JPS61179590A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To limit a laser oscillating section into an extremely narrow region by selectively increasing the thickness of a clad layer in the vicinity of the ridge edge section of a semiconductor substrate. CONSTITUTION:A pair of ridges are projected from the main plane side of a semiconductor substrate 1 while thickness in the vicinity of the ridge side surface sections of an active layer 3 formed onto the main plane is made larger than that of other sections. The relationship of an optical output from the semiconductor laser device and currents has excellent linearity, and operating currents required for oscillating the laser device may be reduced. Since the thickness of a clad layer 2 on the top surfaces of the ridges 1a, 1b is shaped extremely thinly in the laser device, beams are absorbed to the substrate 1 in the sections on the top surfaces of the ridges, and oscillating sections are specified while the thickness of the clad layer 2 is increased in sections in the vicinity of the side surfaces on the outsides of the ridges 1a, 1b. Consequently, it is thought that the extension of currents is inhibited. The active layer 3 is also formed selectively in the same manner as the clad layer 2, thus further improving the effect of the inhibition of the extension of currents.

Description

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

Conventional technology In recent years, the major problem of semiconductor laser device deterioration has been largely solved, and devices with a lifespan of several thousand hours to many hours can now be easily obtained, making them useful in applications such as optical communication and optical information processing. It has come to be used in optical technology application systems.

A typical example of such a semiconductor laser device is a stripe type.

Problems to be Solved by the Invention In order to put a semiconductor laser device into widespread practical use, it is necessary not only to extend its life span, but also to significantly improve its performance. To achieve this, the following requirements are required: spot-like oscillation in the same mode both vertically and horizontally, the spread of the light beam to be small, the quadratic type in the current-light output characteristic to be extremely small, and the operating current to be small. The challenge is how to satisfy this.

In conventional striped semiconductor laser devices, multi-mode oscillation occurs as the current increases, and the linearity of the current-optical output characteristics is very poor due to the occurrence of kinks.

The present invention aims to provide a semiconductor laser device that solves these problems.

Means to solve the problem of leapfrog - In the semiconductor laser device of the present invention, a pair of ridges is formed on the main plane side of the semiconductor substrate and protrudes near the side surface of the ridge of the active layer formed on this plane. The thickness is thicker than that of other parts.

Function: Since the thickness of the cladding layer is selectively increased near the edges of the semiconductor substrate, a high resistance region is formed outside the ridge. Thereby, the spread 9 of the current injected from the electrode can be effectively suppressed, and the laser excavated portion can be limited to an extremely narrow area. One Example Below, regarding one example of the semiconductor laser device of the present invention,
This will be explained using the cross-sectional view of FIG.

In the figure, reference numeral 1 denotes an n-type GaAs substrate, and one main surface side thereof has a shape in which a pair of ridges 1a and 1b protrude from the plane. The width of the top surface of each of the ridges 1a and 1b is 15 μm, the height is 1.6 to 1.7 μm, and the interval therebetween is 5 μm. 2 is U-type Ga1. ．． ．． 8Al engineering As
The cladding layer is formed on the one main surface, and the thickness of the portion between the ridges 1a and Ib is 1.8 μm.
m, the thickness of the top surface of ridges 1a and 1b is 0.3μ
It is m. The thickness of the outer side portions of the ridges 1a and 1b is approximately equal to the thickness of the ridge 1a and the 1-month portion, and the outer portions are thinner than the ridge portions near the side surfaces. There is. 3 is an active layer made of Ga1-yA1A and As having a thickness of about 0.1 μm, and the cladding layer 2
It is formed very thinly on the top. Note that the thickness of the cladding layer 2 is greater in the portions on the slopes located outside the ridges 1a and 1b than in other portions. 4 is p-type G with thickness 2)tm
a1-xAlxAs layer, 5 is P-type Q aA with a thickness of 1 μm
The s-layers are sequentially stacked on the active layer 3.

Here, in the case of an infrared laser, X=0.3, y=
It is set to 0.05. 6 is an n-type Gao with a thickness of 1 μm
, s Al o , s As layers are formed on the p-type GaAs layer 6, and a window is provided in a portion directly above the ridge 1a. A negative electrode 7 is formed directly on the substrate 1. 8 is a positive electrode, n-type Ga o,
It is formed on the 5Alo-s As layer 6 and on the p-type GaAs layer 6 exposed through the window.

When a voltage is applied between the positive electrode 8 and the negative electrode 7 of this semiconductor laser device and electricity is supplied, the ridges 1 & 1 of the active layer 3 are
A single spot of laser oscillation occurred above the lunar groove.

Next, an example of a method for manufacturing the semiconductor laser device will be described with reference to FIG. 2.

First, as shown in FIG. 2A, an n-type GaAs substrate 1 is prepared, and a pair of 15 μm widths with a spacing of 5 μm is formed on one main surface of the substrate using a normal photo-etching technique. A striped pattern mask is formed. Then, using this mask, the substrate 1 is heated to H2°:H2O2:H2S0
1.5 to 1.7 with 4=8=8=1 sulfuric acid etching solution
Etch to a depth of μm. The selective etching ridges 1a and 1b are formed in two parallel protruding shapes on a substantially flat surface.

Next, a double heterostructure is formed on the n-type GaAs substrate 1 having the ridges 1a and 1b by liquid phase epitaxial growth. The mechanism of crystal growth on a substrate with ridges 1a, 1b is different from the mechanism of crystal growth on a flat substrate. That is, in the case of substrates having ridges 1a and 1b, the growth rates on the top surface of the edge portion and other flat surfaces are different even if they are the same (100) plane. For example, in the case of a substrate having a single glue ridge with a pitch of 250 .mu.m and a width of 15 .mu.m, the growth rate on the top surface of the ridge is about % of that on a flat surface. This is because a portion of the ridge melts back and the growth in the January Fuji portion is more dominant on the side surface (111) than on the top surface (1oO). Therefore, the ridge 1a of the substrate 1.

Even on the one-month portion, the crystal growth rate is higher than on the other main surfaces of the substrate 1 and the top surfaces of the Fujis 1a and 1b. Taking advantage of such crystal growth properties, ridge 1a
, 1b on the Ga As substrate 1 with n-type Ga 1
-, Al x A m cladding layer 2, Ga1-, AI
.

to 8 active layer 3, p-type G! , 1-x A I x As layer 4 and p-type Ga As layer 6 are sequentially grown.

The growth process of the cladding layer 2 is different between the side surfaces of the ridges 1a and 1b and the other surfaces. When the cladding layer 2 is grown for 4 minutes at a growth start temperature of 800°C and a cooling rate of 0.5°C/min, the ridges 1a and 1b are grown. 0.3 pm on top of ridge 1a, 1
A film thickness of 1.8 μm is obtained in the portion between b.

The speed of crystal growth on the portion between the edges 1a and Ib of the substrate 1 varies depending on the heights of the ridges 1a and 1b. That is, when ridges 1a and 1b are low (approximately 1 μm or less), they grow to the same height 1 as ridges 1a and 1b, but ridge 1
When a and 1b are about 1 μm or more, the growth becomes concave as shown in FIG. 2B.

On this cladding layer 2, an extremely thin Ga1-yA1As active layer 3 is grown. In this case too, ridge 1
a.

Since the growth rate on 1b is slow, it is advantageous for thin film growth, and a film thickness of 0.1 μm can be obtained with good reproducibility.

On the outer parts of the ridges 1a and 1b of the cladding layer 2, that is, on the sloped parts, the growth rate of the active layer 3 is higher than that on the flat surface, so the thickness of the active layer 3 is smaller than that on the top of the cladding layer 3. It is larger on the slope than on the surface. The film thickness of the active layer 3 between ridges 1a and Ib is ridges 1a and 1b.
It is slightly thicker than the top part of the surface, and has a nearly flat surface. Further on the active layer 3 is a p-type Ga1 layer with a thickness of 2 μm.
- Air AlxAs layer 4 and 1 μm thick p-type Ga A
S-layers 5 are sequentially formed. When using Peter isolation as a striped structure, an additional 1 μm thick n
Type Gao, 6A10.6AS layer 6 is formed (FIG. 2C)
).

Then, an oxide film is formed as a mask, and a 6μ wide film is formed directly above the ridges 1a and 1b using photonotching technology.
Open the window m. Furthermore, p-type G a
n-type Gao, 5A until the s-layer 5 is exposed in a stripe pattern.
Open a 10.5 μm layer 6 window.

After additionally diffusing Zn to make contact with the electrode and forming a p+ layer in the window, Ti-P t -
A positive electrode 8 is formed by vapor depositing Au, and the back surface is further etched so that the total thickness becomes about 100 μm. The solution for back side etch is H2O:H2O2:H2
A solution of S04=1:1:8 is used. After sex, A on the back side
A negative electrode 7 is formed by depositing u-Ge-Ni.

In the manner described above, the semiconductor laser device shown in FIG. 1 is obtained.

As a method for selectively thickening the parts of the ground layer 2 and the active layer 3 near the outside of the ridges 1a and 1b, there are methods other than the method using the crystal growth mechanism described above, which are commonly used in semiconductor manufacturing. Using a technique, the necessary portions may be left and other portions may be etched to make them thinner.

The relationship between optical output and current of this semiconductor laser device has good linearity, and the operating current required for its oscillation may be small. This is Ridge 1a.

Since the thickness of the cladding layer 2 on the top surface of the ridge 1b is very thin, the light is absorbed by the substrate 1 in this part, and the oscillation part is specified, and the thickness of the cladding layer 2 is reduced to the ridge 1a. , 1b is large in the vicinity of the outer side surface, which is considered to be because the spread of the current is suppressed. Regarding the spread of current, the cladding layer 2 has a relatively high resistance, and the parts on both sides of the ridges 1a and 1b are selectively formed to be thick.
There are regions on both sides of ridge 1b that have higher resistance than the regions above ridges 1a and 1b, and this effectively suppresses the resistance. In other words, a large amount of current flows in the portion between the high resistance regions.

Further, since the active layer 3 is also selectively formed thick similarly to the cladding layer 2, the effect of suppressing the spread of current is further enhanced.

Effects of the Invention In the semiconductor laser device of the present invention, one main surface side of the semiconductor substrate is formed in a shape in which paired ridges protrude in parallel on a substantial plane, and has these ridges. A cladding layer and an active layer are sequentially stacked on the substrate surface. The cladding layer is thin on the top surface of Fuji,
Also, the portions near the outer surfaces of the pair of ridges are thicker than the portions farther from the ridge. Therefore, the laser oscillation part can be limited to an extremely narrow area, and not only can single mode oscillation be performed, but also the operating current can be small.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of one embodiment of the semiconductor laser device of the present invention, and FIGS. 2A-2C are cross-sectional views for explaining the assembly process of another embodiment of the present invention. 1--n-GaAs substrate, 2...n-Ga1-
xAlxAs cladding layer, 3...n-Ga
1-yAlyAs active layer, 4...-=p-Ga1-x
AlxAs layer, 5.-p-GaAs layer, 6.
-=n-Ga, 5Al. , 5As layer, 7. ,. . . . n-side electrode, 8 . . . p-side electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
figure

Claims (1)

[Claims] a semiconductor substrate having a pair of ridges protruding from one main plane side; a cladding layer formed on the surface of the semiconductor substrate having the ridge; and an active layer formed on the cladding layer; an electrode disposed above between the pair of ridges, a portion of the cladding layer above the ridge is thinner than other portions, and a side surface portion of the pair of ridges is thinner than the other portion, and a portion of the cladding layer above the ridge is thinner than another portion of the cladding layer; 1. A semiconductor laser device characterized in that the outer portion is thicker than the outer portion.