NbN single-photon detectors with saturated dependence of quantum efficiency
Konstantin Smirnov, Alexander Divochiy, Yury Vakhtomin, Pavel Morozov, Philipp Zolotov, Andrey Antipov, Vitaliy Seleznev · Superconductor Science and Technology · 2018
Abstract The possibility of creating NbN superconducting single-photon detectors with saturated dependence of quantum efficiency (QE) versus normalized bias current was investigated. It was shown that the saturation increases for the detectors based on finer films with a lower value of R s 300 / R s 20 . The decreasing of R s 300 / R s 20 was related to the increasing influence of quantum corrections to conductivity of superconductors and, in turn, to the decrease of the electron diffusion coefficient. The best samples have a constant value of system QE 94% at I b /I c ∼ 0.8 and wavelength 1310 nm.