All‐Metal‐Oxide Heterojunction Optoelectronic Synapses with Multilevel Memory for Artificial Visual Perception Applications
Jo‐Lin Chen, Tsung‐Che Chiang, Po‐Tsun Liu
Abstract
Abstract Metal‐oxide semiconductor‐based optoelectronic synaptic transistors have attracted considerable attention due to their high energy efficiency and stability. This work proposes a novel WO 3 /InWZnO heterojunction optoelectronic synaptic transistor, demonstrating the strong potential for emulating the human visual system. The fabricated heterojunction synaptic transistor achieves an impressive optical responsivity of 58.37 A W −1 when exposed to 650 nm light. Furthermore, it successfully emulates transitions from short‐term memory (STM) to long‐term memory (LTM) by modulating pulse duration, illumination intensity, and pulse number. The heterojunction transistor also exhibits an optimal paired‐pulse facilitation (PPF) index of 176% and post‐tetanic potentiation (PTP) index of 890% under 460 nm light illumination. It also demonstrates long‐term multilevel storage capability via the photogating effect. A multilayer perceptron (MLP) model, employing synaptic weights modulated by 650, 525, and 460 nm light in the long‐term potentiation (LTP) region and by electrical stimuli in the long‐term depression (LTD) region, achieves a high recognition accuracy of 87.4% for severely distorted handwritten digits. Finally, the U‐Net architecture is adopted to evaluate the image segmentation performance through RGB channels, revealing an optimal accuracy of 74.5%, demonstrating the feasibility of the proposed WO 3 /InWZnO heterojunction synaptic transistor for advanced neuromorphic vision system applications.