Defects formed during 1 MeV Si ion-irradiation of GeSi/Si strained-layer heterostructures at elevated temperatures

The strain relief observed in GeSi/Si strained-layer heterostructures irradiated with MeV ions at elevated temperature (253°C) is shown to be consistent with the accumulation of excess vacancies in the alloy layer. Partial recovery of the asgrown strain during subsequent annealing to temperatures <750°C coincides with the appearance of macroscopic voids. Since the tensile strain per vacancy is reduced by clustering this is believed to account for the observed strain recovery. At higher temperatures, >750°C, accelerated strain relaxation is shown to coincide with the growth of large intrinsic dislocation loops from the alloy-substrate interface. After annealing at 900°C, unirradiated alloys contain a low density of orthogonal misfit dislocations. Irradiated samples contain intrinsic irregular loop-like defects extending between the alloy-substrate interface and the surface.