JPH01183191A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To reduce an operation current and to simply form electrodes by narrowing an interval between impurity diffused regions at an active layer position to be diffused with the impurity near an active layer as compared with the width of a clad layer of an electrode forming side. CONSTITUTION:A p-type impurity of Zn, Be or the like is implanted by an ion implanting method to a surface including a MQW active layer 1 of a region etched at both sides for holding a stripe, thereby forming an ion implanted region 60. Then, a mask 50 is removed, the implanted impurity is diffused and moved by heat treating so that the interval between the diffused parts becomes 2mum or less at the layer 1. In this case, the thickness of an n-type AlGaAs clad layer 2 is sufficiently increased to eliminate the influence of the diffused part to an n-type GaAs contact layer 20, and a p-type electrode 100 and an n-type electrode 101 are eventually formed. Thus, the threshold value of an operation current can be reduced, and a laser having a stable oscillation mode is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser that is suitable for integration with electronic devices and has a small operating current.

[Prior art] Fig. 3 is based on, for example, the document "Proceedings of the 48th Academic Conference of the Japan Society of Applied Physics (October 1986) 18a-ZR-9,
1 is a cross-sectional view of the conventional semiconductor laser shown in FIG.
i Quantum Well, MQW) layer, (2)
(3) is an n-type AlGaAs cladding layer, and (3) is a p-type AlGaAs cladding layer.
As cladding layer, 0α is a semi-insulating (Sl) GaAs substrate, (2) is an n-type GaAs contact layer, 00) is an impurity diffusion region, (100) is a P electrode, and (101) is an n electrode.

This semiconductor laser is manufactured by the following procedure.

First, - on a semi-insulating (SI) GaAs substrate 00), a P-type AI GaAs cladding layer (3) - a multiple quantum well (MQW) layer (1) that will become an active region, n fjl A
I A GaA+s cladding layer (2) and an n-type GaAs contact layer (20) are sequentially formed - then impurity zinc (Zn) is selectively diffused to form an impurity diffusion region (2) leaving an n-type region in a stripe shape. Furthermore, the part where the p-n junction appears on the surface of the n1cyaAs cladding layer @) is selectively etched to form a P electrode Q [
KI and n electrodes (101) are formed. In this way, the Zn diffusion portion of the active MQW layer (1) becomes disordered and becomes an AlGaAs layer with an average composition.

Next, the operation will be explained. In such a structure, p −n around the undisordered active region of the NQW layer (1)
Junction and its upper n-type AlGaAs cladding layer (2)
and two P-n junctions formed between the diffusion portions on both sides. p −n around the former MQW active region
Since the diffusion potential of the junction is lower than that of the latter two p-n junctions, when a voltage is applied between both Ptn electrodes, current flows to the p-n junction around the active region where the potential is low - injecting carriers into the active region. do.

Since the active region is surrounded by AlGaAs with a low refractive index on all four sides, it becomes an optical waveguide, and if the width can be made sufficiently narrow, it can oscillate in a stable single transverse mode and obtain a low threshold.

Since both p and n electrodes can be formed on the same main surface and there are very few steps, it is suitable for integration.

[Problem to be solved by the invention]

In the conventional semiconductor laser as described above, since an n-type electrode is formed, the width of the active region cannot be made very narrow, so the threshold value does not decrease much and the mode is not stable. This is because in the conventional technology, it is possible to form an electrode with a width of about 2 μm by photolithography, and on the other hand, the condition for a single transverse mode is that the active layer width is 2 μm or less. Furthermore, even if an electrode width of 1 μm or less is formed, it is difficult to align the electrode, and as a continuous operation laser, 1 tu
There was a problem that the resistance value of ii was too large.

The present invention has been made to solve this problem, and an object of the present invention is to provide a semiconductor laser with a small operating current and simple electrode formation.

[Means to solve the problem]

In the semiconductor laser according to the present invention, impurity is diffused near the active stone so that the distance between the impurity diffusion regions in the active layer is narrower than the width of the cladding layer on the electrode formation side.

[Effect]

In this invention, the distance between the diffusion regions is narrowed in the active layer portion, and the electrode formation portion is left wide, so that the electrode can be made wider.
Since the active region can be made narrower, the threshold value of the operating current can be lowered.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of the present invention.
1) to (3), α01. (20+ is the same as the above conventional element. (4) is the impurity diffusion region - 0 is the P electrode, (101) is the n electrode, and the space between the impurity diffusion region (■) in the MQW active layer (1) is Spacing between cladding layers +21 +31
It is set to 2 μm or less, which is smaller than that in the previous example. Therefore, it is possible to form an n-electrode (101) larger than the gap between the impurity diffusion regions (2) on the cladding layer (2) on the electrode formation side.

FIG. 2 shows an example of a manufacturing method for realizing a semiconductor laser according to an embodiment of the present invention. In the figure, the same reference numerals as in FIGS. 1 and 3 indicate the same parts, the gloss is a mask, (FA is an ion implantation region. First, in FIG. 2(a), a P-type AlGa
Asri5''7 layer (3), MQW active layer (1), n
Type AIGaAII layer 5'/de layer (2), n-type GaAs
:+The contact layer (2) is formed by liquid phase or vapor phase epitaxial method. Next, as shown in Figure 2(b),
A mask group is formed using a resist or the like on a part of the n-type GaAs contact layer (a), and up to two layers on the surface are selectively etched away.
A portion of the GaAs cladding layer (2) is left in a stripe shape. The width of the mask is approximately 5 μm. Next, as shown in FIG. 2(C), P-type impurities such as Zn and Be are implanted into the surface area including the MQW active layer (1) in the etched regions on both sides of the stripe by ion implantation. Then, an ion implantation region (60) is formed. Next, as shown in FIG. 2(d), the mask hammer is removed and heat treatment is performed to diffuse and move the implanted impurities, so that the distance between the diffusion parts in the MQW active layer (1) becomes 2 μm or less. Make it.

At this time, the thickness of the n-type AlGaAs cladding layer (2) is made sufficiently thick so that the diffusion portion becomes the n-type GaAs contact layer (a).
Make sure that it does not extend to Finally, Figure 2 (e)
As shown in the figure, a P electrode (9) and an N electrode (101) are formed to complete the device.

In the semiconductor laser configured as described above, the n-electrode (101) can be formed to have a width of several μm (approximately 2 μm or more),
It can be easily formed using ordinary photolithography technology, and MQW
The active region can be made as narrow as 2 μm or less. Therefore, a laser with stable single transverse mode oscillation and a sufficiently low threshold value can be obtained. In addition, both the P and 1 electrodes are formed on the same main surface, and the step difference is suppressed to a few micrometers, resulting in a semiconductor laser suitable for integration with other electronic circuits.

Note that in the above embodiment, the active layer is made of a multi-cover well (MQW).
), but it is not necessarily necessary to have multiple quantum wells, and a single-layer quantum well may be used. Further, although a GaAs-based laser is given as an example, it is obvious that the present invention can be applied to lasers made of other materials such as InP-based lasers. Furthermore, since ions of n-type impurities such as Si can be implanted, it is clear that a structure in which the P-type and n-type are reversed has the same effect. Even if only the lower cladding layer is made of the opposite conductivity type, the effect is the same, except that carrier injection occurs only from the diffusion regions on both sides and injection from the lower cladding layer as in the example does not occur.

A similar effect can be obtained by stopping the etching midway or by etching slightly below the active layer.

It is clear from the above description that the etching does not have to cover the entire area of the device, but can also be performed in the form of grooves on both sides of the active region. Incidentally, when etching is performed, the interval between the impurity diffusion regions may be narrowed in the active layer portion'.

By the way, in the above explanation, the case where this invention is applied to a single laser is described, but it goes without saying that it can also be applied to other semiconductor lasers such as a semiconductor laser made up of a plurality of lasers or an optoelectronic IC. .

〔Effect of the invention〕

As explained above, this invention narrows the width of the active layer by selectively diffusing impurities without narrowing the width of one electrode too much, making it easy to manufacture and suitable for integration. This has the effect of providing a laser with a stable oscillation mode.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a semiconductor laser according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing an example of a method for manufacturing a semiconductor laser according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view showing a conventional semiconductor laser. FIG. As shown in the figure, (1) is the MQW active layer, (2) is the n-A
IGaA@crat layer, (3) is p-AlGaAs clad layer, 00) is 8l-GaAs substrate, @) is n-Ga
As :ll :/ tact layer, ■ is impurity diffusion region,
■ is the mask, (60) is the ion implantation region, a (g) is P
Electrode (101) is an n-electrode. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A semiconductor laser having cladding layers sandwiching an active layer from both sides, characterized in that the distance between impurity diffusion regions is wider at least in the cladding layer on the electrode formation side than in the active layer.