Cooling Dynamics of Photoexcited Carriers in Si Studied by Using Optical Pump and Terahertz Probe Spectroscopy

摘要

We investigated the photoexcited carrier dynamics in Si by using optical pumpand terahertz probe spectroscopy in an energy range between 2 meV and 25 meV.The formation dynamics of excitons from unbound e-h pairs was studied throughthe emergence of the 1s-2p transition of excitons at 12 meV (3 THz). Werevealed the thermalization mechanism of the photo-injected hot carriers(electrons and holes) in the low temperature lattice system by taking accountof the interband and intraband scattering of carriers with acoustic and opticalphonons. The overall cooling rate of electrons and holes was numericallycalculated on the basis of a microscopic analysis of the phonon scatteringprocesses, and the results well account for the experimentally observed carriercooling dynamics. The long formation time of excitons in Si after the above-gapphotoexcitation is reasonably accounted for by the thermalization process ofphotoexcited carriers.