JPH0580836B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a buried structure semiconductor laser used in optical communication or information processing equipment.

(Prior Art and Its Problems) Research and development of buried structure semiconductor lasers has been actively conducted in order to have excellent characteristics such as low threshold value and high efficiency. In a buried structure semiconductor laser, crystal growth is normally performed twice. As shown in Japanese Journal of Abrid Physics (JJAP) Volume 19, pages L591-L594, when forming a buried structure semiconductor laser with AlGaAs-based materials, the surface of AlGaAs is very easily oxidized. When crystal growth is performed using the liquid phase epitaxial (LPE) method,
The problem was that crystal growth on AlGaAs was difficult. In order to avoid this problem, measures have been taken in the past, such as reducing the Al composition ratio of AlGaAs on the substrate surface during the second growth, and thoroughly baking the LPE growth melt before the second growth. However, the drawback is that the yield is low. Also, instead of the LPE method, the MO-CVD method
The MBE method tends to grow relatively well on AlGaAs. However, when performing the second growth using these growth methods, there is a drawback that the growth yield and reproducibility are poor because the growth is susceptible to the effects of residues on the substrate such as photoresist used during mesa etching.

As explained above, using conventional technology, AlGaAs
When forming a buried structure semiconductor laser using a semiconductor laser based on the above-mentioned materials, there is a drawback that the yield and reproducibility during the second growth are poor.

(Object of the invention) The object of the invention is to eliminate the above-mentioned drawbacks and to
An object of the present invention is to provide a method for manufacturing a buried structure semiconductor laser with good second growth yield and reproducibility using AlGaAs-based materials.

(Structure of the Invention) The method for manufacturing a buried structure semiconductor laser of the present invention includes a step of forming an active layer made of GaAs, and after forming the active layer Al _xc Ga _1-xc As (X _c ≠0).
a step of forming a mesa stripe including at least the semiconductor layer by etching until it reaches the active layer; and a step of evaporating the active layer in a region other than the mesa stripe in an MBE growth chamber. It is characterized by including.

(Example) Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 schematically shows the manufacturing method of the first embodiment of the present invention. In the figure, 1 is n-GaAs
The substrate, 2 is an n-type cladding layer (n-AlGaAs, Al composition ratio 0.2-0.8), 3, 3a, 3b are active layers (GaAs, thickness <200 nm), 4, 4a are the first p-type cladding layer (p- AlGaAs, Al composition ratio 0.2-0.8, thickness <500 nm), 5 is the second p-type cladding layer (p-
AlGaAs, Al composition ratio 0.2 to 0.8, thickness > 0.3 μm), 6
is the cap layer (p-GaAs), 7 is the p-side electrode, 8
is the n-side electrode, 9 is the mesa stripe, 11 is SiO ₂
It is a membrane. At the beginning of the manufacturing process, n-
On a GaAs substrate 1, an n-clad layer 2, an active layer 3,
A first p-type cladding layer 4 is sequentially grown. Next, as shown in Figure b, a mesa stripe 9 made of the first p-type cladding layer 4 is formed using a selective etching method. At this time, the active layer _3b is exposed in the area other than the mesa stripe 9 by etching. Next, as shown in figure c, when the As beam is applied to the wafer in the MBE equipment and the substrate temperature is kept at 700℃ or higher,
Using the fact that only GaAs evaporates, the active layer 3 _b
Remove only by evaporation. At this time, carbon-based dirt and residue after mesa etching are also removed. Then the 2nd p in the same MBE growth chamber
A mold cladding layer 5 and a cap layer 6 are grown in sequence. As described above, in the manufacturing method of the present invention, since the active layer is etched immediately before the second growth, dirt and residues caused by mesa etching etc. can be removed at this time. Furthermore, since the growth is performed using the MBE method, it can be easily grown on AlGaAs. Therefore, the second growth could be performed with very good yield and reproducibility. In the final step (d), the SiO ₂ film 11 and the p-electrode 7 are
Then, the n-electrode 8 is formed and cleaved to cut out pellets and attached to the stem.

In the laser formed by this manufacturing method,
The active layer _3a is surrounded by the first p-type cladding layer 4a, the n-type cladding layer, and the second p-type cladding layer 5, realizing a buried structure, and exhibiting good characteristics of low threshold value and high efficiency.

FIG. 2 schematically shows a manufacturing method of a second embodiment of the present invention. Most of the manufacturing methods are the same as those of the first embodiment described above, except that in step a, a protective layer 10 made of GaAs and having approximately the same thickness as the active layer is formed. This protective layer is coated on the surface of the mesa stripe 9 in the mesa etching step b, and is used for the second growth c.
In the step, the active layer _3b and the active layer 3b are evaporated and removed in the MBE growth chamber. As described above, in the second embodiment, since etching is performed by evaporation not only on the area other than the mesa stripe 9 but also on the mesa stripe 9 in the growth chamber, dirt and residue remaining on the mesa stripe 9 are removed. Objects can also be removed at any time. Therefore, according to the manufacturing method of the second embodiment, there were few defects even on the mesa stripe 9 in the second growth, so that a high-yield, high-performance buried structure semiconductor laser could be obtained.

In the above embodiments, the active layer 3 has a thickness of
A quantum well of 20 nm or less may be used. In this case, as shown in Fig. 3, there are light guide layers 12 and 13 on both sides of the active layer 3, which have a refractive index between the cladding layer 2 and the active layer 3, and the light is well confined and oscillates at a low threshold. . The first optical guide layer 12 and the second optical guide layer 13 may have a so-called GRIN (Graded Index) structure by gradually changing the refractive index in the film thickness direction. In manufacturing such a quantum well buried structure semiconductor laser, it was possible to manufacture the semiconductor laser with a good yield by either the method of the first embodiment or the second embodiment.

In the embodiments described above, the SiO ₂ film 11 was used to concentrate the current only on the mesa stripe 9, but the current is not limited to this, and other methods may be used. For example, there is a method in which the cap layer 6 is made of n-GaAs and only the cap layer 6 above the mesa stripe 9 is inverted to p-type by using Zn diffusion to form a current path. Further, in the above embodiments, the guide layer and the cladding layer have a single layer structure, but are not limited to this, and may have a multilayer structure. Also, a superlattice may be used instead of the AlGaAs mixed crystal.

(Effects of the Invention) Finally, to summarize the advantages and effects of the present invention, the second growth is performed with very few defects and with good reproducibility, so that a buried structure semiconductor laser with a high yield can be obtained.

[Brief explanation of the drawing]

Figures 1 a to d are schematic diagrams of the manufacturing process of the first embodiment, Figures 2 a to d are schematic diagrams of the manufacturing process of the second embodiment, and Figure 3 is a schematic diagram of the manufacturing process of the second embodiment. FIG. 2 is a cross-sectional view of a laser with a buried quantum well structure. In the figure, 1... n-GaAs substrate, 2... n-type clad layer, 3... active layer, 4... first p-type clad layer, 5... second p-type clad layer, 6... cap layer, 7 ... p-type electrode, 8 ... n-type electrode, 9 ... mesa stripe, 10 ... protective layer, 11 ... SiO ₂
12...first guide layer, 13...second guide layer, 14...p-type cladding layer.

Claims (1)

[Claims] 1 In a manufacturing method of _a buried _structure semiconductor laser _mainly composed _{of Al} ≠0), forming a mesa stripe including at least the semiconductor layer by etching until it reaches the active layer, and MBE.
A method for manufacturing a buried structure semiconductor laser, comprising the step of evaporating the active layer in a region other than the mesa stripe in a growth chamber.