JPH03278017A - Optical semiconductor device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical semiconductor device that controls optical properties such as light absorption/transmission and refractive index.

[Conventional technology]

As for the optical properties of ordinary semiconductors such as GaAs, light absorption occurs when electrons rise from the valence band to the conduction band between the conduction band and the valence band, but when the electrons monopolize the conduction band, It is well known that because the movement of electrons from the valence band to the conduction band is restricted, the light absorption characteristics decrease and the transparency of the medium increases.

Therefore, by utilizing these properties, the light absorption characteristics can be controlled by controlling the electrons injected into the semiconductor, and it can be used as a light modulator.

[Problem to be solved by the invention]

However, in the normal semiconductor GaAs, since the conduction band and the valence band each have many levels, various types of light are absorbed, and the absolute value of the light absorption coefficient is small. In addition, as the temperature rises, even if electrons are injected and the conduction band is occupied, the electrons move due to thermal motion, so the conduction band is less occupied and becomes vacant on average. state, and the effect of controlling optical properties by electron injection is weakened. In other words, there is a problem in that it is unstable and highly temperature dependent, and the higher the temperature, the worse its optical characteristics become.

The present invention solves the above-mentioned problems, and aims to provide an optical semiconductor device that is independent of temperature and has a large control effect and absolute value of optical characteristics.

[Means to solve the problem]

To this end, the optical semiconductor device of the present invention is characterized in that a layer having a quantum box structure or a quantum wire structure is used as an optical waveguide layer, and the optical characteristics are controlled by injecting electrons into the optical waveguide layer. It is also characterized by having multiple leading wave layers.

[Effect]

In the optical semiconductor device of the present invention, a layer having a quantum box structure or a quantum wire structure is used as a leading wave layer, and electrons are confined in a limited and specific state, so that the effect of controlling optical properties is remarkable at a specific wavelength. appear. Moreover, since the difference in energy level becomes large, thermally stable characteristics can be obtained.

〔Example〕 Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing one embodiment of an optical semiconductor device according to the present invention, and FIG. 2 is a diagram showing a comparison example of photon energy and light absorption coefficients of a normal semiconductor and a quantum structure semiconductor.

In Fig. 1, the optical waveguide layer (core) l is shown in Fig. 1(b).
The cladding 2.3 is composed of a quantum box 4 structure layer as shown in (C) or a quantum a85a structure layer as shown in FIG. This is a layer with a ratio n1. The quantum box 4 and the quantum wire 5 have an active layer of the same wavelength as the de Broglie wavelength λ of electrons (about 100 A).
A quantum thin film with a thickness of

In the optical waveguide layer 1, when electrons are left empty in the quantum box 4 structure or the quantum wire 5 structure, the quantum box 4 structure or the quantum wire 5 structure exhibits high absorption characteristics for incident light. On the other hand, when electrons are injected into the quantum box 4 structure or the quantum wire 5 structure, the absorption characteristics of the quantum box 4 structure or the quantum wire 5 structure with respect to the incident light are significantly reduced, making it possible to detect transmitted light. .

Figure 2 (a) shows the light absorption characteristics of a normal semiconductor (bulk), and Figure 2 (b) shows the light absorption characteristics of a quantum well (QW). ) shows the light absorption characteristics of the quantum box (QB), and (d) shows the light absorption characteristics of the quantum box (QB). In the figure, the vertical axis shows the absorption coefficient and the horizontal axis shows the photon energy, the solid lines represent the injected electrons at 0, and the dotted lines represent the injected electrons at 0. 5 X 10"Ca1-'1, OX 10
The relationship between the absorption coefficient α and the photon energy (reciprocal of wavelength) is shown in the case of "cm-', 2. OX 10 "am-'. Comparing this with the same figure (c), which shows the light absorption characteristics of quantum wells, thin film quantum wells have more pronounced light absorption characteristics. However, when compared with the same figure (C), which shows the light absorption characteristics of quantum wires, the light absorption characteristics change to a sharp shape, and when compared with the same figure (C), which shows the light absorption characteristics of quantum boxes, the light absorption characteristics change to a sharp shape. It can be seen that the characteristics have become even sharper.

If the size of a quantum box is 100 human angles, then 10', 10 +llc, -3 boxes are lined up with a length of l cm, so two electrons are in one box due to the spin. If the number of electrons is 2. Ox 10 "cm-"
It will be full.

In a quantum box, the variation in the energy at which absorption occurs is reduced, so the absolute value of the energy at which absorption occurs increases, and the number of injected electrons is 2.
The difference from the case where OX 101eco+-3 is used is also large. By the way, looking at the absorption coefficient α when the number of injected electrons is 0, the same figure (a) shown for a normal semiconductor
is 2 to 3 x 10'cm-', whereas the peak value in Fig. 2(d) for the quantum box is 5 x 10'cm-', which is 20 times larger for the quantum box.

In this way, in quantum boxes and quantum wires, electrons are confined, so that when they are in a specific state, they reach the next state, 'J (high energy level), and light absorption is only allowed there. converges around a specific wavelength j, the absorption coefficient increases, and a thermally stable and steep spectrum is exhibited.

Next, an example of an electron injection method will be described.

FIG. 3 is a diagram for explaining an example of an electron injection method for a FET structure, and FIG. 4 is a diagram for explaining an example of an electron injection method for a diode structure. In the figure, 11 is a gate, 12 is an insulating layer, 13 and 15 are cladding layers, 1423.34 is an optical waveguide layer, 16 is a source, 17 is a drain, 21, 25.31.
37 is an electrode, 22 is a p layer, 24.32.36 is an n layer, 3
3 and 35 indicate barrier layers.

In the example shown in FIG. 3, the insulating layer 12 and the gate layer 11 are stacked on one side of the cladding layers 13 and 15 configured in the same manner as in FIG. 1, and the source 16 and drain 17 are placed on the other side.
The structure is such that electrons are injected into the optical waveguide layer 14 by applying a bias to the optical waveguide layer 11 . Therefore, the optical waveguide layer 14 corresponds to the channel of the FET.

In the example shown in FIG. 4, injection is performed using a vertical current, in contrast to the horizontal current injection shown in FIG. In the figure (a), an optical waveguide layer 23 is inserted between a pn junction consisting of nine layers 22 and one layer 24, and electrodes are placed on both sides of the optical waveguide layer 23 and a current is applied to the quantum box or the waveguide layer 23. It is configured to inject electrons into quantum wires.

In the figure (b), both sides of the leading wave layer 33 are sandwiched between barriers 33 and 35, and an n layer is placed outside of the barriers 33 and 35, and a bias voltage is applied from both sides to utilize the resonant tunneling effect of the double barrier. The structure is such that electrons are injected into the quantum box or quantum wire of the leading wave layer 23.

Furthermore, when a control light beam is irradiated from a direction different from that of the detection light, electrons are absorbed and enter the material, causing it to suddenly become transparent. It can also be constructed using such an optical light beam excitation method.

Next, consider the light absorption effect. One layer of a quantum box is about 100 layers thick, but as an optical waveguide it is about 100 layers thick.
If light is introduced with a width of 0 people, it will be absorbed at 1/10. Therefore, we now set the absorption coefficient α to approximately 5XlO'c [
', the intensity of the light is 1 ~ exp (-ad) (d is the propagation distance), so if the propagation distance d is about 20 μm (2X10-3 cm), the intensity of the transmitted light will be less than 1/100. drop down. Therefore, even with a single layer, it is possible to obtain a remarkable effect in lateral propagation that is one order of magnitude higher than that of ordinary semiconductors.

FIG. 5 is a diagram showing an embodiment of a stacked optical semiconductor device.

In the above-mentioned lateral propagation, there are problems such as the difficulty of introducing the light, but in the case of longitudinal (vertical) propagation, absorption control can be performed at the front of the optical waveguide, and lateral It will be advantageous compared to the direction. However, in this case, there is a problem that the propagation distance cannot be secured. For example, considering the effect of one layer, if the absorption coefficient α is 5XIO'cm-',
Since the propagation distance d is less than 100A (-10-'cm) L, an effect of only about 5% can be obtained when ad is 5X10-''.Therefore, as shown in FIG.
-1.41-2, ......, 41-n is stacked, the 5% effect becomes (0,95)'', so for example, if n is stacked with 10 layers, it will be attenuated by absorption. can be reduced to 1710 or less. In this way, with a stack of 10 layers and a thickness of about 1000 A, vertical propagation can also have a large absorption effect. In addition, in this way, in a quantum box, the number of electrons per belly can be reduced. is about 1012cl", but FET
In the structure, the number of electrons of 10130ffl-2 can be controlled at the gate.

Figure 6 is a diagram to explain the difference in characteristics due to temperature. Figure 6 (a) shows the characteristics of ordinary semiconductors, quantum wells, quantum wires, and quantum boxes at 10 degrees; The same characteristics are shown at .degree., the horizontal axis shows the difference between the photon energy and the gap energy (E-Eg), and the vertical axis shows the change in absorption coefficient. A comparison between FIG. 3(a) and (a) shows that quantum boxes and quantum wires have extremely stable thermal properties.

Note that the present invention is not limited to the above embodiments, and various modifications are possible. For example, in the above embodiment, the configuration was explained using a quantum box or a quantum wire that is the size of 100 people, but it goes without saying that the size of the quantum box may be increased or decreased. In addition, although the explanation was given as switching between absorption and transparency by changing the absorption coefficient by injecting electrons, changes in the absorption coefficient are accompanied by changes in the refractive index, so it can also be used as a device that changes the refractive index significantly. Of course, it can be applied to various application fields.

When focusing on the refractive index, if the refractive index changes, the wavelength in the medium also changes, so for example, if the incident light is divided into one beam, the optical semiconductor device of the present invention is placed on one side, and the optical semiconductor device of the present invention is placed on one side, several wavelengths are propagated to the other side. When the light is recombined at the point where it is controlled to shift by half a wavelength using an optical semiconductor device, the light becomes zero at the joining point and becomes an optical switch. That is, by changing the refractive index in the medium and changing the propagation path of light, for example, things that strengthen each other become destructive, and the interference conditions can be changed.

Furthermore, when light attempts to exit from a medium with a high refractive index, total internal reflection occurs, but as the refractive indexes become closer to each other, it becomes easier to transmit. Therefore, by utilizing this property, it is possible to switch from total reflection to transmission by injecting electrons under the condition of almost total reflection, and it can be used as an optical switch. . Furthermore, holes may be used instead of electrons as carriers to be injected.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, since the leading wave layer is composed of quantum boxes or quantum wires, the absorption coefficient has a larger absolute value than that of ordinary semiconductors, and the transparency of the medium can be improved by injecting electrons. It is possible to provide an optical semiconductor device in which the resistance is significantly increased. Moreover, it is possible to provide a thermally stable device with characteristics similar to those at cryogenic temperatures. Also,
It is possible to provide a device with a steep spectrum that has a large absorption coefficient at a specific wavelength.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an optical semiconductor device according to the present invention, FIG. 2 is a diagram showing a comparison example of photon energy and light absorption coefficient of a normal semiconductor and a quantum structure semiconductor, and FIG. 3 is a diagram of an FET.
A diagram for explaining an example of an electron injection method for a structure, FIG. 4 is a diagram for explaining an example of an electron injection method for a diode structure, FIG. 5 is a diagram for explaining an example of a stacked optical semiconductor device, FIG. 6 is a diagram for explaining differences in characteristics depending on temperature. 1... Optical waveguide layer, 2 and 3... Cladding layer, 4...
Quantum box, 5...Quantum wire.

Claims (3)

[Claims] (1) An optical semiconductor device characterized in that a quantum box structure layer is used as an optical waveguide layer, and the optical characteristics are controlled by injecting electrons or holes into the optical waveguide layer. (2) An optical semiconductor device characterized in that a layer having a quantum wire structure is used as an optical waveguide layer, and the optical characteristics are controlled by injecting electrons or holes into the optical waveguide layer. (3) The optical semiconductor device according to claim 1 or 2, comprising multiple optical waveguide layers.