Ultrafast mobility in photoinjected polar semiconductors

Abstract

An analytical study of the ultrafast-mobility transient of central-valley nonequilibrium carriers in a highly photoexcited plasma in semiconductors is presented. General expressions for the mobility of the photoinjected carriers are derived. Numerical results are obtained in the case of low to moderately high fields in GaAs. We show that the mobility transient has a structure (maxima and minima) depending on the degree of photoexcitation and electric field intensity. Three different regimes are present, corresponding to (i) structure without overshoot and an Ohmic steady state, (ii) structure with overshoot and a non-Ohmic steady state, and (iii) normal evolution and an Ohmic steady state. A brief discussion of the diffusion coefficient is given.