Influence of misfit strain on {311} facet development in selective epitaxial growth of Si1-xGex/Si(100) grown by gas-source molecular beam epitaxy

Selective epitaxy of Si1-xGex/Si(100) via gas-source molecular beam epitaxy was carried out to compare facet formations in Si1-xGex to Si. A single {3 11} facet with a pronounced cusp at the intersection with the (100) surface was observed in large windows (25 mu m) However, facet formations occurrin g within smaller windows (less than or equal to 5 mu m) show the developmen t of {311}- and {111}- type facets. For the 1-2 mu m features, no cusps wer e observed, and facet growth was initiated at an earlier stage of developme nt, avoiding contact with the SiO2 mask. While a 1400 Angstrom Si epilayer is expected to have a {311}/{111} ratio of much less than one (similar to 0 .15), for the 1-2 mu m windows, however, it is similar to 2. The persistenc e of the {311}-type facet offers a faster reduction of the original (100) s urface that facilitates the fabrication of a nanoscale template. (C) 2000 E lsevier Science S.A. All rights reserved.