THE MEASUREMENT OF CHARGE CARRIER LIFETIME IN SI-GaAs:Cr AND EL2-GaAs BY PUMP-PROBE TERAHERTZ SPECTROSCOPY

In the present work, the temporal dynamics of relaxation of a nonequilibrium concentration of charge carriers in S7-GaAs:Cr and EL2-GaAs semiconductor crystals has been studied using pump-probe terahertz spectroscopy. The obtained experimental data were analyzed taking into account the mechanisms of surface and bulk Shockley-Reed-Hall recombination, radiative recombination, interband and trap assisted Auger recombination. It was found that at injection levels arising upon excitation of samples by laser radiation with a pulse duration of 35 fs and an energy of 0.1 mJ per pulse at a central wavelength of 791 nm, Auger recombination mechanisms have a significant effect. Auger recombination mechanisms make a dominant contribution to the recombination rate of nonequilibrium charge carriers at injection levels above 2 * [10.sup.18] [cm.sup.-3] for SI-GaAs:Cr and above [10.sup.18] [cm.sup.-3] for EL2-GaAs. At lower injection levels, the bulk and surface Shockley-Reed-Hall recombination are the dominant recombination mechanisms. Keywords: terahertz pump-probe spectroscopy, GaAs:Cr, charge carrier lifetime, Auger recombination