JPH1131865A - Semiconductor laser and method for manufacturing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser together with its manufacturing method, wherein a threshold current value is reduced and differential efficiently is improved, a stable lateral mode oscillation is realized even at a high output, moreover, manufactured with ease. SOLUTION: In an AlGaInP group semiconductor laser, on the both side parts of a ridge stripe part, an n-type current bottleneck layer 11 comprising an n-type GaAs layer 11a which absorbs light from an active layer 4 and, over it, an n--type Alw Ga1-w As layer 11b (0.4<=w<=0.7) of a composition such that it does not absorb the light from the active layer 4 is provided. Instead of the n-type GaAs layer 11a, an n-type Alv Ga1-v As layer (v<w) of a composition such as one absorbing the light from the active layer 4 may be used. Alternatively, an n-type GaAs/Alu Ga1-u As super-lattice layer wherein an n-type GaAs layer and an n-type Alu Ga1-u As layer (0.4<=u<=0.7) of a composition which does not absorb light from the active layer 4 are laminated alternately may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor laser and a method for manufacturing the same, and more particularly, to an AlGaInP-based semiconductor laser and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional refractive index waveguide type AlGa.
It is sectional drawing which shows an InP type semiconductor laser. This conventional AlGaInP-based semiconductor laser has a SCH (Separate C
The active layer has a multiple quantum well (MQW) structure.

As shown in FIG. 7, this conventional AlGaI
In an nP-based semiconductor laser, for example, an n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 102 and an n-type (Al _0.5 Ga) are formed on an n-type GaAs substrate 101 having a main surface turned off from the (001) plane. _0.5 ) _0.5 In _0.5 P optical waveguide layer 103, Ga _x In _1-x P quantum well layer and (Al
_0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer and MQW structure active layer 104, p-type (Al _0.5 Ga _0.5 ) _0.5 In _0.5
P optical waveguide layer 105, p-type (Al _0.7 Ga _0.3 ) _0.5 In
_0.5 P cladding layer 106, p-type Ga _y In _1-y P etching stop layer 107, p-type (Al _0.7 Ga _{0.3) 0.5} In
_{A 0.5} P cladding layer 108, a p-type Ga _z In _{1 -z} P intermediate layer 109 and a p-type GaAs cap layer 110 are sequentially stacked. Here, Ga _x In _1-x P of the active layer 104 is used.
Ga composition ratio in the quantum well layer x, p-type Ga _y In _1-y P Ga composition ratio of the etching stop layer 107 y and p-type Ga _z I
As an example of the Ga composition ratio z of the n _{1 -z} P intermediate layer 109, x = 0.45 and y = z = 0.59.

A p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P
Cladding layer 108, p-type Ga _z In _1-z P intermediate layer 109
The p-type GaAs cap layer 110 has a predetermined ridge stripe shape extending in one direction. The n-type GaAs current confinement layer 1 is formed on both sides of the ridge stripe.
11 are buried, thereby forming a current confinement structure.

On the p-type GaAs cap layer 110 and the n-type GaAs current confinement layer 111, for example, Ti / Pt /
A p-side electrode 112 such as an Au electrode is provided while n
An n-side electrode 113 such as an AuGe / Ni electrode is provided on the back surface of the type GaAs substrate 101.

In the above-described conventional AlGaInP-based semiconductor laser, the n-type GaAs current confinement layer 111 is buried on both sides of the ridge stripe portion, so that the portion corresponding to the ridge stripe portion is refracted laterally. A refractive index step having a high refractive index and a low refractive index in a portion corresponding to both sides thereof is formed, and lateral mode control is performed.

[0007]

However, in the above-described conventional AlGaInP-based semiconductor laser, light loss due to the n-type GaAs current confinement layer 110 buried on both sides of the ridge stripe portion is large, and laser oscillation occurs. There is a problem in that it is difficult to reduce the threshold current value and improve the differential efficiency.

Conventionally, an AlGaInP-based semiconductor laser has been known in which a current constriction layer has a multilayer structure in which different types of semiconductor layers are stacked instead of a single-layer structure of a GaAs layer. For example, Japanese Patent Application Laid-Open No.
Reference numeral 88 denotes a GaAs layer, a GaInP layer and a GaAs layer as a current confinement layer, or an AlGaAs layer and an AlG layer.
AlG in which an aInP layer and an AlGaAs layer are sequentially laminated
The configuration of an aInP-based semiconductor laser is disclosed,
Journal of Selected Topics in Quantum Electronics
Vol. 1 (1995) 723 discloses a configuration of an AlGaInP-based semiconductor laser in which an AlInP layer and a GaAs layer are sequentially stacked as a current confinement layer. These A mentioned above
In an lGaInP-based semiconductor laser, the current confinement layer has a multilayer structure, so that light loss due to the current confinement layer can be reduced. However, since a method of selectively growing a semiconductor layer containing phosphorus (P) in the composition has not been sufficiently established, the above-described AlGaInP-based semiconductor laser has a problem in view of mass production.

On the other hand, Japanese Patent Application Laid-Open No. 3-34595 discloses an AlGaI having a double hetero structure having a stripe-shaped mesa structure.
In an nP-based semiconductor laser, an AlGaAs layer having a wider bandgap and a smaller refractive index than the active layer as a current confinement layer;
A configuration is disclosed in which a GaAs layer having a narrower forbidden band width and a larger refractive index than the active layer is sequentially laminated. However,
In the case of this AlGaInP-based semiconductor laser, when the AlGaAs layer of the current confinement layer is made thick to reduce light loss, the refractive index difference Δn in the lateral direction becomes insufficient, and particularly, a stable transverse mode oscillation at high output is obtained. There is a problem that it becomes difficult.

Accordingly, an object of the present invention is to reduce the threshold current value and improve the differential efficiency, to realize stable transverse mode oscillation even at a high output, and to easily manufacture the device. And a method for manufacturing the same.

[0011]

To achieve the above object, a first aspect of the present invention is to provide a first conductive type first cladding layer, an active layer on the first cladding layer, A current confinement structure having a second conductivity type second cladding layer on the layer, and a first conductivity type current confinement layer embedded in both sides of a ridge stripe portion provided in the second cladding layer. In the AlGaInP-based semiconductor laser having the structure, the current confinement layer has an Al _v Ga composition having a composition for absorbing light from the active layer.
_{A 1-v} As layer and an Al _w Ga _1-w As layer having a composition that does not absorb light from the active layer on the Al _v Ga _1-v As layer (however,
0 ≦ v <w ≦ 1).

According to a second aspect of the present invention, there is provided a first conductive type first cladding layer, an active layer on the first cladding layer, and a second conductive type second cladding layer on the active layer. And the second
In an AlGaInP-based semiconductor laser having a current confinement structure in which a current confinement layer of the first conductivity type is embedded on both sides of a ridge stripe portion provided in a cladding layer, the current confinement layer reflects light from the active layer. A of composition to absorb
l _v Ga _1-v As layer and Al _u Ga _1-u As layer of the composition that does not absorb light from the active layer (where, 0 ≦ v <u ≦ 1 ) Al and are alternately stacked _v Ga _{1- v} As / Al _u Ga
_1-u As superlattice _{layers, Al v Ga 1-v As} / Al u Ga
An Al _w Ga _1-w As layer (0 ≦ v <w ≦ 1) having a composition that does not absorb light from the active layer on the _1-u As superlattice layer is characterized.

According to a third aspect of the invention, there is provided a method of manufacturing a semiconductor laser, comprising: forming a first cladding layer of a first conductivity type on a substrate; and forming an active layer on the first cladding layer. Forming a second cladding layer of the second conductivity type on the active layer, forming a ridge stripe on the second cladding layer by etching, and filling both sides of the ridge stripe. As described above, an Al _v Ga _1-v As layer having a composition for absorbing light from the active layer and an Al _v
Forming a first conductivity type current confinement layer comprising an Al _w Ga _1-w As layer (0 ≦ v <w ≦ 1) having a composition that does not absorb light from the active layer on the Ga _1-v As layer; And a step of performing

According to a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor laser, comprising: forming a first cladding layer of a first conductivity type on a substrate; and forming an active layer on the first cladding layer. Forming a second cladding layer of the second conductivity type on the active layer, forming a ridge stripe on the second cladding layer by etching, and filling both sides of the ridge stripe. As described above, an Al _v Ga _{1 -v} As layer having a composition absorbing light from the active layer and an Al _u Ga _{1 -u} As layer having a composition not absorbing light from the active layer (where 0 ≦ v <u ≦ 1) ) And Al _v Ga alternately stacked
_1-v As / Al _u Ga _1-u As superlattice layer and Al _v Ga
_{1-v As / Al u Ga} 1-u As Al w Ga 1-w As layer of the composition that does not absorb light from the active layer on the superlattice layer (where, 0 ≦ v <w ≦ 1 ) consisting of a first Forming a one-conductivity type current confinement layer.

In the first aspect of the present invention, Al _w G
The Al composition ratio w of the a _1-w As layer is preferably, for example, 0.
It is selected so as to satisfy 4 ≦ w ≦ 0.7. Where Al
The lower limit of the composition ratio w is determined according to the wavelength of light from the active layer. Here, as an example, the lower limit of the Al composition ratio w is set to 0.4. On the other hand, the reason why the upper limit of the Al composition ratio w is 0.7 is that when the Al composition ratio w is larger than 0.7, the Al _w Ga _{1 -w} As layer is etched even with water, and This not only hinders production, but is also undesirable in terms of reliability. Also, A
The Al composition ratio v of the l _v Ga _1-v As layer is preferably selected so as to satisfy, for example, 0 ≦ v ≦ 0.3. Note that Al _v
It is preferable that the Ga _1-v As layer and the Al _w Ga _1-w As layer have compositions different from each other to some extent, and from this viewpoint, the Al _v Ga _1-v As layer is, for example, an Al _v Ga _1-v As layer.
A composition ratio v = 0, that is, a GaAs layer is used.

In the second aspect of the present invention, from the same viewpoint as in the _{first aspect} , Al _v Ga _{1 -v} As / A
l _u Ga _1-u As superlattice layer Al _u Ga _1-u As layer A
The l composition ratio u is selected so as to satisfy 0.4 ≦ u ≦ 0.7, and the Al composition ratio w of the Al _w Ga _1-w As layer is 0.4 ≦ w.
It is selected to satisfy ≦ 0.7. In this case, A
The 1 composition ratio u and the Al composition ratio w may be u = w. _{Also, Al v Ga 1-v As} / Al u Ga 1-u As Al constituting the superlattice layer _v Ga _1-v As layer of Al composition ratio v
Is preferably selected to satisfy, for example, 0 ≦ v ≦ 0.3. _{Incidentally, Al v Ga 1-v As} / Al u Ga 1-u As
Al _v Ga _1-v As layer and Al _u Ga constituting the superlattice layer
It is preferable that the _1-u As layers have different compositions from each other to some extent, and from this viewpoint, Al _v Ga _1-v A
Al _v Ga constituting the s / Al _u Ga _1-u As superlattice layer
As the _1-v As layer, for example, an Al composition ratio of v = 0,
That is, a GaAs layer is used.

According to the semiconductor laser according to the first or second aspect of the present invention configured as described above, the current confinement layer has an Al _v G composition that absorbs light from the active layer.
An a _1-v As layer and an Al _w Ga _1-w As layer having a composition that does not absorb light from the active layer on the Al _v Ga _1-v As layer (where 0 ≦ v <w ≦ 1). Alternatively, the current confinement layer may have a composition of A that absorbs light from the active layer.
l _v Ga _1-v As layer and Al _u Ga _1-u As layer of the composition that does not absorb light from the active layer (where, 0 ≦ v <u ≦ 1 ) Al and are alternately stacked _v Ga _{1- v} As / Al _u Ga
_1-u As superlattice _{layers, Al v Ga 1-v As} / Al u Ga
_By forming an Al _w Ga _1-w As layer (0 ≦ v <w ≦ 1) having a composition that does not absorb light from the active layer on the _1-u As superlattice layer, the refractive index difference in the lateral direction can be improved. While maintaining Δn sufficiently, light loss in the current confinement layer can be reduced. Also, Al _v Ga _1-v A constituting the current confinement layer
s layer and Al _w Ga _{1 -w} As layer, or Al _v G
a _1-v As / Al _u Ga _1-u As superlattice layer and Al _w
Each of the Ga _{1 -w} As layers is made of a material that does not contain phosphorus (P) in the composition, so that selective growth is easy.

According to the method of manufacturing a semiconductor laser according to the third or fourth aspect of the present invention, the semiconductor laser according to the first or second aspect is manufactured, respectively. And at this time,
Al _v Ga _{1 -v} As layer constituting current constriction layer and Al
_w Ga _1-w As layer or Al _v Ga _1-v As / A
l _u Ga _1-u As superlattice layers and Al _w Ga _1-w As layer are both easy to selective growth since a material that does not contain phosphorus (P) in the composition, thus, a semiconductor laser easily Can be manufactured.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment of the present invention will be described. FIG. 1 is a sectional view showing a refractive index guided AlGaInP-based semiconductor laser according to the first embodiment. This AlGaInP semiconductor laser has an SCH structure, and the active layer has an MQW structure.

As shown in FIG. 1, in the AlGaInP-based semiconductor laser according to the first embodiment, for example, n-type GaAs having a main surface turned off from the (001) plane is used.
n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5
P cladding layer 2, n-type (Al _0.5 Ga _0.5 ) _0.5 In
_0.5 P optical waveguide layer 3, Ga _x In _1-x P quantum well layer and (A
_{l 0.5 Ga 0.5) 0.5 In 0.5} P barrier layers and the active layer of the MQW structure 4, p-type _{(Al 0.5 Ga 0.5) 0.5 In} 0.5 P
Optical waveguide layer 5, p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P
Cladding layer 6, p-type Ga _y In _1-y P etching stop layer 7, p-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P cladding layer 8, p-type Ga _z In _1-z P intermediate layer 9 and the p-type GaA
The s cap layers 10 are sequentially stacked. Here, the Ga composition ratio x, p of the Ga _x In _1-x P quantum well layer of the active layer 4
Composition ratio y of p _- type Ga _y In _1-y P etching stop layer 7
An example of the Ga composition ratio z of the p-type Ga _z In _1-z P intermediate layer 9 is x = 0.45, y = z =
0.59.

P-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P
Cladding layer 8, p-type Ga _z In _1-z P intermediate layer 9 and p-type
The type GaAs cap layer 10 has a predetermined ridge stripe shape extending in one direction. An n-type current confinement layer 11 is embedded in both sides of the ridge stripe portion,
As a result, a current confinement structure is formed. here,
n-type current confinement layer 11 is provided via a p-type Ga _y In _1-y P etching stop layer 7 on p-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P cladding layer 6 at opposite sides of the ridge stripe portion N-type GaAs layer 11a
N-type Al _w Ga _1-w provided on the n-type GaAs layer 11a
And an As layer 11b.

A p-side electrode 12 such as a Ti / Pt / Au electrode is provided on the p-type GaAs cap layer 10 and the n-type current confinement layer 11, while AuGe is provided on the back surface of the n-type GaAs substrate 1. / N-side electrode 13 such as Ni electrode
Is provided.

Here, as an example of the thickness of each semiconductor layer constituting this AlGaInP semiconductor laser, the thickness of the n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 2 is 1.1 μm, Mold (Al _0.5 Ga _0.5 ) _0.5 In
_0.5 P optical waveguide layer 3 and p-type (Al _0.5 Ga _0.5 ) _0.5
The thickness of the In _0.5 P optical waveguide layer 5 is 10 nm each, and the Ga _x In _{1 -x} P quantum well layer of the active layer 4 and the (Al _0.5 G
a _0.5 ) _0.5 In _0.5 P barrier layers each have a thickness of 4 n
m, p-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P thickness of the cladding layer 6 is 0.3 [mu] m, the thickness of the p-type Ga _y In _1-y P etching stop layer 7 is 15 nm, a p-type (Al _0.7 Ga
_0.3 ) _0.5 In _0.5 P clad layer 8 has a thickness of 0.8 μm
It is. The active layer 4 having the MQW structure is made of Ga _x In.
For example, five _1-x P quantum well layers are provided.

In this AlGaInP-based semiconductor laser, the n-type GaAs forming the lower side of the n-type current confinement layer 11
The s layer 11a has a band gap smaller than that of the Ga _x In _1-x P quantum well layer of the active layer 4 and absorbs light from the active layer 4. On the other hand, as the n-type Al _w Ga _{1 -w} As layer 11 b constituting the upper layer side of the n-type current confinement layer 11, light from the active layer 4 is used to suppress light loss in the n-type current confinement layer 11. A composition that does not absorb, in other words, a composition whose forbidden bandwidth is larger than the forbidden bandwidth of the Ga _x In _1-x P quantum well layer of the active layer 4 is used. Therefore, in this case, the n-type Al _w Ga _1-w As layer 11b
The lower limit of the composition ratio w is determined according to the wavelength of light from the active layer 4. Specifically, in the case of the first embodiment, since the Ga composition ratio x of the Ga _x In _{1 -x} P quantum well layer of the active layer 4 is 0.45, n-type Al _w Ga _{1 -w} As Layer 11b
Is selected to be 0.4 or more. On the other hand, n-type A
l _w Ga _1-w when the Al composition ratio w of As layer 11b exceeds 0.7, the n-type Al _w Ga _1-w As layer 11b is water (H
Etching occurs even with ₂ O), which not only hinders the manufacture of semiconductor lasers, but is also undesirable in terms of reliability. Therefore, the Al composition ratio w of the n-type Al _w Ga _{1 -w} As layer 11b is preferably 0.7 or less. As described above, in this AlGaInP-based semiconductor laser,
The Al composition ratio w of the n-type Al _w Ga _{1 -w} As layer 11b is:
It is selected so as to satisfy 0.4 ≦ w ≦ 0.7. As an example, w = 0.5.

In this AlGaInP-based semiconductor laser, the n-type GaAs layer 11a for absorbing light from the active layer 4 is provided below the n-type current confinement layer 11, so that the ridge stripe portion is formed in the lateral direction. Is formed, a refractive index step is formed in which the refractive index is high in the portion corresponding to, and the refractive index is low in the portions corresponding to both sides thereof, the lateral mode is controlled, and the active layer 4 is formed on the upper layer side of the n-type current confinement layer 11. N-type Al _w Ga _1-w As layer 11b that does not absorb light
By providing (0.4 ≦ w ≦ 0.7), light loss in the n-type current confinement layer 11 is reduced. In this case, the thickness of the n-type GaAs layer 11a on both sides of the ridge stripe portion is, for example, 20 to such a value that the optical loss does not increase and the refractive index difference Δn in the lateral direction can be sufficiently ensured. It is selected to be about 50 nm. Further, n in the portions on both sides of the ridge stripe portion
The thickness of the type Al _w Ga _{1 -w} As layer 11b is, for example, 1 μm.
Chosen by degree.

Next, a method of manufacturing the semiconductor laser according to the first embodiment will be described. That is, this Al
In order to manufacture a GaInP-based semiconductor laser, first,
As shown in FIG. 2, on an n-type GaAs substrate 1, an n-type (A
_{l 0.7 Ga 0.3) 0.5 In 0.5} P cladding layer 2, n-type _{(Al 0.5 Ga 0.5) 0.5 In} 0.5 P optical waveguide layer 3, Ga
_z In _1-z P quantum well layer and (Al _0.5 Ga _0.5 ) _0.5 I
Active layer 4 of MQW structure with n _0.5 P barrier layer, p-type (Al
_0.5 Ga _0.5 ) _0.5 In _0.5 P optical waveguide layer 5, p-type (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 6, p-type Ga
_y In _1-y P etching stop layer 7, p-type (Al _0.7 Ga
_{0.3) 0.5} In _0.5 P cladding layer 8, p-type Ga _y an In
_1-y P contact layer 9 and p-type GaAs cap layer 1
0 is sequentially grown, for example, by a metal organic chemical vapor deposition (MOCVD) method.

Next, as shown in FIG. 3, a SiO ₂ film or a SiN film is formed on the entire surface of the p-type GaAs cap layer 10 and then patterned by etching to form a striped mask 14 having a predetermined width. I do. Next, using this mask 14 as an etching mask, p-type Ga is formed by a wet etching method using a hydrochloric acid type etching solution and a wet etching method using a sulfuric acid type etching solution.
As cap layer 10, p-type Ga _z In _1-z P intermediate layer 9 and p-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P cladding layer 8, p-type Ga _y In _1-y P etching stop layer 7 is exposed Etching is performed in order. Thereby, the p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 8, the p-type Ga _z In _{1 -z} P intermediate layer 9, and the p-type GaAs
The cap layer 10 is patterned in a predetermined ridge stripe shape extending in one direction.

Next, as shown in FIG. 4, using the mask 14 as a growth mask, an n-type GaAs layer 11a is grown on both sides of the ridge stripe portion by, for example, MOCVD.

Next, as shown in FIG. 5, on the n-type GaAs layers 11a, growing a n-type Al _w Ga _1-w As layer 11b for example by MOCVD. Thereby, n-type Ga
An n-type current confinement layer 11 composed of an As layer 11a and an n-type Al _w Ga _{1 -w} As layer 11b is formed.

Next, the mask 14 is removed by etching and n
After lapping the type GaAs substrate 1 to a thickness of, for example, about 150 μm, as shown in FIG. 1, a p-side electrode 12 is formed on the entire surface of the p-type GaAs cap layer 10 and the n-type GaAs current confinement layer 11 by vapor deposition. With n-type G
An n-side electrode 13 is formed on the back surface of the aAs substrate 1. As described above, the intended AlGaInP-based semiconductor laser is manufactured.

As described above, according to the first embodiment, the n-type current confinement layer 11 is composed of the n-type GaAs layer 11a absorbing light from the active layer 4 and the n-type GaAs layer 11a.
N-type Al _w G having a composition that does not absorb light from the upper active layer 4
a _1-w As layer 11b allows the n-type current confinement layer 11 to be maintained while sufficiently maintaining the refractive index difference Δn in the lateral direction.
Light loss can be reduced. Therefore, the threshold current value of laser oscillation can be reduced and the differential efficiency can be improved, and stable transverse mode oscillation can be realized even at high output. In addition, since the threshold current value is reduced and the differential efficiency is improved, the operating current can be reduced. As a result, the high-temperature characteristics of the semiconductor laser are improved, so that the life can be further extended. it can. Further, the n-type GaAs layer 11a and the n-type Al _w Ga _1-w As layer 11 forming the n-type current confinement layer 11
Since b is composed of a material that does not contain phosphorus in its composition, it is possible to easily perform selective growth of these. For this reason, there is also an advantage that, when manufacturing this AlGaInP-based semiconductor laser, it is possible to easily cope with mass production.

Next, a second embodiment of the present invention will be described. In the AlGaInP-based semiconductor laser according to the second embodiment, instead of the n-type GaAs layer 11a constituting the n-type current confinement layer 11, an n-type Al _v Ga ₁₋ having a composition for absorbing light from the active layer 4 is used. _v As layer is used. In this case, n-type Al _v Ga _1-v As Al composition ratio of the layer v and, the n-type Al _v Ga _1-v As layer of n-type Al _w
The Al composition ratio w of the Ga _1-w As layer 11b satisfies the relationship v <w. The Al composition ratio v of the n-type Al _v Ga _{1 -v} As layer is preferably selected so as to satisfy, for example, 0 ≦ v ≦ 0.3. Further, in this case, it is preferable that the thickness of the n-type Al _v Ga _{1 -v} As layer on both sides of the ridge stripe portion is increased as the Al composition ratio v increases. Other configurations are similar to those of the AlGaI according to the first embodiment.
The description is omitted because it is the same as the nP-based semiconductor laser.

The AlGaInP according to the second embodiment
The method of manufacturing a semiconductor laser according to the first embodiment
Since it is the same as the method of manufacturing the lGaInP-based semiconductor laser, the description is omitted.

According to the second embodiment, the same effect as that of the first embodiment can be obtained.

Next, a third embodiment of the present invention will be described. FIG. 6 is a sectional view showing an AlGaInP semiconductor laser of a refractive index guide type according to the third embodiment. This AlGaInP-based semiconductor laser has an SCH structure, and the active layer has an MQW structure.

As shown in FIG. 6, in this AlGaInP-based semiconductor laser, an n-type GaAs layer and an n-type GaAs layer 11a constituting the n-type current confinement layer 11 are replaced with an n-type GaAs layer.
And the type Al _u Ga _1-u As layer, the n-type are alternately laminated in this order _{GaAs / Al u Ga 1-u} As superlattice layers 11a'
Is used. In this case, n-type GaAs / Al _u G
The n-type GaAs layer of the a ₁ -u As superlattice layer 11 a ′ has a band gap smaller than the band gap of the Ga _x In _{1 -x} P quantum well layer of the active layer 4, and the light from the active layer 4 Absorb. On the other hand, n-type _{GaAs / Al u Ga 1-u} As superlattice layers 11a
As the n-type Al _u Ga _1-u As layer, a layer having a composition that does not absorb light from the active layer 4 is used. Specifically, the n-type _{GaAs / Al u Ga 1-u} As superlattice layers 1
The Al composition ratio u of the n-type Al _u Ga _1-u As layer constituting 1a ′ is selected so as to satisfy, for example, 0.4 ≦ u ≦ 0.7. In this case, the lower limit and the upper limit of the Al composition ratio u are determined for the same reason as that for determining the lower limit and the upper limit of the Al composition ratio w of the n-type Al _w Ga _{1 -w} As layer 11b. In this case, the Al composition ratio u and the Al composition ratio w may be u = w.

Further, n-type GaAs / Al _u Ga _1-u As
The thickness of the n-type GaAs layer and the n-type Al _u Ga _1-u As layer constituting the super lattice layer 11a '(thickness at opposite sides of the ridge stripe portion), respectively, for example, 3 to 15
nm. The total thickness of the n-type GaAs layers on both sides of the ridge stripe is, for example, 20.
N-type GaAs layer and n-type A
l _u Ga _1-u As layer are alternately stacked. The other configuration is the same as that of the AlGaInP-based semiconductor laser according to the first embodiment, and the description is omitted.

The AlGaInP according to the third embodiment
Method of manufacturing a system semiconductor laser, on both sides of the ridge stripe portion, n-type GaAs layer and the n-type Al _u Ga _1-u As
Layers are alternately grown by, for example, MOCVD to obtain n
-Type _{GaAs / Al u Ga 1-u} As after the formation of the superlattice layers 11a ', n-type to the n-type _{GaAs / Al u Ga 1-u} As superlattice layer 11a', for example, by MOCVD Al
Except for growing the _w Ga _1-w As layer 11b, the first
Since the method is the same as the method of manufacturing the AlGaInP-based semiconductor laser according to the embodiment, the description will be omitted.

According to the third embodiment, effects similar to those of the first embodiment can be obtained. Further, in the case of the third embodiment, the following effects can be obtained. That is, the AlGa according to the third embodiment
In the InP-based semiconductor laser, the n-type current confinement layer 11
For the lower side layer has a n-type _{GaAs / Al u Ga 1-u} As superlattice layers 11a ', eg, n-type GaAs layer a lower layer side of the n-type current blocking layer 11 as in the first embodiment The refractive index difference Δn in the horizontal direction can be reduced as compared with the case of the single-layer structure 11a. Therefore, this third
In the AlGaInP-based semiconductor laser according to the embodiment, the thicknesses of the p-type (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P optical waveguide layer 5 and the n-type (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P optical waveguide layer 3 and the p-type (Al Al _0.7 Ga _0.3 ) _0.5 In
_When the thickness of the _0.5 P cladding layer 6 is made larger than the thickness shown in the first embodiment and this AlGaInP-based semiconductor laser is a self-pulsation type semiconductor laser, a large margin is provided for the self-pulsation. As a result, there is an advantage that it is possible to realize self-excited oscillation up to high output and high temperature.

Next, a fourth embodiment of the present invention will be described. That is, the AlG according to the fourth embodiment
In an aInP-based semiconductor laser, n-type GaAs / A
Instead of l _u Ga _1-u As superlattice layers 11a ', a composition that does not absorb the light from the n-type Al _v Ga _1-v As layer and the active layer of the composition that absorbs light from the active layer of n-type Al _u Ga _1-u A
s layer and an n-type Al _v Ga layer alternately stacked in this order.
_{A 1-v} As / Al _u Ga _{1- u} As superlattice layer is used. In this case, n-type _{Al v Ga 1-v As /} Al u Ga
_1-u As the Al composition ratio u of the superlattice layers constituting the n-type Al _v Ga _1-v Al composition ratio of As layer v and n-type Al _u Ga _1-u As layer, v <a relationship u Fulfill. Also, n-type Al _v G
a _1-v As / Al _u Ga _1-u As constituting the superlattice layer n
Al composition ratio v of n _- type Al _v Ga _1-v As layer and n-type Al _w
The Al composition ratio w of the Ga _1-w As layer 11b satisfies the relationship v <w. Other configurations are similar to those of the third embodiment.
The description is omitted because it is the same as that of the 1GaInP-based semiconductor laser.

The AlGaInP according to the fourth embodiment
The method of manufacturing a semiconductor laser according to the third embodiment
Since it is the same as the method of manufacturing the lGaInP-based semiconductor laser, the description is omitted.

According to the fourth embodiment, the same effect as that of the third embodiment can be obtained.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above embodiments, and various modifications based on the technical idea of the present invention are possible. For example, the numerical values, materials, structures, and the like described in the embodiments are merely examples, and the present invention is not limited thereto.

For example, in the first to fourth embodiments described above, the conductivity types of the semiconductor layers constituting the substrate and the semiconductor laser may be reversed. In this case, the conductivity type of the current confinement layer embedded on both sides of the ridge stripe portion is p-type.

For example, in the above-described first to fourth embodiments, the present invention relates to an AlGaIn having a SCH structure.
The case where the present invention is applied to a P-based semiconductor laser has been described.
The present invention provides a DH (Double Heterostructure) structure A
It is also possible to apply to an lGaInP-based semiconductor laser.

[0047]

As described above, according to the first and second aspects of the present invention, the current confinement layer has an Al _v Ga _{1 -v} As layer having a composition for absorbing light from the active layer. And A
l _v Ga _1-v As layer Al _w Ga _1-w As layer of the composition that does not absorb light from the active layer (where, 0 ≦ v <w ≦ 1 )
Alternatively, the current confinement layer has an Al _v Ga _{1 -v} As layer having a composition for absorbing light from the active layer and an Al _u Ga _{1 -u} As layer having a composition for not absorbing light from the active layer. (However, 0 ≦ v <u ≦ 1)
_v Ga _1-v As / Al _u Ga _1-u As superlattice layer and Al
_{v Ga 1-v As / Al} u Ga 1-u As Al w Ga 1-w As layer of the composition that does not absorb light from the active layer on the superlattice layer (where, 0 ≦ v <w ≦ 1 ) from the Accordingly, the optical loss in the n-type current confinement layer 11 can be reduced while the lateral refractive index difference Δn is sufficiently maintained. Therefore, the threshold current value of laser oscillation can be reduced and the differential efficiency can be improved, and stable transverse mode oscillation can be realized even at high output. In addition, since the threshold current value is reduced and the differential efficiency is improved, the operating current can be reduced. As a result, the high-temperature characteristics of the semiconductor laser are improved, so that the life can be further extended. it can. Further, since each of the semiconductor layers constituting the current confinement layer is made of a material containing no phosphorus in the composition and can be easily subjected to selective growth, the semiconductor laser as described above can be easily manufactured.

According to the third and fourth aspects of the present invention, the semiconductor laser according to the first aspect and the semiconductor laser according to the second aspect can be manufactured, respectively, and the current confinement layer is formed. Since each of the semiconductor layers to be formed is made of a material that does not contain phosphorus in any of the compositions, the manufacture of the semiconductor laser is easy, and it is possible to easily cope with mass production of the semiconductor laser.

[Brief description of the drawings]

FIG. 1 shows an AlGaI according to a first embodiment of the present invention.
It is sectional drawing which shows an nP type semiconductor laser.

FIG. 2 shows an AlGaI according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for describing a method for manufacturing an nP-based semiconductor laser.

FIG. 3 shows an AlGaI according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for describing a method for manufacturing an nP-based semiconductor laser.

FIG. 4 shows an AlGaI according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for describing a method for manufacturing an nP-based semiconductor laser.

FIG. 5 shows an AlGaI according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view for describing a method for manufacturing an nP-based semiconductor laser.

FIG. 6 shows an AlGaI according to a third embodiment of the present invention.
It is sectional drawing which shows an nP type semiconductor laser.

FIG. 7 is a cross-sectional view showing a conventional AlGaInP-based semiconductor laser.

[Explanation of symbols]

1 ... n-type GaAs substrate, 4 ... active layer, 6, 8
· · P-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P cladding layer, 7 · · · p-type Ga _y In _1-y P etching stop layer,
9 ... p-type Ga _z In _1-z P intermediate layer, 10 ... p-type GaAs cap layer, 11 ... n-type current confinement layer, 11
a ... n-type GaAs layer, 11a '... n-type GaAs
/ Al _u Ga _1-u As superlattice layer, 11b... N-type Al
_w Ga _1-w As layer

Claims (13)

[Claims] 1. A first cladding layer of a first conductivity type, an active layer on the first cladding layer, and a second cladding layer of a second conductivity type on the active layer, In an AlGaInP-based semiconductor laser having a current confinement structure in which a current confinement layer of a first conductivity type is embedded on both sides of a ridge stripe portion provided in a second cladding layer, the current confinement layer is formed of the active layer An Al _v Ga _1-v As layer having a composition that absorbs light from the substrate, and an Al _w Ga layer having a composition that does not absorb light from the active layer on the Al _v Ga _1-v As layer.
A semiconductor laser comprising a _1-w As layer (where 0 ≦ v <w ≦ 1). 2. The semiconductor laser according to claim 1, wherein the Al composition ratio w of the Al _w Ga _{1 -w} As layer satisfies 0.4 ≦ w ≦ 0.7. 3. The Al _v Ga _1-v As layer has an Al composition ratio v of 0, and the Al _w Ga _1-w As layer has an Al composition ratio v of 0.
2. The semiconductor laser according to claim 1, wherein the composition ratio w satisfies 0.4 ≦ w ≦ 0.7. 4. The semiconductor laser according to claim 3, wherein the thickness of the Al _v Ga.sub.1 _-v As layer on both sides of the ridge stripe is 20 nm or more and 50 nm or less. 5. A first conductive type first optical waveguide layer between the first cladding layer and the active layer, and a second optical waveguide layer between the second cladding layer and the active layer. 2. The semiconductor laser according to claim 1, further comprising a conductive second optical waveguide layer. 6. A first cladding layer of a first conductivity type, an active layer on the first cladding layer, and a second cladding layer of a second conductivity type on the active layer, In an AlGaInP-based semiconductor laser having a current confinement structure in which a current confinement layer of a first conductivity type is embedded on both sides of a ridge stripe portion provided in a second cladding layer, the current confinement layer is formed of the active layer An Al _v Ga _1-v As layer having a composition that absorbs light from the active layer and an Al _u Ga _1-u As layer having a composition that does not absorb light from the active layer (where 0 ≦ v <u).
≦ 1) and Al _v Ga _1-v As / Al
_u Ga _1-u As superlattice layer and the above Al _v Ga _1-v As /
An Al _w Ga _1-w As layer having a composition that does not absorb light from the active layer on the Al _u Ga _1-u As superlattice layer (where 0 ≦
v <w ≦ 1). 7. The _{Al v Ga 1-v As /} Al u Ga
The Al composition ratio u of the Al _u Ga _1-u As layer constituting the _1-u As superlattice layer satisfies 0.4 ≦ u ≦ 0.7.
The Al composition ratio w of the l _w Ga _{1 -w} As layer is 0.4 ≦ w ≦ 0.
7. The semiconductor laser according to claim 6, wherein the following condition is satisfied. 8. The _{Al v Ga 1-v As /} Al u Ga
The Al _v Ga _{1 -v} As layer constituting the _1-u As superlattice layer has an Al composition ratio v of 0 and the Al _v Ga _{1 -v}
The above Al constituting the As / Al _u Ga _1-u As superlattice layer
_u Ga _1-u As layer Al composition ratio u is 0.4 ≦ u ≦ 0.7
7. The Al _w Ga _1-w As layer has an Al composition ratio w satisfying 0.4 ≦ w ≦ 0.7.
A semiconductor laser as described in the above. 9. The Al _v Ga _{1 -v} As / Al _u Ga
9. The method according to claim 8, wherein the total thickness of the Al _v Ga.sub.1 _-v As layer constituting the _1-u As superlattice layer on both sides of the ridge stripe portion is 20 nm or more and 50 nm or less. Semiconductor laser. 10. A first optical waveguide layer of a first conductivity type between the first cladding layer and the active layer,
The semiconductor laser according to claim 6, further comprising a second optical waveguide layer of a second conductivity type between the second cladding layer and the active layer. 11. The semiconductor laser according to claim 6, wherein said semiconductor laser is a self-pulsation type semiconductor laser. 12. A step of forming a first conductive type first cladding layer on a substrate, a step of forming an active layer on the first cladding layer, and a step of forming a second conductive type on the active layer. A step of forming a second clad layer, a step of forming a ridge stripe on the second clad layer by etching, and a step of filling both sides of the ridge stripe.
Al _v Ga _{1 -v} A having a composition that absorbs light from the active layer
a first layer comprising an s layer and an Al _w Ga _1-w As layer having a composition on the Al _v Ga _1-v As layer and not absorbing light from the active layer (where 0 ≦ v <w ≦ 1). Forming a conductive type current constriction layer. 13. A step of forming a first conductive type first clad layer on a substrate, a step of forming an active layer on the first clad layer, and a step of forming a second conductive type on the active layer. A step of forming a second clad layer, a step of forming a ridge stripe on the second clad layer by etching, and a step of filling both sides of the ridge stripe.
Al _v Ga _{1 -v} A having a composition that absorbs light from the active layer
Al _u G having a composition that does not absorb light from the s layer and the active layer
a _1-u As layer (where, 0 ≦ v <u ≦ 1 ) and the Al are alternately laminated _{v Ga 1-v As / Al} u Ga 1-u As superlattice layers, the Al _v Ga _{1- v} As / Al _u Ga _1-u As
A having a composition that does not absorb light from the active layer on the superlattice layer
forming a current confinement layer of the first conductivity type comprising an l _w Ga _1-w As layer (where 0 ≦ v <w ≦ 1).