Density-dependent electron scattering in photoexcited GaAs

In a series of systematic optical pump - terahertz probe experiments we study the density-dependent electron scattering rate in photoexcited GaAs in a large range of carrier densities. The electron scattering time decreases by as much as a factor of 4, from 320 to 60 fs, as the electron density changes by 4 orders of magnitude, from 10¹⁵ to 10¹⁹ cm^-3.