I n s i t u observations of misfit dislocation propagation in GexSi1−x/Si(100) heterostructures

We describe in situ electron microscrope observations of the motion of misfit dislocations in Ge0.3Si0.7/Si(100) heterostructures. A 350 Å Ge0.3Si0.7/Si(100) structure is grown by molecular beam epitaxy at 550 °C. 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 ∼850 °C. We also report preliminary measurements of misfit dislocation velocity, which establish the identical relationship between threading and misfit dislocations in this system.