Intersubband Raman spectroscopy of two-dimensional electron gases in GaSb/InAs quantum wells

Abstract

Raman scattering in GaSb/InAs quantum wells has been studied near the resonance for a series of samples where two subbands are occupied. Up to three high-frequency branches of the coupled LO phonon - intersubband plasmon modes, i.e. , and , are observed. The results are analysed using three alternative models to calculate the energies of the coupled LO phonon - intersubband plasmon modes. Calculations of the intersubband plasmon energies without the inclusion of band non-parabolicity consistently give mode energies which are 8 to 18% higher than experiment. Two theoretical methods have been developed which take into account the subband occupancies and strong band non-parabolicity. The first provides simple analytical solutions and the second is based on a detailed numerical calculation to calculate the energies of the coupled LO phonon - intersubband plasmon modes. Good agreement is achieved with the experimental data.