A Violet-Light-Responsive ReRAM Based on Zn2SnO4/Ga2O3 Heterojunction as an Artificial Synapse for Visual Sensory and In-Memory Computing

Due to the imitation of the neural functionalities of the human brain via optical modulation of resistance states, photoelectric resistive random access memory (ReRAM) devices attract extensive attraction for synaptic electronics and in-memory computing applications. In this work, a photoelectric synaptic ReRAM (PSR) of the structure of ITO/Zn₂SnO₄/Ga₂O₃/ITO/glass with a simple fabrication process is reported to imitate brain plasticity. Electrically induced long-term potentiation/depression (LTP/D) behavior indicates the fulfillment of the fundamental requirement of artificial neuron devices. Classification of three-channeled images corrupted with different levels (0.15–0.9) of Gaussian noise is achieved by simulating a convolutional neural network (CNN). The violet light (405 nm) illumination generates excitatory post synaptic current (EPSC), which is influenced by the persistent photoconductivity (PPC) effect after discontinuing the optical excitation. As an artificial neuron device, PSR is able to imitate some basic neural functions such as multi-levels of photoelectric memory with linearly increasing trend, and learning-forgetting-relearning behavior. The same device also shows the emulation of visual persistency of optic nerve and skin-damage warning. This device executes high-pass filtering function and demonstrates its potential in the image-sharpening process. These findings provide an avenue to develop oxide semiconductor-based multifunctional synaptic devices for advanced in-memory photoelectric systems.