Abstract
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.
Highlights
Quantum tunneling1,2 is important to nanoelectronic circuit designs, tunneling electrical contacts,3 scanning tunneling microscopes (STMs),4,5 plasmonic resonators,6–8 carbon nanotubes,9–13 graphene14,15 and other two-dimensional (2D) materials based devices16,17 and novel vacuum nano-devices.18–21 Quantum tunneling effects impose serious challenges to the physical scaling down of traditional electronic circuits.22 it enables the development of future tunneling field-effect transistors (TFETs), which are envisioned to further extend Moore’s law.23 Tunneling in electrical contacts can be utilized to mitigate current crowding and nonuniform heat deposition in the contact region.3 Tunneling phenomenon may introduce new regimes in quantum plasmonics.24 it is critical to accurately characterize the current density-voltage (J − V) behaviors in nano-scale metal-insulator-metal (MIM) junctions, for a variety of material properties and junction dimensions
The current densities are calculated from the self-consistent model (SCM) with both space charge potential and exchange correlation potential Vxc included
The J − V curves may be roughly divided into three regimes: direct tunneling regime (Vg < 1V), field emission regime (1V < Vg < 10V), and space-chargelimited regime (Vg > 10V), similar to the MIM with electrodes of the same material
Summary
Quantum tunneling is important to nanoelectronic circuit designs, tunneling electrical contacts, scanning tunneling microscopes (STMs), plasmonic resonators, carbon nanotubes, graphene and other two-dimensional (2D) materials based devices and novel vacuum nano-devices. Quantum tunneling effects impose serious challenges to the physical scaling down of traditional electronic circuits. it enables the development of future tunneling field-effect transistors (TFETs), which are envisioned to further extend Moore’s law. Tunneling in electrical contacts can be utilized to mitigate current crowding and nonuniform heat deposition in the contact region. Tunneling phenomenon may introduce new regimes in quantum plasmonics. it is critical to accurately characterize the current density-voltage (J − V) behaviors in nano-scale metal-insulator-metal (MIM) junctions, for a variety of material properties and junction dimensions. Quantum tunneling effects impose serious challenges to the physical scaling down of traditional electronic circuits.. Simmons’ model is reliable only in low voltage regime for limited parameter space (insulator gap > 1 nm, barrier height > 3 eV).. We provide a detailed study of FB and RB asymmetry and its dependence on a wide range of input parameters (work functions of the electrodes, thickness and relative permittivity of the insulator), for different voltage regimes. The asymmetry between the current density profiles increases with the work function difference of the electrodes, the thickness or permittivity of the insulator layer. The strong saturation of tunneling current density in the space charge limited (SCL) regime, which can be achieved under ultrafast pulsed excitation, is explored for different input parameters
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