Cooper pairs and quasi-particles tunneling in light-sensitive junctions

Tunneling experiments have been performed on lead-cadmium sulphide-lead light-sensitive junctions. In the framework of an equivalent rectangular average barrier model and assuming an effective mass approximation, experimental current-voltage and conductance voltage characteristics have been employed to evaluate the tunneling barrier parameters in dark conditions and at increasing light exposure levels. A parabolic shape for the barrier has been assumed to give a qualitative account for the behavior of the junctions with the light exposure time. Measurements of the temperature dependence of the light-induced dc Josephson current also supports the deviation from the "rectangular" shape of the tunneling barrier at heavy illumination levels.