Field Effect Device with a Channel with a Switchable Conductivity

Abstract

A field effect device includes a source electrode, a drain electrode, a channel formed between the source electrode and the drain electrode, and a gate electrode formed directly on the channel and arranged in a gap between the source electrode and the drain electrode. The channel includes a switching material that is reversibly switchable between a lower conductivity state and a higher conductivity state. The first conductivity state has an electrical conductivity which is lower than an electrical conductivity of the second conductivity state. Each of the conductivity states is persistent without the need for a sustaining excitation signal including an electrical field, heat and/or light applied to the device.

1 . A field effect device, comprising:
 a source electrode;   a drain electrode spaced laterally apart from the source electrode;   a channel formed between the source electrode and the drain electrode; and   a gate electrode formed directly on the channel and arranged in a gap between the source electrode and the drain electrode,   wherein the channel comprises a switching material reversibly switchable between a first conductivity state and at least a second conductivity state, the first conductivity state having an electrical conductivity which is lower than an electrical conductivity of the second conductivity state, each of the conductivity states being persistent.   
     
     
         2 . The device according to  claim 1 , wherein the electrical conductivity of each of the first and second conductivity states is persistent without a need for a sustaining excitation signal including at least one of an electrical field, heat and light applied to the device. 
     
     
         3 . The device of  claim 1 , wherein when in a given one of the persistent conductivity states, application of a voltage having a magnitude which is less than or equal to a prescribed voltage level to the gate electrode causes a non-persistent change in electrical conductivity of the given conductivity state, whereby varying voltage applied to the gate electrode causes a modulation of the electrical conductivity of the given conductivity state when the magnitude of the voltage is less than or equal to the prescribed voltage level and causes a switching of the conductivity state when the magnitude of the voltage is greater than the prescribed voltage level. 
     
     
         4 . The device according to  claim 1 , wherein the electrical conductivity of the first conductivity state and the electrical conductivity of the second conductivity state differs by a factor of at least about 1000. 
     
     
         5 . The device according to  claim 1 , wherein the switching material is switchable between the first conductivity state and the second conductivity state by application of at least one of heat and light, and wherein the switching material exhibits hysteresis. 
     
     
         6 . The device according to  claim 1 , wherein the switching material is switchable between the first conductivity state and the second conductivity state by application of a predetermined voltage between the source electrode and the drain electrode or between the gate electrode and at least one of the source electrode and the drain electrode. 
     
     
         7 . The device according to  claim 1 , wherein the switching material at least forms one of a filament within the channel and a part of the channel. 
     
     
         8 . The device according to  claim 1 , wherein the switching material is switchable between the first conductivity state and the second conductivity state by at least one of injection and extraction of charge carriers in the device. 
     
     
         9 . The field effect device according to  claim 1 , wherein the switching material is switchable between the first conductivity state and the second conductivity state by application of a voltage or a current to the switching material in the channel. 
     
     
         10 . A field effect device, comprising:
 a source electrode;   a drain electrode;   a channel formed between the source electrode and the drain electrode; and   a gate electrode separated from the channel by an insulating layer,   wherein the channel comprises a switching material reversibly switchable between a first conductivity state and at least a second conductivity state, the first conductivity state having an electrical conductivity which is lower than an electrical conductivity of the second conductivity state, each of the conductivity states being persistent;   wherein the switching material is switchable between the first conductivity state and the second conductivity state by application of at least one of an electrical field, heat and light, and wherein the respective electrical conductivities of the first and second conductivity states is maintained without a need for a sustaining excitation signal including at least one of an electrical field, heat and light applied to the device.   
     
     
         11 . A sensor circuit with switchable sensitivity, the sensor circuit comprising at least one field effect device, the field effect device comprising:
 a source electrode;   a drain electrode;   a channel formed between the source electrode and the drain electrode; and   a gate electrode separated from the channel by an insulating layer;   wherein the channel comprises a switching material reversibly switchable between a first conductivity state and at least a second conductivity state, the first conductivity state having an electrical conductivity which is lower than an electrical conductivity of the second conductivity state, each of the conductivity states being persistent without a need for a sustaining excitation signal including at least one of an electrical field, heat and light applied to the device, and wherein the sensitivity of the sensor circuit varies as a function of the conductivity state of the switching material.   
     
     
         12 . A memory device including a plurality of storage cells, at least a given one of the storage cells comprising a field effect device, the field effect device comprising:
 a source electrode;   a drain electrode spaced laterally apart from the source electrode;   a channel formed between the source electrode and the drain electrode; and   a gate electrode formed directly on the channel and arranged in a gap between the source electrode and the drain electrode,   wherein the channel comprises a switching material reversibly switchable between a first conductivity state and a second conductivity state, the first conductivity state having an electrical conductivity which is lower than an electrical conductivity of the second conductivity state, each of the conductivity states being persistent without a need for a sustaining excitation signal including at least one of an electrical field, heat and light applied to the device, the first and second conductivity states being indicative of first and second logical states, respectively, of the memory device.   
     
     
         13 . An amplifier circuit having a switchable gain, the amplifier circuit comprising at least one field effect device, the field effect device comprising:
 a source electrode;   a drain electrode;   a channel formed between the source electrode and the drain electrode; and   a gate electrode separated from the channel by an insulating layer;   wherein the channel comprises a switching material reversibly switchable between a first conductivity state and a second conductivity state, the first conductivity state having an electrical conductivity which is lower than an electrical conductivity of the second conductivity state, each of the conductivity states being persistent without a need for a sustaining excitation signal including at least one of an electrical field, heat and light applied to the device, and wherein the gain of the amplifier circuit varies as a function of the conductivity state of the switching material.   
     
     
         14 . A control device for a display device, the display device including a plurality of pixel control cells, at least a given one of the pixel control cells comprising a field effect device, the field effect device comprising:
 a source electrode;   a drain electrode;   a channel formed between the source electrode and the drain electrode; and   a gate electrode separated from the channel by an insulating layer;   wherein the channel comprises a switching material reversibly switchable between a first conductivity state and a second conductivity state, the first conductivity state having an electrical conductivity which is lower than an electrical conductivity of the second conductivity state, each of the conductivity states being persistent without a need for a sustaining excitation signal including at least one of an electrical field, heat and light applied to the device.   
     
     
         15 . A field effect device, comprising:
 a source electrode;   a drain electrode spaced laterally apart from the source electrode;   a channel formed between the source electrode and the drain electrode; and   a gate electrode separated from the channel by an insulating layer,   wherein the channel comprises a switching material reversibly switchable between a first conductivity state and a second conductivity state, the first conductivity state having an electrical conductivity which is lower than an electrical conductivity of the second conductivity state, each of the conductivity states being persistent without a need for a sustaining excitation signal including at least one of an electrical field, heat and light applied to the device;   wherein the device is configured such that: (i) application of a voltage having a magnitude which is greater than a prescribed voltage level to the gate electrode relative to at least one of the source electrode and drain electrode causes the switching material to switch between the first conductivity state and the second conductivity state or between the second conductivity state and the first conductivity state as a function of a polarity of the voltage applied to the gate electrode; and (ii) application of a voltage having a magnitude which is less than or equal to the prescribed voltage level to the gate electrode relative to at least one of the source electrode and drain electrode causes a non-persistent change in the conductivity of the switching material, an amount of non-persistent change in the conductivity being a function of at least one of the magnitude and the polarity of the voltage applied to the gate electrode.