JP2863677B2 - Semiconductor laser and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser and a method for manufacturing the same, and more particularly, to a ridge waveguide type semiconductor laser and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for higher performance such as higher output and longer life of a ridge waveguide semiconductor laser in which an optical waveguide is formed by ridges. With these demands,
There is a demand for a technique that can control the layer thickness (dimension) of each layer at the time of manufacturing a ridge waveguide type semiconductor laser with higher accuracy.
For example, variations in the thickness of the remaining ridge of the upper cladding layer on the active layer greatly affect the light confinement effect. Therefore, it is strongly desired to establish a technique capable of controlling the thickness of the remaining ridge with high accuracy.

FIG. 9 is a cross-sectional view showing a manufacturing process of a ridge waveguide type semiconductor laser capable of controlling the remaining ridge thickness with high precision. In the drawing, reference numeral 51 denotes n-Ga.
As substrate , 52 is an n-Al0.5 Ga0.5 As lower cladding layer, 53 is a p-AlGaAs active layer, 54 is p-Al0.
5 Ga0.5 As first upper cladding layer, 55 is p-Al0.65
Ga 0.35 As etching stopper layer, 57 is p-AlO.
5 Ga0.5 second upper cladding layer, 58 is p-GaAs first
A cap layer, 59 is an SiO2 film, 60 is an n-GaAs current blocking layer, and 61 is a p-GaAs second cap layer.

Hereinafter, the manufacturing process will be described. First, figure9
(a), an n-GaAs substrate (not shown)51Up
To n-Al0.5 Ga0.5 As lower cladding layer 52, p-A
lGaAs active layer 53, p-Al0.5 Ga0.5 As first
Upper cladding layer 54, p-Al0.65Ga0.35As etchin
Stopper layer 55, p-Al0.5 Ga0.5 As
The lad layer 57 and the p-GaAs first cap layer 58 are
Each layer is epitaxially grown by CVD method,
After forming to a predetermined thickness, a SiO2 film is formed on top of it
And strip using standard photoengraving and etching techniques.
Then, an SiO2 film 59 patterned in a step shape is formed.
Then figure9As shown in (b), the SiO2 film 59 is masked.
Wet with a mixture of tartaric acid and aqueous hydrogen peroxide.
By performing the etching, the above p-Al0.5 Ga0.5
As second upper cladding layer 57, p-GaAs first cap
The layer 58 is etched to form an inverted mesa ridge.
At this time, the p-Al0.5 Ga0.5 As second upper cladding layer 5
7 is etched, but p-A having an Al composition of 0.65 is used.
10.65 Ga0.35 As etching stopper layer 55 is etched
Is not etched, and the wet etching is p-Aly Ga1-y
In order to completely stop at the As etching stopper layer 55,
Remaining ridge thickness, that is, p-Al0.5 Ga1-0.5 As
1. Upper cladding layer 54 and p-Al0.65Ga0.35As etch
The total thickness of the stopping stopper layer 55 is, for example, 0.2 to
It can be controlled to about 0.3 μm. And this
Later, figure9As shown in (c), the n-GaAs current blocking layer 6
MOCVD method for the 0 and p-GaAs second cap layers 61
The p-Al0.65Ga0.35As etching strike
By epitaxial growth on the top layer 55.
Buried on both sides of the ridge, AlGaAs ridge waveguide semiconductor
The basic structure of the body laser is completed. And after this,
The SiO2 film 59 is made of plastic using CHF3 gas and O2 gas.
Ridge and p-GaAs
s (not shown) over the upper surface of the second cap layer 61.
A GaAs contact layer is epitaxially grown;
P-side electrode, n-GaAs on the upper surface of the -GaAs contact layer
When an n-side electrode is formed on the back surface of the s substrate,
The edge guided semiconductor laser is completed.

In the above process, both sides of the ridge are n-G
The ridge and the p-GaAs are buried with the aAs current blocking layer 60 and the p-GaAs second cap layer 61.
Although the p-GaAs contact layer is formed on the upper surface of the second cap layer 61, both sides of the ridge are n-GaAs.
Embedding may be performed only with the current blocking layer 60, and thereafter, the ridge and the p-GaAs contact layer may be formed on the upper surface of the n-GaAs current blocking layer 60, and the p-side and n-side electrodes may be formed. Further, both sides of the ridge are buried only with the n-GaAs current blocking layer 60, and thereafter, a p-type dopant is diffused into the n-GaAs current blocking layer 60 to form the n-GaAs current blocking layer 60.
The upper layer of the As current blocking layer 60 is a p-type layer,
A side electrode may be formed.

In the above process, the thickness of the remaining ridge is controlled to about 0.2 to 0.3 μm because the light generated in the p-AlGaAs active layer 53 immediately below the ridge is
The reason for confinement in the ridge (in the region immediately below the ridge) is to confine the horizontal spread along the AlGaAs active layer 53 to p-Al0.5 Ga.
It is most excellent when the above-mentioned ridge remaining thickness including the 1-0.5 As first upper cladding layer 54 is 0.2 to 0.3 μm.

Next, in the above manufacturing process, AlGaAs
The Al composition ratio of the cladding layers 52, 54, and 57 is set to 0.5, and the Al composition ratio of the p-AlGaAs etching stopper layer 55 is set to 0.5.
The reason why the composition ratio is set to 0.65 will be described.

In general, AlGaAs lasers are often used in optical disk devices and the like. In this case, the oscillation wavelength is set to about 800 nm (1.55 eV in terms of energy). In a semiconductor laser, it is necessary to design so that carriers injected into the active layer do not leak into a clad layer sandwiching the active layer. In the case of an AlGaAs laser, the energy is higher than the energy corresponding to the oscillation wavelength from the active layer.
The active layer must be sandwiched between cladding layers having a band gap of 0.3 eV or more. As described above, when the oscillation wavelength is set to around 800 nm, the cladding layer has a band of 1.95 eV or more. An AlGaAs layer having a gap energy is used. For this reason, in such a semiconductor laser, in order to make the band gap energy of the cladding layer 1.95 eV or more, Al x G
a1-x Al composition ratio x of the As cladding layer (hereinafter simply referred to as Al
The composition ratio is used. ) Needs to be 0.42 or more. On the other hand, if the Al composition ratio is too large, the refractive index decreases monotonously, the confinement of the active layer becomes too large, and the laser end face is deteriorated due to the high light density during high-power operation. Therefore, from these two points, it is preferable that the composition ratio of the AlGaAs cladding layer is about 0.5 (range of 0.45 to 0.6).
In this case, the Al composition ratio is set to 0.5.

On the other hand, the Al composition ratio of the p-AlGaAs etching stopper layer 55 formed on the p-AlGaAs first upper cladding layer 54 in which the Al composition ratio is set to 0.5 is the same as that of the p-AlGaAs. If the Al composition ratio of the first upper cladding layer 54 is lower than that, the light confinement coefficient decreases, the full width at half maximum (θ⊥) of the spread of the laser beam in the vertical direction increases, and the laser characteristics deteriorate significantly. . For this reason, it is preferable that the Al composition ratio of the p-AlGaAs etching stopper layer 55 be larger than the Al composition ratio (= 0.5) of the p-AlGaAs first upper cladding layer 54. In order to form a ridge by etching the p-AlGaAs second upper cladding layer 57 with a mixed solution of hydrogen peroxide, and to stop the progress of this etching completely with the p-AlGaAs etching stopper layer 55, it is necessary to use p-AlGaAs.
the Al composition ratio of the second upper cladding layer 57 to 0.6 or less,
It is necessary to make the Al composition ratio of the p-AlGaAs etching stopper layer 5a larger than 0.6. Therefore, in the ridge waveguide type semiconductor laser shown in FIG. Al
The composition ratio is set to 0.65.

[0010]

By the way, in the conventional manufacturing process of a ridge waveguide type semiconductor laser, when a ridge is formed, as described above, a wet liquid using a mixed solution of tartaric acid and hydrogen peroxide as an etching solution is used. Using etching, pA
By making the Al composition ratio of the lGaAs etching stopper layer 55 larger than 0.6, the etching is completely stopped by the p-AlGaAs etching stopper layer 55, and the thickness of the ridge remaining is controlled with high precision. However, the wet-etched AlGaAs layer is easily oxidized. In particular, since the AlGaAs layer has a higher degree of oxidation as its Al composition becomes larger, the Al composition ratio after the ridge formation becomes 0.6 or more. N-G is formed on the enlarged p-AlGaAs etching stopper layer 55.
When the aAs current blocking layer 60 is regrown, the n-GaAs
The crystal quality of the current blocking layer 60 deteriorates (for example,
When the number of surface defects becomes 10 ⁶ / cm ² or more, the surface morphology is extremely reduced. As a result, the resulting semiconductor laser has a problem that the reactive current flowing through the crystal defect during its operation increases with time, and the reliability of the laser decreases.

Although the p-AlGaAs etching stopper layer 55 is necessary to control the ridge remaining thickness with high precision as described above, such a p-AlGaAs etching stopper layer 55 When the AlGaAs etching stopper layer 55 is disposed near the active layer 53 immediately below the ridge, the laser oscillates because the refractive index distribution in the vertical direction with respect to each layer of the laser becomes asymmetric as shown in FIG. The intensity distribution of the laser light is such that the bottom of the laser light is distributed toward the p-AlGaAs etching stopper layer 55 side, and when the laser light is condensed by the lens, there is a problem that it is difficult to condense the laser light.

On the other hand, FIG. 10 shows that the width of the stripe-shaped SiO 2 film 59 is increased to 10 μm in the above-mentioned conventional ridge waveguide type semiconductor laser manufacturing process.
A ridge is formed as described above, and in this state, an n-GaAs current blocking layer 60 is epitaxially grown on both sides of the ridge to bury the both sides of the ridge. When a new semiconductor layer is selectively epitaxially grown on both sides of a ridge having a width of 10 μm or more, a large amount of semiconductor is also formed on the wide stripe SiO2 film 59 on the upper surface of the ridge. A crystalline film 60a is formed, and when removing the stripe-shaped SiO2 film 59 in a later step, the SiO2 film 59 cannot be completely removed due to the influence of the polycrystalline film. There is a problem that the structure cannot be formed with good controllability and reproducibility.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. The thickness of the ridge is adjusted to a predetermined thickness, the crystal defects in the regrown layers on both sides of the ridge are reduced, and It is another object of the present invention to provide a semiconductor laser having improved symmetry in the intensity distribution of oscillating laser light and a manufacturing method capable of manufacturing the semiconductor laser with good reproducibility.

Further, another object of the present invention is that the width is one.
A wide ridge of 0 μm or more is formed, and a stripe-shaped mask disposed on the ridge used for burying and growing a semiconductor epitaxial layer on both sides of the ridge can be completely removed to control a desired laser structure. It is an object of the present invention to provide a method for manufacturing a semiconductor laser that can be formed with good performance.

[0015]

A semiconductor laser according to the present invention is provided.
Are sequentially laminated on a semiconductor substrate, and the Al composition ratio is
Lower claddings each composed of 0.6 or less AlGaAs
Laminated structure having a pad layer, an active layer and a first upper cladding layer
And a first upper cladding disposed on the surface of the laminated structure.
A GaAs thin layer thinner than the pad layer and the GaAs thin layer
Is arranged in a stripe shape extending in the light waveguide direction
And the Al composition ratio exceeds 0.6 and the first upper cladding layer
Thinner AlGaAs layer and the thinner AlGaAs layer
Is arranged in a ridge shape along a stripe on
The second is made of AlGaAs having a composition ratio of 0.6 or less.
Buried both sides of the upper cladding layer and the second upper cladding layer.
Current blocking layer disposed on GaAs thin layer so as to be embedded
And with.

Also, Al is sequentially laminated on a semiconductor substrate.
Each is composed of AlGaAs having a composition ratio of 0.6 or less.
Having a lower clad layer, an active layer and a first upper clad layer
A stacked structure, and Ga on the surface of the stacked structure.
Except for As, the Al composition ratio is less than 0.3
A first thin AlGaAs layer that is thinner than the
Extending partly on the thin AlGaAs layer in the light guiding direction
Arranged in stripes and Al composition ratio exceeds 0.6
Second AlGaAs thinner than the first upper cladding layer
Layer and a stripe on top of this second AlGaAs thin layer.
Are arranged in a ridge along with the Al composition ratio of 0.6 or less.
A second upper cladding layer made of AlGaAs below;
The first upper cladding layer is buried on both sides of the first
A current blocking layer disposed on the AlGaAs thin layer.
It is a thing.

Further, the first upper cladding layer and the GaAs thin
The sum of the thickness of the first layer and the first AlGaAs thin layer is set to 0.
The thickness was 2 to 0.3 μm. Also on a semiconductor substrate
AlGaAs having an Al composition ratio of 0.6 or less
with lower cladding layer and active layer respectively composed of
A laminate structure disposed on a surface of the laminate structure;
1 composed of AlGaAs having a composition ratio of 0.6 or less,
Protrusions that protrude in a ridge shape that extends in the light waveguide direction
And a flat portion extending flat on both sides of the protrusion and covering the active layer.
A first upper cladding layer having
Al composition ratio disposed over the top of the protrusion of the metal layer
Exceeds 0.6 and is thinner than the first upper cladding layer.
A thin GaAs layer and a first
It is disposed on the protrusion of the upper cladding layer, and the Al composition ratio is
A second upper cladding made of AlGaAs of 0.6 or less.
Layer, the second upper cladding layer and the first upper cladding layer
Flat portion of the first upper cladding layer so as to bury the protrusion of
And a current blocking layer disposed thereon.

Also, a method of manufacturing a semiconductor laser according to the present invention.
In the method, an AlG composition having an Al composition ratio of 0.6 or less
The lower cladding layer, the active layer, and the
And the first upper cladding layer are sequentially laminated,
A first AlGaAs thin layer having a ratio of less than 0.3, Al composition
A second thin AlGaAs layer having a ratio greater than 0.6, and Al
Second upper cladding of AlGaAs having a composition ratio of 0.6 or less
A first step of sequentially stacking layers, and a second
A striped insulating film is formed on the surface, and this insulating film is
Etch mixed organic acid and hydrogen peroxide as mask
Until the second AlGaAs thin layer is exposed using the plating solution
Etching to form a striped ridge
Process and a second AlGaAs thin layer exposed in the second process
To expose a first thin layer of AlGaAs.
Process and first AlGa so as to bury both sides of the ridge.
Forming a current blocking layer on the As thin layer;
Including. Further, in the third step, the second
Removal of thin AlGaAs layer using hydrofluoric acid based etchant
This is performed by wet etching.

Further, the second step formed in the first step
When the Al composition ratio of the AlGaAs thin layer is set to 0.8 or more,
First, the removal of the second AlGaAs thin layer in the third step is boiled.
Wet etching using hydrochloric acid
It is what you do. Also, the Al composition ratio on the semiconductor substrate
Is made of AlGaAs of 0.6 or less, respectively.
A lad layer, an active layer, and a first upper cladding layer
AlGaAs having an Al composition ratio of more than 0.6
The thin layer and the AlGaAs having an Al composition ratio of 0.6 or less
A first step of sequentially laminating two upper cladding layers;
Forming a striped insulating film on the surface of the upper cladding layer
Then, using this insulating film as a mask, an organic acid and hydrogen peroxide
A thin AlGaAs layer is exposed using an etching solution mixed with
Etch until it forms, forming a striped ridge
And a second step of reducing the selectivity to AlGaAs.
The thin AlGaAs layer using a new etchant
And a part of the first upper cladding layer is continuously removed and
The thickness of the first upper cladding layer on both sides of the edge from the active layer.
A third step of forming to predetermined dimensions, and after the third step
A first upper cladding layer so as to bury both sides of the ridge.
Forming a current blocking layer on the substrate.
It is.

[0020]

In the semiconductor laser according to the present invention, Al
Each is composed of AlGaAs having a composition ratio of 0.6 or less.
Having a lower clad layer, an active layer and a first upper clad layer
And a first layer disposed on a surface of the first layer and having a first structure.
And a GaAs thin layer thinner than the upper cladding layer.
Stripe extending in the direction of light propagation on a part of s thin layer
In which the Al composition ratio exceeds 0.6 and the first
An AlGaAs thin layer thinner than the lad layer;
Arranged in a ridge along a stripe on a thin As layer
Composed of AlGaAs having an Al composition ratio of 0.6 or less.
A second upper cladding layer,
Current placed on GaAs thin layer to bury both sides
And the blocking layer, the crystal quality of the current blocking layer
Thus, the leakage current can be reduced.

Further , AlGa having an Al composition ratio of 0.6 or less is used.
The lower cladding layer, the active layer, and the
(1) a laminated structure having an upper clad layer;
It is disposed on the surface and has an Al composition ratio of 0.3 except for GaAs.
First AlG that is less than and thinner than the first upper cladding layer
a thin layer of aAs and a part of the first thin layer of AlGaAs.
Arranged in a stripe shape extending in the light waveguide direction,
Composition ratio exceeds 0.6 and thinner than the first upper cladding layer
A second thin AlGaAs layer and the second AlGaAs
On a thin layer, it is arranged in a ridge along the stripe,
It was composed of AlGaAs having an Al composition ratio of 0.6 or less.
A second upper cladding layer and both sides of the second upper cladding layer
Embedded on the first AlGaAs thin layer so as to embed
And a current blocking layer,
The quality is good and the leakage current can be reduced.
You.

Further, the first upper cladding layer and the GaAs thin
The sum of the thickness of the first layer and the first AlGaAs thin layer is set to 0.
2 to 0.3 μm, good light confinement effect
Become . Further, in AlGaAs having an Al composition ratio of 0.6 or less,
Product with lower cladding layer and active layer respectively configured
A layer structure and an Al group disposed on the surface of the laminated structure;
It is composed of AlGaAs having a composition ratio of 0.6 or less, and a part of the light is
A ridge that extends in the waveguide direction
And a flat portion that extends flat on both sides of the projecting portion and covers the active layer.
Having a first upper cladding layer, and the first upper cladding layer
Al covering the top of the protrusion of
AlG exceeding 0.6 and thinner than the first upper cladding layer
a thin layer of aAs and a first upper layer through the thin layer of AlGaAs.
It is disposed on the protrusion of the cladding layer and has an Al composition ratio of 0.
A second upper cladding layer composed of 6 or less AlGaAs
Between the second upper cladding layer and the first upper cladding layer.
On the flat portion of the first upper cladding layer so as to bury the protrusion.
And a current blocking layer disposed therein.
The thickness of the flat part of the pad layer can be adjusted with high accuracy, and light confinement
Excellent effect and good reproducibility.

Also, a method of manufacturing a semiconductor laser according to the present invention.
In the method, the Al composition ratio on the semiconductor substrate is 0.6 or less
Lower cladding layer composed of AlGaAs
An active layer and a first upper cladding layer,
A first AlGaAs thin layer having an Al composition ratio of less than 0.3,
A second AlGaAs thin layer having an Al composition ratio exceeding 0.6,
And the second upper part of AlGaAs having an Al composition ratio of 0.6 or less.
A first step of sequentially laminating a cladding layer, and a second upper cladding layer.
A stripe-shaped insulating film is formed on the surface of the pad layer.
Mix the organic acid and hydrogen peroxide using the insulating film as a mask.
Second AlGaAs thin layer is exposed using the etching solution
To form a stripe-shaped ridge.
A second step, and a second AlGa exposed in the second step.
Removing the As thin layer and exposing the first AlGaAs thin layer
And a first step to bury both sides of the ridge.
Fourth process for forming a current blocking layer on a thin AlGaAs layer
And exposing the first AlGaAs thin layer.
In the third step, oxidation of the first AlGaAs thin layer is performed.
Forming a current blocking layer with good crystal quality
can do. Further, in the third step, the second
Removal of AlGaAs thin layer using hydrofluoric acid based etchant
Since the first etching is performed by wet etching used,
high between the IGaAs thin layer and the second AlGaAs thin layer
Under etch selectivity, the thickness of the first thin AlGaAs layer
The second AlGaAs thin layer is removed while leaving only the
Can be

Furthermore, the second step formed in the first step
When the Al composition ratio of the AlGaAs thin layer is set to 0.8 or more,
First, the removal of the second AlGaAs thin layer in the third step is boiled.
Wet etching using hydrochloric acid
Therefore, the first AlGaAs thin layer and the second AlG
Under high etch selectivity with a thin layer of aAs, the first
The thickness of the AlGaAs thin layer of the second A
The thin lGaAs layer can be removed. Also, Al group
It was composed of AlGaAs having a composition ratio of 0.6 or less.
The lower cladding layer, the active layer, and the first upper cladding layer
AlGa in which the Al composition ratio exceeds 0.6
As thin layer and AlGaAs with Al composition ratio of 0.6 or less
A first step of sequentially laminating a second upper cladding layer of
2 Form a striped insulating film on the surface of the upper cladding layer.
Using this insulating film as a mask, with an organic acid and hydrogen peroxide
A thin AlGaAs layer is formed using an etchant mixed with
Etch until exposed, forming a striped ridge
The second step to be performed and the low selectivity to AlGaAs.
The thin AlGaAs layer using a clean etchant
And removing part of the first upper cladding layer continuously.
Thickness of first upper cladding layer on both sides of ridge from active layer
After the third step of forming a predetermined size
A first upper cladding layer so as to bury both sides of the ridge.
A fourth step of forming a current blocking layer thereon.
From the active layer of the first upper cladding layer on both sides of the ridge.
The thickness can be formed with high accuracy and high reproducibility.

[0025]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. (Embodiment 1) FIG. 1 is a cross-sectional view showing a structure of a ridge waveguide semiconductor laser according to a first embodiment of the present invention, and FIG. It is sectional drawing. In these figures, 1 is n-Ga
As layer 2, lower cladding layer of n-AlGaAs having an Al composition ratio in the range of 0.45 to 0.6, p-AlGaAs active layer having an Al composition ratio of 0.2 or less, 4 and Al composition ratio of 4 P-AlGaAs first in the range of 0.45 to 0.6
The upper cladding layer 5 has an Al composition ratio of p-
AlGaAs second etching stopper layer, 6 is p-Ga
As first etching stopper layer 7 has an Al composition ratio of 0.1.
P-AlGaAs second upper cladding layer in the range of 45 to 0.6, 8 is a p-GaAs first cap layer, 9 is SiO
2 film, 10 is an n-GaAs current blocking layer, 11 is p-Ga
An As second cap layer, 12 is a p-GaAs contact layer, and 13 is an n-GaAs substrate.

Hereinafter, the manufacturing process will be described. First, FIG.
As shown in FIG. 1A, an n-GaAs layer 1 serving as a buffer layer is formed on an n-GaAs substrate (not shown).
N-AlGaAs lower cladding layer in the range of 45 to 0.6, p-AlGaAs active layer with an Al composition ratio of 0.2 or less, p-AlGaAs in the range of 0.45 to 0.6.
AlGaAs first upper cladding layer 4, p-GaAs first etching stopper layer 6, p-AlGaAs second etching stopper layer 5 with Al composition ratio greater than 0.6, Al composition ratio in the range of 0.45 to 0.6 P-AlGaAs
The second upper cladding layer 7 and the p-GaAs first cap layer 8 are epitaxially grown in this order by MOCVD so that the respective layers have a predetermined layer thickness.
After a SiO2 film is formed on the upper surface of the first GaAs cap layer 8, a stripe-shaped SiO2 film 9 is formed by ordinary photolithography and etching techniques. In this case, pA
The thickness of the lGaAs second etching stopper layer 5 is set to 200
Angstrom, and the layer thickness of the p-GaAs first etching stopper layer 6 is 40 angstrom.
The sum of the layer thickness of the GaAs first etching stopper layer 6 and the layer thickness of the p-AlGaAs first upper cladding layer 4 having an Al composition ratio in the range of 0.45 to 0.6 is 0.2 to 0.3 μm.
I made it.

Next, as shown in FIG.
2 Using the film 9 as a mask, the p-GaAs first cap layer 8 and the p-AlzGa1-zAs second upper cladding layer 7 are etched using an etching solution composed of a mixture of tartaric acid and hydrogen peroxide. Form a ridge. The etching at this time is performed by p-AlGa having an Al composition ratio of 0.45 to 0.6.
After the etching of the As second upper cladding layer 7, the etching is completely stopped by the p-AlGaAs second etching stopper layer 5 in which the Al composition ratio is larger than 0.6.

Next, as shown in FIG. 2C, an etching solution composed of a mixture of HF and H 2 O is applied to the p-AlGaAs second etching stopper layer 5 exposed on both sides of the ridge. The wet etching is performed, and the p-
The AlGaAs second etching stopper layer 5 is removed, and p
-Exposing the surface of the GaAs first etching stopper layer 6. The mixture of HF and H2 O used here was GaAs.
Since hardly any etching property is exhibited for s, p
-Only the AlGaAs second etching stopper layer 5 is removed, and the hydrofluoric acid based etching solution is generally SiO2
Has an etching action, for example, H
When an etching solution having a mixing ratio of F: H2 O = 1: 10 is used, the etching rate of AlGaAs having an Al composition ratio larger than 0.6 is about 10 times higher than that of SiO2, so that the SiO2 film 9 is also almost etched. Without removing, only the p-Aly Ga1-y As second etching stopper layer 5 can be removed.

Next, as shown in FIG. 2 (d), the n-GaAs current blocking layer 10 and the p-GaAs
The second cap layer 11 is epitaxially grown in this order by MOCVD.

Thereafter, the SiO2 film 9 is removed by plasma etching using CHF3 gas and O2 gas, and the p-GaAs contact layer 12 is removed by MOCV.
The epitaxial growth is performed by the D method, and the p-side electrode and n
When the side electrodes are formed, the ridge waveguide type semiconductor laser shown in FIG. 1 is completed.

In the manufacturing process of the semiconductor laser according to the present embodiment, p-AlGa having an Al composition ratio of more than 0.6 is used.
In the As second etching stopper layer 5, the etching reaction at the time of ridge formation is completely stopped, and the remaining ridge thickness is p-
Since the AlGaAs first upper cladding layer 4 and the p-GaAs first etching stopper layer 6 are determined by the layer thicknesses of these layers when they are epitaxially grown, the remaining ridge thickness can be accurately adjusted to a predetermined thickness. Also,
Since the n-GaAs current blocking layer 10 is formed on the p-GaAs first etching stopper layer 6 having a small degree of oxidation by wet etching, the crystal quality of the n-GaAs current blocking layer 10 is improved. The fact that the surface defect density was 10 ⁶ / cm ² or more was changed to 10 ³ / cm
It can be reduced to about ² .

The semiconductor laser obtained by such a manufacturing process has a ridge-remaining thickness on both sides of the ridge,
That is, the p-AlGaAs first upper cladding layer 4 and the p-Ga
Since the total thickness of the As first etching stopper layer 6 is adjusted to 0.2 to 0.3 μm, the light confinement effect is excellent, and the crystal quality of the n-GaAs current blocking layer 10 is improved. Therefore, the increase of the leakage current is suppressed, and the lower cladding layer 2 of n-AlGaAs and p-A
The Al composition ratio of the first upper cladding layer 4 is 0.45.
Since it is in the range of about 0.6, an increase in light emission loss and deterioration of the laser end face are suppressed, and a high-performance ridge waveguide semiconductor laser having an oscillation wavelength of about 800 nm is obtained.

As shown in FIG. 11C, p-Ga
The refractive index of the As first etching stopper layer 6 is greater than that of the p-AlGaAs active layer 3 having an Al composition ratio of 0.3 or less, and p-AlGaAs having an Al composition ratio of greater than 0.6.
The refractive index of the s-second etching stopper layer 5 is smaller than that of the p-AlGaAs active layer 3 having an Al composition ratio of 0.3 or less. Offset each other,
As a result, p-AlGa having an Al composition ratio of more than 0.6
Asymmetry in the intensity distribution of the laser light beam is improved as compared with a conventional semiconductor laser provided only with an As etching stopper layer.

(Embodiment 2) Next, a manufacturing process of a semiconductor laser according to a second embodiment will be described. The manufacturing process of the semiconductor laser of this embodiment is basically the same as the manufacturing process of the semiconductor laser of the first embodiment shown in FIG. 2, that is, in this embodiment, the p-AlGaAs second etching stopper layer The Al removal ratio of the p-AlGaAs second etching stopper layer 5 exposed after the formation of the ridge shown in FIG. 2 (c) is increased by wet etching using boiling hydrochloric acid as an etchant. After that, similarly to the first embodiment, the exposed p-GaAs
The n-GaAs current blocking layer 10 is regrown on the first etching stopper layer 6. The boiled hydrochloric acid has an Al composition ratio of AlGaAs larger than 0.8.
Since the s crystal layer is etched and the GaAs crystal layer is not etched, the p-GaAs first etching stopper layer 6 is formed.
Are exposed on the surface without being etched.

In the manufacturing process of the semiconductor laser according to the present embodiment, the Al composition ratio of the p-AlGaAs second etching stopper layer 5 is set to be larger than 0.8, and after the ridge is formed, the p-AlGaAs second etching stopper layer 5 is formed. 5 is selectively removed by wet etching using hydrochloric acid boiled as an etching solution, so that the p-GaAs first etching stopper layer 6 can be exposed on both sides of the ridge and exposed on the ridge, and grow thereon. The crystal quality of the n-GaAs current blocking layer 10 is improved. Further, similarly to the first embodiment, p-AlGa during epitaxial growth is used.
Depending on the thickness of the As first upper cladding layer 4 and the p-GaAs first etching stopper layer 6, the remaining ridge thickness can be controlled with high precision to a predetermined layer thickness, for example, 0.2 to 0.3 μm.

The semiconductor laser obtained by such a manufacturing process has an excellent light confinement effect as well as an increase in light emission loss and deterioration of the laser end face, similarly to the semiconductor laser of the first embodiment. In addition, a high-performance ridge waveguide semiconductor laser with an oscillation wavelength of about 800 nm, in which an increase in leakage current is suppressed, is provided. In the ridge, as in the case of the semiconductor laser of the first embodiment, the p-GaAs first etching stopper layer and the p-AlGaAs having an Al composition larger than 0.8 are formed on the upper cladding layer in the ridge.
s A second etching stopper layer is provided,
The asymmetry in the intensity distribution of the laser light beam is also improved.

(Embodiment 3) Next, a manufacturing process of a semiconductor laser according to a third embodiment will be described. The manufacturing process of the semiconductor laser of this embodiment is basically the same as the manufacturing process of the semiconductor laser of the first and second embodiments shown in FIG.
That is, in this embodiment, the surface-exposed p-GaAs first
Without re-growing the n-GaAs current blocking layer 10 directly on the etching stopper layer 6, the surface of the p-GaAs first etching stopper layer 6 is immersed in a boiled hydrogen peroxide solution for about 20 to 60 minutes. Thereafter, the n-GaAs current blocking layer 10 is grown again. By the dipping step, the surface of the p-GaAs first etching stopper layer 6 is cleaned, and a thermally weak oxide film is formed on the surface. After that, when the n-GaAs current blocking layer 10 is crystal-grown, This oxide film is removed during the temperature rise process during crystal growth,
N-GaAs current blocking layer 1 on the cleaned GaAs surface
0 can grow.

In the manufacturing process of the semiconductor laser according to this embodiment, the surface of the p-GaAs first etching stopper layer 6 exposed on the surface after the formation of the ridge is immersed in a boiled hydrogen peroxide solution for a certain period of time. Since the n-GaAs current blocking layer 10 is regrown, the n-GaAs current blocking layer 10 is formed on the cleaned p-GaAs first etching stopper layer 6.
Can be epitaxially grown, the crystal quality of the n-GaAs current blocking layer 10 can be further improved, and a semiconductor laser in which an increase in leakage current is further suppressed as compared with the first and second embodiments can be obtained. .

In the first to third embodiments, p-G
The thickness of the aAs first etching stopper layer 6 is set to 40 angstroms, and the band gap energy Eg of this layer is made larger than the energy of laser light generated in the active layer to prevent an increase in light emission loss. GaAs
The same effect can be obtained if the thickness of the first etching stopper layer 6 is 60 Å or less.

In the first to third embodiments, p-
AlGaAs second etching stopper layer 5 is made of p-GaAs.
s A mixed solution of hydrofluoric acid and water was used as an etchant used for selective etching removal from the first etching stopper layer 6, but a mixed solution of hydrofluoric acid and hydrogen peroxide or hydrochloric acid was used as an etchant. May be used.

In the first to third embodiments, Al
The p-GaAs first etching stopper layer 6 is formed on the p-AlGaAs first upper cladding layer 4 having a composition ratio of 0.45 to 0.6, but instead of the p-GaAs first etching stopper layer 6. Contains Al in a range that does not degrade the crystal quality of the n-GaAs current blocking layer 10, that is, Al
The same effect can be obtained by forming a p-AlGaAs layer having a composition ratio smaller than 0.3.

In the first to third embodiments, Al
Although the active layer composed of the GaAs layer is used, an active layer composed of a GaAs layer or an active layer composed of a multiple quantum well structure of GaAs and AlGaAs may be used.

(Embodiment 4) FIG. 3 is a sectional view showing the structure of a semiconductor laser according to a fourth embodiment of the present invention.
FIG. 5 is a sectional view showing a step of a manufacturing step of the semiconductor laser shown in FIG. 4. In these figures, the same reference numerals as those in FIGS. 1 and 2 denote the same or corresponding parts, and reference numeral 3a denotes an activity formed of a multiple quantum well structure (MQW structure) of a GaAs layer and an AlGaAs layer having an Al composition ratio of 0.2 or less. Layer, 12a is p
The -GaAs contact layer 13 is a Zn diffusion layer formed by diffusing Zn as a p-type dopant in the upper layer of the n-GaAs current blocking layer 10.

Hereinafter, the manufacturing process will be described. First, nG
On the aAs semiconductor substrate 13, the Al composition ratio is 0.45 to
N-AlGaAs lower cladding layer 2 in the range of 0.6
Active layer 3 having a multiple quantum well structure (MQW structure) of a GaAs layer and an AlGaAs layer having an Al composition ratio of 0.2 or less.
a, p-A having an Al composition ratio in the range of 0.45 to 0.6
lGaAs first upper cladding layer 4, p-AlGaAs etching stopper layer 5, Al composition ratio greater than 0.6
l-p-AlGa having a composition ratio in the range of 0.45 to 0.6
As second upper cladding layer 7, p-GaAs contact layer 1
2a is sequentially epitaxially grown by MOCVD in this order. In this case, the Al composition ratio was 0.45 to
The thickness of the p-AlGaAs first upper cladding layer 4 in the range of 0.6 is adjusted to the range of 0.4 to 0.5 μm. Next, as shown in FIG. 4A, the p-GaAs contact layer 1 is formed by using the striped SiO2 film 9 as a mask and an etching solution comprising a mixed solution of tartaric acid and hydrogen peroxide.
2a, p-AlGaAs second upper cladding layer 7 is removed by etching, and the p-AlGa
The p-AlGaAs etching stopper layer 5 is etched away by using a sulfuric acid-based etching solution to expose the As etching stopper layer 5, and the p-AlGaAs etching stopper layer 5 has an Al composition ratio in the range of 0.45 to 0.6. -The AlGaAs first upper cladding layer 4 is etched away by a predetermined thickness, and p-
An AlGaAs first upper cladding layer 4 is formed on the active layer 3a in a thickness of 0.1 mm.
A ridge is formed leaving a thickness of 2 to 0.3 μm. Here, as described in the first to third embodiments, the etching solution composed of a mixture of tartaric acid and hydrogen peroxide is used as described above.
Etching is exhibited for AlGaAs having an Al composition ratio of 0.45 to 0.6, and is not exhibited for AlGaAs having an Al composition ratio of greater than 0.6. The sulfuric acid-based etchant is AlGaAs of AlGaAs.
The AlGaAs is etched without showing a selectivity in the composition ratio. Next, an n-GaAs current blocking layer 10 is formed on the p-AlGaAs first upper cladding layer 4 having an Al composition ratio of 0.45 to 0.6 exposed on both sides of the ridge.
4 (b), Zn is diffused into the n-GaAs current blocking layer 10 by diffusing Zn as a p-type dopant into the n-GaAs current blocking layer 10 using the SiO2 film 9 in the form of a stripe as a mask. And the n-GaAs
After the Zn diffusion layer 13 is formed in the upper layer of the current blocking layer 10, the striped SiO2 film 9 is removed by plasma etching using CHF3 gas and O2 gas. When formed, the ridge waveguide type semiconductor laser shown in FIG. 3 is completed.

In the manufacturing process of the semiconductor laser according to this embodiment, when the ridge is formed, the etching is temporarily stopped by the p-AlGaAs etching stopper layer 5 having an Al composition ratio larger than 0.6, and the p-AlGaAs etching stopper is stopped. The amount of etching from layer 5, ie, p-AlGaAs
The amount of etching of the s etching stopper layer 5 and the p-AlGaAs first upper cladding layer 4 depends on the amount of etching.
Remaining ridge thickness (p-AlGaAs first upper cladding layer 4
(Remaining thickness) is adjusted, so that a laser structure having an excellent light confinement effect and having a ridge remaining thickness accurately adjusted to 0.2 to 0.3 μm can be formed with good reproducibility. In addition, the ridge remaining thickness is 0.2 to 0.3 μm
In the case of obtaining the laser structure of p-AlGaAs,
The upper cladding layer 4 can be formed to a thickness larger than 0.3 μm (here, 0.4 to 0.5 μm), and as a result, as shown in FIG. P-AlGaAs having an Al composition ratio of more than 0.6 to 3a
The interval between the s etching stopper layers 5 is increased as compared with the prior art, and the refractive index of the active layer 3a is smaller than that of the active layer 3a.
-The refractive index of the AlGaAs etching stopper layer 5 has an exponential effect on the distance from the active layer 3a, and the asymmetry of the intensity distribution of the laser light beam can be improved. Further, the n-GaAs current blocking layer 1
0 is p-AlGaAs which has been strongly oxidized by wet etching with an Al composition ratio of 0.6 or more as in the prior art.
Not formed on the upper surface of the second etching stopper layer 5,
P-A having a composition ratio of 0.45 to 0.6 and a small degree of oxidation
Since it is formed on the lGaAs first upper cladding layer 4, for example, when the Al composition ratio is 0.5, the surface defect density is about 10 ⁴ / cm ² , and the surface defect density is smaller than the conventional one. It is possible to obtain a laser structure which can be formed with high crystal quality (conventional surface defect density is 10 ⁶ / cm ² or more) and an increase in leakage current is suppressed.

Accordingly, the semiconductor laser of the present embodiment obtained by such a manufacturing process has an excellent light confinement effect and prevents an increase in light emission loss and deterioration of the laser end face, similarly to the semiconductor laser of the above embodiment. In addition, a high-performance ridge waveguide semiconductor laser with an oscillation wavelength of about 800 nm, in which an increase in leakage current is suppressed, is provided.

In the first to fourth embodiments, a mixed solution of tartaric acid and aqueous hydrogen peroxide is used as an etching solution for forming the ridge. However, the mixed solution is not compatible with other organic acids such as citric acid and maleic acid. A mixed solution with hydrogen peroxide solution may be used.

In the first to third embodiments, after forming the ridge, the n-GaAs current blocking layer 10 is formed on both sides of the ridge.
And buried with a p-GaAs second cap layer, then p-G
Although the aAs contact layer 12 was epitaxially grown,
After embedding both sides of the ridge with only the n-GaAs current blocking layer 10, the p-GaAs contact layer 12 may be epitaxially grown. Also, as in the fourth embodiment, both sides of the ridge are n-type. After embedding with only the GaAs current blocking layer 10, a p-type dopant may be diffused into the n-GaAs current blocking layer 10 to form a p-type diffusion layer in the upper layer of the n-GaAs current blocking layer 10. .

(Embodiment 5) FIG. 5 is a sectional view showing a structure of a semiconductor laser according to a fifth embodiment of the present invention, and FIG. 6 is a sectional view showing a manufacturing process of the semiconductor laser shown in FIG. FIG. In these figures, the same reference numerals as those in FIGS. 1 and 2 denote the same or corresponding parts, 3b denotes an undoped GaAs active layer, 4a denotes a p-AlGaAs upper cladding layer, 5a denotes a p-type layer having an Al composition ratio of 0.3 or more. AlGaAs
An etching stopper layer, 8a is a p-GaAs cap layer, 9a and 9b are SiO2 films, 10a is n-GaAs having the same crystal composition as the n-GaAs current blocking layer 10.
The layer 15 is a resist film.

Hereinafter, the manufacturing process will be described. First, FIG.
As shown in (a), an n-AlGaAs lower cladding layer 2 and an undoped GaAs are formed on an n-GaAs (100) substrate 40.
s active layer 3b, p-AlGaAs upper cladding layer 4a, p
The -GaAs cap layer 8a and the p-AlGaAs etching stopper layer 5a are epitaxially grown in this order by MOCVD or the like so that each layer has a predetermined thickness. Next, as shown in FIG.
Forming a SiO2 film on the upper surface of the GaAs cap layer 8a;
The width is 10μ by ordinary photoengraving and etching technology
m or more stripe-shaped SiO extending in the <011> direction
2 film 9a is formed, and using the SiO2 film 9a as a mask,
The p-AlGaAs etching stopper layer 5a and the p-GaAs cap layer 8a having a composition ratio of 0.3 or more are etched and removed, and the p-AlGaAs upper cladding layer 4a is etched and removed by a predetermined thickness to form a ridge. Next, as shown in FIG. 6 (c), a stripe-shaped Si having a width of 10 μm or more is formed by using ordinary photolithography and etching techniques.
The inner portion of the O2 film 9a is removed so that both side edges thereof remain at a predetermined width, and a narrow S film is formed on the edge of the upper surface of the ridge.
After forming the iO2 film 9b, as shown in FIG. 6 (d), using the SiO2 film 9b as a mask, the p-sides on both sides of the ridge exposed by the ridge formation are formed by MOCVD or the like.
An n-GaAs current blocking layer 10 is epitaxially grown on the AlGaAs upper cladding layer 4a. At this time, Si
The above p-AlG exposed by etching the O2 film 9a.
n-GaAs is also formed on the aAs etching stopper layer 5a.
N-GaAs having the same crystal composition as the current blocking layer 10
The layer 10a is formed. Next, as shown in FIG.
N-GaAs current blocking layers 10 formed on both sides of the ridge
Then, a resist film 15 is formed so as to cover the upper surface of the ridge and the upper surface of the portion of the SiO2 film 9b on the ridge adjacent to the n-GaAs current blocking layer 10, and then, as shown in FIG. Using the resist film 15 as a mask, the n-GaAs layer 10a formed on the p-AlGaAs etching stopper layer 5a is removed by, for example, wet etching using a mixed solution of ammonia and hydrogen peroxide as an etching solution. At this time, the mixed solution of ammonia and hydrogen peroxide
The p-AlGaAs etching stopper layer 5a having an Al composition ratio of 0.3 or more does not exhibit etching properties, and n-
The n-type GaAs current blocking layer 10 having the same crystal composition
Only the GaAs 10a is removed. Next, the resist film 1
5 is dissolved and removed with a predetermined solvent.
After b was removed by plasma etching using CHF3 gas and O2 gas, as shown in FIG.
When the GaAs contact layer 12 is epitaxially grown by MOCVD or the like, and then a p-side electrode and an n-side electrode (not shown) are formed, the semiconductor laser shown in FIG. 5 is completed.

In the manufacturing process of the semiconductor laser according to the present embodiment, the n-GaAs current blocking layer 10 formed on both sides of the ridge is etched on the upper surface of the p-GaAs cap layer 8a in advance. P-AlGa having an Al composition ratio not exhibiting etchability of 0.3 or more with respect to an etchant comprising a mixed solution of ammonia and hydrogen peroxide shown in FIG.
An As etching stopper layer 5a is formed beforehand, and the width of the S used for forming a wide ridge having a width of 10 μm or more is formed.
The inner portion of the iO2 film 9a is removed after forming the ridge,
Since the n-GaAs current blocking layer 10 is epitaxially grown while the narrow SiO2 film 9b is left on both side edges of the ridge, the narrow width of the n-GaAs current blocking layer 10 is increased during the growth of the n-GaAs current blocking layer 10. No semiconductor layer (n-GaAs layer) is formed on the SiO2 film 9b, and only the above-described ammonia and the ammonia are formed only on the p-AlGaAs etching stopper layer 5a having an Al composition ratio of 0.3 or more in the uppermost layer of the wide ridge. An n-GaAs layer 10a having a crystal composition similar to that of the n-GaAs current blocking layer 10 which can be selectively removed with an etching solution comprising a mixed solution of hydrogen peroxide is formed. The GaAs layer 10a is removed with an etching solution comprising a mixture of ammonia and hydrogen peroxide, and the SiO2 film 9b is removed by plasma etching. Can its width completely removing the insulating film from the above wide ridge 10 [mu] m, for good reproducibility forming a semiconductor laser with a desired laser structure.

(Embodiment 6) FIG. 7 is a sectional view showing a structure of a semiconductor laser according to a fifth embodiment of the present invention, and FIG. 8 is a sectional view showing a manufacturing process of the semiconductor laser shown in FIG. FIG. In these figures, the same reference numerals as those in FIGS. 1, 2, 6, and 7 indicate the same or corresponding parts, and 9
c and 15a are resist films.

Hereinafter, the manufacturing process will be described. First, similarly to the fifth embodiment, as shown in FIG.
The as (100) substrate 40 n-AlGaAs lower cladding layer 2 on the undoped GaAs active layer 3b, p-AlGa
As upper cladding layer 4a, p-GaAs cap layer 8a,
A p-AlGaAs etching stopper layer 5a having an Al composition ratio of 0.3 or more is epitaxially grown by MOCVD or the like so that each layer has a predetermined thickness in this order. Next, as shown in FIG.
A stripe-shaped resist film 9c having a width of 10 μm or more and extending in the <011> direction is formed on the upper surface of the aAs cap layer 8a by ordinary photoengraving. Using the resist film 9c as a mask, the Al composition ratio is 0.3. The above p-AlGaAs
The s etching stopper layer 5a and the p-GaAs cap layer 8a are removed by etching, and the p-AlGaAs upper cladding layer 4a is removed by etching to a predetermined thickness to form a ridge. Next, as shown in FIG.
After removing c, an n-GaAs layer is epitaxially grown on the entire surface of the n-GaAs substrate 40 by MOCVD or the like, as shown in FIG. 8D, the p-AlGaAs upper cladding layer on both sides of the ridge. N-GaAs on 4a
A current blocking layer 10 is formed, and p-AlG on the upper surface of the ridge is formed.
The above n-GaAs is formed on the aAs etching stopper layer 5a.
Or similar crystal composition as the current blocking layer 10 Rana Ru n-GaAs
The layer 10a is formed. Next, as shown in FIG.
The resist film 15 is formed by a normal photolithography technique so as to cover both side edges of the n-GaAs layer 10a on the ridge and the upper surface of the n-GaAs current blocking layer 10 formed on both sides of the ridge.
is formed, and n-G is formed using the resist film 15a as a mask.
When the aAs layer 10a is removed by wet etching using a mixed solution of ammonia and hydrogen peroxide as an etchant, and then the resist film 15a is dissolved and removed with a predetermined solvent, as shown in FIG. Only at both ends of the upper surface of the ridge, the angular n-GaAs layer 10b remains. Here, the resist film 15a is provided so as to cover both end portions of the n-GaAs film 10a on the ridge by wet etching using a mixed solution of ammonia and hydrogen peroxide as an etching solution. This is to ensure that the portion of the n-GaAs current blocking layer 10 adjacent to the ridge formed on both sides of the n-GaAs current blocking layer 10 is not removed so that the portion of the n-GaAs current blocking layer 10 adjacent to the ridge is not removed. In addition, the mixed solution of ammonia and hydrogen peroxide does not exhibit etching properties with respect to the p-AlGaAs etching stopper layer 5a having an Al composition ratio of 0.3 or more,
Only the n-GaAs 10a is removed by etching. next,
As shown in FIG. 8 (g), the p-GaAs contact layer 12
Is epitaxially grown by MOCVD or the like, and then an n-side electrode and a p-side electrode are formed, whereby the semiconductor laser shown in FIG. 7 is completed. In the above process, the semiconductor laser is completed with the square n-GaAs layers 10b remaining at both ends of the upper surface of the ridge.
Layer 10b does not adversely affect the operating characteristics of the laser.

In the manufacturing process of the semiconductor laser according to this embodiment, the n-GaAs current blocking layer 10 formed on both sides of the ridge is etched on the upper surface of the p-GaAs cap layer 8a in advance. P-AlGa having an Al composition ratio not exhibiting etchability of 0.3 or more with respect to an etchant comprising a mixed solution of ammonia and hydrogen peroxide shown in FIG.
After forming the As etching stopper layer 5a, the resist film 15a used for forming a wide ridge having a width of 10 μm or more is completely removed after the formation of the ridge, and in this state, the n-GaAs layer is removed. Epitaxial growth,
Since the n-GaAs current blocking layer 10 is formed on both sides of the ridge, a p-type layer formed simultaneously with the n-GaAs current blocking layer 10 and having a ridge Al composition ratio of 0.3 or more is formed.
-The n-GaAs layer 10a formed on the AlGaAs etching stopper layer 5a can be selectively removed with an etching solution comprising a mixture of ammonia and hydrogen peroxide without leaving a resist film on the ridge. A semiconductor laser having a predetermined laser structure can be formed with good reproducibility.

In the fifth and sixth embodiments, the p-AlGaAs etching stopper layer 5a having an Al composition ratio of 0.3 or more is used to remove the n-GaAs layer 10a formed on the ridge. Although a mixed solution of ammonia and hydrogen peroxide was used as a liquid, a p-GaInp layer was used as an etching stopper layer, and an n-
The same effect can be obtained by using hydrochloric acid as an etchant for removing the GaAs layer 10a.

[0056] Also, the fifth embodiment has formed the stripe-like resist film 9c in SiO2 film 9a and the sixth embodiment of stripes <011> direction in the example, these <0/11> direction The same effect can be obtained by forming the same.

In the fifth and sixth embodiments, p-
The semiconductor laser was completed while leaving the AlGaAs etching stopper layer 5a on the ridge, but after removing the n-GaAs layer 10a formed on the ridge, a p-AlGaAs etching stopper layer such as a hydrofluoric acid-based etching solution was used. 5a is etched, but the p-GaAs cap layer 8 is etched.
An etchant that does not exhibit etchability with respect to a.
-AlGaAs etching stopper layer 5a may be removed by etching.

In the fifth embodiment, the resist film 15 is used as a mask for removing the n-GaAs layer 10a formed on the ridge.
Alternatively, an insulating film such as a SiO2 film may be used. In this case, after removing the n-GaAs layer 10a,
The insulating film such as the film 2 can be removed by etching together with the SiO2 film 9b on the ridge.

In the sixth embodiment, the resist film 9c is used as a mask for forming the ridge. However, an insulating film such as a SiO2 film may be used instead of the resist film 9c. N-GaAs layer 10a formed in
Although the resist film 15a is used as a mask for removing the resist film 15, an insulating film such as a SiO2 film may be used instead of the resist film 15.

In the fifth and sixth embodiments, a semiconductor laser using an AlGaAs-based material for the active layer has been described. However, the present invention relates to an InGaAsP-based material, an InGaAs-based material, and an AlGaInP-based material for the active layer. Needless to say, it can be applied to a semiconductor laser using
In this case, the active layer is made of InGaAsP-based material, InGaAs.
In a semiconductor laser using an s-based material, an InGaAsP layer is used as an etching stopper layer formed on a ridge, hydrochloric acid or the like is used as an etchant having no etching property with respect to the InGaAsP layer, and an Al layer is used as an active layer.
In a semiconductor laser using a GaInP-based material, an AlGaAs layer is used as an etching stopper layer formed on a ridge, and a mixed solution of ammonia and hydrogen peroxide is used as an etchant having no etching property with respect to the AlGaAs layer.

[0061]

As described above, the semiconductor laser according to the present invention is provided.
According to chromatography The, AlGaAs Al composition ratio of 0.6 or less
The lower cladding layer, the active layer and the first
Laminated structure having upper clad layer and surface of this laminated structure
GaAs disposed above and thinner than the first upper cladding layer
A thin layer and a part of the GaAs thin layer extend in the light guiding direction.
And the Al composition ratio is 0.6
AlGaAs thinner that exceeds and is thinner than the first upper cladding layer
Layer and on top of this AlGaAs thin layer, along the stripe
A in which the Al composition ratio is 0.6 or less
a second upper cladding layer made of 1GaAs,
2 GaAs thin layer so as to bury both sides of the upper cladding layer
And a current blocking layer disposed thereon.
The crystal quality of the blocking layer is improved and the leakage current is reduced.
High performance semiconductor laser with low light emission loss
User can be configured.

Further , AlGa having an Al composition ratio of 0.6 or less is used.
The lower cladding layer, the active layer, and the
(1) a laminated structure having an upper clad layer;
It is disposed on the surface and has an Al composition ratio of 0.3 except for GaAs.
First AlG that is less than and thinner than the first upper cladding layer
a thin layer of aAs and a part of the first thin layer of AlGaAs.
Arranged in a stripe shape extending in the light waveguide direction,
Composition ratio exceeds 0.6 and thinner than the first upper cladding layer
A second thin AlGaAs layer and the second AlGaAs
On a thin layer, it is arranged in a ridge along the stripe,
It was composed of AlGaAs having an Al composition ratio of 0.6 or less.
A second upper cladding layer and both sides of the second upper cladding layer
Embedded on the first AlGaAs thin layer so as to embed
And a current blocking layer,
Good quality and reduced leakage current
From high-performance semiconductor lasers with low emission loss
Wear.

Further, the first upper cladding layer and the GaAs thin
The sum of the thickness of the first layer and the first AlGaAs thin layer is set to 0.
2 to 0.3 μm, good light confinement effect
High-performance semiconductor laser with less deterioration of the laser end face
Can be configured. AlG having an Al composition ratio of 0.6 or less
The lower cladding layer and the active layer each composed of aAs
A laminated structure having, disposed on the surface of the laminated structure,
It is composed of AlGaAs having an Al composition ratio of 0.6 or less,
Partially projecting ridges extending in the direction of light propagation
A flat portion extending flat on both sides of the protrusion and the protrusion to cover the active layer.
A first upper cladding layer having a base portion;
Al group disposed over the top of the protrusion of the lad layer
The composition ratio exceeds 0.6 and is thinner than the first upper cladding layer
An AlGaAs thin layer, and a second AlGaAs thin layer
1, disposed on the protrusion of the upper cladding layer, and the Al composition ratio
Is a second upper cladding made of AlGaAs of 0.6 or less.
Layer, the second upper cladding layer and the first upper cladding layer.
Planarization of the first upper cladding layer so as to bury the protrusion of the layer
And a current blocking layer disposed on the portion.
The thickness of the flat part of the upper cladding layer can be precisely adjusted,
Because it can be formed with excellent retraction effect and good reproducibility,
Inexpensive, reliable, high-performance
A conductor laser can be configured.

Also, a method of manufacturing a semiconductor laser according to the present invention.
According to the method, the Al composition ratio is 0.6 or less on the semiconductor substrate.
Lower cladding layer composed of AlGaAs, active
Layer and a first upper cladding layer,
a first AlGaAs thin layer having a composition ratio of less than 0.3;
a second AlGaAs thin layer having a composition ratio of more than 0.6;
And a second overcoat of AlGaAs having an Al composition ratio of 0.6 or less.
A first step of sequentially stacking the lad layers, and a second upper cladding.
Forming a striped insulating film on the surface of the
Organic acid and hydrogen peroxide were mixed using the edge film as a mask
Exposing second AlGaAs thin layer using etchant
To form a striped ridge
The second step and the second AlGaAs exposed in the second step
s thin layer is removed, exposing the first AlGaAs thin layer
A third step, and the first A is buried on both sides of the ridge.
Fourth Step of Forming a Current Blocking Layer on the lGaAs Thin Layer
And exposing the first AlGaAs thin layer.
In the third step, the degree of oxidation of the first thin AlGaAs layer is reduced.
To form a current blocking layer with good crystal quality.
High performance semiconductor with low light emission loss
Lasers can be easily manufactured. In addition, the third
In the step, the removal of the second AlGaAs thin layer is performed using hydrofluoric acid.
Wet etching with a system-based etchant
The first AlGaAs thin layer and the second AlGaAs
under high etch selectivity between the first A
By leaving the thickness of the lGaAs thin layer accurately, the second AlG
aAs thin layer can be removed and laser end face degradation
It is easy to manufacture few high-performance semiconductor lasers.
Wear.

Further, the second step formed in the first step
When the Al composition ratio of the AlGaAs thin layer is set to 0.8 or more,
First, the removal of the second AlGaAs thin layer in the third step is boiled.
Wet etching using hydrochloric acid
Therefore, the first AlGaAs thin layer and the second AlG
Under high etch selectivity with a thin layer of aAs, the first
The thickness of the AlGaAs thin layer of the second A
The thin layer of lGaAs can be removed, and the laser end face is inferior.
Easy production of high performance semiconductor lasers
Can be. AlGaAs having an Al composition ratio of 0.6 or less
s, a lower cladding layer, an active layer, and
The first upper cladding layer is sequentially laminated, and the Al composition ratio is further increased.
AlGaAs thin layer exceeding 0.6 and Al composition ratio
0.6 second or less AlGaAs second upper cladding layer
A first step of laminating and a second step on the surface of the upper cladding layer
Form a striped insulating film and use this insulating film as a mask.
And etchant mixed with organic acid and hydrogen peroxide
Etching until a thin layer of AlGaAs is exposed using
A second step of forming a stripe-shaped ridge;
Using an etchant with low selectivity to aAs
The thin AlGaAs layer is removed and the first upper layer is continuously formed.
A part of the cladding layer is removed and the first upper cladding on both sides of the ridge is formed.
A third step of forming the pad layer from the active layer to a predetermined size.
Burying both sides of the ridge after the step and the third step
Current blocking layer on first upper cladding layer
And a fourth step, so that the first overhang on both sides of the ridge is provided.
Accurate and reproducible thickness of the lad layer from the active layer
Can be formed, laser end face is less deteriorated and reliable
Semiconductor laser with high yield
You.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of a ridge waveguide type semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the steps of manufacturing the ridge waveguide type semiconductor laser shown in FIG.

FIG. 3 is a sectional view showing a structure of a ridge waveguide type semiconductor laser according to a fourth embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the steps of manufacturing the ridge waveguide semiconductor laser shown in FIG.

FIG. 5 is a sectional view showing a structure of a ridge waveguide type semiconductor laser according to a fifth embodiment of the present invention.

6A to 6C are cross-sectional views showing the steps of manufacturing the ridge waveguide semiconductor laser shown in FIG.

FIG. 7 is a sectional view showing a structure of a ridge waveguide type semiconductor laser according to a sixth embodiment of the present invention.

8 is a cross-sectional view showing the steps of manufacturing the ridge waveguide semiconductor laser shown in FIG. 7;

FIG. 9 is a cross-sectional view showing the steps of manufacturing a conventional ridge waveguide semiconductor laser.

FIG. 10 is a cross-sectional view showing one step in a manufacturing process of a conventional ridge waveguide semiconductor laser.

FIG. 11 shows the refractive index and the laser of the active layer and the layers surrounding the active layer in the ridge waveguide semiconductor lasers according to the first and fourth embodiments of the present invention and the conventional ridge waveguide semiconductor laser. FIG. 4 is a diagram illustrating a relationship with a light beam intensity distribution.

[Explanation of symbols]

1 n-GaAs layer 2 n- with Al composition ratio in the range of 0.45 to 0.6
AlGaAs lower cladding layer 3 p-AlGaAs active layer 3a having an Al composition ratio of 0.2 or less AlGaAs having an Al composition ratio of 0.2 or less
active layer having a multiple quantum well structure with s 3b undoped GaAs active layer 4 p- with an Al composition ratio in the range of 0.45 to 0.6
AlGaAs first upper cladding layer 4a p- with Al composition ratio in the range of 0.45 to 0.6
AlGaAs upper cladding layer 5 p-AlGaAs with Al composition ratio larger than 0.6
First etching stopper layer 5a p-AlGaAs with Al composition ratio larger than 0.6
Etching stopper layer 6 p-GaAs Second etching stopper layer 7 p- with Al composition ratio in the range of 0.45 to 0.6
AlGaAs second upper cladding layer 8 p-GaAs first cap layer 8a p-GaAs cap layer 9, 9a, 9b SiO2 film 9c, 15, 15a resist film 10 n-GaAs current blocking layer 10a, 10b n-GaAs layer 11p -GaAs second cap layer 12 p-GaAs contact layer 12a p-GaAs contact layer 13 Zn diffusion layer 20 p-side electrode 30 n-side electrode 40 n-GaAs substrate 51 n-GaAs layer 52 n with an Al composition ratio of 0.5 -AlGaAs lower cladding layer 53 p-AlGaAs active layer 54 p-AlGaAs first upper cladding layer 55 with an Al composition ratio of 0.5 p-AlGaAs etching stopper layer 57 with an Al composition ratio of 0.65 An Al composition ratio of 0. 5 p-AlGaAs second upper cladding layer 58 p-GaAs first cap layer 59 iO2 film 60 n-GaAs current blocking layer 60a polycrystalline film 61 p-GaAs second cap layer

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hirotaka Kitsuki 4-1-1 Mizuhara, Itami-shi, Hyogo Mitsubishi Electric Co., Ltd. Optical and Microwave Device Research Laboratory (72) Inventor Kotaro Mitsui 4-chome, Mizuhara, Itami-shi, Hyogo No. 1 Mitsubishi Electric Corp. Optical and Microwave Devices Laboratory (56) References JP-A-5-335681 (JP, A) JP-A-4-356990 (JP, A) JP-A-3-49289 (JP) JP-A-1-304793 (JP, A) JP-A-3-296290 (JP, A) JP-A-3-222385 (JP, A) JP-A-1-236676 (JP, A) 2-42791 (JP, A) JP-A-4-245490 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01S 3/18

Claims (8)

(57) [Claims] An Al composition is sequentially laminated on a semiconductor substrate.
The lower part made of AlGaAs having a ratio of 0.6 or less, respectively.
A product having a cladding layer, an active layer and a first upper cladding layer
A layer structure; and a first upper cladding disposed on a surface of the laminated structure.
A GaAs thin layer thinner than the doped layer, and a part extending on the GaAs thin layer extending in the light guiding direction.
Arranged in triplicate, Al composition ratio exceeds 0.6 and
AlGaAs thin layer thinner than the first upper cladding layer
On the thin AlGaAs layer, along the stripe
A ridge-shaped AlGaAs having an Al composition ratio of 0.6 or less is arranged in a ridge shape .
2 and the above G so as to embed both sides of the second upper cladding layer.
semiconductor laser and a current blocking layer disposed aAs thin layer. 2. An Al composition which is sequentially laminated on a semiconductor substrate.
The lower part made of AlGaAs having a ratio of 0.6 or less, respectively.
A product having a cladding layer, an active layer and a first upper cladding layer
A layered structure and an Al layer disposed on the surface of the layered structure except for GaAs.
The composition ratio is less than 0.3 and the first upper clad layer
A thin first AlGaAs thin layer, and a part of the first AlGaAs thin layer in a light guiding direction.
It is arranged in an extended stripe shape, and the Al composition ratio is 0.6
And a second A that is thinner than the first upper cladding layer
On the thin layer of lGaAs and on the second thin layer of AlGaAs, the stripe
Along the ridge, the Al composition ratio is 0.6 or less
A second upper cladding layer made of AlGaAs, and the second upper cladding layer so as to embed both sides of the second upper cladding layer.
Semiconductor laser and a current blocking layer disposed on one of the AlGaAs thin layer. 3. A GaAs thin layer and a first upper cladding layer.
Means that the total thickness of the first AlGaAs thin layer is 0.2 to 0.2
3. The method according to claim 1, wherein the thickness is 0.3 μm.
The semiconductor laser of the mounting. 4. An Al composition which is sequentially laminated on a semiconductor substrate.
The lower part made of AlGaAs having a ratio of 0.6 or less, respectively.
A layered structure having a cladding layer and an active layer, and disposed on the surface of the layered structure;
It is composed of 6 or less AlGaAs, and a part of it is in the waveguide direction of light.
Of the ridge extending in the shape of a ridge
A flat portion extending flat on both sides and covering the active layer
A first upper cladding layer; and a first upper cladding layer disposed over the top of the protrusion.
Provided that the Al composition ratio exceeds 0.6 and the first
An AlGaAs thin layer thinner than the cladding layer, and
Al is disposed on the protruding portion and has an Al composition ratio of 0.6 or less.
A second upper cladding layer made of GaAs, and the protrusions of the second upper cladding layer and the first upper cladding layer.
A flat portion of the first upper cladding layer so as to bury the protrusion.
And a current blocking layer disposed thereon . 5. An Al composition ratio of 0.6 or less on a semiconductor substrate.
Lower cladding layer composed of AlGaAs
An active layer and a first upper cladding layer,
A first AlGaAs thin layer having an Al composition ratio of less than 0.3, A
a second AlGaAs thin layer having a composition ratio of more than 0.6;
And a second overcoat of AlGaAs having an Al composition ratio of 0.6 or less.
A first step of sequentially stacking a lad layer, and forming a stripe-shaped insulating film on the surface of the second upper cladding layer.
Then, using this insulating film as a mask, an organic acid and
Second AlGaAs using an etching solution mixed with silicon
s Etch until the thin layer is exposed
A second step of forming an edge, and removing the second AlGaAs thin layer exposed in the second step.
A third step of exposing the first AlGaAs thin layer
And a first AlGaAs thin layer so as to bury both sides of the ridge.
The method of manufacturing a semiconductor laser comprising a fourth step, the forming a current blocking layer on top of. 6. In a third step, a second AlGaAs is formed.
Remove the thin layer by using a hydrofluoric acid-based etchant.
5. The method according to claim 4, wherein the etching is performed by etching.
Manufacturing method of the semiconductor laser described above. 7. A second AlGaAs formed in a first step.
The Al composition ratio of the s thin layer is set to 0.8 or more and the third
The removal of the second thin layer of AlGaAs in the process
This should be performed by wet etching using an etchant.
5. The method of manufacturing a semiconductor laser according to claim 4, wherein
Law. 8. An Al composition ratio of 0.6 or less on a semiconductor substrate.
Lower cladding layer composed of AlGaAs
An active layer and a first upper cladding layer,
An AlGaAs thin layer having an Al composition ratio of more than 0.6;
1 The second upper cladding of AlGaAs having a composition ratio of 0.6 or less.
A first step of sequentially laminating the gate layers, and forming a stripe-shaped insulating film on the surface of the second upper cladding layer.
Then, using this insulating film as a mask, an organic acid and
AlGaAs thin layer using an etching solution mixed with silicon
Until the ridges are exposed.
A second step of forming, and using an etching solution having low selectivity to AlGaAs.
To remove the thin layer of AlGaAs and continuously
1 to remove the upper cladding layer and remove the first
The thickness of the upper cladding layer from the active layer is
A third step, and after the third step, the first step is performed so as to bury both sides of the ridge.
Fourth step of forming a current blocking layer on the upper cladding layer
And a method of manufacturing a semiconductor laser including :