Observation of a large gate-controlled persistent photoconduction in single crystal ZnO at room temperature

Abstract

Gate-controlled enhanced photoconductivity at room temperature is reported in single crystal ZnO using moderate bias and band gap illumination. A substantial part of the enhanced photocurrent is retained over a long time as a persistent photocurrent when the illumination is removed but the gate voltage (applied with a polymer-electrolyte gate) is retained. The current on the removal of illumination shows a stretched exponential decay with time constants more than few hundreds of seconds. An explanation based on change in charge state of oxygen vacancy has been proposed.