Strain relaxation of lattice-mismatched In0.2Ga0.8As/GaAs superlattices on GaAs(001) substrates

A characterization of the strain relaxation of a series of In0.2Ga0.8As/GaAs superlattices grown on GaAs(001) substrates by molecular beam epitaxy has been performed by transmission electron microscopy. The superlattices were found to be partially relaxed with a residual strain of 0.5%, in contrast to predictions of relaxation models minimizing the sum of the strain and the dislocation energies with respect to the strain. A detailed analysis showed that three mechanisms impeding the formation and glide of dislocations mainly contribute to the reduced relaxation.