Evidence for capture of holes into resonant states in boron-doped silicon

The variation of hole population in the resonant states of B-doped Si excited by sequences of short electric-field pulses has been investigated by the technique of time-resolved step-scan far-infrared spectroscopy. From the variation of the p_3/2 absorptions, we find that the hole population in the ground state decreases continuously with the sequential electric pulses, as a result of the breakdown delay and hole accumulation in long-lived excited states. The measured time-varying spectra of the p_1/2 series have been analyzed and attributed to a significant variation of the hole population in the resonant states. We have also observed a new absorption line at 676 cm^-1 which is probably caused by the electric-field induced mixing of the resonant states.