Origins of defects in self assembled GaP islands grown on Si(001) and Si(111)

Microstructures of GaP epitaxial islands grown on Si(001) and Si(111) by chemical beam epitaxy have been investigated by transmission electron microscopy (TEM). Results indicate that planar-defect free GaP islands of sizes <20 nn can be produced at 560 degrees C on Si(001). Some of the islands are faceted on {111} and {113} planes. Subsequent planar defect formation occurs due to stacking errors on the smaller {111} facets of GaP islands that may be P-terminated. These stacking errors are attributed to the low surface mobility on P-terminated facets. A high density of planar defects is observed in smaller islands grown on Si(001) at 420 degrees C, a consequence of reduced atomic mobility at low temperatures that leads to {111} stacking errors. Wurtzite GaP has been observed to coexist with the zinc-blende polytype in some of the islands grown on Si(111) at 560 degrees C. (C) 1999 Elsevier Science S.A. All rights reserved.