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 investigations during growth of the heterostructures reveal an intermixed normal (AlAs-on-GaAs) interface while the inverted one is seen to be abrupt. We measured the Raman shifts of the GaAs-like confined optical phonons. in [001] grown superlattices, we determine the thickness of the intermixed region at the normal interface by comparison of the phonon wave vectors with the dispersion curve. This procedure is also applied 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 one 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.