Overdamped Josephson junctions with Nb/AlOx/Al/AlOx/Nb structure for integrated circuit application

We present characteristics of overdamped Josephson junctions consisting of Nb/AlOx/Al/ AlOx/Nb structures. The junctions were fabricated using a well-developed Nb/AlOx/Nb-junction technology and showed well-defined Josephson characteristics at 4.2 K. The characteristic voltage V-c [the product of the critical current I-c and the effective normal resistance R-n(eff)] of junctions, which determines high-frequency performance of the junction, was in the range of 0.1-0.5 mV, and the critical current density J(c) in the range of 10(2)-10(4) A/cm(2). Maximum-to-minimum variations in I-c over a wafer were +/-4% for junctions with V-c=0.15 mV and +/-13% for junctions with V-c = 0.5 mV. (C) 1997 American Institute of Physics.