Keywords:memristor, synapse, amorphous gallium oxide
Resistance control in memristive devices is one of the most crucial factors for the practical application to synaptic devices in neuromorphic computers. Among various mechanisms of resistive switching (RS), non-filamentary homogeneous RS is promising in terms of device reliability. It has been reported that nonstoichiometric amorphous gallium oxide (a-GaOx) exhibits a non-filamentary RS mechanism based on drift diffusion of oxygen vacancy donors.Since drift diffusion motion of oxygen vacancy induced by external voltage application is highly sensitive to crystallographic defects, such as dislocations and grain boundaries often giving rise to variability of the motion, the use of amorphous phase material is a key to precise control of the oxygen vacancy distribution and associated resistance in the device. In this work, we fabricated Pt-top-electrode/a-GaOx/ITO-bottom-electrode stack memristive devices and characterized RS properties including tunable multi-valued resistance states as well as spike-timing-dependent plasticity (STDP) as a synaptic property.