JPH01136393A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain an SBA laser, the shape of laser beams of which in the horizontal direction takes a single peak and is smoothed with respect to a substrate, by forming a p-type GaAs laser-beam absorption layer at the same position as an active region in the horizontal direction on an n-type GaAs current block layer. CONSTITUTION:A p-type GaAs laser-beam absorption layer 4 is shaped onto an n-type GaAs current block layer, and the laser-beam absorption layer 4 is formed in approximately the same surface as an active region 12 in the horizontal direction. On p-type GaAs, an absorption coefficient larger than n-type GaAs is acquired within a range of photon energy of 1.4-1.6eV (780-890nm in a laser beam wavelength) in carrier concentration of 1.2X10<18>cm<-3>. The absorption coefficient remarkably larger than n-type GaAs is obtained particularly within a range of 1.42-1.50eV (830-870nm in the laser beam wavelength). The laser-beam absorption layer 4 composed of p-type GaAs is shaped anew to an SBA laser, thus sufficiently absorbing laser beams, then forming the shape of laser beams to a single peak shape in the horizontal direction and smoothing it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device, and particularly to a semiconductor laser device manufactured by a vapor phase crystal growth method.

[Conventional technology]

Figure 2 shows an SBA laser (Self), which is a conventional semiconductor laser device manufactured by taking advantage of the characteristics of the MO-CVD method.
aligned 1aser with Bent A
FIG. S.B.A.
Regarding lasers, Mitsuhashi et al. reported at the 1985 Spring Conference of the Japan Society of Applied Physics Related Association Lectures 30a-ZB-4.

In the figure, l is a p-type GaAs substrate and 2 is a p-type AlGa substrate.
As first cladding layer, 3 is n-type GaAs current blocking layer, 5 is p-type AlGaAs second cladding layer, 6 is undoped AlGaAs active layer, 7 is n-type AlGaAs third cladding layer, 8 is n-type GaAs contact layer , 9 is an n-electrode, 10 is a p-electrode, 11 is a striped groove formed in the current blocking layer 3, and 12 is an active region in the active layer.

Next, the operation will be explained.

First, the current confinement mechanism of the SBA laser will be described. S.B.
In the A laser, the current flows through the striped grooves 11 formed in the n-type GaA3 current block 313, and the portion of the active layer 6 located in the area of the striped grooves 11 becomes the active region 12.

If a vapor phase crystal growth method such as MO-CVD is used, the active layer 6 can be bent into a shape close to a groove shape.

Next, the laser light waveguide mechanism of the SBA laser will be described.

In the direction perpendicular to the substrate, it has a DI (structure) in which the active layer 6 is sandwiched between the cladding layers 2.5.Since the refractive index of the active layer is larger than the refractive index of the cladding layer, The laser beam is confined in the active layer with a large refractive index.When the active layer thickness is about 0.1 μm, it is easy to obtain a laser beam with a single peak and a smooth shape in the direction perpendicular to the substrate. In the horizontal direction, the active region 12 that emits laser light is bent into the striped groove 11 and is surrounded by the cladding layer in the horizontal direction as well, so light is confined in the active region 12 with the same effect as in the vertical direction. In addition to this effect, the current blocking layer also contributes to optical confinement by absorbing laser light.With the above two effects, it is easy to form a single peaked and smooth shape horizontally on the substrate. You can get a laser beam.

[Problem that the invention seeks to solve]

The conventional semiconductor laser device is constructed as described above, and since the striped grooves are formed by wet etching in the SBA laser manufacturing process, the width of the grooves changes slightly in the cavity direction. Therefore, the width of the active region formed on the striped grooves also becomes non-uniform. Laser light is sensitively affected by the shape of the active region, and if the width is non-uniform, the shape of the laser beam in the horizontal direction will not be smooth but jittery. If the current blocking layer has a large laser beam absorption effect, the shape of the laser beam will be smooth even if the width of the active region changes somewhat, but in conventional SBA lasers, the current blocking layer is made of n-type GaAs. This n-type GaAs has an oscillation wavelength of 800 nm.
Since the absorption coefficient for laser light of ~880 nn+ is small, the effect of smoothing the shape of the laser beam in the horizontal direction is small, and there is a problem that the shape of the laser beam is distorted.

This invention was made in order to solve the above-mentioned problems, and it is an SBA that can be easily manufactured and in which the shape of the laser beam in the horizontal direction with respect to the substrate is unimodal and smooth.
The purpose is to obtain a laser.

[Means to solve the problem]

The semiconductor laser device according to the present invention includes a p-type GaAs laser light absorption layer on the n-type GaAs current blocking layer and at the same position as the active region in the horizontal direction.

[Effect]

In this invention, p-type CraAs has a larger absorption coefficient than n-type CraAs for laser light with an oscillation wavelength of 800 to 880 nm.
Since the structure has a GaAs laser light absorption layer on the current blocking layer and at the same position as the active region in the horizontal direction, the shape of the laser beam in the horizontal direction is monomodal due to the absorption effect of this laser light absorption layer. It becomes smooth.

〔Example〕

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

FIG. 1 is a sectional view showing an improved SBA laser which is a semiconductor laser device according to an embodiment of the present invention. In the figure, 1 is a p-type GaAs substrate, 2 is a p-type AlGaAs first
cladding layer, 3 is n-type GaAs current blocking layer, 4 is p
5 is a p-type AlGaAs second layer.
cladding layer, 6 undoped AlGaAs active layer, 7
is n-type AlGaAs third cladding layer, 8 is n-type GaAs
In the contact layer, 9 is an n electrode, 10 is a p electrode, 11 is a striped groove formed in the laser light absorption layer 4 and the current block 713, and 12 is an active region in the active layer.

The improved SBA laser according to this embodiment is similar to the conventional SBA laser.
P-type GaAs current blocking layer of laser device
An As laser light absorbing layer N4 is formed on the side thereof, and this laser light absorbing layer 4 is arranged to exist substantially in the same plane as the active region 12 in the horizontal direction.

Figure 3 (a) and (b) are H, C, Ca5ey Jr.
Impurity-doped n-type Ga proposed by et al.
FIG. 3A is a diagram showing the relationship between the absorption coefficient and photon energy of As and p-type GaAs; FIG. 3(a) shows the case of n-type GaAs, and FIG. 3(a) shows the case of p-type GaAs. −
In general, for a current blocking layer to produce a current blocking effect, 6
．． A carrier concentration of OXIO"Ca1-3 or higher is required. However, in the case of n-type GaAs, as shown in FIG. 3(a), the absorption coefficient tends to decrease as the carrier concentration increases. 5,7 In the case of a carrier concentration of xlQ"am-', the photon energy is 1°48eV
In other words, when the laser beam wavelength is 84On+*, its absorption coefficient is at most 100100O', and the absorption effect cannot be said to be sufficient.On the other hand, in the case of p-type GaAs, the carrier concentration is 1,2XIO"elm-' If the photon energy is 1.4eV to 1.6eV (780
A larger absorption coefficient than n-type GaAs can be obtained in the range of 89 nm to 89 nm). Especially 1.42~1, 50eV
(laser light wavelength: 830 to 870 nm)
A significantly higher absorption coefficient is obtained compared to GaAs.

As can be seen from this, p-type Ga
By newly providing the laser light absorption layer 4 made of Aa in the conventional SBA laser, the laser light is sufficiently absorbed, and the shape of the horizontal laser beam becomes smoother with a single peak than before.

In this way, in this example, the oscillation wavelength is 800 to 880 ns.
Since the structure is such that the p-type GaAs laser light absorbing Fi4, which has a larger absorption coefficient than the n-type GaAs for laser light, is provided on the current blocking layer 3 and at the same position as the active region 12 in the horizontal direction, this laser light absorbing layer 4 This absorption effect has the effect of making the shape of the laser beam in the horizontal direction more unimodal and smooth.

In the above embodiment, a GaAs/AlGaAs laser was described, but the present invention can also be applied to a laser device made of other ■-v group semiconductor materials, and the same effects as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, an SBA type semiconductor laser device has a structure in which a laser light absorption layer having a large laser light absorption coefficient is provided on the current blocking layer and at the same position as the active region in the horizontal direction. , it is possible to easily obtain a semiconductor laser device in which the shape of the laser beam in the horizontal direction is more unimodal and smooth.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a conventional SBA laser, and FIG. 3 is a relationship between the absorption coefficient of impurity-doped GaAs and photon energy. FIG. 1 is a p-type GaAs substrate, 2 is a p-type AlGaAs first cladding layer, 3 is an n-type GaAs current blocking layer, 4 is a p-type G
aAs laser light absorption layer, 5 a p-type AlGaAs second cladding layer, 6 an undoped AlGaAs active layer, 7 an n
8 is an n-type GaAs contact layer, 9 is an n-electrode, 10 is a p-electrode, 11 is a striped groove, and 12 is an active region. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (5)

[Claims] (1) A semiconductor substrate of a first conductivity type, a first cladding layer of a first conductivity type, a current blocking layer of a second conductivity type, and a laser light absorption layer of a first conductivity type formed sequentially on the semiconductor substrate. a substrate region having a striped groove formed in the current blocking layer and the laser light absorption layer so that the first cladding layer is exposed at the bottom thereof; and a substrate region of a first conductivity type formed on the substrate region. a second cladding layer; a second cladding layer on the second cladding layer;
an active layer having either a first or second conductivity type formed such that a distance from the cladding layer is equal to a distance from the first cladding layer of the light absorption layer; and an active layer formed on the active layer. A semiconductor laser device comprising: a third cladding layer of a second conductivity type; and a contact layer of a second conductivity type. (2) Claim 1, wherein the substrate, the current blocking layer, and the laser light absorption layer are made of GaAs, and the first, second, and third cladding layers and the active layer are made of AlGaAs. The semiconductor laser device described. (3) Claim 1 or 2, characterized in that the substrate is made of p-type GaAs, the current blocking layer is made of n-type GaAs, and the laser light absorption layer is made of p-type GaAs. semiconductor laser equipment. (4) The carrier concentration of the current blocking layer is 6.0×1
0^1^8 cm^-^3 or more, and the carrier concentration of the laser light absorption layer is 1.0 x 10^1^8 cm^-^3 or more. 3
3. The semiconductor laser device according to any one of the items. (5) The laser light absorbing layer has an absorption coefficient of 2,000 cm^-^1 or more with respect to the laser light emitted by the active layer, according to any one of claims 1 to 4. semiconductor laser equipment.