JPH1126868A - Semiconductor laser and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser which can correct the bias of a light field by means of an etching stop layer and to provide a manufacture method. SOLUTION: An n-type Gau In1-u P light field correction layer 3 is provided between n-type (Al0.7 Ga0.3 )0.5 and In0.5 P clad layers 2 and 4 in the semiconductor layer of a buried ridge-type AlGaInP system, in which p-type (Al0.7 Ga0.3 )0.5 In0.5 P clad layer 10 is provided on a p-type (Al0.7 Ga0.3 )0.5 In0.5 P clad layer 8 through the p-type Gay In1-y P etching stop layer 9. The refractive index, the forbidden band width and the thickness of the n-type Gau In1-y P light field correction layer 3 are set to be equal to those of the p-type Gay In1-y P etching stop layer 9, and the n-type Gay In1-y P light field correction layer 3 is provided in a position which is symmetrical to the p-type Gay In1-y P etching stop layer 9 against an active layer 6.

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 a buried ridge type semiconductor laser and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a buried ridge type AlGaInP semiconductor laser of a real refractive index waveguide type, as disclosed in, for example, Japanese Patent Application Laid-Open No. 3-183180, etching for forming a ridge stripe portion is performed. In order to perform the control with good controllability, a structure in which an etching stop layer is introduced is known.

FIG. 6 is a sectional view showing a conventional buried ridge type AlGaInP-based semiconductor laser having such an etching stop layer. This conventional semiconductor laser has a SCH (Separate Confinement Heterostructure).
The active layer has a multiple quantum well (MQW) structure.

As shown in FIG. 6, in this conventional buried ridge type AlGaInP-based semiconductor laser,
For example, an n-type G having a main surface turned off from the (001) plane
On an aAs substrate 101, an n-type (Al _0.7 Ga _0.3 ) _0.5
In _0.5 P clad layer 102, n-type (Al _0.5 G
a _{0.5) 0.5} In _0.5 P optical waveguide layer 103, Ga _z In
_1-z P quantum well layer and (Al _0.5 Ga _0.5 ) _0.5 In
An active layer 104 having an MQW structure having a _0.5 P barrier layer and a 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 10
6, p-type Ga _y In _1-y P etching stop layer 107, p
Mold (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 10
8, p-type Ga _y In _1-y P contact layer 109 and p
Type GaAs cap layers 110 are sequentially stacked.

[0005] p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P
The cladding layer 108, the p-type Ga _y In _1-y P contact layer 109, and the p-type GaAs cap layer 110 have a ridge stripe shape extending in one direction. Here, in this conventional semiconductor laser, a so-called off-substrate is used as the n-type GaAs substrate 101 in order to shorten the emission wavelength. Therefore, the ridge stripe has an asymmetric shape. An n-type GaAs current confinement layer 111 is buried in both sides of the ridge stripe portion, 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.

Here, the p-type Ga _y In _1-y P etching stop layer 107 is formed from the viewpoint of not absorbing light from the active layer 104 and the viewpoint of not adversely affecting laser characteristics. greater than the forbidden band width of Ga _z in _1-z P quantum well layer of the active layer 104, and, p-type (Al _0.7
Ga _0.3 ) _0.5 In _0.5 P has a band gap smaller than the band gap of the cladding layers 106 and 108. Therefore, p
The Ga composition ratio y of the type Ga _y In _1-y P etching stop layer 107 and the Ga composition ratio _{z of the} G _az In _1-z P quantum well layer of the active layer 104 satisfy the relationship of y> z. As an example, z = 0.45 and y = 0.59. The thickness of the p-type Ga _y In _1-y P etching stop layer 107 is, for example, 15 nm.

In order to manufacture the above-described conventional semiconductor laser, first, as shown in FIG.
01, 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 _0.5 ) _0.5 In
_0.5 P optical waveguide layer _{103, Ga z In 1-z} P quantum well layer _{(Al 0.5 Ga 0.5) 0.5 In} 0.5 MQW with P barrier layer
Active layer 104 having a structure, p-type (Al _0.5 Ga _0.5 ) _0.5 I
n _0.5 P optical waveguide layer 105, p-type (Al _0.7 Ga _0.3 )
_0.5 an 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 an In _0.5 P cladding layer 108, p-type Ga _y In _1-y
P contact layer 109 and p-type GaAs cap layer 1
10 are sequentially grown by, for example, a metal organic chemical vapor deposition (MOCVD) method.

Next, as shown in FIG. 8, a SiO ₂ film or a SiN film is formed on the entire surface of the p-type GaAs cap layer 110, and is patterned by etching to form a stripe-shaped mask 114 having a predetermined width. I do. Next, using this mask 114 as an etching mask, p-type GaAs is used.
First, from the cap layer 110 side, a p-type (Al) is formed by a wet etching method using a hydrochloric acid-based etching solution.
After etching to an intermediate depth in the thickness direction of the _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 108, p-type G is etched by a wet etching method using a sulfuric acid-based etchant.
Etching is performed until the a _y In _1-y P etching stop layer 107 is exposed. At this time, the etching rate of the p-type Ga _y In _1-y P etching stop layer 107 is lower than that of a sulfuric acid-based etchant, and a desired ridge stripe shape can be formed.

Next, as shown in FIG. 9, using the mask 114 as a growth mask, for example, by the MOCVD method,
N-type G so as to fill both sides of the ridge stripe
The aAs current confinement layer 111 is grown.

Next, the mask 114 is removed by etching.
After lapping the n-type GaAs substrate 101 to, for example, a thickness of about 150 μm, as shown in FIG. 6, the p-type GaAs cap layer 110 and the n-type GaAs
A p-side electrode 112 is formed on the entire surface of the current confinement layer 111, and an n-side electrode 11 is formed on the back surface of the n-type GaAs substrate 101.
Form 3 Thus, the intended semiconductor laser is manufactured.

In the above-described conventional semiconductor laser, p
Mold (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 10
On the 6, p-type Ga _y In _1-y P etching stop layer 107
Is provided, so that p-type (Al _0.7 Ga _0.3 ) _0.5
In _0.5 P cladding layer 108, p-type Ga _y In _1-y P contact layer 109 and p-type GaAs cap layer 110
Is excellent in the controllability of etching for patterning into a ridge stripe shape. As a result, in the conventional semiconductor laser, the difference between the refractive index of the portion corresponding to the ridge stripe portion and the refractive index of the portions corresponding to both sides thereof (refractive index difference Δn) and the horizontal direction in the far-field image of the laser light This has the advantage that the divergence angle θ // in the direction can be made almost as designed.

[0013]

By the way, in the above-mentioned conventional semiconductor laser, the shape of the ridge stripe portion is p-type (Al _0.7 Ga
_{0.3) 0.5} In _0.5 P cladding layer 108 and the p-type Ga _y I
is determined by selecting the ratio of n _1-y P etching stop layer 107, therefore, in order to form a ridge stripe steep shape with good controllability is a p-type Ga _y In _1-y P etching stop layer 107 to some extent Must be formed to a thickness of However, usually, the refractive index of the p-type Ga _y In _1-y P etching stop layer 107, p-type (Al _0.7 Ga _0.3)
Since the refractive index of the _0.5 In _0.5 P cladding layers 106 and 108 is higher than the refractive index of the cladding layers 106 and 108, the following problem arises.

That is, FIG. 10 is a schematic diagram showing a distribution of an optical field in a direction (longitudinal direction) perpendicular to the heterojunction plane of the conventional semiconductor laser. In FIG. 10, the horizontal axis indicates the distance in the vertical direction, and the vertical axis indicates the light intensity. As shown in FIG. 10, in this conventional semiconductor laser, a p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 10 is formed.
6, 108, p-type Ga having a higher refractive index than these
_{Since the y} In _1-y P etching stop layer 107 is provided, the light field in the vertical direction does not have a symmetric distribution with respect to the center of the active layer 104, and the p-type Ga _y is viewed from the active layer 104. The distribution becomes asymmetrically biased toward the In _1-y P etching stop layer 107 side. In FIG. 10, p is viewed from the active layer 104.
Position of the sub-peak appearing in the mold Ga _y In _1-y P etching stop layer 107 side corresponds to approximately the center of the p-type Ga _y In _1-y P etching stop layer 107.

Unevenness (asymmetry) of the distribution of the light field due to such a p-type Ga _y In _1-y P etching stop layer 107.
Becomes more prominent when this semiconductor laser is a high-power semiconductor laser. This is a high power semiconductor laser
This is because the light confinement in the active layer 104 is weaker than that of the low power semiconductor laser. Here, the high-power semiconductor laser has, for example, an output of about 20 to 30 mW and a vertical beam divergence angle θ 垂直 in a far-field image.
Is 25 ° or less, specifically, about 20 ° to 24 °. A low-power semiconductor laser is, for example, an output of 5 mW.
And the vertical beam spread angle θ⊥ is 30 ° to 35 °.
About °

In the conventional semiconductor laser shown in FIG. 6, an off-substrate is used for the purpose of shortening the emission wavelength, so that the cross-sectional shape of the ridge stripe portion is asymmetric. FIG. 11 shows a current field distribution and a light field distribution in a direction parallel to the heterojunction plane of the conventional semiconductor laser shown in FIG. 6 and perpendicular to the cavity length direction (hereinafter, this direction is referred to as a lateral direction). FIG. FIG.
In FIG. 1, the distribution of the current field is indicated by a dashed line with a thin line, and the distribution of the light field is indicated by a dashed line with a thick line. In this case, as shown in FIG. 11, since the cross-sectional shape of the ridge stripe portion is asymmetric, the center of the current field and the center of the light field in the lateral direction are shifted from each other, and spatial hole burning is reduced. It is easy to occur. In such off-substrate, the case of forming the structure of a high power semiconductor laser described above, p-type Ga _y an In
_{Since the} light field deflected by the _1-y P etching stop layer 107 is strongly affected by the ridge stripe portion having an asymmetric cross-sectional shape, the difference between the center of the current field and the center of the light field in the lateral direction is remarkable. And spatial hole burning is more likely to occur. The occurrence of such spatial hole burning causes the occurrence of kink in the laser output,
As a result, the operating current and the operating voltage are increased at the time of high output, which is a serious problem in increasing the output of the semiconductor laser.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor laser capable of correcting a bias of a light field due to an etching stop layer and a method of manufacturing the same.

[0018]

Means for Solving the Problems In order to achieve the above object, a first invention of the present invention comprises a substrate, a first cladding layer of a first conductivity type on the substrate, and a first cladding layer on the first cladding layer. And a second conductive type third cladding layer having a ridge stripe shape on the second cladding layer via an etching stop layer on the active layer. And a buried ridge type semiconductor laser having a current confinement structure in which a first confinement type current confinement layer is buried on both sides of the third cladding layer. A light field correction layer for correcting the bias of the light field due to the etching stop layer is provided therein.

According to a second 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 to a first thickness; Forming a light-field correcting layer on the first cladding layer, forming a first cladding layer on the light-field correcting layer to a second thickness,
Forming an active layer on the first cladding layer of the second thickness, forming a second cladding layer of the second conductivity type on the active layer, and stopping etching on the second cladding layer Forming a layer, forming a third cladding layer of the second conductivity type on the etching stop layer, and patterning the third cladding layer into a ridge stripe shape by selectively etching the third cladding layer. Forming a current confinement layer of the first conductivity type so as to fill the portions on both sides of the third cladding layer.

In the present invention, the refractive index of the light field correction layer is higher than the refractive index of the first cladding layer so that the light field correction layer can correct the bias of the light field due to the etching stop layer. Chosen by rate. In this case, in order to effectively obtain the effect of correcting the light field, it is preferable that the refractive index of the light field correction layer is substantially equal to the refractive index of the etching stop layer.

In the present invention, the forbidden band width of the light-field correcting layer is determined from the viewpoint of preventing the light-field correcting layer from absorbing light from the active layer and not adversely affecting the laser characteristics. It is selected to be larger than the forbidden band width of the active layer and smaller than the forbidden band width of the first cladding layer. Here, in general, the refractive index increases when the forbidden band width is small. Therefore, the optical field correction layer has a refractive index higher than the refractive index of the first cladding layer. Therefore, by selecting the forbidden band width of the light field correction layer as described above, the light field correction layer can have an effect of correcting the bias of the light field due to the etching stop layer.
In this case, in order to effectively obtain the effect of correcting the light field, it is preferable that the forbidden band width of the light field correcting layer is substantially equal to the forbidden band width of the etching stop layer.

The light field correcting effect of the light field correcting layer depends on the refractive index or the forbidden band width and the thickness of the light field correcting layer. That is, when the refractive index of the light field correction layer is equal to or greater than the refractive index of the etching stop layer, or when the forbidden band width of the light field correction layer is equal to or less than the forbidden band width of the etching stop layer, the thickness of the light field correction layer is reduced. Even if the thickness is almost the same as the thickness of the etching stop layer, a sufficient light field correcting effect can be obtained. On the other hand, when the refractive index of the light field correction layer is smaller than the refractive index of the etching stop layer, or when the forbidden band width of the light field correction layer is larger than the forbidden band width of the etching stop layer, a sufficient light field correcting effect can be obtained. To achieve this, it is preferred that the thickness of the light field correction layer be greater than the thickness of the etch stop layer.

According to the present invention having the above-described structure, since the first clad layer is provided with the light field correcting layer for correcting the bias of the light field due to the etching stop layer, the active layer is formed. The light field biased toward the etching stop layer as viewed from the layer can be corrected.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the embodiments, the same or corresponding portions are denoted by the same reference numerals.

FIG. 1 is a sectional view showing a buried ridge type AlGaInP semiconductor laser according to a first embodiment of the present invention. This semiconductor laser has an SCH structure, and the active layer has an MQW structure.

As shown in FIG. 1, in this semiconductor laser, for example, an n-type (Al _0.7 Ga _0.3 ) is formed on an n-type GaAs substrate 1 having a main surface turned off from the (001) plane.
_0.5 an In _0.5 P cladding layer 2, n-type Ga _u In _1-u P light field correction layer 3, n-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P
Clad layer 4, n-type (Al _0.5 Ga _0.5 ) _0.5 In _0.5
P optical waveguide layer _{5, Ga z In 1-z} P quantum well layers and (A
_{l 0.5 Ga 0.5) 0.5 In 0.5} P barrier MQW active layer of the layer 6, p-type _{(Al 0.5 Ga 0.5) 0.5 In} 0.5 P optical guide layer 7, 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 9, p-type _{(Al 0.7 Ga 0.3) 0.5 In} 0. 5 P cladding layer 10, p-type Ga _y In _1-y P contact layer 11 and the p-type GaAs The cap layers 12 are sequentially stacked. p
Mold (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 1
0, p-type Ga _y In _1-y P contact layer 11 and the p-type GaAs cap layer 12 has a ridge stripe extending in one direction. In this case, since an off-substrate is used as the n-type GaAs substrate 1, the ridge stripe has an asymmetric cross-sectional shape. An n-type GaAs current confinement layer 13 is buried in both sides of the ridge stripe portion, thereby forming a current confinement structure.

In this semiconductor laser, an n-type (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 2 and n-type (A
between _{l 0.7 Ga 0.3) 0.5 In 0.5} P cladding layer 4, it is characteristic that the n-type Ga _u In _1-u P light field correction layer 3 is provided. As described later, the n-type Ga _u
In _1-u P light field correction layer 3 is by p-type Ga _y In _1-y P etching stop layer 9 is provided, the bias of distribution of the optical field that occurs at the heterojunction surface perpendicular direction (the active layer 6 Te pungency is for correcting the bias) of the p-type Ga _y in _1-y P etching stop layer 9 side.

P-type GaAs cap layer 12 and n-type G
On the aAs current confinement layer 13, for example, Ti / Pt / Au
A p-side electrode 14 such as an electrode is provided, while an n-type Ga
On the back surface of the As substrate 1, an n-side electrode 15 such as an AuGe / Ni electrode is provided.

One example of the thickness of each semiconductor layer constituting this semiconductor laser is n-type (Al _0.7 Ga _0.3 ) _0.5
In _0.5 P clad layer 2 and p-type (Al _0.7 G
a _0.3 ) _0.5 In _0.5 The thickness of the P cladding layer 10 is 1.1 μm each, and n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5
P cladding layer 4 and p-type (Al _0.7 Ga _0.3 ) _0.5 I
The thickness of the n _0.5 P cladding layer 8 is 0.3 μm and n
Type (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P optical waveguide layer 5 and p-type (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P optical waveguide layer 7
Are each 10 nm in thickness, and the Ga _z In _1-z
P quantum well layer and (Al _0.5 Ga _0.5 ) _0.5 In _0.5
Each of the P barrier layers has a thickness of 4 nm and a p-type Ga _y In _1-y
The thickness of the P etching stop layer 9 is 15 nm. Also,
The active layer 6 having the MQW structure has, for example, five Ga _z In ₁ -z P quantum well layers.

In this semiconductor laser, the p-type Ga _y I
The forbidden band width of the n _{1 -y} P etching stop layer 9 is the p-type G
a _y In _1-y P etching stop layer 9, does not absorb light from the active layer 6, and, in view to avoid adversely affecting the laser characteristics, the active layer 6 Ga _z In _1-z P It is larger than the forbidden band width of the quantum well layer and is p-type (Al _0.7 G
a _0.3 ) _0.5 In _0.5 P is selected to be smaller than the forbidden band width of the cladding layers 8 and 10. Similarly, n-type Ga _u In _1-u
The forbidden band width of the P light field correcting layer 3 is the same as that of the Ga _z In
_The n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layers 2, 4 are larger than the forbidden band width of the _1-z P quantum well layer.
Is smaller than the forbidden band.

Therefore, in this case, the n-type Ga _u In
Ga composition ratio u of _1-u P light field correction layer 3 and Ga _{z of} active layer 6
In _1-z P Ga composition ratio of the quantum well layers z and p-type Ga _y
The Ga composition ratio y of the In _1-y P etching stop layer 9 is u,
The relationship of y> z is satisfied. Further, in the case of the first embodiment, n-type Ga _u an In _1-u Ga composition ratio u of the P light field correction layer 3, p-type Ga _y In _1-y P Ga of etch stop layer 9
It is chosen equal to the composition ratio y and, therefore, n-type Ga _u In
_1-u P light field correction layer 3 has a bandgap equal to the bandgap of the p-type Ga _y In _1-y P etching stop layer 9.

Here, an example of the Ga composition ratio z of the G1 _z In _{1 -z} P quantum well layer of the active layer 6 is as follows.
0.45. Further, the n-type Ga _u an In _1-u P light field correction layer 3 of a Ga composition ratio u and p-type Ga _y In _1-y P Ga composition ratio of the etching stop layer 9 y, and an example, respectively, u = y = 0.59.

In this case, the refractive index of the p _- type Ga _y In _1-y P etching stop layer 9 is p-type (Al _0.7 G
a _{0.3) 0.5} In _0.5 P greater than the refractive index of the cladding layers 8 and 10, and the refractive index of the n-type Ga _u In _1-u P light field correction layer 3, n-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 together is greater than the refractive index of the P-cladding layer 2, 4, n-type Ga _u in _1-u P light field correction layer 3, p-type Ga _y
It has a refractive index equal to the refractive index of the In _1-y P etching stop layer 9. In this semiconductor laser, an n-type (A
_{l 0.7 Ga 0.3) 0.5 In 0.5} P between the cladding layers 2, 4, n-type Ga _u In _1-u P having a refractive index as described above
By light-field correction layer 3 is provided, the light of the active layer 6 near, pulled to the n-type Ga _u In _1-u P light field correction layer 3, as a result, p-type Te active layer 6 pungency Ga _y In
_1-y P spread of the optical field into the etch stop layer 9 side is suppressed, deviation of the optical field due to p-type Ga _y In _1-y P etching stop layer 9 is corrected.

[0034] The thickness of the n-type Ga _u In _1-u P light field correction layer 3, p-type Ga _y In _1-y P etching stop layer 9
From the viewpoint of the effect of correcting the deviation of the optical field due to the so obtained sufficiently, it is preferable that the thickness of the same order of p-type Ga _y In _1-y P etching stop layer 9. In this first embodiment, the thickness of the n-type Ga _u In _1-u P light field correction layer 3 is selected to equal 15nm to the thickness of the p-type Ga _y In _1-y P etching stop layer 9. In the case of the first embodiment, n-type Ga _u In _1-u P light field correction layer 3,
The p-type Ga _y In _1-y P etching stop layer 9 is provided symmetrically with respect to the center of the active layer 6.

FIG. 2 is a schematic diagram showing the distribution of the light field in the longitudinal direction of this semiconductor laser. In FIG. 2, the horizontal axis indicates the distance in the vertical direction, and the horizontal axis indicates the light intensity. FIG. 2 shows the n-type Ga _u In _1-u P light field correcting layer 3 and the p-type Ga _y
An In _1-y P and etch stop layer 9 and the same composition (i.e. u = y), n-type Ga _u In _1-u P light field correction layer 3 and the p-type Ga _y In _1-y P-etch stop layer 9 The thickness,
15 nm each, n-type (Al _0.7 Ga _0.3 ) _0.5 In
_0.5 P cladding layer 4 and p-type (Al _0.7 Ga _0.3 )
The thickness of the _0.5 In _0.5 P cladding layer 8 is set to 0.3
4 shows the distribution of the light field in the vertical direction when μm is set.

As shown in FIG. 2, in the semiconductor laser, as compared to the distribution of the optical field of the conventional semiconductor laser shown in FIG. 10, the active layer 6 viewed from Te p-type Ga _y In _1-y P
It can be seen that the spread of the light field toward the etching stop layer 9 is suppressed. In FIG. 2, the position of the sub-peak active layer 6 viewed from Te appearing in p-type Ga _y In _1-y P etching stop layer 9 side, corresponding to approximately the center of the p-type Ga _y In _1-y P etching stop layer 9 And n-type Ga _u I viewed from the active layer 6.
The position of the sub-peak that appears on the n _1-u P light field correction layer 3 side is
n-type Ga _u In _1-u P light field substantially corrective layer 3 corresponding to the center. Thus, in this semiconductor laser, the n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layers 2, 4
By n-type Ga _u In _1-u P light field correction layer 3 is provided between, that deviation of the light field by p-type Ga _y In _1-y P etching stop layer 9 has been corrected Recognize.
In this case, n-type Ga _u In _1-u P light-field light intensity at a position corresponding to the center of the correction layer 3, p-type Ga _y In _1-y
Since the light intensity at the position corresponding to the center of the P etching stop layer 9 is substantially equal, the light field in the vertical direction has a symmetric distribution with respect to the active layer 6.

In order to manufacture this semiconductor laser configured as described above, first, as shown in FIG. 3, an n-type (Al _0.7 Ga _0.3 ) _0.5 I
n _0.5 P cladding layer 2, n-type Ga _u In _1-u P light field correction layer 3, n-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P cladding layer 4, n-type _{(Al 0.5 Ga 0.5) 0.5 In} 0.5 P the optical waveguide layer _{5, Ga z In 1-z} P quantum well layer (Al _0.5 Ga
_0.5 ) _0.5 In _0.5 P barrier layer and an MQW structure active layer 6, p-type (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P optical waveguide layer 7, 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 9, p-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P cladding layer 10,
p-type Ga _y In _1-y P contact layer 11 and p-type Ga
The As cap layer 12 is sequentially grown by, for example, the MOCVD method.

Next, as shown in FIG. 4, a SiO ₂ film or a SiN film is formed on the entire surface of the p-type GaAs cap layer 12, and is patterned by etching to form a stripe-shaped mask 16 having a predetermined width. I do. Next, using this mask 16 as an etching mask, p-type (Al _0.7 Ga) is first formed from the side of the p-type GaAs cap layer 12 by wet etching using a hydrochloric acid-based etchant.
_{0.3) 0.5} In _0.5 after etching to a thickness halfway in the depth direction of the P-cladding layer 10, by wet etching using an etchant of sulfuric acid series, p-type Ga _y an In
Etching is performed until the _1-y P etching stop layer 9 is exposed. At this time, the p-type G
The etching rate of the a _y In _1-y P etching stop layer 9 is low, and a desired ridge stripe shape can be formed.

Next, as shown in FIG. 5, using the mask 16 as a growth mask, for example, the MOCVD method is used to fill the n-type Ga on both sides of the ridge stripe portion.
The As current confinement layer 13 is grown.

Next, the mask 16 is removed by etching and n
After lapping the type GaAs substrate 101 to a thickness of about 150 μm, as shown in FIG.
A p-side electrode 14 is formed on the entire surface of the n-type GaAs cap layer 12 and the n-type GaAs current confinement layer 13, and an n-side electrode 15 is formed on the back surface of the n-type GaAs substrate 1. Thus, the intended semiconductor laser is manufactured.

[0041] As described above, according to this first embodiment, between the n-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P cladding layer 2, 4, p-type Ga _y In _1-y P etching stop n-type Ga _u an in for correcting deviation of an optical field by the layer 9
_1-u by P light field correction layer 3 is provided, p-type Te active layer 6 viewed from Ga _y In _1-y P etching stop layer 9
The light field biased to the side can be corrected. Specifically, in the optical field in the longitudinal direction, p-type Te active layer 6 viewed from Ga _y I
Spreading to the n _1-y P etching stop layer 9 side is suppressed. For this reason, the influence on the distribution of the light field in the lateral direction due to the asymmetric cross-sectional shape of the ridge stripe portion is reduced, and the occurrence of kink in the laser output due to spatial hole burning can be suppressed. The kink level of the output can be improved. This allows
The operating current and operating voltage at the time of high output can be reduced, and as a result, the high-temperature characteristics of the semiconductor laser are improved, so that the life of the semiconductor laser can be extended.

Next, a second embodiment of the present invention will be described. That is, in the semiconductor laser according to the first embodiment described above, the composition of the n-type Ga _u In _1-u P light field correction layer 3, as same as the composition of the p-type Ga _y In _1-y P etching stop layer 9 However, in the semiconductor laser according to the second embodiment, u, y> z (z is Ga in the active layer 6).
_The composition of the n-type Ga _u In _1-u P light field correction layer 3 is within a range satisfying the relationship of ( _z In _{1 -z} P quantum well layer Ga composition ratio).
The composition is different from that of the p-type Ga _y In _1-y P etching stop layer 9. As an example, n-type Ga _u In _1-u P Ga composition ratio u and p-type light-field correction layer _{3 Ga y In 1-y P} Ga composition ratio y of the etching stop layer 9, respectively, u =
0.52, y = 0.59. The other configuration is the same as that of the semiconductor laser according to the first embodiment, and the description is omitted.

The method of manufacturing the semiconductor laser according to the second embodiment is the same as the method of manufacturing the semiconductor laser according to the first embodiment, and a description thereof will not be repeated.

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

Next, a third embodiment of the present invention will be described. That is, in the semiconductor laser according to the first embodiment described above, the thickness of the n-type Ga _u In _1-u P light field correction layer 3, equal to the thickness of the p-type Ga _y In _1-y P etching stop layer 9 Although it has to, in the semiconductor laser according to the third embodiment, n-type Ga _u in _1-u P light field correction layer 3
Is different from the thickness of the p-type Ga _y In _1-y P etching stop layer 9. In this case, n-type Ga _u an In
_1-u P light field the thickness of the correction layer 3, the effect of correcting the deviation of the optical field due to p-type Ga _y In _1-y P etching stop layer 9 is sufficiently obtained, and adversely affect the laser characteristics From the viewpoint of avoiding this, the thickness of the p-type Ga _y In _1-y P etching stop layer 9 is not less than 2/3 and not more than 5/3, preferably not more than 2/3.
It is selected to be not less than 4/3. Specifically, p-type Ga _y I
When the thickness of the n _1-y P etching stop layer 9 is 15 nm,
The thickness of the n-type Ga _u In _1-u P light field correction layer 3 is 10 to 25
nm, preferably 10 to 20 nm. The other configuration is the same as that of the semiconductor laser according to the first embodiment, and the description is omitted.

The method of manufacturing the semiconductor laser according to the third embodiment is the same as the method of manufacturing the semiconductor laser according to the first embodiment, and a description thereof will not be repeated.

According to the third embodiment, effects similar to those of the first embodiment can be obtained.

Next, a fourth embodiment of the present invention will be described. That is, in the semiconductor laser according to the first embodiment described above, the n-type Ga _u In _1-u P light field correction layer 3,
The p-type Ga _y In _1-y P etching stop layer 9 is provided symmetrically with respect to the center of the active layer 6.
In the semiconductor laser according to the embodiment, the n-type Ga _u
The In _1-u P light field correction layer 3 has a p
It is provided at a position different from the position symmetrical with the type Ga _y In _1-y P etching stop layer 9. In this case, p-type Ga _y In _1-y P the deviation of the optical field due to the etching stop layer 9 from the viewpoint of such an effect of straightening can be sufficiently obtained, n-type Ga _u In _1-u P light field correction The layer 3 is provided within a range of 100 nm or less from a position symmetrical with the p-type Ga _y In _1-y P etching stop layer 9 with respect to the center of the active layer 6. The other configuration is the same as that of the semiconductor laser according to the first embodiment, and the description is omitted.

The method of manufacturing the semiconductor laser according to the fourth embodiment is the same as the method of manufacturing the semiconductor laser according to the first embodiment, and a description thereof will not be repeated.

According to the fourth embodiment, effects similar to those of the first embodiment can be obtained.

Next, a fifth embodiment of the present invention will be described. The semiconductor laser according to the fifth embodiment, during the n-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P cladding layers 2 and 4, instead of the n-type Ga _u In _1-u P light field correction layer 3 An n-type (Al _w Ga _1-w ) _v In _1-v P light field correction layer is provided. Here, the n-type (Al _w G
a _1-w ) _v In _1-v P The composition ratio w, v of the light field correction layer is p
It is selected so that the effect of correcting the bias of the optical field due to the type Ga _y In _1-y P etching stop layer 9 can be sufficiently obtained. Specifically, the composition ratio w, v of the n-type (Al _w Ga _1-w ) _v In _1-v P light field correction layer is determined by the n-type (Al _w Ga _1-w ) _v
The refractive index of the In _1-v P light field correction layer is at least n-type (A
l _0.7 Ga _0.3 ) _0.5 In _0.5 P is selected so as to be higher than the refractive index of the cladding layers 2 and 4. Alternatively, n-type (A
l _w Ga _1-w ) _v In _1-v P Composition ratio w, v of the light field correction layer
The forbidden band width of the n-type _{(Al w Ga 1-w)} v In 1-v P light field correction layer is larger than the bandgap of Ga _z In _1-z P quantum well layer of the active layer 6, And n-type (Al _0.7 Ga
_0.3 ) _0.5 In _0.5 P is selected so as to be smaller than the forbidden band width of the cladding layers 2 and 4. In this case, the n-type (A
_{l w Ga 1-w) v} In 1-v refractive index or bandgap of the P light field correction layer is substantially equal to the refractive index or bandgap of the p-type Ga _y In _1-y P etching stop layer 9 Is preferred. The other configuration is the same as that of the semiconductor laser according to the first embodiment, and the description is omitted.

The method of manufacturing the semiconductor laser according to the fifth embodiment is the same as the method of manufacturing the semiconductor laser according to the first embodiment, and a description thereof will not be repeated.

According to the fifth embodiment, effects similar to those of the first 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 concept 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. Specifically, for example, the first
~ In the fifth embodiment, although the thickness of the p-type Ga _y In _1-y P etching stop layer 9 and 15 nm, it may be other than this thickness. Further, p-type Ga _y In _1-y
Although the P etching stop layer 9 and the p-type Ga _y In _1-y P contact layer 11 have the same composition, they may have different compositions.

Further, for example, the above-described first to fifth embodiments may be arbitrarily combined. Further, instead of the n-type GaAs substrate 1 used in the above-described first to fifth embodiments, for example, an n-type AlGaAs substrate or an n-type G
An aP substrate or the like may be used. Further, for example, in the above-described first to fifth embodiments, the conductivity types of the substrate and each semiconductor layer may be reversed.

Further, in the first to fifth embodiments described above, the case where the present invention is applied to a semiconductor laser having an SCH structure has been described.
It is also possible to apply to a semiconductor laser having a Heterostructure) structure.

In the above-described first to fifth embodiments, the case where the present invention is applied to a buried ridge type AlGaInP-based semiconductor laser has been described. The present invention can also be applied to an AlGaAs-based semiconductor laser, a semiconductor laser using a II-VI compound semiconductor, and a semiconductor laser using a nitride III-V compound semiconductor.

[0058]

As described above, according to the present invention, the first cladding layer is provided with the optical field correcting layer for correcting the bias of the optical field due to the etching stop layer, It is possible to correct a light field that is biased toward the etching stop layer as viewed from the active layer. Therefore, in particular, when the cross-sectional shape of the third cladding layer on the etching stop layer is asymmetric, that is, when the cross-sectional shape of the ridge stripe portion is asymmetric, the bias of the optical field due to the etching stop layer is corrected. By doing so, it is possible to suppress the occurrence of kink in the laser output due to spatial hole burning,
The kink level of the laser output can be improved.
As a result, the operating current and the operating voltage at the time of high output can be reduced. As a result, the high-temperature characteristics of the semiconductor laser are improved, and the life of the semiconductor laser can be extended.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram illustrating a distribution of a light field in a vertical direction of the semiconductor laser according to the first embodiment of the present invention.

FIG. 3 is a sectional view for explaining the method for manufacturing the semiconductor laser according to the first embodiment of the present invention;

FIG. 4 is a sectional view for explaining the method for manufacturing the semiconductor laser according to the first embodiment of the present invention;

FIG. 5 is a sectional view for explaining the method for manufacturing the semiconductor laser according to the first embodiment of the present invention;

FIG. 6 is a sectional view showing a conventional semiconductor laser.

FIG. 7 is a cross-sectional view for explaining a conventional method of manufacturing a semiconductor laser.

FIG. 8 is a cross-sectional view for explaining a conventional method of manufacturing a semiconductor laser.

FIG. 9 is a cross-sectional view for explaining a conventional method for manufacturing a semiconductor laser.

FIG. 10 is a schematic diagram illustrating a distribution of a light field in a vertical direction of a conventional semiconductor laser.

FIG. 11 is a schematic diagram showing a current field distribution and a light field distribution in a lateral direction of a conventional semiconductor laser.

[Explanation of symbols]

1 ... n-type GaAs substrate, 2, 4 ... n-type (Al
_0.7 Ga _{0.3) 0.5} In _0.5 P cladding layer, 3 · · · n
Type Ga _u In _1-u P light field leveling layer, 5 · · · n-type (Al
_0.5 Ga _0.5 ) _0.5 In _0.5 P optical waveguide layer, 6 active layer, 7 p-type (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P
Optical waveguide layer, 8, 10,..., P-type (Al _0.7 Ga _0.3 )
_0.5 an In _0.5 P cladding layer, 9 · · · p-type Ga _y an In
_1-y P etching stop layer

Claims (26)

[Claims] 1. A substrate, a first cladding layer of a first conductivity type on the substrate, an active layer on the first cladding layer, and a second cladding of a second conductivity type on the active layer A second conductive type third clad layer having a ridge stripe shape is provided on the second clad layer via an etching stop layer, and both sides of the third clad layer are provided. A buried ridge type semiconductor laser having a current confinement structure in which a current confinement layer of the first conductivity type is buried in a portion of the first cladding layer, in order to correct the bias of the optical field due to the etching stop layer in the first cladding layer. A semiconductor laser, comprising: a light field correction layer. 2. The optical field correcting layer has a refractive index higher than the refractive index of the first cladding layer, and the etching stop layer has a refractive index higher than that of the second cladding layer and the third cladding layer. 2. The semiconductor laser according to claim 1, having a high refractive index. 3. The semiconductor laser according to claim 2, wherein a refractive index of the light field correction layer is substantially equal to a refractive index of the etching stop layer. 4. The light field correcting layer has a forbidden band width larger than a forbidden band width of the active layer and smaller than a forbidden band width of the first cladding layer. 2. The semiconductor laser according to claim 1, wherein the semiconductor laser has a forbidden band width larger than the forbidden band width and smaller than the forbidden band widths of the second clad layer and the third clad layer. 5. The semiconductor laser according to claim 4, wherein a forbidden band width of said light field correction layer is substantially equal to a forbidden band width of said etching stop layer. 6. The semiconductor laser according to claim 1, wherein the thickness of the light field correction layer is substantially equal to the thickness of the etching stop layer. 7. The semiconductor laser according to claim 1, wherein the thickness of the light field correction layer is not less than 2/3 and not more than 5/3 of the thickness of the etching stop layer. 8. The semiconductor laser according to claim 1, wherein the thickness of the light field correction layer is not less than 2/3 and not more than 4/3 of the thickness of the etching stop layer. 9. The semiconductor laser according to claim 1, wherein said light field correction layer is provided at a position substantially symmetric with said etching stop layer with respect to a center of said active layer. 10. The light field correction layer is located one position symmetrical with the etching stop layer with respect to the center of the active layer.
2. The semiconductor laser according to claim 1, wherein the semiconductor laser is provided at a position within 00 nm. 11. The light field correcting layer is provided at a position symmetrical to the etching stop layer with respect to the center of the active layer, and has a refractive index and a thickness of the light field correcting layer, respectively. 2. The semiconductor laser according to claim 1, wherein the refractive index and the thickness of said etching stop layer are substantially equal to each other. 12. The light field correction layer is provided at a position symmetrical to the etching stop layer with respect to the center of the active layer, and the forbidden band width and thickness of the light field correction layer are: 2. The semiconductor laser according to claim 1, wherein the forbidden band width and the thickness of the etching stop layer are substantially equal to each other. 13. The method according to claim 13, wherein the substrate is an off-substrate, and the third substrate is an off-substrate.
2. The semiconductor laser according to claim 1, wherein said cladding layer has a ridge stripe shape having an asymmetric cross section. 14. A first optical waveguide layer of a first conductivity type is provided between the first cladding layer and the active layer, and between the second cladding layer and the active layer. 2. The semiconductor laser according to claim 1, further comprising a second conductive type second optical waveguide layer. 15. The semiconductor laser according to claim 1, wherein said semiconductor laser is an AlGaInP-based semiconductor laser. 16. The light field correcting layer and the etching stop layer are made of GaInP.
5. The semiconductor laser according to 5. 17. The semiconductor laser according to claim 15, wherein said etching stop layer is made of GaInP, and said optical field correction layer is made of AlGaInP having a refractive index smaller than that of said first cladding layer. . 18. The etching stop layer is made of GaInP, and the optical field correction layer is made of AlGaInP having a band gap larger than a band gap of the active layer and smaller than a band gap of the first cladding layer. 16. The semiconductor laser according to claim 15, comprising: 19. The semiconductor laser according to claim 1, wherein said semiconductor laser is an AlGaAs semiconductor laser. 20. The semiconductor laser according to claim 1, wherein said semiconductor laser is a semiconductor laser using a II-VI group compound. 21. A semiconductor laser comprising: a nitride III-
2. The semiconductor laser according to claim 1, wherein the semiconductor laser is a semiconductor laser using a group V compound semiconductor. 22. A step of forming a first cladding layer of a first conductivity type to a first thickness on a substrate; and forming a light field correction layer on the first cladding layer of the first thickness. Forming, forming the first cladding layer to a second thickness on the optical field correction layer, and forming an active layer on the first cladding layer having the second thickness. Forming a second conductive type second cladding layer on the active layer; forming an etching stop layer on the second cladding layer; and forming a second conductive layer on the etching stop layer. Forming a third cladding layer of a mold, patterning the third cladding layer into a ridge stripe shape by selectively etching the third cladding layer, and filling both sides of the third cladding layer. First
Forming a conductive type current constriction layer. 23. The light field correcting layer has a refractive index higher than the refractive index of the first cladding layer, and the etching stop layer has a refractive index higher than that of the second cladding layer and the third cladding layer. 23. The method according to claim 22, wherein the method has a high refractive index. 24. The method according to claim 23, wherein a refractive index of the light field correction layer is substantially equal to a refractive index of the etching stop layer. 25. The light-field correcting layer has a band gap larger than a band gap of the active layer and smaller than a band gap of the first cladding layer, and the etching stop layer is formed of the active layer. 23. The method according to claim 22, wherein the forbidden band width is larger than the forbidden band width and smaller than the forbidden band width of the second clad layer and the third clad layer. 26. The method according to claim 25, wherein a forbidden band width of the light field correction layer is substantially equal to a forbidden band width of the etching stop layer.