PICOSECOND DYNAMICS OF DENSE ELECTRON-HOLE PLASMAS IN InGaAsP FILMS.

Summary form only given. The dynamics of high-density photoexcited carriers in submicron InGaAsP films at 300 K are studied following ultrashort excitation at energies high above the band gap. Bandfilling and a high temperature carrier distribution produce gain at the pumping wavelength for times up to 2 ps after excitation. The time-resolved transmission and reflection from thin-film samples are measured using the pump-probe technique with 0. 5-ps pulses at 0. 625 mu m (2 eV) from a cavity-dumped mode-locked CW ring dye laser. The majority of the experiments are performed using In//0 //. //7 //0 Ga//0 //. //3 //0 As//0 //. //6 //6 P//0 //. //3 //4 (E//6 equals 0. 96 eV, lambda //G 1. 3 mu m) films of 0. 2- mu m thickness. Pump pulses up to 2 nJ are focused to a 10 or 40- mu m diam spot on the sample, producing initial carrier densities of up to 2 multiplied by 10**2 **0 cm** minus **3 .