INTERFACE STRUCTURE OF (001) AND (113)A GAAS ALAS SUPERLATTICES/

The interfaces of short-period GaAs/AlAs superlattices grown oil GaAs (001) and (113)A surfaces are investigated by means of reflection high -energy-electron diffraction(RHEED) and Raman spectroscopy. RHEED inve stigations during growth of the heterostructures reveal an intermixed normal (AlAs-on-GaAs) interface while the inverted one is seen to be a brupt. We measured the Raman shifts of the GaAs-like confined optical phonons. in [001] grown superlattices, we determine the thickness of t he intermixed region at the normal interface by comparison of the phon on wave vectors with the dispersion curve. This procedure is also appl ied to the [113] grown samples, where a splitting of the confined LO3 modes confirms the presence of an interface corrugation. We determine the height of the corrugation to be 3.4 Angstrom, (two bilayers) at on e interface while the other one is intermixed. This model is used for a reinterpretation of previously published Raman data [da Silva er nl. , Phys. Rev. B 53, 1927 (1996)] leading to a better agreement between experiment and theory.