Saturating quantum efficiency of SNSPDs with disorder manipulation of NbN films

Abstract

Quantum efficiency is one of the most important performance metrics for superconducting nanowire single-photon detectors (SNSPDs). Specifically, near-infrared NbN-SNSPDs with high quantum efficiency are extremely desirable in quantum communications. However, due to the high energy gap of NbN, it is difficult to achieve a saturated quantum efficiency. In this paper, we systematically investigated the primary determinants of fabricating highly saturated NbN-SNSPD by changing the stoichiometric ratio during the growth of NbN thin films. Through electron beam lithography and reactive ion etching processes, NbN-SNSPDs with a saturated quantum efficiency were fabricated. It is worth noting that the saturated quantum efficiency is observed to be closely related to the stoichiometric ratio of NbN films. Artificially increasing the disorder in NbN films can enhance the probability of superconducting phase transition during photon detection. Our work provides a consistently simple and effective method for the fabrication of highly efficient quantum devices, which is crucial for achieving higher precision in future quantum communications.