Modulation of Excitatory Behavior by Organic-Inorganic Hybrid Electric-Double-Layers in Polysilicon Synaptic Transistors

In this study, we propose a polysilicon (poly-Si) channel thin-film synaptic transistor based on an organic-inorganic hybrid electric-double-layer (EDL) structured gate dielectric. To implement the hybrid EDLs, which play a key role in artificial synaptic transistors, a protonic mobile ion-based bio-inspired chitosan electrolyte and a high-k Ta
₂
O
₅
dielectric thin-film were applied. Synaptic modulation was realized on the poly-Si channels by the polarization reaction of mobile protonic ions in the organic chitosan electrolyte. The chemically and mechanically stable inorganic Ta
₂
O
₅
dielectric capping layer prevented deterioration of the organic electrolyte due to the patterning and etching processes, enabling the fabrication of large-scale integrated circuits. The fabricated EDL field-effect transistors (FETs) verified essential synaptic behavior. Therefore, polarization and depolarization in EDLs, paired-pulse facilitation, and excitatory post-synaptic current modulation were successfully emulated by applying pre-synaptic stimulation spikes. As a result, the proposed CMOS-compatible poly-Si thin-film synaptic FETs based on hybrid EDLs are suitable for emerging neuromorphic systems and compact artificial neural networks.