Abstract:
A Flip-chip light-emitting device with integral micro-reflector. The flip-chip light-emitting device emits reflected light provided by a light-emitting layer. The micro-reflector reflects light that might otherwise be lost to internal refraction and absorption, so as to increase light-emitting efficiency.

Description:
BACKGROUND OF INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention provides a light-emitting device, and more particularly, a flip-chip light-emitting device with a micro-reflector.  
         [0003]     2. Description of the Prior Art  
         [0004]     The applications of light-emitting diodes are extensive and include optical display devices, traffic signals, data storing devices, communication devices, illumination devices, and medical apparatuses. As such, it is important to increase the brightness of light-emitting diodes, and to simplify manufacturing processes in order to decrease the cost of the light-emitting diode.  
         [0005]     Please refer to  FIG. 1 , which illustrates a schematic diagram of a flip-chip light-emitting device and its related method of manufacture disclosed in TW patent 441 859, in which a first electrode and a second electrode of the flip-chip light-emitting device bring reflected light out from a light-emitting layer. Nevertheless, the prior art method, due to the reason that only light emitted at an angle within the critical angle θc would be completely emitted out, and other light would be reflected and absorbed, has a limited viewing angle and a readily identifiable source of inefficiency in the form of internal absorption of emitted light. In other words, the angle of light of the flip-chip light-emitting device must be within a cone of 2θc to be completely emitted out. Light emitted at an angle larger than 2θc is reflected and absorbed. When light generated within the flip-chip light-emitting device travels from a material with a high refractive index to a material with a low refractive index, the angle of light emitted is limited due to the effect of said refractive indexes. Therefore, an important issue is how to improve the efficiency of light emission, with respect to both viewing angle and intensity.  
       SUMMARY OF INVENTION  
       [0006]     It is therefore a primary objective of the claimed invention to provide a flip-chip light-emitting device with a micro-reflector. The micro-reflector includes a transparent patterned light-emitting stack layer. The transparent patterned light-emitting stack layer may be formed into a variety of shapes, including semicircular, pyramidical, conical, and so on, and can be continuous or discontinuous. The transparent patterned light-emitting stack layer is generated by means of etching on a light-emitting stack layer of the flip-chip light-emitting device, of evaporation deposition, or of a bonding method. Then, a reflective layer is formed over the transparent patterned light-emitting stack layer by means of evaporation deposition, so that the reflective layer includes the specific shapes to form a micro-reflector. The micro-reflector reflects vertical light with incoming light provided by a light-emitting area, so that the normal incidence light is un-affected by the critical angle for improving light extraction.  
         [0007]     Briefly described, the claimed invention discloses a flip-chip light-emitting device with a micro-reflector. The flip-chip light-emitting device with a micro-reflector includes a substrate, a semiconductor stack layer formed over the substrate with a first surface and a second surface, a light-emitting layer formed over the first surface, a semiconductor formed over the light-emitting layer, a micro-reflector formed over the second semiconductor with a transparent patterned layer, a first electrode formed over the reflective layer, and a second electrode formed over the second surface.  
         [0008]     The substrate comprises at least one material selected from a material group consisting of GaP, glass, SiC, GaN, ZnSe, and sapphire or other substitute materials. The reflective layer comprises at least one material selected from a material group consisting of In, Sn, Al, Au, Pt, Zn, Ge, Ag, Ti, Pb, Pd, Cu, AuBe, AuGe, Ni, Cr, PbSn, AuZn, and indium tin oxide, or other substitute materials. The shape of the transparent patterned layer corresponds to at least one graph profile selected from a graph profile group consisting of semicircular, pyramidical, conical, or other substitute graph profiles. The first semiconductor stack layer comprises at least one material selected from a material group consisting of AlGalnP, AlInP, AlN, GaN, AlGaN, InGaN, and AlInGaN, or other substitute materials. The light-emitting layer comprises at least one material selected from a material group consisting of AlGaInP, GaN, InGaN, and AlInGaN, or other substitute materials. The second semiconductor stack layer comprises at least one material selected from a material group consisting of AlGaInP, AlInP, AlN, GaN, AlGaN, InGaN, and AlInGaN, or other substitute materials.  
         [0009]     These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.  
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0010]      FIG. 1  illustrates a schematic diagram of a prior art flip-chip light-emitting device.  
         [0011]      FIG. 2  illustrates a schematic diagram of a present invention flip-chip light-emitting device with a micro-reflector.  
         [0012]      FIG. 3  illustrates a schematic diagram of a present invention flip-chip light-emitting device with a micro-reflector.  
         [0013]      FIG. 4  illustrates a schematic diagram of a present invention flip-chip light-emitting device with a micro-reflector. 
     
    
     DETAILED DESCRIPTION  
       [0014]     Please refer to  FIG. 2 , which illustrates a schematic diagram of a flip-chip light-emitting device  1  with a micro-reflector. The light-emitting device  1  includes a transparent substrate  10 , a first contact layer  11  with a first surface and a second surface on an upper surface formed over the transparent substrate  10 , a first cladding layer  12  formed over the first surface, a light-emitting layer  13  formed over the first cladding layer  12 , a second cladding layer  14  formed over the light-emitting layer  13 , a micro-reflector with a second contact layer  15  formed over the second cladding layer  14 , a reflective layer  16  formed over the second contact layer  15 , a first electrode  17  formed over the second surface, and a second electrode  18  formed over the reflective layer  16 . The second contact layer  15  includes transparent patterned shapes, which can be continuous, or discontinuous.  
         [0015]     Please refer to  FIG. 3 , which illustrates a schematic diagram of a light-emitting device  2  with a micro-reflector. The light-emitting device  2  includes a transparent substrate  20 , a first contact layer  21  with a first surface and a second surface on an upper surface formed over the transparent substrate  20 , a micro-reflector with a transparent patterned light-emitting stack layer formed over the first surface, an insulating layer  29  formed around the transparent patterned light-emitting stack layer, and a reflective layer  26  formed over the insulating layer  29  and on the transparent patterned light-emitting stack layer, an ohmic contact between the reflective layer  26  and the transparent patterned light-emitting stack layer, a first cladding layer  22  of the transparent patterned light-emitting stack layer formed over the first surface, a light-emitting layer  23  formed over the first cladding layer  22 , a second cladding layer  24  formed over the light-emitting layer  23 , a first electrode  27  formed over the second surface, and a second electrode  28  formed over the reflective layer  26 . The transparent patterned light-emitting stack layer includes spread transparent geometric shapes, which can be continuous, or discontinuous.  
         [0016]     Please refer to  FIG. 4 , which illustrates a schematic diagram of a light-emitting device  3  with a micro-reflector. In light-emitting device  3 , a chip is bonded onto a transparent substrate by means of direct pressure bonding, or transparent adhesive layer bonding. The light-emitting device  3  includes a transparent bonding substrate  30 , a bonding interface  300  formed over the transparent bonding substrate  30 , a transparent conductive layer  32  with a first surface and a second surface formed over the bonding interface  300 , a first contact layer  33  formed over the first surface, a first cladding layer  34  formed over the first contact layer  33 , a light-emitting layer  35  formed over the first cladding layer  34 , a second cladding layer  36  formed over the light-emitting layer  35 , a micro-reflector with a second contact layer  37  formed over the second cladding layer  36 , a reflective layer  38  formed over the second contact layer  37 , a first electrode  39  formed over the second surface, and a second electrode  40  formed over the reflective layer  38 . The bonding interface  300  can be formed from adhesive, semiconductor material, transparent oxide, or a transparent metal layer for bonding the substrate  30  to the first contact layer  33 ,  
         [0017]     In the above-mentioned three embodiments, a transparent conductive layer can be between the second electrode and the reflective layer. The transparent patterned shape corresponds to at least one graph profile selected from a graph profile group consisting of semicirclular, pyramidical, conical, or other substitute graph profiles. The transparent substrate includes at least one material selected from a material group consisting of GaP, glass, SiC, GaN, ZnSe, and sapphire or other substitute materials. The reflective layer includes at least one material selected from a material group consisting of In, Sn, Al, Au, Pt, Zn, Ge, Ag, Ti, Pb, Pd, Cu, AuBe, AuGe, Ni, Cr, PbSn, AuZn, and indium tin oxide, or other substitute materials. The transparent conductive layer includes at least one material selected from a material group consisting of indium tin oxide, cadmium tin oxide, antimony tin oxide, zinc oxide, zinc tin oxide, Be/Au, Ge/Au and Ni/Au, or other substitute materials. The first cladding layer includes at least one material selected from a material group consisting of AlGaInP, AlInP, AlN, GaN, AlGaN, InGaN, AlInGaN, and ZnSe, or other substitute materials. The light-emitting layer includes at least one material selected from a material group consisting of AlGaInP, GaN, InGaN, AlInGaN, and ZnSe, or other substitute materials. The second cladding layer includes at least one material selected from a material group consisting of AlGaInP, AlInP, AlN, GaN, AlGaN, InGaN, AlInGaN, and ZnSe, or other substitute materials. The second contact layer includes at least one material selected from a material group consisting of GaP, GaAs, GaAsP, InGaP, AlGaInP, AlGaAs, GaN, InGaN, AlGaN, and ZnSe, or other substitute materials. The first contact layer includes at least one material selected from a material group consisting of GaP, GaAs, GaAsP, InGaP, AlGaInP, AlGaAs, GaN, InGaN, AlGaN, and ZnSe, or other substitute materials. The insulating layer includes at least one material selected from a material group consisting of SiNx and SiO2, or other substitute materials.  
         [0018]     Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.