Electronic states of thin epitaxial layers of Ge on Si(100)

The valence density of states of Ge grown epitaxially on Si(100) is investigated as a function of thickness by yield spectroscopy and photoemission techniques. A double edge is present in the yield data for thicknesses smaller than the lattice relaxation critical thickness. Furthermore, the line-up of the Ge states to the Si valence band varies with overlayer thickness. Photoemission techniques fail to detect this behavior. The causes for the discrepancy are analyzed.