Fluctuating and phase-stiff proximity-induced superconductivity in superconductor-semiconductor junctions

Results from transport measurements made on Nb/InGaAs heterojunctions show evidence of strong coupling across the superconductor-semiconductor interface. A novel 3-Terminal device geometry allows the simultaneous extraction of the specific contact conductance and the 2D sheet resistance in the semiconductor nearby the junction interface. A transition from fluctuating to phase-stiff proximity induced superconductivity is observed in the semiconductor at temperatures often well below the transition temperature of the superconductor. This phenomenological interpretation is supported by the fact that the enhancement observed in the specific contact conductance is too large (greater than a factor of two) to be explained by simple Andreev reflection. Significant and abrupt changes in the semiconductor's 2D sheet resistance also suggest phenomenology beyond simple boundary effects.