JPS61268088A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To prevent the generation of a higher transverse mode by forming a window region transparent to laser beam generated in a thick active layer by cleaving a terrace section with a thin active layer and bringing the terrace section to a resonance surface. CONSTITUTION:An N-GaAs layer 6 is grown on a P-GaAs substrate 1 with a terrace section 9 and a groove section 10 until the surface of the layer 6 is flattened, and a groove section 10' is shaped where conforming to the groove section 10. A terrace section 9' is also formed simultaneously, and a channel section 11 is shaped onto the surface of the terrace section 9' and made to reach the substrate 1 extending over the terrace section 9' and the groove section 10'. The double-hetero structure of a P-GaAlAs clad layer 2, a GaAlAs active layer 3, an N-GaAlAs clad layer 4 and an N-GaAs cap layer 5 is formed. An N-type electrode 7 is shaped onto the cap layer 5 and a P-type electrode 8 onto the back of the substrate, and the central section of the terrace section is cloven to form a reflecting surface. Accordingly, a window section, a band end thereof does not absorb laser beams oscillated on the groove section 10' with the thick active layer, is shaped.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a high-output semiconductor laser device having a window region near an end face that absorbs little laser light.

<Prior Art> It is well known that one of the factors that limits the lifespan of semiconductor laser devices is the deterioration of the resonator end face, which serves as the light emitting surface. Further, when the semiconductor laser device is operated at high output, the end face of the resonator may be destroyed. At this time, the end face destruction output (hereinafter referred to as P wax) was approximately 106 W/cI112 in the conventional semiconductor laser.

In order to stably oscillate the laser beam at high output, Pmax has been increased, and the absorption of laser light at the end facet has been reduced to prevent facet deterioration. A larger 1indo%*5tripe laser (Appl.
, Phys, Lett, 15 Mac, 197
9p, 637), or a window-VSIS laser that uses the Fermi level increase due to carrier accumulation by making the active layer near the end face thinner than that inside.
Appl, Phys, Lett.

I March, 1983 L 406). The latter windows-VSIS laser differs from the former -indo in that an optical waveguide is also formed in the window region.
Although it has features that the w5tripe laser does not have, it also has the drawback that higher-order transverse modes tend to oscillate at approximately 20 mW or more.

The reason for this is that the curvature of the active layer 3 within the channel is used as a means to make the active layer thickness inside the element thicker than near the end face, as shown in the cross-sectional view of FIG. If the active layer is curved, the effective refractive index difference becomes too large, and higher-order transverse modes are likely to occur. Incidentally, FIG. 4 shows a cross-sectional view near the end face.

<Objective of the Invention> The present invention provides a novel window-VSI in which the generation of higher-order transverse modes is prevented by making the active layer inside the element thicker than the active layer near the end face while keeping it flat without curving it.
The purpose of the present invention is to provide an S laser device.

<Structure of the Invention> The present invention provides a semiconductor laser device in which a double heterostructure is grown by a liquid phase epitaxial method on a substrate having a terrace portion and a groove portion, in which an active layer on the terrace portion is grown during the growth of the double heterostructure. It has a thin active layer formed by taking advantage of the phenomenon that the thickness of the active layer becomes thinner than the active layer thickness of the groove part, and is cleaved at the terrace part to form a resonant surface, making it transparent to the laser beam generated in the thick active layer. It is characterized by forming a window area.

<Example> In this example, as shown in FIG. 2, when a double heterostructure is grown by liquid phase epitaxial method on a substrate 1 having a terrace part 9 and a groove part 10, the active layer 3 on the terrace part 9 is grown. This method utilizes the phenomenon that the layer thickness of the active layer 3 on the groove portion 10 becomes thinner than the layer thickness of the active layer 3 on the groove portion 10. This is the G directly above the terrace.
It is interpreted that the solute As in the a solution is pulled from both sides due to active layer growth in the grooves on both sides of the terrace, and the amount of As decreases, resulting in the active layer thickness becoming thinner.

FIGS. 1(a), 1(b), and 1(C) show the structure at each stage of the manufacturing process of a semiconductor laser device. First, as shown in FIG. 1(a), an n-GaAs layer 6 is grown on a P-GaAs substrate 1 having terraces 9 and grooves 10 until its surface becomes flat. Next, as shown in the first section), grooves 10' are formed on the surface of the n-GaAs layer 6 at locations that match the grooves 10 of the substrate 1. At this time, the terrace portion 9' is also formed at the same time. Furthermore, a channel portion 11 is formed on this surface in a direction perpendicular to the groove portion 10', and this channel portion 11 is formed so as to reach the P-GaAs substrate 1 across the terrace portion 9' and the groove portion 10'. The n-Ga on the P-GaAs substrate 1 formed in this way
The As layer 6 serves to block current and limit the current to only the channel portion 11 .

Next, as shown in FIG. 1(C), a P-GaAlAs cladding layer 2. GaAlA
s (or GaAs) active layer 3, n-GaAlAs
A double heterostructure consisting of a cladding layer 4 and an n-GaAs cap layer 5 is formed. At this time, the growth time is adjusted so that the P-cladding layer 2 and the active layer 3 are curved at the end of the groove 10'. With such a structure, the thickness of the active layer 3 on the terrace portion 10' is necessarily the same as that of the active layer 3 on the groove portion 10'.
becomes thinner than the layer thickness of

After forming an n-type electrode 7 on the camp layer 5 and a p-type electrode 8 on the back surface of the substrate, they are separated at the center of the terrace portion to form a reflective surface. Therefore, since the active layer near the reflective surface is thin, more carriers are accumulated than in a thick active layer when the same current is passed through the active layer. In other words, the difference between the Fermi levels of electrons and holes becomes larger (the band gap becomes larger)
, a window portion is formed in which there is no band edge absorption for the laser beam oscillated on the groove portion 10' (excitation portion) having a thick active layer.

According to experiments, the active layer is Gao, so A.
The s+Craft layer is Gao, 6^1 o, 4 A S, and the length of the excitation part is 200 μm.

When the length of the window is 25 μm, the wavelength is 780 na+.

Oscillates at a threshold current of 40mA, and in CW operation
No end face deterioration occurred up to an output of 0 mW or more.

Note that the semiconductor laser device of the present invention is based on the Ga of the above embodiment.
Not limited to As-GaAlAs system, but also InP-InGa
It can be applied to AsP-based and other heterojunction laser elements.

<Effects of the Invention> As explained above, in the present invention, a thin active layer is formed by taking advantage of the phenomenon that the active layer thickness on the terrace portion becomes thinner than the active layer thickness on the groove portion during the growth of a double heterostructure. By cleaving the terrace portion to form a resonant surface, a window region that is transparent to the laser light generated in the thick active layer is formed, thereby making it possible to prevent the generation of higher-order transverse modes.

[Brief explanation of the drawing]

FIGS. 1(al), (b), and (C) are diagrams showing the structure of a semiconductor laser device according to an embodiment of the present invention, and FIG. 2 illustrates that the active layer on the terrace portion of an embodiment of the present invention becomes thinner. 3 and 4 are cross-sectional views of conventional -indow-VSIS laser elements. 1-P-GaAs substrate 2--P-GaAIAs
Craft layer 3 - GaAlAs (or GaA4) active layer 4 - n-GaAIAs ground layer 5 - n-GaAs cap layer 6 - n-GaAs current blocking layer 7 - n-type electrode 8 - p-type electrode 9.9 ′・−・
Terrace section

Claims (1)

[Claims] In a semiconductor laser device in which a double heterostructure is grown by a liquid phase epitaxial method on a substrate having a terrace part and a groove part, when the double hetero structure is grown, the active layer thickness on the terrace part is greater than the active layer thickness in the groove part. The thin active layer is formed by taking advantage of the phenomenon that the active layer becomes thinner, and the terrace section is cleaved to form a resonant surface, thereby forming a window region that is transparent to the laser beam generated in the thick active layer. Features of semiconductor laser device.