High-quality thin Nb and NbN films (60-100 Å) are grown on (100) n+-InAs (n= 1019 cm-3) substrates by dc-magnetron sputter deposition. Studies of the electronic properties of interfaces between the superconductor and the semiconductor are done by Raman scattering measurements. The superconducting proximity effect at superconductor-semiconductor interfaces is observed through its impact on inelastic light scattering intensities originating from the near-interface region of InAs. The InAs longitudinal optical phonon LO mode (237 cm-1) and the plasmon-phonon coupled modes L- (221 cm-1) and L+ (1100 to 1350 cm-1), for n+ = 1 × 1019 - 2 × 1019 cm-3 are measured. The intensity ratio of the LO mode (associated with the near-surface charge accumulation region, in InAs) to that of the L- mode (associated with bulk InAs), is observed to increase by up to 40% below the superconducting transition temperature. This temperature-dependent change in light scattering properties is only observed with high quality superconducting films and when the superconductor and the semiconductor are in good electrical contact. A few possible mechanisms of the observed effect are proposed.
|Original language||English (US)|
|Number of pages||12107710|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Oct 1 2002|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics