ELECTRONIC-STRUCTURE OF INTENTIONALLY DISORDERED ALGS/GAAS SUPERLATTICES

We use realistic pseudopotentials and a plane-wave basis to study the electronic structure of nonperiodic, three-dimensional, 2000-atom (AlAs)n/(GaAs)m (001) superlattices, where the individual layer thicknesses n,m{1,2,3} are randomly selected. We find that while the band gap of the equivalent (n=m=2) 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. © 1995 The American Physical Society.