NbN/MgO/NbN Josephson junctions for integrated circuits

Characteristics of the NbN/MgO/NbN Josephson junction for integrated circuits have been investigated. The deposition process of the MgO film for the tunnel barrier was systematically investigated to obtain the controllability of the Josephson critical current density. The reproducibility of the Josephson critical current density was improved to ±28% with the critical current density of 610 A/cm2 and ±20% with the critical current density of 16 kA/cm2. The uniformity of the Josephson critical current density across a 3 cm-square area on the substrate was improved to ±12% with the critical current density of 650 A/cm2.