Subpicosecond time-resolved Raman studies of LO phonons in GaN: Dependence on photoexcited carrier density

Subpicosecond time-resolved Raman spectroscopy has been used to measure the lifetime of the LO phonon mode in GaN for photoexcited electron-hole pair density ranging from 10 16 to 2 × 10 19 cm − 3 . The lifetime has been found to decrease from 2.5 ps , at low density, to 0.35 ps , at the highest density. The experimental findings should help resolve the recent controversy over the lifetime of LO phonon mode in GaN.