Amorphous Gallium-Oxide-Based Non-Filamentary Memristive Device with Highly Repeatable Multiple Resistance States

A memristive device is presented based on a Ti/GaO_x/W stack with an amorphous GaO_x layer deposited at a low temperature (250 °C) using plasma-enhanced atomic layer deposition. The device fabrication is compatible with a standard complementary metal oxide semiconductor back-end-of-line technology. The area dependence of the resistance values for both high and low resistance states indicates that switching takes place over the entire device area via a non-filamentary-based mechanism. Evidence is provided that the switching process originates from a field-driven oxygen exchange between the interfacial TiO_x layer and the GaO_x one as well as from the charging/discharging of interfacial trap states. The devices reveal self-rectifying characteristics with high cycle-to-cycle reproducibility. Multiple states can be programmed with 12 distinct intermediate states during potentiation, and 11 distinct states during depression. This amorphous GaO_x-based memristive device with highly reproducible multi-level resistance states shows great potential for enabling artificial synapses in neuromorphic applications.