Resonance Raman Scattering in GaAs sub n AlAs sub n Superlattices with n = 1,2,3.

We report Raman results from ultra-thin (GaAs) sub n (AlAs) sub n superlattices grown by molecular beam epitaxy. We observe two resonances in Raman scattering by LO-phonons which can be assigned to the E sub 0 -gap of the superlattice and to transitions from the valence band at GAMMA to folded X sub z states in the conduction band. Both resonances are of comparable intensity when the energy of the X-derived and GAMMA-derived states are close to each other, suggesting a substantial degree of GAMMA-X mixing. We find the E sub 0 -gap energy to increase from n = 1 to n = 3. We also investigate the spatial localization of the electronic wavefunctions by monitoring the relative resonances of GaAs- and AlAs-phonons, which are expected to be well localized in their respective layers for superlattices as thin as n = 2.