Epitaxial aluminum nitride tunnel barriers grown by nitridation with a plasma source

High critical current-density (10 to 420 kA/cm(2)) superconductor-insulator-superconductor tunnel junctions with aluminum nitride barriers have been realized using a remote nitrogen plasma from an inductively coupled plasma source operated in a pressure range of 10(-3)-10(-1) mbar. We find a much better reproducibility and control compared to previous work. From the current-voltage characteristics and cross-sectional transmission electron microscopy images it is inferred that, compared to the commonly used AlO(x) barriers, the polycrystalline AlN barriers are much more uniform in transmissivity, leading to a better quality at high critical current densities. (c) 2007 American Institute of Physics.