Slow positron implantation spectroscopy of edge-defined film-fed growth silicon

An effective diffusion length L+ of 90±10 nm has been measured for thermalised positrons in a number of samples of edge-defined film-fed growth (EFG) silicon at room temperature. This value of L+ is some three times shorter than that observed in undefected Si, whereas the characteristic annihilation lineshape parameters associated with EFG and undefected Si are indistinguishable. These results imply that (a) positron diffusion in EFG Si is hampered by shallow trapping by defects - probably substitutional C - present at a concentration of about 100 ppm, and (b) no opendashvolume defects were detected.