JPH0738193A - Semiconductor laser - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a semiconductor laser capable of achieving high output with short wavelength light emission. The active layer 13 has at least a heat-dissipating body-side cladding layer 14 adjacent to the active layer 13 that has a small thickness on the side in contact with the active layer 13 in a range that exhibits a carrier confinement effect on the active layer 13. The first clad layer 14A made of an AlGaInP layer having a larger energy band gap width than that of AlGaAs, which has a higher thermal conductivity than that of the first clad layer 14A, and a smaller refractive index than that of the active layer, and which mainly has a light confining function. In the semiconductor laser having the second clad layer 14B made of a layer, the high clad guide layer 14B ₀ is provided on the side of the first clad layer 14A of the second clad layer 14B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, and more particularly to an AlGaInP semiconductor laser capable of continuous oscillation at room temperature.

[0002]

2. Description of the Related Art For example, as a light source for optical discs such as compact discs and video discs, and magneto-optical discs,
There is a strong demand for short wavelength semiconductor lasers for high density recording.

This short wavelength semiconductor laser, for example 500 nm
As a semiconductor laser in the so-called 600 nm wavelength band of ˜680 nm, an AlGaInP-based semiconductor laser has been attracting attention, and in particular, as a semiconductor laser capable of continuous oscillation at room temperature, a cladding layer disclosed in JP-A-62-26885 and the like. There is a semiconductor laser (hereinafter referred to as a DSC laser) in which layers are stacked.

This DSC laser has an n-type GaAs substrate 1 and an n-type GaAs substrate 1 as shown in FIG.
Type AlGaInP clad layer (hereinafter referred to as the substrate side clad layer) 2, GaInP active layer 3, p type clad layer (hereinafter referred to as the radiator side clad layer) 4, and p type GaAs cap layer 5 are sequentially epitaxially grown. In the configuration in which the electrode 6 side on the cap layer 5 is thermally and electrically coupled to the radiator 7 such as a header or a heat sink via, for example, a solder layer, the radiator-side clad layer 4 is connected to the first p-type layer. It is constituted by the type clad layer 4A and the second p-type clad layer 4B.

The first cladding layer 4A of the radiator-side cladding layer 14 on the side in contact with the active layer 3 is made of AlGaInP having a band gap sufficiently larger than that of the active layer 3. In this example, the quaternary AlGaI is used for the second cladding layer 4B on the cap layer 5 side.
It is made of ternary AlGaAs, which has higher thermal conductivity than nP.

The first clad layer 4A is made as thin as possible within the range of obtaining the effect of confining carriers, and the second clad layer 4B is confined by both the first and second clad layers 4A and 4B. It is a relatively thick layer that can obtain the effect.

In this way, the AlGaInP having a low thermal conductivity interposed between the active layer 3 and the heat radiator 4 is made as thin as possible to enhance the heat radiation effect and enable oscillation at room temperature.

Further, in this DSC laser having a mesa structure, there is a proposal disclosed in Japanese Patent Application Laid-Open No. 3-276786 for stabilizing the characteristics and reproducibility of manufacturing. .

By the way, in recent years, for example, in magneto-optical recording and the like, along with the demand for short-wavelength semiconductor lasers, the need for high-power short-wavelength semiconductor lasers for performing high-power recording is increasing.

[0010]

DISCLOSURE OF THE INVENTION The present invention provides a semiconductor laser, especially a DSC laser, which is capable of achieving high output together with such short wavelength light emission.

[0011]

The first aspect of the present invention is shown in FIG. 1, which is a schematic cross-sectional view of an example thereof, in which at least the radiator-side cladding layer 14 of the cladding layer adjacent to the active layer 13 is provided.
However, on the side in contact with the active layer 13, the first layer is made of an AlGaInP layer having a small thickness within a range exhibiting a carrier confinement effect on the active layer 13 and having an energy band gap width larger than that of the active layer 13. Clad layer 14A
AlGaA, which has a higher thermal conductivity than that of the active layer and a smaller refractive index than that of the active layer, and which mainly has a light confining function.
DSC having a second clad layer 14B composed of an s layer
In the semiconductor laser, the high refractive index guide layer 14B _{0 is provided} on the side of the first cladding layer 14A of the second cladding layer 14B.
It is configured to have.

That is, the second clad layer 14B is composed of a high refractive index guide layer 14B ₀ and AlG having a lower refractive index than that of the high refractive index guide layer 14B _0.
It is composed of a layer made of aAs (hereinafter referred to as a low refractive index layer) 14B ₁ .

Further, in the second aspect of the present invention, the high refractive index guide layer 14B ₀ in the above structure is used as an etching stopper layer 22 for mesa etching formed on the radiator-side cladding layer 14.

[0014]

According to the present invention, the high-refractive-index guide layer 14B ₀ is provided in the cladding layer 14 on the radiator side, so that the light distribution as a whole is drawn toward the cladding layer 14. Therefore, since the light density near the active layer can be reduced, CO
The D (optical damage) level can be increased and high power can be achieved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the present invention will be described in detail with reference to FIG.

In this example, an n-type AlGaInP substrate-side clad layer 12, an undoped GaInP active layer 13, a p-type radiator-side clad layer 14, and a p-type radiator-side clad layer 14 are formed on an n-type GaAs substrate 11 having a (100) crystal plane. Type GaA
The cap layer 15 of s is sequentially epitaxially grown.

The clad layer 14 is a first clad layer 14A made of p-type AlGaInP in order from the active layer 13 side.
And a second cladding layer 14B having a higher thermal conductivity than this.

Particularly, in the present invention, the second cladding layer 14B is composed of the high refractive index guide layer 14B ₀ and AlG.
It is composed of a low refractive index layer 14B _{1 made of} aAs.

Low refractive index clad layer 14B₁Is Al_zG
a_1-zMade of As, high refractive index 14B₀Is Al_z0Ga
_1-z0It is composed of As. In this case, the
Z ₀But z₀<Z, for example z₀= 0.40 to 0.5
Selected as 5.

Each layer 12, 13, 14A, 14B ₀ , 14
B ₁ and 15 can be successively and epitaxially grown by MOCVD (metal organic chemical vapor deposition) method, MBE (molecular beam epitaxy) or the like.

The active layer 13 is made of, for example, Ga._0.52In_0.48P
And the substrate-side clad layer 12 and the radiator side.
The first clad layer 14A of the clad layer 14 of
Al _0.6It may be composed of GaInP.

The first cladding layer 14A is made of, for example, Al.
_{It is made of 0.73} GaAs and its thickness is such that it has a carrier confinement effect on the active layer 13, but it is as thin as possible, for example, 0.1 to 0. 3 μm. However, the total thickness of the first and second cladding layers 14A and 14B is selected to be, for example, 1 μm or more so that light can be confined by them.

The low refractive index layer 14 of the second cladding layer 14B
The thickness of B ₁ is, for example, 0.70 μm to 0.76 μm, and the high refractive index guide layer 14 B ₀ has a thickness of, for example, 4
It is assumed that _{0 nm to 100} nm, for example, z _{0 of} Al _z0 Ga _{1 -z0} As is 0.40 to 0.55.

Then, one electrode 16 is formed on the cap layer 15.
Is ohmic-deposited, and is bonded to a radiator 17 such as a header or a heat sink on the electrode 16 side via a solder layer, for example.

In the present invention, as shown in FIG. 2 which is a schematic cross-sectional view of an example thereof, the electrode 16 of the above-mentioned structure is provided.
Cap layer 15 and second cladding layer 14 on the side where
2, the central portion of B is left in a stripe shape extending in a direction orthogonal to the paper surface, and mesa etching is performed on both sides of the stripe portion to fill the etching groove 18 with a current constricting layer 19 that blocks or reduces the current flow. Mesa type DS to take
It can be applied to the C semiconductor laser structure.

Here, in FIG. 2, portions corresponding to those in FIG. 1 are designated by the same reference numerals to omit redundant description, but in this case, for example, p-type Al is formed on the first cladding layer 14A.
_A deterioration preventing layer 21 made of _0.73 GaInP and, for example, p-type Al for keeping mesa etching at a predetermined depth.
_An etching stopper layer 22 made of _0.6 GaInP is epitaxially grown in the same manner as the above-mentioned layers.

Japanese Patent Laid-Open No. 3-276786 discloses that the characteristics and reproducibility of a semiconductor laser having this mesa structure are improved by providing a deterioration preventing layer and an etching stopper layer. In this case, although not shown on the cap layer 15, an etching mask such as SiO ₂ or Si is formed on the cap layer 15.
An etching stopper layer 22 containing phosphorus P is formed by forming N or the like in a stripe shape at the center and etching both sides of this stripe portion from the cap layer 15 side with, for example, a sulfuric acid-based etching solution using this as an etching resist.
Since the etching rate is reduced when the film is exposed, the etching is apparently stopped, and the mesa groove 18 having a required depth can be formed by stopping the etching here.

Then, in the mesa groove 18, for example, n-type GaAs of a conductivity type different from the cap layer 15 and the radiator side clad layer 14 which constitute the current confinement layer 19 which blocks the energization or has a high resistance is epitaxially grown. Embed.

In this case, since phosphorus P is vaporized by the heating temperature when GaAs is epitaxially grown in the mesa groove 18, if the first cladding layer 14A of AlGaInP is exposed by etching, its composition becomes unstable. However, in the configuration of FIG. 2, under the etching stopper layer 22, for example, Al
By providing the deterioration preventing layer 21 of GaAs, it is possible to prevent the evaporation of phosphorus P from the cladding layer 14A, and thus it is possible to determine and obtain a semiconductor laser having the desired characteristics.

Further, in this example, the provision of the etching stopper layer 22 allows the depth of the mesa etching for forming the mesa groove 18 to be defined. However, the etching stopper layer 22 has a high refractive index. The index guide layer 14B ₀ can also serve as the structure.
FIG. 3 is a schematic cross-sectional view of an example of this case.

In this case, the high refractive index guide layer 14B ₀ is made of p-type GaInP.

Further, the high refractive index guide layer 14B ₀ has a structure shown in FIG.
As shown in the schematic cross-sectional view of FIG.
It may be arranged between the first cladding layers 14A.

In FIGS. 3 and 4, FIGS.
Portions corresponding to are denoted by the same reference numerals, and redundant description will be omitted.

According to each of the above configurations, the high refractive layer guide 1
By providing 4B ₀ , the light distribution can be widened and the light density near the active layer can be reduced. In particular, in the present invention, the high refractive index guide layer 14B ₀ is provided on the radiator side clad layer 14 side. The COD level can be further increased and the power can be increased by disposing the light distribution on the side of the heat radiator.

In the present invention, this guide layer 14B is used.
_{Since 0} is not configured to reduce the amount of Al in the entire second cladding layer 14B, but is configured by a part of the layers of the cladding layer 14B, stable fundamental mode oscillation is performed without disturbing the overall refractive index balance. be able to.

Further, as described above, when the mesa structure is formed into a stripe structure, the light distribution is widened to the stripe side, that is, the mesa side, so that the effective refractive index difference inside and outside the stripe becomes large. The effect of reducing the light spot aberration of the light emission spot can be obtained.

The present invention is not limited to the illustrated examples, but the conductivity types of the illustrated parts may be opposite conductivity types, for example.

[0038]

According to the present invention, since the high refraction guide layer 14B ₀ is provided in the clad layer 14 on the radiator side, the distribution of light can be attracted to the clad layer 14 side as a whole.
By reducing the light density near the active layer,
The COD level can be increased and higher power can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an example of the present invention.

FIG. 2 is a schematic cross-sectional view of another example of the present invention.

FIG. 3 is a schematic cross-sectional view of another example of the present invention.

FIG. 4 is a schematic cross-sectional view of another example of the present invention.

FIG. 5 is a schematic cross-sectional view of a conventional example.

[Explanation of symbols]

11 Substrate 12 Base Side Clad Layer 13 Active Layer 14 Radiator Side Clad Layer 14A First Cladding Layer 14B Second Cladding Layer 14B ₀ High Refractive Index Guide Layer

Claims (2)

[Claims] 1. The active layer, wherein at least the radiator-side cladding layer of the cladding layer adjacent to the active layer has a small thickness on the side in contact with the active layer within the range of exhibiting a carrier confinement effect on the active layer. A first cladding layer made of an AlGaInP layer having a larger energy band gap width than that of AlGaInP layer, and an AlGaAs layer having a higher heat conductivity than that of the active layer and a smaller refractive index than that of the active layer and mainly having a light confining function. A semiconductor laser having a second clad layer made of: a high refractive index guide layer provided on the side of the first clad layer of the second clad layer. 2. The semiconductor laser according to claim 1, wherein the high refractive index guide layer is an etching stopper layer for mesa etching.