PHOTOREFLECTANCE AND RESONANT RAMAN-SCATTERING OF ABOVE-BARRIER TRANSITIONS IN A GAAS ALGAAS SUPERLATTICE/

We have investigated the energy states above the barrier potential (ab ove-barrier states) in a (GaAs)(10)/(Al0.3Ga0.7As)(10) superlattice us ing photoreflectance and resonant-Raman scattering spectroscopies. The energies of the photoreflectance signals observed in the above-barrie r region higher than the band-gap energy of Al0.3Ga0.7As just agree wi th the peak energies of the resonant-Raman profiles of the longitudina l-optical phonons. From the miniband energies calculated by an effecti ve-mass approximation, we conclude that the photoreflectance signals a nd the resonant Raman profiles are caused by the transitions associate d with the above-barrier states at the mini-Brillouin-zone edge.