PIXEL DEVICE AND DISPLAY APPARATUS HAVING THE SAME

A pixel device includes a first light emitting device; a second light emitting device horizontally disposed adjacent to the first light emitting device; a first cover layer covering the first light emitting device and the second light emitting device; and connection layers disposed on the first cover layer and electrically connected to the first and second light emitting devices, wherein the first light emitting device includes a first light emitting structure, and the second light emitting device includes a second light emitting structure and a third light emitting structure, the first light emitting structure emitting light having a longer peak wavelength than peak wavelengths of light emitted from the second and third light emitting structures, the second and third light emitting structures emitting light having different peak wavelengths.

TECHNICAL FIELD

Embodiments of the present disclosure relate to a pixel device and a display apparatus including the same, and more particularly, to a pixel device capable of emitting various colors of light and a display apparatus including the same.

BACKGROUND

Light emitting devices are semiconductor devices that use light emitting diodes as an inorganic light source and are widely used in various fields, such as displays, vehicular lamps, and general lighting. The light emitting diodes have various advantages, such as long lifespan, low power consumption, and fast response, and are rapidly replacing traditional light sources.

Although the light emitting diodes have been generally used as a light source of a backlight unit in a typical display, displays capable of directly implementing images using the light emitting diodes have been developed in recent years. These displays are sometimes referred to as micro-LED displays.

In general, a display apparatus implements a variety of colors using a mixture of blue, green, and red. To implement various images, the display apparatus includes a plurality of pixels, each of which includes blue, green and red subpixels. A color of a certain pixel is determined through colors of these subpixels and an image is implemented through combination of these pixels.

In a micro-LED display, micro-LEDs are arranged corresponding to each subpixel on a plane and a large number of micro-LEDs is mounted on a single substrate. However, since the micro-LEDs are as small as 200 μm or less and even 100 μm or less, it is difficult to transfer all micro-LEDs to a single circuit board. To reduce the number of micro-LEDs, pixel modules with blue, green, and red light emitting devices stacked vertically one above another may be used. However, these pixel modules have a disadvantage of relatively low intensity of red light.

SUMMARY

Problems to be Solved

Embodiments of the present disclosure provide a novel pixel device capable of reducing the number of micro-LEDs mounted thereon without decrease in intensity of red light and a display apparatus including the same.

Embodiments of the present disclosure provide a novel pixel device capable of further increasing the intensity of red light and a display apparatus including the same.

Means for Solving Problems

In accordance with one exemplary embodiment, a pixel device includes: a first light emitting device; a second light emitting device horizontally disposed adjacent to the first light emitting device; a first cover layer covering the first light emitting device and the second light emitting device; and connection layers disposed on the first cover layer and electrically connected to the first and second light emitting devices, wherein the first light emitting device includes a first light emitting structure, and the second light emitting device includes a second light emitting structure and a third light emitting structure, the first light emitting structure emitting light having a longer peak wavelength than peak wavelengths of light emitted from the second and third light emitting structures, the second and third light emitting structures emitting light having different peak wavelengths.

The first light emitting structure may include an arsenide or phosphide-based semiconductor layer and the second and third light emitting structures may include a nitride-based semiconductor layer.

The second light emitting structure and the third light emitting structure may be stacked in a vertical direction.

The pixel device may further include a bonding layer bonding the second light emitting structure to the third light emitting structure.

Each of the second light emitting structure and the third light emitting structure may include a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer, the first conductivity type semiconductor layers of the second and third light emitting structures may be electrically connected to each other, and the second conductivity type semiconductor layers of the second and third light emitting structures may be electrically insulated from one another.

The second light emitting device may include an electrode pad electrically connecting the first conductivity type semiconductor layers of the second and third light emitting structures to each other and one of the connection layers may be electrically connected to the electrode pad.

The second light emitting device may include electrode pads electrically connected to the first conductivity type semiconductor layers of the second and third light emitting structures, respectively, and one of the connection layers may be connected to the electrode pads to electrically connect the electrode pads to each other.

The third light emitting structure may be disposed on the second light emitting structure and may emit light having a shorter wavelength than the second light emitting structure.

The pixel device may further include a substrate, the first and second light emitting devices may be disposed on the substrate, and an upper surface of the substrate facing the first and second light emitting devices may include a roughness pattern.

Lower surfaces of the first and second light emitting devices facing the substrate may have a roughness pattern.

The pixel device may further include a second cover layer covering the first cover layer and the connection layers, and the second cover layer may be disposed to partially expose the connection layers.

The second cover layer may be formed of the same material as the first cover layer.

The first and second cover layers may be formed of polyimide.

The second cover layer may partially cover edges of the connection layers.

The first light emitting device may further include a sub-light emitting structure in addition to the first light emitting structure, and the sub-light emitting structure may emit light having a longer peak wavelength than light emitted from the second and third light emitting structures.

The first light emitting structure may be bonded to the sub-light emitting structure via a tunnel layer.

The first light emitting structure and the sub-light emitting structure may emit the same color of light.

In accordance with another exemplary embodiment, a display apparatus includes: a circuit substrate; and a pixel device disposed on the circuit substrate, wherein the pixel device may be the pixel device described above.

In accordance with one exemplary embodiment, a light emitting diode may include: a first light emitting stack, a second light emitting stack disposed on the first light emitting stack, a third light emitting stack disposed the second light emitting stack, and a bonding layer bonding the first light emitting stack to the second light emitting stack. At least some fraction of light emitted from the second light emitting stack may be emitted through a region of the bonding layer formed on a side surface of the first light emitting stack and an upper surface of the second light emitting stack. In addition, the first light emitting stack may include a region at least partially not overlapping the third light emitting stack and may at least partially overlap the second light emitting stack in top view of the first light emitting stack. In addition, the first light emitting stack may be disposed at an outer periphery to surround the second light emitting stack and the third light emitting stack, and the second light emitting stack and the third light emitting stack may be disposed to pass through a center of the light emitting diode.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the following embodiments are provided for complete disclosure and thorough understanding of the present disclosure by those skilled in the art. Therefore, the present disclosure is not limited to the following embodiments and may be embodied in different ways. In addition, the drawings may be exaggerated in width, length, and thickness of components for descriptive convenience and clarity only. When an element is referred to as being “on” or “under” another element, it may be directly on or under the other element or intervening elements or layers may be present. Like components will be denoted by like reference numerals throughout the specification.

FIG.1Ais a schematic plan view of a display apparatus according to an exemplary embodiment, andFIG.1B,FIG.1CandFIG.1Dare schematic perspective views of various display apparatuses1000a,1000b,1000c,1000d,1000eaccording to exemplary embodiments.

Referring toFIG.1A, the display apparatus10000may include a panel substrate2100and multiple pixel modules1000.

The display apparatus10000may include a smart watch1000a, a wearable display apparatus1000b, such as a VR headset or glasses, an AR display apparatus1000c, such as augmented reality glasses, or indoor or outdoor display apparatuses1000d,1000e, such as micro-LED TVs and sign boards, without being limited thereto. The panel substrate2100and the multiple pixel modules1000may be disposed inside the display apparatus.

The panel substrate2100may be formed of various materials, such as polyimide (PI), FR4, glass, and the like, and may include circuits for passive matrix driving or active matrix driving. In one exemplary embodiment, the panel substrate2100may include interconnections and resistors therein. In another exemplary embodiment, the panel substrate2100may include interconnections, transistors, capacitors, and the like. The panel substrate2100may include pads for electrical connection to circuits on an upper surface thereof.

The multiple light emitting modules1000may be arranged on the panel substrate2100. The light emitting modules1000may be arranged at certain intervals or may be arranged to contact each other. A distance between the light emitting modules1000may be set in consideration of a space between pixel devices100described below. For example, a distance between two adjacent pixel devices100disposed in adjacent light emitting modules1000may be substantially the same as the distance between the pixel devices100in one light emitting module1000. However, it should be understood that other implementations are possible. Next, the pixel device100will be described in detail with reference toFIG.2AtoFIG.2C.

FIG.2Ais a schematic plan view of a pixel device according to an exemplary embodiment,FIG.2Bis a cross-sectional view taken along line A-A′ ofFIG.2A, andFIG.2Cis a cross-sectional view taken along line B-B′ ofFIG.2A.

Referring toFIG.2A,FIG.2BandFIG.2C, the pixel device100may include a first light emitting device10R, a second light emitting device10GB, and connection layers129a,129b,129c,129d. In certain exemplary embodiments, the pixel device100may further include a transparent substrate121, a surface layer122, a light blocking layer123, a bonding layer125, a first cover layer127, or a second cover layer131.

The pixel device100provides a single pixel including first and second light emitting devices10R,10GB to implement various colors. The first and second light emitting devices10R,10GB will be described below in detail with reference toFIG.3A,FIG.3B,FIG.4A, andFIG.4B.

The transparent substrate121is a light-transmissive substrate, such as PET, a glass substrate, quartz, a sapphire substrate, and the like. The transparent substrate121is disposed on a light emission surface of a light emitting module1000and light emitted from light emitting devices10R,10GB is discharged through the transparent substrate121. The transparent substrate121may have an upper surface and a lower surface. The transparent substrate121may include a roughness pattern121pformed on a surface thereof facing the light emitting devices10R,10GB, that is, on the upper surface thereof. The roughness pattern121pincreases the beam angle by scattering light emitted from the light emitting devices10R,10GB. In addition, the roughness pattern121pmay allow light emitted from the light emitting devices10R,10GB having different beam angles to be emitted at a uniform beam angle. As a result, the roughness patterns can prevent color differences from occurring depending on viewing angle.

The roughness pattern121pmay be regular or irregular. For example, the roughness pattern121pmay have a pitch of 3 μm, a diameter of 2.8 μm, and a height of 1.8 μm. The roughness pattern121pmay be a typical pattern applied to a patterned sapphire substrate, without being limited thereto.

The transparent substrate121may further include an anti-reflective coating or an anti-glare layer, or may be subjected to anti-glare treatment. The transparent substrate121may have a thickness of, for example, 50 μm to 300 μm. The thickness of the transparent substrate121may be greater than a thickness of each of the light emitting devices10R,10GB.

Since the transparent substrate121is disposed on the light emission surface, the transparent substrate121does not include a circuit. However, it should be understood that other implementations are possible. Alternatively, the transparent substrate121may include a circuit. On the other hand, although a single pixel device100is formed on the transparent substrate121, multiple pixel devices100may be formed on a single transparent substrate121.

The surface layer122may cover the roughness pattern121on the transparent substrate121. The surface layer122may be formed corresponding to the shape of the roughness pattern121p. The surface layer122may enhance bonding strength of the light blocking layer123formed thereon. For example, the surface layer122may be formed of silicon oxide. The surface layer122may be omitted depending on the kind of transparent substrate121.

The light blocking layer123is formed on the upper surface of the transparent substrate121. The light blocking layer123may adjoin the surface layer122. The light blocking layer123may include a light absorbing material, such as carbon black. The light absorbing material prevents light generated from the light emitting devices10R,10GB from leaking laterally from a region between the transparent substrate121and the light emitting devices10R,10GB and improves contrast of the display apparatus.

The light blocking layer123may have windows123a,123b,123cfor light traveling paths along which light generated by the light emitting devices10R,10GB enters the transparent substrate121. To this end, the light blocking layer123may be patterned to expose the transparent substrate121. The windows123a,123b,123cmay have a greater width than the light emitting device, without being limited thereto. Alternatively, the windows may have the same width as or a smaller width than the light emitting device.

The window123aof the light blocking layer123may define alignment positions of the light emitting devices10R,10GB. Accordingly, it is possible to omit separate alignment markers for defining the alignment positions of the light emitting devices10R,10GB. However, it should be understood that other implementations are possible and the alignment markers for defining the alignment positions of the light emitting devices10R,10GB may be disposed on the transparent substrate121, the light blocking layer123or the bonding layer125. The light blocking layer123may be omitted.

The bonding layer125is attached to the upper surface of the transparent substrate121. The bonding layer125is disposed between the upper surface of the transparent substrate121having the roughness pattern121pand the light emitting devices10R,10GB. The bonding layer125may cover the light blocking layer123. The bonding layer125may be attached to an overall surface of the transparent substrate121, without being limited thereto. Alternatively, the bonding layer125may be attached to some region of the transparent substrate121so as to expose a region near a periphery of the transparent substrate121. The bonding layer125serves to attach the light emitting devices10R,10GB to the transparent substrate121. The window123aof the light blocking layer123may be filled with the bonding layer125.

The bonding layer125may be formed of a light transmitting material and transmits light emitted from the light emitting devices10R,10GB. The bonding layer125may be formed of an organic bonding agent. For example, the bonding layer125may be formed of a transparent epoxy. In addition, the bonding layer125may contain a light diffusive material, such as SiO2, TiO2, ZnO, and the like, in order to spread light. The light diffusive material prevents the light emitting devices10R,10GB from being observed on the light emission surface.

As shown inFIG.2BandFIG.2C, the bonding layer125may partially cover side surfaces of the light emitting devices10R,10GB. That is, some region of the light emitting devices10R,10GB may be buried in the bonding layer125, thereby preventing separation of the light emitting devices10R,10GB from the pixel device while preventing moisture from entering a space at an interface between the bonding layer125and the light emitting devices10R,10GB. On the other hand, the bonding layer125may cover the roughness pattern121pand thus may include regions having different thicknesses. A region of the bonding layer125having a greater thickness than other regions thereof enhances bonding strength of the bonding layer125. The light emitting devices10R,10GB can be detached from the pixel device due to heat generated from the light emitting devices10R,10GB upon operation of the light emitting devices. As the bonding layer125has both a thick region and a thin region, the bonding layer125can absorb shrinkage and expansion due to heat from the light emitting devices10R,10GB, thereby preventing separation of the light emitting devices from the pixel device.

The first and second light emitting devices10R,10GB are disposed on the transparent substrate121. The first and second light emitting devices10R,10GB may be attached to the transparent substrate121by the bonding layer125. The first and second light emitting devices10R,10GB may be disposed corresponding to the windows123aof the light blocking layer123. When the light blocking layer123is omitted, alignment markers may be added to provide the alignment positions of the light emitting devices10R,10GB.

The first and second light emitting devices10R,10GB may share a single transparent substrate121. The first and second light emitting devices10R,10GB may be disposed adjacent to each other. The first light emitting device10R may be disposed in a first region of the pixel device100and the second light emitting device10GB may be disposed in a second region of the pixel device100. The first light emitting device10R may include a first light emitting structure emitting light having the longest peak wavelength in the pixel device100and the second light emitting device10GB include second and third light emitting structures emitting light having shorter peak wavelengths than the first light emitting device10R. The second and third light emitting structures may emit light having different peak wavelengths.

The first and second light emitting devices10R,10GB may be arranged side by side, as shown inFIG.2A. The first light emitting structure may have a greater thickness than each of the second and third light emitting structures. In addition, a first plane of the first light emitting structure disposed in the first region may face first planes of the second and third light emitting structures disposed in the second region. A vertical height of the first plane of the first light emitting structure may be smaller than the total vertical height of the first planes of the second and third light emitting structures. Further, light emitted from the first region may have a different peak wavelength than light emitted from the second region. Further, the light emitted from the first region may have different color coordinates than the light emitted from the second region, and white light may be generated by simultaneously applying electric current to the first and second regions. The second light emitting structure may include an upper surface facing the light transmitting substrate and a lower surface opposite the upper surface thereof. The third light emitting structure is formed on the lower surface of the second light emitting structure. The second light emitting structure and the third light emitting structure may at least partially overlap each other, thereby enabling minimization of the pixel device.

For example, the first light emitting structure of the first light emitting device10R may have the narrowest energy band-gap and may emit red light. The second light emitting structure of the second light emitting device10GB may have a wider energy band-gap than the first light emitting structure and may emit green light. The third light emitting structure of the second light emitting device10GB may have a wider energy band-gap than the second light emitting structure and may emit blue light. Since the first light emitting device10R emitting red light does not overlap the light emitting structures emitting light having different peak wavelengths, red light can be discharged without any light loss that can occur while passing through the other light emitting structures, thereby improving emission efficiency of red light.

The first light emitting device10R will be described in detail with reference toFIG.3AandFIG.3Band the second light emitting device10GB will be described in detail with reference toFIG.4AandFIG.4B.

The first cover layer127covers the first and second light emitting devices10R,10GB. The first cover layer127has openings127hthat expose electrode pads of the light emitting devices10R,10GB. The first cover layer127assists in stable formation of the connection layers129a,129b,129c,129dthrough adjustment in height of a plane on which the connection layers129a,129b,129c,129dare formed. The first cover layer127may be formed of a material, for example, polyimide, epoxy molding compounds, silicone, and the like. The first cover layer127may include a light reflective material or a light absorbing material. The first cover layer127covering the first and second light emitting devices10R,10GB may have a lower surface contacting the bonding layer125, whereby the light emitting devices10R,10GB are buried in the bonding layer125and the first cover layer127, thereby preventing deformation, such as bending and the like, of the light emitting devices10R,10GB and damage thereto in the course of moving and mounting the pixel device100.

The first cover layer127may be disposed in a region surrounded by the periphery of the bonding layer125, without being limited thereto. For example, the first cover layer127may be formed to expose a portion of the periphery of the bonding layer125.

The first to fourth connection layers129a,129b,129c,129dare formed on the first cover layer127. The first to fourth connection layers129a,129b,129c,129dmay contact the electrode pads61a,61b,161a,161b,161cof the first and second light emitting devices10R,10GB through the openings127hof the first cover layer127. The first to fourth connection layers129a,129b,129c,129dare electrically connected to the first and second light emitting devices10R,10GB and extend to the outside of the first and second regions in which the first and second light emitting devices10R,10GB are disposed.

In one exemplary embodiment, as shown inFIG.2AandFIG.2B, the first connection layer129amay be electrically connected to a second conductivity type semiconductor layer of the first light emitting structure of the first light emitting device10R; the second connection layer129bmay be electrically connected to the second conductivity type semiconductor layer of the second light emitting structure of the second light emitting device10GB; the third connection layer129cmay be electrically connected to the second conductivity type semiconductor layer of the third light emitting structure of the second light emitting device10GB; and the fourth connection layer129dmay be commonly electrically connected to a first conductivity type semiconductor layers of the first and second light emitting devices10R,10GB. In another exemplary embodiment; the first connection layer129amay be electrically connected to the first conductivity type semiconductor layer of the first light emitting structure of the first light emitting device10R; the second connection layer129bmay be electrically connected to the first conductivity type semiconductor layer of the second light emitting structure of the second light emitting device10GB; the third connection layer129cmay be electrically connected to the first conductivity type semiconductor layer of the third light emitting structure of the second light emitting device10GB; and the fourth connection layer129dmay be commonly electrically connected to the second conductivity type semiconductor layers of the first and second light emitting devices10R,10GB. The first to fourth connection layers129a,129b,129c,129dmay be formed on the first cover layer127and may include, for example, Au.

The second cover layer131may have a thinner thickness than the first cover layer127. The sum of the thicknesses of the second cover layer131and the first cover layer127may range from 1 μm to 50 μm, without being limited thereto.

The second cover layer131may cover a side surface of the first cover layer127and the connection layers129a,129b,129c,129d. In addition, the second cover layer131may cover a portion of the bonding layer125. The second cover layer131may include openings131a,131b,131c,131dthat expose the connection layers129a,129b,129c,129d, whereby pad regions of the pixel device100can be defined. The pad regions may be placed near corners of the pixel device100, respectively, and may be symmetrical with respect to a central line of the pixel device100. The pad regions may be formed outside upper regions of the first and second light emitting devices10R,10GB so as not to overlap the first and second light emitting devices10R,10GB in the vertical direction. However, it should be understood that other implementations are possible.

A length of an edge of at least one of the pad regions may be 25% or less of a length of at least one edge of the pixel device100. The edges of the connection layers129a,129b,129c,129dmay be covered by the second cover layer131and the pad regions may be covered by pads or a bonding material on the circuit substrate.

In one exemplary embodiment, the second cover layer131may be formed of a translucent organic or inorganic material. The second cover layer131may be formed of the same material as the first cover layer127. This structure can minimize formation of an interface inside the pixel device100to prevent generation of air gaps due to heat generated upon operation of the pixel device. For example, both the first cover layer127and the second cover layer131may be formed of polyimide. In this case, lower, side and upper surfaces of the connection layers129a,129b,129c,129dexcluding the pad regions may be surrounded by polyimide.

The pixel device100may be mounted on the circuit substrate by a bonding material, such as solders and the like. The bonding material bonds the connection layers129a,129b,129c,129d, which are exposed through the openings131a,131b,131c,131dof the second cover layer131, to the pads on the circuit substrate.

According to this embodiment, the pixel device100does not include separate bumps and uses the connection layers129a,129b,129c,129das bonding pads, without being limited thereto. Alternatively, the pixel device100may further include bonding pads that cover the openings131a,131b,131c,131dof the second cover layer131. In one exemplary embodiment, the bonding pads may be formed to partially cover the light emitting devices10R,10GB outside upper regions of the first to fourth connection layers129a,129b,129c,129d.

Referring again toFIG.2A, one side surface of the pixel device100may have a length W1of 300 μm or less and the pixel device100may have an area of 300 μm×300 μm or less. One side surface of each of the first light emitting device10R and the second light emitting device10GB may have a length W2of 100 μm or less and each of the first and second light emitting devices10R,10GB may have an area of 100 μm×100 μm or less, 50 μm×50 μm or less, or 10 μm×10 μm or less. On the other hand, one side surface of the openings of the second cover layer131may have a length of W3or 70 μm or less. In one exemplary embodiment, W1, W2and W3may be set to satisfy a relation: W1>W2>W3. When W3is set to the smallest value, the length W1of the pixel device100can be minimized. In addition, when W2is less than W3, with pixel devices100disposed adjacent each other, a distance between the first region of one pixel device and the second region of another pixel device adjacent to the one pixel device increases, thereby making it difficult to increase pixel density. When W2is greater than W3, the distance between adjacent pixel devices100can be reduced.

Although the light emitting devices10R,10GB are illustrated as being attached to the transparent substrate121by the bonding layer125in this embodiment, the light emitting devices10R,10GB may be coupled to the transparent substrate121by other couplers instead of the bonding layer125. For example, the light emitting devices10R,10GB may be coupled to the transparent substrate121by spacers, whereby regions between the light emitting devices10R,10GB and the transparent substrate121may be filled with a gas or liquid. By the gas or the liquid, an optical layer allowing transmission of light emitted from the light emitting devices10R,10GB may be formed. The bonding layer125described above is one example of the optical layer. Here, the optical layer is formed of a different material, for example, a gas, a liquid, or a solid, from the material of the light emitting devices10R,10GB. Accordingly, the material of the optical layer is distinguished from the materials of the semiconductor layers in the light emitting devices10R,10GB.

In this embodiment, the first region and the second region may have a square shape. However, it should be understood that other implementations are possible. Alternatively, the first region and the second region may have a rectangular shape. In this embodiment, the long sides of the first and second regions may be placed side by side so as to face each other. When multiple light emitting structures are stacked in the first region or in the second region, the multiple light emitting structures may have different sizes. Preferably, a light emitting structure disposed near the transparent substrate121has a greater size than other light emitting structures.

According to this embodiment, the pixel device100includes the light emitting devices10R,10GB arranged on the same plane. The pixel device100may realize various colors of light using the light emitting devices10R,10GB. Hereinafter, the light emitting devices10R,10GB according to one exemplary embodiment will be described in detail.

FIG.3Ais a schematic plan view of the light emitting device10R according to an exemplary embodiment andFIG.3Bis a cross-sectional view taken along line C-C′ ofFIG.3A.

Referring toFIG.3AandFIG.3B, the light emitting device10R may include a first light emitting structure, which includes a first conductivity type semiconductor layer21, an active layer23and a second conductivity type semiconductor layer25, an ohmic contact layer27, a first contact pad53a, a second contact pad53b, an insulating layer59, a first electrode pad61a, and a second electrode pad61b.

The first light emitting structure, that is, the first conductivity type semiconductor layer21, the active layer23and the second conductivity type semiconductor layer25, may be grown on the substrate. The substrate may be selected from various substrates, such as a gallium nitride substrate, a GaAs substrate, a Si substrate, a sapphire substrate, and the like, particularly, a patterned sapphire substrate, which can be used for growth of semiconductor layers. The growth substrate may be separated from the semiconductor layers using techniques such as mechanical polishing, laser lift-off, chemical lift-off, and the like. The substrate may be, for example, a GaAs substrate, and may be removed from the first conductivity type semiconductor layer21by chemical etching technology.

In one exemplary embodiment, the first light emitting structure may include aluminum gallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP), aluminum gallium indium phosphide (AlGaInP), or gallium phosphide (GaP), and may emit red light.

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

The first conductivity type semiconductor layer21, the active layer23and the second conductivity type semiconductor layer25may be grown on the substrate in a chamber by a method known in the art, such as metal organic chemical vapor deposition (MOCVD). In addition, the first conductivity type semiconductor layer21includes n-type dopants (for example, Si, Ge, and Sn) and the second conductivity type semiconductor layer25includes p-type dopants (for example, Mg, Sr, and Ba).

Although each of the first conductivity type semiconductor layer21and the second conductivity type semiconductor layer25is shown as a single layer, these layers may be composed of multiple layers and may include super-lattice layers. The active layer23may include a single quantum well structure or a multi-quantum well structure and may have a semiconductor composition to emit light in a target wavelength. For example, the active layer23may emit red light.

The second conductivity type semiconductor layer25and the active layer23may have a mesa structure and may be disposed on the first conductivity type semiconductor layer21. The mesa may include the second conductivity type semiconductor layer25and the active layer23, and may include a portion of the first conductivity type semiconductor layer21, as shown inFIG.3B. The mesa may be placed in some region on the first conductivity type semiconductor layer21and an upper surface of the first conductivity type semiconductor layer21may be exposed around the mesa.

In this embodiment, the mesa may be formed to expose the first conductivity type semiconductor layer21therearound. In another exemplary embodiment, a through-hole may be form in the mesa to expose the first conductivity type semiconductor layer21.

On the other hand, the first conductivity type semiconductor layer21may have a roughness pattern21pformed through surface texturing. The roughness pattern21pmay be formed on a light emission surface of the first conductivity type semiconductor layer21. Surface texturing may be performed by patterning using, for example, dry etching or wet etching.

In one exemplary embodiment, cone-shaped protrusions may be formed at an interval of 1.5 μm to 2 μm thereon and may have a height of 2 μm to 3 μm and a bottom diameter of about 3 μm to about 5 μm. The cones may have a frustoconical shape, which may have a diameter of about 2 μm to 3 μm on an upper surface thereof.

In another exemplary embodiment, the roughness pattern21pmay include a first roughness pattern and a second roughness pattern formed on the first roughness pattern. The second roughness pattern may have a finer size than the first roughness pattern. With the structure that the roughness pattern21pis formed on the surface of the first conductivity type semiconductor layer21, the light emitting device can improve light extraction efficiency through reduction in internal total reflection.

The ohmic contact layer27is disposed on the second conductivity type semiconductor layer25to form ohmic contact with the second conductivity type semiconductor layer25. The ohmic contact layer27may be composed of a single layer or multiple layers and may be a transparent conductive layer or a metal layer. The transparent conductive layer may be formed of, for example, ITO, ZnO, or the like, and the metal layer may be formed of, for example, a metal, such as Al, Ti, Cr, Ni, Au, and the like, and alloys thereof.

The first contact pad53ais disposed in an exposed region on the first conductivity type semiconductor layer21. The first contact pad53amay form ohmic contact with the first conductivity type semiconductor layer21. For example, the first contact pad53amay be an ohmic metal layer forming ohmic contact with the first conductivity type semiconductor layer21. The ohmic contact layer of the first contact pad53amay be suitably selected depending on the semiconductor material of the first conductivity type semiconductor layer21. The first contact pad53amay be omitted.

The second contact pad53bmay be disposed on the ohmic contact layer27. The second contact pad53bmay be electrically connected to the ohmic contact layer27. The second contact pad53bmay be omitted.

The insulating layer59may cover the mesa, the ohmic contact layer27, the first contact pad53a, and the second contact pad53b. The insulating layer59has openings59a,59bthat expose the first contact pad53aand the second contact pad53b. The insulating layer59may be composed of a single layer or multiple layers. Furthermore, the insulating layer59may include a distributed Bragg reflector in which insulating layers having different indexes of refraction are stacked one above another. For example, the distributed Bragg reflector may include at least two types of insulating layers selected from among SiO2, Si3N4, SiON, TiO2, Ta2O5, and Nb2O5.

The distributed Bragg reflector reflects light emitted from the active layer23. The distributed Bragg reflector may exhibit high reflectance over a relatively wide wavelength range including the peak wavelength of light emitted from the active layer23and may be designed in consideration of incidence angle of light. In one exemplary embodiment, the distributed Bragg reflector may exhibit higher reflectance with respect to light incident thereon at an incidence angle of 0 degrees than light incident at other incidence angles. In another exemplary embodiment, the distributed Bragg reflector may exhibit higher reflectance with respect to light incident at other incidence angles than light incident thereon at an incidence angle of 0 degrees. For example, the distributed Bragg reflector may exhibit higher reflectance with respect to light incident at an incidence angle of 10 degrees than light incident thereon at an incidence angle of 0 degrees.

The first electrode pad61aand the second electrode pad61bare disposed on the insulating layer59. The first electrode pad61amay extend from the top of the first contact pad53ato the top of the mesa and the second electrode pad61bmay be disposed in an upper region of the mesa. The first electrode pad61amay be electrically connected to the first contact pad53athrough the opening59aand the second electrode pad61bmay be electrically connected to the second contact pad53b. The first electrode pad61amay form direct ohmic contact with the first conductivity type semiconductor layer21. In this case, the first contact pad53amay be omitted. When the second contact pad53bis omitted, the second electrode pad61bmay be directly connected to the ohmic contact layer27.

The first and/or second electrode pads61a,61bmay be composed of a single metal layer or multiple metal layers. The first and/or second electrode pads61a,61bmay be formed of a metal, such as Al, Ti, Cr, Ni, Au, and the like, and alloys thereof.

Although the light emitting device10R according to the exemplary embodiment is briefly described above with reference to the drawings, the light emitting device10R may further include other functional layers. For example, the light emitting device may further include a reflective layer, an additional insulating layer for insulation of a particular component, an anti-solder layer for preventing diffusion of solders, and the like.

Further, in formation of a flip-chip type light emitting device, the mesa may be formed in various shapes and the positions or shapes of the first and second electrode pads61a,61bmay be changed in various ways. Further, the ohmic contact layer27may be omitted and the second contact pad53bor the second electrode pad61bmay directly contact the second conductivity type semiconductor layer25.

Although the first light emitting device10R is illustrated by way of example as having the flip-chip structure in this embodiment, it should be understood that other implementations are possible. Alternatively, the first light emitting device10R may be a horizontal type light emitting device.

FIG.4Ais a schematic plan view of a second light emitting device10GB according to an exemplary embodiment andFIG.3Bis a cross-sectional view taken along line D-D′ ofFIG.4A.

Referring toFIG.4AandFIG.4B, the second light emitting device10GB includes a second light emitting structure including a first conductivity type semiconductor layer31, an active layer33and a second conductivity type semiconductor layer35, and a third light emitting structure including a first conductivity type semiconductor layer41, an active layer43and a second conductivity type semiconductor layer45. The second light emitting device10GB may include ohmic contact layers37,47, first contact pads153a,155a, second contact pads153b,155b, electrode pads161a,161b,161c, a bonding layer34, and an insulating layer159.

Light generated from the active layer33of the second light emitting structure and the active layer43of the third light emitting structure is discharged through the first conductivity type semiconductor layer31of the second light emitting structure. In general, the active layer43of the third light emitting structure may emit light having a longer peak wavelength than the active layer33of the second light emitting structure. For example, the third light emitting structure may emit green light and the second light emitting structure may blue light. In some embodiments, in order to adjust relative intensity of light emitted from the second light emitting structure and the third light emitting structure, the second light emitting structure may emit light having a longer wavelength than the third light emitting structure. For example, the second light emitting structure may emit green light and the third light emitting structure may emit blue light. With this structure, the second light emitting device can reduce the intensity of light emitted from the third light emitting structure while increasing the intensity of light emitted from the second light emitting structure.

Semiconductor layers in the second and third light emitting structures may be selected to emit light having target peak wavelengths. The first conductivity type semiconductor layers31,41and the second conductivity type semiconductor layers33,43may be composed of a single layer or multiple layers, and the active layers33,43may have a single quantum well structure or a multi-quantum well structure. For a light emitting structure emitting green light, the semiconductor layers may include indium gallium nitride (InGaN), gallium nitride (GaN), gallium phosphide (GaP), aluminum gallium indium phosphide (AlGaInP), or aluminum gallium phosphide (AlGaP), and for a light-emitting structure emitting blue light, the semiconductor layers may include gallium nitride (GaN), indium gallium nitride (InGaN), or zinc selenide (ZnSe).

The ohmic contact layer37is disposed on the second conductivity type semiconductor layer35to form ohmic contact with the second conductivity type semiconductor layer35. The ohmic contact layer37may be composed of a single layer or multiple layers and may be a transparent conductive layer or a metal layer. The transparent conductive layer may be formed of, for example, ITO, ZnO, or the like, and the metal layer may be formed of, for example, a metal, such as Al, Ti, Cr, Ni, Au, and the like, and alloys thereof. The ohmic contact layer37may be formed of a light transmitting material that transmits light generated from the third light emitting structure.

The ohmic contact layer47is disposed on the second conductivity type semiconductor layer45to form ohmic contact with the second conductivity type semiconductor layer45. The ohmic contact layer47may be composed of a single layer or multiple layers and may be a transparent conductive layer or a metal layer. The transparent conductive layer may be formed of, for example, ITO, ZnO, or the like, and the metal layer may be formed of, for example, a metal, such as Al, Ti, Cr, Ni, Au, and the like, and alloys thereof.

The bonding layer34may bond the second light emitting structure to the third light emitting structure. The bonding layer34may include an optically clear adhesive (OCA), for example, epoxy, polyimide, SU8, spin-on-glass (SOG), and benzocyclobutene (BCB), without being limited thereto.

The first contact pads153a,155amay be disposed on the first conductivity type semiconductor layers31,41to form ohmic contact therewith, respectively. The first conductivity type semiconductor layer31may be partially exposed and the first contact pad153amay be formed in an exposed region on the first conductivity type semiconductor layer31. In addition, the first conductivity type semiconductor layer41may be partially exposed and the first contact pad155amay be formed in an exposed region on the first conductivity type semiconductor layer41.

The second contact pads153b,155bare electrically connected to the second conductivity type semiconductor layers33,43, respectively. The second contact pads153b,155bmay be formed on the ohmic contact layers37,47, respectively.

The insulating layer159may cover the second light emitting structure and the third light emitting structure, and may also cover the ohmic contact layers37,47, the first contact pads153a,155aand the second contact pads153b,155b. The insulating layer159may cover a side surface of the first conductivity type semiconductor layer31. The insulating layer159may have openings159a,159b,159c,159dthat expose the first contact pads153a,155aand the second contact pads153b,155bto allow electrical connection thereto.

The electrode pads161a,161b,161care formed on the insulating layer159and may be electrically connected to the first contact pads153a,155aand the second contact pads153b,155b. The electrode pad161amay electrically connect the first contact pad153ato the first contact pad155a. Accordingly, the first conductivity type semiconductor layer31may be electrically connected to the first conductivity type semiconductor layer41. The electrode pad161bmay be electrically connected to the second contact pad153band the electrode pad161cmay be electrically connected to the second contact pad155b. The electrode pads161a,161b,161care electrically insulated from one another. On the other hand, as shown inFIG.2A, the fourth connection layer129dmay be connected to the electrode pad161ato be commonly electrically connected to the first conductivity type semiconductor layers31,41of the second light emitting device10GB.

In this embodiment, the third light emitting structure may have a smaller area than the second light emitting structure. However, it should be understood that other implementations are possible. For example, electrical connection may be achieved through contact holes that expose the first conductivity type semiconductor layer31, the ohmic contact layer37, and the first conductivity type semiconductor layer41. In this example, the second light emitting structure may have the same external area as the third light emitting structure.

The second light emitting device10GB may be formed at the wafer level using wafer bonding technology. After separation of the first conductivity type semiconductor layer31from the growth substrate, a roughness31pmay be formed on an exposed surface of the first conductivity type semiconductor layer31, and the beam angle of light emitted from the second light emitting structure and the third light emitting structure may be adjusted using the roughness31p. Furthermore, light extraction efficiency can be improved using light scattering by the roughness31p.

According to this embodiment, the first light emitting device10R emitting red light may be disposed independently of the second light emitting device10GB emitting green light and blue light, thereby improving the intensity of red light. Furthermore, with the second light emitting device10GB having the stack structure of the second light emitting structure and the third light emitting structure, the pixel device100can be minimized while enabling further simplification of a process of mounting the light emitting devices.

As shown inFIG.1, the pixel device100is disposed on a circuit substrate1001to be mounted on the panel substrate2100. Multiple pixel devices100are disposed on the circuit substrate1001to form light emitting modules1000. Since pixels are disposed on the panel substrate2100by forming the light emitting modules1000, a defective light emitting module1000can be repaired or replaced after identifying poor pixels within each of the light emitting modules1000. Since only the defective light emitting module can be repaired or replaced, the display apparatus does not need to be entirely repaired or discarded, thereby reducing costs associated with defects.

Although the light emitting modules1000are illustrated as being mounted on the panel substrate2100in this embodiment, the light emitting modules1000may be mounted on a cabinet and multiple cabinets each having the light emitting modules1000mounted thereon may be mounted on the panel substrate2100.

FIG.5is a schematic cross-sectional view of a second light emitting device according to another exemplary embodiment andFIG.6is a schematic cross-sectional view of a pixel device according to another exemplary embodiment.

Referring toFIG.5, the second light emitting device according to this embodiment is generally similar to the second light emitting device10GB described with reference toFIG.4AandFIG.4Band is distinguished therefrom in that electrode pads161a′,161a″ are disposed on the first contact pads153a,155a, respectively. Since the electrode pads161a′,161a″ are disposed on the first contact pads153a,155a, the first contact pads153a,155aare not required to be disposed adjacent each other, thereby increasing process tolerance.

Referring toFIG.6, the connection layer129dmay be electrically connected to all of the electrode pads161a′,161a″ through the openings127hof the first cover layer127. As a result, the electrode pads161a′,161a″ may be electrically connected to each other. Thus, the first conductivity type semiconductor layers31,41are electrically connected to each other.

FIG.7is a schematic cross-sectional view of a first light emitting device10R′ according to another exemplary embodiment andFIG.8is a schematic cross-sectional view of a pixel device according to another exemplary embodiment.

Referring toFIG.7, the first light emitting device10R′ according to this embodiment is generally similar to the first light emitting device10R described with reference toFIG.3AandFIG.3Band is distinguished therefrom in that the first light emitting device10R′ includes multiple active layers23a,23b. That is, the first light emitting device10R′ may include a first light emitting structure including an active layer23aand a sub-light emitting structure including an active layer23b. The active layer23bof the sub-light emitting structure may emit light having a longer wavelength than the second light emitting structure and the third light emitting structure. The active layers23a,23bmay be formed of the semiconductor materials described with reference toFIG.3AandFIG.3B. The first light emitting structure and the sub-light emitting structure may be coupled to each other through a tunnel layer and may operate together. Accordingly, for example, when the active layers23a,23bemit light having the same or similar peak wavelengths, the intensity of light emitted from the first light emitting device10R′ can be increased. As shown inFIG.8, the first light emitting device10R′ may be mounted on the pixel device instead of the first light emitting device10R. The connection layer129amay be electrically connected to the second conductivity type semiconductor layer25of the sub-light emitting structure and the first conductivity type semiconductor layer21may be electrically connected to the connection layer129d, as shown inFIG.2C.

FIG.9is a schematic plan view of a pixel device according to a further exemplary embodiment.

Referring toFIG.9, the pixel device according to this embodiment is generally similar to the pixel device100described with reference toFIG.2A,FIG.2B, andFIG.2and is distinguished therefrom in that a second cover layer131′ covers the first cover layer127and the connection layers129a,129b,129c,129d. As shown inFIG.9, the second cover layer131′ exposes a central region of the pixel device while exposing corner regions thereof in the longitudinal direction and the transverse direction. In particular, the second cover layer131′ does not cover regions of the connection layer near the peripheries of the pixel device. Accordingly, the area of the exposed regions of the upper surfaces of the connection layers, that is, the area of pad regions, can be increased. That is, a length W3′ of the pad regions may be greater than the length W3of the pad region of the pixel device shown inFIG.2A. Accordingly, it is possible to secure sufficient pad regions while achieving minimization of the pixel device.

FIG.10Ashows a light emitting device according to an exemplary embodiment, which is disposed on a first substrate S. Referring toFIG.10A, the light emitting device according to the exemplary embodiment includes a first light emitting stack210, a second light emitting stack220disposed under the first light emitting stack210, and a third light emitting stack230disposed under the second light emitting stack220. The first light emitting stack210includes a first conductivity type semiconductor layer211, an active layer212, and a second conductivity type semiconductor layer213. The second light emitting stack220includes a first conductivity type semiconductor layer221, an active layer222, and a second conductivity type semiconductor layer223. The third light emitting stack230includes a first conductivity type semiconductor layer231, an active layer232, and a second conductivity type semiconductor layer233. In addition, the active layers212,222,232of the light emitting stacks210,220,230may emit light having different peak wavelengths. For example, a process of bonding the light emitting stacks formed on a wafer to each other in a stack structure and dicing the light emitting stacks into individual chips may be performed at the same time, thereby enabling reduction in process time through elimination of a process of individually dicing the light emitting stacks.

The first light emitting stack210may emit light having the highest peak wavelength. Preferably, the first light emitting stack210emits red light. The first light emitting stack210may include at least one selected from among InGaN, InAlGaN, GaN, AlGaN, AlGaAs, GaAsP, AlGaInP, and GaP, without being limited thereto. However, it should be understood that any material capable of emitting red light may be used.

The second light emitting stack220may emit light having a shorter peak wavelength than the first light emitting stack210. Preferably, the second light emitting stack220emits green light. The second light emitting stack220may include at least one selected from among GaN, InGaN, AlGaN, InGaN, GaP, AlGaInP, and AlGaP, without being limited thereto.

The third light emitting stack230may emit light having the shortest peak wavelength. The third light emitting stack230may emit blue light. For example, the third light emitting stack230may include semiconductor materials, such as GaN, InGaN, ZnSe, and the like, which emit blue light, without being limited thereto. It should be understood that the colors of light emitted from the semiconductor layer stacks are not limited thereto and various combinations of semiconductor layer stacks may be used.

The third light emitting stack230is disposed on the first substrate S. The first substrate S may be a substrate, for example, a sapphire substrate, which allows epitaxial growth of the third light emitting stack230, for example, a stack of semiconductor layers emitting blue light. However, the substrate according to the present disclosure is not limited to the sapphire substrate and may include various transparent insulating materials. For example, the first substrate S may include glass, quartz, silicone, an organic polymer, or an organic-inorganic complex material, and may be, for example, silicon carbide (SiC), gallium nitride (GaN), indium gallium nitride (InGaN), aluminum gallium nitride (AlGaN), aluminum nitride (AlN), gallium oxide (Ga2O3), or a silicone substrate.

Although not shown in the drawings, the first substrate S may have a roughness on an upper surface thereof, and may be, for example, a patterned sapphire substrate. The roughness formed on the upper surface of the first substrate S can improve efficiency in extraction of light generated from the third light emitting stack230adjoining the first substrate S. In another exemplary embodiment, the first substrate S may be removed.

FIG.10Bis a view of the first light emitting stack210before the first light emitting stack210is bonded to the second light emitting stack220and the third light emitting stack230. According to the exemplary embodiment, among the multiple light emitting stacks, the first light emitting stack210emits light having the longest wavelength and may be, for example, semiconductor layers emitting red light. Accordingly, the second substrate G may be a growth substrate formed of a different material than the first substrate S. For example, the second substrate G may be a GaAs substrate, without being limited thereto.

In addition, before the second and third light emitting stacks220,230are bonded to each other, lower contact layers242,243may be disposed on the second semiconductor layers223,233of the second light emitting stack220and the third light emitting stack230.

A second bonding layer252may be interposed between the lower contact layers242,243to bond the second light emitting stack220to the third light emitting stack230. The second bonding layer252may include a non-conductive material that transmits light. For example, the second bonding layer252may include an optically clear adhesive (OCA), more specifically epoxy, polyimide, SU8, spin-on-glass (SOG), and benzocyclobutene (BCB), without being limited thereto.

In addition, although not shown in the drawings, a bonding reinforcement layer may be further interposed between the second light emitting stack220and the second bonding layer252. For example, the bonding reinforcement layer may be disposed between the second bonding layer252and the second lower contact layer242to bond the second bonding layer252to the second lower contact layer242. The bonding reinforcement layer can prevent the second light emitting stack220from being peeled off of the second bonding layer252in a process entailing rapid change in stress, such as a laser lift-off process and the like, while preventing breakage of the second light emitting stack. The bonding reinforcement layer may be formed of, for example, a silicon oxide layer, without being limited thereto.

For the same reasons, the bonding reinforcement layer may be further interposed between the second bonding layer252and the third light emitting stack230, more specifically between the second bonding layer252and the third lower contact layer243. In addition, the bonding reinforcement layer may have a smaller thickness than the second and third lower contact layers242,243. For example, the bonding reinforcement layer may have a thickness of about 100 nm.

Further, a roughness R may be formed on the upper surface of the first conductivity type semiconductor layer221of the second light emitting stack220. The roughness R may have various shapes and sizes. For example, the roughness R may be formed by pattering in various shapes, for example, a wave shape, an embossed shape, a zigzag shape, and the like. By forming the roughness R on the first conductivity type semiconductor layer221, it is possible to reduce probability of reflection of light into the first conductivity type semiconductor layer due to total reflection of light upon emission of light to the outside. Accordingly, the roughness can improve luminous efficacy by allowing efficient extraction of light from the semiconductor layer. However, the roughness R is not necessary and the upper surface of the first conductivity type semiconductor layer221may have a flat surface.

The growth substrate G of the first light emitting stack210, that is, the second substrate G, is removed and, like the second bonding layer252, a first bonding layer251is disposed under the first lower contact layer241of the first light emitting stack220to bond the first light emitting stack210to the second and third light emitting stacks220,230. As the second substrate G is removed, the first conductivity type semiconductor layer211of the first light emitting stack210disposed under the second substrate G may be exposed. A roughness R′ may be formed in an exposed region on the first conductivity type semiconductor layer211. The roughness R′ may have various shapes and sizes. For example, the roughness R′ may be formed by pattering in various shapes, for example, a wave shape, an embossed shape, a zigzag shape, and the like, and may have a regular shape or an irregular shape.

Referring again toFIG.10A, by forming the roughnesses R, R′ on the first conductivity type semiconductor layer211of the first light emitting stack210and on the first conductivity type semiconductor layer221of the second light emitting stack220, it is possible to reduce the probability of reflection of light into the first conductivity type semiconductor layer due to total reflection of light upon emission of light to the outside. Accordingly, the roughnesses can improve luminous efficacy by allowing efficient emission of light from the semiconductor layers.

Referring toFIG.11A, the first light emitting stack210may be partially removed by etching and the like. As the first light emitting stack210is partially removed, the first lower contact layer241may be exposed through a removed region of the first light emitting stack210. However, it should be understood that the present disclosure is not limited to removal of only the first light emitting stack210and the first lower contact layer241may also be removed together with the first bonding layer251disposed under the first lower contact layer241. A removed region of the first light emitting stack210may be a central region of the first light emitting stack210, without being limited thereto. Alternatively, the removed region of the first light emitting stack210may be placed at one side to adjust viewing angle or luminous intensity.

Although not shown in the drawings, a roughness may be formed on the exposed surface of the first lower contact layer241. The roughness may have various shapes and sizes. For example, the roughness may be formed by pattering in various shapes, for example, a wave shape, an embossed shape, a zigzag shape, and the like, and may have a regular shape or an irregular shape. By forming the roughness on the exposed surface of the first lower contact layer, it is possible to improve luminous efficacy through efficient extraction of light.

The first lower contact layer241may include a transparent conductive material allowing transmission of light. The lower contact layer is disposed on one surface of each of the first, second and third light emitting stacks210,220,230. For example, the first, second and third lower contact layers241,242,243may include a transparent conductive oxide, for example, SnO, InO2, ZnO, ITO, ITZO, and the like, without being limited thereto. Alternatively, the lower contact layer may be optionally omitted. Further, the first lower contact layer241may have a thinner thickness than the second and third lower contact layers242,243. For example, the first lower contact layer241may have a thickness of about 240 nm and the second and third lower contact layers242,243may have a thickness of about 300 nm. Further, each of the lower contact layers may optionally include a roughness to improve light extraction efficiency.

Referring toFIG.11B, as an insulating layer, a reflective layer214may be formed in at least some region on a side surface of the first light emitting stack210and may include a light reflective material. For example, the reflective layer214may include various organic or inorganic insulating materials, such as SiO2, SiNx, Al2O3, TiO2, and the like, and may include a distributed Bragg reflector (DBR). For example, the reflective layer214may have a single layer structure or a multilayer structure in which two or more insulating layers having different indexes of refraction are formed. The materials for the reflective layer are not limited thereto and any insulating material capable of reflecting light may be used as the materials for the reflective layer. In other words, the reflective layer214can improve luminous efficacy by reflecting light, which is emitted from the first light emitting stack210and travels in a lateral direction, such that the light can be extracted in a light emission direction, that is, in an upward direction, instead of spreading in the lateral direction.

Although not shown in the drawings, the side surface of the first light emitting stack210may be a slanted surface inclined at a predetermined angle. By forming the slanted side surface of the first light emitting stack210to which the reflective layer214is applied, the reflective layer214can be deposited without generation of cracks, thereby improving reliability and product characteristics.

Referring toFIG.12andFIG.13, a third bonding layer253may be disposed to fill a space formed by partial removal of the first light emitting stack210, in other words, a lower space of the second light emitting stack220and the third light emitting stack230while covering the side surface and the upper surface of the first light emitting stack210. The third bonding layer253can bond a third substrate S′ to the upper surface of the first light emitting stack210, whereby the third substrate S′ can be disposed at the uppermost portion in the light emission direction. Further, the third bonding layer253may allow a post-process to be performed after removal of the first substrate S from the third light emitting stack230.

In addition, the third bonding layer253may be formed of a light transmitting material to allow light emitted from the first, second and third light emitting stacks210,220,230to be emitted towards the third substrate S′. Further, the third bonding layer253may exhibit bonding properties to bond the first light emitting stack210to the third substrate S′ while exhibiting insulating properties. The first and second bonding layers251,252also have such properties and thus the third bonding layer253may be formed of the same material as the first and second bonding layers251,252. However, it should be understood that other implementations are possible and the first, second and third bonding layers251,252,253may be formed of different materials.

A region of the third bonding layer253overlapping the first light emitting stack210may have a different thickness from a region of the third bonding layer253not overlapping the first light emitting stack210. Preferably, the region of the third bonding layer253overlapping the first light emitting stack210may have a thinner thickness and the region of the third bonding layer253not overlapping the first light emitting stack210may have a thicker thickness. Accordingly, since light generated from the first light emitting stack210can be effectively emitted through the third bonding layer253while being blocked in some region of the third bonding layer253having a thicker thickness, the third bonding layer253can prevent light emitted from the second and third light emitting stacks220,230from entering and being interfered and absorbed by the first light emitting stack210.

FIG.14AandFIG.15are views obtained by rotatingFIG.13by 180 degrees such that, among the first, second and third light emitting stacks210,220,230, the first light emitting stack210is placed under the second and third light emitting stacks220,230, that is, such that the third substrate S′ corresponding to the light emission direction is placed at the lowermost side and the third light emitting stack230is placed at the uppermost side. Accordingly, referring toFIG.14AandFIG.15, the light emission direction corresponds to a downward direction, that is, a direction of the third substrate S′. Further, first to fourth electrode pads271,272,273,274may be formed through etching of the first, second and third light emitting stacks210,220,230, deposition and the like to supply electricity to a stack type light emitting diode, that is, to the first, second and third light emitting stacks210,220,230.

Further, as the second and third light emitting stacks220,230are subjected to etching, the first lower contact layer241disposed on at least part of the first light emitting stack210, more specifically on one surface of the first light emitting stack210, may be exposed.

Further, in top plan view of the stack type light emitting diode, the first light emitting stack210may be disposed so as not to overlap the second and third light emitting stacks220,230. In other words, the first light emitting stack210may include a region not overlapping the second and third light emitting stacks220,230. That is, at least some fraction of light emitted from the second light emitting stack220or the third light emitting stack230may be discharged outside without passing through the first light emitting stack210. In other words, light generated from the second light emitting stack220may be discharged after passing through the side surface of the side surface of the first light emitting stack210and a region of the third bonding layer253disposed on the second light emitting stack220. Thus, as the first light emitting stack210is disposed so as not to overlap the third light emitting stack230, a traveling path along which light emitted from the light emitting stacks is discharged outside, that is, the number of light emitting stacks through which light passes, can be efficiently reduced to improve light extraction efficiency. Further, a light emitting area can be maximized by using the area of the stack type light emitting diode as much as possible, thereby improving luminous efficacy.

Further, in top plan view of the stack type light emitting diode, the second light emitting stack220and the third light emitting stack230may be disposed to overlap each other in at least some regions thereof.

Although not shown in the drawings, in top plan view of a stack type light emitting diode according to another exemplary view, the first light emitting stack210may partially overlap the second light emitting stack220depending upon the degree of etching the second and third light emitting stacks220,230. In a further exemplary embodiment, the first, second and third light emitting stacks210,220,230may be disposed to overlap each other in at least some regions thereof or may be disposed so as not to overlap each other in at least some regions thereof.

The first light emitting stack210may at least partially overlap the second light emitting stack in a region near an outer periphery thereof. Accordingly, an overlapping region can be minimized to secure effective light extraction.

FIG.14Bis a plan view obtained fromFIG.14AandFIG.15. That is,FIG.14Ais a cross-sectional view taken along line E-E′ ofFIG.14BandFIG.15is a cross-sectional view taken along line F-F′ ofFIG.14B.

Referring toFIG.14B, in one exemplary embodiment, at least some region of the first light emitting stack210may be exposed instead of overlapping the second and third light emitting stacks220,230in plan view. The first light emitting stack210may be disposed in an outer peripheral region of the light emitting diode, in which the first, second and third light emitting stacks210,220,230are stacked one above another, and may be removed in the central region thereof, as described above, to expose at least some regions of the second light emitting stack220and the third light emitting stack230. In other words, the first light emitting stack210may be disposed in the outer peripheral region to surround the second light emitting stack220and the third light emitting stack230and the second light emitting stack220and the third light emitting stack230may be placed closer to the central region than the first light emitting stack210, when viewed in top plan view. More specifically, the first light emitting stack210may be disposed so as not to pass through the central region of the stack type light emitting diode and the second and third light emitting stacks220,230may be disposed to pass through the central region of the stack type light emitting diode. Accordingly, the area of the first light emitting stack210can be secured as large as possible while minimizing an area where light emitted from the first light emitting stack210passes through other light emitting stacks, thereby improving luminous efficacy.

According to an exemplary embodiment, the area occupied by the first light emitting stack210, that is, the area of the outer peripheral region of the stack type light emitting diode, may be larger than the area occupied by the second light emitting stack220and the third light emitting stack230, that is, the area of the central region of the stack type light emitting diode. In other words, a light emitting stack having a relatively low intensity of light, for example, the first light emitting stack210having lower intensity of light than the second and third light emitting stacks220,230, may be formed to have the largest light emitting area, whereby the intensity of light can be efficiently adjusted through reduction in difference between quantities of light emitted from the first, second and third light emitting stacks210,220,230so as to improve luminous efficacy as much as possible.

For example, a full color display device may be implemented by stacking light emitting diodes that emit red, green and blue colors to display a trichromatic pixel. Here, a light emitting stack having an insufficient intensity of light is provided as the first light emitting stack210to maximize the light emitting area, thereby improving the intensity of light. As such, the stack type light emitting diode according to this exemplary embodiment allows efficient adjustment in intensity of light through reduction in difference in intensity of light between the red, green and blue light emitting stacks, thereby improving luminous efficacy and product quality.

Although not shown in the drawings, according to another exemplary embodiment, the area occupied by the first light emitting stack210, that is, the area of the outer peripheral region of the stack type light emitting diode, may be smaller than the area occupied by the second light emitting stack220and the third light emitting stack230. In this exemplary embodiment, the intensity of light emitted from the second light emitting stack220and the third light emitting stack230may be lower than the intensity of light emitted from the first light emitting stack210. In other words, when the first light emitting stack210provides the highest intensity of light, the first light emitting stack210may be disposed in the outer peripheral region with the smallest area to minimize a difference between the intensities of light emitted from the first, second and third light emitting stacks210,220,230, thereby effectively improving luminous efficacy. However, it should be understood that other implementations are possible and the area of the outer peripheral area of the light emitting diode may be similar to the area of the central region thereof. For example, when the first, second and third light emitting stacks210,220,230emit a similar intensity of light, the light emitting stacks may be formed to have a similar light emitting area.

Referring again toFIG.5B, the central region of the stack type light emitting diode, that is, the shape of the second and third light emitting stack220,230, is not limited to a particular shape, and may have various partially angled shapes, that is, polygonal shapes, for example, a rectangular shape, a triangular shape, a hexagonal shape, an octagonal shape, a rhombus shape, and the like, or various partially curved shapes, for example, a circular shape, an elliptical shape, and the like.

Referring again toFIG.11A, according to another exemplary embodiment, the second light emitting stack220may also be removed together with the first light emitting stack210upon removal of a portion or the central region of the first light emitting stack210. The second light emitting stack220may also be removed to expose the second lower contact layer242in some region or the central region of the first light emitting stack210. Further, the third bonding layer253may be disposed to cover some region or central region of the first light emitting stack210, that is, a space formed by removing the first and second light emitting stacks210,220, and the side surfaces of the first and second light emitting stacks210,220while covering the upper surface of the first light emitting stack210to bond the third substrate S′ to the first light emitting stack210.

In addition, when the light emitting structure is rotated by 180 degrees after the first substrate S is removed, the third light emitting stack230may be placed at an upper side. The second lower contact layer242disposed on at least part of the second light emitting stack220, more specifically on one surface of the second light emitting stack220, may be exposed at the outer periphery of the stacked semiconductor layers through etching of the first, second and third light emitting stacks210,220,230, deposition, and the like. As a result, the third light emitting stack230is disposed at the uppermost side of the central region of the stack type light emitting diode, and the second light emitting stack220and the first light emitting stack210may be sequentially stacked in the outer peripheral region surrounding the third light emitting stack230.

Further, in top plan view of the stack type light emitting diode, the third light emitting stack230may be disposed to have at least some region not overlapping the first light emitting stack210. Since the third light emitting stack230is disposed to have at least some region not overlapping the first light emitting stack210, the traveling path along which light emitted from the light emitting stacks is discharged outside, that is, the number of light emitting stacks through which light passes, can be efficiently reduced while minimizing the probability that light is lost inside the semiconductor layers, thereby efficiently improving light extraction efficiency.

Further, the first light emitting stack210and the second light emitting stack220may be disposed to overlap each other in at least some regions thereof when viewed in plan view. Further, the first, second and third light emitting stacks210,220,230may be disposed to overlap each other in at least some regions thereof or may be disposed so as not to overlap each other in at least some regions thereof.

Further, in top plan view of the stack type light emitting diode, the area occupied by the third light emitting stack230may be smaller or larger than the area occupied by the first and second light emitting stacks210,220. In other words, the outer peripheral region of the stack type light emitting diode may have a smaller or larger area than the central region thereof. Here, the stack type light emitting diode can improve luminous efficacy by selectively maximizing the light emitting area of a light emitting stack having insufficient intensity of light among the first, second and third light emitting stacks210,220,230. Further, the shape of the third light emitting stack230, that is, the shape of the central region of the stack type light emitting diode, may have various shapes without being limited to a particular shape.

Referring toFIG.16AtoFIG.17, in the course of stacking and electrically connecting the first, second and third light emitting stacks210,220,230, the side surfaces of the first, second and third light emitting stacks210,220,230may be formed in a stepped shape. Although not shown in the drawings, the stepped side surfaces of the first, second and third light emitting stacks210,220,230may include various shapes. For example, the side surfaces of the first, second and third light emitting stacks210,220,230may include slanted side surfaces inclined at a predetermined angle. By forming the slanted side surfaces of the first, second and third light emitting stacks210,220,230, the first to fourth electrode pads271,272,273,274and first and second insulating layers261,262can be deposited on the side surfaces of the light emitting stacks without generation of cracks, thereby improving reliability and product characteristics.

The first and second insulating layers261,262may be disposed to insulate the side surfaces of the first, second and third light emitting stacks210,220,230and the first, second and third lower contact layers241,242,243from the first to fourth electrode pads271,272,273,274and to insulate the first to fourth electrode pads271,272,273,274from the first to fourth connection electrodes271,272,273,274.

Further, at least one of the first and second insulating layers261,262may include a reflective material. For example, the insulating layers may include various organic or inorganic materials, such as SiO2, SiNx, Al2O3, TiO2, and the like, and at least one of the insulating layers may include a distributed Bragg reflector (DBR). For example, the insulating layers may have a single layer structure or a multilayer structure composed of at least two insulating layers having different indexes of refraction, without being limited thereto. It should be understood that the first and second insulating layers may be formed of any material capable of improving luminous efficacy through emission of light in the direction of the third substrate S′.

FIG.16Bis a plan view obtained fromFIG.16AandFIG.17. That is,FIG.16Ais a cross-sectional view taken along line E-E′ ofFIG.16BandFIG.17is a cross-sectional view taken along line F-F′ ofFIG.16B. Referring toFIG.16B, which is a plan view taken in an electrode bonding direction instead of the light emission direction, that is, the direction of the third substrate S′, the first, second and third light emitting stacks210,220,230may be electrically connected to the outside by the connection electrodes291,292,293,294and bonding metal layers291′,292′,293′,294′. Here, the first electrode pad271is a P-electrode pad of the first light emitting stack210, the second electrode pad272is a P-electrode pad of the second light emitting stack220, and the third electrode pad273is a P-electrode pad of the third light emitting stack230. In addition, the fourth electrode pad274is a common N-electrode pad connected to the first, second and third light emitting stacks210,220,230. However, it should be understood that other implementations are possible. Alternatively, the first electrode pad271may be an N-electrode pad of the first light emitting stack210, the second electrode pad272may be an N-electrode pad of the second light emitting stack220, the third electrode pad273may be an N-electrode pad of the third light emitting stack230, and the fourth electrode pad274may be a common P-electrode pad connected to the first, second and third light emitting stacks210,220,230.

Further, the pixel device may further include a protective layer100that fills spaces between the first to fourth connection electrodes291,292,293,294while covering side surfaces of the first to fourth connection electrodes291,292,293,294. The protective layer100may be formed of an insulating material that insulates the first to fourth connection electrodes291,292,293,294from one another. In addition, the protective layer100may include a material, which does not absorb light and can reflect light, to improve light extraction efficiency by reflecting light in the direction of the third substrate S′ corresponding to the light emission direction.

Although not shown in the drawings, according to an exemplary embodiment, the pixel device may further include a contact electrode on the first conductivity type semiconductor layer231of the third light emitting stack230. The contact electrode may form ohmic contact with the first conductivity type semiconductor layer231. A portion of the first conductivity type semiconductor layer231may be recessed by patterning and the contact electrode may be disposed in a recessed region of the first conductivity type semiconductor layer231to improve ohmic contact efficiency. The contact electrode may have a single layer structure or a multilayer structure, and may include Al, Ti, Cr, Ni, Au, Ag, Sn, W, Cu, or alloys thereof, for example, Au—Te alloys or Au—Ge alloys, without being limited thereto. In addition, for example, the contact electrode may have a thickness of about 100 nm and may include a meal having high reflectance in order to improve an effect of emitting light in a downward direction towards the third substrate S′ corresponding to the light emission direction. In other words, a metal reflective layer having high reflectance may be disposed on the first conductivity type semiconductor layer231of the third light emitting stack230disposed at the lowermost side in the light emission direction. Accordingly, the metal reflective layer can improve light extraction efficiency through effective discharge of light by reflecting light, which travels towards the first conductivity type semiconductor layer231of the third light emitting stack230, towards the third substrate S′, that is, in the light emission direction.

FIG.18is a schematic cross-sectional view of a pixel device according to yet another exemplary embodiment andFIG.19is a schematic plan view showing relative positions of some components shown inFIG.18. Descriptions of the same components as the above embodiments will be omitted.

Referring toFIG.18andFIG.19, the pixel device includes a first light emitting structure310, a second light emitting structure320disposed under the first light emitting structure310, a third light emitting structure330disposed horizontally side-by-side to the first light emitting structure310, and a first molding layer410disposed on the third light emitting structure330.

The first light emitting structure310and the third light emitting structure330may have substantially coplanar upper surfaces and may be disposed to have a height difference of 50 μm or less between the upper surfaces thereof. Accordingly, it is possible to prevent generation of deviation in viewing angle due to the height difference when observed from outside. The first light emitting structure310and the third light emitting structure330may be grown on the same growth substrate and may be disposed on a single substrate. The growth substrate may be removed or may remain to allow light generated from the first to third light emitting structures310,320,330to be discharged outside through the growth substrate.

The first light emitting structure310includes a first conductivity type semiconductor layer311, a second conductivity type semiconductor layer312, and an active layer313; the second light emitting structure320includes a first conductivity type semiconductor layer321, a second conductivity type semiconductor layer322, and an active layer323; and the third light emitting structure330includes a first conductivity type semiconductor layer331, a second conductivity type semiconductor layer332, and an active layer333. The first conductivity type semiconductor layer311may include a light spreading surface having a roughness to improve visibility by scattering light incident on the light emitting structure while enabling effective extraction of light generated from the active layer323.

A second molding layer420may be disposed on the first light emitting structure310and the first molding layer410may be formed to substantially the same height as the second molding layer420. A height difference between the first molding layer410and the second molding layer420may be 50 μm or less. Accordingly, it is possible to prevent generation of deviation in viewing angle due to the height difference when observed from outside.

The first molding layer410may include a wavelength conversion material. That is, light emitted from the third light emitting structure330may excite the wavelength conversion material while passing through the first molding layer410. Light subjected to wavelength conversion by the first molding layer410may have a narrow peak wavelength with a full width at half maximum (FWHM) of 50 nm or less, preferably 20 nm or less.

As such, the light having emitted from the first molding layer410has a peak wavelength with a narrow full width at half maximum (FWHM), thereby realizing high color clarity. The wavelength conversion material may include phosphors and/or quantum dots. The wavelength conversion material may be distributed in a transparent resin. The wavelength conversion material may have a circular shape, an elongated bar shape or an amorphous shape.

The wavelength conversion material may be garnet-based phosphors represented by (A, B, C)8-xO12:Ce. Here, A may include at least one element selected from among Y, Lu, Tb, Gd, La, and Sm. C may include at least one element selected from among Al, Si, Ga, and In. B may be one of the elements of A or the elements of B. Alternatively, B may be the same element as A or B. When B is one of the elements of C, the sum of moles of B and C may be greater than 5 and less than 7. When B is one of the elements of A, the sum of moles of A and B may be greater than 1 and less than 5. X may be greater than 0.001 and less than or equal to 0.5.

The phosphors may include at least one type of phosphor selected from among garnet-based phosphors, silicate-based phosphors, sulfide-based phosphors, oxynitride-based phosphors, nitride-based phosphors, and aluminate-based phosphors. For example, the garnets-based phosphors may be represented by A3B5O12:C. Here, A may include at least one element selected from among Y, Lu, Tb, and Gd. B may include at least one element selected from among Al, Ga, Si, and In. In addition, C may include at least one element selected from among Ce, Nd, Er, and Th. The sulfide-based phosphors may include red phosphors of (Ca,Sr)S:Eu. The nitride-based phosphors may include red phosphors of CaAlSiN3:Eu, red phosphors of (Sr,Ca)AlSiN3:Eu, red phosphors of Sr2Si5N8:Eu, and the like.

The phosphors may include fluoride phosphors. The fluoride phosphors may include phosphors represented by A2SiF6:Mn. Here, A may be an alkali metal element including at least potassium. For example, The fluoride phosphors may include red phosphors of K2SiF6:Mn.

In addition, the phosphors may include manganese-containing fluoride phosphors of A2[M1-aMnaF6]. Here, A may be at least one element selected from the group consisting of K, Li, Na, Rb, Cs and NH4. M may be at least one element selected from the group consisting of group IV elements and group XIV elements. a may satisfy a relation: 0<a<0.2.

The manganese-containing fluoride phosphors (hereinafter referred to as KSF phosphors) are prepared by doping tetravalent manganese ions and may emit red light having a wavelength of about 630 nm. In addition, the manganese-containing fluoride phosphors may emit colors at two peak wavelengths, thereby providing an advantage of high color reproducibility.

Further, the manganese-containing fluoride phosphors may include red phosphors represented by (A4-aBa)m/2+n/2X2m[MX4O2]nbased on an oxiodohalide host lattice. Here, A may be selected from the group consisting of hydrogen (H), deuterium (D), or mixtures thereof. B may be selected from the group consisting of Li, Na, K, Rb, Cs, NH4, ND4, NR4or mixtures thereof. R may be an alkyl or aryl radical. X may be selected from the group consisting of F, Cl or mixtures thereof. M may be selected from the group consisting of Cr, Mo, W, Re or mixtures thereof. a, m and n satisfy relations: 0≤a≤4, 0<m≤10, and 1≤n≤10.

When the wavelength conversion material includes quantum dots, the first molding layer410may be provided in any form of a sheet and a resin. When the quantum dots include group II-VI compounds, the quantum dots may include Cd and Se. In addition, when the quantum dots include group III-V compounds, the quantum dots may include In and P.

The quantum dots may include a core comprising group II-VI compounds or group III-V compounds and a protective layer surrounding the core to protect the core. Here, the protective layer may include a shell and a ligand. The protective layer may include Zn, S, and the like.

The quantum dots may generate light from the cores thereof. As the size of the quantum dots decreases, the band gap of the quantum dots increases, thereby enabling emission of light having a short wavelength. In addition, as the size of the quantum dots increases, the band gap of the quantum dots decreases, thereby enabling emission of light having a long wavelength. That is, the wavelength of light emitted from the quantum dots may be shortened with decreasing size of the quantum dots and may be increased with increasing size of the quantum dots. As such, the wavelength of light emitted from the quantum dots may be determined depending on the size of the cores or the size of the quantum dots. For example, the quantum dots or the cores may have a diameter of about 10 nm or less, preferably about 2 nm to 5 nm.

In order to reduce the full width of the peak wavelength of light having passed through the first molding layer410, a band pass filter may be disposed on the first molding layer410.

Unlike the first molding layer410, the second molding layer420may transmit light emitted from the first or second light emitting structure310or320without wavelength conversion of the light.

The first light emitting structure310and the third light emitting structure330may emit the same color-based light, and the second light emitting structure320may emit different color-based light than the first light emitting structure310. Here, although the first light emitting structure310and the third light emitting structure330emit the same color-based light, the first light emitting structure310and the third light emitting structure330may emit light having different peak wavelengths. A difference between the peak wavelengths of light generated from the first light emitting structure310and the third light emitting structure330may be less than 5 nm. The peak wavelength of light generated from the second light emitting structure320may be longer than the peak wavelength of light generated from the first light emitting structure310by 50 nm to 150 nm.

The peak wavelength of light generated from the first light emitting structure310may have a first full width at half maximum(FWHM) F1in the range of 10 nm to 25 nm. The peak wavelength of light generated from the second light emitting structure320may have a second FWHM F2in the range of 20 nm to 40 nm. The peak wavelength of light generated from the third light emitting structure330may have a third FWHM F3in the range of 10 nm to 25 nm, and the peak wavelength of light generated from the first molding layer410may have a fourth FWHM F4in the range of 3 nm to 50 nm. The first FWHM F1may be smaller than the second FWHM F2. The third FWHM F3may be smaller than the second FWHM F2.

The fourth FWHM F4may be smaller than the second FWHM F2. Preferably, the first to fourth full half widths at half maximum have a relation: fourth FWHM F4<first FWHM F1<second FWHM F2. Alternatively, the first to fourth full half widths at half maximum may have a relation: fourth FWHM F4<third FWHM F3<second FWHM F2. As a result, a clearer display can be implemented.

By way of example, both the first light emitting structure310and the third light emitting structure330may have a peak wavelength in the range of 430 nm to 470 nm and may emit blue-based light. The second light emitting structure320may have a peak wavelength in the range of 520 nm to 580 nm and may emit green-based light. Further, light emitted from the third light emitting structure330may be converted into red-based light having a peak wavelength in the range of 600 nm to 680 nm by the first molding layer410before the light is discharged outside.

In general, a chip emitting red-based light has lower efficiency than a chip emitting blue or green-based light. Accordingly, in order to adjust a light ratio of red, green and blue light, a greater quantity of electric current is supplied to the chip emitting red-based light whereby a large quantity of heat is generated from the chip emitting red-based light, thereby making it difficult to control the chips due to increase in deviation of electric current between the chips.

According to this embodiment, the third light emitting structure330emits blue-based light and the first molding layer410performs wavelength conversion of light emitted from the third light emitting structure330into red-based light, thereby securing better efficiency than the structure in which the third light emitting structure330emits red-based light.

In addition, although stacking of multiple chips in the vertical direction has an advantage in minimization of a light emitting device as compared with stacking of the multiple chips in the horizontal direction, there is a problem in that light emitted from a lower chip is absorbed by an upper chip.

According to this embodiment, the first light emitting structure310and the second light emitting structure320are stacked one above another and the third light emitting structure330is disposed horizontally side-by-side thereto, thereby securing an advantage in minimization of the light emitting device without absorption of light emitted from the third light emitting structure330, as compared with a structure in which all chips are horizontally arranged side by side.

A third molding layer430may be formed in a region where the first molding layer410or the second molding layer420is not formed. The third molding layer430may act as a partition wall that prevents the first molding layer410and the second molding layer420, which have a liquid phase in manufacture of the light emitting device, from flowing before the first and second molding layers are cured. When the first molding layer410and the second molding layer420are provided in a sheet form, a curing process is not required and the third molding layer430may be omitted. In addition, the third molding layer430may contain a light blocking material to prevent light passing through the first molding layer410or the second molding layer420from leaking out through side surfaces thereof. The third molding layer430may divide a window region.

The third molding layer430may include at least some region at least partially overlapping a region between the first light emitting structure310and the second light emitting structure320. Alternatively, the third molding layer430may include at least some region vertically overlapping a region between the active layer312of the first light emitting structure310and the active layer332of the third light emitting structure330.

A lower surface of the second molding layer420may have a smaller width than the upper surface of the first conductivity type semiconductor layer311of the first light emitting structure310. Accordingly, at least part of the third molding layer430may cover a portion of the upper surface of the first conductivity type semiconductor layer311of the first light emitting structure310. The lower surface of the second molding layer420may have a smaller width than the upper surface of the first conductivity type semiconductor layer331of the third light emitting structure330. Accordingly, at least part of the third molding layer430may cover a portion of the upper surface of the first conductivity type semiconductor layer331of the third light emitting structure330.

AlthoughFIG.18shows that the width of the second light emitting structure320is narrower than the width of the first light emitting structure310, it should be understood that other implementations are possible. Alternatively, the first light emitting structure310may have the same width as the second light emitting structure320, or the second light emitting structure320may have a greater width than the first light emitting structure310, as needed. When the same quantity of electric current is supplied, the second light emitting structure320may have a different current density than the first light emitting structure310.

Each of the light emitting structures310,320,330may have a peak wavelength and a dominant wavelength and a difference between the peak wavelength and the dominant wavelength of the first light emitting structure310may be greater than a difference between the peakwavelength and the dominant wavelength of the second light emitting structure320. Alternatively, a difference between the peak wavelength and the dominant wavelength of the third light emitting structure330may be greater than a difference between the peak wavelength and the dominant wavelength of the second light emitting structure320. The second light emitting structure320having the smallest difference between the peak wavelength and the dominant wavelength may be placed near a lower end of the pixel device, thereby enabling stable implementation of colors even when light generated from the second light emitting structure320passes other materials or other light emitting structures. The difference between the peak wavelength and the dominant wavelength of the first light emitting structure310may be 10 nm or less from the difference between the peak wavelength and the dominant wavelength of the second light emitting structure320.

Accordingly, color deviation of the light emitting devices can be reduced by arranging multiple light emitting structures side by side.

A first cover layer390may be disposed to surround the exposed side surfaces and lower surfaces of the first light emitting structure310, the second light emitting structure320and the third light emitting structure330. The first cover layer390may be formed of an insulating material and multiple openings361a,362a,363a,363b,363c,364amay be formed at the lower sides of the first light emitting structure310, the second light emitting structure320, and the third light emitting structure330.

The first cover layer390is provided at the lower side thereof with multiple electrode pads361,362,363,364.

A first electrode pad361is electrically connected to the second conductivity type semiconductor layer312of the first light emitting structure310through a first opening361a.

The first light emitting structure310may further include an ohmic layer340disposed under the second conductivity type semiconductor layer312to secure efficient ohmic contact with the first electrode pad361.

A second electrode pad362is electrically connected to the second conductivity type semiconductor layer322of the second light emitting structure320through a second opening362a. The second light emitting structure320may further include an ohmic layer340disposed under the second conductivity type semiconductor layer322to secure efficient ohmic contact with the second electrode pad362.

A third electrode pad363is electrically connected to the second conductivity type semiconductor layer322of the second light emitting structure320through a third opening363a, electrically connected to the first conductivity type semiconductor layer311of the first light emitting structure310through a fourth opening363b, and electrically connected to the first conductivity type semiconductor layer311of the third light emitting structure330through a fifth opening363c. That is, the third electrode pad363is commonly connected to the first, second and third light emitting structures310,320,330.

A fourth electrode pad364is electrically connected to the second conductivity type semiconductor layer322of the third light emitting structure330through a sixth opening364a. The third light emitting structure330may further include an ohmic layer340disposed under the second conductivity type semiconductor layer332to secure efficient ohmic contact with the fourth electrode pad364.

The first light emitting structure310may be bonded to the second light emitting structure320by a bonding layer350. For the first light emitting structure310including the ohmic layer340, the bonding layer350is disposed between the ohmic layer340of the first light emitting structure310and the first conductivity type semiconductor layer321of the second light emitting structure320.

A second cover layer380may be disposed to surround the first cover layer390and the exposed side surfaces and lower surfaces of the first light emitting structure310, the second light emitting structure320and the third light emitting structure330. The second cover layer380may be formed of an insulating material and multiple openings371a,372a,373a,374aare formed at lower sides of the multiple electrode pads361,362,363,364, respectively.

Multiple connection layers371,372,373,374may be disposed under the second cover layer380. A first connection layer371may be electrically connected to the first electrode pad361through a seventh opening371a, a second connection layer372may be electrically connected to the second electrode pad362through an eighth opening372a, a third connection layer373may be electrically connected to the third electrode pad363through a ninth opening373a, and a fourth connection layer374may be electrically connected to a fourth electrode pad364through a tenth opening374a.

The third connection layer373may be disposed under a region between the first light emitting structure310and the third light emitting structure330. Accordingly, the third connection layer373may perpendicularly overlap the third molding layer430formed between the first molding layer410and the second molding layer420, and a region between the first light emitting structure310and the third light emitting structure330.

The multiple openings371a,372a,373a,374amay be formed to different depths and the ninth opening373amay have the deepest depth. When the ninth opening373ais formed to the deepest depth, the third connection layer373place at the middle among the multiple connection layers371,372,373,374may have the highest height to efficiently support the light emitting device.

According to this embodiment, the first conductivity type semiconductor layer311of the first light emitting structure310is separated from the first conductivity type semiconductor layer331of the third light emitting structure330. Accordingly, the first cover layer390, the third electrode pad363and the second cover layer380may be disposed between the first conductivity type semiconductor layer311of the first light emitting structure310and the first conductivity type semiconductor layer331of the third light emitting structure330.

The upper surfaces of the first light emitting structure310and the third light emitting structure330may be subjected to texturing. In addition, light transmitting layers having different indexes of refraction may be disposed between the first light emitting structure310and the second molding layer420and between the third light emitting structure330and the first molding layer410, respectively. The light transmitting layer may be a substrate.

The first to third light emitting structures310,320,330may be individually operated.

FIG.20is a schematic cross-sectional view of a pixel device according to yet another exemplary embodiment. The pixel device according to this exemplary embodiment is distinguished from the pixel device shown inFIG.19in that the first conductivity type semiconductor layer311of the first light emitting structure310is integrally formed with the first conductivity type semiconductor layer331of the third light emitting structure330.

Although the first conductivity type semiconductor layer311of the first light emitting structure310is integrally formed with the first conductivity type semiconductor layer331of the third light emitting structure330, the first light emitting structure310and the third light emitting structure330are divided into individual light emitting regions to be individually operated.

The third molding layer430disposed between the first molding layer410and the second molding layer420may be provided at the lower side thereof with a semiconductor connector, which connects the first conductivity type semiconductor layer311of the first light emitting structure310to the first conductivity type semiconductor layer331of the third light emitting structure330, (hereinafter, “semiconductor connector”), and a height h1of the semiconductor connector may be lower height than a height h2of the third molding layer430(h1<h2). Accordingly, even when the semiconductor connector connects the first conductivity type semiconductor layer311of the first light emitting structure310to the first conductivity type semiconductor layer331of the third light emitting structure330, it is possible to prevent light leakage by the semiconductor connector.

The third connection layer373may be disposed under the semiconductor connector.

Accordingly, the third connection layer373may perpendicularly overlap the third molding layer430formed between the first molding layer410and the second molding layer420and the semiconductor connector. Descriptions of the same components as those of the exemplary embodiment shown inFIG.19will be omitted.

FIG.21is a schematic cross-sectional view of a pixel device according to yet another exemplary embodiment. Like the pixel device shown inFIG.20, the pixel device according to this embodiment has the structure in which the first conductivity type semiconductor layer311of the first light emitting structure310is integrally formed with the first conductivity type semiconductor layer331of the third light emitting structure330. However, the pixel device according to this embodiment is distinguished from the pixel device shown inFIG.20in that a concave portion is formed under a region corresponding to a connecting portion between the first conductivity type semiconductor layer311of the first light emitting structure310to the first conductivity type semiconductor layer331of the third light emitting structure330.

Accordingly, a height h1corresponding to the connecting portion between the first conductivity type semiconductor layer311of the first light emitting structure310and the first conductivity type semiconductor layer331of the third light emitting structure330is lowered, as compared with the pixel device shown inFIG.20, and a step is formed under the first conductivity type semiconductor layer311of the first light emitting structure310.

The height h1of the semiconductor connector, the height h2of the third molding layer430disposed on the semiconductor connector and the height h3of the third connection layer373may satisfy a relation: h1<h3<h2or h1<h2<h3.

AlthoughFIG.21shows the step vertically formed under the first conductivity type semiconductor layer311of the first light emitting structure310, the step may have a slanted side surface having an inclination. Further, the inclination of the side surface of the step formed under the first conductivity type semiconductor layer311of the first light emitting structure310may be different from an inclination of the outer peripheral region of the light emitting device.

Descriptions of the same components as the exemplary embodiments shown inFIG.19andFIG.20will be omitted.

Although some exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that the foregoing embodiments are provided for illustration only and are not to be in any way construed as limiting the technical idea of the present disclosure. In addition, it should be understood that features or components described with respect to one exemplary embodiment may be applied to other embodiments without departing from the spirit of the present disclosure.