Redistribution of epitaxial Si on -001- GaAs during overgrowth by GaAs.

We examine the stability of pseudomorphic submonolayer Si films embedded in (001) GaAs by molecular-beam epitaxy. Secondary ion-mass spectrometry depth profiling reveals the presence of 10high19 Si- atoms/ccm in the first 40 nm of the GaAs cap layer. The systematic investigation of samples having different cap thickness by Hall effect measurements and local vibrational mode Raman spectroscopy allows us to identify the site distribution of Si atoms in the cap layer and yields insight into the migration mechanism.