Internally shunted sputtered NbN Josephson junctions with a TaNx barrier for nonlatching logic applications

Abstract

We report on the growth, fabrication, and device characterization of NbN internally shunted Josephson junctions with a TaNx barrier. The resistivity of TaNx films could be varied from a few hundred micro-ohms to a few hundred milliohms by increasing the N 2 pressure during reactive sputtering. The temperature dependence of I c R n of the junctions with ∼13 mΩ cm barrier resistivity was measured for various barrier thicknesses. The coherence length of the barrier was determined to be 5 nm. By adjusting the barrier thickness, I c R n values >500 μV were observed up to 8.3 K, with I c and R n of magnitudes that are suitable for single-flux-quantum digital circuits.