Electrical characterization of Nb/Al-oxide/Nb Josephson junctions with high critical current densities

Transport in Nb/AlO/sub x//Nb junctions involves two parallel channels, barrier defects (pinholes) with sub-nanometer dimensions and nearly-ideal tunneling regions. We fit junction characteristics using only a single parameter, the ratio of the normal state conductances of these current paths. Our barrier model accounts for the excellent Josephson behavior and highly non-ideal quasiparticle characteristics of junctions with critical current densities as high as 4 mA//spl mu/m/sup 2/. It appears to be quite generally applicable to tunnel junctions.<
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