Coupled electron-hole plasma-phonon system in far-from-equilibrium semiconductors

Zubarev's nonequilibrium statistical thermodynamic method is applied to the study of the time evolution of a coupled carrier-LO-phonon system in polar direct-gap semiconductors. The carrier system is composed of a photoexcited electron-hole plasma, strongly departed from thermal equilibrium, generated by a pulse of laser light. The macroscopic description is done in terms of time-dependent quasitemperatures for the carriers and for the different phonon modes. These quasitemperatures can be determined by means of ultrafast optical spectroscopy; a calculation of the expected time-resolved Raman spectrum with numerical applications for the case of GaAs is presented.