Electronic band structure of the (GaAs)1/(InAs)1 (111) superlattice.

Abstract

We present a first-principles calculation of the electronic band structure of (GaAs${)}_{1}$/(InAs${)}_{1}$ (111) superlattice, performed by using ab initio norm-conserving pseudopotentials. The folding in the smaller Brillouin zone and the new symmetry properties of the electronic states have been thoroughly investigated by a comparison with the band structure of the corresponding disordered alloy treated within the virtual-crystal approximation. The interactions between the folded states giving rise to energy splittings and electronic charge localization on given layers have been analyzed at the high-symmetry points. The effects of the new ordering potential, introduced by differentiating the two cations in the virtual crystal, and of the strain potential---arising when the superlattice is subjected to a lateral strain on the (111) planes---are separately investigated. We find a strong charge localization in the first two conduction states at the \ensuremath{\Gamma} point and a considerable minimum-band-gap reduction in the new ordered structure with respect to the virtual crystal. The strength of this localization and the fundamental band gap depend on the superlattice orientation and on the strain condition.