The parameters of the tunneling barrier of Nb/Al-AlOx/Nb Josephson junctions were estimated in a wide range of current densities using the Simmons method. It is shown that with an increase in resistivity RnS from 60 to 2100 omega mu m(2) (a reduction in the density of the tunneling current of junction J from 3.5 to 0.1 kA/cm(2)), the height of the tunneling barrier increases from 0.85 to 1.18 eV and its width increases from 10.7 to 13.3 angstrom. The experimentally observed linear dependence of the tunneling barrier parameters on RnS made it possible to estimate the capacitance of junctions in the range of RnS 10-30 omega mu m(2) required to create low-noise submillimeter-range receivers.
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