Light emitting device

A light emitting device may include a light emitting structure that includes a first semiconductor layer, a second semiconductor layer and an active layer between the first semiconductor layer and the second semiconductor layer, wherein the active layer includes a light emitting layer adjacent to the second semiconductor layer and that includes a well layer and a barrier layer and a super-lattice layer between the light emitting layer and the first semiconductor layer, the super-lattice layer including at least six pairs of a first layer and a second layer, wherein a composition of the first layer includes indium (In) and the second layer includes indium (In), and the composition of the first layer is different from the composition of the second layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority benefit from Korean Patent Application No. 10-2010-0114036, filed Nov. 16, 2010, the subject matter of which is hereby incorporated by reference.

BACKGROUND

Embodiments may relate to a light emitting device.

A light emitting device may include, for example, a light emitting diode (LED) including a semiconductor device that converts electrical energy into light.

The light emitting diode is a device that converts electricity into infrared light, visible light, etc., using characteristics of compound semiconductors.

Light emitting diodes may be applied to devices such as home appliances, remote controls, electronic signboards, displays, a variety of automatic appliances and/or the like.

A miniaturized light emitting diode may be fabricated as a surface mount device such that the light emitting diode may be directly provided on a printed circuit board (PCB). Accordingly, an LED lamp used as a display device may be developed as a surface mount device-type. Such a surface mount device may substitute for a lamp and may be used as a lighting display, a character display, an image display and/or the like, for rendering various colors.

DETAILED DESCRIPTION

Reference may now be made in detail to exemplary embodiments, examples of which may be illustrated in the accompanying drawings. The same reference numbers may be used throughout the drawings to refer to the same or like parts.

It may be understood that when an device such as a layer (film), a region, a pad and/or a pattern is referred to as being “on” or “under” another device, it may be directly or indirectly on or under the other device. Further, the “on” or “under” positioning of each layer may be described based on illustration in the drawings.

In the drawings, thicknesses or sizes of respective layers may be exaggerated, omitted, and/or schematically illustrated for ease of convenience and clarity. Therefore, sizes of respective devices shown in the drawings do not necessarily denote actual sizes thereof.

Angles and directions referred to during description of a structure of a light emitting device array may be described with reference to the drawings. In a description of the structure of the light emitting device array, if reference points with respect to the angles and positional relations are not clearly stated, related drawings may be relied upon.

FIG. 1is a cross-sectional view of a light emitting device in accordance with an embodiment. Other embodiments and configurations may also be provided.

FIG. 1shows a light emitting device100that may include a substrate110and a light emitting structure120disposed on the substrate110. The light emitting structure120may have a first semiconductor layer122, a second semiconductor layer124and an active layer126between the first semiconductor layer122and the second semiconductor layer124.

The light emitting device100may include a light emitting diode (LED) using a compound semiconductor layer composed of Group III to V elements. The LED may be a color LED to emit blue, green or red light, or may be an ultraviolet (UV) LED. The emitted light of the LED may be embodied using various semiconductors within technical ranges as described.

The substrate110may be formed using translucent materials including sapphire (Al2O3), for example. Other than sapphire, the substrate110may include zinc oxide (ZnO), gallium nitride (GaN), silicon carbide (SiC), aluminum nitride (AlN), and/or so forth.

A refractive index of the substrate110may be less than a refractive index of the first semiconductor layer122, which may improve light extraction efficiency.

The substrate110may have a patterned substrate (PSS) structure to increase light extraction efficiency. The substrate110may or may not have a PSS structure.

The substrate110may have a buffer layer112in order to reduce a lattice mismatch between the substrate110and the light emitting structure120, and to facilitate growth of the semiconductor layer.

The buffer layer112may be formed under a low temperature atmosphere. The buffer layer112may be formed using specific materials that can reduce a difference in lattice constant between the substrate110and the light emitting structure120. These specific materials may include at least one selected from GaN, InN, AlN, AlInN, InGaN, AlGaN, InAlGaN, etc., without being particularly limited thereto.

The buffer layer112may be grown into single crystals on the substrate110. The single crystal-grown buffer layer112may enhance crystallinity of the light emitting structure120that is grown on the buffer layer112.

The light emitting structure120may include a first semiconductor layer122, a second semiconductor layer124, and an active layer126between the first semiconductor layer122and the second semiconductor layer124.

The first semiconductor layer122may be an N type semiconductor layer, wherein the N type semiconductor layer may be formed using any one selected from semiconductor materials represented by the formula of InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1), for example, a group consisting of GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, etc., and n-type dopants such as Si, Ge, Sn, etc. may be doped thereon.

The first semiconductor layer122may supply electrons to the active layer126, and the first semiconductor layer122may be an n-doped semiconductor layer having conductivity formed by doping n-type dopants, or the first semiconductor layer122may include an undoped semiconductor layer without n-type dopant doping under the doped semiconductor layer, and without being particularly limited thereto.

In this example, the undoped semiconductor layer may improve crystallinity of the first semiconductor layer122and may be substantially identical to the first semiconductor layer122, other than the undoped semiconductor layer has a lower electrical conductivity than the first semiconductor layer122, since it is not doped with an n-type dopant.

The first semiconductor layer122may have the active layer126and the second semiconductor124, which may be grown in a sequential order.

The active layer126may be formed in a single or multi-quantum well structure, a quantum-wire structure or a quantum dot structure and/or the like, using compound semiconductor materials based on elements of Groups III to V.

The active layer126may include a region in which electrons are re-combined with holes, and a transition to lower energy levels may occur owing to recombination of such electrons and holes, in turn emitting light at corresponding wavelengths.

The active layer126may be formed using a semiconductor material represented by the formula of InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1), for example, and the active layer126may have a single quantum well structure or a multi-quantum well (MQW) structure.

In the example where the active layer126has a quantum well structure, the active layer126may have a single or multi-quantum well structure that includes a well layer having the formula of InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1) and a barrier layer having the formula of InaAlbGa1-a-bN (0≦a≦1, 0≦b≦1, 0≦a+b≦1). The well layer may be formed of a material having a smaller band gap than the barrier layer.

Embodiments may describe the active layer126formed of InGaN containing In, without being particularly limited thereto.

The active layer126may include a light emitting layer126_1formed in a quantum well structure that includes an InGaN barrier layer and an InGaN well layer, as well as a super-lattice layer126_2(SL) which is arranged on bottom of the light emitting layer126_1and has a super-lattice structure formed by laminating at least 6 groups (or pairs) of first and second InGaN layers having different In concentrations.

The InGaN barrier layer and InGaN well layer may be represented by the formulae of InxGa(1-x)N and InyGa(1-y)N (0<x<1, 0<y<1, x<y), respectively. Similarly, the first InGaN and second InGaN may be expressed by the formulae of InaGa(1-a)N and InbGa(1-b)N (0<a<1, 0<b<1, a<b), respectively.

At least six (6) groups (or pairs) of first InGaN layer and the second InGaN layer may be repeatedly laminated to form the super-lattice layer126_2, a growth surface may be rendered to facilitate growth of a high quality light emitting layer126_1, and under influence of such lamination upon a working voltage of the light emitting device100, variables such as an appropriate thickness of the super-lattice layer126_2and In content may reduce the working voltage, and in turn increase an optical efficiency.

The super-lattice layer126_2may improve internal quantum efficiency by reducing stress in the active layer126, and may suitably restrain electrons and holes in the light emitting layer126_1.

A structure of the active layer126may be described with reference toFIG. 2.

A second semiconductor layer124may introduce a carrier into the active layer126and may be embodied as a p-type semiconductor layer. The p-type semiconductor layer may include any one selected from semiconductor materials having the formula of InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1) such as GaN, AlN, AlGaN, InGaN, InN, InAlGaN and AlInN, and may be doped with a p-type dopant such as Mg, Zn, Ca, Sr or Ba.

The first semiconductor layer122, the active layer126and the second semiconductor layer124may be fabricated by methods, such as metal organic chemical vapor deposition (MOCVD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), and/or so forth, for example. However, embodiments are not limited thereto.

A third semiconductor layer having a polarity opposite to the second semiconductor layer124may be provided above the second semiconductor layer124. For example, if the second semiconductor layer124is a p-type semiconductor layer, the third semiconductor layer may be an n-type semiconductor layer.

The second semiconductor layer124may be a p-type semiconductor layer while the first semiconductor layer122is an n-type semiconductor layer. Accordingly, the light emitting device100may include at least one of N-P, P-N, N-P-N and P-N-P junction structures, without being limited thereto.

A doping concentration of a conductive dopant in the first semiconductor layer122and the second semiconductor layer124may be uniform or non-uniform. That is, a structure of plural semiconductor layers may vary, without being limited thereto.

The position of the first semiconductor layer122and the second semiconductor layer124may be reversed around the active layer126. The first semiconductor layer122that includes an n-type semiconductor layer and is laminated on the substrate110may be described below.

At least one region of the active layer126, the second semiconductor layer124and the first semiconductor layer122may be removed, the first semiconductor layer122may be partially exposed by mesa-etching, and/or a first electrode130may be provided on a top of the exposed first semiconductor layer122.

A light transmitting electrode layer150may be provided on the second semiconductor layer124, and a second electrode140may be provided on an outer side of the light transmitting electrode layer150.

Each of the first electrode130and the second electrode140may be formed to have a single layer or a multi-layer structure using conductive materials such as metals or alloys selected from In, Co, Si, Ge, Au, Pd, Pt, Ru, Re, Mg, Zn, Hf, Ta, Rh, Ir, W, Ti, Ag, Cr, Mo, Nb, Al, Ni, Cu and WTi, for example.

The light transmitting electrode layer150may include at least one of ITO, IZO(In—ZnO), GZO(Ga—ZnO), AZO(Al—ZnO), AGZO(Al—Ga ZnO), IGZO(In—Ga ZnO), IrOx, RuOx, RuOx/ITO, Ni/IrOx/Au and/or Ni/IrOx/Au/ITO. The light transmitting electrode layer150may transmit light from the active layer126to outside of the light emitting device100. The light transmitting electrode layer150may be formed on an outer side of the second semiconductor layer124such that the light transmitting electrode layer150has a step with the second semiconductor layer124. Otherwise, the light transmitting electrode layer150may be formed in an entire region of the outer side thereof, thus preventing current crowding.

Although embodiments may describe a horizontal type light emitting device, such embodiments may also be applied to a vertical type light emitting device or other types of light emitting devices, without limitation thereof.

FIGS. 2 and 3illustrate structures of an active layer of a light emitting device (shown inFIG. 1). Other embodiments and configurations may also be provided.

As shown inFIG. 2, the active layer126may include the light emitting layer126_1and the super-lattice layer126_2.

The light emitting layer126_1may have a quantum well structure including an InGaN barrier layer ‘b’ and an InGaN well layer ‘w.’ The InGaN barrier layer ‘b’ and the InGaN well layer ‘w’ may be formed into one to five groups (pairs).

Each of the InGaN barrier layer ‘b’ and the InGaN well layer ‘w’ may have an In content of 3% to 18%. That is, the In content of the InGaN well layer ‘w’ is 4 to 7 times greater than the In content of the InGaN barrier layer ‘b,’ where the InGaN barrier layer ‘b’ is represented by the formula of In0.03Ga0.97N and the InGaN well layer ‘w’ is represented by the formula of In0.18Ga0.82N.

In this regard, a thickness of the InGaN barrier layer ‘b’ may be 1.7 to 2.0 times greater than a thickness of the InGaN well layer ‘w’, and the thickness may vary based on the In content.

In other words, referring to GRAPH 1 shown inFIG. 10, when a thickness of the InGaN well layer ‘w’ is maintained at 3 nm while a thickness of the InGaN barrier layer ‘b’ changes to 4 nm, 5 nm, 6 nm and 9 nm, respectively, and a rated current of 800 mA is applied, a light output PO graph and data thereof may be expressed as follows:

For example, when a thickness of the InGaN well layer ‘w’ is 3 nm, it may be seen from GRAPH 1 shown inFIG. 10that the InGaN barrier layer ‘b’ having a thickness of 4 nm may exhibit a PO of 59.463, the InGaN barrier layer ‘b’ having a thickness of 5 nm may exhibit a PO of 72.485, and the InGaN barrier layers ‘b’ having thicknesses of 6 nm and 9 nm may exhibit POs of 70.580 and 68.286, respectively.

GRAPH 1 shown inFIG. 10also shows that if the thickness of the InGaN barrier layer ‘b’ is 1.7 to 2 times greater than the thickness of the InGaN well layer ‘w,’ a range of variation in PO may be relatively reduced. It may also be seen that, when the thickness of the InGaN barrier layer ‘b’ is outside the foregoing range (i.e., less than 1.6 times or more than 2.0 times that of the InGaN well layer ‘w’), then the PO is decreased.

The super-lattice layer126_2may have a super-lattice structure formed by laminating at least six (6) groups (or pairs) of first InGaN ‘c1’ and second InGaN ‘c2’, and a thickness of the super-lattice layer126_2may be 8 to 10 times greater than a thickness of the light emitting layer126_1, or 12 to 14 times greater than a thickness of the InGaN barrier layer ‘b.’

FIG. 2illustrates 6 groups (or pairs) of the first InGaN c1and the second InGaN c2, which have a same formulae (or composition), respectively.

The In content of the second InGaN c2may be 3 to 5 times greater than the In content of the first InGaN c1, and the first InGaN c1and the second InGaN c2may be represented by the formulae In0.02Ga0.98N and In0.09Ga0.91N, respectively.

As such, when repeatedly laminating groups (or pairs) of the first InGaN c1and the second InGaN c2represented by the formulae of In0.02Ga0.98N and In0.09Ga0.91N, respectively, a large amount of electrons may move and may be collected at a low energy level of the light emitting layer126_1, which may in turn increase recombination probability of electrons and holes and thus improve light emitting efficiency.

The super-lattice layer126_2may effectively relieve stress caused by a lattice mismatch between the light emitting layer126_1and the first semiconductor layer122.

In this example, a thickness of the first InGaN c1may be 4 to 5 times greater than a thickness of the second InGaN c2, or may be 2 to 4 times greater than a thickness of at least one of the InGaN well layer ‘a’ and/or the InGaN barrier layer ‘b’, and the thickness may be controlled based on the In content.

As the In content decreases, an energy gap increases. On the contrary, the energy gap may be reduced with an increase in In content.

In describingFIG. 3, a same portion as inFIG. 2may be omitted or may be briefly described.

With reference toFIG. 3, a detailed description of the light emitting layer126_1may be omitted since it is substantially the same as described with respect toFIG. 2.

The super-lattice layer126_2may have a super-lattice structure formed of at least 6 groups (or pairs) including a first InGaN ‘c1’, at least one InGaN ‘c11’ having a formula (or composition) different from that of the first InGaN c1, a second InGaN ‘c2,’ and at least one InGaN ‘c21’ having a formula (or composition) different from that of the second InGaN c2. A detailed description thereof may be omitted since it is substantially the same as described in relation toFIG. 2.

As shown inFIG. 3, the first InGaN c1and the second InGaN c2are located on a lowermost of the super-lattice layer126_2and the foregoing InGaN c11and the InGaN c21may be laminated on the first InGaN c1and the second InGaN c2.

The thicknesses of the first InGaN c1and the second InGaN c2may be different from the thicknesses of the InGaN c11and the InGaN c21.

For example, a lowermost group (or pair) of the first InGaN c1and the second InGaN c2may be provided at the bottom of the super-lattice layer126_2and five (5) groups (or pairs) of InGaN c11and InGaN c21may be repeatedly laminated on the lowermost group (or pair), as described above.

In this example, thicknesses of the first InGaN c1and the second InGaN c2may be different from thicknesses of the other five groups (or pairs) of InGaN c11and InGaN c21.

That is, a thickness of each of the first InGaN c1and the second InGaN c2placed on the first semiconductor layer122may be 1.5 to 2 times greater than of each of the five groups (or pairs) of InGaN c11and InGaN c21. This may increase stress between the first semiconductor layer122and upper groups (or pairs) of InGaN c11and InGaN c21through the first InGaN c1and the second InGaN c2.

The lowermost layer composed of the first InGaN c1provided on the first semiconductor layer122may enhance strain of other InGaN c11and InGaN c21as well as growth uniformity thereof by decreasing a Si doping level and increasing a thickness thereof than that of InGaN c11.

The first InGaN c1and the second InGaN c2may contain Al, without being particularly limited thereto.

FIG. 4is an experimental graph showing reliability test results of the light emitting device.

FIG. 4illustrates graphs of severity test results regarding reliability of the first InGaN c1and the second InGaN c2which are formed in 6 groups (or pairs), 8 groups (or pairs) and 11 groups (or pairs), respectively, to form each of the super-lattice layers126_2in the active layer126shown inFIGS. 2 and 3, respectively.

In this regard, the foregoing 6, 8 and 11 groups (or pairs) respectively refer to overall groups (or pairs) including one group (or pair) of a second InGaN c2and a first InGaN c1laminated thereon, as well as a plurality of groups (or pairs) of first InGaN c1and the second InGaN c2alternately laminated thereon.

InFIG. 4, a left side may be rated voltage VF_V and a right side may be a test period of time (h) and each of the graphs may be obtained when a rated current of 2 μA is applied thereto.

More particularly, with regard to the light emitting device, if a super-lattice layer126_2includes each of 6, 8 or 11 groups (or pairs) of the first InGaN c1and the second InGaN c2, a drop rate at ageing is near 0%. However, a 6 group (or pair) based light emitting device may exhibit a decreased variation in a rated voltage VF_V, compared to light emitting devices including 8 and 11 groups (or pairs).

FIG. 4also demonstrates an average for seven (7) samples, each having a super-lattice layer126_6including 6, 8 or 11 groups (or pairs), as described above. Depending upon individual periods, respective values may be slightly different from the illustrated graph; however, is not particularly limited thereto.

FromFIG. 4, it may be seen that the super-lattice layer126_2formed by repeatedly laminating 6 groups (or pairs) of first InGaN c1and second InGaN c2is more beneficial than similar ones having 8 and 11 groups (or pairs), respectively, in consideration of production process and cost.

FIG. 5is a cross-sectional view of a light emitting device package in accordance with an embodiment. Other embodiments and configurations may also be provided.

FIG. 5shows that a light emitting device package200includes a body210having a cavity, a light emitting device220mounted at a bottom of the body210, and a resin (or a resin layer)230that fills the cavity. The resin layer230may include a phosphor240.

The body210may be formed using at least one selected from resin materials such as polyphthalamide (PPA), silicon (Si), aluminum nitride (AlN), liquid crystal polymer (photo sensitive glass, PSG), polyamide 9T (PA9T), syndiotactic polystyrene (SPS), metal materials, sapphire (Al2O3), beryllium oxide (BeO), printed circuit boards (PCB), and/or etc. The body210may be formed by a process such as injection molding, etching, etc., without being particularly limited thereto.

An inner surface of the body210may have an inclined surface. A reflective angle of light emitted from the light-emitting device220may vary, depending on the angle of the inclined surface. Accordingly, an orientation angle of light emitted to the outside may be controlled.

As seen from the top, the cavity in the body210may have various shapes including, but not limited to, a circular shape, a rectangular shape, a polygonal shape, an oval shape and/or a shape with curved corners.

The light emitting device220may be mounted on the bottom of the body210, and the light emitting device220may correspond to the light emitting device100ofFIG. 1. The light emitting device220may include, but may not be limited thereto, color light emitting devices to emit red, green, blue and/or white light, and UV light emitting devices to emit ultraviolet light. At least one light emitting device may be mounted on the body210.

The body210may include a first lead frame252and a second lead frame254. The first and second lead frames252and254may be electrically connected to the light emitting device220to supply power thereto.

The first and second lead frames252and254may be electrically isolated from each other, may reflect light emitted by the light emitting device220so as to increase light efficiency, and may discharge heat generated by the light emitting device220.

The first and second lead frames252and254may include a metal material selected from titanium (Ti), copper (Cu), nickel (Ni), gold (Au), chrome (Cr), tantalum (Ta), platinum (Pt), tin (Sn), silver (Ag), phosphorus (P), aluminum (Al), indium (In), palladium (Pd), cobalt (Co), silicon (Si), germanium (Ge), hafnium (Hf), ruthenium (Ru), iron (Fe), and/or alloys thereof, for example. The first and second lead frames252and254may have a monolayer structure or a multilayer structure, without being limited thereto.

The resin230may fill the cavity, and may include at least one of the phosphor240and/or a light diffusing material.

The resin230may include a transparent silicon, epoxy and/or any other resin material, and the resin230may fill (or partly fill) a cavity with such material, followed by UV or heat curing the same.

The phosphor240may be selected based on the wavelength of light emitted from the light emitting device220, to allow the light emitting device package200to render white light.

The phosphor240contained in the resin230may be any one selected from a blue light emitting phosphor, a blue-green light emitting phosphor, a green light emitting phosphor, a yellow-green light emitting phosphor, a yellow light emitting phosphor, a yellow-red light emitting phosphor, an orange light emitting phosphor and/or a red light emitting phosphor, based on the wavelength of light emitted from the light emitting device220.

The phosphor240may be excited by first light emitted from the light emitting device220to create second light. For example, in the example where the light emitting device220is a blue light emitting diode (LED) and the phosphor240is a yellow phosphor, the yellow phosphor may be excited by blue light to emit yellow light, and blue light emitted from the blue LED and yellow light excited from the blue light may be combined, and the light emitting device package200may emit white light.

If the light emitting device220is a green LED, a magenta phosphor as well as blue and red phosphors240may be employed together. Alternatively, when the light emitting device220is a red LED, a cyan phosphor as well as blue and green phosphors may be employed together.

FIG. 6shows an illumination device that includes a light emitting device in accordance with an embodiment.FIG. 7is a cross-sectional view taken along line A-A′ ofFIG. 6. Other embodiments and configurations may also be provided.

FIG. 6shows a lighting instrument300. A description may be provided in terms of a length direction Z, a horizontal direction Y perpendicular to the length direction Z, and a height direction X perpendicular to both the length direction Z and the horizontal direction Y.

FIG. 7is a cross-sectional view when viewing in the horizontal direction Y after cutting the lighting instrument300along a plane formed of the length direction Z and the height direction X.

The lighting instrument300may include a body310, a cover330coupled with the body310, and end caps350provided to both ends of the body310.

The body310may be connected with a light emitting device module340at a bottom side thereof. In order to discharge heat generated from the light emitting device module340to the outside through a top of the body310, the body310may be made of metal materials having excellent thermal conductivity and heat dissipation effects.

The light emitting device module340may include a light emitting device package344having a PCB342and a light emitting device. The package344may be mounted on the PCB342with multiple colors and in multiple rows to form an array, and may be spaced from one another by a predetermined interval or if necessary, by different distances, to control brightness. The PCB342may be a metal core PCB (MPPCB) or a PCB made of FR4.

The cover330may be circular in shape to surround a bottom of the body310, without being limited thereto.

The cover330may protect the light emitting device module340from foreign substances. The cover330may prevent glare occurred by the light emitting device package344and may include diffusion particles to uniformly discharge light to the outside. A prism pattern or the like may be formed on at least one of the inner and outer surfaces of the cover330. Alternatively, a phosphor may be applied to at least one of the inner and outer surfaces of the cover330.

The cover330may exhibit superior light transmittance to discharge light emitted by the light emitting device package344through the cover330to the outside. The cover330may exhibit sufficient heat resistance to endure heat generated by the light emitting device package344. The cover330may be composed of a material including polyethylene terephthalate (PET), polycarbonate (PC) or polymethyl methacrylate (PMMA) and/or the like.

The end cap350may be arranged on both ends of the body310, and may be used to seal a power device. Additionally, the end cap350may be provided with a power pin352to allow the lighting instrument300to be applied to a terminal from which a fluorescent light has been removed, without using any additional device.

FIG. 8shows a liquid crystal display device that includes a light emitting device in accordance with an embodiment. Other embodiments and configurations may also be provided.

FIG. 8illustrates an edge-light type liquid crystal display device400that includes a liquid crystal display panel410and a backlight unit470to supply light to the liquid crystal display panel410.

The liquid crystal display panel410may display an image using light supplied from the backlight unit470. The liquid crystal display panel410may include a color filter substrate412and a thin film transistor substrate414that face each other with a liquid crystal interposed therebetween.

The color filter substrate412may render color images to be displayed through the liquid crystal display panel410.

The thin film transistor substrate414may be electrically connected to a printed circuit board418on which a plurality of circuit components are mounted through a driving film417. The thin film transistor substrate414may respond to drive signals supplied from the printed circuit board418, and may apply a drive voltage from the printed circuit board418to liquid crystals.

The thin film transistor substrate414may include a thin film transistor and a pixel electrode formed as a thin film on other substrates composed of a transparent material such as glass or plastic.

The backlight unit470may include a light emitting device module420to emit light, a light guide plate430to convert light emitted by the light emitting device module420into surface light and supply the light to the liquid crystal display panel410, a plurality of films450,466and464to uniformize a brightness distribution of light emitted by the light guide plate430and improve vertical incidence, and a reflective sheet440to reflect light emitted to the back of the light guide plate430.

The light emitting device module420may include a plurality of light emitting device packages424and a PCB422on which the light emitting device packages424are mounted to form an array.

The light emitting device in the light emitting device package424may correspond to the light emitting device shownFIG. 1.

The backlight unit470may include a diffusion film466to diffuse light projected from the light guide plate430toward the liquid crystal display panel410, a prism film450to concentrate the diffused light and thus improve a vertical incidence, and a protective film464to protect the prism film450.

FIG. 9shows a liquid crystal display device that includes a light emitting device. Other embodiments and configurations may also be provided.

FIG. 9illustrates a direct-type liquid crystal display device500that includes a liquid crystal display panel510and a backlight unit570to supply light to the liquid crystal display panel510.

The liquid crystal display panel510may be substantially the same as described inFIG. 8, and a further explanation may be omitted.

The backlight unit570may include a plurality of light emitting device modules523, a reflective sheet524, a lower chassis530in which the light-emitting device modules523and the reflective sheet524are accepted, a diffusion plate540arranged on the light-emitting device modules523, and a plurality of optical films560.

Each light emitting device module523may include a plurality of light-emitting device packages522and a PCB521on which the light-emitting device packages522are mounted to form an array.

The reflective sheet524may reflect light emitted from the light emitting device package522toward the liquid crystal display panel510, so as to improve a luminous efficiency.

Light emitted from the light emitting device module523may be projected onto the diffusion plate540and an optical film560may be arranged on the diffusion plate540. The optical film560may include a diffusion film566, a prism film550and a protective film564.

The lighting instrument300and the liquid crystal displays400and500may be included in a lighting system.

A light emitting device as embodied and broadly described herein may include an active layer having a super-lattice structure, so as to attain improvement in brightness and ESD characteristics while decreasing (covalent) bonds in crystals.

A light emitting device may include an active layer having a super-lattice layer, and crystal defects occurring between a light emitting layer and a buffer layer may be decreased while enhancing brightness and reliability.