Nb/AIN/Nb Josephson Junctions with High Critical Current Density

Abstract

We have produced Nb/AINX/Nb Josephson tunnel junctions with the aims of improving the control of critical current density Jc in the high-Jc range and exploring the possibility of high-Jc junctions with low subgap quasiparticle currents. Conventional Nb/AIOx/Nb junction barriers are formed by oxidizing a thin Al overlayer on the Nb base electrode, and precise control of the oxidation process is difficult at low levels of oxygen exposure. The reactivity of Al with N2 is very low, and AINX barriers are therefore formed using an N2 plasma. We report the fabrication of AINX barrier junctions with Jc as large as 4 mA//μm2 and compare their properties to Nb/AIOx/Nb ones of similar Jc. © 1995 IEEE