Nb Josephson junction with an AlN<i>x</i> barrier made by plasma nitridation

Abstract

We studied Nb junctions with aluminum nitride, AlNx, tunnel barriers formed by plasma nitridation on aluminum film surfaces. The AlNx barrier junctions show current-voltage characteristics with leakage currents small enough and critical current densities large enough for use in Josephson digital circuits. The AlNx barrier junction exhibited improved annealing stability as compared to AlOx barrier junctions. For the AlNx barrier junction, decreases in critical current during annealing at 250 °C are remarkably suppressed.