Superconducting detector of IR single-photons based on thin WSi films
V A Seleznev, A V Divochiy, Yu B Vakhtomin, Pavel Morozov, Philipp I. Zolotov, Д.Д. Васильев, Konstantin M. Moiseev, Elizaveta I. Malevannaya, K V Smirnov · Journal of Physics Conference Series · 2016
We have developed the deposition technology of WSi thin films 4 to 9 nm thick with high temperature values of superconducting transition (T c ~4 K). Based on deposed films there were produced nanostructures with indicative planar sizes ~100 nm, and the research revealed that even on nanoscale the films possess of high critical temperature values of the superconducting transition (T c ~3.3-3.7 K) which certifies high quality and homogeneity of the films created. The first experiments on creating superconducting single-photon detectors showed that the detectors' SDE (system detection efficiency) with increasing bias current (I b ) reaches a constant value of ~30% (for X=1.55 micron) defined by infrared radiation absorption by the superconducting structure. To enhance radiation absorption by the superconductor there were created detectors with cavity structures which demonstrated a practically constant value of quantum efficiency >65% for bias currents I b >0.6-I c . The minimal dark counts level (DC) made 1 s -1 limited with background noise. Hence WSi is the most promising material for creating single-photon detectors with record SDE/DC ratio and noise equivalent power (NEP).