JPH03225985A - Semiconductor laser device of refractive-index waveguide type - Google Patents

Abstract

PURPOSE:To prevent that a dislocation caused in a blocking layer is propagated to an inner-clad layer and an active layer as a light-emitting region by a method wherein a layer composed of a superlattice is formed between the inner clad layer and an outer clad layer formed as a ridge structure. CONSTITUTION:An n-clad layer 2 is grown on a substrate 1; an active layer 3 and a p-inner-clad layer 4 are laminated and grown on it in this order by an MOCVD method. A p-etching-stopper layer 11 of a superlattice is grown on the p-inner-clad layer 4. The p-inner-clad layer 4 of the superlattice is formed by laminating p-In0.5Ga0.5P in 20Angstrom and p-In0.5(Ga0.5Al0.5)0.5P in 100Angstrom five times each thus producing a laminated structure composed of total ten layers. A p-outer-clad layer 6 of p-In0.5(Ga0.5Al0.5)P is laminated on the p-etching-stopper layer 11 composed of the superlattice. Then, an SiO2 film 9 is formed on the p-outer-clad layer 6 by a sputtering operation or the like; it is etched; a stripe of the SiO2 film 9 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an index-guided semiconductor laser device having a ridge structure.

(Prior Art) The structure of a conventional refractive index guided semiconductor laser device and its manufacturing method will be described below.

FIGS. 2A to 2F are diagrams showing a conventional method for manufacturing a refractive index waveguide type semiconductor laser device.

First, as shown in FIG. 2(A), MOCVD (iet
alorganic chen+1cal vapor
An n-type cladding layer 2 is grown on a substrate 1 using a deposition method (organic metal vapor phase epitaxy), and an active layer 3, a p-type inner cladding layer 4, an etching stopper layer 5, and a p-outer cladding layer are formed thereon. 6 are sequentially stacked and grown.

Next, as shown in FIG. 2(B), a 5102 film 9 is provided on this p-outer cladding layer 6 by sputtering or the like.
Etching is performed using a hydrofluoric acid solution to form stripes of the SiOz film 9.

Then, using the stripes of the 5i02 film 9 as a mask, the p-outer cladding layer 6 is etched with a sulfuric acid or nitric acid solution up to the etching stopper layer 5.
A ridge of the p-outer cladding layer 6 is formed (FIG. 2(C)).

Furthermore, the flock layer 7 is formed again on the etching stopper layer 5 exposed by this step using the MOCVD method, but at this time the block layer 7 does not grow on the SiO2 film 9 (see FIG. 2(D). )).

After removing the SiO2 film 9 using a hydrofluoric acid solution (FIG. 2(E)), the contact layer 8 is grown thereon (FIG. 2(F)).

A semiconductor laser device is obtained as described above, but the etching stopper layer 5 is provided on the inner cladding layer 4 to accurately stop the etching when the outer cladding layer 6 is etched. The material of this etching stopper layer 5 is a single layer with a composition different from that of the p-outer cladding layer 6, and
In order not to absorb the oscillation wavelength of the laser emitted from the active layer 3, a semiconductor material having a larger band gap energy than the active layer 3 was used.

(Problems to be Solved by the Invention) Incidentally, in semiconductor devices, lattice defects called "dislocations" often occur when external force is applied during or after crystal growth in semiconductor devices.

This is because when an external force is applied to a crystal, lattice plane slip is induced, and dislocations multiply one after another at the intersection of the two slip planes. Especially when crystals of the same material are stacked, These dislocations also propagate to the next layer.

Furthermore, when crystals of different materials are stacked, there are cases in which dislocations propagate to the side of the different materials, and cases in which they bend at the stacked surface and do not propagate to the side of the different materials. No method has been found so far to control this.

In the conventional index-guided semiconductor laser device, dislocations generated from the dislocation generation surface 10 shown in FIG. The problem is that the light propagates to the layer 4 and further reaches the active layer 3, which is the light emitting region, resulting in the semiconductor laser device not operating or having a shortened lifespan.

Therefore, the present invention solves the problems of the conventional technology described above, and provides a structure in which even if dislocations occur during growth of the block layer, these dislocations are not propagated to the inner cladding layer, thereby achieving high reliability and long life. An object of the present invention is to provide a long refractive index guided semiconductor laser device.

<Means for Solving the Problems> As a means for achieving the above object, at least a substrate, a first cladding layer, an active layer, and a second cladding layer are provided in this order, and the second cladding layer is In a refractive index waveguide semiconductor laser device which is separated into an inner clad layer and an outer clad layer and has a ridge structure by etching the outer clad layer, the inner clad layer and the outer clad layer have a ridge structure. An object of the present invention is to provide a refractive index waveguide type semiconductor laser device characterized in that a layer made of a superlattice is provided between the semiconductor laser device and the semiconductor laser device.

(Example) An example of the structure of a short wavelength semiconductor laser device using the present invention is shown in FIG. 1 as the main side of the refractive index guided semiconductor laser device of the present invention.

In this short wavelength semiconductor laser device, the substrate 1 has n-GaA
n-1n□, 5 (GaO', 5A
t, 5). An n-cladding layer 2 of sP is grown, on which an active layer 3 of Ino, 5'''0.5 P, p-1no,
s (Ga, s^0.5). , 5P p-inner cladding layer 4 is MOCVDed in this order in the same manner as the conventional example.
They are grown in layers by a method.

Next, a superlattice etching stopper layer 11 is grown on the p-inner cladding layer 4.

The p-inner cladding layer 4 of this superlattice is p-In0
．． 5 GaO, 5P for 20 people, p-1no, 5 (Gao
, 5AI, 5) 0.5P were stacked 5 times by 100 people each, resulting in a stacked structure consisting of a total of 10 layers.

Then, on the p-etching stopper layer 11 made of this superlattice, p-In, s (Gao, s^'0
．． 5. A p-outer cladding layer 6 with >P is laminated.

Next, similarly to the conventional example, this p-outer cladding layer 6
A SiO2 film 9 with a thickness of about 3,000 mm is provided on the top by sputtering, etc., and etched with a hydrofluoric acid solution.
Stripes of SiO2 film 9 are formed.

Then, using the stripes of the SiO2 film 9 as a mask, the p-outer cladding layer 6 is etched with a sulfuric acid or nitric acid-based solution up to the superlattice p-etching stopper layer 11, and the p-outer cladding layer 6 is removed. 6 ridges are formed.

Furthermore, an n-GaAs block layer 7 is formed again using the MOCVD method on the p-etching stopper layer 11 that is not exposed in this step, which is the part other than on the SiO2 film 9.
form.

After removing the SiO2 film 9 with a hydrofluoric acid solution, a p-GaAs contact layer 8 was grown thereon to obtain a semiconductor laser device.

In this semiconductor laser device, a superlattice with a multilayer structure is used as the p-etching stopper layer 11. Therefore, some of the dislocations generated during the growth of the block layer 7 are transferred to the p-1n□, 5 Gao, s P layer and p-I
n(GaAt)P layer, some layers are propagated through the laminated plane of 0.5 0.5 0.5 0.5, or are finally bent at the laminated plane in the middle, Since the propagation to the p- inner cladding layer 4 and the active layer 3 is almost eliminated, the problems of malfunction and shortened waiting life of the semiconductor laser device are solved.

In this example, a superlattice was used as the p-etching stopper layer, but the same effect can be obtained by using a superlattice as the n-etching stopper layer in a semiconductor laser device with opposite polarities of p and H. Of course.

In addition, in this example, p-In□, 5G
ao, 20 people with 5P, p-In, 5 (G'ao, 5^
'0.5 ) 0.5 P was stacked 5 times by 100 people each to have a stacked structure consisting of 10 layers, but the material of the superlattice is not limited to this. It is sufficient that the semiconductor material has a lattice structure and also functions as an etching stopper layer.

Furthermore, if a superlattice with a more multilayered structure is used, the probability of dislocation propagation decreases accordingly, and since it is better to have a thinner etching stopper layer for a semiconductor laser device, this superlattice should be made as thin as possible and as thin as possible. A material with a multilayer structure is suitable.

(Effects of the Invention) Since the refractive index guided semiconductor laser device of the present invention uses a superlattice as an etching stopper layer, dislocations generated in the block layer are bent at the lamination plane in the middle of the superlattice. It does not propagate to the inner cladding layer or the active layer 3 which is the light emitting region.

Therefore, it is possible to provide an index-guided semiconductor laser device that is free from malfunctions and has a long life.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the refractive index guided semiconductor laser device of the present invention, and FIGS. 2 (A) to (F) illustrate the manufacturing process of a conventional index guided semiconductor laser device. This is a diagram for 1... n-substrate, 2... n-cladding layer, 3...
active layer, 4... p-inner cladding layer, 5... (single layer) etching stopper layer, 6...
p-outer cladding layer, 7...n-block layer, 8
...p-contact layer, 9...5i02 film, O...dislocation generation surface, 1... (superlattice) etching stopper layer. patent

Claims (1)

[Claims] At least a substrate, a first cladding layer, an active layer, and a second cladding layer are provided in this order, and the second cladding layer is separated into an inner cladding layer and an outer cladding layer, In a refractive index guided semiconductor laser device in which the outer cladding layer is etched to have a ridge structure, a layer made of a superlattice is provided between the inner cladding layer and the outer cladding layer having the ridge structure. A refractive index guided semiconductor laser device characterized by: