Variation in misfit dislocation behavior as a function of strain in the GeSi/Si system

We show how strained-layer relaxation via misfit dislocation introduction varies significantly in GexSi1−x/Si (100) epitaxy as a function of the strain in this system. It is found that for samples grown by molecular beam epitaxy at a substrate temperature of 550 °C, structures with lower strain (x=0.15) are highly metastable, relaxing most of their excess stress on annealing to temperatures ∼650–750 °C. Structures with higher strain (x=0.25) are observed to relax far more gradually over the temperature range 550–900 °C. In situ electron microscope observations explain this behavior in terms of misfit dislocation interactions in the relaxing material.