Electrical activity of multivacancy defects in silicon



The formation processes and properties of multivacancy defects in Si have been recently the subject of several re-search studies. Here we report on density functional calculations concerning the stability and electrical activity of the tetravacancy, pentavacancy and hexavacancy complexes in Si. Formation energy calculations indicate that Four-Fold Coordinated (FFC) V4 and V5 are more stable than Part-of-Hexagonal-Ring (PHR) or planar structures by at least 1.2 eV and 0.6 eV, respectively. This relative stability order between configurations remains unchanged for different charged states from double plus to double minus. Calculations of the electrical activity predict deep acceptor levels for the FFC defects. Accordingly, electron traps related to (–/0) and (=/–) levels near Ec – 0.5 eV were found for V4 and V5, whereas levels for V6 were estimated at Ec – 0.35 eV. No donor levels were found for these defects. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)