Charge-Modulated Conductance and Synaptic Behavior in Access-Region WSe2/h-BN/Gr van der Waals Floating-Gate Transistors for Nonvolatile Memory

S.-P. Lin (National Yang Ming Chiao Tung Univ. and National Chung Hsing Univ., Taiwan)

Neuromorphic hardware requires nonvolatile memory and continuously tunable conductance to emulate synaptic plasticity in biological neural systems. Here, we report a van der Waals floating-gate field-effect transistor (FGFET) incorporating specially designed geometrical structures, namely access regions (ARs), based on a tungsten diselenide (WSe2)/ hexagonal boron nitride (h-BN)/ graphene (Gr) heterostructure, and systematically investigate its nonvolatile memory and synaptic characteristics. The AR geometry effectively regulates the tunneling pathway between the semiconductor channel and the graphene floating gate, enabling stable Fowler–Nordheim tunneling and gradual conductance modulation. Under gate-voltage pulse stimulation, the device exhibits excitatory and inhibitory postsynaptic current (EPSC/IPSC)-like responses, with conductance states gradually tuned by pulse amplitude, number, and duration. These results demonstrate that the WSe2/h-BN/Gr floating-gate platform is a promising candidate for compact neuromorphic and optoelectronic synaptic applications.