High-temperature superconductor vertically-stacked Josephson junctions

We study vertically-stacked interface-treated Josephson junctions (ITJs). The barriers of ITJs are formed by Ar ion etching and subsequent annealing, not by depositing an artificial barrier. We have investigated the dependences of the junction properties on the processing parameters. It is found that the control of junction properties can be realized by controlling the incidence angle of Ar, and that the higher accelerating voltage of Ar reduces leakage paths in a barrier. Moreover, we have successfully eliminated the excess current of the junctions using the PrGaO₃ (PGO) doping process. We conclude that the conjunction of the interface treatment and the PGO doping technique leads to highly integrated Josephson circuits.