High-speed photoresponse properties of ultraviolet (UV) photodiodes using vertically aligned Al:ZnO nanowires

Ultraviolet (UV) photodiodes with fast photoresponse properties were fabricated using vertically aligned aluminum doped ZnO nanowires. Stable p-type ZnO have been achieved by doping equimolar concentration of P-N (0.75at.%) simultaneously in ZnO. The vertically aligned and electrically conducting n-type Al (3at.%) doped ZnO nanowires were grown by a simple aqueous chemical growth process. The structural, morphological, optical, and electrical properties were investigated. For the fabrication of UV photodiodes, the optimum p-type ZnO layers and n-type ZnO nanowires were stacked upon ITO substrate. A 250nm thin NiO was deposited as an electron blocking layer (EBL) in between the ZnO p-n junctions. The current density-voltage (J-V) characteristic of the fabricated UV photodiode was measured under dark and UV illumination conditions. Under a reverse bias of 3V, the device exhibits a high photoresponsivity (R) value of 15.07 (A/W) upon illumination of UV light (=365nm). The fabricated photodiode exhibits a fast photoresponse switching characteristics with a response and recovery time calculated as 61 +/- 11 and 455 +/- 41ms, respectively. The role of vertically aligned nanowires in the formation of oxygen interstitial (O-i) defects and its impact on improving the UV photoresponse properties were investigated. [GRAPHICS] . (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim