Defect controlled ultra high ultraviolet photocurrent gain in Cu-doped ZnO nanorod arrays: De-trapping yield

Abstract

Understanding the mechanism behind high photocurrent gain is very important to realize a highly functional material for photodetector devices. Herein, we report a very high ultraviolet photocurrent gain of 2.8 × 105 in hydrothermally grown Cu-doped ZnO nanorod arrays which is two orders of magnitude higher as compared to the undoped sample. Trapping of carriers under dark and de-trapping them under illumination by Cu-related defects is responsible for high gain. The trap state at ∼1.65 eV is attributed to the [{CuZn+(3d10)}− − Zni+(4s1)]0 type of defects. A model is shown to explain the dark and photocurrent states in the doped samples.