Structural characterization of SiGe step graded buffer layers grown on prestructured Si[001] substrates by molecular beam epitaxy

A SiGe graded buffer with a Si1-xGex/Si superlattice on top was grown on to p of long, Line shaped mesa structures being 2-10 mu m in width. Although e xtended over a length of 2 mm the drastic reduction of the dislocation dens ity, as recently reported for small mesas, was maintained if the mesas were aligned along certain crystallographic directions. Depending on the crysta llographic orientation, an asymmetric strain relaxation was observed. Regar ding band engineering this adds geometry as a new free parameter. (C) 1998 Elsevier Science S.A. All rights reserved.