JPS62296581A - Semiconductor laser array device - Google Patents

Abstract

PURPOSE:To lower the optical density of laser beams on the end surfaces of a laser crystal while reducing the generation of heat on the end surfaces by making the film thickness of an active layer at both resonator end surface sections of the laser crystal thinner than the inside of the crystal and preventing the flowing of currents through the end surface sections. CONSTITUTION:A mesa 9 is formed onto a p-type GaAs substrate 1 through etching, the mesa 9 is buried completely through a liquid phase epitaxial growth method, an n-type GaAs layer 2 is grown so that the surface is flattened, and ridges 11 and three grooves 10 are shaped through etching. The grooves 10 are made to reach the mesa 9 at a section where there is the mesa 9, the width of the ridges 11 is narrowed at sections where there is no mesa, and second liquid phase epitaxial growth is conducted onto the substrate, thus growing multilayered structure. Since a growth rate on the ridges 11 is decreased with the narrowing of the width of the ridges 11 at that time, an active layer is thinned at end surface sections where the width of the ridges is made narrower than the inside of a crystal. When the active layer is thinned, the confinement of beams is deteriorated, and the beam diameter of laser beams is increased in the vicinity of the end surfaces, thus reducing optical density.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention Industrial Application Field The present invention relates to a semiconductor laser used as a high-power infrared laser light source for recording and erasing optical discs, medical applications, etc. This invention relates to array devices.

2. Description of the Related Art In recent years, semiconductor laser devices have been used to read signals on optical disks such as CDs, and as light sources for laser beam printers.
In optical communications, it has come into the limelight as a central device in the optical industry.

In most of these optical information devices, the requirement for the optical output of the laser is 10 to 20 mW or less. However, in recent years, there has been an increase in demand for high-output (2 ohmW or more) laser devices for use in recording and erasing optical disks, speeding up printers, and medical equipment.

Problems that the invention aims to solve There are two obstacles to increasing the output power of semiconductor lasers.
There is one. One of them is that when the output is increased, the mode of the optical electric field propagating within the crystal tends to shift from the fundamental mode to the higher-order mode as the optical density within the laser crystal increases. When oscillating in a higher-order mode, the intensity distribution of the laser beam emitted from the crystal end face is not single-peaked, but has multiple peaks, which poses a major obstacle in practical use. This problem was solved by reducing the thickness of the oscillation region (active layer) within the laser crystal. And the so-called Buriθd Twin
In Ridge 5ubstrate v-the,
200mW due to thinning of the active layer and improvement of current injection efficiency
The above continuous oscillation output was obtained. (Institute of Electronics and Communication Engineers Technical Research Report 1CD84-94 (1984)) The second point is that as the optical density increases at the end face of a laser crystal, deterioration progresses in the vicinity of the end face, shortening the life of the laser.

At the laser end face, heat dissipates poorly compared to inside the crystal.
It has been reported by Todoroki et al. that the temperature locally reaches 200'C or more in the oscillation region near the end face. (Journal Op Applied Physics, 58, Pl 12
4 (1985)) This local heat generation promotes the generation and proliferation of dislocations within the crystal, which repeats a vicious cycle (thermal runaway) in which the dislocations become non-emissive centers, absorb laser light, and generate further heat, significantly shortening the lifespan. It will be shortened.

The present invention lowers the optical density of laser light at the crystal end face of a semiconductor laser, reduces the generation of heat at the end face, prevents damage to the end face due to heat and deterioration of reliability due to thermal runaway during laser operation, and extends the life of the laser. A semiconductor laser array device is provided.

Means for Solving the Problems In order to solve the above problems, in the semiconductor laser array device of the present invention, the thickness of the active layer at the end faces of both resonators of the laser crystal is made thinner than that inside the crystal, and This prevents current from flowing through the parts.

By making the active layer thinner at the working end face, the beam diameter of the laser beam at the end face becomes larger and the light density decreases. Furthermore, by passing current through the end face, heat generation inside the crystal near the end face is eliminated and temperature rise is prevented. Due to these two effects, the occurrence of deterioration at the laser end face is suppressed, and a laser array device with high output and long life can be realized.Example 51・-゛Hereinafter, an example of the present invention will be described with reference to the drawings. I will explain while referring to it.

FIG. 1 shows a cross section of a semiconductor laser array device in an embodiment of the present invention. In FIG. 1, a shows a cross section near the end face, and b shows a cross section inside the end face. P
The n-type GaAs layer 2 on the type GaAs substrate 1 is provided to block current, and therefore no current flows near the end face (see figure a). Inside the crystal, as shown in the cross section of figure b,
There is a mesa 9 on the GaAS substrate 1, and three grooves 10 provided in the GaAs current blocking layer 2 reach the mesa 9, and current is injected into the active layer 4 from the grooves 10. The ridge 11 of the block layer is formed in the active layer 4 during liquid phase epitaxial growth.
This is to facilitate film thickness control.

That is, 1. The crystal growth rate on the ridge 11 is slow in liquid phase growth, which is utilized.

FIG. 2 shows a part of the manufacturing process of the semiconductor laser array device of the present invention. P-type GILAI! ! A mesa 9 is formed on the substrate 1 by etching. Mesa length is 200μ
m, the height is 3 μm, and the width is 30 μm. The resonator end face is often formed between the folds at the front and rear portions of the mesa. (FIG. 2, 1) Next, the mesa is filled up by liquid phase epitaxial growth, and the first growth is performed so that the surface becomes flat.

(FIG. 2) The thickness of the n-type GaAS layer 2 on the mesa is 1.
It is set to 0 μm. A ridge 11 and three grooves 1o are formed by etching. (Figure 2 3) The depth of the groove is 1.5μ
m, the width of the groove is 2 μm, and the interval between each groove is 3 μm. In the part where the mesa 9 is located, the groove should reach the mesa.

In this way, current can flow from the groove in areas where there are mesas, and no current can flow in areas where there are no mesas. At this time,
The width of the ridge 11 is made narrower in the part where there is no mesa. That is, 100 μm on one side of the groove where there is a mesa.
In the part without 1, it is 40 μm. Then, a second liquid phase epitaxial growth is performed on the substrate shown in FIG.
Grow the multilayer structure shown in the figure. At this time, the growth rate on the ridge becomes slower as the width of the ridge becomes narrower.
The active layer is thinner at the end face portion where the ridge width is narrower than inside the crystal.

No. 7: If the active layer is thin, light confinement will be poor, and the beam diameter of the laser beam will increase near the end facet. Therefore, the light density can be reduced. After the electrodes 7.8 are deposited, a resonator end face is created between the folds, and the special opening position is such that the distance between the mesa and the end face is about 20 μm.

FIG. 3 shows the current vs. optical output characteristics of a laser array device in which the width of the ridge is narrowed by not injecting current at the end facet, and a laser array device in which these measures are not taken.

A significant increase in saturation power is observed due to the decrease in optical density at the end face and the suppression of heat generation.

FIG. 4 shows the change over time of the operating current in constant first output drive. A laser array device that does not take the measures according to the present invention has a short life at high output, but the element according to the present invention has a sufficiently long life for practical use.

Effects of the Invention As described above, the present invention can significantly extend the life of a semiconductor laser array device by providing a current non-injection region near the end facet and thinning the active layer at the end facet, thereby improving its practical use. The effect is like a dog.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor laser array device according to an embodiment of the present invention, FIG. 2 is a perspective view showing a part of the manufacturing process, and FIG. 3 is a characteristic showing the relationship between current and optical output of the semiconductor laser array device. 4 are characteristic diagrams showing changes over time in the operating current of a semiconductor laser array device when driven with a constant optical output. 1...P-type GaAs substrate, 2...n-type GaA3 block layer, 3...P-type Ga, Al
yAS cladding layer, 4...Ga, -xA#xA
s active layer, 6... mountain n-type Ga, -yAlyAs 7 rad layer, 6-... n-type GaAs layer, 7.8...
・Electrode, 9...Mesa, 10...Mountain/Groove, 11...
·····ridge.

Claims (1)

[Claims] Striped protrusions are formed on the surface of a semiconductor substrate of one conductivity type except near opposite end faces of the semiconductor substrate, and a layer of a conductivity type opposite to the one conductivity type is formed on the surface of the semiconductor substrate. , a plurality of striped grooves are formed from the surface of the layer of the opposite conductivity type to a depth that reaches the protrusion immediately above the protrusion and does not reach the semiconductor substrate near both end surfaces where the protrusion does not exist. At the same time, two ridges parallel to each other are formed on the outside of the two outermost grooves of the plurality of grooves so that the width becomes narrow near the both end faces, and the substrate having the ridges is A semiconductor laser array device characterized in that each layer including an active layer is formed.