Electron Transport in Semiconductors Under a Strong High Frequency Electric Field

We study the nonlinear effects of the electron conductivity in semiconductors when a strong high frequency (HF) electric field is applied together with a direct (DC) electric field. The dynamic equation we used is different from Boltzmann equation by considering the memory effect for drift oscillating motion of electrons. Using the drifted temperature model, we derive a set of equations, from which the amplitude and phase of each harmonic component of the electron drift velocity and the electron temperature can be obtained. In the weak HF field limit our approach reduces to the well-known memory function method. We have calculated the conductivity of electrons in a bulk n-GaAs sample. The nonlinear effects are shown. Especially, the conductivity to DC decreases and becomes absolutely negative with increasing the first and second harmonic components of the applied HF field. Comparison is made with experiments.