Heteroepitaxy of Ge x Si1-x (x ∼ 0.4-0.5) films on Si(001) substrates misoriented to (111): Formation of short edge misfit dislocations alone in the misorientation direction

Relaxation of mechanical misfit stresses in Ge (x) Si1 - x (x similar to 0.4-0.5) epitaxial films grown by molecular epitaxy on Si substrates misoriented from the exact orientation (001) by an angle of 6A degrees has been studied. Possible cases of induced nucleation and interaction of 60A degrees misfit dislocations (MDs) propagating in the misorientation direction with the formation of short edge MD segments are considered. Such configurations are classified and their various forms experimentally detected by TEM are presented. It is shown that short edge MDs are formed by two different mechanisms: (A) correlated or induced nucleation of a complementary 60A degrees dislocation half-loop followed by the formation of an edge dislocation segment; and (B) the formation of a 90A degrees MD segment upon intersection of the already existing complementary 60A degrees MDs gliding in oppositely inclined {111} planes. The nonequivalency of the interaction of 60A degrees MDs propagating in opposite directions along the substrate misorientation is shown.