JP2003174232A - Semiconductor laser device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device having stable characteristics in a high output range without protrusion of a cap layer on the mesa part of a clad layer and to provide a method for manufacturing the same. <P>SOLUTION: The method for manufacturing the semiconductor laser device comprises the step of sequentially crystal growing an n-type GaAs buffer layer 4, an n-type Al<SB>0.5</SB>Ga<SB>0.5</SB>As first clad layer 5, an AlGaAs quantum well active layer 6, a p-type Al<SB>0.5</SB>Ga<SB>0.5</SB>As second lower side clad layer 7, a p-type GaAs etching stop layer 10, a p-type Al<SB>0.5</SB>Ga<SB>0.5</SB>As second upper side clad layer 11, and a p-type GaAs cap layer 12 on an n-type GaAs substrate 1. The method further comprises the steps of disposing a resist film on the surface of the layer 12 near the layer 7, bringing an etching liquid into contact with the surface of the layer 12 at the side farther from the active layer 7 and removing by etching the protrusion of the cap layer protruding from both lateral ends of the top of the layer 11. Since a cavity is not formed in a current blocking layer 18a, the semiconductor laser device having good characteristics is obtained. <P>COPYRIGHT: (C)2003,JPO

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 and its manufacturing method.

[0002]

2. Description of the Related Art Conventionally, as a method for manufacturing a semiconductor laser device, there is one disclosed in Japanese Patent Application Laid-Open No. 4-322482. FIG. 26 is a sectional view showing a semiconductor laser device manufactured by the above manufacturing method. It is a figure. This semiconductor laser device is a real refractive index type ridge stripe type semiconductor laser device. In FIG. 26, 101 is n-
This is a GaAs (n-type gallium arsenide) substrate, and this substrate 1
An n-side electrode 122 is provided on the lower side of. N- above
An n-GaAs buffer layer 10 is formed on the GaAs substrate 1.
4, n-AlGaAs (n-type aluminum gallium arsenide) first cladding layer 105, AlGaAs active layer (or quantum well layer) 106, p-AlGaAs (p-type aluminum gallium arsenide) second cladding layer 107, p-Ga
As (p-type gallium arsenide) cap layers 112 are sequentially stacked to form a double hetero structure. Above p
The -AlGaAs second clad layer 107 forms a ridge-shaped mesa portion 115, and n-AlGaAs current blocking layers 118a and n-Ga are formed on both sides of the mesa portion 115.
The As current blocking layer 118b is provided so as to perform current confinement and optical waveguide action in a self-aligned manner. The above p-GaA
s cap layer 112 and n-GaAs current blocking layer 11
The p-GaAs contact layer 119 is formed on the entire upper surface of 8b.
Is provided, and the p-side electrode 121 is further provided thereon.

The above-mentioned ridge stripe type semiconductor laser device has the following problems during manufacturing. That is,
When the ridge-shaped mesa portion 115 is formed on the p-AlGaAs second cladding layer 107 by etching, the cap layer remains protruding from the top of the mesa portion in an eaves-like shape,
The protrusions 230, 230 are formed. This cause is p-
This is because the AlGaAs second cladding layer 107 and the p-GaAs cap layer 112 have different Al compositions, and therefore have different etching rates. In other words, the etching solution for the GaAs-based material that has been conventionally used is generally slower in etching than GaAs.
However, since the etching proceeds faster, the second clad layer 107 made of AlGaAs below the cap layer 112 is more etched and removed than the cap layer 112 made of GaAs, and the protrusion 230 is formed on the cap layer 112. , 230 are formed.

After the protrusion 230 of the cap layer is formed, the n-AlGaAs current blocking layers 118a and n are formed.
When the -GaAs current blocking layer 118b is grown, cavities may be formed in these current blocking layers 118a and 118b. The formation of this cavity is remarkable in the semiconductor laser device shown in FIG.

The semiconductor laser device shown in FIG. 27 is a semiconductor laser device manufactured using the method for manufacturing a semiconductor laser device disclosed in US Pat. No. 5,297,158. 27, parts having the same functions as those in FIG. 26 are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 27
Of the semiconductor laser device of p-
The GaAs layer etching stop layer 110 is provided, and the n-AlGaAs current blocking layer 118a and the p-AlGaAs second upper cladding layer 111 are arranged on the etching stop layer 110. This second upper cladding layer 11
1, the cap layer 112 is formed on the upper end of the mesa portion 1.
I'm 15. In this semiconductor laser device,
When the -AlGaAs current blocking layer 118a is formed by MOCVD (Metal Organic Chemical Vapor Deposition) method, the growth rate of the MOCVD method varies depending on the crystal plane orientation.
, The n-GaAs under the protrusion 230 is
The cavities 135 and 135 are formed in the current blocking layer 118b. Further, when the current blocking layers 118a and 118b are formed by the MBE (Molecular Beam Epitaxy) method, the protruding portion 230 blocks the irradiated molecular beam, and the portion directly below the protruding portion 230 becomes a shadow of growth. Thus, a cavity larger than that formed by the MOCVD method is formed in the current blocking layer 118b.

In the semiconductor laser device in which the cavities 135, 135 are formed in the current blocking layer, light absorption occurs in the cavities during operation, or the cavities have a great difference in light refractive index from other portions. Therefore, or because the electric field distribution in the current blocking layer 118a changes, it has been an impeding factor for obtaining highly efficient and stable performance in the high output region. In addition, when the semiconductor laser device is operated for a long period of time particularly in a high output region, the current blocking layer deteriorates from the cavity, resulting in a decrease in reliability during long-term operation.

In order to solve the above problems, Japanese Patent Laid-Open No. 3-64
In the method of manufacturing a semiconductor laser device described in Japanese Patent Publication No. 980, the etching rate is fast for GaAs,
An etching solution having a low etching rate is used for AlGaAs so that the cap layer 112 made of GaAs does not protrude from the top of the mesa portion 115 made of AlGaAs to both sides in the width direction.

[0008]

However, there is a problem that the above-mentioned conventional method for manufacturing a semiconductor laser device cannot be applied to the semiconductor laser device shown in FIG. This semiconductor laser device is manufactured by using p-AlGaAs in the manufacturing process.
When the second upper clad layer 111 is formed on the ridge-shaped mesa portion 115, first, a sulfuric acid-based etching solution is used to p-
The GaAs cap layer 112 and the p-AlGaAs second upper cladding layer 111 are partially etched in the thickness direction. Then, using a hydrofluoric acid-based etching solution, p-
Only the AlGaAs second upper cladding layer 111 is p-Ga
Etching is performed up to the As layer etching stop layer 110.

Here, the second upper cladding layer 1
The etching solution for etching 11 is p-AlG
It is necessary that the liquid is a solution that does not corrode the p-GaAs layer etching stop layer 110 while corroding the aAs second upper cladding layer 111. That is, this etching solution is made of the same material as the etching stop layer 110.
-The GaAs cap layer 112 is also not corroded. Therefore, as disclosed in Japanese Patent Application Laid-Open No. 3-64980, although GaAs and AlG have different etching rates,
An etching solution that corrodes aAs together cannot be used when the semiconductor laser device of FIG. 27 is manufactured.

Therefore, an object of the present invention is to obtain stable characteristics such as a transverse mode of laser light, a far field pattern, and a threshold current without the projection of the cap layer on the mesa portion of the cladding layer. The present invention provides a semiconductor laser device and a manufacturing method thereof.

[0011]

In order to achieve the above object, a semiconductor laser device of the present invention comprises a substrate, at least a first conductivity type clad layer, an active layer, and a second conductivity type lower clad layer. An etching stop layer, an upper clad layer of the second conductivity type formed in a stripe-shaped protrusion shape, a cap layer formed in contact with the top of the upper clad layer, and formed on both sides of the upper clad layer. And a current blocking layer having a bandgap larger than that of the active layer, the width W1 of the top of the upper cladding layer and the width W2 of the surface of the cap layer on the active layer side. Between the width W3 of the surface of the cap layer on the side opposite to the active layer side, W2 <W3, and approximately W2 = W
The feature is that the relationship of 1 is established.

According to the above structure, the width W1 of the top of the upper cladding layer and the width W2 of the surface of the cap layer on the side of the active layer satisfy the relationship of W1 = W2. The clad layer and the cap layer are continuously connected with almost no step. This avoids the formation of a cavity in the current blocking layer below the protrusion formed by the cap layer discontinuously protruding from the top of the upper clad layer in the current blocking layer.

Further, the relationship W2 <W3 is established between the width W3 of the surface of the cap layer opposite to the active layer side and the width W2 of the surface of the cap layer on the active layer side. A substantially uniform current blocking layer is grown on the upper portion of the cap layer without being affected by the side portions of the cap layer.

The semiconductor laser device of the present invention comprises a substrate,
A clad layer of at least a first conductivity type, an active layer, a second layer
A conductive type lower clad layer, an etching stop layer,
A second conductivity type upper clad layer formed in a stripe-shaped protrusion shape, a cap layer formed in contact with the top of the upper clad layer, and a cap layer formed on both sides of the upper clad layer more than the active layer. In a semiconductor laser device including a current blocking layer having a large bandgap, W1 = W2 or W1 between the width W1 of the top of the upper cladding layer and the width W2 of the surface of the cap layer on the active layer side. > W
The relationship of 2 is established, and the relationship of W23 <W1 is established between the width W23 at a predetermined position in the thickness direction of the cap layer and the width W1 of the top portion of the upper cladding layer.

According to the above structure, in the cap layer, the width of the lower end of the cap layer is equal to or smaller than the width of the top of the clad layer, and the width of the cap layer in the thickness direction is the upper clad. Less than the width of the top of the layer. As a result, unlike the conventional case, no cavity is formed below the cap layer having the width larger than the top of the cladding layer and having the protrusion in the width direction and in the current blocking layer. Further, even if a cavity is formed in the current blocking layer, the cap layer has a width smaller than that of the upper clad layer at almost all positions in the thickness direction, so that the cavity is closer to the top of the upper clad layer. Also occurs on the side of the cap layer in the thickness direction. That is, since the cavity is formed at a position farther from the active layer in the thickness direction than in the conventional case, the influence of the cavity on various characteristics such as the transverse mode, the far field pattern, and the threshold current is smaller than in the conventional case. A semiconductor laser device having good characteristics can be obtained.

The semiconductor laser device of the present invention comprises a substrate,
A clad layer of at least a first conductivity type, an active layer, a second layer
A conductive type lower clad layer, an etching stop layer,
A second conductivity type upper clad layer formed in a stripe-shaped protrusion shape, a cap layer formed in contact with the top of the upper clad layer, and a cap layer formed on both sides of the upper clad layer more than the active layer. In a semiconductor laser device including a current blocking layer having a large band gap, the current blocking layer has a cavity at a position farther from the active layer in the thickness direction than the top of the projection shape of the upper cladding layer. Is characterized by.

According to the above configuration, in the current blocking layer,
Since the cavity is located farther from the active layer in the thickness direction than the protrusion-shaped top of the upper clad layer, the cavity has relatively little influence on the refractive index of light and the electric field distribution in the current blocking layer. Therefore, it is possible to effectively prevent the characteristics of the semiconductor laser device from being deteriorated due to the cavities formed at a position closer to the active layer in the thickness direction than in the top portion of the upper cladding layer as in the conventional case.

In the semiconductor laser device of one embodiment, the etching stop layer and the cap layer are made of the same material, or the constituent elements of the etching stop layer and the cap layer are at least two elements. Is common.

According to the above embodiment, the etching stop layer and the cap layer are made of the same material, or at least two elements are common to the constituent elements of the etching stop layer and the cap layer. Therefore, a semiconductor laser device having good characteristics can be obtained.

The semiconductor laser device of one embodiment is
The composition formula of the etching stop layer is Al _xGa_1-xIn As
And the composition formula of the upper clad layer is Al_yGa_1-y
As and the composition formula of the cap layer is Al._zGa
_1-zAs, the composition formula of the etching stop layer
X in the above, y in the composition formula of the upper cladding layer, and
In the composition formula of the cap layer, z means x <y and z <y
The relationship is established.

According to the above embodiment, the Al content ratio in the composition formula of the etching stop layer and the cap layer is smaller than that of the upper cladding layer, so that the upper cladding layer has a good light and carrier confinement effect. In addition, the cap layer provides good electrical contact between the contact layer and the upper clad layer, and the etching stop layer allows the lower clad layer to be formed to a predetermined thickness with good control. It

In the semiconductor laser device of one embodiment, the substrate is made of GaAs, the clad layer and the active layer are made of AlGaAs, and the current blocking layer is AlGa.
It is made of As.

According to the above-described embodiment, the substrate made of GaAs is used, and the real refractive index distribution is formed by the current blocking layer made of AlGaAs.
A GaAs semiconductor laser device can be obtained.

The method of manufacturing a semiconductor laser device according to the present invention comprises:
The step of sequentially stacking at least a first-conductivity-type cladding layer, an active layer, a second-conductivity-type cladding layer, and a cap layer on the substrate, and using the photolithography technique and the etching technique, the second A step of patterning the conductivity type clad layer and the cap layer into a ridge stripe shape to form a mesa portion; and a step of forming a mesa portion having a width larger than an upper end width of the mesa portion of the second conductivity type clad layer. Regarding a cap layer having protrusions protruding from the upper end of the mesa portion on both sides in the width direction, a protective film against etching is arranged on at least the surface of the protrusion of the cap layer on the side close to the active layer. And a step of removing at least the protruding portion of the cap layer by etching.

According to the above structure, the first conductivity type clad layer, the active layer, the second conductivity type clad layer, and the cap layer are laminated on the substrate, and the second conductivity type clad layer is formed. Further, the cap layer is patterned to form a mesa portion, and at this time, a protruding portion is formed in which the cap layer protrudes more like a canopy in the width direction than the clad layer of the second conductivity type. A protective film is disposed on at least a surface of the protrusion portion closer to the active layer, and at least the protrusion portion of the cap layer is removed by etching. by this,
At least the protruding portion of the cap layer is etched off with good control without etching other portions such as the connecting portion between the second conductivity type cladding layer and the cap layer. As a result, it is possible to effectively avoid the formation of a cavity in the current blocking layer formed in contact with the cap layer, and to obtain a semiconductor laser device having good characteristics.

In the method of manufacturing a semiconductor laser device according to one embodiment, at least the protruding portion of the cap layer is removed by using a chemical etching solution.

According to the above embodiment, at least the protruding portion of the cap layer is easily and effectively removed by using the chemical etching solution.

The method of manufacturing a semiconductor laser device according to the present invention comprises:
The step of sequentially stacking at least a first-conductivity-type cladding layer, an active layer, a second-conductivity-type cladding layer, and a cap layer on the substrate, and using the photolithography technique and the etching technique, the second Patterning the conductivity type clad layer and the cap layer into a ridge stripe shape to form a mesa portion; and forming a mesa portion on the surfaces of flat portions located on both sides in the width direction of the mesa portion of the second conductivity type cladding layer,
A step of disposing a protective film against etching;
For a cap layer having a width larger than the width of the upper end of the mesa portion of the conductivity type clad layer and having protrusions protruding from the upper end of the mesa portion on both sides in the width direction in the shape of eaves, at least the protrusion And a step of removing the portion by etching.

According to the above structure, the first conductivity type clad layer, the active layer, the second conductivity type clad layer, and the cap layer are laminated on the substrate to form the second conductivity type clad layer. Further, the cap layer is patterned to form a mesa portion, and at this time, a protruding portion is formed in which the cap layer protrudes more like a canopy in the width direction than the clad layer of the second conductivity type. A protective film is arranged on the surface of the flat portion on both sides in the width direction of the mesa portion, and at least the protruding portion of the cap layer,
The flat portion is etched away with little influence. This effectively prevents formation of a cavity in the current blocking layer formed in contact with the cap layer, and a semiconductor laser device having excellent characteristics can be obtained.

In the method of manufacturing a semiconductor laser device according to one embodiment, at least the protruding portion of the cap layer is removed by etching using gas phase plasma.

According to the above embodiment, at least the protruding portion of the cap layer is effectively removed by using the plasma in the gas phase.

In the method of manufacturing a semiconductor laser device according to one embodiment, at least a part of the upper surface of the cap layer is protected against the etching before the step of removing the eave-shaped protrusions of the cap layer by etching. The step of disposing a membrane is provided.

According to the above-described embodiment, the protective layer is disposed on at least a part of the upper surface of the cap layer, and then the eave-shaped protrusion of the cap layer is removed by etching. Therefore, in the cap layer, the protrusion is removed without reducing the thickness.

In the method for manufacturing a semiconductor laser device according to one embodiment, the cap layer is formed on the surface of at least a portion near the active layer of the protrusion of the cap layer immediately before the protective film is arranged, or the cladding layer of the second conductivity type. Of the cap layer immediately before disposing the protective film on the surfaces of the flat portions located on both sides in the width direction of the mesa portion, the width of the surface of the cap layer on the active layer side is the active layer side of the cap layer. And greater than the width of the opposite surface.

According to the above-described embodiment, when a positive photoresist for removing an exposed portion is used as the protective film, the cap layer has a width on the side of the active layer immediately before disposing the protective film. However, since it is larger than the width of the surface on the side opposite to the active layer side, the side surface between the surface on the active layer side of the cap layer and the surface on the side opposite to the active layer side,
It faces the contact layer side. Therefore, when the protective film is arranged on the surface of the cap layer, the side surface of the cap layer is exposed by development by exposing the protective film on the side surface with light from the contact layer side. Therefore, since the side surface of the cap layer is directly etched, the eave-shaped protrusion of the cap layer is effectively removed with good controllability.

In the method of manufacturing a semiconductor laser device according to one embodiment, the mesa portion of the second conductivity type cladding layer is AlGaAs.
The cap layer is made of GaAs, and the protective film is made of AlGaAs.

According to the above embodiment, the controllability of the protruding portion of the cap layer made of GaAs is improved by using the protective film made of AlGaAs without affecting the mesa portion of the clad layer made of AlGaAs. Since it can be removed by etching with, a semiconductor laser device having good characteristics can be stably obtained.

In the method of manufacturing a semiconductor laser device according to one embodiment, at least the protruding portion of the cap layer is removed using a mixed solution of sulfuric acid and hydrogen peroxide solution.

According to the above embodiment, at least the protruding portion of the cap layer is effectively removed by using the mixed solution of sulfuric acid and hydrogen peroxide solution.

In the method for manufacturing a semiconductor laser device according to one embodiment, at least the protruding portion of the cap layer is removed using a mixed solution of ammonia water and hydrogen peroxide solution.

According to the above embodiment, at least the protruding portion of the cap layer is effectively removed by using the mixed solution of the ammonia water and the hydrogen peroxide solution.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings.

(First Embodiment) FIG. 1 is a sectional view showing a ridge stripe type semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device according to the first embodiment. Hereinafter, a method for manufacturing this semiconductor laser device will be described with reference to FIGS.

First, as shown in FIG. 2A, an n-GaAs buffer layer 4 (having a thickness of 0.5 μm) is formed on an n-GaAs substrate 1 having a plane orientation (100) by using a MOCVD apparatus.
m) and n-Al as a first conductivity type cladding layer
_0.5 Ga _0.5 As first cladding layer 5 (1 μm),
AlGaAs quantum well active layer 6 (0.05 μm) and p-Al _0.5 Ga as a second conductivity type lower cladding layer.
_0.5 As second lower cladding layer 7 (0.2 μm), p
-GaAs etching stop layer 10 (5 nm) and p-Al _0.5 Ga as an upper cladding layer of the second conductivity type
_0.5 As second upper cladding layer 11 (1.0 μm),
The p-GaAs cap layer 12 (0.6 μm) is sequentially crystal-grown and laminated. Then, a resist film 26 is applied on the surface of the cap layer 12 to a thickness of about 0.2 μm.

Next, the resist film 26 is formed in a stripe shape having a width of 6 μm by the photo-etching method (FIG. 2).
(B)). Then, by using a sulfuric acid-based etching solution having no selectivity between GaAs and AlGaAs, all of the p-GaAs cap layer 12 in the thickness direction, which is not covered by the stripe-shaped resist film 26, and p-Al _{0. .5} Ga
_{0. The} striped mesa portion 15 is formed by etching the ₅ As second upper cladding layer 11 up to the middle of the thickness direction (FIG. 3A).

Furthermore, in the process of FIG.
P-Al etched by_0.5Ga_0.5As second
It is not covered with the resist film 26 of the upper clad layer 11.
P-GaA using a hydrofluoric acid-based etching solution.
Etching until s layer etching stop layer 10 appears
To run. Thereby, the second upper cladding layer 11
Are formed into stripe-shaped protrusions. At this time,
Note p-Al_0.5Ga _0.5As second upper cladding layer 1
1, the side surface of the mesa portion 15 is etched, and the p-
Whether both ends of the GaAs cap layer 12 are the tops of the above protrusions
From both sides in the width direction to project like eaves
It is formed. The resist is formed on the cap layer 12.
The film 26 remains (FIG. 3 (b)).

At this stage, p-Al _0.5 Ga _0.5 A
s The width W0 of the lower end of the mesa portion 15 of the second upper cladding layer 11 is 2.5 μm. The reason why the etching is performed in two steps using the sulfuric acid-based etching solution in the step of FIG. 3A and the hydrofluoric acid-based etching solution in the step of FIG. This is because the width W0 is formed with good controllability.

In addition, the p-GaAs etching stopper described above is used.
The etching layer 10 is etched by the hydrofluoric acid-based etching solution.
Stop progress. The etching stop layer 10
Is the optimum thickness d for predetermined lateral mode control, etc.
P-Al formed_0.5Ga _0.5As second lower club
The hydrofluoric acid-based etching, which is disposed on the pad layer 7.
Make sure to stop the etching by the liquid. Therefore,
The second lower clad layer 7 is formed in the same wafer and different
Since the thickness d does not vary between different wafers,
Between the second lower clad layer 7 and the current blocking layer 18 of
The refractive index difference or the actual refractive index difference can be stably set to a predetermined value.
To stabilize the characteristics such as the transverse mode of the semiconductor laser device.
Wear.

After the step shown in FIG. 3B, the resist film 26 is completely removed, and a new resist film 28 is applied over the entire surface of the substrate. After the application of the resist film 28, the substrate is rotated at a rotational speed of 6000 rpm for 1 minute so that the flat portions 16, which are located on both sides of the mesa portion 15,
The thickness of the resist film 28 on 16 is set to approximately 1 μm (FIG. 4A). At this point, the resist film 28 remains extremely thin on the cap layer 12, so the resist film 28 on the cap layer 12 is removed by bringing the surface of the resist film 28 into contact with a developing solution. As a result, the surface of the resist film 28 on both sides in the width direction of the cap layer has the contour shown by the broken line a in FIG. That is, the active layer 6 of the cap layer 12
A resist film 28 as a protective film is arranged on the surface close to the.

After the surface of the cap layer is exposed from the resist film 28, the portion of the cap layer 12 including the protruding portion 30 is removed by etching. The etching liquid used at this time is a mixed liquid of ammonia water and hydrogen peroxide water. This etching solution is used for the protrusion 3 of the cap layer 12.
Not only 0, but also the central upper portion of the cap layer 12 is corroded, so p-Ga at the time when the removal of the protrusion 30 is completed.
The layer thickness of the As cap layer 12 is half or less than the initial thickness.
Since the resist film 28 is disposed on the surface of the cap layer 12 near the active layer 6 of the cap layer 12, for example, the periphery of the connection portion between the cap layer 12 and the second upper cladding layer 11 is adversely affected. It is possible to surely remove at least the protrusions 30 and 30 only in the cap layer 12 without applying the above.

Subsequently, the resist film 28 is completely removed (FIG. 4B), and the n-AlGaAs current blocking layer 18 is formed on the etching stop layer 10 and the mesa portion 15.
a and the n-GaAs current blocking layer 18b are sequentially MOC
It grows using a VD apparatus (FIG. 5A). N-A above
The l _0.7 Ga _0.3 As current blocking layer 18 a includes the mesa portion 1.
1.1 μm on the flat parts 16, 16 located on both sides of
Grow to a thickness of. This n-Al _0.7 Ga _0.3 A
The s current blocking layer 18 a forms a real refractive index distribution inside and outside the mesa portion 15. The n-GaAs current blocking layer 18b prevents the Al component contained in the n-Al _0.7 Ga _0.3 As current blocking layer 18a from being surface-oxidized, and is on the n-GaAs current blocking layer 18b layer. Plays a role in improving the growth of the p-GaAs contact layer 19 formed in the above.

Then, as shown in FIG.
The portions of the -AlGaAs current blocking layer 18a and the n-GaAs current blocking layer 18b located on the p-GaAs cap layer 12 are removed by etching to expose the upper side surface of the p-GaAs cap layer 12.

Then, on the wafer having the laminated structure shown in FIG. 5B, the p-GaAs contact layer 19 (about 40
μm) is grown by the LPE method (FIG. 6A).

After that, the lower surface of the n-GaAs substrate 1 is polished so that the thickness of the entire wafer having the laminated structure formed by the above steps is 120 μm, and then the upper surface of the contact layer 19 and the n layer are formed. -On the lower surface of the GaAs substrate 1,
A p-side electrode 21 and an n-side electrode 22 are formed respectively (see FIG. 6).
(B)).

Finally, after cleaving the wafer so that the cavity length is 800 μm, an Al ₂ O ₃ protective film is formed on the light emitting end face by electron beam evaporation to obtain a low reflectance (about 5).
%) On the other hand, while Al on the end face facing the light emitting end face
A ridge stripe type semiconductor laser device according to the present invention is completed by forming a multilayer film of ₂ O ₃ / a-Si (aluminum oxide / amorphous silicon) to have a high reflectance (about 95%).

The mesa portion 1 of the semiconductor laser device of this embodiment
The current constriction to 5 is caused by the n-AlGaAs current blocking layer 18a.
While the lateral mode control is performed by the real refractive index distribution in the n-AlGaAs current blocking layer 18a, while the pnpn structure is performed through the.

The characteristics of the semiconductor laser device of this embodiment are as follows.
The oscillation wavelength was 780 nm, the threshold current was 35 mA, and the optical output was kink-free up to 180 mW. A reliability test was conducted by continuously emitting light from this semiconductor laser device with an optical output of 120 mW in an environment of an ambient temperature of 70 ° C. The result is shown in FIG. In FIG. 28, the horizontal axis represents the drive time and the vertical axis represents the drive current of the semiconductor laser device. As indicated by the straight line 201 in FIG. 28, the semiconductor laser device of the present embodiment emitted light stably for 3000 hours, and no characteristic deterioration such as an increase in operating current was observed during light emission. From the above results, it can be said that the semiconductor laser device according to the present embodiment is excellent in reliability especially at a high output of 50 mW or more.

(Second Embodiment) FIG. 7 is a sectional view showing a ridge stripe type semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device of the second embodiment.

A method of manufacturing the semiconductor laser device of this embodiment will be described with reference to FIGS. 8 and 9
In the above, in the first embodiment, parts having the same functions as those in FIGS. 1 to 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

First, the n-GaAs substrate 1 having the plane orientation (100) is subjected to the same steps as those in the first embodiment, and then, as shown in FIG.
The semiconductor structure shown in (b) is formed.

In the structure shown in FIG. 3B, a resist film 28 is applied on the etching stop layer 10 and the resist film 26 over the entire surface of the substrate. Resist film 2
After applying 8, the substrate is rotated for 1 minute at a rotation speed of 6000 rpm so that the thickness of the resist film 28 on the flat portions 16 and 16 on both sides of the mesa portion 15 is about 3 μm (see FIG. a)).

Then, the resist film 28 is removed by a photolithography method by adjusting the exposure amount and the developing time until the flat portions on both sides of the mesa portion 15 have a thickness of about 0.5 μm. At this time, as shown in FIG. 8B, part of the left and right ends of the protrusion 30 of the cap layer is exposed without being covered with the resist film 28.

The portion of the p-GaAs cap layer 12 including the protruding portion 30 is removed by using an etching solution formed by mixing ammonia water and hydrogen peroxide water. The protrusion 30 of the cap layer is eroded from the exposed portion of the resist film 28 by the etching solution. In the present embodiment, unlike the first embodiment, the central portion of the p-GaAs cap layer 12 is protected by the resist film 26 and is not corroded, so the film thickness is not reduced. Therefore, p-G at the time when the removal of the protrusions 30, 30 is completed
The layer thickness of the aAs cap layer 12 is the same as the initial layer thickness. Then, the resist films 26 and 28 are removed, and a structure as shown in FIG. 9 is obtained.

Then, the etching stop layer 10 and the second
N-AlG is formed on the upper clad layer 11 and the cap layer 12.
The aAs current blocking layer 18a and the n-GaAs current blocking layer 18b are sequentially grown by the MOCVD apparatus. Then, as in the first embodiment, p− is formed on the current blocking layer 18b.
A GaAs contact layer 19 is formed, and p is formed on the upper surface of the contact layer 19 and the lower surface of the n-GaAs substrate 1.
The side electrode 21 and the n-side electrode 22 are formed respectively, and the ridge stripe type semiconductor laser device shown in FIG. 7 is completed.

Also in the semiconductor laser device of the present embodiment, the current confinement to the mesa portion 15 is the n-AlGaAs current blocking layer 18a as in the semiconductor laser device of the first embodiment.
And the lateral mode control is performed in the n-
This is performed by the actual refractive index distribution in the AlGaAs current blocking layer 18a.

The characteristics of the semiconductor laser device according to the second embodiment are that the oscillation wavelength is 780 nm and the threshold current is 35 m.
A, and the light output was kink-free up to 180 mW. Further, this semiconductor laser element was subjected to a reliability test by continuously emitting light with an optical output of 120 mW in an environment of an ambient temperature of 70 ° C. As a result,
As shown in FIG. 8, stable light emission was performed over the light emission time of 3000 hours, and no characteristic deterioration such as an increase in operating current was observed during light emission. It can be said that the semiconductor laser device according to the present embodiment is excellent in reliability especially at a high output of 50 mW or more.

(Third Embodiment) FIG. 10A is a sectional view showing a ridge stripe type semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device of the third embodiment.

A method of manufacturing the semiconductor laser device of this embodiment will be described with reference to FIGS. 11 to 13 showing each step.
Also in this embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

First, similarly to the first embodiment, the n-GaAs buffer layer 4 and the n-Al _0.5 Ga _0.5 As first cladding layer are formed on the n-GaAs substrate 1 having the plane orientation (100). 5, AlGaAs quantum well active layer 6, p-Al
_0.5 Ga _0.5 As Second lower cladding layer 7, p-Ga
As etching stop layer 10, p-Al _0.5 Ga _{0
． The 5} As second upper cladding layer 11 and the p-GaAs cap layer 12 are sequentially laminated to obtain the same semiconductor laminated body as shown in FIG.

Next, a resist film 24 is applied to the entire surface of the substrate to a thickness of about 0.2 μm, and a stripe-shaped opening 31 having a width W3 is formed in the resist film 24 by photolithography. Further, plasma CVD is performed on the resist film 24 and the cap layer 12 in the opening 31 of the resist film.
Method is used to form a SiO ₂ film 32 having a thickness of 0.10 μm. The width W3 of the striped opening 31 is set to be substantially the same as the width W1 of the top of the striped ridge of the p-AlGaAs second cladding layer 11 which will be formed later. (FIG. 10B) Subsequently, the portion of the SiO ₂ film 32 other than the portion formed on the cap layer 12 in the opening 31 is removed together with the resist film 24 by the lift-off method. As a result, a stripe-shaped SiO ₂ film 23 having a width W1 is formed on the cap layer 12. A resist film 26 of about 0.4 μm is formed on the cap layer 12 so as to include the stripe-shaped SiO ₂ film 23.
Apply to the thickness of. Subsequently, the resist film 26 is
Strips having a width of 6 μm are formed by photolithography (FIG. 11A). At this time, the photomask position at the time of exposing the resist film 26 is adjusted so that the stripe-shaped SiO ₂ film 23 previously formed is located at the center of the resist film 26 in the width direction. At this point, the striped S
The entire surface of the iO ₂ film 23 is surrounded by the p-GaAs cap layer 12 and the stripe-shaped resist film 26.

Next, using a sulfuric acid-based etching solution having no selectivity between GaAs and AlGaAs, p-G is applied to a portion not covered with the stripe-shaped resist film 26.
All of the aAs cap layer 12 in the thickness direction and p-Al
_{The 0.5} Ga _0.5 As second upper clad layer 11 is partially etched in the thickness direction to form a stripe-shaped mesa portion 15. Furthermore, in the above etching step, p-Al is etched halfway in the thickness direction.
_{The portion of the 0.5} Ga _0.5 As second upper clad layer 11 not covered with the resist film 26 is etched with a hydrofluoric acid-based etching solution until the p-GaAs layer etching stop layer 10 appears. . By the two-step etching process using the sulfuric acid-based etching solution and the hydrofluoric acid-based etching solution, the stripe-shaped mesa portion 15 having a desired ridge width is formed. At this time, p-Al
The side surface of the _0.5 Ga _0.5 As second upper clad layer 11 is etched, and the portions on both sides in the width direction of the p-GaAs cap layer 12 remain as the protrusions 30 and 30 (FIG. 11).
(B)).

At this stage, the p-Al _0.5 Ga _0.5 As second upper cladding layer 11 formed as the mesa portion 15 is formed.
The width of the lower end of is about 2.5 μm. In order to accurately form the width of the lower end of the mesa portion, two-step etching was performed using a sulfuric acid-based etching solution and a hydrofluoric acid-based etching solution.

Next, after the resist film 26 is completely removed, a resist is applied over the entire surface of the substrate, and the substrate coated with the resist is rotated for 1 minute at a rotation speed of 6000 rpm to obtain a new one. A resist film 28 is formed. The resist film 28 is formed so that the flat portions on both sides in the width direction of the mesa portion 15 have a thickness of about 3 μm. (FIG. 12A).

Next, the resist film 28 is exposed and developed for a predetermined amount and for a predetermined time so that the thickness of the resist film 28 on the flat portions on both sides of the mesa portion 15 is about 0.5 μm.
The resist film 28 on the cap layer 12 and the SiO ₂ film 32 is removed. As a result, the flat portions 16 on both sides of the mesa portion 15 are completely protected by the resist, as shown in FIG. On the other hand, the surface of the p-GaAs cap layer 12 at the center in the width direction is protected by the SiO 2 film 23, while the surfaces of the protrusions 30 at both ends in the width direction are exposed without being covered by the resist film 28 or the SiO 2 film 23. .

In this state, plasma of reactive gas is used.
Then, the protrusion 30 of the cap layer is removed by etching.
It That is, boron trichloride is placed between the parallel plate electrodes.
Flowing gas diluted with gon, high frequency of 13.56MHz
The plasma is excited using an AC power source
Then, the sample is left to stand, and the physical shock of the plasma is generated.
The protrusion 30 is removed using a biological reaction. By this
As a result, a structure as shown in FIG. 13 (a) is obtained. This and
The flat portions 16 on both sides of the mesa portion 15 are formed by the resist 28.
Since it is completely protected,
p-Al_0.5Ga _0.5As second lower cladding layer 7
There is no plasma or ion damage to the throat. Also
Also in the widthwise central portion of the p-GaAs cap layer 12,
Striped SiO_TwoProtected by the membrane 23
So there is no plasma or ion damage.

Then, the resist film 28 is entirely removed, and the n-AlGaAs current blocking layers 18a and n-GaAs are formed on the etching stop layers 10 on both sides of the mesa portion 15 in the width direction.
The current blocking layer 18b and the current blocking layer 18b are sequentially grown by the MOCVD apparatus (FIG. 13B). Here, on the SiO2 film,
Since AlGaAs and GaAs do not grow, the current blocking layer 18a made of AlGaAs and the current blocking layer 18b made of GaAs are selectively grown on the flat portions 16 on both sides of the mesa portion 15.

Subsequently, the striped SiO ₂ film 23 on the p-GaAs cap layer 12 is removed by etching with hydrofluoric acid to expose the upper surface of the cap layer 12.

Then, the n-GaAs current blocking layer 18 is formed.
b on the cap layer 12 and about 40 μm by the LPE method.
A p-GaAs contact layer 19 having a thickness of m is grown.

Then, similarly to the first embodiment, a p-side electrode 21 and an n-side electrode 22 are formed on the upper surface of the contact layer 19 and the lower surface of the n-GaAs substrate 1, respectively,
The ridge stripe type semiconductor laser device shown in FIG. 10A is completed.

In the semiconductor laser device of the third embodiment, the current confinement to the mesa portion 15 is performed by the pnpn structure with the n-AlGaAs current blocking layer 18a interposed therebetween.
The lateral mode control is performed by the real refractive index distribution in the n-AlGaAs current blocking layer 18a.

The characteristics of the semiconductor laser device according to the present embodiment are that the oscillation wavelength is 780 nm and the threshold current is 35 mA.
And the light output was kink-free up to 180 mW. In addition, this semiconductor laser device is set at an ambient temperature of 70 ° C.
A reliability test was performed by continuously emitting light with an optical output of 120 mW in the environment. As a result, as shown in FIG.
Stable light emission was carried out for 00 hours, and no characteristic deterioration such as an increase in operating current was observed during the light emitting operation. The semiconductor laser device according to the above embodiment is excellent in reliability especially at a high output of 50 mW or more.

(Fourth Embodiment) FIG. 14 is a sectional view showing a ridge stripe type semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device of the fourth embodiment.

The method of manufacturing the semiconductor laser device of this embodiment will be described below with reference to FIGS.

First, similarly to the first embodiment, the plane orientation (1
00) on the n-GaAs substrate 1 and n-GaAs buffer layer 4 (thickness 0.5 μm) and n-Al _0.5 Ga.
_0.5 As first clad layer 5 (thickness 1 μm) and AlG
aAs quantum well active layer 6 (thickness 0.05 μm), p−A
l _0.5 Ga _0.5 As second lower cladding layer 7 (thickness: 0.2 μm) and p-GaAs etching stop layer 1
0 (thickness 5 nm), p-Al _0.5 Ga _0.5 As second upper cladding layer 11 (thickness 1.0 μm), and p-Ga
The As cap layer 12 (having a thickness of 0.6 μm) is sequentially crystal-grown. Then, as shown in FIG. 15A, an Al _0.3 Ga _0.7 As surface protective film 13 (thickness: 0.2 μm) is laminated on the cap layer 12.

Next, a resist film 26 is applied to the surface protective film 13 to a thickness of about 0.2 μm, and the resist film 26 is formed in a stripe shape having a width of 6 μm by photolithography (FIG. 15 ( b)). After this, GaAs and AlGa
Using a sulfuric acid-based etching solution having no selectivity with As, the entire area of the Al _0.3 Ga _0.7 As surface protective film 13 in the thickness direction of the portion not covered with the striped resist film 26, All of the p-GaAs cap layer 12 in the thickness direction and part of the p-Al _0.5 Ga _0.5 As second upper cladding layer 11 in the thickness direction are etched to form a stripe-shaped mesa portion 15. Yes (Fig. 16
(A)). Furthermore, the p-Al _0.5 Ga _{0 . 5} As
The part of the second upper clad layer 11 that has been partially etched in the thickness direction is etched using a hydrofluoric acid-based etching solution until the p-GaAs layer etching stop layer 10 appears. By the two-step etching process, a stripe-shaped mesa portion having a predetermined width is formed. At this time, the p-Al _0.5 Ga _0.5 As second
Since the side surface of the upper clad layer 11 is etched, p
The -GaAs cap layer 12 and the resist film 26 project from the upper end of the second upper clad layer 11 on both sides in the width direction in an eaves-like shape (Fig. 16 (b)).

At this point, the shape of the cap layer is
Unlike the second to third embodiments, the upper end width W3 of the cap layer is narrower than the lower end width W2. This shape is
Al _0.3 Ga is formed on the p-GaAs cap layer 12.
It is obtained by disposing the _0.7 As surface protective film 13 (0.2 μm).

In the structure of FIG. 16B, after the resist film 26 is completely removed, new resist is applied on the entire surface of the substrate. After the application of the resist, the substrate is rotated at a rotation speed of 6000 rpm for 1 minute to make the film thickness on the flat portions on both sides of the mesa portion 15 3 μm to form the resist film 28 (FIG. 17A). ).

Subsequently, the resist film 28 on the cap layer 12 and the surface protective film 13 is removed, and
As shown by the broken line b in FIG. 17A, the resist film 28 is exposed and developed so that the thickness of the resist film 28 on the flat parts on both sides of the mesa 15 is approximately 0.5 μm. As a result, the structure shown in FIG. 17B is obtained. At this time,
The flat portions 16 and 16 on both sides of the mesa portion 15 and the p-GaA
The lower side surface of the s cap layer 12 is protected by the resist film 28. On the other hand, the p-GaAs cap layer 1
2, the side surface is exposed. This can be realized by making the upper end width W3 of the cap layer smaller than the lower end width W2. That is, the upper end width W of the cap layer 12
3 is smaller than the lower end width W2, the resist film 28 in contact with the side surface connecting the lower end and the upper end of the cap layer
The portion can be developed and removed by irradiating the exposure light emitted from above the substrate. Therefore, the side surface of the cap layer 12 can be completely exposed. Here, in the cap layer having a shape in which the upper end width is larger than the lower end width as in the second to third embodiments, the portion of the resist film 28 contacting the side surface of the p-GaAs cap layer 12 at the time of exposure is the cap layer. There is no light exposure because it is blocked by the top edge. Therefore, even after development, the p-GaAs cap layer 12
The side surface of is still covered with the resist film 28.

Further, the p-GaAs cap layer 12 is formed.
Almost all of the upper surface is covered with the Al _0.3 Ga _0.7 As surface protective film 13.

As described above, the p-GaAs cap layer 12 is formed.
Of the resist film 28 and the surface protection film 13
The exposed protruding portions 30 on both sides in the width direction of the cap layer 12 are removed by etching. The etching liquid used at this time is an etching liquid prepared by mixing ammonia water and hydrogen peroxide water. By this step, the cap layer 12 has a contour as shown by a broken line c in FIG.

Not only the GaAs cap layer 12 but also Al _0.3 Ga _{0 . 7} As The surface protective film is also corroded. However, by adjusting the mixing ratio of ammonia and hydrogen peroxide in the etching solution,
The etching rate of GaAs is Al _0.3 Ga _0.7 A
GaAs and Al
Selectivity is made to be between _0.3 Ga _0.7 As. Specifically, the ammonia water and the hydrogen peroxide solution are mixed such that the ratio of the number of molecules of ammonia to the number of molecules of hydrogen peroxide is between 1: 6 and 1: 270. As a result, Al _{0 .} The etching rate of ₃ Ga _0.7 As can be suppressed to 1/100 or less of the etching rate of GaAs. In this case, Al _0.3 Ga
_{The 0.7} As surface protective film 13 functions as a protective film of the p-GaAs cap layer 12 against the etching solution.

In the present embodiment, the cap layer 12 is eroded from the side surface by using an etching solution composed of a mixed solution of ammonia: hydrogen peroxide at a mixing ratio of 1:30, and the protrusion 3 is formed.
Remove 0,30. Thereby, the cap layer 1
The lower end width W2 of No. 2 is made substantially equal to the upper end width W1 of the second upper clad layer 11 formed in the ridge stripe shape. In this embodiment, since the etching proceeds from the entire side surface of the cap layer 12 in one width direction, the cap layer 12 exposed from the resist film 28 as in the second embodiment.
The area of the side surface after the etching is kept substantially constant, rather than the etching progressing from a part of both ends of the.
Therefore, it is possible to remove the protruding portion 30 with good reproducibility. Furthermore, the control of the lower end width W2 width of the p-GaAs cap layer 12 is also facilitated. Further, since the cap layer 12 is protected by the Al _0.3 Ga _0.7 As surface protective film 13, it is not corroded in the film thickness direction. Therefore, the thickness of the cap layer 12 at the time when the removal of the protruding portion 30 is completed is the same as the layer when the cap layer 12 was initially formed.

After the removal of the protrusions 30 is completed, the resist film 28 is entirely removed, and both sides of the second upper clad layer 11, the cap layer 12 and the surface protection film 13 and on the etching stop layer 10, and An n-AlGa film is formed on the surface protective film 13 by an MOCVD device.
As current blocking layer 18a and n-GaAs current blocking layer 18b
And are sequentially grown (FIG. 18). Here, since the lower end width of the cap layer 12 is made substantially equal to the upper end width W1 of the second upper clad layer 11 formed in the ridge stripe shape, the width of the second upper clad layer 11 below the cap layer 12 is the same. The cavities 135, 135 unlike those in the conventional semiconductor laser device of FIG. 27 are not formed on both sides in the direction.

Then, the surface protective film 13 on the cap layer 12, the central portion in the width direction of the current blocking layer 18a, and n-G
The central portion in the width direction of the aAs current blocking layer 18b is removed.
Then, the contact layer 19 is laminated on the current blocking layer 18a, the n-GaAs current blocking layer 18b exposed at the surface after the part is removed, and the cap layer 12. Finally, as in the first embodiment, p is formed on the upper surface of the contact layer 19 and the lower surface of the n-GaAs substrate 1.
The side electrode 21 and the n-side electrode 22 are formed respectively, and the ridge stripe type semiconductor laser device shown in FIG. 14 is completed.

In the semiconductor laser device of the present embodiment, the current confinement in the mesa portion 15 is prevented by the n-AlGaAs current blocking layer 18.
The lateral mode control is performed by the real refractive index distribution in the n-AlGaAs current blocking layer 18a while the pnpn structure via a is performed.

The semiconductor laser device of this embodiment has the structure shown in FIG.
As shown in FIG. 3, the protrusions 30, 30 of the cap layer are removed so that the lower end width of the cap layer and the upper end width of the second upper cladding layer 11 are substantially the same size. The step is virtually eliminated. As a result, it is possible to form a semiconductor laser device having good characteristics in a stable manner by eliminating almost all the cavities formed in the current blocking layer in the conventional semiconductor laser device.

Regarding the characteristics of the semiconductor laser device of this embodiment, the oscillation wavelength is 780 nm and the threshold current is 35.
It was mA, and the light output was kink-free up to 180 mW. In addition, this semiconductor laser device is provided with an ambient temperature of 70
A reliability test was performed by continuously emitting light with an optical output of 120 mW in an environment of ° C. As a result, as shown in FIG. 28, stable light emission was performed for 3000 hours, and no characteristic deterioration such as an increase in operating current was observed during light emission. It can be said that the semiconductor laser device according to the above embodiment is excellent in reliability especially at a high output of 50 mW or more.

(Fifth Embodiment) FIG. 19 is a view showing a semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device according to the fifth embodiment. In the method of manufacturing the semiconductor laser device according to the present embodiment, the width of the p-GaAs cap layer 12 is set to the fourth width in the step following FIG. 17B of the fourth embodiment.
The difference is that it is formed smaller than the embodiment. That is,
In the fourth embodiment, as shown by the broken line c in FIG. 17 (b), the protrusions at both ends in the width direction of the cap layer 12 are removed by etching, so that the lower end width of the cap layer 12 becomes smaller than that of the second upper cladding layer 11. It was almost the same as the top width. On the other hand, in the present embodiment, as shown in FIG. 20, the cap layer 12 is etched more in the width direction than in the fourth embodiment, and the lower end width W2 of the cap layer 12 is changed to the upper end width of the second upper clad layer 11. It was formed smaller than W1. This is the cap layer 1
2 the width direction length of the surface protective film 13 disposed on the upper surface of
This is achieved by making it shorter than in the fourth embodiment. The structure of FIG. 20A corresponds to that of the fourth embodiment shown in FIG.
To 17 and the same process except that the length in the width direction of the surface protective film 13 is formed to be different.

After removing the protruding portion of the cap layer 12 by etching, the resist film 28 shown in FIG. 20A is entirely removed, and the second upper clad layer 11 and the cap layer 12 are removed.
MO on both sides of the surface protection film 13 in the width direction and on the etching stop layer 10 and on the surface protection film 13.
The n-AlGaAs current blocking layer 18 is formed by a CVD device.
a and the n-GaAs current blocking layer 18b are sequentially grown (FIG. 20B). Here, the cap layer 12
The lower end width W2 of the second ridge stripe shape
Since the upper clad layer 11 is formed to have a width smaller than the upper end width W1, the current blocking layer 18b has the cap layer 12 formed thereon.
The cavities 36, 36 are formed near the boundary between the second upper clad layer 11 and the second upper clad layer 11. This cavity 36,36
Is the cavity 13 formed by the eave-shaped cap layer 112 protruding in the width direction as in the conventional case of FIG.
The size is much smaller than 5,135. The formation positions of the cavities 36, 36 are the p-GaAs cap layer 1
It is a position farther from the active layer 6 in the thickness direction than the lower end of 2 and farther from the active layer than the conventional cavities 135 and 135. Therefore, in the semiconductor laser device of the present embodiment, the cavities 36, 36 do not substantially affect the characteristics of the semiconductor laser device, so that the same good characteristics as in the case where the cavities are substantially eliminated can be obtained. .

In the structure of FIG. 20B, the surface protective film 13 on the cap layer 12, the widthwise central portion of the current blocking layer 18a, and the widthwise central portion of the n-GaAs current blocking layer 18b are removed. . A contact layer 19 is laminated on it,
A p-side electrode 21 and an n-side electrode 22 are formed on the upper surface of the contact layer 19 and the lower surface of the n-GaAs substrate 1, respectively, to complete the ridge stripe type semiconductor laser device shown in FIG.

The characteristics of the semiconductor laser device of this embodiment are as follows.
The oscillation wavelength was 780 nm, the threshold current was 35 mA, and the optical output was kink-free up to 180 mW. A reliability test was conducted by continuously emitting light from this semiconductor laser device with an optical output of 120 mW in an environment of an ambient temperature of 70 ° C. As a result, as shown in FIG.
Emission was stable for 0 hours, and no characteristic deterioration such as an increase in operating current was observed during the light emitting operation. It can be said that the semiconductor laser device according to the above embodiment is excellent in reliability especially at a high output of 50 mW or more.

(Sixth Embodiment) FIG. 21 is a diagram showing a semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device according to the sixth embodiment. The fifth embodiment is different from the fifth embodiment only in that the etching solution used for etching the p-GaAs cap layer 12 is different in the step shown in FIG. 20A of the method for manufacturing a semiconductor laser device according to the fifth embodiment. Different from the form. That is, as an etching solution that erodes the protrusions 30 and 30 from the side surface of the cap layer 12 in the width direction, the etching solution is mixed with ammonia water so that the ratio of the number of ammonia molecules to the number of hydrogen peroxide molecules is 1:90. An etching solution mixed with hydrogen oxide water is used.

In this embodiment, the shape of the cap layer 12 is changed to that shown in FIG. 22A by using an etching solution having a larger mixture ratio of hydrogen peroxide water than in the fourth to fifth embodiments. In addition, the side surface is shaped so as to be constricted at the center in the thickness direction. At this point, there is a gap W1 between the upper side W3 of the cap layer and the width W1 of the top of the striped ridge.
= W3 is established.

After that, the resist film 28 is completely removed,
As shown in FIG. 22B, the second upper cladding layer 1
1 and the cap layer 12 and the surface protection film 13 on both sides in the width direction and on the etching stop layer 10 and on the surface protection film 13 by an MOCVD apparatus.
GaAs current blocking layer 18a and n-GaAs current blocking layer 1
8b and grow sequentially. At this time, the cap layer 12
N-AlGaA has a constricted side surface.
The cavities 36, 36 formed in the s current blocking layer 18a are
It is formed at substantially the same thickness direction position on both sides of the constriction.

After that, the upper portion of the cap layer 12 above the constriction, the cavity 36 of the current blocking layer 18a,
The portion above 36 and the portion of the current blocking layer 18b above the second upper cladding layer 11 are removed. As a result, the cavities 36, 36 in the current blocking layer 18a are removed. A contact layer 19 is laminated thereon, and a p-side electrode 21 and an n-side electrode 22 are formed on the upper surface of the contact layer 19 and the lower surface of the n-GaAs substrate 1, respectively,
The ridge stripe type semiconductor laser device shown in FIG. 21 is completed.

In the semiconductor laser device of this embodiment, the upper end width W3 of the cap layer 12, the lower end width W2, the upper end width W1 of the second upper cladding layer 11, and the upper end and the lower end of the cap layer 12 are included. About a width W23 at a predetermined position of W1 = W2 or W1> W2,
<W1 relationship is established. In this relationship, when the side surface of the cap layer 12 has a shape narrowed in the width direction as in the present embodiment, the cavities 36 and 36 formed in the n-AlGaAs current blocking layer 18a have the width of the narrowed portion. It is formed at substantially the same thickness direction position on both sides in the direction. Therefore, the cavities 36, 36 are located farther from the active layer 6 in the thickness direction than the upper end of the second upper cladding layer 11.
That is, it is formed at a position farther from the active layer than before. As a result, the cavities 36, 36 form the current blocking layer 1
8a and can be easily removed, and the cavities 36, 36
Has little effect on the semiconductor laser device even if it remains in the current blocking layer 18a. Therefore, the semiconductor laser device of this embodiment can obtain substantially the same good characteristics as the semiconductor laser device having substantially no cavity.

The characteristics of the semiconductor laser device of this embodiment are as follows.
The oscillation wavelength was 780 nm, the threshold current was 35 mA, and the optical output was kink-free up to 180 mW. A reliability test was conducted by continuously emitting light from this semiconductor laser device with an optical output of 120 mW in an environment of an ambient temperature of 70 ° C. As a result, as shown in FIG.
Emission was stable for 0 hours, and no characteristic deterioration such as an increase in operating current was observed during light emission. It can be said that the semiconductor laser device according to the above embodiment is excellent in reliability especially at a high output of 50 mW or more.

(Seventh Embodiment) FIG. 23 is a diagram showing a semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device according to the seventh embodiment. The method for manufacturing the semiconductor laser device according to the present embodiment is different from the method for manufacturing the semiconductor laser device according to the sixth embodiment only in that the etching solution for etching the p-GaAs cap layer 12 is different. That is,
As an etching solution for removing the protrusions 30, 30 of the cap layer 12, an etching solution in which ammonia water and hydrogen peroxide solution are mixed so that the ratio of the number of ammonia molecules to the number of hydrogen peroxide molecules is 1: 200 is used. .

In this embodiment, the shape of the cap layer 12 is changed to that shown in FIG. 24 by using an etching solution having a larger mixture ratio of hydrogen peroxide water than that in the fifth embodiment.
The shape shown in FIG. That is, p-GaA
The upper end width W3 of the s cap layer 12 and the second upper cladding layer 1
The shape is such that the relationship of W3 <W1 is established between the upper end width W1 and the upper end width W1.

Then, after removing the resist film 28, as shown in FIG. 24 (b), the second upper cladding layer 11 is formed.
N-AlG is formed on both sides of the cap layer 12 and the surface protection film 13 in the width direction and on the etching stop layer 10 and the surface protection film 13 by an MOCVD apparatus.
aAs current blocking layer 18a and n-GaAs current blocking layer 18
and b are sequentially grown. Then, the surface protective film 13 on the cap layer 12, the widthwise central portion of the current blocking layer 18a, and the widthwise central portion of the current blocking layer 18b are removed. A contact layer 19 is laminated thereon, and the p-side electrode 2 is formed on the upper surface of the contact layer 19 and the lower surface of the n-GaAs substrate 1.
The 1 and n-side electrodes 22 are formed respectively, and the ridge stripe type semiconductor laser device shown in FIG. 23 is completed.

In the method of manufacturing the semiconductor laser device of this embodiment, the upper end width W3 of the cap layer 12 and the upper end width W1 of the second upper cladding layer 11 are shaped so that the relationship of W3 <W1 is established. Therefore, a cavity is not formed in the n-AlGaAs current blocking layer 18a, and a semiconductor laser device having excellent characteristics can be obtained.

(Eighth Embodiment) The method for manufacturing a semiconductor laser device according to the eighth embodiment is the same as the process for manufacturing a semiconductor laser device according to the seventh embodiment in FIG.
GaAs current blocking layer 18a and n-GaAs current blocking layer 1
8b differs from the MOCVD apparatus in that it is grown by an MBE apparatus. FIG. 25A shows the above nA.
It is a figure which shows a mode that the 1GaAs current blocking layer 18a and the n-GaAs current blocking layer 18b were grown with the MBE apparatus.
As shown in FIG. 25A, no cavity is formed in the current blocking layer 18a as in the conventional case.

The surface protective film 13 of FIG. 25A and the current blocking layers 18a and 18b on the surface protective film 13 are removed, and the contact layer 19 is laminated thereon. A p-side electrode 21 and an n-side electrode 22 are formed on the upper surface of the contact layer 19 and the lower surface of the n-GaAs substrate 1, respectively, to complete the ridge stripe type semiconductor laser device shown in FIG. 25 (b). To do.

In the semiconductor laser device of this embodiment, since no cavity is formed in the current blocking layer 18a, good characteristics can be obtained. (Comparative Example) Here, with respect to the conventional semiconductor laser device as a comparative example and the semiconductor laser device of the first embodiment of the present invention, an experiment for measuring an optical output with respect to a drive current was conducted to compare the characteristics. It was

First, in the manufacturing method of the first embodiment,
By deleting the steps shown in FIGS. 4A and 4B, p-Ga
The n-AlGaAs current blocking layer 18a and n-GaAs are left without removing the protruding portions 30 and 30 of the As cap layer 12.
The current blocking layer 18b is sequentially grown by the MOCVD apparatus to manufacture the conventional semiconductor laser device shown in FIG.

An experiment was conducted by measuring the light output characteristics of the conventional semiconductor laser device and the semiconductor laser device of the first embodiment when the drive current was gradually increased.
FIG. 29 is a graph showing the results of this experiment. In FIG. 29, the horizontal axis represents drive current and the vertical axis represents optical output.
In FIG. 29, a straight line 202 shows the experimental result of the conventional semiconductor laser device, and a straight line 204 shows the experimental result of the semiconductor laser device of the first embodiment. As can be seen from FIG. 29,
The conventional semiconductor laser device and the semiconductor laser device of the first embodiment have the same threshold current value of about 35 mA. On the other hand, the differential efficiency, which has a correlation with the rate of increase in the optical output with respect to the drive current, is 0.93 in the conventional semiconductor laser device.
While it was 0.97 W / A, in the semiconductor laser device of the first embodiment, it is improved to 1.08-1.12 W / A. Therefore, according to the semiconductor laser device of the first embodiment, it can be said that the light output characteristics can be improved as compared with the conventional case.

In the above embodiment, the etching stop layer 10 is replaced with p-Al instead of p-Al.
_It may be formed of _0.3 Ga _0.7 As. p-A
When the first _0.5 Ga _0.5 As second upper cladding layer 11 is etched with hydrofluoric acid, the p-Al _0.3 Ga _{0.7 is formed.}
The etching stop layer 10 formed of As is the second
Since the composition of Al is smaller than that of the upper clad layer 11, the etching rate is sufficiently slower than that of the second upper clad layer 11, so that the progress of etching can be stopped and the etching stopper layer can sufficiently function.

In the above embodiment, the cap layer 12 may be formed of p-Al _0.1 Ga _0.9 As having a low Al composition ratio instead of p-GaAs.

That is, the composition formula of the etching stop layer 10 is Al _x Ga _1-x As, the composition formula of the second upper cladding layer 11 is _Aly Ga _1-y As, and the composition formula of the cap layer 12 is Al _z. As Ga _1-z As, if the relationship of x <y and z <y is satisfied with respect to the above x, y and z, the second upper clad layer 11 is satisfactorily formed in a predetermined shape and the cap layer 12 is also formed. Electrical contact between the contact layer 19 and the second upper clad layer 11 is satisfactorily obtained via the via.

In addition, in the above-described embodiment, G is formed on the substrate.
The case where an aAlAs-based material is grown has been described, but other materials including Ga and Al in the clad layer, such as A
The present invention can also be applied to a semiconductor laser device using an 1GaInP-based material or an AlGaInAs-based material.

In the above embodiment, each semiconductor layer was grown on the substrate 1 by the MOCVD apparatus.
MBE other than D, ALE (atomic layer epitaxy),
The semiconductor layer may be formed by an apparatus using another method such as LPE (liquid layer epitaxy).

In the above embodiment, the etching solution for removing the protruding portion of the cap layer is an etching solution in which ammonia water and hydrogen peroxide solution are mixed.
A mixed solution of sulfuric acid and hydrogen peroxide may be used as the etching solution. In particular, when a mixed solution having a mixture ratio of the number of sulfuric acid molecules and the number of hydrogen peroxide molecules of 1: 1 to 1:20 is used, at least the protruding portion of the cap layer can be effectively removed.

[0123]

As is apparent from the above, according to the semiconductor laser device of the present invention, at least the first conductivity type cladding layer, the active layer, and the second conductivity type lower cladding layer are provided on the substrate. An etching stop layer, a second conductivity type upper clad layer formed in a stripe-shaped protrusion shape, a cap layer formed in contact with the top of the upper clad layer, and formed on both sides of the upper clad layer. In a semiconductor laser device including a current blocking layer having a bandgap larger than that of the active layer, a width W1 of a top portion of the upper cladding layer and a width W2 of a surface of the cap layer on the active layer side.
And the width W of the surface of the cap layer opposite to the active layer side.
3 and W2 <W3, and generally W2 = W1, the upper clad layer and the cap layer are continuously connected with almost no step, so that the current blocking layer is formed. It is possible to avoid the formation of a cavity as in the conventional case, and it is possible to grow a substantially uniform current blocking layer on the upper portion of the cap layer without being substantially affected by the side portion of the cap layer.

According to the semiconductor laser device of the present invention, at least the first conductivity type cladding layer, the active layer, the second conductivity type lower cladding layer, the etching stop layer, and the stripe-shaped protrusions are formed on the substrate. Second conductive type upper clad layer formed in a shape, a cap layer formed in contact with the top of the upper clad layer, and a band gap larger than the active layer formed on both sides of the upper clad layer In a semiconductor laser device including a current blocking layer, a relationship of W1 = W2 or W1> W2 is established between a width W1 of the top of the upper cladding layer and a width W2 of the surface of the cap layer on the side of the active layer. And the width W23 of the cap layer at a predetermined position in the thickness direction and the width W1 of the top portion of the upper cladding layer satisfy the relationship of W23 <W1. It is possible to prevent the formation of cavities below the cap layer having a width larger than the top of the clad layer and having protrusions in the width direction and in the current blocking layer, and also to form cavities in the current blocking layer. Also, since this cavity can be formed on the side of the cap layer in the thickness direction with respect to the vicinity of the top of the upper cladding layer, and the cavity can be formed at a position further in the thickness direction than the active layer, the characteristics of the semiconductor laser device can be improved. It is possible to obtain a semiconductor laser device having good characteristics by almost eliminating the influence of the above-mentioned cavity.

According to the semiconductor laser device of the present invention, at least the first conductivity type cladding layer, the active layer, the second conductivity type lower cladding layer, the etching stop layer, and the stripe-shaped protrusions are formed on the substrate. Second conductive type upper clad layer formed in a shape, a cap layer formed in contact with the top of the upper clad layer, and a band gap larger than that of the active layer formed on both sides of the upper clad layer In the semiconductor laser device including a current blocking layer, the current blocking layer has a cavity at a position farther from the active layer in the thickness direction than the top of the projection shape of the upper cladding layer, and thus the cavity has a current Since the influence on the refractive index of light and the electric field distribution in the blocking layer is relatively small, deterioration of the characteristics of the semiconductor laser device can be effectively prevented.

According to the semiconductor laser device of the first embodiment,
The etching stop layer and the cap layer are made of the same material, or the constituent elements of the etching stop layer and the cap layer are at least 2
Since the two elements are common, a semiconductor laser device with good characteristics can be obtained.

According to the semiconductor laser device of one embodiment,
The composition formula of the etching stop layer is Al _x Ga _1-x.
As, and the compositional formula of the upper cladding layer is Al _y Ga.
_{1- y} As, and the composition formula of the cap layer is Al _z G.
a _1-z As, where x in the composition formula of the etching stop layer, y in the composition formula of the upper cladding layer, and z in the composition formula of the cap layer are x <y and z < y
Since the etching stop layer and the cap layer have a smaller Al content ratio in the composition formula than the upper clad layer, the upper clad layer can exhibit a good light and carrier confinement effect. And the cap layer can form a good electrical connection between the contact layer and the upper cladding layer, and
The etching stop layer can controlably form the lower clad layer to a predetermined thickness.

According to the semiconductor laser device of the first embodiment,
The substrate is made of GaAs, the clad layer and the active layer are made of AlGaAs, and the current blocking layer is made of A.
As it is made of lGaAs, it has good efficiency.
An aAs-based semiconductor laser device can be constructed.

According to the method of manufacturing a semiconductor laser device of the present invention, at least the first conductivity type cladding layer, the active layer, the second conductivity type cladding layer, and the cap layer are sequentially laminated on the substrate. A step of patterning the second conductivity type clad layer and the cap layer into a ridge stripe shape using a photolithography technique and an etching technique to form a mesa portion; and a step of forming the second conductivity type clad layer. For a cap layer having a width larger than the width of the upper end of the mesa portion and having protrusions protruding from the upper end of the mesa portion on both sides in the width direction in at least two eaves-like protrusions of the cap layer. A step of disposing a protective film against etching on a surface close to the active layer, and a step of removing at least the protruding portion of the cap layer by etching Therefore, at least the protruding portion of the cap layer can be etched off with good control without etching other portions such as a connecting portion between the second conductivity type cladding layer and the cap layer. The formation of cavities in the blocking layer can be effectively avoided, and a semiconductor laser device with good characteristics can be manufactured.

According to the method of manufacturing a semiconductor laser device of one embodiment, at least the protruding portion of the cap layer is removed by using a chemical etching solution, so that at least the protruding portion of the cap layer is easily and effectively removed. it can.

According to the method for manufacturing a semiconductor laser device of the present invention, at least the first conductivity type cladding layer, the active layer, the second conductivity type cladding layer, and the cap layer are sequentially laminated on the substrate. A step of patterning the second conductivity type clad layer and the cap layer into a ridge stripe shape using a photolithography technique and an etching technique to form a mesa portion; and a step of forming the second conductivity type clad layer. A step of disposing a protective film against etching on the surfaces of the flat portions located on both sides in the width direction of the mesa portion, and having a width larger than the width of the upper end of the mesa portion of the second conductivity type cladding layer, Regarding the cap layer having protrusions protruding from the upper end of the mesa portion on both sides in the width direction,
Since at least the protruding portion of the cap layer is removed by etching, at least the protruding portion of the cap layer can be removed by etching with less influence on the flat portion, so that a cavity is formed in the current blocking layer. Is effectively avoided, and a semiconductor laser device having good characteristics can be manufactured.

According to the method for manufacturing a semiconductor laser device of one embodiment, at least the protruding portion of the cap layer is removed by etching using vapor phase plasma.
At least the protruding portion of the cap layer can be effectively removed.

According to the method for manufacturing a semiconductor laser device of one embodiment, at least a part of the upper surface of the cap layer is subjected to the etching before the step of removing the eave-shaped protrusions of the cap layer by etching. Since the step of disposing the protective film is provided, the protrusion can be removed without reducing the thickness of the cap layer.

According to the method of manufacturing a semiconductor laser device of one embodiment, immediately before the protective film is arranged on at least the surface of the protruding portion of the cap layer closer to the active layer, or of the second conductivity type. The cap layer immediately before disposing the protective film on the surfaces of the flat portions located on both sides in the width direction of the mesa portion of the clad layer is such that the width of the surface of the cap layer on the active layer side is the same as that of the active layer of the cap layer. Since the width is greater than the width of the surface on the side opposite to the layer side, the contact is made with the protective film disposed adjacent to the side surface between the surface on the active layer side of the cap layer and the surface on the side opposite to the active layer side. By exposing light from the layer side, the side surface of the cap layer can be exposed, and the side surface of the cap layer can be directly etched, so that the eave-shaped protrusion of the cap layer can be effectively removed. With controllability It can be removed by.

According to the method of manufacturing a semiconductor laser device of one embodiment, the mesa portion of the second conductivity type cladding layer is made of AlG.
aAs, the cap layer is GaAs,
Since the protective film is made of AlGaAs,
Since the protruding portion of the cap layer made of AlGaAs can be removed by etching with good controllability without affecting the mesa portion of the second-conductivity-type cladding layer made of AlGaAs by using the protective film made of AlGaAs, good characteristics can be obtained. The semiconductor laser device can be stably formed.

According to the method for manufacturing a semiconductor laser device of one embodiment, at least the protruding portion of the cap layer is removed by using a mixed solution of sulfuric acid and hydrogen peroxide solution, so that at least the protruding portion of the cap layer is removed. Can be effectively removed.

According to the method of manufacturing a semiconductor laser device of one embodiment, at least the protruding portion of the cap layer is removed by using a mixed solution of ammonia water and hydrogen peroxide water. Therefore, at least the protruding portion of the cap layer. Can be effectively removed.

[Brief description of drawings]

FIG. 1 is a sectional view showing a ridge stripe type semiconductor laser device manufactured by a method for manufacturing a semiconductor laser device according to a first embodiment.

FIG. 2A and FIG. 2B are process drawings showing the method for manufacturing the semiconductor laser device of the first embodiment.

3A and 3B are process diagrams showing a method of manufacturing the semiconductor laser device according to the first embodiment, following FIG. 2.

4A and 4B are process diagrams showing the method for manufacturing the semiconductor laser device of the first embodiment, following FIG.

5A and 5B are process diagrams showing the method of manufacturing the semiconductor laser device of the first embodiment, following FIG.

6A and 6B are process diagrams showing the method for manufacturing the semiconductor laser device of the first embodiment, following FIG.

FIG. 7 is a sectional view showing a ridge stripe type semiconductor laser device manufactured by a method for manufacturing a semiconductor laser device according to a second embodiment.

8A and 8B are process diagrams showing a method for manufacturing a semiconductor laser device according to a second embodiment.

FIG. 9 is a process chart showing the method for manufacturing the semiconductor laser device according to the second embodiment, following FIG. 8;

10A is a cross-sectional view showing a ridge stripe type semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device according to the third embodiment, and FIG.
FIG. 11A is a process diagram showing the manufacturing method of the semiconductor laser device in FIG.

11A and 11B are process diagrams showing a method of manufacturing the semiconductor laser device of the third embodiment, following FIG. 10B.

12A and 12B are process diagrams showing the method for manufacturing the semiconductor laser device of the third embodiment, following FIG. 11.

FIG. 13A and FIG. 13B are process drawings showing the method of manufacturing the semiconductor laser device of the third embodiment, following FIG. 12.

FIG. 14 is a sectional view showing a ridge stripe type semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device according to the fourth embodiment.

FIG. 15A and FIG. 15B are process drawings showing the method for manufacturing the semiconductor laser device of the fourth embodiment.

16A and 16B are process diagrams showing the method for manufacturing the semiconductor laser device of the fourth embodiment, following FIG. 15.

FIG. 17A and FIG. 17B are process drawings showing the method of manufacturing the semiconductor laser device of the fourth embodiment, following FIG. 16.

FIG. 18 is a process chart showing the method for manufacturing the semiconductor laser device according to the fourth embodiment, following FIG. 17;

FIG. 19 is a diagram showing a semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device according to the fifth embodiment.

FIGS. 20A and 20B are process drawings showing the method for manufacturing the semiconductor laser device according to the fifth embodiment.

FIG. 21 is a view showing a semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device according to the sixth embodiment.

22A and 22B are process drawings showing the method for manufacturing the semiconductor laser device according to the sixth embodiment.

FIG. 23 is a diagram showing a semiconductor laser device manufactured by the method for manufacturing a semiconductor laser device according to the seventh embodiment.

FIG. 24A and FIG. 24B are process drawings showing the method for manufacturing the semiconductor laser device of the seventh embodiment.

25 (a) is a process chart showing the method of manufacturing the semiconductor laser device of the eighth embodiment, and FIG.
[FIG. 9] is a diagram showing a semiconductor laser device according to an eighth embodiment.

FIG. 26 is a diagram showing a semiconductor laser device manufactured by a conventional method for manufacturing a semiconductor laser device.

FIG. 27 is a diagram showing a semiconductor laser device manufactured by a conventional method for manufacturing a semiconductor laser device.

FIG. 28 is a graph showing the result of a reliability test of the semiconductor laser device of the present invention.

FIG. 29 is a graph showing changes in optical output with respect to changes in drive current for the semiconductor laser device of the present invention and the conventional semiconductor laser device.

[Explanation of symbols]

1 n-GaAs substrate 4 n-GaAs buffer layer 5 n-Al _0.5 Ga _0.5 As first cladding layer 6 AlGaAs quantum well active layer 7 p-Al _0.5 Ga _0.5 As second lower cladding Layer 11 p-Al _0.5 Ga _0.5 As Second upper cladding layer 12 p-GaAs cap layer 18a n-AlGaAs current blocking layer 18b n-GaAs current blocking layer 19 p-GaAs contact layer 21 p-side electrode 22 n Side electrode

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5F043 AA20 BB06 FF05 FF10                 5F073 AA07 AA53 AA73 CA05 CB02                       CB07 DA05 DA22 DA24 EA16                       EA28

Claims (15)

[Claims] 1. A substrate having at least a first conductivity type cladding layer, an active layer, and a second conductivity type lower cladding layer on a substrate.
An etching stop layer, a second conductivity type upper clad layer formed in a stripe-shaped protrusion shape, a cap layer formed in contact with the top of the upper clad layer, and formed on both sides of the upper clad layer. In a semiconductor laser device including a current blocking layer having a bandgap larger than that of the active layer, a width W1 of a protrusion-shaped top portion of the upper cladding layer and a width W2 of a surface of the cap layer on the active layer side, Between the width W3 of the surface of the cap layer opposite to the active layer side, W
A semiconductor laser device having a relationship of 2 <W3 and approximately W2 = W1. 2. A clad layer of at least a first conductivity type, an active layer, and a lower clad layer of a second conductivity type on a substrate,
An etching stop layer, a second conductivity type upper clad layer formed in the shape of stripes, a cap layer formed in contact with the top of the upper clad layer, and formed on both sides of the upper clad layer. In a semiconductor laser device including a current blocking layer having a bandgap larger than that of the active layer, a width W1 of a protrusion-shaped top portion of the upper cladding layer and a width W2 of a surface of the cap layer on the active layer side. In the meantime, W1
= W2 or W1> W2, and the width W23 of the cap layer at a predetermined position in the thickness direction.
And a width W1 at the top of the upper cladding layer, W2
A semiconductor laser device having a relationship of 3 <W1. 3. A clad layer of at least a first conductivity type, an active layer, and a lower clad layer of a second conductivity type on a substrate,
An etching stop layer, a second conductivity type upper clad layer formed in a stripe-shaped protrusion shape, a cap layer formed in contact with the top of the upper clad layer, and formed on both sides of the upper clad layer. In a semiconductor laser device comprising a current blocking layer having a bandgap larger than that of the active layer, in the current blocking layer, at a position farther from the active layer in the thickness direction than the top of the protrusion shape of the upper cladding layer. A semiconductor laser device having a cavity. 4. The semiconductor laser device according to claim 1, wherein the etching stop layer and the cap layer are made of the same material, or constituent elements of the etching stop layer and the cap are included. The constituent element of the layer is at least 2
A semiconductor laser device in which two elements are common. 5. The semiconductor laser device according to claim 1, wherein the etching stop layer has a composition formula of Al _x Ga _1-x.
As, and the compositional formula of the upper cladding layer is Al _y Ga.
_1-y As, and the composition formula of the cap layer is Al _z G.
a _1-z As, where x in the composition formula of the etching stop layer, y in the composition formula of the upper cladding layer, and z in the composition formula of the cap layer are x <y and z < A semiconductor laser device having a relationship of y. 6. The semiconductor laser device according to claim 1, wherein the substrate is made of GaAs, the clad layer and the active layer are made of AlGaAs, and the current blocking layer is made of AlGaAs. A semiconductor laser device characterized by being formed. 7. A step of sequentially laminating at least a first conductivity type cladding layer, an active layer, a second conductivity type cladding layer, and a cap layer on a substrate, and using a photolithography technique and an etching technique. And patterning the second conductivity type clad layer and the cap layer into a ridge stripe shape to form a mesa, and a width larger than the width of the upper end of the mesa part of the second conductivity type clad layer. With respect to the cap layer having protrusions protruding from the upper end of the mesa portion on both sides in the width direction in an eaves shape, etching is performed on at least the surface of the protrusions of the cap layer on the side close to the active layer. A semiconductor laser device comprising: a step of disposing a protective film for the cap layer; and a step of removing at least the protruding portion of the cap layer by etching. Manufacturing method. 8. The method of manufacturing a semiconductor laser device according to claim 7, wherein at least the protruding portion of the cap layer is removed by using a chemical etching solution. 9. A step of sequentially laminating at least a first conductivity type cladding layer, an active layer, a second conductivity type cladding layer, and a cap layer on a substrate, and using a photolithography technique and an etching technique. And forming a mesa portion by patterning the second conductivity type clad layer and the cap layer into a ridge stripe shape, and flat portions located on both sides in the width direction of the mesa portion of the second conductivity type clad layer. A step of disposing a protective film against etching on the surface of, and having a width larger than the width of the upper end of the mesa portion of the second-conductivity-type cladding layer, and the eaves-shaped on both sides in the width direction from the upper end of the mesa portion. And a step of removing at least the protruding portion of the cap layer by etching. Production method. 10. The method of manufacturing a semiconductor laser device according to claim 9, wherein at least the protruding portion of the cap layer is removed by etching using gas phase plasma. . 11. The method for manufacturing a semiconductor laser device according to claim 7, wherein before the step of removing the eave-shaped projection of the cap layer by etching, the cap layer of the cap layer is removed. A method for manufacturing a semiconductor laser device, comprising the step of disposing a protective film against the etching on at least a part of the upper surface. 12. The method of manufacturing a semiconductor laser device according to claim 7, wherein the protective film is provided at least on the surface of the protrusion of the cap layer on the side close to the active layer. Or the above second
The cap layer immediately before disposing the protective film on the surface of the flat portion located on both sides in the width direction of the mesa portion of the conductivity type cladding layer is such that the width of the surface of the cap layer on the active layer side is the cap layer. 2. The method for manufacturing a semiconductor laser device, wherein the width is larger than the width of the surface opposite to the active layer side. 13. The method for manufacturing a semiconductor laser device according to claim 7, wherein the mesa portion of the second conductivity type cladding layer is made of AlGaAs, and the cap layer is made of GaAs. The method for manufacturing a semiconductor laser device, wherein the protective film is made of AlGaAs. 14. The method of manufacturing a semiconductor laser device according to claim 7, wherein at least the protruding portion of the cap layer is removed by using a mixed solution of sulfuric acid and hydrogen peroxide solution. And a method for manufacturing a semiconductor laser device. 15. The method for manufacturing a semiconductor laser device according to claim 7, wherein at least the protruding portion of the cap layer is removed by using a mixed solution of ammonia water and hydrogen peroxide solution. A method of manufacturing a semiconductor laser device, comprising: