Influence of He implantation dose on strain relaxation of pseudomorphic SiGe/Si heterostructure

The influence of He implantation dose on the strain relaxation of 180nm Si0.75Ge0.25/Si layers epitaxially grown on silicon is investigated. It is found that the strain relaxation of SiGe epilayer is facilitated by helium implantation, and the degree of strain relaxation increases with implantation dose. During the strain relaxation, misfit dislocation are mainly formed at the SiGe/Si interface, while no threading dislocations are observed in the epilayer. The dislocation loops emitted by the overpressurized He-filled nano-cavities promotes strain relaxation via both the propagation of two threading dislocation segments through the epilayer and the extension of the misfit dislocation segment located at the SiGe/Si heterointerface.