Investigations of photoresponse characteristics of ultrasonic spray pyrolysis deposited zinc oxide-based phototransistors at different quiescent points.

How quiescent-points affect the performance of the ultrasonic spray pyrolysis deposited zinc oxide-based phototransistor is investigated in this study. It is well known that gate bias and drain bias control quiescent-points. By changing gate bias, strong accumulation, weak accumulation, weak depletion, and strong depletion in the active layer of the phototransistor are obtained. Meanwhile, by changing drain bias, either triode or saturation operation regions of the phototransistor is obtained. Therefore, total 8 different quiescent-points are investigated in this study. The material characteristics such as crystal structure, oxygen deficiency, bandgap, and trap energy levels are characterized. Moreover, the performance of the phototransistor at different quiescent-points are investigated. The present phototransistor shows four operation modes, including high responsivity, high UV-to-visible rejection ratio, fast response speed, and high specific detectivity, and each mode corresponds to a specific quiescent point. [ABSTRACT FROM AUTHOR]