Photoinduced multistable phenomena in the tunneling current through doped superlattices

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