Fabrication of superconducting nanowire single proton detectors

Abstract

The future NASA Mars project will need an ultra-fast, highly sensitive photodetector to increase the bandwidth of free-space long-range communication, which is now done primarily using RF signals. Our original motivation in fabricating superconducting nanowire single-photon detectors (SN-SPD) is to fulfill this need. The SN-SPD's reported GHz counting rates [1] make it very attractive for this application. A new fabrication process for making SN-SPDs using hydrogen-silsesqioxane (HSQ), a high-resolution electron-beam lithography resist will be presented. An electron-beam proximity-effect correction program was developed to achieve nanowires with uniform linewidths, which is important for device performance. Finally, we present initial test results that show device functionality and performance. Our best device has a detection efficiency of [approx.] 10 % at 1064 nm photon wavelength at 2.1 K and a photon-induced voltage-pulse duration of [approx.] 3 ns.