Light emitting diode and light emitting device package including the same

A light emitting diode is disclosed. The disclosed light emitting diode includes a light emitting structure including a first-conductivity-type semiconductor layer, an active layer, and a second-conductivity-type semiconductor layer. The first-conductivity-type semiconductor layer, active layer, and second-conductivity-type semiconductor layer are disposed to be adjacent to one another in a same direction. The active layer includes well and barrier layers alternately stacked at least one time. The well layer has a narrower energy bandgap than the barrier layer. The light emitting diode also includes a mask layer disposed in the first-conductivity-type semiconductor layer, a first electrode disposed on the first-conductivity-type semiconductor layer, and a second electrode disposed on the second-conductivity-type semiconductor layer. The first-conductivity-type semiconductor layer is formed with at least one recess portion.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to Korean Patent Application No 10-2011-0089492, filed in Korea on Sep. 5, 2011, which is hereby incorporated in their entirety by reference as if fully set forth herein.

TECHNICAL FIELD

Embodiments relate to a light emitting diode and a light emitting device package including the same.

BACKGROUND

Light emitting devices, such as light emitting diodes (LEDs) and laser diodes (LDs), which use a Group III-V or Group II-VI compound semiconductor material, may render various colors such as red, green, blue, and ultraviolet by virtue of development of thin film growth technologies and device materials. It may also be possible to produce white light at high efficiency using fluorescent materials or through color mixing. Further, the light emitting devices have advantages, such as low power consumption, semi-permanent lifespan, fast response time, safety, and environmental friendliness as compared to conventional light sources, such as fluorescent lamps and incandescent lamps.

Therefore, these light emitting elements are increasingly applied to transmission modules of optical communication units, light emitting diode backlights as a replacement for cold cathode fluorescent lamps (CCFLs) constituting backlights of liquid crystal display (LCD) devices, lighting apparatuses using white light emitting diodes as a replacement for fluorescent lamps or incandescent lamps, headlights for vehicles and traffic lights.

Nitride semiconductor light emitting devices employ a sapphire substrate, which is an insulating substrate, because there is no commercially-available substrate having the same crystalline structure as a nitride semiconductor material such as GaN while being lattice matchable with the nitride semiconductor material. In such a nitride semiconductor light emitting device, there may be lattice constant and thermal expansion coefficient differences between the sapphire substrate and a GaN layer grown over the sapphire substrate. As a result, lattice mismatch may occur between the sapphire substrate and the GaN layer, so that numerous crystal defects may be present in the GaN layer.

Such crystal defects may cause an increase in leakage current. When external static electricity is applied to the light emitting device, the active layer of the light emitting device, which has numerous crystal defects, may be damaged by an intense field generated due to the static electricity. Generally, it is known that there are crystal defects (threading defects) in a GaN thin film at a density of 1010to 1012/cm2.

Such a nitride semiconductor light emitting device, which has numerous crystal defects, may be very weak against electrical impact. To this end, technologies and standardization for protection of nitride semiconductor light emitting devices from static electricity and lightning are being highlighted as very important technical issues.

Generally, a conventional GaN light emitting device has electrostatic discharge (ESD) characteristics that the device can withstand, in a human body mode (HBM), static electricity of up to several thousand volts in a forward direction, but cannot withstand static electricity of several hundred volts in a reverse direction. Such ESD characteristics are exhibited mainly due to the crystal detects of the device, as mentioned above.

In order to improve such ESD characteristics, and thus to protect the light emitting device from ESD, a proposal to connect a Schottky diode or a Zener diode with the light emitting device in parallel has been made. However, such a proposal causes troublesomeness and an increase in manufacturing costs in that a Schottky diode or a Zener diode is separately required.

Therefore, it is necessary to improve the structure of the light emitting device, and thus to improve the ESD characteristics of the light emitting device.

SUMMARY

Embodiments achieve an improvement in the electrostatic discharge (ESD) characteristics of a light emitting device, and thus achieve an enhancement in reliability.

In one embodiment, a light emitting device includes a light emitting structure including a first-conductivity-type semiconductor layer, an active layer, and a second-conductivity-type semiconductor layer, wherein the first-conductivity-type semiconductor layer, the active layer, and the second-conductivity-type semiconductor layer are disposed to be adjacent to one another in a same direction, the active layer includes well and barrier layers alternately stacked at least one time, and the well layer has a narrower energy bandgap than the barrier layer, a mask layer disposed in the first-conductivity-type semiconductor layer, a first electrode disposed on the first-conductivity-type semiconductor layer, and a second electrode disposed on the second-conductivity-type semiconductor layer, wherein the first-conductivity-type semiconductor layer is formed with at least one recess portion.

In another embodiment, a light emitting device includes a light emitting structure including a first-conductivity-type semiconductor layer, an active layer, and a second-conductivity-type semiconductor layer, a mask layer disposed in the first-conductivity-type semiconductor layer, the mask layer including a window region, a first electrode disposed on the first-conductivity-type semiconductor layer, and a second electrode disposed on the second-conductivity-type semiconductor layer, wherein the first-conductivity-type semiconductor layer includes at least one recess portion formed to vertically overlap the window region of the mask layer.

In another embodiment, a light emitting device package includes a package body, first and second lead frames disposed on the package body, and a light emitting device disposed on the package body, and electrically connected to the first and second lead frames, wherein the light emitting device includes a substrate, a light emitting structure disposed on the substrate, the light emitting structure including a first-conductivity-type semiconductor layer, an active layer, and a second-conductivity-type semiconductor layer, wherein the first-conductivity-type semiconductor layer, the active layer, and the second-conductivity-type semiconductor layer are disposed to be adjacent to one another in a same direction, the active layer includes well and barrier layers alternately stacked at least one time, and the well layer has a narrower energy bandgap than the barrier layer, a mask layer disposed in the first-conductivity-type semiconductor layer, a first electrode disposed on the first-conductivity-type semiconductor layer, and a second electrode disposed on the second-conductivity-type semiconductor layer, and wherein the first-conductivity-type semiconductor layer is formed with at least one recess portion.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, embodiments will be described with reference to the annexed drawings.

It will be understood that when an element is referred to as being “on” or “under” another element, it can be directly on/under the element, and one or more intervening elements may also be present. When an element is referred to as being “on” or “under”, “under the element” as well as “on the element” can be included based on the element.

In the drawings, the thickness or size of each layer is exaggerated, omitted, or schematically illustrated for convenience of description and clarity. Also, the size or area of each constituent element does not entirely reflect the actual size thereof.

FIG. 1is a sectional view illustrating a light emitting device according to an exemplary embodiment.FIG. 1illustrates a horizontal light emitting device.

In these embodiments or other embodiments, the light emitting device may be semiconductor light emitting device, for example, light emitting diode.

Referring toFIG. 1, a light emitting device100is shown. The light emitting device100includes a buffer layer120disposed over a substrate110, an undoped semiconductor layer130disposed over the buffer layer120, and a light emitting structure disposed on the undoped semiconductor layer130. The light emitting structure includes a first-conductivity-type semiconductor layer140, an active layer160, and a second-conductivity-type semiconductor layer180, which are sequentially disposed on the undoped semiconductor layer130in this order.

The buffer120is adapted to reduce lattice mismatch and thermal expansion coefficient differences between the substrate110and the semiconductor layer grown over the substrate110. Of course, the buffer120is not a necessity.

The first-conductivity-type semiconductor layer140, active layer160, and second-conductivity-type semiconductor layer180are stacked in the same direction while being arranged to be adjacent to one another. The first-conductivity-type semiconductor layer140, active layer160, and second-conductivity-type semiconductor layer180may have different thicknesses.

A mask layer150may be disposed in the first-conductivity-type semiconductor layer140. A recess portion145may also be formed on the first-conductivity-type semiconductor layer140. recess portionrecess portion

The mask layer150may have a single layer structure or a multilayer structure.

The mask layer150has a masking region covered by a mask, and a window region not covered by the mask. This will be described hereinafter. The recess portion150may be formed on a portion of the first-conductivity-type semiconductor layer140, namely, a first-conductivity-type semiconductor layer140b, to correspond to the window region of the mask layer150.

The mask layer150may be disposed between the window region and the active layer160.

The recess portion145may have a V-pit shape, an inverted polygonal corn shape, or an inverted pyramid shape.

The light emitting device may also include an electron blocking layer170disposed between the active layer160and the second-conductivity-type semiconductor layer180.

The light emitting structure may be mesa-etched from the second-conductivity-type semiconductor layer180to a portion of the first-conductivity-type semiconductor layer140. A first electrode182may be disposed on a portion of the first-conductivity-type semiconductor layer140exposed in accordance with the mesa-etching, namely, a first-conductivity-type semiconductor layer140a.

A second electrode184may be disposed on the second-conductivity-type semiconductor layer180.

A current spreading layer190may be formed between the second-conductivity-type semiconductor layer180and the second layer184.

The current spreading layer190may be arranged such that at least a portion thereof contacts the second electrode184.

The current spreading layer190is electrically connected with the second electrode184, to uniformly diffuse current supplied from the second electrode184, and thus to achieve an enhancement in the light emission efficiency of the light emitting device100.

The current spreading layer190may be made of a metal having high electrical conductivity. For example, the current spreading layer190may selectively include at least one selected from the group consisting of Ti, Au, Ni, In, Co, W, and Fe, although the embodiment is not limited thereto.

The current spreading layer190may be formed at a portion or entirety of the upper surface of the second-conductivity-type semiconductor layer180, although the embodiment is not limited thereto. For example, the current spreading layer190may be formed such that at least a portion thereof vertically overlaps the second electrode184.

FIGS. 2 to 9are views illustrating a method for manufacturing the light emitting device in accordance with an exemplary embodiment. Hereinafter, the light emitting device manufacturing method according to the illustrated embodiment will be described with reference toFIGS. 2 to 9.

The substrate110may be formed using a material suitable for growth of a semiconductor material or a carrier wafer. The substrate110may also be made of a material having excellent thermal conductivity. The substrate110may be a conductive substrate or an insulating substrate. For example, the substrate110may be made of at least one of sapphire (Al2O3), SiC, GaAs, GaN, ZnO, Si, GaP, InP, Ge, or Ga2O3. Wet washing may be performed upon the substrate110, to remove impurities from the surface of the substrate110.

A light extraction structure115such as a roughness may be formed over a surface of the substrate110, to which the light emitting structure will be adjacent.

The light extraction structure115may have periodic patterns or non-periodic patterns.

Light generated from the light emitting structure is outwardly emitted from the light emitting device after being irregularly reflected by the light extraction structure115. Thus, the light extraction efficiency of the light emitting device100is enhanced.

The buffer layer120, which is stacked over the substrate110, is adapted to reduce lattice mismatch and thermal expansion coefficient differences between the material of the substrate110and the material of the layer formed over the substrate110. The buffer layer120may be made of a Group III-V compound semiconductor, for example, at least one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, or AlInN.

The undoped semiconductor layer130is formed to achieve an enhancement in the crystallinity of the first-conductivity-type semiconductor layer140, which will be subsequently grown. The undoped semiconductor layer130may be identical to the first-conductivity-type semiconductor layer140, except that it has considerably low electrical conductivity, as compared to the first-conductivity-type semiconductor layer140, because the undoped semiconductor layer130is not doped with an n-type dopant.

Alternatively, the undoped semiconductor layer130may not be grown.

Referring toFIG. 3, the first-conductivity-type semiconductor layer140ais then grown over the undoped semiconductor layer130.

The first-conductivity-type semiconductor layer140amay be made of a semiconductor compound, for example, a Group III-V or Group II-VI compound semiconductor. The first-conductivity-type semiconductor layer140amay be doped with a first-conductivity-type dopant. When the first-conductivity-type semiconductor layer140ais an n-type semiconductor layer, the first-conductivity-type dopant is an n-type dopant. The n-type dopant may include Si, Ge, Sn, Se, or Te, although the embodiment is not limited thereto. When the first-conductivity-type semiconductor layer140ais a p-type semiconductor layer, the first-conductivity-type dopant is a p-type dopant. The p-type dopant may include Mg, Zn, Ca, Sr, Ba, or the like, although the embodiment is not limited thereto.

The first-conductivity-type semiconductor layer140amay include a semiconductor material having a formula of AlxInyGa1-x-yN (0≦x≦1, 0≦y≦1, and 0≦x+y≦1). For example, the first-conductivity-type semiconductor layer140amay be made of at least one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, or AlInGaP.

Referring toFIG. 4, the mask layer150is then formed over the first-conductivity-type semiconductor layer140a.

FIG. 4Ais a sectional view illustrating a structure obtained after formation of the mask layer150.FIGS. 4B to 4Gare plan views of the structure obtained after formation of the mask layer150.

In an exemplary embodiment, the first-conductivity-type semiconductor layers140aand140bare grown in accordance with an epitaxial lateral overgrowth (ELO) process.

Crystal defects such as threading dislocations advancing from an interface between the substrate110and a nitride (GaN) semiconductor layer grown over the substrate110to an upper surface of the light emitting device may be formed due to a lattice constant difference between the substrate110and the nitride semiconductor layer. The ELO process is a process for reducing crystal defects as described above.

The ELO process is a method for suppressing migration of crystal defects formed at the substrate and the nitride semiconductor layer toward a top of the light emitting device by growing a nitride semiconductor layer in a lateral direction.

The mask layer150has a masking region M covered by a mask, and a window region W not covered by a mask. Although the mask layer150can have several window regions W in the illustrated case, the following description will be given only in conjunction with one window region W, for simplicity of description.

The mask layer may include a silicon oxide film (SiO2) or a silicon nitride film (SiN).

The mask layer150may have a thickness d1 of 0.01 to 1.5 μm. When the mask layer150is excessively thin, it may not perform a mask function required in the ELO process. On the other hand, when the mask layer150is excessively thick, the resultant light emitting device may be unnecessarily thickened. In the latter case, the mask layer150may interfere with lateral growth of the first-conductivity-type semiconductor layer.

The width ratio between the window region W and the masking region M may be 1:0.1 to 10. In this case, the width of the window region W may be at least 0.5 μm.

Referring toFIG. 4A, the width of the window region W means a horizontal width of the light emitting device not covered by the mask, whereas the width of the masking region M means a horizontal width of the light emitting device covered by the mask. As described above with reference toFIG. 1, the width of the window region W has a relation with formation of the recess portion145because the recess portion145is formed at a portion of the first-conductivity-type semiconductor layer140bcorresponding to the window region W

Accordingly, when the window region W has a width dwless than 0.5 μm, it may interfere with formation of the recess portion145. In this case, the effects of enhancing the ESD characteristics of the light emitting device may be greatly reduced.

The mask layer150may be patterned such that the masking region M and window region W have certain horizontal section shapes when viewed from the top side.

The mask layer150suppresses migration of crystal defects formed at an interface between the substrate and the nitride semiconductor layer toward the top of the light emitting device. Accordingly, it may be possible to control formation of a threading dislocation such that the threading dislocation is formed at a desired position when viewed from the top side of the light emitting device.

For example, the horizontal section shape of the mask layer150may be a lattice shape, a stripe shape, a circular shape, an oval shape, or a polygonal shape when viewed from the top side.

The patterning of the mask layer150may be achieved such that the masking region M covered by the mask has a lattice shape, a stripe shape, a circular shape, an oval shape, or a polygonal shape. Alternatively, the pattering of the mask layer150may be achieved such that the window region W not covered by the mask has a lattice shape, a stripe shape, a circular shape, an oval shape, or a polygonal shape. Of course, the embodiment is not limited to the above-described conditions.

Referring toFIG. 4B, it can be seen that the mask layer150in the light emitting device ofFIG. 4Ais patterned to have a stripe shape.

Also, for example, the mask layer150may be patterned such that the masking region M has a lattice shape, and the window region W has a polygonal shape, as shown inFIG. 4C. On the other hand, as shown inFIG. 4D, the mask layer150may be patterned such that the masking region M has a polygonal shape. Also, as shown inFIG. 4E, the mask layer150may be patterned such that the masking region M has another stripe shape. As shown inFIG. 4F, the mask layer150may be patterned such that the masking region M has a circular shape. Also, as shown inFIG. 4G, the mask layer150may be patterned such that the masking region M has another polygonal shape.

Referring toFIG. 5, the first-conductivity-type semiconductor layer140bis re-grown over the window region W where no mask is formed.

The first-conductivity-type semiconductor layer140bhas the same composition as the material of the first-conductivity-type semiconductor layer140a.

As the first-conductivity-type semiconductor layer140bre-grown over the window region W is laterally grown in directions indicated by opposite arrows ofFIG. 5such that growing portions thereof are joined, the first-conductivity-type semiconductor layer140bhas an integrated structure.

Referring toFIG. 5, it can be seen that a threading dislocation Dw, which is formed at an upper interface of the substrate110, reaches a portion of the first-conductivity-type semiconductor layer140bre-grown in the region exposed through the window region W, whereas a threading dislocation DM, which is formed at the upper interface of the substrate110, cannot reach a portion of the first-conductivity-type semiconductor layer140blaterally grown in a region covered by the masking region M.

Accordingly, it may be possible to control the position of the threading dislocation D reaching the top of the light emitting device in accordance with the pattern shape of the mask layer150.

Referring toFIG. 6, the recess portion145is formed at a portion of the first-conductivity-type semiconductor layer140bwhere a threading dislocation Dwreaches after passing through the window region W of the mask layer150.

That is, as shown inFIG. 6, the recess portion145may be disposed over the window region W of the mask layer150.

The recess portion145may be naturally formed during the growth of the first-conductivity-type semiconductor layer140b. That is, the recess portion145may be formed simultaneously with the growth of the first-conductivity-type semiconductor layer140b.

For example, the recess portion145may be formed through control of the crystal growth rate of the first-conductivity-type semiconductor layer140b. The crystal growth rate may be controlled in accordance with, for example, the precursor flow rate, growth pressure, growth temperature, doping level, or the like of the first-conductivity-type semiconductor layer140b

The recess portion145is formed around the threading dislocation Dwthreading through the light emitting structure. Accordingly, it may be possible to avoid a phenomenon in which current is concentrated on the threading dislocation Dw. That is, the rate of carriers contributing to emission of light is increased, thereby suppressing generation of leakage current. Thus, the light emission efficiency of the light emitting device may be enhanced.

Thereafter, as shown inFIG. 7, the active layer160is grown over the first-conductivity-type semiconductor layer140b, which is provided, at the upper surface thereof, with the recess portion145.

In the active layer160, electrons injected through the first-conductivity-type semiconductor layer140meet holes injected through the subsequently-formed second-conductivity-type semiconductor layer180, thereby emitting light with energy determined by the intrinsic energy band of the material of the active layer160(light emitting layer).

The active layer160may have at least one of a single quantum well structure, a multi quantum well structure, a quantum wire structure, and a quantum dot structure. For example, the active layer160may have a multi quantum well structure through injection of tri-methyl gallium gas (TMGa), ammonia gas (NH3), nitrogen gas (N2), and tri-methyl indium gas (TMIn), although the embodiment is not limited thereto.

The active layer160may have a multilayer structure having well and barrier layers alternating at least one time. The well/barrier layers may have a layer pair structure made of at least one of InGaN/GaN, InGaN/InGaN, GaN/AlGaN, InAlGaN/GaN, GaAs(InGaAs)/AlGaAs, and GaP(InGaP)/AlGaP, although the embodiment is not limited thereto. The well layer may be made of a material having a narrower band gap than that of the barrier layer.

Since the active layer160is grown to conform to the structure of the upper surface of the first-conductivity-type semiconductor layer140b, the active layer can have a recess portion which is formed at a portion of the upper surface of the active layer160corresponding to the recess portion145of the first-conductivity-type semiconductor layer140b.

Referring toFIG. 8, the second-conductivity-type semiconductor layer180is subsequently formed over the active layer160.

The second-conductivity-type semiconductor layer180may be made of a semiconductor compound, for example, a Group III-V compound semiconductor doped with a second-conductivity-type dopant. For example, the second-conductivity-type semiconductor layer180may include a semiconductor material having a formula of InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1). When the second-conductivity-type semiconductor layer180is a p-type semiconductor layer, the second-conductivity-type dopant is a p-type dopant. The p-type dopant may include Mg, Zn, Ca, Sr, Ba, or the like, although the embodiment is not limited thereto. When the second-conductivity-type semiconductor layer180is an n-type semiconductor layer, the second-conductivity-type dopant is an n-type dopant. The n-type dopant may include Si, Ge, Sn, Se, or Te, although the embodiment is not limited thereto.

The light emitting structure, which includes the above-described first-conductivity-type semiconductor layer140, active layer160, and second-conductivity-type semiconductor layer180, may be formed using 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), or the like. Of course, the formation method is not limited to the above-described methods.

An electron blocking layer170may be interposed between the active layer160and the second-conductivity-type semiconductor layer180.

The electron blocking layer170may include AlGaN. The electron blocking layer170functions as a potential barrier to prevent electrons injected from the first-conductivity-type semiconductor layer140from migrating to the second-conductivity-type semiconductor layer180.

As the active layer160and electron blocking layer170are sequentially stacked, the recess portion formed at the region corresponding to the recess portion145has inclined surfaces having a reduced inclination. When the recess portion is completely filled with the material of the second-conductivity-type semiconductor layer180, the upper surface of the second-conductivity-type semiconductor layer180may be flat without having a recess portion. The current spreading layer190may then be formed over the second-conductivity-type semiconductor layer180.

The current spreading layer190may be formed on a portion or entirety of the upper surface of the second-conductivity-type semiconductor layer180, although the embodiment is not limited thereto. For example, the current spreading layer190may be formed such that at least a portion thereof vertically overlaps the second electrode184, which will be subsequently formed.

The current spreading layer190may be disposed such that at least a portion thereof contacts the second electrode184.

Referring toFIG. 9, the resulting structure is then mesa-etched from the second-conductivity-type semiconductor layer180to a portion of the first-conductivity-type semiconductor layer140.

The first electrode182may be disposed on a portion of the first-conductivity-type semiconductor layer140exposed in accordance with the mesa-etching. The second electrode184may be disposed on the second-conductivity-type semiconductor layer180.

The first and second electrodes182and184may be made of at least one of aluminum (Al), titanium (Ti), chromium (Cr), nickel (Ni), copper (Cu), or gold (Au), to have a single layer structure or a multilayer structure. As described above, the position of the threading dislocation reaching the top of the light emitting device is controlled using the mask layer150. Also, the recess portion is formed at the position where the threading dislocation reaching the first-conductivity-type semiconductor layer is present. Accordingly, it may be possible to reduce the stress of the active layer and to improve the ESD characteristics of the light emitting device. Thus, the reliability of the light emitting device is enhanced.

FIG. 10is a sectional view illustrating a light emitting device according to another embodiment.

FIG. 1illustrates an embodiment of a horizontal light emitting device. On the other hand,FIG. 10illustrates an embodiment of a vertical light emitting device.

No description will be given of the configuration ofFIG. 10identical to the configuration described with reference toFIG. 1. That is, the following description will be given only in conjunction with the configurations of the light emitting device ofFIG. 10different than those of the light emitting device ofFIG. 1.

The vertical light emitting device, which is designated by reference numeral “200”, has a structure vertically inverted from the structure of the horizontal light emitting device100. Accordingly, the recess portion145may have a structure having a width gradually reduced toward the top of the light emitting structure, namely, toward the first-conductivity-type semiconductor layer140.

The vertical light emitting device200may be fabricated by separating the substrate110, buffer layer120, and undoped semiconductor layer130, and then disposing an ohmic layer220and/or a reflection layer240, and a support substrate210on the second-conductivity-type semiconductor layer180.

The separation of the substrate110, buffer layer120, and undoped semiconductor layer130may be achieved through a laser lift-off (LLO) method using an excimer layer, or a dry or wet etching method.

When the second-conductivity-type semiconductor layer180is a p-type semiconductor layer, it has high contact resistance due to a low dopant concentration thereof. For this reason, the second-conductivity-type semiconductor layer180may exhibit poor metal ohmic characteristics. The ohmic layer220is adapted to improve the ohmic characteristics. The ohmic layer220is not a necessity.

The reflection layer240may be disposed beneath the ohmic layer220. The reflection layer240may be made of, for example, a selective combination of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, or Hf. Alternatively, the reflection layer240may be formed to have a multilayer structure, using the metal materials and a light-transmitting conductive material such as IZO, IZTO, IAZO, IGZO, IGTO, AZO, or ATO. The reflection layer240may have a lamination structure of IZO/Ni, AZO/Ag, IZO/Ag/Ni, AZO/Ag/Ni, or the like. When the reflection layer240is made of a material ohmic-contacting the light emitting structure (for example, the second-conductivity-type semiconductor layer180), the ohmic layer220may be dispensed with, although the embodiment is not limited thereto.

The reflection layer240may effectively reflect light emitted from the active layer160, thereby achieving a great enhancement in the light extraction efficiency of the light emitting device.

A current spreading layer230may be disposed beneath the second-conductivity-type semiconductor layer180of the light emitting structure. When the ohmic layer220is present, the current spreading layer230may be surrounded by the ohmic layer220.

The current spreading layer230may be made of a metal having high electrical conductivity. For example, the current spreading layer230may selectively include at least one selected from the group consisting of Ti, Au, Ni, In, Co, W, or Fe, although the embodiment is not limited thereto.

The current spreading layer230may be formed such that at least a portion thereof vertically overlaps the first electrode182.

The current spreading layer230uniformly spreads current flowing in the light emitting structure, thereby achieving an enhancement in the light emission efficiency of the light emitting device.

The support substrate210is disposed beneath the reflection layer240. A bonding layer250may be interposed between the reflection layer240and the support substrate210.

The bonding layer250may include a barrier metal, a bonding metal, or the like. For example, the bonding layer250may include at least one of Ti, Au, Sn, Ni, Cr, Ga, In, Bi, Cu, Ag, or Ta, although the embodiment is not limited thereto.

The support substrate120may be a conductive substrate in order to function as the second electrode while supporting the light emitting structure. The support substrate210may be made of a material having high electrical conductivity and high thermal conductivity. For example, the support substrate210may be formed as a base substrate having a certain thickness, using a material selected from the group consisting of molybdenum (Mo), silicon (Si), tungsten (W), copper (Cu), aluminum (Al), and alloys thereof. Also, the support substrate210may selectively include gold (Au), a Cu alloy, Ni, Cu—W, a carrier wafer (for example, GaN, Si, Ge, GaAs, ZnO, SiGe, SiC, SiGe, Ga2O3, or the like), a conductive sheet, or the like.

FIG. 11is a view illustrating a light emitting device package according to an exemplary embodiment.

The light emitting device package according to the illustrated embodiment, which is designated by reference numeral “300”, includes a body310formed with a cavity, first and second lead frames321and322mounted on the body310, a light emitting device mounted on the body310while being electrically connected to the first and second lead frames321and322, and a mold340formed in the cavity. The light emitting device may be the light emitting device100or200according to one of the above-described embodiment. In the illustrated case, the light emitting device is the light emitting device100.

The cavity may function as a reflector for reflecting light generated from the light emitting device included in the light emitting device package300. The cavity is not necessarily required, and the body310may have a flat upper surface.

The body310may be made of a silicon material, a synthetic resin material, or a metal material. When the body210is made of a conductive material such as a metal material, an insulating layer is coated over the surface of the body310, although not shown, in order to avoid electrical short circuit between the first and second lead frames321and322.

The first and second lead frames321and322are electrically isolated from each other, and supply current to the light emitting device100. The first and second lead frames321and322may also reflect light generated from the light emitting device100so as to achieve an enhancement in luminous efficiency. In addition, the first and second lead frames321and322may function to outwardly dissipate heat generated from the light emitting device100.

The light emitting device100may be mounted on the body310or on the first lead frame321or second lead frame322. In the illustrated embodiment, the light emitting device100is directly electrically connected to the first lead frame321while being connected to the second lead frame322via a wire330. The light emitting device100may be connected to the lead frames321and322, using a flip-chip method or a die-bonding method, in place of the wire-bonding method.

The mold340encapsulates the light emitting device100, to protect the light emitting device100. The mold340includes phosphors350, to change the wavelength of light emitted from the light emitting device100.

Light of a first wavelength range emitted from the light emitting device100is excited by the phosphors350, so that it is changed into light of a second wavelength range. As the light of the second wavelength range passes through a lens (not shown), the optical path thereof may be changed.

A plurality of light emitting device packages, each of which has the above-described structure according to the illustrated embodiment, is prepared, and is then arrayed on a substrate. Optical members, namely, light guide plates, prism sheets, diffusion sheets, etc., may be arranged on optical paths of the light emitting device packages. Such light emitting device packages, substrate, optical members may function as a light unit. In accordance with another embodiment, a display apparatus, an indication apparatus or a lighting system may be implemented using the semiconductor light emitting devices or light emitting device packages described in conjunction with the above-described embodiments. The lighting system may include, for example, a lamp or a street lamp.

Hereinafter, a lighting apparatus, a head lamp, and a backlight unit as embodiments of the lighting system including the above-described light emitting device packages will be described.

FIG. 12is an exploded perspective view illustrating a lighting apparatus according to an exemplary embodiment, which include the light emitting device packages according to the above-described embodiment.

Referring toFIG. 12, the lighting apparatus according to the illustrated embodiment includes a light source600for projecting light, a housing400in which the light source600is mounted, a heat dissipation unit500for dissipating heat generated from the light source600, and a holder700for coupling the light source600and heat dissipation unit500to the housing400.

The housing400includes a socket connection part410connected to an electric socket (not shown), and a body part420connected to the socket connection part410. The light source600is received in the body part420. A plurality of air holes430may be formed through the body part420.

Although a plurality of air holes430are formed through the body part420of the housing400in the illustrated case, a single air hole430may be formed through the body part420. Although the plural air holes430are circumferentially arranged, various arrangements thereof may be possible.

The light source600includes a circuit board610and a plurality of light emitting device packages650mounted on the circuit board610. Here, the circuit board610may be shaped to be fitted in an opening formed at the housing400. Also, the circuit board610may be made of a material having high thermal conductivity so as to transfer heat to the heat dissipation unit500, as will be described later.

The holder700is disposed under the light source600. The holder700includes a frame and air holes. Although not shown, an optical member may be disposed under the light source600so as to diffuse, scatter or converge light projected from the light emitting device packages650of the light source600.

FIG. 13is a view illustrating a head lamp according to an exemplary embodiment, in which the light emitting device according to one of the above-described embodiments is disposed.

Referring toFIG. 13, light emitted from a light emitting module710, in which the light emitting device according to one of the above-described embodiments is disposed, passes through a lens740after being reflected by a reflector720and a shade730, so as to be directed forwardly of a vehicle body.

As described above, the light emitting device according to the above-described embodiment, which is used in the light emitting module710, has ESD characteristics improved by the recess portion, and thus achieves an enhancement in reliability.

The light emitting device package, which is included in the light emitting module710, may include a plurality of light emitting devices, although the embodiment is not limited thereto.

FIG. 14is a view illustrating a display apparatus according to an exemplary embodiment in which light emitting device packages according to the above-described embodiment are arranged.

As shown inFIG. 14, the display apparatus according to the illustrated embodiment, which is designated by reference numeral “800”, includes a light source module, a reflection plate820disposed on a bottom cover810, a light guide plate840disposed in front of the reflection plate820to guide light emitted from the light source module to a front side of the display apparatus800, first and second prism sheets850and860disposed in front of the light guide plate840, a panel870disposed in front of the second prism sheet860, and a color filter880disposed in front of the panel870.

The light source module includes a circuit board830and light emitting device packages835mounted on the circuit board830. Here, a printed circuit board (PCB) may be used as the circuit board830. The light emitting device packages835may have the configuration described above in conjunction withFIG. 11.

The bottom cover810serves to receive the constituent elements of the display apparatus800. The reflection plate820may be provided as a separate element, as shown inFIG. 14, or may be provided as a material having high reflectivity is coated over a rear surface of the light guide plate840or a front surface of the bottom cover810.

Here, the reflection plate820may be made of a material having high reflectivity and capable of being formed into an ultra thin structure. Polyethylene terephthalate (PET) may be used for the reflection plate820.

The light guide plate840serves to scatter light emitted from the light source module so as to uniformly distribute the light throughout all regions of a liquid crystal display apparatus. Therefore, the light guide plate840may be made of a material having high refractivity and transmissivity. The material of the light guide plate840may include polymethylmethacrylate (PMMA), polycarbonate (PC) or polyethylene (PE). The light guide plate may be dispensed with. In this case, an air guide system, which transfers light in a space over the reflective sheet820, may be implemented.

The first prism sheet850may be formed by coating a polymer exhibiting light transmittance and elasticity over one surface of a base film. The first prism sheet850may have a prism layer having a plurality of three-dimensional structures in the form of a repeated pattern. Here, the pattern may be a stripe type in which ridges and valleys are repeated.

The second prism sheet860may have a similar structure to the first prism sheet850. The second prism sheet860may be configured such that the orientation direction of ridges and valleys formed on one surface of the base film of the second prism sheet860is perpendicular to the orientation direction of the ridges and valleys formed on one surface of the base film of the first prism sheet850. Such a configuration serves to uniformly distribute light transmitted from the light module and the reflective sheet820toward the entire surface of the panel870.

In the illustrated embodiment, an optical sheet may be constituted by the first prism sheet850and second prism sheet860. However, the optical sheet may include other combinations, for example, a microlens array, a combination of a diffusion sheet and a microlens array, and a combination of a prism sheet and a microlens array.

A liquid crystal display panel may be used as the panel870. Further, instead of the liquid crystal display panel870, other kinds of display devices requiring light sources may be provided.

The display panel870is configured such that a liquid crystal layer is located between glass bodies (transparent substrates), and polarizing plates are mounted on both glass bodies so as to utilize polarizing properties of light. Here, the liquid crystal layer has properties between a liquid and a solid. That is, in the liquid crystal layer, liquid crystals which are organic molecules having fluidity like the liquid are regularly oriented, and the liquid crystal layer displays an image using change of such molecular orientation due to an external electric field.

The liquid crystal display panel used in the display apparatus is of an active matrix type, and uses transistors as switches to adjust voltage applied to each pixel.

The color filter880is provided on the front surface of the panel870, and transmits only an R, G or B light component of light projected from the panel870per pixel, thereby displaying an image.

As is apparent from the above description, the embodiments improve the ESD characteristics of the light emitting device, and thus enhance the reliability of the light emitting device.