Raman scattering as a probe of the superconducting proximity effect

Temperature-dependent Raman spectroscopy is used to investigate the effect of superconductivity on the near-surface electronic structure of a semiconductor in good electrical contact with a superconductor. The light scattering is performed through a high-quality thin (60-100 Angstrom) film of Nb, grown directly onto in-situ Ar+-etched (100)-n(+)InAs. Below T-c, the LO mode, associated with the surface charge accumulation layer in the InAs, is enhanced by similar to 40% in comparison with the nearby L_ bulk phonon mode. This change, reversible upon temperature cycling, is observed only when the Nb is in good electrical contact with the InAs. Preliminary results show a similar effect on NbN/InAs. Our results constitute the first optical detection of the superconducting proximity effect.