Electron-hole interaction and high-field transport of photoexcited electrons in GaAs

We use a theoretical ensemble Monte Carlo method to study the response of carriers photoexcited by a 1.55-eV laser pulse to applied electric fields (less than 5 kV/cm) for excited carrier densities between 10¹⁷ cm^-3 and 10¹⁸ cm^{- 3}. It is found that the electron-hole interaction reduces the fraction of electrons that transfer to the upper valleys and reduces the velocity of the electrons. These effects are more significant at low electric fields and higher excitation levels. The energy of the holes rises initially due to the energy transfer from the hot electrons through the electron-hole interaction. This is also reflected in a higher velocity for the holes during the first picosecond.