Hot, tepid and temperate electrons in bulk GaAs

By means of the Monte Carlo particle model, the transport properties of bulk intrinsic GaAs have been studied for a uniform electric field ranging from 0 to 20 MV/m. As this model is based on first principles, a profound insight into the physics of the material has been obtained. The ¿, L and X minima of the conduction band have been treated like separate bands in the effective mass approximation. The energy distribution has been found to deviate increasingly from the displaced Maxwellian as the field increases; there are additional peaks due to transfer of carriers between the different minima of the conduction band. The time and path of free flights have been analysed for each minimum during steady state and found to be more complex than that described by simple theory based on current drift and relaxation times. The population ratio and the relative strengths of the principal scattering mechanisms have also been obtained against the electric field. By assuming an initial state of zero field and thermal distribution of the conduction electrons, the evolution of the population of the different minima and of the drift velocities have been followed until the steady state has been reached. This information may prove valuable in improving the diffusion type numerical modelling of semiconductor microcomponents where nonstationary transport is significant.