STRESS ACCOMMODATION IN LARGE-MISMATCH SYSTEMS

Accommodation of lattice mismatch is investigated for the case of large (epsilon > 0.02) mismatch. In particular, the regime where the separation D between misfit dislocations is much less than the strained layer thickness h is considered here. The conventional Matthews-Blakeslee mechanism for creation of misfit dislocations is found to be inadequate for the case of large lattice relaxation owing to interactions amongst the misfit dislocation at the interface. According to St. Venant's principle, the stress fields of the dislocation network are screened beyond a distance D from the dislocation cores. This observation has several consequences, including large densities of threading dislocations and the "melting" of moderately relaxed heterointerfaces at conventional semiconductor growth temperatures. A number of experimental observations may be explained via these models.