Electronic Structure of Intentionally Disordered AlAs/GaAs Superlattices

Abstract

We use realistic pseudopotentials and a plane-wave basis to study the electronic structure of nonperiodic, three-dimensional, 2000-atom (AlAs${)}_{\mathit{n}}$/(GaAs${)}_{\mathit{m}}$ (001) superlattices, where the individual layer thicknesses $n,m\in \{1,2,3\}$ are randomly selected. We find that while the band gap of the equivalent ( $n=m=2\mathrm{}$) ordered superlattice is indirect, random fluctuations in layer thicknesses lead to a direct gap in the planar Brillouin zone, strong wave function localization along the growth direction, short radiative lifetimes, and a significant band-gap reduction, in agreement with experiments on such intentionally grown disordered superlattices.