US20110198645A1 - Light emitting device and light emitting device package - Google Patents

Abstract

Disclosed are a light emitting device, a method of manufacturing the same and a light emitting device package. The light emitting device of the embodiment includes a light emitting structure including a first conductive semiconductor layer, a second conductive semiconductor layer and an active layer between the first and second conductive semiconductor layers; a fluorescent layer on the light emitting structure; and a light extracting structure on the fluorescent layer. The light extracting structure extracts light, which is generated in the light emitting structure and incident into an interfacial surface between the fluorescent layer and the light extracting structure, to an outside of the light emitting structure.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This application claims under 35 U.S.C. §119 to Korean Patent Application No. 10-2010-0013553, filed Feb. 12, 2010, which is hereby incorporated by reference in its entirety.
BACKGROUND
• The embodiment relates to a light emitting device, a method of manufacturing the same, and a light emitting device package.
• A light emitting device (LED) includes a p-n junction diode having a characteristic of converting electric energy into light energy. The p-n junction diode can be formed by combining group III and V elements of the periodic table. The LED can represent various colors by adjusting the compositional ratio of compound semiconductors.
• When forward voltage is applied to the LED, electrons of an n layer are bonded with holes of a p layer, so that energy corresponding to an energy gap between a conduction band and a valance band may be generated. This energy is mainly realized as heat or light, and the LED emits the energy as the light.
• A nitride semiconductor represents superior thermal stability and wide bandgap energy, so the nitride semiconductor has been spotlighted in the field of optical devices and high-power electronic devices. In particular, blue, green, and UV light emitting devices employing the nitride semiconductor have already been developed and extensively used.
• Meanwhile, in order to realize a white LED package, LEDs of red, green and blue colors, which are three primary colors of light, are combined with each other, the yellow phosphor (YAG or TAG) is added to the blue LED, or red/green/blue phosphors are employed in the UV LED.
• However, in the white LED package using the phosphor according to the related art, the phosphor may not be uniformly distributed around an LED chip, resulting in the wide color temperature distribution.
• In addition, according to the related art, the distribution area of the phosphor is relatively larger than the area of the LED, so that the phosphor may not be uniformly distributed around the LED, resulting in the wide color temperature distribution.
• In addition, according to the related art, the light converted by the phosphor is total-reflected from a boundary surface of the background material and then introduced again into the LED chip, so that the efficiency of the white LED may be degraded.
BRIEF SUMMARY
• The embodiment provides a light emitting device, a method of manufacturing the same, and a light emitting device package, capable of improving the extraction efficiency of light converted by a phosphor and reducing the variation in the color temperature according to the radiation angle.
• A light emitting device according to the embodiment includes a light emitting structure including a first conductive semiconductor layer, a second conductive semiconductor layer and an active layer between the first and second conductive semiconductor layers; a fluorescent layer on the light emitting structure; and a light extracting structure on the fluorescent layer, wherein the light extracting structure extracts light, which is generated in the light emitting structure and incident into an interfacial surface between the fluorescent layer and the light extracting structure, to an outside of the light emitting structure.
• A method of manufacturing the light emitting device according to the embodiment includes forming a light emitting structure including a first conductive semiconductor layer, an active layer and a second conductive semiconductor layer; forming a fluorescent layer on the light emitting structure; and forming a light extracting structure on the fluorescent layer.
• A light emitting device package according to the embodiment includes a light emitting device having a fluorescent layer on a light emitting structure and a light extracting structure on the fluorescent layer wherein the light extracting structure extracts light, which is generated in the light emitting structure and incident into an interfacial surface between the fluorescent layer and the light extracting structure, to an outside of the light emitting structure; and a package body to install the light emitting device therein.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a sectional view showing a light emitting device according to the embodiment;
• FIG. 2 is a view showing a light emitting pattern of a light emitting device according to the related art;
• FIG. 3 is a view showing a light emitting pattern of a light emitting device according to the embodiment;
• FIGS. 4 to 7aare sectional views showing the procedure for manufacturing a light emitting device according to the embodiment;
• FIG. 7bis a sectional view showing a light emitting device according to another embodiment;
• FIG. 8 is a sectional view showing a light emitting device package according to the embodiment;
• FIG. 9 is a perspective view showing a lighting unit according to the embodiment; and
• FIG. 10 is an exploded perspective view showing a backlight unit according to the embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
• Hereinafter, a light emitting device, a method of manufacturing the same and a light emitting device package according to the embodiments will be described in detail with reference to accompanying drawings.
• In the description of embodiments, it will be understood that when a layer (or film) is referred to as being ‘on’ another layer or substrate, it can be directly on another layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being ‘under’ another layer, it can be directly under another layer, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being ‘between’ two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
Embodiments
• FIG. 1 is a sectional view showing alight emitting device100 according to the embodiment.
• Thelight emitting device100 according to the embodiment includes alight emitting structure110 having a firstconductive semiconductor layer112, anactive layer114 and a secondconductive semiconductor layer116, afluorescent layer130 formed on thelight emitting structure110, and a light extractingstructure140 formed on thefluorescent layer130.
• In detail, thelight extracting structure140 may include patterns. The patterns may be periodic patterns or non-periodic patterns. In addition, the patterns may have the same shape or different shapes, which are repeated periodically or non-periodically.
• The patterns diffract, disperse or scatter the light incident into the interfacial surface between thefluorescent layer130 and thelight extracting structure140, and may have various shapes without limitation.
• Thefluorescent layer130 may have a uniform thickness.
• Thelight extracting structure140 may include a dielectric substance including at least one of oxide, nitride and chloride, but the embodiment is not limited thereto.
• Thelight extracting structure140 may include a material having a refractive index different from that of thefluorescent layer130. For instance, the light extractingstructure140 may have the refractive index higher or lower than that of thefluorescent layer130.
• According to the embodiment, a background material (not shown) may be formed on the light extractingstructure140, in which the background material has a refractive index different from that of thelight extracting structure140.
• Thelight extracting structure140 may have periodicity in the range of 50 nm to 3000 nm, but the embodiment is not limited thereto.
• According to the light emitting device of the embodiment, the light extraction efficiency in the phosphor can be improved due to thefluorescent layer130 so that the efficiency of the white LED can be improved. In addition, since the emission distribution in the phosphor can be adjusted, the variation in color temperature according to the radiation angle of the white LED can be reduced. Hereinafter, thelight emitting device100 according to the embodiment will be described.
• The white LED can be realized in the form of a combination of a blue LED and a phosphor. One of important factors in the white LED is to reduce the variation in the color temperature according to the radiation angle. In this regard, the fluorescent layer having the uniform thickness is formed on a top of a chip through a conformal coating process. That is, the phosphor is prepared as a light source having the position and area identical to those of the blue LED, thereby reducing the variation of the color temperature in the package according to the light route except for the chromatic aberration.
• The travelling route of the light having the long wavelength, which is converted by the phosphor, is substantially identical to the travelling route of the blue light, which is not absorbed in the phosphor, so the variation in the color temperature according to the travelling route of the light can be disregarded.
• FIG. 2 is a sectional view showing the light emitting pattern of a light emitting device according to the related art.
• As shown inFIG. 2, the color temperature variation may occur according to the radiation angle even if the fluorescent layer having the uniform thickness is coated through the conformal coating process.
• This is because the distribution A of the blue light emitted from thelight emitting structure10 is different from the distribution B of the light converted by thephosphor30.
• That is, the distribution A of the blue light is determined depending on the interfacial surface between GaN and the background material (air or Si gel) and the light extracting structure. In detail, the blue light is more concentrated in the vertical direction.
• In contrast, since the light having the long wavelength, which is converted by the phosphor, is emitted through the spontaneous emission, the light can be distributed in the lateral direction with the same probability. Thus, if the white LED is realized by combining these two lights, the light intensity may be increased in the vertical direction, that is, the relatively higher color temperature is obtained as the radiation angle is directed in the vertical direction.
• In particular, since the vertical type GaN LED has the emission distribution concentrated in the vertical direction more than the lateral type GaN LED, it is necessary to design and develop a chip having the emission distribution similar to that of the light converted by the phosphor.
• In addition, according to the related art, the light converted by the phosphor is total-reflected from a boundary surface of the background material and then introduced again into the GaN LED, so that the efficiency of the white LED may be degraded.
• FIG. 3 is a sectional view showing a light emitting pattern of a light emitting device according to the embodiment.
• The light emitting device according to the embodiment may include alight emitting structure110, and afluorescent layer130 formed on the light emitting structure. In addition, a background material (not shown) having the uniform thickness and alight extracting structure140 having a refractive index different from that of thefluorescent layer130 may be formed on thefluorescent layer130. Thelight extracting structure140 may include a material selected from oxide, nitride or chloride, such as SiO₂, Si₃N₄, or TiO₂. In addition, the refractive index, the pattern period and the pattern height of the material for maximizing the extraction efficiency can be determined depending on the type of the background material (air or Si gel).
• Due to thelight extracting structure140 having the above structure, the emission distribution in thefluorescent layer130 may be directed in the vertical direction C rather than the lateral direction while representing the light extraction efficiency the same as that of the square lattice pattern having periodicity according to the related art.
• The light can be concentrated in the vertical direction by thelight extracting structure140 because the light diffraction occurs due to the periodicity of the pattern lattice. If the fluorescent layer having the uniform thickness is formed on the vertical type chip having the patterns, the variation in the color temperature can be reduced.
• According to the light emitting device of the embodiment, the light extraction efficiency in the phosphor can be improved due to the fluorescent layer including the patterns, so that the efficiency of the white LED can be improved. In addition, the variation in the color temperature according to the radiation angle of the white LED can be reduced by adjusting the emission distribution in the phosphor.
• Hereinafter, the method for manufacturing the light emitting device according to the embodiment will be described with reference toFIGS. 4 to 7a.
• First, afirst substrate105 is prepared as shown inFIG. 1. Thefirst substrate105 may include a conductive substrate or an insulating substrate. For instance, thefirst substrate105 may include at least one of Al₂O₃, SiC, Si, GaAs, GaN, ZnO, Si, GaP, InP, Ge, and Ga₂O₃. A concave-convex structure can be formed on thefirst substrate105, but the embodiment is not limited thereto.
• Thefirst substrate105 can be subject to the wet cleaning to remove impurities from the surface of thefirst substrate105.
• Then, thelight emitting structure110 including the firstconductive semiconductor layer112, theactive layer114 and thesecond semiconductor layer116 is formed on thefirst substrate105.
• A buffer layer (not shown) can be formed on thefirst substrate105. The buffer layer may attenuate lattice mismatch between thelight emitting structure110 and thefirst substrate105. The buffer layer may include the group III-V compound semiconductor. For instance, the buffer layer may include at least one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, and AlInN. An undoped semiconductor layer can be formed on the buffer layer, but the embodiment is not limited thereto.
• The firstconductive semiconductor layer112 may include a group III-V compound semiconductor doped with a first conductive dopant. If the firstconductive semiconductor layer112 is an N type semiconductor layer, the first conductive dopant is an N type dopant, such as Si, Ge, Sn, Se, or Te, but the embodiment is not limited thereto.
• The firstconductive semiconductor layer112 may include semiconductor material having the compositional formula of In_xAl_yGa_1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1).
• In addition, the firstconductive semiconductor layer112 may include at least one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, and InP.
• The firstconductive semiconductor layer102 may include an N type GaN layer, which is formed through the CVD (Chemical Vapor Deposition), MBE (Molecular Beam Epitaxy), sputtering or HVPE (Hydride Vapor Phase Epitaxy).
• In addition, the firstconductive semiconductor layer112 can be formed by injecting trimethyl gallium (TMGa) gas, ammonia (NH₃) gas, nitrogen (N₂) gas and silane (SiH₄) gas including n type impurities, such as silicon, into the chamber.
• Electrons injected through the firstconductive semiconductor layer112 meet holes injected through the secondconductive semiconductor layer116 at theactive layer114, so that theactive layer114 can emit the light having energy determined based on the intrinsic energy band of the active layer (light emitting layer)114.
• Theactive layer114 may include at least one of a single quantum well structure, a multiple quantum well (MQW) structure, a quantum wire structure and a quantum dot structure. For instance, theactive layer114 can be formed with the MQW structure by injecting TMGa gas, NH3 gas, N2 gas, and trimethyl indium (TMIn) gas, but the embodiment is not limited thereto.
• Theactive layer114 may have a well/barrier layer including at least one of InGaN/GaN, InGaN/InGaN, GaN/AlGaN, InAlGaN/GaN, GaAs(InGaAs)/AlGaAs and GaP(InGaP)/AlGaP, but the embodiment is not limited thereto. The well layer may include material having the bandgap energy lower than that of the barrier layer.
• A conductive clad layer (not shown) can be formed on and/or under theactive layer114. The conductive clad layer may include an AlGaN-based semiconductor having the bandgap energy higher than that of theactive layer114.
• The secondconductive semiconductor layer116 may include the group III-V compound semiconductor doped with the second conductive dopant. For instance, the secondconductive semiconductor layer116 may include the semiconductor material having the compositional formula of In_xAl_yGa_1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1). In detail, the secondconductive semiconductor layer116 may include one selected from the group consisting of GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP. If the secondconductive semiconductor layer116 is a P type semiconductor layer, the second conductive dopant includes the P type dopant such as Mg, Zn, Ca, Sr, or Ba. The secondconductive semiconductor layer116 can be prepared as a single layer or a multiple layer, but the embodiment is not limited thereto.
• The secondconductive semiconductor layer116 may include a p type GaN layer, which can be formed by injecting TMGa gas, NH3 gas, N2 gas and (EtCp₂Mg){Mg(C₂H₅C₅H₄)2} gas including p type impurities (for example, Mg) into the chamber, but the embodiment is not limited thereto.
• According to the embodiment, the firstconductive semiconductor layer112 may include an N type semiconductor layer and the second conductive semiconductor layer106 may include a P type semiconductor layer, but the embodiment is not limited thereto. In addition, a semiconductor layer, such as an N type semiconductor layer (not shown) having polarity opposite to that of the secondconductive semiconductor layer116, can be formed on the secondconductive semiconductor layer116. Thus, thelight emitting structure110 may include one of an N-P junction structure, a P-N junction structure, an N-P-N junction structure, and a P-N-P junction structure.
• After that, thesecond electrode layer120 is formed on the secondconductive semiconductor layer116.
• Thesecond electrode layer120 may include an ohmic layer, areflective layer122, an adhesive layer (not shown) and asupport substrate123.
• For instance, thesecond electrode layer120 may include the ohmic layer that comes into ohmic contact with thelight emitting structure110 to easily supply power to thelight emitting structure110. The ohmic layer can be prepared as a multiple layer by stacking a metal, a metal alloy, and metal oxide.
• For instance, the ohmic layer may include at least one selected from the group consisting of ITO (indium tin oxide), IZO (indium zinc oxide), IZTO (indium zinc tin oxide), IAZO (indium aluminum zinc oxide), IGZO (indium gallium zinc oxide), IGTO (indium gallium tin oxide), AZO (aluminum zinc oxide), ATO (antimony tin oxide), GZO (gallium zinc oxide), IZON (IZO nitride), AGZO (Al—Ga ZnO), IGZO (In—Ga ZnO), ZnO, IrOx, RuOx, NiO, RuOx/ITO, Ni/IrOx/Au, Ni/IrOx/Au/ITO, Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and Hf, but the embodiment is not limited thereto.
• In addition, thesecond electrode layer120 may include thereflective layer122 to reflect the light incident from thelight emitting structure110, thereby improving the light extraction efficiency.
• For instance, thereflective layer122 may include a metal or a metal alloy including at least one selected from the group consisting of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and Hf. In addition, thereflective layer122 can be prepared as a multiple layer by using the above metal or metal alloy and transmissive conductive material, such as IZO, IZTO, IAZO, IGZO, IGTO, AZO, or ATO. For instance, thereflective layer122 may have the stack structure including IZO/Ni, AZO/Ag, IZO/Ag/Ni, or AZO/Ag/Ni.
• In addition, if thesecond electrode layer120 includes the adhesive layer, thereflective layer122 may serve as a bonding layer or may include barrier metal or bonding metal. For instance, the adhesive layer may include at least one selected from the group consisting of Ti, Au, Sn, Ni, Cr, Ga, In, Bi, Cu, Ag and Ta.
• Thesecond electrode120 includes thesupport substrate123. Thesupport substrate123 supports thelight emitting structure110 to supply power to thelight emitting structure110. Thesupport substrate123 may include a metal having superior electric conductivity, a metal alloy or a conductive semiconductor material.
• For instance, thesupport substrate123 may include at least one selected from the group consisting of Cu, a Cu alloy, Au, Ni, Mo, Cu—W, and a carrier wafer, such as Si, Ge, GaAs, GaN, ZnO, SiGe, and SiC.
• Thesupport substrate123 may have a thickness of about 30 μm to 500 μm which may vary depending on the design rule of the light emitting device.
• Thesupport substrate123 can be formed through the electrochemical metal deposition scheme, the plating scheme or the bonding scheme using eutectic metal.
• Then, as shown inFIG. 5, thefirst substrate105 is removed such that the firstconductive semiconductor layer112 can be exposed. Thefirst substrate105 can be removed through the laser lift off scheme or the chemical lift off scheme. In addition, thefirst substrate105 can be removed by physically grinding thefirst substrate105.
• According to the laser lift off scheme, predetermined energy supplied in the normal temperature is absorbed in the interfacial surface between thefirst substrate105 and the light emitting structure, so that the bonded surface of the light emitting structure is thermally decomposed, thereby separating thesubstrate105 from the light emitting structure.
• Then, as shown inFIG. 6, thefluorescent layer130 is formed on thelight emitting structure110. Thefluorescent layer130 has a uniform thickness.
• Thefluorescent layer130 can be formed by adding the yellow phosphor (YAG or TAG) to the blue LED, or by combining red/green/blue phosphors with the UV LED, but the embodiment is not limited thereto.
• The phosphor may include a host material and an active material. For instance, a cesium (Cs) active material can be added to a YAG (yttrium aluminum garnet) host material, or a europium (Er) active material can be added to a silicate-based host material, but the embodiment is not limited thereto.
• The top surface of thefluorescent layer130 may be planarized through the conformal coating process, but the embodiment is not limited thereto. Thefluorescent layer130 may have the uniform thickness. Since thefluorescent layer130 having the planar top surface is uniformly formed on thelight emitting structure110, the phosphors can be uniformly distributed around the chip of the light emitting device and surface light emission is possible so that the optical design can be facilitated.
• Then, thelight extracting structure140 is formed on thefluorescent layer130 as shown inFIG. 7a.
• Thelight extracting structure140 may include a dielectric substance including at least one of oxide, nitride and chloride, such as SiO₂, Si₃N₄, and TiO₂, but the embodiment is not limited thereto.
• For instance, thelight extracting structure140 can be formed by forming a dielectric layer (not shown) on thefluorescent layer130 and then patterning the dielectric layer.
• Besides the patterns formed by patterning the dielectric layer using a mask, thelight extracting structure140 may include a plurality of protrusions for improving the light extraction efficiency. For instance, thelight extracting structure140 may include a roughness formed by wet-etching the dielectric layer.
• Thelight extracting structure140 can be formed by using a material having the refractive index different from that of thefluorescent layer130. For instance, thelight extracting structure140 may have the refractive index higher or lower than that of thefluorescent layer130.
• Thelight extracting structure140 may have periodicity in the range of 50 nm to 3000 nm, but the embodiment is not limited thereto.
• According to the embodiment, a background material (air or Si gel) may be additionally formed on thelight extracting structure140, in which the background material may have the refractive index different from that of thelight extracting structure140.
• Since thelight extracting structure140 has the periodicity, the light extraction efficiency can be improved, so that the emission distribution in thefluorescent layer130 may be directed in the vertical direction rather than the lateral direction, thereby reducing the variation in the color temperature.
• According to the light emitting device and the method of manufacturing the same of the embodiment, the light extraction efficiency in the phosphor can be improved due to the fluorescent layer including the patterns, so that the efficiency of the white LED can be improved. In addition, the variation in the color temperature according to the radiation angle of the white LED can be reduced by adjusting the emission distribution in the phosphor.FIG. 7bis a cross-sectional view illustrating a light emitting device according to another embodiment.
• Alight emitting device102 according to the other embodiment may include alight emitting structure110 including a firstconductive semiconductor layer112, anactive layer114, and a secondconductive semiconductor layer116, a firstdielectric layer151 formed on a part of an upper surface of thelight emitting structure110, and apad electrode160 formed on thefirst dielectric layer151.
• In the embodiment, adielectric layer150 may include thefirst dielectric layer151 and asecond dielectric layer152 formed on a side of thelight emitting structure110. Herein, thefirst dielectric layer151 and thesecond dielectric layer152 may be connected to each other.
• In the embodiment, afirst electrode161 may be included on thelight emitting structure110. Thepad electrode160 may be electrically connected to thefirst electrode161.
• Thelight extracting structure140 may be formed at the upper surface of thelight emitting structure110 to improving the light extraction efficiency.
• Asecond electrode layer120 is formed under thelight emitting structure110. Thesecond electrode layer120 may include anohmic layer121, areflection layer122, ajunction layer123, and asupport substrate124.
• Aprotection member190 may be formed obliquely below thelight emitting structure110. A Current Blocking Layer (CBL)139 may be formed between thelight emitting structure110 and theohmic layer121.
• Theprotection member190 may be formed circumferentially between thelight emitting structure110 and thejunction layer123. Accordingly, theprotection member190 may be formed as a ring shape, a loop shape, or a square shape. A part of theprotection member190 may be overlapped with thelight emitting structure110 in a vertical direction.
• Theprotection member190 may reduce a possibility of a short circuit between thejunction layer123 and theactive layer114 by increasing a distance between each side of thejunction layer123 and theactive layer114.
• Theprotection member190 may also prevent occurrence of the short circuit during a chip separation process.
• Theprotection member190 may be formed with electric insulative material, material having lower electric conductivity than thereflection layer122 or thejunction layer123, or material forming a Schottky connection with the secondconductive semiconductor layer116. For instance, theprotection member190 may include at least one of ITO, IZO, IZTO, IAZO, IGZO, IGTO, AZO, ATO, ZnO, SiO2, SiOx, SiOxNy, Si₃N₄, Al₂O₃, TiOx, TiO2, Ti, Al or Cr.
• FIG. 8 is a view showing a light emittingdevice package200 including the light emitting device according to the embodiments.
• The light emittingdevice package200 according to the embodiment includes apackage body205, third and fourth electrode layers213 and214 formed on thepackage body205, thelight emitting device100 provided on thepackage body205 and electrically connected to the third and fourth213 and214 and amolding member240 that surrounds thelight emitting device100.
• Thepackage body205 may include silicon, synthetic resin or metallic material. An inclined surface may be formed around thelight emitting device100.
• The third and fourth electrode layers213 and214 are electrically isolated from each other to supply power to thelight emitting device100. In addition, the third and fourth electrode layers213 and214 reflect the light emitted from thelight emitting device100 to improve the light efficiency and dissipate heat generated from thelight emitting device100 to the outside.
• The vertical type light emitting device shown inFIG. 1 can be employed as thelight emitting device100, but the embodiment is not limited thereto. For instance, the lateral type light emitting device can be used as thelight emitting device100.
• Thelight emitting device100 can be installed on thepackage body205 or the third and fourth electrode layers213 and214.
• Thelight emitting device100 is electrically connected to thethird electrode layer213 and/or thefourth electrode layer214 through at least one of a wire bonding scheme, a flip chip bonding scheme and a die bonding scheme. According to the embodiment, thelight emitting device100 is electrically connected to thethird electrode layer213 through awire230 and electrically connected to thefourth electrode layer214 through the die bonding scheme.
• Themolding member240 surrounds thelight emitting device100 to protect thelight emitting device100. In addition, themolding member240 may include phosphors to change the wavelength of the light emitted from thelight emitting device100.
• A plurality of light emitting device packages according to the embodiment may be arrayed on a substrate, and an optical member including a light guide plate, a prism sheet, a diffusion sheet or a fluorescent sheet may be provided on the optical path of the light emitted from the light emitting device package. The light emitting device package, the substrate, and the optical member may serve as a backlight unit or a lighting unit. For instance, the lighting system may include a backlight unit, a lighting unit, an indicator, a lamp or a streetlamp.
• FIG. 9 is a perspective view showing alighting unit1100 according to the embodiment. Thelighting unit1100 shown inFIG. 9 is an example of a lighting system and the embodiment is not limited thereto.
• Referring toFIG. 9, thelighting unit1100 includes acase body1110, alight emitting module1130 installed in thecase body1110, and aconnection terminal1120 installed in thecase body1110 to receive power from an external power source.
• Preferably, thecase body1110 includes material having superior heat dissipation property. For instance, thecase body1110 includes metallic material or resin material.
• Thelight emitting module1130 may include asubstrate1132 and at least one light emittingdevice package200 installed on thesubstrate1132.
• The substrate1123 includes an insulating member printed with a circuit pattern. For instance, thesubstrate1132 includes a PCB (printed circuit board), an MC (metal core) PCB, an F (flexible) PCB, or a ceramic PCB.
• In addition, thesubstrate1132 may include material that effectively reflects the light. The surface of thesubstrate1132 can be coated with a color, such as a white color or a silver color, to effectively reflect the light.
• At least one light emittingdevice package200 can be installed on thesubstrate1132. Each light emittingdevice package200 may include at least one light emittingdevice100. Thelight emitting device100 may include a colored LED that emits the light having the color of red, green, blue or white and a UV (ultraviolet) LED that emits UV light.
• The light emitting device packages200 of thelight emitting module1130 can be variously arranged to provide various colors and brightness. For instance, the white LED, the red LED and the green LED can be arranged to achieve the high color rendering index (CRI).
• Theconnection terminal1120 is electrically connected to thelight emitting module1130 to supply power to thelight emitting module1130. Theconnection terminal1120 has a shape of a socket screw-coupled with the external power source, but the embodiment is not limited thereto. For instance, theconnection terminal1120 can be prepared in the form of a pin inserted into the external power source or connected to the external power source through a wire.
• FIG. 10 is an exploded perspective view showing abacklight unit1200 according to the embodiment. Thebacklight unit1200 shown inFIG. 10 is an example of a lighting system and the embodiment is not limited thereto.
• Thebacklight unit1200 according to the embodiment includes alight guide plate1210, alight emitting module1240 for providing the light to thelight guide plate1210, areflective member1220 positioned below the light guide plate, and abottom cover1230 for receiving thelight guide plate1210, light emittingmodule1240, and thereflective member1220 therein, but the embodiment is not limited thereto.
• Thelight guide plate1210 diffuses the light to provide surface light. Thelight guide1210 includes transparent material. For instance, thelight guide plate1210 can be manufactured by using acryl-based resin, such as PMMA (polymethyl methacrylate), PET (polyethylene terephthalate), PC (polycarbonate), COC or PEN (polyethylene naphthalate) resin.
• Thelight emitting module1240 supplies the light to the lateral side of thelight guide plate1210 and serves as the light source of the display device including the backlight unit.
• Thelight emitting module1240 can be positioned adjacent to thelight guide plate1210, but the embodiment is not limited thereto. In detail, thelight emitting module1240 includes asubstrate1242 and a plurality of light emitting device packages200 installed on thesubstrate1242 and thesubstrate1242 can be adjacent to thelight guide plate1210, but the embodiment is not limited thereto.
• Thesubstrate1242 may include a printed circuit board (PCB) having a circuit pattern (not shown). In addition, thesubstrate1242 may also include a metal core PCB (MCPCB) or a flexible PCB (FPCB), but the embodiment is not limited thereto.
• In addition, the light emitting device packages200 are arranged such that light exit surfaces of the light emitting device packages200 are spaced apart from thelight guide plate1210 by a predetermined distance.
• Thereflective member1220 is disposed below thelight guide plate1210. Thereflective member1220 reflects the light, which is travelled downward through the bottom surface of thelight guide plate1210, toward thelight guide plate1210, thereby improving the brightness of the backlight unit. For instance, thereflective member1220 may include PET, PC or PVC resin, but the embodiment is not limited thereto.
• Thebottom cover1230 may receive thelight guide plate1210, thelight emitting module1240, and thereflective member1220 therein. To this end, thebottom cover1230 has a box shape with an open top surface, but the embodiment is not limited thereto.
• Thebottom cover1230 can be manufactured through a press process or an extrusion process by using metallic material or resin material.
• As described above, the lighting system according to the embodiment includes the light emitting device package, so that the reliability of the lighting system can be improved.
• Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.
• Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

Claims (8)

1. A light emitting device comprising:

a light emitting structure including a first conductive semiconductor layer, a second conductive semiconductor layer and an active layer between the first and second conductive semiconductor layers;

a fluorescent layer on the light emitting structure; and

a light extracting structure on the fluorescent layer,

wherein the light extracting structure extracts light which is generated in the light emitting structure and incident into an interfacial surface between the fluorescent layer and the light extracting structure, to an outside of the light emitting structure.

2. The light emitting device as claimed inclaim 1, wherein the light extracting structure comprises a periodic pattern or a non-periodic pattern.

3. The light emitting device as claimed inclaim 1, wherein the fluorescent layer has an uniform thickness.

4. The light emitting device as claimed inclaim 1, wherein the light extracting structure comprises a dielectric substance including at least one of oxide, nitride and chloride.

5. The light emitting device as claimed inclaim 1, wherein the light extracting structure comprises a material having a refractive index different from that of the fluorescent layer.

6. The light emitting device as claimed inclaim 1, further comprising a background material on the light extracting structure, wherein the background material has a refractive index different from that of the light extracting structure.

7. The light emitting device as claimed inclaim 2, wherein the pattern has a period of 50 nm to 3000 nm.

8. A light emitting device package comprising:

a light emitting device claimed inclaim 1; and

a package body to install the light emitting device therein.

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