Threading dislocation reduction by SiGeC domains in SiGe/SiGeC heterostructure: Role of pure edge dislocations

The authors previously reported an unusual phenomenon of strain relaxation accompanied by a reduction in threading dislocation density (TDD) on a Si0.77 Ge0.23 layer grown on top of alternating layers of Si0.77 Ge0.23 Si0.76 Ge0.23 C0.01 [Appl. Phys. Lett. 88, 041915 (2006)]. In this letter, the mechanism by which SiGeC domains, formed during annealing at 1000 °C, assist in TDD annihilation process is further investigated. A gb analysis of transmission electron microscope images showed the formation of pure edge dislocations from the reaction of two 60° misfit dislocations, which glide and/or slip with the assistance of the localized interfacial strain of the SiGeC domains. TDD reduction in this structure is thus due to the annihilation of threading dislocation arms during misfit dislocation combination.