All-solid-state Li-ion-based electrolyte-gated synaptic transistors with dual modes of excitatory and inhibitory plasticity

Abstract

Artificial synapses are essential elements for building artificial neural networks for neuromorphic computing. Both excitatory and inhibitory responses are recognized forms of synaptic plasticity and contribute equally to the biological nervous system. To date, electrolyte-gated transistors (EGTs) have been considered among the most promising synaptic devices and have been demonstrated to simultaneously emulate both excitatory and inhibitory synaptic plasticity in a single device. However, complex architectures and non-compatible solution-based processes hinder the development of EGT synaptic devices for further integration. Moreover, the reported excitatory and inhibitory responses are mainly modulated through dual voltage supplies, which may require complex circuit structures. Herein, an inorganic all-solid-state Li-ion-based EGT, employing LiPON and IGZO as the electrolyte and channel layer, respectively, was demonstrated using a compatible all-sputtering method. Dual modes of excitatory and inhibitory plasticity, induced by the inherent predominance of the electrical double layer and electron trapping effect, respectively, could be simultaneously realized in a single device through modulation with a single positive voltage supply. The device exhibited a low operation voltage of 2 V and low energy consumption of ∼80 pJ for the inhibitory mode and 4 V and ∼800 pJ for the excitatory mode. In addition, Pavlovian experiment and the learning-forgetting-relearning processes of human memory were successfully demonstrated. This work may provide a solid hardware foundation for complex brain-like computing tasks, such as pattern recognition, decision-making, and associative learning and offers new insights into the development of neuromorphic devices compatible with mass production processes.