Abstract:
A method of manufacturing a laser diode array capable of inhibiting electric cross talk is provided. The method of manufacturing a laser diode array includes a processing step of forming a peel layer containing an oxidizable material and a vertical resonator structure over a first substrate sequentially from the first substrate side by crystal growth, and then selectively etching the peel layer and the vertical resonator structure to the first substrate, thereby processing into a columnar shape, a peeling step of oxidizing the peel layer from a side face, and then peeling the vertical resonator structure of columnar shape from the first substrate, and a rearrangement step of jointing a plurality of vertical resonator structures of columnar shape obtained by the peeling step to a surface of a metal layer of a second substrate formed with the metal layer on the surface.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present invention contains subject matter related to Japanese Patent Application JP 2007-216401 filed in the Japanese Patent Office on Aug. 22, 2007, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a laser diode array including a columnar vertical resonator structure, a method of manufacturing the same, a printer including the laser diode array, and an optical communication device including the laser diode array. 
         [0004]    2. Description of the Related Art 
         [0005]    In recent years, in the field of laser diodes (LD), a laser array in which a plurality of Vertical Cavity Surface Emitting Lasers (VCSEL) is formed on the same substrate has been actively developed. The laser array is used as a light source for an optical communication device, a laser printer and the like. 
         [0006]    In the field of optical communication devices, the laser printers and the like, because of downsizing, it has been desired to propagate laser light emitted from each laser diode formed on the same substrate by a single optical system. However, when the distance between each laser diode is reduced, cross talk due to heat generated from each laser diode and current leaked from each laser diode becomes significant. As a result, interference, color blur and the like occur. 
         [0007]    Therefore, for example, in Japanese Unexamined Patent Application Publication No. 11-274633, a technique in which a groove is provided between each laser diode and a terminal section is provided on the both ends of the groove has been proposed. In the application, the following is represented. That is, a path to conduct generated heat to a region other than an adjacent laser diode is secured, and in addition to that a heat conduction path to the adjacent laser diode is blocked. Accordingly, thermal cross talk is decreased without deterioration of the characteristics of each laser diode. 
       SUMMARY OF THE INVENTION 
       [0008]    However, in the technique of Japanese Unexamined Patent Application Publication No. 11-274633, it is difficult to increase the width and the depth of the groove so much, and thus laser diodes adjacent to each other are not able to be totally separated electrically. Therefore, there is an issue that electric cross talk occurs. 
         [0009]    In view of the foregoing, in the invention, it is desirable to provide a laser diode array capable of inhibiting electric cross talk, a method of manufacturing the same, a printer including the laser diode array, and an optical communication device including the laser diode array. 
         [0010]    According to an embodiment of the invention, there is provided a method of manufacturing a laser diode array including the following respective steps A1 to A3:
       Step A1: a processing step of forming a peel layer containing an oxidizable material and a vertical resonator structure over a first substrate sequentially from the first substrate side by crystal growth, and then selectively etching the peel layer and the vertical resonator structure to the first substrate, thereby processing into a columnar shape;   Step A2: a peeling step of oxidizing the peel layer from a side face, and then peeling the vertical resonator structure of columnar shape from the first substrate; and   Step A3: a rearrangement step of jointing a plurality of vertical resonator structures of columnar shape obtained by the peeling step to a surface of a metal layer of a second substrate formed with the metal layer on a surface.       
 
         [0014]    In the method of manufacturing a laser diode array according to the embodiment of the invention, the peel layer provided between the first substrate and the vertical resonator structure is oxidized from the side face. Thereby, a stress due to oxidation is generated in the peel layer. Thus, by applying an external force to the peel layer, the vertical resonator structure is easily peeled from the first substrate. After that, the plurality of columnar vertical resonator structures obtained by the peeling step is jointed to the surface of the metal layer of the second substrate. Thereby, a resistance component of the first substrate that is connected in series to each vertical resonator structure is separated from each vertical resonator structure. 
         [0015]    According to an embodiment of the invention, there is provided a laser diode array including a first substrate in which a metal layer is formed on a surface thereof and a plurality of vertical resonator structures of columnar shape. The respective vertical resonator structures are jointed to a surface of the metal layer. According to embodiments of the invention, there are provided a printer and an optical communication device using the foregoing laser diode array as a light source. 
         [0016]    In the laser diode array, the printer, and the optical communication device according to the embodiments of the invention, the respective vertical resonator structures are jointed to the surface of the metal layer. Therefore, a resistance component of the common substrate that is connected in series to each vertical resonator structure (common substrate used for forming each vertical resonator structure) is separated from each vertical resonator structure. 
         [0017]    According to the method of manufacturing a laser diode array of the embodiment of the invention, the plurality of columnar vertical resonator structures peeled from the first substrate with the use of oxidation of the peel layer is jointed to the surface of the metal layer of the second substrate. Thus, the resistance component of the first substrate that is connected in series to each vertical resonator structure is separated from each vertical resonator structure. Thereby, electric cross talk generated when the plurality of vertical resonator structures are formed on the common substrate is inhibited from being generated. 
         [0018]    According to the laser diode array, the printer, and the optical communication device of the embodiments of the invention, the respective vertical resonator structures are jointed to the surface of the metal layer. Therefore, the resistance component of the common substrate that is connected in series to each vertical resonator structure is separated from each vertical resonator structure. Thereby, electric cross talk generated when the plurality of vertical resonator structures are formed on the common substrate is inhibited from being generated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a top view of a laser diode array according to an embodiment of the invention; 
           [0020]      FIG. 2  is a cross section view taken along arrows A-A of the laser diode array of  FIG. 1 ; 
           [0021]      FIGS. 3A and 3B  are cross section views for explaining an example of a method of manufacturing the laser diode array of  FIG. 1 ; 
           [0022]      FIGS. 4A and 4B  are cross section views for explaining steps following  FIGS. 3A and 3B ; 
           [0023]      FIG. 5  is a top view for explaining a step following  FIGS. 4A and 4B ; 
           [0024]      FIG. 6  is a cross section view taken along arrows A-A of  FIG. 5 ; 
           [0025]      FIG. 7  is an equivalent circuit diagram of the laser diode array of FIG.  1 ; 
           [0026]      FIGS. 8A and 8B  are waveform charts of a CW waveform and a pulse waveform inputted to the laser diode array of  FIG. 1 ; 
           [0027]      FIGS. 9A and 9B  are cross section views for explaining another example of a method of manufacturing the laser diode array of  FIG. 1 ; 
           [0028]      FIGS. 10A and 10B  are cross section views for explaining steps following  FIGS. 9A and 9B ; 
           [0029]      FIGS. 11A and 11B  are cross section views for explaining steps following  FIGS. 10A and 10B ; 
           [0030]      FIGS. 12A and 12B  are cross section views for explaining steps following  FIGS. 11A and 11B ; 
           [0031]      FIG. 13  is a top view of a modification of the laser diode array of  FIG. 1 ; 
           [0032]      FIG. 14  is a cross section view taken along arrows A-A of the laser diode array of  FIG. 13 ; 
           [0033]      FIG. 15  is a schematic structural view of a printer according to an application example; 
           [0034]      FIG. 16  is a schematic structural view of an optical communication device according to another application example; 
           [0035]      FIG. 17  is a cross section view of a laser diode array of a related art; 
           [0036]      FIG. 18  is an equivalent circuit diagram of the laser diode array of  FIG. 11 ; and 
           [0037]      FIGS. 19A and 19B  are waveform charts for explaining cross talk in the laser diode array of  FIG. 11 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0038]    Descriptions will be given of an embodiment of the invention in detail with reference to the drawings. 
         [0039]      FIG. 1  shows a top view of a laser diode array  1  according to an embodiment of the invention.  FIG. 2  shows a cross sectional configuration taken along arrows A-A of the laser diode array  1  of  FIG. 1 .  FIG. 1  and  FIG. 2  schematically show the laser diode array  1 , and the dimensions and the shapes in the figures are different from those actually used. 
         [0040]    The laser diode array  1  includes a plurality of Vertical Cavity Surface Emitting Laser (VCSEL) devices  20  (vertical resonator structure) on a support substrate  10 . The laser diode array  1  has a function to concurrently output a plurality of laser lights having the same wavelength. 
         [0041]    Further, in the laser diode array  1 , the plurality of laser diode devices  20  is arranged on the surface on a metal layer  14  (described later) side of the support substrate  10 , so that the distance P between each optical axis AX of each laser light emitted from each laser diode device  20  is as short as possible. For example, as shown in  FIG. 1 , the respective laser diode devices  20  are arranged in a lattice pattern at almost even intervals. However, the laser diode devices  20  are not necessarily arranged in a vertical and reticular pattern at almost even intervals, but they may be, for example, arranged in a line at almost even intervals. 
       Support Substrate  10   
       [0042]    The support substrate  10  has, for example, a support base  11 , an insulating layer  12 , an adhesive layer  13 , the metal layer  14 , a via  15  (connection part), and an electrode layer  16 . The insulating layer  12 , the adhesive layer  13 , and the metal layer  14  are layered in this order from the support base  11  side on one face side of the support base  11 . The electrode layer  16  is formed on the other face side of the one face of the support base  11 . The via  15  is formed to penetrate through the support base  11 , the insulating layer  12 , and the adhesive layer  13 . One end thereof is in contact with the lower face of the metal layer  14 , and the other end thereof is in contact with the top face of the electrode layer  16 . 
         [0043]    The support base  11  is made of a material different from that of the laser diode device  20 . The support base  11  is made of, for example, a silicon substrate. The insulating layer  12  is made of an insulative material such as silicon oxide (SiO 2 ) and silicon nitride (SiN). The adhesive layer  13  is made of, for example, multicrystalline silicon, amorphous silicon or the like. The multicrystalline silicon and the amorphous silicon have a high affinity with the insulative material, such as silicon oxide (SiO 2 ) and silicon nitride (SiN). Thus, when the insulative material such as silicon oxide (SiO 2 ) and silicon nitride (SiN) is used as the insulating layer  12  and the multicrystalline silicon or the amorphous silicon is used as the adhesive layer  13 , the contact characteristics between the insulating layer  12  and the adhesive layer  13  become strong. 
       Laser Diode Device  20   
       [0044]    The laser diode device  20  is joined to the metal layer  14  of the support substrate  10 . The laser diode device  20  has a columnar vertical resonator structure in which, for example, a lower contact layer  21 , a lower DBR layer  22 , a lower spacer layer  23 , an active layer  24 , an upper spacer layer  25 , a current confinement layer  26 , an upper DBR layer  27 , and an upper contact layer  28  are layered in this order from the metal layer  14  side. That is, the laser diode device  20  is obtained by removing a separately prepared semiconductor substrate  40  (described later) from a structure in which the foregoing vertical resonator structure is formed by crystal growth on the semiconductor substrate  40 . 
         [0045]    The lower contact layer  21  is made of, for example, n-type Al x1 Ga 1-x1 As (0≦x1&lt;1). The lower DBR layer  22  is formed by alternately layering a low refractive index layer (not shown) and a high refractive index layer (not shown). The low refractive index layer is made of, for example, n-type Al x2 Ga 1-x2 As (0&lt;x2&lt;1) having an optical thickness of λ 1 /4 (λ 1  is an oscillation wavelength). The high refractive index layer is made of, for example, n-type Al x3 Ga 1-x3 As (0≦x3&lt;x2) having an optical thickness of λ 1 /4. The lower spacer layer  23  is made of, for example, n-type Al x4 Ga 1-x4 As (0≦x4&lt;2). The lower contact layer  21 , the lower DBR layer  22 , and the lower spacer layer  23  contain a n-type impurity, such as silicon (Si). 
         [0046]    The active layer  24  has a multi-quantum well structure in which a well layer (not shown) made of undoped In x5 Ga 1-x5 As (0&lt;x5&lt;1) and a barrier layer (not shown) made of undoped In x6 Ga 1-x6 N (0&lt;x6&lt;x5) are alternately layered. Of the active layer  24 , the region opposed to a current injection region  26 A (described later) is a light emitting region  24 A. 
         [0047]    The upper spacer layer  25  is made of, for example, p-type Al x7 Ga 1-x7 As (0≦x7&lt;1). The upper DBR layer  27  is formed by alternately layering a low refractive index layer (not shown) and a high refractive index layer (not shown). The low refractive index layer is made of, for example, p-type Al x8 Ga 1-x8 As (0&lt;x8&lt;1) having an optical thickness of λ 1 /4. The high refractive index layer is made of, for example, p-type Al x9 Ga 1-x9 N (0≦x9&lt;x8) having an optical thickness of λ 1 /4. The upper contact layer  28  is made of, for example, p-type Al x10 Ga 1-x10 N (0≦x10&lt;1). The upper spacer layer  25 , the upper DBR layer  27 , and the upper contact layer  28  include a p-type impurity, such as magnesium (Mg). 
         [0048]    The current confinement layer  26  has a current confinement region  26 B in the peripheral region of a current injection region  26 A. 
         [0049]    The current injection region  26 A is made of, for example, p-type Al x11 Ga 1-x11 As (0&lt;x11≦1). The current injection region  26 A is preferably made of a material having an oxidation rate equal to or slower than that of a peel layer  41 D described later. 
         [0050]    For example, when the peel layer  41 D is made of AlAs, the current injection region  26 A is made of Al x11 Ga 1-x11 As (0.98≦x11≦1). In the case where the current injection region  26 A is made of AlAs (x11=1), the thickness of the current injection region  26 A needs to be smaller than the thickness of the peel layer  41 D. Meanwhile, when the current injection region  26 A is made of Al x11 Ga 1-x11 As (0.98≦x11&lt;1), the thickness of the current injection region  26 A may be equal to or smaller than the thickness of the peel layer  41 D. However, as will be described later, when the oxidation step of the peel layer  41 D is performed separately from the oxidation step of the current confinement layer  26 D, the material of the current injection region  26 A is not particularly limited in relation to the peel layer  41 D. 
         [0051]    Meanwhile, the current confinement region  26 B contains, for example, Al 2 O 3  (aluminum oxide). As will be described later, the current confinement region  26 B is obtained by oxidizing concentrated Al contained in a current confinement layer  26 D from the side face. Therefore, the current confinement layer  26  has a function of confining a current. 
         [0052]    In the laser diode device  20  of this embodiment, a circular electrode layer  30  is formed on the top face of the upper contact layer  28 . The electrode layer  30  is formed by layering, for example, a Ti layer, a Pt layer, and an Au layer in this order. The electrode layer  30  is electrically connected to the upper contact layer  28 . 
         [0053]    Further, an insulating film  31  is formed over the entire surface including each laser diode device  20  and the electrode layer  30 . The insulating film  31  is made of an insulative material, such as silicon oxide (SiO 2 ) and silicon nitride (SiN). An aperture is formed in part of the region opposed to the electrode layer  30  of the insulating film  31 . An electrode pad  33  electrically connected to a wiring layer  32  through the aperture is formed on the surface of the insulating film  31  (refer to  FIG. 1 ). 
         [0054]    The laser diode array  1  having the foregoing configuration may be manufactured as follows, for example. 
         [0055]    First, the laser diode device  20  is manufactured. For example, in the case where the vertical resonator structure is formed from GaAs-based Group III-V compound semiconductor, for example, the vertical resonator structure is formed by the Metal Organic Chemical Vapor Deposition (MOCVD) method with the use of TMA (trimethyl aluminum), TMG (trimethyl gallium), TMIn (trimethyl indium), or AsH 3  (arsine) as a raw material gas. 
         [0056]    The GaAs-based Group III-V compound semiconductor represents a semiconductor that contains at least Ga out of the Group 3B elements in the short period periodic table and at least As (arsenic) out of the Group 5B elements in the short period periodic table. 
         [0057]    Specifically, the peel layer  41 D, the lower contact layer  21 , the lower DBR layer  22 , the lower spacer layer  23 , the active layer  24 , the upper spacer layer  25 , the current confinement layer  26 D (layer to be oxidized), the upper DBR layer  27 , and the upper contact layer  28  are layered in this order over the semiconductor substrate  40  (GaAs substrate) ( FIG. 3A ). 
         [0058]    The foregoing current confinement layer  26 D is made of the same material as that of the current injection region  26 A, and will become the current confinement layer  26  by the after-mentioned oxidation treatment. The peel layer  41 D is preferably structured to have a faster oxidation rate in the lamination in-plane direction than that of the current confinement layer  26 D. 
         [0059]    For example, in the case where the current confinement layer  26 D is made of the same material as that of the peel layer  41 D (for example, Al x11 Ga 1-x11 As (0.98&lt;x11≦1), the thickness of the peel layer  41 D is preferably larger than that of the current confinement layer  26 D. In the case where the current confinement layer  26 D is made of Al x11 Ga 1-x11 As (0.98&lt;x11&lt;1), the peel layer  41 D is preferably made of AlAs. In the case where the current confinement layer  26 D is made of Al x11 Ga 1-x11 As (0.98&lt;x11&lt;1) and the peel layer  41 D is made of AlAs, that is, when the peel layer  41 D is made of a material having a faster oxidation rate than that of the current confinement layer  26 D, the thickness of the peel layer  41 D may be equal to or larger than the thickness of the current confinement layer  26 D. 
         [0060]    Next, a region from the upper contact layer  28  to part of the semiconductor substrate  40  is selectively etched by, for example, the dry etching method to form a mesa shape ( FIG. 3B ). Thereby, the peel layer  41 D is exposed on the side face of a mesa M. 
         [0061]    Next, heat treatment is performed at high temperature in a water vapor atmosphere, and the current confinement layer  26 D and the peel layer  41 D are concurrently oxidized from the side face of the mesa M. The oxidation treatment is performed until almost all of the peel layer  41 D is oxidized and the diameter of the non-oxidized region of the current confinement layer  26 D becomes a desired value. Thereby, almost all of the peel layer  41 D becomes an insulating layer (aluminum oxide), and an oxidized peel layer  41  is formed ( FIG. 4A ). Further, since the outer edge region of the current confinement layer  26 D becomes an insulating layer (aluminum oxide), the current confinement region  26 B is formed in the outer edge region, and the current injection region  26 A is formed in the central region thereof. Accordingly, the laser diode device  20  is formed over the semiconductor substrate  40  ( FIG. 4A ). 
         [0062]    Next, for example, the laser diode device  20  is peeled from the semiconductor substrate  40  by, for example, vacuum contact or by using a light curable adhesive sheet or the like ( FIG. 4B ). Out of the interfaces between each layer composing the laser diode device  20 , at the interface between the oxidized peel layer  41  and the lower contact layer  21 , the oxidized peel layer  41  and the lower contact layer  21  are not contacted with each other in a graded manner. That is, at the interface between the oxidized peel layer  41  and the lower contact layer  21 , an interlayer in which the both materials are mixed with each other does not exist. Otherwise, even if such an interlayer exists, the interlayer slightly exists to the degree that the interlayer is ignorable compared to the thickness of interlayer at the other interfaces. Thus, since a stress caused by oxidation has been applied to the interface between the oxidized peel layer  41  and the lower contact layer  21 , the laser diode device  20  is able to be relatively easily peeled at the interface between the oxidized peel layer  41  and the lower contact layer  21  or in the vicinity thereof by the peeling step. 
         [0063]    Heating (alloying) may be performed at about from 300 deg C. to 400 deg C. before the peeling step. In this case, the stress at the interface between the oxidized peel layer  41  and the lower contact layer  21  is further increased, and thus the laser diode device  20  is able to be easily peeled. If the oxidized peel layer  41  remains on the laser diode device  20  side, the portion of the oxidized peel layer  41  remaining on the laser diode device  20  side is removed by wet etching. 
         [0064]    Next, the plurality of laser diode devices  20  is arranged with the lower contact layer  21  side downward on the metal layer  14  of the support substrate  10  and jointed to the metal layer  14  ( FIG. 5  and  FIG. 6 ).  FIG. 6  is a cross sectional configuration view taken along arrows A-A of  FIG. 5 . 
         [0065]    Next, the circular electrode layer  30  is formed on the top face of the laser diode device  20  ( FIG. 2 ). Subsequently, the insulating film  31  is formed over the entire surface including the laser diode device  20  and the electrode layer  30 . After that, the electrode pad  33  is formed in a place with a given distance from the laser diode  20  in the surface of the insulating film  31 . After that, the aperture (not shown) is formed in part of the region opposed to the electrode layer  30  in the insulating film  31 . After that, the wiring layer  32  extending from the surface of the electrode layer  30  exposed in the aperture to the electrode pad  33  is formed. Accordingly, the laser diode array  1  of this embodiment is manufactured. 
         [0066]    In the laser diode array  1  of this embodiment, when a given voltage is applied between the connection pad  33  electrically connected to the electrode layer  30  on each laser diode device  20  and the electrode layer  16 , a current is injected into the active layer  24 , light emission is generated by electron-hole recombination, and stimulated emission is repeated in the device. As a result, laser oscillation is generated in a given wavelength λ 1 , and laser light in wavelength λ 1  is outputted outside from the light emitting region  24 A of each laser diode device  20  through the aperture of the electrode layer  30 . 
         [0067]    In a laser diode array  100  of the related art shown in  FIG. 17 , that is, in the laser array in which a columnar VCSEL  120  obtained by layering, for example, a lower DBR layer  121 , a lower spacer layer  122 , an active layer  123 , an upper spacer layer  124 , a current confinement layer  125  (current injection region  125 A and a current confinement region  125 B), an upper DBR layer  126 , and an upper contact layer  127  in this order over a common substrate  110  is directly formed by crystal growth, as shown in the equivalent circuit shown in  FIG. 18 , a resistance component R3 exists between each laser diode  120  and a ground GND independently of a current path of other laser diode  120 , and a resistance component R4 exists on the current path common to each laser diode  120 . 
         [0068]    The resistance component R4 is a resistance component of the common substrate  110 . In the case where the resistance component R4 exists, for example, when one laser diode device  120  is CW-driven as shown in  FIG. 8A  and another laser diode device  120  adjacent to the foregoing one laser diode device  120  is pulse-driven as shown in  FIG. 8B , in the equivalent circuit of  FIG. 18 , an input voltage V L1  of the CW-driven laser diode device  120  has a wavy waveform including noise as shown in  FIG. 19A , and an input voltage V L2  of the pulse-driven laser diode device  120  has a distorted rectangular waveform including noise as shown in  FIG. 19B . That is, electric cross talk is generated between the laser diode devices  120  adjacent to each other. 
         [0069]    Meanwhile, in this embodiment, each laser diode device  20  is jointed to the surface of the metal layer  14  of the support substrate  10 . Thus, as shown in  FIG. 7 , in the equivalent circuit of the laser diode array  1 , the resistance component R3 exists between each laser diode device  20  and the ground GND independently of a current path of the other laser diode device  20 , but no resistance component exists on the current path common to each laser diode device  20 . This is because, in the manufacturing course of this embodiment, the semiconductor substrate  40  is removed (peeled) from the structure in which the vertical resonator structure is formed by crystal growth over the semiconductor substrate  40 , and thereby the resistance component of the semiconductor substrate  40  that is connected in series to each vertical resonator structure is separated from each vertical resonator structure. 
         [0070]    Thereby, for example, in the case where one laser diode device  20  is CW-driven as shown in  FIG. 8A  and another laser diode device  20  adjacent to the foregoing one laser diode device  20  is pulse-driven as shown in  FIG. 8B , in the equivalent circuit of  FIG. 7 , the input voltage V L1  of the CW-driven laser diode device  20  has a flat waveform not including noise as an input voltage waveform, and the input voltage V L2  of the pulse-driven laser diode device  20  has a rectangular waveform not including noise as the input voltage waveform. That is, electric cross talk is not generated between the laser diode devices  20  adjacent to each other. 
         [0071]    As described above, in this embodiment, since each laser diode device  20  is jointed to the surface of the metal layer  14  of the support substrate  10 , the resistance component of the semiconductor substrate  40  that is connected in series to each laser diode device  20  is separated from each laser diode device  20 . Thereby, electric cross talk between the laser diode devices  20  adjacent to each other is inhibited from being generated. 
       Modification 
       [0072]    In the foregoing embodiment, the oxidation steps of the peel layer  41 D and the current confinement layer  26 D are concurrently performed. However, each oxidation step may be performed separately. For example, it is possible that after the side face of the current confinement layer  26 D is coated with a protective film so that the side face of the peel layer  41 D is not coated therewith, the oxidized peel layer  41  is formed by oxidizing the peel layer  41 D from the side face, the protective film is removed, and then the current confinement layer  26 D is oxidized from the side face to form the current confinement layer  26 . 
         [0073]    Further, the formation step of the laser diode device  20  may be performed, for example, as follows. First, the peel layer  41 D, the lower contact layer  21 , the lower DBR layer  22 , the lower spacer layer  23 , the active layer  24 , the upper spacer layer  25 , the current confinement layer  26 D (layer to be oxidized), the upper DBR layer  27 , and the upper contact layer  28  are layered in this order over the semiconductor substrate  40  (GaAs substrate) ( FIG. 3A ). Then, a region from the upper contact layer  28  to part of the lower DBR layer  22  is selectively etched by, for example, a dry etching method to form a mesa shape. 
         [0074]    Next, heat treatment is performed at a high temperature in the water vapor atmosphere, the current confinement layer  26 D is oxidized from the side face of the mesa M to form the current confinement layer  26  ( FIG. 9B ). Since the peel layer  41 D is not exposed on the side face of the mesa M, the peel layer  41 D is not oxidized. 
         [0075]    Next, a protective film  19  is formed on the entire surface including the mesa M ( FIG. 10A ). After that, a groove  29 A penetrating thorough the protective film  19  is formed to surround the mesa M ( FIG. 10B ). Thereby, the lower DBR layer  22  is exposed on the bottom face of the groove  29 A. 
         [0076]    Next, for example, the lower DBR layer  22  and the lower contact layer  21  that are directly under the groove  29 A are selectively removed by using, for example, a phosphoric acid etchant ( FIG. 11A ). After that, the peel layer  41 D is selectively removed by using a fluorinated acid etchant ( FIG. 11B ). Thereby, the contact force by the peel layer  41 D between the semiconductor substrate  40  and the lower DBR layer  22  is lowered. 
         [0077]    Next, a support substrate  42  is bonded to the top face of the protective film  19  ( FIG. 12A ). After that, by using the support substrate  42 , the laser diode device  20  is peeled from the semiconductor substrate  40  ( FIG. 12B ). Accordingly, the laser diode device  20  is able to be formed as well. 
         [0078]    In the foregoing embodiment, the VCSEL  20  is jointed to the surface of the metal layer  14  of the support substrate  10  having the via  15 . However, for example, as shown in  FIG. 13  and  FIG. 14 , it is possible that a support substrate  50  in which the insulating layer  12 , the adhesive layer  13 , and the metal layer  14  are sequentially layered from the support base  11  side is prepared on one surface of the support base  11 , and the VCSEL  20  is jointed to the surface of the metal layer  14  of the support substrate  50 . However, in this case, for example, it is necessary that an aperture  31 A is formed in part of the insulating layer  31  formed on the surface of the metal layer  14 , part of the metal layer  14  is exposed from the aperture, and the exposed section is used as an electrode pad  14 A to decrease the potential of the metal layer  14  to the ground potential. 
         [0079]    Further, in the foregoing embodiment, the wiring layer  32  and the electrode pad  33  are formed over the support substrate  10  with the insulating layer  31  in between. However, for example, it is possible to provide a buried layer made of an insulative material, such as polyimide, around the laser diode device  20 , the wiring layer  32  and the electrode pad  33  that are formed on the top face of the buried layer, and thereby the capacity component generated between the wiring layer  32  electrode pad  33  and the metal layer  14  is decreased as much as possible. 
       Application Example 
       [0080]    The laser diode array  1  according to the foregoing embodiment or the modification thereof is suitably applicable to, for example, a printer, such as a laser printer, and an optical communication device, such as a multichannel optical integrated device. For example, as shown in  FIG. 15 , as a light source  61  in a laser printer  60  including the light source  61 , a polygon mirror  62  for reflecting light from the light source  61  and scanning the reflected light, a fθ lens  63  for guiding the light from the polygon mirror  62  to a photoconductive drum  64 , the photoconductive drum  64  receiving the light from the fθ lens  63  to form an electrostatic latent image, and a toner supplier (not shown) adhering the toner according to the electrostatic latent image to the photoconductive drum  64 , the laser diode array  1  may be used. Further, for example, as shown in  FIG. 16 , as a light source  72  in an optical communication device  70  including the light source  72 , a light guide  73  in which a light input end is arranged correspondingly to a light output end of the light source  72 , and an optical fiber  74  in which a light input end is provided correspondingly to a light output end of the light guide  73  on a support substrate  71 , the laser diode array  1  may be used. 
         [0081]    While the descriptions hereinbefore have been given of the invention with reference to the embodiment and the like, the invention is not limited to the foregoing embodiment and the like, and various modifications may be made. 
         [0082]    It should be understood by those skilled in the art that various modifications, combinations, subcombinations and alternations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.