  A study on a parametrized model of a composite barrier FTJ (three-interface
system, with a non-polar dielectric layer) under an external bias voltage and
at room temperature, using FEM-based simulations, was performed. The approach
involves the Thomas-Fermi model assuming incomplete screening of polarization
charges for building the energy barrier profile, and numerically simulates the
electron transport through the barrier by bias-voltage-dependent tunneling,
using Tsu-Esaki formulation. That naturally include the temperature dependent
contributions to the total current density. The TER coefficient and current
densities are computed considering variation of a large set of parameters that
describe the composite barrier FTJ system in realistic physical range of values
with respect to a reference (prototypical) system. In this study, the
parametric simulations were performed starting from selected data reported on
the SRO/STO/BTO/SRO heterostructure. The most important results of our work can
be stated as follows: i) The FEM simulations prove to be reliable approach when
we are interested in the prediction of FTJ characteristics at temperatures
close to 300 K, and ii) We show that several configurations with large TER
values may be predicted, but at the expense of very low current densities in
the ON state. We suggest that the results may be useful for assessing the FTJ
performances at ambient temperature, as well as to design preoptimized FTJs by
using different combinations of materials to comply with a set of properties of
a specific model.
