JPS62296576A - Semiconductor laser array device - Google Patents

Abstract

PURPOSE:To remove the deterioration in reliability due to thermorunaway, and to obtain a semiconductor laser array device operating with a high output and having a long life by preventing the flow of currents through both resonator end-surfacc sections in a laser crystal. CONSTITUTION:Since an n-type GaAs layer 2 on a p-type GaAs substrate 1 is formed for stopping currents, currents do not flow in sections in the vicinity of end surfaces. A mesa 9 is shaped onto the GaAs substrate 1 in a crystal, three grooves 10 formed to the GaAs current block layer 2 reach the mesa 9, and currents are injected into an active layer 4 from the grooves 10. The ridges 11 of the block layer are shaped for easily controlling the film thickness of the active layer 4 in liquid phase epitaxial growth, and the decrease of a crystal growth rate is utilized in liquid growth on the ridges 11. Since currents are not flowed through end surface sections, heat generation in the crystal in the vicinity of the end surfaces is removed, thus preventing a temperature rise. Accordingly, the generation of deterioration in laser end surfaces is inhibited, thus lengthening life even by high-output operation.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention Industrial Application Field The present invention is a semi-conductor laser array used as a high-power infrared laser light source for recording and erasing optical discs, medical purposes, and other purposes. It is related to the device.

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.
It has come to be in the spotlight as a central device for optical communications and optical communications.

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

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 end face of the crystal does not have a single peak, but instead has multiple peaks, which poses a major practical problem. This problem was solved by reducing the thickness of the oscillation region (active layer) within the laser crystal. And Buriecl Twin Rid
In the geSubstrate laser, a continuous oscillation output of 200 mW or more is obtained by thinning the active layer and improving current injection efficiency (IEICE technical research report ED84-94 (1984)). The second point is that as the optical density increases at the laser crystal end face, deterioration progresses near the end face, shortening the life of the laser. It has been reported by Todoroki et al. that heat dissipates poorly at the laser end face compared to inside the crystal, and that the temperature locally reaches 200'C or more in the oscillation region near the end face (Journal of Applied Physics, 58. P1124 (1985)
).

This local heat generation promotes the generation and proliferation of dislocations within the crystal,
A vicious cycle (thermal runaway) in which dislocations become non-emissive centers, absorb laser light, and generate further heat is repeated, significantly shortening the lifetime.

Problems to be Solved by the Invention The present invention provides a semiconductor laser array device that reduces heat generation at the crystal end face of a semiconductor laser, eliminates deterioration of reliability due to thermal runaway, and operates at high output and has a long life. It is something.

Means for Solving the Problems In order to solve the above problems, the semiconductor laser array device of the present invention prevents current from flowing through the end faces of both resonators of the laser crystal.

By not passing current through the active end face, heat generation inside the crystal near the end face is eliminated and temperature rise is prevented. Therefore, the occurrence of deterioration at the laser end face is suppressed, and a laser array device with a long life even when operated at high output can be realized.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a cross section of a semiconductor laser array device in an embodiment of the present invention. In FIG. 1, (2L) shows a cross section near the end face, and (b) shows a cross section inside the end face. The n-type 0418 layer 2 on the p-type G4AS substrate 1 is provided to block current, and therefore no current flows near the 5/7 end faces (see figure (a)). Inside the crystal, (raAs
There is a mesa 9 on the substrate 1, and three grooves 1o provided in the CrILAS current blocking layer 2 reach the mesa 9, and the grooves 1o
A current is injected into the active layer 4 from. The ridge 11 of the block layer is provided to facilitate control of the thickness of the active layer 4 during liquid phase epitaxial growth.

That is, 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. A mesa 9 is formed on a p-type GaAS substrate 1 by etching. The length of the mesa is 200 μm, the height is 3 μm, and the width is 30 μm. The resonator end face will be formed by opening the front and rear parts of the mesa (see Figure 2).
1)). Next, the first growth is performed by liquid phase epitaxial growth to completely fill the mesa and make the surface flat (FIG. 2 (2)). The thickness of the n-type G&M S layer 2 on the mesa is 1.0 μm. Ridge 11 by etching
and three grooves 10 are created (FIG. 2 (3)). groove 6
Base 7: The depth is 1.5 μm, the width of the groove is 2 μm, and the groove interval is 3 μm, and in the part where the mesa 9 is located, the groove reaches 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. Then, a second liquid phase epitaxial growth is performed on the substrate shown in FIG. 2(3) to grow the multilayer structure shown in FIG. 1(b). After the electrodes 7.8 are deposited, a resonator end face is created between the folds, and the special open position is such that the distance between the mesa and the end face is in the range of 10 to 60 μm.

FIG. 3 shows the current-optical output characteristics of the semiconductor laser array device when the resonator length is 250 μm and the lengths of the current non-injected region between the mesa and the end face are 0 μm, 20 μm, and 60 μm. Since the generation of heat at the end face is suppressed, the saturation power increases.

If the non-injected portion is made too long, the saturation power will decrease because some laser light will be absorbed in this portion.

A practical value is 20 μm to 30 p II. FIG. 4 shows the change in operating current over time in constant first output drive. In a laser device in which the non-injected region is 20μ, the effect of suppressing thermal expansion works and no rapid deterioration is observed.

Effects of the Invention As described above, the present invention can suppress deterioration due to thermal expansion of a semiconductor laser array device by providing a current non-injection region near the end face, and has a great practical effect. .

[Brief explanation of drawings]

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 device when driven at a constant output. 1...p-type GILAS substrate, 2...n
type GaAs block layer, 3... p-type Ga1yA
%Ascrand layer, 4”' -G4 j-2AJzA
s active layer, 5...n-type G! L” -7 people 717
As clad layer, 6...n-type G1118 layer, 7
, 8... Electrode, 9... Mesa, 10...
...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. and two parallel ridges are formed on the outside of the two outermost grooves of the plurality of grooves, and each layer including the active layer is formed on the substrate having the ridges. Features of semiconductor laser array device.