Ultrafast carrier dynamics and terahertz conductivity of photoexcited GaAs under electric field

The ultrafast carrier dynamics and terahertz conductivity in semi-insulating GaAs have been investigated under electric field (E) by using optical pump-terahertz probe technique. The measurements indicate that the terahertz transmission change induced by the pump pulses at high E is smaller than that without E. We attribute this phenomenon to carrier scattering into the L valley, which leads to a drop in carrier mobility. The calculated transient photoconductivities fit well with the Drude–Smith model, being consistent with our intervalley scattering model.