SURFACE-MORPHOLOGY OF MOLECULAR-BEAM EPITAXIALLY GROWN SI1-XGEX LAYERS ON (100) AND (110) SI

The surface morphology and dislocation structure of Si1-xGex layers grown on (100) and (110) Si substrates have been investigated using atomic force microscopy, and scanning and transmission electron microscopy. The layers, which have up to a 1.2% lattice mismatch with the substrates, were grown by molecular-beam epitaxy at 550-degrees-C at thicknesses above those required for the introduction of dislocations. Si1-xGex, layers grown on (100) show a crosshatch morphology which is correlated to the underlying misfit dislocation network. Annealing greatly enhances the surface roughness producing a partial islanding growing on the pre-existing crosshatch morphology. On the (110) substrates no annealing is necessary to produce a roughened surface. The roughened surface morphology is analyzed as a strain-reducing growth mode which enables partial relaxation of the near-surface atomic planes.