Bi-wavelength-Gated Plasticity in Defect-Engineered β - Ga2O3 Optoelectronic Synapses for Bioinspired Visual Systems
Abstract
Abstract Optoelectronic synapses that integrate light sensing, memory, and preprocessing are highly desirable for neuromorphic vision. However, most reported optoelectronic synapses rely on a single optical stimulus and mainly exhibit passive modulation of the photoresponse, making it difficult to actively distinguish transient interference from information that should be retained. Here, we report a wavelength-gated optoelectronic synapse based on defect-engineered β-Ga2O3, in which short-term (STP) and long-term synaptic plasticity (LTP) can be selectively programmed by dual-wavelength ultraviolet illumination. X-ray photoelectron spectroscopy (XPS) and temperature-dependent photoluminescence (PL) measurements indicate that N incorporation change the defect states of β-Ga2O3 by introducing N-related defect states and altering oxygen vacancy (VO), which provide effective pathways for wavelength-dependent carrier trapping, release, and recombination dynamics. Under 254 nm illumination, near-band-edge excitation leads to fast carrier recombination and STP, whereas 365 nm photons activate sub-bandgap defect states, enabling persistent photoconductivity and LTP. Benefiting from this wavelength-selective memory behavior, a physical-layer encrypted image transmission strategy is further demonstrated. Furthermore, a wavelength-gated reservoir-computing framework is constructed for noise-robust face recognition by coupling device-level preprocessing with reservoir readout. Owing to the transient erasure of noise information and the long-term retention of valid visual features, the system with preprocessing achieves a recognition accuracy of 94%, outperforming the system without preprocessing, which achieves 83%. This work provides a defect-engineering strategy for wavelength-programmable β-Ga2O3 optoelectronic synapses and highlights their potential for selective memory, secure optical communication, and neuromorphic visual.
