Inelastic light scattering by collective charge-density excitations in GaAs-Ga1-xAlxAs superlattices.

Abstract

We consider the collective excitations of a finite GaAs-${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Al}}_{\mathrm{x}}$As superlattice with arbitrary subband structure and electronic density. The density-density correlation function is calculated with use of the random-phase approximation, augmented by the local-density-functional theory. Exchange and correlation effects, self-consistent subband wave functions and energies, and intersubband scattering for arbitrary electron densities are taken into account. The resonant inelastic-light-scattering spectra by collective excitations are calculated. It is found that coupling between intersubband and intrasubband modes is very important when several subbands are occupied, in contrast to the results obtained with only a single subband occupied. The effects of exchange and correlation are found to be small.