Light scattering from slightly rough semiconductor surfaces near exciton resonance

Abstract

The phenomenon of light scattering by a randomly rough surface and fluctuations of the excitonic surface potential is investigated by means of a first-order perturbation theory. We employ the generalized Morse potential to describe both intrinsic (repulsive) potentials and extrinsic near-surface potential wells. Frequency and angle dependencies of the light-scattering cross section are calculated. A considerable increase of the scattering cross section, as the correlation between the surface roughness and the excitonic potential fluctuations diminishes, is observed. Our theory describes very well available experimental results for samples with a repulsive surface potential. Also, the optical manifestation of excitonic bound states, generated within a surface-potential well, is analyzed. We find that the near-surface localized excitons produce a resonance structure in the spectrum of the light-scattering cross section, which is very sensitive to the degree of correlation between surface roughness and potential-well fluctuations.