JP2012253205A - Semiconductor laser element and optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser element that allows suppression of the occurrence of cracks and chips in a semiconductor laser element part.SOLUTION: A blue-violet semiconductor laser element 100 (semiconductor laser element) comprises: a semiconductor laser element part 10 including a substantially flat surface 10b, a surface 10a formed on the opposite side of the surface 10b, and an active layer 12 formed between the surface 10a and the surface 10b; and an n-side electrode 30 formed on the substantially flat surface 10b of the semiconductor laser element part 10. The n-side electrode 30 includes a bottom surface 30b that is substantially flat over the substantially entire region facing the surface 10b, a top surface 30a that is formed on the opposite side of the bottom surface 30b, and a recess 35 that is formed in the top surface 30a and hollows toward the bottom surface 30b.

Description

  The present invention relates to a semiconductor laser element and an optical device, and more particularly to a semiconductor laser element and an optical device provided with a semiconductor laser element part and an electrode.

  Conventionally, a semiconductor laser element including a semiconductor laser element portion and an electrode is known (see, for example, Patent Document 1).

  Patent Document 1 discloses a semiconductor laser element including a semiconductor laser element part including an n-type GaN substrate and an n-side electrode formed on the surface of the n-type GaN substrate. In this semiconductor laser element, a concave portion (stepped portion) that is recessed toward the lower active layer is formed on the upper surface of the n-type GaN substrate. The n-side electrode is formed along the step shape of the recess so as to cover the bottom surface and the inner side surface of the recess of the n-type GaN substrate. Therefore, the distance (thickness) from the n-side electrode formed on at least one of the inner surface or the bottom surface of the recess to the active layer is from the top surface of the n-type GaN substrate where the n-side electrode is not formed to the active layer. Is smaller than the distance (thickness). The semiconductor laser element is bonded to a wiring electrode in the semiconductor laser device by a junction down method via a p-side pad electrode formed on the side opposite to the n-side electrode with respect to the active layer.

JP 2010-153710 A

  In the semiconductor laser device disclosed in Patent Document 1, a recess is formed in the n-type GaN substrate, so that the thickness of the n-type GaN substrate varies between a portion where the recess is provided and a portion where the recess is not provided. Is different. In this case, since the thickness of the n-type GaN substrate is locally different, it is considered that the mechanical strength of the n-type GaN substrate is not substantially constant over the entire area of the substrate. Therefore, when this semiconductor laser element is bonded to a heat dissipation base (submount) or the like, it is considered that cracks and chips are likely to occur in the semiconductor laser element portion together with the bonding due to non-uniformity of the substrate strength. In addition, when a bonding wire is connected to the n-side electrode formed in the recess, the n-type GaN substrate in the recess has a small thickness, and thus is susceptible to wire bond impact. Even in this case, there is a problem that the semiconductor laser element portion is likely to be cracked or chipped.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a semiconductor laser element capable of suppressing the occurrence of cracks and chips in the semiconductor laser element portion. And providing an optical device.

Means for Solving the Problems and Effects of the Invention

  To achieve the above object, a semiconductor laser device according to a first aspect of the present invention includes a substantially flat first surface, a second surface formed on the opposite side of the first surface, a first surface, and a second surface. A semiconductor laser element portion including an active layer formed between the surface and an electrode formed on a substantially flat first surface of the semiconductor laser element portion, wherein the electrode is a region facing the first surface A substantially flat third surface, a fourth surface formed on the opposite side of the third surface, and a recess formed on the fourth surface and recessed toward the third surface.

  In the semiconductor laser device according to the first aspect of the present invention, as described above, the semiconductor laser element portion including the substantially flat first surface, and the electrode formed on the substantially flat first surface of the semiconductor laser element portion, And the electrode includes a substantially flat third surface over substantially the entire region facing the first surface, so that the thickness from the substantially flat first surface of the semiconductor laser element portion to the active layer is substantially constant. Therefore, non-uniformity does not occur in the mechanical strength of the semiconductor laser element portion. Therefore, the semiconductor laser element can be bonded to a heat dissipation base or the like without causing cracks or chipping in the semiconductor laser element portion. In addition, since an electrode having a substantially flat third surface is formed on the first surface of the semiconductor laser element portion having a substantially uniform mechanical strength, a recess is formed when a bonding wire is connected to the electrode. Even when the thickness of the included electrode is not uniform, the semiconductor laser element portion can withstand the impact of wire bonding. As a result, it is possible to prevent the semiconductor laser element portion from being cracked or chipped.

  In the present invention, the semiconductor laser element portion has a laser element structure in which a semiconductor layer including an active layer is stacked on the main surface of a semiconductor substrate, and only a semiconductor layer including an active layer is stacked without using a semiconductor substrate. This is a broad concept including a laser element structure, or a laser element structure in which a semiconductor layer including an active layer is bonded to a support base (support substrate).

  In the semiconductor laser device according to the first aspect, the electrode includes a recess formed on the fourth surface and recessed toward the third surface, so that the fourth surface of the electrode is formed from other than the recess and the recess. It has an uneven shape. Here, when dividing a plurality of semiconductor laser element portions formed on the wafer, the wafer is bonded with a sheet such as an expanded polypropylene (OPP) film attached to the surface of the electrode in the semiconductor laser element portion before the element division. There is a case where the element is divided. In this case, by sticking the OPP film to the surface of the electrode, elements such as carbon (C) and silicon (Si) constituting the organosilicon compound (eg, organic siloxane) contained in the OPP film adhere to the surface of the electrode. To do. When wire bonding is performed on the surface of the electrode from which the OPP film has been peeled after the element division, the above-described elements are interposed between the electrode and the bonding wire (metal wire). If the semiconductor laser element is operated in this state, the attached element becomes a barrier and an extra electrical resistance is generated between the electrode and the bonding wire, which increases the operating voltage of the semiconductor laser element. Occurs. The inventor of the present application diligently studied a method for solving such inconvenience in manufacturing a semiconductor laser device. As a result, by providing a recess on the fourth surface of the electrode of the present invention, even if the OPP film temporarily used in the manufacturing process is attached to the surface of the electrode, the recess is recessed, so the bottom surface of the recess And the OPP film does not stick to the inner surface. Therefore, even if the OPP film is peeled from the semiconductor laser element after the element division, elements such as carbon (C) and silicon (Si) can be prevented from adhering to the bottom surface and the inner surface of the recess. As a result, the bottom surface and the inner side surface of the recess of the electrode are kept clean, so that it is possible to suppress the occurrence of excessive electrical resistance between the recess of the electrode and the bonding wire. As a result, an increase in the operating voltage of the semiconductor laser element can be suppressed.

  In the semiconductor laser device according to the first aspect, preferably, the semiconductor laser device portion further includes a ridge formed on the second surface, and the recess and the ridge of the electrode are each of the recess and the ridge as viewed in a plan view. The semiconductor laser element portion is joined to the heat dissipation base on the second surface side where the ridge is formed. As described above, even when the semiconductor laser element is joined to the heat radiation base by the junction down method, the semiconductor laser element part does not have non-uniform mechanical strength, so the semiconductor laser element part is not cracked or chipped. Junction down junction can be performed without generating. In addition, since the semiconductor laser element portion can withstand the impact of wire bonding, it is possible to prevent the ridge from being damaged even if the recesses of the electrode and the formation regions of the ridge overlap each other.

  In the semiconductor laser device according to the first aspect, preferably, the concave portion of the electrode is configured such that a bonding wire can be connected to the bottom surface of the concave portion and can be connected in a state where the bonding wire is in contact with the inner side surface of the concave portion. Has been. If comprised in this way, conduction | electrical_connection with a bonding wire and an electrode can be aimed at easily in the bottom face of the recessed part of the electrode in which the deposit | attachment was removed as much as possible and kept clean. In addition, since the contact area of the bonding wire with the electrode can be increased, the electrical resistance between the electrode and the bonding wire can be further reduced.

  In the semiconductor laser device according to the first aspect, preferably, the electrode includes an ohmic electrode layer having a substantially flat third surface contacting the first surface of the semiconductor laser element portion, and a semiconductor laser element portion of the ohmic electrode layer; Is disposed on the opposite side and includes a pad electrode layer having a fourth surface in which a recess is formed, and the depth of the recess is smaller than the thickness of the pad electrode layer in a portion where the recess is not formed. If comprised in this way, the ohmic electrode layer used as a lower layer will not be exposed to the bottom face of a recessed part. That is, since the bonding wire is prevented from being directly bonded to the ohmic electrode layer, it is possible to prevent the ohmic electrode layer from being damaged due to the wire bond.

  In the semiconductor laser device according to the first aspect, preferably, the inner surface of the recess is located at a position spaced inward by a predetermined distance along the direction in which the resonator extends from the resonator surface formed in the semiconductor laser element portion. Is formed. If comprised in this way, the bottom face of a recessed part will not be exposed to a resonator surface. Therefore, even when an end face coat film made of a dielectric material or the like is formed on the resonator surface in the manufacturing process, it is possible to effectively suppress the end face coat film from entering and attaching to the bottom surface of the recess of the electrode. . As a result, the bottom surface of the recess of the electrode can be kept clean.

  An optical device according to a second aspect of the present invention includes the semiconductor laser element according to the first aspect and an optical system that controls the emitted light of the semiconductor laser element.

  Since the optical device according to the second aspect includes the semiconductor laser element according to the first aspect, the semiconductor laser element is prevented from being cracked or chipped and the operating voltage is increased. Is suppressed. As a result, it is possible to obtain a highly reliable optical device that can stably operate the semiconductor laser element and withstand long-time use.

It is the perspective view which showed the state which joined the blue-violet semiconductor laser device by 1st Embodiment of this invention to the submount by the junction down system. In the blue-violet semiconductor laser device by 1st Embodiment of this invention, it is sectional drawing at the time of cut | disconnecting perpendicularly to the direction where a resonator is extended in the position where the metal wire was wire-bonded. 1 is a top view of a blue-violet semiconductor laser device according to a first embodiment of the present invention. It is sectional drawing for demonstrating the manufacturing process of the blue-violet semiconductor laser device by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the blue-violet semiconductor laser device by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the blue-violet semiconductor laser device by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the blue-violet semiconductor laser device by 1st Embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the blue-violet semiconductor laser device by 1st Embodiment of this invention. It is the figure which showed the result of the confirmation experiment performed in order to confirm the effect of this invention. It is the perspective view which showed the state which joined the blue-violet semiconductor laser element by 2nd Embodiment of this invention to the submount by the junction down system. It is sectional drawing which showed the structure of the 3 wavelength semiconductor laser apparatus by 3rd Embodiment of this invention. It is the schematic which showed the structure of the optical pick-up apparatus by 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the structure of a blue-violet semiconductor laser device 100 according to an embodiment of the present invention will be described with reference to FIGS. 2 is a cross-sectional view taken along line 150-150 in FIG. The blue-violet semiconductor laser element 100 is an example of the “semiconductor laser element” in the present invention.

  As shown in FIG. 1, the blue-violet semiconductor laser device 100 includes an n-type GaN substrate 1 having a thickness of about 100 μm and an active layer 12 formed on the main surface (C1 side) of the n-type GaN substrate 1. A semiconductor laser element portion 10 including the semiconductor element layer 2 is provided. The semiconductor element layer 2 is made of a nitride-based semiconductor having an oscillation wavelength of about 405 nm band. In the blue-violet semiconductor laser device 100, the p-side electrode 20 is formed on the surface 10a (C1 side) on the semiconductor element layer 2 side, and n is formed on the surface 10b (C2 side) on the n-type GaN substrate 1 side. A side electrode 30 is formed. The surface 10b and the surface 10a are examples of the “first surface” and the “second surface” in the present invention, respectively. The n-side electrode 30 is an example of the “electrode” in the present invention.

  As shown in FIG. 3, the semiconductor laser element portion 10 has a resonator length of about 800 μm (length between laser element end portions (A direction)) and an element width of about 100 μm (B direction). The semiconductor element layer 2 is formed with a light emitting surface 2a (A1 side) and a light reflecting surface 2b (A2 side) orthogonal to the direction in which the resonator extends (A direction). The light emitting surface 2a and the light reflecting surface 2b are distinguished by the magnitude relationship of the intensity of the laser light emitted from each of the pair of resonator surfaces formed. That is, the side with a relatively large laser beam emission intensity is the light emission surface 2a. Further, the light reflection surface 2b is the side where the emission intensity of the laser light is relatively small. The light emitting surface 2a and the light reflecting surface 2b are examples of the “resonator surface” in the present invention.

A low-reflectivity dielectric multilayer film (not shown) is formed on the light emitting surface 2a, and a high-reflectivity dielectric multilayer film (not shown) is formed on the light-reflecting surface 2b. Is formed. Here, the dielectric multilayer film is composed of GaN, AlN, BN, Al ₂ O ₃ , SiO ₂ , ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , La ₂ O ₃ , SiN, AlON and MgF ₂ , and these A multilayer film made of Ti ₃ O ₅ , Nb ₂ O _3, or the like that is a material having a different mixing ratio can be used.

  Further, as shown in FIGS. 1 and 2, the blue-violet semiconductor laser device 100 is fixed on the submount 120 by a junction down method through a conductive adhesive layer 5 made of AuSn solder or the like. Specifically, the blue-violet semiconductor laser device 100 is a submount in which the p-side electrode 20 is interposed through the conductive adhesive layer 5 with the surface 10a side of the semiconductor laser device section 10 on which a ridge 3 described later is formed facing down. Bonded to a pad electrode 121 formed on the upper surface of 120. The submount 120 is an example of the “heat dissipation base” in the present invention.

  In the blue-violet semiconductor laser device 100, one end of a metal wire 91 made of Au and having a wire diameter of about 50 μm or more and about 60 μm or less is connected to the upper surface 30a of the n-side electrode 30. Further, the lower surface (C1 side) of the submount 120 is fixed to a metal stem (not shown) via a conductive adhesive layer (not shown). The other end of the metal wire 91 is connected to a negative electrode terminal (not shown), and the metal stem is electrically connected to a positive electrode terminal (not shown). The metal wire 91 is an example of the “bonding wire” in the present invention.

  Here, in the first embodiment, as shown in FIG. 2, the n-side electrode 30 includes an ohmic electrode layer 31 made of a metal layer such as Al and a metal such as Pt in order from the side closer to the n-type GaN substrate 1. It has a structure in which a barrier layer 32 made of layers and a pad electrode layer 33 made of a metal layer such as Au are laminated. The n-side electrode 30 includes a recess 35 formed on the upper surface 30a side. That is, the concave portion 35 has a top surface 30a that is recessed in the C1 direction toward the bottom surface 30b. Therefore, the upper surface 30a of the n-side electrode 30 has a concavo-convex shape by a region where the recess 35 is formed and a region where the recess 35 is not formed. On the other hand, the lower surface 30 b of the n-side electrode 30 forms a substantially flat surface over substantially the entire region facing the surface 10 b of the n-type GaN substrate 1. The upper surface 30a and the lower surface 30b are examples of the “fourth surface” and the “third surface” in the present invention, respectively.

  Further, when the blue-violet semiconductor laser device 100 is taken as a whole, the thickness (C direction) is changed by forming the concave portion 35 in the n-side electrode 30, while the substantially flat surface 10 b is changed in the semiconductor laser device portion 10. The thickness t5 from the active layer 12 to the active layer 12 is substantially constant. Here, the thickness t5 indicates the total thickness of the n-type GaN substrate 1, the n-type cladding layer 11, and the active layer 12.

  In the first embodiment, the depth D1 of the recess 35 is smaller than the thickness t1 of the pad electrode layer 33 in the portion where the recess 35 is not formed (D1 <t1). That is, the recess 35 is formed only in the pad electrode layer 33. Therefore, the bottom surface 35a is the pad electrode layer 33, and the lower barrier layer 32 and the ohmic electrode layer 31 are not exposed to the bottom surface 35a. Note that the thickness (t1-D1) of the pad electrode layer 33 on the bottom surface 35a may be in the range of about 200 nm to about 300 nm. Further, the depth D1 of the recess 35 may be about 3 μm or more and 5 μm or less.

  In addition, when the n-side electrode 30 is viewed in plan, the recess 35 is formed inside the n-side electrode 30 as shown in FIG. That is, the concave portion 35 has a bottom surface 35a and four inner side surfaces that surround four sides of the bottom surface 35a. The pair of inner side surfaces 35b are opposed to the direction in which the resonator extends (A direction), and the pair of inner side surfaces 35c are opposed to the width direction (B direction) of the element substantially orthogonal to the A direction. Therefore, the n-side electrode 30 includes a wall portion 33a whose outer side of the inner side surface 35b (the side opposite to the bottom surface 35a along the A direction) is thicker than the bottom surface 35a, and the outer side of the inner side surface 35c (along the B direction). The opposite side of the bottom surface 35a) has a wall portion 33b having a larger thickness than the bottom surface 35a. Further, the wall 33a and the wall 33b are connected to each other at the four corners of the recess 35 to have an integral structure. Here, the semiconductor laser element portion 10 has an element width (B direction) of about 100 μm, whereas the n-side electrode 30 has a width (B direction) of about 70 μm.

  The wall 33a has a width W1 from the end 30h in the A direction of the n-side electrode 30 to the inner side surface 35b. Further, the end 30h of the n-side electrode 30 is formed at a position spaced inward by a distance L1 along the A2 direction (A1 direction) from the light emitting surface 2a (light reflecting surface 2b). Therefore, the inner side surface 35b of the recess 35 is located on the inner side by a distance L1 + width W1 along the A2 direction (A1 direction) from the light emitting surface 2a (light reflecting surface 2b). Similarly, the wall portion 33b has a width W2 from the end portion 30j in the B direction of the n-side electrode 30 to the inner side surface 35c. The end 30j of the n-side electrode 30 is formed at a position spaced inward from the side end face 2c (2d) of the semiconductor laser element portion 10 by a distance L2 (about 15 μm) along the B2 direction (B1 direction). Yes. Accordingly, the inner side surface 35c of the recess 35 is located on the inner side by a distance L2 + width W2 along the B2 direction (B1 direction) from the side end surface 2c (2d). As a result, the recess 35 formed in the pad electrode layer 33 opens only upward (in the C2 direction), while the end 30h and the end 30j of the n-side electrode 30 do not have openings.

  Note that the magnitude relationship between the width W1 and the width W2 may be W1> W2 as shown in FIG. 3, or the width W1 and the width W2 may be substantially equal. In FIG. 3, the width W1 of the wall 33a is substantially symmetrical in the resonator direction (A direction), and the width W2 of the wall 33b is substantially symmetrical in the element width direction (B direction). However, it does not have to be a substantially symmetrical length. For example, the width W1 of the wall 33a may be different between the light emitting surface 2a side and the light reflecting surface 2b in order to distinguish the main emitting direction of the laser beam.

  In the first embodiment, as shown in FIG. 2, the recess 35 can be connected to the metal wire 91 on the bottom surface 35a, and the metal wire 91 is attached to at least one of the inner side surface 35b and the inner side surface 35c of the recess 35. It is comprised so that it can connect in the state which contacted. Here, the metal wire 91 has a wire diameter of about 50 μm or more and about 60 μm or less, and even if compared with the width of the n-side electrode 30 (B direction: about 70 μm), the width of the recess 35 (A direction and Slightly smaller than (B direction). Therefore, even if the metal wire 91 is connected to the bottom surface 35a of the recess 35, a part of the metal wire 91 melted at the time of joining by an ultrasonic bonder device or the like is applied from the bottom surface 35a to the inner surface 35b (35c), Is solidified in a state of slightly extending to the wall 33a (see FIG. 1) and the wall 33b (see FIG. 2). Thus, the metal line 91 is joined along the undulations formed on the upper surface 30a of the n-side electrode 30.

  As shown in FIG. 2, in the semiconductor element layer 2, an n-type cladding layer 11 made of n-type AlGaN having a thickness of about 2 μm is formed on the main surface (C1 side) of the n-type GaN substrate 1. ing. An active layer 12 having a multiple quantum well (MQW) structure is formed on the lower surface of the n-type cladding layer 11. The active layer 12 has four barrier layers (not shown) each having a thickness of about 30 nm and made of undoped GaInN, and three well layers (not shown) each having a thickness of about 7 nm and made of undoped GaInN. Are stacked alternately. A p-type cladding layer 13 made of Mg-doped p-type AlGaN having a thickness of about 0.5 μm is formed on the lower surface of the active layer 12. The p-type cladding layer 13 includes a convex portion 13a having a width of about 1.5 μm extending in a stripe shape (elongated shape) along a direction (A direction) in which the resonator extends, and a width direction (B direction) of the convex portion 13a. And flat portions 13b having a thickness of about 80 nm on both sides (B1 side and B2 side).

  A p-side contact layer 14 made of undoped GaInN having a thickness of about 3 nm is formed on the convex portion 13a (C1 side) of the p-type cladding layer 13. The p-side contact layer 14 and the convex portion 13a of the p-type cladding layer 13 constitute a ridge 3 having a width of about 1.5 μm and extending in a stripe shape in the A direction. Further, the ridge 3 constitutes an optical waveguide of the blue-violet semiconductor laser device 100.

A current blocking layer made of SiO ₂ having a thickness of about 0.2 μm is formed on both side surfaces of the convex portion 13 a of the p-type cladding layer 13, on the lower surface of the flat portion 13 b and on both side surfaces of the p-side contact layer 14. 19 is formed. The current blocking layer 19 is formed so as to expose the lower surface of the ridge 3 (the lower surface of the p-side ohmic electrode 15 (C1 side)).

  A p-side ohmic electrode 15 composed of a Pd layer, a Pt layer, and an Au layer is formed on the lower surface of the p-side contact layer 14 in order from the side close to the p-side contact layer 14. On the lower surface of the p-side ohmic electrode 15 and the lower surface of the current blocking layer 19, a Ti layer having a thickness of about 0.1 μm and a thickness of about 0.1 μm are sequentially formed from the side closer to the p-side ohmic electrode 15. A p-side electrode 20 is formed which includes a Pd layer having an Au layer having a thickness of about 3 μm.

  In the first embodiment, as shown in FIGS. 2 and 3, the recess 35 and the ridge 3 of the n-side electrode 30 are overlapped with each other when the recess 35 and the ridge 3 are formed in a plan view. Has been placed. In this case, the center line 170 (see FIG. 3) in the B direction of the recess 35 substantially coincides with the center line of the ridge 3. In this way, the blue-violet semiconductor laser device 100 is configured.

  A manufacturing process for the blue-violet semiconductor laser device 100 according to the first embodiment of the present invention is now described with reference to FIGS.

  First, as shown in FIG. 4, an n-type cladding layer 11, an active layer 12, and a p-type cladding layer are formed on the upper surface (main surface) of the n-type GaN substrate 1 using a metal organic chemical vapor deposition (MOCVD) method. 13, the p-side contact layer 14 and the p-side ohmic electrode 15 are sequentially stacked. Then, after patterning a mask (not shown) on the upper surface of the p-side ohmic electrode 15 using photolithography, the p-side ohmic electrode 15 exposed from the mask, the lower p-side contact layer 14 and the p-type cladding layer 13 are formed. The ridge 3 is formed by etching a part of the region. Thereafter, the mask left on the ridge 3 is removed.

  Thereafter, the upper surface of the flat portion 13b other than the convex portion 13a of the p-type cladding layer 13, the upper surface of the p-side ohmic electrode 15, and both side surfaces of the ridge 3 are continuously formed using plasma CVD or vacuum deposition. The current blocking layer 19 is formed so as to cover it. Thereafter, the p-side electrode 20 is formed on the current blocking layer 19 and on the p-side ohmic electrode 15 where the current blocking layer 19 is not formed by using a vacuum deposition method and a lift-off method.

  Thereafter, the surface 10b side of the n-type GaN substrate 1 is polished so that the n-type GaN substrate 1 has a thickness of about 100 μm, the damaged layer due to the polishing is removed by dry etching, and then a vacuum evaporation method and a lift-off method are used. Then, the n-side electrode 30 is formed on the surface 10b (C2 side) of the n-type GaN substrate 1 so as to be in contact with the n-type GaN substrate 1.

  Specifically, the ohmic electrode layer 31 is deposited on the lower surface (surface 10b) of the n-type GaN substrate 1 using a vacuum deposition method. Next, a barrier layer 32 is deposited so as to cover the ohmic electrode layer 31. Further, an Au layer having a thickness of about 300 nm is deposited on the lower surface of the barrier layer 32 to form a flat Au metal layer 33u. Thereby, as shown in FIG. 5, a plurality of Au metal layers 33 u having a rectangular shape are formed on the lower surface (surface 10 b) of the n-type GaN substrate 1. Here, the end portions 30h in the A direction of the Au metal layer 33u face each other with an interval L3 (= L1 × 2), and the end portions 30j in the B direction have an interval L4 (= L2 × 2). Opposite each other. Further, the Au metal layer 33u is formed so as to overlap with a region where the ridge 3 is formed in the lower part.

  After that, as shown in FIG. 6, the ohmic electrode layer 31 (see FIG. 4), the barrier layer 32 (see FIG. 4), and the Au metal layer 33u (see FIG. 4) are formed from the surface 10b of the n-type GaN substrate 1 using photolithography. The resist 50 is patterned so as to cover the side surface (the end 30h and the end 30j) and the predetermined region on the surface (C2 side) of the Au metal layer 33u. Thereby, the resist 50 is patterned so that only the outer edge portion of the Au metal layer 33u and a region in the vicinity thereof are exposed.

  Then, in this state, an Au metal layer 33v is deposited using a vacuum evaporation method in an opening 50a (a portion where the Au metal layer 33u is exposed) formed in a frame shape of the resist 50 when viewed in plan. Thereby, the Au metal layer 33v is formed on the surface of the Au metal layer 33u so as to have a frame shape. Thereafter, the resist 50 is removed. As a result, as shown in FIG. 7, the pad electrode layer 33 is formed on the upper surface (C2 side) of the barrier layer 32. The pad electrode layer 33 has the recess 35 and the Au metal layers 33u and 33v are integrated. In this way, the n-side electrode 30 is formed.

  Thereafter, the wafer is cleaved in a bar shape along the B direction so as to have a resonator length (A direction) of about 800 μm. Specifically, the wafer is cleaved at the position of the separation line 190 shown in FIG. Thereby, the bar 105 in a state in which a plurality of semiconductor laser element portions 10 are connected in the B direction is obtained.

  Thereafter, an end face coating film (not shown) is applied to the resonator surface (light emitting surface 2a and light reflecting surface 2b) formed of the cleavage surface formed on the bar 105 by cleavage using an ECR sputtering film forming apparatus or the like. Form. At this time, in the first embodiment, as shown in FIG. 3, since the concave portion 35 is not opened in the end portion 30h on the side facing the resonator surface of the n-side electrode 30, it is made of a dielectric material or the like. It is easy to prevent the end face coating film from entering and adhering into the recess 35. Therefore, the bottom surface 35a and the inner side surfaces 35b and 35c of the recess 35 are kept clean.

  Thereafter, as shown in FIG. 7, an oriented polypropylene (OPP) film 60 is attached to the surface 10 a side of the bar 105. Here, the OPP film 60 has a thickness of about 40 μm, and after peeling (separating) the release sheet 61 (see FIG. 8) that was originally integral, the OPP film 60 has a bar on the adhesive surface 60 a of the OPP film 60. The surface (C1 side) of the p-side electrode 20 at 105 is uniformly attached. Thereafter, a linear scribe along the direction (A direction) in which the resonator extends from the surface 10b side of the semiconductor laser element portion 10 opposite to the OPP film 60 (C2 side) by mechanical scribe or laser scribe. A plurality of grooves 51 are formed at a predetermined interval (pitch) in the B direction. Here, the pitch between the scribe grooves 51 is substantially equal to the element width (about 100 μm) of the blue-violet semiconductor laser element 100 (see FIG. 2).

  Thereafter, as shown in FIG. 8, the release sheet 61 that has been peeled off from the OPP film 60 in the above-described step is replaced with the upper surface 30a (C2 side) of the n-side electrode 30 of the blue-violet semiconductor laser device 100 in the bar state. Paste to. At this time, since the concave portion 35 is formed in the n-side electrode 30, the release sheet 61 is attached to the surface of the n-side electrode 30 (pad electrode layer 33) other than the concave portion 35. Therefore, in the recess 35, a space is formed between the adhesive surface 61 a and the bottom surface 35 a and the inner surface 35 b (35 c) of the release sheet 61, and the adhesive surface 61 a of the release sheet 61 corresponds to the bottom surface 35 a of the recess 35 and It does not contact the inner side surface 35b (35c).

  In this state, a predetermined value on the upper surface side (side on which the OPP film 60 is attached (C1 side)) of the bar 105 so that the lower surface side (side on which the release sheet 61 is attached (C2 side)) of the bar 105 opens. The blade-like metal fitting 52 is pressed in the direction of the arrow C2 at the position. The tip of the blade-shaped fitting 52 pierces the OPP film 60 in the C2 direction, and the load of the blade-like fitting 52 is applied to the semiconductor element layer 2 along the separation line 195, so that the bar 105 is formed in the scribe groove 51. Divide by position (separation line 195). In this way, a large number of chips (see FIG. 2) of the blue-violet semiconductor laser device 100 are formed.

  In the first embodiment, as described above, the semiconductor laser element portion 10 including the substantially flat surface 10b and the n-side electrode 30 formed on the substantially flat surface 10b of the semiconductor laser element portion 10 are provided. The side electrode 30 includes a substantially flat lower surface 30b over substantially the entire region facing the surface 10b, whereby a thickness t5 from the substantially flat surface 10b of the semiconductor laser element portion 10 to the active layer 12 (see FIG. 2). ) Is substantially constant, the non-uniformity in mechanical strength of the semiconductor laser element portion 10 does not occur. Therefore, the blue-violet semiconductor laser device 100 can be bonded to the submount 120 without causing cracks or chipping in the semiconductor laser device section 10. In addition, since the n-side electrode 30 is formed on the surface 10b of the semiconductor laser element portion 10 having substantially uniform mechanical strength, the recess 35 is included when the metal wire 91 is connected to the n-side electrode 30. Even when the thickness (C direction) of the n-side electrode 30 is not uniform, the semiconductor laser element portion 10 can withstand the impact of wire bonding. As a result, it is possible to prevent the semiconductor laser element unit 10 from being cracked or chipped.

  In the first embodiment, the n-side electrode 30 includes the recess 35 that is formed on the upper surface 30 a and that is recessed toward the lower surface 30 b, so that the upper surface 30 a of the n-side electrode 30 is other than the recess 35 and the recess 35. It has an uneven shape consisting of Even if the release sheet 61 peeled from the OPP film 60 that is temporarily used in the manufacturing process is attached to the surface of the n-side electrode 30, the recess 35 is depressed, so the bottom surface 35a and the inner surface 35b of the recess 35 The adhesive surface 61a of the release sheet 61 does not stick to the surface. Therefore, even if the release sheet 61 is peeled from the blue-violet semiconductor laser element 100 after the element division, elements such as carbon (C) and silicon (Si) are prevented from adhering to the bottom surface 35a and the inner side surface 35b of the recess 35. be able to. As a result, the bottom surface 35a and the inner side surface 35b of the recess 35 of the n-side electrode 30 are kept clean, so that an extra electrical resistance is generated between the recess 35 of the n-side electrode 30 and the metal wire 91. Can be suppressed. Thereby, it can suppress that the operating voltage of the blue-violet semiconductor laser element 100 rises.

  In the first embodiment, the concave portion 35 and the ridge 3 of the n-side electrode 30 are arranged so that the respective formation regions of the concave portion 35 and the ridge 3 overlap each other when seen in a plan view. The surface 10 a side on which the ridge 3 is formed is bonded to the submount 120. As described above, even when the blue-violet semiconductor laser device 100 is joined to the submount 120 by the junction down method, the semiconductor laser device portion 10 has no non-uniform mechanical strength. It is possible to perform junction down joining without causing cracks or chipping. Further, since the semiconductor laser element portion 10 can withstand the impact of wire bonding, even if the formation regions of the concave portion 35 of the n-side electrode 30 and the ridge 3 are overlapped, the ridge 3 is prevented from being damaged. Can do.

  In the first embodiment, the recess 35 of the n-side electrode 30 can be connected in a state where the metal wire 91 can be connected to the bottom surface 35 a of the recess 35 and the metal wire 91 is in contact with the inner surface 35 b of the recess 35. It is configured as follows. Thereby, electrical conduction between the metal wire 91 and the n-side electrode 30 can be easily achieved on the bottom surface 35a of the concave portion 35 of the n-side electrode 30 in which deposits are eliminated as much as possible and kept clean. In addition, since the contact area of the metal wire 91 with the n-side electrode 30 can be increased, the electrical resistance between the n-side electrode 30 and the metal wire 91 can be further reduced.

  In the first embodiment, the n-side electrode 30 includes the ohmic electrode layer 31 and the pad electrode layer 33, and the depth D1 of the recess 35 is that of the pad electrode layer 33 in the portion where the recess 35 is not formed. It is smaller than the thickness t1 (D1 <t1). As a result, the lower ohmic electrode layer 31 is not exposed on the bottom surface 35 a of the recess 35. That is, since the metal wire 91 is prevented from being directly joined to the ohmic electrode layer 31, it is possible to prevent the ohmic electrode layer 31 from being damaged due to the wire bond.

  In the first embodiment, the inner side surface 35b of the recess 35 has a predetermined distance along the A direction in which the resonator extends from each of the light emitting surface 2a and the light reflecting surface 2b formed in the semiconductor laser element portion 10 ( = L1 + W1). As a result, the bottom surface 35a of the recess 35 is not exposed to each of the light emitting surface 2a and the light reflecting surface 2b. Therefore, in the manufacturing process, even when an end face coat film made of a dielectric film or the like is formed on each of the light emitting surface 2a and the light reflecting face 2b, the end face coat film enters the bottom face 35a of the recess 35 of the n-side electrode 30. Can be effectively suppressed. As a result, the bottom surface 35a of the recess 35 of the n-side electrode 30 can be kept clean.

  Next, with reference to FIG. 1, FIG. 2, FIG. 4, FIG. 8, and FIG. 9, the confirmation experiment by comparison with the comparative example performed in order to confirm the effect of above-described 1st Embodiment is demonstrated. In this confirmation experiment, a blue-violet semiconductor laser device 100 (see FIG. 1) as an example corresponding to the first embodiment described above was manufactured, and a blue-violet semiconductor laser device as a comparative example with respect to the example was manufactured. The operating voltages of the respective semiconductor laser elements were compared.

  First, for the blue-violet semiconductor laser device as an example corresponding to the first embodiment described above, after forming the pad electrode layer 33 (see FIG. 4) having a flat surface (upper surface) constituting the n-side electrode, By mechanically cutting the surface of the pad electrode layer 33 using a cutting tool, an organic silicon compound such as an organic siloxane adhering to the surface of the pad electrode layer 33 (the release sheet 61 (see FIG. 8)) is used as a material or adhesive component. Carbon (C) and silicon (Si) included) were removed. Here, along with the removal of the organosilicon compound, the Au in the surface layer portion of the pad electrode layer 33 is also removed to some extent, so that the inner Au metal layer is exposed to the pad electrode layer 33 and a certain level of cleanness is maintained. It became a state. Thus, in the blue-violet semiconductor laser device of the example, the n-side electrode 30 (see FIG. 2) shown in the first embodiment has the concave portion 35 (see FIG. 2), so that the release sheet 61 (see FIG. 2). 8) was reproduced in a state substantially the same as the state in which the material or the like did not adhere to the recess 35.

  Further, for the blue-violet semiconductor laser device as a comparative example with respect to the above-described embodiment, the element chip is left in a state where the release sheet 61 is peeled off without cutting the surface of the pad electrode layer 33 with respect to the n-side electrode using a cutting metal fitting. Prepared. In other words, the state in which the organosilicon compound remained adhered to substantially the entire surface of the pad electrode layer 33 in the comparative example was reproduced. Then, each blue-violet semiconductor laser element is bonded to the submount 120 (see FIG. 1) by a junction down method, and a metal wire 91 (see FIG. 1) is wire-bonded to the n-side electrode for electrical connection. It was.

  And the current-voltage characteristic about each of the blue-violet semiconductor laser device produced as the said Example and a comparative example was investigated. In addition, about the current-voltage characteristic, it measured using the semiconductor parameter analyzer (electrical characteristic evaluation apparatus) which is one of the semiconductor characteristic measuring devices.

  As a result, as shown in FIG. 9, when the example and the comparative example were compared, the result was that the operating voltage at the same current value was lower in the example than in the comparative example. Moreover, the decreasing range of the operating voltage tended to increase as the current value increased. That is, unlike the comparative example, in the n-side electrode 30 in the example, it is considered that the organosilicon compound attached to the surface of the pad electrode layer 33 was removed and the pad electrode layer 33 was kept clean. Thereby, it is considered that the generation of an extra electrical resistance between the pad electrode layer 33 and the metal wire 91 is suppressed, and the operation voltage is reduced. From this result, in order to keep the surface of the n-side electrode 30 clean, the usefulness of wire bonding to the bottom surface of the recess was confirmed in the state where the “recess” of the present invention was formed in the n-side electrode 30. .

(Second Embodiment)
Next, with reference to FIGS. 5 and 10, a blue-violet semiconductor laser device 200 according to a second embodiment of the present invention will be described. In the blue-violet semiconductor laser device 200, the bottom surface 235a of the recess 235 penetrates the n-side electrode 230 in the width direction (B direction) of the device. In the figure, components similar to those in the first embodiment are denoted by the same reference numerals as those in the first embodiment. The blue-violet semiconductor laser element 200 is an example of the “semiconductor laser element” in the present invention.

  More specifically, as shown in FIG. 10, the recess 235 has a pair of inner side surfaces 235 b facing the extending direction of the resonator (A direction), while the inner side surface in the width direction (B direction) of the element. I don't have it. That is, when the blue-violet semiconductor laser device 200 is viewed from the side along the B direction, an opening through which the concave portion 235 can be confirmed is formed in the end portion 230j of the n-side electrode 230.

  Also in the blue-violet semiconductor laser element 200, one end of a metal wire 91 made of Au is connected to the upper surface 230a of the n-side electrode 230. Here, since the bottom surface 235a penetrates in the B direction in the recess 235, a part of the metal wire 91 melted at the time of wire bonding flows out to the surface 10b of the n-type GaN substrate 1 outside the bottom surface 235a. May be solidified. However, since the thickness of the n-type GaN substrate 1 is substantially constant at about 100 μm, and the blue-violet semiconductor laser device 200 is joined to the submount 120 by the junction down method, the semiconductor layer can be connected to the semiconductor from the bottom surface 235a of the n-side electrode 230. The distance to the pn junction in the element layer 2 is relatively large. Therefore, even if a part of the molten metal wire 91 flows out of the bottom surface 235a and is solidified, the pn junction is hardly short-circuited. The upper surface 230a is an example of the “fourth surface” in the present invention. The other configuration of the blue-violet semiconductor laser element 200 is the same as that of the first embodiment.

  In the manufacturing process of the blue-violet semiconductor laser device 200, when the pad electrode layer 233 of the n-side electrode 230 is formed, the frame-shaped Au metal layer 33v (see FIG. 5) is formed on the flat Au metal layer 33u (see FIG. 5). In this case, the Au metal layer 33v is increased in a state in which a resist pattern is formed so that the Au metal layer 33v is deposited only on the region near the end 30h in the A direction of the flat Au metal layer 33u. The n-side electrode 230 is formed by using a process of increasing. Other processes are substantially the same as the manufacturing process of the first embodiment.

  In the blue-violet semiconductor laser device 200, as described above, the bottom surface 235a of the recess 235 penetrates the n-side electrode 230 in the width direction (B direction) of the device. Thereby, in the manufacturing process, the n-side electrode 230 is formed using a simpler resist pattern than the case where the n-side electrode 30 having the recess 35 surrounded by the wall as in the first embodiment is formed. Can be formed. The remaining effects of the second embodiment are similar to those of the aforementioned first embodiment.

(Third embodiment)
Next, with reference to FIG. 11, a three-wavelength semiconductor laser device 300 according to a third embodiment of the invention will be described. In the figure, components similar to those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  The three-wavelength semiconductor laser device 300 includes the blue-violet semiconductor laser element 100 shown in the first embodiment, the red semiconductor laser element 320 having an oscillation wavelength of about 650 nm, and the infrared semiconductor laser element 330 having an oscillation wavelength of about 780 nm. A two-wavelength semiconductor laser element 350 monolithically formed on a common n-type GaAs substrate 351 is fixed on the upper surface 125a (C2 side) of the heat dissipation base 125 made of Si. In addition, the lower surface side (C1 side) of the heat radiation base 125 is joined to the upper surface 130a of the base portion 130 via the conductive fusion layer 6 such as AuSn solder.

  The red semiconductor laser element 320 is formed on one side (B1 side) on the lower surface of the n-type GaAs substrate 351, and the infrared semiconductor laser element 330 is formed on the other side (B2) on the lower surface of the n-type GaAs substrate 351. Side). Further, the red semiconductor laser element 320 and the infrared semiconductor laser element 330 are arranged at a predetermined distance by a groove portion 352 formed substantially at the center in the B direction.

  In the red semiconductor laser device 320, an n-type cladding layer 321, an active layer 322, a p-type cladding layer 323, a current blocking layer 329, and a p-side electrode 328 are formed on the B1 side on the lower surface of the n-type GaAs substrate 351. Is formed. The ridge portion 325 is formed in a region closer to the blue-violet semiconductor laser device 100 side (B1 side) than the central portion of the red semiconductor laser device 320 in the device width direction.

  In the infrared semiconductor laser device 330, the n-type cladding layer 331, the active layer 332, the p-type cladding layer 333, the current blocking layer 339, and the p-side are formed on the B2 side on the lower surface of the n-type GaAs substrate 351. An electrode 338 is formed. The ridge portion 335 is formed in a region closer to the blue-violet semiconductor laser device 100 side (B1 side) than the central portion of the infrared semiconductor laser device 330 in the device width direction. Further, a common n-side electrode 359 is formed in substantially the entire region on the upper surface of the n-type GaAs substrate 351.

An insulating film 126 made of SiO ₂ is formed on substantially the entire upper surface 125 a of the heat dissipation base 125. On the insulating film 126, pad electrodes 301, 302, and 303 made of a metal material such as Au are provided at positions where the blue-violet semiconductor laser element 100, the red semiconductor laser element 320, and the infrared semiconductor laser element 330 are joined. The heat dissipating base 125 is provided in an insulated state. Further, the pad electrodes 301, 302 and 303 are insulated from each other by being arranged at a predetermined distance from each other when seen in a plan view.

  Similarly to the blue-violet semiconductor laser device 100, the two-wavelength semiconductor laser device 350 is a junction-down method in which the active layers 322 and 332 are closer to the heat radiation base 125 side (C1 side) than the n-type GaAs substrate 351. It is joined. The p-side electrode 328 of the red semiconductor laser element 320 and the pad electrode 302 are electrically connected through the conductive fusion layer 5. Further, the p-side electrode 338 of the infrared semiconductor laser element 330 and the pad electrode 303 are electrically connected via the conductive fusion layer 5.

  Further, the ridge 3 of the blue-violet semiconductor laser element 100 is formed in a region closer to the two-wavelength semiconductor laser element 350 side (B2 side) than the central portion of the blue-violet semiconductor laser element 100 in the element width direction (B direction). Has been. Thus, in the blue-violet semiconductor laser element 100 and the two-wavelength semiconductor laser element 350, the light emitting points of the respective laser elements are collected at the center in the width direction of the three-wavelength semiconductor laser device 300.

  Also, one end of a metal wire 92 made of Au or the like is connected to the pad electrode 301 that is electrically connected to the p-side electrode 20 of the blue-violet semiconductor laser device 100, and the other end is connected to a lead terminal (positive electrode side) (not shown). It is connected. In addition, one end of a metal wire (not shown) made of Au or the like is connected to the pad electrode 302 in the region behind the red semiconductor laser element 320 (the back side in the drawing), and the other end is a lead (not shown). It is connected to the terminal (positive electrode side). One end of a metal wire 93 made of Au or the like is connected to the pad electrode 303, and the other end is connected to a lead terminal (positive electrode side) not shown. One end of a metal wire 94 is connected to the n-side electrode 359 of the two-wavelength semiconductor laser element 350, and the other end is connected to the base portion 130. Thereby, it is possible to individually supply current to each semiconductor laser element from the positive lead terminal, and each semiconductor laser element has an n-side electrode connected to a common terminal (negative terminal). The three-wavelength semiconductor laser device 300 is configured in this way.

  In the third embodiment, as described above, the three-wavelength semiconductor laser device 300 that is an integrated semiconductor laser device includes the blue-violet semiconductor laser element 100. Here, a semiconductor laser element (two-wavelength semiconductor laser element 350) composed of a GaAs-based semiconductor substrate and a semiconductor layer generates a relatively large amount of heat during the operation of the laser element. Be joined. Therefore, in order to align the light emitting point height (horizontal position) of each semiconductor laser element, the blue-violet semiconductor laser element 100 also needs to be joined to the heat radiation base 125 by the junction down method as shown in FIG. is there. By forming the recess 35 in the n-side electrode 30, the blue-violet semiconductor laser device 100 can be easily joined to the heat dissipation base 125 without causing cracks or chips. The remaining effects of the third embodiment are similar to those of the aforementioned first embodiment.

(Fourth embodiment)
Next, with reference to FIG. 11 and FIG. 12, an optical pickup device 400 according to a fourth embodiment of the present invention will be described. The optical pickup device 400 is an example of the “optical device” in the present invention.

  As shown in FIG. 12, an optical pickup device 400 according to the fourth embodiment of the present invention includes a can-type semiconductor laser device 410 on which a three-wavelength semiconductor laser device 300 (see FIG. 11) according to the third embodiment is mounted. An optical system 420 that adjusts the laser light emitted from the semiconductor laser device 410 and a light detection unit 430 that receives the laser light are provided.

  The optical system 420 includes a polarizing beam splitter (PBS) 421, a collimator lens 422, a beam expander 423, a λ / 4 plate 424, an objective lens 425, a cylindrical lens 426, and an optical axis correction element 427.

  Further, the PBS 421 totally transmits the laser light emitted from the semiconductor laser device 410 and totally reflects the laser light returning from the optical disk 440. The collimator lens 422 converts the laser light from the semiconductor laser device 410 that has passed through the PBS 421 into parallel light. The beam expander 423 includes a concave lens, a convex lens, and an actuator (not shown). The actuator has a function of correcting the wavefront state of the laser light emitted from the semiconductor laser device 410 by changing the distance between the concave lens and the convex lens.

  The λ / 4 plate 424 converts the linearly polarized laser light converted into substantially parallel light by the collimator lens 422 into circularly polarized light. The λ / 4 plate 424 converts the circularly polarized laser beam fed back from the optical disk 440 into linearly polarized light. In this case, the polarization direction of the linearly polarized light is orthogonal to the direction of the linearly polarized light of the laser light emitted from the semiconductor laser device 410. Thereby, the laser beam returning from the optical disk 440 is substantially totally reflected by the PBS 421. The objective lens 425 converges the laser light transmitted through the λ / 4 plate 424 on the surface (recording layer) of the optical disk 440. The objective lens 425 is movable by an objective lens actuator (not shown).

  In addition, a cylindrical lens 426, an optical axis correction element 427, and a light detection unit 430 are arranged along the optical axis of the laser light totally reflected by the PBS 421. The cylindrical lens 426 imparts astigmatism to the incident laser light. The optical axis correction element 427 is configured by a diffraction grating, and a spot of 0th-order diffracted light of each of blue-violet, red, and infrared laser beams transmitted through the cylindrical lens 426 is on a detection region of the light detection unit 430 described later. They are arranged to match.

  The light detection unit 430 outputs a reproduction signal based on the intensity distribution of the received laser light. In this way, the optical pickup device 400 including the semiconductor laser device 410 is configured.

  In the optical pickup device 400, the semiconductor laser device 410 separates red, blue-violet and infrared laser beams from the red semiconductor laser element 320, the blue-violet semiconductor laser element 100 and the infrared semiconductor laser element 330 (see FIG. 9). It is possible to emit light. Further, as described above, the laser light emitted from the semiconductor laser device 410 is transmitted by the PBS 421, the collimator lens 422, the beam expander 423, the λ / 4 plate 424, the objective lens 425, the cylindrical lens 426, and the optical axis correction element 427. After the adjustment, the light is irradiated onto the detection region of the light detection unit 430.

  Here, when reproducing the information recorded on the optical disk 440, the laser power emitted from the red semiconductor laser element 320, the blue-violet semiconductor laser element 100, and the infrared semiconductor laser element 330 is made constant. In this way, it is possible to irradiate the recording layer of the optical disc 440 with laser light and to obtain a reproduction signal output from the light detection unit 430. When information is recorded on the optical disk 440, the laser power emitted from the red semiconductor laser element 320 (infrared semiconductor laser element 330) and the blue-violet semiconductor laser element 100 is controlled based on the information to be recorded. However, the optical disk 440 is irradiated with laser light. Thereby, information can be recorded on the recording layer of the optical disc 440. In this manner, recording and reproduction on the optical disk 440 can be performed using the optical pickup device 400 including the semiconductor laser device 410.

  In the fourth embodiment, as described above, the optical pickup device 400 includes the semiconductor laser device 410 including the three-wavelength semiconductor laser device 300 of the third embodiment. Thereby, in the blue-violet semiconductor laser device 100 mounted on the three-wavelength semiconductor laser device 300, the occurrence of cracks and chipping is suppressed, and the increase in operating voltage is suppressed. As a result, it is possible to obtain a highly reliable optical pickup device 400 that can stably operate the blue-violet semiconductor laser element 100 in the semiconductor laser device 410 and can withstand long-term use. The remaining effects of the fourth embodiment are similar to those of the aforementioned third embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first to fourth embodiments, the example in which the n-side electrode 30 in which the concave portion 35 is formed on the back surface of the n-type GaN substrate 1 has been shown, but the present invention is not limited to this. For example, after forming the semiconductor element layer 2 having the ridge 3 using the growth substrate, the semiconductor element layer 2 is joined to the support substrate by junction down, and the growth substrate is removed from the semiconductor element layer 2 to obtain the semiconductor laser element. A part may be formed. Then, the “electrode” of the present invention may be formed on the substantially flat surface (first surface) of the n-type cladding layer from which the growth substrate has been removed. Alternatively, the “electrode” of the present invention is formed on the substantially flat surface (first surface) of the support base in a state where the support base (support base) is bonded to the surface of the n-type clad layer from which the growth substrate has been removed Can also be formed.

  In addition, among the above-described modifications, the surface of the support base (first surface) bonded to the surface of the semiconductor layer from which the growth substrate has been removed (first surface) or the surface of the semiconductor layer from which the growth substrate has been removed (first surface). In the case of a laser element structure in which the “electrode” of the present invention is formed on one surface), in the semiconductor element layer having the active layer, the conductivity on the side opposite to the conductivity type on the side where the optical waveguide (ridge) is formed. The “electrode” of the present invention may be formed on a substantially flat surface of a semiconductor layer having a mold. That is, when the optical waveguide (ridge) is formed in the n-type semiconductor layer, the “electrode” of the present invention may be formed on the substantially flat surface of the semiconductor layer made of the p-type semiconductor.

  In the manufacturing processes of the first and second embodiments, the Au metal is formed through the opening 50a formed in the frame shape of the resist 50 in a state where the resist 50 is patterned on the Au metal layer 33u having a flat surface. Although an example in which the pad electrode layer 33 having the recesses 35 is formed by depositing the layer 33v and then removing (lifting off) the resist 50 is shown, the present invention is not limited to this. For example, by forming a Au metal layer having a flat surface on the barrier layer 32 with a predetermined thickness and then forming a recess not reaching the barrier layer 32 in the Au metal layer using photolithography and etching. The pad electrode layer 33 may be formed. Any of the above-exemplified forming methods can easily form an electrode having a recess according to the present invention.

In the first to fourth embodiments, an example in which the blue-violet semiconductor laser device 100 is formed by forming the convex ridge 3 on the p-type cladding layer 13 of the semiconductor device layer 2 has been described. It is not limited to this. A nitride-based semiconductor laser device having a gradient index waveguide type ridge waveguide structure in which a ridge is embedded with a current blocking layer made of SiO ₂ or AlGaN may be formed. Alternatively, a gain waveguide type nitride-based semiconductor laser device in which a current blocking layer having a stripe-shaped opening is formed on a flat upper cladding layer to provide a current passage portion may be formed. In the case of a semiconductor laser device having such an element structure, when joining to a heat dissipation base by a junction-up method with the side (substrate side) opposite to the side where the current path portion (optical waveguide) is formed facing down Since the surface of the semiconductor layer on the side where the current path portion (optical waveguide) is formed (the “first surface” of the present invention) is substantially flat, the surface of the semiconductor layer on the side opposite to the heat dissipation base is In addition, the “electrode” of the present invention having a recess may be formed.

  In the first to fourth embodiments, the “electrode” of the present invention is shown as being formed in the blue-violet semiconductor laser device 100 which is a nitride semiconductor laser device. However, the present invention is not limited to this. Absent. The “electrode” of the present invention is formed for a semiconductor laser element (a red LD, an infrared LD, or a semiconductor laser element having a monolithic structure such as a two-wavelength semiconductor laser element 350) made of a GaAs-based semiconductor or a GaInP-based semiconductor. May be. In addition, the nitride-based semiconductor laser element may be formed with the “electrode” of the present invention for a blue semiconductor laser element or a green semiconductor laser element other than the blue-violet semiconductor laser element.

  In the first to fourth embodiments, the semiconductor element layer 2 of the blue-violet semiconductor laser element 100 is shown as being formed of a nitride semiconductor layer such as AlGaN or InGaN. However, the present invention is not limited to this. First, the semiconductor element layer 2 may be formed of a nitride-based semiconductor layer having a wurtzite structure made of AlN, InN, BN, TlN, and mixed crystals thereof.

In the above-mentioned first to fourth embodiments show an example of forming the current blocking layer 19 by using SiO _2, the present invention is not limited thereto. For example, the current blocking layer may be formed using another insulating material such as SiN or a semiconductor material such as AlInP or AlGaN.

  In the third embodiment, an example in which the three-wavelength semiconductor laser device 300 includes the blue-violet semiconductor laser element 100, the red semiconductor laser element 320, and the infrared semiconductor laser element 330 has been described. Not limited to. In the present invention, an RGB three-wavelength semiconductor laser device may be configured using a green semiconductor laser element and a blue semiconductor laser element made of a nitride semiconductor and a red semiconductor laser element 320. In this case, it is preferable to form the “electrode” of the present invention on the green semiconductor laser element and the blue semiconductor laser element.

  In the fourth embodiment, the example in which the three-wavelength semiconductor laser device 300 is mounted on the can-type semiconductor laser device 410 is shown, but the present invention is not limited to this. In the present invention, the three-wavelength semiconductor laser device 300 may be mounted on a frame-type package having a flat planar structure.

  In the fourth embodiment, the optical pickup device 400 including the three-wavelength semiconductor laser device 300 including the blue-violet semiconductor laser element 100 has been described. However, the present invention is not limited thereto, and the blue-violet semiconductor laser device 100 is The three-wavelength semiconductor laser device 300 may be applied to an optical device such as an optical disc device that records or reproduces an optical disc such as a CD, DVD, or BD, or an optical device such as a projector device.

2a Light exit surface (resonator surface)
2b Light reflecting surface (resonator surface)
3 Ridge 10 Semiconductor laser element portion 10a Surface (second surface)
10b Surface (first surface)
12 Active layer 30 n-side electrode (electrode)
30a, 230a Upper surface (fourth surface)
30b Lower surface (third surface)
31 Ohmic electrode layer 33, 233 Pad electrode layer 35, 235 Recess 35a, 235a Bottom surface 35b Inner side surface 91 Metal wire (bonding wire)
100, 200 Blue-violet semiconductor laser element (semiconductor laser element)
120, 125 Submount (Heat dissipation base)
400 Optical pickup device (optical device)
420 Optical system

Claims (6)

A semiconductor laser element portion including a substantially flat first surface, a second surface formed on the opposite side of the first surface, and an active layer formed between the first surface and the second surface; ,
An electrode formed on the substantially flat first surface of the semiconductor laser element portion,
The electrode is formed on a third surface that is substantially flat over substantially the entire region facing the first surface, a fourth surface that is formed on the opposite side of the third surface, and the fourth surface. And a recess recessed toward the third surface. The semiconductor laser element portion further includes a ridge formed on the second surface,
The concave portion and the ridge of the electrode are arranged so that the formation regions of the concave portion and the ridge overlap each other in a plan view.
2. The semiconductor laser element according to claim 1, wherein the semiconductor laser element portion is bonded to a heat dissipation base on the second surface side where the ridge is formed.   The concave portion of the electrode is configured so that a bonding wire can be connected to a bottom surface of the concave portion and can be connected in a state where the bonding wire is in contact with an inner side surface of the concave portion. The semiconductor laser device described. The electrode is disposed on a side of the ohmic electrode layer opposite to the semiconductor laser element part, the ohmic electrode layer having the substantially flat third surface contacting the first surface of the semiconductor laser element part, A pad electrode layer having the fourth surface in which a recess is formed,
The depth of the said recessed part is a semiconductor laser element of any one of Claims 1-3 smaller than the thickness of the said pad electrode layer in the part in which the said recessed part is not formed.   The inner surface of the recess is formed at a position spaced inward by a predetermined distance along a direction in which the resonator extends from a resonator surface formed in the semiconductor laser element portion. The semiconductor laser device according to claim 1. A semiconductor laser device according to any one of claims 1 to 5;
An optical device comprising: an optical system that controls light emitted from the semiconductor laser element.

Images