Anomalous confinement effects in HgTe-CdTe superlattices

We show that superlattices consisting of materials A and B such that isolated atoms of type A behave as deep impurities when introduced in a bulk sample of B (e.g., Hg in CdTe) exhibit anomalous confinement which is outside the conceptual framework of particle-in-a-box models. Our theory is implemented in a full-scale pseudopotential calculation for HgTe-CdTe(001) superlattices of period {}60 A{}. The valence-band offset ({Δ}Eᵥ=370 meV) and the variation of the forbidden gap versus composition are obtained in good agreement with recent experimental data.