Superconducting a-WxSi1-x nanowire single-photon detector with saturated internal quantum efficiency from visible to 1850 nm

We have developed a single-photon detector based on superconducting amorphous tungsten-silicon alloy (a-WxSi1-x) nanowire. Our device made from a uniform a-WxSi1-x nanowire covers a practical detection area (16 mu mx16 mu m) and shows high sensitivity featuring a plateau of the internal quantum efficiencies, i.e., efficiencies of generating an electrical pulse per absorbed photon, over a broad wavelength and bias range. This material system for superconducting nanowire detector technology could overcome the limitations of the prevalent nanowire devices based on NbN and lead to more practical, ideal single-photon detectors having high efficiency, low noise, and high count rates. (C) 2011 American Institute of Physics. [doi:10.1063/1.3600793]