RESONANT-TUNNELING IN SEMICONDUCTOR QUANTUM-WELLS AND SUPERLATTICES

Semiconductor superlattices with an electric field applied perpendicular to the layers exhibit tunneling resonances at field strengths, which are determined by the subband spacings and the superlattice period. Time-of-flight experiments are used to identify the tunneling resonances. The injection of carriers into higher subbands at resonance can be directly observed in photoluminescence experiments. The relative occupation gives information about the intersubband scattering time. By applying a magnetic field perpendicular to the layers in addition to the electric field, resonant tunneling between Landau levels, which are forming zero-dimensional states, is investigated. At large carrier densities the applied electric field breaks up into several regions, i.e. domains, of different field strengths, which are determined by the resonant tunneling condition between electronic subbands.