Abstract
In this paper, we demonstrate that the momentum relaxation time of photoexcited carriers in wurtzite InN can be directly determined by investigating the rapid dephasing nature of coherent upper-branched longitudinal optical phonon-plasmon coupling (L+) mode. It is found that coherent L+ mode is a plasmonlike vibration mode and its dephasing time reduces from 120to60fs when the photoexcited carrier density increases from 2×10 17 /cm 3 to2×10 18 /cm 3 . The measured dephasing time is attributed to the momentum relaxation of photoexcited carriers, which is governed by the screened Coulomb interaction among photoexcited and background carriers in the bulk region of InN. © 2007 American Institute of Physics.