Abstract:
In a semiconductor laser device including a semiconductor laser element that emits laser light from an emission region thereof, a cap having a peripheral wall and a ceiling wall that cover the semiconductor laser element and having a window portion formed in the ceiling wall to face the emission region, and a transparent optical member that fills the window portion, the optical member is formed by curing a liquid resin and holds the ceiling wall, and a light incidence surface of the optical member faces the emission region and is formed by natural flow of the liquid resin.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Phase patent application of PCT/JP2014/073048, filed on Sep. 2, 2014, which claims priority to Japanese Application No. 2013-216593, filed on Oct. 17, 2013, each of which is hereby incorporated by reference in the present disclosure in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a semiconductor laser element of one-surface-two-contact type and a heat-assisted magnetic recording head using the same. Besides, the present invention relates to a method for manufacturing the semiconductor laser element of one-surface-two-contact type. 
       BACKGROUND OF THE INVENTION 
       [0003]    Following development of information societies in recent years, high-definition of a sound and image is progressing and data communication amount on the internet is increasing remarkably. Besides, because of development of so-called cloud computing, data amount stored on the internet is increasing extraordinarily dramatically, and it is forecast that this tendency continues to rise in the future. Under these circumstances, expectations are increasing for large-capacity information recording systems that store electronic data. 
         [0004]    As large-capacity information recording apparatuses, magnetic recording apparatuses such as a hard disc drive and the like are playing a major role. To increase recoding density of the magnetic recording apparatuses, vertical magnetic recording capable of achieving minuscule recording bits are realized, further, development of a heat-assisted magnetic recording technology is underway. 
         [0005]    As to heat-assisted magnetic recording, a magnetic recording medium, which is formed of a magnetic material having large magnetic anisotropic energy, is used in such a manner that magnetization stabilizes. And, an anisotropic magnetic field at a data writing portion of the magnetic recording medium is lowered by heating, and immediately thereafter, a writing magnetic field is added to perform minuscule-size writing. As a method for heating the magnetic recording medium, it is general to use light such as near-field light and the like, and as a light source for the purpose, a semiconductor laser element is generally used. 
         [0006]    A patent literature 1 discloses a conventional heat-assisted magnetic recording head that includes a semiconductor laser element.  FIG. 12  shows a schematic front view of the heat-assisted magnetic recording head. The heat-assisted magnetic recording head  1  includes a slider  10  and a semiconductor laser element  30 , and is disposed over a magnetic disc (not shown). 
         [0007]    The slider  10  floats over the rotating magnetic disc, and one end portion opposing the magnetic disc is provided with a magnetic recording portion  13  and a magnetic reproducing portion  14 . An optical waveguide  15  is disposed near the magnetic recording portion  13 , and an element (not shown) for generating near-field light is disposed in the optical waveguide  15 . 
         [0008]    As to the semiconductor laser element  30 , a semiconductor multilayer  32  is formed on a substrate  31 , and a stripe-shaped optical waveguide  36  is formed by means of a ridge structure of the semiconductor multilayer  32 . A first contact (not shown) is formed on a bottom surface of the substrate  31 , and a second contact (not shown) is formed on an upper surface of the semiconductor multilayer  32 . 
         [0009]    A front surface  21   a  of a sub-mount  21  is bonded to a disposition surface  10   a  of a rear side (side opposite to the magnetic disc) of the slider  10  via an adhesive  19 . The semiconductor laser element  30  is bonded to a vertical surface  21   b  perpendicular to the front surface  21   a  of the sub-mount  21  via a solder material  29  disposed on the second contact. At this time, an emitting portion  36   a  of one facet of the optical waveguide  36  is disposed to oppose the optical waveguide  15  of the slider  10 . 
         [0010]    Besides, the vertical surface  21   b  of the sub-mount  21  is provided with a terminal portion (not shown) that electrically communicates with the second contact via the solder material  29 . In this way, the first contact and the terminal portion are disposed to face the same direction (left direction in the figure), and it is possible to easily connect a lead wire to each of the first contact and the terminal portion. 
         [0011]    When a voltage is applied between the first contact and the terminal portion, laser light is emitted from the emitting portion  36   a.  The emitted laser light from the emitting portion  36   a  propagates in the optical waveguide  15  of the slider  10  to generate near-field light. As to the magnetic disc, an anisotropic magnetic field weakens locally because of heat of the near-field light, and magnetic recording is performed by the magnetic recording portion  13 . Data recorded on the magnetic disc are read by the magnetic reproducing portion  14 . 
         [0012]    Besides, heat generated from the semiconductor laser element  30  is conducted to the sub-mount  21  via the solder material  29  and conducted to the slider  10  via the adhesive  19 . In this way, the heat generated from the semiconductor laser element  30  is radiated from the sub-mount  21  and the slider  10 . 
         [0013]    As to the semiconductor laser element  30 , the first contact and the second contact are respectively disposed on the bottom surface of the substrate  31 , and the upper surface of the semiconductor multilayer  32  in such a manner that either of the first contact and the second contact is disposed on either of both surfaces of the substrate  31  to oppose each other. In contrast to this, a non-patent literature 1 discloses a semiconductor laser element of one-surface-two-contact type in which the first contact and the second contact are disposed on one surface of a substrate. 
         [0014]      FIG. 13  shows a front view of a semiconductor laser element  40  of the one-surface-two-contact type. In the semiconductor laser element  40 , a semiconductor multilayer  42  is laminated on a substrate  41  such as sapphire or the like. The semiconductor multilayer  42  is formed by means of epitaxial growth by using a ground layer (not shown) disposed on the substrate  41  as a ground, and has an n-type semiconductor layer  43 , an active layer  44 , and a p-type semiconductor layer  45  in this order from the substrate  41 . 
         [0015]    Besides, a concave portion  51  and a light emitting portion  52  are formed adjacently to each other on the substrate  41  by means of the semiconductor multilayer  42 . The concave portion  51  is formed by carving the semiconductor multilayer  42  to a middle portion of the n-type semiconductor layer  43  by means of etching. A first contact  47  is disposed on a bottom surface of the concave portion  51 . 
         [0016]    As to the light emitting portion  52 , a stripe-shaped narrow-width ridge portion  49  is disposed to protrude on an upper portion of the semiconductor multilayer  42 . The ridge portion  49  is formed by carving both sides of the ridge portion  49  to a middle portion of the p-type semiconductor layer  45  by means of etching. An upper surface of the ridge portion  49  is provided with a second contact  48 . Active layer  44  is injected an electric current via the ridge portion  49 , and forms a stripe-shaped optical waveguide  46 , so that laser light is emitted from an emitting portion  46   a  of a facet of optical waveguide  46 . 
         [0017]    In the meantime, the first, second contacts  47 ,  48  are disposed on the one surface of the substrate  41 ; accordingly, it is possible to easily connect a lead wire to each of the first, second contacts  47 ,  48 . 
       Patent Literature 
       [0018]    PLT1: JP No. 4635607 (page 7-page 12, FIG. 1) 
         [0019]    PLT2: JP-A-2012-18747 (page 7-page 22, FIG. 2) 
         [0020]    PLT3: JP-A-2003-45004 (page 5-page 11, FIG. 1) 
       Non-Patent Literature 
       [0021]    Non-patent document 1: Bernard Gil, “Group III-Nitride Semiconductor Compounds”, (Great Britain), Clarendon Press, Apr. 23, 1998, p. 405 
       SUMMARY OF THE INVENTION 
       [0022]    According to the heat-assisted magnetic recording head  1  disclosed in the patent literature 1, the semiconductor laser element  30  is mounted on the vertical surface  21   b  of the sub-mount  21  bonded to the slider  10 . Because of this, if the semiconductor laser element  30  inclines in a surface parallel to the vertical surface  21   b  or in a surface perpendicular to the front surface  21   a  and vertical surface  21   b,  it becomes hard to perform the positioning between the emitting portion  36   a  and the optical waveguide  15 . Accordingly, it is necessary to position the semiconductor laser element  30  at high accuracy with respect to the sub-mount  21 , so that there is a problem that the man-hours of the heat-assisted magnetic recording head  1  becomes large and the yield declines. 
         [0023]    Besides, the heat generated from the semiconductor laser element  30  is conducted to the sub-mount  21  via the solder material  29 , thereafter, conducted to the slider  10  via the adhesive  19 . Because of this, two interfaces exist on the heat radiation route of the heat-assisted magnetic recording head  1 ; accordingly, the heat radiation of the heat-assisted magnetic recording head  1  declines. Because a failure rate of the semiconductor laser element  30  increases exponentially for temperature rising, there also is a problem that reliability of the heat-assisted magnetic recording head  1  deteriorates because of the decline in the heat radiation. 
         [0024]    On the other hand, if a volume of the sub-mount  21  is made large to improve the heat radiation of the heat-assisted magnetic recording head  1 , a weight of the heat-assisted magnetic recording head  1  becomes heavy. In this way, there is a problem that attitude control of the heat-assisted magnetic recording head  1  floating over the magnetic disc becomes hard. 
         [0025]    To solve these problems, it is conceivable that the sub-mount  21  is removed and an emitting facet  40   a  of a front surface of the semiconductor laser element  40  of one-surface-two-contact type is boned to the disposition surface  10   a  of the slider  10 . According to this structure, the positioning of the semiconductor laser element  40  with respect to the sub-mount  21  becomes unnecessary; accordingly, it is possible to achieve reduction in the man-hours of the heat-assisted magnetic recording head  1  and improvement in the yield. Besides, there is only one interface on the heat radiation route of the heat-assisted magnetic recording head  1 ; accordingly, the heat radiation is improved. 
         [0026]    However, in the semiconductor laser element  40 , the first contact  47  is disposed near the substrate  41  (e.g., several micrometers). Because of this, to improve the heat radiation, if the adhesive  19  is applied to a wide area of the emitting facet  40   a  of the semiconductor laser element  40 , there is a case where the adhesive  19  adheres to the first contact  47 . In this way, a problem occurs in which the connection of a lead to the first contact  47  becomes hard and the reduction in the man-hours of the heat-assisted magnetic recording head  1  cannot be achieved sufficiently. 
         [0027]    Besides, the substrate  41  is formed of a material such as sapphire or the like different from the semiconductor multilayer  42 , and the heat conduction at the interface between the substrate  41  and the semiconductor multilayer  42  is low. Because of this, a problem also occurs in which the heat radiation of the heat-assisted magnetic recording head  1  cannot be improved sufficiently. 
         [0028]    Further, during a production time of the semiconductor laser element  40 , first, the semiconductor multilayer  42  is formed on the wafer-shaped substrate  41 . Thereafter, a scribe groove is formed in a direction perpendicular to the ridge portion  49  and in a direction parallel to the ridge portion  49 , and stress is exerted onto the scribe groove to cleave the substrate  41  to obtain the discrete semiconductor laser element  40 . Here, the light emitting portion  52  and the concave portion  51  are repeated alternately; accordingly, there is a case where the cleavage direction deviates and flatness of the emitting facet  40   a  deteriorates. In this way, a problem also occurs in which tight contact between the semiconductor laser element  40  and the slider  10  declines and the heat radiation of the heat-assisted magnetic recording head  1  cannot be improved sufficiently. 
         [0029]    In addition, a volume difference between the light emitting portion  52  and the concave portion  51  is large; accordingly, internal strain is formed unevenly. In this way, there is also a problem in which the tight contact between the semiconductor laser element  40  and the slider  10  further deteriorates and stability of the laser light emission by the semiconductor laser element  40  deteriorates. 
         [0030]    It is an object of the present invention to provide: a heat-assisted magnetic recording head that is capable of achieving the man-hours reduction and yield improvement and improving the heat radiation and the stability of laser light emission; a semiconductor laser element used for the heat-assisted magnetic recording head; and a method for manufacturing the semiconductor laser element. 
         [0031]    To achieve the object, a semiconductor laser element according to the present invention includes: a substrate formed of a semiconductor; a light emitting portion that includes a semiconductor multilayer in which the substrate is used as a ground to laminate successively a first electro-conductive-type semiconductor layer, an active layer, and a second electro-conductive-type semiconductor layer by means of epitaxial growth; and a stripe-shaped optical waveguide is formed of the active layer; an annular protective wall that is formed of the semiconductor multilayer adjacently to the light emitting portion and encloses a concave portion which uses the substrate or the first electro-conductive-type semiconductor layer as a bottom surface; a first contact disposed on the bottom surface of the concave portion; and a second contact disposed on an upper surface of the light emitting portion. 
         [0032]    Besides, the present invention has a feature that in the semiconductor laser element having the above structure, the light emitting portion and the protective wall are separated by a separation groove that uses the substrate or the first electro-conductive-type semiconductor layer as a bottom surface. 
         [0033]    Besides, the present invention has a feature that in the semiconductor laser element having the above structure, the protective wall is opened through a surface that opposes the light emitting portion. 
         [0034]    Besides, the present invention has a feature that in the semiconductor laser element having the above structure, the substrate and the active layer are formed of a GaAs-based semiconductor. 
         [0035]    Besides, a heat-assisted magnetic recording head according to the present invention has a feature to include: the semiconductor laser element and a slider that performs magnetic recording; wherein an end surface of the substrate perpendicular to the optical waveguide is bonded to the slider. 
         [0036]    Besides, a method for manufacturing the semiconductor laser element according to the present invention has a feature to include: a semiconductor multilayer forming step for forming a semiconductor multilayer in which a first electro-conductive-type semiconductor layer, an active layer, and a second electro-conductive-type semiconductor layer are successively laminated on a substrate formed of a semiconductor; a ridge forming step for forming a stripe-shaped ridge by etching the second electro-conductive-type semiconductor layer; a concave portion forming step for forming a concave portion enclosed by a protective wall by etching a region adjacent to the ridge to a layer lower than the active layer; a first metal film laminating step for forming a first metal film on a bottom surface of the concave portion; and a second metal film forming step for laminating a second metal film on the first metal film and the ridge portion; wherein a first contact is formed on the bottom surface of the concave portion by means of the first metal film and the second metal film; and a second contact is formed on the ridge portion by means of the second metal film. 
         [0037]    According to the present invention, in the semiconductor laser element, the substrate is used as a ground to form the semiconductor multilayer by means of epitaxial growth, and the protective wall enclosing the concave portion, in which the first contact is disposed, and the light emitting portion, which has the optical guide and in which the second contact is disposed, are formed by means of the semiconductor multilayer adjacently to each other. 
         [0038]    In this way, it is possible to form the heat-assisted magnetic recording head by boding a bond surface perpendicular to the optical waveguide of the semiconductor laser element to the slider. Because of this, it is possible to easily perform the positioning between the semiconductor laser element and the slider. Besides, when bonding the semiconductor laser element, it is possible to prevent an adhesive from adhering to the first contact by means of the protective wall and to easily connect a lead wire to the first contact. Accordingly, it is possible to achieve the man-hours reduction of the heat-assisted magnetic recording head and the yield improvement. 
         [0039]    Further, the substrate and the semiconductor multilayer are joined to each other by a continuous crystal lattice, and heat conduction between both improves. Besides, when forming the semiconductor multilayer on the wafer-shaped substrate and separating it into pieces, a scribe groove is formed on the light emitting portion and the protective wall; accordingly, flatness of the bond surface formed of a cleavage surface improves. Accordingly, it is possible to improve heat radiation of the heat-assisted magnetic recording heat that uses the semiconductor laser element. In addition, a volume difference between the light emitting portion and the protective wall is small; accordingly, it is possible to even an internal strain of the semiconductor laser element and thereby to improve the stability of the laser light emission. 
         [0040]    Besides, according to the present invention, the method for manufacturing the semiconductor laser element includes: the first metal film forming step for laminating the first metal film on the bottom surface of the concave portion enclosed by the protective wall, and the second metal film forming step for laminating the second metal film on the first metal film and the ridge portion; wherein the first contact is formed by means of the first metal film and the second metal film; and the second contact is formed by means of the second metal film. In this way, during the time of forming the second metal film, it is possible to prevent the first metal film from being etched and thereby to maintain a desired shape of the first contact. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]      FIG. 1  is a front view showing a heat-assisted magnetic recording head according to a first embodiment of the present invention. 
           [0042]      FIG. 2  is a perspective view showing a semiconductor laser element of the heat-assisted magnetic recording head according to the first embodiment of the present invention. 
           [0043]      FIG. 3  is a step flow chart of the semiconductor laser element of the heat-assisted magnetic recording head according to the first embodiment of the present invention. 
           [0044]      FIG. 4  is a front view showing a semiconductor multilayer forming step of the semiconductor laser element of the heat-assisted magnetic recording head according to the first embodiment of the present invention. 
           [0045]      FIG. 5  is a front view showing a ridge portion forming step of the semiconductor laser element of the heat-assisted magnetic recording head according to the first embodiment of the present invention. 
           [0046]      FIG. 6  is a front cross-sectional view showing a concave portion forming step of the semiconductor laser element of the heat-assisted magnetic recording head according to the first embodiment of the present invention. 
           [0047]      FIG. 7  is a front cross-sectional view showing a first metal film forming step of the semiconductor laser element of the heat-assisted magnetic recording head according to the first embodiment of the present invention. 
           [0048]      FIG. 8  is a front cross-sectional view showing a buried layer forming step of the semiconductor laser element of the heat-assisted magnetic recording head according to the first embodiment of the present invention. 
           [0049]      FIG. 9  is a front cross-sectional view showing a second metal film forming step of the semiconductor laser element of the heat-assisted magnetic recording head according to the first embodiment of the present invention. 
           [0050]      FIG. 10  is a perspective view showing a semiconductor laser element of a heat-assisted magnetic recording head according to a second embodiment of the present invention. 
           [0051]      FIG. 11  is a perspective view showing a semiconductor laser element of a heat-assisted magnetic recording head according to a third embodiment of the present invention. 
           [0052]      FIG. 12  is a front view showing a conventional heat-assisted magnetic recording head. 
           [0053]      FIG. 13  is a front view showing a conventional semiconductor laser element of one-surface-two-contact type 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0054]    Hereinafter, embodiments of the present invention are described with reference to the drawings. For the sake of description, the same portions as the conventional examples shown in  FIG. 12  and  FIG. 13  are indicated by the same reference numbers.  FIG. 1  shows a front view of a heat-assisted magnetic recording head according to a first embodiment. A heat-assisted magnetic recording head  1  is incorporated in a HDD device and the like and supported by a suspension (not shown) to be disposed over a magnetic disc movably in a shaft direction. 
         [0055]    The heat-assisted magnetic recording head  1  includes a slider  10  that opposes the magnetic disc D and a semiconductor laser element  40  bonded to the slider  10  by means of a heat-conductive adhesive  19 . The slider  10  floats over the magnetic disc D that rotates in an arrow A direction, and has a magnetic recording portion  13  and a magnetic reproducing portion  14  at an end portion on a medium exit side. The magnetic recording portion  13  performs magnetic recording and the magnetic reproducing portion  14  detects magnetization of the magnetic disc D and outputs it. 
         [0056]    An optical waveguide  15 , which conducts the laser light emitted from the semiconductor laser element  40 , is disposed near the magnetic recording portion  13 . The optical waveguide  15  is provided therein with an element (not shown) that generates near-field light. 
         [0057]    As detailed later, in the semiconductor laser element  40 , a semiconductor multilayer  42  is formed on a substrate  41 , and a stripe-shaped optical waveguide  46  is formed by means of a ridge structure of the semiconductor multilayer  42 . An emitting facet  40   a  perpendicular to the optical waveguide  46  of the semiconductor laser element  40  is bonded to a disposition surface  10   a  of a rear side (opposite to the magnetic disc) of the slider  10  via the adhesive  19 . At this time, an emitting portion  46   a  of one facet of the optical waveguide  46  is disposed to oppose the optical waveguide  15 . The sub-mount  21  (see  FIG. 12 ) shown in the conventional example is removed; accordingly, it is possible to achieve a light weight of the heat-assisted magnetic recording head  1 . 
         [0058]      FIG. 2  shows a perspective view of the semiconductor laser element  40 . In the semiconductor laser element  40 , the semiconductor multilayer  42  is laminated on the substrate  41 . The semiconductor multilayer  42  has an n-type semiconductor layer  43 , an active layer  44 , and a p-type semiconductor layer  45  in this order from the substrate  41 . 
         [0059]    Besides, a light emitting portion  52  and an annular protective wall  53  formed by means of the semiconductor multilayer  42  are formed on the substrate  41  adjacently to each other via a separation groove  54 . The concave portion  51  enclosed by the annular protective wall  53  is formed by carving the semiconductor multilayer  42  to the substrate  41  or a middle portion of n-type semiconductor layer  43  by means of etching. The first contact  47  is disposed on the bottom surface of the concave portion  51 . 
         [0060]    As to the light emitting portion  52 , a stripe-shaped narrow-width ridge portion  49  is disposed to protrude on an upper portion of the semiconductor multilayer  42 . The ridge portion  49  is formed by carving both sides to a middle portion of the p-type semiconductor layer  45  by means of etching. An upper surface of the light emitting portion  52  is provided with a buried layer  50  formed of an insulating film except for an upper surface of the ridge portion  49 , and the second contact  48  is formed on upper surfaces of the ridge portion  49  and buried layer  50 . Active layer  44  is injected an electric current injected via the ridge portion  49 , and forms the stripe-shaped optical waveguide  46 , so that the laser light is emitted from the emitting portion  46   a  of the facet of optical waveguide  46 . 
         [0061]    In the meantime, the first, second contacts  47 ,  48  are disposed on the one surface of the substrate  41 ; accordingly, it is possible to easily connect a lead wire to each of the first, second contacts  47 ,  48 . 
         [0062]      FIG. 3  shows a step flow chart of the semiconductor laser element  40 . As to the semiconductor laser element  40 , a semiconductor multilayer forming step, a ridge portion forming step, a concave portion forming step, a first metal film forming step, a buried layer forming step, a second metal film forming step, and a lapping step are performed successively on the wafer-shaped substrate  41  (see  FIG. 2 ). Thereafter, a first cutting step, a coat film forming step, and a second cutting step are performed successively, so that the wafer is divided into pieces to obtain the discrete semiconductor laser element  40 . 
         [0063]      FIG. 4  shows a front view of the semiconductor multilayer forming step. In the semiconductor multilayer forming step, the substrate  41  formed of GaAs is used as a ground to form the semiconductor multilayer  42  by means of epitaxial growth of a GaAs-based semiconductor by using metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) and the like. 
         [0064]    In other words, the substrate  41  is provided thereon with: a first buffer layer  43   a,  a second buffer layer  43   b,  an n-type clad layer  43   c,  an n-side light guide layer  43   d,  a hole barrier layer  43   e,  the active layer  44 , a p-side light guide layer  45   a,  a first p-type clad layer  45   b,  an etch stop layer  45   c,  a second p-type clad layer  45   d,  an intermediate layer  45   e,  and a cap layer  45   f  in this order produced by means of epitaxial growth. 
         [0065]    A multilayer n-type semiconductor layer  43  is composed of the first buffer layer  43   a,  the second buffer layer  43   b,  the n-type clad layer  43   c,  the n-side light guide layer  43   d,  and the hole barrier layer  43   e.  A multilayer p-type semiconductor layer  45  is composed of the p-side light guide layer  45   a,  the first p-type clad layer  45   b,  the etch stop layer  45   c,  the second p-type clad layer  45   d,  the intermediate layer  45   e,  and the cap layer  45   f.    
         [0066]    The first buffer layer  43   a  is formed of n-type GaAs. The second buffer layer  43   b  is formed of n-type GaInP. The n-type clad layer  43   c  is formed of n-type AlGaInP. The n-side light guide layer  43   d  is formed of n-type AlGaAs. The hole barrier layer  43   e  is formed of AlGaAs. The active layer  44  is formed into a multiple quantum well structure by means of InGaAs and AlGaAs. 
         [0067]    The p-side light guide layer  45   a  is formed of p-type AlGaAs. The first p-type clad layer  45   b  is formed of p-type AlGaInP. The etch stop layer  45   c  is formed of p-type GaInP. The second p-type clad layer  45   d  is formed of p-type AlGaInP. The intermediate layer  45   e  is formed of p-type GaInP. The cap layer  45   f  is formed of p-type GaAs. In the meantime, it is possible to suitably change the order and composition of each layer to be optimum for the designing of the semiconductor laser element  40 . 
         [0068]    The substrate  41  and the semiconductor multilayer  42  including the active layer  44  are formed of semiconductors joined to each other by lattice combination; accordingly, the semiconductor multilayer  42  is formed by means of epitaxial growth by using the substrate  41  as a ground. Because of this, the substrate  41  and the semiconductor multilayer  42  are joined to each other by means of continuous crystal lattice, and it is possible to improve heat conduction between both. 
         [0069]      FIG. 5  shows a front view of the ridge portion forming step. In the ridge portion forming step, a predetermined region of the semiconductor multilayer  42  is provided with a mask (not shown) by means of a photolithography technique. Next, the n-type semiconductor layer  45 , that is, a layer higher than the etch stop layer  45   c,  is removed by dry etching and wet etching to form a pair of groove portions  49   a,  thereafter, the mask is removed. In this way, the narrow-width (e.g., 2 μm) mesa-shaped ridge portion  49  is formed between the pair of groove portions  49   a  to have a stripe shape that extends in a direction perpendicular to the emitting facet  40   a  (see  FIG. 2 ). It is possible to protect the ridge portion  49  by leaving terraces equal to each other in height on both sides of the ridge portion  49 . 
         [0070]      FIG. 6  shows a front cross-sectional view of the concave portion forming step. In the concave portion forming step, a predetermined region of the semiconductor multilayer  42  is provided with a mask (not shown) formed of SiO 2  by means of the photolithography technique and etching. Next, the trench-shaped concave portion  51  and the separation groove  54 , which use the substrate  41  as the bottom surface, are formed by means of dry etching and wet etching, and the mask is removed. In this way, the annular protective wall  53  is formed around the concave portion  51 . 
         [0071]    Besides, the protective wall  53  is separated from the light emitting portion  52  having the ridge portion  49  by means of the separation groove  54 . The separation groove  54  may be formed in a step different form the concave portion  51 . However, by forming them at the same time, it is possible to reduce the man-hours. 
         [0072]      FIG. 7  shows a front cross-sectional view of the first metal film forming step. In the first metal film forming step, a first metal film  61 , which is a layer under the first contact  47  (see  FIG. 2 ), is formed on the bottom surface of the concave portion  51 . As to the first metal film  61 , a film is formed on a whole wafer surface by using AuGe/Ni, NiGe (In) or the like having a general ohmic structure, and a pattern is formed by using photolithography and etching. Thereafter, annealing is performed at about 200 to 450° C. 
         [0073]    In the meantime, to form an N-type ohmic contact on the bottom surface of the concave portion  51  by means of the first metal film  61 , the concave portion  51  using the substrate  41  formed of GaAs as the bottom surface is formed in the concave portion forming step. At this time, in a case where it is possible to form the ohmic contact by raising the doping concentration of the first buffer layer  43   a,  second buffer layer  43   b  or n-type clad layer  43   c,  the etching of the concave portion  51  may be shallow. In other words, the concave portion  51  and the separation groove  54  may be formed which use the first buffer layer  43   a,  second buffer layer  43   b,  or n-type clad layer  43   c  of the n-type semiconductor layer  43  as the bottom surface by which the ohmic contact can be formed. 
         [0074]    Besides, in a case where the substrate  41  is formed of semi-insulating GaAs, an n-type contact layer in which the doping amount is adjusted may be formed to be in contact with the substrate  41 . And, it is possible to form the concave portion  51  and the separation groove  54  that use the n-type contact layer of the n-type semiconductor layer  43  as the bottom surface, and to form the first metal film  61  on the n-type contact layer. 
         [0075]      FIG. 8  shows a front cross-sectional view of the buried layer forming step. In the buried layer forming step, the buried layer  50  formed of SiO 2  is formed on the whole wafer surface. Next, an opening portion for supplying electric power is formed on an upper surface of the ridge portion  49  and on an upper surface of the first metal film  61  by using photolithography and etching. 
         [0076]      FIG. 9  shows a front cross-sectional view of the second metal film forming step. 
         [0077]    In the second metal film forming step, a second metal film  62  is formed on the upper surface of the ridge portion  49  and on the upper surface of the first metal film  61 . As to the second metal film  61 , a metal film having Au as a main body is formed on the whole wafer surface, and a pattern is formed by using photolithography and etching. In this way, the first contact  47 , in which the first, second metal films  61 ,  62  are laminated, is formed on the bottom surface of the concave portion  51 , and the second contact  48  formed of the second metal film  62  is formed on the upper surface of the ridge portion  49 . 
         [0078]    If the first contact  47  is formed of a single layer formed of the first metal film  61 , it is necessary to remove the second metal film  62  from the first metal film  61 ; accordingly, there is a case where the first metal film  61  is etched and a desired shape is unmaintainable. Because of this, by laminating the second metal film  62  on the first metal film  61  to form the first contact  47  and preventing the first metal film  61  from being etched, it is possible to maintain the desired shape of the first contact  47 . 
         [0079]    According to the above steps, a semiconductor wafer is formed to be used to produce the semiconductor laser element  40  of one-side-two-contact type in which the first contact  47  and the second contact  48  are disposed on the one side of the substrate  41 . In this semiconductor wafer, it is possible to position the structures such as the contact, the ridge-type optical waveguide and the like by means of photolithography. Because of this, it is possible to form a positional relationship among them at high accuracy. 
         [0080]    In the lapping step, a rear surface (surface opposite to the surface for forming the semiconductor multilayer  42 ) of the substrate  41  of the semiconductor wafer is lapped to form the substrate  41  having a predetermined thickness t (see  FIG. 2 ). The substrate  41  is used as a base to be fixed to the slider  10 ; accordingly, if the thickness t is made large, the heat radiation improves. However, it becomes hard to form the discrete semiconductor laser element  40  (see  FIG. 1 ). Because of this, the thickness t is decided to have a suitable dimension considering the heat radiation and the man-hours at the time of forming the discrete device. 
         [0081]    In the first cutting step, a scribe groove is formed on the semiconductor wafer in a direction perpendicular to the ridge portion  49 . Next, stress is exerted on the scribe groove to cut the semiconductor wafer by means of cleavage, and a strip-shaped member having the emitting facet  40   a  (see  FIG. 2 ) on one surface is formed. At this time, it is possible to dispose the scribe groove on the light emitting portion  52  and the protective wall  53  that are formed to have the same height as each other. In this way, there are no wide concaves and convexes in the cleavage direction of the wafer; accordingly, it is possible to prevent deviation in the cleavage direction during the cutting time and thereby to prevent deterioration in the flatness of the emitting facet  40   a.    
         [0082]    In the coat film forming step, a facet coat film (not shown) is formed on the emitting facet  40   a  and a facet that opposes the emitting facet  40   a.  By means of the facet coat film, the facets of the semiconductor laser element  40  are protected and reflectivity of the facets is adjusted. At this time, by means of the protective wall  53 , it is possible to prevent the facet coat film from extending onto the first contact  47 . 
         [0083]    In the second cutting step, a scribe groove is formed on the strip-shaped member in a direction perpendicular to the emitting facet  40   a,  and stress is exerted on the scribe groove to cut the strip-shaped member by means of cleavage. In this way, the semiconductor laser element  40  is formed to be discrete. At this time, the scribe groove is formed on the protective wall  53 ; accordingly, it is possible to easily cut the strip-shaped member linearly and thereby to reduce defects caused by curves of the cutting line. 
         [0084]    As to the heat-assisted magnetic recording head  1  having the above structure, as shown in  FIG. 1 , the magnetic recording portion  13  and the magnetic reproducing portion  14  oppose the magnetic disc D, and the slider  10  floats over the magnetic disc D. When a voltage is applied between the first contact  47  and the second contact  48 , the laser light propagates through the optical waveguide  46  to be emitted forward (to the slider  10 ) from the emitting facet  40   a.    
         [0085]    The laser light emitted from the emitting portion  46  propagates in the optical waveguide  15  of the slider  10  to generate the near-field light. As to the magnetic disc D, the anisotropic magnetic field weakens locally because of the heat of the near-field light, and the magnetic recording is performed by the magnetic recording portion  13 . In this way, it is possible to use the magnetic disc D that has large magnetic anisotropic energy and thereby to improve the recoding density of the magnetic disc D. 
         [0086]    Besides, the magnetization of the magnetic disc D is detected by the magnetic reproducing portion  14 , and it is possible to read data recorded on the magnetic disc D. 
         [0087]    The heat generated from the semiconductor laser element  40  caused by the generation of the laser light is conducted to the substrate  41 , thereafter, conducted to the slider  10  via the heat-conductive adhesive  19 . In this way, the heat is radiated from the substrate  41  and slider  10 . 
         [0088]    According to the present embodiment, in the semiconductor laser element  40 , the substrate  41  is used as the ground to form the semiconductor multilayer  42  by means of epitaxial growth. And, the protective wall  53 , which encloses the concave portion  51  in which the first contact  47  is disposed, and the light emitting portion  52 , which has the optical waveguide  46  and on which the second contact  48  is disposed, are formed adjacently to each other by means of the semiconductor multilayer  42 . 
         [0089]    In this way, it is possible to bond the emitting facet  40   a  of the semiconductor laser element  40  to the slider  10 , connect a lead wire to each of the first, second contacts  47 ,  48 , and thereby to form the heat-assisted magnetic recording head  1 . Because of this, it is possible to easily perform the positioning between the semiconductor laser element  40  and the slider  10  in such a manner that the emitting portion  46   a  of the optical waveguide  46  opposes the optical waveguide  15 . Besides, when bonding the semiconductor laser element  40 , it is possible to prevent the adhesive  19  from adhering to the first contact  47  by means of the protective wall  53  and easily connect the lead wire to the first contact  47 . Accordingly, it is possible to achieve the man-hours reduction, yield improvement, and light weight of the heat-assisted magnetic recording head  1 . 
         [0090]    Further, the substrate  41  and the semiconductor multilayer  42  are joined to each other by means of continuous crystal lattice through epitaxial growth, and the heat conduction between both improves. Besides, when dividing the semiconductor wafer into pieces, the scribe groove is formed on the light emitting portion  52  and the protective wall  53 ; accordingly, the flatness of the bond surface (emitting facet  40   a ) formed of the cleavage surface improves. Accordingly, it is possible to improve the heat radiation of the heat-assisted magnetic recording heard  1  that uses the semiconductor laser element  40 . In addition, a volume difference between the light emitting portion  52  and the protective wall  53  is small; accordingly, it is possible to even an internal strain of the semiconductor laser element  40  and thereby to improve the stability of the laser light emission. 
         [0091]    Here, the concave portion  51  uses the substrate  41  or the n-type semiconductor layer  43  as the bottom surface; accordingly, a short-circuit between the active layer  44  and the first contact  47  and a short-circuit between the p-type semiconductor layer  45  and the first contact  47  are prevented. 
         [0092]    Besides, the light emitting portion  52  and the protective wall  53  are separated by the separation groove  54  that uses the substrate  41  or the n-type semiconductor layer  43 . In this way, it is possible to more surely prevent the short-circuit between the active layer  44  and the first contact  47  and the short-circuit between the p-type semiconductor layer  45  and the first contact  47 . 
         [0093]    Besides, the substrate  41  and the active layer  44  are formed of the GaAs-based semiconductor; accordingly, it is possible to easily form the semiconductor multilayer  42  including the active layer  44  by means of epitaxial growth by using the substrate  41  as the ground. In the meantime, if it is possible to produce the semiconductor multilayer  42  by means of epitaxial growth by using the substrate  41  as the ground, the substrate  41  and the active layer  44  may be formed by means of another semiconductor (e.g., InP-based semiconductor and the like). 
         [0094]    Besides, there included are the first metal film forming step for laminating the first metal film  61  on the bottom surface of the concave portion  51 , and the second metal film forming step for laminating the second metal film  62  on the first metal film  61  and the ridge portion  49 . And, the first contact  47  is formed by means of the first metal film  61  and the second metal film  62 , and the second contact  48  is formed by means of the second metal film  62 . In this way, during the time of forming the second metal film  62 , it is possible to prevent the first metal film  61  from being etched and thereby to maintain the desired shape of the first contact  47 . 
         [0095]    Next,  FIG. 10  shows a perspective view of the semiconductor laser element  40  of the heat-assisted magnetic recording head  1  according to a second embodiment. For the sake of description, the same portions as the first embodiment shown in  FIG. 2  described above are indicated by the same reference numbers. In the present embodiment, the shape of the protective wall  53  is different from the first embodiment. The other portions are the same as the first embodiment. 
         [0096]    The protective wall  53  is opened through a surface that opposes the light emitting portion  52 . Even in such a structure, it is possible to obtain the same effects as the first embodiment. Here, the separation groove  54  is formed not to overlap the first contact  47  projected on the emitting facet  40   a.  In this way, it is possible to prevent the adhesive  19  (see  FIG. 1 ) from adhering to the first contact  47 . 
         [0097]    Next,  FIG. 11  shows a perspective view of the semiconductor laser element  40  of the heat-assisted magnetic recording head  1  according to a third embodiment. For the sake of description, the same portions as the first embodiment shown in  FIG. 2  described above are indicated by the same reference numbers. In the present embodiment, the shape of the protective wall  53  is different from the first embodiment. The other portions are the same as the first embodiment. 
         [0098]    The protective wall  53  is cut by groove portions  53   a  at a plurality of positions in a circumferential direction. Even in such a structure, it is possible to obtain the same effects as the first embodiment. Here, the groove portions  53   a  are disposed not to overlap the first contact  47  projected on the emitting facet  40   a.  In this way, it is possible to prevent the adhesive  19  (see  FIG. 1 ) from adhering to the first contact  47 . In the meantime, the groove portions  53   a  may not be formed on the emitting facet  40   a.    
         [0099]    The semiconductor multilayer  42  of the semiconductor laser element  40  according to the first embodiment is formed of the n-type semiconductor layer  43 , the active layer  44 , and the p-type semiconductor layer  45  that are laminated in this order on the substrate  41 . In contrast to this, in the semiconductor laser element  40  according to the present embodiment, the semiconductor multilayer  42  is formed by laminating the p-type semiconductor layer  45 , the active layer  44 , and the n-type semiconductor layer  43  in this order on the substrate  41 . In this way, it is possible to obtain the same effects as the first embodiment. 
         [0100]    In other words, the semiconductor multilayer  42  may be formed on the substrate  41  by successively laminating the first electro-conductive semiconductor layer, the active layer  44 , and the second electro-conductive layer. The semiconductor multilayer  42  of the semiconductor laser element  40  of the heat-assisted magnet recording head  1  according to each of the second embodiment and the third embodiment may be formed in the same way as the present embodiment. 
         [0101]    The semiconductor laser element  40  of the heat-assisted magnetic recording head  1  according to the first embodiment is formed into the ridge type that has the stripe-shaped ridge portion  49 . In contrast to this, the semiconductor laser element  40  according to the present embodiment is formed into an inner stripe type or BH (Buried Heterostructure) type. According to this structure as well, it is possible to obtain the same effects as the first embodiment. 
         [0102]    In other words, in the semiconductor laser element  40 , the stripe-shaped optical waveguide  46  may be formed by means of the active layer  44 . The semiconductor laser element  40  of the heat-assisted magnet recording head  1  according to each of the second embodiment and the third embodiment may be formed in the same way as the present embodiment. 
         [0103]    The present invention is usable for a heat-assisted magnetic recording head that performs heat-assisted magnetic recording. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  heat-assisted magnetic recording head 
           10  slider 
           13  magnetic recording portion 
           14  magnetic reproducing portion 
           15  optical waveguide 
           19  adhesive 
           21  sub-mount 
           21   a  front surface 
           21   b  vertical surface 
           29  solder material 
           30 ,  40  semiconductor laser elements 
           31 ,  41  substrates 
           32 ,  42  semiconductor multilayers 
           36 ,  46  optical waveguides 
           36   a,    46   a  emitting portions 
           43  n-type semiconductor layer 
           44  active layer 
           45  p-type semiconductor layer 
           47  first contact 
           48  second contact 
           49  ridge portion 
           50  buried layer 
           51  concave portion 
           52  light emitting portion 
           53  protective wall 
           54  separation groove 
           61  first metal film 
           62  second metal film 
         D magnetic disc