EXPERIMENTAL S-2DEG-S JUNCTION CHARACTERISTICS AND A NOVEL INTERPRETATION

We present experimental transport characteristics of long and ballisti c superconductor - 2-dimensional electron gas - superconductor junctio ns obtained in a temperature range from 1K down to 10mK. Surprisingly the critical current I-c can be fitted to the ideal junction temperatu re dependence, I-c(T) proportional to exp(-T/T-0) approximate to exp(- L/xi(T)), with xi(T) the thermal coherence length, despite the presenc e of interface barriers and a to small I-c. We propose that the confli ct between the experimental data and the theoretical predictions for t hese non ideal junctions might be resolved by employing concepts from the theory of disorder induced opening of tunnel channels.