Retina-Inspired Artificial Synapses with UV Modulated and Immediate Switchable Plasticity

As the most promising candidates for implementing in-sensor computing and lower power consumption, retina-inspired morphometric vision sensors must be able to perceive and discriminate images under various illumination conditions. However, integrating invisible ultraviolet (UV) light sensing and memory in a device is valuable for exploring advanced neuromorphic visual perception systems. Here, a retina-inspired artificial neuromorphic vision sensor based on GaN/BiFeO₃ heterojunction, which integrates sensing, memory, and processing functions, is presented. The device exhibits immediate switchable synapse plasticity-modulated ultra-weak UV illumination, including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), short-term and long-term plasticity (STP/LTP), and the learning-forgetting-relearning process. The maximum PPF index of the device is 200%, and the minimum excitation light intensity is 0.68 µW cm⁻². The phenomenon is attributed to the effective UV light modulation for negative polarization, ionization and de-ionization of the oxygen vacancies, further enhancing the persistent photoconductive (PPC) effect. In addition, the device successfully mimics human-like visual memory behavior by identifying the “BINN” letter pattern, which is extracted and visualized by invisible UV information from the learning-forgetting-relearning process. This work provides valuable insights into next-generation low-power and multi-functional photovoltaic artificial synapses.