JP3280558B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device exhibiting a negative resistance characteristic and an application thereof, and more particularly to a resistance fuse element having a voltage-current characteristic symmetric with respect to an applied voltage and an image processing apparatus of the element. Related to the application.

[0002]

2. Description of the Related Art FIG. 6A is a sectional view of a negative resistance element using GaAs and AlGaAs called a resonance tunnel diode, and FIG. 6B is a conduction band diagram thereof. The two intrinsic AlGaAs layers 4 function as barrier layers, and the intermediate intrinsic GaAs quantum well layers 5
, A quantum level 9 is formed. In this structure the collector 7
When the voltage applied to the quantum well is changed, the quantum level 9 in the quantum well changes accordingly, the energy of the electron on the emitter 8 side (the electron exists from the conduction band edge to the vicinity of the Fermi level 10) and the quantum level When the positions 9 match, a large current flows. Therefore, a differential negative resistance appears in the current-voltage characteristic as shown in FIG. Utilizing this differential negative resistance, there has been proposed an ultra-high frequency oscillation from microwaves to a millimeter wave band, a functional logic element combined with a transistor, and the like. (Note that, among the resonant tunneling diodes, there are interband resonant tunneling diodes using the valence band level, but the following problems are the same.) These diodes are basically symmetric structures. ,
The current-voltage characteristics are symmetric with respect to the polarity of the applied voltage, and there are applications that are not possible with an essentially asymmetric Esaki diode or the like. One of them is the network shown in FIG. This is a network called an initial visual process resistance fuse network, which can restore image information from a signal containing noise. That is, according to the network shown in FIG. 8, 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 represent the input and output voltages at point ij, respectively. FIG. 9 shows the ideal characteristics of the resistance fuse element used in this network. (JGHarris, 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 resistance 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. The use of (inter-band) resonant tunneling diodes as this resistance fuse has been reported (HJ Levy, 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 element is that non-resonant current components increase in the high voltage portion, causing a sudden current to flow.
As a result, the voltage range which can be used as a resistance fuse is limited, and there is a problem that a considerably limited noise reduction effect can be obtained.

On the other hand, a series connection circuit of a resonant tunneling 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 operation principle of this circuit will be described with reference to FIG. This circuit utilizes the fact that the source potential of a field effect transistor changes due to the switching operation of a resonant tunneling diode. Here, the switching of the diode means that the voltage applied to both ends of the diode changes from the low voltage state shown at point a in FIG. 11 to the high voltage state shown at point b in FIG. Means Since the effective gate voltage of a field effect transistor is the potential difference between the gate potential and the source potential, when the diode switches to a 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 an increase in current on the high voltage side can be realized. However, in this case, the current-voltage characteristics are asymmetric with respect to the polarity of the polarity of the applied voltage, and there is a problem that the above-mentioned application requiring symmetry cannot be performed.

[0005]

As described above, the resistance fuse element using the conventionally known resonant tunneling diode has a current increase on the high voltage side, so that the operating voltage range is limited. In a circuit configuration in which a resonant tunneling diode and a field effect transistor in which a current rise in the voltage region is suppressed are connected in series, the polarity of the applied voltage becomes asymmetrical due to the polarity of the polarity, which is not suitable as a resistance fuse for reducing noise of the image information. Proper properties.

According to the present invention, there is provided a negative resistance two-terminal element which solves the above-mentioned problems and is symmetric with respect to the polarity of the terminal voltage polarity and has a sufficiently wide and flat low current region on the high voltage side. It is another object of the present invention to provide a semiconductor device using the above-described resistor fuse network for an initial visual process.

[0007]

In order to achieve the above object, according to the present invention, a diode having an N-type negative differential resistance characteristic for both positive and negative polarities and a negative threshold value are provided. It consists of two field-effect transistors with the source or drain electrode of the first transistor connected to one terminal of the diode, and the source or drain electrode of the second transistor connected 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 Resistive fuse elements that exhibit symmetrical characteristics with respect to the polarity of the applied voltage and have 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 formed by connecting a 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 provided at the connection point. By inputting a signal voltage through a resistance component and extracting an output from a connection point of the network, the resistance fuse network for the initial visual process is formed.

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

[0010]

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

[0011]

Embodiment 1 FIG. 1 shows a first embodiment of the present invention. This is a combination of a resonant tunneling 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 apparent that the circuit shown in FIG. 1 has symmetrical characteristics with respect to the polarity of the polarity of the applied voltage at the terminals A and B. Accordingly, here, the operation thereof will be described for the case of adding the positive polarity and becomes the voltage V _B relative to the voltage V _A of the terminal A to the terminal B, and vice versa. In this case, the gate voltage of the field effect transistor 1 is always a positive value with respect to the voltage _VA applied to the terminal A,
Since the field effect transistor 1 is in a conductive state, its conductance is sufficiently larger than that of the resonance tunnel diode and the field effect transistor 2. Therefore, in this direction, the effect on the current-voltage characteristics of the circuit of the field effect transistor 1 is always small and can be almost ignored. Here, the current-voltage characteristics when the voltage applied to the resonant tunneling diode is sufficiently small will be considered. At this time, the resonant tunneling diode is in the region of the (i) Figure 2, the gate voltage applied to the field effect transistor 2 has a negative polarity with respect to the applied voltage V _B to the terminal B, resonance Since the tunnel diode 3 is in a conductive state, its absolute value is small. Therefore, since the gate bias voltage of the field effect transistor 2 is small, it is almost conductive, its conductance is large, and the current value of the whole circuit is determined by the conductive resistance in the region (i) of the resonant tunneling 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 applied voltage reaches the negative resistance region will be described. At this time, since the negative resistance portion (ii) of the resonant tunneling diode is unstable, the voltage applied to the diode is near the valley indicated by * 1 in FIG.

At this time, the gate voltage of the field effect transistor 2 has a negative value whose absolute value is substantially equal to the valley voltage of the resonant tunneling diode (in this case, -0.4).
V). Accordingly, characteristics of the field effect transistor 2 is changed from the curve of the gate voltage V _g is shown by * 2 in Figure 3 the curve shown by the valley voltage * 3, the current flowing through the circuit becomes very small. Even if the applied voltage is further increased, all the voltages are applied to the field effect transistor 2 because the drain conductance of the transistor is small, and the current value is constant. Therefore, a negative resistance characteristic having a symmetrical flat low current region as shown in FIG. 4 is 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]

Embodiment 2 FIG. 5 shows a second embodiment of the present invention, and is an image processing apparatus in which the above-described resistance fuse element is applied to the resistance fuse network for the initial visual process shown in FIG. . An image signal is applied via a resistor, and the output is taken from each connection point. As described in the section of the related art, this network has a feature that a discontinuity (edge) of an image itself is left from a signal including noise and only the noise can be reduced. The semiconductor device described in the first embodiment of the present invention is close to ideal resistance fuse characteristics, and can effectively reduce noise as compared with the case where only a resonant tunnel diode is used.

[0014]

As described above, according to the present invention, a negative resistance element exhibiting a symmetric, wide and flat valley current characteristic can be easily obtained. By using this, a 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 with a photoelectric conversion element)
Can be constructed on one chip.

[Brief description of the 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.

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

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 noise is removed from the image while applying discontinuous portions by applying the resistance fuse element in the first embodiment.

FIG. 6A is a cross-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 noise from an image 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 for explaining the operation of a conventional example of a negative resistance element showing a flat valley voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Field effect transistor 1 2 ... Field effect 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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 29/86 H01L 29/88 H01C 13/00 H01L 21/8234 H01L 27/06

Claims (2)

(57) [Claims] 1. A diode having an N-type negative differential resistance in both positive and negative directions and two field-effect transistors having a negative threshold, wherein the source or drain electrode of the first transistor is the diode. The source or drain electrode of the second transistor is connected to another terminal of the diode, and the gate electrode of the first transistor is connected to the connection point of 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, wherein the semiconductor device is connected in a two-dimensional network, a signal voltage is input to a connection point via a resistance component, and an output is taken out from the connection point of the network. A semiconductor device characterized by the above-mentioned.