All-Optical-Controlled Excitatory and Inhibitory Synaptic Signaling through Bipolar Photoresponse of an Oxide-Based Phototransistor

Using light signals for computation and communication is a vital approach for advanced neuromorphic designs. In this study, an all-optical-controlled IGZO/ZrO_x phototransistor is demonstrated to emulate synaptic functions via both positive and negative photoresponse arisen from the ionization of neutral oxygen vacancies (V_O) and metal.metal bonding (M.M) defects in IGZO at an illumination with visible light (405 and 520 nm) and near-infrared light (750, 890, and 980 nm), respectively. With the coupling effect of photogenerated electrons and the charged M.M⁺⁺ defect scattering, the IGZO/ZrO_x photosynaptic transistor not only shows broadband photosensing performance but also emulates the excitatory/inhibitory contrasting synaptic functions, such as learning- and regulating-experience behavior of human brain, via applying 405 and 890 nm light pulses, respectively. The all-optical-controlled IGZO/ZrO_x photosynaptic transistor therefore may convey optical information effectually for the streaming sensor processing in biologically inspired computer vision application.