JPH0446476B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a semiconductor laser device, particularly an internal current confinement type semiconductor laser device.

BACKGROUND ART FIG. 3 shows a cross-sectional structure of a VSIS type semiconductor laser device as an example of a conventional internal current confinement type semiconductor laser device. P-type GaAs substrate 1 has N-type GaAs.
A current confinement layer 2, a P-type GaAlAs cladding layer 3,
A P-type GaAlAs active layer 4, an N-type GaAlAs cladding layer 5, and an N-type GaAs cap layer 6 are laminated in this order by liquid phase growth, vapor deposition, or the like.

In this structure, the P side (P-type GaAs substrate 1)
When a positive voltage is applied to the N-side (N-type GaAs cap layer 6) and a negative voltage is applied to the N-side (N-type GaAs cap layer 6), a current flows through the device. At this time, the current flow is constricted by the N-type GaAs current confinement layer 2, so that only the groove 7 flows, and the active layer 4 above the groove 7 emits light. A part of the laser oscillated light seeps into the cladding layer 3 and becomes N-type.
is absorbed by the GaAs current confinement layer 2, and as a result, PN
There is also an effective refractive index difference in the direction parallel to the junction, and light is confined.

FIG. 4 is a graph showing the absorption coefficient of N-type GaAs at 25°C (297〓). As is clear from FIG. 4, the absorption of the N-type GaAs layer varies greatly depending on the absorbed light energy E and the carrier concentration n ₀ of the N-type GaAs layer.

The energy E of light with a wavelength of 780 nm is 1.59 eV, and at this time the carrier concentration of the N-type GaAs layer n ₀
Absorption is large whether it is low or high. However, for light with a wavelength of 870nm, the energy E is 1.42V, and N
Absorption varies greatly depending on the carrier concentration n ₀ of the type GaAs layer. The carrier concentration ^of the N-type GaAs current confinement layer 2 of ^the VSIS type laser shown in FIG. 2, light cannot be absorbed, and as a result, there is no effective refractive index difference in the direction parallel to the PN junction, and the semiconductor laser device in this case becomes a gain waveguide laser, resulting in a large astigmatism difference. A drawback arises.

Problems to be Solved by the Invention The purpose of the present invention is to solve the above-mentioned technical problems,
In particular, it is an object of the present invention to provide a semiconductor laser element with good characteristics for wavelengths longer than 870 nm.

Means for Solving the Problems The present invention provides an internal current confinement semiconductor laser device having an N-type GaAs current confinement layer on a P-type GaAs substrate. This is a semiconductor laser device characterized by providing a P-type GaAs light absorption layer having a groove portion therebetween that is continuous with a groove portion of an N-type GaAs current confinement layer.

Effect According to the present invention, more of the light emitted from the active layer is absorbed by the P-type GaAs light absorption layer, creating an effective refractive index difference in the direction parallel to the PN junction.
Even if the wavelength is longer than 870 nm, a semiconductor laser element with good characteristics can be obtained.

Example Figure 1 shows an example of the present invention with a light absorption layer.
FIG. 2 is a cross-sectional view of the structure of a VSIS type semiconductor laser device.
An N-type GaAs current confinement layer 12a and a P-type layer are formed on a P-type GaAs substrate 11 by liquid phase growth or vapor deposition.
GaAs light absorption layer 12b, P-type GaAlAs cladding layer 13, P-type GaAlAs active layer 14, and N-type
A GaAlAs clad layer 15 and an N-type GaAs cap layer 16 are laminated in this order from the bottom to the top in FIG. Note that the groove is made of N-type GaAs.
It is formed after the current confinement layer 12a and the P-type GaAs light absorption layer 12b are laminated. Thereafter, a P-type GaAlAs cladding layer 13 is laminated. Therefore, outside the trench, the N-type GaAs current confinement layer 12a
and the P-type GalAs cladding layer 13.
A GaAs type light absorption layer 12b is provided.

Therefore, even if a laser with a wavelength of 870 nm is manufactured, for example, more of the light generated in the P-type GaAlAs active layer 14 will be absorbed by the P-type GaAs light absorption layer 12b, and as a result, the light will also be absorbed in the direction parallel to the PN junction. This creates an effective refractive index difference, and can prevent the astigmatism difference from increasing.

FIG. 2 is a graph showing the absorption coefficient of P-type GaAs at 25°C (297〓). As is clear from FIG. 2, for light with an energy lower than 1.42 eV, that is, a wavelength longer than 870 nm, the absorption coefficient of P-type GaAs is larger than that of non-doped GaAs. Therefore, more of the light generated in the active layer 14 can be absorbed by the P-type GaAs light absorption layer 12b.

Effects As described above, according to the present invention, it is possible to obtain an effective internal current confinement type semiconductor laser device with good characteristics, particularly in a GaAs semiconductor laser having a wavelength longer than 870 nm.

[Brief explanation of drawings]

FIG. 1 is a structural sectional view showing one embodiment of the present invention;
Figure 2 is a graph showing the absorption coefficient of P-type GaAs, Figure 3 is a cross-sectional view of the structure of a conventional example, and Figure 4 is a graph showing the absorption coefficient of P-type GaAs.
It is a graph showing the absorption coefficient of GaAs. DESCRIPTION OF SYMBOLS 11... P-type GaAs substrate, 12a... N-type GaAs current confinement layer, 12b... P-type GaAs light absorption layer, 13...
P-type GaAlAs cladding layer, 14...P-type GaAlAs active layer, 15...N-type GaAlAs cladding layer.

Claims (1)

[Claims] 1. A P-type GaAlAS cladding layer and an active layer are laminated on a P-type GaAs substrate via an N-type GaAs current confinement layer in which a groove reaching the P-type GaAs substrate is formed. In an internal current confinement type semiconductor laser device that outputs laser at a wavelength longer than 870 nm, the N-type GaAs current confinement layer and the P-type GaAlAs
A semiconductor laser device characterized in that a P-type GaAs light absorption layer having a groove portion continuous with the groove portion of the N-type GaAs current confinement layer is provided between the cladding layer and the cladding layer.