Fabrication of an efficient GLAD-assisted p-NiO nanorod/n-ZnO thin film heterojunction UV photodiode

The glancing angle deposition (GLAD) configuration in RF magnetron sputtering has been utilized to deposit p-type NiO nanorods, which are integrated with n-type ZnO thin film to realize a high performance p-n heterojunction diode for the efficient detection of UV photoradiation. The fabricated nano p-NiO/n-ZnO heterojunction shows excellent rectifying characteristics (rectification ratio similar to 4 x 10(3)) with a very low reverse saturation current (similar to 10(-10) A). The heterojunction photodiode exhibits a high current gain (3.71 x 10(3)), high photoresponsivity (3.24 x 10(5) A W-1), with a relatively fast response (similar to 200 ms) and recovery speed (similar to 25 ms) towards a very low UV intensity of 0.62 mu W cm(-2) (lambda = 300 nm). Recombination tunneling and space-charge limited current are the probable conduction mechanisms at low and high applied voltages respectively for the fabricated heterojunction diode. The observed high response speed and excellent responsivity of the diode towards deep-UV (lambda = 300 nm) radiation might lead to potential military applications such as missile tracking, in addition to optical communications.