JPH02302718A - Semiconductor optical element having quantum well structure - Google Patents

Abstract

PURPOSE:To ensure a large energy shift and high sensitivity to an electric field by making the axis of quantization of the quantum well structure of a semiconductor parallel to the [111] crystal orientation. CONSTITUTION:A III-V compd. semiconductor having zinc-blende structure and quantum well structure is used. When an electric field parallel to the axis of quantization of the quantum well structure is impressed, the quantum well level changes. The axis of quantization is made to practically coincide with the [111] crystal orientation. A semiconductor optical element having large effective mass of grains related to quantum confining Stark effect and a large energy shift of the peak of an exciter is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor optical device having a semiconductor quantum well structure and utilizing the quantum confined Stark effect.

[Prior art] As this type of semiconductor optical device, for example,
There is an optical modulator shown in Vol. 3, No. 3 (1986) p., p. 210-218.

The optical modulator is shown in FIG. The optical modulator shown in FIG. 3 has an n-type semiconductor region 31. It consists of an i-type semiconductor region 32° and a p-type semiconductor region 33, and a multiple quantum well structure 34 is formed in the i-type semiconductor region 32.

When a reverse bias is applied to an optical element having such a pin structure and an electric field is applied parallel to the quantization axis of the multiple quantum well structure, the optical constant of the multiple quantum well structure changes. For example, in FIG. 4, one curve C1 has lX in the optical modulator in FIG.
The absorption spectrum is shown when an electric field of 10'V/am is applied, while C2 has an electric field of 4.7 X 10' V/c.
The absorption spectrum is shown when an electric field of m is applied. As is clear from comparing curves C1 and 02, the absorption peak shifts to the lower energy side as the electric field strength increases.

Here, peaks A and A' are exciton peaks formed at the lowest quantum levels of electrons and heavy holes, and peak B is peak B.

B' is an exciton peak formed at the lowest quantum level of electrons and light holes. This electric field effect on the optical constant of a semiconductor quantum well is called the quantum-confined Stark effect. Note that the amount of energy shift of the exciton peak increases as the effective mass of the hole increases.

A wavelength-selectable photodetector is a semiconductor optical device that utilizes such a quantum-confined Stark effect.

Furthermore, optical bistable devices are also being considered.

Conventionally, semiconductor optical devices having a quantum well structure made of these ■-V group compound semiconductors with a zincblende structure have (100)
It is made using a substrate.

[Problems to be Solved by the Invention] However, in a ■-v group compound semiconductor with a zincblende structure, the effective mass of holes has strong anisotropy with respect to the crystal orientation, and its size is [ 100] is the smallest in the direction,
Therefore, it has been found that there is a problem in that the amount of energy shift of the exciton peak is small.

An object of the present invention is to provide a semiconductor optical device in which the effective mass of particles involved in the quantum-confined Stark effect is large and the amount of energy shift of the exciton peak is large.

[Means for Solving the Problems] The present invention is composed of a ■-V group compound semiconductor having a zincblende crystal structure, has a quantum well structure, and has an electric field parallel to the quantization axis of the quantum well structure. A semiconductor optical device in which a quantum well level is changed by applying , is characterized in that the quantization axis substantially coincides with a [111] crystal orientation.

[Example] The present invention will be described in detail below with reference to the drawings.

An optical modulator will be described as an embodiment of the semiconductor optical device of the present invention.

The optical modulator of this example is manufactured using a (111) substrate, and its structure is the same as that of the optical modulator shown in FIG.

According to experiments conducted by the present inventors, it has been found that the effective mass of holes in a ■-V group compound semiconductor having a zincblende structure is greatest in the [111] direction. Therefore, (111)
The amount of shift of the exciton peak in the optical modulator of the present invention manufactured using a substrate is larger than when a (100) substrate is used.

In order to clarify the effects of the present invention, the conventional (100)
An optical modulator manufactured using a substrate and the present invention (111)
A comparison was made with an optical modulator using a substrate.

In each optical modulator, n-type AlGaAs is used as the n-type semiconductor region, and p-type AlGaAs is used as the p-type semiconductor region.
, ANGaAs is used as the n-type semiconductor region, and the central part of the n-type semiconductor region is made of GaAs with a thickness of 1 and
A 20-period superlattice made of 5ns AlGaAs,
The thickness of the n-type semiconductor region was 1 μm.

FIG. 1 shows the photoluminescence measurement results of each optical modulator at 77K. FIG. 1(a) shows an optical modulator of the present invention (using a (111) substrate).

Figure 1(b) shows a conventional optical modulator (using a (100) substrate)
These are the photoluminescence measurement results.

The energy shift of the exciton peaks AI, A2 formed at the lowest quantum levels of electrons and heavy holes is shown in FIG. 2 as a function of the magnitude of the applied electric field.

As is clear from FIG. 2, the optical modulator of the present invention using a (111) substrate (indicated by .) has more energy than the conventional optical modulator using a (100) substrate (indicated by 0). The shift is large.

In addition, the effective masses of heavy holes in the [1001 direction and [1111 direction] are respectively m '' hb = 0.34 m 11
.

Theoretical values of the energy shift obtained by dividing m'' mb=0.9 m are shown by broken lines and solid lines.These theoretical values substantially agree with the experimental results, demonstrating the effectiveness of the present invention.

[Effects of the Invention] According to the present invention, the quantization axis of the multiple quantum well structure is set to [11
11 By making the crystal orientation parallel to the crystal orientation, a semiconductor element with a large energy shift and high sensitivity to electric fields can be obtained.

Margin below

[Brief explanation of the drawing]

FIG. 1 shows the photoluminescence vector of an optical modulator. FIG. 1(a) shows the photoluminescence vector of an optical modulator having a quantum well quantized in the [111] direction, and FIG.
] Figure 2 is a graph showing the energy shift of the exciton peak in Figure 1, and Figure 3 is a schematic diagram showing a normal incidence optical modulator. 4 are graphs of absorption coefficients for explaining the quantum confined Stark effect. 31...n-type semiconductor region, 32...i-type semiconductor region. 33...p-type semiconductor region, 34... multiple quantum well. 27 Applied voltage (V) Electric field (X10'V/cm) Figure 1 (a) Energy (eV) Wavelength (field) Figure 1 (b) Energy (eV) 1.55 1.54 1.53 795 800 805 870 8i5 wave
Length (nm)

Claims (1)

[Claims] 1. It is composed of a III-V group compound semiconductor with a zincblende crystal structure and has a quantum well structure, and the quantum well level can be changed by applying an electric field parallel to the quantization axis of the quantum well structure. 1. A semiconductor optical device having a quantum well structure, wherein the quantization axis substantially coincides with a [111] crystal orientation.