Niobium nitride thin films prepared by atomic layer deposition for efficient superconducting nanowire single-photon detectors

High-quality ultra-thin films of niobium nitride (NbN) are developed by plasma-enhanced atomic layer deposition (PEALD) technique. Superconducting nanowire single-photon detectors (SNSPDs) patterned from this material exhibit high switching currents and saturated internal efficiencies over a broad bias range at 1550 nm telecommunication wavelength. Statistical analyses on hundreds of fabricated devices show near-unity fabrication yield due to exceptional homogeneity of the films with few defects. This ALD-NbN material is an ideal superconducting material for fabricating large single-photon detector arrays combining high efficiency, low jitter, low dark counts as well as large detection area.