Semiconductor laser device and method of manufacturing the same

A semiconductor laser device includes a first semiconductor laser element formed on a surface of a first conductive type substrate, obtained by stacking a first conductive type first semiconductor layer, a first active layer and a second conductive type second semiconductor layer successively from the first conductive type substrate and a second semiconductor laser element obtained by successively stacking a first conductive type third semiconductor layer, a second active layer and a second conductive type fourth semiconductor layer, wherein the third semiconductor layer is electrically connected to the first semiconductor layer by bonding a side of the third semiconductor layer to the surface of the first conductive type substrate through a fusible layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The priority application number JP2007-159903, Semiconductor Laser Device and Method of Manufacturing the Same, Jun. 18, 2007, Yasuyuki Bessho, JP2008-148021, Semiconductor Laser Device and Method of Manufacturing the Same, Jun. 5, 2008, Yasuyuki Bessho, upon which this patent application is based is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor laser device and a method of manufacturing the same, and more particularly, it relates to a semiconductor laser device integrating a plurality of semiconductor laser elements and a method of manufacturing the same.

2. Description of the Background Art

A semiconductor laser element (infrared semiconductor laser element) emitting infrared light having a wavelength of about 780 nm is employed as a light source for a CD (compact disk)/CD-R (compact disk-recordable) drive in general. A semiconductor laser element (red semiconductor laser element) emitting red light having a wavelength of about 650 nm is employed as a light source for a DVD (digital versatile disc) drive.

On the other hand, a DVD allowing writing and reading by employing blue-violet light having a wavelength of about 405 nm has recently been developed. For writing and reading of such a DVD, a next generation DVD drive employing a semiconductor laser element (blue-violet semiconductor laser element) emitting blue-violet light having a wavelength of about 405 nm has also simultaneously been developed. This DVD drive requires compatibility for conventional CD/CD-R and DVD.

In this case, the compatibility for the conventional CD/CD-R and DVD is attained by a method of providing a plurality of optical pickups emitting infrared light, red light and blue-violet light respectively in a DVD drive or a method of individually providing an infrared semiconductor laser element, a red semiconductor laser element and a blue-violet semiconductor laser element in one optical pickup. However, these methods cause increase of the number of components, and hence downsizing, simplified configuration or price-reduction of the optical pickup system is disadvantageously difficult.

In order to suppress the increase of the number of components, a semiconductor laser element in which an infrared semiconductor laser element (laser having a wavelength of about 780 nm) and a red semiconductor laser element (laser having a wavelength of about 650 nm) formed on a gallium arsenide substrate are integrated in one chip has been put into practice in general. In the integrated semiconductor laser element in the one chip, the light emission positions of the respective wavelength semiconductor laser elements are accurately formed.

The blue-violet semiconductor laser element not formed on the gallium arsenide substrate, on the other hand, it is very difficult to integrate the blue-violet semiconductor laser element together with the infrared semiconductor laser element and the red semiconductor laser element in one chip. The light emission positions of the respective wavelength semiconductor laser elements must be arranged as close as possible in order to reduce loss or aberration to laser beams emitted from the respective wavelength semiconductor laser elements.

A semiconductor laser device having a structure, in which semiconductor laser elements are individually formed on different growth substrates and thereafter are bonded to each other such that emission layers of the semiconductor laser elements are opposed to each other, is proposed in general, as disclosed in Japanese Patent Laying-Open Nos. 2005-209950 and 2007-488100, for example.

The aforementioned Japanese Patent Laying-Open No. 2005-209950 discloses an integrated semiconductor light-emitting device having a structure in which emission layers (semiconductor element layers) of a red semiconductor laser element and a blue semiconductor laser element are bonded to be opposed to each other. In the integrated semiconductor light-emitting device described in Japanese Patent Laying-Open No. 2005-209950, the emission layer of the blue semiconductor laser element is fitted into a recess portion (groove) formed on a prescribed region of the emission layer of the red semiconductor laser element and reaching the growth substrate through a bonding layer so that p-side semiconductor layers of the red semiconductor laser element and the blue semiconductor laser element are electrically connected to each other. In particular, the bonding layer are so formed as to cover the overall surface region of the semiconductor laser element including portions where the growth substrate and an n-side semiconductor layer are exposed, and a p-side electrode is mounted on a first end of the bonding layer, so that the integrated semiconductor light-emitting device can be employed in a common anode type (p-side common electrode).

In the integrated semiconductor light-emitting device described in Japanese Patent Laying-Open No. 2005-209950, insulating layers are provided between the growth substrate and the n-side semiconductor layer of the red semiconductor laser element and the bonding layer so as to cause no electrical short circuit between the growth substrate as a cathode side (n-side) and the n-side semiconductor layer of the red semiconductor laser element and a region of the bonding layer (p-side). Additionally, insulating layers are provided between the growth substrate and the n-side semiconductor layer of the blue semiconductor laser element and the bonding layer so as to cause no electrical short circuit between the growth substrate as the cathode side (n-side) and the n-side semiconductor layer of the blue semiconductor laser element and the region of the bonding layer (p-side).

The aforementioned Japanese Patent Laying-Open No. 2007-488100 discloses a semiconductor laser having structure in which a blue-violet semiconductor laser element (first light-emitting element) and a semiconductor laser element (second light-emitting element) integrally formed with a red semiconductor laser element and an infrared semiconductor laser element are bonded to a support substrate in a state where the emission layers (semiconductor element layers) of the first light-emitting element and the second light-emitting element are opposed and bonded to each other. In the semiconductor laser described in Japanese Patent Laying-Open No. 2007-488100, p-side semiconductor layers of the first light-emitting element and the second light-emitting element are arranged so as to be opposed to each other and insulating layers are provided between the opposed p-side semiconductor layers, whereby the p-side semiconductor layers of the respective light-emitting elements are electrically insulated from each other. Therefore, electrodes connected to the p-side semiconductor layers of the respective light-emitting elements are formed on the support substrate and an electrode connected to the n-side semiconductor layer of the first light-emitting element is also connected to the support substrate.

In the integrated semiconductor light-emitting device disclosed in Japanese Patent Laying-Open No. 2005-209950, however, the p-side semiconductor layers of the red semiconductor laser element and the blue semiconductor laser element are electrically connected to each other through the bonding layer, while the insulating layers for preventing a short circuit must be formed between the portions of the growth substrates and the n-side semiconductor of the respective semiconductor laser elements layers are exposed and the bonding layer as an anode side (p-side) respectively, and hence an inner structure of the semiconductor laser element is disadvantageously complicated.

In the semiconductor laser disclosed in Japanese Patent Laying-Open No. 2007-488100, the insulating layers must formed in order to electrically isolate the p-side semiconductor layers of the first and second light-emitting elements while the p-side semiconductor layers of the respective light-emitting elements are arranged to be close to each other. Thus, the inner structure of the semiconductor element is disadvantageously complicated.

SUMMARY OF THE INVENTION

A semiconductor laser device according to a first aspect of the present invention comprises a first semiconductor laser element formed on a surface of a first conductive type substrate, obtained by stacking a first conductive type first semiconductor layer, a first active layer and a second conductive type second semiconductor layer successively from the first conductive type substrate and a second semiconductor laser element obtained by successively stacking a first conductive type third semiconductor layer, a second active layer and a second conductive type fourth semiconductor layer, wherein the third semiconductor layer is electrically connected to the first semiconductor layer by bonding a side of the third semiconductor layer to the surface of the first conductive type substrate through a fusible layer.

A method of manufacturing a semiconductor laser device according to a second aspect of the present invention comprises steps of forming a first semiconductor laser element on a surface of a first conductive type substrate by successively growing a first conductive type first semiconductor layer, a first active layer and a second conductive type second semiconductor layer, forming a second semiconductor laser element on a surface of a growth substrate by growing a first conductive type third semiconductor layer, a second active layer and a second conductive type fourth semiconductor layer and bonding the first semiconductor laser element and the second semiconductor laser element in a state where the third semiconductor layer and the first semiconductor layer are electrically connected to each other by bonding a side of the third semiconductor layer to the surface of the first conductive type substrate through a fusible layer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be hereinafter described with reference to the drawings.

A structure of a semiconductor laser device100comprising a three-wavelength semiconductor laser element portion50according to a first embodiment of the present invention will be now described with reference toFIGS. 1 and 2.

In the semiconductor laser device100according to the first embodiment of the present invention, the three-wavelength semiconductor laser element portion50is fixed to a base (submount)70made of AlN through conductive bonding layers1made of metal layers such as AuSn solder, as shown inFIG. 1. In the three-wavelength semiconductor laser element portion50, a blue-violet semiconductor laser element40having a lasing wavelength of about 405 nm is bonded to a monolithic two-wavelength semiconductor laser element portion30in which an infrared semiconductor laser element10having a lasing wavelength of about 780 nm and a red semiconductor laser element20having a lasing wavelength of about 650 nm are formed on the n-type GaAs substrate51through a fusible layer60. The infrared semiconductor laser element10and the red semiconductor laser element20are each an example of the “first semiconductor laser element” in the present invention and the blue-violet semiconductor laser element40is an example of the “second semiconductor laser element” in the present invention. The n-type GaAs substrate51is an example of the “first conductive substrate” in the present invention. The base70is an example of the “heat radiator base” in the present invention.

In the infrared semiconductor laser element10of the three-wavelength semiconductor laser element portion50, an n-type AlGaAs cladding layer11, an active layer12having a MQW structure formed by alternately staking quantum well layers made of AlGaAs having a lower Al composition and barrier layers AlGaAs having a higher Al composition and a p-type AlGaAs cladding layer13are formed on the n-type GaAs substrate51, as shown inFIG. 1. Therefore the infrared semiconductor laser element10is made of a semiconductor layer of a compound containing As. The n-type AlGaAs cladding layer11, the active layer12and the p-type AlGaAs cladding layer13are examples of the “first conductive type first semiconductor layer”, the “first active layer” and the “second conductive type second semiconductor layer” in the present invention, respectively.

The first semiconductor layer may include other semiconductor layer such as a light guide layer (not shown) or a carrier blocking layer (not shown) between the n-type AlGaAs cladding layer11and the active layer12. The first semiconductor layer may include other semiconductor layer such as a contact layer (not shown) on a side of the n-type AlGaAs cladding layer11opposite to the active layer12. The second semiconductor may include other semiconductor layer such as a light guide layer (not shown) or a carrier blocking layer (not shown) between the active layer12and the p-type AlGaAs cladding layer13. The second semiconductor layer may include other semiconductor layer such as a contact layer (not shown) on a side of the p-type AlGaAs cladding layer13to opposite the active layer12. The active layer12may have a single-layer or single quantum well (SQW).

As shown inFIG. 1, the p-type AlGaN cladding layer13is provided with a ridge portion13ahaving a width of about 3 μm, extending in a direction A (seeFIG. 2) which is a direction perpendicular to the drawing, thereby forming a waveguide structure. As shown inFIG. 1, insulating films14made of SiO2are formed on a surface of the p-type AlGaAs cladding layer13except the ridge portion13a. A p-side electrode15is formed on a lower surface of the ridge portion13aof the p-type AlGaAs cladding layer13and the insulating films14. A contact layer (not shown) or the like having a smaller band gap than the p-type AlGaAs cladding layer13may be preferably formed between the ridge portion13aand the p-side electrode15. The p-side electrode15is formed by stacking a Cr layer having a thickness of about 10 nm and an Au film having a thickness of about 2.2 μm. As shown inFIG. 1, the lower surface of the p-side electrode15and an upper surface of an electrode layer71formed on the base70are bonded to each other.

In the red semiconductor laser element20of the three-wavelength semiconductor laser element portion50, an n-type AlGaInP cladding layer21, an active layer22having a MQW structure formed by alternately staking quantum well layers made of GaInP and barrier layers made of AlGaInP and a p-type AlGaInP cladding layer23are formed on the n-type GaAs substrate51, as shown inFIG. 1. Therefore the red semiconductor laser element20is made of a semiconductor layer of a compound containing P (phoshporus). The n-type AlGaInP cladding layer21, the active layer22and the p-type AlGaInP cladding layer23are examples of the “first conductive type first semiconductor layer”, the “first active layer” and the “second conductive type second semiconductor layer” in the present invention, respectively.

The first semiconductor layer may include other semiconductor layer such as a light guide layer (not shown) or a carrier blocking layer (not shown) between the n-type AlGaInP cladding layer21and the active layer22. The first semiconductor layer may include other semiconductor layer such as a contact layer (not shown) on a side of the n-type AlGaInP cladding layer21opposite to the active layer22. The second semiconductor layer may include other semiconductor layer such as a light guide layer (not shown) or a carrier blocking layer (not shown) between the active layer22and the p-type AlGaInP cladding layer23. The second semiconductor layer may include other semiconductor layer such as a contact layer (not shown) on a side of the p-type AlGaInP cladding layer23opposite to the active layer22. The active layer22may have a single-layer or single quantum well (SQW).

As shown inFIG. 1, the p-type AlGaInP cladding layer23is provided with a ridge portion23ahaving a width of about 2 μm, extending in the direction A (seeFIG. 2) which is a direction perpendicular to the drawing, thereby forming a waveguide structure. As shown inFIG. 1, insulating films24made of SiO2are formed on a surface of the p-type AlGaInP cladding layer23except the ridge portion23a. A p-side electrode25is formed on a lower surface of the ridge portion23aof the p-type AlGaInP cladding layer23and the insulating films24. A contact layer (not shown) or the like having a smaller band gap than the p-type AlGaInP cladding layer23may preferably be formed between the ridge portion23aand the p-side electrode25. The p-side electrode25is formed by stacking a Cr layer having a thickness of about 10 nm and an Au film having a thickness of about 2.2 μm. As shown inFIG. 1, the lower surface of the p-side electrode25and an upper surface of an electrode layer72formed on the base70are bonded to each other.

As shown inFIG. 1, an n-side electrode52formed by stacking an AuGe layer, an Ni layer and an Au film successively from the n-type GaAs substrate51is formed on an overall upper surface of the n-type GaAs substrate51formed with the three-wavelength semiconductor laser element portion50.

In the blue-violet semiconductor laser element40of the three-wavelength semiconductor laser element portion50, an n-type AlGaN cladding layer41, an active layer42having a MQW structure formed by alternately staking quantum well layers made of InGaN having a higher In composition and barrier layers made of InGaN having a lower In composition and a p-type AlGaN cladding layer43are formed, as shown inFIG. 1. Therefore the blue-violet semiconductor laser element40is made of a semiconductor layer of a nitride-based compound. The n-type AlGaN cladding layer41, the active layer42and the p-type AlGaN cladding layer43are examples of the “first conductive type third semiconductor layer”, the “second active layer” and the “second conductive type fourth semiconductor layer” in the present invention, respectively.

The third semiconductor layer may include other semiconductor layer such as a light guide layer (not shown) or a carrier blocking layer (not shown) between the n-type AlGaN cladding layer41and the active layer42. The third semiconductor layer may include other semiconductor layer such as a contact layer (not shown) on a side of the n-type AlGaN cladding layer42opposite to the active layer41. The fourth semiconductor layer may include other semiconductor layer such as a light guide layer (not shown) or a carrier blocking layer (not shown) between the active layer42and the p-type AlGaN cladding layer43. The fourth semiconductor layer may include other semiconductor layer such as a contact layer (not shown) on a side of the p-type AlGaN cladding layer43opposite to the active layer42. The active layer42may have a single-layer or single quantum well (SQW).

As shown inFIG. 1, the n-type AlGaN cladding layer41is provided with a ridge portion41a having a width of about 1.5 μm, extending in the direction A (seeFIG. 2) which is the direction perpendicular to the drawing, thereby forming a waveguide structure. As shown inFIG. 1, insulating films44made of SiO2are formed on a surface of the n-type AlGaN cladding layer41except the ridge portion41a. An n-side electrode45is formed on upper surfaces of the ridge portion41aof the n-type AlGaN cladding layer41and the insulating films44. The n-side electrode45is an example of the “first electrode” in the present invention. A contact layer (not shown) or the like having a smaller band gap than the n-type AlGaN cladding layer41may be preferably formed between the ridge portion41aand the n-side electrode45. The n-side electrode45is formed by stacking an Al layer having a thickness of about 10 nm and a Pd layer having a thickness of about 20 nm and has an outer most surface coated with an Au layer having a thickness of about 1000 nm. As shown inFIG. 1, a p-side electrode46formed by stacking a Pt layer, a Pd layer and an Au layer successively from the p-type AlGaN cladding layer43is formed on a lower surface of the p-type AlGaN cladding layer43. The n-side electrode46is an example of the “second electrode” in the present invention. A contact layer (not shown) or the like having a smaller band gap than the p-type AlGaN cladding layer43may be preferably formed between the p-type AlGaN cladding layer43and the p-side electrode46. As shown inFIG. 1, the lower surface of the p-side electrode46and an upper surface of an electrode layer73formed on the base70are bonded to each other.

According to the first embodiment, a step portion51ahaving a bottom51breaching the n-type GaAs substrate51is formed on a region held between the infrared semiconductor laser element10and the red semiconductor laser element20of the monolithic two-wavelength semiconductor laser element portion30, as shown inFIG. 1. An electrode layer53is formed on the bottom51bof the step portion51a. The blue-violet semiconductor laser element40is bonded to the n-type GaAs substrate51in a state where the n-type AlGaN cladding layer41is electrically connected to the bottom51bof the step portion51athrough the fusible layer60.

As shown inFIG. 1, isolation grooves51creaching the n-type GaAs substrate51are formed on sides (both side ends of the element portion) where the step portion51ais not formed among the monolithic two-wavelength semiconductor laser element portion30. These isolation grooves51care provided for dividing three-wavelength semiconductor laser element portions50to be in the form of chips (second cleavage) along the isolation grooves51cin a manufacturing process of the semiconductor laser device100described later.

According to the first embodiment, emission regions (around the active layers12and22) of the infrared semiconductor laser element10and the red semiconductor laser element20and an emission region (around the active layer42) of the blue-violet semiconductor laser element40are arranged at prescribed intervals in a direction along substantially the same plane (on positions in a thickness direction of each semiconductor layer (direction C inFIG. 1), where distances H of the emission regions from the upper surface of the n-type GaAs substrate51are substantially equal), as shown inFIG. 1.

As shown inFIGS. 1 and 2, the electrode layers71,72and73are formed on an upper surface of the base70. The electrode layers71,72and73are electrically separated from each other. The electrode layer71is formed on a region corresponding to a position of the p-side electrode15of the infrared semiconductor laser element10. The electrode layer72is formed on a region corresponding to a position of the p-side electrode25of the red semiconductor laser element20. The electrode layer73is formed on a region corresponding to a position of the p-side electrode46of the blue-violet semiconductor laser element40.

A metal underlayer74formed by a Ti layer having a thickness of about 100 nm and a Pt layer having a thickness of about 200 nm and an Au layer having a thickness of about 300 nm is formed on an overall lower surface of the base70. The metal underlayer74is provided for bonding a conductive bonding layer2made of a metal layer such as AuSn solder to the base70. The base70is fixed to a stem made of a metal such as copper or iron (not shown) through the conductive bonding layer2.

As shown inFIGS. 1 and 2, the electrode layers71,72and73have regions (where the laser elements are not bonded to the upper surfaces of the electrode layers) projecting from the infrared semiconductor laser element10, the red semiconductor laser element20and the blue-violet semiconductor laser element40in plan view, on the base70respectively. An Au wire90is wire-bonded to the upper surface of the projecting region of the electrode layer71provided on the infrared semiconductor laser element10and an Au wire91is wire-bonded to the upper surface of the projecting region of the electrode layer72provided on the red semiconductor laser element20. As shown inFIG. 2, an Au wire92is wire-bonded to the upper surface of the projecting region of the electrode layer73provided on the blue-violet semiconductor laser element40. As shown inFIGS. 1 and 2, an Au wire93is wire-bonded to a prescribed region of the upper surface of the n-side electrode52provided on the n-type GaAs substrate51. The Au wires90,91and92of the semiconductor laser device100are provided for connecting lead terminals (anode terminals: not shown) of the stem (not shown), and the Au wire93is provided for connecting a lead terminal (cathode terminal: not shown) of the stem (not shown). Thus, the semiconductor laser device100according to the first embodiment is so formed that a current can be individually supplied from the lead terminals on anode sides to the respective semiconductor laser elements and the respective semiconductor laser elements are connected in a common cathode type (n-side common electrode).

The infrared semiconductor laser element10, the red semiconductor laser element20and the blue-violet semiconductor laser element40constituting the three-wavelength semiconductor laser element portion50are provided with light emitting surfaces10a,20aand40aand light reflecting surfaces10b,20band40bon both ends of the extensional direction (direction A) of a cavity respectively, as shown inFIG. 2. According to the first embodiment, the light emitting surfaces10a,20aand40aand the light reflecting surfaces10b,20band40bare distinguished from each other through the high-low direction between the intensity levels of laser beams emitted from cavity facets respectively. In other words, the light emitting surfaces boa,20aand40ahave relatively higher laser beam intensity, and the light reflecting surfaces10b,20band40bhave relatively lower laser beam intensity. The light emitting surfaces10a,20aand40aand the light reflecting surfaces10b,20band40bof the respective semiconductor laser elements are formed with the dielectric multilayer films (not shown) made of AlN or Al2O3by cavity facet coating treatment in the manufacturing process, respectively.

The manufacturing process of the semiconductor laser device100according to the first embodiment will be now described with reference toFIGS. 1 and 3to11.

In the manufacturing process for the semiconductor laser device100according to the first embodiment, wafer-state three-wavelength semiconductor laser element portions50are formed by a “forming step of monolithic two-wavelength semiconductor laser element portions” and a “forming step of blue-violet semiconductor laser element” and thereafter a “bonding step of semiconductor laser elements”, and a “separation step of a growth substrate” and an “electrode forming step”. Thereafter the three-wavelength semiconductor laser element portion50as a component is formed by a “cleavage plane forming step” and a “mounting step”. The detailed description of the respective steps will be hereinafter described in order.

In the “forming step of monolithic two-wavelength semiconductor laser element portions”, the infrared semiconductor laser elements10and the red semiconductor laser elements20are formed on the upper surface of the n-type GaAs substrate51at prescribed intervals, as shown inFIG. 3. Then the step portions51aand the isolation grooves51care formed by etching. The step portions51aand the isolation grooves51care formed such that the depths thereof reach the n-type GaAs substrate51. Thereafter the p-type AlGaAs cladding layers13and the p-type AlGaInP cladding layers23are formed with the ridge portions13aand23aby etching respectively, and the insulating films14and24made of SiO2are formed on the upper surfaces of the p-type AlGaAs cladding layers13and p-type AlGaInP cladding layers23except the ridge portions13aand23arespectively. The p-side electrodes15(p-side electrodes25) each having an outermost surface made of an Au film are formed on the upper surfaces of the ridge portions13a(ridge portions23a) and the insulating films14(insulating films24) by vacuum evaporation.

As shown inFIG. 4, the electrode layers53are formed on the step portions51aof the n-type GaAs substrate51by vacuum evaporation and the fusible layers60are formed on the electrode layers53. The monolithic two-wavelength semiconductor laser element portions30are manufactured in the aforementioned manner.

In the “forming step of blue-violet semiconductor laser elements”, an InGaN separative layer81, the p-type AlGaN cladding layer43, the active layer42and the n-type AlGaN cladding layer41are successively stacked on the upper surface of the n-type GaN substrate80, thereby forming the blue-violet semiconductor laser elements40, as shown inFIG. 5. The ridge portions41aare formed on the upper surface of the n-type AlGaN cladding layer41by etching and thereafter the insulating films44made of SiO2are formed on the upper surface of the n-type AlGaN cladding layer41except the ridge portions41a. Then the n-side electrodes45each having an outermost surface made of an Au film are formed on the upper surfaces of the ridge portions41aand the insulating films44by vacuum evaporation. The n-type GaN substrate80is an example of the “growth substrate” in the present invention.

Thereafter step portions80aare formed by etching as shown inFIG. 6. The step portions80aare so formed as to reach the n-type GaN substrate80. The blue-violet semiconductor laser elements40are formed in the aforementioned manner.

In the “bonding step of semiconductor laser elements”, the electrode layers53provided on the step portions51aof the monolithic two-wavelength semiconductor laser element portions30and the n-side electrodes45of the blue-violet semiconductor laser elements40formed on the n-type GaN substrate80are opposed and bonded to each other through the fusible layers60with a load of about 100 N at a temperature of about 295° C., as shown inFIG. 7.

In the “separation step of a growth substrate”, second harmonics of an Nd:YAG laser beam (wavelength: about 532 nm), adjusted to energy density of about 500 mJ/cm2to about 1000 mJ/cm2is applied to the n-type GaN substrate80from a back surface of the n-type GaN substrate80(upper surface of the n-type GaN substrate80inFIG. 8), as shown inFIG. 8. The binding of crystals of InGaN separative layers81stacked therein is totally or locally destroyed by the irradiation of the laser beam. Thus, the n-type GaN substrate80can be easily separated from the blue-violet semiconductor laser elements40along the breakdown region of the InGaN separative layers81. The n-type GaN substrate80after separation is used as the growth substrate for forming the blue-violet semiconductor laser elements40again by flattening unevenness on the surfaces formed with the step portions80a(seeFIG. 6) and the InGaN separative layer81by polishing the surfaces.

In the “electrode forming step”, the p-side electrodes46are formed on the upper surfaces of the p-type AlGaN cladding layer43exposed on the upper surfaces of the blue-violet semiconductor laser element40through the “separation step of a growth substrate”, by vacuum evaporation, as shown inFIG. 9. The thickness of the n-type GaAs substrate51forming the monolithic two-wavelength semiconductor laser element portions30is reduced by a prescribed thickness by etching and thereafter the n-side electrode52is formed on the (overall) surface of the n-type GaAs substrate51by vacuum evaporation. The wafer-state three-wavelength semiconductor laser element portion50is formed in the aforementioned manner.

According to the first embodiment, the three-wavelength semiconductor laser element portions50are formed through the aforementioned manufacturing process, whereby the n-type AlGaN cladding layers41of the blue-violet semiconductor laser elements40are rendered conductive through the step portions51awhile having the same polarity (n-type) as the n-type GaAs substrate51and hence the three-wavelength semiconductor laser element portions50each having a simplified inner structure can be formed.

In the “cleavage plane forming step”, scribe lines800(alternate long and short dash lines) are lined at cavity length pitches in a direction (direction B) perpendicular to the extensional direction (direction A) of the cavities by laser scribing, and the wafer-state three-wavelength semiconductor laser element portions50are cleaved along the scribe line800, as shown inFIG. 10. Thus, the three-wavelength semiconductor laser element portions50are so divided as to be in the form of bars (seeFIG. 10) and the light emitting surfaces10a,20aand40aand the light reflecting surfaces10b,20band40bare formed on the both ends in the extensional direction (direction A) of the cavities, as shown inFIG. 2.

Thereafter dielectric multilayer films (oxide films, etc.) (not shown) are formed on cavity facets (the light emitting surfaces10aand the light reflecting surfaces10b(seeFIG. 2) of the infrared semiconductor laser elements10, the light emitting surfaces20aand the light reflecting surfaces20b(seeFIG. 2) of the red semiconductor laser elements20and the light emitting surfaces40aand the light reflecting surfaces40bof the blue-violet semiconductor laser elements40(seeFIG. 2)) of the three-wavelength semiconductor laser element portions50by facet coating treatment. As shown inFIG. 11, element division is performed along the isolation grooves51c(seeFIG. 10) of the bar-state three-wavelength semiconductor laser element portions50in the extensional direction (direction A inFIG. 10) of the cavities in a manner similar to the aforementioned manner. Thus, the individual three-wavelength semiconductor laser element portions50in the form of chips.

In the “mounting step”, each three-wavelength semiconductor laser element portion50is bonded to the base70as shown inFIG. 1. The p-side electrodes14,24and46of the three-wavelength semiconductor laser element portion50are arranged so as to be opposed to the electrode layers71,72and73on the upper surface of the base70arranged with the conductive bonding layers1on prescribed regions (upper surfaces of the electrode layers71,72and73). The three-wavelength semiconductor laser element portion50is pressed against the base70through the conductive bonding layers1with a collet (not shown) made of ceramics, thereby melting the conductive bonding layers1. Thereafter the conductive bonding layers1are solidified and the three-wavelength semiconductor laser element portion50is fixed on the base70through the conductive bonding layers1.

The semiconductor laser device100(seeFIG. 1) comprising the three-wavelength semiconductor laser element portion50(seeFIG. 1) according to the first embodiment is formed in the aforementioned manner.

According to the first embodiment, as hereinabove described, the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40is bonded to the n-type GaAs substrate51through the fusible layer60so as to be electrically connected to the n-type AlGaAs cladding layer11of the infrared semiconductor laser element10and the n-type AlGaInP cladding layer21of the red semiconductor laser element20, whereby the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40has the same polarity (common negative polarity) as the n-type GaAs substrate51forming the infrared semiconductor laser element10and the red semiconductor laser element20and hence no insulating layer for preventing an electrical short circuit between the n-type GaAs substrate51and the n-type AlGaN cladding layer41may be provided. Thus, the inner structure of the three-wavelength semiconductor laser element portion50in which the infrared and red semiconductor laser elements10and20and the blue-violet semiconductor laser element40are connected to each other in a common cathode type can be simplified. In particular, when a multiple wavelength semiconductor laser element is applied to an optical pickup system, the semiconductor laser elements are preferably employed in the common cathode type (as an n-side common electrode) and hence the semiconductor laser device100according to the first embodiment can be easily built into the optical pickup system.

According to the first embodiment, the step portion51ahaving the bottom51breaching the n-type GaAs substrate51is formed on the region held between the infrared semiconductor laser element10and the red semiconductor laser element20and the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40is bonded to the bottom51bof the step portion51athrough the fusible layer60, whereby the infrared and red semiconductor laser elements10and20and the blue-violet semiconductor laser element40can be easily connected to each other in the common cathode type.

According to the first embodiment, the active layer12of the infrared semiconductor laser element10, the active layer22of the red semiconductor laser element20and the active layer42of the blue-violet semiconductor laser element40are arranged at prescribed intervals in the direction along substantially the same plane (on positions in a thickness direction of each semiconductor layer (direction C inFIG. 1), where distances H of the emission regions from the upper surface of the n-type GaAs substrate51are substantially equal, whereby the emission region of each semiconductor laser element (10,20,40) can be arranged on substantially the same plane surface and hence light from the semiconductor laser elements (10,20,40) can be emitted at emission positions in substantially the same straight line. Thus, when the semiconductor laser device100is applied to the optical pickup system, light emitted from each semiconductor laser element can be incident at substantially the same angle with respect to (in a direction perpendicular to) a recording surface of an optical disk and hence optical spot quality of the semiconductor laser element in each recording medium can be inhibited from dispersion.

According to the first embodiment, the n-type AlGaAs cladding layer11, the active layer12and the p-type AlGaAs cladding layer13of the infrared semiconductor laser element10and the n-type AlGaInP cladding layer21, the active layer22and the p-type AlGaInP cladding layer23of the red semiconductor laser element20are formed by a compound semiconductor layer containing arsenic or phosphorus, and the n-type AlGaN cladding layer41, the active layer42and the p-type AlGaN cladding layer43of the blue-violet semiconductor laser element40are formed by a nitride-based compound semiconductor, whereby the three-wavelength semiconductor laser element portion50can be constituted by the monolithic two-wavelength semiconductor laser element portion30emitting an infrared laser beam and an red laser beam and the blue-violet semiconductor laser element40emitting a laser beam having a wavelength different from the monolithic two-wavelength semiconductor laser element portion30.

According to the first embodiment, the semiconductor laser device100further comprises the base70for mounting the infrared semiconductor laser element10, the red semiconductor laser element20and the blue-violet semiconductor laser element40constituting the three-wavelength semiconductor laser element portion50, and the infrared semiconductor laser element10, the red semiconductor laser element20and the blue-violet semiconductor laser element40are fixed such that the p-type cladding layers (the p-type AlGaAs cladding layer13, the p-type AlGaInP cladding layer23and the p-type AlGaN cladding layer43) are fixed on the base70, whereby heat generated from the three-wavelength semiconductor laser element portion50by emission of laser beams in a laser operation can be effectively radiated through the base70having more excellent radiation performance than the n-type GaAs substrate51.

According to the first embodiment, the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40is bonded to the n-type GaAs substrate51through the fusible layer60made of AuSn solder so as to be electrically connected to the n-type GaAs substrate51, whereby the active layer42of the blue-violet semiconductor laser element40and the active layers12and22of the infrared semiconductor laser element10and the red semiconductor laser element20can be easily on the same plane surface by controlling the thickness of the fusible layer60when the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40is bonded to the n-type GaAs substrate51.

According to the first embodiment, the n-side electrode45and the p-side electrode46are formed on the blue-violet semiconductor laser element40, whereby bondability between the n-side electrode45and the fusible layer60can be improved when bonding the blue-violet semiconductor laser element40to the monolithic two-wavelength semiconductor laser element portion30. Additionally bondability between the p-side electrode46and the conductive bonding layers1can be improved when bonding the three-wavelength semiconductor laser element portion50to the base70.

(First Modification of First Embodiment)

In the semiconductor laser device150according to a first modification of the first embodiment, an isolation groove51dreaching an n-type GaAs substrate51is formed on a region held between an infrared semiconductor laser element10and a red semiconductor laser element20of a monolithic two-wavelength semiconductor laser element portion31and a step portion11ahaving a bottom11bis formed on an n-type AlGaAs cladding layer11of the infrared semiconductor laser element10as shown inFIG. 12, dissimilar to the aforementioned first embodiment. An electrode layer53is formed on the bottom11bof the step portion11a. Thus, the blue-violet semiconductor laser element40is bonded to the n-type AlGaAs cladding layer11in a state where the n-type AlGaN cladding layer41is electrically connected to the bottom11bof the step portion11athrough a fusible layer60. The remaining structure and manufacturing process of a three-wavelength semiconductor laser element portion31according to the first modification of the first embodiment are similar to those of the aforementioned first embodiment.

According to the first modification, as hereinabove described, the step portion11ahaving the bottom11bis formed on the n-type AlGaAs cladding layer11of the infrared semiconductor laser element10and the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40is bonded to the bottom11bof the step portion11athrough the fusible layer60, whereby the infrared and red semiconductor laser elements10and20and the blue-violet semiconductor laser element40can be easily connected to each other in a cathode common type similarly to the aforementioned first embodiment. The remaining effects of the first modification of the aforementioned first embodiment are also similar to those of the aforementioned first embodiment.

While the step portion11ais formed on the n-type AlGaAs cladding layer11of the infrared semiconductor laser element10in the aforementioned first modification of the first embodiment, a step portion may be formed on an n-type AlGaInP cladding layer21of the red semiconductor laser element20and an n-type AlGaN cladding layer41of a blue-violet semiconductor laser element40may be bonded to the step portion through an fusible layer60.

(Second Modification of First Embodiment)

In a semiconductor laser device200according to a second modification of the first embodiment, a two-wavelength semiconductor laser element portion250, in which a blue-violet semiconductor laser element40is bonded to a red semiconductor laser element20formed on an n-type GaAs substrate251through an fusible layer60, is fixed to a base70through conductive bonding layers1made of a metal layer such as AuSn solder as shown inFIG. 13, dissimilarly to the aforementioned first embodiment. The n-type GaAs substrate251is an example of the “first conductive substrate” in the present invention.

The remaining structure and manufacturing process of the two-wavelength semiconductor laser element portion250according to the second modification of the first embodiment are similar to those of the aforementioned first embodiment.

According to the second modification, as hereinabove described, the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40is bonded on the n-type GaAs substrate251through the fusible layer60so as to be electrically connected to the n-type AlGaInP cladding layer21of the red semiconductor laser element20, whereby the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40has the same polarity (common negative polarity) as the n-type GaAs substrate251of the red semiconductor laser element20and hence no insulating layer for preventing an electrical short circuit between the n-type GaAs substrate251and the n-type AlGaN cladding layer41may be provided. Thus, the inner structure of the two-wavelength semiconductor laser element portion250in which the red semiconductor laser element20and the blue-violet semiconductor laser element40are connected to each other in a common cathode type can be simplified similarly to the aforementioned first embodiment. The remaining effects of the second modification of the first embodiment are similar to those of the aforementioned first embodiment.

In a semiconductor laser device300according to a second embodiment, a three-wavelength semiconductor laser element portion350, in which a blue-violet semiconductor laser element40is bonded to a surface of a region held between an infrared semiconductor laser element10and a red semiconductor laser element20through an fusible layer60, is fixed to a base370through conductive bonding layers1made of metal layers such as AuSn solder. The semiconductor laser device300according to the second embodiment will be described with reference toFIG. 14. The base370is an example of the “heat radiator base” in the present invention.

According to the second embodiment, a conduction portion352reaching from a surface (electrode layer353) of a semiconductor layer to an n-type GaAs substrate351is provided on a inner portion (inner surface of a hole351b) of the region held between the infrared semiconductor laser element10and the red semiconductor laser element20, as shown inFIG. 14. Thus, the blue-violet semiconductor laser element40is electrically connected to the n-type GaAs substrate351through the fusible layer60, the electrode layer353and the conduction portion352. The n-type GaAs substrate351is an example of the “first conductive substrate” in the present invention and the conduction portion352is an example of the “connection region” in the present invention.

According to the second embodiment, a recessed step portion370bis formed on a surface of the base370to which the blue-violet semiconductor laser element40is bonded, by etching, as shown inFIG. 14. An electrode layer73is formed on a bottom370cof the step portion370b. Thus, the blue-violet semiconductor laser element40having a projecting shape in the three-wavelength semiconductor laser element portion350is bonded to the base370through the conductive bonding layers1in a state of entering in the recessed step portion370bof the base370.

The remaining structure of the semiconductor laser device300according to the second embodiment is similar to that of the aforementioned first embodiment.

A manufacturing process of the semiconductor laser device300according to the second embodiment will be now described with reference toFIGS. 14 to 20.

In a “forming step of a monolithic two-wavelength semiconductor laser element portion”. the infrared semiconductor laser elements10and the red semiconductor laser elements20are formed on an upper surface of the n-type GaAs substrate351through a manufacturing process similar to that of the aforementioned first embodiment, as shown inFIG. 15.

According to the second embodiment, pairs of insulating grooves351aand the holes351band isolation grooves351care formed on the regions held between the infrared semiconductor laser elements10and the red semiconductor laser elements20by etching as shown inFIG. 16. The pairs of insulating grooves351aand the holes351bare formed such that the depths thereof reach the n-type GaAs substrate351. Thereafter the conduction portions352are formed on the inner surfaces of the holes351bby vacuum evaporation as shown inFIG. 16.

As shown inFIG. 17, the electrode layers353are formed on the conduction portions352of the n-type GaAs substrate351by vacuum evaporation and the fusible layers60are formed on the electrode layers353. Thus, the n-type GaAs substrate351can be electrically connected to the fusible layers60through the conduction portions352and the electrode layers353. A monolithic two-wavelength semiconductor laser element portion330is formed in the aforementioned manner.

In a “bonding step of semiconductor laser elements”, the blue-violet semiconductor laser elements40formed through a manufacturing process similar to that of the aforementioned first embodiment and the electrode layer353of the monolithic two-wavelength semiconductor laser element portion330are opposed and bonded to each other through the fusible layers60with a load of about 100 N at a temperature of about 295° C., as shown inFIG. 18

In a “separation step of a growth substrate”, second harmonics of an Nd:YAG laser beam (wavelength: about 532 run) is applied to the n-type GaN substrate80from a back surface of the n-type GaN substrate80(upper surface of the n-type GaN substrate80inFIG. 19), whereby the n-type GaN substrate80is separated from the blue-violet semiconductor laser elements40along the breakdown region of the InGaN separative layers81, as shown inFIG. 19.

As shown inFIG. 20, p-side electrodes46are formed on upper surfaces of the p-type AlGaN cladding layers43exposed on upper surfaces of the blue-violet semiconductor laser element40by vacuum evaporation. The thickness of the n-type GaAs substrate351of the monolithic two-wavelength semiconductor laser element portion330is reduced by a prescribed thickness by etching and thereafter the n-side electrode52is formed on the (overall) surface of the n-type GaAs substrate351by vacuum evaporation. The wafer-state three-wavelength semiconductor laser element portion350is formed in the aforementioned manner.

According to the second embodiment, the three-wavelength semiconductor laser element portion350is formed through the aforementioned manufacturing process, whereby the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40conducts with the n-type GaAs substrate351through the conduction portion352electrically connecting to the n-type GaAs substrate351formed on the region (semiconductor layer) held between the infrared semiconductor laser element10and the red semiconductor laser element20of the monolithic two-wavelength semiconductor laser element portion330while having the same polarity (n-type) as the n-type GaAs substrate351, and hence the three-wavelength semiconductor laser element portion350having a simplified inner structure can be formed.

In the remaining manufacturing process such as an “electrode forming step” and the like is similar to that of the aforementioned first embodiment.

The semiconductor laser device300(seeFIG. 14) comprising the three-wavelength semiconductor laser element portion350(seeFIG. 14) according to the second embodiment is formed in the aforementioned manner.

According to the second embodiment, as hereinabove described, the conduction portion352and the electrode layer353covered with semiconductor layer and the electrically conducting with the n-type GaAs substrate351are provided on the surface of the region (semiconductor layer) held between the infrared semiconductor laser element10and the red semiconductor laser element20and the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40is bonded to the electrode layer353through the fusible layer60, whereby the infrared and red semiconductor laser elements10and20and the blue-violet semiconductor laser element40can be easily connected in the cathode common type without providing a step portion reaching the n-type GaAs substrate351on the region (semiconductor layer) held between the infrared semiconductor laser element10and the red semiconductor laser element20.

The remaining effects of the second embodiment are similar to those of the aforementioned first embodiment.

(First Modification of Second Embodiment)

In a semiconductor laser device400according to a first modification of the second embodiment, electrode layers401and402each having a thickness corresponding to the thickness (height) of a blue-violet semiconductor laser element40are formed on regions bonded with an infrared semiconductor laser element10and a red semiconductor laser element20in an upper surface of a flat base470with no etching so that the base470is formed to have a recess portion, as shown inFIG. 21, dissimilarly to the aforementioned second embodiment. Thus, a three-wavelength semiconductor laser element portion350having a projecting shape corresponding to a portion of the blue-violet semiconductor laser element40is bonded to the base470. The base470is an example of the “heat radiator base” in the present invention.

The remaining structure of the three-wavelength semiconductor laser element portion350according to the first modification of the second embodiment is similar to that of the aforementioned second embodiment.

(Second Modification of Second Embodiment)

In a semiconductor laser device500according to a second modification of the second embodiment, insulating films501and502made of SiO2each having a thickness corresponding to the thickness (height) of a blue-violet semiconductor laser element40are formed on regions bonded with an infrared semiconductor laser element10and a red semiconductor laser element20in an upper surface of a flat base470respectively and electrode layers71and72each having a thickness similar to the second embodiment are formed on upper surfaces of the insulating films501and502respectively so that the base470is formed to have a recess portion, as shown inFIG. 22, dissimilarly to the aforementioned second embodiment. Thus, a three-wavelength semiconductor laser element portion350having a projecting shape which is a portion of the blue-violet semiconductor laser element40is bonded to the base470.

The remaining structure of the three-wavelength semiconductor laser element portion350according to the second modification of the second embodiment is similar to that of the aforementioned second embodiment.

(Third Modification of Second Embodiment)

In a semiconductor laser device600according to a third modification of the second embodiment, an electrode layer601is formed on an overall upper surface of a flat base470and insulating films602and603made of SiO2each having a thickness corresponding to the thickness (height) of a blue-violet semiconductor laser element40are formed on regions bonded with an infrared semiconductor laser element10and a red semiconductor laser element20respectively as shown inFIG. 23, dissimilarly to the aforementioned second embodiment. Electrode layers71and72each having a thickness similar to the second embodiment are formed on upper surfaces of the insulating films602and603respectively so that the base470is formed to have a recess portion. Thus, a three-wavelength semiconductor laser element portion350having a projecting shape which is a portion of the blue-violet semiconductor laser element40is bonded to the base470.

The remaining structure of the three-wavelength semiconductor laser element portion350according to the third modification of the second embodiment is similar to that of the aforementioned second embodiment.

According to the first to third modifications of the second embodiment, the semiconductor laser devices400,500and600comprising three-wavelength semiconductor laser element portions350having simplified inner structures can be formed in the aforementioned manner similarly to the aforementioned second embodiment. The remaining effects of the first to third modifications of the second embodiment are similar to those of the aforementioned second embodiment.

(Fourth Modification of Second Embodiment)

In a semiconductor laser device650according to a fourth modification of the second embodiment, an isolation groove351dreaching an n-type GaAs substrate351and a hole351ereaching an n-type AlGaAs cladding layer11of the infrared semiconductor laser element10are formed on a region held between the infrared semiconductor laser element10and the red semiconductor laser element20of a monolithic two-wavelength semiconductor laser element portion331as shown inFIG. 24, dissimilarly to the aforementioned second embodiment. A conduction portion355reaching from a surface of a semiconductor layer (electrode layer353) to the n-type AlGaAs cladding layer11is provided on an inner surface of the hole351e. Thus, the blue-violet semiconductor laser element40is electrically connected to the n-type AlGaAs cladding layer11through an fusible layer60, the electrode layer353and the conduction portion355. The conduction portion355is an example of the “connection region” in the present invention. The remaining structure and manufacturing process of the three-wavelength semiconductor laser element portion350according to the fourth modification of the second embodiment is similar to those of the aforementioned first embodiment.

According to the fourth modification of the second embodiment, the conduction portion355and the electrode layer353electrically conducting with the n-type AlGaAs cladding layer11of the infrared semiconductor laser element10are provided on the surface of the region (semiconductor layer) held between the infrared semiconductor laser element10and the red semiconductor laser element20and the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40is bonded to the electrode layer353through the fusible layer60, whereby the infrared and red semiconductor laser elements10and20and the blue-violet semiconductor laser element40can be easily connected in a cathode common type similarly to the aforementioned second embodiment. The remaining effects of the fourth modification of the second embodiment are also similar to those of the aforementioned second embodiment.

While the hole351ereaching the n-type AlGaAs cladding layer11is provided on the infrared semiconductor laser element10in the aforementioned fourth modification of the second embodiment, the present invention is not restricted to this, but a hole and a conduction portion reaching the n-type AlGaInP cladding layer21may be provided on the red semiconductor laser element20and the n-type AlGaN cladding layer41of the blue-violet semiconductor laser element40may be electrically connected to the conduction portion through the fusible layer60.

In a semiconductor laser device700according to a third embodiment, an RGB multiple wavelength semiconductor laser element portion750, in which a blue semiconductor laser element710having a lasing wavelength of about 450 nm and a green semiconductor laser element720having a lasing wavelength of about 532 nm are bonded to a red semiconductor laser element20formed on an n-type GaAs substrate751through fusible layers60, is fixed to a base70through a conductive bonding layer1made of a metal layer such as AuSn solder as shown inFIG. 25, dissimilarly to the aforementioned first embodiment. The n-type GaAs substrate751is an example of the “first conductive substrate” in the present invention and the blue semiconductor laser element710and the green semiconductor laser element720are each an example of the “second semiconductor laser element” in the present invention.

The blue semiconductor laser element710is constituted by an n-type AlGaN cladding layer711, an active layer712having an MQW structure and a p-type AlGaN cladding layer713, as shown inFIG. 25. The n-type AlGaN cladding layer711is provided with a ridge portion711aextending in a direction A (seeFIG. 2) which is a direction perpendicular to the drawing. Insulating films714are formed on a surface of the n-type AlGaN cladding layer711except the ridge portion711ain addition to the aforementioned structure. An n-side electrode715is formed on upper surfaces of the ridge portion711aof the n-type AlGaN cladding layer711and the insulating films714. A p-side electrode716is formed on a lower surface of the p-type AlGaN cladding layer713. As shown inFIG. 25, a lower surface of the p-side electrode716and an upper surface of the electrode layer73formed on the base70are bonded to each other. The n-type AlGaN cladding layer711, the active layer712and the p-type AlGaN cladding layer713are examples of the “first conductive type third semiconductor layer”, the “second active layer” and the “second conductive type fourth semiconductor layer” in the present invention respectively. The n-side electrode715and the p-side electrode716are examples of the “first electrode” and the “second electrode” in the present invention respectively.

The green semiconductor laser element720is constituted by an n-type AlGaN cladding layer721, an active layer722having an MQW structure and a p-type AlGaN cladding layer723, as shown inFIG. 25. The n-type AlGaN cladding layer721is provided with a ridge portion721aextending in the direction A (seeFIG. 2) which is the direction perpendicular to the drawing. Insulating films724are formed on a surface of the n-type AlGaN cladding layer721except the ridge portion721ain addition to the aforementioned structure. An n-side electrode725is formed on upper surfaces of the ridge portion721aof the n-type AlGaN cladding layer721and the insulating films724. A p-side electrode726is formed on a lower surface of the p-type AlGaN cladding layer723. As shown inFIG. 25, a lower surface of the p-side electrode726and an upper surface of the electrode layer73formed on the base70are bonded to each other.

The n-type AlGaN cladding layer721, the active layer722and the p-type AlGaN cladding layer723are examples of the “first conductive type third semiconductor layer”, the “second active layer” and the “second conductive type fourth semiconductor layer” in the present invention respectively. The n-side electrode725and the p-side electrode726are examples of the “first electrode” and the “second electrode” in the present invention respectively.

As shown inFIG. 25, the blue semiconductor laser element710and the green semiconductor laser element720are formed with light emitting surfaces710aand720arespectively. The remaining structure of the semiconductor laser device700according to the third embodiment is similar to that of the aforementioned first embodiment.

A manufacturing process of the semiconductor laser device700according to the third embodiment will be now described with reference toFIGS. 25 to 28.

As shown inFIG. 26, the red semiconductor laser elements20are formed on the upper surface of the n-type GaAs substrate751through a manufacturing process similar to the manufacturing process of the aforementioned first embodiment. The p-side electrodes25each having an outermost surface made of an Au film are formed on the upper surfaces of the ridge portions23aand the insulating films24of the red semiconductor laser element20by vacuum evaporation.

As shown inFIG. 26, the blue semiconductor laser elements710formed through a manufacturing process similar to that of the aforementioned first embodiment and the electrode layers53provided on bottoms751bof step portions751aof the n-type GaAs substrate751are opposed and bonded to each other through the fusible layers60with a load of about 100 N at a temperature of about 295° C. The n-type GaN substrate80is separated from the blue-violet semiconductor laser elements710along the breakdown region of InGaN separative layers81with second harmonics of an Nd:YAG laser beam.

As shown inFIG. 27, the green semiconductor laser element720formed through a manufacturing process similar to that of the aforementioned first embodiment and the electrode layers53provided on step portions751aof the n-type GaAs substrate751are opposed and bonded to each other, similarly to the blue-violet semiconductor laser elements40. The n-type GaN substrate780is separated from the green semiconductor laser element720along the breakdown region of the InGaN separative layers781with second harmonics of an Nd:YAG laser beam.

As shown inFIG. 28, p-side electrodes716and726are formed on upper surfaces of the p-type AlGaN cladding layer713and723exposed on upper surfaces of the blue semiconductor laser elements710and the green semiconductor laser elements720by vacuum evaporation, respectively. The thickness of the n-type GaAs substrate751is reduced by a prescribed thickness by etching and thereafter the n-side electrode52is formed on the n-type GaAs substrate751by vacuum evaporation.

The remaining manufacturing process of the third embodiment is similar to that of the aforementioned first embodiment. Thus, the semiconductor laser device700(seeFIG. 25) comprising the RGB multiple wavelength semiconductor laser element portion750(seeFIG. 25) according to the third embodiment is formed in the aforementioned manner. The effects of the third embodiment are similar to those of the aforementioned first embodiment.

Referring toFIGS. 1 and 29, the cavity length of a blue-violet semiconductor laser element440is smaller than the cavity lengths of an infrared semiconductor laser element10and a red semiconductor laser element20in a fourth embodiment, dissimilarly to the aforementioned first embodiment. The blue-violet semiconductor laser element440is an example of the “second semiconductor laser element” in the present invention.

In a three-wavelength semiconductor laser element portion450according to the fourth embodiment, the cavity lengths L1of the infrared semiconductor laser element10and the red semiconductor laser element20are about 2 mm, while the cavity length L2of the blue-violet semiconductor laser element440is about 1 mm, as shown inFIG. 29. Light emitting surfaces (light emitting surfaces10a,20aand440a) of the respective semiconductor laser elements are arranged on substantially the same plane. Therefore, a region of a step portion51b, bonded with no blue-violet semiconductor laser element440remains in the back of a light reflecting surface440bof the blue-violet semiconductor laser element440. The three-wavelength semiconductor laser element portion450is fixed to a base70(seeFIG. 1) in a junction-down system similarly to the aforementioned first embodiment.

The remaining structure of a semiconductor laser device100a(seeFIG. 1) according to the fourth embodiment is similar to the aforementioned first embodiment.

The manufacturing process of the semiconductor laser device100aaccording to the fourth embodiment will be now described with reference toFIGS. 1, and3to11,29and30.

Wafer-state monolithic two-wavelength semiconductor laser element portions30(seeFIG. 4) are formed through a manufacturing process similar to that of the aforementioned first embodiment shown inFIGS. 3 and 4.

Wafer-state blue-violet semiconductor laser elements440(seeFIG. 6) are formed through a manufacturing process similar to that of the aforementioned first embodiment shown inFIGS. 5 and 6.

In the manufacturing process of the fourth embodiment, step portions80ais formed by etching before a step of forming the n-side electrodes45as shownFIG. 30. A plurality of grooves47extending in a direction (direction B) perpendicular to an extensional direction of ridge portions41aare formed on prescribed positions of the blue-violet semiconductor laser elements440at prescribed intervals in the extensional direction (direction A) of the ridge portions41aby etching. At this time, the grooves47are preferably formed by removing the InGaN separative layers81from the n-type AlGaN cladding layers41toward the n-type GaN substrate80by etching. Therefore, the surface (upper surface) of the n-type GaN substrate80are exposed on the bottoms of the grooves47. Thereafter the n-side electrodes45are formed on the upper surfaces of the ridge portions41aand the insulating films44having the cavity lengths L2. Thus, a plurality of the blue-violet semiconductor laser elements440having pairs of cavity facets (the light emitting surfaces440aand the light reflecting surfaces440b) are formed on a wafer.

As shown inFIG. 7, the wafer-state blue-violet semiconductor laser elements440formed with the cavity facets are bonded to the monolithic two-wavelength semiconductor laser element portions30. The n-type GaN substrate80are separated and the p-side electrodes46are formed on the upper surfaces of the p-type AlGaN cladding layers43exposed on the upper surfaces of the blue-violet semiconductor laser elements440through a manufacturing process similar to that of the aforementioned first embodiment shown inFIGS. 8 and 9. Thereafter the wafer-state three-wavelength semiconductor laser element portions450(seeFIG. 9) are cleaved to be in the form of bars through a manufacturing process similar to the aforementioned first embodiment shown inFIG. 10. At this time, the monolithic two-wavelength semiconductor laser element portions30are cleaved such that the light emitting surface10aand20aof the monolithic two-wavelength semiconductor laser element portions30and the light emitting surfaces440aof the blue-violet semiconductor laser elements440are arranged on substantially the same plane, as shown inFIG. 29. The elements are divided through a manufacturing process similar to the aforementioned first embodiment shown inFIG. 11. A plurality of the three-wavelength semiconductor laser element portions450according to the fourth embodiment shown inFIG. 29are formed in the aforementioned manner. The remaining manufacturing process for the semiconductor laser device100a(seeFIG. 1) according to the fourth embodiment is similar to that of the aforementioned first embodiment.

According to the fourth embodiment, as hereinabove described, the plurality of semiconductor laser elements having the different cavity lengths L1and L2are bonded to each other so that the three-wavelength semiconductor laser element portion450is formed, whereby the semiconductor laser element (three-wavelength semiconductor laser element portion450) integrated in one chip is formed in consideration of the operating characteristics (light output-current characteristics or temperature characteristics) of the respective semiconductor laser element, also when the semiconductor laser elements having different lasing wavelengths are combined with each other. Thus, the operating characteristics of the semiconductor laser element can be optimized.

According to the fourth embodiment, the cavity length L2of the blue-violet semiconductor laser element440is shorter than the cavity lengths L1of the infrared semiconductor laser element10and the red semiconductor laser element20, whereby the infrared semiconductor laser element10and the red semiconductor laser element20having longer cavity lengths for reducing current density or improving temperature characteristics and the blue-violet semiconductor laser element440having a shorter cavity length for suppressing increase in a threshold current or reduction in a slop efficiency are integrated in one chip so that the three-wavelength semiconductor laser element portion450can be formed, and hence operating characteristics of the laser element of one chip can be easily optimized.

(Modification of Fourth Embodiment)

Referring toFIGS. 1,4,6,7,9,31and32, a first cavity facet of a blue-violet semiconductor laser element440is formed by etching while a second cavity facet of the blue-violet semiconductor laser element440is formed by cleavage in a modification of the fourth embodiment, dissimilarly to the manufacturing process of the aforementioned fourth embodiment.

Wafer-state monolithic two-wavelength semiconductor laser element portions30(seeFIG. 4) and wafer-state blue-violet semiconductor laser elements440(seeFIG. 6) are formed through a manufacturing process similar to that of the aforementioned fourth embodiment.

In the manufacturing process of the modification of the fourth embodiment, step portions80aare formed by etching before a step of forming the n-side electrodes45as shownFIG. 32. A plurality of grooves47extending in a direction (direction B) perpendicular to an extensional direction of ridge portions41aare formed on prescribed positions of the blue-violet semiconductor laser elements440at prescribed intervals in the extensional direction (direction A) of the ridge portions41aby etching. Thus, a plurality of wafer-state blue-violet semiconductor laser elements440having only first cavity facets (light reflecting surfaces440b, for example) are formed. Thereafter the n-side electrodes45are formed on upper surfaces of the ridge portions41aand insulating films44.

As shown inFIG. 7, the aforementioned wafer-state blue-violet semiconductor laser elements440are bonded to the monolithic two-wavelength semiconductor laser element portions30. At this time, the fusible layers60are previously formed only on regions of the electrode layers53of the monolithic two-wavelength semiconductor laser element portions30, bonded with the blue-violet semiconductor laser elements440. Then the n-type GaN substrate80is separated similarly to the aforementioned fourth embodiment. The p-side electrodes46are formed on upper surfaces of the p-type AlGaN cladding layers43after separation, and then wafer-state three-wavelength semiconductor laser element portions451(seeFIG. 9) are cleaved to be in the form of bars. At this time, light emitting surfaces10aand20aof the monolithic two-wavelength semiconductor laser element portions30and light emitting surfaces440aof the blue-violet semiconductor laser element440are so cleaved as to be arranged on substantially the same plane, as shown inFIG. 31, thereby forming the bar state three-wavelength semiconductor laser element portions451.FIG. 32shows an example of the blue-violet semiconductor laser elements440formed with the light emitting surfaces440acleaved together with the monolithic two-wavelength semiconductor laser element portions30at cleavage positions shown by a dotted line to be in the form of bars.

A plurality of chip-state three-wavelength semiconductor laser element portions451according to a modification of the fourth embodiment shown inFIG. 31are formed by element division. As shown inFIG. 31, a semiconductor layer440cformed with a p-side electrode46remains in the back of the light reflecting surface440bof the blue-violet semiconductor laser element440with a groove47(seeFIG. 32) therebetween. Therefore, the semiconductor layer440cformed with the p-side electrode46of the three-wavelength semiconductor laser element portion451is also bonded to a base70through the conductive bonding layers1(seeFIG. 1) when bonding the three-wavelength semiconductor laser element portion451to the base70(seeFIG. 1). The remaining manufacturing process for a semiconductor laser device100b(seeFIG. 1) according to the modification of the fourth embodiment is similar to the aforementioned first embodiment.

According to the modification of the fourth embodiment, as hereinabove described, the semiconductor layer440cis provided on the three-wavelength semiconductor laser element portion451, whereby the bonding area of the three-wavelength semiconductor laser element portion451and the base70can be ensured even when the cavity length L2of the blue-violet semiconductor laser element440is short, and hence the bonding strength between the three-wavelength semiconductor laser element portion451and the base70can be maintained.

According to the modification of the fourth embodiment, the light emitting surface440aof the blue-violet semiconductor laser element440is formed by cleavage, whereby the light emitting surface440aformed by a cleavage plane and having an improved planarity can be formed dissimilarly to the light reflecting surface440bhaving microscopic unevenness by etching. Thus, a laser beam can be stably emitted. The remaining effects of a modification of the fourth embodiment is similar those of the aforementioned fourth embodiment.

Referring toFIGS. 33 and 34, each of a plurality of blue-violet semiconductor laser elements441, previously formed in a bar state from a wafer state, is bonded to a monolithic two-wavelength semiconductor laser element portion30so that a three-wavelength semiconductor laser element portion452according to a fifth embodiment is formed, dissimilarly to the aforementioned fourth embodiment. The blue-violet semiconductor laser element441is an example of the “second semiconductor laser element” in the present invention.FIG. 34shows a sectional structure of a semiconductor laser device900formed with the three-wavelength semiconductor laser element on the base471with step on the1000-1000plane (in a direction along a cavity direction (direction A) of the three-wavelength semiconductor laser element portion452except a ridge portion13a) inFIG. 33.

According to the fifth embodiment, a bar-state blue-violet semiconductor laser element441having a p-type GaN substrate801is bonded to the monolithic two-wavelength semiconductor laser element portion30in the three-wavelength semiconductor laser element portion452, as shown inFIG. 33. Therefore, an upper surface of the monolithic two-wavelength semiconductor laser element portion30is partially covered with the p-type GaN substrate801extending in a direction B of the blue-violet semiconductor laser element441in plan view. The p-type GaN substrate801is an example of the “second conductive type nitride-based semiconductor substrate” in the present invention.

As shown inFIG. 34, the three-wavelength semiconductor laser element portion452is formed such that a thickness t1of a portion bonded with the blue-violet semiconductor laser element441is bonded is larger than a thickness t2of a portion bonded with no blue-violet semiconductor laser element441. Thus, the semiconductor laser device900according to the fifth embodiment is formed such that the three-wavelength semiconductor laser element portion452and a base471formed to correspond to a stepped shape (seeFIG. 34) in a direction A of a lower surface of the three-wavelength semiconductor laser element portion452. The base471is an example of the “heat radiator base” in the present invention. The remaining structure of the semiconductor laser device900according to the fifth embodiment is similar to that of the aforementioned first embodiment.

A manufacturing process for the semiconductor laser device900according to the fifth embodiment will be now described with reference toFIGS. 4 and 33to37.

The wafer-state monolithic two-wavelength semiconductor laser element portions30(seeFIG. 4) are formed through a manufacturing process similar to the aforementioned first embodiment.

As shown inFIG. 35, p-type AlGaN cladding layers43, active layers42and n-type AlGaN cladding layers41are successively staked on an upper surface of the p-type GaN substrate801, thereby forming the blue-violet semiconductor laser elements441. Ridge portions41aare formed on upper surfaces of the n-type AlGaN cladding layer41by etching and thereafter insulating films44are formed on the upper surfaces of the n-type AlGaN cladding layers41except the ridge portions41a. Thereafter n-side electrodes45are formed on upper surfaces of the ridge portion41aand the insulating films44. Step portions801areaching the p-type GaN substrate801are formed by etching.

As shown inFIG. 36, the thickness of the p-type GaN substrate801is reduced by a prescribed thickness by etching or polishing and thereafter p-side electrodes46are formed on a lower surface of the p-type GaN substrate801. The wafer-state blue-violet semiconductor laser elements441are formed in the aforementioned manner.

In the manufacturing process according to the fifth embodiment, a plurality of bar-state blue-violet semiconductor laser elements441are formed by cleavage. Thus, the bar-state blue-violet semiconductor laser elements441are formed with pairs of cavity facets (the light emitting surfaces441aand the light reflecting surface441b(seeFIG. 34)).

As shown inFIG. 37, the bar-state blue-violet semiconductor laser elements441are bonded to the wafer-state monolithic two-wavelength semiconductor laser element portions30at prescribed intervals. At this time, fusible layers60on the lower surfaces of the blue-violet semiconductor laser elements441are previously formed only on portions of the electrode layers53of the monolithic two-wavelength semiconductor laser element portion30, bonded with the blue-violet semiconductor laser elements441.

The monolithic two-wavelength semiconductor laser element portions30are cleaved to be in the form of bars and divided along the extensional direction (direction A inFIG. 37) of the cavities by element division, thereby forming a plurality of the three-wavelength semiconductor laser element portions452constituting the semiconductor laser device900shown inFIG. 33.

Finally, the three-wavelength semiconductor laser element portion452and a base471formed to correspond to the stepped shape of the lower surface of the three-wavelength semiconductor laser element portion452(seeFIG. 34). The remaining manufacturing process for the semiconductor laser device900according to the fifth embodiment is similar to that of the aforementioned first embodiment.

As hereinabove described, the manufacturing process of the fifth embodiment comprises a step of bonding the plurality of blue-violet semiconductor laser elements441previously formed in the form of bars to the wafer-state monolithic two-wavelength semiconductor laser element portions30at prescribed intervals, whereby the wafer-state three-wavelength semiconductor laser element portion452can be easily cleaved on portions where the monolithic two-wavelength semiconductor laser element portions30have the thickness t2, to be in the form of bars. The remaining effects of the fifth embodiment are similar to those of the aforementioned fourth embodiment.

Referring toFIGS. 38 and 39, a blue-violet semiconductor laser element442is bonded to a monolithic two-wavelength semiconductor laser element portion30in a state where a support substrate802of a blue-violet semiconductor laser element442does not cover an upper surface of a monolithic two-wavelength semiconductor laser element portion30in a sixth embodiment, dissimilarly to the aforementioned fifth embodiment. The blue-violet semiconductor laser element442is an example of the “second semiconductor laser element” in the present invention.

In the blue-violet semiconductor laser element442of a three-wavelength semiconductor laser element portion453constituting a semiconductor laser device910according to the sixth embodiment, a p-type AlGaN cladding layer43, an active layer42and an n-type AlGaN cladding layer41are formed on an upper surface of a support substrate802made of Ge through an electrode layer53and an fusible layer60, as shown inFIG. 39. An electrode803electrically connected to a p-side electrodes46is formed on a prescribed region of a lower surface of the support substrate802.

According to the sixth embodiment, the blue-violet semiconductor laser element442bonded to the support substrate802, having a width slightly smaller than the width in a direction B of the step portion51aof the monolithic two-wavelength semiconductor laser element portion30, is bonded to the monolithic two-wavelength semiconductor laser element portion30, as shown inFIG. 38. Thus, the overall upper surface (p-side electrodes15and25inFIG. 38) of the monolithic two-wavelength semiconductor laser element portion30is so formed as to be exposed.

In the semiconductor laser device910, the three-wavelength semiconductor laser element portion453is fixed to the base370in a junction-down system, as shown inFIG. 39. At this time, the support substrate802of the blue-violet semiconductor laser element442is so formed as to be bonded to a bottom of a recess portion370apreviously formed in the base370. The remaining structure of the semiconductor laser device910according to the sixth embodiment is similar to the aforementioned fifth embodiment.

A manufacturing process of a semiconductor laser device910according to the sixth embodiment will be now described with reference toFIGS. 4 and 38to43.

The wafer-state monolithic two-wavelength semiconductor laser element portions30(seeFIG. 4) are formed through a manufacturing process similar to the aforementioned first embodiment.

As shown inFIG. 40, InGaN separative layers81, the n-type AlGaN cladding layers41, the active layers42and the p-type AlGaN cladding layers43are successively stacked on the upper surface of the n-type GaN substrate80. Then the ridge portions43aare formed on upper surfaces of the p-type AlGaN cladding layers43by etching and thereafter insulating films44are formed on upper surfaces of the p-type AlGaN cladding layers43except the ridge portions43a. Thereafter p-side electrodes46are formed on upper surfaces of the ridge portions43aand the insulating films44. The step portions80areaching the n-type GaN substrate80are formed by etching.

As shown inFIG. 41, the support substrate802made of Ge previously formed with the electrode layers53on prescribed regions are bonded on upper surfaces of the p-side electrodes46through the fusible layers60. Then the n-type GaN substrate80is separated along the breakdown region of the InGaN separative layers81by laser beam irradiation, as shown inFIG. 41. Thus, the wafer-state blue-violet semiconductor laser elements442bonded from the n-type GaN substrate80to the support substrate802are formed.

The blue-violet semiconductor laser elements442are bonded to the monolithic two-wavelength semiconductor laser element portion30. At this time, the fusible layers60are previously formed only on regions of the electrode layers53of the monolithic two-wavelength semiconductor laser element portions30, bonded with the blue-violet semiconductor laser elements442. The thickness of the support substrate802is formed by a prescribed thickness by polishing, as shown inFIG. 42and thereafter the electrodes803are formed on the upper surface of the support substrate802by vacuum evaporation. The electrodes803are formed on the upper surface of the support substrate802corresponding to positions of the p-type AlGaN cladding layers43including the ridge portions.

As shown inFIG. 42, scribing grooves804(shown by thick broken lines) are formed on prescribed positions of the support substrate802. As shown inFIG. 43, regions of the support substrate802, formed with no electrode803are divided along the scribing grooves804, thereby partially removing the support substrate802formed with no electrode803. Thus, the upper surfaces of the infrared semiconductor laser elements10and the red semiconductor laser elements20of the monolithic two-wavelength semiconductor laser element portions30are open.

Thereafter the elements are divided to be in the form of chips, thereby forming a plurality of the three-wavelength semiconductor laser element portions453according to the sixth embodiment shown inFIG. 38.

The recess portion370ais previously formed on the prescribed region of the base370(seeFIG. 39). In this state, the three-wavelength semiconductor laser element portion453is bonded to the base370through a manufacturing process similar to the aforementioned first embodiment. At this time, the blue-violet semiconductor laser element442is bonded to correspond to the recess portion370aof the base370. The semiconductor laser device910according to the sixth embodiment shown inFIG. 39is formed in the aforementioned manner. The remaining manufacturing process for the semiconductor laser device910according to the sixth embodiment is similar to that of the aforementioned fifth embodiment.

According to the sixth embodiment, as hereinabove described, the three-wavelength semiconductor laser element portion453is formed such that the overall upper surfaces of the infrared semiconductor laser element10and the red semiconductor laser element20of the monolithic two-wavelength semiconductor laser element portion30are exposed, whereby the overall upper surfaces of the infrared semiconductor laser element10and the red semiconductor laser element20of the monolithic two-wavelength semiconductor laser element portion30can be bonded to the base370, dissimilarly to the three-wavelength semiconductor laser element portion452according to the fifth embodiment shown inFIG. 33, and hence the three-wavelength semiconductor laser element portion453and the base370can be further reliably bonded to each other. The remaining effects of the sixth embodiment are similar to those of the aforementioned fourth embodiment.

Referring toFIGS. 40,44to46, a blue-violet semiconductor laser element443formed on a provisional support substrate805is bonded to a monolithic two-wavelength semiconductor laser element portion30in a modification of the sixth embodiment and thereafter the provisional support substrate805is completely removed from the blue-violet semiconductor laser element443, dissimilarly to the manufacturing process of the aforementioned sixth embodiment. The blue-violet semiconductor laser element443is an example of the “second semiconductor laser element” in the present invention.

As shown inFIG. 40, the blue-violet semiconductor laser elements443are formed on the n-type GaN substrate80through a manufacturing process similar to that of the aforementioned sixth embodiment. Thereafter the provisional support substrate805is bonded to upper surfaces of the p-side electrodes46as shown inFIG. 45. A thermal release sheet formed with a thermal release adhesive material on a surface of a film such as polyester is employed as the provisional support substrate805, the surface on which the thermal release adhesive material of the film is formed is bonded to the p-side electrodes46. As shown inFIG. 45, the n-type GaN substrate81is separated along the breakdown region of the InGaN separative layers81by laser beam irradiation. Thus, the wafer-state blue-violet semiconductor laser elements443bonded to the provisional support substrate805are formed.

In the manufacturing process for the semiconductor laser device920according to the modification of the sixth embodiment, the wafer-state blue-violet semiconductor laser elements443bonded to the provisional support substrate805are bonded to the monolithic two-wavelength semiconductor laser element portions30and thereafter all the provisional support substrate805is removed from the blue-violet semiconductor laser elements443by heating as shown inFIG. 46. Consequently, the wafer-state three-wavelength semiconductor laser element portions454are formed as shown inFIG. 46.

A plurality of the three-wavelength semiconductor laser element portions454constituting semiconductor laser devices920shown inFIG. 44are formed by cleaving to be in the form of bars and dividing the elements.

Finally, the three-wavelength semiconductor laser element portion454is bonded to the base70though a manufacturing process similarly to that of the aforementioned first embodiment. The remaining manufacturing process for the semiconductor laser device920according to the modification of the sixth embodiment is similar to that of the aforementioned first embodiment.

In the manufacturing process according to the modification of the sixth embodiment, as hereinabove described, the provisional support substrate805is removed form the wafer-state blue-violet semiconductor laser elements443bonded to the monolithic two-wavelength semiconductor laser element portions30and hence the three-wavelength semiconductor laser element portion454formed by a substantially flat surface, in which any portion of the blue-violet semiconductor laser element443does not protrude above the monolithic two-wavelength semiconductor laser element portion30, can be formed. Thus, the three-wavelength semiconductor laser element portion454can be easily fixed to the base70in a junction-down system. The remaining effects of the modification of the sixth embodiment is similar to that of the aforementioned first embodiment.

Referring toFIGS. 47 to 50, the wafer-state blue-violet semiconductor laser elements444are divided along an extensional direction of cavities and thereafter each of the strip-shaped blue-violet semiconductor laser elements444is bonded to a monolithic two-wavelength semiconductor laser element portion30in a seventh embodiment, dissimilarly to the manufacturing processes of the aforementioned first to sixth embodiments. The blue-violet semiconductor laser element444is an example of the “second semiconductor laser element” in the present invention.

In a semiconductor laser device930according to the seventh embodiment of the present invention, a three-wavelength semiconductor laser element portion455formed by bonding the blue-violet semiconductor laser element444to the monolithic two-wavelength semiconductor laser element portion30is fixed to a base370in a junction-down system, as shown inFIG. 47.

According to the seventh embodiment, an n-type GaN substrate80(n-side electrode45) of the blue-violet semiconductor laser element444is bonded to a bottom51bof a step portion51aof a monolithic two-wavelength semiconductor laser element portion30through an fusible layer60. A p-side electrode46of the blue-violet semiconductor laser element444is bonded to a bottom of a recess portion370apreviously formed on the base370through a conductive bonding layers1. The n-type GaN substrate80is an example of the “first conductive type nitride-based semiconductor substrate” in the present invention. The remaining structure of the semiconductor laser device930according to the seventh embodiment is similar to that of the aforementioned first embodiment.

A manufacturing process for the semiconductor laser device930according to the seventh embodiment will be now described with reference toFIGS. 4,47to50.

The wafer-state monolithic two-wavelength semiconductor laser element portions30(seeFIG. 4) are formed through a manufacturing process similar to the aforementioned first embodiment.

As shown inFIG. 48, an n-type AlGaN cladding layer41, an active layer42and a p-type AlGaN cladding layer43are successively formed on an upper surface of the n-type GaN substrate80. Ridge portions43aare formed on upper surface of the p-type AlGaN cladding layer43by etching and thereafter insulating films44are formed on the upper surface of the p-type AlGaN cladding layer except the ridge portions43a. Thereafter the p-side electrodes46are formed on upper surfaces of the ridge portions43aand the insulating films44. The n-side electrode45is formed on a lower surface of the n-type GaN substrate80.

In the manufacturing process of the seventh embodiment, the elements are divided along an extensional direction (direction perpendicular to the plane of paper) of the ridge portions43aas shown inFIG. 48. The aforementioned element division is performed at positions shown by broken lines inFIG. 48. Thus, a plurality of the blue-violet semiconductor laser elements444formed in strip shapes in the cavity direction (direction perpendicular to the plane of paper) are formed as shown inFIG. 49.

As shown inFIG. 50, electrode layers53provided on the step portions51aof the monolithic two-wavelength semiconductor laser element portions30and the n-type GaN substrate80of the strip-shaped blue-violet semiconductor laser elements444are opposed and bonded to through fusible layers60. The wafer-state three-wavelength semiconductor laser element portions455are formed in the aforementioned manner.

Thereafter the elements are divided to be in the form of chips, thereby forming a plurality of the three-wavelength semiconductor laser element portion455shown inFIG. 50.

The recess portion370ais previously formed on a prescribed region of the base370(seeFIG. 47) similarly to the manufacturing process of the aforementioned fifth embodiment. In this state, the three-wavelength semiconductor laser element portion455is bonded to the base370. At this time, the recess portion370aof the base370is bonded to correspond to the blue-violet semiconductor laser element444. The semiconductor laser device930according to the seventh embodiment shown inFIG. 47is formed in the aforementioned manner.

As hereinabove described, the manufacturing process of the seventh embodiment comprises a step of bonding the plurality of strip-shaped blue-violet semiconductor laser elements444previously formed by element division along the extensional direction of the cavities to the monolithic two-wavelength semiconductor laser element portions30, whereby the number of the plurality of blue-violet semiconductor laser elements444formed on one n-type GaN substrate80can be increased and hence the yield in formation of the semiconductor laser element can be improved.

For example, while the base to which the multiple wavelength semiconductor laser element portion is bonded is formed by the substrate made of AlN in each of the aforementioned first to seventh embodiments, the present invention is not restricted to this but the base may be formed by a substrate made of an insulating material having an excellent thermal conductivity such as SiC, Si, diamond and cubic boron nitride (CBN).

While the hole351breaching from the surface formed with the semiconductor layer of the monolithic two-wavelength semiconductor laser element portion330to the n-type GaAs substrate351is provided and the conduction portion352is formed in the inner surface of the hole351bby vacuum evaporation in the aforementioned second embodiment, the present invention is not restricted to this but a conductive material may fill up the hole351bfor forming a conduction portion structure.

While the semiconductor laser device is formed in the junction-down system where the multiple wavelength laser element portion (p-n junction) is directed downward with respect to the base (submount) in each of the aforementioned first to seventh embodiments, the present invention is not restricted to this but the semiconductor laser device may be formed in a junction-up system where the multiple wavelength laser element portion is directed upward with respect to the base.

While one blue-violet semiconductor laser element40is bonded to the monolithic two-wavelength semiconductor laser element portion30(330) constituted by the two semiconductor laser elements so that the three-wavelength semiconductor laser element portion50(350) is formed in each of the aforementioned first and second embodiments, the present invention is not restricted to this but the multiple wavelength laser element constituted by a plurality of semiconductor laser element portions other than two semiconductor laser element portions may be formed on the same growth substrate and two or more semiconductor laser element portions emitting laser beams having different wavelengths may be bonded so that the multiple wavelength laser element portion is formed.

While the blue semiconductor laser element710and the green semiconductor laser element720are successively bonded to the red semiconductor laser element20formed on the n-type GaAs substrate751so that the RGB multiple wavelength semiconductor laser element portion750is formed in the aforementioned third embodiment, the present invention is not restricted to this but the RGB multiple wavelength semiconductor laser element portion may be formed by successively bonding the green semiconductor laser element and the blue semiconductor laser element.

While the individually formed blue semiconductor laser element710and green semiconductor laser element720are successively bonded to the red semiconductor laser element20formed on the n-type GaAs substrate751so that the RGB multiple wavelength semiconductor laser element portion750is formed, the present invention is not restricted to this but a monolithic two-wavelength semiconductor laser element portion, in which a blue semiconductor laser element and a green semiconductor laser element are formed on the same GaN substrate, may be bonded to the red semiconductor laser element, so that the RGB multiple wavelength semiconductor laser element portion is formed.

While an AlN film or an Al2O3film containing Al elements is applied to the dielectric multilayer films formed on the cavity facets (the light emitting surface and the light reflecting surface) of each of the semiconductor laser elements forming the multiple wavelength semiconductor laser element portion in each of the aforementioned first to seventh embodiments, the present invention is not restricted to this but a single layer or a multilayer film made of SiO2, TiO2, ZrO2, Ta2O5, Nb2O5, La2O3, SiN, MgF2, GaN or BN, or Ti3O5or Nb2O3which is a material having the different composition ratio thereof.