Three-dimensional dislocation loops generated from a weak inclusion in a strained material heterostructure

Heterogeneous nucleation and spread of dislocation loops driven by high epitaxial strain characterizes a conceivable failure mode of multi-layer material structures of potential interest for microelectronic applications. A three-dimensional boundary element method with a singularity exclusion scheme is applied herein for dislocation loops nucleated from a weak spherical inclusion bisecting the epitaxial interface between a strained layer and its substrate. The results show that the critical epitaxial strain to nucleate a dislocation loop minimizes at an intermediate range of defect sizes, namely, from about 5 to 500 nm for a GeSi alloy strained layer on a Si substrate. The expansion of the nucleated dislocation loops around the weak inclusion is simulated numerically, and the results depict the formation of threading dislocations in both uncapped and capped epitaxial surface layers. The pair of threading dislocations are driven out on opposite sides of the inclusion, leaving behind arrays of misfit dislocations along the interface. The interaction of multiple dislocation loops generated from one inclusion is also considered.