Isotope dependence of the vibrational lifetimes of light impurities in Si from first principles

The vibrational lifetimes of a range of H-related defects and interstitial O (Oᵢ) in Si, including isotopic substitutions, are calculated from first principles as a function of temperature. The theoretical approach is explained in detail. The vibrational lifetimes of highest-frequency local vibrational modes of HBC⁺, D₂*, HD*, DH*, HBC⁺, DBC⁺, HV∙VH, DV∙VH, DV∙VD, IH₂, ID₂, and various O and Si isotopic combinations of Oᵢ are predicted and the decay channels analyzed. We show that the complete vibrational spectrum of the defects must be known in order to predict vibrational lifetimes. We also show that the ``frequency-gap law'' is not always valid for high-frequency local vibrational modes.