Strained-layer relaxation by partial dislocations

A new strain relief mechanism in strained heteroepitaxial structures of fcc semiconductors is identified. The signature defect of the proposed mechanism is a microtwin along a {111} plane spanning an embedded strained layer. This defect can form when two partial dislocations with antiparallel Burgers vectors of the <112>/6 type are generated inside the strained layer and glide to the opposite interfaces, leaving a stacking fault between them. We show that, for typical semiconductor strained layers with misfits ≳0.7%, the microtwin formation is the lowest-energy strain relaxation channel and poses fundamental limitations for strained layer device structures.