A generalized self-consistent model for quantum tunneling current in dissimilar metal-insulator-metal junction

We study the current density-voltage (J − V) characteristics of dissimilar metal-insulator-metal (MIM) nanoscale tunneling junctions using a self-consistent quantum model. The model includes emissions from both cathode and anode, and the effects of image charge potential, space charge and exchange correlation potential. The J − V curves span three regimes: direct tunneling, field emission, and space-charge-limited regime. Unlike similar MIM junctions, the J − V curves are polarity dependent. The forward (higher work function metal is negatively biased) and reverse (higher work function metal is positively biased) bias J − V curves and their crossover behaviors are examined in detail for various regimes, over a wide range of material properties (work function of the electrodes, electron affinity and permittivity of the insulator). It is found that the asymmetry between the current density profiles increases with the work function difference between the electrodes, insulator layer thickness and relative permittivity of the insulator. This asymmetry is profound in the field emission regime and insignificant in the direct tunneling, and space charge limited regimes.