JPS6088487A - semiconductor laser equipment - Google Patents

Abstract

PURPOSE:To realize high output by enabling the lamination of an active layer while keeping a low threshold value and the basic lateral mode oscillation by a method wherein an internal stripe type laser is constructed on a substrate having a mesa. CONSTITUTION:The mesa is formed on the P type GaAs substrate 1, an N type GaAs current stricture layer 2 being grown by the liquid phase epitaxial method, and a groove being then formed in the surface. A P type Ga0.57Al0.43As clad layer 3, a non-doped Ga0.92Al0.08As active layer 4, an N type Ga0.57Al0.43As clad layer 5, and an N type GaAs cap layer 6 are successively grown by the liquid phase epitaxial method, and N-side and P-side ohmic contact electrodes 7 and 8 are formed. Since the growth in the upper part of the mesa is more inhibited than that of its skirt on account of the anisotropy of crystal growth, an extremely thin active layer 4 can be formed in the upper part of the mesa with good reproducibility.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a semiconductor laser device.

Conventional configurations and their problems In recent years, semiconductor lasers that oscillate in fundamental transverse mode at a low threshold have been required as light sources for writing and reading information into DADs, optical disk files, etc., and as light sources for optical communications. ing. One effective means for achieving this is to incorporate an original current constriction mechanism (internal stripe) into the structure of a semiconductor laser using double growth. FIG. 1 shows a cross-sectional view of an example of a conventional semiconductor laser using internal stripes. This conventional semiconductor laser will be explained with reference to the following drawings.

In FIG. 1, 1 is a p-type GaAs substrate, 2 is an n-type GaAs substrate, and 2 is an n-type GaAs substrate.
As current constriction layer, 3 is p-type Ga 1-xAl xAs
cladding layer, 4 is non-doped Ga1-νsyAs active constant layer, 6 is n-type Ga1-, AlxAm cladding layer, 6 is n-type GaAs cap layer, 7 is n-side ohmic electrode, 8 is p
It is a side ohmic electrode.

The operation of the semiconductor laser device configured as described above will be described below.

The current injected into the substrate from the p-side electrode is blocked by the current narrowing layer 2 in areas other than the groove, and therefore flows intensively into the active layer 4 directly above the groove. The light generated in the active layer by this injected current seeps into the cladding layer, but the first
The light seeping into the cladding layer 3 is absorbed by the current narrowing N2 on the substrate in parts other than the structural part, so the light is confined only in the active layer above the groove, where stable fundamental transverse mode oscillation occurs. is obtained.

However, as the field of use of semiconductor lasers has expanded, the demand for semiconductor lasers that can achieve not only low threshold voltage and fundamental transverse mode oscillation but also high output has rapidly increased.

One of the very effective means of increasing the output power of a semiconductor laser is to grow the active layer very thinly (about 0.05 μm).
This is a method of increasing the light emitting area in the cross section of the semiconductor laser by increasing the leakage into the cladding layer, thereby reducing the optical output density per unit area.

Figure 2 shows the results of theoretical calculations. In Figure 2, the horizontal axis shows the film thickness of the active layer, and the vertical axis shows the maximum optical output emitted from the laser end face when the optical power density leading to end face destruction is constant pd = 2MW/Cd. . As is clear from the figure, as the active layer thickness decreases from around 0.1 to 0.2 μm, the obtained light output increases significantly. However, in the structure shown in Figure 1, in order to grow a flat active layer on a flat substrate, it is difficult to control the thinning of the active layer, and the limit is about 0.1 μm. . Therefore, although the structure shown in Figure 1 is advantageous for low thresholds and fundamental transverse mode oscillation, it is extremely disadvantageous for increasing output power, and so far, an output of several MW has not been achieved. .

Purpose of the Invention In view of the above drawbacks, the present invention provides a semiconductor with a new structure that utilizes internal stripes to maintain low threshold voltage and fundamental transverse mode oscillation while making it possible to thin the active layer and achieve high output. The object of the present invention is to provide a laser device.

Structure of the Invention In order to achieve this object, the semiconductor laser device of the present invention includes at least one semiconductor layer formed on a substrate having a mesa so that its conductivity types alternately change, so that the mesa portion of the substrate is closer to the semiconductor surface. The semiconductor device is characterized in that a trench is formed that reaches the semiconductor surface, and each layer including the active layer is formed as a first layer having a conductivity type different from that of the semiconductor surface layer.

With this configuration, it is possible to achieve thinning of the active layer with good reproducibility by utilizing the anisotropy of crystal growth while maintaining the advantages of internal stripes.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 (→ to (C) are cross-sectional views at each step of a method for manufacturing a semiconductor laser device according to an embodiment of the present invention.

First, a p-type GaAs substrate 1 (100) surface is etched to form a pattern with a height of 3 μm and a width of 15 μm as shown in FIG. 3(a).
form a mesa. On the substrate, an n-type GaAs current narrowing layer 2 of 0.8 μm was formed on the mesa by liquid phase epitaxial method.
Growth is performed so that the thinnest part of the flat part of the substrate other than the mesa has a thickness of 1 μm (FIG. 3(a)).

On the surface of Ueno after this first growth (01
1) Form a groove in the direction. The groove is positioned directly above the mesa on the substrate, with the bottom of the groove reaching the substrate.

The first P-type "0.67AI0.43" cladding layer 3 is formed on the grooved substrate surface again by liquid phase epitaxial method.
0.2 μm on the mesa near the groove, the second layer is non-doped.”
0.92A60.08” Active layer 4 at the same location Q, 0
5/jms 3rd layer n-type Gao, 5□Al. , 43AB cladding layer 6 at the same location with approximately 1.6 μm 1 fourth layer n-type G
The aAs cap layer 6 is continuously grown to a thickness of approximately 2 μm. After that, a metal for the n-side electrode is deposited,
An alloying process is performed to form the n-side ohmic electrode 7. A metal for the p-side electrode is deposited on the substrate side, and an alloying process is performed to form the p-side ohmic electrode 8 (FIG. 3(C)).
.

The semiconductor wafer fabricated in this way was cleaved,
Mount it on the St block and complete.

The operation of the semiconductor laser device configured as described above will be described below. Due to the action of the current confinement layer formed in the first epitaxial growth, the current injected from the substrate side is intensively injected into the active layer above the trench.As a result, fundamental transverse mode oscillation occurs here at a low threshold. It can be obtained with Furthermore, due to the effect of the protrusions previously formed on the substrate, the current constriction layer formed in the first epitaxial growth has a shape that trails toward the image side of the mesa, as shown in FIG. 3(a).

Therefore, when a second growth is performed on top of this, due to the anisotropy of crystal growth, the growth at the top of the mesa is suppressed more than at the other skirts, so it is difficult to reproducibly grow an extremely thin active layer on the top of the mesa. Can be formed well.

As described above, according to this embodiment, by forming a mesa on the umbrella plate prior to growth, fundamental transverse mode oscillation,
A stable high output with a threshold of 30 mA and an optical output of 30 MW was achieved.

Although this embodiment shows the case of a p-type substrate, exactly the same effect can be expected in the case of an n-type substrate.

Effects of the Invention As described above, the present invention can achieve high output while maintaining a low threshold value and fundamental transverse mode oscillation by configuring an internal stripe type laser on a substrate having a mesa. Its practical effects are significant.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an example of a conventional semiconductor laser using internal stripes, Figure 2 is a diagram showing the results of theoretical calculations of the relationship between active layer thickness and maximum optical output, and Figures 3 (-) to ( C)
1A and 1B are cross-sectional views at each step of a manufacturing method according to an embodiment of the present invention. 1...p-type GaAs substrate, 2...n-type GaAs current narrowing layer, 3...p-type Ga1-air A
lxAs cladding layer, 4...Non-doped Ga1
-yAlyAs active layer, 6...n-type Ga1-x
A1xAB cladding layer, 6...-n-type GaAs cap layer, 7...n-side ohmic electrode, 8...
...p-side ohmic electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 2 Figure 5 Paleo-l membrane 4 (xmn Figure 3 (a,) (b)

Claims (1)

[Claims] At least one semiconductor layer is formed on a substrate having a mesa so that the conductivity type changes alternately, a groove is formed from the surface of the semiconductor layer to the mesa portion of the substrate, and an active layer is formed on the surface of the semiconductor layer. 1. A semiconductor laser device, wherein each of the layers includes a layer having a conductivity type different from that of the surface layer of the semiconductor layer as a first layer.