JPS6350874B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor device, and particularly to a semiconductor laser that oscillates in the visible range.

(Prior Art) Semiconductor lasers in the infrared wavelength region of 0.8 μm or more have been actively developed and put into practical use as light sources for optical communications in recent years. On the other hand, a semiconductor laser with an active layer of AlGaAs has been studied as a device that oscillates in the visible region, and has succeeded in oscillating at a wavelength of around 0.7 μm.

(Problems to be Solved by the Invention) Since it is difficult in principle to shorten the wavelength of this material any further, it is desired to develop other compound semiconductor materials.

The characteristics of visible light semiconductor lasers are most demonstrated when applied to optical recording and optical measurement. In these applications, it is desirable to have as short a wavelength as possible, that is, to have a high photon energy, from the standpoint of the wavelength sensitivity and measurement resolution of the recording medium. Compounds are one type of material that can oscillate at short wavelengths, but current injection type semiconductor lasers have not been realized because it is currently difficult to form a pn junction with materials that have a large forbidden band width.

On the other hand, it is a material that is easy to form p-n junctions.
As a compound, InAlGaP-based mixed crystal is a promising material for visible light semiconductor lasers. In this mixed crystal system
It is epitaxially grown using GaAs as a substrate and lattice matched, making it possible to oscillate at a wavelength of around 0.6 μm. However, it is theoretically difficult to make the wavelength shorter than this, considering the band energy of this material system.

An object of the present invention is to solve this problem and provide a semiconductor laser that oscillates at a shorter wavelength.

(Means for Solving the Problems) The semiconductor laser of the present invention includes at least an active layer for laser oscillation, a clad layer sandwiching the active layer, and an ohmic layer provided with an electrode.
The type cladding layer is characterized in that it is made up of two or more layers of p-type -group semiconductors and -group semiconductors stacked alternately.

(Function) When the above-described structure of the present invention is used, the p-type cladding layer is formed by stacking two or more layers of p-type - group semiconductors and - group semiconductors, so that the - group semiconductors are electrically positively charged. If the thickness is made thinner than the hole diffusion length, holes generated in the p-type semiconductor can be injected into the active layer. Also, optically p
Conventionally, it has been used as a p-type cladding layer by keeping the thickness of the type-group semiconductor to an appropriate level.
The refractive index can be lower than that of group semiconductors,
It becomes possible to oscillate at a shorter wavelength.

(Example) Hereinafter, an example of the present invention will be described using the drawings.

FIG. 1 shows a cross-sectional view of a semiconductor laser which is an embodiment of the present invention, and FIG. 2 shows its band diagram.

An n-doped ZnSe _0.9 S _0.1 cladding layer (film thickness:
1μm) 2, undoped (Al _0.65 Ga _0.35 ) _0.51 In _0.49 P
Active layer (film thickness 0.1 μm) 3, undoped ZnSe _0.9 S _0.1
P-clad layer 4, which is made of 100 periods (total film thickness 1 μm) of 50 Å and p-doped Al _0.51 In _0.49 P50 Å stacked alternately.
A doped GaAs layer (1 μm thick) 5 was grown to obtain a structure with the band diagram shown in FIG. This wafer has a striped opening with a width of 7 μm.
A SiO ₂ film 6 is formed, and a Ti/Pt/Au film is formed as the p-electrode 7.
AnGeNi was formed as the n-electrode 8 to obtain the semiconductor laser shown in FIG. In this example, the wavelength
Short wavelength oscillation of up to about 0.54 μm was possible.

In this example, all the epitaxial layers were made of a mixed crystal lattice-matched to GaAs.
It is also possible to use ZnSe, which requires only a lattice mismatch of about 50%. There is also a method of using GaAsP instead of GaAs or using GaInAs which is lattice matched to ZnSe. Although the composition of each mixed crystal is defined in the above-mentioned embodiments, this composition is determined based on the required oscillation wavelength and lattice matching conditions, and is not restricted by the above-mentioned embodiments.

(Effects of the Invention) As described above, according to the present invention, a semiconductor laser capable of oscillating at a shorter wavelength can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a semiconductor laser which is an embodiment of the present invention. FIG. 2 is a diagram showing the band diagram. In the figure, 1 is an n-GaAs substrate, 2 is an n-doped ZnSe _0.9 S _0.1 clad layer, 3 is an undoped (Al _0.65 Ga _0.35 ) _0.51 In _0.49 P active layer, and 4 is an undoped layer.
p consisting of ZnSe _0.9 S _0.1 and p-doped Al _0.51 In _0.49 P
Cladding layer, 5 is p-doped GaAs layer, 6 is SiO ₂
In the membrane, 7 is a p-electrode, and 8 is an n-electrode.

Claims (1)

[Claims] 1. Comprising at least an active layer for laser oscillation, cladding layers sandwiching the active layer, and ohmic layers providing electrodes, the p-type cladding layer is p-type.
A semiconductor laser comprising two or more layers of alternating group semiconductors and - group semiconductors. 2. The semiconductor laser according to claim 1, wherein the group semiconductor is a ZnSeS mixed crystal.