Ferroelectric Tunnel Junction Based on Asymmetric Barrier–Well–Barrier Structure: The Role of Resonant Tunneling

An innovative resonant ferroelectric tunnel junction (FTJ) based on asymmetric barrier–well–barrier structure is theoretically proposed. It is achieved by metal–ferroelectric–dielectric–dielectric–metal (M-F-
$\text{I}_{{1}}$
-
$\text{I}_{{2}}$
-M) stack, where a low-barrier dielectric
$\text{I}_{{1}}$
is inserted to form a quantum well. Physical modeling of self-consistent potential and carrier transport is established to bridge the polarization reversal and resonant tunneling (RT). The resonant FTJ shows improved ON-current and ON/OFF tunneling electroresistance (TER) ratio while maintaining a relatively low depolarization field. Compared with FE -HfO2/SiO2 or FE -HfO2/Ta2O5 bilayer FTJs, the resonant FTJ using FE -HfO2/Ta2O5/HfO2 stack exhibits a larger TER ratio by several orders of magnitude, which can be further enhanced using FE -HfO2/Ta2O5/SiO2 stack. The underlying physics is attributed to the RT, of which contribution to TER effect is qualitatively and quantitatively analyzed. The resonant band engineering, through enhancing the device asymmetry, including the geometry asymmetry and the material asymmetry, is to shift the resonance peak close to or away from the Fermi energy depending on the polarization direction. This work is useful for FTJ design for large array circuit applications.