Fabrication of Superconducting Nanowire Single-Photon Detectors Using MoN

We report the fabrication of superconducting nanowire single-photon detector (SNSPD, SSPD) based on molybdenum nitride (MoN) film with and without a cavity structure. Ultrathin polycrystalline γ-Mo
₂
N films with a
T
_c
about 6 K were obtained by reactive DC magnetron sputtering. The absorption efficiency of the device was calculated by the finite-difference time-domain (FDTD) method using the optical constants of MoN determined by ellipsometry measurements. The SNSPD with a meander of 150-nm-width and 7-nm-thick nanowire showed a long saturation plateau in the bias current dependence of the system detection efficiency (SDE) at visible wavelength. The SNSPD with a cavity structure showed an SDE of 37% and a timing jitter of 79 ps at a wavelength of 1560 nm. The results show that MoN is a promising alternative to amorphous superconductors for high-performance SNSPD.