Vibrational properties and infrared spectra of AlxGa1-xAs systems. II. Order and disorder features in superlattice configuration.

Abstract

Within the framework developed in the preceding paper (referred to herein as paper I) for the homogeneous alloys, we report our calculation of the dynamical properties for (${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As${)}_{\mathit{p}}$/(${\mathrm{Al}}_{\mathit{y}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{y}}$As${)}_{\mathit{p}}$ superlattices. In particular, Im${\mathrm{\ensuremath{\chi}}}_{\mathit{x}\mathit{x}}$, -Im${\mathrm{\ensuremath{\epsilon}}}_{\mathit{z}\mathit{z}}^{\mathrm{\ensuremath{-}}1}$, and reflectivity spectra are evaluated, within a bond-charge-model, mass-defect scheme, for superlattice periods corresponding to p=5 and p=3. Compositional disorder has been treated both by an average-t-matrix approximation and a supercell calculation. Features arising from the compositional disorder, structures originating from the superlattice configuration, and their interactions are discussed.