Semiconductor laser device and method of manufacturing the same

【0001】

[Technical field to which the invention belongs]

The present invention relates to a semiconductor laser device capable of oscillating a laser beam having a mid-infrared wavelength of 5 to 20 μm.

【0002】

[Conventional technology]

Semiconductor lasers are often used in optical disks and optical communications. The oscillation wavelengths of the semiconductor laser used there are 1.55 / 1.3 μm (for optical fiber communication), 0.98 μm (for fiber amplifier), 0.78 μm (for compact disk (CD) / mini disk (MD)), 0.65 μm (for DVD). ), 0.41 μm (for high-density DVD), etc., and the semiconductor materials and laser structures used for these are almost established in mass production. On the other hand, as a wavelength at which a semiconductor laser can oscillate, the so-called mid-infrared region in the vicinity of 3 μm to 20 μm has been attracting attention in recent years. This wavelength band includes absorption wavelengths of various organic substances. The realization of semiconductor lasers in this wavelength band is expected to open new markets, including sets in fields such as atmospheric analysis and medicine.

【0003】

As a semiconductor laser in the mid-infrared region, an approach has been made in which a material having a narrow band gap is used as an active layer of the semiconductor laser. For example, studies have been conducted using group III-V semiconductors (such as InGaAsSb) and group IV-VI semiconductors (such as PbTeSe). However, group III-V semiconductors physically have Auger recombination, and the Auger recombination increases significantly due to the narrowing of the bandgap. For this reason, non-emission recombination increases, the threshold current rapidly increases, and laser oscillation becomes difficult. Further, the IV-VI group semiconductor cannot bring a material having a sufficiently large band gap to the clad layer, and cannot have a large hetero barrier (ΔEc, ΔEv) at the conduction band (valence band) hetero interface. Therefore, there are many carrier leaks from the active layer to the clad layer. These (narrow bandgap) III-V / IV-VI semiconductors have the drawbacks of materials, which makes laser oscillation extremely difficult when the temperature is close to room temperature. Therefore, the oscillation of the semiconductor laser in the 3 to 20 μm band can be obtained only at a low temperature (about 100 to 200 kelvin), and it is difficult to use it for general industrial applications.

【0004】

On the other hand, as a new light emitting mechanism of a semiconductor laser, a quantum cascade laser (hereinafter abbreviated as QC laser) has been realized in recent years (Jerome Faist et al., "Quantum Cascade Laser", Science, vol.264, p.553, 1994). Conventional semiconductor light emitting elements (semiconductor lasers, light emitting diodes, etc.) emit light between bands of semiconductor materials constituting the active layer (electrons in the conduction band recombine with holes in the valence band to combine with the conductor and valence. It emits photons with an energy difference in the electron band).

【0005】

FIG. 15 shows a typical structure of a QC laser (see, for example, Non-Patent Document 1).

【0006】

In FIG. 15, the n-InP first clad layer 82, the InGaAs quantum well layers 83 and 84, the AlInAs quantum barrier layer 85, the n-InP second clad layer 86, and the InGaAs contact layer 87 are formed on the n-type InP substrate 81. Has been done. An insulating InP embedded layer 88 is formed except for the light emitting portion. And AuGe electrodes 89 and 90 are formed. In this QC laser, electrons existing in a high energy level (level A) transition to a low energy level (level B) in a plurality of quantum levels formed in the conduction band of the quantum well layer 84. It emits light by so-called subband transition. For this reason, Auger recombination as described above does not occur, and the heterobarrier can be increased by appropriately selecting the material of the semiconductor superlattice, and the problems of the conventional 3 to 20 μm band semiconductor laser can be raised at once. Can be resolved. The region where the quantum well that emits light is located is called the light emitting region. On the other hand, the electrons that have completed light emission are injected into the level A formed in the light emission region of the next stage in the quantum well layer 83. The region that moves electrons to the higher level of the conduction band is called the injection region.

【0007】

[Non-Patent Document 1]

Mattias Beck et.al., "Continuous Wave Operation of a Mid-Infrared Semiconductor Laser at Room Temperature", Science vol.295, p.301 [0008]

[Problems to be Solved by the Invention]

In FIG. 15, the injection region and the light emitting region are drawn with the quantum well as one layer, but in the actual device, both the light emitting region and the injection region are composed of 5 to 10 layers of superlattices (quantum well and quantum barrier). In addition, in the QC laser, the electrons that have finished emitting light do not disappear due to recombination with holes, but can contribute to the emission again by putting them in the injection layer again and putting them in a higher level, so that one electron can be used again. It emits a large number of photons. Therefore, the more pairs of injection region and emission region, the better the slope efficiency (eg, F. Capasso et al., IEEE Journal on Selected Topics in Quantum Electronics, vol.6, No.6, p.931 (2000). )).

【0009】

Therefore, in a QC laser, 20 to 30 pairs are usually used as a pair of an injection region and a light emitting region. Therefore, the number of layers is (injection layer 5 to 10 layers + light emitting layer 5 to 10 layers) x (20 to 30 stages) = 200 to 600 layers. Although it is experimentally possible to produce such a number of layers at the atomic level of each layer (several to a dozen nm), it is extremely difficult to produce such a number of layers according to the design of each layer with good mass productivity. The variation of each layer causes the variation of the quantum level, which causes a decrease in the optical gain, in other words, an increase in the threshold current and an instability of the oscillation wavelength, which poses a problem in terms of mass production.

【0010】

[Means for solving problems]

In order to solve the above problems, the semiconductor laser apparatus according to claim 1 of the present invention emits photons by energy transition of electrons or holes between specific energy levels formed in the potential well. In addition, in a semiconductor laser in which the energy transition process exists a plurality of times for one electron or hole, the light emitting region has a plurality of potential wells in a direction parallel to the crystal growth plane and is formed in the potential wells. The energy level to be generated is modulated in a direction parallel to the crystal growth plane, and electrons or holes in the light emitting layer move in a direction parallel to the crystal growth plane.

【0011】

This makes it possible to fabricate a quantum cascade structure parallel to the crystal plane, instead of having a quantum cascade structure perpendicular to the crystal plane. That is, if there is at least one controlled crystal growth at the atomic level, a QC laser can be produced, and the conventional atomic level crystal growth of 100 layers or more is not required.

【0012】

In particular, as shown in the semiconductor laser device according to claim 2 of the present invention, if a quantum wire is used as the potential well in the light emitting region, a quantum level suitable for intersubband transition is formed in the potential well. can do.

【0013】

Further, as shown in the semiconductor laser apparatus according to claim 3 of the present invention, if quantum dots are used as potential wells in the light emitting region, the quantum level is larger in size than the minimum line width of the quantum wire. Can be formed, and the production becomes easy.

【0014】

Further, as shown in the semiconductor laser apparatus according to claim 4 of the present invention, it is desirable that the region of the semiconductor adjacent to the light emitting layer that sandwiches the light emitting layer parallel to the crystal plane is an insulating semiconductor. As a result, electrons (or holes) can efficiently flow parallel to the crystal plane.

【0015】

Further, as shown in the semiconductor laser apparatus according to claim 5 of the present invention, the light emitting layer is composed of two or more layers, and electrons or holes move in the direction parallel to the crystal growth plane in each light emitting layer. It is desirable to do. As a result, more photons can be emitted in proportion to the number of layers at the same voltage value, which is suitable for high output.

【0016】

Next, as shown in the semiconductor laser apparatus according to claim 6 of the present invention, such a QC laser can have a positive electrode and a negative electrode on the same surface. This simplifies the mounting process without the need to remove electrodes from the back surface of the laser with a wire bond or the like.

【0017】

Further, as shown in the semiconductor laser apparatus according to claim 7 of the present invention, by using an insulating substrate, parasitic capacitance can be removed and high-speed operation becomes possible.

【0018】

Next, the method for manufacturing a semiconductor laser apparatus according to claim 8 of the present invention includes a step of forming a first conductive clad layer and a first insulating clad layer on a substrate, and the first insulation. A step of forming an active layer having a super lattice cascade structure formed by a photolithography step on the sex clad layer, and a step of forming a second insulating clad layer and a second conductive clad layer on the active clad layer. It is characterized by having. In such a QC laser, it is possible to determine a change in the shape of a quantum wire or a quantum dot, that is, a modulation of an energy level formed in a potential well, by using photolithography frequently used in a semiconductor process. .. Therefore, the modulation of the energy level is determined by one mask, which facilitates the fabrication of a QC laser.

【0019】

In that case, it is desirable to use X-rays as a light source for photolithography as shown in the method for manufacturing a semiconductor laser device according to claim 9 of the present invention. Since X-rays have a wavelength of 0.1 to 1 nm, quantum wires and quantum dot shapes can be produced extremely precisely.

【0020】

Further, as shown in the method for manufacturing a semiconductor device laser device according to claim 10 of the present invention, it is desirable that the superlattice cascade structure portion is formed in one photolithography step. According to this method, a plurality of parts of the semiconductor forming the potential well are formed at a time, and a plurality of parts of the semiconductor forming the potential barrier surrounding the potential well are also formed at a time, thereby forming between the potential wells and between the potential wells. The semiconductor composition fluctuation between the potential barriers is eliminated, and the deviation from the design (oscillation wavelength variation, etc.) due to the composition fluctuation can be suppressed.

【0021】

Next, the method for manufacturing a semiconductor device laser device according to claim 11 of the present invention includes a step of forming a first insulating clad layer on a substrate and photolithography on the first insulating clad layer. A step of forming an active layer having a super lattice cascade structure formed in the step, a step of forming a second insulating clad layer on the active layer, and the first insulating clad layer and the second insulating clad layer. It is characterized by having a part of the insulating clad layer, a portion for flowing electrons or holes into the light emitting region of the active layer, and a step of changing the portion where electrons or holes flow out to be conductive. According to this method, at the stage of crystal growth, the layer in contact with the light emitting layer is an insulating semiconductor, and the portion of the insulating semiconductor that allows electrons or holes to flow into and out of the light emitting region is changed to conductive. Electrons can be efficiently injected into and extracted from the active layer.

【0022】

Next, it is desirable that the method for manufacturing the semiconductor device laser device according to claim 12 of the present invention uses thermal diffusion or ion implantation as a method for changing to the conductivity. These methods are widely used semiconductor processes and do not require special manufacturing equipment.

【0023】

BEST MODE FOR CARRYING OUT THE INVENTION [Embodiments of the Invention]

Hereinafter, the present invention will be described in more detail using embodiments.

【0024】

FIG. 1A is a cross-sectional view (direction perpendicular to the resonator) of the semiconductor laser device according to the first embodiment of the present invention. An insulating InP first clad layer 2 and a conductive InP first clad layer 3 are formed on the n-InP substrate 1. An active layer 4 including a superlattice cascade structure composed of an InGaAs well 5 (In composition 60%) and an AlInAs barrier 6 (In composition 40%) is formed on the upper part of these first clad layers. (AlInAs (In composition 40%) except for the well part 5 and the barrier part 6 in the active layer 4). The widths of the InGaAs well portion 5 and the AlInAs barrier portion 6 differ depending on the location, and form the optimum quantum level in the injection region 12 and the light emitting region 13. An insulating InP second clad layer 7 and a conductive InP second clad layer 8 are formed on the active layer 4. A conductive InGaAs contact layer 9 (In composition 60%) and an AuGe electrode 10 are formed on the second clad layers 7 and 8. The AuGe electrode 11 is also formed on the back surface of the substrate 1.

【0025】

In this embodiment, an electric current is passed between the electrodes 10 and 11. For example, when the electrode 11 is negative and the electrode 10 is positive, electrons are injected from the conductive region 3 into the active layer 4, and subband transition is performed in the super lattice cascade structure portion composed of the injection region 12 and the light emitting region 13 to emit light. After that, it is injected from the active layer 4 into the conductive region 8. The current light output characteristics of this laser are shown in Fig. 1 (b). The measurement was performed at 25 ° C with continuous oscillation. The threshold current is extremely small, about 0.2mA. This is because the cross-sectional area through which the current flows is extremely small. The light output was 1 mW or more, and the slope efficiency was about 0.2 W / A. The oscillation spectrum is shown in Fig. 1 (c). Laser oscillation occurs at the transition between subbands, and the oscillation wavelength is about 9 μm.

【0026】

FIGS. 2 to 6 show a method for manufacturing the present semiconductor laser. The Fe-doped insulating InP first clad layer 2 is crystallized with a thickness of 3 μm using the organic metal vapor phase growth method (MOCVD) on the n-InP substrate 1 (Fig. 2 (a)). Then, after covering the portion to be left as the insulating InP by photolithography, Si is ion-implanted by the ion implantation method to form the conductive InP first clad layer 3 (Fig. 2 (b)). Next, using MOCVD, InGaAs5 (In composition 60%) is crystal-grown by a thickness of 5 nm (Fig. 3 (c)). SiO on its surface₂After forming, only the part corresponding to the well part in the cascade structure is SiO using photolithography.₂Leave stripe 21 (Fig. 3 (d)). As a light source for photolithography that leaves this well, X-rays (wavelength 0.1 nm) using synchrotron radiation of electrons were used. For the sake of simplicity in this figure, SiO is used as the part where InGaAs is left.₂Five stripes are formed, but in the actual device, SiO₂The stripes were left as follows.

【0027】

Injection area: (Unit nm, interval in ()) 2.1 + (1.2) +6.5 + (1.2) +5.3 + (2.3) Emission area: (Unit nm, interval in ()) 4.0+ (1.1) +3.6 + (1.2) +3.0 + (1.6) That is, 6 SiO per set of this injection region / light emission region₂Stripe 21 remains. This time, 30 sets of injection / emission regions are arranged in sequence, so 180 SiO₂Stripe 21 remains. Since the width of this cascade structure is determined by using photolithography, it can be formed extremely easily and freely. That is, in the past, the cascade direction in which the electrons of the QC laser were sequentially emitted was perpendicular to the crystal growth plane, so the QC laser structure was determined by the crystal growth, but the QC laser structure this time can be determined by photolithography. ..

【0028】

After this, SiO is used by citric acid-based wet etching.₂InGaAs unmasked by stripe 21 was selectively removed (Fig. 4 (e)). Then, using MOCVD selective growth, SiO₂The active layer 4 (excluding the well 5) and the AlInAs barrier 6 are formed only where the stripe 21 is not masked (Fig. 4 (f)).

【0029】

Since these In compositions are carried out by the same crystal growth, the In composition of both the active layer 4 (excluding the well portion 5) and the barrier portion 6 is 40%. After that, SiO₂Stripe 21 is removed with a phosphoric acid-based etchant (Fig. 5 (g)). Next, MOCVD is used to form the insulating InP second clad layer 7 (Fig. 5 (h)). Then, as in FIG. 3 (c), the conductive InP second clad layer 8 is formed by using photolithography and ion implantation (FIG. 6 (i)) (this conductive second clad layer is formed by InGaAs. After forming the contact layer 9).

【0030】

Finally, after forming the InGaAs contact layer 9 (In composition 60%) by MOCVD, AuGe electrodes 10 and 11 are formed. Then the wafer is cleaved and the laser is completed. The cavity length is 1 mm and the width is 300 μm.

【0031】

FIG. 7 is a cross-sectional view (direction perpendicular to the resonator) of the semiconductor laser device according to the second embodiment of the present invention. The insulating InP first clad layer 2 is formed on the insulating InP substrate 30. An active layer 4 including a superlattice cascade structure composed of an InGaAs well portion 5 (In composition 60%) and an AlInAs barrier portion 6 (In composition 40%) is formed on the upper part of the first clad layer.

【0032】

The widths of the InGaAs well portion 5 and the AlInAs barrier portion 6 differ depending on the location, and form the optimum quantum level in the injection region 12 and the light emitting region 13.

【0033】

The material other than the superlattice cascade structure portion in the light emitting region is AlInAs (In composition 40%) as in the barrier portion 6. An insulating InP second clad layer 7 is formed on the active layer 4. An insulating InGaAs contact layer 31 (In composition 60%) is formed on the second clad layer 7.

【0034】

Conductive regions 35 and 36 in which Si is thermally diffused are formed on both sides of the injection region 12 / light emitting region 13 in the clad layer and the contact layer. AuGe electrodes 32 and 33 are separated and formed on the surfaces of the conductive regions 35 and 36. No electrode is formed on the back surface of the substrate 1.

【0035】

In this embodiment, a current is passed between the electrodes 32 and 33. For example, when the electrode 32 is negative and the electrode 33 is positive, electrons are injected into the active layer 4 from the region 35 where Si ions are thermally diffused and become conductive, and subband transitions are performed in cascade portions 12 and 13 to emit light. After that, it is injected from the active layer 4 into the conductive region 36.

【0036】

Unlike the first embodiment, this structure is easy to mount because it can be electrically connected from the electrodes 32 and 33 on the same surface.

【0037】

The threshold current of this laser was 0.2mA, and the maximum output was 10mW in room temperature pulse operation. The oscillation wavelength is about 9 μm. In the case of this second embodiment, since the electrodes are only on the surface, mounting is easy (no wire bond is required).

【0038】

In addition, by using the insulating substrate 30, the parasitic capacitance was reduced and modulation was possible up to 10 GHz or higher.

【0039】

8 to 11 show a method for manufacturing the present semiconductor laser. Using the metalorganic vapor phase growth method (MOCVD) on the insulating InP substrate 30, crystal growth of the insulating InP first clad layer 2 with a thickness of 3 μm and InGaAs5 (In composition 60%) with a thickness of 5 nm (Fig. 8 (Fig. 8)). a)).

【0040】

SiO on its surface₂After forming, only the part corresponding to the well part in the cascade structure is SiO using photolithography.₂Leave stripe 21 (Fig. 8 (b)).

【0041】

For simplicity in this figure, SiO is used as the part where InGaAs is left.₂Five stripes are formed, but in the actual device, SiO₂The stripes were left as follows.

【0042】

Injection area: (Unit nm, interval in ()) 2.1 + (1.2) +6.5 + (1.2) +5.3 + (2.3) Emission area: (Unit nm, interval in ()) 4.0+ (1.1) +3.6 + (1.2) +3.0 + (1.6) That is, 6 SiO per set of this injection region / light emission region₂Stripe 21 remains. This time, 30 sets of injection / emission regions are arranged in sequence, so 180 SiO₂Stripe 21 remains. Since the width of this cascade structure is determined by using photolithography, it can be formed extremely easily and freely.

【0043】

That is, in the past, the cascade direction in which the electrons of the QC laser were sequentially emitted was perpendicular to the epiplane, so the QC laser structure was determined by crystal growth, but the QC laser structure this time can be determined by photolithography.

【0044】

After this, SiO is used by citric acid-based wet etching.₂InGaAs unmasked by stripe 21 was selectively removed (Fig. 9 (c)).

【0045】

Then, using MOCVD selective growth, SiO₂The active layer 4 (excluding the well 5) and the AlInAs barrier 6 are formed only where the stripe 21 is not masked (Fig. 9 (d)). Since these In compositions are carried out by the same crystal growth, both have an In composition of 40%.

【0046】

After that, SiO₂Stripe 21 is removed with a hydrofluoric acid-based etchant (Fig. 10 (e)).

【0047】

Next, using MOCVD, an insulating InP second clad layer 7 and an insulating InGaAs contact layer 31 (In composition 60%) are formed (Fig. 10 (f)).

【0048】

Next, using photolithography, conductive portions 35 and 36 are formed by thermal diffusion of Si (Fig. 11 (g)). Further, photolithography is used to form AuGe electrodes 32 and 33 (Fig. 11 (h)). Then the wafer is cleaved and the laser is completed.

【0049】

The second embodiment is characterized in that the number of crystal growths is small and the process is easy as compared with the first embodiment.

【0050】

FIG. 12 is a third embodiment of the present invention. The basic structure (current flow path, etc.) is the same as in Fig. 7, but quantum dots 41 are used instead of quantum wires (in the figure, many quantum dots formed are simplified and described). ..

【0051】

The length of the quantum dot 41 changes in the direction parallel to the cleavage plane (the length direction in which the current flows in each dot). As the width, injection area: (unit nm, interval in ()) 4.1+ (2.2) +8.5 + (2.2) +7.3 + (4.3) Emission area: (unit nm, interval in ()) 6.0+ (3.1 ) + 5.6 + (3.2) + 5.0 + (3.6) was used.

【0052】

The width of the quantum dots in the direction perpendicular to the cleavage plane (the width at which the current in each dot flows) was set to 5 nm.

【0053】

By making quantum dots, the size required to form the same quantum level can be made larger than the quantum wire (for example, the minimum value of the shape dimension is 1.1 nm for the quantum wire (first, first). 2), quantum dots achieve the same function at 2.2 nm), which facilitates fabrication.

【0054】

The manufacturing method of this quantum dot is basically the same as that shown in the second embodiment (FIGS. 8 to 11), but the SiO of the well portion.₂Make the photolithography pattern of mask 42 square and SiO₂SiO instead of Figure 9 (c) where the stripe was made₂Change the mask pattern into dots as shown in Fig. 13 (a).

【0055】

As a result, the active layer 43 including the barrier portion is embedded and SiO₂After removing, the result is as shown in Fig. 13 (b). After this, the process is the same as in FIGS. 10 (f) to 11 (h).

【0056】

A fourth embodiment of the present invention is shown in FIG. A second active layer 52 is formed via an insulating InP intermediate layer 51, and a second InGaAs well portion 53 and a second AlInAs barrier portion 54 are formed inside the second active layer 52 (both are quantum wires perpendicular to the paper surface). ). By forming the cascade structure into two layers in this way, more electrons can be contributed to light emission, and the output can be increased. Specifically, in this laser structure, as compared with the first embodiment, twice the current can be passed for the same applied voltage value, and about twice the light output can be obtained. In the present embodiment, the cascade structure has two layers, but three or more layers may be used.

【0057】

[Effect of the invention]

The common features of the above embodiments 1 to 4 will be summarized. Conventionally, a cascade structure was created by depositing epi membranes. For this reason, not only the crystal growth is extremely troublesome, but also the compositions of the films during the crystal growth are slightly different from each other, resulting in variations in the oscillation wavelength.

【0058】

In the structure of the present invention, each crystal composition of the well portion / barrier portion is the same regardless of any two in each portion. Therefore, it is possible to suppress wavelength fluctuations in the cascade operation and obtain excellent laser characteristics. For example, conventional QC lasers often oscillate in multi-vertical mode due to variations in composition. The structure of the present invention has many advantages such as being able to obtain a single longitudinal mode because there is no composition variation in the superlattice in both the first to fourth embodiments.

[Simple explanation of drawings]

FIG. 1 (a) Cross-sectional view of the semiconductor laser diode according to the first embodiment of the present invention (b) Current light output characteristic diagram of the semiconductor laser diode according to the first embodiment of the present invention (c) The present invention FIG. 2 is an oscillation wavelength spectrum diagram of the semiconductor laser device according to the first embodiment of the present invention. FIG. 2A is a diagram showing a method for manufacturing a semiconductor laser according to the first embodiment of the present invention. The figure which shows the manufacturing method of the semiconductor laser in an Embodiment [FIG. 3] (c) The figure which shows the manufacturing method of the semiconductor laser in the 1st Embodiment of this invention (d) in the 1st Embodiment of this invention FIG. 4 showing a method for manufacturing a semiconductor laser [Fig. 4] (e) Fig. 4 showing a method for manufacturing a semiconductor laser according to the first embodiment of the present invention (f) Manufacture of a semiconductor laser according to the first embodiment of the present invention. FIG. 5 (g) A diagram showing a method for manufacturing a semiconductor laser according to the first embodiment of the present invention (h) A diagram showing a method for manufacturing a semiconductor laser according to the first embodiment of the present invention. FIG. 6 (i) is a diagram showing a method for manufacturing a semiconductor laser according to the first embodiment of the present invention (j) is a diagram showing a method for manufacturing a semiconductor laser according to the first embodiment of the present invention [FIG. 7]. Cross-sectional view of the semiconductor laser diode device according to the second embodiment of the present invention [Fig. 8] (a) A diagram showing a method for manufacturing the semiconductor laser diode device according to the second embodiment of the present invention (b) Second embodiment of the present invention. FIG. 9 (c) Fig. 9 (c) Fig. 9 showing the manufacturing method of the semiconductor laser device according to the second embodiment of the present invention (d) The second embodiment of the present invention. FIG. 10 (e) Fig. 10 showing a method of manufacturing a semiconductor laser device according to the second embodiment of the present invention (f) Fig. 10 showing a method of manufacturing a semiconductor laser device according to the second embodiment of the present invention. FIG. 11 (g) is a diagram showing a method of manufacturing a semiconductor laser diode according to a second embodiment of the present invention (h) a diagram showing a method of manufacturing a semiconductor laser diode according to a second embodiment of the present invention. FIG. 12 is a cross-sectional view of a semiconductor laser diode according to a third embodiment of the present invention [FIG. 13] (a) a third embodiment of the present invention.FIG. 6 showing a method of manufacturing a semiconductor laser device in a state (b) FIG. 14 showing a method of manufacturing a semiconductor laser device according to a third embodiment of the present invention. FIG. [Fig. 15] Cross-sectional view of a conventional semiconductor laser device [Explanation of reference numerals]

1, 81 n-InP substrate 2 Insulating InP 1st clad layer 3 Conductive InP 1st clad layer 4 AlInAs active layer (including InGaAs well 5 and AlInAs barrier 6) 5 InGaAs well 6 AlInAs barrier 7 Insulation InP second clad layer 8 Conductive InP second clad layer 9 Conductive InGaAs contact layer 10, 11, 32, 33, 89, 90 AuGe electrode 12 Injection region 13 Light emitting region 21, 42 SiO₂Mask 30 Insulating InP substrate 31 Insulating InGaAs contact layers 35, 36 Si Thermal diffusion conductive part 41 Quantum dots 43 Active layer including barrier part 51 Insulating InP intermediate layer 52 Second active layer 53 Second InGaAs well part 54 Second AlInAs barrier Part 82 n-InP 1st clad layer 83, 84 InGaAs quantum well layer 85 AlInAs Quantum barrier layer 86 n-InP 2nd clad layer 87 n-InGaAs contact layer 88 Insulating InP embedded layer