  It was investigated the possibility of creating NbN superconducting
single-photon detectors with saturated dependence of quantum efficiency versus
normalized bias current. It was shown that the saturation increases for the
detectors based on finer films with a lower value of Rs300/Rs20. The decreasing
of Rs300/Rs20 related to increasing influence of quantum corrections to
conductivity of superconductors and, in its turn, to decreasing electron
diffusion coefficient. The best samples has constant value of system quantum
effi-ciency 94% at Ib/Ic~0.8 and wavelength 1.31 mkm.
