Comparison of Hot Spot Formation in NbN and MoN Thin Superconducting Films After Photon Absorption

In superconducting single-photon detectors (SSPD), the efficiency of local suppression of superconductivity and hot-spot formation is controlled by diffusivity and electron–phonon interaction time. Here, we selected a material, 3.6-nm-thick MoN ${}_{x}$ film, which features diffusivity close to those of NbN traditionally used for SSPD fabrication, but with electron–phonon interaction time an order of magnitude larger. In MoN ${}_{x}$ detectors, we study the dependence of detection efficiency on bias current, photon energy, and strip width, and compare it with NbN SSPD. We observe nonlinear current-energy dependence in MoN ${}_{x}$ SSPD and more pronounced plateaus in dependences of detection efficiency on bias current, which we attribute to longer electron–phonon interaction time.