Evidence of electronic confinement in pseudomorphic Si/GaAs superlattices

We report the observation of coupling between intersubband plasmons and longitudinal-optical phonons in Si/GaAs superlattices pseudomorphically grown on GaAs-(001). Measurement of both phononlike (Formula presented) and plasmonlike (Formula presented) coupled modes by Raman scattering unambiguously demonstrated electronic confinement within pseudomorphic Si layers and allowed us to determine the (Formula presented)1 intersubband transition energy. Comparison with the results of tight-binding calculations indicated a type-I band alignment across the Si/GaAs heterojunctions, with a conduction-band offset of 0.61 eV and a valence-band offset of 0.25 eV.