JPH05167174A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser device for a light source of an optical disk or the like wherein noise is low, power consumption is small, and mass- productivity is high. CONSTITUTION:At least on one side of main surfaces of a Ga1-XAlXAs layer 4 turning to an active layer, the following are formed in order; a first clad layer 5 of a conductivity type Ga1-Y1AlY1As, an etching stopper layer 6 of Ga1-CAlCAs, and a ridge type second clad layer 7 of Ga1-Y2AlY2As. Along the side surface of the ridge in the longitudinal direction, a current block layer 8 of opposite conductivity type Ga1-ZAZAs is formed. As to AlAs mixed crystal ratio, the following relations are satisfied between X, Y and Z; Z>Y2>X>=0 and Y1>C>X.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device which is suitable as a light source for optical disks and has a low noise and a low operating current value and which can be easily mass-produced.

[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. This semiconductor laser has a so-called loss guide structure, and is of n-type gallium arsenide (GaAs).
An n-type GaAs buffer layer 22 is formed on a substrate 21, and n-type gallium aluminum arsenide (Ga) is formed thereon.
_0.5 Al _0.5 As) clad layer 23, Ga _0.85 Al _0.15 A
p-type Ga _0.5 A having s active layer 24 and ridge 25a
There is an l _0.5 As clad layer 25, and an n-type GaAs current block layer 26 is formed in a portion other than the ridge 25a which serves as a current channel due to current confinement. In addition, 27 is a p-type GaAs protective layer, 28 is a p-type GaA
s contact layer.

A conventional example will be described below. In the structure of FIG. 13, the current injected from the p-type GaAs contact layer 28 is effectively confined within the ridge 25a, the laser oscillation occurs at a Ga _0.85 Al _{0. 15} As active layer 24 of the lower ridge 25a. At this time, the refractive index of the n-type GaAs current blocking layer 26 is higher than that of the p-type Ga _0.5 Al _0.5 As clad layer 25, but Ga _0.85
Al _0.15 As more than n-type Ga than the forbidden band width of the active layer 24
Since the forbidden band width of the As current block layer 26 is smaller,
The n-type GaAs current blocking layer 26 serves as an absorber for the laser light, and the laser light is effectively confined in the ridge 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.

As a similar structure, as shown in FIG.
On the n-type GaAs substrate 21, from the n-type GaAs buffer layer 22 to the n-type gallium aluminum arsenide (Ga _0.5 Al).
_0.5 As) clad layer 23, Ga _0.85 Al _0.15 As active layer 24, p-type Ga _0.5 Al _0.5 As clad layer 25, n
After forming the mold current block layer 26 by one crystal growth process, a stripe-shaped groove is formed by etching,
By regrowth, p-type Ga _0.5 Al _0.5 As clad layer 2
There is also a conventional structure in which a semiconductor laser device is manufactured by forming a p-type GaAs contact layer 28. In this structure,
Since the regrowth interface (25b) is close to the active layer, there is a problem that the light distribution is affected by the growth conditions and the yield becomes lower than that of the structure of FIG. That is, the regrowth interface (25
From b), there is a problem that since the dopant Zn or the like is diffused during the regrowth, the refractive index in the stripe becomes high, the spectrum is likely to be a single mode, and a defect occurs in the noise inspection.

[0006]

In the semiconductor laser having the above-mentioned 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. Since the laser light is sharply confined in the stripe due to the light absorption of the GaAs current blocking layer 26, the spectrum is likely to be a single mode. Under the conventional structure, in order to obtain the multimode oscillation of the spectrum, GaAs is used. The current blocking layer 26 is Ga
There has been a problem that it must be separated from the _0.85 Al _0.15 As active layer 24 to some extent or more, and the lateral leakage current in the lower portion of the ridge (25a) increases, which further increases the operating current.

Further, the stripe width (ridge (25a)
When the width at the lower end is narrowed, the light absorption by the current blocking layer 26 increases, so that the stripe width also becomes larger than a certain level.
There is a restriction that it cannot be narrowed, which has been an obstacle to lowering the operating current.

In addition, the thickness of the p-type Ga _0.5 Al _0.5 As clad layer 25 under the GaAs current blocking layer 26, which determines the noise characteristics, needs to be controlled by time-controlled etching, resulting in poor yield and mass productivity. There was a problem.

SUMMARY OF THE INVENTION 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 multi-mode spectrum, low noise, excellent mass productivity and a low operating current value.

[0010]

In order to achieve this object, the semiconductor laser device of the present invention has a Ga _{1 -X} to be an active layer.
A Ga ₁ -Y ₁ Al _{Y 1} As layer of one conductivity type, a Ga _{1 -C} Al _C As layer, and at least one side of the main surface of the Al _x As layer, and
A ridge-shaped Ga _{1 -Y 2} Al _{Y 2} As layer is sequentially provided, and a Ga _{1 -Z} Al _Z As layer having a conductivity type opposite to those of the ridge portion is provided along the longitudinal side surface of the ridge, Al
As mixed crystal ratio, between X, Y1, Y2, C and Z, Z>
The configuration is such that Y2> X ≧ 0 and Y1>C> X are satisfied.

[0011]

With this structure, Ga that becomes the current blocking layer is formed.
Ga _1-X Al _X which becomes an active layer by a current injected from a stripe-shaped window of the _1-Z Al _Z As layer, that is, a ridge
Laser oscillation occurs in the As layer. Here, the refractive index of the Ga _{1 -Z} Al _Z As layer, which is the current blocking layer, is smaller than that of the Ga _{1 -Y 2} Al _Y2 As layer, which is the cladding layer inside the stripe, so that the laser light has a refractive index difference within the stripe. Effectively trapped in.

Further, Ga _{1 -Z} A which becomes a current blocking layer
The forbidden band width of the l _Z As layer is the Ga _{1 -X} Al _x As layer which becomes the active layer.
Since it is much larger than the band gap of the layer, there is no absorption of laser light by the current blocking layer, and the light is widely distributed in the current blocking layer and in the active layer below the current blocking layer, so the spectrum is large. Easy to enter mode.

In addition, during the etching for forming the ridge, an etchant capable of selectively etching a layer having a high AlAs mixed crystal ratio is used to surely stop the etching on the Ga _{1 -C} Al _C As layer. it can.

[0014]

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. An n-type GaAs buffer layer 2 is formed on an n-type GaAs substrate 1, and an n-type Ga _0.5 Al _0.5 As clad layer 3 and Ga are formed on the n-type GaAs buffer layer 2.
_0.85 Al _0.15 As active layer 4, p-type Ga _0.5 Al _0.5 As
First clad layer 5, p-type Ga _0.8 Al _0.2 As etching stop layer 6, ridge-shaped p-type Ga _0.5 Al _0.5 As
The second clad layer 7 is formed, and n-type G is formed in a region other than the ridge that serves as a current channel due to current confinement.
The a _0.4 Al _0.6 As current blocking layer 8 is formed.
9 is a p-type GaAs protective layer and 10 is a p-type GaAs
It is a contact layer.

Here, in order to obtain stable single transverse mode oscillation, the AlAs mixed crystal ratio of the current block layer 8 is set to p-type Ga.
_0.5 Al _0.5 As It is set higher than the AlAs mixed crystal ratio of the second cladding layer 7. If the AlAs of the current blocking layer 8
When the mixed crystal ratio is the same as that of the second cladding layer, there is a decrease in the refractive index in the stripe due to the plasma effect, the waveguide becomes an antiguide, and a single transverse mode oscillation cannot be obtained. In other words, the AlAs mixed crystal ratio of the current block layer 8 is p.
When it is lower than the Ga _0.5 Al _0.5 As second cladding layer 7 of the type, the transverse mode becomes completely unstable, and it is not possible to achieve the target low operating current. In this embodiment, FIG.
As shown in, the AlAs mixed crystal ratio of the current block layer 8 is p
The ratio is set to 0.6, which is 0.1 higher than the AlAs mixed crystal ratio of the second Ga _0.5 Al _0.5 As second cladding layer 7.

In this structure, the current injected from the p-type GaAs contact layer 10 is confined in the ridge, and laser oscillation occurs in the Ga _0.85 Al _0.15 As active layer 4 below the ridge. Here, since the refractive index of the n-type Ga _0.4 Al _0.6 As current blocking layer 8 is sufficiently smaller than the refractive index of the p-type Ga _0.5 Al _0.5 As second cladding layer 7 inside the current channel, the laser light is The laser light is confined in the ridge due to the difference in refractive index, and laser light of a single transverse mode is obtained.

The forbidden band width of the n-type Ga _0.4 Al _0.6 As current block layer 8 is Ga _0.85 Al _0.15 As active layer 4
Since it is larger than the forbidden band width, the current blocking layer does not absorb light unlike the conventional structure, and the loss of the waveguide can be greatly reduced, and the operating current can be reduced. Further, since there is no light absorption, the laser light is n-type Ga _0.4 Al _{0
.6 The} current spreads to the lower part of the As current blocking layer 8 so that the spectrum is likely to be multimode and a low noise laser can be easily obtained.

However, this is because the current blocking layer 8 uses the GaAlAs system, which is the same material system as the active layer and the cladding layer, and therefore the refractive index of the p-type Ga _0.5 Al _0.5 As second cladding layer 7 is increased. , About 3.3 for the current blocking layer 8
Since the refractive index of the stripe can be selected as a delicately low value of about 3.2, the effective refractive index difference between the inside and the outside of the stripe, which is almost the same as in the conventional loss guide structure (Fig. 13), can be obtained. It can be formed. For example, when ZnSe, which is a different material system, is used for the current blocking layer, its refractive index is about 2.4, so the effective refractive index difference inside and outside the stripe is too large, and the light does not spread to the lower part of the current blocking layer 6. , The spectrum is unlikely to be multimode.

FIG. 3 shows an experimental result of the relationship between the spectral characteristic and the structural parameter in the laser of the present invention and the conventional structure. The active layer thickness (da) and the p-type clad layer thickness (d) between the current block layer and the active layer are higher than those in the conventional case.
It can be seen that multimode oscillation can be sufficiently obtained even if p) is thin. In particular, since the dp may be thin, a low noise laser can be obtained with a small leakage current to the outside of the stripe, and the operating current can be further reduced. In particular,
In the conventional structure, it was difficult to obtain multimode oscillation with dp of 0.3 μm or less, whereas according to the structure of the present invention, multimode oscillation can be sufficiently obtained even with dp of 0.2 μm or less. Be done.

FIG. 4 shows the relationship between the stripe width (width at the bottom of the ridge) and the operating current value. In the structure of the present invention, when the stripe width is narrowed as in the conventional structure, the light absorption of the current block layer does not increase the operating current value. Therefore, the stripe width is much narrower than the conventional structure. It can be set to a value, and also in this respect, low operating current can be achieved. Specifically, in the conventional structure, the stripe width is 4 μm.
At m or less, the operating current value increased, whereas
According to the structure of the present invention, when the stripe width is narrowed, the operating current value is further reduced. Here, in the structure of the present invention,
When the stripe width is narrowed, the multimode property of the spectrum is further enhanced because the exudation of light into the current blocking layer is relatively increased as compared with the light inside the stripe.
Become stronger. That is, the noise is further reduced by narrowing the stripe width.

FIG. 2 is a manufacturing process diagram of a semiconductor laser device in one embodiment of the present invention. As shown in FIG. 2A, an n-type GaAs buffer layer 2 (thickness: 0.5 μm) and an n-type Ga _0.5 Al _0.5 are formed on the n-type GaAs substrate 1 by MOCVD or MBE growth. As clad 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 first cladding layer 5 (thickness, 0.15 μm), p-type Ga
_0.8 Al _0.2 As Etching stop layer 6 (thickness, 0.0
3 μm), p-type Ga _0.5 Al _0.5 As second cladding layer 7
(Thickness, 1 μm) p-type GaAs protective layer 9 (thickness, 0.
2 μm) is formed. This protective layer 9 has p
It is necessary to protect the upper portion of the ridge of the second Ga _0.5 Al _0.5 As second cladding layer 7 of the mold from surface oxidation. Although the conductivity type of the active layer is not particularly described in FIG.
It may be a mold or of course undoped.

Next, as shown in FIG. 2B, a dielectric film 11 such as a nitride film (silicon nitride, tungsten nitride) or silicon oxide is formed in a stripe shape, and this dielectric film 11 is used as a mask. , Etching is performed to form a ridge. The etching is performed by first using an etchant having no selectivity with respect to the AlAs mixed crystal ratio such as sulfuric acid or tartaric acid, and p-type Ga _0.5 Al _0.5 As before the p-type Ga _0.8 Al _0.2 As etching stop layer 6. The etching is stopped in the two-clad layer 7, and secondly, the p-type Ga _0.8 Al _0.2 As etching stop layer 6 is selectively used by using hydrochloric acid at 60 ° C. which can selectively etch the layer having a high AlAs mixed crystal ratio. To stop the etching. For this reason, the problem that the characteristics are varied and the yield is low due to the variation of dp in the related art is solved, and a laser with high mass productivity can be obtained.

At this time, the width of the lower end of the ridge, which is the stripe width, is 2.5 μm, and the p-type Ga _{0.5 in} the region other than the ridge is _0.5.
The thickness (dp) of the Al _0.5 As first cladding layer 7 is 0.
It was set to 15 μm. In this structure, since there is no light absorption loss due to the current blocking layer 8, as compared to the stripe width (about 5 μm) and the value of dp (0.3 μm or more) of the conventional structure, as shown in FIGS. 3 and 4. Both of them can be halved, and compared with the conventional structure (Fig. 13) in terms of the size of the structure,
A low operating current can be achieved.

Next, using the dielectric film 9 as shown in FIG.
As shown in FIG. 3, n-type Ga _0.4 A is formed by the MOCVD method.
l _0.6 As current blocking layer 8 (thickness: 1 μm) is selectively grown.

Here, the shape of the ridge is preferably a forward mesa shape rather than an inverted mesa shape. This is because when the inverted mesa shape is formed, crystal growth becomes difficult as compared with the case where the forward mesa shape is formed, and the yield may be reduced due to the deterioration of the characteristics. In fact, in the case of the inverted mesa shape, the crystallinity of GaAlAs selectively grown on the side surface of the ridge was impaired, and the threshold current of the fabricated device was about 10 mA higher than that of the forward mesa shaped device. .. The characteristics of the element to be described later show a forward mesa shape.

Regarding the film thickness of the current blocking layer,
When the thickness of the current blocking layer 8 is thin, the p-type GaA on the upper side is
Since the s contact layer 10 absorbs the laser beam, 0.4 μm is the minimum.

Next, as shown in FIG. 2D, the dielectric film 11 is removed, and the p-type GaAs contact layer 10 is formed by MOCVD or MBE growth. Finally, electrodes are formed on the n-type GaAs substrate 1 and the p-type GaAs contact layer 10, respectively.

FIG. 5 is a current-light output characteristic diagram of the semiconductor laser device in one embodiment of the present invention. For comparison,
The characteristics of the conventional semiconductor laser device are also shown. In the semiconductor laser device of the present invention, since the loss of the waveguide is small, the threshold value is low, the efficiency is high, and the operating current value is significantly reduced. Specifically, the resonator length is 200μ
In the device of m, the operating current value required to emit a laser beam of 3 mW at room temperature could be reduced from 50 mA to 25 mA. The spectrum also oscillates in multiple modes causing self-pulsation, and the RIN value of -130 dB / Hz was obtained within the range of the return light rate of 0 to 10%, and the low noise characteristic was obtained.

In the above-described embodiment, when the n-type current blocking layer 8 is grown directly on the p-type second cladding layer 7 during the second crystal growth, the regrowth interface is a pn junction. Therefore, a deep interface state is formed, which may adversely affect the temperature dependence of the laser current-optical output characteristic. That is, there may occur a problem that the characteristic temperature becomes low. To prevent this, at the time of the second crystal growth, first p
It is effective to form the n-type current blocking layer after forming the thin layer of the mold. In this case, the regrowth interface is pn
Since it is not a junction, the formation of deep interface states is also eliminated.

FIG. 6 shows a sectional view of the structure in one embodiment when p-type Ga _0.4 Al _0.6 As was formed during the second growth. Since the AlAs mixed crystal ratio of this p-type layer needs to be transparent to the laser light, it is larger than the AlAs mixed crystal ratio of the active layer, and in order to reduce the leakage current in the lateral direction, the film is formed. The thickness needs to be 0.1 μm or less. In FIG. 6, the AlAs mixed crystal ratio of the current block layer 8 is the same as that of the current block layer 8 in order to make the refractive index the same as when there is no p-type layer. The film thickness is 0.01 μm, which has almost no influence on the current distribution. With the structure shown in FIG. 6, a semiconductor laser having a low operating current, low noise, and excellent temperature characteristics can be obtained.

In the above embodiment, the dielectric film 11 is also used.
However, for example, in the case of a silicon nitride film, if an HF-based etchant is used for removal, the n-type current block layer 8 formed by the second growth may also be etched at the same time. In order to prevent this, it is effective to introduce a layer having a lower AlAs mixed crystal ratio on the n-type current blocking layer 8 than the current blocking layer 8 at the time of the second growth so as not to be etched. This layer also has an effect of protecting the current block layer 8 having a high AlAs mixed crystal ratio from surface oxidation.

In FIG. 7, the n-type GaAs layer is 0.5 μm,
The structural sectional view at the time of introducing is shown. The current blocking layer 8 has a thickness of 0.5 μm, which is thinner than that in FIG. 1, in order to maintain flatness. The conductivity type of the introduced layer is preferably n-type in terms of blocking current, but when the current blocking layer 8 has a thickness of 0.4 μm or more, the current is blocked, so it is p-type. However, of course, it may be a high resistance layer. Further, it may be a multilayer of two or more layers. With the structure shown in FIG. 7, it is possible to obtain a stable semiconductor laser device from the viewpoint of process as well, which has a low operating current, low noise, and is easy to manufacture.

Since the structure of the present invention has a low operating current value, it is also effective for increasing the output of the semiconductor laser. Particularly, in this structure, the active layer thickness is 0.03-0.05 μm.
As shown in FIG. 3, even if the thickness is reduced, the spectrum can be set to multiple modes unlike the conventional case, so that a semiconductor laser with low noise and high output can be realized. is there.

Actually, by producing a device with a resonator length of 350 μm for high output and coating the end face, an optical output of 100 mW or more could be obtained. If such a semiconductor laser is used as a light source for an optical disc, a high frequency superimposing circuit for reducing noise during reading is not required, and the pickup can be significantly downsized. Further, if dp is made thin and leakage current in the lateral direction is made small, a single longitudinal mode is obtained, but it goes without saying that higher output can be achieved.

Further, if the LOC structure having an optical guide layer as shown in FIG. 8 is used to improve the destruction level of the end face due to the light, the output can be further increased. AlA of light guide layer
The s mixed crystal ratio should be higher than the AlAs mixed crystal ratio of the active layer, but considering the temperature characteristics, the forbidden band width is 0.3 than that of the active layer.
It is desirable to be larger than eV, and in FIG. 8, the AlAs mixed crystal ratio of the light guide layer was set to 0.4. The layer thickness is as thin as 0.1 μm in order to reduce the leakage current in the lateral direction. This light guide layer need not be on the upper part of the active layer as shown in FIG. 8, but may be on the lower part or, of course, on both sides. With the structure shown in FIG. 8, a semiconductor laser having a low operating current and a high output can be obtained.

The effects of the structures shown in FIGS. 6, 7 and 8 are independent of each other, and by combining them,
It is possible to obtain a superior semiconductor laser having both effects. An example of the combination will be described below.

FIG. 9 shows an embodiment in which the structure of FIG. 6 and the structure of FIG. 7 are combined. In this case, in addition to low operating current and low noise characteristics, a semiconductor laser having a high characteristic temperature and easy to manufacture can be obtained.

FIG. 10 shows an embodiment in which the structure of FIG. 6 and the structure of FIG. 8 are combined. The light guide layer need not be on the upper part of the active layer as shown in FIG. 10, but may be on the lower part or, of course, on both sides. In this case, in addition to the low operating current and low noise characteristic characteristics, the characteristic temperature is high and higher output can be obtained.

FIG. 11 shows an embodiment in which the structure of FIG. 7 and the structure of FIG. 8 are combined. The light guide layer need not be on the upper part of the active layer as shown in FIG. 11, but may be on the lower part or, of course, on both sides. In this case, in addition to low operating current and low noise characteristics, it is possible to obtain a semiconductor laser which has higher output and is easy to manufacture.

FIG. 12 shows an embodiment in which the structures shown in FIGS. 6, 7 and 8 are combined. The light guide layer need not be on the upper portion of the active layer as shown in FIG. 12, but may be on the lower portion or, of course, on both sides. In this case, in addition to low operating current and low noise characteristic characteristics, high characteristic temperature
It is possible to obtain a semiconductor laser with higher output and easier to manufacture.

In all of the above embodiments, the substrate is n-type and only the case where the n-type current blocking layer is used is shown. However, if the substrate is p-type and the p-type current blocking layer is also used. I do not care. That is, the AlAs mixed crystal ratio of the current block layer is high. In the case of the conventional GaAs current blocking layer (FIG. 13), the diffusion length of electrons from the clad layer into the p-type GaAs layer is 2-3 μm, which is longer than the thickness of the current blocking layer, and is a p-type blocking layer. However, in the case of the p-type GaAlAs layer having a high mixed crystal ratio, the diffusion of electrons is suppressed, so that the p-type block layer can be realized.

In all of the above embodiments, only the case where the ridge is on the active layer, that is, on the side opposite to the substrate when viewed from the active layer is shown. However, even when the ridge is in the same direction as the substrate,
The same effect can be obtained. That is, it goes without saying that if a double-confidence structure in which the ridge portion is in both directions is adopted, the leakage current can be further reduced, and a low operating current can be achieved.

Needless to say, if the active layer has a quantum well structure, lower operating current and higher output can be achieved.

[0045]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, the active layer G
On one side of the main surface of the a _{1 -X} Al _X As layer, a Ga ₁ -Y ₁ Al _{Y 1} As layer of one conductivity type, a Ga _{1 -C} Al _C As layer, and a ridge-shaped Ga _{1 -Y 2} Al _{Y 2} layer are formed. And a Ga _{1 -Z} Al _Z As layer having a conductivity type opposite to those of the As layer along the longitudinal side surface of the ridge.
lAs mixed crystal ratio, between X, Y1, Y2, C and Z, Z
A semiconductor laser device with low noise and a significantly lower operating current value than that of the conventional one, which is excellent in mass productivity, is formed by the structure that satisfies the relations of>Y2> X ≧ 0 and Y1>C> X. It can be realized.

That is, since the AlAs mixed crystal ratio of the current block layer is set to be higher than the AlAs mixed crystal ratio of the cladding layer, oscillation occurs in a single transverse mode and laser light is not absorbed by the current block layer. Therefore, the loss of the waveguide can be significantly reduced, and the operating current value can be reduced.

Further, since light spreads to the current blocking layer and the active layer thereunder, it is easier to obtain multimode oscillation of the spectrum as compared with the conventional one, and even if the distance between the active layer and the current blocking layer is made shorter than before. , Low noise characteristics can be obtained.

Further, since there is no light absorption by the current blocking layer, the stripe width can be made narrower than before. The effect of reducing the leakage current and the effect of narrowing the stripe width, that is, the dimension can be set in the direction of lowering the operating current value. It can be reduced.

In addition, when the ridge is formed by etching, the Ga _{1 -C} Al _C As layer acts as an etching stop layer, so that an element with small variations in etching and high mass productivity can be obtained.

Since the reduction of the operating current value leads to the reduction of the heat generation amount in the active layer, the light output becomes higher than the conventional one. In particular, by thinning the active layer, high output can be obtained. If the semiconductor laser of the present invention having such characteristics is used as a light source of an optical disk, it becomes possible to eliminate a high frequency superimposing circuit for reducing noise during reading,
A drastic downsizing of the pickup can be realized.

Further, the reduction of the operating current value brings about the reduction of the heat generation amount of the laser mount portion, and the use of a smaller and lighter heat sink becomes possible. As a result, the laser package, which was conventionally made of metal, can be made resinous, and the pickup can be significantly downsized and the cost can be reduced.

From the viewpoint of device fabrication, the ridge structure as shown in FIG. 1 makes the regrowth interface separate from the active layer, and a high yield can be expected, as compared with the structure of FIG. Such a semiconductor laser device exerts an effect when used as a light source for an optical disc for which the miniaturization of an optical pickup is required.

[Brief description of drawings]

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

FIG. 2 is a manufacturing process diagram of a semiconductor laser device according to an embodiment of the present invention.

FIG. 3 Relationship between spectral characteristics and structural parameters

[Fig. 4] Relationship between operating current value and stripe width

FIG. 5 is a current-light output characteristic diagram of a semiconductor laser device according to an embodiment of the present invention.

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

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

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

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

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

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

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

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

FIG. 14 is a sectional view of a conventional semiconductor laser device in which a regrowth interface is close to an active layer.

[Explanation of symbols]

1 n-type GaAs substrate 2 n-type GaAs buffer layer 3 n-type Ga _0.5 Al _0.5 As clad layer 4 Ga _0.85 Al _0.15 As active layer 5 p-type Ga _0.5 Al _0.5 As first clad layer 6 p-type Ga _0.8 Al _0.2 As etching stop layer 7 p-type Ga _0.5 Al _0.5 As second cladding layer 8 n-type Ga _0.4 Al _0.6 As current blocking layer 9 p-type GaAs protective layer 10 p-type GaAs contact layer 11 dielectric film 12 p-type Ga _0.4 Al _0.6 As layer 13 n-type GaAs layer 14 p-type Ga _0.6 Al _0.4 As optical guide layer 21 n-type GaAs substrate 22 n-type GaAs buffer layer 23 n-type Ga _0.5 Al _0.5 As Cladding layer 24 Ga _0.85 Al _0.15 As active layer 25 p-type Ga _0.5 Al _0.5 As clad layer 25a ridge 25b regrowth interface 26 p-type GaAs protection layer Protective layer 27 n-type GaAs current blocking layer 28 p-type GaAs contact layer 29 p-type Ga _0.5 Al _0.5 As second cladding layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuichi Shimizu 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electronics Industrial Co., Ltd.

Claims (8)

[Claims] 1. A Ga ₁ -Y ₁ Al _{Y 1} A of one conductivity type is provided on at least one side of a main surface of a Ga _{1 -X} Al _x As layer serving as an active layer.
s layer, Ga _1-C Al _C As layer, and ridge-shaped Ga _{1-Y 2}
An Al _Y2 As layer is sequentially provided, and Ga having a conductivity type opposite to those of Ga is provided along the longitudinal side surface of the ridge.
_1-Z Al _Z As layer, AlAs mixed crystal ratio, X, Y
Between 1, Y2, C and Z, Z>Y2> X ≧ 0, Y1
A semiconductor laser device having a relationship of>C> X. 2. _One conductivity type Ga ₁ -Y ₁ Al _Y1 A is provided on at least one side of the main surface of the Ga _{1 -X} Al _x As layer to be an active layer.
s layer, Ga _1-C Al _C As layer, and ridge-shaped Ga _{1-Y 2}
An Al _Y2 As layer is sequentially provided, and Ga having a conductivity type opposite to those of Ga is provided along the longitudinal side surface of the ridge.
_1-Z Al _Z As layer and the Ga _{1- Y2} Al _Y2 As layer
Layer between the Ga _{1 -Z} Al _Z As layer and the Ga _{1 -Y 2} Al layer.
Ga with the same conductivity type as the _Y2 As layer and a layer thickness of 0.1 μm or less
_1-B Al _B As layer is formed, AlAs mixed crystal ratio,
Between X, Y1, Y2, C, Z and B, Z>Y2> X
A semiconductor laser device characterized in that the relations ≧ 0, Y1>C> X, B> X are established. 3. _One conductivity type Ga ₁ -Y ₁ Al _{Y 1} A is provided on at least one side of the main surface of the Ga _{1 -X} Al _x As layer to be an active layer.
s layer, Ga _1-C Al _C As layer, and ridge-shaped Ga _{1-Y 2}
An Al _Y2 As layer is sequentially provided, and Ga having a conductivity type opposite to those of Ga is provided along the longitudinal side surface of the ridge.
It comprises a _1-Z Al _Z As layer and the Ga _{1- Z} Al _Z As layer than said Ga _1-Z Al Z As layer, a low AlAs mole fraction, at least, consist of one or more layers A GaAlAs layer or a GaAs layer is formed, and Z>Y2> between the AlAs mixed crystal ratios, X, Y1, Y2, C, and Z.
A semiconductor laser device having a relationship of X ≧ 0 and Y1>C> X. 4. A Ga ₁ -Y ₁ Al _{Y 1} A of one conductivity type is provided on at least one side of a main surface of a Ga _{1 -X} Al _x As layer to be an active layer.
s layer, Ga _1-C Al _C As layer, and ridge-shaped Ga _{1-Y 2}
An Al _Y2 As layer is sequentially provided, and Ga having a conductivity type opposite to those of Ga is provided along the longitudinal side surface of the ridge.
Ga having a _1-Z Al _Z As layer and serving as the active layer
_A Ga _1-D Al _D As layer is formed in contact with the _1-X Al _X As layer, and Z>Y2> between the AlAs mixed crystal ratios, X, Y1, Y2, Z, C and D. D> X ≧ 0, Y1>C> X
A semiconductor laser device characterized by satisfying the following relationship. 5. Ga to be an active layer_1-XAl_XMain surface of As layer
Ga of one conductivity type on at least one side of_1-Y1Al_Y1A
s layer, Ga_1-CAl_CAs layer and ridge Ga
_1-Y2Al_Y2The As layer is sequentially provided, and the ridge is formed.
G of opposite conductivity type along the longitudinal side of
a_1-ZAl_ZAn As layer, and the Ga _1-Y2Al_Y2A
s layer and Ga_1-ZAl_ZBetween the As layer, the Ga_1-Y2A
l_Y2G with the same conductivity type as the As layer and a layer thickness of 0.1 μm or less
a_1-BAl_BAn As layer is formed, and the Ga
_1-ZAl_ZOn the As layer, the Ga_1-ZAl_ZThan the As layer
Low AlAs mixed crystal ratio, consisting of at least one layer
GaAlAs layer or GaAs layer is formed,
AlAs mixed crystal ratio, between X, Y1, Y2, Z, B and C
And Z> Y2> X ≧ 0, Y1> C> X, B> X
A semiconductor laser device characterized by being established. 6. A Ga ₁ -Y ₁ Al _{Y 1} A of one conductivity type is provided on at least one side of a main surface of a Ga _{1 -X} Al _x As layer to be an active layer.
s layer, Ga _1-C Al _C As layer, and ridge-shaped Ga _{1-Y 2}
An Al _Y2 As layer is sequentially provided, and Ga having a conductivity type opposite to those of Ga is provided along the longitudinal side surface of the ridge.
_1-Z Al _Z As layer and the Ga _{1- Y2} Al _Y2 As layer
Layer between the Ga _{1 -Z} Al _Z As layer and the Ga _{1 -Y 2} Al layer.
Ga with the same conductivity type as the _Y2 As layer and a layer thickness of 0.1 μm or less
_{A 1-B} Al _B As layer is formed, and a Ga _1-D Al _D As layer is formed in contact with the Ga _1-x Al _x As layer serving as the active layer. , X, Y1, Y2,
Between Z, B, C and D, Z>Y2>D> X ≧ 0, Y
A semiconductor laser device characterized in that the relationships 1>C> X and B> X are established. 7. Ga serving as an active layer_1-XAl_XMain surface of As layer
Ga of one conductivity type on at least one side of_1-Y1Al_Y1A
s layer, Ga_1-CAl_CAs layer and ridge Ga
_1-Y2Al_Y2The As layer is sequentially provided, and the ridge is formed.
G of opposite conductivity type along the longitudinal side of
a_1-ZAl_ZAn As layer, and the Ga _1-ZAl_ZAs
On the layer, the Ga_1-ZAl_ZAlAs mixed crystal rather than As layer
GaAlAs with low ratio and consisting of at least one layer
Layer or GaAs layer is formed, and
Ga that becomes the functional layer_1-XAl_XIn contact with the As layer, Ga_1-DAl_D
As layer is formed, AlAs mixed crystal ratio, X, Y1,
Between Y2, Z, C and D, Z> Y2> D> X ≧ 0,
Semi-conductor characterized by establishing the relationship of Y1> C> X
Body laser device. 8. Ga as an active layer_1-XAl_XMain surface of As layer
Ga of one conductivity type on at least one side of_1-Y1Al_Y1A
s layer, Ga_1-CAl_CAs layer and ridge Ga_1-Y2
Al_Y2Along with the As layer, the ridge has a longitudinal direction.
Of the opposite conductivity type along the side surface of_1-ZAl_Z
An As layer, and the Ga_1-Y2Al _Y2As layer and the above
Ga_1-ZAl_ZBetween the As layer, the Ga_1-YAl_YAs layer
Ga of the same conductivity type and a layer thickness of 0.1 μm or less_1-BAl_BA
s layer is formed, and the Ga_1-ZAl_ZAs layer
Above the Ga_1-ZAl_ZAlAs mixed crystal ratio rather than As layer
GaAlAs layer having low lowness and at least one layer
Alternatively, a GaAs layer is formed and the active
Ga as a layer_1-XAl_XIn contact with the As layer, Ga_1-DAl_DA
s layer is formed, AlAs mixed crystal ratio, X, Y1, Y
Between 2, Z, B, C and D, Z> Y2> D> X ≧
0, Y1> C> X, B> X
Semiconductor laser equipment to be used.