Local-density theory of band offsets in strained superlattices: (InAs)n/(InP)n (001)

A systematic study of the electronic properties of (InAs)n/(InP)n (001) superlattices (n=2,3) using the full-potential linearized augmented-plane-wave (FLAPW) method is presented. We consider superlattices chosen to simulate two different stress conditions represented by (i) a free-standing mode (no substrate is assumed) and (ii) the superlattice grown epitaxially on an InP substrate. The valence-band lineup is determined by two different methods: by using the core levels as energy references and by evaluation of the potential discontinuity at the interface. We find that the charge readjustment at the interface is rather small, and that it does not contribute significantly to the potential lineup nor is it sensibly affected by the strain conditions. The strain is seen to affect mainly the energy position of the valence-band maximum in the two constituents, suggesting the suitability of these materials for band-offset tailoring by means of a proper adjustment of the strain. The agreement with the experimental results available for the valence-band offset to date is very good. Effects of the strain on the valence-band discontinuity are discussed.