Stress accommodation in large-mismatch systems.

摘要

Accommodation of lattice mismatch is investigated for the case of large ((epsilon) > 0.02) mismatch. 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 dislocations at the interface. In particular, the regime where the separation D between misfit dislocations is much less than the strained layer thickness h is considered here. The energetics of insertion of dense misfit dislocation networks is examined. According to St Venant's Principle, the existence of a new length scale, D, serves as a cutoff for the stress fields of the dislocation network. This observation has several consequences, including the prevention of relaxation by repulsive interaction amongst threading dislocation segments and the ''melting'' of moderately relaxed heterointerfaces at conventional semiconductor growth temperatures. A number of experimental observations may be explained via these models.