Nb/Al-AlN/Nb superconducting tunnel junctions: fabrication process and characterization results

Modern radio astronomy demands for broadband receiver systems. For SIS mixers, this translates into objective to employsuperconducting tunnel junctions with very low RnA and low specific capacitance. The traditionally used Nb/AlOx/Nb junctions have largely approached their physical limit of minimizing those parameters. It is commonly recognized that it is AlN-barrier junctions, which are needed for further progressing of the broadband instrumentation for radio astronomy. In manuscript we present results of developing a fabrication process for high quality Nb/Al-AlN/Nb junctions and characterization the junctions\u27 DC electric properties and their aging and annealing stability, as well as the junctions\u27 specific capacitance