Enhanced response from metal/ZnO bilayer ultraviolet photodetector

Enhanced ultraviolet (UV) photoresponse is observed in rf magnetron sputtered ZnO thin films interfaced with ultrathin overlayers of different metals (Al, Cu, Sn, Pb, Au, and Te). Electrons transferred from a metal layer to the semiconductor at the interface compensate the surface states and increase the dark conductivity. Depending on the number of injected electrons, surface states are compensated to different extents and correspondingly increase the photoconductivity. The photoresponse of the Sn/ZnO bilayer sample exhibits the highest responsivity (similar to 6 kV/W) at low UV intensity of 140 mu W/cm(2) (lambda=365 nm) with a relatively fast response speed of 65 ms. (c) 2007 American Institute of Physics.