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 T-c for NbxTi1-xN films show a dome-like behavior on the Nb content, with a maximal T-c at x(Nb) similar to 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 mu A, and saturated intrinsic detection efficiency with a plateau of more than 2 mu A 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.
Funding Agencies|National Natural Foundation of China [61971408, 61827823]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Knut and Alice Wallenberg foundation through the Wallenberg Academy Fellows program [KAW-2020.0196]; Swedish Foundation for Strategic Research (SSF) [RIF 14-0074]; Swedish Research Council VR-RFI [201900191]; Swedish Foundation for Strategic Research [RIF14-0053]; Linkoeping Electron Microscopy Laboratory