Highly efficient light emitting device, unit pixel having the same, and display device having the same

Abstract

In one embodiment, the light-emitting element is a microscale light-emitting element comprising a semiconductor stack including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer; an insulating layer covering the top and side surfaces of the semiconductor stack; and a metal reflective layer disposed on the insulating layer and covering at least a portion of the side surface of the semiconductor stack, wherein the insulating layer includes a distributed Bragg reflector.

Description

[Technical Field]

[0001] Exemplary embodiments relate to a micro LED display device, and in particular to a high-efficiency light-emitting element, a unit pixel having the same, and a display device having the same. [Background technology]

[0002] Light emitting devices are semiconductor devices that use light emitting diodes (LEDs), which are inorganic light sources, and are used in a variety of fields such as display devices, vehicle lamps, general lighting, etc. Light emitting diodes have the advantages of long life, low power consumption, and fast response speed, and are rapidly replacing existing light sources.

[0003] While conventional light-emitting diodes (LEDs) have been used primarily as backlight sources in display devices, display devices that directly display images using LEDs have recently been developed. These displays are also called micro LED displays.

[0004] A display device generally uses a mixture of blue, green, and red colors to realize various colors. The display device includes a plurality of pixels to realize various images, and each pixel includes blue, green, and red sub-pixels. The color of a specific pixel is determined by the colors of these sub-pixels, and an image is realized by combining these pixels.

[0005] In a micro LED display, micro LEDs are arranged on a two-dimensional plane corresponding to each sub-pixel, which requires a large number of micro LEDs to be arranged on a single substrate. However, micro LEDs are very small, for example, less than 200 micrometers or even less than 100 micrometers, and their small size causes various problems. In particular, it is difficult to handle small light emitting diodes, making it difficult to directly mount light emitting diodes on a display substrate.

[0006] However, a significant portion of the light generated by micro LEDs is lost without being emitted to the outside, which makes the light efficiency of micro LEDs relatively lower than that of regular LEDs. Therefore, it is necessary to improve the light efficiency of micro LEDs. Summary of the Invention [Problem to be solved by the invention]

[0007] In an exemplary embodiment, a microscale light emitting device with improved light efficiency is provided.

[0008] In an exemplary embodiment, a method for manufacturing a light emitting module that can easily implement a unit pixel using a high-efficiency light emitting element and / or a transparent molding part and is suitable for mass production is provided. [Means for solving the problem]

[0009] In an exemplary embodiment, a microscale light-emitting device is provided, the light-emitting device including a semiconductor 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; an insulating layer covering a top surface and side surfaces of the semiconductor stack; and a metal reflective layer disposed on the insulating layer and covering at least a portion of the side surfaces of the semiconductor stack, the insulating layer including a distributed Bragg reflector.

[0010] In an exemplary embodiment, a microscale light-emitting element is provided, which includes a semiconductor 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; an insulating layer covering a top surface and a side surface of the semiconductor stack; and a metal reflective layer disposed on the insulating layer and covering at least a portion of the side surface of the semiconductor stack, wherein the thickness of the insulating layer disposed on the top surface of the semiconductor stack is greater than the thickness of the insulating layer disposed on the side surface of the semiconductor stack.

[0011] In an exemplary embodiment, a unit pixel is provided, the unit pixel including: a transparent substrate; a light-blocking layer disposed on the transparent substrate and having a window that transmits light; and a plurality of light-emitting elements disposed on the light-blocking layer to be aligned with the window, the light-emitting elements each including a semiconductor 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; an insulating layer covering a top surface and side surfaces of the semiconductor stack; and a metal reflective layer disposed on the insulating layer and covering at least a portion of the side surfaces of the semiconductor stack, the insulating layer including a distributed Bragg reflector.

[0012] In an exemplary embodiment, a display device is provided, the display device including: a circuit board; unit pixels mounted on the circuit board; and a molding portion covering the unit pixels, wherein the unit pixels include a transparent substrate and a plurality of light-emitting elements disposed on the transparent substrate, and the light-emitting elements each include a semiconductor stack including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer; an insulating layer covering a top surface and side surfaces of the semiconductor stack; and a metal reflective layer disposed on the insulating layer and covering at least a portion of the side surfaces of the semiconductor stack, the insulating layer including a distributed Bragg reflector. [Brief explanation of the drawings]

[0013] [Figure 1A] 1 is a schematic plan view illustrating a display device according to an embodiment; [Figure 1B] 1B is a schematic cross-sectional view taken along the cut line AA' of FIG. 1A. [Figure 2A] 1 is a schematic plan view illustrating a light-emitting module according to an embodiment. [Figure 2B] 2B is a schematic cross-sectional view taken along the cut line BB' of FIG. 2A. [Figure 3A] FIG. 2 is a schematic plan view illustrating a unit pixel according to an embodiment. [Figure 3B] 3B is a schematic cross-sectional view taken along the cut line CC' of FIG. 3A. [Figure 4A] FIG. 1 is a schematic plan view illustrating a light emitting element according to an embodiment. [Figure 4B] FIG. 4B is a schematic cross-sectional view taken along the cut line DD' of FIG. 4A. [Figure 5A] FIG. 10 is a schematic plan view illustrating a light emitting element according to still another embodiment. [Figure 5B] FIG. 10 is a schematic plan view illustrating a light emitting element according to still another embodiment. [Figure 6A] 1A and 1B are schematic plan views for explaining a method for forming a metal reflective layer according to one embodiment. [Figure 6B] 1A and 1B are schematic plan views for explaining a method for forming a metal reflective layer according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The embodiments described below are provided as examples to fully convey the concept of the present disclosure to those skilled in the art. Therefore, the present disclosure is not limited to the embodiments described below and may be embodied in other forms. In the drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. Furthermore, when a component is described as being "on top of" or "on" another component, this includes not only the case where each component is "directly on top of" or "directly above" the other component, but also the case where another component is interposed between the other component and the other component. The same reference numerals refer to the same components throughout the specification.

[0015] A light-emitting element according to an exemplary embodiment is a microscale light-emitting element comprising a semiconductor stack including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer; an insulating layer covering the top and side surfaces of the semiconductor stack; and a metal reflective layer disposed on the insulating layer and covering at least a portion of the side surface of the semiconductor stack, wherein the insulating layer includes a distributed Bragg reflector.

[0016] In this specification, the micro-scale light-emitting element has a size generally used in a micro LED display. The micro-scale light-emitting element may have a major axis length of 200 μm or less, and may further have a major axis length of 100 μm or less.

[0017] The thickness of the insulating layer covering the top surface of the semiconductor stack may be greater than the thickness of the insulating layer covering the side surface of the semiconductor stack.

[0018] The insulating layer covering the top surface of the semiconductor stack may have a higher reflectivity than the insulating layer covering the side surface of the semiconductor stack.

[0019] The metal reflective layer may include a first metal reflective layer and a second metal reflective layer spaced apart from each other, and the first metal reflective layer and the second metal reflective layer may each partially cover a side surface of the semiconductor stack.

[0020] The light emitting element may further include a first electrode pad and a second electrode pad disposed on the insulating layer and electrically connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively, and the first metal reflective layer may cover the first electrode pad and the second metal reflective layer may cover the second electrode pad.

[0021] The light emitting device may further include a first electrode pad and a second electrode pad disposed on the insulating layer and electrically connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively.

[0022] In one embodiment, the metal reflective layer may be spaced apart from the first electrode pad and the second electrode pad.

[0023] The metal reflective layer may be disposed in a ring shape along the side surface of the light emitting element.

[0024] The metal reflective layer may cover the first electrode pad and may be spaced apart from the second electrode pad.

[0025] The semiconductor stack may further include a mesa disposed on the first conductive type semiconductor layer, the mesa including the active layer and the second conductive type semiconductor layer, a portion of the first electrode pad may be located on the mesa, and the second electrode pad may be located on the mesa.

[0026] The light emitting device may further include a first contact pad disposed on the first conductive type semiconductor layer adjacent to the mesa, and the first electrode pad may be electrically connected to the first contact pad through an opening in the insulating layer.

[0027] The light-emitting device may further include an ohmic contact layer disposed on the second conductive type semiconductor layer; and a second contact pad disposed on the ohmic contact layer, and the second electrode pad may be electrically connected to the second contact pad through an opening in the insulating layer.

[0028] The light-emitting element according to an exemplary embodiment is a microscale light-emitting element that includes a semiconductor stack including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer; an insulating layer covering the top and side surfaces of the semiconductor stack; and a metal reflective layer disposed on the insulating layer and covering at least a portion of the side surfaces of the semiconductor stack, wherein the insulating layer disposed on the top surface of the semiconductor stack is thicker than the insulating layer disposed on the side surfaces of the semiconductor stack.

[0029] The insulating layer disposed on the top surface of the semiconductor stack may have a higher reflectivity than the insulating layer disposed on the side surface of the semiconductor stack.

[0030] The metal reflective layer may include a first metal reflective layer and a second metal reflective layer spaced apart from each other.

[0031] The light emitting device may further include a first electrode pad electrically connected to the first conductive type semiconductor layer; and a second electrode pad electrically connected to the second conductive type semiconductor layer, wherein the first metal reflective layer may cover the first electrode pad, and the second metal reflective layer may cover the second electrode pad.

[0032] The metal reflective layer may cover the entire side surface along the side surface of the light emitting element.

[0033] A unit pixel according to an exemplary embodiment includes a transparent substrate; a light-blocking layer disposed on the transparent substrate and having a window that transmits light; and a plurality of light-emitting elements disposed on the light-blocking layer so as to be aligned with the window, each of the light-emitting elements including a semiconductor stack including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer disposed between the first conductive type semiconductor layer and the second conductive type semiconductor layer; an insulating layer covering an upper surface and side surfaces of the semiconductor stack; and a metal reflective layer disposed on the insulating layer and covering at least a portion of the side surfaces of the semiconductor stack, the insulating layer including a distributed Bragg reflector.

[0034] The metal reflective layer may include a first metal reflective layer and a second metal reflective layer spaced apart from each other.

[0035] A display device according to an exemplary embodiment includes a circuit board; unit pixels mounted on the circuit board; and a molding part covering the unit pixels, wherein the unit pixels include a transparent substrate and a plurality of light-emitting elements arranged on the transparent substrate, and the light-emitting elements each include a semiconductor stack including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer arranged between the first conductive type semiconductor layer and the second conductive type semiconductor layer; an insulating layer covering an upper surface and side surfaces of the semiconductor stack; and a metal reflective layer arranged on the insulating layer and covering at least a portion of the side surfaces of the semiconductor stack, and the insulating layer includes a distributed Bragg reflector.

[0036] Hereinafter, embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings.

[0037] FIG. 1A is a schematic plan view illustrating a display device according to an embodiment of the present disclosure, and FIG. 1B is a schematic cross-sectional view taken along the line AA' in FIG. 1A.

[0038] 1A and 1B, a display device 10000 may include a panel substrate 2100 and a plurality of light-emitting modules 1000.

[0039] The display device 10000 may include, but is not limited to, a micro LED TV, a smart watch, a VR display device such as a VR headset, or an AR display device such as augmented reality glasses.

[0040] The panel substrate 2100 may include circuitry for passive matrix driving or active matrix driving. In one embodiment, the panel substrate 2100 may include wiring and resistors therein, while in another embodiment, the panel substrate 2100 may include wiring, transistors, and capacitors. The panel substrate 2100 may also have pads on its top surface that can be electrically connected to arranged circuitry.

[0041] In one embodiment, a plurality of light emitting modules 1000 are arranged on a panel substrate 2100. Each light emitting module 1000 may include a circuit board 1001 and a plurality of unit pixels 100 arranged on the circuit board 1001, as shown in FIG. 2A. Each unit pixel 100 includes a plurality of light emitting elements. The light emitting elements can emit light of different colors.

[0042] Hereinafter, each component of the display device 10000 will be described in detail in the order of the light emitting module 1000 arranged in the display device 10000, the unit pixels 100 arranged in the light emitting module 1000, and the light emitting elements.

[0043] FIG. 2A is a schematic plan view illustrating a light emitting module 1000 according to an embodiment of the present disclosure, and FIG. 2B is a schematic cross-sectional view taken along the line BB' in FIG. 2A.

[0044] Referring to Figures 2A and 2B, the light emitting module 1000 may further include a circuit board 1001, unit pixels 100 arranged on the circuit board 1001, a molding portion 1003 covering the unit pixels 100, and an anti-glare layer 1005.

[0045] The circuit board 1001 may have a circuit for electrically connecting the panel substrate 2100 and the unit pixels 100. The circuit in the circuit board 1001 may be formed in a multi-layer structure. The circuit board 1001 may also include a passive circuit for driving the unit pixels 100 in a passive matrix driving manner or an active circuit for driving the unit pixels 100 in an active matrix driving manner. The circuit board 1001 may have pads exposed on its surface, and the unit pixels 100 may be bonded to the pads of the circuit board 1001 by a bonding material.

[0046] The unit pixels 100 may be arranged on a circuit board 1001. The unit pixels 100 may be arranged in a 4x4 matrix as shown in FIG. 2A, but are not limited to this and may be arranged in various other matrixes such as 2x2, 3x3, 5x5, etc.

[0047] The unit pixels 100 are bonded to the circuit board 1001 by a bonding material. For example, the bonding material may be solder, and after a solder paste is placed on a pad on the circuit board 1001 using a technique such as screen printing, the unit pixels 100 and the circuit board 1001 can be bonded by a reflow process. The specific configuration of the unit pixels 100 will be described in detail later with reference to FIGS. 3A and 3B.

[0048] The molding portion 1003 covers the unit pixels 100. The molding portion 1003 may be in contact with the surface of the circuit board 1001 and cover the upper surfaces of the unit pixels 100. The molding portion 1003 may also have a flat upper surface. In particular, unlike the prior art, no recesses are formed on the regions between the unit pixels 100.

[0049] The molding portion 1003 may be formed using an ultraviolet curing resin. By using an ultraviolet curing resin, the hardness of the molding portion 1003 can be increased compared to a thermosetting resin. The molding portion 1003 may be formed using, for example, DFSR (dry-film type solder resist), PSR (photoimageable solder resist), or BM (black material). The molding portion 1003 can prevent light interference between the unit pixels 100 and improve the contrast of the display device 10000.

[0050] The anti-glare layer 1005 can cover the molding part 1003. The anti-glare layer 1005 prevents light reflection and reduces eye fatigue for the user. The anti-glare layer 1005 can be formed by mixing fine particles of silica, melamine, acrylic, or the like with a curable resin to form an ink, which can be coated on the surface of the molding part 1003 and cured using ultraviolet light.

[0051] In this embodiment, the unit pixel 100 is formed by the light emitting module 1000, and a plurality of light emitting modules 1000 are mounted on a panel substrate 2100 to provide a display device 10000, thereby improving the process yield of the display device 10000.

[0052] FIG. 3A is a schematic plan view illustrating a unit pixel 100 according to an embodiment of the present disclosure, and FIG. 3B is a schematic cross-sectional view taken along the cutting line CC' of FIG. 3A.

[0053] Referring to Figures 3A and 3B, the unit pixel 100 may include a transparent substrate 121, a first light-emitting element 10a, a second light-emitting element 10b, a third light-emitting element 10c, a surface layer 122, a light-blocking layer 123, an adhesive layer 125, a step adjustment layer 127, connection layers 129a, 129b, 129c, and 129d, and an insulating material layer 131.

[0054] The unit pixel 100 includes a first light emitting element 10a, a second light emitting element 10b, and a third light emitting element 10c, which emit light of different colors and each correspond to a sub-pixel.

[0055] The transparent substrate 121 is a light-transmitting substrate such as a PET (polyethylene terephthalate) substrate, a glass substrate, a quartz substrate, or a sapphire substrate. The transparent substrate 121 is disposed on the light emitting surface of the light emitting module 1000, and light emitted from the light emitting elements 10a, 10b, and 10c is emitted to the outside through the transparent substrate 121. The transparent substrate 121 may have an upper surface and a lower surface. The transparent substrate 121 may include a concave-convex pattern 121p on the surface facing the light emitting elements 10a, 10b, and 10c, i.e., the upper surface. The concave-convex pattern 121p scatters the light emitted from the light emitting elements 10a, 10b, and 10c, increasing the directivity angle. In addition, the concave-convex pattern 121p allows light emitted from the light emitting elements 10a, 10b, and 10c, which have different directivity angle characteristics, to be emitted at a uniform directivity angle. This prevents color differences depending on the viewing angle.

[0056] The uneven pattern 121p may be regular or irregular. For example, the uneven pattern 121p may have a pitch of 3 μm, a diameter of 2.8 μm, and a height of 1.8 μm. The uneven pattern 121p may be a pattern typically applied to a patterned sapphire substrate, but is not limited thereto.

[0057] The transparent substrate 121 may also include an anti-reflection coating, or may include an anti-glare layer or be anti-glare treated. The transparent substrate 121 may have a thickness of, for example, 50 μm to 300 μm.

[0058] Since the transparent substrate 121 is disposed on the light emitting surface, the transparent substrate 121 does not include a circuit, but the present disclosure is not limited thereto and may include a circuit.

[0059] Meanwhile, although one unit pixel 100 is formed on one transparent substrate 121 in the drawing, a plurality of unit pixels 100 may be formed on one transparent substrate 121 .

[0060] The surface layer 122 covers the uneven pattern 121p of the transparent substrate 121. The surface layer 122 can be formed to fit the shape of the uneven pattern 121p. The surface layer 122 can improve the adhesive strength of the light-blocking layer 123 and the adhesive layer 125 formed thereon. For example, the surface layer 122 can be formed of a silicon oxide film. The surface layer 122 may be omitted depending on the type of transparent substrate 121.

[0061] The light-blocking layer 123 is formed on the upper surface of the transparent substrate 121. The light-blocking layer 123 may be in contact with the surface layer 122. The light-blocking layer 123 may include a light-absorbing material such as carbon black. The light-absorbing material prevents light generated by the light-emitting elements 10a, 10b, and 10c from leaking laterally in the region between the transparent substrate 121 and the light-emitting elements 10a, 10b, and 10c, thereby improving the contrast of the display device.

[0062] The light-blocking layer 123 may have windows 123a, 123b, and 123c for the propagation path of light generated by the light emitting elements 10a, 10b, and 10c so that the light can enter the transparent substrate 121. For this purpose, the light-blocking layer 123 may be patterned on the transparent substrate 121 to expose the transparent substrate 121. The widths of the windows 123a, 123b, and 123c may be smaller than the width of the light emitting elements, but are not limited thereto, and may be larger than or the same as the width of the light emitting elements.

[0063] The windows 123a of the light-blocking layer 123 also define the alignment positions of the light-emitting elements 10a, 10b, and 10c. Therefore, separate alignment markers for defining the alignment positions of the light-emitting elements 10a, 10b, and 10c can be omitted. However, the present disclosure is not limited thereto. Alignment markers may be provided on the transparent substrate 121, the light-blocking layer 123, or the adhesive layer 125 to provide positions for aligning the light-emitting elements 10a, 10b, and 10c.

[0064] The adhesive layer 125 is attached on the transparent substrate 121. The adhesive layer 125 may cover the light-blocking layer 123. The adhesive layer 125 may be attached on the entire surface of the transparent substrate 121, but is not limited thereto. The adhesive layer 125 may be attached to a portion of the transparent substrate 121 so as to expose an area near the edge of the transparent substrate 121. The adhesive layer 125 is used to attach the light-emitting elements 10a, 10b, and 10c to the transparent substrate 121. The adhesive layer 125 may fill the windows 123a, 123b, and 123c formed in the light-blocking layer 123.

[0065] The adhesive layer 125 may be formed of a light-transmitting layer, allowing light emitted from the light emitting elements 10a, 10b, and 10c to pass through. The adhesive layer 125 may be formed using an organic adhesive. For example, the adhesive layer 125 may be formed using transparent epoxy. The adhesive layer 125 may also include a diffuser, such as SiO2, TiO2, or ZnO, to diffuse light. The light-diffusing material prevents the light emitting elements 10a, 10b, and 10c from being observed through the light emission surface.

[0066] Meanwhile, the first light emitting element 10a, the second light emitting element 10b, and the third light emitting element 10c are disposed on a transparent substrate 121. The first light emitting element 10a, the second light emitting element 10b, and the third light emitting element 10c may be attached to the transparent substrate 121 by an adhesive layer 125. The first light emitting element 10a, the second light emitting element 10b, and the third light emitting element 10c may be disposed corresponding to windows 123a, 123b, and 123c of the light blocking layer 123. If the light blocking layer 123 is omitted, alignment markers may be added to provide alignment positions for the light emitting elements 10a, 10b, and 10c.

[0067] The first light-emitting element 10a, the second light-emitting element 10b, and the third light-emitting element 10c can be, for example, a red light-emitting element, a green light-emitting element, and a blue light-emitting element. The light-emitting elements 10a, 10b, and 10c can each have a major axis length of 200 μm or less, or even 100 μm or less. The specific configurations of the first light-emitting element 10a, the second light-emitting element 10b, and the third light-emitting element 10c will be described in detail later with reference to FIGS. 4A and 4B.

[0068] The first light-emitting element 10a, the second light-emitting element 10b, and the third light-emitting element 10c can be arranged in a row, as shown in FIG. 3A. In particular, when the transparent substrate 121 is a sapphire substrate, the sapphire substrate can include clean cut surfaces (e.g., m-planes) and unclean cut surfaces (e.g., a-planes) along the crystal planes along the cutting direction. For example, when cutting into a rectangular shape, two cut surfaces (e.g., m-planes) on both sides can be cleanly cut along the crystal planes, while two other cut surfaces (e.g., a-planes) perpendicular to these cut surfaces may not be cleanly cut. In this case, the clean cut surfaces of the sapphire substrate 121 can be aligned in the alignment direction of the light-emitting elements 10a, 10b, and 10c. For example, in FIG. 3A, clean cut surfaces (e.g., m-planes) can be arranged vertically, and two other cut surfaces (e.g., a-planes) can be arranged horizontally.

[0069] The step adjusting layer 127 covers the first light emitting element 10a, the second light emitting element 10b, and the third light emitting element 10c. The step adjusting layer 127 has openings 127a that expose the electrode pads of the light emitting elements 10a, 10b, and 10c. The step adjusting layer 127 adjusts the height of the surfaces on which the connection layers 129a, 129b, 129c, and 129d are formed to a constant level, thereby helping to safely form the connection layers. The step adjusting layer 127 can be formed of, for example, photosensitive polyimide.

[0070] The step adjusting layer 127 may be disposed within a region surrounded by the edge of the adhesive layer 125, but is not limited thereto. For example, the step adjusting layer 127 may be formed so as to partially expose the edge of the adhesive layer 125.

[0071] The first connection layer 129a, the second connection layer 129b, the third connection layer 129c, and the fourth connection layer 129d are formed on the step adjusting layer 127. The connection layers 129a, 129b, 129c, and 129d can be connected to the electrode pads of the first light emitting element 10a, the second light emitting element 10b, and the third light emitting element 10c through the openings 127a of the step adjusting layer 127.

[0072] 3A and 3B, the first connection layer 129a may be electrically connected to the second conductive type semiconductor layer of the first light emitting element 10a, the second connection layer 129b may be electrically connected to the second conductive type semiconductor layer of the second light emitting element 10b, the third connection layer 129c may be electrically connected to the second conductive type semiconductor layer of the third light emitting element 10c, and the fourth connection layer 129d may be electrically connected in common to the first conductive type semiconductor layers of the first light emitting element 10a, the second light emitting element 10b, and the third light emitting element 10c. The first connection layer 129a, the second connection layer 129b, the third connection layer 129c, and the fourth connection layer 129d may be formed together on the step adjustment layer 127 and may have a single layer or multiple layers. For example, the first connection layer 129a may include at least one of Cr, Ti, Ni, Cu, Al, Pt, and Au.

[0073] In another embodiment, the first connection layer 129a may be electrically connected to the first conductive type semiconductor layer of the first light emitting element 10a, the second connection layer 129b may be electrically connected to the first conductive type semiconductor layer of the second light emitting element 10b, the third connection layer 129c may be electrically connected to the first conductive type semiconductor layer of the third light emitting element 10c, and the fourth connection layer 129d may be electrically connected in common to the second conductive type semiconductor layers of the first light emitting element 10a, the second light emitting element 10b, and the third light emitting element 10c. The first connection layer 129a, the second connection layer 129b, the third connection layer 129c, and the fourth connection layer 129d may be formed together on the step adjusting layer 127.

[0074] The insulating material layer 131 may be formed thinner than the step adjusting layer 127. The total thickness of the insulating material layer 131 and the step adjusting layer 127 may be, but is not limited to, 1 μm to 50 μm.

[0075] The insulating material layer 131 covers the side surfaces of the step adjusting layer 127 and the connecting layers 129a, 129b, 129c, and 129d. The insulating material layer 131 may also cover a portion of the adhesive layer 125. The insulating material layer 131 has openings 131a, 131b, 131c, and 131d that expose the connecting layers 129a, 129b, 129c, and 129d, thereby defining pad regions of the unit pixels 100.

[0076] In one embodiment, the insulating material layer 131 may be a semi-transparent material and may be formed of an organic or inorganic material. The insulating material layer 131 may be formed of, for example, polyimide. When the insulating material layer 131 is formed of polyimide together with the step adjustment layer 127, the bottom, side, and top surfaces of the connection layers 129a, 129b, 129c, and 129d may all be surrounded by polyimide except for the pad region.

[0077] Meanwhile, the unit pixel 100 can be mounted on a circuit board using a bonding material such as solder, and the bonding material can bond the connection layers 129a, 129b, 129c, and 129d exposed in the openings 131a, 131b, 131c, and 131d of the insulating material layer 131 to pads on the circuit board.

[0078] According to this embodiment, the unit pixel 100 does not include separate bumps, and the connection layers 129a, 129b, 129c, and 129d are used as bonding pads. However, the present invention is not limited thereto, and bonding pads may be formed to cover the openings 131a, 131b, 131c, and 131d of the insulating material layer 131. In one embodiment, the first connection layer 129a, the second connection layer 129b, the third connection layer 129c, and the fourth connection layer 129d may be formed to partially cover the light emitting elements 10a, 10b, and 10c, away from the upper regions of the first connection layer 129a, the second connection layer 129b, the third connection layer 129c, and the fourth connection layer 129d.

[0079] In this embodiment, the light-emitting elements 10a, 10b, and 10c are described as being attached to the transparent substrate 121 by the adhesive layer 125. However, the light-emitting elements 10a, 10b, and 10c may be coupled to the transparent substrate 121 using other couplers instead of the adhesive layer 125. For example, the light-emitting elements 10a, 10b, and 10c may be coupled to the transparent substrate 121 using spacers, thereby filling the region between the light-emitting elements 10a, 10b, and 10c and the transparent substrate 121 with a gas or liquid. This gas or liquid may form an optical layer that transmits light emitted from the light-emitting elements 10a, 10b, and 10c. The adhesive layer 125 described above is also an example of an optical layer. Here, the optical layer may be formed of a material different from the light-emitting elements 10a, 10b, and 10c, such as a gas, liquid, or solid, and thus be distinct from the material of the semiconductor layer in the light-emitting elements 10a, 10b, and 10c.

[0080] According to the present embodiment, a unit pixel 100 is provided in which light emitting elements 10a, 10b, and 10c are arranged on the same plane. The unit pixel 100 can embody light of various colors using the light emitting elements 10a, 10b, and 10c. The light emitting elements 10a, 10b, and 10c according to an embodiment will be described in detail below.

[0081] Fig. 4A is a schematic plan view illustrating a light-emitting device 10a according to one embodiment of the present disclosure, and Fig. 4B is a schematic cross-sectional view taken along the line D-D' in Fig. 4A. Here, the light-emitting device 10a will be described as an example, but since the light-emitting devices 10b and 10c have similar structures, overlapping descriptions will be omitted.

[0082] Referring to Figures 4A and 4B, the light-emitting element 10a may include a light-emitting structure including a first conductive type semiconductor layer 21, an active layer 23, and a second conductive type semiconductor layer 25, an ohmic contact layer 27, a first contact pad 53, a second contact pad 55, an insulating layer 59, a first electrode pad 61, a second electrode pad 63, a first metal reflective layer 65a, and a second metal reflective layer 65b.

[0083] The light emitting structure, i.e., the first conductive type semiconductor layer 21, the active layer 23, and the second conductive type semiconductor layer 25, may be grown on a substrate. The substrate may be a variety of substrates that can be used for semiconductor growth, such as a gallium nitride substrate, a GaAs substrate, a Si substrate, or a sapphire substrate, particularly a patterned sapphire substrate. The growth substrate may be separated from the semiconductor layer using techniques such as mechanical polishing, laser lift-off, or chemical lift-off. However, the present invention is not limited thereto, and a portion of the substrate may remain and constitute at least a portion of the first conductive type semiconductor layer 21.

[0084] In one embodiment, for the light-emitting element 10a that emits red light, the semiconductor layer may include aluminum gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP), aluminum gallium indium phosphide (AlGaInP), or gallium phosphide (GaP).

[0085] For the light-emitting element 10b that emits green light, the semiconductor layer may include indium gallium nitride (InGaN), gallium nitride (GaN), gallium phosphide (GaP), aluminum gallium indium phosphide (AlGaInP), or aluminum gallium phosphide (AlGaP).

[0086] In one embodiment, for the light-emitting element 10c that emits blue light, the semiconductor layer may include gallium nitride (GaN), indium gallium nitride (InGaN), or zinc selenide (ZnSe).

[0087] The first conductivity type and the second conductivity type are opposite polarities, and when the first conductivity type is n-type, the second conductivity type is p-type, and when the first conductivity type is p-type, the second conductivity type is n-type.

[0088] The first conductivity type semiconductor layer 21, the active layer 23, and the second conductivity type semiconductor layer 25 can be grown on a substrate in a chamber using a known method such as metalorganic chemical vapor deposition (MOCVD). The first conductivity type semiconductor layer 21 includes n-type impurities (e.g., Si, Ge, Sn), and the second conductivity type semiconductor layer 25 includes p-type impurities (e.g., Mg, Sr, Ba). In one embodiment, the first conductivity type semiconductor layer 21 can include GaN or AlGaN including Si as a dopant, and the second conductivity type semiconductor layer 25 can include GaN or AlGaN including Mg as a dopant.

[0089] Although the first conductive type semiconductor layer 21 and the second conductive type semiconductor layer 25 are illustrated as single layers in the drawings, these layers may be multiple layers or may include superlattice layers. The active layer 23 may include a single quantum well structure or a multiple quantum well structure, and the composition ratio of the nitride-based semiconductor is adjusted to emit a desired wavelength. For example, the active layer 23 may emit blue light, green light, red light, or ultraviolet light.

[0090] The second conductivity type semiconductor layer 25 and the active layer 23 may have a mesa M structure and be disposed on the first conductivity type semiconductor layer 21. The mesa M includes the second conductivity type semiconductor layer 25 and the active layer 23, and may also include a portion of the first conductivity type semiconductor layer 21, as shown in FIG. 4B . The mesa M may be located on a partial region of the first conductivity type semiconductor layer 21, and the top surface of the first conductivity type semiconductor layer 21 may be exposed around the mesa M.

[0091] In this embodiment, the mesa M is formed to expose the first conductive type semiconductor layer 21 at its periphery. In another embodiment, a through-hole may be formed that penetrates the mesa M and exposes the first conductive type semiconductor layer 21.

[0092] Meanwhile, the first conductive type semiconductor layer 21 may have a concave-convex pattern 21p formed by surface texturing. The concave-convex pattern 21p may be formed on the light emitting surface side of the first conductive type semiconductor layer 21. The surface texturing may be performed by patterning using, for example, a dry or wet etching process.

[0093] In one embodiment, cone-shaped protrusions may be formed, with the cone height being 2 μm to 3 μm, the spacing between the cones being 1.5 μm to 2 μm, and the diameter of the bottom of the cone being about 3 μm to 5 μm. The cone may also be truncated, in which case the diameter of the top of the cone may be about 2 μm to 3 μm.

[0094] In another embodiment, the uneven pattern 21p may include a first uneven pattern and a second uneven pattern formed on the first uneven pattern. The second uneven pattern may be formed to be finer than the first uneven pattern.

[0095] Forming the uneven pattern 21p on the surface of the first conductive type semiconductor layer 21 can reduce total internal reflection and increase light extraction efficiency. Surface texturing can be performed on the first conductive type semiconductor layers of all of the first light emitting element 10a, the second light emitting element 10b, and the third light emitting element 10c, thereby making the directivity angles of light emitted from the first light emitting element 10a, the second light emitting element 10b, and the third light emitting element 10c uniform. However, the present invention is not limited thereto, and some light emitting elements may have a flat surface without including the uneven pattern 21p.

[0096] At least one of the first conductivity type semiconductor layers 21 of the light emitting elements 10a, 10b, and 10c may have an inclined side surface, as shown in FIG. 4B. The inclined side surface of the first conductivity type semiconductor layer 21 may be formed by an element isolation process. The inclination angle of the side surface of the first conductivity type semiconductor layer 21 may be within a range of about 40 degrees to about 80 degrees with respect to the bottom surface of the first conductivity type semiconductor layer 21. The mesa M may also have an inclined side surface, which may be within a range of about 40 degrees to about 80 degrees with respect to the bottom surface of the mesa M. Since the first conductivity type semiconductor layer 21 and the mesa M have inclined side surfaces, the metal reflective layers 65a and 65b, which will be described later, can be easily formed.

[0097] The ohmic contact layer 27 is disposed on the second conductive type semiconductor layer 25 and makes ohmic contact with the second conductive type semiconductor layer 25. The ohmic contact layer 27 may be formed as a single layer or multiple layers and may be formed of a transparent conductive oxide film or a metal film. Examples of the transparent conductive oxide film include ITO or ZnO, and examples of the metal film include metals such as Al, Ti, Cr, Ni, and Au, and alloys thereof.

[0098] The first contact pad 53 is disposed on the exposed first conductive type semiconductor layer 21. The first contact pad 53 may be in ohmic contact with the first conductive type semiconductor layer 21. For example, the first contact pad 53 may be formed of an ohmic metal layer that is in ohmic contact with the first conductive type semiconductor layer 21. The ohmic metal layer of the first contact pad 53 may be appropriately selected depending on the semiconductor material of the first conductive type semiconductor layer 21. The first contact pad 53 may be omitted.

[0099] The second contact pad 55 may be disposed on the ohmic contact layer 27. The second contact pad 55 is electrically connected to the ohmic contact layer 27. The second contact pad 55 may be omitted.

[0100] The insulating layer 59 covers the mesa M, the ohmic contact layer 27, the first contact pad 53, and the second contact pad 55. The insulating layer 59 has openings 59a and 59b that expose the first contact pad 53 and the second contact pad 55. The insulating layer 59 may include a distributed Bragg reflector formed by stacking insulating layers having different refractive indices. For example, the distributed Bragg reflector may include at least two types of insulating layers selected from SiO2, Si3N4, SiON, TiO2, Ta2O5, Nb2O5, MgF2, etc.

[0101] The distributed Bragg reflector may include, for example, a plurality of pairs of low and high refractive index layers, for example, 10 or more pairs of low and high refractive index layers.

[0102] The distributed Bragg reflector reflects light emitted from the active layer 23. The distributed Bragg reflector can exhibit high reflectivity over a relatively wide wavelength range, including the peak wavelength of light emitted from the active layer 23, and can be designed taking into account the angle of incidence of light. In one embodiment, the distributed Bragg reflector can have a higher reflectivity for light incident at an incident angle of 0 degrees than for light incident at a different incident angle. In another embodiment, the distributed Bragg reflector can have a higher reflectivity for light incident at another specific incident angle than for light incident at an incident angle of 0 degrees. For example, the distributed Bragg reflector can have a higher reflectivity for light incident at an incident angle of 10 degrees than for light incident at an incident angle of 0 degrees.

[0103] On the other hand, the light-emitting structure of the blue light-emitting element 10c has a higher internal quantum efficiency than the light-emitting structures of the red light-emitting element 10a and the green light-emitting element 10b. This allows the blue light-emitting element 10c to exhibit a higher light extraction efficiency than the red light-emitting element 10a and the green light-emitting element 10b. This can make it difficult to maintain an appropriate color mixing ratio of red, green, and blue light.

[0104] In order to adjust the color mixing ratio of red, green, and blue light, the distributed Bragg reflectors applied to the light emitting devices 10a, 10b, and 10c may be formed to have different reflectivities. For example, the blue light emitting device 10c may have a distributed Bragg reflector with a relatively lower reflectivity than the red light emitting device 10a and the green light emitting device 10b. For example, the distributed Bragg reflector formed in the blue light emitting device 10c may have a reflectivity of less than about 95% or even less than 90% for blue light generated in the active layer 23 at an incident angle of 0 degrees. The green light emitting device 10b may have a reflectivity of between about 95% and 99% for green light at an incident angle of 0 degrees. The red light emitting device 10a may have a reflectivity of 99% or more for red light at an incident angle of 0 degrees.

[0105] In one embodiment, the distributed Bragg reflectors applied to the red light-emitting element 10a, the green light-emitting element 10b, and the blue light-emitting element 10c may have approximately similar thicknesses. For example, the difference in thickness between the distributed Bragg reflectors applied to these light-emitting elements 10a, 10b, and 10c may be less than 10% of the thickness of the thickest distributed Bragg reflector. By reducing the difference in thickness between the distributed Bragg reflectors, the process conditions applied to the red light-emitting element 10a, the green light-emitting element 10b, and the blue light-emitting element 10c, such as the process of patterning the insulating layer 59, can be set similarly, further reducing the complexity of the unit pixel manufacturing process. Furthermore, the distributed Bragg reflectors applied to the red light-emitting element 10a, the green light-emitting element 10b, and the blue light-emitting element 10c may have approximately similar numbers of stacked layers. However, the present invention is not limited thereto.

[0106] The first electrode pad 61 and the second electrode pad 63 are disposed on the insulating layer 59. The first electrode pad 61 may extend from the top of the first contact pad 53 to the top of the mesa M, and the second electrode pad 63 may be disposed within the upper region of the mesa M. The first electrode pad 61 may be connected to the first contact pad 53 through the opening 59a, and the second electrode pad 63 may be electrically connected to the second contact pad 55. The first electrode pad 61 may be in direct ohmic contact with the first conductive type semiconductor layer 21, in which case the first contact pad 53 may be omitted. Alternatively, if the second contact pad 55 is omitted, the second electrode pad 63 may be directly connected to the ohmic contact layer 27.

[0107] The first electrode pad 61 and / or the second electrode pad 63 can be formed of a single layer or multi-layer metal. The first electrode pad 61 and / or the second electrode pad 63 can be made of metals such as Al, Ti, Cr, Ni, Au, and alloys thereof.

[0108] On the other hand, when low-refractive-index layers and high-refractive-index layers are alternately formed, the thickness of the insulating layer 59 formed on the side surface of the mesa M and the side surface of the first conductive-type semiconductor layer 21 is smaller than the thickness of the insulating layer 59 formed on the top surface of the second conductive-type semiconductor layer 25. That is, the insulating layer 59 formed on the side surface of the light emitting device 10a is relatively thinner than the insulating layer 59 formed on the top surface. In particular, when the insulating layer 59 includes a distributed Bragg reflector, a distributed Bragg reflector with a well-controlled optical thickness can be formed on the top surface of the light emitting device 10a, but it is difficult to form a distributed Bragg reflector with a well-controlled optical thickness on the side surface of the light emitting device 10a. As a result, the insulating layer 59 formed on the side surface of the light emitting device 10a and the insulating layer 59 formed on the top surface thereof exhibit different reflectivities, which may cause light leakage through the side surface of the light emitting device 10a.

[0109] Light leakage due to the insulating layer 59 at the side surfaces of the light-emitting element 10a can be prevented by using the first metal reflective layer 65a and the second metal reflective layer 65b. The first metal reflective layer 65a and the second metal reflective layer 65b, together with the insulating layer 59, can form an omnidirectional reflector, thereby not only preventing light leakage but also increasing light efficiency in the light-emitting direction. The first metal reflective layer 65a can cover the first electrode pads 61 and the side surfaces of the light-emitting element 10a around the first electrode pads 61. As shown in FIG. 4A , the first metal reflective layer 65a can cover the first electrode pads 61 and further cover the side surfaces of the first conductive type semiconductor layer 21, the active layer 23, and the second conductive type semiconductor layer 25. The second metal reflective layer 65b can cover the second electrode pads 63 and the side surfaces of the light-emitting element 10a around the second electrode pads 63. Furthermore, the first electrode pad 61 may cover a portion of the side surface of the mesa M, particularly a portion of the side surface of the mesa M located between the first electrode pad 61 and the mesa M. As shown in FIG. 4A , the second metal reflective layer 65b may cover the second electrode pad 63 and may cover the side surfaces of the first conductive type semiconductor layer 21, the active layer 23, and the second conductive type semiconductor layer 25.

[0110] The first metal reflective layer 65a and the second metal reflective layer 65b are spaced apart from each other to prevent electrical shorting. The distance between the first metal reflective layer 65a and the second metal reflective layer 65b may be closer than the distance between the first electrode pad 61 and the second electrode pad 63, but is not limited thereto. The first metal reflective layer 65a and the second metal reflective layer 65b may include Cr, Ni, Al, Pt, Ag, or Au.

[0111] Although the light emitting device 10a according to one embodiment of the present disclosure has been briefly described with reference to the drawings, the light emitting device 10a may further include layers having additional functions in addition to the layers described above. For example, various layers may further be included, such as an additional insulating layer for insulating specific components, a solder barrier layer for preventing solder diffusion, etc.

[0112] In addition, in forming the flip-chip type light emitting device, the mesa may be formed in various shapes, and the positions and shapes of the first electrode pad 61 and the second electrode pad 63 may also be changed in various ways. In addition, the ohmic contact layer 27 may be omitted, and the second contact pad 55 or the second electrode pad 63 may be in direct contact with the second conductive type semiconductor layer 25.

[0113] In this embodiment, the first light-emitting element 10a, the second light-emitting element 10b, and the third light-emitting element 10c are described as having a flip-chip structure as an example, but the present invention is not limited to this and may also include light-emitting elements having a horizontal structure.

[0114] FIG. 5A is a schematic plan view illustrating a light emitting device according to still another embodiment.

[0115] Referring to FIG. 5A, the light emitting device according to this embodiment is generally similar to the light emitting device 10a described above, except for the shape of the metal reflective layer 165.

[0116] In this embodiment, the metal reflective layer 165 is disposed in a ring shape along the side surface of the light emitting element and is spaced apart from the first electrode pad 61 and the second electrode pad 63. The metal reflective layer 165 covers the side surfaces of the first conductive type semiconductor layer 21, the active layer 23, and the second conductive type semiconductor layer 25.

[0117] According to this embodiment, the metal reflective layer 165 can cover the entire side surface of the light emitting element, thereby further preventing light leakage from the side surface of the light emitting element. Furthermore, since the metal reflective layer 165 is spaced apart from the first electrode pad 61 and the second electrode pad 63, an electrically stable micro LED can be provided.

[0118] FIG. 5B is a schematic plan view illustrating a light emitting device according to still another embodiment.

[0119] Referring to FIG. 5B, the light emitting device according to this embodiment is generally similar to the light emitting device described with reference to FIG. 5A, except that a metal reflective layer 265 covers the first electrode pad 61.

[0120] 5B, the second electrode pad 63 is surrounded by a white space that separates the second electrode pad 63 from the metal reflective layer 265. The second electrode pad 63 is spaced apart from the metal reflective layer 265 and the first electrode pad 61 that is covered by the metal reflective layer 265.

[0121] The metal reflective layer 265 can cover the side surfaces of the first conductive type semiconductor layer 21, the active layer 23, and the second conductive type semiconductor layer 25 along the side surfaces of the light emitting element, and can further at least partially cover the first electrode pad 61. The metal reflective layer 265 can also cover the side surfaces of the mesa M located between the first electrode pad 61 and the mesa M. This can further prevent light leakage from the light emitting element.

[0122] The metal reflective layer 265 may cover the second electrode pad 63 instead of the first electrode pad 61. However, because the thickness of the first conductive type semiconductor layer 21 is greater than the thicknesses of the active layer 23 and the second conductive type semiconductor layer 25, if a defect such as a pinhole occurs in the insulating layer 59, the metal reflective layer 265 may short-circuit to the first conductive type semiconductor layer 21 on the side of the light emitting device. Therefore, by electrically connecting the metal reflective layer 265 to the first electrode pad 61, an electrically safe light emitting device can be provided.

[0123] 6A and 6B are schematic plan views for explaining a method of forming the first metal reflective layer 65a and the second metal reflective layer 65b.

[0124] First, the light emitting element having the first electrode pad 61 and the second electrode pad 63 formed thereon is arranged on the substrate 11. The substrate 11 may be a growth substrate for growing the first conductive type semiconductor layer 21, the active layer 23, and the second conductive type semiconductor layer 25, or may be a temporary substrate on which the light emitting element having the first electrode pad 61 and the second electrode pad 63 formed thereon is separated from the growth substrate and attached.

[0125] Next, a metal reflective layer 65 is formed to cover the light emitting element. The metal reflective layers 65 can be formed parallel to each other using a lift-off technique.

[0126] The metal reflective layer 65 may be formed as a single layer or multiple layers of a metal material that reflects light, such as Ni, Cr, Pt, Al, Ag, or Au, and may be formed to a thickness of, for example, about 100 nm.

[0127] Referring to Figure 6B, the metal reflective layer 65 around the light-emitting element can then be removed using photo and etching techniques to form a first metal reflective layer 65a and a second metal reflective layer 65b on each light-emitting element.

[0128] According to this embodiment, the first metal reflective layer 65a and the second metal reflective layer 65b can be safely formed on the light emitting elements arranged at close intervals.

[0129] In the above embodiment, it has been described that the metal reflective layers 65a and 65b are formed in a two-step process using both lift-off and etching techniques. However, the metal reflective layers 65a and 65b may be formed in a single process using either lift-off or photolithography and etching techniques.

[0130] Although various embodiments of the present disclosure have been described above, the present disclosure is not limited to these embodiments, and matters and components described in one embodiment may also be applied to other embodiments without departing from the technical spirit of the present disclosure.

Claims

1. 1. A microscale light-emitting device, comprising: a semiconductor 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; an insulating layer covering the top and side surfaces of the semiconductor stack; a metal reflective layer disposed on the insulating layer and covering at least a portion of a side surface of the semiconductor stack; the insulating layer includes a distributed Bragg reflector; the metal reflective layer includes a first metal reflective layer and a second metal reflective layer spaced apart from each other; The first metal reflective layer and the second metal reflective layer each partially cover a side surface of the semiconductor stack.

2. The light-emitting element according to claim 1 , wherein the thickness of the insulating layer covering the top surface of the semiconductor stack is greater than the thickness of the insulating layer covering the side surface of the semiconductor stack.

3. The light-emitting element according to claim 2 , wherein the insulating layer covering the top surface of the semiconductor stack has a reflectance higher than that of the insulating layer covering the side surface of the semiconductor stack.

4. further comprising a first electrode pad and a second electrode pad disposed on the insulating layer and electrically connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively; the first metal reflective layer covers the first electrode pad; The light emitting device according to claim 1 , wherein the second metal reflective layer covers the second electrode pad.

5. The light emitting device of claim 1 , further comprising a first electrode pad and a second electrode pad disposed on the insulating layer and electrically connected to the first conductive type semiconductor layer and the second conductive type semiconductor layer, respectively.

6. The light emitting device of claim 5 , wherein the metal reflective layer is spaced apart from the first electrode pad and the second electrode pad.

7. The light-emitting element according to claim 6 , wherein the metal reflective layer is disposed in a ring shape along a side surface of the light-emitting element.

8. The light emitting device of claim 5 , wherein the metal reflective layer covers the first electrode pad and is spaced apart from the second electrode pad.

9. the semiconductor stack further includes a mesa disposed on the first conductive type semiconductor layer; the mesa includes the active layer and the second conductivity type semiconductor layer; a portion of the first electrode pad is located on the mesa; The light emitting device according to claim 5 , wherein the second electrode pad is located on the mesa.

10. a first contact pad disposed on the first conductive type semiconductor layer adjacent to the mesa; The light emitting device according to claim 9 , wherein the first electrode pad is electrically connected to the first contact pad through an opening in the insulating layer.

11. an ohmic contact layer disposed on the second conductivity type semiconductor layer; and further comprising a second contact pad disposed on the ohmic contact layer; The light emitting device according to claim 5 , wherein the second electrode pad is electrically connected to the second contact pad through an opening in the insulating layer.

12. A transparent substrate; a light-blocking layer disposed on the transparent substrate and having a window for transmitting light; a plurality of light-emitting elements disposed on the light-blocking layer so as to be aligned with the windows; Each of the plurality of light-emitting elements is a semiconductor 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; an insulating layer covering the top and side surfaces of the semiconductor stack; a metal reflective layer disposed on the insulating layer and covering at least a portion of a side surface of the semiconductor stack; the insulating layer includes a distributed Bragg reflector; The metal reflective layer includes a first metal reflective layer and a second metal reflective layer spaced apart from each other.

13. A circuit board; a unit pixel mounted on the circuit board; a molding part covering the unit pixel, The unit pixel includes a transparent substrate and a plurality of light-emitting elements disposed on the transparent substrate; Each of the plurality of light-emitting elements is a semiconductor 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; an insulating layer covering the top and side surfaces of the semiconductor stack; a metal reflective layer disposed on the insulating layer and covering at least a portion of a side surface of the semiconductor stack; the insulating layer includes a distributed Bragg reflector; The display device, wherein the metal reflective layer includes a first metal reflective layer and a second metal reflective layer spaced apart from each other.

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