Photoluminescence study of AlAs/GaAs superlattices containing enlarged wells

Photoluminescence (PL) spectra of MBE grown short-period AlAs/GaAs superlat tices with one or two enlarged wells (5 and 12 nm) have been measured at 2 K. Sharp PL peaks corresponding to excitonic transitions between the lowest electron and heavy-hole states in the enlarged wells are observed. The exc itonic transition energies are calculated by means of an envelope function based model, taking into account the exciton binding energies. The model in corporates a smooth potential at the interfaces, which is represented by a diffusion potential, the diffusion length being a parameter. The calculated and experimentally observed excitonic transition energies agree well if di ffusion lengths of 3.5 and 4.5 monolayers are considered in the samples wit h and without a buffer layer, respectively. These values are consistent wit h the complicated nature of the growth kinetics and mechanisms of quantum h eterostructures. The PL spectra reveal also complicated structures connecte d with the superlattice. Their qualitative discussion confirms the smooth p otential model. Thus, an attempt is made to extend the analysis of complica ted AlAs/GaAs heterostructures towards real interfaces, which is essential for advanced device fabrication. (C) 2000 Elsevier Science S.A. All rights reserved.