The phonon dynamics of both the A
1(LO) and the E
1 (LO) phonons in InN has been studied by time-resolved Raman spectroscopy on a subpicosecond time scale. From the temperature-dependence of their lifetimes, we demonstrate that both phonons decay primarily into a large wavevector TO phonon and a large wavevector TA/LA phonon consistent with the accepted phonon dispersion relationship for wurtzite InN. Their lifetimes have been found to decrease from 2.2 ps, at the low electron-hole pair density of5x1017
-3 to 0.25 ps, at the highest density of2x1019
-3. Our experimental findings demonstrate that carrier-density dependence of LO phonon lifetime is a universal phenomenon in polar semiconductors.