JPH084183B2 - Semiconductor laser - Google Patents

Description

The active layer of a semiconductor laser has a multi-quantum well structure in which barrier layers and well layers are alternately laminated, and the barrier layers and well layers of the multi-quantum well are superlattice structures. And As a result, it can be expected that a semiconductor laser with good temperature characteristics, a short wavelength and a low threshold is realized.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser having a quantum well as an active layer.

Prior art and its problems A conventional quantum well laser using a quantum well as an active layer is disclosed in Japanese Patent Laid-Open No. 62-98690. This is GaAs
This is a semiconductor laser in which each thin film layer of Al _x Ga _1-x As and Al _x Ga _1-x As is set to have a thickness of 3 molecular layers or less, and superlattice quantum wells alternately stacked are used as active layers. The use of superlattice quantum wells provides an active layer with excellent in-plane uniformity, and provides high-performance, low-threshold short-wavelength semiconductor lasers.

However, the above-mentioned superlattice quantum well laser has a problem that the temperature characteristics are poor because the active layer is thin.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor laser which utilizes the characteristics of the above superlattice quantum well laser such as low threshold and short wavelength and has improved temperature characteristics.

Structure and Effect of the Invention A semiconductor laser according to the present invention is characterized in that an active layer is composed of a multiple superlattice quantum well structure in which superlattice barrier layers and superlattice well layers are alternately laminated.

Both the superlattice barrier layer and the superlattice well layer are composed of two types of thin layers each having a composition of 5 molecular layers or less, such as Ga.
It is configured by alternately stacking As layers and AlGaAs layers.

The multi-quantum well structure has a characteristic that the oscillation wavelength is relatively long but the temperature characteristic is good. So, in this invention,
The superlattice structure was applied to a multiple quantum well structure with excellent temperature characteristics, and the active layer was composed of a multiple superlattice quantum well structure in which superlattice quantum well layers and superlattice barrier layers were alternately stacked. Since crystal growth can be performed while maintaining excellent in-plane flatness, it is expected that the temperature characteristics will be improved without lowering the threshold and the short wavelength characteristic of the superlattice structure. .

Description of Embodiments FIG. 1 shows an embodiment of the present invention and is a schematic sectional view of an AlGaAs semiconductor laser. FIG. 2 shows the Al average mixed crystal distribution in the vicinity of the multiple superlattice quantum well active layer.

n on an n-GaAs substrate (carrier concentration Si = 10 ¹⁸ cm ⁻³ ) 1
−GaAs buffer layer (Si = 10 ¹⁸ cm ⁻³ , thickness 0.5 μm) 2, n−A
l _0.7 Ga _0.3 As clad layer (Si = 10 ¹⁸ cm ^-3 , thickness 1.5 μm)
3, non-doped Al _x Ga _{1-x As} GRIN (granded-index) layer (thickness 0.2 μm) 4, non-doped Al _0.1 Ga _0.9 As / Al _0.3 Ga _0.7 As active layer with multiple superlattice quantum well structure (total thickness About 720Å)
5, undoped Al _x Ga _{1-x As} GRIN layer (thickness 0.2 μm) 6, p-Al
_0.7 Ga _0.3 As clad layer (Be = 10 ¹⁸ cm ^-3 , thickness 1.5 μm) 7,
p-GaAs cap layer (Be = 10 ¹⁸ cm ^-3 , thickness 0.5 μm) 8
A semiconductor laser is manufactured by continuously growing by the BE method. The multiple superlattice quantum well active layer 5 is formed by alternately superposing superlattice barrier layers 21 and superlattice well layers 22, as shown in an enlarged view in FIG. In this embodiment, four superlattice barrier layers 21 and five superlattice well layers 22 are provided.

The superlattice barrier layer 21 has an Al _0.4 Ga _0.6 As layer (three layers with a thickness of 9Å) 31a and a GaAs layer (thickness 3Å with a thickness of 3Å) as shown in FIG. 2 layers) are laminated alternately, and the total thickness is 33Å. The superlattice well layer 22 is composed of GaAs layers (10 layers having a thickness of 9Å) 32a and Al _0.4 Ga _0.6 As layers (9 layers having a thickness of 3Å) 32b alternately laminated, and the total thickness is 117Å. ing.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a semiconductor laser according to an embodiment of the present invention, and FIG. 2 is a graph showing an Al average mixed crystal distribution in the semiconductor laser of FIG. 5 ... Multiple superlattice quantum well active layer, 21 ... Superlattice barrier layer, 22 ... Superlattice well layer, 31a, 32b ... Al _0.4 Ga _0.6 As layer, 31b, 32a ... GaAs layer.

Claims (2)

[Claims] 1. A semiconductor laser having an active layer having a multiple superlattice quantum well structure in which superlattice barrier layers and superlattice well layers are alternately laminated. 2. The superlattice barrier layer and the superlattice well layer are both constituted by alternately laminating GaAs layers and AlGaAs layers each having 5 or less molecular layers. ) The semiconductor laser according to the paragraph.