【Device Papers】Ultraviolet to Red Wavelength-Dependent Gallium Oxide Memristor-Based Multi-Level Optoelectronic Synapse Device

      Researchers from the Tech University of Korea have published a dissertation titled "Ultraviolet to Red Wavelength-Dependent Gallium Oxide Memristor-Based Multi-Level Optoelectronic Synapse Device" in Journal of Alloys and Compounds.

Abstract

      We developed a Pt/Ga₂O₃/Pt optoelectronic synaptic device with tunable memory properties under different light wavelengths. The amorphous Ga₂O₃ film confirmed through X-ray diffraction, high-resolution transmission electron microscopy, and atomic force microscopy analysis, exhibited visible light absorption due to shallow defect levels. Despite requiring relatively high optical power due to the lower absorption efficiency of visible light in Ga₂O₃, these wavelengths enable distinct resistive switching behaviors and multiple resistance states, effectively tuning device response without relying on UV-only absorption. Enhanced paired-pulse facilitation values reached 149.1% for 365 nm and 137.5% for 660 nm, indicating wavelength-based modulation of short-term memory (STM) and long-term memory (LTM). STM was observed at 660 nm, while 365 nm exposure promoted LTM, demonstrating the wavelength-dependency of memory functions. Neural network simulations demonstrated high learning efficiency, with pattern recognition accuracy exceeding 95%. This study reveals the potential of Ga₂O₃-based synaptic devices for flexible, wavelength-dependent neuromorphic applications, even under less efficient visible light exposure.

DOI：

https://doi.org/10.1016/j.jallcom.2025.179053