Visible light-driven synaptic transistors based on bilayer InGaZnO homojunction for neuromorphic computing

The development of photoelectric synaptic transistors (PSTs) using visible light-driven mimicking synaptic behaviors represents a key advancement toward biomimetic visual systems. This study proposes a PST based on bilayer indium-gallium-zinc-oxide (IGZO) homojunctions with tunable gallium ratios. By optimizing the gallium content, oxygen vacancy concentrations in the channel were precisely controlled, suppressing deionization processes and enhancing device performance. The IGZO homojunction PST demonstrated outstanding electrical characteristics (Ion/Ioff = 1.2 × 107, μ = 3.88 cm2/Vs, Vth = 0 V) and exhibited high photocurrent and robust persistent photoconductivity under visible light. The device mimicked various synaptic behaviors, including excitatory postsynaptic current, paired-pulse facilitation, the transition from short-term plasticity to long-term plasticity, spiking-rate-dependent plasticity, and spike-timing-dependent plasticity. Furthermore, leveraging the potentiation and depression behaviors of the IGZO homojunction PST, a triple-layer neural network achieved 96.8% accuracy in pattern recognition tasks. These results underscore the IGZO homojunction PST's immense potential for advancing artificial vision systems.