JPH1174603A - Semiconductor laser element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such an element as both operational current and noise are reduced by, relating to a self-excited oscillation type semiconductor laser element, realizing a high-efficient photon recycle operation wherein a carrier generated in an oversaturation absorption layer is re-injected only in a stripe. SOLUTION: The semiconductor laser element comprises, on a first conductive type semiconductor substrate 101, a first conductive type clad layer 102, an active layer 103, a second conductive type first clad layer 104, and a current constriction layer which has a stripe-like groove 106 reaching the second conductive type first clad layer 104, and whose band gap is larger than the active layer, and a second conductive type second clad layer 108. On the upper surface of the region where no current constriction layer is formed of the second conductive type first clad layer 104 and on the upper surface of the current constriction layer, a continuous oversaturation absorption layer 107 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-sustained pulsation type semiconductor laser device which operates with low current and low noise for various optical disk systems, in particular, a light source of a rewritable optical disk system, and a method of manufacturing the same. Things.

[0002]

2. Description of the Related Art In a conventional semiconductor laser device used for an optical disk system or the like, so-called "return light noise" is problematic in that noise is generated when laser light reflected by a disk or the like re-enters the semiconductor laser device. Has become.
As a means for reducing this return light noise, a method utilizing the self-excited oscillation phenomenon is known.
Japanese Patent No. 18160 discloses a self-pulsation type semiconductor laser device as described below.

(Conventional Example 1) FIG. 5 shows a structural sectional view of a first self-pulsation type semiconductor laser device disclosed in the above publication. This semiconductor laser has an n-GaAs substrate 1 on which n-
GaAs buffer layer 2, n-AlGaAs cladding layer 3, undoped active layer 4, p-AlGaAs first cladding layer 5, p-AlGaAs saturable absorbing layer 6, p-AlG
An aAs second cladding layer 7 and a p-GaAs cap layer 8 are formed. The p-AlGaAs second cladding layer 7 and the p-GaAs cap layer 8 are etched into a ridge shape, and the p-AlGaAs saturable absorption layer 6 outside the ridge is formed.
Above the p-AlGaAs second cladding layer 7 and p-G
n-AlGaAs so as to bury the aAs cap layer 8
A current blocking layer 9 is formed. Further, a p-GaAs contact layer 10 is formed on the p-GaAs cap layer 8 and the n-AlGaAs current blocking layer 9.

In this configuration, it is shown that the self-excited oscillation of the oscillation spectrum is caused by the p-AlGaAs saturable absorption layer 6 and the coherence is reduced, so that the return optical noise is reduced.

(Conventional Example 2) FIG. 6 is a sectional view showing the structure of a second self-pulsation type semiconductor laser device disclosed in the above publication. In this semiconductor laser, the p-AlGaAs saturable absorption layer 6 in the self-pulsation type semiconductor laser device of the conventional example 1 is formed only in the p-AlGaAs second cladding layer 7 inside the ridge.

[0006] In this configuration, due to the decrease in volume, p
It is shown that since the light density in the saturable absorption layer 6 of AlGaAs is increased, the range of conditions under which self-pulsation can occur becomes wider.

(Conventional Example 3) FIG.
FIG. 1 shows a structural sectional view of a third self-pulsation type semiconductor laser device disclosed in No. 083. This semiconductor laser is n-GaAs
This is a self-aligned self-sustained pulsation laser in which a stripe-shaped groove 16 is formed in the s light absorbing layer 15, and the n-GaAs light absorbing layer also has a current confinement mechanism.

In this configuration, self-excited oscillation occurs between the two modes whose phases are inverted by the p-AlGaAs saturable absorption layer 17.

[0009]

However, the conventional examples 1 and 2 have the following problems. In the semiconductor laser device of Conventional Example 1, as shown in FIG. 7, most of the carriers generated in the saturable absorbing layer inside the ridge stripe due to light absorption diffuse into the saturable absorbing layer outside the ridge stripe due to the concentration gradient. Among the generated carriers, the electrons diffuse into the current blocking layer having a low potential barrier and recombine with the injected holes to disappear. On the other hand, the generated holes easily overflow into the p-first cladding layer, which does not have a very high potential barrier, so that the current caused by the holes spreads more than the ridge width and is re-injected into the active layer.

The operation in which carriers generated by light absorption again contribute to light emission is called photon recycling, which contributes to a reduction in laser operating current and an increase in self-excited oscillation output. There is a problem that the photon recycling efficiency is low because the injection current spreads much larger than the stripe width.

In the semiconductor laser device structure of Conventional Example 2, the current blocking layer epitaxially grows upward from the surface of the p-first cladding layer during the crystal growth.
At the crystal interface between the saturable absorption layer and the current blocking layer, there are surface defects composed of crystal defects and high resistance layers. The generated electrons are blocked from diffusing by the surface states, and recombine with holes in the saturable absorption layer and disappear. That is, there is a disadvantage that the photon recycling operation is not performed.

In addition, since the lifetime of carriers that disappear in such a process is longer than the lifetime of carriers that disappear by diffusion, saturation of light absorption in the saturable absorbing layer is apt to occur, and the self-excited oscillation output increases. There is a problem that it is difficult.

In the semiconductor laser device structure of Conventional Example 3, since the saturable absorbing layer outside the ridge stripe is separated by the light absorbing layers of different conductivity types, carriers generated by light absorption are re-transmitted to the active layer in the stripe. Although it is easy to inject, as shown in FIG. 11, there is a problem that the efficiency is low as in the first conventional example.

As described above, in the conventional self-pulsation type semiconductor laser device, since photon recycling is not performed efficiently, it has been difficult to achieve both a reduction in operating current and an increase in self-pulsation output.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has as its object to provide a semiconductor laser device having high photon recycling efficiency.

[0016]

According to the present invention (claim 1), a semiconductor laser device is provided on a first conductivity type semiconductor substrate.
A first conductivity type cladding layer, an active layer, a second conductivity type first cladding layer, a current confinement layer having a stripe-shaped groove reaching the second conductivity type first cladding layer and having a larger band gap than the active layer; In a semiconductor laser device having at least a second conductive type second cladding layer, a saturable absorbing layer continuous with the upper surface of the current confining layer non-forming region and the upper surface of the current constricting layer of the second conductive type first cladding layer. The above-mentioned object is achieved by forming a.

According to a second aspect of the present invention, there is provided a semiconductor laser device comprising: a first conductive type clad layer, an active layer, a second conductive type first clad layer, an etching stop layer, A current confinement layer having a stripe-shaped groove reaching the etching stop layer and having a larger band gap than the active layer; an upper surface of the non-current confinement layer forming region of the second cladding layer of the second conductivity type; A saturable absorption layer formed continuously, and a second cladding layer of a second conductivity type, wherein the etching stop layer has a band gap larger than that of the active layer, and the second cladding layer of the second conductivity type. By being smaller, the above objective is achieved.

In the semiconductor laser device according to the present invention (claim 3), the etching stop layer has a film thickness that produces a quantum effect, and has a band gap larger than that of the active layer. To achieve.

According to the semiconductor laser device of the present invention (claim 4), a first conductivity type clad layer, an active layer, a second conductivity type first clad layer, an etching stop layer, A semiconductor laser device having a stripe-shaped groove reaching an etching stop layer, a current confinement layer having a larger band gap than the active layer, and a second cladding layer of a second conductivity type, wherein An electron barrier layer having a band gap substantially equal to that of the second conductive type second cladding layer is formed in the stripe-shaped groove, and a saturable absorption layer continuous with the upper surface of the electron barrier layer and the upper surface of the current confinement layer. The above-mentioned object is achieved by forming.

In the semiconductor laser device according to the present invention (claim 5), the current confinement layer having the stripe-shaped grooves may be:
The film thickness in a region without a stripe-shaped groove is 0.1 μm or more and 1
The above-mentioned object is achieved by the fact that the thickness is not more than μm.

In the semiconductor laser device according to the present invention (claim 6), the above object is achieved by forming the saturable absorption layer in a single crystal growth step.

The operation of the present invention will be described below. According to the first aspect of the present invention, the saturable absorbing layer is continuous from the inside of the stripe to the outside of the stripe, and the saturable absorbing layer outside the stripe is formed by a current blocking layer having a large potential barrier against holes. 1 It is formed separately from the upper cladding layer. Therefore, the holes generated in the saturable absorption layer in the stripe do not overflow into the first upper cladding layer outside the stripe but are re-injected only into the active layer in the stripe. Due to this highly efficient photon recycling operation, current spread is suppressed and the current of the semiconductor laser device is reduced. In addition, high-efficiency photon recycling can maintain the self-sustained pulsation of the laser element up to high output, so that return light noise can be avoided even when writing to an optical disc system, and both low noise operation and high output operation are realized. You.

According to the second and third aspects of the present invention, even when an etching stop layer reaching the outside of the stripe is formed at the interface between the saturable absorption layer and the first upper cladding layer within the stripe, the etching is performed. By making the band gap of the stop layer larger than the band gap of the saturable absorbing layer and the active layer, diffusion of electrons from the saturable absorbing layer to the etching stop layer is prevented, and holes are re-injected only into the stripe. Can be done. Thus, as in the first aspect, a highly efficient photon recycling operation can be obtained.

According to the fourth aspect of the present invention, by forming a semiconductor layer of the second conductivity type having a band gap sufficiently larger than that of the etching stop layer and the saturable absorption layer and isolating both layers, light is removed. Electrons generated by absorption can be prevented from diffusing into the etching stop layer. Thus, a highly efficient photon recycling operation can be obtained as in the first and second aspects of the invention. Further, by making the band gap of the semiconductor layer substantially equal to that of the second upper cladding layer, a change in optical characteristics can be reduced.

According to the fifth aspect of the present invention, the current confinement layer having the stripe-shaped groove has a thickness outside the stripe of 0.1 μm or more and 1 μm or less because the region without the stripe-shaped groove has a thickness of 0.1 μm or more and 1 μm or less. The saturable absorbing layer is formed so as to be separated from the first upper cladding layer by 0.1 μm or more in the stacking direction, and the carriers generated in the saturable absorbing layer are located at the interface between the current blocking layer and the first upper cladding layer. It is not affected by the resulting depletion layer. Therefore, a highly efficient photon recycling operation can be realized without hindering the diffusion of carriers. Although the upper limit of the thickness of the current confinement layer is considered to be theoretically non-existent, when forming a groove by etching, if the thickness is too large, it is necessary to lengthen the etching time, and as a result, it is difficult to control the stripe width. Becomes Therefore, in order to control the stripe width (1 to 4 μm) with good reproducibility, it is preferable that the current confinement layer is 1 μm or less.

According to the sixth aspect of the present invention, the saturable absorbing layer inside and outside the stripe is formed simultaneously in the crystal growth step, so that the high resistance region and the defective region are formed in the saturable absorbing layer. Does not exist. Therefore, the electrons generated in the saturable absorption layer smoothly diffuse from inside the stripe to outside the stripe, and a highly efficient photon recycling operation can be realized.

[0027]

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

(Embodiment 1) FIG. 1 is a sectional view of a semiconductor laser device according to an embodiment of the present invention. This semiconductor laser device is manufactured as follows.

First, a 1.0 μm n-Al _0.5 Ga _0.5 A is formed on the n-GaAs substrate 101 by the first crystal growth.
s cladding layer 102, non-doped quantum well active layer 10
3. A 0.2 μm p-Al _0.5 Ga _0.5 As first cladding layer 104 and a 0.6 μm n-Al _0.7 Ga _0.3 As current blocking layer 105 are sequentially stacked. The non-doped quantum well active layer 103 is formed of a 0.01 μm Al _0.14 Ga _0.86 As well layer, a 0.01 μm Al _0.3 Ga _0.7 As barrier layer, and a guide layer having the same structure. In the present embodiment, the number of well layers is three. Next, using known photolithography technology and selective etching technology,
A stripe-shaped groove 106 is formed in the n-AlGaAs current blocking layer 105 so as to reach the p-AlGaAs first cladding layer 104. The width of the striped groove 106 is pA.
1 at the interface with the first cladding layer 104
4 μm. After that, the second crystal growth was performed to reduce
01 μm p-Al _0.14 Ga _0.86 As saturable absorption layer 10
7,1.2μm of p-Al _{0. 5} Ga _0.5 As second cladding layer 108,2.0μm of the p-GaAs cap layer 109
Are sequentially laminated. Finally, the p-GaAs cap layer 109
Ohmic electrodes are formed on the upper surface and the lower surface of the n-GaAs substrate 101, respectively. The cavity length is adjusted to 300 μm by a cleavage method, and a coating film having a reflectivity of 30% is formed on both end surfaces of the cleavage. Obtained.

The room temperature of the semiconductor laser device of this embodiment is 25.
The operating current at a light output of 30 mW and the maximum output of self-sustained pulsation at 30 ° C. are shown in Table 1 below. As a comparative example, a semiconductor laser device having the same structure as that of the conventional example 1 was manufactured from the material of the present embodiment, and the result of the same evaluation is also shown.

[0031]

[Table 1]

As can be understood from Table 1, the semiconductor laser device of this embodiment in which the p-AlGaAs saturable absorbing layer outside the stripe is formed separately from the p-AlGaAs first cladding layer, -The operating current is smaller than that of the semiconductor laser device of the comparative example in which the AlGaAs saturable absorbing layer is formed in contact with the p-AlGaAs first cladding layer, and the maximum self-excited oscillation output is more than doubled.

The reason why such a result is obtained is considered as follows. FIG. 2 shows the p-AlGaAs saturable absorption layer 107 due to light absorption in the present embodiment.
4 shows the diffusion path of the carrier generated in step (1).

The electrons diffused outside the stripe are n-AlG
The process of diffusion to the aAs current blocking layer is the same as in the case of Conventional Example 1, except that holes have a potential barrier on the n-AlGaAs current blocking layer side and a carrier concentration gradient on the p-AlGaAs second cladding layer side. Therefore, the diffusion current due to holes is re-injected into the active layer region immediately below the stripe. By this operation, the current spread outside the stripe can be suppressed, the operating current is reduced, and the carriers generated in the saturable absorbing layer are efficiently consumed, so that the light absorption is less likely to be saturated and the self-excited oscillation output is increased. I do.

In this embodiment, n-AlGaAs
The current blocking layer 105 is composed of the p-AlGaAs saturable absorption layer 10.
7, the current blocking layer 1 is made of n-GaAs as in the conventional example 3.
When the layer 05 is formed, the potential barrier against holes cannot be increased, so that when holes are excessively generated, the holes easily overflow into the current blocking layer, and the effect of the present invention cannot be obtained.

The n-AlGaAs current blocking layer and the p-
A depletion layer due to the pn junction exists at the interface with the AlGaAs first cladding layer, and its thickness is estimated to be within 0.1 μm from the pn junction interface in the laminating direction. In this region, the diffusion of carriers is hindered by the electric field in the depletion layer. Therefore, the saturable absorption layer outside the current confinement portion is formed to be separated from the p-first cladding layer by 0.1 μm or more in the stacking direction. Is preferred.

In this embodiment, the active layer has three quantum well layers. However, the effect of the present invention is not impaired even in a so-called multiple quantum well structure employing another number of well layers.

(Embodiment 2) FIG. 3 is a sectional view of a semiconductor laser device of an embodiment according to the second invention. This embodiment is different from the first embodiment in that p-AlGaAs
0.05 μm p-Al _0.2 on the first cladding layer 104
The point is that a Ga _0.8 As etching stop layer 110 is formed. Since the p-AlGaAs etching stop layer 110 in the present embodiment has a lower Al mixed crystal ratio than the p-Al _0.5 Ga _0.5 As second cladding layer 108, the first embodiment
As compared with the above, the selectivity at the time of etching the stripe-shaped groove 106 can be improved. Since an Al oxide is less likely to be formed than in the first embodiment, interface defects during crystal regrowth can be reduced, and the reliability and yield of the semiconductor laser device can be greatly improved. Further, since the etching stop layer 110 does not absorb laser light, it does not affect the saturable absorption effect at all.

The thickness of the etching stopper layer 110 of this embodiment containing Al is preferably 100 to 200 ° or more, more preferably 500 ° (0.05 μm) or more.

In this embodiment, the band gap of the p-AlGaAs etching stop layer 110 is 1.67 eV.
Then, as shown in FIG. 9, the p-AlGaAs saturable absorption layer 1
A substantial band gap of 1.45 due to the quantum level of 07
greater than eV. For this reason, electrons generated by light absorption cannot diffuse from the saturable absorption layer to the etching stop layer, but diffuse and disappear along the same path as described in the first embodiment. For holes generated by light absorption,
Since the barrier between the saturable absorber layer and the etch stop layer is not very high, it is re-injected only into the stripe with excess injected carriers. Thus, as in the first invention,
A highly efficient photon recycling operation can be obtained.
Optical output 3 at room temperature 25 ° C. of the semiconductor laser device of this embodiment
The operating current at 0 mW and the maximum output of self-excited oscillation were 55 mA and 45 mW, respectively. As a result, the interface defects were reduced, and it was found that the photon recycling operation was performed with higher efficiency than in the first embodiment.

In this embodiment, n-AlGaAs
The groove 106 is formed by etching the current blocking layer 105 in a stripe shape. The current blocking layer 105 has an Al mixed crystal ratio of ~
Since it is as high as 0.7, etching is performed using hydrofluoric acid (HF). The HF etching rate changes exponentially with respect to the Al mixed crystal ratio, and is hardly etched when the Al mixed crystal ratio is ０．４0.4 or less. In this embodiment, since the etching stop layer 110 is relatively thick, 0.05 μm, even if it is slightly etched, the function as the etching stop layer can be sufficiently performed. Therefore, the upper limit of the Al mixed crystal ratio is 0.1.
4, more preferably 0.25 or less.

(Embodiment 3) In this embodiment, a semiconductor laser device of the present invention was manufactured in exactly the same manner as in Embodiment 2, except that the etching stop layer 110 was made of p-GaAs having a thickness of 0.003 μm.

In this embodiment, the p-GaAs etching stop layer 110 is made of Al _0.2 Ga _0.8 A in Embodiment 2.
Since the Al mixed crystal ratio is lower than s, the reliability and yield of the semiconductor laser device can be further improved. Further, since the etching stopper layer 110 is very thin, the etching stopper layer itself does not work as a saturable absorbing layer.

The layer thickness of the etching stopper layer 110 of this embodiment which does not contain Al sufficiently fulfills its function at 20 ° or more. On the other hand, whether or not to absorb laser light is determined by the band gap, so that the Al mixed crystal ratio is involved with the layer thickness. The GaAs etching stop layer 110 of the present embodiment has a thickness of up to 30 °.
The following quantum well layer does not absorb laser light at all.

In this embodiment, the p-GaAs etching stop layer 110 is a p-AlGaAs saturable absorption layer 10.
Since the Al mixed crystal ratio is lower than 7, light absorption and diffusion of generated carriers occur in the stripe. However, outside the stripe, the p-GaAs etching stop layer 1
Since the layer is sandwiched by layers having an Al mixed crystal ratio higher than 10, the substantial band gap due to the quantum level becomes larger than that in the stripe. Due to this band gap difference, the generated electrons cannot diffuse from inside the stripe to outside the stripe,
The same effects as described in the second embodiment can be obtained.

Room temperature of the semiconductor laser device of the present embodiment 25
The operating current and the maximum output of self-sustained pulsation at an optical output of 30 mW at 50 ° C. were 50 mA and 50 mW, respectively. As a result, the interface defects were further reduced. As a result, it was found that the photon recycling operation was performed more efficiently than in the second embodiment. .

(Embodiment 4) FIG. 4 is a sectional view of a semiconductor laser device according to an embodiment of the third invention. This embodiment is different from the previous embodiment 3 in that the striped groove 1
06 internal p-GaAs etching stop layer 110 and p-
The point is that the 0.1 μm p-Al _0.5 Ga _0.5 As electron barrier layer 111 is formed between the saturable absorption layer 107 and the AlGaAs. This semiconductor laser device is manufactured as follows.

First, as in the third embodiment, the layers up to the n-AlGaAs current blocking layer 105 are sequentially stacked on the n-GaAs substrate 101. Next, the n-AlGaAs current blocking layer 105
A 1.0 μm SiO ₂ film is deposited thereon, and the Si ₂ film is formed using known photolithography and selective etching techniques.
Only the O ₂ film is processed into a stripe shape. Furthermore, p-GaAs is used as an etching mask using the stripe-shaped SiO ₂ film.
n-AlG to reach the s etching stop layer 111.
A stripe-shaped groove 106 is formed in the aAs current blocking layer 105. With the SiO ₂ film remaining, the p-AlGaAs electron barrier layer 111 is grown only inside the stripe-shaped groove 106 by a known selective growth technique, and the sample is transferred to another reaction chamber so as not to be exposed to the atmosphere. Only the SiO ₂ film is removed by the etching technique. The sample was returned to the crystal growth apparatus again so as not to be exposed to the atmosphere, and the p-AlGaAs saturable absorption layer 107 and the p-AlGaAs second cladding layer 10 were removed.
8. The p-GaAs cap layer 109 is sequentially stacked.

In the present embodiment, since both layers are separated by the electron barrier layer 111 having a band gap sufficiently larger than that of the etching stop layer and the saturable absorption layer, electrons generated by light absorption are emitted from the saturable absorption layer. Diffusion to the etching stop layer can be prevented.

In the present embodiment, the thickness of the electron barrier layer 111 is set to 0.1 μm. However, in order to prevent electrons from passing through the barrier layer by a tunnel effect, the thickness of the barrier layer is set to 0.05 μm or more. Is preferred.

The band gap of the electron barrier layer 111 is
The effect of the present invention can be obtained if it is sufficiently larger than the etching stop layer and the saturable absorption layer. However, by making the band gap of the barrier layer equal to that of the second upper cladding layer as in the present embodiment shown in FIG. In addition, changes in optical characteristics can be reduced.

The room temperature of the semiconductor laser device of this embodiment is 25.
The operating current and the maximum output of self-sustained pulsation at an optical output of 30 mW at 45 ° C. were 45 mA and 60 mW, respectively, and the effect of preventing the diffusion of electrons was increased. Therefore, the photon recycling operation was more efficient than in the third embodiment. It turned out that it was being done. The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. Although only the AlGaAs-based material is shown as a material system, other material systems such as AlGaAsP and AlGaIn
Similar effects can be obtained with a P-based material. Even when the active layer has a bulk structure having no quantum effect, or when the saturable absorber layer has a bulk structure or a multiple quantum well structure, the same effect can be obtained as long as the gist of the present invention is not contradicted. Further, even if the oscillation wavelength of the active layer, the absorption coefficient of the saturable absorption layer, or the resonator length or the end face reflectivity are changed, the effects of the present invention are not impaired.

[0053]

As described above, according to the present invention, the carriers generated in the saturable absorption region are re-injected into the active layer inside the stripe by the high-efficiency photon recycling operation. It is possible to reduce the operating current by suppressing the current spread and increase the self-excited oscillation output. This makes it possible to operate a semiconductor laser used in an optical disk system or the like with low current and low noise.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a diffusion path of a carrier generated in a saturable absorption layer in the first embodiment of the present invention.

FIG. 3 is a sectional view of a semiconductor laser device according to Embodiments 2 and 3 of the present invention.

FIG. 4 is a sectional view of a semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view of a semiconductor laser device in Conventional Example 1.

FIG. 6 is a sectional view of a semiconductor laser device in Conventional Example 2.

FIG. 7 is an explanatory diagram showing a diffusion path of carriers generated in a saturable absorption layer in Conventional Example 1.

FIG. 8 is a cross-sectional view of a semiconductor laser device in Conventional Example 3.

FIG. 9 is a band diagram in Embodiments 2 and 3 of the present invention.

FIG. 10 is a band diagram according to a fourth embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a diffusion path of carriers generated in a saturable absorption layer in a conventional example.

[Explanation of symbols]

 1, 101 n-GaAs substrate 2 n-GaAs buffer layer 3, 102 n-AlGaAs cladding layer 4, 103 active layer 5, 104 p-AlGaAs first cladding layer 9, 105 n-AlGaAs current blocking layer 106 striped groove 6 , 107 p-AlGaAs saturable absorption layer 7, 108 p-AlGaAs second cladding layer 8, 109 p-GaAs cap layer 10 p-GaAs contact layer 110 p-etch stop layer 111 p-electron barrier layer

Claims (6)

[Claims] A first conductive type cladding layer, an active layer, a second conductive type first cladding layer, and a stripe-shaped groove reaching the second conductive type first cladding layer. A current confinement layer having a larger band gap than the active layer;
And a second cladding layer of a second conductivity type, wherein a continuous saturable absorption is provided on an upper surface of the non-current constriction layer forming region of the second cladding layer of the second conductivity type and on an upper surface of the current confinement layer. A semiconductor laser device comprising a layer. A first conductive type clad layer, an active layer, a second conductive type first clad layer, an etching stop layer, and a striped groove reaching the etching stop layer on the first conductive type semiconductor substrate. A current confinement layer having a band gap larger than that of the active layer, an upper surface of the non-current confinement layer forming region of the first cladding layer of the second conductivity type, a saturable absorption layer formed continuously on the upper surface of the current confinement layer; A second conductive type second clad layer, wherein the etching stop layer has a band gap larger than the active layer and smaller than the second conductive type second clad layer. 3. The semiconductor laser device according to claim 2, wherein the etching stop layer has a film thickness that causes a quantum effect to have a band gap larger than that of the active layer. 4. A semiconductor substrate having a first conductivity type, a first conductivity type clad layer, an active layer, a second conductivity type first clad layer, an etching stop layer, and a stripe-shaped groove reaching the etching stop layer. A semiconductor laser device having at least a current confinement layer having a band gap larger than that of the active layer and a second conductive type second clad layer, wherein:
An electron barrier layer having substantially the same band gap as the second conductive type second cladding layer is formed, and a saturable absorption layer is formed continuously on the upper surface of the electron barrier layer and the upper surface of the current confinement layer. Characteristic semiconductor laser device. 5. The current confinement layer having a stripe-shaped groove has a thickness of 0.1 μm in a region without a stripe-shaped groove.
The thickness is not less than 1 μm and not more than 1 μm.
5. The semiconductor laser device according to any one of items 3 and 4. 6. The semiconductor laser device according to claim 1, wherein said saturable absorption layer is formed in a single crystal growth step. Laser element.