Structural features of MBE grown very short period GaAs-AlAs superlattices

Abstract

Very short period GaAs-AlAs superlattices (period less than 25 Å) were grown by molecular beam epitaxy. Three techniques were carried out to study these samples: transmission electron microscopy, X-ray diffraction, and photoluminescence. Diffraction techniques have proved to be particularly suitable for the analysis of this type of samples. By combining electron and X-ray diffraction, the origin of the fine structure of diffraction peaks could be explained with respect to the growth process. Owing to the high sensitivity of diffraction techniques, very small period variations (less than one monolayer) could be evidenced. The period of the three described samples was shown to be a fractional number of monolayers, which is related to the growth conditions used in this MBE set-up. Photoluminescence results give evidence of the high quality of the superlattices, and are fully consistent with those given by the diffraction techniques.