An optically controlled synaptic device based on a PdSe2/α-In2Se3 vdW heterostructure FET

Abstract

Visual synaptic devices show great promise for advanced neuromorphic hardware, offering a viable solution to the von Neumann bottleneck. However, achieving bidirectional optical control remains a considerable challenge. Herein, we demonstrate an all 2D heterostructure FET consisting of few-layer PdSe₂ and α-In₂Se₃, designed as an optically controlled synaptic device with ferroelectric assisted tunability. The device emulates multiple forms of spike-dependent plasticity, exhibiting excitatory and inhibitory synaptic responses in the 642–980 nm and 406–520 nm spectral range, respectively. Moreover, the optically induced excitatory and inhibitory synapses can be modulated by an electrical gate pulse, utilizing the spontaneous polarization of α-In₂Se₃. By leveraging the coupled ferroelectric and optical properties of In₂Se₃, the device exhibits an extended retention time of post-synaptic current (PSC) and enhanced device performance in terms of responsivity (R) and detectivity (D) compared with its PdSe₂-based counterparts. Logic gate operations (OR and AND) were demonstrated using 642 nm, 785 nm and 406 nm wavelengths as optical inputs. In addition, a three-layer artificial neural network (ANN) was trained to recognize a 28 × 28 pixel handwritten MNIST dataset by a backpropagation algorithm demonstrating high recognition accuracy of 96% and 97% under wavelengths of 642 nm and 406 nm, respectively. This study provides an effective strategy for the development of versatile optically controlled neuromorphic devices as fundamental building blocks for on-chip optical communication, optoelectronic logic, and Internet of Things (IoT) applications.