Colossal electroresistance in metal/ferroelectric/semiconductor tunnel diodes for resistive switching memories

We propose a tunneling heterostructure by replacing one of the metal electrodes in a metal/ferroelectric/metal ferroelectric tunnel junction with a heavily doped semiconductor. In this metal/ferroelectric/semiconductor tunnel diode, both the height and the width of the tunneling barrier can be electrically modulated due to the ferroelectric field effect, leading to a colossal tunneling electroresistance. This idea is implemented in Pt/BaTiO3/Nb:SrTiO3 heterostructures, in which an ON/OFF conductance ratio above 10$^4$ can be readily achieved at room temperature. The colossal tunneling electroresistance, reliable switching reproducibility and long data retention observed in these ferroelectric tunnel diodes suggest their great potential in non-destructive readout nonvolatile memories.