LIGHT-SCATTERING-STUDIES OF ZNSE GAAS HETEROSTRUCTURES/

Raman studies using the allowed and the forbidden longitudinal optical (LO) Frohlich interactions are employed to investigate the heterostru cture of ZnSe/GaAs as a counterpart to three-photon mixing or second h armonic generation studies. Our samples are an undoped ZnSe/GaAs (001) heterojunction with a ZnSe overlayer varying from 50 to 5000 angstrom . The scattering intensities for the allowed and the forbidden LO inte ractions at both resonant and nonresonant incident frequencies for ZnS e are investigated. The nonresonant forbidden LO phonon shows the effe ct previously observed for the pseudomorphic region of ZnSe thickness as well as for thicker films. The allowed LO intensities show a clear interference effect similar to recent interference effects observed in second harmonic generation for identical ZnSe/GaAs heterostructures. At resonant incident frequency in ZnSe, forbidden LO phonon scattering shows strong enhancement and is an order of magnitude larger than the allowed scattering due to wave-vector-dependent scattering in ZnSe.