Short lifetime components in the relaxation of boron acceptors in silicon

We present time-resolved measurements of the relaxation between the orbital states of the shallow acceptor boron in silicon. The silicon host was enriched Si28, which exhibits lifetime broadened absorption lines. We observed a wide range of T1 lifetimes from 6 ps to 130 ps depending on the excited state and the pump intensity. The fastest transients have not been observed previously in the time domain, and they are caused by the phonon relaxation responsible for the small-signal frequency domain linewidth. We identify the slower components with an ionization/recombination/cascade pathway.