Excitons, phonons, and interfaces in GaAs/AlAs quantum-well structures

We report photoluminescence and resonant-Raman-scattering studies of single GaAs/AlAs quantum-well structures. Splittings of the exciton peaks show that there is a large-scale island structure at the interfaces. Shifts in the absolute exciton energies of quantum wells grown at different substrate temperatures and also the form of the optical-phonon energies as a function of both mode index and quantum-well width indicate that there also exists a small-scale structure on the interfaces.