JPH0732280B2 - Semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention comprises an active layer having the same forbidden band width and refractive index as a quaternary mixed crystal semiconductor and a light or carrier confinement layer in a superlattice type laminated structure. And a heterojunction semiconductor laser device.

[Conventional technology]

Conventionally, a heterojunction semiconductor laser device has three semiconductors which are basic constituent elements, that is, an active layer semiconductor having a forbidden band width required to obtain a predetermined oscillation wavelength, and an active layer semiconductor satisfying a lattice matching condition with the active layer semiconductor. The second clad layer semiconductor has a larger forbidden band width and a smaller refractive index, and a substrate for epitaxially growing those semiconductors with high quality. When manufacturing a heterojunction semiconductor laser device having a predetermined oscillation wavelength band, if the crystal of the substrate is first determined, it is necessary to match the lattice constant with that of the substrate crystal. There is little room to choose the bandwidth (Kayce & Panish Heterostructure Lasers, 1978, Academic Press (Gasey & Panish, Heterostructure Lasers, 197
8, Academic Press)). On the other hand, if the dimension of the mixed crystal semiconductor is as high as 4 or more, there is room for selection of the forbidden band width, but there is a general difficulty that the composition control of the mixed crystal semiconductor for lattice matching with the substrate crystal becomes difficult. Exists.

Figure 2 shows an example of In _0.53 Ga _0.47 As / In _0.52 Al _0.48 As / In
1 shows the basic configuration of a P-based long wavelength semiconductor laser device. In Figure 2, 1 is an n-type metal electrode 2 is n-type InP substrate, 3 an undoped In _0.53 Ga _0.47 As, 5 is n-type _{In 0 · 52 Al 0.48 As,} 4 is a lower cladding layer is the active layer Is an upper clad layer of p-type In _0.52 Al _0.48 As, 6 is a cap contact layer of p-type In _0.53 Ga _0.47 As, and 7 is a p-type metal electrode.

[Problems to be solved by the invention]

In the conventional semiconductor laser device shown in FIG. 2, the ternary mixed crystal semiconductor composition of the clad layer and the active layer is uniquely determined so that the InP substrate 2 has the same lattice constant. Therefore, the forbidden band width and the refractive index of the cladding layers 3 and 5 and the active layer 4 are also uniquely determined. Therefore, in order to change the physical constants such as the forbidden band width, it is necessary to use a quaternary or higher multi-element mixed crystal semiconductor having a high dimensional number such as a quaternary system and difficult to manufacture. There was a problem.
In the above example, the cladding layer semiconductor In _0.52 Al _0.48 As
Since the Al composition is large, there is a drawback that deterioration due to oxidation is likely to occur.

The present invention has been made in order to solve the above problems, and it is possible to obtain a physical constant equivalent to or better than a quaternary mixed crystal semiconductor in terms of device function, and to achieve device function such as oscillation wavelength. It is an object of the present invention to obtain a semiconductor laser device capable of increasing the degree of freedom in selecting physical constants related to.

[Means for solving problems]

A semiconductor laser according to the present invention is a semiconductor laser device having a laser structure in which a plurality of semiconductor layers are laminated on an InP substrate, and an InGaAs layer lattice-matched to the substrate and
InAlAs layers are alternately laminated in three or more layers, and have a forbidden band width and a refractive index desired as an optical confinement layer, a carrier confinement layer or an active layer constituting the above laser structure, and the substrate and the lattice. Matching single-layer InGa
The optical confinement layer, the carrier confinement layer, or the active layer has a laminated structure that achieves the same forbidden band width and refractive index as the AlAs layer.

[Action]

In the present invention, in a semiconductor laser device having a laser structure in which a plurality of semiconductor layers are laminated on an InP substrate, three or more InGaAs layers and InAlAs layers lattice-matched with the substrate are alternately laminated, and the laser A forbidden band width and a refractive index desired as an optical confinement layer or a carrier confinement layer or an active layer constituting the structure, and the same forbidden band width as a single-layer InGaAlAs layer lattice-matched with the substrate, and Since a laminated structure having a refractive index is provided as the optical confinement layer, the carrier confinement layer, or the active layer, it is a quaternary mixed crystal semiconductor.
GaAlAs manufacturing difficulties and physical constant selection constraints can be solved. The laminated structure as described above has a molecular beam epitaxy method or an organic metal CVD (Chemical Vapor Depositi
It can be easily prepared by the on) method or a similar method.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
The figure shows an embodiment in which the present invention is applied to an In _0.53 Ga _0.47 As / In _0.52 Al _0.48 As / InP long-wavelength semiconductor laser device.

In FIG. 1, the same symbols as in FIG. 2 indicate the same parts,
3a and 5a are cladding layers having an n-type and p-type superlattice structure, respectively.
Ultra-thin In _0.52 Al _0.48 As barrier layer 8 and In _0.53 Ga _0.47 As well layer 9 lattice-matched with the P substrate 2, that is, two kinds of ternary composition different compositions of quaternary mixed crystal semiconductor A superlattice structure composed of the above compound semiconductor ultrathin films is used.

In _0.53 Ga _0.47 As / In _0.52 Al _0.48 As When a cladding layer with a superlattice structure is used, In _1-xy Ga _x Al _y lattice-matched with InP is used.
As (x <0.47, y <0.48) In _0.52 Al _0.48 which does not use a quaternary mixed crystal semiconductor and has a large Al content and is easily oxidized.
It is possible to configure a semiconductor laser device without using an As thick film. Bandgap of In _0.53 Ga _0.47 As and In _0.52 Al _0.48 As is 0.77eV and 1.7 eV, since the difference is large enough and about 0.9 eV, the _{In 0.53 Ga 0.47 As / In 0.52} Al 0.48 As superlattice structure Even when used as a clad layer, it is possible to obtain a difference in forbidden band width that does not impair the function as a semiconductor laser device, and further reduce the Al average composition of the clad layer,
It is possible to overcome drawbacks such as being easily oxidized.

Figure 3 shows the results of calculation of the effective band gap in the In _0.53 Ga _0.47 As / In _0.52 Al _0.48 As superlattice structure using the Klenig-Penny model. In _0.53 Ga _0.47 As If the well layer 9 has a thickness of about 15 Å, a band gap difference of 0.3 eV between the active layer and the cladding layer, which is necessary to function as a heterojunction semiconductor laser, can be easily obtained. You can see that

Further, if the thickness of the In _0.53 Al _0.48 As barrier layer 8 is about 30 Å, the average Al composition of the cladding layer can be reduced from 48% to 32%, and the cladding layer which is not easily oxidized is provided. It is possible.

As described above, instead of using a quaternary mixed crystal semiconductor, a superlattice structure composed of two kinds of mixed crystal semiconductors having different ternary compositions whose composition is easily controlled to achieve lattice matching is used. And an active layer necessary for constructing a heterojunction semiconductor laser while ensuring the degree of freedom in selecting physical constants,
A clad layer can be formed, and it is possible to provide an advantageous method for manufacturing a semiconductor laser.

Although the superlattice structure made of two kinds of ternary mixed crystal semiconductors is used for the clad layer in the above-mentioned embodiments, these superlattice structures may be used for the active layer and the contact depending on the required function of the device. It can also be used in layers.

〔The invention's effect〕

As described above, according to the present invention, in a semiconductor laser device having a laser structure in which a plurality of semiconductor layers are laminated on an InP substrate, three or more InGaAs layers and InAlAs layers lattice-matched with the substrate are alternately stacked. A single layer of In that has a forbidden band width and a refractive index desired as an optical confinement layer or a carrier confinement layer or an active layer constituting the laser structure and is lattice-matched with the substrate.
Since the laminated structure that achieves the same forbidden band width and refractive index as the GaAlAs layer is provided as the optical confinement layer, the carrier confinement layer, or the active layer, the device can be easily manufactured, and the reliability and characteristics are excellent. There is an effect that the device can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a diagram showing a structure of a conventional semiconductor laser device, and FIG. 3 is a well layer thickness and a forbidden band of an embodiment of the present invention. It is a figure which shows the calculation result of the relationship of width. 1 is an n-type metal electrode, 2 is an n-type substrate, 3 and 3a are n-type cladding layers, 4 is an active layer, 5 and 5a are p-type cladding layers, 6 is a p-type cap contact layer, and 7 is a p-type metal electrode. , 8 is a superlattice barrier layer, and 9 is a superlattice well layer. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A semiconductor laser device having a laser structure in which a plurality of semiconductor layers are laminated on an InP substrate, wherein three or more InGaAs layers and InAlAs layers lattice-matched with the substrate are alternately laminated to form the laser. A forbidden band width and a refractive index desired as an optical confinement layer or a carrier confinement layer or an active layer constituting the structure, and the same forbidden band width as a single-layer InGaAlAs layer lattice-matched with the substrate, and A semiconductor laser device comprising a laminated structure having a refractive index as the optical confinement layer, the carrier confinement layer, or the active layer.