IR studies of oxygen-vacancy related defects in irradiated silicon

The microscopic identification of a defect, i.e. its chemical nature, its physical structure and its geometrical configuration, is one of the most important aims of semiconductor research. In relation to that, a characteristic fingerprint of a defect is its corresponding Localised Vibrational Mode (LVM) signals in the IR spectra. Inversely, from the LVM frequency of a defect signal we Set information for its structure. In this work, we mainly present infrared absorption measurements of irradiation-induced defects in Cz-grown Si. The work is primarily focused on oxygen vacancy-related defects formed in oxygen rich Si upon irradiation with subsequent thermal annealing. First, the structural properties of the various multivacancy-multioxygen (VnOm) defects, chiefly known from EPR studies, are reviewed. Certainly, direct correlations of LVMs bands with defects is a difficult task and theoretical calculations could provide guidance in interpreting experimental results. Thus, we subsequently report on systematic calculations of the vibrational frequencies of the centers VOm (m=2,3,4), VnO (n=2,3) and the [VO+O-i] defect. Among the larger complexes VnOm, we especially calculate the frequencies of the V2O2, V3O2 defects. We put forward a semiempirical model from which we estimate the frequencies of VOm (m=2,3,4) defects. The frequencies of VnO (n=2,3) defects result from the well-known valence force treatment model. The frequencies of V2O7, V3O2 complexes result from a semiempirical model employing dipole-dipole moment interactions. Next, the calculated values are discussed and compared with the values taken from other theoretical works. Finally, taking into account results from other experimental techniques cited in the literature, correlations are made of defect structures with LVM bands.