ZnO tetrapod Schottky photodiodes

The fabrication of an ultraviolet photodiode employing a single ZnO tetrapod nanocrystal is reported. This diode structure is prepared by depositing W and Pt electrodes to form Ohmic and Schottky contacts, respectively. Dark current-voltage measurements show rectifying behavior. The properties of the metal-semiconductor interface are studied with above and below band gap illumination. It is found that with increasing UV excitation the device converts from a rectifying to an Ohmic behavior. This effect is attributed to a flattening of the energy bands due to the migration of photogenerated carriers within the space charge region at the metal-semiconductor interface. (c) 2006 American Institute of Physics.