Stationary properties of SINIS double-barrier Josephson junctions

This paper reports on the evaluation of the effective suppression parameter eff in double-barrier Josephson junctions realized in Nb-Al/Alx Oy /Al/Alx Oy /Al-Nb SINIS technology. This parameter describes the overall resistance of current flow across the interfaces within the whole structure configuration and characterizes its I C R N product attainable. By comparison with theoretical descriptions of tunnelling structures in the dirty-limit approximation, the effective suppression parameter eff has been extracted from the measured temperature dependence of the I C R N product. For SINIS junctions of a series of different wafer productions with various critical currents of the fabricated junctions, the evaluated values of eff range between 80 and 250. With reference to the proximity effect and to the possibility of removing the Al layers at the Nb electrodes, a value of eff has been deduced, which ranges between 50 and 120. This is very close to the assigned value between 10 and 20 ideally suitable for integrated circuit applications, e.g. Josephson voltage standards and rapid single flux quantum circuits.