Semiconductor-Like Behavior in Superconducting <font>Nb</font>/<font>Al</font> Films

We report here the experimental evidence of semiconductor-superconductor transitions in relatively thick Nb/Al structures. The temperature dependence of resistivity ρ(T) shows a sharp superconducting transition followed by either a normal metallic behavior in low-resistivity samples, or a semiconducting behavior when the sample resistivity at 10 K is above 100 μΩ cm. We discuss here the fabrication conditions and the electron localization regime associated with the measured ρ(T) dependence.