Long- and Short-Term Memory Characteristics Controlled by Electrical and Optical Stimulations in InZnO-Based Synaptic Device for Reservoir Computing

In this study, the resistive switching phenomenon and synaptic mimicry characteristics of an indium tin oxide (ITO)/indium zinc oxide (IZO)/Al₂O₃/TaN device are characterized. The insertion of a thin Al₂O₃ layer via atomic layer deposition improves the resistive switching characteristics such as cycle-to-cycle and device-to-device uniformity and reduces the power consumption of the proposed device with respect to a single-layer ITO/IZO/TaN device. The proposed device exhibits the coexistence of volatile and nonvolatile characteristics under optical and electrical measurement conditions. Nonvolatile memory characteristics with stable retention results are used for synaptic applications by emulating potentiation, depression, and spike-timing-dependent plasticity. Furthermore, the device shows volatile characteristics under ultraviolet-light illumination, emulating paired-pulse facilitation and excitatory post-synaptic current responses. Finally, optical-enhanced reservoir computing is implemented based on the nonlinear and volatile nature of the IZO-based resistive random-access memory device.