Investigation of the electrical properties of vertically stacked interface-treated Josephson junctions

In order to understand the barrier structure of vertically stacked-type interface-treated Josephson junctions, we compared the electrical properties of the stacked junctions with those of ramp-edge junctions. With increasing critical current density (Jc), IcRn products for both types of junction increased and the spread of critical current decreased. Nevertheless, the stacked junctions had higher IcRn products and lower spreads than those of ramp-edge junctions with Jc of the same order. Moreover, we investigated the temperature dependence of the critical current and the conductance for junctions with Jc values of around 103 A cm−2. No significant difference was found for the dependence of Ic. In contrast, the conductance of stacked junctions somewhat increased with increasing temperature, which resulted in the reduction of IcRn. The reduction is small at 4.2–30 K; we thus think that the reduction is negligible for applications.