Structure-Dependent Vibrational Lifetimes of Hydrogen in Silicon

The lifetimes of the Si-H vibrational stretch modes of the H₂^* ( 2062cm^-1) and HV̇VH₍₁₁₀₎ ( 2072.5cm^-1) defects in crystalline Si are measured directly by transient bleaching spectroscopy from 10 K to room temperature. The interstitial-type defect H₂^* has a lifetime of 4.2 ps at 10 K, whereas the lifetime of the vacancy-type complex HV̇VH₍₁₁₀₎ is 2 orders of magnitude longer, 295 ps. The temperature dependence of the lifetime of H₂^* is governed by TA phonons, while HV̇VH₍₁₁₀₎ is governed by LA phonons. This behavior is attributed to the distinctly different local structure of these defects and the accompanying local vibrational modes.