JPH05235468A - Semiconductor laser apparatus - Google Patents

Abstract

PURPOSE:To provide a semiconductor laser apparatus of low current operation with low noise for use in a light source for an optical disk. CONSTITUTION:There are provided a one conductivity type Ga1-YAlYAs layer 5 formed on at least one surface of a Ga1-XAlXAs active layer 4 and having a ridge 5a, and an opposite conductivity type Ga1-ZAlZAs layer 6 formed along the longitudinal side surface of the ridge 5a. A relationship Z>Y>X>=0 holds among X, Y, and Z which specify the AlAs mixed crystal ratio. Si is added as an impurity in a GaAlAs layer being an n-type among those respective layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low noise semiconductor laser device which is suitable as a light source for an optical disk or the like with a low operating current value.

[0002]

2. Description of the Related Art A conventional semiconductor laser device will be described below. FIG. 13 is a sectional view of a conventional semiconductor laser device. An n-type GaAs buffer layer 22 is formed on an n-type gallium arsenide (GaAs) substrate 21, and n-type gallium aluminum arsenide (Ga _0.5 Al _0.5 As) is formed thereon.
A p-type Ga _0.5 Al _0.5 As clad layer 25 having a clad layer 23, a Ga _0.85 Al _0.15 As active layer 24, and a ridge 25 a is formed, and a portion other than the ridge 25 a serving as a current channel is provided for current confinement. n-type GaAs
The current blocking layer 26 is formed. Reference numeral 27 is a p-type GaAs protective layer, and 28 is a p-type GaAs contact layer.

In the structure shown in FIG. 13, p-type GaA is used.
The current injected from the s contact layer 28 is the ridge 25a.
Is effectively confined inside, and Ga under the ridge 25a is
Laser oscillation occurs in the _0.85 Al _0.15 As active layer 24. At this time, the refractive index of the n-type GaAs current blocking layer 26 is p.
The refractive index of the n-type GaAs current blocking layer 26 is larger than that of the n-type Ga _0.5 Al _0.5 As clad layer 25.
Since towards the forbidden band width smaller than the forbidden band width of the Ga _{0. 85} Al _0.15 As active layer 24, the n-type with respect to the laser beam Ga
The As current blocking layer 26 serves as an absorber. Therefore, the laser light is effectively confined in the ridge 25a by being absorbed by the n-type GaAs current blocking layer 26.
Generally, by setting the width of the lower end of the ridge 25a, that is, the stripe width to about 5 μm, laser oscillation of a single transverse mode used for an optical disk or the like can be obtained.

[0004]

However, in the above conventional structure, the threshold and efficiency of the laser are limited by the loss of the waveguide due to the optical absorption of the n-type GaAs current blocking layer 26, and the GaAs current is further reduced. Since the laser light is steeply confined in the stripe due to the light absorption of the block layer 26, the spectrum tends to be a single mode, and in order to obtain the multimode oscillation of the spectrum in the conventional structure, the GaAs current block layer 26 is made of Ga. _0.85 Al
_There are problems such as the fact that it must be separated from the _0.15 As active layer 24 to some extent or more, and the operating current is increased due to an increase in the lateral leakage current in the lower portion of the ridge 25a.

Further, if the width of the stripe is narrowed, the absorption of light by the current blocking layer 26 is increased, so that there is a restriction that the width of the stripe cannot be narrowed to a certain extent or less, which has been an obstacle to lowering the operating current.

An object of the present invention is to solve the above-mentioned conventional problems, and an object thereof is to provide a semiconductor laser device having a low operating current, a spectrum of more modes, and a low noise.

[0007]

SUMMARY OF THE INVENTION The semiconductor laser device of the present invention to achieve this object, Ga _1-X Al _X As is formed on at least one surface of the active layer of one conductivity type Ga ₁ with ridges _-Y Al _Y As layer and a Ga ₁ -Z Al _Z As layer of opposite conductivity type formed along the longitudinal side surface of the ridge, and between X, Y and Z that determine the AlAs mixed crystal ratio. Z
>Y> X ≧ 0, and among these layers, n
It has a structure in which Si is added as an impurity to a GaAlAs layer that is a mold.

[0008]

With this configuration, Ga_1-ZAl_ZAs's stra
Ip-shaped window, that is, the current injected from the ridge
Ga_1-XAl_XLaser oscillation occurs in the As active layer, and Ga
_1-ZAl_ZThe refractive index of the As layer is Ga inside the stripe._1-YA
l_YSince the laser light is smaller than the As clad layer, this
It is effectively confined in the stripe due to the difference in folding rate. It
Rani Ga_1-ZAl_ZThe forbidden band width of the As layer is Ga_1-XAl_XAs
Since it is much larger than the forbidden band width of the active layer,
There is almost no light absorption by the current blocking layer, and the current blocking
Light also spreads to the active layer inside the layer and below the current blocking layer.
Well distributed and the spectrum becomes multimodal.

Further, an n-type Ga that guides the laser light is used.
Since Si is added as an impurity to the AlAs layer, it is possible to obtain sufficient multimode oscillation with almost no formation of a loss grating in the n-type GaAlAs layer, which interferes with multimode oscillation.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a semiconductor laser device according to an embodiment of the present invention. n-type GaAs substrate 1
An n-type GaAs buffer layer 2 is formed on the
On top of that, n-type Ga _0.5 Al _0.5 As clad layer 3, Ga
A p-type Ga _0.5 Al _0.5 As clad layer 5 having a _0.85 Al _0.15 As active layer 4 and a ridge 5a is formed, and n-type Ga _0.35 is formed in a region other than the ridge 5a which becomes a current channel due to current constriction. al _{0. 65} As current blocking layer 6
Are formed. 7 is a p-type GaAs protective layer, 8
Is a p-type GaAs contact layer.

Here, in order to obtain a stable single transverse mode oscillation, A of the n-type Ga _0.35 Al _0.65 As current blocking layer 6 is obtained.
p-type Ga _0.5 Al _0.5 As clad layer 5 having a mixed crystal ratio of ₁ As
10% or more higher than the AlAs mixed crystal ratio. If n
Type Ga _0.35 Al _0.65 As AlAs of the current blocking layer 6
When the mixed crystal ratio is about the same as that of the p-type Ga _0.5 Al _0.5 As clad layer 5, there is a decrease in the refractive index in the stripe due to the plasma effect, so that it becomes an anti-guide waveguide,
A single transverse mode oscillation cannot be obtained. Much less n-type Ga
_If the AlAs mixed crystal ratio of the _0.35 Al _0.65 As current blocking layer 6 is lower than that of the p-type Ga _0.5 Al _0.5 As clad layer 5, the transverse mode becomes completely unstable, and even the target low operating current cannot be achieved. In this embodiment, as shown in FIG. 1, A of the n-type Ga _0.35 Al _0.65 As current blocking layer 6 is
p-type Ga _0.5 Al _0.5 As clad layer 5 having a mixed crystal ratio of ₁ As
It is set to 0.65, which is 0.15 higher than that.

In such a structure, p-type GaA
The current injected from the s contact layer 8 is confined in the ridge 5a, and Ga _0.85 Al _0.15 A under the ridge 5a is included.
Laser oscillation occurs in the s active layer 4. Where n-type Ga
_Since the refractive index of the _0.35 Al _0.65 As current blocking layer 6 is sufficiently smaller than the refractive index of the p-type Ga _0.5 Al _0.5 As cladding layer 5 inside the current channel, the laser light is confined in the ridge 5 a due to this refractive index difference, One transverse mode laser light is obtained.

N-type Ga_0.35Al_0.65As current flow
The forbidden band width of the back layer 6 is Ga_0.85Al _0.15As active layer 4
Since it is larger than the forbidden band, the current
There is no light absorption by the lock layer, which significantly reduces the waveguide loss.
Therefore, the operating current can be reduced. Light absorption
The laser light is almost n-type, so the laser light is n-type Ga_0.35Al_{0. 65}
The spectrum spreads also under the As current blocking layer 6 and has many spectra.
Easy to enter mode.

However, each n-type GaAlAs that guides light
Layer, Ga _0.35 Al _0.65 of Ga _0.5 Al _{0 .5} As cladding layer 3 and the n-type n-type in this embodiment As current blocking layer 6
Liquid phase growth method (L
Te in PE method, and metal organic vapor phase epitaxy method (MOC).
In the VD method), when Se is added, these impurities are G
Becomes DX center in aAlAs, from several mW to several tens mW
Since the saturable absorption effect becomes significant in the optical density of the main mode oscillating at, the loss grating is formed by the standing wave of the oscillating main mode. For this reason, modes other than the oscillating main mode are suppressed, conversely the single mode property is strengthened, and the multimode property, which is an advantage of this structure, is impaired.

In order to solve this problem, Si was added as an impurity to each GaAlAs layer that guides light in the semiconductor laser of this structure. In this case, S in the GaAlAs layer
Since the activation energy of thermal capture and emission of carriers between the DX center level and the conduction band generated by i is different from that when Se or Te is used as an impurity, the optical absorption is saturated at a very low optical density. Since the loss grating due to the oscillating main mode is hardly formed, the multimode property is not impaired, sufficient multimode oscillation can be obtained, and noise reduction is facilitated.

Next, the spectral characteristics of the semiconductor laser device having the above structure will be described. FIG. 2A is a diagram showing the relationship between the spectral characteristics and the structural parameters of the semiconductor laser device according to an embodiment of the present invention, and FIG. 2B is a diagram showing the relationship between the spectral characteristics and the structural parameters of the conventional semiconductor laser device. Is. In these figures, the horizontal axis represents the thickness (dp) of the p-type cladding layer between the current blocking layer and the active layer, and the vertical axis represents the thickness of the active layer (da). In the present embodiment shown in FIG. 2A, FIG.
As compared with the conventional example shown in (1), even if either or both of da and dp are thin, multimode oscillation is sufficiently obtained.
In particular, since the dp may be thin, a low noise laser can be obtained in the state where the leakage current to the outside of the stripe is small, and the operating current can be further reduced. Specifically, it was difficult to obtain multimode oscillation with a dp of 0.3 μm or less in the structure of the conventional example, whereas the dp of 0.2 μm in the structure of the present embodiment.
Even below, multimode oscillation can be sufficiently obtained.

Next, the relationship between the stripe width and the operating current value of the semiconductor laser device in one embodiment of the present invention will be described with reference to FIG. For reference, a conventional example is also shown. In the structure of this embodiment, unlike the conventional example, the operating current value does not increase due to the increase in light absorption by the current blocking layer even when the stripe width is narrowed. Therefore, the stripe width is considerably narrower than that of the conventional example. Can be set to, and from this point as well, low operating current can be achieved. Specifically, in the structure of the conventional example, the operating current value increased when the stripe width was 4 μm or less, whereas in the structure of the present embodiment, when the stripe width was narrowed, the operating current value was proportional to the stripe width. Reduce. Further, when the stripe width is narrowed in the structure of the present embodiment, light seeping out to the current blocking layer is relatively increased as compared with light inside the stripe, so that the multimode property of the spectrum becomes stronger. That is, narrowing the stripe width results in lower noise.

Next, a method of manufacturing the semiconductor laser device of the present invention will be described. FIG. 4 is a manufacturing process diagram of the semiconductor laser device. First, as shown in FIG. 4A, n-type G
The n-type GaAs buffer layer 2 (thickness: 0.5 μm) is formed on the aAs substrate 1 by MOCVD or MBE growth method.
m), n-type Ga _0.5 Al _0.5 As cladding layer 3 (thickness,
1 μm), Ga _0.85 Al _0.15 As active layer 4 (thickness, 0.
07 μm), p-type Ga _0.5 Al _0.5 As clad layer 5
(Thickness, 1 μm) and p-type GaAs protective layer 7 (thickness, 0.2 μm) are formed. This protective layer 7 is necessary to prevent surface oxidation of the p-type Ga _0.5 Al _0.5 As cladding layer 5 through which a current flows. Although the conductivity type of the active layer 4 is not particularly described, it may be p-type or n-type,
Further, it may be undoped.

Next, as shown in FIG. 4B, stripes
Nitride film (silicon nitride, tungsten nitride) or
A dielectric film 9 such as a silicon oxide film is formed, and the dielectric film 9 is formed.
9 is used as a mask to perform etching to form a ridge 5a.
To do. At this time, the lower end of the ridge 5a having the stripe width is
The width is 2.5 μm, and p-type Ga in the region other than the ridge 5a
_0.5Al_0.5The thickness (dp) of the As clad layer 5 is 0.1
It was 5 μm.

Next, as shown in FIG. 4C, the dielectric film 9
N-type Ga _0.35 Al by the MOCVD method using as a mask
_{A 0.65} As current blocking layer 6 (thickness, 1 μm) is selectively formed. If the film thickness of the n-type Ga _0.35 Al _0.65 As current blocking layer 6 is thin, the laser light is absorbed in the p-type GaAs contact layer 8 thereover, so that the minimum thickness is 0.4.
A thickness of μm is required. All of the above n-type GaA
Si is added as an impurity to the 1As layer.

Next, as shown in FIG. 4D, the dielectric film 9
And the p-type GaAs contact layer 8 is formed by MOCVD or MBE growth. Finally n-type Ga
An electrode is formed on each of the As substrate 1 side and the p-type GaAs contact layer 8 side to form a semiconductor laser device.

In the semiconductor laser of this embodiment, the operating current value required for emitting a laser beam of 3 mW at room temperature in an element having a cavity length of 200 μm is as low as 25 mA, and the spectrum is self-pulsating. )
It oscillated in multiple modes sufficient to cause. Actual noise characteristics are -135 dB / Hz within the range of 0-10% return light rate.
The following RIN values were obtained and low noise was realized.

In the manufacturing process shown in FIG. 4, the n-type Ga _0.35 Al _0.65 As current blocking layer 6 is grown directly on the p-type Ga _0.5 Al _0.5 As cladding layer 5 during the second crystal growth. The regrowth interface serves as a pn junction to form a deep interface state, which may adversely affect the temperature dependence of the laser current-optical output characteristic. To prevent this, the second Ga _{0. 35} Al _0.65 n-type after forming the thin p-type layer on the first time of crystal growth of As current blocking layer 6
Is effective. In this case, the regrowth interface is p-
Since it is not an n-junction, no deep interface state is formed.

Another embodiment of the present invention will be described below with reference to FIGS.
This will be described with reference to FIG. FIG. 5 is a cross-sectional view of a semiconductor laser device according to the second embodiment of the present invention, showing an example in which a p-type Ga _0.35 Al _0.65 As current blocking layer 6 is formed during the second crystal growth. In this case, the n-type Ga _0.35 Al _0.65 As current blocking layer 6 is a p-type Ga _0.35 Al _0.65 As current blocking layer 6.
_{It is formed on the 0.5} Al _0.5 As clad layer 5 via the Si-added n-type Ga _0.35 Al _0.65 As layer 17. The n-type Ga _0.35 Al _0.65 As current blocking layer 6
Must be transparent to the laser light, so A
lAs mixed crystal ratio is Ga _0.85 Al _0.15 As active layer 4 AlA
The film thickness needs to be 0.1 μm or less in order to increase the s mixed crystal ratio and reduce the leakage current in the lateral direction. Further, in the present embodiment, the AlAs of the n-type Ga _0.35 Al _0.65 As layer 17 is set in order to make the refractive index the same as when there is no p-type layer.
Mixed crystal ratio of n-type Ga _0.35 Al _0.65 As current blocking layer 6
Same as. Further, the film thickness of the n-type Ga _0.35 Al _0.65 As layer 17 is 0.01 μm, which is a film thickness that hardly affects the current distribution. With the structure shown in FIG. 5, a semiconductor laser having a low operating current, low noise and excellent temperature characteristics can be obtained.

When a semiconductor laser device having the above-mentioned effects is manufactured on a p-type GaAs substrate, the p-type and n-type conductivity types in the above embodiment are reversed to grow a crystal. However, in this case, the n-type Ga _0.35 Al _0.65 As layer 17 in FIG. 5 becomes p-type. Further, the addition of Si as an impurity to the p-type thin layer at this time does not impair the multimodality in this layer.

FIG. 6 shows a semiconductor device according to the third embodiment of the present invention.
2 is a cross-sectional view of a body laser device on a p-type GaAs substrate
The formed example is shown. As shown in FIG.
P-type GaAs buffer layer 1 on GaAs substrate 10
1, p-type Ga_0.5Al_0.5As clad layer 12, Ga
_0.85Al_0.15As active layer 4, Si-added ridge 13
n-type Ga having a_0.5Al_0.5As clad layer 13,
p-type Ga_0.35Al_0.65As current blocking layer 14, lid
N-type GaAs protective layer 15 on
A GaAs contact layer 16 is formed. P-type
Ga_0.35Al_0.65The As current blocking layer 14 has Si added thereto.
Added n-type Ga_0.5Al_0.5On the As clad layer 13
Si-added n-type Ga_0.35Al_0.65Via the As layer 17
Is formed. Each layer in the structure of this embodiment is a diagram
The conductivity type of the structure shown in FIG.
It has the same effect as the case. Moreover, this n-type Ga
_0.35Al _0.65Si is added as an impurity to the As layer 17.
That the multimodality is lost in this layer.
, A semiconductor with low operating current, low noise and excellent temperature characteristics
Body laser can be obtained.

Further, in the manufacturing process shown in FIG.
When an aAs substrate is used, an HF-based etchant is used when removing the silicon nitride film forming the dielectric film 9. At this time, the n-type Ga _0.35 Al formed by the second growth is used.
_{The 0.65} As current blocking layer 6 may also be etched at the same time. In order to prevent this, it is effective to introduce a layer having a low AlAs mixed crystal ratio for preventing etching onto the n-type Ga _0.35 Al _0.65 As current blocking layer 6 during the second growth. This layer has a high AlAs mixed crystal ratio of Ga _0.35 Al _0.65 A
It also has an effect of protecting the s current blocking layer 6 from surface oxidation. Also, by adding Si as an impurity to this layer, the multimodal property is not impaired in this layer.

FIG. 7 is a sectional view of a semiconductor laser device according to a fourth embodiment of the present invention, in which an n-type GaAlAs layer 1 is formed.
An example in which 8 is introduced at 0.5 μm is shown. In FIG. 7, the thickness of the n-type Ga _0.35 Al _0.65 As current blocking layer 6 is 0.5 μm, which is smaller than that of the embodiment shown in FIG. 1, in order to maintain flatness. This introduced GaAlAs layer 18
The conductivity type of the layer is preferably n-type in terms of blocking current, and the addition of Si as an impurity can reduce noise without impairing multimodality. In addition, n-type GaAlAs
The layer 18 may be a multilayer including two or more layers. With the structure shown in FIG. 7, a semiconductor laser device having a low operating current, low noise, and excellent mass productivity can be obtained.

The structure in the above-described embodiment has a low operating current value and can be operated in multiple modes as compared with the prior art, so that a semiconductor laser with low noise and high output can be realized. By actually producing a high-power semiconductor laser device with a cavity length of 350 μm and coating the end face, an optical output of 100 mW or more can be obtained, and multimode oscillation can be performed at a low output of several mW. It was By using such a semiconductor laser device as a light source of an optical disc, a high frequency superimposing circuit for reducing noise during reading is not required, and a drastic downsizing of the pickup can be realized.

FIG. 8 is a sectional view of a semiconductor laser device according to the fifth embodiment of the present invention, in which p-type Ga _0.6 Al _0.4 A is used.
An example of the LOC structure having the s light guide layer 19 is shown. In the structure shown in FIG. 8, the destruction level of the end face due to the light is improved, so that the output can be further increased. p-type Ga _0.6
The AlAs mixed crystal ratio of the Al _0.4 As optical guide layer 19 is Ga _0.
85 Al _0.15 As long as it is higher than the AlAs mixed crystal ratio of the active layer 4, its band gap is Ga _0.85 considering the temperature characteristics.
It is desirable that the Al _0.15 As active layer 4 is larger than the active layer 4 by 0.3 eV or more. In this embodiment, the AlAs mixed crystal ratio of the p-type Ga _0.6 Al _0.4 As optical guide layer 19 is 0.4, and the layer thickness thereof is in the lateral direction. In order to reduce the leakage current of, the thickness is made as thin as 0.1 μm. When this light guide layer is n-type, the addition of Si as an impurity prevents the multimode property of this layer from being impaired. The light guide layer is shown in FIG.
It may be on the upper side or both sides of the active layer instead of the lower side. With the structure of this embodiment, a semiconductor laser device with low operating current, high output and low noise can be obtained.

The effects of the structure shown in FIG. 5, the structure shown in FIG. 6, the structure shown in FIG. 7, and the structure shown in FIG. 8 are independent of each other. By combining these structures, an excellent semiconductor laser device having both effects can be obtained. Can be obtained. An example of the combination will be described below.

FIG. 9 is a sectional view of a semiconductor laser device according to a sixth embodiment of the present invention, showing an example in which the structure of FIG. 5 and the structure of FIG. 7 are combined. In this case, it is possible to obtain a semiconductor laser device which has a low operating current, low noise characteristics, a high characteristic temperature, and excellent mass productivity.

FIG. 10 is a sectional view of a semiconductor laser device according to a seventh embodiment of the present invention, showing an example in which the structure of FIG. 5 and the structure of FIG. 8 are combined. Light guide layer 1
9 may be on the lower side or both sides of the active layer 4. In this case, in addition to the low operating current and low noise characteristics, the characteristic temperature is high, and a higher output semiconductor laser device can be obtained.

FIG. 11 is a sectional view of a semiconductor laser device according to the eighth embodiment of the present invention, showing an example in which the structure of FIG. 7 and the structure of FIG. 8 are combined. Light guide layer 1
9 may be on the lower side or both sides of the active layer 4. In this case, in addition to low operating current and low noise characteristics, a semiconductor laser device having higher output and excellent mass productivity can be obtained.

FIG. 12 is a sectional view of a semiconductor laser device according to a ninth embodiment of the present invention, showing an example in which the structure of FIG. 5, the structure of FIG. 7 and the structure of FIG. 8 are combined.
The light guide layer 19 need not be on the upper part of the active layer 4, but may be on the lower part or both sides. In this case, it is possible to obtain a semiconductor laser device which has a high operating temperature, a low noise characteristic, a high characteristic temperature, a higher output, and excellent mass productivity.

It should be noted that in each of the above embodiments, an n-type substrate,
Either p-type may be used for manufacturing, but when the substrate is n-type, the current blocking layer is n-type, and when the substrate is p-type, the clad layer in which the ridge is formed is n-type. In these structures, an n-type Ga that guides laser light is also used.
By adding Si as an impurity to the AlAs layer,
The noise can be reduced without impairing the multimodality in that layer.

[0037]

As described above, according to the present invention, Ga _{1 -X} Al _X A
s _One- conductivity type Ga _1-Y Al _Y As layer having a ridge formed on at least one surface of the s active layer and an opposite-conductivity type Ga _1-Z Al layer formed along the longitudinal side surface of the ridge. _Z A
S, and X, Y and Z for determining the AlAs mixed crystal ratio
Is Z>Y> X ≧ 0, and an excellent semiconductor laser having a low operating current value and low noise is obtained by adding Si as an impurity to the GaAlAs layer which is an n-type among these layers. The device can be realized.

Further, according to the present invention, A of the current blocking layer is
Since the 1As mixed crystal ratio is set higher than the AlAs mixed crystal ratio of the clad layer, it oscillates in a single transverse mode, there is almost no optical absorption of the laser light by the current block layer, and the loss of the waveguide is greatly reduced. Therefore, the operating current value can be reduced.

Further, according to the present invention, since light spreads in the current blocking layer and the active layer thereunder, it is easy to obtain multimode oscillation of the spectrum. Therefore, the distance between the active layer and the current blocking layer can be made shorter than before. In addition, a low-noise semiconductor laser device having excellent multi-mode characteristics with almost no loss grating due to the main mode oscillating by adding Si as an impurity to each n-type GaAlAs layer that guides light can be formed. Is obtained.

Further, according to the present invention, since there is almost no light absorption by the current blocking layer, the stripe width can be made narrower than before, and as a result, the synergistic action of the effect of reducing the leakage current and the effect of narrowing the stripe width can be achieved. The dimension can be set in the direction of lowering the operating current value, and the operating current value can be further reduced as a low noise laser for a compact disc or the like.

Further, according to the present invention, since the reduction of the operating current value brings about the reduction of the amount of heat generated in the active layer, the optical output is also increased as compared with the conventional one, and even when the high output semiconductor laser device is constructed, the output is low. Multimode oscillation is possible, and when such a semiconductor laser device is used as a light source of an optical disc, a high frequency superimposing circuit for reducing noise during reading is not required, and the optical pickup can be significantly downsized.

[Brief description of drawings]

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

FIG. 2A is a diagram showing the relationship between spectral characteristics and structural parameters of a semiconductor laser device according to an embodiment of the present invention. FIG. 2B is a diagram showing the relationship between spectral properties and structural parameters of a conventional semiconductor laser device.

FIG. 3 is a diagram showing a relationship between a stripe width and an operating current value of a semiconductor laser device according to an embodiment of the present invention.

4A to 4D are manufacturing process diagrams of a semiconductor laser device according to an embodiment of the present invention.

FIG. 5 is a sectional view of a semiconductor laser device according to a second embodiment of the present invention.

FIG. 6 is a sectional view of a semiconductor laser device according to a third embodiment of the present invention.

FIG. 7 is a sectional view of a semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view of a semiconductor laser device according to a fifth embodiment of the present invention.

FIG. 9 is a sectional view of a semiconductor laser device according to a sixth embodiment of the present invention.

FIG. 10 is a sectional view of a semiconductor laser device according to a seventh embodiment of the present invention.

FIG. 11 is a sectional view of a semiconductor laser device according to an eighth embodiment of the present invention.

FIG. 12 is a sectional view of a semiconductor laser device according to a ninth embodiment of the present invention.

FIG. 13 is a sectional view of a conventional semiconductor laser device.

[Explanation of symbols]

4 Ga _0.85 Al _0.15 As active layer (Ga _1-X Al _X As active layer) 5 p-type Ga _0.5 Al _0.5 As clad layer (one conductivity type Ga _1-Y Al _Y As layer) 5a ridge 6 n-type Ga _0.35 Al _0.65 As current blocking layer (reverse conductivity type Ga _1-Z Al _Z As layer)

Claims (8)

[Claims] _1. A Ga _{1-Y of} one conductivity type having a ridge formed on at least one surface of a Ga _1-x Al _x As active layer.
An Al _Y As layer and a Ga ₁ -Z Al _Z As layer of opposite conductivity type formed along the side surface of the ridge in the longitudinal direction,
lAs mixed crystal ratio which determines Z>Y> X between Y and Z
Ga having a relation of ≧ 0 and being n-type in each of the layers
A semiconductor laser device, wherein Si is added as an impurity to the AlAs layer. 2. A Ga _{1 -Y of} one conductivity type having a ridge formed on at least one surface of a Ga _1-x Al _x As active layer.
An Al _Y As layer, a Ga ₁ -Z Al _Z As layer of opposite conductivity type formed along the side surface of the ridge in the longitudinal direction, and the Ga layer.
One conductivity type Ga _1-B Al _B A having a layer thickness of 0.1 μm or less formed between the _1-Y Al _Y As layer and the Ga _1-Z Al _Z As layer.
a GaAlAs layer which has an s-layer, has a relationship of Z>Y> X ≧ 0, and B> X among X, Y, Z, and B, which determines an AlAs mixed crystal ratio, and is an n-type among the layers. A semiconductor laser device, wherein Si is added as an impurity to the semiconductor laser device. 3. A Ga _{1 -Y of} one conductivity type having a ridge formed on at least one surface of a Ga _1-x Al _x As active layer.
An Al _Y As layer, a Ga ₁ -Z Al _Z As layer of opposite conductivity type formed along the side surface of the ridge in the longitudinal direction, and the Ga layer.
_1-Z Al _Z As formed on said layer Ga _1-Z than Al _Z As layer and a GaAlAs layer or GaAs layer AlAs mixed crystal ratio is formed of at least one layer lower, AlAs
GaAlA which has a relationship of Z>Y> X ≧ 0 among X, Y and Z which determine the mixed crystal ratio and which is n-type in each of the layers.
A semiconductor laser device, wherein Si is added as an impurity to the s layer. 4. A Ga _{1 -Y of} one conductivity type having a ridge formed on at least one surface of a Ga _1-x Al _x As active layer.
An Al _Y As layer, a Ga ₁ -Z Al _Z As layer of opposite conductivity type formed along the side surface of the ridge in the longitudinal direction, and the Ga layer.
Ga _1-C Al _C A formed in contact with _1-X Al _X As active layer
s layer, which has a relationship of Z>Y>C> X ≧ 0 among X, Y, Z, and C that determines the AlAs mixed crystal ratio, and has an impurity in the GaAlAs layer that is n-type among the layers. As S
A semiconductor laser device having i added thereto. 5. A Ga _{1-Y of} one conductivity type having a ridge formed on at least one surface of a Ga _1-x Al _x As active layer.
An Al _Y As layer, a Ga ₁ -Z Al _Z As layer of opposite conductivity type formed along the side surface of the ridge in the longitudinal direction, and the Ga layer.
One conductivity type Ga _1-B Al _B A having a layer thickness of 0.1 μm or less formed between the _1-Y Al _Y As layer and the Ga _1-Z Al _Z As layer.
s layer and the G formed on the Ga _{1 -Z} Al _Z As layer
a _1-Z Al _Z As layer having a lower AlAs mixed crystal ratio and at least one GaAlAs layer or a GaAs layer, and Z> Y between X, Y, Z and B for determining the AlAs mixed crystal ratio. > X ≧ 0, B> X, and Si is used as an impurity in the GaAlAs layer that is n-type among the layers.
A semiconductor laser device comprising: 6. A Ga _{1-Y of} one conductivity type having a ridge formed on at least one surface of a Ga _1-x Al _x As active layer.
An Al _Y As layer, a Ga ₁ -Z Al _Z As layer of opposite conductivity type formed along the side surface of the ridge in the longitudinal direction, and the Ga layer.
One conductivity type Ga _1-B Al _B A having a layer thickness of 0.1 μm or less formed between the _1-Y Al _Y As layer and the Ga _1-Z Al _Z As layer.
s layer and a Ga _1-C Al _C As layer formed in contact with the Ga _1-x Al _x As active layer, and between X, Y, Z, B and C that determine the AlAs mixed crystal ratio. Z>Y>C> X ≧ 0,
G which has a relation of B> X and is n-type in each of the layers
A semiconductor laser device, wherein Si is added as an impurity to the aAlAs layer. 7. A Ga _{1-Y of} one conductivity type having a ridge formed on at least one surface of a Ga _1-x Al _x As active layer.
An Al _Y As layer, a Ga ₁ -Z Al _Z As layer of opposite conductivity type formed along the side surface of the ridge in the longitudinal direction, and the Ga layer.
_1-Z Al _Z As formed on said layer Ga _1-Z Al Z As layer and GaAlAs layer or GaAs layer AlAs mixed crystal ratio is formed of at least one layer lower than the Ga _1-X A
and a Ga _1-C Al _C As layer formed in contact with the l _x As active layer to determine the AlAs mixed crystal ratios X, Y, Z and C.
And Z>Y>C> X ≧ 0, and Si is added as an impurity to the GaAlAs layer which is the n-type of each of the layers. 8. A Ga _{1-Y of} one conductivity type having a ridge formed on at least one surface of a Ga _1-x Al _x As active layer.
An Al _Y As layer, a Ga ₁ -Z Al _Z As layer of opposite conductivity type formed along the side surface of the ridge in the longitudinal direction, and the Ga layer.
One conductivity type Ga _1-B Al _B A having a layer thickness of 0.1 μm or less formed between the _1-Y Al _Y As layer and the Ga _1-Z Al _Z As layer.
s layer and the G formed on the Ga _{1 -Z} Al _Z As layer
a _1-Z Al Z As layer and GaAlAs layer or GaAs layer AlAs mixed crystal ratio is formed of at least one layer lower than the Ga _1-X Al X As active layer G formed in contact with
a _1-C Al _C As layer, and Z>Y>C> X ≧ 0, B between X, Y, Z, B and C that determine the AlAs mixed crystal ratio.
> X, and n-type GaAl in each of the layers
A semiconductor laser device, wherein Si is added to the As layer as an impurity.