JPH09213972A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a resistance fuse element which has a symmetrical characteristic against the polarity of signal voltage and a continuity resistance characteristic in the specified range of low voltage and has also a quietly wide and flat area of low current in a high voltage area, and a resistance fuse network for picture processor using the fuse element, in a resistance fuse element having a negative resistance characteristic. SOLUTION: First and second boundary effect transistors 1 and 2 are connected respectively to both terminals of a resonant tunnel diode 3 which has a symmetrical characteristic against the polarity of applied voltage, and the gate electrode of the first transistor 1, the second transistor 2 and the diode 4 are connected with each other at the connection point, and at the same time the gate electrode of the transistor 2 is connected with the connection point between the diode 3 and the transistor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a negative resistance characteristic and its application, and more particularly to a resistive fuse element having symmetrical voltage-current characteristics with respect to an applied voltage and an image processing apparatus for the element. Regarding the application of.

[0002]

2. Description of the Related Art FIG. 6 (a) is a sectional view of a negative resistance element called a resonant tunneling diode using GaAs and AlGaAs, and FIG. 6 (b) is its conduction band diagram. The two intrinsic AlGaAs layers 4 function as barrier layers, and the intermediate intrinsic GaAs quantum well layer 5
To form a quantum level 9. In this structure collector 7
When the voltage applied to is changed, the quantum level 9 in the quantum well changes accordingly, and the energy of the electron on the emitter 8 side (electron exists from the conduction band edge to near Fermi level 10) and the quantum level A large current flows when positions 9 match. Therefore, a differential negative resistance as shown in FIG. 7 appears in the current-voltage characteristic. Utilizing this differential negative resistance, there has been proposed a super-high frequency oscillation that reaches from microwave to millimeter wave band, a functional logic element combined with a transistor, and the like. (Resonant tunnel diodes include interband resonant tunnel diodes that use valence band levels, but the following problems are the same.) These diodes are basically symmetrical structures. ,
The current-voltage characteristics are symmetrical with respect to the positive and negative polarities of the applied voltage, and an application that cannot be performed with an essentially asymmetrical Esaki diode or the like occurs. One of them is the network shown in FIG. This is a circuit network called a resistance fuse network for the initial visual process, and image information can be restored from a noisy signal. That is, the network of FIG. 8 has a feature that only the discontinuous portion (edge portion) of the image itself is left and the noise component can be suppressed. In FIG. 8, d _ij and f _ij respectively indicate the input and output voltages at the point ij, and FIG. 9 shows the ideal characteristics of the resistance fuse element used in this network. (JG Harris, C. Koch, and J. Lou, "A two-d
imensional analog VLSI circuit for detecting disco
ntinuities in earlyvision, "Science, vol.248, pp120
9-1210, 1990).

The resistive fuse element used in the above network acts as a resistor when the voltage difference between signals at adjacent points in FIG. 8 is smaller than a certain value, and the output is smoothed. The connection is broken and no smoothing occurs. As a result, noise can be suppressed while leaving the discontinuous portion of the edge portion of the image. As this resistive fuse, one using a resonant tunnel diode (between bands) has been reported (HJLevy, DACollins,
and TCMcGill, "Extracting discontinuities inearl
y vision with networks of resonant tunneling diode
s, "Proc.1992IEEEInt. Symp. Circuits and Systems,
pp.2041-2044). In this case, the difference between the current-voltage characteristics of the resonance tunnel element and the resistance fuse becomes a problem. That is,
The problem with an actual resonant tunneling device is that non-resonant current components increase in the high voltage portion, causing a rapid current flow.
As a result, the voltage range that can be used as the resistance fuse is limited, and there is a problem in that the noise reduction effect is quite limited.

On the other hand, a series connection circuit of a resonance tunnel diode and a field effect transistor as shown in FIG. 10 is known as a negative resistance element having a flat valley current characteristic while suppressing an increase in current on the high voltage side. (Technica
l Digest of the 1995 International Electron Deveic
e Meeting, p.379). FIG. 11 is a load curve diagram of the circuit shown in FIG. The operating principle of this circuit will be described with reference to FIG. This circuit utilizes the fact that the source potential of the field effect transistor changes due to the switching operation of the resonant tunnel diode. Here, the switching of the diode means the transition of the voltage across the diode from the low voltage state shown at point a in FIG. 11 to the high voltage state shown at point b in FIG. 11, that is, the valley voltage position of the negative resistance characteristic. Means Since the effective gate voltage of the field effect transistor is the potential difference between the gate potential and the source potential, when the diode switches to the high voltage state, the effective gate voltage decreases and the current of the field effect transistor also decreases. Therefore, a flat current-voltage characteristic without increasing the current on the high voltage side can be realized. However, in this case, there is a problem that the current-voltage characteristics are asymmetric with respect to the positive and negative polarities of the applied voltage, and the above-mentioned application requiring symmetry cannot be applied.

[0005]

As described above, in the resistance fuse element using the conventionally known resonant tunneling diode, the operating voltage range is limited due to the current rise on the high voltage side, and this high voltage range is limited. In a circuit configuration in which a resonant tunneling diode that suppresses a current rise in a voltage region and a field effect transistor are connected in series, asymmetric characteristics occur depending on whether the polarity of the applied voltage is positive or negative, which is not suitable as a resistance fuse for reducing noise of the image information. It was a proper property.

In the present invention, the above-mentioned problems are solved, and a negative resistance two-terminal element that is symmetrical with respect to the positive and negative polarities of the terminal voltage and has a sufficiently wide and flat low current region on the high voltage side, and Another object of the present invention is to provide a semiconductor device using the resistance fuse network for the initial visual process.

[0007]

In order to achieve the above object, in claim 1, a diode having an N-type negative differential resistance characteristic for both positive and negative polarities and a negative threshold value are provided. It has two field-effect transistors, the source or drain electrode of the first transistor is connected to one terminal of the diode, and the source or drain electrode of the second transistor is to the other terminal of the diode. Connected, the gate electrode of the first transistor is connected to the connection point of the second transistor and the diode, the gate electrode of the second transistor is connected to the connection point of the first transistor and the diode, this connection A resistive fuse element that exhibits symmetrical characteristics with respect to the polarity of the applied voltage and has a flat low current region even in the high voltage region And it represents.

According to a second aspect of the present invention, a resistance fuse element constituted by connecting the diode having the negative differential resistance characteristic and a field effect transistor in series is connected in a two-dimensional network, and the connection point is formed. The resistance fuse network for the initial visual process is constructed by inputting a signal voltage via the resistance component and further taking out an output from the connection point of the network.

As described above, according to the present invention, the field effect transistors are provided at both ends of the diode having the negative differential resistance characteristic, and the gate electrodes of these field effect transistors are connected to the opposite terminals of the diode. Since it is connected, it is symmetric with respect to the positive and negative of the voltage applied to both terminals of the resistive fuse element, and it is possible to obtain a negative resistance characteristic with a sufficiently wide and flat low current region on the high voltage side. Have

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings.

[0011]

First Embodiment FIG. 1 shows a first embodiment of the present invention. This is a combination of a resonance tunnel diode having a current-voltage characteristic as shown in FIG. 2 and a depletion type field effect transistor having a current-voltage characteristic as shown in FIG. Here, the threshold voltage of the field effect transistor is -0.5V. Since this circuit has a symmetrical structure, it is obvious that the circuit exhibits symmetrical characteristics with respect to the positive and negative polarities of the applied voltage at the terminals A and B in FIG. Therefore, here, the operation will be described in the case where the voltage V _B having a positive polarity with respect to the voltage V _{A of the} terminal A is applied to the terminal B, but the reverse case is also the same. In this case, the gate voltage of the field effect transistor 1 is always a positive value with respect to the applied voltage V _A of the terminal A,
Since the field effect transistor 1 is in the conductive state, its conductance is sufficiently larger than that of the resonance tunnel diode or the field effect transistor 2. Therefore, in this direction, the influence on the current-voltage characteristics of the circuit of the field effect transistor 1 is always small and can be almost ignored. Here, consider the current-voltage characteristic when the voltage applied to the resonant tunnel diode is sufficiently small. At this time, the resonance tunnel diode is in the region (i) of FIG. 2, and the gate voltage applied to the field effect transistor 2 has a negative polarity with respect to the voltage V _B applied to the terminal B, but the resonance Since the tunnel diode 3 is conductive, its absolute value is small. Therefore, since the gate bias voltage of the field effect transistor 2 is small, the field effect transistor 2 is in a substantially conductive state, its conductance is large, and the current value of the entire circuit is determined by the conduction resistance in the region (i) of the resonant tunnel diode. Next, the case where the applied voltage increases and the voltage applied to the resonant tunnel diode exceeds the peak voltage, that is, the case where the voltage reaches the negative resistance region will be described. At this time, since the negative resistance portion (ii) of the resonant tunnel diode is unstable, the voltage applied to the diode is near the valley shown by * 1 in FIG.

At this time, the gate voltage of the field effect transistor 2 has a negative value whose absolute value is almost equal to the valley voltage of the resonant tunnel diode (in this case, -0.4).
V). Therefore, in the characteristic of the field effect transistor 2, the gate voltage V _g changes from the curve shown by * 2 in FIG. 3 to the curve shown by the above valley voltage * 3, and the current flowing through the circuit becomes very small. Even if the applied voltage is further increased from here, since the drain conductance of the transistor is small, all the voltages are applied to the field effect transistor 2, and the current value is constant. Therefore, the negative resistance characteristic having a symmetrical and flat low current region as shown in FIG. 4 can be obtained. Since this circuit has two terminals, it is added that the current is determined only by the potential difference between both terminals and does not depend on the absolute value of the voltage applied to those terminals.

[0013]

Second Embodiment FIG. 5 shows a second embodiment of the present invention, which is an image processing apparatus in which the above resistance fuse element is applied to the resistance fuse network for the initial visual process shown in FIG. . The image signal is given through the resistor, and the output is taken from each connection point. As described in the section of the prior art, this network has a feature that it is possible to reduce only noise by leaving the discontinuity (edge) of the image itself from the signal containing noise. The semiconductor device described in the first embodiment of the present invention is close to the ideal resistance fuse characteristic, and can effectively reduce noise as compared with the case where only the resonant tunnel diode is used.

[0014]

As described above, according to the present invention, it is possible to easily obtain a negative resistance element exhibiting symmetrical and wide and flat valley current characteristics. By using this, an extremely highly integrated and high-performance network can be configured, so a circuit system that can directly process image information in real time (a neural network circuit that also incorporates an input / output system using photoelectric conversion elements)
Can be built on one chip.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a resistance fuse element according to a first embodiment.

FIG. 2 is a characteristic diagram of the resonant tunnel diode used in the first embodiment.

3 is a current-voltage characteristic diagram of the field-effect transistor used in Embodiment 1. FIG.

FIG. 4 is a current-voltage characteristic diagram of the resistance fuse element according to the first embodiment.

FIG. 5 is a neural network circuit diagram showing a second embodiment in which the resistance fuse element in the first embodiment is applied to remove noise from an image while holding a discontinuous portion.

FIG. 6A is a sectional view of a resonant tunneling diode and
(b) Conductor diagram.

FIG. 7 is a current-voltage characteristic diagram of a resonant tunnel diode.

FIG. 8 is a circuit diagram of a neural network that removes image noise while retaining discontinuous portions.

FIG. 9 is a current-voltage characteristic diagram of a resistance fuse element.

FIG. 10 is a circuit diagram of a conventional example of a negative resistance element showing a flat valley voltage.

FIG. 11 is a load curve diagram illustrating an operation of a conventional example of a negative resistance element that exhibits a flat valley voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Field effect type transistor 1 2 ... Field effect type transistor 2 3 ... Resonant tunnel diode 4 ... Intrinsic-AlGaAs layer 5 ... Intrinsic-GaAs quantum well layer 6 ... Substrate 7 ... Collector 8 ... Emitter 9 ... Quantum level 10 Fermi level 11 AlGaAs barrier 12 GaAs layer

Claims (2)

[Claims] 1. A diode comprising an N-type negative differential resistance characteristic in both positive and negative directions, and two field effect transistors having a negative threshold value, wherein the source or drain electrode of the first transistor is the diode described above. The source or drain electrode of the second transistor is connected to the other terminal of the diode, and the gate electrode of the first transistor is connected to the second transistor and the diode. And a gate electrode of the second transistor is connected to a connection point between the first transistor and the diode. 2. The semiconductor device according to claim 1 is connected in a two-dimensional network, a signal voltage is input to the connection point via a resistance component, and an output is taken out from the connection point of the network. A semiconductor device characterized by: