JPH067621B2 - Semiconductor laser device and method of manufacturing the same - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device, which has been rapidly expanded in use and is in high demand as a light source for various electronic devices and optical devices.

Configuration of Conventional Example and its Problems One of the important performances required of a semiconductor laser as a coherent light source for electronic equipment and optical equipment is single-spot oscillation, that is, single transverse mode oscillation. In order to realize this, it is necessary to suppress the spread and confine the light so that the current flowing in the laser element is concentrated near the active region where the laser light propagates. Such a semiconductor laser is usually called a stripe type semiconductor laser.

A relatively simple striping method uses only current narrowing. Although these lasers realize single transverse mode oscillation, their threshold value is high. There is a buried stripe type semiconductor laser (generally called a BH laser) as a stripe structure which has the lowest threshold value. However, in order to manufacture this laser, the crystal growth step, which is usually performed once with other lasers, is required twice, and it is technically somewhat difficult to manufacture.

SUMMARY OF THE INVENTION In view of the above drawbacks, the present invention provides a semiconductor laser device capable of producing a single lateral mode oscillation and a buried stripe structure required for low threshold operation by a single crystal growth and a method of manufacturing the same. Is provided.

To achieve this object, the semiconductor laser device of the present invention comprises a multi-layer thin film having a double heterostructure including an active layer on a stripe-shaped convex portion of a conductive substrate, and also on both side surfaces of the convex portion. , At least up to the thin film layer directly above the active layer,
In the stacking direction, multilayer thin films are independently configured in the same order,
Immediately above the multilayer thin film, a thin film having the same conductivity as the substrate is formed.

With the above structure, a current can be narrowed in the active layer on the stripe-shaped convex portion, and a semiconductor laser device with single transverse mode oscillation and low threshold operation can be realized. Further, as a method of manufacturing the above semiconductor laser device, if a metal organic vapor phase epitaxial growth method or a molecular beam epitaxial growth method is used,
A buried stripe structure can be easily formed by performing crystal growth once.

Description of Embodiments A semiconductor laser device and a method of manufacturing the same according to the present invention will be specifically described with reference to an embodiment.

As an example, an n-type GaAs substrate is used as the conductive substrate. n-type Ga
On the (100) surface of the As substrate 10, as shown in FIG.
Using the photoresist 16 as a mask, chemical etching is used to form irregularities parallel to the <011> direction. Thus, as shown in FIG. 3, a stripe-shaped convex shape having a width of 5 μm and a height of 1.5 μm is formed.

Next, metalorganic vapor phase epitaxial growth method (usually MOCV
D method), the n-type Ga _1-x Al _x As cladding layer 11 is
μm, undoped Ga _1-y Al _y As (0 ≦ y ≦ x) active layer 12
Is 0.08 μm, and the p-type Ga _1-x Al _x As cladding layer 13 is 1.
After forming 2 μm, the n-type GaAs substrate cap layer 14 is formed to 2
Grow a μm crystal. As an example, the crystal growth conditions are a growth rate of 2 μm / hour, a growth temperature of 770 ° C., and a total gas flow rate of 5
/ Min, the molar ratio of Group V element to Group III element is 40.

As shown in FIG. 4, up to the p-type Ga _1-x Al _x As clad layer 13, the convex portion and the other portion are epitaxially grown independently, and the direction parallel to the growth substrate surface of the growth material. No crystal growth with additional effects such as diffusion is observed.

After the crystal growth, the surface is washed, and then the photoresist 17 is applied and rotated at 5000 rpm. As shown in FIG. 4, the photoresist film 17 becomes thin at the convex portions and becomes thick at other portions. By optimizing the exposure conditions, only the photoresist film 17 on the convex portion is removed, and the convex portion of the n-type GaAs cap layer is removed by etching to form the surfaces 18 and 19 shown in FIG. To do. Further, Zn is diffused with a width w to form stripes. As a result, the semiconductor laser structure shown in FIG. 1 is formed, and ohmic electrodes are attached to the surfaces 20 and 21. When current injection is performed, the current is narrowed in the vertical direction by the convex portion of the n-type GaAs substrate 10 and the p-type GaAs region 15 formed by diffusion. As a result, a semiconductor laser device having a single transverse mode oscillation with a threshold current value of 30 mA was obtained.

Further, the semiconductor laser structure of the present invention is of a buried type, and other buried lasers require crystal growth twice, whereas the buried laser of the present invention can be manufactured by one crystal growth. It is possible.

Similar results were obtained with the structure shown in FIG. 1 in which an n-type GaAs buffer layer was inserted between the n-type GaAs substrate 10 and the n-type Ga _1-x Al _x As cladding layer 11.

In this embodiment, the GaAs-based, GaAlAs-based, and semiconductor lasers are described, but the present invention can be similarly applied to a semiconductor laser made of a compound semiconductor containing InP-based or other multi-element mixed crystal. . Further, a p-type substrate may be used as the conductive substrate, or another substance supply rate controlling and crystal growth method, for example, a molecular beam epitaxial growth method (MBE method) may be used for crystal growth.

EFFECTS OF THE INVENTION The semiconductor laser device and the method of manufacturing the same according to the present invention realize an embedded laser that oscillates in a single transverse mode at a low threshold with a single crystal growth, and its practical effects are remarkable.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor laser device according to an embodiment of the present invention, and FIGS. 2, 3, and 4 are views showing manufacturing steps of the device. 10 ... n-type GaAs substrate, 11 ... n-type Ga _1-x Al _x As clad layer, 12 ... Ga _1-y Al _y As active layer, 13 ... p-type Ga _1-x A
l _x As clad layer, 14 ... n-type GaAs region, 15 ... p-type
GaAs region, 16 ... Photoresist film for mesa etching, 1
7 ... Photoresist film, 18 ... Epi growth surface, 19
…… Surface after etching, 20, 21 …… Ohmic electrode fabrication surface, w …… Current narrowing stripe width, d …… Mesa mask width.

Claims (3)

[Claims] 1. A first multi-layered thin film having a double heterostructure including an active layer is formed on a stripe-shaped convex portion of a substrate of one conductivity type, and the thin film immediately above the active layer is formed on both side surfaces of the convex portion. Up to the layer, a second multilayer thin film is independently formed in the same order in the stacking direction, a thin film having a conductivity type opposite to that of the substrate is formed immediately above the first multilayer thin film, and the second multilayer thin film is formed. 2. A semiconductor laser device, wherein a thin film having the same conductivity type as the substrate is formed on the multilayer thin film. 2. A double heterostructure including an active layer on the convex portion and a region other than the convex portion is formed on the one conductivity type substrate having a stripe-shaped convex portion by a metal organic vapor phase epitaxial growth method. The thin film layer directly above the layers is independently formed, and a thin film having the same conductivity type as that of the substrate is grown on the uppermost layer on the double heterojunction, and the region immediately above the convex portion of the uppermost layer is formed by Zn diffusion. A method of manufacturing a semiconductor laser device, wherein only the thin film layer has a conductivity type opposite to that of the substrate. 3. A double heterostructure including an active layer on the convex portion and on a region other than the convex portion is formed directly on the active layer by a molecular beam epitaxial growth method on a one conductivity type substrate having a stripe-shaped convex portion. Up to the thin film layer, and a thin film showing the same conductivity type as that of the substrate is grown on the uppermost layer on the double heterojunction, and only the region immediately above the convex portion of the uppermost layer is grown by Zn diffusion. A method of manufacturing a semiconductor laser device, comprising forming a thin film layer having a conductivity type opposite to that of the substrate.