Femtosecond response times and high optical nonlinearity in beryllium-doped low-temperature grown GaAs

Abstract

We have investigated the effect of beryllium doping on the optical nonlinearity and on the carrier dynamics in low-temperature (LT) grown GaAs for various growth temperatures and doping levels. Pump–probe experiments with 20 fs pulses and quantitative measurements of the nonlinear absorption show that in undoped LT GaAs, ultrafast response times are only obtained at the expense of low absorption modulation. In contrast, in Be-doped LT GaAs, high absorption modulation is maintained for response times as short as 100 fs. These results are qualitatively explained accounting for the point-defect-related optical transitions in LT-GaAs.