Inclusion-generated dislocation clusters in liquid phase epitaxy

Abstract

Dislocation clusters generated by inclusions during the liquid phase epitaxial (L.P.E.) growth of GaAs/GaAlAs material have been analysed by transmission electron microscopy and found to fall into four basic categories distinguished by the nature of the Burgers vector diagram. The clusters appear to obey a Burgers vector sum rule. In this material a[001] screw dislocations have also been observed. A model for the generation of the clusters has been developed. It is based on the assumption that dislocations are nucleated in the first monolayer to solidify over the inclusion and is consistent with the experimental observations. It seems likely that only sessile portions of the clusters remain after growth and cool-down of the material, consistent with recent photo-excitation observations (Monemar and Woolhouse 1977).