Enhanced UV photodetector response and recovery times using a nonpolar ZnO sensing layer

A plasma-enhanced chemical vapor deposition system was used to fabricate ultraviolet (UV) photodetectors based on polar and nonpolar zinc oxide (ZnO) thin films combined with interdigitated platinum top electrodes. The performance of photodetectors was demonstrated by current-voltage characteristics and time-dependent photoresponse measurements. Both polar and nonpolar detectors showed a prominent photocurrent gain under UV light illumination, compared with dark conditions. However, the response and recovery times for the nonpolar detectors were significantly faster compared to the polar detectors. These variations in response and recovery times can be explained by the dipole effect between the electrode and sensing thin film, which is due to the adsorption and desorption of gas molecules on polar and nonpolar ZnO thin film surfaces. (C) 2016 American Vacuum Society.