Relaxation of strained-layer semiconductor structures via plastic flow

An outstanding puzzle concerning strained-layer semiconductors is that metastable structures can be grown in which exact coherence with the lattice is apparently conserved in layers much thicker than the equilibrium critical thickness. Using standard descriptions of dislocation dynamics and relaxation via plastic flow, a model for the relaxation of an initially coherent metastable strained layer is developed. This model is applied to relief of mismatch strain in the SiGe/Si(100) system, and good agreement with experimental data is found. Furthermore, the combined effect of relaxation kinetics and finite instrumental resolution on the observed critical thickness was calculated. The results successfully reproduce experimental data on metastable critical thickness in the SiGe/Si(100) system.