Abstract:

We calculate the conductance through double junctions of the type M(inf.)-Sn-Mm-Sn-M(inf.) and triple junctions of the type M(inf.)-Sn-Mm-Sn-Mm-Sn-M(inf.), where M(inf.) are semi-infinite metallic electrodes, Sn are 'n' layers of semiconductor and Mm are 'm' layers of metal (the same as the electrodes), and compare the results with the conductance through simple junctions of the type M(inf.)-Sn-M(inf.). The junctions are bidimensional and their parts (electrodes and 'active region') are periodic in the direction perpendicular to the transport direction. To calculate the conductance we use the Green's functions Landauer formalism. The electronic structure of the junction is modeled by a tight-binding Hamiltonian. For a simple junction we find that the conductance decays exponentially with semiconductor thickness. For double and triple junctions, the conductance oscillates with the metal in-between thickness, and presents peaks for which the conductance is enhanced by 1-4 orders of magnitude. We find that when there is a conductance peak, the conductance is higher than in a simple junction. The maximum ratio between the conductance of a double junction and the conductance of a simple junction is 146%, while for a triple junction it is 323%. These oscillations in conductance are explained in terms of the energy spectrum of the junction's active region. © 2006 Elsevier B.V. All rights reserved.