Feature Article - Semiconductor Superlattices with Small Band Offsets

Abstract

Optical transitions in small band offset superlattices are studied within the framework of the nearly free electron approximation, in which the weak superlattice potential is treated as a perturbation. Interband selection rules are derived for transitions involving conduction and valence band states at the superlattice Brillouin zone center and the zone edge. It is found that a number of new transitions can occur in such small-offset superlattices due to wave function mixing of different subband states. The effect of the effective mass on the optical transitions is also discussed. The theory is used to explain the results observed in magneto-optical absorption experiment in ZnSe/Zn1-xMnxSe small-offset superlattices. Furthermore, the nearly free electron formulation is fouud to be in excellent agreement with rigorous multi-band numerical calculation on superlattices involving small band offsets.