Defect Characterization in SiGe/SOI Epitaxial Semiconductors by Positron Annihilation

R Ferragut*, A Calloni, A Dupasquier and G Isella

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L-NESS, Dipartimento di Fisica, Politecnico di Milano, via Anzani 42, 22100, Como, Italy

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Nanoscale Research Letters 2010, 5:1942-1947  doi:10.1007/s11671-010-9818-4

Published: 24 October 2010


The potential of positron annihilation spectroscopy (PAS) for defect characterization at the atomic scale in semiconductors has been demonstrated in thin multilayer structures of SiGe (50 nm) grown on UTB (ultra-thin body) SOI (silicon-on-insulator). A slow positron beam was used to probe the defect profile. The SiO2/Si interface in the UTB-SOI was well characterized, and a good estimation of its depth has been obtained. The chemical analysis indicates that the interface does not contain defects, but only strongly localized charged centers. In order to promote the relaxation, the samples have been submitted to a post-growth annealing treatment in vacuum. After this treatment, it was possible to observe the modifications of the defect structure of the relaxed film. Chemical analysis of the SiGe layers suggests a prevalent trapping site surrounded by germanium atoms, presumably Si vacancies associated with misfit dislocations and threading dislocations in the SiGe films.

Positron annihilation spectroscopy; Ultra-thin body films; SiGe semiconductors; Point defects