Highly selective spectral response with enhanced responsivity of n-ZnO/p-Si radial heterojunction nanowire photodiodes

A radial heterojunction nanowire diode (RND) array consisting of a ZnO (shell)/Si (core) structure was fabricated using conformal coating of a n-type ZnO layer that surrounded a p-type Si nanowire. In both ultraviolet (UV) and visible ranges, the photoresponsivity of the RND was larger than that of a planar thin film diode (PD) owing to the efficient carrier collection with improved light absorption. Compared to a PD, in the forward bias, a 6 mu m long RND resulted in a similar to 2.7 times enhancement of the UV responsivity at lambda = 365 nm, which could be explained based on the oxygen-related hole-trap mechanism. Under a reverse bias, UV-blind visible detection was observed while the UV response was suppressed. (c) 2011 American Institute of Physics. [doi:10.1063/1.3543845]This work was supported by the Pioneer Research Center Program (Grant No. 2010-0002231) and Nano R&D Program (Grant No. 20090083229) through the National Research Foundation grant funded by the Ministry of Education, Science and Technology. This work was supported by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning grant funded by the Ministry of Knowledge Economy (Grant No. 2009T100100614). H.-D.U., K.-T.P., and S.-W.J. acknowledge financial support of the fifth-stage Brain Korea 21 Project in 2010