Initial Strain Relaxation in S0.91Ge0.09/Si Superlattice Structures via Misfit-Dislocations

Abstract

ABSTRACTWe addressed the initial strain relaxation of symmetric 95 Å period Si0.91Ge0.09/Si heterostructures grown by ultra-high vacuum chemical vapor deposition on vicinal substrates miscut 2.04° from (001) in a direction 36° from a [110]. Double-axis x-ray topography revealed misfit-dislocation sources in the as-grown samples with an average density of about 60 cm−2, although the distribution of these sites was not homogeneous. The progression of dislocation nucleation and growth was observed during subsequent rapid thermal annealing (800°C, 20s-320s). Physical heterogeneities were identified as dislocation sources, and they gave rise to orthogonal misfit dislocation bundles, which on a macroscopic scale resemble crosses. Upon longer annealing, a more homogeneous distribution of defects was observed without measurable relaxation. These original defects did propagate; however, they did not spur a cross-slip multiplication sequence.