Single photon detection performance of highly disordered NbTiN thin films

We experimentally investigated the detection performance of highly disordered NbxTi1−xN based superconducting nanowire single photon detectors (SNSPDs). The dependence on the composition of the transition temperature Tc for NbxTi1−xN films show a dome-like behavior on the Nb content, with a maximal Tc at xNb∼0.65, and the Nb0.65Ti0.35N films also combine relatively large sheet resistance and intermediate residual resistivity ratio. Moreover, 60-nm-wide and 7-nm-thick Nb0.65Ti0.35N nanowires show a switching current as high as 14.5 μA, and saturated intrinsic detection efficiency with a plateau of more than 2 μA at 2.4 K. Finally, the corresponding SNSPDs on an alternative SiO2/Ta2O5 dielectric mirror showed a system detection efficiency of approximately 92% for 1550 nm photons, and the timing jitter is around 26 ps. Our results demonstrate that the highly disordered NbxTi1−xN films are promising for fabricating SNSPDs for near- and middle-infrared single photons with high detection efficiency and low timing jitter.