Secondary defect evolution in a multilayered Si/SiGe structure was studied after 1MeV Sn+-ion implantation to a fluence of 2 x 1014/cm2 followed by annealing in a dry nitrogen atmosphere. Formation of a buried amorphous layer was noted after ion implantation. Thermal treatment led to the formation of dislocation loops in an EOR-defect band, and a mixture of tangled dislocations and “clamshell” defects at a depth of 200 to 500nm. In addition, self-assembling of voids in a near-surface SiGe layer structure was observed. The voids were of nm size and were preferably located in thin SiGe layers. The results were explained in terms of the separation of the vacancy and interstitial depth profiles attributed to the preferential forward momentum of recoiling Si atoms. The compressively strained SiGe layers played the role of vacancy accumulator, prevented in-surface diffusion of vacancies and, in this way, resulted in self-assembling of voids within compressively strained SiGe layers.

Strain-Driven Defect Evolution in Sn+ Implanted Si/SiGe Multilayer Structure. P.I.Gaiduk, A.Nylandsted Larsen, W.Wesch: Nuclear Instruments and Methods in Physics Research B, 2009, 267[8-9], 1239-42