JPH01281784A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To facilitate realization of an active layer composed of a narrow MQW(Multilayer Quantum Well) structure by a method wherein only the region of the MQW into which a second impurity is implanted is not disordered in an annealing process and the region is used as the active layer. CONSTITUTION:The width of an active layer composed of GaAs layers 3a and AlzGa1-zAs layers 3b is limited by an Si diffused region 7 formed by diffusion from the tip of a V-groove 11 and the sufficiently narrow active layer can be realized easily. If a forward bias is applied to this laser, a current is injected from a Zn diffused region 6 into the active layer in the Si diffused region 7 which is not disordered and has a low built-in potential from both the sides of it. The active layer has not only the function of confining a current and a light in the vertical direction but also has the function of a waveguide region in the horizontal direction because both the sides of the active layer are disordered and has lower refractive indices. Moreover, as the amplifying region of the light is also limited, the light can be confined efficiently, so that a stable laser oscillation can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention provides an active layer with MQW (Multi
The present invention relates to a method of manufacturing a semiconductor laser equipped with a quantum well layer.

[Conventional technology]

Conventionally, in order to lower the threshold voltage of semiconductor lasers, efforts have been made to improve the current narrowing effect within the semiconductor laser by improving the structure, and as a result, a device with a threshold voltage of less than 10 mA at a practical level has been developed. ing.

However, when considering the integration of lasers and electronic devices, unlike when using individual elements, there is no way to effectively release the heat generated from the laser, so it is no longer possible to flow the same current as when they are integrated. . This problem becomes even more serious when there are multiple lasers, and it is said that the only allowable driving current for the laser is about 1 mA at most.
Against this background, low threshold lasers are being developed.

Figure 3 (a) and (b) are Electronics L
1117 is a cross-sectional view showing the element structure of a conventional semiconductor laser and its double heterostructure shown in No. 1117. In these figures, 21 is a substrate made of n-GaAs, 22 is a lower cladding layer made of n-AlGaAs, 23 is an MQW layer, 23a is a GaAs layer, and 23b is an A
lzGat-gAs layer, 23c is AI,
24 is an upper cladding layer made of p-AIGaAs, 25 is a cap layer made of p-GaAs,
26 is a p''-Zn diffusion region, 27 is a natural oxide film, 28
is a p-electrode, and 29 is an n-electrode.

In this laser, the aAs layer 23a in the second and third MQW layers and the AI, Gap-, As layer 23b are used as active layers, so the density of states of electrons and holes is localized, and the gain is large and low. A threshold is being established. Since the AI and Ga1-yAs layers 23c, the upper cladding layer 24, and the lower cladding layer 22 are provided above and below the active layer, light and injected carriers are confined in the vertical direction. In addition, both ends of the active layer are removed by etching, and part of the MQW is disordered due to the diffusion of Zn from both sides.
The active layer is narrowed.

[Problem to be solved by the invention] The conventional semiconductor laser as described above achieves a low threshold of about 1 mA by adopting an MQW structure and narrowing the active layer. It is technically difficult to etch both sides of the film, and Zn diffusion also has poor reproducibility, making it unsuitable for practical use.This invention was made to solve these problems, and An object of the present invention is to obtain a method for manufacturing a semiconductor laser that can easily realize an active layer having a narrow MQW structure.

(Means for Solving the Problems) A method for manufacturing a semiconductor laser according to the present invention includes the steps of sequentially forming a lower cladding layer, an MQW layer containing a first impurity, and an upper cladding layer on a semi-insulating substrate; A step of forming a groove in the upper cladding layer and implanting a second impurity from the groove to the MQW layer, and a step of annealing at a temperature such that only the region of the MQW layer where the second impurity is not implanted is disordered. This includes:

[Effect]

In this invention, only the region of the MQW layer into which the second impurity is implanted is not disordered in the annealing step, and this region becomes the active layer.

(Example) FIGS. 1(a) to (d) are cross-sectional views for explaining an example of the method of manufacturing a semiconductor laser of the present invention, and FIGS. 2(a) to (C) are cross-sectional views of the present invention. 1 is a cross-sectional view showing the structure of a semiconductor laser, a double heterostructure, and a disordered double heterostructure obtained by the method. In these figures, 1 is a substrate made of semi-insulating GaAs, and 2 is a p- A
IXGax-, lower cladding layer made of As, 3 is MQW
layers, 3a is a GaAs layer, 3b is AllGa, -.

As layer, 3c is AI, Gap-, As layer, 3d is AI generated by disordering, 'Ga+-, 'As layer, 3'
is the disordered MQW layer, 4 is p-A 1 x G
a Upper cladding layer consisting of I-X A S, 5 is p-
A cap layer made of GaAs, 6 a p + -Zn diffusion region, 7 an n''-SL diffusion region, 8 an insulating film, 9 a p electrode, 10 an n electrode, and 11 a V groove.

Next, the manufacturing process will be explained.

First, as shown in FIG. 2(a), layers from the lower cladding layer 2 to the cap layer 5 are sequentially grown on the substrate 1 by molecular beam epitaxy. At this time, Be as the first impurity is added to the GaAs layer 3a in the MQW layer 3 which becomes the active layer.
,AI,Ga,-.

The As layer 3b is doped in advance.

Next, as shown in FIG. 2(b), after selectively etching the cap layer 5 so as to leave the electrode forming portion, the MQ
A V-groove 11 is formed up to just above the W layer 3.

Next, as shown in FIG. 2(C), from the V groove 11 to the MQW
After St is implanted as a second impurity so as to reach layer 3, annealing is performed.

At this time, in the region of the MQW layer 3 where Si has been implanted, the MQW structure remains as is due to the so-called "Co-DOPE" effect. And, outside the St diffusion region 7, Be
Similarly to the case where A is diffused alone, the GaAs layer 3a and A
1 z G a I - z A disorder occurs due to interdiffusion of the s layers 3b, and AI with an intermediate composition of both layers, 'G
ap-,' As layer 3d is generated (o<z'<z
). Since the above-mentioned diffusion of Si is performed in the shape of the groove 11, the MQW region to be saved is narrowed down to a very narrow width.

Finally, as shown in FIG. 2(d), after forming the Zn diffusion region 6, the insulating film 8. The device is completed by forming the p-side electrode 9 and the n-side electrode 10.

Next, the operation will be explained.

In the semiconductor laser thus obtained, the width of the active layer consisting of the GaAs layer 3a and the AI, Ga+-, Ass layer b is limited by the St diffusion region 7 diffused from the tip of the groove 11; A sufficiently narrow active layer can be easily realized. Then, if we apply a forward bias to this laser,
The current injected from the Zn diffusion region 6 flows into the St diffusion region 7.
selectively injected from both sides into the active layer, which is not disordered and has a low built-in potential. This active layer has the function of confining current and light in the vertical direction, as shown in the conventional example, and also in the lateral direction, because both sides are disordered and the refractive index is low. Functions as a wave area. Furthermore, since the light amplification region is also limited, the light can be effectively confined, making stable laser oscillation possible.

Although the above embodiments have been described using a GaAs-based semiconductor laser, the present invention can also be applied to semiconductor lasers made of other materials such as InP-based.

Furthermore, although the case has been described in which Be is doped into the active layer in advance as the first impurity, it may be doped after crystal growth by ion implantation.

Also, Be as the first impurity and S as the second impurity.
Although t is used, combinations other than those described above may be used as long as the "Co-DOPE" effect can be obtained.

(Effects of the Invention) As explained above, the present invention includes a step of sequentially forming a lower cladding layer, an MQW layer containing a first impurity, and an upper cladding layer on a semi-insulating substrate, and forming a groove in the upper cladding layer. However, since it includes a step of implanting a second impurity from this trench to the MQW layer, and a step of annealing at a temperature such that only the region of the MQW layer where the second impurity is not implanted becomes disordered, the MQW structure can be improved. It is possible to easily disorder only a part of the active layer of the semiconductor laser, and it is possible to obtain a semiconductor laser with good reproducibility, which has a narrow width and a low threshold value, and is suitable for integration with electronic devices.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining an embodiment of the semiconductor laser manufacturing method of the present invention, FIG. 2 is a cross-sectional view showing the structure of the semiconductor laser obtained by the present invention, and FIG. FIG. 2 is a cross-sectional view showing the structure of a laser. In the figure, 1 is a substrate made of semi-insulating GaAs, 2 is a lower cladding layer made of p-AlxGa1-xAs, 3 is an MQW layer, 3a is a GaAs layer, 3b is A1. Ga+-,
As layer, 3C is AI, Ga, -. As layer, 3d is A I ,' generated by disordering.
3' is a disordered MQW layer, 4 is an upper cladding layer made of p-AlxGap-XAs, 5 is a cap layer made of p-GaAs, 6
7 is a p''-Zn diffusion region, 7 is an n''-St diffusion region, 8 is an insulating film, 9 is a p electrode, 10 is an n electrode, and 11 is a V groove. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Figure 1 + 1J, n' Toichi Figure 2 3d:'! Ah'Ga+-z generated by a
'As/W(a) "== ]-1□□-- Shikub)1 [Figure 3□-□□□□

Claims (1)

[Claims] a step of sequentially forming a lower cladding layer, an MQW layer containing a first impurity, and an upper cladding layer on a semi-insulating substrate; forming a groove in the upper cladding layer; and forming a groove with a second impurity from the groove to the MQW layer. A method for manufacturing a semiconductor laser, comprising the steps of: implanting a second impurity; and performing annealing at a temperature at which only a region of the MQW layer where the second impurity is not implanted becomes disordered.