JPH0740623B2 - Semiconductor laser manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an embedded semiconductor laser which is important as a light source for optical fiber communication.

[0002]

2. Description of the Related Art As a structure of a semiconductor laser, a buried hetero structure is widely used in which a periphery of an active layer is covered with a semiconductor material having a larger energy gap and a smaller refractive index. This embedded heterostructure semiconductor laser has attracted attention as a light source for optical fiber communication because it has excellent characteristics such as a low oscillation threshold current value and stable oscillation transverse mode.

As a conventional manufacturing method, for example, there is one described in Technical Report OQE85-8, P55 of the Institute of Electronics, Information and Communication Engineers. A conventional manufacturing method is shown in FIG.

As shown in FIG. 7A, first, an n-InGaAsP optical guide layer 5 is formed on an n-InP substrate 101 whose main surface is a (100) substrate.
01, the InGaAsP active layer 103, the p-InGaAsP buffer layer 502, and the p-InP clad layer 503 with a thickness of about 1.5 μm are epitaxially grown in this order, and then the stripes are formed on the p-InP cladding layer 503 in the <011> direction. The mask pattern is formed of an insulating film 504 such as SiO ₂ or Si ₃ N ₄ (FIG. 7B). Next, the p-InP clad layer 503 is formed.
Is an etchant of InP and InGaAsP after selective etching of a mixed solution of hydrochloric acid and phosphoric acid (Fig. 7 (c)).
Mesa Stripe 505 by etching with Br-methanol solution
Are formed (FIG. 7D). Finally, after removing the insulating film 504, the p-InP current blocking layer 108 and the n-InP current blocking layer 109 are grown by a liquid phase epitaxial growth method so as not to be stacked on the cladding layer 503 of the mesa stripe 505. A p-InP buried layer 110 and a p-InGaAsP contact layer 111 are grown to form a buried hetero structure.
(FIG.7 (e)).

[0005]

However, as a problem of the manufacturing method of the above constitution, the use of Br-methanol solution
In etching, Br easily evaporates and the change over time is large, resulting in large variations in the etching rate.
There is a problem that it is difficult to control the stripe width of 03.

In addition, when the Br-methanol solution is etched, the stripe shape becomes an inverted mesa. Here, thinning the p-InP cladding layer 503 reduces the voltage applied to the n-InP current blocking layer 109 formed during the buried epitaxial growth, and suppresses the thyristor operation and the output saturation during the high output operation, It is also effective from the standpoint of improving temperature characteristics. Usually, the mesa stripe 505 needs to have a height enough to fill both sides of the current blocking layers 108 and 109, and therefore etching must be performed until the height is obtained. However, the clad layer 503 is 1μ
When the thickness is reduced to about m, the InGaAsP active layer 103 comes to be located above the constriction as shown in FIG. 8, and it is easy to form an interface state on the side surface of the active layer during crystal growth (111) A plane 601. It has been confirmed in our experiments that the laser characteristics are deteriorated such that the threshold current value is increased and the laser characteristics are deteriorated.

Besides the Br-methanol solution used for etching, a mixed solution of hydrogen peroxide solution and hydrochloric acid is known as an etchant for InP and InGaAsP. However, if a wafer with a stripe-shaped insulating film mask formed in the <011> direction on the p-InP clad layer 503 is etched with this etching solution as in the conventional case, the reverse mesa like the Br-methanol solution is etched. Because of the shape, good laser characteristics cannot be obtained.

Therefore, there is a need for a method in which the shape of the mesa stripe does not become an inverted mesa. As one method of not exposing the (111) A surface 601 by etching the Br-methanol solution,
There is a method using a negative resist mask. As shown in FIG. 9, the resist has poor adhesion to the semiconductor wafer as compared with the insulating film, and a side etch is formed under the resist mask 701.
Therefore, the mesa stripe 700 becomes narrower in the width direction than the resist 701. This is convenient because the etching shape generally becomes a forward mesa and the (111) A plane 601 which is likely to form an interface state is not exposed. However, the resist mask 701 and the p-InP clad layer 50
The degree of adhesion with 3 is not stable, and the shape of the mesa stripe 700 formed by etching changes, and the control of the stripe width becomes unstable.

Further, in the conventional buried epitaxial growth, since the uppermost layer of the mesa stripe is the p-InP clad layer 503, the p-In layer is soaked before the current block layer is soaked.
Direct exposure of the P-clad layer 503 causes dissociation of P atoms with high vapor pressure, and the resulting defects are
-If the InP clad layer 503 is thin, p-InP clad layer 503
Not only that, it may reach the interface between the p-InP cladding layer 503 and the InGaAsP active layer 103, which may reduce the emission efficiency of the laser and adversely affect the reliability.

As mentioned above, B is used as an etchant for InP and InGaAsP.
Etching with a r-methanol solution or a mixture of hydrogen peroxide and hydrochloric acid makes the stripe shape an inverted mesa, making it difficult to control the stripe width, and reducing the thickness of the p-InP cladding layer causes the side surface of the active layer (111). There is a problem that the laser characteristics are deteriorated by exposing the A surface.

Further, according to the conventional manufacturing method, p-InP is used when soaking the buried epitaxial growth of the current block layer.
The direct exposure of the clad layer causes defects in the p-InP clad layer, which causes deterioration of laser characteristics and reliability. Therefore, there is a problem that the p-InP clad layer cannot be made very thin.

An object of the present invention is to improve the stripe width controllability of the mesa stripe in the etching process and to stabilize the side surface of the active layer in order to stably manufacture an embedded semiconductor laser having good laser characteristics and high reliability. To (1
11) To obtain a mesa stripe in which the A-plane is not exposed and to prevent a defect from occurring in the p-InP cladding layer during the buried epitaxial growth.

[0013]

In order to solve the above-mentioned problems, the present invention provides an InGaAsP active layer and a second conductivity type on an InP substrate of the first conductivity type whose main surface is a (100) plane. A step of forming a semiconductor multilayer film structure having an InP clad layer and an InGaAsP surface protective layer on the uppermost layer, and <011> on the surface protective layer.
Forming a stripe-shaped insulating film mask in a direction, and using the insulating film mask as a mask, the InGaA adjacent to both sides of the stripe-shaped mask is etched by a mixed solution containing hydrochloric acid and hydrogen peroxide solution.
a step of removing the sP surface protective layer, the second conductivity type InP clad layer, and the InGaAsP active layer to form a mesa stripe; and a step of stacking a current block layer by performing buried epitaxial growth on both sides of the mesa stripe. A method of manufacturing a semiconductor laser having

Further, a step of forming a diffraction grating for defining an oscillation wavelength on a first conductivity type InP substrate having a (100) plane as a main surface, and a first conductivity type InGaAsP light on the diffraction grating. A step of sequentially epitaxially growing a guide layer, an InGaAsP active layer, a second conductivity type InP clad layer, and a second conductivity type InGaAsP surface protective layer; and a striped insulating film as an etching mask on the surface protective layer. And etching with a mixed solution containing hydrochloric acid and hydrogen peroxide using the insulating film as a mask, and then etching the semiconductor layers adjacent to both sides of the striped mask with a mixed solution containing hydrochloric acid and phosphoric acid. And forming a mesa stripe by the method and a method for manufacturing a semiconductor laser in which a current block layer is formed on both sides of the mesa stripe by liquid phase epitaxial growth.

[0015]

As described above, in the method of forming the insulating film mask for etching on the InGaAsP surface protective layer and then etching with the mixed solution containing hydrochloric acid and hydrogen peroxide solution, since the surface protective layer is present, the mesa Since the shape of the stripe is a regular mesa, the (111) A plane is not exposed and the laser characteristics do not deteriorate. Further, since the change with time of the etching solution is smaller than that of Br-methanol, the controllability of the stripe width is improved.

Further, in the present invention, even when the p-InP clad layer is thinned, liquid phase epitaxial growth is carried out with the p-InGaAsP surface protective layer provided. Therefore, the surface of the p-InP clad layer is not exposed and vapor pressure Since the high P atoms are not dissociated, it is possible to prevent defects from being generated in the p-InP cladding layer and obtain a semiconductor laser having good characteristics.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a first embodiment of the present invention. First, as shown in FIG. 1A, an n-InP buffer layer 102 having a thickness of 5 μm and a thickness of 0.2 μm is formed on an n-InP substrate 101 having a (100) plane as a main surface.
The InGaAsP active layer 103, the p-InP cladding layer 104 with a thickness of 1.0 μm or more, and the p-InGaAsP surface protective layer 105 with a thickness of 0.2 μm are sequentially epitaxially grown by the liquid phase epitaxial growth method on the semiconductor multilayer film structure wafer, After depositing an insulating film such as SiO ₂ or Si ₃ N ₄ by CVD (or plasma CVD), an etching mask 106 having a stripe shape having a width of 8 μm parallel to the <011> direction is formed by photolithography and dry etching. To form. The n-InP buffer layer 102 is etched to a depth of 2 μm below the InGaAsP active layer 103 with a mixed solution containing hydrochloric acid, hydrogen peroxide solution and acetic acid (volume ratio is 3: 1: 36) to form a mesa stripe 107 ( Figure 1
(B)). This etching solution is used for the InP-based multilayer structure on the (100) InP substrate in which the InGaAsP layer is laminated on the uppermost layer.
As in the case of the conventional example, when the insulating film mask having a stripe shape in the <011> direction is formed and etching is performed, a mesa stripe having a normal mesa shape is obtained, and therefore the (111) A surface 601 is not exposed on the side surface. At this time, the width of the uppermost layer of the mesa stripe 107 is about 1.5 μm.

Next, the insulating film 106 is removed with a hydrofluoric acid-based solution, and then the p-InGaAsP surface protective layer 105 is removed with a mixed solution of sulfuric acid and hydrogen peroxide solution, and then the mesa stripe 107 is formed by liquid phase epitaxial growth. P-InP current blocking layer 10 on both sides of
8, n-InP current blocking layer 109 to the mesa stripe 107 pI
It is grown selectively so that it does not grow on the nP cladding layer 104.
Let After that, p-InP buried layer 110 and p-InGaAsP
The contact layer 111 is sequentially grown to form a buried hetero structure. Generally, in liquid phase epitaxial growth, when the height of the mesa stripe is about 2 μm or more and the stripe width is about 5 μm or less, the n-InP current blocking layer 109 is not stacked on the mesa stripe 107, so that the mesa stripe is not formed. stripe
Good current blocking layers are formed on both sides of 107, and current is effectively injected into the active layer. In this method, since the stripe mask is an insulating film, the p-InGaAsP surface protection layer 105
Adhesion between the insulating film mask 106 and the insulating film mask 106 is good, and a regular mesa shape is stably obtained, and the (111) A surface 601 is not exposed on the side surface of the InGaAsP active layer 103.

In the first embodiment, the mesa stripe 10
For forming 7, an etchant of InP is a well-known mixed solution containing hydrochloric acid, hydrogen peroxide solution, and acetic acid (volume ratio 3: 1: 36). However, the mesa stripe does not become an inverted mesa as in the conventional case because the surface protective layer 105 is used on the p-InP clad layer 104. Due to this layer, the shape of the mesa stripe becomes a forward mesa structure convenient for the embedded laser even when it is etched with a mixed solution of hydrochloric acid, hydrogen peroxide and acetic acid.

FIG. 2 shows a second embodiment of the present invention. In FIG. 2A, light C is formed on the semiconductor multilayer film structure semiconductor wafer by epitaxial growth as in the first embodiment.
After depositing an insulating film such as SiO ₂ or Si ₃ N ₄ by VD (or plasma CVD), a strut having a width of 8 μm parallel to the <011> direction is formed by photolithography and dry etching.
An IP-shaped etching mask 106 is formed. The difference from the first embodiment is that the thickness of the p-InP cladding layer 201 is about 0.
This is a thin point of 3 μm. As described above, thinning the clad layer on the active layer reduces the voltage applied to the n-InP current block layer formed during buried epitaxial growth, and allows thyristor operation and output saturation during high power operation. This is because it is effective from the standpoint of suppressing the above, and further improving the temperature characteristics. Therefore, the n-InP buffer layer 102 is etched to a depth of about 3 μm below the InGaAsP active layer 103 with a mixed solution containing hydrochloric acid, hydrogen peroxide solution and acetic acid so that the mesa stripe has a predetermined height.
02 is formed (FIG. 2B). After removing the insulating film mask 106, the p-InP current blocking layer 108, the n-InP current blocking layer 109, and the p-InP buried layer are formed by liquid phase epitaxial growth.
110 and a p-InGaAsP contact layer 111 are sequentially grown to form a buried hetero structure. Difference from the first embodiment
Shows that the p-InP clad layer 201 is thin, the active layer 103 is immediately below the buried layer 110 via the p-InP clad layer 201, and the p-InGaAsP surface protective layer 105 is left. This is a point for performing buried epitaxial growth of the layer 108. Here, in the first embodiment, there is no problem because the p-InP cladding layer 301 is thick as shown in FIG.
As shown in (b), when the p-InP clad layer 302 becomes thinner than 0.5 μm, the defect L caused by the dissociation of P atoms having a high vapor pressure in the p-InP clad layer 302 during soaking before growth becomes In
There is concern that the GaAsP active layer 103 may be adversely affected and the laser characteristics may be deteriorated, such as a decrease in light emission efficiency. However, in the second embodiment, as shown in FIG. 3C, the p-InGaAsP surface protection layer 105 is formed, and the buried epitaxial growth is performed with the surface protection layer 105 left. No defects occur in the clad layer 303. This is to protect the p-InP clad layer 303 with the p-InGaAsP layer that is resistant to heat.

The p-InGaAsP surface protective layer 105 is made of p-InP.
Since the current blocking layer 108 is automatically melted back into the liquid phase during the growth, it does not remain in the structure after the buried epitaxial growth. This is because the InP layer does not grow on the narrow mesa stripe, which is a feature of the liquid phase epitaxial growth method, so that the InGaAsP layer that is easily melted back is selectively removed. In the structure manufactured in this way, the p-InP clad layer 201 is thin, so the series resistance of the p-InP clad layer 201 itself is small, and the n-InP block layer 109 is
Since the voltage applied to V is small, thyristor operation at high output and output saturation can be suppressed, and the temperature characteristics are improved, so good laser characteristics can be obtained.

FIG. 4 shows a third embodiment of the present invention. Figure 4
As shown in (a), a photo-CVD (or plasma CV) method is applied on the same semiconductor multilayer film structure wafer as in the second embodiment.
After depositing an insulating film (SiO ₂ , Si ₃ N _4, etc.) by D), a stripe-shaped etching mask parallel to the <011> direction with a width of 4 μm is formed by photolithography and dry etching.
The sk 401 is formed. N-InP to a depth of about 1 μm below the InGaAsP active layer 103 with a mixed solution containing hydrochloric acid, hydrogen peroxide and acetic acid.
The buffer layer 102 is etched to completely remove the InGaAsP active layer 103 (FIG. 4B). Then, the n-InP buffer layer 102 is further mixed with a mixed solution of hydrochloric acid and phosphoric acid (volume ratio 1: 2) to about 2%.
Etching is performed substantially vertically to the μm (FIG. 4C). Liquid phase epitaxial growth is performed as in the second embodiment to form a buried hetero structure (FIG. 4D). In this embodiment, a mixed solution containing hydrochloric acid and hydrogen peroxide solution is mainly used only for removing the InGaAsP active layer 103, and hydrochloric acid that does not include side etching is used for etching the n-InP buffer layer 102. And a mixture of phosphoric acid is used. A mixture of hydrochloric acid and phosphoric acid
Since the InGaAsP layer has the property of etching only the InP layer without etching, when the p-InP cladding layer is made thin, first the active layer is etched with a mixed solution containing hydrochloric acid, hydrogen peroxide solution and acetic acid. Then, the depth required for forming the blocking layer can be adjusted with a mixed solution of hydrochloric acid and phosphoric acid. Therefore, according to the etching method of the third embodiment, since the side etching amount with respect to the width of the insulating film mask 402 can be reduced, the controllability of the stripe width is better than that of the first and second embodiments, and the activity in the wafer can be improved. The variation in layer width can be reduced by 30% as compared with the conventional manufacturing method using Br-methanol, so that a laser element with stable characteristics can be obtained.

FIG. 5 shows an example of manufacturing an embedded structure of a DFB laser used for optical fiber communication. The present invention can also be applied to the fabrication of DFB lasers. The manufacturing method will be described below with reference to the drawings.

In FIG. 5A, n having the (100) plane as the main surface
-A diffraction grating is formed on the InP substrate 101 using a known method. That is, a photoresist is applied on the substrate 1 to a thickness of about 1000 A, and a diffraction grating pattern is formed by a two-beam interference exposure method of He-Cd laser (wavelength 345 nm). The resist on the surface of the substrate is selectively etched by using the diffraction grating pattern. A diffraction grating can be formed on the substrate by removing the photoresist with an organic solvent. After forming a diffraction grating with a period of 2000 A in this way, a 0.2 μm thick n-InGaAsP optical guide layer 501 with a thickness of 0.2 μm was formed.
InGaAsP active layer 103, 0.3 μm thick p-InP clad layer 10
4. An insulating film 106 such as SiO ₂ or Si ₃ N ₄ is deposited by photo CVD (or plasma CVD) on the semiconductor multilayer film structure wafer on which a 0.2 μm thick p-InGaAsP surface protection layer 105 is sequentially epitaxially grown. After that, an insulating film mask 106 for etching is formed in a stripe shape having a width of 4 μm parallel to the <011> direction by photolithography and dry etching (FIG. 5B). After that, as in the third embodiment, a mixed solution containing hydrochloric acid, hydrogen peroxide solution and acetic acid (volume ratio 3: 1: 36) was used to reach a depth of about 1 μm below the InGaAsP active layer 103 by nI.
Etch nP substrate 101 to remove InGa
The AsP active layer 103 was completely removed, and the n-InP substrate 101 was further etched approximately 2 μm vertically with a mixed solution of hydrochloric acid and phosphoric acid (volume ratio 1: 2) to form a mesa stripe 107 (Fig. 5 (c)). After removing the insulating film 106 with a hydrofluoric acid-based solution, a p-InP current blocking layer 108 and an n-InP current blocking layer 109 are grown in a region other than the mesa stripe 107 by liquid phase epitaxial growth, and then p-InP is further grown. Buried layer
110 and p-InGaAsP contact layer 111 are sequentially grown to form a buried hetero structure (FIG. 5D).

The linearity in the light output characteristic of the laser manufactured according to the present invention is shown by the threshold value I as shown in FIG.
The external differential quantum efficiency at _th eta _0, the external differential quantum efficiency in the threshold I _th + 100 mA and _{η 100, (η 0 -η 100} ) / η 0 X10
It is 11% when expressed by 0, and is 17 for the laser manufactured by the conventional method.
%, And it was found that the linearity was significantly improved. As a result, higher output and improved distortion characteristics during analog transmission can be expected.

Although the semiconductor wafer in which the InGaAsP active layer is laminated on the n-InP buffer layer is used in the above-mentioned embodiment, a wafer in which the InGaAsP active layer is laminated directly on the n-InP substrate or The present invention can be applied to a wafer in which an InGaAsP meltback prevention layer is laminated on an InGaAsP active layer.

Further, in this embodiment, a mixed solution containing hydrochloric acid, hydrogen peroxide solution and acetic acid was used as the etching solution, but a similar effect can be obtained by using a weak acid such as phosphoric acid or pure water instead of acetic acid. To be Further, in this example, in order to prevent the dissociation of P atoms in the p-InP cladding layer during the buried epitaxial growth, the mesa stripe having the InGaAsP layer as the uppermost layer was etched by a mixed solution containing hydrochloric acid, hydrogen peroxide solution and acetic acid. Although formed, the same mesa stripe may be formed using another etching solution such as Br-methanol.

Although the p-InP current blocking layer and the n-InP current blocking layer are used as the current blocking layer, the current blocking layer is not limited to the InP layer and the In having a larger energy gap than the active layer.
A GaAsP layer or a semi-insulating InP layer may be used.

[0029]

As described above in detail, the present invention has the following effects.

(1) At least an InGaAsP active layer, a second conductivity type InP clad layer, and an InGaAsP surface protective layer as the uppermost layer on a first conductivity type InP substrate having a (100) plane as a main surface. The stripe width can be easily controlled by forming a stripe-shaped insulating film mask in the <011> direction on the semiconductor multilayer film structure wafer and then etching with a mixed solution containing hydrochloric acid and hydrogen peroxide solution. Therefore, a mesa stripe having a regular mesa shape can be stably obtained. Therefore, even if the p-InP clad layer is thinned, the (111) A plane is not exposed on the side surface of the InGaAsP active layer, and a good current blocking layer can be formed on both sides of the mesa stripe, resulting in good characteristics. A laser can be obtained.

(2) At least a first conductivity type InP layer and I
a mesa stripe having an nGaAsP active layer, a second conductivity type InP clad layer, and an InGaAsP surface protective layer as the uppermost layer;
In the case where the p-InP clad layer is thin by performing buried epitaxial growth on the InP substrate including the region other than the mesa stripe formed of the first conductivity type InP layer.
However, the top InGaAsP surface protective layer of the mesa stripe suppresses the occurrence of defects in the p-InP cladding layer during soaking before growth, so that it is possible to prevent deterioration of laser characteristics such as a decrease in luminous efficiency due to the occurrence of defects. A laser having good characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a manufacturing process of a semiconductor laser of the present invention.

FIG. 2 is a cross-sectional view of the manufacturing process of the semiconductor laser of the present invention.

FIG. 3 is a cross-sectional view of one step of manufacturing the semiconductor laser of the present invention.

FIG. 4 is a cross-sectional view of the manufacturing process of the semiconductor laser of the present invention.

FIG. 5 is a perspective view of the manufacturing process of the DFB laser of the present invention.

FIG. 6 is a diagram showing a light output characteristic of a semiconductor laser according to the present invention.

FIG. 7 is a sectional view of a manufacturing process of a conventional buried hetero structure.

FIG. 8 is a cross-sectional view of a manufacturing process of a conventional buried hetero structure.

FIG. 9 is a cross-sectional view of a manufacturing process of a conventional buried hetero structure.

[Explanation of symbols]

 101 (100) n-InP substrate 102 n-InP buffer layer 103 InGaAsP active layer 104 p-InP clad layer 201 p-InP clad layer 301 p-InP clad layer 302 p-InP clad layer 303 p-InP clad layer 401 p -InP clad layer 503 p-InP clad layer 105 p-InGaAsP surface protective layer 106 Insulating film 402 Insulating film 504 Insulating film 107 Mesa stripe 202 Mesa stripe 403 Mesa stripe 505 Mesa stripe 108 p-InP current blocking layer 109 n-InP current Block layer 110 p-InP buried layer 111 p-InGaAsP contact layer 501 n-InGaAsP optical guide layer 502 p-InGaAsP buffer layer 601 (111) A surface 701 Resist mask

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Matsui 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A 63-56983 (JP, A) JP-A-2-146778 (JP, A) JP-A-3-112185 (JP, A)

Claims (6)

[Claims] 1. A first conductivity type InP having a (100) plane as a main surface.
A semiconductor multilayer film forming step of forming a semiconductor multilayer film structure having an InGaAsP active layer, a second conductivity type InP clad layer, and an InGaAsP surface protective layer on the uppermost layer, and <011 A mask forming step of forming a stripe-shaped insulating film mask in the> direction, and an InGaAsP surface adjacent to both sides of the stripe-shaped mask by etching with a mixed solution containing hydrochloric acid and hydrogen peroxide using the insulating film mask as a mask. protective layer, and the second conductive type InP cladding layer, a mesa stripe forming step of forming a forward main <br/> striped removing the InGaAsP active layer,
Liquid phase epitaxial growth on both sides of the normal mesa stripe
And the current blocking layer formed <br/> step of stacking a current blocking layer by, InGaAs second conductivity type in the current blocking layer
And a contact layer forming step of forming a P contact layer . 2. The current block layer forming step is a forward mesastra.
Current block by liquid phase epitaxial growth on both sides of the
Layer and the InGaAsP surface protection layer
The method of manufacturing a semiconductor laser according to claim 1, wherein the step is a step of performing a back-back . 3. The semiconductor multi-layer film forming process is mainly performed on the (100) plane.
Define the oscillation wavelength on the first conductivity type InP substrate
Diffraction grating, first conductivity type optical guide layer, InGaAsP active layer,
Second conductivity type InP clad layer and InGaAsP layer on top layer
In the step of forming a semiconductor multilayer film structure having a surface protective layer
A method of manufacturing a semiconductor laser according to claim 1 or 2, wherein the that. 4. The forward mesa stripe forming step comprises insulating film mass
With a mixture of hydrochloric acid and hydrogen peroxide as a mask.
Adjacent to both sides of the striped mask by etching
InGaAsP surface protection layer, second conductivity type InP clad layer, In
Liquid mixture containing GaAsP active layer and hydrochloric acid and phosphoric acid
The InP layer under the InGaAsP active layer is etched with
The step of forming a tripe.
The method for manufacturing a semiconductor laser according to any one of 1 to 3 . 5. An InP substrate of the first conductivity type and InGaAsP activity.
Forming an InP buffer layer of the first conductivity type between
The method for manufacturing a semiconductor laser according to any one of claims 1 to 4, further comprising : 6. The semiconductor laser according to claim 1, wherein a second conductivity type InP and a first conductivity type InP are formed from the substrate side as the current blocking layer. Production method.