JPS6118189A - Semiconductor laser array device and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable realization of a semiconductor laser array device which operates at a low threshold and is fabricated with a high degree of integration in a single crystal growth, by forming an active layer directly above recesses or projections so that the dimensions of the active layer in directions which are respectively parallel to the cavity resonator surface and the semiconductor junction surface are sufficient to provide two oscillation regions. CONSTITUTION:Stripe-shaped grooves are formed in the surface of a p type GaAs substrate 10 by chemical etching. Then, n type GaAs current blocking layers 11, 20 whose film thickness is smaller than the depth of the grooves are formed. A p type GaAs layer 12, a p type clad layer 13, an active layer 14, an n type clad layer 15 and an n type layer 16 are formed on the layers 11, 20. Although current concentrates on and near the part above each groove, as the current comes closer to the GaAs substrate 10, it diverges and flows along both side surfaces of the groove, thereby forming two laser oscillation regions within the groove. Thus, oscillations take place substantially simultaneously at or near a threshold of 70mA, and stable single transverse mode oscillation is obtained. The volume of each chip of this laser array is reduced to about half of that in a conventional laser array having the same number of laser oscillation regions. Thus, it is possible to reduce the size of the laser array device.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is applicable to various electronic devices as a coherent light source or as a high output, high density, high brightness light source.

The present invention relates to a semiconductor laser array device used in optical equipment.

(Conventional Structure and its Problems) One of the important uses of semiconductor laser array devices is as a high-output, highly integrated light source. That is, it is necessary to have a large number of laser oscillation regions within one chip, each of which is close to each other, and whose characteristics such as the oscillation wavelength and phase of laser light are uniform.

Laser array devices fabricated using the conventional liquid phase epitaxial growth method have a single stripe on the substrate,
Since Zn diffusion on the growth layer, proton irradiation, and stripes made of an insulating film are used, the chip area occupied by a unit laser oscillation area is relatively large, and many oscillation areas can be integrated into an appropriately sized chip. When, the degree of integration is low.

However, since the liquid phase epitaxial growth method is used, there are large variations in characteristics such as variations in the oscillation wavelength of laser light.

(Object of the Invention) In view of the above-mentioned drawbacks, the present invention provides a semiconductor laser array having a structure that has little variation in characteristics such as variation in the oscillation wavelength of LED light and that allows laser oscillation regions to be integrated on a chip with a relatively large degree of integration. The present invention provides a device and a manufacturing method that can realize the semiconductor laser array device with one crystal growth.

(Structure of the Invention) To achieve this object, the semiconductor laser array device of the present invention is provided by forming a film on a conductive substrate having a concave portion or a convex portion with a film thickness smaller than the height of the concave portion or the convex portion. has thin film layers exhibiting opposite conductivity types and additionally has a multilayer thin film containing a double heterostructure on said thin film layers. Moreover, the length of the active layer directly above the recess or projection on the substrate in the direction parallel to the resonator surface and the semiconductor junction surface is sufficient to have two oscillation regions. The above structure is achieved by one-time crystal growth, and with this structure, there is little variation in characteristics.
It is possible to integrate the Rade oscillation region with a relatively large degree of integration.

(Description of Embodiment) The semiconductor radar array device of the present invention will be specifically described using one embodiment.

- As an example, a p-type GaAs substrate is used as the conductive substrate.

FIG. 1 shows a first embodiment of the invention. p-type GaAs substrate (carrier concentration about 2 to 1018i3) of 10 (10
0) surface, by chemical etching in the <110) direction,
Form striped grooves (concavities) in an inverted mesa shape. In addition,
The depth of the groove was 1.5 μm and the width of each groove was 10 μm. Next, organometallic vapor phase epitaxial (carrier concentration: 1 × 10
1 to 3) with a thickness of 1 μm. At this time, the nm GaAs layer grows only in the portions shown in FIGS. 11 and 20. After that, the n-type GaAs layer 11
and 2o, a p-type GaAs layer 12 . p-type Ga1xAZxA
a-class 22 layer 13°Ga1-yASAs active layer 14 (
0≦y<x) p n-type Gal xAAx A
s cladding layer 15. An n-type GaAs layer 16 is formed.

An example of crystal growth conditions by the MOCVD method is shown below.

Growth rate: 2 μm/hour, growth temperature: 770°C.

The total gas flow rate was 51/min, and the molar ratio of Group V elements to Group II elements was 40.

When an electrode is made in this structure and a current is passed through it, the current is concentrated near the top of the groove forming part, but as it approaches 1° of the GaAs substrate, it branches and flows to both sides of the groove.

As a result, two laser oscillation regions were formed inside the groove. At this time, in the two laser oscillation regions, 70. m
Oscillations occurred almost simultaneously near the threshold value of k, and stable single-transverse mode oscillations were obtained in each case.

In a normal laser array device, only one laser oscillation region can be obtained with one groove, since the method of flowing current in the groove is different from that of the present invention, and this serves as the basic unit to configure the laser array. However, in the case of the present invention, one groove has two laser oscillation regions, so if a laser array with the same number of laser oscillation regions is manufactured, the chip will have about half the volume, allowing for miniaturization.

As a second example, a semiconductor laser array device was similarly fabricated by forming a convex portion on a conductive substrate as shown in FIG. 2, and the same results as in the first example were obtained.

Note that the width of the recess (groove) and the width of the protrusion are 8 μm or more and 2
If four or more laser oscillation regions can be realized and four or more laser oscillation regions are desired, the first embodiment and the second embodiment described above may be combined as a basic unit.

Although this embodiment describes a GaAs + GaAtAa semiconductor laser, the present invention is also applicable to semiconductor laser array devices made of compound semiconductors including InP and other multi-component mixed crystal systems. It is possible. Furthermore, even if an n-type base material is used as the conductive substrate, other material supply rate-limiting crystal growth methods,
For example, molecular beam epitaxial growth may be used.

(Effects of the Invention) The semiconductor laser array device of the present invention has a structure that allows a highly integrated semiconductor laser array device that operates at a low threshold and oscillates in a single transverse mode to be realized by one crystal growth. Yes, its practical effects are remarkable.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a semiconductor laser array device according to a +1"IJ11+1 embodiment of the present invention, and FIG. 2 is a sectional view of a second embodiment. 10-p-type GaAs substrate, 11-n-type GaAs current Blocking layer, 12...p-type GaAs buffer layer, 13...
p-type GaAAAs cladding layer, 14- GaAtAs active layer, 15'''n-type GaAtAs cladding layer, 16-
n-type GaAs layer, '20- n-type GaAs current blocking layer, 21... Ohmic electrode, 22... Insulating film. Figure 1

Claims (2)

[Claims] (1) A thin film layer having a thickness smaller than the height of the recesses or projections and having a conductivity type opposite to that of the substrate is formed on a conductive substrate having recesses or projections, and further on the thin film layer. A multilayer thin film including a double heterostructure is formed on the substrate, and the length of the active layer directly above the recess or protrusion on the substrate in the direction parallel to the resonator surface and the semiconductor junction surface has two oscillation regions. A semiconductor laser array device characterized by having a length sufficient for (2) Using a metal organic vapor phase epitaxial growth method or a molecular beam epitaxial growth method, a conductive substrate having a concave portion or a convex portion is coated with a film having a thickness smaller than the height of the concave portion or convex portion and having a conductivity opposite to that of the substrate. 1. A method for manufacturing a semiconductor laser array device, comprising forming a thin film layer showing a pattern, and then forming a multilayer thin film including a double heterostructure on the thin film layer.