Abstract:
A light-emitting device and method for manufacturing the same are described. A method for manufacturing a light-emitting device comprising steps of: providing a growth substrate, wherein the growth substrate has a first surface and a second surface; forming a light-absorbable layer on the first surface of the growth substrate; forming an illuminant epitaxial structure on the light absorbable layer; providing a laser beam and irradiating the second surface of the growth substrate, wherein the laser beam wavelength is greater than 1000 nm; and removing the growth substrate.

Description:
TECHNICAL FIELD 
     The present application relates to a light-emitting device and a method for manufacturing the same, and more particularly to a III-V compound semiconductor light-emitting device by removing a growth substrate therein to avoid the light being absorbed by the growth substrate. 
     BACKGROUND 
     The structure of the active layer of a conventional AlGaInP light-emitting device is normally a double heterostructure (DH) or multi-quantum wells (MQWs), and a portion of the light emitted from the active layer towards the growth substrate is totally absorbed by GaAs substrate used in the AlGaInP light-emitting device. Therefore, the external quantum efficiency of this kind of conventional AlGaInP light-emitting device is low. Besides, the thermal conductivity of GaAs is only about 44 W/m−° C. which is too low to dissipate the heat generated by the device. 
     SUMMARY 
     The present application provides a method for manufacturing a light-emitting device, comprising: providing a growth substrate, wherein the growth substrate has a first surface and a second surface; forming a light-absorbable layer on the first surface of the growth substrate; forming an illuminant epitaxial structure on the light absorbable layer; providing a laser beam and irradiating the second surface of the growth substrate, wherein the laser beam wavelength is greater than 1000 nm; and removing the growth substrate. 
     According to the aforementioned aspects, the present application provides a method for manufacturing a light-emitting device, further removing the light-absorbable layer by wet etching with a solution of HCl and KOH. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of this application are more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1A  through  FIG. 1C  are schematic flow diagrams showing the process for manufacturing a light-emitting device in accordance with a first embodiment of the present application; 
         FIG. 2A  through  FIG. 2C  are schematic flow diagrams showing the process for manufacturing a light-emitting device in accordance with a second embodiment of the present application; and 
         FIG. 3  shows a cross-sectional view of a light-emitting device structure in accordance with a third embodiment of the present application. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present application discloses a light-emitting device and a method for manufacturing the same. In order to make the illustration of the present application more explicit, the following description is stated with reference to  FIG. 1A  through  FIG. 3 . 
       FIG. 1A  through  FIG. 1C  are schematic flow diagrams showing the process for manufacturing a light-emitting device  100  in accordance with a first embodiment of the present application. In the present embodiment, a growth substrate  1  having a first surface S 1  and a second surface S 2  is provided for the epitaxial growth of epitaxial materials formed thereon, wherein a material of the growth substrate  1  may be GaAs and the thickness of the growth substrate  1  is greater than 100 μm. A light-absorbable layer  2  is grown on the first surface S 1  of the growth substrate  1 , and an illuminant epitaxial structure  20  is grown on the light-absorbable layer  2  by, for example, a metal organic chemical vapor deposition (MOCVD) method, a liquid phase deposition (LPD) method, or a molecular beam epitaxy (MBE) method. The light-absorbable layer  2  band-gap is smaller than 1.24 eV, which means the wavelength of the light-absorbable layer  2  is greater than 1000 nm. In the embodiment, the light-absorbable layer  2  comprises a semiconductor material having a composition of In x Ga (1-x) As (1-y) N y , wherein 0≦x≦1 and 0≦y&lt;1. The illuminant epitaxial structure  20  comprises a first conductivity type group III-V compound semiconductor layer  3 , an active layer  4  and a second conductivity type group III-V compound semiconductor layer  5  stacked on the light-absorbable layer  2  in sequence. For example, the first conductivity type group III-V compound semiconductor layer is n-type AlGaInP series material, the active layer is AlGaInP series material, and the second conductivity type group III-V compound semiconductor layer is p-type AlGaInP series material. 
     Next, a window layer  6  is deposited on the second conductivity type group III-V compound semiconductor layer  5  of the illuminant epitaxial structure  20 . Next, irradiating the second surface S 2  of the growth substrate  1  by a laser beam  7  to decompose the interface material between the growth substrate  1  and the light-absorbable layer  2  when the energy of the laser beam is absorbed, and the growth substrate  1  is removed. The light-absorbable layer  2  is then removed by wet etching with a solution of HCl and KOH. In another embodiment, the second surface S 2  of the growth substrate  1  is irradiated by a laser beam  7  to decompose the material of the light-absorbable layer  2  when the energy of the laser beam is absorbed, and the growth substrate and the light-absorbable layer  2  are removed. The wavelength of the laser beam is greater than 1000 nm. The removed growth substrate is reusable for epitaxially growing another light-emitting device structure. The window layer material can be GaP, and the thickness of the window layer  6  is greater than 20 μm. Next, an electrode  9  is formed on the window layer  6 , wherein the electrode  9  is the second conductivity type. For example, a material of the electrode  9  is Ni/Au, NiO/Au, Pd/Ag/Au/Ti/Au, Pt/Ru, Ti/Pt/Au, Pd/Ni, Ni/Pd/Au, Pt/Ni/Au, Ru/Au, Nb/Au, Co/Au, Pt/Ni/Au, Ni/Pt, NiIn, or Pt 3 In 7 . Furthermore, an electrode  8  is formed on a first conductivity type group III-V compound semiconductor layer  3  such that the electrode  9  and the electrode  8  are respectively on opposite sides of the illuminant epitaxial structure  20 , wherein the electrode  8  is the first conductivity type. For example, a material of the electrode  8  is In, Al, Ti, Au, W, InSn, TiN, WSi, PtIn 2 , Nd/Al, Ni/Si, Pd/Al, Ta/Al, Ti/Ag, Ta/Ag, Ti/Al, Ti/Au, Ti/TiN, Zr/ZrN, Au/Ge/Ni, Cr/Ni/Au, Ni/Cr/Au, Ti/Pd/Au, Ti/Pt/Au, Ti/Al/Ni/Au, Au/Si/Ti/Au/Si, or Au/Ni/Ti/Si/Ti. Now, the fabrication of a light-emitting device  100  is substantially completed as shown in  FIG. 1C . 
       FIG. 2A  through  FIG. 2C  are schematic flow diagrams showing the process for manufacturing a light-emitting device  200  in accordance with a second embodiment of the present application. In the present embodiment, the light-absorbable layer  2 , the illuminant epitaxial structure  20 , and the window layer  6  are grown on the first surface  51  of the growth substrate  1  in sequence, wherein the thickness of the window layer  6  is smaller than 5 μm. A bonding layer  10  is used to attach a permanent substrate  11  to the window layer  6 , wherein the bonding layer  10  may be initially formed on the surface of the permanent substrate  11  or on the window layer  6 , as shown in  FIG. 2A . The material of the bonding layer  10  may be Al, Au, Pt, Zn, Ag, Ni, Ge, In, Sn, Ti, Pb, Cu, Pd, or alloys of the aforementioned metals. In another embodiment, the material of the bonding layer  10  may be silver glue, spontaneous conductive polymer, polymer materials mixed with conductive materials, or Anisotropic Conductive Glue (ACF). The permanent substrate  11  comprises a conductive material such as Si, Al, or Cu. As shows in  FIG. 2B , after the permanent substrate  11  is bonded to the window layer  6 , irradiating the second surface S 2  of the growth substrate  1  by a laser beam  7  to decompose the interface material between the growth substrate  1  and the light-absorbable layer  2  when the energy of the laser beam is absorbed, and the growth substrate  1  is removed. The light-absorbable layer  2  is then removed by wet etching with a solution of HCl and KOH. In another embodiment, the second surface S 2  of the growth substrate  1  is irradiated by a laser beam  7  to decompose the material of the light-absorbable layer  2  when the energy of the laser beam is absorbed, and the growth substrate  1  and the light-absorbable layer  2  are removed, so the first conductivity type group III-V compound semiconductor layer  3  of the illuminant epitaxial structure  20  is exposed. The wavelength of the laser beam is greater than 1000 nm. The removed growth substrate is reusable for epitaxially growing another light-emitting device structure. 
     Next, an electrode  9  is formed on the other surface opposite to the bonding layer  10  of the permanent substrate  11 , wherein the electrode  9  is the second conductivity type. Furthermore, an electrode  8  is formed on a first conductivity type group III-V compound semiconductor layer  3 , such that the electrode  9  and the electrode  8  are respectively on opposite sides of the illuminant epitaxial structure  20 , wherein the electrode  8  is the first conductivity type. Now, the fabrication of a light-emitting device  200  is substantially completed as shown in  FIG. 2C . 
       FIG. 3  shows a cross-sectional view of the light-emitting device structure  300  in accordance with a third embodiment of the present application. After the growth substrate  1  and the light-absorbable layer  2  are removed, the first conductivity type group III-V compound semiconductor layer  3  of the illuminant epitaxial structure  20  is exposed. A pattern-defining step is performed on the illuminant epitaxial structure  20  by, for example, a photolithography and etching method. In the pattern defining step, a portion of the first conductivity type group III-V compound semiconductor layer  3  and a portion of the active layer  4  are removed until a portion of the surface of the second conductivity type group III-V compound semiconductor layer  5  is exposed. Next, an electrode  9  is formed on the exposed surface of the second conductivity type group III-V compound semiconductor layer  5 , wherein the electrode  9  is the second conductivity type. Furthermore, an electrode  8  is formed on a first conductivity type group III-V compound semiconductor layer  3 , wherein the electrode  8  is the first conductivity type. The permanent substrate  11  comprises a non-conductive material such as sapphire, SiC, AlN, or GaN. 
     As is understood by a person skilled in the art, the foregoing preferred embodiments of the present application are illustrated of the present application rather than limiting of the present application. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.