Effects of high carrier densities on phonon and carrier lifetimes in Si by time-resolved anti-Stokes Raman scattering

Abstract

The relaxation times T1 of nonequilibrium populations of elementary excitations in Si are studied by time-resolved Raman scattering using a subpicosecond pump-probe method. Incoherent anti-Stokes Raman scattering is used to monitor the decay of the nonequilibrium populations of holes and the generation and decay of zone-center longitudinal optical (LO) phonons. At lower levels of laser excitation, hole and LO phonon T1 lifetimes are less than 0.2ps and greater than 1.6ps, respectively. At higher laser intensities, the lifetime of holes increases and the lifetime of LO phonons decrease toward a common value of T1∼0.4ps.