Coherence control of currents in semiconductors: a materials perspective

The phase of optical beams can induce and control novel effects in solids via quantum interference. Our focus has primarily been on generation and control of photocurrents in bulk semiconductors using harmonically related beams and GaAs as a prototypical material. Here we consider a general bulk semiconductor and investigate how its material properties influence photocurrent generation and evolution. The main factors to consider are the current injection efficacy, determined by the current injection tensor, as well as optical and carrier dephasing effects. From a simple Kane band model and k.p perturbation theory the magnitude of the injection tensor is seen to scale with the band gap, E-g, as E-g(-2). Lack of phase-matching between beams due to material dispersion can reduce the peak current by up to an order of magnitude but its influence differs significantly among such common semiconductors as Ge, GaAs, GaP and ZnSe and there is no direct correlation with E-g. In general, the rate of carrier dephasing can be expected to increase with increasing band gap. Finally, we consider a simple treatment of the dynamics of the injected currents and identify dissipative and collective (plasmon) excitation regimes. From the k.p model we also provide insight into the initial k-space carrier distributions for excitation from heavy or light hole bands. (C) 2000 Published by Elsevier Science B.V. All rights reserved.