DYNAMICS OF NONTHERMAL-CARRIER DISTRIBUTIONS IN GAAS GENERATED BY FEMTOSECOND LASER-PULSES

We have studied hot electron to neutral acceptor recombination lumines cence in p-type GaAs held at liquid-helium temperature. We are able to inject a moderate density (10(15) cm-1 to 10(17) cm-3) of carriers in to the sample using femtosecond laser pulses. Two excitation energies are studied, 1.7 eV and 1.97 eV. At both energies the unrelaxed peak, due to electrons recombining with neutral acceptors before scattering, is attenuated considerably at higher carrier densities. The experimen tal data indicate that rapid carrier-carrier scattering within the hig hly nonequilibrium injected distribution occurs in the first 150 fs at carrier densities as low as 8.10(15) cm-3.