b, 265c), respectively.

[0114] Meanwhile, connectors (267e, 267f) electrically connect the first light-emitting cell (C1) and the second light-emitting cell (C2). Specifically, connector (267e) electrically connects the embedded vias (265a, 265c) of the first light-emitting cell (C1) and the embedded via (265d) of the second light-emitting cell (C2) to each other, and connector (267f) electrically connects the embedded vias (265a, 265c) and the embedded via (265c) of the second light-emitting cell (C2) to each other.

[0115] Accordingly, as illustrated in FIG. 16, a light-emitting element (500) is provided in which the short-wavelength light-emitting part (BL1) and the long-wavelength light-emitting part (YL1) of the first light-emitting cell (C1), and the short-wavelength light-emitting part (BL2) and the long-wavelength light-emitting part (YL2) of the second light-emitting cell (C2) are connected in series and parallel. In particular, the first conductive semiconductor layers (23, 33) of the short-wavelength light-emitting part (BL1) and the long-wavelength light-emitting part (YL1) of the first light-emitting cell (C1) are electrically connected to each other, and furthermore, the second conductive semiconductor layers (27, 37) of the short-wavelength light-emitting part (BL2) and the long-wavelength light-emitting part (YL2) of the second light-emitting cell (C2) are also electrically connected.

[0116] In the present embodiment, through holes (H1, H2, H3, H4) are shown and described as being formed in each of the light-emitting cells (C1, C2), but the present invention is not necessarily limited thereto. Instead of forming through holes, various techniques such as mesa etching can be used to expose the first and second conductive semiconductor layers (23, 33, 27, 37) or the first and second transparent electrodes (29, 39), and electrical connections can be formed therein.

[0117] There are various ways to connect multiple light-emitting cells (C1, C2). Below, light-emitting devices connecting light-emitting cells (C1, C2) are described using a circuit diagram.

[0118] FIGS. 17 to 19 are schematic circuit diagrams for explaining light-emitting elements (600, 700, 800) according to some embodiments of the present disclosure.

[0119] First, referring to FIG. 17, the light-emitting element (600) according to the present embodiment is generally similar to the light-emitting element (500) described with reference to FIG. 16, but differs in that the first conductive semiconductor layers (23, 33) of the short-wavelength light-emitting part (BL1) of the first light-emitting cell (C1) and the long-wavelength light-emitting part (YL1) are electrically separated from each other. Furthermore, the second conductive semiconductor layers (27, 37) of the short-wavelength light-emitting part (BL2) of the second light-emitting cell (C2) and the long-wavelength light-emitting part (YL2) are also electrically separated. For example, in the embodiment of FIG. 14, the connectors (267e, 267f) are separated from each other, thereby providing a light-emitting element (600) of the circuit diagram as in FIG. 17.

[0120] Referring to FIG. 18, the light-emitting element (700) according to the present embodiment is generally similar to the light-emitting element (500) described with reference to FIG. 16, but differs in that the short-wavelength light-emitting part (BL1) of the first light-emitting cell (C1) and the second conductive semiconductor layers (27, 37) of the long-wavelength light-emitting part (YL1) are electrically connected in common, and the short-wavelength light-emitting part (BL2) of the second light-emitting cell (C2) and the second conductive semiconductor layers (27, 37) of the long-wavelength light-emitting part (YL2) are electrically separated from each other. The first conductive semiconductor layers (23, 33) of the short-wavelength emitting part (BL1) and the long-wavelength emitting part (YL1) of the first light-emitting cell (C1) are electrically connected in common, and the first conductive semiconductor layers (23, 33) of the short-wavelength emitting part (BL2) and the long-wavelength emitting part (YL2) of the second light-emitting cell (C2) are electrically connected to each other.

[0121] Referring to FIG. 19, in the light-emitting element (800) according to the present embodiment, the short-wavelength light-emitting part (BL1) of the first light-emitting cell (C1) is connected in series with the short-wavelength light-emitting part (BL2) of the second light-emitting cell (C2), and the long-wavelength light-emitting part (YL1) of the first light-emitting cell (C1) is connected in series with the long-wavelength light-emitting part (YL2) of the second light-emitting cell (C2). Meanwhile, the short-wavelength light-emitting part (BL1, BL2) and the long-wavelength light-emitting part (YL1, YL2) are electrically separated from each other.

[0122] Above, several embodiments are described for connecting the short-wavelength emitting part (BL1) and the long-wavelength emitting part (YL1) of the first light-emitting cell (C1) and the short-wavelength emitting part (BL2) and the long-wavelength emitting part (YL2) of the second light-emitting cell (C2), but the present invention is not limited to the specific embodiments described above.

[0123] Although various embodiments of the present disclosure have been described above, the present disclosure is not limited to these embodiments. Furthermore, matters or components described for one embodiment may be applied to other embodiments without departing from the technical spirit of the present disclosure.

Claims

Claim 1 A light-emitting device comprising: a short-wavelength emitting part; a long-wavelength emitting part; a coupling layer combining the short-wavelength emitting part and the long-wavelength emitting part; and a reflective metal layer, wherein the short-wavelength emitting part and the long-wavelength emitting part each comprise a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, wherein the active layer of the long-wavelength emitting part contains more indium (In) than the active layer of the short-wavelength emitting part, and the short-wavelength emitting part emits light with a shorter wavelength than the long-wavelength emitting part, and the reflective metal layer is formed on the second conductive semiconductor layer of the long-wavelength emitting part or the short-wavelength emitting part and is electrically connected to the second conductive semiconductor layer of the long-wavelength emitting part or the short-wavelength emitting part. Claim 2 A light-emitting element according to claim 1, further comprising a substrate disposed on the side of the short-wavelength light-emitting part or the long-wavelength light-emitting part. Claim 3 A light-emitting element according to claim 1, wherein the short-wavelength light-emitting part emits blue light and the long-wavelength light-emitting part emits yellow light. Claim 4 A light-emitting element according to claim 1, wherein light emitted from the long-wavelength light-emitting part is emitted to the outside through the short-wavelength light-emitting part. Claim 5 A light-emitting element according to claim 1, wherein the bonding layer is an insulating layer or a transparent electrode. Claim 6 A light-emitting element according to claim 5, further comprising: a first bonding pad electrically connected in common to the short-wavelength light-emitting part and the long-wavelength light-emitting part; and a second bonding pad and a third bonding pad electrically connected to the short-wavelength light-emitting part and the long-wavelength light-emitting part, respectively. Claim 7 A light-emitting device according to claim 6, wherein the first bonding pad is electrically connected in common to the first conductivity type semiconductor layers of the short wavelength emitting part and the long wavelength emitting part, the second bonding pad is electrically connected to the second conductivity type semiconductor layer of the short wavelength emitting part, and the third bonding pad is electrically connected to the second conductivity type semiconductor layer of the long wavelength emitting part. Claim 8 A light-emitting device according to claim 7, further comprising buried vias that electrically connect the first to third bonding pads to the first conductivity type semiconductor layer and the second conductivity type semiconductor layer. Claim 9 A light-emitting element according to claim 8, further comprising a planarization layer, wherein the buried vias penetrate the planarization layer, and the first to third bonding pads are disposed on the planarization layer. Claim 10 A light-emitting device according to claim 6, wherein the first bonding pad is electrically connected in common to the second conductivity type semiconductor layers of the short wavelength emitting part and the long wavelength emitting part, the second bonding pad is electrically connected to the first conductivity type semiconductor layer of the short wavelength emitting part, and the third bonding pad is electrically connected to the first conductivity type semiconductor layer of the long wavelength emitting part. Claim 11 In claim 1, the light-emitting element in which the short-wavelength emitting part and the long-wavelength emitting part are driven together. Claim 12 A light-emitting device according to claim 1, further comprising a substrate; and a plurality of light-emitting cells disposed on the substrate, wherein each light-emitting cell comprises the short-wavelength light-emitting part, the long-wavelength light-emitting part, and the bonding layer. Claim 13 A light-emitting element according to claim 12, further comprising connectors that electrically connect the plurality of light-emitting cells. Claim 14 In claim 13, the plurality of light-emitting cells are light-emitting elements connected in series and parallel to each other. Claim 15 A method for manufacturing a light-emitting device comprising forming a first LED stack on a first substrate, forming a second LED stack on a second substrate, combining the first LED stack and the second LED stack using a bonding layer, removing the first substrate or the second substrate, and forming a reflective metal layer on the first LED stack or the second LED stack, wherein the first and second LED stacks each comprise a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer, the active layer of the second LED stack contains more indium (In) than the active layer of the first LED stack, the first LED stack is configured to emit light of a shorter wavelength than the second LED stack, and the reflective metal layer is formed on the second conductive semiconductor layer of the first or second LED stack and is electrically connected to the second conductive semiconductor layer of the first or second LED stack. Claim 16 A method for manufacturing a light-emitting device according to claim 15, wherein the first LED stack is configured to emit blue light and the second LED stack is configured to emit yellow light. Claim 17 A method for manufacturing a light-emitting device according to claim 15, further comprising forming a first transparent electrode and a second transparent electrode on the first LED stack and the second LED stack, respectively, before bonding the first LED stack and the second LED stack. Claim 18 A method for manufacturing a light-emitting device according to claim 17, further comprising forming a lower p-electrode pad on the first transparent electrode. Claim 19 A method for manufacturing a light-emitting device according to claim 18, further comprising, before bonding the first LED stack and the second LED stack, patterning the first transparent electrode and the first LED stack to expose the first conductive semiconductor layer of the first LED stack, and forming a lower n electrode on the exposed first conductive semiconductor layer. Claim 20 A method for manufacturing a light-emitting device according to claim 17, further comprising forming an upper p-electrode pad on the second transparent electrode.

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