Pseudomorphic growth of Si_xGe_1-x on GaAs(110)

Si_xGe_1-x films were grown on cleaved GaAs(110) surfaces by molecular beam epitaxy at growth temperatures between 20 and 500 degrees C. The lattice mismatch between substrate and overlayer can be varied continuously between 0 and 4% by changing the Si_xGe_1-x composition from x=0 (pure Ge) to x=1 (pure Si). The lateral lattice constant of the overlayer was determined as a function of coverage by quantitative analysis of the respective LEED pattern. This gives the critical thickness h_c up to which the overlayer is elastically accommodated to the substrate. The segregation of Ga and As on top of the Si_xGe_1-x layers is studied as a function of growth temperature and composition with Auger electron spectroscopy.