JPH06123908A - Shift register having optical bistable element - Google Patents

Abstract

PURPOSE:To simplify a wiring structure, to integrate plural optical bistable element to a high density and to enable high-speed operation by shifting the light radiated from the optical bistable elements in a light emitting state via optical waveguide means to the other arbitrary optical bistable elements. CONSTITUTION:The plural optical bistable elements are disposed on one n-InP semiconductor substrate 100 and optical waveguide layer 101 consisting of n- InGaAsP is formed on this n-InP semiconductor subtrate 100. The optical waveguide layer 101 is commonly used as an emitter layer of the phototransistors of the respective optical bistable elements. The state of the optical bistable elements changes to the light emitting state in spite of incidence of light of a relatively low set power if the bias voltage to be applied to anode electrodes is increased. The state of the optical bistable elements, therefore, changes to the light emitting state when an extremely high bias voltage is applied to the optical bistable elements. Then, the light emitting state is shifted from the optical bistable elements in the light emitting state to the desired optical bistable elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift register for shifting an optical signal, and more particularly to a shift register having an optical bistable element. Such shift registers are used in the field of optoelectronics.

[0002]

2. Description of the Related Art A device in which a plurality of elements each having a bistable state (bistable element) are arranged and the state of one element is sequentially transferred to another adjacent element is generally a shift device. It is called a register. A flip-flop circuit and a charge-coupled device (CCD) are known as a plurality of elements that are in an electrically bistable state.

Several types of shift registers have been proposed as shift registers having a plurality of optically bistable elements. For example, it is reported in the Proceedings of the 1990 IEICE Spring National Convention, pp. 4-23, the Institute of Electronics, Information and Communication Engineers Technical Report OQE89-141, and the 1990 Lecture Meeting of the Applied Physics Society, Autumn Meeting. ing.

FIG. 8 shows a conventional shift register having a plurality of optically bistable elements. This shift register includes a p-GaAs substrate and a plurality of light emitting thyristors arranged on the p-GaAs substrate. Each of the light emitting thyristors has a first p-GaAs layer (anode layer), a first n-GaAs layer, a second p-GaAs layer (gate layer), which are sequentially deposited on a p-GaAs substrate. And a second n-GaAs layer (cathode layer). A gate electrode is provided on the second p-GaAs layer of each light emitting thyristor. Each gate electrode has
A voltage of −5 V is supplied from the DC power supply V _GA through the resistor network. The second n of each light emitting thyristor
A cathode electrode is provided on the -GaAs layer. Three-phase clock voltages φ1 and
φ2 and φ3 are applied. In addition, the p-GaAs substrate is grounded, whereby the first p-type of each light emitting thyristor is connected.
A voltage of zero volt is supplied to the GaAs layer (anode layer).

When the clock voltage φ3 applied to the cathode electrode of the third light emitting thyristor rises from a low level to a high level at a certain time, the light emitting thyristor is turned on and light emission starts. Then, the potentials of the gate electrode and the second p-GaAs layer (gate layer) become the first potential.
P-GaAs layer (anode layer) potential (zero volt)
Is almost equal to. Therefore, a current flows between the gate layer and the cathode layer of the third light emitting thyristor via the resistance network. As a result, the potential distributed in a stepwise manner with the potential (about zero volt) of the gate layer of the third light-emitting thyristor in the on-state as a peak is at each gate electrode
Applied to zero. Thus, the voltage that decreases with distance from the third light emitting thyristor causes the gate electrode 800
Is supplied to each. Specifically, the voltage applied to the gate electrode 800 of the fourth light emitting thyristor is higher than the voltage applied to the gate electrode 800 of the first light emitting thyristor.

At a next time, when φ1 becomes high level, a high voltage is applied to the cathode electrodes of the first and fourth light emitting thyristors. However, only the fourth light emitting thyristor, in which the potential of the gate electrode is relatively high, is turned on,
Light emission starts. The first with a relatively low potential of the gate electrode
The light-emitting thyristor does not turn on.

After that, when φ1 is changed from the high level to the low level, the third light emitting thyristor is turned off and the light emission is stopped. Thus, the light emitting state of the thyristor is "shifted" from the third light emitting thyristor to the fourth light emitting thyristor.

[0008]

However, in the above-mentioned conventional shift register, it is necessary to provide a gate electrode for each light emitting thyristor, and a complicated resistor network must be formed on the substrate. As described above, it is difficult to integrate a large number of light emitting thyristors because the area occupied by the elements other than the light emitting thyristor on the substrate is large.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a shift register having an optical bistable element, which is suitable for high integration.

[0010]

A shift register according to the present invention comprises a plurality of first electrodes and at least one second electrode.
Voltage applying means for applying a voltage to each of the plurality of first electrodes, a plurality of optical bistable elements connected to each of the plurality of first electrodes and the at least one second electrode, A shift register comprising optical waveguide means for optically coupling the plurality of optical bistable elements to each other, each of the plurality of optical bistable elements corresponding to one of the plurality of first electrodes. A phototransistor and a light emitting element connected in series are provided between a first electrode and the at least one second electrode, the phototransistor including the corresponding first electrode and the at least one second electrode. When light is received while a predetermined voltage is applied between the electrodes, the first
An electrical non-conduction state between the electrode and the second electrode is changed to an electrical conduction state, whereby a current is passed through the light emitting element, and the light emitting element emits light when a current flows through the light emitting element. Thereby providing a portion of the light to the phototransistor while providing a further portion of the light to the phototransistor of another optical bistable element via the optical waveguide means,
This solves the above problem.

In one embodiment, the phototransistor is a heterojunction phototransistor having an emitter region, a base region, and a collector region, and the light emitting device is a heterojunction phototransistor of the heterojunction phototransistor. It is a diode having a terminal connected to either one.

In one embodiment, the optical waveguide means has a semiconductor layer capable of guiding the light emitted by the light emitting element, and the plurality of optical bistable elements are arranged on the semiconductor layer. ing.

In one embodiment, the semiconductor layer is formed on a semiconductor substrate. In one embodiment, the semiconductor layer is a semiconductor substrate having a reflective film formed on the back surface.

In one embodiment, the light guiding means has a semiconductor layer capable of guiding the light emitted by the light emitting element, and the semiconductor layer also serves as the emitter regions of the plurality of phototransistors. There is.

In one embodiment, the light guiding means has a semiconductor layer capable of guiding the light emitted by the light emitting element, and the semiconductor layer also serves as a collector region of the plurality of phototransistors. There is.

In one embodiment, the semiconductor layer has an energy gap larger than the energy of light emitted by the light emitting element.

[0017]

The series connection of the heterojunction phototransistor and the light emitting diode is an optical bistable element having an on and off bistable state, and emits light when it is on. When the incident light enters the first optical bistable element and is turned on, the light exits from the surface of the substrate as signal light and at the same time propagates through the optical waveguide layer and enters the adjacent optical bistable element. Light propagates because the energy gap of the optical waveguide layer is set larger than the energy gap of the light emitting diode in the optical bistable element. At this time, the bias voltage is first set by the three-phase clock
If the optical bistable element is added so that it travels in either the row direction or the column direction, only the second optical bistable element adjacent in the traveling direction receives the propagating light and is turned on. The other three adjacent optical bistable elements do not turn on because no bias voltage is applied. An element separated from the first optical bistable element by two in the traveling direction of the clock voltage is not turned on due to the propagation of light from the first optical bistable element because no voltage is applied. Since the bias voltage is applied to the elements located at three positions,
Although it is possible to shift to the ON state by receiving the propagating light from the optical bistable element of, this can be avoided by controlling the bias voltage. In this way, the optical information incident on a certain position can be shifted in any direction.
The direction in which the optical signal is transferred can be changed depending on whether the clock voltage is sent in the row direction or the column direction.

[0018]

EXAMPLES The present invention will be described below with reference to examples.

(Embodiment 1) FIG. 1 shows a sectional view of an embodiment of a shift register according to the present invention, and FIG. 2 shows an equivalent circuit thereof. First, the outline of the present embodiment will be described with reference to FIG.

As is apparent from FIG. 2, this shift register has a plurality of first electrodes (anode electrodes) and one cathode electrode (second electrode). A predetermined bias voltage (clock voltage) is applied to each of the plurality of anode electrodes by a voltage applying unit not shown in FIG. A plurality of optical bistable elements are connected between each of the plurality of anode electrodes and the cathode electrode as shown in FIG.

Each optical bistable element is an element that can be in either a light emitting state or a non-light emitting state. For example, the light emission state is a binary logic “High” state (logic “high” state).
Also, the non-emissive state may be associated with a binary logic "Low" state (logic "low" state). These optical bistable elements are optically coupled to each other by an optical waveguide layer not shown in FIG. According to the present invention, the "light emitting state" of the optical bistable element is shifted through the optical waveguide layer to another optical bistable element to which a predetermined voltage is applied. That is, the light emitted from the optical bistable element in the light emitting state is
Optically propagates to other thyristors. In this respect, the shift register according to the present invention is significantly different from the above-mentioned prior art. According to the above-mentioned conventional technique, the light emitted from the light emitting thyristor in the light emitting state has no optical effect on other light emitting thyristors. The shift of the light emitting state is performed electrically.

Each of the optical bistable elements used in this example is provided with a light emitting element connected in series between the corresponding anode and cathode electrodes (indicated by the symbol "diode" in FIG. 2). ) And a phototransistor (given the symbol “bipolar transistor” in FIG. 2). This phototransistor changes from an electrically non-conducting state to an electrically conducting state when a base receives a light of a predetermined amount or more while a voltage of a predetermined value or more is applied between the anode electrode and the cathode electrode. Changes to. The relationship between the voltage of the predetermined value and the light amount of the predetermined value is shown in FIG.

This phototransistor changes the state between the anode electrode and the cathode electrode from the electrically non-conducting state to the electrically conducting state, thereby causing a current to flow to the light emitting element connected in series to the phototransistor. do. This light emitting element is an element that converts current energy into light energy. A light emitting diode (LED) is used in the shift register of this embodiment. When a predetermined voltage is applied between the anode electrode and the cathode electrode, and a current flows between the anode electrode and the cathode electrode due to the action of the phototransistor that receives light, the corresponding light emitting element emits light. To do.

A part of the light emitted from the light emitting element is given to the phototransistor (base) of the optical bistable element to which the light emitting element belongs. As long as a predetermined voltage is applied between the anode electrode and the cathode electrode, a current flows between the anode electrode and the cathode electrode through the light emitting element and the phototransistor, so that light is emitted from the light emitting element. to continue. Even when the external light that changes the phototransistor from the electrically non-conducting state to the electrically conducting state is stopped, the light from the light emitting element maintains the phototransistor in the conducting state and the light is emitted from the light emitting element. The state is maintained. In this way, the optical stable state of the optical bistable element continues (maintaining the stable state by positive feedback) until the application of a voltage equal to or higher than a predetermined value between the anode electrode and the cathode electrode is stopped.

Another part of the light emitted from the light emitting element is
It can also be provided to the phototransistors of other optical bistable elements via an optical waveguiding layer not shown in FIG. The intensity of light emitted from a particular light emitting element is attenuated during its propagation through the optical waveguide layer. Each phototransistor receiving such attenuated light will change from an electrically non-conducting state to an electrically conducting state if a sufficiently large voltage is applied to the optical bistable element containing the phototransistor. You can The intensity of light incident on the phototransistor is shown in the graph of FIG. By adjusting the magnitude of each voltage applied to each of the plurality of anode electrodes, the phototransistor of the desired optical bistable element can be changed from the electrically non-conducting state to the electrically conducting state. In this respect, the present invention is significantly different from the above-mentioned prior art.

Next, the structure of this embodiment will be described in detail with reference to FIG. As shown in FIG. 1, in the shift register of this embodiment, a plurality of optical bistable elements are arranged on one n-InP semiconductor substrate 100. n-I
An optical waveguide layer (thickness: 1.5 μm) 101 made of n-InGaAsP is formed on the nP semiconductor substrate 100, and the optical waveguide layer 101 also serves as the emitter layer of the phototransistor of each optical bistable element. ing.

Each optical bistable element has a phototransistor and a light emitting diode as described above. The phototransistor of the present embodiment has an emitter layer (optical waveguide layer 10
1), a base layer (thickness: 0.3 μm) 102 made of p-InGaAsP on the emitter layer, and a base layer 102.
N-InP collector layer (thickness: 0.6 μm
m) 103 and a heterojunction phototransistor. The light emitting diode has an n-I on the collector layer 103.
n-clad layer made of nP (thickness: 0.6 μm) 10
4, an active layer (thickness: 0.15 μm) 105 made of InGaAsP on the n-clad layer 104, and an active layer 10.
P-cladding layer made of p-InP on (5) (thickness: 0.
8 μm) 106 and p-In on the p-clad layer 106.
Cap layer made of GaAsP (thickness: 0.1 μm) 1
And 07.

Such a structure is manufactured, for example, as follows. First, on the n-InP semiconductor substrate 100, the optical waveguide layer 101 made of n-InGaAsP, p-, is formed by the MBE method, the MOCVD method, the LPE method, or the like.
A base layer 102 made of InGaAsP and n-InP
Collector layer 103 made of n-InP and n-
Clad layer 104 and active layer 1 made of InGaAsP
05, a p-clad layer 106 made of p-InP,
A cap layer 107 made of p-InGaAsP is continuously grown.

After that, a predetermined portion of the laminated structure composed of the above layers is removed by using the photolithography technique and the etching technique, whereby the structure as shown in FIG. 1 is obtained. The portion removed by etching (separation groove 108) has a width of, for example, about 40 μm, and the portion not removed (optical bistable element) has a width of, for example, about 20 μm.
Is. In this case, each optical bistable element is 20 μm × 20
It has a size of μm and is arranged at a pitch of 60 μm.

After the above structure is formed, each cap layer 1
The anode electrode 109 is formed on the optical waveguide layer 101.
One cathode electrode 110 is formed on the top. These electrodes 109 and 110 are preferably formed from a metallic material. The surfaces of the optical waveguide layer 101 and the optical bistable element are covered with a polyimide 111 in order to protect each optical bistable element and the electrodes 109 and 110 from the outside air.
Further, the anode electrodes 109 are respectively connected to the clock line 112, and via the clock line 112,
A three-phase clock signal, for example, is applied to the anode electrode 109.

In the shift register shown in FIG. 1, the wavelength of light emitted from the light emitting element is determined by the energy band gap of the active layer 105 of the light emitting diode. Since the active layer 105 of this embodiment is made of InGaAsP, the wavelength of emitted light is about 1.3 μm. In addition, the heterojunction phototransistor of this embodiment is InGaAs
Since it has the base layer 102 made of P, about 1.3 μm
Efficiently absorbs light having a wavelength of, and changes from an electrically non-conducting state to an electrically conducting state. Therefore, the light emitted from the light emitting diode can efficiently change the state of the heterojunction phototransistor to the electrically conductive state. In order to make the heterojunction phototransistor conductive by the light from the light emitting diode, the material of the active layer 105 and the base layer 102 are arranged so that the phototransistor can efficiently absorb the light emitted from the light emitting diode.
Are selected from various semiconductors. Active layer 105
The energy bandgap of is preferably equal to or larger than the energy bandgap of the base layer 102. In this embodiment, the active layer 105 and the base layer 102
Are formed of p-InGaAsP, and both have the same energy band gap.

On the other hand, the optical waveguide layer 101 is made of a material which hardly absorbs light from the light emitting element. That is,
The energy bandgap of the optical waveguide layer 101 is the active layer 1
To be larger than the energy band gap of 05,
Each material of the optical waveguide layer 101 and the active layer 105 is selected.

In the shift register shown in FIG. 1, the optical waveguide layer 102 is formed on the n-InP substrate 100. Instead of such a configuration, a configuration in which the substrate itself is used as a waveguide layer may be adopted. In such a configuration, it is preferable to provide a reflective film on the back surface of the substrate for reflecting the light emitted from the light emitting element above the substrate on the back surface of the substrate. As the reflection film, a high reflectance film provided on the end face of the semiconductor laser is suitable.

FIG. 3 shows the waveform of the voltage (clock voltage) applied to the anode electrode 109. For the first optical bistable element to which the clock voltage φ1 is applied,
When an optical signal is input from the outside when the clock voltage φ1 is at a high level (1.1 V, for example), the first optical bistable element is in a light emitting state. Even if the input of the optical signal from the outside is stopped, the light emitting state is maintained as described above. A part of the light emitted from the first optical bistable element propagates in the optical waveguide layer 101. A part of the light propagating through the optical waveguide layer 101 is generated by the second and third portions adjacent to the first optical bistable element.
Incident on the optical bistable element of. At this time, the clock voltage φ3 applied to the third optical bistable element is low level (for example, 0 volt), and the clock voltage φ2 applied to the second optical bistable element is high level. (For example,
1.1 volt). Therefore, the light emitted from the first optical bistable element causes the second optical bistable element to change to the light emitting state, while the third optical bistable element remains in the non-light emitting state. After that, when the clock voltage φ1 becomes low level, the first optical bistable element returns to the non-light emitting state. In this way, the light emission state of the first optical bistable element is shifted to the second optical bistable element.

Among the optical bistable elements located at two or more positions away from the first optical bistable element, the optical bistable element to which the clock voltage φ1 is applied is radiated from the first optical bistable element. Almost no incident light is incident. This is the optical waveguide layer 1
This is because the light is sufficiently attenuated while propagating through 01 so that the phototransistor of such an optical bistable element cannot be changed to the conductive state. The light energy (set power) required to change the phototransistor of the optical bistable element to the conductive state depends on the bias voltage (clock voltage φj) applied to the anode electrode.
As can be seen from FIG. 4, when the bias voltage is increased,
Even if light with a relatively low set power is incident, the state of the optical bistable element changes to a light emitting state. Even if the optical bistable element is located at a long distance from the optical bistable element that is emitting light,
When an extremely high bias voltage is applied to the optical bistable element, the optical bistable element can be changed to a light emitting state.

In this way, by controlling the magnitude of the bias voltage, the light emitting state can be shifted from the light bistable element in the light emitting state to the desired light bistable element. In this way, in the shift register of this embodiment in which a plurality of optical bistable elements are arranged in an array, an optical signal can be transferred from any optical bistable element to any other optical bistable element.

When a normal PN junction type light emitting diode is used as the light emitting element, the bias voltage needs to be 0.7 V or higher. This is because when a bias voltage lower than that is applied, the light emitting element does not emit light even if the phototransistor is turned on. In such a case, the bias voltage is preferably 0.8 V or more in order to maintain the light emitting state stably by setting the gain of the optical bistable element to 1 or more.
Further, if the bias voltage exceeds a certain value and becomes too large, even a slight leakage of light incident from the outside may erroneously change the light emitting state. In the above embodiment, such a problem can be avoided if the bias voltage is 1.5 V or less. In the above embodiment, the bias voltage is
It is preferable that the voltage is in the range of 0.9 V or more and 1.1 V or less. However, since the optimum value of the bias voltage changes depending on the optical coupling ratio between the light emitting element and the phototransistor, it may change depending on the size of the element and the processing method.

In order to change the optical bistable element from the non-conducting state to the conducting state, it is necessary to apply a bias voltage to the anode for a certain time or longer. When the clock voltage as shown in FIG. 3 is used as the bias voltage to be applied, if the clock width is 2 microseconds or more, the adjacent optical bistable element can be surely changed to the conductive state. Therefore, according to the present embodiment, it is possible to perform high-speed signal shift.

(Embodiment 2) FIG. 5 shows another shift register according to the present invention. In the shift register of this embodiment, optical bistable elements are arranged two-dimensionally. In FIG. 5, 3 × 3 = 9 optical bistable elements are arranged in rows and columns. FIG. 6 shows an equivalent circuit of this shift register. In FIG. 6, the optical bistable element located at the Nth row and the Mth column is denoted by (N, M).

First, the configuration of the shift register will be described with reference to FIG. This shift register has nine first electrodes (anode electrodes) and three cathode electrodes (second electrodes). Via the first word line 601a, the optical bistable elements (1, 1), (1, 2) and (1,
The clock voltage φ1 is applied to the anode electrode of 3). A clock voltage φ2 is applied to the anode electrodes of the optical bistable elements (2,1), (2,2) and (2,3) via the second word line 601b. The optical bistable element (3, 1) via the third word line 601c,
A clock voltage φ3 is applied to the anode electrodes of (3, 2) and (3, 3).

Also, via the first bit line 602a, the optical bistable elements (1, 3), (2, 3) and (3,
A clock voltage φ4 is applied to the cathode electrode of 3). A clock voltage φ5 is applied to the cathode electrodes of the optical bistable elements (1, 2), (2, 2) and (3, 2) via the second bit line 602b. An optical bistable element (1, 1) via a third bit line 602c,
A clock voltage φ6 is applied to the cathode electrodes of (2,1) and (3,1). Clock voltage φ1, φ2, φ
3, φ4, φ5 and φ6 have waveforms as shown in FIG.

According to this embodiment, by adjusting the timing of applying the clock voltage to the bit line 602 and the word line 601, and adjusting the value of the clock voltage, the optical signal transfer can be performed two-dimensionally. . An example of the operation of this shift register will be described below.

First, when the clock voltage φ1 is at a high level, an optical signal is externally input to the optical bistable element (1, 1). Then, the phototransistor of the optical bistable element (1, 1) becomes conductive, and the light emitting element connected in series to the phototransistor starts emitting light. After the light emitted from the light emitting element enters the optical waveguide layer,
The light propagates through the optical waveguide layer and is incident on the surrounding optical bistable element. When the clock voltages φ1, φ2 and φ3 as shown in FIG. 3 are applied to the word line 601, the optical bistable element (2, 1) changes to the conductive state and starts emitting light. At this point, no voltage pulse is applied to the bit line 602. Therefore, the optical signal is transferred in the column direction.

When a negative voltage pulse is applied to the bit line 602, the light emission state is changed to the optical bistable element (1, 2).
Transferred to. At this time, no voltage pulse is applied to the word line 601. In this case, the optical signal is transferred in the row direction.

It should be noted that the optical bistable elements other than the optical bistable element adjacent to the optical bistable element (1, 1) do not emit light.
The value of the applied voltage is adjusted in consideration of the relationship shown in the graph of FIG.

Next, the structure of this embodiment will be described in detail with reference to FIG. FIG. 7 is a sectional view taken along the line AA ′ of FIG.

As shown in FIG. 7, in the shift register of this embodiment, a plurality of optical bistable elements are integrated into one n-type.
It is arranged on the InP semiconductor substrate 700. n-InP
An optical waveguide layer (thickness: 1.5 μm) 702 made of n-InGaAsP is formed on the semiconductor substrate 700. The optical waveguide layer 702 also serves as the emitter layer of the phototransistor of each optical bistable element. There is.

Each optical bistable element has a phototransistor and a light emitting diode as described above. The phototransistor of this embodiment has an emitter layer (optical waveguide layer 70).
2), a base layer (thickness: 0.3 μm) 703 made of p-InGaAsP on the emitter layer, and a base layer 703.
N-InP collector layer (thickness: 0.6 μm
m) 704 and a heterojunction phototransistor. The light emitting diode has an n-I on the collector layer 704.
n-clad layer made of nP (thickness: 0.6 μm) 70
5, an active layer (thickness: 0.15 μm) 706 made of InGaAsP on the n-clad layer 705, and an active layer 70.
P-cladding layer made of p-InP (thickness: 0.
8 μm) 707 and p-In on the p-clad layer 707.
GaAsP cap layer (thickness: 0.1 μm) 7
08 and. The optical waveguide layer 702 is provided with a lattice-shaped insulating layer 701, and the insulating layer 702 electrically separates the optical bistable elements from each other.

This embodiment is manufactured, for example, using a method similar to the method of manufacturing the first embodiment.

[0050]

According to the shift register of the present invention, light emitted from an optical bistable element in a light emitting state among a plurality of optical bistable elements having a phototransistor and a light emitting element interconnected in series is used. , Can be shifted to any other optical bistable element via the optical waveguide means. Therefore, the wiring structure is simplified as compared with the conventional technique. As a result, a plurality of optical bistable elements can be integrated one-dimensionally or two-dimensionally with high density.

Further, since the shift register of the present invention can transfer the light emitting state of the optical bistable element by a short voltage pulse, it can operate at a high speed. Also,
It is possible to easily shift the light emitting state from one position to another arbitrary position. Therefore, the present invention is expected to create new uses for shift registers.

[Brief description of drawings]

FIG. 1 is a sectional view of a shift register according to the present invention.

FIG. 2 is a diagram showing an equivalent circuit of the shift register shown in FIG.

3 is a diagram showing a waveform of a voltage (clock voltage) applied to an anode electrode of the shift register shown in FIG.

FIG. 4 is a characteristic diagram showing a relationship between set power and bias voltage.

FIG. 5 is a diagram showing another shift register according to the present invention.

6 is a diagram showing an equivalent circuit of the shift register shown in FIG.

7 is a cross-sectional view of the shift register shown in FIG.

FIG. 8 is a sectional view showing a conventional technique.

[Explanation of symbols]

100 n-InP semiconductor substrate 101 Optical waveguide layer (emitter layer) made of n-InGaAsP 102 Base layer made of p-InGaAsP 103 Collector layer made of n-InP 104 n-clad layer made of n-InP 105 Active made of InGaAsP Layer 106 p-clad layer made of p-InP, 107 cap layer made of p-InGaAsP

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location H01L 31/10 31/14 A 7210-4M 33/00 A 7514-4M H03K 3/42 8124-5J

Claims (8)

[Claims] 1. A plurality of first electrodes, at least one second electrode, voltage applying means for applying a voltage to each of the plurality of first electrodes, and each of the plurality of first electrodes. A shift register comprising: a plurality of optical bistable elements connected to the at least one second electrode; and an optical waveguide means for optically coupling the plurality of optical bistable elements to each other. Each of the optical bistable elements comprises a phototransistor and a light emitting element connected in series between a corresponding first electrode of the plurality of first electrodes and the at least one second electrode. The phototransistor receives the light when a predetermined voltage is applied between the corresponding first electrode and the at least one second electrode, and the phototransistor receives the light from the first electrode and the second electrode. Between electrically non-conducting state and electrically conducting A state, thereby causing a current to flow through the light emitting element, which emits light when a current flows through the light emitting element, thereby providing a portion of the light to the phototransistor while A shift register for giving another part of light to a phototransistor of another optical bistable element via the optical waveguide means. 2. The phototransistor is a heterojunction phototransistor having an emitter region, a base region, and a collector region, and the light emitting device is one of the collector region and the emitter region of the heterojunction phototransistor. 2. The shift register according to claim 1, which is a diode having a terminal connected to. 3. The light guiding means has a semiconductor layer capable of guiding light emitted by the light emitting element, and the plurality of optical bistable elements are arranged on the semiconductor layer. The shift register according to item 1. 4. The shift register according to claim 3, wherein the semiconductor layer is formed on a semiconductor substrate. 5. The shift register according to claim 3, wherein the semiconductor layer is a semiconductor substrate having a reflective film formed on a back surface thereof. 6. The light guiding means has a semiconductor layer capable of guiding light emitted from the light emitting element, and the semiconductor layer also serves as an emitter region of the plurality of phototransistors. 2. The shift register described in 2. 7. The optical waveguide means has a semiconductor layer capable of guiding light emitted from the light emitting element, and the semiconductor layer also serves as a collector region of the plurality of phototransistors. 2. The shift register described in 2. 8. The shift register according to claim 6, wherein the semiconductor layer has an energy gap larger than the energy of light emitted by the light emitting element.