RESONANT-TUNNELING IN TIME-DEPENDENT FIELDS THROUGH LATERALLY CONFINED DOUBLE BARRIERS

We analyze the tunneling current through resonant heterostructures in the presence of a time-dependent field. We compare two different cases : an AC potential where the external field is position-dependent throu gh the heterostructure versus the case where an electromagnetic field irradiates homogeneously the whole sample. While in the presence of an AC potential the tunneling takes place mainly through photo sidebands , in the case of homogeneous illumination the main effective tunneling channels correspond to the coupling between different electronic stat es due to photon absorption and emission. The difference in the tunnel ing mechanisms between these configurations is strongly reflected in t he transmission and current, which present different features in both cases. In order to analyze these effects, we have obtained the transit ion probability for resonant coherent tunneling in terms of the Green' s function of the system. We have applied this model to analyze the ef fect of light in the current steps which are present in a laterally co nfined double barrier where the Coulomb interaction is considered in a mean field approximation.