Study of the photoconductive ZnO UV detector based on the electrically floated nanowire array

ZnO nanowires have been shown to have high sensitivity for detecting UV light. In this paper, we report a low-cost fabricated metal-semiconductor-metal (MSM) structure, consisting of ZnO nanowire array as outer-layer photo absorber supported by a ZnO nanocrystalline film. The ZnO film is bridged between two electrically interdigitated metal electrodes for collecting photo-generated charges. Different from previous approaches, in which nanowires were directly connected with two metal electrodes [1,2], our MSM structure allows direct exposure of dense ZnO nanowires to UV light. In such a way, the outer ZnO nanowires serve as antireflective traps, and the ZnO film are used for both charge transport and seeding ZnO nanowire array self-assembly growth. The photoresponse characteristics for the detector were measured in detail and then the carriers transport model was given to explain the theoretical mechanism for the enhanced photocurrent. The oxygen exchange processes were suggested to be responsible for the slow transient properties. Finally, nanowire surfaces were modified using surface passivation with polymer and Ar ion bombardment to verify the surface depletion effect. It has been shown that transient response for the detector with the polymer passivation become much faster than that original one without the passivation. (C) 2012 Elsevier B.V. All rights reserved.