Enhancing photoresponse by synergy of gate and illumination in electric double layer field effect transistors fabricated on n-ZnO

We report that photoresponse of ZnO in ultraviolet (UV) can be enhanced substantially by simultaneously applying a gate bias in an Electric Double Layer Field Effect Transistor configuration fabricated on ZnO as a channel. The effect arises from synergy between UV illumination and applied gate bias, which leads to a substantial enhancement in the device current. We propose that large carrier density created by the illumination and the gate leads to neutralization of some of the oxygen charged vacancies which in turn reduce potential scattering leading to enhanced field effect mobility. This is verified by gate bias controlled Photo Luminescence experiment.