The strain relaxation behavior of Si_(0.82)Ge_(0.18) films on silicon-on-insulator (SOI) substrates was investigated for films grown beyond the critical thickness and strain-relaxed during growth and metastable films, grown beyond the critical thickness, which relaxed during subsequent thermal annealing. The thickness of the top silicon layer of the SOI substrate was varied over a range from 40 nm to 10 μm. In all cases, the SiGe film relaxation occurred via the nucleation and propagation of dislocations with the same onset of film relaxation and same relaxation rate for both SOI and bulk Si substrates. The SOI substrate does not serve as a compliant substrate but does alter the dislocation structure and motion. The buried amorphous oxide layer in the SOI substrate leads to the relaxation of the dislocation strain field through the removal of the dislocation line tension. This removal of the dislocation line tension drives dislocation motion and leads to the development of strain in the thin Si layer of the SOI substrate. Models of this dislocation behavior for SiGe growth on the SOI substrate are presented and calculation of the equilibrium strain of the thin Si substrate layer closely fits the measured strain of several SOI substrates. The article addresses the implications of the modified dislocation structure and kinetics for film relaxation on SOI substrates.
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