Recovery from ultraviolet-induced threshold voltage shift in indium gallium zinc oxide thin film transistors by positive gate bias

Abstract

The effect of short-duration ultraviolet (UV) exposure on the threshold voltage (Vth) of amorphous indium gallium zinc oxide thin film transistors (TFTs) and its recovery characteristics were investigated. The Vth exhibited a significant negative shift after UV exposure. The Vth instability caused by UV illumination is attributed to the positive charge trapping in the dielectric layer and/or at the channel/dielectric interface. The illuminated devices showed a slow recovery in threshold voltage without external bias. However, an instant recovery can be achieved by the application of positive gate pulses, which is due to the elimination of the positive trapped charges as a result of the presence of a large amount of field-induced electrons in the interface region.