Patent Publication Number: US-8120041-B2

Title: Semiconductor light-emitting device and method of manufacturing the same

Description:
This nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2006-311646 filed in Japan on Nov. 17, 2006, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a semiconductor light-emitting device to be used for, for example, a communication device, a road, rail way, or guide display panel device, an advertisement display device, a mobile telephone, a display backlight, lighting equipment, or the like, and a method of manufacturing the semiconductor light-emitting device. 
     In recent years, technologies of manufacturing a semiconductor light-emitting diode (referred to as an “LED” hereinafter), which is one of semiconductor light-emitting devices, have rapidly progressed, and in particular, LEDs for primary colors of light have been completed after the blue LED was developed, so that it has become possible to produce light of every wavelength by combinations of LEDs for primary colors of light. As a result of this, the scope of application of LEDs has been rapidly widened, and in particular, in the field of lighting, attention is being given to an LED as a natural-light or white-light source which is an alternative to an electric bulb or fluorescent lamp, with the increase of awareness of environmental and energy issues. 
     However, current LEDs are inferior in efficiency of conversion of applied energy into light as compared with an electric bulb or fluorescent lamp, and therefore research aimed at developing LEDs having a higher conversion efficiency and higher luminance has been underway. 
     In the past, the focus of the research and development of a higher luminance LED was on epitaxial growth technologies. However, the intracrystalline illumination efficiency (internal quantum efficiency) has been sufficiently improved by the optimization of the band structure such as a multiquantum well structure, meaning that the technologies have matured. Therefore, the approach to an increased luminance of LEDs is being sifted to the development which centers on process technologies. 
     Increase in luminance by a process technology means increase in external extraction efficiency, and specifically there are process technologies such as technologies for microfabricating LEDs, and forming reflecting films and transparent electrodes, etc. Among others, some techniques of increasing the luminance by wafer bonding have been established for red and blue LEDs, and high luminance LEDs were invented and have appeared on the market. 
     Techniques of increasing the luminance by wafer bonding are broadly divided into two types. 
     One is a technique of attaching an opaque substrate such as a silicon substrate or a germanium substrate to an epitaxial layer directly or through a metallic layer. The other one is a technique of attaching a substrate which is pervious to an emission wavelength, such as a glass substrate, a sapphire substrate, or a GaP substrate, to an epitaxial layer directly or through a bonding layer. 
     The former allows the attached substrate or the metallic layer to function as a reflecting layer to increase the luminous by reflecting light, which is absorbed by a substrate for epitaxial growth in a conventional LED, to the outside before absorbing the light. The latter extracts light to the outside through a transparent substrate to increase the efficiency of extracting light to the outside. 
       FIG. 1  is a schematic cross-sectional view of a semiconductor light-emitting device in which an example of the former technique is used. In  FIG. 1 , the reference numeral  101  denotes a silicon substrate,  102  denotes metal for reflection,  103  denotes a luminous layer,  104  and  105  each denote an electrode, and the reference symbol L denotes emitted light. 
       FIG. 2  is a schematic cross-sectional view of a semiconductor light-emitting device in which an example of the latter technique is used. In  FIG. 2 , the reference numeral  201  denotes a transparent substrate,  202  denotes a luminous layer,  203  denotes a window layer,  204  and  205  each denote an electrode, and the reference symbol L denotes emitted light. 
     In particular, the technique of attaching a transparent substrate to an epitaxial layer does not use reflection, so that light emitted by the luminous layer does not pass through the luminous layer again, thereby being not absorbed by the luminous layer. As a result, it is possible to develop an LED which is capable of extracting the emitted light from substantially the whole surface of the device to the outside and has a higher conversion efficiency (light extraction efficiency). 
     As conventional techniques of attaching a transparent substrate to an epitaxial layer, techniques of attaching a GaP (gallium phosphide) transparent substrate directly to an AlGaInP (aluminum gallium indium phosphide) semiconductor layer which is a 4-element LED structure part are known (see, for example, JP3230638B2, JP3532953B2, and JP3477481B2). 
     In the case of a technique of attaching a transparent substrate to a semiconductor layer, an electrode is formed on a non-joint surface of the transparent substrate, while the interface between the metal of the electrode and the transparent substrate which are in ohmic contact with each other is generally an alloy layer. The alloy layer absorbs light which has passed through the transparent substrate, so that the larger the area of the electrode, the more the loss of light increases. Furthermore, when the area of the electrode is reduced to reduce the loss of light, the electrical resistance between the electrode and the transparent substrate increases, so that there arises a problem that the driving voltage of the device increases. 
     A problem similar to the above problem arises also when an opaque substrate such as a silicon substrate is attached to an LED structure part through metal. 
     When an opaque substrate is attached to an LED structure part through metal, metal for reflection may be formed on the whole of the joint surface of the opaque substrate. However, heat treatment and the like in the joining process makes the metal for reflection react with the metal for electrical connection so that the metals become an alloy layer reducing the reflection factor or become a light absorbing layer. 
     Thus, any one of the above attaching techniques has a problem that light is absorbed by the electrode or the metal for reflection, and the reflection effect is thus reduced. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a semiconductor light-emitting device having an increased light-extraction efficiency, and a method of manufacturing it. 
     The present invention provides a semiconductor light-emitting device, including: 
     a first conductivity type first semiconductor layer; 
     a luminous layer formed on the first semiconductor layer; 
     a second conductivity type second semiconductor layer formed on the luminous layer; and 
     a first reflecting layer which is formed under the first semiconductor layer and composed of stacked two or more first conductivity type semiconductor layers, and at least part of which has reflectivity for an emission wavelength of the luminous layer. 
     In this specification, the “first conductivity type” means a p-type or an n-type, and the “second conductivity type means” the n-type when the first conductivity type is p-type, and means the p-type when the first conductivity type is n-type. 
     In the semiconductor light-emitting device of this configuration, when an electrode for reflecting layer use, for example, is formed under the first reflecting layer, light emitted by the luminous layer is reflected by the first reflecting layer before being absorbed by the electrode for reflecting layer use, so that the light extraction efficiency is prevented from reducing. 
     Thus, the light extraction efficiency of the semiconductor light-emitting device can be increased. The effect of increasing the light extraction efficiency can be increased by optimizing the arrangement of the first reflecting layer and the electrode for reflecting layer use formed under the first reflecting layer. 
     In one embodiment, the semiconductor light-emitting device further has a transmissive substrate which is mounted on the second semiconductor layer and is pervious to the emission wavelength of the luminous layer. 
     In the semiconductor light-emitting device of this embodiment, the transmissive substrate which is pervious to the emission wavelength of the luminous layer is mounted on the second semiconductor layer, so that light emitted by the luminous layer can be extracted efficiently from the transmissive substrate. 
     Furthermore, when an electrode is formed on a surface of the transmissive substrate opposite from the second semiconductor layer side surface, the amount of light incident on the electrode can be reduced provided that the electrode is shaped like an electrode for reflecting layer use  504  shown in  FIG. 6B . 
     When the electrode is formed as the electrode for reflecting layer use  504  shown in  FIG. 6B , the electrical resistance between the electrode for reflecting layer use  504  and the transmissive substrate can also be prevented from increasing. 
     Furthermore, since the transmissive substrate is mounted on the second semiconductor layer, the distance between the luminous layer and a die bond surface on which the semiconductor light-emitting device is die bonded can be small. 
     Thus, heat generated near the luminous layer is radiated or discharged efficiently to the die bond surface, and thereby the reliability of the semiconductor light-emitting device can be increased. 
     In one embodiment, the transmissive substrate is composed of a second conductivity type semiconductor layer, an electrode for transmissive substrate use is formed on the transmissive substrate, and an electrode for reflecting layer use is formed underneath the first reflecting layer. 
     In the semiconductor light-emitting device of this embodiment, light emitted by the luminous layer is reflected by the first reflecting layer before absorbed by the electrode for reflecting layer use, so that the light extraction efficiency is prevented from reducing. 
     Furthermore, if the electrode for reflecting layer use is formed on the whole of a surface of the first reflecting layer opposite from the first semiconductor layer, heat generated near the luminous layer is discharged efficiently to the outside through the electrode for reflecting layer use, and thereby the reliability of the semiconductor light-emitting device can be increased. 
     In one embodiment, an electrode for reflecting layer use is formed on part of a surface of the first reflecting layer opposite from the first semiconductor layer. 
     In one embodiment, a second reflecting layer which has reflectivity for the emission wavelength of the luminous layer is formed on the surface of the first reflecting layer opposite from the first semiconductor layer, in an area other than an area where the electrode for reflecting layer use is formed. 
     In one embodiment, the second reflecting layer is formed so as to cover the first reflecting layer and the electrode for reflecting layer use. 
     In one embodiment, the second reflecting layer is composed of one or more layers made of at least one or more elements of Au, Ag, Al, Ti, Cu, Mo, Sn, W, Ta, Pt, Ge, Si, Zn, Be, Cr, Se, and Ni. 
     In the semiconductor light-emitting device of this embodiment, when an Au layer, an Mo layer, and an AuSn layer, for example, are stacked in this order on a relevant crystal face of the first reflecting layer, light which has passed through the first reflecting layer is reflected by the Au layer. 
     Furthermore, one surface of the AuSn layer serves as a die bond surface for fixing the semiconductor light-emitting device, so that eutectic bonding by AuSn can be applied. 
     As a matter of course, also when all of the Au layer, Mo layer, and AuSn layer is not stacked, but only the Au layer is stacked, in other words, an Au single layer is provided, sufficient electrical conductivity and reflectivity can be ensured. 
     For a usual semiconductor light-emitting device, die bonding is performed with a pasty material such as silver paste or solder. At the die bonding, however, the pasty material can creep up the side of the device and reach the side of the luminous layer. 
     When the pasty material has reached the side of the luminous layer, the pasty material may form a current path so that current leak arises. 
     By taking advantage of the eutectic of AuSn, the problem of current leak as described above is solved. However, formation of the eutectic requires heating at hundreds of degrees centigrade, so that when, for example, an Au layer and an AuSn layer are stacked in this order on the crystal face of the first reflecting layer, the Au layer and the AuSn layer which have reflectivity will be disadvantageously alloyed with each other and function as a light-absorbing layer. 
     In order to avoid this alloying, it is sufficient to provide a Mo layer between the Au layer and the AuSn layer. Mo is not alloyed with Au or AuSn material, thus functioning as a layer for blocking the alloying. 
     Alternatively, an Au layer, a W layer, and an AuSn layer may be stacked in this order on the crystal face of the first reflecting layer. Alternatively, an Al layer, a Ti layer, and an AuSi layer may be stacked in this order on the crystal face of the first reflecting layer. Alternatively, an Ag layer, a Ti layer, and an AuGe layer may be stacked in this order on the crystal face of the first reflecting layer. Alternatively an Ag layer, a Ti layer, a Mo layer, and an AuSi layer may be stacked in this order on the crystal face of the first reflecting layer. However, there is no limit to the number of layers and materials, and materials most suitable for the emission wavelength and the crystal material may be selected as appropriate, provided that any combination of Au, Ag, Al, Ti, Cu, Mo, Sn, W, Ta, Pt, Ge, Si, Zn, Be, Cr, Se, and Ni is used. 
     In one embodiment, the transmissive substrate comprises a semiconductor layer including at least two or more elements of Ga, Si, P, C, Zn, Se, Cd, Te, B, N, Al, In, Hg, S, and O. 
     In the semiconductor light-emitting device of this embodiment, because the semiconductor layer constituting the transmissive substrate includes at least two or more elements of Ga, Si, P, C, Zn, Se, Cd, Te, B, N, Al, In, Hg, S, and O, the substrate is able to have electrical conductivity and is also pervious to the emission wavelength of the luminous layer. 
     As the material of the transmissive substrate, material which is pervious to the emission wavelength of the light-emitting device, in other words, has a broad band gap, such as GaP, SiC, ZnSe, ZnTe, or the like may be selected. 
     In one embodiment, the semiconductor light-emitting device further includes a supporting substrate placed underneath the first reflecting layer. 
     In one embodiment, the supporting substrate is joined to the first reflecting layer through a metal. 
     In one embodiment, the metal is composed of a metal for ensuring electrical conductivity of a joint between the supporting substrate and the first reflecting layer, and a metal for ensuring the reflectivity for the emission wavelength of the luminous layer. 
     In one embodiment, the metal is composed of one or more layers made of at least one or more elements of Au, Ag, Al, Ti, Cu, Mo, Sn, W, Ta, Pt, Ge, Si, Zn, Be, Cr, Se, and Ni. 
     In the semiconductor light-emitting device of this embodiment, because the metal is composed of one or more layers made of at least one or more elements of Au, Ag, Al, Ti, Cu, Mo, Sn, W, Ta, Pt, Ge, Si, Zn, Be, Cr, Se, and Ni, the metal can provide an AuSi alloy layer for electrical joint and an Au layer as an example of the metallic reflecting layer, for example. 
     There is a sufficient distance between the luminous layer and the die bond surface due to the supporting substrate, so that it is not necessary to take countermeasures such as use of eutectic joint or the like to prevent current leak. Also, provided that a substrate of high thermal conductivity is selected as the supporting substrate, there will not arise a problem regarding the heat radiation or dissipation. 
     In one embodiment, the supporting substrate is made of material including at least one or more elements of Au, Ag, Al, Ti, Cu, Mo, Sn, W, Ta, Pt, Ge, Si, Ga, Zn, Be, Cr, Se, and Ni. 
     In the semiconductor light-emitting device of this embodiment, because the supporting substrate is made of material including at least one or more elements of Au, Ag, Al, Ti, Cu, Mo, Sn, W, Ta, Pt, Ge, Si, Ga, Zn, Be, Cr, Se, and Ni, the supporting substrate makes an electrically conductive substrate. 
     For example, a single metallic substrate of Ag, Al, Mo, or the like, an electrically conductive supporting substrate made of AuAg alloy, TiW alloy, or the like, or an electrically conductive supporting substrate having a metallic multi-layer structure can be obtained. 
     Furthermore, an electrically conductive supporting substrate made of semiconductor such as AlGaAs, GaP, or SiC can be obtained. 
     The present invention also provides a method of manufacturing the semiconductor light-emitting device according to one embodiment, including: 
     a stacking process of stacking the first reflecting layer, the first semiconductor layer, the luminous layer, and the second semiconductor layer on a substrate; 
     a substrate mounting process of mounting the transmissive substrate directly or indirectly on the second semiconductor layer after the stacking process; 
     a substrate removing process of removing the substrate to expose a surface of the first reflecting layer opposite from the first semiconductor layer after the substrate mounting process; and 
     an electrode forming process of forming an electrode on part or the whole of the surface of the first reflecting layer opposite from the first semiconductor layer after the substrate removing process. 
     Furthermore, the present invention provides a method of manufacturing the semiconductor light-emitting device of another embodiment, including: 
     a stacking process of stacking the second semiconductor layer, the luminous layer, the first semiconductor, and the first reflecting layer on a substrate; 
     a substrate mounting process of mounting the supporting substrate directly or indirectly on a surface of the first reflecting layer opposite from the first semiconductor layer after the stacking process; 
     a substrate removing process of removing the substrate to expose a surface of the second semiconductor layer opposite from the luminous layer after the substrate mounting process; and 
     an electrode forming process of forming an electrode on the whole or part of a surface of the supporting substrate opposite from the first reflecting layer, and an electrode on the whole or part of the surface of the second semiconductor layer opposite from the luminous layer, after the substrate removing process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not intended to limit the present invention, and wherein: 
         FIG. 1  is a schematic cross-sectional view of a conventional light-emitting device; 
         FIG. 2  is a schematic cross-sectional view of another conventional light-emitting device; 
         FIG. 3  is a schematic cross-sectional view of a light-emitting device according to an embodiment of the present invention; 
         FIG. 4  is a schematic cross-sectional view of a light-emitting device according to an embodiment of the present invention; 
         FIG. 5  is a schematic cross-sectional view of a light-emitting device according to an embodiment of the present invention; 
         FIG. 6A  shows the shape of an electrode for reflecting layer use in the light-emitting device shown in  FIG. 5 ; 
         FIG. 6B  shows the shape of an electrode for reflecting layer use in the light-emitting device shown in  FIG. 5 ; 
         FIG. 7  shows the manner of reflection of a DBR layer in the light-emitting device shown in  FIG. 5 ; 
         FIG. 8  is a schematic cross-sectional view of a light-emitting device according to an embodiment of the present invention; 
         FIG. 9  is a schematic cross-sectional view of a light-emitting device according to an embodiment of the present invention; 
         FIG. 10  is a schematic cross-sectional view of a light-emitting device according to an embodiment of the present invention; 
         FIG. 11  is a schematic cross-sectional view of a light-emitting device according to an embodiment of the present invention; 
         FIG. 12  is a schematic cross-sectional view of a light-emitting device according to an embodiment of the present invention; 
         FIG. 13  shows the manner in which outgoing light is reflected in the light-emitting device of  FIG. 12 ; 
         FIG. 14  is a schematic cross-sectional view of a light-emitting device according to Embodiment 1 of the present invention; 
         FIG. 15A  shows a step in a process of manufacturing the semiconductor light-emitting device of Embodiment 1; 
         FIG. 15B  shows a step in the process of manufacturing the semiconductor light-emitting device of Embodiment 1; 
         FIG. 15C  shows a step in the process of manufacturing the semiconductor light-emitting device of Embodiment 1; 
         FIG. 15D  shows a step in the process of manufacturing the semiconductor light-emitting device of Embodiment 1; 
         FIG. 15E  shows a step in the process of manufacturing the semiconductor light-emitting device of Embodiment 1; 
         FIG. 16  is a schematic cross-sectional view of a light-emitting device according to Embodiment 2 of the present invention; 
         FIG. 17A  shows a step in a process of manufacturing the semiconductor light-emitting device of Embodiment 2; 
         FIG. 17B  shows a step in the process of manufacturing the semiconductor light-emitting device of Embodiment 2; 
         FIG. 17C  shows a step in the process of manufacturing the semiconductor light-emitting device of Embodiment 2; 
         FIG. 17D  shows a step in the process of manufacturing the semiconductor light-emitting device of Embodiment 2; and 
         FIG. 17E  shows a step in the process of manufacturing the semiconductor light-emitting device of Embodiment 2. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The semiconductor light-emitting device of the present invention will be described in detail below with reference to the embodiments shown in the figures. 
     As is apparent from the above description, the semiconductor light-emitting device of the present invention basically has a first conductivity type fist semiconductor layer, a luminous layer formed on the first semiconductor layer, a second conductivity type second semiconductor layer formed on the luminous layer, and a first reflecting layer which is formed under the first semiconductor layer and composed of stacked two or more first conductivity type semiconductor layers, and at least part of which has reflectivity for an emission wavelength of the luminous layer. And, the semiconductor light-emitting device of the present invention may also have various additional features, as described below. 
       FIG. 3  is a schematic cross-sectional view of an example of a semiconductor light-emitting device having a transmissive substrate which is pervious to the emission wavelength of the luminous layer. In  FIG. 3 , the reference numeral  301  denotes a distributed Bragg reflector (DBR) layer as an example of the first reflecting layer,  302  denotes a luminous layer, and  303  denotes a transmissive substrate. 
     The n-type DBR layer  301  is composed of two or more semiconductor epitaxial layers. Furthermore, layers between the n-type DBR layer  301  and the luminous layer  302  and layers between the luminous layer  302  and the transmissive substrate  303  are also composed of semiconductor epitaxial layers. 
       FIG. 4  is a schematic cross-sectional view showing an example of a semiconductor light-emitting device having an electrode for transmissive substrate use formed on the transmissive substrate, and an electrode for reflecting layer use formed on the under surface of the first reflecting layer. In  FIG. 4 , the reference numeral  401  denotes a DBR layer as an example of the first reflecting layer,  402  denotes a luminous layer,  403  denotes the transmissive substrate,  404  denotes the electrode for reflecting layer use, and  405  denotes the electrode for transmissive substrate use. 
     The DBR layer  401  is composed of tow or more semiconductor epitaxial layers. Furthermore, layers between the DBR layer  401  and the luminous layer  402  and layers between the luminous layer  402  and the transmissive substrate  403  are also composed of semiconductor epitaxial layers. 
       FIG. 5  is a schematic cross-sectional view of an example of a semiconductor light-emitting device having an electrode for reflecting layer use formed on part of a surface of the first reflecting layer opposite from the first semiconductor layer. In  FIG. 5 , the reference numeral  501  denotes a DBR layer as an example of the first reflecting layer,  502  denotes a luminous layer,  503  denotes a transmissive substrate,  504  denotes the electrode for reflecting layer use, and  505  denotes an electrode for transmissive substrate use. 
     The DBR layer  501  is composed of two or more semiconductor epitaxial layers. Furthermore, the electrode for reflecting layer use  504  is formed on part of a surface of the DBR layer  501  opposite from the luminous layer. In other words, only part of the surface is covered with the electrode for reflecting layer use  504 . 
     In general, the DBR layer  501  is very effective in reflecting light vertically incident on the DBR layer  501 . 
     However, the DBR layer  501  does not have the reflection factor of 100%, and is pervious to part of the incident light. 
     Furthermore, the DBR layer  501  is almost ineffective in reflecting light obliquely incident on the DBR layer  501 , i.e., light other than light vertically incident on the DBR layer  501 . 
     Thus, in order to achieve a larger reflection effect which reduces the amount of absorbed light, it is preferred that the area of the electrode for reflecting layer use  504  is smaller, so that it is desirable that the electrode for reflecting layer use  504  is shaped like a dot as shown in  FIG. 6A . 
     However, as described above, when the area of the electrode is reduced, the resistance of it increases accordingly. Therefore, in order to expand the area through which an electric current flows, it is desirable that the electrode for reflecting layer use  504  is shaped like dots as shown in  FIG. 6B . 
     For example, when the electrode for reflecting layer use  504  is formed on only the center part of the device as shown in  FIG. 6A , only the center part of the luminous layer  502  emits light because the position of the electrode for reflecting layer use  504  is about the same as the luminous position of the luminous layer  504 , so that light emitted from the luminous layer  502  to the electrode for reflecting layer use  504  is reflected by the DBR layer  501 . On the other hand, some components of light emitted from the luminous layer  502  in a direction different from the direction of the electrode  504  are reflected by the DBR layer  501 , and the remaining light components are once released out of the crystal and then reflected by, for example, silver paste used for supporting the device, or the frame material. 
     Furthermore, when the electrode for reflecting layer use is formed over the entire surface of the DBR layer  501  opposite from the luminous layer  502 , the electric current spreads to the whole of the device. 
     For this reason, the luminous area of the luminous layer  502  also expands. However, light components obliquely incident on the first reflecting layer also increase, so that light components absorbed by the electrode also increase accordingly. As a result, an effect of outputting more light more efficiently cannot be expected. 
       FIG. 7  shows the manner of reflection of the DBR layer  701 . In  FIG. 7 , the numeral  702  denotes a luminous area,  703  denotes loci of emitted light, and  704  denotes an electrode for reflecting layer use. 
     As can be understood from the figure, in order to make the expansion of the luminous area compatible with the increase of the reflection effect, it is preferred that the electrode for reflecting layer use is shaped like dots, which are arranged evenly on the opposite side of the first reflecting layer from the first semiconductor layer. 
     Furthermore, the electrode for reflecting layer use may be made into a given shape. 
       FIG. 8  is a schematic cross-sectional view of a semiconductor light-emitting device in which a second reflecting layer capable of reflecting the emission wavelength of the luminous layer is formed on the surface of the first reflecting layer opposite from the first semiconductor layer in an area other than an area in which the electrode for reflecting layer use is formed. In  FIG. 8 , the reference numeral  801  denotes a DBR layer as an example of the first reflecting layer,  802  denotes a luminous layer,  803  denotes a transmissive substrate,  804  denotes the electrode for reflecting layer use,  805  denotes an electrode for transmissive substrate use, and  806  denotes a reflecting metal as an example of the second reflecting layer. 
     The DBR layer  801  is composed of two or more semiconductor epitaxial layers. A surface of the electrode for reflecting layer use  804  opposite from the DBR layer  801  is not covered with the reflecting metal  806  but is exposed. In more detail, the surface of the electrode for reflecting layer use  804  opposite from the DBR layer  801  is substantially flush with a surface of the reflecting metal  806  opposite from the DBR layer  801 . 
     As described above, the DBR layer  801  has a little effect in reflecting light obliquely incident on it. 
     In order to surely reflect such light, it is preferred to provide a metallic reflecting layer such as the reflecting metal  806 , and when the electrode for reflecting layer use  804  and the reflecting metal  806  are arranged alternately as shown in  FIG. 8 , a larger effect of reflecting light can be obtained. 
       FIG. 9  is a schematic cross-sectional view of an example of a semiconductor light-emitting device in which the second reflecting layer is formed so as to cover both the first reflecting layer and the electrode for reflecting layer use. In  FIG. 9 , the reference numeral  901  denotes a DBR layer as an example of the first reflecting layer,  902  denotes a luminous layer,  903  denotes a transmissive substrate,  904  denotes an electrode for reflecting layer use,  905  denotes an electrode for transmissive substrate use, and  906  denotes a reflecting metal as an example of the second reflecting layer. 
     The DBR layer  901  is composed of two or more semiconductor epitaxial layers. Furthermore, a surface of the electrode for reflecting layer use  904  opposite from the DBR layer  901  is covered with the reflecting metal  906  and is not exposed. In other words, the reflecting metal  906  is formed underneath the DBR layer  901  and the electrode for reflecting layer use  904 . 
     The reflecting metal  906  covers the DBR layer  901  and the whole of a surface opposite from the DBR layer  901  of the electrode for reflecting layer use  904 , so that a larger effect of reflecting light can be obtained. In addition, the process of shaping and patterning the reflecting metal  906  is not required, which contributes to the simplification and facilitation of the manufacturing process. 
       FIG. 10  is a schematic cross-sectional view of an example of a semiconductor light-emitting device having a supporting substrate mounted under the first reflecting layer. In  FIG. 10 , the reference numeral  1001  denotes the supporting substrate,  1002  denotes a DBR layer, and  1003  denotes a luminous layer. 
     The DBR layer  1002  is composed of two or more semiconductor epitaxial layers. Furthermore, layers between the DBR layer  1002  and the luminous layer  1003  and on the luminous layer  1003  are also composed of semiconductor epitaxial layers. 
     After two or more semiconductor epitaxial layers are stacked, the DBR layer  1002  is stacked on the surface of the semiconductor epitaxial layers, and then the supporting substrate  1001  is mounted on the surface of the DBR layer  1002 . The supporting substrate  1001  is joined directly or indirectly to the DBR layer  1002 . In other words, there may be an additional layer or no layers between the supporting substrate  1002  and the DBR layer  1002 . 
     Light emitted by the luminous layer  1003  is reflected by the DBR layer  1002  and extracted to the outside. 
     Thus, the supporting substrate  1001  does not need to be transmissive, and is mounted to support the semiconductor laminated structure including the luminous layer  1003 . 
     Although the supporting substrate  1001  can be joined to the DBR layer  1002  directly or indirectly through metal or the like, heat treatment is required in either case, and an alloy layer or a light-absorbing layer is formed at the joint interface during the heat treatment. 
     Even if the light-absorbing layer is formed at the joint interface between the supporting substrate and the DBR layer, the DBR layer  1002  is located between the supporting substrate  1001  and the luminous layer  1003 , so that light emitted by the luminous layer  1003  is reflected by the DBR layer  1002  before reaching the light-absorbing layer. 
     Thus, the loss of light that may be caused by light absorption of the light-absorbing layer is little. 
       FIG. 11  is a schematic cross-sectional view of an example of a semiconductor light-emitting device in which the supporting substrate is joined to the first reflecting layer through metal. In  FIG. 11 , the reference numeral  1101  denotes the supporting substrate,  1102  is a DBR layer as the first reflecting layer,  1103  denotes a luminous layer,  1104  denotes an electrode,  1105  denotes an electrode, and  1106  denotes a joining metal as an example of the metal. 
     The DBR layer  1102  is composed of two or more semiconductor epitaxial layers. Furthermore, the layer between the DBR layer  1102  and the luminous layer  1103  and the layer on the luminous layer  1103  are also composed of semiconductor epitaxial layers. 
     The joining metal  1106  is provided for the purpose of ensuring the electrical joint and securely reflecting light which has entered the DBR layer  1102  obliquely and passed through the DBR layer  1102 . 
     Furthermore, since the supporting substrate  1102  and the DBR layer  1102  are joined through the joining metal  1106 , the supporting substrate  1101  can be joined to the DBR layer  1102  at a relatively low temperature (e.g. a temperature in the neighborhood of 400 degrees centigrade) in the manufacturing process. 
     Thus, phenomena affecting the reliability of the device, such as diffusion phenomenon, alloying, and dislocation growth in the semiconductor layers which would occur at high temperature processing, can be suppressed. 
     In addition, the joining metal  1106  is not limited to a single layer structure, and may be of a multi-layer structure. Furthermore, the joining metal  1106  may be made in a given shape, for example, patterning as shown in  FIG. 6A  or  6 B may be performed, provided that a sufficient joint strength can be ensured. 
       FIG. 12  is a schematic cross-sectional view of a semiconductor light-emitting device in which the metal is composed of a metal for ensuring the electrical conductivity of a joint between the supporting substrate and the first reflecting layer, and a metal for surely providing reflectivity for the emission wavelength of the luminous layer, i.e., for surly reflecting light of the emission wavelength of the luminous layer. In  FIG. 12 , the reference numeral  1201  denotes the supporting substrate,  1202  denotes a DBR layer,  1203  denotes the luminous layer,  1204  denotes an electrode,  1205  denotes an electrode,  1206  denotes a joining metal, and  1207  denotes a metallic reflecting layer. The joining metal  1206  is an example of the metal for ensuring the electrical conductivity of a joint between the supporting substrate and the first reflecting layer. The metallic reflecting layer  1207  is an example of the metal for surely providing the reflectivity for the emission wavelength of the luminous layer. 
     The DBR layer  1202  is composed of two or more semiconductor epitaxial layers. Furthermore, the layer between the DBR layer  1202  and the luminous layer  1203  and the layer on the luminous layer  1203  are also composed of semiconductor epitaxial layers. 
     As described above, the DBR layer  1202  is most effective in reflecting light vertically incident on it. 
     Thus, even if there is an alloy layer serving as a light-absorbing layer in a position (joint position) on the DBR layer  1202  where light vertically enters, there would be no loss of light caused by light absorption of the light-absorbing layer. 
     As described above, metallic material allowing electrical connection is used only in the above position, and metal for reflection is provided on the joint surface excepting the position, so that the electrical characteristic and optical characteristic of the semiconductor light-emitting device can be more improved. 
     In more detail, as shown in  FIG. 13 , of light emitted from the luminous area  1208 , light going in a direction substantially perpendicular to the surface of the supporting substrate  1201  is reflected by the joining metal  1206 . Furthermore, light going in a direction oblique to the surface of the supporting substrate  1201  of the emitted light is reflected by the metallic reflecting layer  1207 . In  FIG. 13 , the reference numeral  1209  denotes loci of light emitted from the luminous area  1208 . 
     More specific embodiments of the present invention will be described in detail below. 
     Embodiment 1 
       FIG. 14  is a schematic cross-sectional view of a semiconductor light-emitting device according to Embodiment 1 of the present invention. 
     The semiconductor light-emitting device includes an n-type DBR layer  3 , an n-type Al 0.5 In 0.5 P cladding layer  4 , a 4-element AlGaInP active layer  5 , a p-type Al 0.5 In 0.5 P cladding layer  6 , a p-type GaInP intermediate layer  7 , a p-type GaP contact layer  8 , a p-type GaP transparent substrate  9 , ohmic electrodes  10  and  11 , and a reflecting layer  12 . 
     The n-type DBR layer  3  is composed of 20 pairs of an n-type AlAs light reflection layer and an n-type Al 0.61 Ga 0.39 As light reflection layer. Furthermore, the n-type DBR layer  3  is able to reflect light of the emission wavelength of the AlGaInP active layer  6 . 
     The AlGaInP active layer  5  emits red light. Furthermore, the AlGaInP active layer  5  has a quantum well structure. In more detail, the AlGaInP active layer  5  is formed by stacking (Al 0.05 Ga 0.95 ) 0.5 In 0.5 P well layers and (Al 0.50 Ga 0.50 ) 0.5 In 0.5 P barrier layers alternately. The number of pairs of the well layer and the barrier layer is twenty. 
     The p-type GaP transparent substrate  9  is pervious to the emission wavelength of the AlGaInP active layer  5 . 
     The ohmic electrode  10  is formed so as to cover part of the under surface of the n-type DBR layer  3  in  FIG. 14 . The ohmic electrode  10  is composed of an AuSi layer and an Au layer. Furthermore, the under surface of the ohmic electrode  10  in  FIG. 14  is covered with an Au layer  13 . It is desirable that the ohmic electrode  10  is shaped like a dot or dots as shown in  FIG. 6A  or  6 B. 
     The ohmic electrode  11  is formed so as to cover part of the upper surface of the p-type GaP transparent substrate  9  in  FIG. 14 . The ohmic electrode  11  is composed of an AuBe layer and an Au layer. 
     The reflecting layer  12  is composed of an Au layer  13 , a Mo layer  14 , and an AuSn layer  15 . The Au layer  13  is provided to reflect light which has passed through the n-type DBR layer  3 . The Mo layer  14  is provided to prevent the Au layer  13  and the AuSu layer  15  from being alloyed with each other. The AuSn layer  15  is provided to be eutectically bonded to a die bond surface. 
     In Embodiment 1, the n-type DBR layer  3  is an example of the first reflecting layer, the n-type Al 0.5 In 0.5 P cladding layer  4  is an example of the first semiconductor layer, the AlGaInP active layer  5  is an example of the luminous layer, the p-type Al 0.5 In 0.5 P cladding layer  6  is an example of the second semiconductor layer, the p-type GaInP intermediate layer  7  is an example of the second semiconductor layer, the p-type GaP contact layer  8  is an example of the second semiconductor layer, the p-type GaP transparent substrate  9  is an example of the transmissive substrate, the ohmic electrode  10  is an example of the electrode for reflecting layer use, the ohmic electrode  11  is an example of the electrode for transmissive substrate use, and the reflecting layer  12  is an example of the second reflecting layer. 
     In the semiconductor light-emitting device as configured above, although the ohmic electrode  10  is formed underneath the n-type DBR layer  3 , light emitted by the AlGaInP active layer  5  is reflected by the n-type DBR layer  3  before being absorbed by the ohmic electrode  10 , so that the light extraction efficiency can be prevented from reducing. 
     Thus, the light extraction efficiency of the semiconductor light-emitting device can be increased. 
     Furthermore, since the p-type GaP transparent substrate  9  which is pervious to the emission wavelength of the AlGaInp active layer  5  is mounted on the p-type GaP contact layer  8 , light emitted by the AlGaInP active layer  5  can be extracted efficiently through the p-type GaP transparent substrate  9 . 
     Furthermore, although the ohmic electrode  11  is formed on the p-type GaP transparent substrate  9 , it covers only part of the upper surface of the p-type GaP transparent substrate  9  in  FIG. 14 , so that a decreased amount of light components of the light emitted from the AlGaInP active layer  5  can enter the ohmic electrode  11 . 
     Furthermore, since the p-type GaP transparent substrate  9  is mounted on the p-type GaP contact layer  8 , the distance between a die bond surface for die-bonding the semiconductor light-emitting device and the AlGaInP active layer  5  can be reduced. 
     Thus, heat generated near the AlGaInP active layer is radiated or released efficiently to the die bond surface, and thereby the reliability of the semiconductor light-emitting device can be increased. 
     A method of manufacturing a semiconductor light-emitting device will be described below with reference to  FIGS. 15A to 15E . In this manufacturing method, an n-type GaAs substrate  1  and a p-type GaP transparent substrate  9  shown in  FIG. 15A  are used. 
     At first, as shown in  FIG. 15B , an n-type GaAs buffer layer  2 , an n-type DBR layer  3 , an n-type Al 0.5 In 0.5 P cladding layer  4 , an AlGaInP active layer  5 , a p-type Al 0.5 In 0.5 P cladding layer  6 , a p-type GaInP intermediate layer  7 , and a p-type GaP contact layer  8  are stacked in this order on the n-type GaAs substrate  1  by a MOCVD method to form an epitaxial wafer having an LED structure. 
     The thicknesses of the substrates and the layers are 250 μm of the n-type GaAs substrate  1 , 1.0 μm of the n-type GaAs buffer layer  2 , 2.0 μm of the n-type DBR layer  3 , 1.0 μm of the n-type Al 0.5 In 0.5 P cladding layer  4 , 0.5 μm of the AlGaInP active layer  5 , 1.0 μm of the p-type Al 0.5 In 0.5 P cladding layer  6 , 1.0 μm of the p-type GaInP intermediate layer  7 , and 4.0 μm of the p-type GaP contact layer  8 . 
     When the epitaxial wafer is formed, Si is used as n-type dopant, while Zn is used as p-type dopant. As a matter of course, dopant for forming the epitaxial wafer is not limited to Si and Zn. For example, Te or Se may be used as n-type dopant, while Mg or carbon may be used as p-type dopant. 
     The carrier concentrations of the substrates and the layers are 1.0×10 18  cm −3  of the n-type GaAs substrate  1 , 5×10 17  cm −3  of the n-type GaAs buffer layer  2 , 5×10 17  cm −3  of the n-type DBR layer  3 , 5×10 17  cm −3  of the n-type Al 0.5 In 0.5 P cladding layer  4 , 0 cm −3  (non-doped) of the AlGaInP active layer  5 , 5×10 17  cm −3  of the p-type Al 0.5 In 0.5 P cladding layer  6 , 1.0×10 18  cm −3  of the p-type GaInP intermediate layer  7 , and 2.0×10 18  cm −3  of the p-type GaP contact layer  8 . 
     Next, the p-type GaP transparent substrate  9  is placed on the epitaxial surface of the epitaxial wafer. In other words, the p-type GaP transparent substrate  9  is mounted directly on the upper surface of the p-type GaP contact layer  8  in  FIG. 15B . 
     Next, a compressive force is applied to the contact surface between the epitaxial wafer and the p-type GaP transparent substrate  9 , and the contact surface is heated for about 30 minutes in an atmosphere of hydrogen at the neighborhood of 800 degrees centigrade. As a result, the p-type GaP transparent substrate  9  is joined to the epitaxial wafer as shown in  FIG. 15C . The heating is performed after the epitaxial wafer and the p-type GaP transparent substrate  9  have been put in a heating furnace. 
     The carrier concentration of the p-type GaP transparent substrate  9  is 5.0×10 17  cm −3  in the embodiment, but is not limited to 5.0×10 17  cm −3 , and may be any in a range where electrical continuity is achievable. 
     Next, the epitaxial wafer is cooled, and is then taken out from the heating furnace. After that, the n-type GaAs substrate  1  and the n-type GaAs buffer layer  2  are dissolved away, as shown in  FIG. 15D , with the mixture of ammonia water, hydrogen peroxide, and water. As a result, the under surface of the n-type DBR layer  3  in  FIG. 15D  is exposed. Because the n-type DBR layer  3  has a high Al mole fraction, this layer  3  also functions as an etching stop layer. 
     If it is desired that the etching by the mixture be more surely stopped, an AlGaAs layer, for example, may be formed between the n-type GaAs buffer layer  2  and the n-type DBR layer  3 . 
     Next, as shown in  FIG. 15E , an ohmic electrode  10  is formed on the exposed surface of the n-type DBR layer  3  (one surface of an n-type AlAs light reflection layer or of an n-type Al 0.61 Ga 0.39 As light reflection layer), and an ohmic electrode  11  is formed on the upper surface of the p-type GaP transparent substrate  9  in  FIG. 15E . 
     AuSi/Au is selected as the material of the ohmic electrode  10 , while AuBe/Au is selected as the material of the ohmic electrode  11 , and then these materials are worked into optional shapes by photolithography method and wet etching. 
     After that, in order to enhance the effect of reflecting light emitted by the AlGaInP active layer  5 , a reflecting layer  12  composed of a multi-layer film of an Au layer, a Mo layer and an AuSn layer is formed on the surface on which the ohmic electrode  10  is formed, that is, on the exposed surface of the DBR layer  3 . The reflecting layer  12  serves as a reflecting layer composed of tow or more layers, and an electrode for bonding. 
     Next, half-dicing is performed on the epitaxial wafer, on which the ohmic electrodes  10  and  11  and the reflecting layer  12  are formed, to facilitate the division of the epitaxial wafer into chips having a predetermined size. 
     The half-dicing can be performed with various materials and techniques. For example, wet etching or dry etching may be used. However, dry etching may be more suitable for the half-dicing than wet etching in that it is compatible with any material to divide. Materials and techniques for the half-dicing are not limited to those of Embodiment 1. 
     Finally, the half-diced epitaxial wafer is divided into chips having a predetermined size, and a plurality of semiconductor light-emitting devices are thus obtained. These semiconductor light-emitting devices are high luminance red light-emitting devices having the emission wavelength of 640 nm. 
     The manufacturing process described above may be applied to not only light-emitting diodes having an AlGaInP 4-element luminous layer but also semiconductor light-emitting devices the luminous layers of which are made of other semiconductor crystal. 
     In Embodiment 1, the ohmic electrode  10  is formed so as to cover part of the under surface of the n-type DBR layer  3  in  FIG. 14 , but may be formed so as to cover the whole of the under surface of the n-type DBR layer  3  in  FIG. 14 . 
     In Embodiment 1, the reflecting layer  12  which covers the under surface of the ohmic electrode  10  in  FIG. 14  is used. However, a reflecting layer which does not cover the under surface of the ohmic electrode  10  in  FIG. 14  may be used. When this reflecting layer is formed, the under surface of the ohmic electrode  10  in  FIG. 14  is exposed. One surface of the reflecting layer may be made flush with the under surface of the ohmic electrode  10  in  FIG. 14 . 
     In Embodiment 1, the reflecting layer  12  composed of the Au layer  13 , the Mo layer  14 , and the AuSn layer  15  is used. However, a reflecting layer composed of only the Au layer  13  may be used. 
     In Embodiment 1, the reflecting layer  12  is composed of the Au layer  13 , the Mo layer  14 , and the AuSn layer  15 , but may be composed of one or more layers made of at least one or more elements of Au, Ag, Al, Ti, Cu, Mo, Sn, W, Ta, Pt, Ge, Si, Zn, Be, Cr, Se, and Ni. 
     In Embodiment 1, a semiconductor layer including at least two or more elements of Ga, Si, P, C, Zn, Se, Cd, Te, B, N, Al, In, Hg, S, and O may be used instead of the p-type GaP transparent substrate  9 , provided that the semiconductor layer is pervious to the emission wavelength of the luminous layer of the semiconductor light-emitting device. 
     In Embodiment 1, the conductivity types of the substrates and the layers may be reversed. In this case, the semiconductor light-emitting device is manufactured using not the n-type GaAs substrate  1  but a p-type GaAs substrate. 
     Embodiment 2 
     Embodiment 2 is different from Embodiment 1 in that in Embodiment 2 a supporting substrate is attached to the DBR layer through a metal. 
       FIG. 16  is a schematic cross-sectional view of the semiconductor light-emitting device of Embodiment 2 of the present invention. 
     The semiconductor light-emitting device includes an n-type Al 0.6 Ga 0.4 As current diffusion layer  23 , an n-type Al 0.5 In 0.5 P cladding layer  24 , an AlGaInP active layer  25 , a p-type Al 0.5 In 0.5 P cladding layer  26 , a p-type DBR layer  27 , a p-type AlGaAs contact layer  28 , ohmic electrodes  29 ,  35  and  36 , a reflecting layer  30 , and a p-type Si substrate  34 . 
     The AlGaInP active layer  25  emits red light. Furthermore, the AlGaInP active layer  25  has a quantum well structure. In more detail, the AlGaInP active layer  25  is formed by stacking (Al 0.05 Ga 0.95 ) 0.5 In 0.5 P well layers and (Al 0.50 Ga 0.50 ) 0.5 In 0.5 P barrier layers alternately. The number of pairs of the well layer and the barrier layer is twenty. 
     The p-type DBR layer  27  is composed of 20 pairs of a p-type AlAs light reflection layer and a p-type Al 0.61 Ga 0.39 As light reflection layer. Furthermore, the p-type DBR layer  27  is able to reflect the emission wavelength of the AlGaInP active layer  25 . 
     The ohmic electrode  29  is formed so as to cover part of the under surface of the p-type AlGaAs contact layer  28  in  FIG. 16 . The ohmic electrode  29  is composed of an AuBe layer and an Au layer. Furthermore, the under surface of the ohmic electrode  29  in  FIG. 16  is covered with an Au layer  31 . 
     The reflecting layer  30  is composed of an Au layer  31 , a Mo layer  32 , and an Au layer  33 . Light which has passed through the p-type DBR layer  27  can be reflected by the Au layer  31 . 
     In Embodiment 2, the n-type Al 0.6 Ga 0.4 As current diffusion layer  23  is an example of the second semiconductor layer, the n-type Al 0.5 In 0.5 P cladding layer  24  is an example of the second semiconductor layer, the AlGaInP active layer  25  is an example of the luminous layer, the p-type Al 0.5 In 0.5 P cladding layer  26  is an example of the first semiconductor layer, the p-type DBR layer  27  is an example of the first reflecting layer, the p-type AlGaAs contact layer  28  and the ohmic electrode  29  are an example of the metal with which the supporting substrate is joined to the first reflecting layer, the reflecting layer  30  is an example of the metal with which the supporting substrate is joined to the first reflecting layer, and the p-type Si substrate  34  is an example of the supporting substrate. 
     In the semiconductor light-emitting device as configured above, although the ohmic electrode  29  is formed underneath the p-type DBR layer  27 , light emitted by the AlGaInP active layer  25  is reflected by the p-type DBR layer  27  before absorbed by the ohmic electrode  29 , so that the light extraction efficiency can be prevented from reducing. 
     Thus, the light extraction efficiency of the semiconductor light-emitting device can be increased. 
     A method of manufacturing the semiconductor light-emitting device will be described below with reference to  FIGS. 17A to 17E . In this manufacturing method, an n-type GaAs substrate  21  and a p-type Si substrate  34  shown in  FIG. 17A  are used. 
     At first, as shown in  FIG. 17B , an n-type GaAs buffer layer  22 , an n-type Al 0.6 Ga 0.4 As current diffusion layer  23 , an n-type Al 0.5 In 0.5 P cladding layer  24 , an AlGaInP active layer  25 , a p-type Al 0.5 In 0.5 P cladding layer  26 , a p-type DBR layer  27 , and a p-type AlGaAs contact layer  28  are stacked in this order on the n-type GaAs substrate  21  by a MOCVD method to form an epitaxial wafer having an LED structure. 
     The thicknesses of the substrates and the layers are 250 μm of the n-type GaAs substrate  21 , 1.0 μm of the n-type GaAs buffer layer  22 , 5.0 μm of the n-type Al 0.6 Ga 0.4 As current diffusion layer  23 , 1.0 μm of the n-type Al 0.5 In 0.5 P cladding layer  24 , 0.5 μm of the AlGaInP active layer  25 , 1.0 μm of the p-type Al 0.5 In 0.5 P cladding layer  26 , 2.0 μm of the p-type DBR layer  27 , and 1.0 μm of the p-type AlGaAs contact layer  28 . 
     When the epitaxial wafer is formed, Si is used as n-type dopant, while Zn is used as p-type dopant. As a matter of course, dopant for forming the epitaxial wafer is not limited to Si and Zn. For example, Te or Se may be used as n-type dopant, while Mg or carbon may be used as p-type dopant. 
     The carrier concentrations of the substrates and the layers are 1.0×10 18  cm −3  of the n-type GaAs substrate  21 , 5×10 17  cm −3  of the n-type GaAs buffer layer  22 , 1.0×10 18  cm −3  of the n-type Al 0.6 Ga 0.4 As current diffusion layer  23 , 5×10 17  cm −3  of the n-type Al 0.5 In 0.5 P cladding layer  24 , 0 cm −3  (non-doped) of the AlGaInP active layer  25 , 5×10 17  cm −3  of the p-type Al 0.5 In 0.5 P cladding layer  26 , 5×10 17  cm −3  of the p-type DBR layer  27 , and 5.0×10 17  cm −3  of the p-type AlGaAs contact layer  28 . 
     Next, as shown in  FIG. 17C , an ohmic electrode  29  is formed on part of the epitaxial surface of the epitaxial wafer. In other words, the ohmic electrode  29  is formed on part of the upper surface of the p-type AlGaAs contact layer  28  in  FIG. 17B . 
     AuSi/Au is selected as the material of the ohmic electrode  29 , and then this material is worked into a desired shape by photolithography method and wet etching. 
     Next, an Au layer  31 , an Mo layer  32 , and an Au layer  33  are stacked in this order on the p-type AlGaAs contact layer  28  and the ohmic electrode  29  to form a reflecting layer  30 . 
     Next, the p-type Si substrate  34  is placed on the upper surface of the reflecting layer  30  in  FIG. 17C . In other words, the p-type Si substrate  34  is mounted directly on the upper surface of the Au layer  33  in  FIG. 17C . 
     Next, a compressive force is applied to the contact surface between the epitaxial wafer and the p-type Si substrate  34 , and the contact surface is heated for about 30 minutes in an atmosphere of hydrogen at the neighborhood of 450 degrees centigrade. As a result, the p-type Si substrate  34  is joined to the epitaxial wafer as shown in  FIG. 17D . The heating is performed with the epitaxial wafer and the p-type Si substrate  34  put in a heating furnace. 
     The carrier concentration of the p-type Si substrate  34  is but not limited to 5.0×10 17  cm −3 , and may be in a range where electrical continuity is possible. Furthermore, when a substrate is joined to the reflecting layer through metal, the conductivity type of the substrate may be either p-type or n-type. 
     Next, the epitaxial wafer is cooled, and is then taken out from the heating furnace. After that, the n-type GaAs substrate  21  and the n-type GaAs buffer layer  22  are dissolved away with the mixture of ammonia water, hydrogen peroxide, and water. As a result, one surface of the n-type Al 0.6 Ga 0.4 As current diffusion layer  23  is exposed. 
     Next, as shown in  FIG. 17E , an ohmic electrode  35  is formed on the under surface of the n-type Al 0.6 Ga 0.4 As current diffusion layer  23  in  FIG. 17E , and an ohmic electrode  36  is formed on the whole of the under surface of the p-type Si substrate  34  in  FIG. 17E . There is an upside-down relation between  FIG. 17E  and  FIG. 17D . 
     Next, the epitaxial wafer on which the ohmic electrodes  35  and  36  and the reflecting layer  30  are formed is half-diced for dividing the epitaxial wafer into chips having a predetermined size. 
     The half-dicing can be performed for every material using every technique. For example, wet etching or dray etching may be used. However, dry etching is assumed to be more suitable for the half-dicing than wet etching in that the wet etching it compatible with any material to divide. Materials and techniques for the half-dicing are not limited to those of Embodiment 2. 
     Finally, the half-diced epitaxial wafer is divided into chips having a predetermined size, and a plurality of semiconductor light-emitting devices can be thus obtained. These semiconductor light-emitting devices are high-luminance red light-emitting devices having the emission wavelength of 640 nm. 
     The manufacturing process described above may be applied to not only light-emitting diodes having an AlGaInP 4-element luminous layer but also semiconductor light-emitting devices the luminous layers of which are made of semiconductor crystal. 
     In Embodiment 2, the reflecting layer  30  composed of the Au layer  31 , the Mo layer  32 , and the Au layer  33  is used. However, a reflecting layer composed of one or more layers made of at least one or more elements of Au, Ag, Al, Ti, Cu, Mo, Sn, W, Ta, Pt, Ge, Si, Zn, Be, Cr, Se, and Ni may be used provided that the reflecting layer surely reflects the emission wavelength of the AlGaInP active layer  25 . For example, a reflecting layer composed of only the Au layer  31  may be used instead of the reflecting layer  30  composed of the Au layer  31 , the Mo layer  32 , and the Au layer  33 . 
     In Embodiment 2, the ohmic electrode  29  composed of an AuBe layer and an Au layer is used. However, an ohmic electrode composed of one or more layers made of at least one or more elements of Au, Ag, Al, Ti, Cu, Mo, Sn, W, Ta, Pt, Ge, Si, Zn, Be, Cr, Se, and Ni may be used provided that the ohmic electrode ensures the electrical conductivity to the p-type DBR layer  27 . 
     In Embodiment 2, the p-type Si substrate  34  is used. However, a substrate made of material including at least one or more elements of Au, Ag, Al, Ti, Cu, Mo, Sn, W, Ta, Pt, Ge, Si, Ga, Zn, Be, Cr, Se, and Ni may be used. 
     In Embodiment 2, the conductivity types of the substrates and the layers may be reversed. In this case, the semiconductor light-emitting device is manufactured using not the n-type GaAs substrate  21  but a p-type GaAs substrate. 
     Embodiment 1 and Embodiment 2 may be combined appropriately according to the present invention. 
     Embodiments of the invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.