JP3115490B2 - Semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-yield, low-cost, low-operating-current, real-refraction-guided semiconductor laser device suitable as a light source for an optical information processing device or the like.

[0002]

2. Description of the Related Art A conventional semiconductor laser device will be described below.

[0003] A single mode light source is required as a light source for information processing devices such as optical communication and optical disks.
A semiconductor laser device having a refractive index waveguide structure is used. In particular, in recent years, a high yield semiconductor laser device formed by using a vapor phase growth method having good film thickness uniformity as a crystal growth method has become mainstream.

Hereinafter, a conventional refractive index guided semiconductor laser device which can be realized by a vapor phase growth method will be described. 9 to 14 are schematic cross-sectional views of a semiconductor laser chip in a conventional typical refractive index guided semiconductor laser device. 9 to 14, the electrode layers formed on the upper and lower surfaces of the semiconductor substrate are omitted.

FIG. 9 shows a semiconductor laser chip used in applications to optical disks such as CDs (see JJAP, vol. 24, p. L89 (1985)). As shown in FIG. 9, an n-type cladding layer 12 made of gallium aluminum arsenide (GaAlAs) is formed on an n-type semiconductor substrate 11 made of gallium arsenide (GaAs).
2, an active layer 13 of GaAlAs is formed,
A p-type first cladding layer 14 made of GaAlAs is formed on the active layer, and a region other than the stripe region 15a serving as a current channel on the first cladding layer 14 is formed of GaAs made of GaAs for current confinement. Type current block layer 15 is formed, and GaAlAs is formed on the first clad layer 14 and the current block layer 15 by a regrowth method.
A second p-type cladding layer 16A is formed.
A p-type contact layer 17 made of GaAs is formed on the cladding layer 16A.

In the semiconductor laser chip having this structure, the current injected from the contact layer 17 is effectively confined in the stripe region 15a by the presence of the current blocking layer 15, and the active layer 13 below the stripe region 15a is formed. Causes laser oscillation. At this time, since the forbidden band width of the current blocking layer 15 is smaller than the energy of the wavelength of the laser light, laser light other than the stripe region 15a is absorbed by the current blocking layer 15, so that the laser light is effective in the stripe region 15a. And a single-mode laser oscillation is obtained.

In the semiconductor laser chip shown in FIG. 10, an n-type cladding layer 12 of GaAlAs is formed on an n-type semiconductor substrate 11, and an active layer 13 of GaAlAs is formed on the cladding layer 12. A stripe-shaped cladding layer 16B is formed on the active layer 13, and a current blocking layer 15 is formed in a region other than the stripe region on the cladding layer 16B.
A p-type cap layer 18 made of GaAs is formed on the stripe region on 6B and the current blocking layer 1 is formed.
A p-type contact layer 17 made of GaAs is formed on the cap layer 5 and the cap layer 18.

The basic operation principle of the semiconductor laser chip shown in FIG. 10 is the same as that of the semiconductor laser chip shown in FIG. 9, and the presence of the current blocking layer 15 confines current and laser light in the stripe region. Single-mode laser oscillation is obtained (JJAP, vol. 25, p. L498 (1986).
reference).

The semiconductor laser chip shown in FIG.
0 has a ridge waveguide structure in which the current blocking layer 15 is not formed (see SPIE, vol. 1043, p. 61 (1989)). . Here, reference numeral 19 in FIG. 11 denotes a dielectric film. Since the surface of the semiconductor laser chip shown in FIG. 11 is not flat, there are problems such as occurrence of cracks at the time of cleaving and an increase in thermal resistance. The semiconductor laser chip is not mass-produced and is shown in FIG. Structures are widely used. That is, the current blocking layer 15 also has the effect of flattening the surface and increasing mass productivity.

In recent years, a real-refractive-index guided semiconductor laser chip using a current blocking layer made of GaAlAs has also been developed (JP-A-62-73687). According to this structure, the laser light is confined in the stripe region by forming the refractive index of the current blocking layer lower than the refractive index of the cladding layer, so that the laser light is confined by the light absorption of the current blocking layer 15. Unlike the structure shown in FIGS. 9 and 10, a single-mode semiconductor laser chip with low internal loss and low operating current can be obtained.

FIG. 12 shows a semiconductor laser chip having a buried hetero (BH) structure applied in the field of optical communication and the like (IEEE, J. Quantum Electron., QE-16,
p.205 (1980). In FIG. 12, reference numeral 20 denotes a buried high resistance layer, and reference numeral 21 denotes a zinc diffusion region. FIG.
In the semiconductor laser chip shown in FIG. 1, the buried high-resistance layers 20 on both sides of the active layer 13 function as a current blocking layer, and the laser light is applied to the stripe region due to a difference in the refractive index between the active layer 13 and the buried high-resistance layer 20. Is sharply confined inside. This structure is not suitable for obtaining a high output because steep light confinement increases the light density in the active layer 13, and is generally applied to a low output semiconductor laser chip. Further, the problem that the active layer 13 is exposed to the air when forming the stripe region and defects are introduced into the active layer 13 is also unsuitable for increasing the output.

FIG. 13 shows a conventional example in which a light guide layer 22 is formed on a cladding layer 12 and a stripe-shaped active layer 13 is formed on the light guide layer 22 (IEEE, J. Quantu).
m Electron., QE-15, p. 451 (1979)). According to the semiconductor laser chip having this structure, when the active layer 13 is etched in a stripe shape, the active layer 13 is exposed to the air, so that it has a disadvantage that reliability is reduced. Further, since the current block layer 23 made of GaAlAs is formed on the uppermost surface of the growth layer, there is a problem that the current spreads greatly and the threshold value becomes high.
It has not been put to practical use.

FIG. 14 shows a conventional example using a p-type semiconductor substrate reported in a semiconductor laser chip manufactured by a vapor growth method (Tech. Digest IEDM85, p. 646).
(1985)). That is, the p-type cladding layer 16B made of GaAlAs is formed on the p-type semiconductor substrate 1 made of GaAs, and the n-type current blocking layer 23 made of GaAlAs is formed outside the stripe region on the cladding layer 16B. And GaAs on the stripe region on the cladding layer 16B and the current block layer 23.
An n-type cladding layer 24 of lAs is formed, an active layer 13 of GaAlAs is formed on the cladding layer 24, an n-type cladding layer 12 of GaAlAs is formed on the active layer 13, An n-type contact layer 8 made of GaAs is formed on the cladding layer 12 of FIG. According to the semiconductor laser chip having this structure, since the active layer 13 is formed after the formation of the stripe region, the active layer 13 is bent in the stripe region, and the light confinement in the stripe region is too strong and the lateral direction is reduced. Since there is a problem that mode control is difficult, it has not been put to practical use.

In short, in each of the above-described conventional structures, the semiconductor laser chips currently in practical use are limited to those shown in FIGS. 9, 10 and 12. Here, the structure shown in FIG. 12 is not suitable for increasing the output and is used as a part of a semiconductor laser chip for optical communication.
The structure shown in FIGS. 9 and 10 having
It is most widely used as a light source for optical disks such as CDs. In order to realize the structure shown in FIGS. 9 and 10 at low cost, it is indispensable to manufacture it by a vapor phase growth method with good film thickness uniformity.

Here, since it is more advantageous to form the current blocking layer for holes whose diffusion length is shorter than about half of the electron diffusion length, the conductivity type of the current blocking layer must be n-type. There is. When a p-type current block layer is used, its thickness is 2 to 3 μm, which is more than twice the thickness of the n-type current block layer, and the etching depth when forming the stripe region is reduced. About the same as the width. Therefore, it is very difficult to control the stripe width, and good crystal growth cannot be expected.

When the current blocking layer is n-type, the semiconductor substrate also becomes n-type as shown in FIGS. Generally, in a semiconductor laser device, a package is used as a negative terminal, so in a conventional semiconductor laser device, it is necessary to electrically connect a semiconductor substrate to the package.

However, in the case of a semiconductor laser chip, it is necessary to bring the surface on which the crystal is grown into contact with the heat sink from the viewpoint of reliability. The reason is that the heat generated at the time of current injection is generated in the active layer in the crystal growth layer, and unless this heat is immediately conducted to the heat sink,
This is because the crystals in the active layer are deteriorated by heat generation. While the thickness of the semiconductor substrate is about 100 μm, the thickness of the crystal growth layer is several μm to 10 μm, and unless the surface on the crystal growth layer side of the semiconductor chip is brought into contact with a heat sink having high thermal conductivity, The reliability of the semiconductor laser device cannot be ensured.

FIG. 15 shows a schematic structure of a conventional semiconductor laser device using a semiconductor laser chip formed by a high-yield vapor phase growth method. As shown in FIG. 15, an electrode pattern 25a is placed on an insulating heat sink 25 such as SiC.
Is formed, and the electrode 30a on the crystal growth surface side of the laser chip 30 is connected to the electrode pattern 25a via the solder layer 25b.
Mounted on. The solder layer 25b is electrically connected to a laser voltage application terminal 26 by a first wire 27. The electrode 30 b on the semiconductor substrate side of the laser chip 30 is electrically connected to another electrode pattern 25 a by the second wire 28, and is electrically connected to the package 10 through the side surface of the heat sink 30. With the above configuration, electrical connection with the package 10 as a negative terminal can be realized.

In addition, heat sinks having an insulating film formed on a conductive Si substrate have been put into practical use.
The basic configuration for electrically connecting the electrode on the semiconductor substrate side of the semiconductor laser chip to the package on the heat sink is the same.

[0020]

As described above, the conventional semiconductor laser device has a structure in which a current and a laser beam are confined in a stripe region by using a current blocking layer. In the steps, a step of etching the current block layer in a stripe shape or a step of selectively forming the current block layer outside the stripe region is indispensable.

The current blocking layer required to block the current needs to have a thickness about the same as the diffusion length for electrons or holes. Therefore, in the case of an n-type current blocking layer made of GaAs, 0 is required. A thickness of about 0.5 to 1 μm is required, and a p-type current blocking layer made of GaAs requires a thickness of 2 to 3 μm. As the thickness of the current block layer is smaller, the semiconductor laser chip can be more easily manufactured. Therefore, an n-type is used as the conductivity type of the current block layer, and about 1 μm is used for forming the n-type current block layer. Requires etching of a stripe region having a depth of.
Deep etching lowers the yield due to variations in stripe width after etching. The stripe width after the etching is, for example, 2 ±
It is necessary to control the width to about 0.2 μm, and in a semiconductor laser chip whose light distribution is directly affected by the stripe width, control of the stripe width is very important.

The problem of controlling the stripe width is particularly problematic when performing selective etching by providing an etching stop layer in order to stably perform etching in the depth direction.
For example, in FIG. 9, even if an etching solution that can selectively etch the current blocking layer 15 is used, when the current blocking layer 15 is thick, the thickness of the current blocking layer 15 varies greatly. This is because the stripe width largely varies due to the side etching until all the regions to be removed are removed.

Specifically, when the in-plane variation of the thickness of the current block 15 layer is ± 10%, the thickness of the current block layer 15 is 1 ± 0.1 μm, and the side etch and the depth direction are different. Even if the etching rate is the same,
± 0.2 variation in stripe width due to side etch
μm. Actually, furthermore, since the variation in the mask width due to the photolithography process is added to the above-mentioned variation, the stripe width cannot be controlled to 2 ± 0.2 μm, which causes a decrease in the yield of the semiconductor laser chip. There's a problem. As described above, since the p-type current blocking layer is thicker than the n-type current blocking layer, the p-type current blocking layer cannot be practically used at all.

As shown in FIG. 10, the current blocking layer 1
Even when 5 is selectively formed outside the stripe region, a step of etching the p-type cladding layer 16 to a thickness of about 1 μm is necessary, and the difficulty in controlling the stripe width is the same as described above. That is, the current blocking layer 15
The problem of controlling the stripe width by deep etching is unavoidable as long as is required.

However, in the structure of FIG. 9, a method of selectively growing the current blocking layer 15 on the first cladding layer 14 is considered. For this purpose, the first cladding layer 15 in the stripe region is considered. 14 as a mask for selective growth, a dielectric film such as a nitride film is formed before plasma selective growth.
A step of removing the dielectric film by reactive ion etching or the like after selective growth is required. However, this method has not been realized because it has a problem that a large number of crystal defects are introduced into the first cladding layer 14 near the light emitting region of the active layer 13 and a problem that the manufacturing process becomes complicated. .

Since the conductivity type of the current blocking layer 15 is limited to n-type, in the conventional semiconductor laser chip, the conductivity type of the semiconductor substrate 11 is also n-type as shown in FIGS. Therefore, in a normal use mode in which the package of the semiconductor laser device has a negative terminal, it is necessary to electrically connect the electrode on the crystal growth surface side of the semiconductor substrate to the heat sink on an insulating heat sink as shown in FIG. is there.

However, an insulating heat sink such as SiC is expensive, and is an obstacle to reducing the cost of the semiconductor laser device. To reduce the cost, the conductive S
Although a method of forming an insulating film on the i and providing an appropriate electrode pattern on the heat sink has been put to practical use, cost reduction is limited as long as a device for making electrical connection to the heat sink is added. There is.

In view of the above, it is an object of the present invention to easily and reliably realize a semiconductor laser device by a vapor deposition method that oscillates in a single transverse mode at a high yield and at a low cost without using a current blocking layer. I do.

[0029]

In order to achieve the above object, the present invention provides a structure in which a stripe region has a low resistance and a region other than the stripe region has a high resistance so that current flows only in the stripe region. This eliminates the need for a current blocking layer in a semiconductor laser having a refractive index waveguide structure, and mounts a semiconductor laser chip formed on a p-type semiconductor substrate on a conductive heat sink. .

Specifically, a solution according to the first aspect of the present invention is to provide a semiconductor laser device in which an active layer having a refractive index of n _x is formed above a p-type semiconductor substrate, and the active layer is formed on the active layer. An n-type first semiconductor layer having a refractive index of n _Y1 is formed, and an n-type second semiconductor layer having a refractive index of n _Y2 is formed in a stripe on the first semiconductor layer. An n-type third semiconductor layer having a refractive index of n _Y3 is formed on the first semiconductor layer and the second semiconductor layer, and the active layer, the first semiconductor layer, the second semiconductor layer, The third semiconductor layer has an interface resistance between the first semiconductor layer and the third semiconductor layer, an interface resistance between the first semiconductor layer and the second semiconductor layer, and an interface resistance between the first semiconductor layer and the second semiconductor layer. 3 and the refractive index n _X of the active layer is larger than the refractive index n _Y1 of the first semiconductor layer. A semiconductor laser chip formed so as to be large and having a refractive index n _Y2 of the second semiconductor layer larger than a refractive index n _{Y3 of} the third semiconductor layer is provided on a heat sink made of a conductive material. The heat sink is mounted so that its side surface is in contact with the heat sink.

According to a second aspect of the present invention, in the first aspect, an oxide film is formed on a surface layer of a region of the first semiconductor layer in contact with the third semiconductor layer. It is to be added.

According to a third aspect of the present invention, there is provided a semiconductor laser device comprising: an active layer made of Ga _1-x Al _x As formed on a p-type semiconductor substrate made of GaAs;
An n-type _first layer made of Ga _{1 -Y 1} Al _Y1 As is formed on the active layer.
Is formed, and G is formed on the first light guide layer.
An n-type second light guide layer made of a _{1 -Y 2} Al _Y2 As is formed in a stripe shape, and Ga _{1 -Y 3} Al _Y3 As is formed on the first light guide layer and the second light guide layer. The active layer, the first light guide layer, the second light guide layer, and the clad layer have an interface resistance between the first light guide layer and the clad layer of the first type. And the interface resistance between the second light guide layer and the cladding layer is larger than the interface resistance between the second light guide layer and the second light guide layer. A semiconductor laser chip formed so as to satisfy the relationship of Y3> Y2, Y1> X ≧ 0 between Y2 and Y3 is placed on a heat sink made of a conductive material such that the surface on the cladding layer side is in contact with the heat sink. It is configured to be mounted.

According to a fourth aspect of the present invention, in addition to the configuration of the third aspect, a configuration is provided in which the second light guide layer is transparent to a wavelength of laser light oscillated by the active layer. According to a fifth aspect of the present invention, in the configuration of the fourth aspect, the active layer and the second light guide layer are each composed of X and Y having a mixed crystal ratio.
2 is added so as to satisfy the relationship of Y2> X.

According to a sixth aspect of the present invention, in the structure of the fourth aspect, the active layer and the second light guide layer have a relation of X ≧ Y2 ≧ 0 between X and Y2 of each mixed crystal ratio. In addition, a configuration is added in which the second light guide layer is formed to have a film thickness exhibiting a quantum effect.

According to a seventh aspect of the present invention, in addition to the third aspect, a configuration is provided in which an oxide film is formed on a surface layer of the first light guide layer in a region in contact with the clad layer. Things.

According to an eighth aspect of the present invention, in addition to the configuration of the seventh aspect, a configuration is provided in which the second light guide layer is transparent to a wavelength of laser light oscillated by the active layer. According to a ninth aspect of the present invention, in the configuration of the eighth aspect, the active layer and the second light guide layer are each composed of X and Y having a mixed crystal ratio.
2 is added so as to satisfy the relationship of Y2> X.

According to a tenth aspect of the present invention, in the configuration of the eighth aspect,
The active layer and the second light guide layer are formed such that the relationship of X ≧ Y2 ≧ 0 is established between X and Y2 of the respective mixed crystal ratios, and the second light guide layer has a film thickness exhibiting a quantum effect. Is added.

According to another aspect of the present invention, there is provided a semiconductor laser device, wherein an active layer having a quantum well structure is formed above a p-type semiconductor substrate made of GaAs, and Ga ₁ is formed on the active layer. _An n-type first light guide layer made of _-Y1 Al _Y1 As is formed, and Ga is formed on the first light guide layer.
_An n-type second light guide layer made of _1-Y2 Al _Y2 As is formed in a stripe shape, and the first light guide layer and the second
An n-type clad layer made of Ga _{1 -Y 3} Al _Y3 As is formed on the light guide layer of the above, and the active layer, the first light guide layer, the second light guide layer, and the clad layer are formed of a first layer. The interface resistance between the light guide layer and the clad layer is any one of the interface resistance between the first light guide layer and the second light guide layer and the interface resistance between the second light guide layer and the clad layer. Each of the second light guide layer and the cladding layer.
The configuration is such that the relationship of Y3> Y2 is established between Y2 and Y3 of the 1As mixed crystal ratio.

According to a twelfth aspect of the invention, in addition to the configuration of the eleventh aspect, a configuration is provided in which the second light guide layer is transparent to a wavelength of laser light oscillated by the active layer. .

According to a thirteenth aspect of the present invention, in the structure of the twelfth aspect, the second light guide layer has a forbidden band width large enough not to absorb the wavelength of the laser light oscillated by the active layer. Is added.

According to a fourteenth aspect of the present invention, in the configuration of the twelfth aspect, the second light guide layer is formed such that the second light guide layer has a film thickness exhibiting a quantum effect. Is added.

According to a fifteenth aspect of the present invention, in addition to the structure of the eleventh aspect, a structure is provided in which an oxide film is formed on a surface layer of a region of the first light guide layer in contact with the cladding layer. Things.

According to a sixteenth aspect of the present invention, in addition to the configuration of the fifteenth aspect, a configuration is provided in which the second light guide layer is transparent to a wavelength of laser light oscillated by the active layer. According to a seventeenth aspect of the present invention, in the configuration of the sixteenth aspect, the second light guide layer is formed such that its forbidden band width is a size that does not absorb the wavelength of laser light oscillated by the active layer. Is added.

According to an eighteenth aspect of the present invention, in the configuration of the sixteenth aspect, the second light guide layer is formed such that the second light guide layer has a film thickness exhibiting a quantum effect. Is added.

[0045]

According to the structure of the first aspect, the first semiconductor layer and the third semiconductor layer
Interface resistance between the first semiconductor layer and the second semiconductor layer.
Current is larger than both the interface resistance between the first semiconductor layer and the third semiconductor layer and the interface resistance between the second semiconductor layer and the third semiconductor layer. In the case of, it is difficult to flow into a region where the second semiconductor layer is not formed, that is, a region other than the stripe region, while it is easy to flow into a region where the second semiconductor layer is formed, that is, the stripe region. Therefore, the current can be confined to the stripe region without forming the current block layer.

The refractive index n _X of the active layer is larger than the refractive index n _Y1 of the first semiconductor layer, and the refractive index n _Y2 of the second semiconductor layer is larger than the refractive index n _Y3 of the third semiconductor layer. Since it is large, the effective refractive index of the stripe region becomes higher than the effective refractive index outside the stripe region, and a stable single transverse mode oscillation by the refractive index waveguide mechanism can be obtained.

Further, since the semiconductor laser chip uses a p-type semiconductor substrate, the surface of the semiconductor laser chip on the third semiconductor layer side, that is, the surface on the side opposite to the semiconductor substrate is used as a conductive heat sink. By mounting the package so as to make contact with the package, the package can be used as a negative terminal.

According to the second aspect of the present invention, an oxide film is formed on a surface layer of the first semiconductor layer in a region in contact with the third semiconductor layer. The interface resistance with the semiconductor layer can be easily and reliably increased.

According to the third aspect, the active layer is made of GaAl.
In the semiconductor laser chip made of As, the interface resistance between the first light guide layer and the clad layer is the interface resistance between the first light guide layer and the second light guide layer, and the second light guide layer. Since the current is larger than any of the interface resistance between the second optical guide layer and the cladding layer, the current can easily flow only in the region where the second light guide layer is formed, that is, the stripe region. It can be formed in a stripe region.

The Al, X, and Y crystal ratios of the active layer, the first light guide layer, the second light guide layer, and the cladding layer are set as follows.
Since the relationship of Y3> Y2, Y1> X ≧ 0 holds between 1, Y2 and Y3, the refractive index of the second optical guide layer becomes larger than the refractive index of the cladding layer, so that the effective refraction of the stripe region. The index becomes higher than the effective refractive index outside the stripe region, and a stable single transverse mode oscillation can be obtained.

Furthermore, since a p-type semiconductor substrate made of GaAs is used, the semiconductor laser chip is connected to the conductive heat sink such that the surface on the cladding layer side of the semiconductor laser chip, that is, the surface on the side opposite to the semiconductor substrate contacts the heat sink. By mounting, the package can be a negative terminal.

According to the fourth aspect, the active layer is made of GaAl.
In a semiconductor laser device made of As, the second light guide layer is transparent to the wavelength of laser light oscillated by the active layer, so that heat generation near the active layer is suppressed.

According to the fifth aspect, the active layer is made of GaAl.
In the semiconductor laser device made of As, the active layer and the second optical guide layer have a Y ratio between X and Y2 of each mixed crystal ratio.
Since the relationship 2> X is established, the second light guide layer is transparent to the wavelength of the laser light oscillated by the active layer, and heat generation near the active layer is suppressed.

According to a sixth aspect of the present invention, the active layer is made of GaAl.
In the semiconductor laser device made of As, the active layer and the second optical guide layer are formed such that X and Y2 of the mixed crystal ratio are between X and Y2.
Since the relationship of ≧ Y2 ≧ 0 is satisfied and the second light guide layer is formed to have a film thickness exhibiting the quantum effect, the second light guide layer has a wavelength of the laser light oscillated by the active layer. And the heat generation near the active layer is suppressed.

According to the seventh aspect, the active layer is made of GaAl.
In the semiconductor laser device made of As, an oxide film is formed on a surface layer of a region of the first optical guide layer which is in contact with the clad layer, so that an interface between the first optical guide layer and the clad layer is formed. The resistance can be increased simply and reliably.

According to the eighth aspect, the active layer is made of GaAl.
In a semiconductor laser device made of As, the interface resistance between the first light guide layer and the cladding layer can be easily and surely increased, and the second light guide layer is used for the laser light oscillated by the active layer. Since it is transparent to the wavelength, heat generation near the active layer can be suppressed.

According to the ninth aspect, the active layer is made of GaAl.
In the semiconductor laser device made of As, the interface resistance between the first optical guide layer and the cladding layer can be easily and reliably increased, and the active layer and the second optical guide layer have a mixed crystal ratio of X. The second light guide layer is transparent to the wavelength of the laser light oscillated by the active layer, and generates heat in the vicinity of the active layer. Can be suppressed.

According to the tenth aspect, the active layer is made of GaAs.
In the semiconductor laser device composed of 1As, the interface resistance between the first optical guide layer and the cladding layer can be easily and surely increased, and the active layer and the second optical guide layer have different mixed crystal ratios. Since the relationship of X ≧ Y2 ≧ 0 is established between X and Y2, and the second light guide layer is formed to have a film thickness exhibiting the quantum effect, the second light guide layer is formed by the active layer. It becomes transparent to the wavelength of the oscillated laser light, and can suppress heat generation near the active layer.

According to the eleventh aspect, since the active layer has the quantum well structure, the threshold value and the output of the semiconductor laser device can be reduced.

The interface resistance between the first light guide layer and the clad layer is the same as the interface resistance between the first light guide layer and the second light guide layer and the second light guide layer and the clad layer. Claim 1 because it is greater than any of the interfacial resistances between the layers.
Similarly to the invention of the first aspect, the current can be confined in the stripe without forming the current block layer.

Since the relationship of Y3> Y2 is established between the AlAs mixed crystal ratios Y2 and Y3 of the second light guide layer and the cladding layer, the refractive index of the second light guide layer is determined by the refractive index of the cladding layer. Index, and a stable single transverse mode oscillation can be obtained by the refractive index waveguide mechanism.

Further, since a p-type semiconductor substrate made of GaAs is used, the semiconductor laser chip is connected to the conductive heat sink such that the surface on the cladding layer side of the semiconductor laser chip, that is, the surface on the side opposite to the semiconductor substrate is in contact with the heat sink. By mounting, the package can be a negative terminal. .

According to the twelfth aspect, in the GaAlAs-based semiconductor laser device in which the active layer has a quantum well structure, the second light guide layer is transparent to the wavelength of the laser light oscillated by the active layer. In addition, heat generation near the active layer can be suppressed.

According to the thirteenth aspect, in the GaAlAs-based semiconductor laser device in which the active layer has a quantum well structure, the bandgap of the second optical guide layer does not absorb the wavelength of the laser light oscillated by the active layer. Since the second light guide layer is formed in a size, the second light guide layer is transparent to the wavelength of the laser light oscillated by the active layer, and heat generation near the active layer is suppressed.

In the GaAlAs-based semiconductor laser device having the quantum well structure, the second optical guide layer is formed so as to have a thickness exhibiting the quantum effect. The second light guide layer is transparent to the wavelength of the laser light oscillated by the active layer, and can suppress heat generation near the active layer.

According to the fifteenth aspect, in the GaAlAs-based semiconductor laser device in which the active layer has a quantum well structure, an oxide film is formed on a surface layer of the first optical guide layer in a region in contact with the clad layer. The first
The interface resistance between the light guide layer and the cladding layer can be easily and reliably increased.

In the GaAlAs-based semiconductor laser device in which the active layer has a quantum well structure, the interface resistance between the first optical guide layer and the cladding layer can be easily and reliably increased. Since the second light guide layer is transparent to the wavelength of the laser light oscillated by the active layer, heat generation in the vicinity of the active layer can be suppressed.

According to the seventeenth aspect, in the GaAlAs-based semiconductor laser device in which the active layer has a quantum well structure, the interface resistance between the first optical guide layer and the cladding layer can be simply and reliably increased. Since the bandgap of the second light guide layer is formed so as not to absorb the wavelength of the laser light oscillated by the active layer, the second light guide layer is formed by the laser light oscillated by the active layer. And the heat generation near the active layer is suppressed.

According to the eighteenth aspect, in the GaAlAs-based semiconductor laser device in which the active layer has a quantum well structure, the interface resistance between the first optical guide layer and the cladding layer can be easily and reliably increased. Since the second light guide layer is formed so as to have a film thickness exhibiting a quantum effect, the second light guide layer is transparent to the wavelength of the laser light oscillated by the active layer and is close to the active layer. Can be suppressed.

[0070]

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 chip in a semiconductor laser device according to one embodiment of the present invention. G
A p-type buffer layer 2 (thickness: 0.5 μm) of GaAs is formed on a p-type semiconductor substrate 1 of aAs, and a p-type clad of Ga _0.5 Al _0.5 As is formed on the buffer layer 2. Layer 3 (thickness: 1.5 μm) is formed,
An active layer 4 (thickness: 0.06 μm) made of Ga _0.85 Al _0.15 As is formed on the cladding layer 3, and an n-type as a first semiconductor layer made of Ga _0.5 Al _0.5 As is formed on the active layer 4. Is formed (thickness: 0.1 μm), and Ga _0.8 Al _0.2 A is formed on the first light guide layer 5.
A p-type second optical guide layer 6 (thickness: 20 nm) is formed as a stripe-shaped second semiconductor layer made of s.
On the first light guide layer 5 and the second light guide layer 6,
Ga _0.5 Al _{0. 5} n-type buried cladding layer 7 made of As (thickness: 1.5 [mu] m) by the re-growth method is formed, the contact layer 8 made of GaAs on the buried cladding layer 7 (thickness: 2 [mu] m ) Is formed.

In this case, in order to obtain a stable single transverse mode oscillation, the refractive index of the second optical guide layer 6 is formed higher than the refractive index of the buried cladding layer 7. In this embodiment, this is realized by making the AlA mixed crystal ratio of the second optical guide layer 6 lower than the AlAs mixed crystal ratio of the buried cladding layer 7.

If the AlAs mixed crystal ratio of the second optical guide layer 6 is the same as the AlAs mixed crystal ratio of the buried cladding layer 7, the refractive index of the stripe region is reduced due to the plasma effect, and the anti-guide conductivity is reduced. As a result, a single transverse mode oscillation cannot be obtained. Furthermore, the second light guide layer 6
The AlAs mixed crystal ratio of A is AlAs of the buried cladding layer 7.
When the mixed crystal ratio is higher than that, the transverse mode oscillation becomes extremely unstable. In this embodiment, as shown in FIG. 1, the AlAs mixed crystal ratio of the second optical guide layer 6 is set to 0.2 which is sufficiently lower than the AlAs mixed crystal ratio of the buried cladding layer 7.

FIG. 2 shows an example of the result of numerical calculation of the effective refractive index difference (Δn) inside and outside the stripe. When the cladding mixed crystal ratio used for the wavelength of the 780 nm band used for the optical disk is 0.5, the mixed crystal ratio (Y2) of the second optical guide layer 6 is set to 0.2, and the thickness thereof is set to 0.2. 20nm
It can be seen that by setting the value to about, a value of the effective refractive index difference Δn = 7 × 10 ⁻³ sufficient to obtain the refractive index waveguide structure can be obtained. Thus, in this embodiment, by setting the AlAs mixed crystal ratio of the second light guide layer 6 appropriately, it is possible to design the second light guide layer 6 which is extremely thin. Therefore, there is almost no step in the etching of the stripe region, and the problem of a decrease in yield due to side etching or the like does not occur. Actually, the variation in the stripe width is reduced to a very small variation in the mask width due to the photolithography process. Also, since the etching step is small,
A semiconductor laser chip having a flat surface can be easily realized.

When a non-selective liquid such as tartaric acid or sulfuric acid is used as an etching solution, a slight overetch occurs in the depth direction, but the AlAs mixed crystal ratio of the first optical guide layer 5 and the buried cladding layer 7 When the AlAs mixed crystal ratio is the same, the effective refractive index difference Δn does not change as long as the etching is stopped in the first optical guide layer 5 and is the same with good reproducibility between lots or within the wafer surface. A semiconductor laser chip having the following characteristics is obtained. In the present embodiment, the thickness of the first light guide layer 5 is set to 0.1 μm and ten times the thickness of the second light guide layer 6, so that a non-selective etchant is used. Also, the etching can be reliably stopped in the first light guide layer 5.

Next, the principle of current confinement will be described.
The current confinement in the stripe region is caused by the first light guide layer 5.
The resistance can be easily realized by making the interface resistance between the second optical guide layer 6 and the buried cladding layer 7 sufficiently higher than the interface resistance between the second optical guide layer 6 and the buried cladding layer 7. In the present embodiment, this is realized by making the AlAs mixed crystal ratio of the first light guide layer 5 sufficiently higher than the AlAs mixed crystal ratio of the second light guide layer 6. That is, in the case of exposing the surface of the GaAlAs-based material to the atmosphere, the higher the AlAs mixed crystal ratio, the more defect levels caused by oxidation of Al are introduced. Therefore, when regrowth is performed on a semiconductor substrate having a high AlAs mixed crystal ratio, the crystallinity at the regrowth interface deteriorates, and the resistance at the interface essentially increases.

FIG. 3 shows experimental results of current-voltage characteristics with respect to the AlAs mixed crystal ratio on the surface of the semiconductor substrate obtained by experiments. The semiconductor substrate used in the experiment was obtained by removing the second light guide layer 6 in the semiconductor laser chip shown in FIG. 1 and changing the AlAs mixed crystal ratio (Y1) of the first light guide layer 5. is there. That is, regrowth is performed on the first light guide layer 5 by the MOCVD method. It can be seen that the voltage increases as the AlAs mixed crystal ratio increases. In particular, when the AlAs mixed crystal ratio is 0.5
In the above, a potential barrier is formed along with the increase in the resistance of the interface, and a dip is seen in the rise of the voltage. Here, the driving voltage of the semiconductor laser is at most 2 V
Therefore, no current flows in the region where the dip is formed. That is, in this embodiment, the AlAs mixed crystal ratio of the first light guide layer 5 is set to 0.5 and the second light guide layer 6
By setting the AlAs mixed crystal ratio of 0.2 to 0.2, current constriction in the stripe region is realized. At this time, it is desirable that the AlAs mixed crystal ratio of the second optical guide layer 6 be 0.3 or less in order to perform current injection into the stripe region satisfactorily without problems of the interface.

This phenomenon is not limited to the GaAlAs-based material, but is also observed in other Al-containing material systems, for example, InGaAlP-based materials, and similar current confinement is possible.

In this embodiment, only the case of oxidation of Al has been described. However, other semiconductor materials (materials containing no Al, such as InP, InGaAsP, Zn
In the case of (Se-based), a similar current confinement can be realized by forcibly oxidizing the first optical guide layer 5. That is, after the second light guide layer 6 is masked in a stripe shape and etched and before the mask is removed, the first light guide layer 5 is exposed to an oxygen atmosphere to form the first light guide layer. By oxidizing 5, an oxide layer can be formed on the surface layer of the first optical guide layer 5 in a region in contact with the buried cladding layer 7. Unlike the liquid phase growth method, which is crystal growth in a thermal equilibrium state, the use of vapor phase growth, which is a crystal growth in a non-equilibrium state, results in semi-forced growth of crystals, so that a semiconductor with an oxide film formed somewhat Crystal growth is also possible on the layer. Of course, A
Also in the system containing l, the vapor phase growth method is used to increase the interface resistance between the first optical guide layer 5 and the buried cladding layer 7 outside the stripe region and to improve current confinement. Is also good. With this method, the stability between processes can be achieved.

In this structure, the p-type GaAs
The current injected from the contact layer 8 is confined in the stripe region, and Ga _0.85 Al
Laser oscillation in the 780 nm band occurs in the active layer 4 made of _0.15 As. In addition, since the semiconductor laser chip is a real refractive index waveguide type and does not have a scattering loss due to the side surface of the active layer being etched as in the BH structure, a semiconductor laser chip having a small internal loss and a low operating current can be obtained.

Furthermore, in this structure, a small effective refractive index difference Δn can be formed by changing the film thickness of each layer. It is possible to easily obtain a laser chip with semi-uniform noise.

FIG. 4 shows an experimental result of a relationship between a spectral characteristic and a structural parameter in the semiconductor laser chip according to the present embodiment. In the 780 nm wavelength band, the layer thickness (da) of the active layer 4 and the layer thickness (d
It can be seen that multimode oscillation can be obtained in a wide range of p). In this case, the thickness of the second optical guide layer 6 for making the effective refractive index difference Δn small and performing multi-mode is 10n.
m. By manufacturing a semiconductor laser chip in such a range, a low-noise semiconductor laser chip used for a CD or the like can be easily realized.

However, each GaAlAs layer capable of guiding light,
That is, Te is added to the first and second optical guide layers 5 and 6 made of n-type GaAlAs in the present embodiment as an impurity which is conventionally used in the liquid phase growth method. In the (MOCVD method), when Se is added, these impurities become DX centers in GaAlAs, and cause a saturable absorption effect at the light density of the main mode oscillating at several mW to several tens mW. For this reason, a loss grating is formed for the standing wave of the oscillating main mode, and other modes other than the oscillating main mode are suppressed, thereby increasing the single mode property.

In order to solve this problem, in this embodiment, Si is added as an impurity to each layer of GaAlAs that can guide light. Since the activation energy of thermal capture and emission of carriers between the DX center level and the conduction band in GaAlAs is different from that of Te and Se, light absorption is saturated at a very low optical density. Seldom forms a loss grating for the oscillating main mode. Therefore, there is no problem that the multi-modality of the spectrum is impaired, and the noise can be easily reduced. For the same reason, the use of Si is also effective when the spectrum is made multimode by high-frequency superposition to reduce noise. That is,
Conventionally, in order to reduce the noise in the structure of a semiconductor laser chip in which the effective refractive index difference Δn in the horizontal direction is increased at the junction and the oscillation mode spectrum is set to a single mode, a high frequency is superimposed on the operating current and the spectrum is multimode. However, compared to the case of Te and Se in which a loss grating is formed, Si has a more easily multimode spectrum and low noise characteristics can be realized.

Hereinafter, a method for manufacturing a semiconductor laser chip in a semiconductor laser device according to one embodiment of the present invention will be described with reference to FIGS. 5 (a), 5 (b) and 5 (c).

First, as shown in FIG.
A p-type buffer layer 2 of GaAs (thickness: 0.5 μm) and a p-type cladding layer of Ga _0.5 Al _0.5 As are formed on a p-type semiconductor substrate 1 by MOCVD or MBE growth. 3 (thickness: 1.5 μm), Ga
Active layer 4 of _0.85 Al _0.15 As (thickness: 0.04 μm)
m), an n-type first optical guide layer 5 of Ga _0.5 Al _0.5 As (thickness: 0.1 μm), Ga _0.8 Al _0.2 As
N-type second light guide layer 6 (thickness: 20 nm)
Are sequentially formed. The AlAs mixed crystal ratio of the second light guide layer 6 is desirably 0.3 or less, which facilitates regrowth, and is preferably a mixed crystal ratio transparent to laser light. Because
Even if the layer is very thin, the absorption of the laser beam leads to heat generation in the vicinity of the active layer 4, which may hinder high output and long life of the semiconductor laser chip. . From this point, in this embodiment,
As the AlAs mixed crystal ratio of the second light guide layer 6, the active layer 4
The value of 0.2, which is sufficiently larger than the AlAs mixed crystal ratio of 0.15, is used.

Here, the layer thickness of the active layer 4 and the layer thickness of the first light guide 5 are effective refractive index difference Δn = 5 × 10 ^{−3 in} order to obtain stable single transverse mode oscillation. It is thick. The conductivity type of the active layer 4 is not specifically described, but may be p-type, n-type, or of course, undoped.

Next, as shown in FIG. 5B, a stripe-shaped mesa is formed by etching using photolithography. Since the thickness of the first optical guide layer 5 is 20 nm, even if there is a side etch, the etching depth is at most that much, and the etching variation in the stripe region hardly occurs. When the stripe width is 2.0 μm, the variation of the stripe width of the actually manufactured semiconductor laser chip is ± 0.1 μm or less, and the variation of the conventional semiconductor laser chip shown in FIGS. It is significantly reduced as compared with 0.5 μm.

Next, as shown in FIG.
Ga _0.5 Al _0.5 As by D method or MBE growth method
A p-type buried cladding layer 7 of GaAs and a p-type contact layer 8 of GaAs are sequentially formed by regrowth. At this time, in the stripe region where the current flows, p-type Ga _0.8 Al _0.2 As having a low AlAs mixed crystal ratio is used.
Since the growth is performed on the second light guide layer 6 made of the material, the growth can be easily performed.

Next, electrodes are formed on the p-type semiconductor substrate 1 made of GaAs and the n-type contact layer 8 made of GaAs, respectively.

In the above embodiment, in order to make the second light guide layer 6 transparent to laser light, the AlAs mixed crystal ratio of the second light guide layer 6 is changed to the AlAs mixed crystal of the active layer 4. Although it is larger than the ratio, the following may be used instead. That is, the AlAs of the second light guide layer 6
The mixed crystal ratio can be made equal to or lower than the AlAs mixed crystal ratio of the active layer 4, and the thickness of the second optical guide layer 6 can be made thin enough to produce a quantum effect, so that it is transparent to laser light.

FIG. 6 shows a calculation result when the second light guide layer 6 has a quantum effect. The vertical axis is a value obtained by converting the interband energy obtained by the quantum effect of the second light guide layer 6 into a wavelength. When the semiconductor laser chip has an oscillation wavelength in the 780 nm band as in the above embodiment, even if the second optical guide layer 6 is made of GaAs (Y2 = 0), if the layer thickness is 3 nm or less, the second light guide layer 6 becomes the second light guide layer. It can be seen that the light guide layer 6 becomes transparent due to the quantum effect. In this case, since the AlAs mixed crystal ratio of the second optical guide layer 6 can be set lower than in the embodiment shown in FIG. 1, the crystallinity at the regrowth interface in the stripe region becomes better, and The growth process can be stabilized. Further, the layer thickness of the second optical guide layer 6 is reduced in this case for obtaining the quantum effect, but the AlAs mixed crystal ratio of the second optical guide layer 6 can be considerably low (the refractive index is high). Effective refractive index difference Δ required for refractive index guide
n can be secured.

Further, in the above embodiment, only the case where GaAlAs having a low AlAs mixed crystal ratio is used for the second light guide layer 6 is shown, but other materials which can lattice-match with GaAs may be used. However, it is desirable that the second light guide layer 6 has a forbidden band width larger than the wavelength of the laser light in order to suppress light absorption. For example, In _0.5 Ga _{0. 5}
A second light guide layer 6 made of P may be used. At this time, similar characteristics can be obtained.

The same characteristics as described above can be obtained by using the second light guide layer 6 made of In ₁ -x Ga _x As _Y P _{1 -Y} . In this case, X and Y are 0.189Y−0.418X + 0.01 in order to obtain lattice matching with GaAs.
It is necessary to satisfy the relationship of 3XY + 0.127 = 0.

The forbidden band width of the second light guide layer 6 is:
Since it is necessary to be larger than the energy (E) of the wavelength of the laser beam, 1.35 + 0.672X-1.601Y +
0.758X ² + 0.101Y ² -0.157XY-
It is desirable to satisfy the relationship of 0.312X ² Y + 0.109XY ² > E.

Further, In _0.5 (Ga _1-x Al _x ) _0.5 P
A second light guide layer 6 may be used. In this case, the forbidden bandwidth becomes larger than the wavelength of the laser beam regardless of X, and lattice matching is obtained. However, if X is too large, there is a problem of oxidation. Therefore, it is preferable that X <0.3.

In order to lower the threshold value and increase the output of the semiconductor laser chip, it is effective to use a quantum well structure. That is, the active layer 4 has a single quantum well (SQW) structure, a double quantum well (DQW) structure, a triple quantum well (TQW) structure, a green (GRIN) structure, or a separate confinement heterostructure (SCH) structure thereof. It is preferable to use the quantum well structure described above. The reason is that the quantum effect in the active layer 4 increases the gain, the threshold current is reduced, and the light confinement coefficient in the well layer becomes smaller than the confinement coefficient in the bulk active layer 4. It is to improve.

Next, a semiconductor laser device in which the semiconductor laser chip is mounted on a heat sink will be described with reference to FIG.

In the semiconductor laser device, in order to ensure reliability, the semiconductor laser chip 30 is placed such that the electrode 30a on the crystal growth surface side of the semiconductor laser chip 30 including the active layer, which is a heating section, contacts the heat sink 9. Since it is necessary to mount the semiconductor laser chip 30 on the heat sink 9, the semiconductor laser chip 30 is mounted on the conductive heat sink 9 made of Si in the above-described state. As the material of the heat sink 9, other materials may be used as long as they are conductive, but Si which can be manufactured at the lowest cost is optimal. Also, unlike Cu and the like, Si is the same material as the semiconductor substrate forming the semiconductor laser chip, and therefore has a similar thermal expansion coefficient and the like.

In the semiconductor laser device according to the present invention, since the p-type semiconductor substrate 1 is used, the package 10 is connected to the negative terminal on the heat sink 9 as in the conventional semiconductor laser device represented by FIG. It is not necessary to make electrical connection to the heat sink 9 such that the semiconductor laser chip 30 is mounted on the heat sink 9 made of Si having a solder layer 9b formed on the entire surface of both surfaces, and the package 10 is connected to a negative terminal. It can be.

In the semiconductor laser device according to the present invention, since it is not necessary to change the electrical connection on the heat sink 9, the wire 27 is connected from the laser terminal 26 to the electrode 30 b on the semiconductor substrate side of the semiconductor laser chip 30.
Since only books are required, the number of wire bonding steps can be reduced.

As described above, in the semiconductor laser device according to the present invention, the cost of assembling the semiconductor laser device by the low-cost vapor deposition method can be further reduced.

Further, as a conventional semiconductor laser device,
A structure in which an insulating film is formed on a conductive heat sink made of Si, which is lower in cost than an insulating heat sink made of an expensive material such as SiC, and the electrical connection is changed on the heat sink is widely used. ing. However, in the conventional semiconductor laser device, since the semiconductor laser chip is mounted on the heat sink via the insulating film, there is a problem that heat conduction from the semiconductor laser chip to the heat sink deteriorates. When an experiment was conducted by mounting a semiconductor laser chip having a cavity length of 250 μm on a heat sink, the thermal resistance without an insulating film was 50%.
In contrast to K / W, the thermal resistance in the presence of the insulating film was 90 K / W, which was almost doubled. This means that the amount of heat generated by the semiconductor laser chip is approximately doubled due to the presence of the insulating film, and in the conventional semiconductor laser device, deterioration is promoted and reliability is impaired. .
On the other hand, in the semiconductor laser device according to the present embodiment, since there is no heat generated by the insulating film as described above,
The heat generation in the active layer is small, and a longer life can be obtained than in the conventional case.

As a test item before shipment of a semiconductor laser device, there is a test called a screening test for removing a short-lived semiconductor laser device in advance, and this test compares the difference in the yield of the semiconductor laser device depending on the presence or absence of an insulating film. 1.5 is better with a heat sink without insulating film
The yield was about twice as high. Needless to say, the improvement in the yield in the inspection process of the final assembly contributes to low cost.

FIG. 7A is a characteristic diagram of current-light output of the semiconductor laser chip shown in FIG. As a result of coating a front end face of 10% and a rear end face of 75% on a semiconductor laser device having a cavity length of 400 μm, a threshold value of 20% was obtained.
As a result, a low current consumption characteristic of mA and a slope efficiency of 0.9 mW / mA was obtained. Horizontal mode and vertical mode are 780 nm
Was a stable single mode at the wavelength of

Hereinafter, the low noise characteristics of the semiconductor laser chip shown in FIG. 1 will be described. Resonator length is 200μ
m, and the end face reflectance is 32%. In order to reduce noise, FIG. 4 shows that da = 0.04 μm and dp = 0.22 μm.
m. The operating current required to emit 3 mW laser light at room temperature is 25 mA. The transverse mode oscillated in a stable fundamental mode. The spectrum oscillates in multiple modes causing self-pulsation in the 780 nm band, and has a wavelength of -130 dB / H within a return light rate of 0 to 10%.
The value of relative intensity noise (RIN) of z was obtained, and low noise characteristics were obtained.

Hereinafter, a case where a quantum well structure is used for the active layer 4 to improve the performance of the semiconductor laser chip will be described. That is, when the active layer 4 has a quantum well structure, the threshold value can be further reduced and a high output can be obtained. FIG. 7B shows a quantum well structure having a thickness of 10 nm and a thickness of Ga _0.95 Al _{0. 0} oscillating 780 nm laser light _.
05 As 4 well layers and 4 nm thick Ga
_It shows current-light output characteristics when a multiquantum well (MQW) structure having five barrier layers made of _0.7 Al _0.3 As is used. An optical output of 200 mW or more can be realized in a semiconductor laser chip having a cavity length of 400 μm and front and rear surfaces coated with 10% and 75%.

[0108]

According to the semiconductor laser device of the first aspect, the interface resistance between the first semiconductor layer and the third semiconductor layer is set between the first semiconductor layer and the second semiconductor layer. Resistance and the interface resistance between the second semiconductor layer and the third semiconductor layer. Therefore, even if the current blocking layer is not formed, it is thin and uniform formed by, for example, a vapor phase growth method. The current can be confined to the stripe region by the appropriate second semiconductor layer. Therefore, deep etching for forming the current block layer is not required, and stripes can be formed by shallow etching for forming the second semiconductor layer. A real-refractive-index guided semiconductor laser device having an operating current value can be realized at low cost and high yield.

A semiconductor laser device operating at a low current is most suitable as a light source for all optical disks including a compact disk. In particular, a reduction in the operating current value results in a reduction in the amount of heat generated in the laser mount portion, and a smaller and lighter heat sink can be used. As a result, the laser package, which has conventionally been made of metal, can be made of resin, and the size and cost of the pickup device can be significantly reduced.

Further, since the p-type semiconductor substrate is used, the semiconductor laser chip is connected to the conductive heat sink such that the surface of the semiconductor laser chip on the third semiconductor layer side, that is, the surface on the side opposite to the semiconductor substrate is in contact with the heat sink. , The package can be a negative terminal. For this reason, it is not necessary to change the electrical connection on the heat sink, so that the number of bonding wires can be reduced, whereby the number of wire bonding steps can be reduced, and the assembly cost of the semiconductor laser device can be greatly reduced.

According to the semiconductor laser device of the second aspect, the interface resistance between the first semiconductor layer and the third semiconductor layer can be easily increased, and therefore, the semiconductor laser device of the first aspect. Can be realized easily and reliably.

According to the GaAlAs-based semiconductor laser device according to the third aspect of the present invention, the interface resistance between the first light guide layer and the clad layer is higher than that of the first light guide layer and the second light guide layer. The current is stripped by the thin second light guide layer without forming a current blocking layer because it is larger than the interface resistance between the second light guide layer and the interface resistance between the second light guide layer and the clad layer. The region can be constricted. Therefore, similar to the first aspect of the present invention, since a deep etching for forming the current block layer is not required, the variation in the stripe width is reduced, and the real refractive index guided semiconductor laser device having a low operating current value is provided. Can be realized at low cost and high yield.

Further, since the p-type semiconductor substrate is used, the package can be a negative terminal as in the first aspect of the present invention, and there is no need to change the electrical connection on the heat sink. The number of processes can be reduced, and the assembly cost of the semiconductor laser device can be greatly reduced.

According to the GaAlAs-based semiconductor laser device according to the present invention, the second light guide layer is transparent to the wavelength of the laser light oscillated by the active layer. Since no heat is generated, it is possible to increase the output and extend the life of the semiconductor laser device.

According to the GaAlAs-based semiconductor laser device of the present invention, the interface resistance between the first optical guide layer and the cladding layer can be easily increased. The device can be realized easily and reliably.

GaAlAs according to claims 8 to 10
According to the semiconductor laser device of the present invention, the interface resistance between the first light guide layer and the cladding layer can be easily increased to realize the semiconductor laser device of claim 3 easily and reliably. Since the layer is transparent to the wavelength of the laser light oscillated by the active layer, no heat is generated in the vicinity of the active layer, so that the output of the semiconductor laser device can be increased and the life thereof can be extended.

According to the GaAlAs-based semiconductor laser device including the active layer having the quantum well structure according to the eleventh aspect of the present invention, similar to the first aspect of the present invention, deep etching for forming a current blocking layer becomes unnecessary. Therefore, the variation in stripe width is reduced, and the effect of the active layer having the quantum well structure realizes a low refractive index waveguide type semiconductor laser device with a lower operating current value and a higher output at a lower cost and a higher yield. be able to.

Further, since a p-type semiconductor substrate is used, the package can be a negative terminal as in the first aspect of the invention, and there is no need to change the electrical connection on the heat sink. The number of processes can be reduced, and the assembly cost of the semiconductor laser device can be greatly reduced.

According to the GaAlAs-based semiconductor laser device including the active layer having the quantum well structure according to the twelfth to fourteenth aspects, the second optical guide layer has a wavelength corresponding to the wavelength of the laser light oscillated by the active layer. Since heat is not generated in the vicinity of the active layer due to the effect of the transparent and active layer having the quantum well structure, higher output and longer life of the semiconductor laser device can be achieved.

According to the GaAlAs-based semiconductor laser device including the active layer having the quantum well structure according to the fifteenth aspect, the interface resistance between the first optical guide layer and the cladding layer can be easily increased. Therefore, the semiconductor laser device according to claim 11 can be easily and reliably realized.

According to the GaAlAs-based semiconductor laser device including the active layer having the quantum well structure according to the sixteenth aspect of the present invention, the second optical guide layer is provided for the wavelength of the laser light oscillated by the active layer. Heat is not generated in the vicinity of the active layer due to the effect of the transparent active layer having the quantum well structure, so that the semiconductor laser device can have higher output and longer life.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an example of a numerical calculation result of an effective refractive index difference (Δn) inside and outside a stripe region in the semiconductor laser device according to the embodiment.

FIG. 3 is a view showing an experimental result of a relationship between a current-voltage characteristic and an AlAs mixed crystal ratio of a semiconductor substrate in the semiconductor laser device according to the embodiment.

FIG. 4 is a view showing an experimental result of a relationship between a spectral characteristic and a structural parameter in the semiconductor laser device according to the embodiment.

FIG. 5 is a sectional view showing each step of a method for manufacturing a semiconductor laser chip in the semiconductor laser device according to the embodiment.

FIG. 6 is a diagram illustrating a calculation result of energy when the second light guide layer has a quantum effect in the semiconductor laser device according to the embodiment.

FIG. 7 is a diagram showing current-light output characteristics in the semiconductor laser device according to the one embodiment.

FIG. 8 is a perspective view showing a semiconductor laser device according to one embodiment of the present invention.

FIG. 9 is a sectional view of a semiconductor laser chip in a conventional semiconductor laser device.

FIG. 10 is a sectional view of a semiconductor laser chip in a conventional semiconductor laser device.

FIG. 11 is a sectional view of a semiconductor laser chip in a conventional semiconductor laser device.

FIG. 12 is a cross-sectional view of a semiconductor laser chip in a conventional semiconductor laser device.

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

FIG. 14 is a sectional view of a semiconductor laser chip in a conventional semiconductor laser device.

FIG. 15 is a perspective view showing a conventional semiconductor laser device.

[Explanation of symbols]

1 of p-type semiconductor substrate 2 GaAs consisting GaAs p-type buffer layer 3 Ga _0.5 Al _0.5 As of p-type cladding layer 4 Ga _0.85 Al _0.15 active layer 5 Ga _0.5 consisting As Al _0.5 As of n -Type first optical guide layer 6 n-type second optical guide layer made of Ga _0.8 Al _0.2 As 7 n-type buried cladding layer made of Ga _0.5 Al _0.5 As 8 n-type contact layer made of GaAs 9 Si 9a Electrode formed on heat sink 9b Solder layer 10 Package 11 n-type semiconductor substrate made of GaAs 12 n-type clad layer made of GaAlAs 13 Active layer made of GaAlAs 14 p-type made of GaAlAs First cladding layer 15 n-type current blocking layer 15a made of GaAs 15a stripe region 16A p-type second cladding layer made of GaAlAs 16B p-type cladding layer made of GaAlAs 17 p-type contact layer made of GaAs 18 p-type cap layer made of GaAs 19 dielectric film 20 buried high resistance layer 21 zinc Diffusion region 22 n-type optical guide layer made of GaAlAs 23 n-type current blocking layer made of GaAlAs 24 n-type second clad layer made of GaAlAs 25 heat sink (insulating) made of SiC 25a electrode formed on heat sink 25b Solder layer 26 Laser terminal 27 Wire 28 Wire 30 Laser chip 30a Electrode on crystal growth surface side 30b Electrode on semiconductor substrate side

Continuation of the front page (56) References JP-A-63-164290 (JP, A) JP-A-62-20392 (JP, A) JP-A-53-6591 (JP, A) JP-A-63-81884 (JP, A) JP-A-7-142765 (JP, A) JP-A-5-167174 (JP, A) JP-A-6-196801 (JP, A) JP-A-50-788 (JP, A) 1-115186 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (18)

(57) [Claims] 1. The method according to claim 1, wherein the refractive index is n _{x above the} p-type semiconductor substrate.
An active layer having a refractive index of n _Y1 is formed on the active layer.
Is formed, and an n-type second semiconductor layer having a refractive index of n _Y2 is formed on the first semiconductor layer in the form of a stripe. An n-type third semiconductor layer having a refractive index of n _Y3 is formed on the layer and the second semiconductor layer, and the active layer, the first semiconductor layer, and the second
The third semiconductor layer and the third semiconductor layer have an interface resistance between the first semiconductor layer and the third semiconductor layer, and an interface resistance between the first semiconductor layer and the second semiconductor layer and a second semiconductor layer. Is larger than any of the interface resistances between the first semiconductor layer and the third semiconductor layer, the refractive index n _X of the active layer is larger than the refractive index n _Y1 of the first semiconductor layer, and A semiconductor laser chip formed such that the refractive index n _Y2 is larger than the refractive index n _{Y3 of} the third semiconductor layer is provided on a heat sink made of a conductive material, and the surface on the third semiconductor layer side is in contact with the heat sink. Semiconductor laser device characterized by being mounted as described above. 2. The semiconductor laser device according to claim 1, wherein an oxide film is formed on a surface layer of the first semiconductor layer in a region in contact with the third semiconductor layer. Wherein the active layer of Ga _1-X Al _X As above the p-type semiconductor substrate made of GaAs is formed, the n-type composed of Ga _1-Y1 Al _Y1 As on the active layer One light guide layer is formed, and Ga is formed on the first light guide layer.
_An n-type second light guide layer made of _1-Y2 Al _Y2 As is formed in a stripe shape, and the first light guide layer and the second
An n-type clad layer made of Ga _{1 -Y 3} Al _Y3 As is formed on the light guide layer of the above, and the active layer, the first light guide layer, the second light guide layer, and the clad layer are formed of a first layer. The interface resistance between the light guide layer and the clad layer is any one of the interface resistance between the first light guide layer and the second light guide layer and the interface resistance between the second light guide layer and the clad layer. A heat sink made of a conductive material, wherein the semiconductor laser chip is formed such that the relationship of Y3> Y2, Y1> X ≧ 0 is established between X, Y1, Y2 and Y3 of each AlAs mixed crystal ratio. A semiconductor laser device mounted thereon such that the surface on the side of the cladding layer is in contact with the heat sink. 4. The semiconductor laser device according to claim 3, wherein said second light guide layer is transparent to a wavelength of laser light oscillated by said active layer. 5. The active layer and the second light guide layer,
5. The semiconductor laser device according to claim 4, wherein a relationship of Y2> X is established between X and Y2 of each mixed crystal ratio. 6. The active layer and the second light guide layer,
9. The method according to claim 8, wherein a relationship of X ≧ Y2 ≧ 0 is established between X and Y2 of each mixed crystal ratio, and the second light guide layer is formed to have a film thickness exhibiting a quantum effect. 5. The semiconductor laser device according to 4. 7. The semiconductor laser device according to claim 3, wherein an oxide film is formed on a surface layer of the first light guide layer in a region in contact with the clad layer. 8. The semiconductor laser device according to claim 7, wherein said second light guide layer is transparent to a wavelength of laser light oscillated by said active layer. 9. The active layer and the second light guide layer,
9. The semiconductor laser device according to claim 8, wherein a relationship of Y2> X is established between X and Y2 of each mixed crystal ratio. 10. The active layer and the second light guide layer have a relationship of X ≧ Y2 ≧ 0 between X and Y2 of each mixed crystal ratio, and the second light guide layer has a quantum effect. 9. The film according to claim 8, wherein the film is formed to have a thickness.
3. The semiconductor laser device according to item 1. 11. An active layer having a quantum well structure is formed above a p-type semiconductor substrate made of GaAs, and an n-type first light guide made of Ga _{1 -Y1} Al _Y1 As is formed on the active layer. A layer is formed, and Ga _{1 -Y 2} is formed on the first light guide layer.
An n-type second light guide layer made of Al _Y2 As is formed in a stripe shape, and an n-type second light guide layer made of Ga _{1 -Y 3} Al _Y3 As is formed on the first light guide layer and the second light guide layer. A clad layer is formed, and the active layer, the first light guide layer, the second light guide layer, and the clad layer have an interface resistance between the first light guide layer and the clad layer that is the first light guide layer. Resistance of the second light guide layer and the cladding layer is larger than the interface resistance between the second light guide layer and the cladding layer.
A semiconductor laser chip formed so as to satisfy the relationship of Y3> Y2 between the mixed crystal ratios Y2 and Y3 is mounted on a heat sink made of a conductive material so that the surface on the cladding layer side is in contact with the heat sink. A semiconductor laser device comprising: 12. The semiconductor laser device according to claim 11, wherein said second light guide layer is transparent to a wavelength of laser light oscillated by said active layer. 13. The second light guide layer is formed such that its forbidden band has a size that does not absorb the wavelength of laser light oscillated by the active layer. 13. The semiconductor laser device according to item 12. 14. The semiconductor laser device according to claim 12, wherein the second light guide layer is formed such that the second light guide layer has a film thickness exhibiting a quantum effect. . 15. The semiconductor laser device according to claim 11, wherein an oxide film is formed on a surface layer of the first light guide layer in a region in contact with the cladding layer. 16. The semiconductor laser device according to claim 15, wherein said second light guide layer is transparent to a wavelength of laser light oscillated by said active layer. 17. The semiconductor device according to claim 1, wherein the second light guide layer is formed such that its forbidden band width does not absorb the wavelength of laser light oscillated by the active layer. 17. The semiconductor laser device according to item 16. 18. The semiconductor laser device according to claim 16, wherein the second light guide layer is formed such that the second light guide layer has a film thickness exhibiting a quantum effect. .