Fabrication and characterization of epitaxial NbN/MgO/NbN Josephson tunneljunctions

We fabricated epitaxial NbN/MgO/NbN Josephson tunnel junctions with good tu nneling characteristics in the range of J(C)=0.2-70 kA/cm(2). The counter a nd base NbN electrodes of the tunnel junctions had the same T-C and 20 K re sistivity at about 15.7 K and 60 mu Omega -cm, respectively. X-ray analysis showed that all the layers that formed the tunnel junctions grew epitaxial ly. In the range of J(C)=0.2-15 kA/cm(2), the tunnel junctions fabricated h ad large gap voltages (5.6-5.9 mV), narrow gap widths (less than 0.1 mV), h igh ICRN products (2.6-3.8 mV), and small subgap leakage current (V-m=40-96 mV). (C) 2001 American Institute of Physics.