SUPERLATTICE TRANSPORT IN INTENSE TERAHERTZ ELECTRIC-FIELDS

The low DC field conductance and the nonlinear I-V characteristics of GaAs/Al0.70Ga0.30As superlattices have been measured in the presence of intense electric fields produced by UCSB's free-electron lasers. The DC conductance exhibits oscillatory behavior as a function of terahertz field strength that resembles the zeroth-order Bessel function, J0(edE(AC)/HomegaBAR), where e, d, and E(AC) are the electron charge, superlattice period and AC field strength, respectively. The I-V characteristics, measured between 600 GHz and 3.1 THz, display new steps and plateaus. The dependence of the new structure of frequency suggests the presence of new conduction channels that are most naturally assigned to photon-mediated sequential tunneling.