Ab initio(GaAs)3(AlAs)3(001) superlattice calculations: Band offsets and formation enthalpy

Abstract

We have performed self-consistent semirelativistic ab initio pseudopotential calculations of the (GaAs${)}_3$(AlAs${)}_3$ (001) superlattice. The valence-band offset is obtained by adding the energy of the top of the valence band relative to the average crystal potential in bulk GaAs and AlAs to the average crystal potential in the central sections on both sides of the superlattice. The 0.446-eV offset obtained is in good agreement with current experimental values. The formation enthalpy of the three-layer superlattice is found to be 1.2 meV (per twelve-atom unit cell) in comparison with 14.9 meV for the monolayer superlattice (per four-atom unit cell); this is attributed to a Coulomb repulsion between the interfacial planes.