Long-Term Persistent Photoconductivity in n-IGZO/p-Si Heterostructure for Photomemory Application

In this study, we present an indium gallium zinc oxide (IGZO) synaptic device that emulates human brain functions such as learning, memorizing, and forgetting, with capabilities similar to those of human visual perception and memory processes. The device, constructed with IGZO sputtered on a Si substrate and interdigitated Au electrodes, demonstrates long-term memory performance through engineering the Si substrate's conductivity. Optimized Si substrate resistivity enhances long-term persistent photoconductivity, achieving memory retention for up to 9 days, a dramatic improvement over the retention of minutes to hours typically observed in similar systems. Thermal annealing at 300 °C in a nitrogen atmosphere effectively causes the memory to be forgotten. Detailed analysis using X-ray photoelectron spectroscopy and Tauc plots reveals critical insights into the role of oxygen vacancies and band alignment in this memory and forgetting behavior. The IGZO synaptic device's unique photomemory properties and tunable performance highlight its potential for applications in neuromorphic computing and advanced photomemory storage systems.