Raman Scattering from Plasmons in Photoexcited GaP

The plasmon modes of the electron-hole plasma in GaP are investigated by pulsed Raman scattering. The two branches of the coupled plasmon-phonon modes are undamped and are observed over a wide energy range, depending on the excitation density. From this variation it is deduced that the density of electron-hole pairs varies in the range of (1-4) × ${10}^{18}$ ${\mathrm{cm}}^{-3\mathrm{}}$.