The strain of a SiGe alloy epitaxially grown on Si could be released by heating at 750C. However the strain relaxation was accompanied by the generation of threading dislocations and associated point defects. The attempted remedy was to let SiGe grow on a very thin Si substrate on top of a SOI heterostructure, with the purpose of concentrating the defects at the Si-SiO2 interface of the SOI substrate. A slow positron beam was used to investigate the effectiveness of the remedy. The positron diffusion length in SiGe decreased after the thermal treatment. This result showed the generation of lattice defects still occurred in the SiGe layer, in spite of the deposition on SOI.

Positron Annihilation Studies of Defects in Si1-xGex/SOI Heterostructures. A.Calloni, R.Ferragut, F.Moia, A.Dupasquier, G.Isella, D.Marongiu, G.Norga, A.Fedorov, D.Chrastina: Physica Status Solidi C, 2009, 6[11], 2304-6