Resonant tunneling is a quantum‐mechanical effect in which electron transport is controlled by the discrete energy levels within a quantum‐well (QW) structure. A ferroelectric resonant tunneling diode (RTD) exploits the switchable electric polarization state of the QW barrier to tune the device resistance. Here, the discovery of robust room‐temperature ferroelectric‐modulated resonant tunneling and negative differential resistance (NDR) behaviors in all‐perovskite‐oxide BaTiO3/SrRuO3/BaTiO3 QW structures is reported. The resonant current amplitude and voltage are tunable by the switchable polarization of the BaTiO3 ferroelectric with the NDR ratio modulated by ≈3 orders of magnitude and an OFF/ON resistance ratio exceeding a factor of 2 × 104. The observed NDR effect is explained an energy bandgap between Ru‐t2g and Ru‐eg orbitals driven by electron–electron correlations, as follows from density functional theory calculations. This study paves the way for ferroelectric‐based quantum‐tunneling devices in future oxide electronics.

The current−voltage (I−V) characteristics and ON/OFF ratio in hafnium oxide (HfO 2 )-based ferroelectric tunnel junctions (FTJs) were investigated under different poling sequences. When −5 V poling pulse is applied prior to +5 V pulse (−5 Vpoling-first operation), both ON-state and OFF-state show relatively low currents, whereas the ON/OFF ratio is more than doubled, as compared to the reverse poling sequence (+5 V-poling-first operation, i.e., + 5 V pulse applied prior to −5 V). Interestingly, the ON-state I−V curves exhibit the Ohmic behavior, while the OFF-state curves are nonlinear that can be described by direct tunneling across a barrier, regardless of the poling sequence. The poling sequence-dependent tunneling electroresistance in our FTJs is explained by the evolution of domain structure in the ferroelectric films driven by the poling pulse, as supported by both I−V measurements and data fitting. This work provides a guidance to modulate the performance of FTJs, and further help understand the structure−property relationship of HfO 2 -based ferroelectric memories at the nanoscale.