Semiconductor laser device and fabrication method thereof

A method of fabricating a ridge-waveguide type semiconductor laser device having a large half-value width and a high kink level is provided. First, an effective refractive index difference Δn between an effective refractive index neff1 of the ridge and an effective refractive index neff2 of a portion on each of both sides of the ridge is taken as Δn=neff1−neff2, and a ridge width is taken as W. On such an assumption, constants “a”, “b”, “c”, and “d” of the following three equations are set on X-Y coordinates (X-axis: W, Y-axis: Δn) The first equation is expressed by Δn≦a×W+b, where “a” and “b” are constants determining a kink level. The second equation is expressed by W≧c, where “c” is a constant specifying a minimum ridge width at the time of formation of the ridge. The third equation is expressed by Δn≧d, where “d” is a constant specified by a desired half-width value θpara. Then at least either of a kind and a thickness of an insulating film, a thickness of an electrode film on the insulating film, and a kind and a thickness of a portion, located on each of both the sides of the ridge, of the upper cladding layer is set in such a manner that a combination of Δn and W satisfies the above three equations.

BACKGROUND OF THE INVENTION

The present invention relates to a ridge-waveguide type semiconductor laser device, and particularly to a ridge-waveguide type semiconductor laser device having a large half-width value θparaof a far-field pattern (FFP) in a direction horizontal to a hetero-interface, and having a desired laser characteristic at the time of operation with a high power.

In semiconductor laser devices including long-wavelength GaAs or INP based semiconductor laser devices and short-wavelength nitride based III-V group compound semiconductor laser devices, a ridge-waveguide type semiconductor laser device has been often used in various applications for a reason of easy fabrication and the like.

A ridge-waveguide type semiconductor laser is one of index guided types configured such that an upper portion of an upper cladding layer and a contact layer are formed into a stripe-shaped ridge, and both sides of the ridge and portions, located on both sides of the ridge, of the upper cladding layer are covered with an insulating layer to form a current construction layer and also an effective refractive index difference is provided in the lateral direction, whereby a mode control is performed.

A configuration of a short-wavelength ridge-waveguide type nitride based III-V group compound semiconductor laser device (hereinafter, referred to as “nitride based semiconductor laser device”) will be described with reference to FIG.4.FIG. 4is a sectional view showing a configuration of a nitride based semiconductor laser device.

Referring toFIG. 4, a nitride based semiconductor laser device10basically has a stacked structure in which a plurality of layers are stacked on a sapphire substrate12via a GaN buffer layer (not shown). The plurality of layers stacked on the sapphire substrate12are an n-GaN contact layer14, an N—AlGaN (content of A1:8%) cladding layer16having a thickness of 1.0 μm, an n-GaN optical guide layer18having a thickness of 0.1 μm, an MQW (Multiple Quantum Well) active layer20of three well layers, a p-GaN optical guide layer22having a thickness of 0.1 μm, a p-(GaN:Mg/AlGaN)-SLS (strained-layer superlattice) cladding layer24, and a p-GaN contact layer26having a thickness of 0.1 μm.

In this stacked structure, an upper portion of the p-cladding layer24and the p-contact layer26are formed as a stripe-shaped ridge28. An upper portion of the n-contact layer14, the n-cladding layer16, the n-optical guide layer18, the MQW active layer20, the p-optical guide layer22, and remaining layer portions24aof the p-cladding layer24are formed as a mesa structure extending in the same direction as the extending direction of the ridge28.

A ridge width W of the ridge28is typically set to 1.6 μm, a ridge height H is typically set to 0.6 μm, and a thickness T of each of the remaining layer portions24a, located on both sides of the ridge28, of the p-cladding layer24is typically set to 0.15 μm.

An insulating film30composed of an SiO2film is formed on both side surfaces of the ridge28and the remaining layer portions24a, located on both the sides of the ridge28, of the p-cladding layer24.

A p-side electrode32composed of a multi-layer metal film made from Pd/Pt/Au is formed on the insulating film30in such a manner as to be brought into contact with the p-contact layer26via a window formed in the insulating film30. An n-side electrode34composed of a multi-layer metal film made from Ti/Pt/Au is formed on the n-contact layer14.

By the way, along with the expanded applications of nitride based semiconductor laser devices, it has been required to increase a half-value width (hereinafter, referred to as “θpara”) of a far-field pattern (FFP) in the direction being horizontal to a hetero interface of a resonance structure, and to keep a desired optical power-injected current characteristic up to a high power region by increasing a kink level.

For example, when used as a light source of an optical pickup, a nitride based semiconductor laser device has been required to have the half-value width θparaas large as 7° or more and a kink level as high as about 60 mW.

However, in the case of setting structure factors, such as a ridge width or a thickness of a remaining layer portion of an upper cladding layer, of a nitride based semiconductor laser device, any design criterion being necessary and sufficient to meet the above-described strict requirement has not been established.

For example, since a design range of a nitride based semiconductor laser device is very narrow, if the half-value width θparaof the far-field pattern (FFP) for an elliptic beam in a direction parallel to the hetero interface is set to 7° or more, then the kink characteristic may be degraded. Accordingly, it becomes very important to clarify such a design range.

While the problem of the related art has been described by example of a nitride based semiconductor laser device, a long-wavelength ridge-waveguide type semiconductor laser device, which is longer in oscillation wavelength than the nitride based semiconductor laser device, for example, a GaAs or InP based ridge-waveguide type semiconductor laser device has the same problem.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a ridge-waveguide type semiconductor laser device having a large half-value width θpara, and keeping a desired optical power-injected current characteristic up to a high power region, that is, having a high kink level, and to provide a method of fabricating the ridge-waveguide type semiconductor laser device.

As a result of various experiments in the course of studies made for solving the above-described problems, the present inventor has found that as shown inFIG. 5, a half-value width θparahas a close relationship with an effective refractive index difference Δn of a ridge waveguide, and that in order to make a half-value width θparalarge, it is required to make the effective refractive index difference Δn large. It is to be noted that marks indicating the experimental results are omitted for simplicity in FIG.5.

The effective refractive index difference Δn of a ridge waveguide is, as shown inFIG. 4, is defined as a difference (neff1−neff2) between an effective refractive index neff1of the ridge for an oscillation wavelength and an effective refractive index neff2of a portion located on each of both sides of the ridge for the oscillation wavelength.

However, as the effective refractive index difference Δn becomes large, a cutoff ridge width against a higher-order horizontal transverse mode tends to become narrow. The cutoff ridge width against a higher-order horizontal transverse mode means a ridge width which does not allow occurrence of any higher-order horizontal transverse mode. If the ridge width is a cutoff ridge width value or more, the horizontal transverse mode is easier to be shifted from a fundamental mode to a primary mode. If a hybrid mode of the fundamental horizontal transverse mode and a higher-order horizontal transverse mode occurs, then as shown inFIG. 6, in the step of increasing an injected current for making an optical power large, a kink occurs in an optical power-injected current characteristic, thereby degrading a laser characteristic at the time of operation with a high power.

With respect to the above kink level, the present inventor has made various experiments, and found that as shown inFIG. 5, the kink level has a close relationship with the effective refractive index difference Δn of a ridge waveguide, and that in order to make the kink level high, it is required to make the effective refractive index difference Δn small. It is to be noted that difference marks inFIG. 5show the experimental results.

On the basis of the studies made by the present inventor, since a ridge-waveguide type nitride based semiconductor laser device has a small effective refractive index difference Δn and has a short oscillation wavelength, a cutoff ridge width against a higher-order horizontal transverse mode is narrow as shown in FIG.7.FIG. 7is a graph showing a relationship between an effective refractive index difference Δn between an effective refractive index of the ridge formed by a GaN layer and an effective refractive index of a portion located on each of both sides of the ridge, which relationship is obtained under a condition that the refractive index of the GaN layer is set to 2.504 and the oscillation wavelength λ is set to 400 nm.

For example, when the effective refractive index difference Δn of a ridge waveguide is set to be in a range of 0.005 to 0.01, a ridge width is required to be narrowed to about 1 μm for keeping the ridge width in a range of a cutoff ridge width value or less.

If the half-value width θparais made large by making the effective refractive index difference Δn large, the cutoff ridge width becomes small, with a result that the laser characteristic at the time of operation with a high power is degraded. Accordingly, with respect to the ridge width, the increase in half-value width and the enhancement of the laser characteristic at the time of operation with a high power is, as shown inFIG. 8, inconsistent with each other. It is to be noted that different marks such as closed circles, open circles, closed squares, and open squares shows experimental results.

The present inventors has further made studies and experiments, and found that a desired effective refractive index difference Δn, that is, a desired half-value width θparacan be determined by adjusting at least either of a thickness of an electrode film, a kind and thickness of an insulating film, and a kind and a thickness of a portion, located on each of both sides of the ridge, of a cladding layer. The present inventor has further found that if the semiconductor laser device is a GaN based semiconductor laser device, a desired effective refractive index Δn, that is, a desired half-value width θparacan be determined by adjusting at least either of a thickness of an electrode film, a kind and thickness of an insulating film, a kind and a thickness of a portion, located on each of both sides of the ridge, of a cladding layer, an Al composition ratio and a thickness of an AlGaN cladding layer, a thickness of a GaN optical guide layer, a thickness and an In composition ratio of a well layer of a GaInN.MQW active layer, and an In composition ratio of a barrier layer of the GaInN.MQW active layer.

The present inventor has further found that a ridge-waveguide type semiconductor laser device having a desired half-value width θparawhile keeping a desired kink level by combining a ridge width W in a specific range with an effective refractive index difference Δn in a specific range. The present inventor has thus accomplished the present invention.

FIG. 9is a graph showing combinations of W and Δn, each of which can realize a desired half-value width θparaand a desired kink level, on X-Y coordinates on which W (μm) is plotted on the X-axis and Δn is plotted at a rate of 0.001 on the Y-axis, wherein Δn, which is an effective refractive index difference between an effective refractive index neff1of a ridge for an oscillation wavelength and an effective refractive index neff2of a portion on each of both sides of the ridge for the oscillation wavelength, is taken as Δn=neff1−neff2, and W is a ridge width.

InFIG. 9, a slant line, that is, Δn≦a×W+b shows the kink level. For example, a slant line M is Δn≦−0.004×W+0.0157, which shows that the kink level is 30 mW.

To achieve the above object, on the basis of the above-described knowledge, according to a first aspect of the present invention, there is provided a ridge-waveguide type semiconductor laser device including: a stripe-shaped ridge formed in an upper portion of at least an upper cladding layer, and an insulating film functioning as a current constriction layer, the insulating film being formed on both side surfaces of the ridge and on portions, located both the sides of the ridge, of the upper cladding layer. In this method, first, an effective refractive index difference Δn between an effective refractive index neff1of the ridge for an oscillation wavelength and an effective refractive index neff2of a portion on each of both sides of the ridge for the oscillation wavelength is taken as Δn=neff1−neff2, and a ridge width is taken as W. On such an assumption, at least either of a kind and thickness of the insulating film, a thickness of an electrode film on the insulating film, a ridge height, a kind of the upper cladding layer, and a thickness of a remaining layer portion, located on each of both the sides of the ridge, of the upper cladding layer is set such that a combination of W and Δn is located in a specific Δn-W region on X-Y coordinates on which W (μm) is plotted on the X-axis and Δn is plotted on the Y-axis. The specific Δn-W region is defined so as to satisfy the following three equations. The first equation (1) is expressed by Δn≦a×W+B, where “a” and “b” are constants determining a kink level. The second equation (2) is expressed by W≧c, where “c” is a constant specifying a minimum ridge width at the time of formation of the ridge. The third equation (3) is expressed by Δn≧d, where “d” is a constant specified by a desired half-width value θparaof a far-field pattern in a direction horizontal to a hetero-interface of a resonance structure of the laser device.

According to the present invention, at least either of a thickness of an electrode film, a kind and thickness of an insulating film, and a kind and a thickness of a remaining layer portion, located on each of both the sides of the ridge, of the upper cladding layer is set such that a combination of the effective refractive index difference Δn and the ridge width W satisfies the equations (1), (2) and (3), to thereby adjust the effective refractive index difference Δn and set the ridge width W, so that it is possible to realize a semiconductor laser device having a desired kink level specified by the equation (1) and a desired half-value width θparaspecified by the equation (3).

To achieve the above object, according to a second aspect of the present invention, there is provided a method of fabricating a ridge-waveguide type semiconductor laser device having a structure that an upper portion of at least an upper cladding layer is formed into a stripe-shaped ridge, and an insulating film functioning as a current constriction layer is formed on both side surfaces of the ridge and on portions, located both the sides of the ridge, of the upper cladding layer. The method includes a constant setting step of assuming that an effective refractive index difference Δn between an effective refractive index neff1of the ridge for an oscillation wavelength and an effective refractive index neff2of a portion on each of both sides of the ridge for the oscillation wavelength is taken as Δn=neff1−neff2, and a ridge width is taken as W, and setting, on X-Y coordinates on which W (μm) is plotted on the X-axis and Δn is plotted on the Y-axis, constants “a”, “b”, “c”, and “d” of the following three equations. The first equation (1) is expressed Δn≦a×W+B, where “a” and “b” are constants determining a kink level. The second equation (2) is expressed by W≧c, where “c” is a constant specifying a minimum ridge width at the time of formation of the ridge. The third equation (3) is expressed by Δn≧d, where “d” is a constant specified by a desired half-width value θparaof a far-field pattern in a direction horizontal to a hetero-interface of a resonance structure of the laser device.

Since the constants “a”, “b”, “c” and “d” in the three equations (1), (2) and (3) to be set in the constant setting step differ depending on a thickness of an electrode film, a kind and a thickness of the insulating film, a ridge height, and a kind and a thickness of the portion, located on each of both the sides of a ridge, of the upper cladding layer, and therefore, they are required to be experimentally determined.

To be more specific, the constants “a” and “b” in the equation (1) may be determined by establishing a relationship between Δn and the kink level, for example, a relationship shown on the right side ofFIG. 5, by experiments, and the constant “d” in the equation (3) may be determined by establishing a relationship between Δn and θpara, for example, a relationship shown on the left side ofFIG. 5, by experiments. In addition, the constant “c” in the equation (2) is a value limited by an etching step at the time of formation of the ridge.

The application of the nitride semiconductor laser and the fabrication method thereof according to the present invention is not limited to a nitride based III-V group compound semiconductor laser device. The nitride semiconductor laser and the fabrication method thereof according to the present invention can be applied to GaAs based, InP based, AlGaAs based, and GaN based semiconductor laser devices irrespective of a kind of a compound semiconductor layer forming a resonance structure of the semiconductor laser device and a kind of a contact layer insofar as the semiconductor laser is of a ridge-waveguide type.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described in detail by way of examples with reference to the accompanying drawings.

In this embodiment, the semiconductor laser device of the present invention is applied to a nitride based III-V group compound semiconductor laser device (hereinafter, referred to as “nitride based semiconductor laser device”).FIG. 1is a sectional view showing a configuration of the nitride based semiconductor laser device according to this embodiment.

Referring toFIG. 1, a nitride based semiconductor laser device40according to this embodiment has a stacked structure in which a plurality of layers are stacked on a sapphire substrate42via a GaN buffer layer (not shown). The plurality of layers stacked on the sapphire substrate42are an n-Al0.05Ga0.95N contact layer44having a thickness of 5 μm, an n-(GaN:Si/Al0.1Ga0.9N)-SLS cladding layer46, an n-GaN optical guide layer48having a thickness of 0.15 μm, a GaInN.MQW active layer50having three well layers each having a thickness of 4 nm and four barrier layers each having a thickness of 10 nm, a p-Al0.35Ga0.65N deterioration preventing layer52having a thickness of 0.01 μm, a p-GaN optical guide layer54having a thickness of 0.15 μm, a p-(GaN:Mg/Al0.1Ga0.9N)-SLS cladding layer56, and a p-GaN contact layer58having a thickness of 0.015 μm.

In this stacked structure, an upper portion of the p-cladding layer56and the p-contact layer58are formed as a stripe-shaped ridge60. An upper portion of the n-contact layer44, the n-cladding layer46, the n-optical guide layer48, the MQW active layer50, the p-deterioration preventing layer52, the p-optical guide layer54, and both remaining layer portions56aof the p-cladding layer56are formed as a mesa structure extending in the same direction as the extending direction of the ridge60.

A ridge width W of the ridge60is typically set to 1.6 μm, a ridge height H is typically set to 0.35 μm, and a thickness T of each of the remaining layer portions56a, located on both sides of the ridge60, of the p-cladding layer56is typically set to 0.15 μm.

A ZrO2film62having a thickness of 0.2 μm is formed as a current constriction layer on both side surfaces of the ridge60and the remaining layer portions56a, located on both the sides of the ridge60, of the p-cladding layer56.

A p-side electrode64composed of a multi-layer metal film made from Ti/Au is formed on the ZrO2film62in such a manner as to be brought into contact with the p-contact layer58via a window formed in the ZrO2film62. An n-side electrode66composed of a multi-layer metal film made from Ti/Al is formed on the n-contact layer44.

The nitride based semiconductor laser device40according to this embodiment is fabricated in the following manner. First, an effective refractive index difference Δn between an effective refractive index neff1of the ridge for an oscillation wavelength and an effective refractive index neff2of a portion on each of both sides of the ridge for the oscillation wavelength is taken as Δn=neff1−neff2, and a ridge width is taken as W. On such an assumption, constants “a”, “b”, “c”, and “d” of the following three equations are set on X-Y coordinates on which W (μm) is plotted on the X-axis and Δn is plotted at a rate of 0.001 on the Y-axis.

The first equation is expressed by
Δn≦a×W+B(1)
where “a” and “b” are constants determining a kink level.

The second equation is expressed by
W≧c  (2)
where “c” is a constant specifying a minimum ridge width at the time of formation of the ridge.

The third equation is expressed by
Δn≧d  (3)
where “d” is a constant specified by a desired half-width value θpara.

The constant “d” is determined by using a graph, for example, as shown inFIG. 5, which is previously prepared by experiments.

After the constants “a”, “b”, “c”, and “d” are set, the effective refractive index difference Δn and the ridge width W are set by adjusting at least either of a thickness of an electrode film, a kind and a thickness of an insulating film, and a kind and a thickness of a portion, located on each of both the sides of the ridge, of the upper cladding layer in such a manner that a combination of Δn and W satisfies the above-described three equations (1), (2) and (3).

In the case of the nitride based semiconductor laser device40according to this embodiment, for example, in order to set the kink level to 50 mW or more and also set the half-value width θparato 7.5° or more, the constant “a” in the equation (1) is set to −0.004, and the constant “b” is set to 0.0123; the constant “c” in the equation (2) is set to 1.0 μm from the limitation at the time of formation of the ridge; and the constant “d” in the equation (3) is set to 0.0056.

When the thickness T of the remaining layer portion56aof the p-cladding layer56is set to 0.15 μm, the ridge width W is set to 1.6 μm, and the Al composition y of the p-(GaN:Mg/AlyGal-yN)-SLS cladding layer56is set to 0.1, the effective refractive index difference Δn becomes 0.0063. Accordingly, as shown in character A1ofFIG. 2, the half-value width θparabecomes 8.7° and the kink level becomes 57 mW.

The laser device in Inventive Example 1 can satisfy the requirement that the kink level is 50 mW or more and the half-value width θparais 7.5° or more.

Comparative Example 1

When the thickness T of the remaining layer portion56aof the p-cladding layer56is set to 0.12 μm, the ridge width W is set to 1.6 μm, and the Al composition y of the p-(GaN:Mg/AlyGal-yN)-SLS cladding layer56is set to 0.1, the effective refractive index difference Δn becomes 0.0102. Accordingly, as shown in character A2ofFIG. 2, the half-value width θparabecomes as high as 10.2° or more but the kink level becomes as low as 20 mW.

The laser device in Comparative Example 1 cannot satisfy the requirement that the kink level is 50 mW or more and the half-value width θparais 7.5° or more.

In this embodiment, the semiconductor laser device of the present invention is applied to a nitride based semiconductor laser device different from that in Embodiment 1.FIG. 3is a sectional view showing a configuration of the nitride based semiconductor laser device according to this embodiment.

Referring toFIG. 3, a nitride based semiconductor laser device70according to this embodiment has a stacked structure in which a plurality of layers are stacked on a sapphire substrate72via a GaN buffer layer (not shown). The purality of layers stacked on the sapphire substrate72are an n-GaN contact layer74having a thickness of 5 μm, an n-AlxGal-xN cladding layer76having a thickness of 1.0 μm, an n-GaN optical guide layer78having a thickness of 0.10 μm, a GaInN.MQW active layer80having three well layers each having a thickness of 3.5 nm and four barrier layers each having a thickness of 70 nm, a p-Al0.18Ga0.82N deterioration preventing layer82having a thickness of 0.01 μm, a p-GaN optical guide layer84having a thickness of 0.10 μm, a p-(GaN:Mg/Al0.14Ga0.86N)-SLS cladding layer86, and a p-GaN contact layer88having a thickness of 0.1 μm.

In this stacked structure, an upper portion of the p-cladding layer86and the p-contact layer88are formed as a stripe-shaped ridge90. An upper portion of the n-contact layer74, the n-cladding layer76, the n-optical guide layer78, the MQW active layer80, the p-deterioration preventing layer82, the p-optical guide layer84, and both remaining layer portions86aof the p-cladding layer86are formed as a mesa structure extending in the same direction as the extending direction of the ridge90.

A ridge width W of the ridge90is typically set to 1.7 μm, a ridge height H is typically set to 0.35 μm, and a thickness T of each of the remaining layer portions86a, located on both sides of the ridge90, of the p-cladding layer86is typically set to 0.15 μm.

A SiO2film92having a thickness of 0.2 μm is formed as a current constriction layer on both side surfaces of the ridge90and the remaining layer portions86a, located on both the sides of the ridge90, of the p-cladding layer86.

A p-side electrode94composed of a multi-layer metal film made from Pd/Pt/Au is formed on the SiO2film92in such a manner as to be brought into contact with the p-contact layer88via a window formed in the SiO2film92. An n-side electrode96composed of a multi-layer metal film made from Ti/Pt/Au is formed on the n-contact layer74.

In the case of the nitride based semiconductor laser device70according to this embodiment, for example, in order to set the kink level to 50 mW or more and also set the half-value width θparato 7.5° or more, the constant “a” in the equation (1) is set to 0.004, and the constant “b” is set to 0.0123; the constant “c” in the equation (2) is set to 1.0 μm from the limitation at the time of formation of the ridge; and the constant “d” in the equation (3) is set to 0.0056.

When the thickness T of the remaining layer portion86aof the p-cladding layer86is set to 0.15 μm, the ridge width W is set to 1.7 μm, and the A1composition y of the p-(GaN:Mg/AlyGal-yN)-SLS cladding layer86is set to 0.05, the effective refractive index difference Δn becomes 0.0062. Accordingly, as shown in character B1ofFIG. 2, the half-value width θparabecomes 8.53° and the kink level becomes 55 mW.

The laser device in Inventive Example 2 can satisfy the requirement that the kink level is 50 mW or more and the half-value width θparais 7.5° or more.

Comparative Example 2

When the thickness T of the remaining layer portion86aof the p-cladding layer86is set to 0.15 μm, the ridge width W is set to 1.7 μm, and the Al composition y of the p-(GaN:Mg/AlyGal-yN)-SLS cladding layer86is set to 0.07, the effective refractive index difference Δn becomes 0.0081. Accordingly, as shown in character B2ofFIG. 2, the half-value width θparabecomes as high as 9.3° but the kink level becomes as low as 33 mW.

The laser device in Comparative Example 2 cannot satisfy the requirement that the kink level is 50 mW or more and the half-value width θparais 7.5° or more.

According to Embodiments 1 and 2, a nitride based semiconductor laser device having a desired half-width value θparaand a desired kink level while keeping a specific ridge width can be easily designed by determining an effective refractive index difference Δn with a kind of an upper cladding layer and a thickness of a remaining layer portion of an upper cladding layer taken as parameters. In other words, according to these embodiments, a nitride based semiconductor laser device having a desired half-value width θparaand a desired kink level can be easily designed by using the equations (1), (2) and (3) as a criterion of the design.

As described above, according to the present invention, a semiconductor laser device having a desired half-value width θparaand a desired kink level can be easily designed and fabricated by setting at least either of a kind and thickness of an insulating film, a thickness of an electrode film on the insulating film, a ridge height, a kind of an upper cladding layer, and a thickness of a remaining layer portion, located on each of both the sides of the ridge, of the upper cladding layer in such a manner that a combination of the ridge width W and an effective refractive index difference Δn is located in a specific Δn-W region.

The fabrication method of the present invention can provide a design technique suitable for fabricating the semiconductor laser device of the present invention. A nitride based III-V group compound semiconductor laser device having a desired half-width value θparaof, for example, 7° or more and a high kink level can be easily designed by using the fabrication method of the present invention.