  Electron transport through fully depleted ferroelectric tunnel barriers
sandwiched between two metal electrodes and its dependence on ferroelectric
polarization direction are investigated. The model assumes a polarization
direction dependent ferroelectric barrier. The transport mechanisms, including
direct tunneling, Fowler-Nordheim tunneling and thermionic injection, are
considered in the calculation of the electroresistance as a function of
ferroelectric barrier properties, given by the properties of the ferroelectric,
the barrier thickness, and the metal properties, and in turn of the
polarization direction. Large electroresistance is favored in thicker films for
all three transport mechanisms but on the expense of current density. However,
switching between two transport mechanisms, i.e., direct tunneling and
Fowler-Nordheim tunneling, by polarization switching yields a large
electroresistance. Furthermore, the most versatile playground in optimizing the
device performance was found to be the electrode properties, especially
screening length and band offset with the ferroelectric.
