Host: The Japan Society of Vacuum and Surface Science
Ultrafast relaxation dynamics of photoinjected holes in the valence band of silicon has been studied using time- and angle-resolved two-photon photoelectron differential spectroscopy. We found that the photoexcitation with fs laser pulses causes a transient reduction in intensity of direct bulk transition peak, together with a peak broadening and a low-energy peak shift. The observed peak broadening and energy shift recovered completely in several ps, while the intensity shows a partial recovery in the same time range followed by a slow relaxation lasting a few hundreds of ps. Also. the temporal evolution of the difference photoemission image reveals that the photoinjected holes initially form a non-equilibrated distribution and then establish a quasi-thermalized distribution during the rapid relaxation process. We will discuss the many-body effects in the valence band states in photoexcited silicon, which rule the ultrafast relaxation process.
