Nanowire single-photon detectors are fabricated on MgO substrates

Single-photon detectors are highly desirable for quantum information systems (see “Photons promise an exciting route to quantum computing,” p. 80). Federico Marsili at the Ecole Polytechnique Fédérale de Lausanne (Lausanne, Switzerland) and his team have fabricated a new type of superconducting single-photon detector (SSPD) based on high-performance nanowire and thin films grown at a temperature compatible with monolithic integration. His team deposited niobium nitrate (NbN) films ranging from 7 to 3 nm in thickness using dc magnetron sputtering onto magnesium oxide (MgO) substrates at 400ºC. The film thickness was controlled by fixing the plasma current at 250 mA for a constant deposition rate. The researchers then fabricated the SSPDs on the NbN films under optimal conditions using electron-beam lithography and reactive ion etching. The detectors were 5 × 5 µm2 in size, composed of nanowires ranging from 60 to 100 nm in diameter laid out in a meandering switchback pattern, and had fill factors of 40% to 60%. Electrical and optical characterizations performed on the SSPDs showed a high quantum efficiency of 20% at 1300 nm, measured at 4.2 K. Contact Francesco Marsili at [email protected].