Coherence control of currents in semiconductors: a materials perspective

The phase of optical beams can induce and control novel effects in solids v ia quantum interference. Our focus has primarily been on generation and con trol of photocurrents in bulk semiconductors using harmonically related bea ms and GaAs as a prototypical material. Here we consider a general bulk sem iconductor and investigate how its material properties influence photocurre nt generation and evolution. The main factors to consider are the current i njection efficacy, determined by the current injection tensor, as well as o ptical 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 d ue to material dispersion can reduce the peak current by up to an order of magnitude but its influence differs significantly among such common semicon ductors 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 w ith increasing band gap. Finally, we consider a simple treatment of the dyn amics of the injected currents and identify dissipative and collective (pla smon) excitation regimes. From the k.p model we also provide insight into t he initial k-space carrier distributions for excitation from heavy or light hole bands. (C) 2000 Published by Elsevier Science B.V. All rights reserve d.