Excitons in semiconductor superlattices: Heuristic description of the transfer between Wannier-like and Frenkel-like regimes

In this paper, we present a straightforward model calculation, based on a heuristic approach, which gives a satisfactory description of excitons in quantum-confined heterostructures, varying continuously from isolated quantum wells to superlattices. In particular, we show how it is possible to account for the progressive crossing from a Wannier-like regime, for short periods, to a Frenkel-like behavior, when the quantum wells become decoupled. We propose a comparison with previous variational approaches.