Ultrafast dynamics of nonlinear absorption in low-temperature-grown GaAs

We present the results of a study of the subpicosecond dynamic behavior of optically induced absorption changes in low-temperature-grown GaAs. We show that the observed behavior is dominated by mid-gap trap states, and can be accurately modeled by the rate equations previously developed to describe quasi-cw results. Our data give the first approximate values for trap emptying times in this material.