Trapping-tunable dual-mode optoelectronic device for optoelectronic synapse and photodetector

We propose a thickness-modulated strategy for implementing two operations (optoelectronic synapse and photodetector) simultaneously in the same device structure. For the MoS 2 thickness of <56 nm, the device works as an optoelectronic synapse with some neuromorphic functionalities such as spike-interval-dependent plasticity, spike-rate-dependent plasticity and short-to-long-term plasticity. By combining synaptic plasticity with an artificial neural network, it achieves precise image recognition and classification with an accuracy >95%. As the thickness increases, excitons and trapping sites are separated by an increasing gap that facilitates a mode transition from synapse to detector. For 368-nm thickness, devices exhibit a photodetector mode with the response speed at millisecond level and responsivity of 163 mA/W.