Structural stability and valence charge density in (GaAs)1(InAs)1 (111) superlattice

We present a theoretical study of the structural stability and the ground-state electronic distribution of a (GaAs)1/(InAs)1 superlattice grown along the [111] direction. The calculations were carried out self-consistently using norm-conserving pseudopotentials in the local-density approxima- tion. We find that the unrelaxed superlattice with a single anion-cation bond length is unstable with respect to disproportionation into the binary systems. By allowing for relaxation through plane displacements along the [111] directions under the constraints of having only two different bond lengths, the energy may be significantly lowered, but the superlattice remains unstable. The effects of deformation, chemical exchange, and relaxation on the valence charge distribution are investigated and the peculiar characteristics of the chemical bond in the superlattice are pointed out.