JP2556296B2 - Semiconductor quantum wire laser - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor quantum wire laser, and more particularly to a structure of a semiconductor quantum wire laser having a quantum wire as an active layer.

[0002]

2. Description of the Related Art Achieving a semiconductor laser structure having a small threshold current density is important in developing an optical integrated circuit.
This is one of the necessary conditions. As a semiconductor laser structure having a low threshold current density, a semiconductor quantum well laser structure having a quantum well as an active layer is used. For example, Tang (WT Tsang) et al. Applied Physics Letters (Applied Physics)
Letters), vol. 39, 1981, p. 7
86, it is reported that the threshold current density in the semiconductor quantum wire laser structure is smaller than that of the conventional double hetero semiconductor laser. Furthermore, in recent years, it has been found that the threshold current density of a quantum well laser can be further reduced by using a strained quantum well in the active layer. For example, TR Chen et al.
LEOS 1991 Conference Digest,
In paper SDL16.6, it is reported that a laser structure using a strained quantum well in the active layer has realized a semiconductor laser structure having a smaller threshold current density.

In a semiconductor quantum wire laser having a quantum wire as an active layer, the threshold current density is theoretically smaller than that of a conventional quantum well laser, according to M. Asada et al. EE Journal of Quantum Electronics (IEEE Journal of Quantum
Electronics), vol. QE-22,19
86, p. 1915. Experimentally, the fabrication of several quantum wire lasers has been reported so far. For example, E. Kapon et al., Physical Review Letters (Physical Rev)
new Letters), vol. 63, 1989,
p. In 430, the laser characteristics of a quantum wire laser having quantum wires oriented in the <110> direction on a patterned (100) substrate are reported. As in this example, all quantum wire laser structures reported so far use a quantum wire oriented in the <110> direction as an active layer.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the quantum wire laser using a quantum wire oriented in the <110> direction as an active layer,
So far, no one has reported a threshold current density smaller than that of the conventional quantum well laser. This is because, in a quantum wire oriented in the <110> direction, the optical transition probability of emitting linearly polarized light having an electric field component in the quantum wire direction, which is involved in laser oscillation, becomes small due to the effect of the anisotropy of the valence band. This is one of the causes.

The present invention has been made in consideration of such conventional circumstances, and an object thereof is to provide a semiconductor quantum wire laser structure having a small threshold electric density.

[0006]

The present invention provides a semiconductor quantum wire laser structure having a quantum wire as an active layer, wherein <0.
The semiconductor quantum wire laser structure is characterized in that a quantum wire structure is produced in a direction tilted within 5 degrees in an arbitrary direction from the 01> direction or the <001> direction.

[0007]

The reason why the quantum wire laser structure according to the present invention has a small threshold current density will be explained. In a quantum wire laser, linearly polarized light having an electric field component in the quantum wire direction oscillates. The higher the optical transition probability that the quantum wire emits this light, the smaller the threshold current density of this lasing. Calculating the above-mentioned optical transition probability in the case of using a cleaved {110} surface for the cavity surface in order to reduce the loss of light at the time of reflection for a quantum wire oriented in any direction, Due to the effect of band anisotropy,
It was found that the quantum wire oriented in the 001> direction has the highest optical transition probability. The optical transition probability also shows a high value in a quantum wire oriented in a direction inclined by 5 ° or less from the <001> direction, and the value of the optical transition probability of the quantum wire oriented in the <001> direction. To 0.1% or less.

Due to this effect, the quantum wire laser structure according to the present invention has a lower threshold current density than the conventional one.

[0009]

Embodiments of the present invention will now be described with reference to the drawings.
While explaining in detail. Here, AlGaAs / Ga
A book on quantum confinement laser structure with As-system
An embodiment to which the invention is applied will be described. 1 and 2
Shows the user structure. Figure 2 faces the conventional <110> direction
A quantum wire laser having quantum wires is shown in FIG.
An example is a quantum wire laser structure that faces the <001> direction.
It is a construction. Metal-organic vapor phase epitaxy for sample preparation
(MOCVD method), the conventional structure is n type (00
1) The GaAs substrate 11 is an n type in this embodiment.
A (110) GaAs substrate 12 was used. The sample is shown in Figure 1.
In both cases, firstly, the thickness of 1.5 μm
n type Al_0.45Ga_0.55As layer 13 is grown and the second
In addition, the thickness of 20 nm that is the source of the GaAs quantum wires 14
Undoped GaAs layer is 20 nm thick on both sides of undoped A
l_0.3Ga_0.7Al with a structure sandwiched between As layers 15_0.3G
a_0.7Growth of As / GaAs quantum well layer
1.5 μm p-type Al_{0. 45}Ga_0.55As layer 16,
A p-type GaAs layer 17 having a thickness of 0.3 μm is grown in order.
And fourth, electron beam lithography and dry etching.
Stripes with a cycle of 100 nm and a width of 20 nm
Etching p-type region and non-doped region other than
Fifthly, the groove formed by etching is made of
Doped Al_0.3Ga_0.7As layer 15, thickness of 1.5 μm
p type Al_0.45Ga_0.55As layer 16, thickness 0.3 μm
By sequentially embedding the p-type GaAs layer 17 in
Was obtained. The sample has a 20 nm square GaAs quantum wire 14.
Formed and by electron beam lithography of FIG.
In the conventional structure, the quantum wire faces the [110] direction,
In the example, the direction is [001]. Which sample
By injecting current, the [1, -1,0] direction
The cleaved surface 18 facing in the direction is used as the cavity surface, and
Linearly polarized light having an electric field component in the line direction lases.
The results of comparing the threshold current densities of laser oscillation with these two
As a result, the threshold of this example is about 10% lower than that of the conventional structure.
The current density could be obtained.

[0010]

As described above, the semiconductor quantum wire laser structure according to the present invention has a <001> direction or <0.
There is an effect that a small threshold current density can be obtained by manufacturing the quantum wire structure in a direction inclined at an angle of 5 degrees or less from the 01> direction.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a semiconductor quantum wire laser structure used in an example.

FIG. 2 is a schematic perspective view of a conventional semiconductor quantum wire laser structure.

[Explanation of symbols]

11 n type (001) GaAs substrate 12 n type (110) GaAs substrate 13 n type Al _0.45 Ga _0.55 As layer 14 GaAs quantum wire 15 undoped Al _0.3 Ga _0.7 As layer 16 p type Al _0.45 Ga _0.55 As layer 17 p type GaAs Layer 18 Cleaved surface facing the [1, -1,0] direction

Claims (1)

(57) [Claims] 1. In a semiconductor quantum wire laser structure having a quantum wire as an active layer, a <001> direction or a <001> direction.
A semiconductor quantum wire laser characterized by producing a quantum wire structure in a direction tilted at an angle of 5 degrees or less from any direction.