Abstract
We demonstrate that a device composed of sputtered amorphous chalcogenide Ge2Se3/M + Ge2Se3 (M = Sn or Cu) alternating layers functions as an optically gated transistor (OGT) and can be used as an access transistor for a memristor memory element. This transistor has only two electrically connected terminals (source and drain), with the gate being optically controlled, thus allowing the transistor to operate only in the presence of light (385–1200 nm). The switching speed of the OGTs is <15 μs. The OGT is demonstrated in series with a Ge2Se3 + W memristor, where we show that by altering the light intensity on the OGT gate, the memristor can be programmed to a continuous range of nonvolatile memory states using the saturation current of the OGT as a programming compliance current. By having a continuous range of nonvolatile states, one memory cell can potentially achieve 2n levels. This high density, combined with optical programmability, enables hybrid electronic/photonic memory.
Highlights
The use of resistive random access memory (ReRAM), known as memristor devices,[1,2] in circuits such as cross-point arrays,[3] spiking neural networks,[4] or other computing applications[5−7] where a large number of these memristive memory elements need to be incorporated into the circuit has been challenging due to their resistive nature
A multipurpose optically gated transistor has been demonstrated that enables nonvolatile photonic memory and (1) functions as an access transistor for a memristor device, (2) enables uniform voltage memristor programming, (3) allows a memristor to be programmed within a continuous range of states by using light intensity applied to the OGT gate, and (4) includes built-in compliance current limiting via the OGT saturation current
The applied gate light intensity controls the saturation current level of the OGT. This is an advantage of amorphous materials and their large concentration of trap states: the series resistance in the saturation state acts as a current limiter for the memristor, in the same role as a compliance current limit
Summary
The use of resistive random access memory (ReRAM), known as memristor devices,[1,2] in circuits such as cross-point arrays,[3] spiking neural networks,[4] or other computing applications[5−7] where a large number of these memristive memory elements need to be incorporated into the circuit has been challenging due to their resistive nature. The resistive nature of these memory elements can create multiple unwanted paths of current flow in a cross-point array even when only a single element is being addressed Because they traverse a path through nonaddressed memristor elements, these currents are termed sneak path currents. Circuit techniques to eliminate or reduce sneak path current have included addition of a diode in the memristor device array element.[10,12] A diode in series with each memristor prevents access to a nonaddressed element because the voltage at that node remains lower than the forward voltage of the diode, preventing current flow through the memristor element This is a reasonable approach for the case of unipolar memristor elements that can change state with the application of a single polarity electronic input signal, such as phase-change devices. The variable resistance creates a variable voltage across the memristor due to the voltage divider and can lead to Received: October 29, 2018 Accepted: December 20, 2018 Published: December 20, 2018
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
