JPS5932075B2 - Semiconductor laser device and its manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a semiconductor laser device.

Various proposals and prototypes of single transverse mode oscillation semiconductor lasers have been made so far. By narrowing the stripe width of the active layer and confining only the lowest order transverse mode of light, single mode oscillation becomes possible. The most typical single mode oscillation laser has a buried stripe structure as shown in FIG. The manufacturing method for this structure is
n-type Gal-xAιxAs2 on n-type GaAs substrate 1;
n-type GaAs active layer 3, p-type Gal-xAlxAs4,
N-type GaAs 5 is sequentially grown, and then a VCSi02 film is applied to form a stripe pattern, and mesa etching is performed using the film as a mask to form the grown layer in a stripe pattern.

Thereafter, a buried layer 6 having a wider forbidden band width and higher specific resistance than the active layer is grown. Finally, the ohmic electrode T is formed to complete the process. However, in this manufacturing process, it is necessary to attach a SiO2 film to the stripe portion as a mask to prevent the buried layer 6 from growing above the stripe.

During the growth of the buried layer 6, the SiO2 film and the vicinity of the active layer are left in close contact with each other at high temperatures, so stress is applied to the active layer due to the difference in thermal expansion coefficient between the SiO2 film and the GaAs layer, which can cause deterioration. Become. Furthermore, impurities that form deep energy levels are used to increase the specific resistance of the buried layer 6, but these impurities diffuse and invade the active layer, causing deterioration of characteristics. Recently, in order to overcome these problems of the buried stripe type laser, single mode oscillation has been developed using a new structure.

An example of its configuration is shown in FIG. The manufacturing method is to deposit n-type Gal-XAtXAS on a grooved n-type GaAs substrate 8.
9, n-type GaAs active layer 10, p-type Gal-XAlxA
sll, p-type GaAsl2 are grown sequentially, and S is deposited on the surface.
Attach the iO2 film 13 and place it opposite to the grooved position.
Striped windows are formed in the O2 film 13. Thereafter, an ohmic electrode 14 is formed to complete the process. During growth, the first
The layer n type Gal-XAt X
The structure is such that it passes through the AtXAS layer 9 and is absorbed by the n-type GaAs substrate 8, and single mode oscillation becomes possible in the active layer in the groove.

However, in this structure, the active layer 10 is flat, and the light generated in the active layer in the groove portion easily propagates and spreads in the lateral direction, so that the oscillation mode is distorted in the lateral direction.

The present invention is different from the above structure and provides a new structure for realizing a single mode oscillation semiconductor laser and a method for manufacturing the same.

The present invention will be described below based on examples together with drawings.

Step-like steps are formed on the n-type substrate 15 as shown in FIG. 3a.

Using this as a substrate, as shown in FIG. 3b, a VC n-type clad layer 16, a non-doped active layer 17, a p-type clad layer 18,
A p-type ohmic electrode forming layer 19 is continuously grown. Subsequently, an insulating film 20 is deposited on the surface, and a striped window is formed above the stepped portion of the substrate, as shown in FIG. 3c. A p-type ohmic electrode 21 is formed thereon, and
An ohmic electrode 22 is also provided on the n side, and a laser device is fabricated as shown in FIG. 3d. The feature of this structure is that the first cladding layer 16 is made thick enough that the light leaking from the active layer 17 is not absorbed by the substrate 15 in the step portion, and that the light is absorbed by the substrate 15 in the portion other than the step portion. The active layer 17 is made very thin to suppress the spread of light, which has the same effect as the structure shown in FIG. It's there.

Controlling the step height of the substrate 15 so that only the lowest order transverse mode light is confined between the folds of the active layer 17;
Single mode oscillation is obtained. The laser fabricated using this manufacturing method does not have the problems that occur in the manufacturing process of the buried stripe structure, and also has a more stable oscillation mode than the laser with the structure shown in Figure 2. ing.

A specific example of a method for manufacturing a single mode oscillation semiconductor laser having this new structure will be described below.

GaAs, Gal-XAtx. A
A single mode oscillation semiconductor laser constructed by s is shown below.

As shown in FIG. 3a, the 110 plane, which is the cleavage plane of the substrate, is etched by chemical etching on the 100 plane of the n-type GaAs substrate 15.
A step of 1 μm is formed perpendicular to the surface.

Next, the liquid phase epitaxial method is applied to the surface as shown in Fig. 3b.
As shown in the figure, the first layer n-type Gal-XAt
．． A third layer of p-type Gal-Atr'ASl8 of 1.5 μm and a fourth layer of p-type GaAsl9 of 1 μm are continuously grown. Subsequently, a Si3N4 film 20 is applied to the entire surface, and a stripe-shaped window with a width of 5 μm is formed at a step position on the substrate to produce a structure as shown in FIG. 3c. Next, as shown in Figure 3d, after zinc was diffused onto the p-type GaAsl9 surface,
A p-side ohmic electrode 21 is formed by vacuum-depositing a p-type electrode metal and performing an alloying process. Subsequently, a metal for an n-type electrode is vacuum-deposited on the entire surface of the GaAs substrate 15, and an alloying process is performed to form an n-side ohmic electrode 22. Finally, the device is separated into element pieces, the p-side electrode 21 is adhered to a heat sink, and a gold wire is connected on the n-side electrode metal film 22 to complete the process. The GaAs-Gal-XAtxAs semiconductor laser constructed in this manner performed single mode continuous wave operation at room temperature and exhibited excellent characteristics.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a laser with a buried stripe structure, FIG. 2 is a cross-sectional view of a laser constructed on a substrate with grooves, and FIGS. It is a process sectional view. 15...n-type GaAs substrate, 16...
n-type Gal-0AtXAS117...n-type Ga
Asll8...p-type Gal-E'AtXlAS
ll9...P-type GaAsl2O...S
i3N4 film, 21... p-side electrode metal film,...
...N-side electrode metal film.

Claims (1)

[Scope of Claims] 1. An active layer is formed on a semiconductor substrate having a step on its main surface, with a cladding layer interposed therebetween, so that the active layer is inclined with respect to the main surface at the step, and the slope of the active layer is A current limiting layer defining a stripe-shaped current injection region is formed at a position opposite to the part, the inclined part forms a striped active region, and the cladding layer prevents light from being absorbed by the semiconductor substrate in the stepped part. A semiconductor laser device having a thickness such that light is absorbed by the semiconductor substrate in areas other than the stepped portion. 2. The semiconductor laser device according to claim 1, wherein the current limiting layer is an insulating layer having striped openings. 3. Forming a step on the surface of the semiconductor substrate, and forming a cladding layer on the semiconductor substrate to a thickness such that light is not absorbed by the semiconductor substrate in the step portion, and light is not absorbed into the semiconductor substrate in areas other than the step portion. a step of forming an active layer on the cladding layer to a thickness that absorbs the absorption; a step of forming an active layer on the cladding layer so as to be inclined with respect to the main surface at the stepped portion; and a step of applying an electric current to a position opposite to the inclined portion of the active layer. A method of manufacturing a semiconductor laser device, comprising the step of forming a current limiting layer that defines an injection region. 4. The method of manufacturing a semiconductor laser device according to claim 3, wherein the current limiting layer is an insulating layer having striped openings.