Parametric Characterization and Macroscopic Quantum Tunneling of $\hbox{Nb}/\hbox{AlO}_{\rm x}/\hbox{Nb}$ Josephson Junctions

Parameters of
$\hbox{Nb}/\hbox{AlO}_{\rm x}/\hbox{Nb}$
Josephson including its critical current and capacitance which determine the dynamic energy consumption and speed of the superconducting electronics have been measured. The critical current of a
$22 \times 22 \ \mu\hbox{m}^{2}$
junction is
$1801 \pm 52 \ \mu\hbox{A}$
calculated from the dependent curve between the lifetime of zero-voltage and switching current. The specific capacitance is
$0.051 \pm 0.008 \ \hbox{pF}/\mu\hbox{m}^{2}$
obtained by observing Fiske self-resonant step when applied several Gauss magnetic field. Critical current distributions had been measured as a function of temperature from 900 mK to 40 mK. The distribution widths become independent of temperature below 200 mK, which indicates the transition between thermal activation and macroscopic quantum tunneling of junction phase.