JPH10173278A - Manufacture of semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser having a high basic transverse mode output which is obtained by realizing a uniform refractive index difference and a high fiber coupling efficiency with a high yield by making the remaining thickness of an external clad layer uniform. SOLUTION: An n-type Al0.3 Ga0.7 As external clad layer 2, an n-type Al0.45 Ga0.55 As etching stop layer 3, an n-type Al0.3 Ga0.7 As internal clad layer 4, an n-type Al0.2 Ga0.8 As light guide layer 5, and an In0.24 Ga0.76 As/GaAs double quantum well active layer 6 are successively formed on an n-type GaAs substrate 1. In addition, a p-type Al0.2 Ga0.8 As light guide layer 7, a p-type Al0.3 Ga0.7 As internal clad layer 8, a p-type Al0.45 Ga0.55 As etching stop layer 9, a p-type Al0.3 Ga0.7 As external clad layer 10, and a p-type GaAs cap layer 11 are successively formed on the active layer 6. When an SiO2 thin film 12 which becomes a mask is deposited on the cap layer 11 and an area which becomes a waveguide is etched, a laser element having a high basic mode output and a high fiber coupling efficiency can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a single transverse mode control type semiconductor laser with a high yield, more particularly, to a method of manufacturing _{Al x Ga 1-x As /} In y Ga 1-y As compound semiconductor laser .

[0002]

2. Description of the Related Art Al _x Ga _{1 -x} As / In _y Ga _{1 -y} A
An s-based semiconductor laser has a feature of oscillating in a short wavelength region. In particular, a 980 nm band semiconductor laser is important as an excitation light source in an erbium-doped fiber amplifier (EDFA). A method of manufacturing a 980 nm band laser by a conventional technique is described in, for example, Electronics Letters (1991).
27, No. 22, pp. 2032-2033). Hereinafter, referring to FIG. 4, 980n using the conventional example will be described.
A method for manufacturing an m-band semiconductor laser will be described. First,
Using a normal pressure MBE (Molecular Beam Crystal Growth) apparatus, a 1 μm thick n-type Al _0.22 Ga
_0.78 As inner cladding layer 52, 200 nm thick GaAs
Light guide layer 53 (no addition), In _{0.2 with} well thickness of 10 nm
Ga _0.8 As single quantum well active layer 54 (no addition), 20
GaAs optical guide layer 55 of 0 nm thickness (no addition), 130
nm thick p-type Al _0.22 Ga _0.78 As inner cladding layer 5
6, an AlAs etching stop layer 57 having a thickness of 3 nm (no addition), a p-type Al _0.22 Ga _0.78 As outer cladding layer 58 having a thickness of 870 nm, and a p-type GaAs cap layer 59 having a thickness of 100 nm (adding Be) are added. (FIG. 2A). The substrate temperature during crystal growth is In _0.2 G
a _0.8 As single quantum well active layer, GaAs layer, Al _0.22
For each of the Ga _0.78 As inner cladding layer and the AlAs etching stop layer, 530 ° C., 600 ° C.,
50 ° C and 650 ° C. A region to be a waveguide is covered with a SiO ₂ mask 60 formed in a stripe shape by photolithography (FIG. 4A). Next, an etching solution is prepared. The etching solution was prepared by dissolving 200 g of succinic acid in 1 liter of water and adding ammonium hydroxide to the solution.
H is adjusted to 5 and the succinic acid and ammonium hydroxide solution 15 are prepared by adding 30% hydrogen peroxide solution 1 thereto. Subsequently, etching for forming a mesa stripe is performed using this etching solution, and a p-type GaAs cap layer having a thickness of 100 nm and a p-type Al _0.22 layer having a thickness of 870 nm are formed.
The Ga _0.78 As outer cladding layer is selectively etched. Etching stops at a 3 nm thick AlAs etch stop layer. Next, the entire surface of the wafer is covered with a SiO ₂ current block layer 61 by a sputtering method, and the top of the mesa stripe is opened. Ti (titanium), Au on the p side
An electrode 62 is formed in the order of (gold), and an electrode 63 is formed in the order of Au and Sn (tin) on the n side (FIG. 4C). Finally, a cavity is formed by cleaving the wafer, and each element is cut to complete a laser element.

[0003]

One of the performances required of a semiconductor laser is a high fundamental transverse mode output. In particular, since a semiconductor laser in the 980 nm band is required to supply a high optical output to an erbium-doped fiber amplifier, in order to efficiently couple the laser output to the optical fiber, the semiconductor laser operates in a fundamental transverse mode until a high optical output. It is important to keep The fundamental transverse mode output of a semiconductor laser largely depends on two factors, that is, the difference between the bottom width of the mesa stripe and the equivalent refractive index inside and outside the mesa stripe.
In order to obtain the basic lateral mode output described above, it is necessary to make the bottom width of the mesa stripe 3 μm or less and give an appropriate difference in refractive index. The difference in equivalent refractive index between the inside and outside of the mesa stripe is determined by the thickness of the inner cladding layer immediately above the active layer beside the mesa stripe after etching.

It is also important to enlarge the light emitting spot in the vertical direction (layer thickness direction). The enlargement of the light emitting spot is achieved by reducing the vertical radiation angle and concentrating more light output within the effective diameter of an optical element (such as a lens) used for coupling with the optical fiber, and by increasing the light emitting spot shape closer to a circle. This has the effect of increasing the overlap integral with the circular field propagating in the fiber, leading to an increase in the coupling efficiency with the fiber. In order to reduce the influence of the GaAs cap layer and the high refractive index layer of the GaAs substrate, the size of the light emitting spot is reduced.
It is important that the thickness of the inner cladding layer be sufficiently large.

However, the conventional manufacturing method is excellent in that the difference in the equivalent refractive index between the inside and outside of the mesa stripe is made uniform in the wafer, but the etching in the lateral direction at the time of selective etching when forming the mesa stripe is performed. Large volume, 3μ
It is extremely difficult to form a mesa stripe having a mesa bottom width of less than m over the entire surface of the wafer from the viewpoint of uniformity and reproducibility of photolithography and etching processes. In addition, since the anisotropy of the etching shape is large and the etching rate in the lateral direction is high, particularly, the plane orientation (−110)
When a mesa stripe with a thick inner cladding layer is formed in parallel with the above, the width of the p-type GaAs cap layer becomes too small due to side etching, and the SiO ₂ mask may fall off. Therefore, it has been extremely difficult with the conventional method to manufacture a semiconductor laser with higher performance required for realizing a module having higher fiber light output with a high yield.

The present invention has a high fundamental transverse mode output,
It is another object of the present invention to manufacture a semiconductor laser having a high fiber coupling efficiency with a high yield.

[0007]

According to a method of manufacturing a semiconductor laser of the present invention, a step of forming a multi-layer semiconductor film including an active layer and an inner cladding layer on a substrate, and at least an etching stop layer on the semiconductor film. Forming an external cladding layer, a cap layer, and a mask layer in this order, performing dry etching to a depth reaching the external cladding layer to form a mesa stripe, and further etching the external cladding layer with an etchant. And a step. Therefore, the remaining thickness of the outer cladding layer can be made uniform, so that a uniform refractive index difference can be realized.

Further, according to the method of manufacturing a semiconductor laser of the present invention, a step of forming a multi-layer semiconductor film including an active layer and an inner cladding layer on a substrate, and forming at least an etching stop layer and an Al _x1 Ga _1-x1 As (1 ≧ X ₁ ≧
0) Outer cladding layer, Al _x2 Ga _1-x2 As (1 ≧ X ₂ >)
X ₁ ≧ 0) a step of forming an external cladding layer, a cap layer, and a mask layer in this order; and a step of forming a mesa stripe by performing dry etching to a depth reaching the Al _x1 Ga _1-x1 As external cladding layer. Further etching the Al _x1 Ga _1-x1 As outer cladding layer with an etchant. For this reason, the speed of the side etching can be further suppressed, and the uniformity of the width of the mesa stripe bottom can be further improved.

The semiconductor laser of the present invention has a multi-layer semiconductor film including an active layer and an inner cladding layer on a substrate, and at least Al _x1 Ga _{1 -x1} As (1 ≧ X ₁
≧ 0) outer cladding layer and Al _x2 Ga _1-x2 As (1 ≧ X
₂ > X ₁ ≧ 0) and an outer cladding layer in this order. For this reason, the width of the bottom of the mesa stripe is excellent in uniformity, and the mask can be effectively prevented from dropping off at the time of side etching, and the productivity is excellent.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method of manufacturing a semiconductor laser according to the present invention, a vertical mesa stripe is uniformly formed on the entire surface of a wafer by dry etching, and then a rectangular mesa stripe is hardly deformed by selective etching.
The outer cladding layer is etched right above the etching stop layer.

The etching stop layer in the present invention is a layer for stopping etching by an etching solution, and may be an AlAs layer or the like.

The outer cladding layer in the present invention is a cladding layer located outside the etching stop layer as viewed from the active layer. As the material of the outer cladding layer, for example, A
l _x Ga _1-x As (1 ≧ X ≧ 0) can be used.
The outer cladding layer may be composed of two or more layers. As shown in FIGS. 2 and 3, an Al _x1 Ga _{1 -x1} As layer 31 (1 ≧ X ₁ ≧
0), and an Al _{x 2} Ga _1-x2 As layer 32 (1 ≧ X ₂ >)
By setting (X ₁ ≧ 0), controllability and reproducibility of the bottom width of the mesa stripe can be further improved. This is for the following reason. The Al _x2 Ga _1-x2 As layer 32 is made of A
Since the Al composition ratio is higher than that of the l _x1 Ga _1-x1 As layer 31, when a citric acid-based etchant is used, etching is difficult. Therefore, the Al _x1 Ga _1-x1 As layer 31 has a structure sandwiched between the Al _x2 Ga _1-x2 As layer 32 and the etching stop layer 30 which are hard to be etched. Therefore, the effect of side etching at the time of selective etching can be suppressed, and controllability and reproducibility of the mesa stripe bottom width can be improved. Further, this effect becomes more remarkable when 1 ≧ X ₂ > 0.35 and 0.35 ≧ X ₁ ≧ 0, and 0.55 ≧ X ₂ > 0.45 and 0.2 ≧ X ₁
More preferably, ≧ 0.

[0013] The mask layer in the present invention has a resistance to the etching solution, when burying growth of the mesa stripe sides, a dielectric layer such as the semiconductor layer does not grow thereon, typically SiO ₂ or the like Is used.

The dry etching in the present invention means an etching method such as reactive ion beam etching (RIBE), reactive ion etching (RIE), and electron cyclotron resonance (ECR) etching.

As the etching solution in the present invention, for example, succinic acid, ammonium hydroxide, an aqueous solution of hydrogen peroxide or the like can be used, but the inner cladding layer is formed of Al _x Ga _{1 -x} A.
When the s (1 ≧ X ≧ 0) layer is used, it is preferable to use a liquid containing citric acid. This is because delicate pH control is not required, and the temporal stability of the etching solution is high.
For example, a mixed solution of citric acid and aqueous hydrogen peroxide is preferably used.

The semiconductor laser of the present invention has a structure in which two or more external cladding layers are provided, and the external cladding layer located at the bottom of the mesa stripe is sandwiched between another external cladding layer which is hardly selectively etched and an etching stop layer. By doing so, the speed of side etching is suppressed, and the uniformity of the width of the bottom of the mesa stripe is improved.
Specifically, an Al _x1 Ga _1-x1 As (1 ≧ X ₁ ≧ 0) outer cladding layer and an Al _x2 Ga _1-x2 As (1 ≧ X ₂ > X ₁ ≧
0) The outer cladding layer is provided in this order, but it is particularly preferable that 1 ≧ X ₂ > 0.35, 0.35 ≧ X ₁ ≧ 0, and 0.55 ≧ X ₂ > 0 .45, 0.2
It is more preferred that ≧ X ₁ ≧ 0.

[0017]

【Example】

 (Embodiment 1) Example of a method of manufacturing a semiconductor laser according to the present invention
An embodiment will be described with reference to FIG. First, the plane orientation
A normal pressure MOVP is placed on the (001) n-type GaAs substrate 1.
2.0 μm using an E (metalorganic vapor phase crystal growth) apparatus
Thick n-type Al_0.3 Ga_0.7 As outer cladding layer 2 (1 ×
10¹⁷(Cm ^-3)) At a concentration of Si)
0 nm thick n-type Al_0.45Ga_0.55As etching stock
Layer 3 (1 × 10¹⁷(Cm^-3)) Concentration of Si),
200 nm thick n-type Al_0.3 Ga_0.7 As inner cladding
Layer 4 (1 × 10¹⁷(Cm ^-3)), 5)
0 nm thick n-type Al_0.2 Ga_0.8 As light guide layer 5 (1
× 10¹⁷(Cm^-33.) Si concentration is added), and the well thickness is 4.
5nm, barrier thickness 5nm In_0.24Ga_0.76As / Ga
As double quantum well active layer 6 (no addition), 50 nm thick p
Type Al_0.2 Ga_0.8 As light guide layer 7 (1 × 10¹⁸(C
m^-3)), Mg (magnesium) added), 200
nm thick p-type Al_0.3 Ga_0.7 As inner cladding layer 8
(1 × 10¹⁸(Cm ^-3Mg is added at a concentration of)), 100
nm thick p-type Al_0.45Ga_0.55As etching stop
Layer 9 (1 × 10¹⁸(Cm^-3Mg is added at a concentration of)),
2.0 μm thick p-type Al_0.3 Ga_0.7 As outer cladding
Layer 10 (1 × 10¹⁸(Cm^-3Mg is added at a concentration of)),
0.5 μm thick p-type GaAs cap layer 11 (1 × 10
¹⁸(Cm^-3) Is added in this order.
You. Next, SiO serving as a mask for selective growth_Two Thin film 1
2 is deposited on the surface by a sputtering device to a thickness of 200 nm.
Then, the area to be a waveguide is scanned by photolithography.
It is coated with a photoresist 13 in a tripe form,
Pattern using SiO_Two (FIG. 1A).
By using this two-stage mask, the side of the region to be an optical waveguide
Part is p-type Al_0.45Ga_0.55As etching stop layer 9
Dry etching to a depth of about 200 nm just above
(FIG. 1B). Next, remover, butanone, alcohol
And ultrasonic cleaning using the
Remove the pattern. This is followed by aqueous citric acid and peracid
Immerse the wafer in an etchant mixed with hydrogen chloride water, and
Etching is performed for 30 seconds (FIG. 1C). 3 minutes
After washing with water, use an aqueous solution of fluoric acid for 10 seconds_Two Wash the mask
Clean and dry. After that, the SiO_Two As a selective growth mask
Selective burying is performed on the side of the mesa stripe. 1.
6 μm thick n-type Al_0.45Ga_0.55As low refractive index current blow
Layer 14 (1 × 10¹⁷(Cm^-3) With Si
) And then use the same technique to
Thick n-type GaAs current blocking layer 15 (1 × 10¹⁷(Cm
^-3) And Si is added). After that, the SiO
_Two The mask 13 is removed with a fluoric acid (FIG. 2E),
0.5 μm thick p-type GaAs contact layer 16 (1 × 1
0¹⁸(Cm^-3) Is added over the entire surface of the wafer.
Lengthen. Ti (titanium) on the n side by sputtering,
The electrodes 17 are formed in the order of Pt (platinum) and Au (gold).
Further, the wafer was polished from the substrate side to a thickness of 80 μm.
Then, Au, Ge (germanium)
Electrode 18 is formed in the order of Ni) and Ni (nickel).
2 (d)). Finally, by cleaving the wafer,
To form a laser element
The child is completed. Citric acid and peracid used for selective etching
Hydrogen water mixture is Al_0.32Ga_0.7 As inner cladding
Approximately 800 nm / min etch rate for layer
With Al_0.45Ga_0.55As etching stop layer
Etching rate to one-hundredth of that is a sufficient choice
With a ratio. Surface condition after etching is good, then
The state of the subsequent buried growth is also good. In this embodiment,
Using a layer with a large composition as an etch stop layer
But stop etching small layer of aluminum composition
There is no particular problem compared to when using as a layer
Absent. An etching stop layer is formed near the active layer.
Even if it is formed, it traps carriers and injects it into the active layer.
Of light, or distribution of light to the etching stop layer
Attracting and lowering the light confinement rate of the active layer
Absent.

(Embodiment 2) An embodiment of a method for manufacturing a semiconductor laser according to the present invention will be described with reference to FIG.
First, an n-type Al _0.4 Ga _0.6 As outer cladding layer 22 (2.0 μm thick) is formed on a (001) n-type GaAs substrate 21 using a normal pressure MOVPE (metal organic chemical vapor phase epitaxy) apparatus. Si (silicon) is added at a concentration of 1 × 10 ¹⁷ (cm ⁻³ )), and n-type Al _0.3 Ga _0.7 A having a thickness of 500 nm.
s outer cladding layer 23 (adding Si {silicon} at a concentration of 1 × 10 ¹⁷ (cm ⁻³ )), 50-nm thick n-type Al _0.45 Ga
_0.55 As etching stop layer 24 (1 × 10 ¹⁷ (cm
^-3 ) concentration of Si), 200 nm thick n-type Al
_0.3 Ga _0.7 As inner cladding layer 25 (1 × 10 ¹⁷ (c
m ⁻³ ), n-type Al with a thickness of 50 nm
_0.2 Ga _0.8 As light guide layer 26 (1 × 10 ¹⁷ (c
m ⁻³ ), a well thickness of 4.5 nm, a barrier thickness of 5 nm, an In _0.24 Ga _0.76 As / GaAs double quantum well active layer 27 (no addition), and a 50 nm thickness of p-type Al _0.2.
Ga _0.8 As light guide layer 28 (Mg (magnesium) is added at a concentration of 1 × 10 ¹⁸ (cm ⁻³ )), p-type Al _0.3 Ga _0.7 As inner cladding layer 29 (1 × 1
0 ¹⁸ (cm ⁻³ ) Mg), a 50 nm thick p
Type Al _0.45 Ga _0.55 As etching stop layer 30 (1
× 10 ¹⁸ (cm ⁻³ ) at a concentration of Mg), 500 nm
Thick p-type Al _0.3 Ga _0.7 As outer cladding layer 31 (1
× 10 ¹⁷ (cm ⁻³ ) Mg added), 2.0 μm
Thick p-type Al _0.3 Ga _0.7 As outer cladding layer 32 (1
× 10 ¹⁸ (cm ⁻³ ) Mg added), 0.5 μm
Thick p-type GaAs cap layer 33 (1 × 10 ¹⁸ (c
m ⁻³ ) at a concentration of m ⁻³ ). Deposited on the surface of about 200nm thickness of SiO ₂ thin film 34 serving as a selective growth mask by a sputtering apparatus, an area where the waveguide is coated with a photoresist 35 in a stripe shape by photolithography, SiO ₂ pattern using a fluorine acid (FIG. 3A). Using this two-stage mask, the side of the region to be an optical waveguide is p-type Al _0.45 Ga _0.55 A
Dry etching is performed to a depth of about 200 nm immediately above the s etching stop layer 30 (FIG. 3B). Next, ultrasonic cleaning is performed using a stripper, butanone, and alcohol in this order to remove the photoresist pattern. Thereafter, the wafer is immersed in an etching solution obtained by mixing a citric acid aqueous solution and a hydrogen peroxide solution, and etching is performed for about 30 seconds (FIG. 3C). After washing with water for 3 minutes, the SiO ₂ mask is washed with an aqueous solution of fluoro acid for 10 seconds and dried. Then, S
The selective growth burying is performed on the side of the mesa stripe using iO ₂ as a selective growth mask. 1.6 μm thick n-type Al _0.45 G
a _0.55 As low refractive index current blocking layer 36 (1 × 10
¹⁷ (cm ⁻³ ) concentration, and then using the same technique, 0.5 μm thick n-type GaAs current blocking layer 37 (1 × 10 ¹⁷ (cm ⁻³ ) concentration Si added).
(FIG. 2D). Then, SiO ₂ mask 3
4 was removed with fluoroacid (FIG. 2 (e)), and 0.5 μm
Thick p-type GaAs contact layer 38 (1 × 10 ¹⁸ (cm
^-3 ) Mg is added to the entire surface of the wafer. An electrode 39 is formed on the n side in the order of Ti (titanium), Pt (platinum), and Au (gold) by a sputtering method. Further, after the wafer is polished from the substrate side to a thickness of 80 μm, Au, Ge (germanium), Ni
The electrodes 40 are formed in the order of (nickel) (FIG. 3)
(D)). Finally, a cavity is formed by cleaving the wafer, and each element is cut to complete a laser element.

In this embodiment, the outer cladding layer of Al _0.3 Ga _0.7 As which determines the width of the bottom of the mesa stripe is made of Al _0.45 Ga _0.55 A which is not etched at the time of selective etching.
The structure is sandwiched between an s etching stop layer and an Al _0.4 Ga _0.6 As outer cladding layer. For this reason,
The speed of side etching by the etchant is further suppressed, the uniformity of the width of the bottom of the mesa stripe can be improved, and a thicker inner cladding layer can be realized. Further, if the inner cladding layer parallel to the plane orientation (-110) to create a thick mesa stripe, also prevent falling off of the SiO ₂ mask 34 by the width of the p-type GaAs cap layer 33 by the side etching becomes too narrow it can.

[0020]

As described above, according to the present invention, after the rectangular mesa stripe is uniformly formed by dry etching, the outer cladding layer is further etched by using an etching solution. Without changing, the uniformity of the width of the bottom of the mesa stripe can be improved. Further, since the remaining thickness of the outer cladding layer can be made uniform, a uniform refractive index difference can be realized. In particular, by providing two or more external cladding layers, the external cladding layer located at the bottom of the mesa stripe is sandwiched between the other external cladding layer that is hardly selectively etched and the etching stop layer, so that the side etching speed can be improved. Can be further suppressed, and the uniformity of the width of the mesa stripe bottom can be further improved.

Therefore, according to the semiconductor laser manufacturing method of the present invention, it is possible to make the outer cladding layer thicker,
It is possible to enlarge the light emitting spot in the vertical direction. In addition, it is possible to effectively prevent the mask from falling off during the side etching. Therefore, a semiconductor laser device having high fundamental mode output and high fiber coupling efficiency can be manufactured with high yield.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a method for manufacturing a semiconductor laser according to the present invention.

FIG. 2 is a schematic sectional view showing an example of the semiconductor laser of the present invention.

FIG. 3 is a schematic process sectional view illustrating an example of a method for manufacturing a semiconductor laser according to the present invention.

FIG. 4 is a schematic process sectional view showing an example of a conventional method for manufacturing a semiconductor laser.

[Explanation of symbols]

Reference Signs List 1 n-GaAs substrate 2 n-Al _0.3 Ga _0.7 As outer cladding layer 3 n-Al _0.45 Ga _0.55 As etching stop layer 4 n-Al _0.3 Ga _0.7 As inner cladding layer 5 n-Al _0.2 Ga _0.8 As optical guiding layer 6 In _0.24 Ga _0.76 As / GaAs active layer 7 p-Al _0.2 Ga _0.8 As light guide layer 8 p-Al _0.3 Ga _0.7 As inner cladding layer 9 p-Al _0.45 Ga _0.55 As etching stop layer 10 p-Al _0.3 Ga _0.7 As Outer cladding layer 11 p-GaAs cap layer 12 SiO ₂ mask 13 photoresist mask 14 n-Al _0.45 Ga _0.55 As low refractive index current blocking layer 15 n-GaAs current blocking layer 16 p-GaAs contact layer 17 TiPtAu electrode 18 AuGeNi electrode 21 n-GaAs substrate 22 n-Al _0.4 Ga _0.6 As external Rudd layer 23 n-Al _0.3 Ga _0.7 As outer cladding layer 24 n-Al _0.45 Ga _0.55 As etching stop layer 25 n-Al _0.3 Ga _0.7 As inner cladding layer 26 n-Al _0.2 Ga _0.8 As optical guide layer 27 an In _0.24 Ga _0.76 As / GaAs active layer 28 p-Al _0.2 Ga _0.8 As light guide layer 29 p-Al _0.3 Ga _0.7 As inner cladding layer 30 p-Al _0.45 Ga _0.55 As etching stop layer 31 p-Al _0.3 Ga _0.7 As outer cladding layer 32 p-Al _0.4 Ga _0.6 As outer cladding layer 33 p-GaAs cap layer 34 SiO ₂ mask 35 photoresist mask 36 n-Al _0.45 Ga _0.55 As low refractive index current blocking layer 37 n-GaAs current blocking layer 38 p-GaAs Contact layer 39 TiPtAu electrode 40 AuGeNi electrode 51 n-GaAs substrate 52 n-Al _0.22 Ga _0.78 As inner cladding layer 53 n-GaAs optical guiding layer 54 In _0.2 Ga _0.8 As single quantum well active layer 55 p-GaAs optical guiding layer 56 p-Al _0.22 Ga _0.78 As Cladding layer 57 AlAs etching stop layer 58 p-Al _0.22 Ga _0.78 As outer cladding layer 59 p-GaAs cap layer 60 SiO ₂ mask 61 SiO ₂ current blocking layer 62 TiAu electrode 63 AuSn electrode

Claims (7)

[Claims] 1. A step of forming a multi-layer semiconductor film including an active layer and an inner cladding layer on a substrate, and forming at least an etching stop layer, an outer cladding layer, a cap layer, and a mask layer on the semiconductor film in this order. Performing dry etching to a depth reaching the outer cladding layer to form a mesa stripe, and further etching the outer cladding layer with an etchant. . 2. The method according to claim 1, wherein the outer cladding layer is made of Al _x Ga _{1 -x} A.
The method for manufacturing a semiconductor laser according to claim 1, wherein the s (1 ≧ X ≧ 0) layer is provided. 3. An active layer and an inner cladding layer on a substrate.
Forming a multi-layered semiconductor film;
Etching stop layer, Al_x1Ga _1-x1As
(1 ≧ X₁≧ 0) Outer cladding layer, Al_x2Ga_1-x2As
(1 ≧ X_Two > X₁≧ 0) outer cladding layer, cap layer,
Forming a mask layer in this order;_x1Ga
_1-x1Dry etch to a depth that reaches the As outer cladding layer
Forming a mesa stripe by etching, and etching
The Al_x1Ga_1-x1As outer cladding layer
Further etching.
A method for manufacturing a conductor laser. 4. A method for manufacturing the semiconductor laser according to claim 3.
In the method, 1 ≧ X _Two> 0.35, 0.35 ≧ X₁≧ 0
A method for manufacturing a semiconductor laser. 5. The method according to claim 1, wherein the etching solution is a solution containing citric acid. 6. A multi-layer semiconductor film including an active layer and an inner cladding layer on a substrate, and at least A
l _x1 Ga _1-x1 As (1 ≧ X ₁ ≧ 0) outer cladding layer;
A semiconductor laser comprising: an Al _x2 Ga _{1 -x2} As (1 ≧ X ₂ > X ₁ ≧ 0) outer cladding layer in this order. 7. The semiconductor laser according to claim 6, wherein 1 ≧ X ₂ > 0.35 and 0.35 ≧ X ₁ ≧ 0.