Vibrational Lifetime of Bond-Center Hydrogen in Crystalline Silicon

The lifetime of the stretch mode of bond-center hydrogen in crystalline silicon is measured to be $T_1=7.8\mathrm{}\pm 0.2\mathrm{ps}$ with time-resolved, transient bleaching spectroscopy. The low-temperature spectral width of the absorption line due to the stretch mode converges towards its natural width for decreasing hydrogen concentration $C_{\mathrm{H}}$, and nearly coincides with the natural width for $C_{\mathrm{H}}\sim 1\mathrm{ppm}$. The lifetimes of the Si-H stretch modes of selected hydrogen-related defects are estimated from their spectral widths and shown to range from 1.6 to more than 37 ps.