JPH09232678A - Semiconductor device, manufacturing method thereof, semiconductor laser and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser having a high kink level and high efficiency by devising the layer structure formed by the crystal growth to improve the mesa shape formed by wet etching. SOLUTION: A first and second outer clad layers 206, 207, hetero buffer layer 208 and cap layer 209 are laminated to form a multilayer structure on a substrate 201. The clad layers 206, 207 are made of materials different in etching rates. Thereby when the mesa forming is made by wet etching, a mesa shape having a small difference between the mesa top and bottom widths results.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, and has a two-step mesa structure, a multi-step mesa structure, a rectangular mesa structure, or an angle of 55 ° or more with respect to the base of the mesa side. The present invention relates to a semiconductor device having a mesa structure of a certain shape, a manufacturing method thereof, a semiconductor laser and a manufacturing method thereof.

[0002]

2. Description of the Related Art A conventional method of manufacturing a semiconductor laser, which is a kind of semiconductor device having a mesa structure, and a semiconductor laser will be described with reference to the drawings. As shown in FIG. 3A, n-type G
On the aAs substrate (plane orientation: (001)) 101, n-type (A
l _0.6 Ga _0.4 ) _0.5 In _0.5 P cladding layer 102, multiple quantum well active layer 103, p-type (Al _0.6 Ga _0.4 ) _0.5 In _0
.5 P inner clad layer 104, p-type GaInP etching stopper layer 105, p-type (Al _0.6 Ga _0.4 ) _0.5 I
n _0.5 P outer cladding layer 106, p-type GaInP heterobuffer layer 107, p-type GaAs cap layer 108
Are sequentially epitaxially grown, and the SiO ₂ film 9 is used as a mask by processes such as thermal CVD and photolithography.
The stripes are formed in the 1 (reverse) 10> direction.

Next, as shown in FIG. 3B, p-type GaAs
Cap layer 108, p-type GaInP heterobuffer layer 1
07, p-type (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P outer cladding layer 106 is sequentially etched up to the etching stopper layer by using an appropriate etching solution such as phosphoric acid type and hydrogen bromide type to form a mesa. .

Thereafter, as shown in FIG. 3C, the side surface of the mesa is embedded with an n-type GaAs current blocking layer 110, and S
After removing the iO ₂ film 109, a p-type GaAs contact layer 111 is laminated.

A semiconductor laser can be manufactured by attaching both the wafer p and n electrodes thus prepared, cleaving them so as to have a cavity length of about 300 to 1000 μm, and disassembling into individual chips. A method of manufacturing a semiconductor device having the above-described structure and a semiconductor laser are described, for example, in Eye Triple E Journal of Quantum Electronics, Vol. 29, page 1851 (Author: Ueno
Other) has been published.

[0006]

In the conventional method of manufacturing a semiconductor device and semiconductor laser, the p-type outer cladding layer 1 is used.
Since 06 is a single composition and stripes are formed in the <1 (reverse) 10> direction, etching is performed when a sulfuric acid-based, hydrochloric acid-based, hydrobromic acid-based etching solution or the like is used. As shown in FIG. 3 (c), the selectivity of (1 (reverse)
10) A trapezoidal mesa whose side wall when viewed in a sectional shape forms an angle of 54.7 ° with the (001) plane.

On the other hand, when the relationship between the mesa shape and the laser characteristics is examined in detail, it has been found that the mesa shape is greatly related to the external differential quantum efficiency and the transverse mode stability. When compared with the same clad layer thickness, the external differential quantum efficiency during oscillation of the semiconductor laser is high when the mesa top width is wide, and the optical output that disturbs the transverse mode control, so-called kink level, is high when the mesa bottom width is narrow.

Therefore, in the trapezoidal mesa of the semiconductor laser manufactured by the conventional manufacturing method, since the mesa top width is narrow and the mesa bottom width is wide, it is difficult to simultaneously achieve both high external differential quantum efficiency and high kink level. There is a point.

An object of the present invention is to devise a layer structure to be laminated by epitaxial growth so that the mesa top width is wider and the mesa bottom width is narrower than the conventional one, that is, the mesa shape in which the difference between the mesa top width and the mesa bottom width is small. The present invention provides a semiconductor device and a method of manufacturing the same, and further, by applying these to a semiconductor laser, a semiconductor laser having high oscillation efficiency and a high kink level, and a method of manufacturing the same.

[0010]

In order to achieve the above-mentioned object, a semiconductor device according to the present invention is a semiconductor device in which a mesa-type stripe is formed on a semiconductor substrate, wherein The vertical cross-sectional shape is a shape in which trapezoids are stacked in two steps or three or more steps. In the multi-trapezoidal shape, the length of the lower base of the trapezoid far from the active layer is closer to the active layer. The composition of the semiconductor, which is longer than the length of the upper base of the trapezoid and constitutes the trapezoidal portion on the side far from the active layer of the multiple trapezoidal shape, is higher than the composition of the semiconductor which constitutes the trapezoidal portion on the side closer to the active layer with respect to the etchant. The composition has a slow etching rate.

The semiconductor device according to the present invention is a semiconductor device in which mesa-shaped stripes are formed on a semiconductor substrate, and the cross-sectional shape of the mesa perpendicular to the stripe direction is the bottom base of a trapezoidal mesa. In the shape in which both ends of the trapezoid are cut off, that is, a double trapezoidal shape, and the length of the lower base of the trapezoid farther from the active layer is substantially the same as the length of the upper base of the trapezoid closer to the active layer. The composition of the semiconductor forming the trapezoidal portion on the side far from the multi-trapezoidal active layer is such that the etching rate is slower than the composition of the semiconductor forming the trapezoidal portion on the side closer to the active layer with respect to the etchant. Is.

The semiconductor device according to the present invention is a semiconductor device in which mesa-shaped stripes are formed on a semiconductor substrate, and the cross-sectional shape of the mesa perpendicular to the stripe direction is a rectangle or a side of a mesa. Angle to the base of is 5
The composition of the mesa portion is 5 ° or more and 90 ° or less, and the composition of the mesa is continuous with the etchant from the far side to the near side of the active layer so that the etching rate becomes faster. Is changing.

The semiconductor laser according to the present invention is a semiconductor laser having a mesa-type cladding layer for transverse mode control, and the cross-section of the mesa perpendicular to the waveguide direction is a trapezoid in two steps or three steps. In the multi-trapezoidal shape, the length of the lower base of the trapezoid farther from the active layer is longer than the length of the upper base of the trapezoid closer to the active layer. The composition of the semiconductor forming the trapezoidal portion on the side farther from the active layer has a slower etching rate than the composition of the semiconductor forming the trapezoidal portion on the side closer to the active layer with respect to the etchant.

In the semiconductor laser, the cladding layer forming the mesa is (Al _x Ga _{1 -x} ) _0.5.
It includes a semiconductor layer made of In _0.5 P (0.5 ≦ x ≦ 0.8).

In the semiconductor laser, in particular, the composition of the semiconductor forming each trapezoidal portion of the multi-trapezoidal shape is (Al _x1 Ga _{1 -x1} ) in order from the side far from the active layer.
_{0.5 In 0 .5 P, (Al} x2 Ga 1-x2) 0.5 In 0.5 P, (A
l _x3 Ga _1-x3 ) _0.5 In _0.5 P ... (Al _xn Ga _1-xn )
_0.5 In _0.5 P (0.5 ≦ x1 <x2 <x3 <... <xn ≦
0.8).

The semiconductor laser according to the present invention is a semiconductor laser having a mesa-type cladding layer for lateral mode control, wherein the cross section of the mesa perpendicular to the waveguide direction has a trapezoidal mesa lower base. In the shape in which both ends of the trapezoid are cut off, that is, a double trapezoidal shape, and the length of the lower base of the trapezoid farther from the active layer is substantially the same as the length of the upper base of the trapezoid closer to the active layer. The composition of the semiconductor forming the trapezoidal portion on the side far from the multi-trapezoidal active layer is such that the etching rate is slower than the composition of the semiconductor forming the trapezoidal portion on the side closer to the active layer with respect to the etchant. Is.

In the semiconductor laser, in particular, the cladding layer forming the mesa is (Al _x Ga _1-x ) _0.5.
It includes a semiconductor layer made of In _0.5 P (0.5 ≦ x ≦ 0.8).

In the semiconductor laser, in particular, the composition of the semiconductor forming each trapezoidal portion of the multi-trapezoidal shape is (Al _x1 Ga _{1 -x1} ) in order from the side farther from the active layer.
_{0.5 In 0 .5 P, (Al} x2 Ga 1-x2) 0.5 In 0.5 P (0.
The composition is such that 5 ≦ x1 <x2 ≦ 0.8).

The semiconductor laser according to the present invention is a semiconductor laser having a mesa-type cladding layer for lateral mode control, wherein the cross section of the mesa perpendicular to the waveguide direction is a rectangle or a side of the mesa. Angle to the base of is 55
The composition of the semiconductor, which has a shape of not less than 90 ° and not more than 90 °, is such that the etching rate becomes faster from the far side to the closer side of the etchant with respect to the etchant. It is continuously changing.

In the semiconductor laser, particularly, the cladding layer forming the mesa is (Al _x Ga _{1 -x} ) _0.5.
It includes a semiconductor layer made of In _0.5 P (0.5 ≦ x ≦ 0.8).

Further, in the semiconductor laser, in particular, the composition of the semiconductor forming the mesa portion is (Al _x
Ga _1-x ) _0.5 In _0.5 P, x is x 1
To x2 (0.5≤x1 <x2≤0.8).

Further, in the method for manufacturing a semiconductor device according to the present invention, a multi-layer compound semiconductor layer having a different etching rate with respect to an etchant is continuously laminated on the semiconductor substrate so that the smaller etching rate is on the upper side. A mask is formed on the continuously stacked uppermost compound semiconductor layer, and then the compound semiconductor layer is etched using the etchant.

Two compound semiconductor layers are laminated on the semiconductor substrate, and two compound semiconductor layers having different etching rates with respect to the etchant are successively laminated so that the smaller etching rate is the upper side. Then, after forming a mask on the uppermost compound semiconductor layer, the compound semiconductor layer is etched using the etchant.

Further, in the method for manufacturing a semiconductor device according to the present invention, a compound semiconductor layer whose composition continuously changes so that the etching rate becomes faster as the etching progresses with respect to the etchant is laminated on the semiconductor substrate, After forming a mask on the uppermost compound semiconductor layer, the compound semiconductor layer is etched using the etchant.

Further, in the method of manufacturing a semiconductor device according to the present invention, a multi-layer compound semiconductor layer having a different etching rate with respect to an etchant is successively laminated on the semiconductor substrate so that the smaller etching rate is the upper side, A mask is formed on the continuously stacked uppermost compound semiconductor layer, and then the compound semiconductor layer is etched using the etchant.

In particular, the multi-layer compound semiconductor layer is formed from the side farther from the active layer in order of (Al _x1 Ga _{1 -x1} ) _0.5 In _0.5.
P, (Al _x2 Ga _{1 -x2} ) _0.5 In _0.5 P, (Al _x3 Ga
_1-x3 ) _0.5 In _0.5 P ... (Al _xn Ga _1-xn ) _0.5 In
_0.5 P (0.5≤x1 <x2 <x3 <... <xn≤0.
8) is laminated so as to have a composition as described above, and hydrobromic acid is used as the etchant.

Two compound semiconductor layers are laminated on the semiconductor substrate, and two compound semiconductor layers having different etching rates with respect to the etchant are continuously formed so that the smaller etching rate is the upper side. The compound semiconductor layer is laminated on a substrate, a mask is formed on the continuously laminated uppermost compound semiconductor layer, and then the compound semiconductor layer is etched using the etchant.

Further, in particular, the two-layer compound semiconductor layer is (Al _x1 Ga _{1 -x1} ) _0.5 In _{0.5 in} order from the side distant from the active layer.
P, (Al _x2 Ga _{1 -x2} ) _0.5 In _0.5 P (0.5 ≦ x1 <
x2 ≦ 0.8), and hydrobromic acid is used as the etchant.

The method of manufacturing a semiconductor device according to the present invention comprises stacking on a semiconductor substrate a compound semiconductor layer whose composition continuously changes so that the etching rate becomes faster as the etching progresses with respect to the etchant. A mask is formed on the continuously stacked uppermost compound semiconductor layer, and then the compound semiconductor layer is etched using the etchant.

In particular, when the composition of the compound semiconductor layer is written as (Al _x Ga _{1 -x} ) _0.5 In _0.5 P, x is from x1 to x2 (0.5≤x1 <x2≤0. The composition is continuously changed up to 8), and hydrobromic acid is used as the etchant.

[0031]

Function The etching rate of the compound semiconductor varies depending on the composition ratio and the material of the compound semiconductor. In the present invention, the compound semiconductor layers are successively laminated so that the composition ratio of each layer is different on the semiconductor substrate and the etching rate of each layer is decreased in order, and after forming a mask, the compound semiconductor layer is etched. Thus, a semiconductor device having a mesa structure with a small difference between the mesa top width and the mesa bottom width is manufactured. Here, an AlGaInP layer is used as an example of a compound semiconductor device for forming a mesa having a small difference between the mesa top width and the mesa bottom width.

In (Al _S Ga _1-S ) _t In _1-t P,
In the range of 0.7 ≧ s ≧ 0.5 and 0.6 ≧ t ≧ 0.4, the AlGaInP crystal laminated on the (001) plane was etched at 23 ° C. with a mixed solution of hydrobromic acid and water. The etching rate in the depth direction and the etching rate in the lateral direction substantially follow the following equations. Etching rate in the depth direction: Vd (μm / min.) = 13.8139 × s × u−
4.56084 x s-6.30373 x u + 2.046
188. Lateral etching rate: Vs (μm / min.) = − 0.395 × s × u + 0.
237 x s + 0.7179 x u-0.30784

Here, u is a value obtained by dividing the volume of hydrobromic acid water by the total volume of hydrobromic acid and water. For example, s =
When 0.5, t = 0.5 and u = 0.4, Vd =
0.00756 (μm / min.), Vs = 0.018
82 (μm / min.), S = 0.7, t = 0.5, u
= 0.4, Vd = 0.2 (μm / mi
n. ), Vs = 0.03462 (μm / min.).

As described above, the etching rates in the depth direction and the lateral direction change depending on the composition of the AlGaInP crystal and the composition of the etching solution. Furthermore, when a semiconductor layer having a different composition is etched to form a mesa, the amount of ion consumption in the etching solution caused by the above-mentioned difference in the etching rate differs at each part of the mesa, and the ion concentration distribution affects the mesa shape. give.

For example, the composition is 0.7 ≧ x on a semiconductor substrate.
(Al _x Ga ₁ -x) _Z In ₁ -z p layer such that ≧ y ≧ 0.5, 0.6 ≧ z, w ≧ 0.4, and a position farther from the substrate (Al _y Ga _1-y ) _w In _1-w P layer has a continuous mesa structure formed by etching with a mixed solution of hydrobromic acid and water as shown in FIG.
It becomes a step mesa. Further, when the difference between the etching rates of the upper and lower layers is large, the shape is as shown in FIG.
These shapes can be changed depending on x, y and the composition of the etching solution.

Further, when three or more layers are laminated on the substrate so that the etching rate increases from the side farther from the substrate, a mesa structure as shown in FIG. 2C is obtained.
When the composition of the semiconductor layer is continuously changed so that the etching rate becomes continuously higher as it gets closer to the substrate, a rectangular mesa as shown in FIG. 2D is formed by wet etching. It is possible. In addition, the cross-sectional shape of the mesa perpendicular to the stripe direction is a rectangle or a shape in which the angle of the side of the mesa with respect to the base is 55 ° or more and 90 ° or less, and the composition forming the mesa portion is With respect to the etchant, the etching rate continuously changes from the far side to the near side of the active layer so as to increase the etching rate.

As described above, the mesa shape can be controlled relatively freely by continuously growing semiconductor layers having different etching rates on the substrate. In particular, when the etching rate of the semiconductor layer on the side closer to the substrate is increased, the mesa shape approaches a rectangle. In the above example, the explanation was made using AlGaInP as the semiconductor material and a mixed solution of hydrobromic acid and water as the etchant, but the semiconductor device and the manufacturing method thereof, and the semiconductor laser and the manufacturing method according to the present invention are the same as those of other semiconductors. The material can also be implemented by using an appropriate etchant.

The semiconductor laser having the mesa shape as described above has a smaller difference between the mesa top width and the mesa bottom width than the semiconductor laser having the mesa shape as shown in FIG. 3C of the conventional example. In addition, it is characterized by high efficiency during laser oscillation and high kink level.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION A semiconductor device and a method for manufacturing the same according to the present invention will be described below with reference to embodiments in which the semiconductor laser and the method for manufacturing the same are applied. In this embodiment, an AlGaInP-based semiconductor laser is used as the semiconductor laser.

As shown in FIG. 1A, an n-type (Al _0.6 Ga) is formed on an n-type GaAs substrate (plane orientation: (001)) 201.
_0.4 ) _0.5 In _0.5 P clad layer 202 (thickness: 1.5 μ
m), multiple quantum well active layer 203, p-type (Al _0.6 Ga
_0.4 ) _0.5 In _0.5 P inner clad layer 204 (thickness:
0.3 μm), p-type GaInP etching stopper layer 2
05 (thickness: 0.01 μm), p-type (Al _0.65 G
a _0.35 ) _0.5 In _0.5 P first outer cladding layer 206
(Thickness: 0.3 μm), p-type (Al _0.6 Ga _0.4 ) _0.5 I
n _0.5 P second outer cladding layer 207 (thickness: 0.9
μm), p-type GaInP heterobuffer layer 208 (thickness: 0.02 μm), p-type GaAs cap layer 209.
(Thickness: 0.3 μm) is epitaxially grown by the MOVPE method, and stripes are formed in the <1 (recession) 10> direction using the SiO ₂ film 210 (thickness: 0.3 μm) as a mask by a process such as thermal CVD or photolithography. Form.

Next, as shown in FIG. 1B, the GaAs cap layer 209, the GaInP hetero buffer layer 208,
The (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P second outer clad layer 207 and the (Al _0.65 Ga _0.35 ) _0.5 In _0.5 P first outer clad layer 206 are sequentially provided with phosphoric acid, hydrogen peroxide solution, and water.
Etching is performed up to the etching stopper layer using a mixed solution of hydrobromic acid, hydrogen peroxide and water, or hydrobromic acid and water to form a mesa. When the first and second outer clad layers 206 and 207 are etched with an etching solution having a mixing ratio of hydrobromic acid and water of 1: 1, for example, FIG.
A two-step mesa as shown in can be formed.

After that, as shown in FIG. 1C, the side surface of the mesa is covered with an n-type GaAs current blocking layer 211 (thickness: 1 μm).
m), the SiO ₂ film 210 is removed, and then a p-type GaAs contact layer 212 (thickness: 3 μm) is laminated.

The wafer p and n electrodes thus formed are attached, cleaved so as to have a cavity length of about 700 μm, and disassembled into individual chips to manufacture a semiconductor laser.

An end face coating having a front surface reflectance of 30% and a rear surface reflectance of 85% was applied to the semiconductor laser thus manufactured, and the characteristics of the laser having a mesa bottom width of 5 μm were evaluated. Efficiency is 0.55W /
A, the kink level was 55 mW, whereas the laser of the present invention had an efficiency of 0.6 W / A and a kink level of 60.
mW.

[0045]

As described above, according to the present invention, the mesa shape can be controlled relatively freely by continuously growing the semiconductor layers having different etching rates on the substrate.
In particular, when the etching rate of the semiconductor layer on the side closer to the substrate is increased, the cross section of the mesa perpendicular to the stripe direction is rectangular, or the angle of the side of the mesa with respect to the bottom is 55 ° or more and 90 ° or more. The following shapes can be formed.

When applied to a semiconductor laser, the mesa shape formed by wet etching can be improved, and a semiconductor laser having a high kink level and high efficiency can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention in process order.

FIG. 2 is a sectional view showing the operation of the present invention.

FIG. 3 is a sectional view showing a conventional example in the order of steps.

[Explanation of symbols]

 201 substrate 202 clad layer 203 multiple quantum well active layer 204 inner clad layer 205 etching stopper layer 206 first outer clad layer 207 second outer clad layer 208 heterobuffer layer 209 cap layer

Claims (21)

[Claims] 1. A semiconductor device in which mesa-shaped stripes are formed on a semiconductor substrate, wherein a cross-sectional shape of the mesa perpendicular to the stripe direction is a trapezoid formed in two or three or more stacked layers. In the multi-trapezoidal shape, the length of the lower base of the trapezoid on the side farther from the active layer is longer than the length of the upper base of the trapezoid on the side closer to the active layer, and the side farther from the active layer of the multi-trapezoidal shape. The semiconductor device that constitutes the trapezoidal portion of the semiconductor device has a slower etching rate than the composition of the semiconductor that constitutes the trapezoidal portion on the side closer to the active layer than the etchant. 2. A semiconductor device in which mesa-shaped stripes are formed on a semiconductor substrate, wherein a cross-sectional shape of the mesa perpendicular to the stripe direction is a shape in which both ends of a lower base of a trapezoidal mesa are cut off, That is, in the double trapezoidal shape, the length of the lower base of the trapezoid farther from the active layer is substantially the same as the length of the upper base of the trapezoid closer to the active layer. A semiconductor device, wherein the composition of the semiconductor forming the trapezoidal portion on the far side is a composition having an etching rate slower than that of the semiconductor forming the trapezoidal portion on the side closer to the active layer with respect to the etchant. 3. A semiconductor device having a mesa-shaped stripe formed on a semiconductor substrate, wherein the cross-section of the mesa perpendicular to the stripe direction is rectangular, or the angle of the side of the mesa with respect to the bottom is 55 °. It has a shape of 90 ° or less, and the composition of the mesa portion is such that the etching rate increases continuously from the far side to the near side of the active layer with respect to the etchant. A semiconductor device characterized by being changed. 4. A semiconductor laser having a mesa-type cladding layer for transverse mode control, wherein the cross-section of the mesa perpendicular to the waveguide direction has a trapezoidal shape.
In the multi-trapezoidal shape, the length of the lower base of the trapezoid farther from the active layer is longer than the length of the upper base of the trapezoid closer to the active layer, The composition of the semiconductor forming the trapezoidal portion on the side far from the multi-trapezoidal active layer is such that the etching rate is slower than that of the semiconductor forming the trapezoidal portion on the side closer to the active layer with respect to the etchant. A semiconductor laser characterized by the above. 5. In the semiconductor laser, in particular, the cladding layer forming the mesa is (Al _x Ga _{1 -x} ) _0.5 I.
The semiconductor laser according to claim 4, further comprising a semiconductor layer made of n _0.5 P (0.5 ≦ x ≦ 0.8). 6. In the semiconductor laser, in particular, the composition of the semiconductor constituting each trapezoidal portion of the multiple trapezoidal shape is
From the side farther from the active layer, (Al _x1 Ga _{1 -x1} ) _0.5 I
n _0.5 P, (Al _x2 Ga _{1 -x2} ) _0.5 In _0.5 P, (Al _{x3
Ga 1-x3) 0.5 In 0} .5 P ··· (Al xn Ga 1-xn) 0.5
In _0.5 P (0.5 ≦ x1 <x2 <x3 <... <xn ≦
The semiconductor laser according to claim 4, which has a composition such as 0.8). 7. A semiconductor laser having a mesa-type cladding layer for lateral mode control, wherein a cross-sectional shape of the mesa perpendicular to the waveguide direction is a trapezoidal mesa with the lower base side cut off at both ends. That is, in the double trapezoidal shape, the length of the lower base of the trapezoid farther from the active layer is substantially the same as the length of the upper base of the trapezoid closer to the active layer. A semiconductor laser, wherein the composition of the semiconductor forming the trapezoidal portion on the far side is a composition having an etching rate slower than that of the semiconductor forming the trapezoidal portion on the side closer to the active layer with respect to the etchant. 8. In the semiconductor laser, in particular, the cladding layer forming the mesa is (Al _x Ga _{1 -x} ) _0.5 I.
The semiconductor laser according to claim 7, further comprising a semiconductor layer made of n _0.5 P (0.5 ≦ x ≦ 0.8). 9. In the semiconductor laser, in particular, the composition of the semiconductor constituting each trapezoidal portion of the multiple trapezoidal shape is
From the side farther from the active layer, (Al _x1 Ga _{1 -x1} ) _0.5 I
n _0.5 P, (Al _x2 Ga _{1 -x2} ) _0.5 In _0.5 P (0.5 ≦
8. The semiconductor laser according to claim 7, wherein the composition is such that x1 <x2 ≦ 0.8). 10. A semiconductor laser having a mesa-type cladding layer for lateral mode control, wherein the cross section of the mesa perpendicular to the waveguide direction is rectangular, or the angle of the side of the mesa with respect to the base is 55 °. 90 ° or more
It has the following shape, and the composition of the semiconductor forming the mesa portion continuously changes with respect to the etchant from the far side to the near side of the active layer so that the etching rate becomes faster. A semiconductor laser characterized in that 11. In the semiconductor laser, in particular, the cladding layer forming the mesa is (Al _x Ga _{1 -x} ) _0.5.
The semiconductor laser according to claim 10, comprising a semiconductor layer made of In _0.5 P (0.5 ≦ x ≦ 0.8). 12. In the semiconductor laser, in particular, a composition of a semiconductor forming the mesa portion has a composition of (Al _x
Ga _1-x ) _0.5 In _0.5 P, x is x 1
11. The semiconductor laser according to claim 10, wherein the composition has a composition that continuously changes from 1 to x2 (0.5≤x1 <x2≤0.8). 13. A compound semiconductor layer, which is a multi-layered compound semiconductor layer having a different etching rate with respect to an etchant, is continuously laminated on a semiconductor substrate so that the smaller etching rate is on the upper side, and the continuously laminated uppermost compound semiconductor layer is formed. A method of manufacturing a semiconductor device, comprising: forming a mask on a layer; and etching the compound semiconductor layer using the etchant. 14. The compound semiconductor layer to be laminated on the semiconductor substrate is made into two layers, and two compound semiconductor layers having different etching rates with respect to the etchant are continuously formed so that the smaller etching rate is the upper side. 14. The method for manufacturing a semiconductor device according to claim 13, wherein the compound semiconductor layer is stacked, a mask is formed on the uppermost compound semiconductor layer, and then the compound semiconductor layer is etched using the etchant. 15. A compound semiconductor layer, the composition of which continuously changes so that the etching rate increases as the etching progresses with respect to the etchant, is stacked on a semiconductor substrate, and a mask is formed on the uppermost compound semiconductor layer. After the formation, the compound semiconductor layer is etched using the etchant, the method for manufacturing a semiconductor device. 16. A compound semiconductor layer, which is a multi-layered compound semiconductor layer having different etching rates with respect to an etchant, is continuously laminated on a semiconductor substrate so that the smaller etching rate is on the upper side, and the continuously laminated uppermost compound semiconductor layer. A method of manufacturing a semiconductor laser, comprising forming a mask on a layer, and etching the compound semiconductor layer using the etchant. 17. Particularly, the multi-layer compound semiconductor layer is formed from a side farther from an active layer in order of (Al _x1 Ga _{1 -x1} ) _0.5 In.
_0.5 P, (Al _x2 Ga _{1 -x2} ) _0.5 In _0.5 P, (Al _x3 G
a _1-x3 ) _0.5 In _0.5 P ... (Al _xn Ga _1-xn ) _0.5 I
n _0.5 P (0.5 ≦ x1 <x2 <x3 <... <xn ≦ 0.
The semiconductor laser according to claim 16, wherein the semiconductor lasers are stacked so as to have a composition like 8), and hydrobromic acid is used as the etchant. 18. The compound semiconductor layer laminated on the semiconductor substrate is made into two layers, and the two compound semiconductor layers having different etching rates with respect to the etchant are consecutively arranged so that the smaller etching rate is higher. 17. The semiconductor laser according to claim 16, wherein the compound semiconductor layer is stacked on a semiconductor substrate, a mask is formed on the continuously stacked uppermost compound semiconductor layer, and then the compound semiconductor layer is etched using the etchant. Manufacturing method. 19. Particularly, the two-layer compound semiconductor layer is formed in order from the side farther from the active layer to (Al _x1 Ga _{1 -x1} ) _0.5 In.
_0.5 P, (Al _x2 Ga _{1 -x2} ) _0.5 In _0.5 P (0.5 ≦ x1
19. The semiconductor laser according to claim 18, wherein the layers are stacked to have a composition of <x2 <≦ 0.8), and hydrobromic acid is used as the etchant. 20. A compound semiconductor layer, the composition of which continuously changes so that the etching rate becomes faster as the etching progresses with respect to the etchant, is stacked on a semiconductor substrate, and the continuously stacked uppermost compound semiconductor layer. A method of manufacturing a semiconductor laser, comprising forming a mask on a layer, and etching the compound semiconductor layer using the etchant. 21. In particular the compound semiconductor layer, when expressed writes the composition as _{(Al x Ga 1-x)} 0. 5 In 0.5 P, x is x1 from x2 (0.5 ≦ x1 <x2 ≦ The method of manufacturing a semiconductor laser according to claim 20, wherein the composition has a composition that continuously changes up to 0.8), and hydrobromic acid is used as the etchant.