In-situ observations of misfit dislocation propagation in Ge sub x Si sub (1-x) /Si (100) heterostructures.

We describe in-situ electron microscope observations of the motion of misfit dislocations in Ge sub (0.3) Si sub (0.7) /Si (100) heterostructures. A 450angstrom Ge sub (0.3) Si sub (0.7) /Si (100) structure is grown by Molecular Beam Epitaxy at 550C. Although this is below the critical thickness for this composition and growth temperature, we observe misfit dislocation nucleation and propagation as a function of in- situ annealing temperature in the electron microscope. This confirms the metastable nature of GeSi strained layer growth. The misfit dislocation density increases continuously with temperature, passing through an accelerated transition at ~850C. We also report preliminary measurements of misfit dislocation velocity, which establish the identical relationship between threading and misfit dislocations in this system.