Fabrication of germanium-silicon strained-layer superlattices by molecular beam epitaxy

By using the molecular beam epitaxy (MBE), 2 types of germanium-silicon superlattices have been successfully fabricated. One is the ultra short period GE/Si superlattice, in which the thickness of alternately stacked pure Si and pure Ge layers are controlled below the critical thicknesses of pseudomorphic growth. Another type superlattice consists of Si and GexSi1-x alloy as alternated layers and is denoted as alloy composition GexSi1-x/Si superlattice. The growth techniques and the characterization by electron microscope, Rutherford backscattering, X-ray diffraction and optical measurements are presented. The ultra-short period Ge/Si superlattices grown by the phase locked epitaxy method under moderate temperature show sharp and abrupt interfaces. The effect of misfit strains built in different layers of the alloy composition GexSi1-x/Si superlattices is investigated by the Raman scattering spectroscopy. (author). 19 refs.; 5 figs