Photoluminescence from 'spike doped' hydrogenic donors in Al0.3Ga0.7As-GaAs quantum wells

We have performed photoluminescence (PL) measurements on GaAs-Al0.3Ga0.7As superlattices where Si donors have been selectively doped at the center of the non-interacting quantum wells. A PL feature is shown to be donor related and is attributed to the radiative recombination of an electron of a neutral donor at the center of a quantum well with a heavy hole. Furthermore, our measurements indicate that the binding energy of the electron bound at a neutral donor is slightly larger than that of a coupled electron heavy hole exciton and, in addition, is significantly larger than that observed for donors in bulk GaAs. These observations are in substantial agreement with recent theoretical calculations.