Spatially Resolved Transient Response in Amorphous Oxide Semiconductor Transistors

The non-equilibrium carrier dynamics in amorphous oxide semiconductors are important for the understanding of charge transport mechanism and trapping/releasing processes. Using a microwave impedance microscope, we study the spatially resolved transient response of an amorphous In-Ga-Zn-O field-effect transistor to square-wave-like gate voltages. The charge dynamics in this configuration are purely driven by diffusion as both the source and drain electrodes are grounded during the measurement. By fitting the rising and falling transient signals, we can extract the characteristic time scales of carrier transport across shallow and deep trap states, ranging from micro-seconds to milli-seconds. Our results demonstrate the crucial role of localized states and provide quantitative information of the trapping and releasing processes in amorphous oxide semiconductors.