JPH0640179B2 - Semiconductor optical switch - Google Patents

Description

The present invention relates to an optical switch used in an optical communication device, an information processing device, or the like.

<Conventional Technology and Its Problems> In the conventional optical switch of this type, a device using the Franz-Keldysh effect using a semiconductor is small and excellent. The Franz-Keldysh effect is an effect in which the absorption edge wavelength shifts to a longer wavelength when an electric field is applied to the semiconductor. As for this semiconductor, each forbidden band width is 500
Å A waveguide type optical switch using a multi-quantum well structure in which the following layers are alternately laminated is considered (1985, National Institute of Electronics and Communication Engineers general conference S3-4). In such a waveguide type optical switch, the switching speed is mainly determined by the CR time constant which is the product of the capacitance of the device and the series resistance. The capacitance of the device is determined by the depletion layer capacitance of the PN junction, which is proportional to the PN junction area. In the conventional device as shown in FIG. 2, the stripe for performing the switch operation is as large as about 10 × 500 μm ² , and another area of about 100 × 100 μm ² is required for bonding, so that a relatively large PN junction area is required. I needed it. Therefore, the capacitance of the device is relatively large, 3 to 5 pF, and the CR time constant (~) determined by this capacitance and the series resistance of 50Ω.
The operation speed was limited at 300 psec). To further improve the operation speed, the capacitance is reduced, that is, P
It is necessary to reduce the N-junction area. However, in the optical switch of the conventional structure, there is a situation that the area of the bonding pad is required, and that if the stripe width is made narrower than the current state, the scattering of the signal light is increased due to the disturbance of the side surface due to the etching. And no more PN
It was difficult to reduce the bonding area.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a semiconductor optical switch that eliminates the above-mentioned drawbacks, can easily reduce the PN junction area, has a small capacitance, and has a high operating speed.

<Means for Solving Problems> In order to solve the above-mentioned problems, the semiconductor optical switch provided by the present invention has a thickness of not more than the mean free path of electrons (≦ 10
00 Å) A quantum well thin wire made of a semiconductor, a semiconductor barrier that surrounds the quantum well thin wire and has a bandgap larger than that of the quantum well thin wire, and a quantum well thin wire region composed of the semiconductor barrier and the quantum well thin wire on two sides. A p-type semiconductor region and an n-type semiconductor region formed respectively are provided.

<Example> Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a semiconductor optical switch according to an embodiment of the present invention.
In the figure, 1 is a semi-insulating substrate (GaAs), 2 is the first cladding layer (undoped high resistance) 0.2 ≦ X _c1 ≦ 0.8, thickness 0.5 to 3 μm, typically X _c1
= 0.4, thickness to 1.5 μm), 3 is a quantum well thin wire region (undoped high resistance, thickness 0.1 to 1 μm, width 0.5 to 3 μm,
Typically, the thickness is 0.5 μm and the width is 1 μm. 3a is a quantum well thin wire (thickness 40 to 200 Å, width 40 to 1000 Å, Al _xw Ga _1-Xw A
s, 0 ≦ Xw <Xb, typically thickness 100Å, width 100-500
Å, X _w = 0), 3b is a barrier (width 40 to 1000Å, Al _xb
Ga _1-xb As, 0.1 ≦ Xb <X _c1 , X _c2 , typically width 100
~ 500Å, Xb = 0.2), 4 is the second cladding layer (undoped high resistance) 0 ≦ X _c2 ≦ 0.8, thickness 0.5 to 3 μm, typically X _c2 =
0.4, thickness ~ 1.5 μm), 5a is a p-type cap layer (p-Ga
As), 5b is an n-type cap layer (n-GaAs), 6 is a p-type region, 7 is an n-type region, 8 is a p-type electrode, and 9 is an n-type electrode.

In this embodiment, the p-type region 6 and the n-type region 7 are in the same plane of the semiconductor film, so that when a voltage is applied between them, the electric field is applied in the direction parallel to the semiconductor film surface. At this time, in this embodiment, since the quantum well thin wire 3a is provided, carriers are confined in the lateral direction as well, and when the electric field is applied in the lateral direction, the quantum level shifts to the low energy shift side and good switching occurs. The characteristics were obtained.

The PN junction area of this embodiment is determined by the total thickness and the element length.
The thickness can be controlled with high accuracy by advanced epitaxy technology such as molecular beam epitaxy method. Therefore, the thickness can be suppressed to the minimum thickness of 2 to 3 μm required for the device, and since the interface is flat, light scattering is small. Further, in this embodiment, since the p-type region 6 and the n-type region 7 are formed on the semi-insulating substrate 1, the capacitance does not increase even if these areas are increased, so that the bonding is easily performed. You can Due to these effects, the electrostatic capacitance in this embodiment is 0.5 pF or less, and the operating speed of 100 psec or less is realized.

Next, an example of a method of manufacturing the semiconductor optical switch of this embodiment will be described with reference to FIG. First, in the first crystal growth, as shown in FIG. 3A, the first cladding layer 2 and the multiple quantum well 10 are grown on the semi-insulating substrate 1. Next, Fig. 3 (b)
Ga as shown in Fig.
Are ion-implanted in stripes and then annealed to disorder the Ga-implanted quantum well to form the quantum well thin-line region 3. Next, as shown in FIG. 3C, the second cladding layer 4 and the cap layer 5 are formed in the second crystal growth. After that, as shown in FIG. 3 (d), Si
Are selectively diffused to form an n-type region 7, and then Zn is selectively diffused to form a p-type region 6. During this diffusion, the quantum well wire regions included in the p-type region 6 and the n-type region 7 are disordered and become a uniform semiconductor. Finally, the p-type electrode 8 and the n-type electrode 9 are formed, and the cap layer 5 on the stripe is removed to complete the process.

Although GaAs / AlGaAs is used as the material in the above-mentioned embodiments, the present invention is not limited to this, and other materials such as InGaAsP / InP and In are used.
The present invention can be implemented using GaAlAs / InP or the like.

<Effects of the Invention> As described in detail above, according to the present invention, a semiconductor optical switch having a small capacitance and a high operation speed can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a perspective view of a conventional example, and FIG. 3 is a view showing a manufacturing process of the embodiment shown in FIG. In the figure, 1 ... Semi-insulating substrate, 2 ... First cladding layer, 3
・ ・ ・ Quantum well wire region 3a ・ ・ ・ Quantum well wire 3b
… Barrier, 4 …… Second clad layer, 5 …… Cap layer,
5a ... p-type cap layer, 5b ... n-type cap layer, 6
... p-type region, 7 ... n-type region, 8 ... p-type electrode, 9 ...
... n-type electrode, 10 ... multiple quantum well, 20 ... n-type GaAs
Substrate, 21 ... N-type cladding layer, 22 ... Multiple quantum well, 23 ... P-type cladding layer, 24 ... Cap layer, 2
5 ... P-type electrode, 26 ... N-type electrode.

Claims (1)

[Claims] 1. A quantum well thin wire made of a semiconductor whose thickness is equal to or less than the mean free path of electrons, a semiconductor barrier surrounding this quantum well thin wire and having a forbidden band width larger than this quantum well thin wire, this semiconductor barrier and the quantum. 1. A semiconductor optical switch comprising a p-type semiconductor region and an n-type semiconductor region formed on two side surfaces of a quantum well thin line region formed of a well thin line, respectively.