JPS60258986A - Manufacture of semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain the titled device of single lateral mode oscillation at low threshold values by a method wherein a multilayer thin film including a double hetero structure is formed by the liquid phase epitaxial method after a thin film layer showing reverse conductivity type to that of a substrate is formed on the surface of the conductive substrate having a stepwise difference by ion implantation and then partly removed. CONSTITUTION:A photo resist film 22 is left on the surface in the upper part of the stepwise difference by coating the surface 20 with photo resist. The surface 21 is exposed by etching with an H2SO4 series etchant. This can form the part without an N-type GaAs layer 11 at the slope of the stepwise difference. Thereafter, the substrate surface is cleanned by removing the photo resist film 22; then, crystal growth is carried out by LPE. After etching treatment, a P-type Ga1-xAlxAs clad layer 12, a Ga1-yAlyAs active layer 13, an N-type Ga1-xAlxAs clad layer 14, and an N-type GaAs layer 15 are formed on the surface 21, so that the growing surface may become flat. When current is passed after preparation of electrodes on both the P-type GaAs substrate 10 and the N-type GaAs 15, the current is injected from the substrate 10 to the P-type Ga1-xAlxAs layer 12 with a width W, resulting in the realiztion of current stricture.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a semiconductor laser device, whose use has been rapidly expanding in recent years as a light source for various electronic and electrical devices for consumer and industrial use. It is related to.

(Conventional configuration and its problems) One of the important performances required of a semiconductor laser as a coherent light source for electronic and optical equipment is oscillation in a single spot, that is, single-transverse mode oscillation. . To achieve this, it is necessary to suppress the spread of the current flowing through the semiconductor laser device and to confine light near the active region. Such a semiconductor laser is generally called a striped semiconductor laser.

A relatively simple method for forming stripes is to use only current narrowing.

Specifically, examples include those in which a planar semiconductor laser is subjected to proton irradiation, one in which Zn is diffused, and one in which an insulating film such as an oxide film is formed. Each of these methods has significant drawbacks. That is, when proton irradiation is applied, some crystals in each layer of the semiconductor laser may be damaged during the proton irradiation, which may impair the characteristics of the semiconductor laser.

In addition, in the case of Zn diffusion type, processing is often performed at high temperatures such as 700 to 850°C, which causes migration of dopants such as Zn in the crystal, making it possible to form stripes, but it is difficult to form narrow stripes. difficult. The method using an insulating film such as an oxide film has a disadvantage in that the effect of narrowing the current in the manufactured semiconductor laser is weaker than the above two methods.

(Object of the invention) In view of the above drawbacks, the present invention provides a current limiting layer on a substrate,
A multilayer thin film including a double heterostructure is formed on the current limiting layer, the current limiting layer forms a narrow stripe structure inside, and the semiconductor laser device oscillates in a fundamental transverse mode at a low threshold. The present invention provides a method for manufacturing a semiconductor laser device.

(Structure of the Invention) In order to achieve this object, the method for manufacturing a semiconductor laser device of the present invention includes forming a thin film layer having a conductivity type opposite to that of the substrate on the surface of a conductive substrate having a step by ion implantation. death,
After removing a portion of the thin film layer, a multilayer thin film including a double heterostructure is formed by an LPE method (liquid phase epitaxial method). With this configuration, it is possible to easily manufacture a semiconductor laser device that has a stripe structure for current confinement inside, and has fundamental transverse mode oscillation and low threshold operation.

(3) (Description of Embodiment) An embodiment of the present invention will be specifically described with reference to the drawings.

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

A step is provided on the (100) plane of the p-type GaAs substrate 10 by photolithography. At this time, the cross-sectional shape of the step is as shown in FIG. 1 or 2.

Next, by ion implantation, from the surface 20 of the p-type GaAs substrate 10 (carrier concentration ~1018cIrL-3),
n static strain pure (e.g. s i20 + ) at 600 keV
1 μm thick n-type GaAs was implanted with an accelerating voltage of
A layer 11 (carrier concentration ~5×10 cIrL) is formed. After the ion implantation, capless annealing was performed at 800° C. for 20 minutes in an As atmosphere. In this case, in FIG. 1, there is a portion in the step slope where the n-type GaAs layer 1 is not present. In the case of Fig. 2, unlike Fig. 1, the surface n-type Ga
There is no part without the As layer 11. In the case of FIG. 2, a photoresist is applied to the surface 20, and a photoresist film 22 is left on the surface above the step as shown in FIG. Etching is performed using an H2SO4-based etching solution, and (4) the surface 21 shown by the broken line in FIG. 2 is exposed. As a result, as in FIG. 1, n-type GaAs is
A portion without layer 11 can be formed. Thereafter, the photoresist film 22 is removed and the substrate surface is cleaned, followed by crystal growth using the LPE method. In the case of FIG. 1, the ion-implanted and annealed substrate is used as it is, and crystal growth is performed by the LPE method. Growth temperature 850℃, supersaturation degree 7
Crystal growth was performed at a cooling rate of 0.5°C/min. On the surface 20 of FIG. 1 or the etched surface 21 of FIG. -xAtXA
A cladding layer 14 and an n-type GaAs layer 15 are formed on the S cladding layer 12, Ga, -yALyAs active layer 13 (0≦y<x), n-type Ga1, AtX88, and the growth surface is made flat. . p-type GaAs substrate 10 and n-type Ga
When electrodes are made on both sides of the As layer 15 and a current is applied, the p-type GaH-, AtxAs layer 1 is removed from the p-type GaAs substrate 10.
2, a current is injected with a width W shown in FIG. 3, and current narrowing is realized. This means that the n-type GaAs layer 11 is
This is because a p/n junction is formed with the -XAtxAs cladding layer 12, and the p/n junction becomes biased in the reverse (5) direction during electrical injection. As a result, a low threshold semiconductor laser device with W=2 μm and a threshold current of 20 mA was obtained. At this time, single-transverse mode oscillation was also achieved.

In this embodiment, GaAs-based and GaAtAs-based semiconductor lasers have been described, but the present invention can be similarly applied to semiconductor laser devices made of compound semiconductors including InP-based and other multi-component mixed crystal systems.

(Effects of the Invention) The present invention provides a method for manufacturing a semiconductor laser device that oscillates in a single transverse mode at a low threshold value, and its practical effects are remarkable.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a thin film formed by the ion implantation method shown in this example on a reverse mesa substrate, and Figure 2 is a diagram showing the thin film formed by the ion implantation method when a forward mesa substrate is used. FIG. 3, which is a diagram showing a later cross section and a method of forming internal stripes, is a diagram showing an example of a semiconductor laser device manufactured by applying the present invention. (6) 10 - p-type GaAs substrate, 11- n-type GaAs layer,
12''' p-type GaAtAs cladding layer,] 3-Ga
AAAs active layer, 14- n-type GaA7As cladding layer, 15- n-type GaAs layer, 20... surface of substrate having a step, 21... substrate surface before performing LPE method, W
...Injection current stripe width. Ya (7) Figure 1 Figure 2 Figure 2

Claims (1)

[Claims] A thin film layer having a conductivity type opposite to that of the substrate is formed on the surface of a semiconductor substrate having a step by an ion implantation method, and a multilayer thin film including a double heterostructure is formed by an LPE method (liquid phase epitaxial method). A method of manufacturing a semiconductor laser device, characterized in that: