PHOTOINDUCED MULTISTABLE PHENOMENA IN THE TUNNELING CURRENT THROUGH DOPED SUPERLATTICES

We investigate theoretically the effect of intense THz radiation on th e nonlinear properties of doped semiconductor superlattices (SL's). Fo r the first time, the fully nonlinear current through the SL with an a rbitrary combination of ac and de voltages is calculated from a micros copic self-consistent model. We focus on the formation of electric fie ld domains and the appearance of new multistability regions caused by the interplay of the strong nonlinearity, due to the Coulomb interacti on, and the new photon-assisted channels. For low de bias voltages and for some frequencies and intensities of the ac field the system is bi stable with either positive or negative electron pumping, [S0031-9007( 98)07733-3].