Ge/Si(100) heterostructures: a photoemission and low-energy yield spectroscopy investigation

Heterostructures formed by epitaxial Ge grown in situ on Si(100) substrates were characterized by photoelectric yield spectroscopy, UPS and XPS. It is shown that both substrate and overlayer valence-band tops can be identified in the photoelectric-yield spectrum, thus allowing a direct and precise determination of the band lineup. We find a valence band discontinuity of 0.36 ± 0.02 eV for heterojunctions whose overlayers were grown according to the Stranski-Krastanov mechanism. A considerably larger offset is obtained from the analysis of the XPS data.