Photo‐Synaptic Oxide Transistors with Al2O3/SiOx Stacked Gate Dielectric Exhibiting 1024 Conduction States with Good Linearity

Abstract

AbstractTiO2‐based photo‐synaptic transistors employing a stacked SiOX/Al2O3 gate dielectric are fabricated. The trapped charges at the interface between the gate dielectric and the channel induce a channel current threshold shift that displays synaptic behavior. When a positive gate voltage pulse is applied, the transfer curve shifts positively. In contrast, the curve shifts negatively under 365 nm wavelength UV pulses. The magnitude of the threshold shift is dependent on the optical pulse time. A 5 ms optical pulse shifts the transfer curve to the negative direction but the semiconducting properties of the channel are maintained. Increasing the optical pulse time to 0.5 s causes the channel to exhibit metallic behavior. When optical and electrical pulses are applied alternately, reversible shifts between the metallic and semiconducting states can be induced. The pulse‐paired facilitation time constants of the device for an optical pulse stimuli of 2 ms are 0.9 s and 26.6 s, verifying excellent photo‐synaptic properties. Short‐term plasticity measurements revealed 1024 distinctly separate conduction states with good linearity. Synaptic potentiation and depression are simulated by applying a continuous supply of optical pulses followed by an idle dark condition and good symmetric behavior is observed.