Optoelectronic synapses combine non-volatile memory and photodetection functionalities in the same device. It paves the path for the realization of artificial retina systems which can capture, pre-process, and identify images on the same platform. Researchers have used a graphene/Ta2O5/graphene heterostructure to demonstrate optoelectronic synapses. The graphene interface exhibits synapse characteristics when visible electromagnetic radiation of wavelength 405 nm illuminates the device.
The photocurrent is retained after light withdrawal when a positive gate voltage applies to the device. The device exhibits distinct conductance states modulated by different parameters of the incident light, such as pulse width and the number of pulses.
The conductance state can be retained for 104 s, indicating long-term potentiation (LTP), similar to biological synapses. The graphene interface device uses optical and electrical pulses to show optical potentiation and electrical LTD. The device implies its applicability in neural networks for pattern recognition.