Elimination of microtwins in silicon grown on sapphire by molecular beam epitaxy

Publisher Website
Google Scholar
Abstract
Using transmission electron microscopy, we have examined a number of (001) silicon thin films grown on (1̄012) sapphire substrates by molecular beam epitaxy (MBE). We have found that for silicon films less than 0.55 μm thick, microtwins are very much in evidence. For silicon films greater than 700 nm thick, however, dislocations, rather than microtwins, are the predominant defect. It is our conjecture that dislocation extension, and the associated disappearance of microtwins in thicker MBE-grown SOS films, is analogous to the generation of misfit dislocations in silicon-germanium films grown on silicon or germanium substrates by MBE; furthermore, these observations can be understood via the concept of excess stress that has been recently formulated by Tsao, Dodson, and others. The persistence of microtwins in SOS grown by chemical vapor deposition, as opposed to MBE-grown SOS, can be understood in terms of Dodson and Tsao’s formulation of plastic deformation kinetics in thin films.