JPS6377186A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To be able to accurately control the thickness of a layer by foring a multiplex quantum well layer in which a band gap after disorder is larger than that of an active layer as an etching stopper layer, and disordering the well layer after the etching is finished. CONSTITUTION:A clad layer 2, an active layer 3, a clad layer 4a, a multiplex quantum well layer 10, a clad layer 4b and a contact layer 5 are sequentially grown on a substrate 1. Then, a ridge is formed by etching. That is, since the layer 10 acts as an etching stopper due to the difference of the etching speeds, the thickness of the clad layer outside the ridge can be controlled with good reproducibility over the whole wafer surface. The layer 10 is disordered by annealing, diffusing Zn, or implanting Si ions as an impurity to form an insulating film, a p-type side electrode and n-type side electrode, thereby obtaining the same structure as a semiconductor laser without reducing the efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor laser.

[Conventional technology]

FIG. 5 is a structural sectional view of a conventional semiconductor laser called a Fuji waveguide laser. In this figure, 1 is n-
Substrate made of GaAs, 2 is n-A 1. Gal-y
Cla-Sodo layer consisting of A s, 3 is n or p-A
active layer consisting of lyG a, -yA s, 4 is p-A
I XG al-, A! a cladding layer consisting of 5
6 is a contact layer made of p-GaAs, and 6 is SiO.
7 is a p-side electrode, and 8 is an n-side electrode. In addition, cladding layer 2. Active layer 3. The cladding layer 4 has a double heterostructure, and X>y.

Next, the operation will be explained.

Since the insulating film 6 is present, current is injected only from the contact layer 5 on top of the metal layer 5. Therefore, the cladding layer 2. Active layer 3. In the double heterostructure formed from the Kurasod layer 4h), only the portion below the ridge into which current is injected emits light, leading to laser oscillation. by the way,
In order to control the transverse mode, the semiconductor laser of B has been devised as shown below.

In other words, the thickness of the cladding layer 4 is set to 0.3 on the outside of the ridge.
Thinly cut down to about μm, 1.5 μm under the ridge.
In addition, the thickness of the active layer 3 is set to 0.1
The thickness is about μm or less. The thickness of active layer 3 is 0.1
If the thickness is about μm or less, from the active layer 3 to the cladding layers 2 and 4
Each of the light that seeps out has a diameter of about 0.5 μm, and the light that seeps out outside the ridge reaches the insulating film 6. On the other hand, since the cladding layer 4 is sufficiently thick at 1.5 μm below the ridge, all of the seeping light exists within the cladding layer 4. For this reason, a difference in refractive index is effectively generated in the outer portion of the portion under the glue/strip of the active layer 3, and the transverse mode can be controlled.

[Problems to be Solved by the Invention] In the conventional semiconductor laser as described above, in order to control the transverse mode, the thickness of the cladding layer 4 is reduced to 1 at the lower part of the ridge.
．． It must be about 5 μm or more and about 0.3 μm or less on the outside of the ridge. By the way, in order to partially change the thickness of the cladding H4 as described above, it is necessary to first change the thickness to 1.5μ.
After growing a cladding layer 4 of m thickness over the entire surface of the wafer, it is etched to a thickness of 0.3 μm, leaving a portion that will become a ridge.
Keep it below that level. In order to stably control the transverse mode characteristics of a semiconductor laser, it is necessary to accurately control the thickness of the cladding layer 4 outside the ridge. It was difficult to stop.

As a method of improving such etching accuracy, it is conceivable to create a structure having an etching stopper d as shown in FIG. In this figure, the same reference numerals as in FIG. 5 indicate the same parts, and 9 is an etching stopper layer 4a made of p-GaAs.

Reference numeral 4b denotes a cladding layer made of p-A I In the case of this structure, after forming each layer from the cladding layer 2 to the contact layer 5 on the substrate 1, etching is performed using a selective etching solution such as potassium iodide-iodine, and the portions that will become the outside of the ridge are etched. Clad N4
When the etching layer b is etched and reaches the etching stopper layer 9, the etching speed at this part becomes significantly slow.
The thickness of the cladding layer 4b on the outside of the cladding can be controlled to 0.3 μm with good precision. However, in this structure, the etching stopper layer 9 remaining under the ridge is the active layer 3.
There was a problem in that the efficiency of the semiconductor laser deteriorated because it absorbed the light emitted by the semiconductor laser.

The present invention was made to solve these problems, and it is an object of the present invention to provide a method for manufacturing a semiconductor laser that can precisely control the layer thickness by etching without reducing the efficiency of the semiconductor laser.

[Means for solving problems]

The method for manufacturing a semiconductor laser according to the present invention includes the steps of forming a multiple quantum well layer as an etching stopper layer whose band gap after disordering is larger than that of the active layer, and disordering the multiple quantum well layer after etching is completed. The method includes the step of:

[Effect]

In this invention, the multiple quantum well layer functions as an etching stopper layer, and after etching is completed, the multiple quantum well layer becomes disordered and becomes negligible.

〔Example〕

1 to 3 are structural cross-sectional views for explaining an embodiment of the method for manufacturing a semiconductor laser according to the present invention. In these figures, the same reference numerals as in FIG. 6 indicate the same parts, and 1o
is an AJGaAs-based multiple quantum well layer, and its composition is
The film thickness can be selectively etched between the cladding layers 4a and 4b, and the film thickness is, for example, 936 Ai? It is composed of five layers of As and GaAs with a thickness of 83 mm, and when disordered, it becomes A1.
It becomes a mixed crystal of o, s, G Iio, and 47A s.

Next, the process will be explained. First, as shown in FIG. 1, a cladding layer 2 is placed on a substrate 1.
Active layer 3. Cladding layer 4a, multiple quantum well layer 10. Cladding layer 4b and contact layer 5 are grown in sequence. At this time, the thickness of each layer can be controlled very precisely by using a crystal growth method such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). Next, by etching, a ridge as shown in FIG. 2 is formed. At this time, if a mixed solution of iodine: potassium iodide: pure water = 55: 113: 100 is used as the etchant, A I 6.53G a (1,4
Etching speed for 7A S is 1.6μm/n
ain at 20°C, and the etching rate for GaAs is O,OSμffI/min at 20°C.

In other words, because the multi-quantum well layer 10 acts as an etching I/flange layer due to the difference in etching speed, it is possible to control the thickness of the cladding layer outside the ridge with good reproducibility over the entire wafer surface. The final thickness is the sum of the thickness of the cladding layer 4a and the thickness of the multiple quantum well layer 1o. As mentioned above, these thicknesses can be controlled very precisely by crystal growth methods such as MOCVD and MBE, and therefore the transverse mode characteristics can also be controlled precisely.

Next, annealing or diffusion of Zn as an impurity, Si
After the multi-quantum well layer 1o is disordered by ion implantation such as ion implantation to form the structure shown in FIG. 3, the insulating film SFP side electrode 7. By forming the n-side electrode 8, the same structure as the semiconductor laser shown in FIG. 5 can be obtained, and no reduction in efficiency occurs. Furthermore, a precisely controlled film thickness can be obtained with good reproducibility over the entire wafer surface.

Furthermore, the method for manufacturing a semiconductor laser of the present invention can also be applied to a semiconductor laser having the structure shown in FIG. In this figure, the same reference numerals as in Fig. 1 indicate the same parts, and 1
0a is the multi-quantum well layer after disordering, 11 is A
a current blocking layer consisting of l zG al-zA s;
By appropriately selecting the value of 2, a loss guide type waveguide mechanism or a rib type waveguide mechanism can be obtained. 12 is a groove formed by etching.

In the case of this semiconductor laser, in the first crystal growth, the cladding layer 2. Active layer 3. Cladding layer 4a.

Multiple quantum well layer 10. After growing each layer of the current blocking layer 11, the same etching as in the above embodiment is performed to form the groove 1.
2 and disordered the multi-quantum well layer 10,
In the second crystal growth, the cladding layer 4b and the contact layer 5
grow and form.

In this case as well, the multi-quantum well layer 1o acts effectively when forming the grooves 12, so that the grooves can be formed with high accuracy without reducing laser efficiency, and the transverse mode can be controlled with high accuracy.

In each of the above embodiments, n -GaA is deposited on the substrate 1.
Although the case using p-GaAs has been described, the same effect can be obtained when p-GaAs is used by reversing the conductivity of each layer.

Further, in the above embodiments, an ANGaAs-based laser has been described, but the same effect can be achieved in an InGaAsP-based laser if the multiple quantum well layer is made of an InGaAsP-based laser.

〔Effect of the invention〕

As explained above, the invention of B includes the steps of forming a multiple quantum well layer as an etching stopper layer whose band gap after disordering is larger than that of the active layer, and disordering the multiple quantum well layer after etching is completed. Since the etching process includes steps, the etching accuracy can be improved without reducing the efficiency of the semiconductor laser, and a semiconductor laser with good characteristics can be obtained with high accuracy.

[Brief explanation of the drawing]

1 to 3 are structural cross-sectional views for explaining one embodiment of the method for manufacturing a semiconductor semiconductor device of the present invention, and FIG. 4 is a structural cross-sectional view for explaining another embodiment of the present invention. Figure, 5th
6 are structural sectional views showing a conventional semiconductor laser. In the figure, 1 is a substrate, 2, 4, 4a, db are cladding layers, 3 is an active layer, 5 is a contact layer, 6 is an insulating film, 7 is a 'p m electrode, 8 is an n-side electrode, 10 is a multiple quantum quantum well layer,
11 is a current blocking layer, and 12 is a groove. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Procedural amendment (voluntary) 1. Indication of the incident: Patent Application No. 1981-222811 2,
Title of the invention Semiconductor laser manufacturing method 3, relationship to the amended case Patent applicant address 2-3 Marunouchi-chome, Chiyoda-ku, Tokyo. Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 4, Agent Address 2-3-5 Marunouchi-chome, Chiyoda-ku, Tokyo
, the following is inserted between lines 14 and 15 on page 7 of the description of the contents of the amendment in column 6 of the detailed description of the invention in the specification to be amended. [For example, assuming that the A-texture composition X of the cladding layer 4b is 0.53, the time required to etch the 1.2Bm cladding layer 4b is approximately 45 seconds. On the other hand, the multiple quantum well layer 10 contains 5 layers of 83 GaAs.
The etching rate of this GaAs layer is 0.05 gm/
□. Since etching is slow, it takes about 50 seconds to remove the multiple quantum well layer 10 having a thickness of 880 mm, making it easy to stop the etching at the multiple quantum well layer 10. "that's all

Claims (3)

[Claims] (1) In a method for manufacturing a semiconductor laser including a step of performing selective etching using an etching stopper layer, a multiple quantum well layer whose band gap after disordering is larger than that of the active layer is formed as the etching stopper layer. A method for manufacturing a semiconductor laser, comprising the steps of: and disordering the multi-quantum well layer after etching. (2) The method for manufacturing a semiconductor laser according to claim (1), wherein the multiple quantum well layer is an AlGaAs-based multiple quantum well layer. (3) The method for manufacturing a semiconductor laser according to claim (1), wherein the multiple quantum well layer is an InGaAsP-based multiple quantum well layer.