Light emitting device and lighting system with the same

Embodiments provide a light emitting device including a light emitting structure having a first conduction type semiconductor layer, an active layer, and a second conduction type semiconductor layer, a metal filter of an irregular pattern on the light emitting structure, and openings between the irregular patterns in the metal filter.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2011-0064933, filed in Korea on Jun. 30, 2011, which is hereby incorporated in its entirety by reference as if fully set forth herein.

TECHNICAL FIELD

Embodiments relate to a light emitting device and a lighting system with the same.

BACKGROUND

The light emitting device, such as a light emitting diode of III-V group or II-VI group compound semiconductor or a laser diode, can produce various colors, such as red, blue, and ultra-violet owing to development of the thin film growth technology and device materials therefor, as well as a white color of good efficiency by using a fluorescent material or mixing colors.

Owing to development of such technologies, application of the light emitting device is expanding, not only to the display device, but also even to transmission modules of optical communication means, a light emitting diode back light unit which is replacing CCFL (Cold Cathode Fluorescence Lamp) of the back light unit in an LCD (Liquid Crystal Display) device, white light emitting diode lighting fixtures, car head lights, and signal lamps.

SUMMARY

Embodiments provide a light emitting device and a lighting system with the same.

In one embodiment, a light emitting device includes a light emitting structure having a first conduction type semiconductor layer, an active layer, and a second conduction type semiconductor layer, a metal filter of an irregular pattern disposed on the light emitting structure, andopenings disposed between the irregular patterns in the metal filter.

The metal filter may include aluminum or Titanium.

The metal filter may reflect a light from the light emitting structure.

The light emitting structure may have a roughness disposed on a surface thereof.

The metal filter may have a stripe type pattern.

The metal filter may have a mesh type pattern.

The pattern may have irregular widths.

The openings may have irregular widths.

At least one of the patterns may have a first side width different from a second side width.

The pattern width may be 10 to 20% of the opening width.

The metal filter may have a thickness of 1 μm to 10 μm.

The light emitting device may further include a transparent conductive layer disposed on the first conduction type semiconductor layer and the metal filter.

The light emitting device may further include a transparent conductive layer disposed on the first conduction type semiconductor layer, and the metal filter may be disposed on the transparent conductive layer.

The light emitting device may further include a transparent conductive layer disposed on the first conduction type semiconductor layer, and the metal filter may be arranged in the transparent conductive layer.

The transparent conductive layer may include a first transparent conductive layer disposed on the first conduction type semiconductor layer, and a second transparent conductive layer disposed on the first transparent conductive layer, and the metal filter may be disposed between the first transparent conductive layer and the second transparent conductive layer.

The light emitting device may further include a passivation layer disposed at a side of the light emitting structure extended to sides and a top side of the transparent conductive layer.

The passivation layer may be formed of an insulating material.

The passivation layer may be formed of a non-conductive oxide or a non-conductive nitride.

The passivation layer may be disposed at a portion of a side of the second conduction type semiconductor layer, with an open region in the side of the second conduction type semiconductor layer.

In another embodiment, a lighting system includes a first lead frame and a second lead frame, a light emitting device package having the light emitting device, a circuit board for supplying a current to the light emitting device package, and an optical member for forwarding a light from the light emitting device package.

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.

FIG. 1Ais a view illustrating a light emitting device in accordance with one embodiment.

Referring toFIG. 1A, the light emitting device100includes, on a metal support160, a bonding layer150, a reflective layer140, an ohmic layer130, a light emitting structure120, and a transparent conductive layer170having a metal filter180patterned thereon.

In these embodiments or other embodiments, the light emitting device100may be semiconductor light emitting device, for example light emitting diode.

Since the metal support160can serve as a second electrode, the metal support160may be formed of a metal having good electric conductivity, and, since the metal support160is required to dissipate heat generated during operation of the light emitting device adequately, the metal support160may be formed of a metal having good heat conductivity.

The metal support160may be formed of a material selected from a group of materials including Mo, Si, W, Cu and Al, or an alloy of above, and may include Au, a Cu Alloy, Ni, Cu—W, a carrier wafer (For an example: GaN, Si, Ge, GaAs, ZnO, SiGe, SiC, SiGe, Ga2O3and so on), selectively.

And, the metal support160may have enough mechanical strength to be split into individual chips by scribing and breaking while causing no bending of an entire nitride semiconductor.

The bonding layer150bonds the reflective layer140to the metal support160, and the reflective layer140may serve as an adhesion layer. The bonding layer150may be formed of a material selected from a group of materials including Au, Sn, In, Ag, Ni, Nb and Cu, or an alloy of above.

The reflective layer140may have a thickness of about 2500 Å. The reflective layer140may be constructed of a metal layer including an alloy of aluminum (Al), silver (Ag), nickel (Ni), platinum |(Pt), |[b1] and rhodium (Rh), or an alloy including aluminum (Al), silver (Ag), platinum (Pt), or rhodium (Rh). Aluminum (Al) or silver (Ag) makes effective reflection of the light from the active layer124to improve light extraction efficiency of the light emitting structure, significantly.

Since the light emitting structure120, particularly, the second conduction type semiconductor layer126, has light impurity doping concentration to have high contact resistance and a poor ohmic characteristic, in order to improve the ohmic characteristic, the ohmic layer130may be formed to be transparent.

The light emitting structure120is formed on the first conduction type semiconductor layer122, to include an active layer124which emits a light and a second conduction type semiconductor layer126disposed on the active layer124.

The first conductive type semiconductor layer122may be embodied with a III-V group compound semiconductor doped with first conduction type dopant, and, if the first conduction type semiconductor layer122is an N type semiconductor layer, the first conduction type dopant may include, but not limited to, Si, Ge, Sn, Se, and Te as an N type dopant.

The first conduction type semiconductor layer122may include a semiconductor material having composition of AlxInyGa(1-x-y)N (0≦x≦1, 0≦y≦1, 0≦x+y≦1). And, the first conductive type semiconductor layer122may be formed of at least one selected from a group of materials including GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, InP.

The active layer124is a layer which emits the light having energy fixed by an energy bandgap unique to a material of the active layer (a light emitting layer) as an electron injected thereto through the first conductive type semiconductor layer122and a hole injected thereto through the second conductive type semiconductor layer126to be formed later meet with each other, and, besides the visible light band, the active layer124may emit a light of an UV light band.

The active layer124may be formed as at least one of single quantum well structure, MQW (Multi Quantum Well) structure, a Quantum-Wire structure, or a Quantum dot structure. For an example, the active layer124may be formed as the MQW (Multi Quantum Well) structure by injection of, but not limited to, TMGa gas, NH3gas, N2gas, and TMIn gas.

The active layer124has a pair structure of well layer/barrier layer constructed of at least any one of, but not limited to, InGaN/GaN, InGaN/InGaN, AlGaN/GaN, InAlGaN/GaN, GaAs/AlGaAs (InGaAs), and GaP/AlGaP (InGaP). The well layer may be formed of a material having a bandgap lower than a bandgap of the barrier layer.

There may be a conductive clad layer (Not shown) disposed on or/and underside of the active layer124. The conductive clad layer may be formed of an AlGaN group semiconductor to have an energy bandgap higher than the energy bandgap of the active layer124.

The second conduction type semiconductor layer126may include a III-V group compound semiconductor doped with second conductive type dopant, for an example, a semiconductor having composition of InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1). If the second conduction type semiconductor layer126is a P type semiconductor layer, the second conduction type dopant may include Mg, Zn, Ca, Sr, and Ba as a P type dopant.

In the meantime, the first conduction type semiconductor layer122may include the P type semiconductor layer, and the second conduction type semiconductor layer126may include the N type semiconductor layer.

The transparent conductive layer170may be disposed on the light emitting structure120of a translucent material, such as ITO. The metal filer180may be disposed on the transparent conductive layer170in a form of a pattern of a metal, such as aluminum or titanium, for serving as an optical block portion for reflecting the light from the light emitting structure120.

The metal filter180may have a thickness of 1 micron to 10 microns, and detail of which will be described later.

There may be a first electrode190disposed on the transparent conductive layer170and/or the metal filter180in single layer or multiple layer of a material including at least one of Al, Ti, Cr, Ni, Cu, and Au.

And, there may be a roughness (Not shown) disposed on a surface of the light emitting structure120, on a surface of the first conduction type semiconductor layer122, for enhancing light extraction efficiency.

And, there may be a passivation layer195disposed at a side of the light emitting structure120.

The passivation layer195may be formed of an insulating material, and the insulating material may be a non-conductive oxide or nitride. As an example, the passivation layer195may be constructed of a silicon oxide SiO2layer, a silicon nitride layer, or an aluminum oxide layer.

Though similar to the embodiment illustrated inFIG. 1A, an embodiment illustrated inFIG. 1Bhas a first electrode190in contact both with the transparent conductive layer170and the metal filter180.

An embodiment illustrated inFIG. 1Chas the passivation layer195disposed at a portion of the second conduction type semiconductor layer126to form an open region B in a surface of the second conduction type semiconductor layer126.

FIGS. 2A to 4are views each illustrating a metal filter structure of a light emitting device.FIGS. 2A to 4show an ‘A’ part inFIG. 1seen from above while omitting the electrode and the passivation layer to show the transparent conductive layer170and the metal filter180.

The transparent conductive layer170may be formed of a translucent material, such as ITO, or the transparent conductive layer may be omitted, to dispose the metal filter180on the light emitting structure. The metal filter180is disposed in a form of stripes as shown inFIG. 2A. A region a having no metal filter180disposed thereon is an opening.

The metal filter180which forms above pattern may have a width w which is 10% to 20% of a width d of the opening. If the width w of the metal filter180is large excessively, light transmissivity is liable to become poor, and if the width d of the opening is large excessively, making refraction of the light unfavorable, the light transmissivity is liable to become poor.

An embodiment illustrated inFIG. 2Bshows the metal filter180having irregular widths w, and the opening a having regular widths d. An embodiment illustrated inFIG. 2Cshows the metal filter180having regular widths w, and the opening a having irregular widths d. In another embodiment, both the widths w and the widths d may be irregular. The light from the active layer in the light emitting device does not make regular incident on the metal filter180. Therefore, the metal filter180having the irregular pattern can diffuse the light toward an upper side of the light emitting device.

An embodiment illustrated inFIG. 2Dshows the metal filter180having irregular widths w, and the opening a having irregular widths d.

An embodiment illustrated inFIG. 2Eshows the metal filter180having a pattern with widths w1in one side and widths w2in the other side different from each other to provide non-uniform pattern widths.

Embodiments illustrated inFIGS. 3A to 3Eshow the metal filters180patterned in mesh types, respectively. In this instance, as described before, the width w of the metal filter180may be 10 to 20% of the width d of the opening.

And, an embodiment illustrated inFIG. 3Ashows the metal filter180with regular widths w and the opening a with regular widths d, an embodiment illustrated inFIG. 3Bshows the metal filter180with irregular widths w and the opening a with regular widths d, an embodiment illustrated inFIG. 3Cshows the metal filter180with regular widths w and the opening a with irregular widths d, and another embodiment may show the metal filter180with irregular widths w and the opening a with irregular widths d.

An embodiment illustrated inFIG. 3Dshows the metal filter180with irregular widths w and the opening a with irregular widths d.

An embodiment illustrated inFIG. 3Eshows the metal filter180having a pattern with a first side width w1and a second side width w2different from each other to provide non-uniform widths of the pattern.FIG. 4illustrates the metal filter180having an irregular pattern and the opening a having an irregular pattern, with widths w or areas of the metal filter180to be 10% to 20% of the widths d or areas of the opening.

FIGS. 5A to 5Care views each illustrating other embodiment and operation of a light emitting device.

An embodiment illustrated inFIG. 5Ashows the metal filter180disposed on a surface of the light emitting structure120, i.e., a surface of the first conduction type semiconductor layer122, and the transparent conductive layer170covered on the opening region and the metal filter180.

The light from the light emitting structure120may be shielded by the metal filter180, or travels upward through the openings between the metal filter180. And, as shown, when the light passes the opening, since the light may reach to a back side of the metal filter180which is an obstacle, travelling away from a geometrical optic straight path according to a principle of refraction, the light can be emitted throughout an entire surface of the light emitting device100.

An embodiment illustrated inFIG. 5Bhas a first transparent conductive layer170aon a surface of the light emitting structure120, i.e., a surface of the first conduction type semiconductor layer122, the metal filter180on a surface of the first transparent conductive layer170a, and a second transparent conductive layer170bto cover the first transparent conductive layer170aand the metal filter180.

Though similar toFIG. 5B, an embodiment illustrated inFIG. 5Chas a roughness disposed on the surface of the first conduction type semiconductor layer122for widening an angle of outward light emission from the active layer124.FIG. 6is a view illustrating a light emitting device in accordance with another embodiment.

FIG. 6illustrates a horizontal type light emitting device having the second conduction type semiconductor layer126, the active layer124, and a portion of the first conduction type semiconductor layer122subjected to MESA etching to expose a portion of the first conduction type semiconductor layer122. That is, if the substrate110is formed of an insulating material, a portion of the first conduction type semiconductor layer122is exposed for securing a space for forming an electrode required for supplying a current to a portion of the first conduction type semiconductor layer122.

A buffer layer115may be disposed between the light emitting structure120and the substrate110for moderating lattice mismatch and a difference of thermal expansion coefficients of materials between the light emitting structure120to be described later and the substrate110. The buffer layer115may be formed of a III-V group compound semiconductor, for an example, at least one of GaN, InN, AIN, InGaN, AlGaN, InAlGaN, and AlInN.

And, a second electrode195and a first electrode190are disposed on the second conduction type semiconductor layer126and the first conduction type semiconductor layer122exposed thus, respectively. Both the first electrode190and the second electrode195may be a single or multiple layered structure of at least one of Al, Ti, Cr, Ni, Cu, and Au.

FIGS. 7 to 13are views illustrating the steps of a method for fabricating the light emitting device inFIG. 1in accordance with one embodiment.

Referring toFIG. 7, a light emitting structure120is disposed on a substrate110to include a buffer layer115, a first conduction type semiconductor layer122, an active layer124, and a second conduction type semiconductor layer126.

The substrate110may be a conductive or insulating substrate, for an example, at least one of, sapphire Al2O3, SiC, Si, GaAs, GaN, ZnO, Si, GaP, InP, Ge, and Ga2O3. A roughness structure may be disposed on, but not limited to, the substrate110. The substrate110may be subjected to wet washing, to remove impurity from a surface thereof.

A buffer layer (Not shown) may be grown between the light emitting structure and the substrate110for moderating lattice mismatch and a difference of thermal expansion coefficients of materials. The buffer layer may be formed of a III-V group compound semiconductor, for an example, at least one of GaN, InN, AIN, InGaN, AlGaN, InAlGaN, and AlInN. An undoped semiconductor layer may be disposed on the buffer layer, but not limited to this.

The light emitting structure may be grown by vapor deposition, such as MOCVD (Metal Organic Chemical Vapor Deposition), MBE (Molecular Beam Epitaxy), and HVPE (Hydride Vapor Phase Epitaxy).

The first conduction type semiconductor layer122has composition as described before, and can be formed as an N type GaN layer by CVD, MBE, sputtering, or HYPE. And, the first conduction type semiconductor layer122may be formed by injecting silane gas SiH4including n type impurities, such as TMGa, NH3, N2, and Si, into a chamber.

The active layer124has composition as described before, and can be formed as an MQW (Multi Quantum Well) structure by injecting, but not limited to, TMGa gas, NH3gas, N2gas, and TMIn gas.

The second conduction type semiconductor layer126has composition as described before, and can be formed as a p type GaN layer by injecting (EtCp2Mg){Mg(C2H5C5H4)2} including p type impurities, such as TMGa gas, NH3gas, N2gas, and magnesium into a chamber, but not limited to this.

And, referring toFIG. 8, an ohmic layer130and a reflective layer140may be disposed on the light emitting structure120. The ohmic layer130and the reflective layer140have composition as described before, and may be formed by sputtering or MBE.

If the ohmic layer130is formed of ITO, transmission efficiency of a UV beam from the active layer124may become poor, and the ohmic layer130may be formed of Ni/Au.

And, referring toFIG. 9, a bonding layer150and a metal support160may be disposed on the reflective layer140. The metal support160may be formed by electro-chemical metal deposition, or bonding by using a eutectic metal, or a separate adhesion layer160may be formed.

Then, referring toFIG. 10, the substrate110is separated. The substrate110may be separated by laser lift off (LLO) by using an excimer laser, or dry or wet etching.

In the laser lift off, if an excimer laser beam of a predetermined wavelength band is focused toward, for an example, the substrate110, focusing thermal energy at a boundary of the substrate110and the light emitting structure120to separate gallium molecules from nitrogen molecules, the substrate110is separated instantly at a portion the laser beam passes.

Then, referring toFIG. 11, after dicing each of the light emitting devices, ITO may be deposited on the light emitting structure120as a transparent conductive layer170.

Then, referring toFIG. 12, a metal filter is disposed on the transparent conductive layer170by depositing and patterning metal with a mask, or depositing metal, such as aluminum or titanium, in a form of oxide.

And, though not shown, a surface of the light emitting structure120, i.e., a surface of the first conduction type semiconductor layer122, may be etched to form a roughness structure thereon. And, as shown inFIG. 13, a passivation layer195may be deposited at a side of the light emitting structure120, and a first electrode190may be disposed on the surface of the light emitting structure120. The passivation layer195may be disposed to cover even a top side of the transparent conductive layer170.

Since the light from the active layer can reach to a back side of the metal filter according to a principle of refraction, the light can be emitted throughout an entire surface of an upper side of the light emitting device.

FIG. 14is a view illustrating a light emitting device package having a light emitting device disposed thereto in accordance with one embodiment.

Referring toFIG. 14, the light emitting device package200includes a body210having a cavity, a first lead frame221and a second lead frame222mounted to the body210, a light emitting device100of the embodiment mounted to the body210connected to the first lead frame221and the second lead frame222electrically, and a molded portion270formed in the cavity.

The body210may be formed of PPA resin, silicon, synthetic resin, or metal. Though not shown, if the body210is formed of a conductive material, such as metal, electric short circuit between the body210and the first and second lead frames221and222may be prevented by coating an insulating layer on a surface of the body210.

The first lead frame221and the second lead frame222are isolated from each other electrically, and provide a current to the light emitting device100. And, the first lead frame221and the second lead frame222may increase optical efficiency by reflecting the light from the light emitting device100, and may also dissipate heat from the light emitting device100to an outside of the light emitting device package.

The light emitting device100may be mounted on the body210, the first lead frame221, or the second lead frame222. The embodiment suggests the first lead frame221and the light emitting device100in communication with each other electrically, and the second lead frame222and the light emitting device100connected with a wire to each other. Besides the wire bonding type, the light emitting device100may be connected to the first and the second lead frames221, and222by flip chip type, or die bonding type, electrically.

The molded portion270may enclose the light emitting device100to protect the same. And, though the molded portion270may have a fluorescent material included thereto, the embodiment may suggest arranging a fluorescent body280provided separate from the molded portion270, or a conformal coating of the fluorescent material on the light emitting device100.

A light of a first wavelength band from the light emitting device100may be excited into a light of a second wavelength band by the fluorescent body280, and the light of the second wavelength band may be involved in a light path change as the light of the second wavelength band passes a lens (Not shown).

An array of the light emitting device packages of the embodiment may be on a substrate, and a light guide plate, a prism sheet, a diffusion sheet, and the like that are optical members may be disposed on a light path of the light emitting device package. The light emitting device package, the substrate, and the optical members may function as a lighting unit. As another embodiment, a display device, an indicating device, or a lighting system may be produced, which includes the semiconductor light emitting device or the light emitting device package described in the foregoing embodiments, and the lighting system may include, for an example, a lamp or a street light.

As one embodiment of a lighting system having the foregoing light emitting device package mounted thereto, a lighting device and a backlight unit will be described.

FIG. 15is a view illustrating an exploded perspective view of a lighting device in accordance with one embodiment.

Referring toFIG. 15, the lighting device includes a light source600for projecting a light, a housing400for housing the light source600, a heat dissipating unit500for dissipating heat from the light source600, and a holder700for fastening the light source600and the heat dissipating unit500to the housing400.

The housing400includes a socket fastening portion410for fastening the housing400to an electric socket (Not shown) and a body portion420connected to the socket fastening portion410for housing the light source600. The body portion420may have an air flow opening430passing therethrough.

The body portion420of the housing400has a plurality of air flow openings430. The air flow opening430may be singular or plural disposed radially as shown in the drawing. Besides this, the arrangement of the air flow opening430may vary.

And, the light source600has a plurality of light emitting device modules650provided on a circuit board610. The circuit board610may have a shape that may be placed in an opening of the housing400, and may be formed of a material having high heat conductivity for transfer of heat to the heat dissipating unit500, to be described later.

The holder700is provided under the light source, including a frame and another air flow openings. And, though not shown, an optical member may be provided to a lower side of the light source600for making the light from the light emitting device package600of the light source600to diverge, scatter, or converge.

FIG. 16illustrates an exploded perspective view of a display device having a light emitting device package in accordance with one embodiment applied thereto.

Referring toFIG. 16, the display device800includes a light source module830and835, a reflective plate820on a bottom cover810, a light guide plate840disposed in front of the reflective plate820for guiding the light from the light source module to a front of the display device, a first prism sheet850and a second prism sheet860disposed in front of the light guide plate840, a panel870disposed in front of the second prism sheet860, a picture signal forwarding circuit872connected to the panel870for supplying a picture signal to the panel870, and a color filter880disposed throughout the panel870.

The light source module includes a light emitting device package835on a circuit board830. In this instance, the circuit board830may be constructed of PCB, and the light emitting device package835is the same with the description made with reference toFIG. 14.

The bottom cover810may accommodate elements of the display device800. And, the reflective plate820may be an individual element as shown in the drawing, or may be a coat of a material with a high reflectivity on a rear of the light guide plate840or on a front of the bottom cover810.

In this instance, the reflective plate820can be formed of a material which has high reflectivity and can form a micron-film, such as PET (PolyEthylene Terephtalate).

The light guide plate840scatters the light from the light emitting device package module for uniform distribution of the light to an entire region of a screen of the liquid crystal display device. Accordingly, the light guide plate840is formed of a material having good refractivity and transmissivity, such as PolyMethylMethAcrylate PMMA, PolyCarbonate PC, or PolyEthylene PE. And, it is viable that the light guide plate may be omitted to have an air guide type in which the light is transmitted through a space over the reflective plate820.

And, the first prism sheet850may be formed of a polymer having light transmissivity and elasticity on one side of a supporting film. The polymer may have a prism layer with a plurality of three dimensional structures disposed thereon, repeatedly. In this instance, as shown, the plurality of patterns can be a stripe type with repetitive ridges and grooves.

And, a direction of the ridges and the grooves in the second prism sheet860may be perpendicular to a direction of the ridges and the grooves in the first prism sheet850, for uniform distribution of the light from the light source module and the reflective sheet to an entire surface of the panel870.

In the embodiment, the first prism sheet850and the second prism sheet860construe the optical sheet. The optical sheet may be constructed of other combination, for an example, a microlens array, a combination of the diffusion sheet and the microlens array, a combination of one prism sheet and the microlens array, or so on.

As the panel870, a liquid crystal panel may be applied, and other kinds of display devices each of which requires a light source may be applied.

The panel870has liquid crystals disposed between glass panels, and a polarizing plate placed on both of the glass panels for utilizing polarizability of a light. The liquid crystals have intermediate characteristics of liquid and solid, in which the liquid crystals, organic molecules with fluidity like the liquid, are arranged regularly like crystal. By utilizing a characteristic of the liquid crystals in which a molecular arrangement varies with an external electric field, a picture is displayed.

The liquid crystal panel used in the display device has an active matrix system, in which a transistor is used as a switch for controlling a voltage supplied to pixels.

The panel870has a color filter880on a front for each of pixels to transmit only red, green and blue lights of the light from the panel870, thereby displaying a picture.