The Critical Role of Charge Balance on the Memory Characteristics of Ferroelectric Field-Effect Transistors

Ferroelectric field-effect transistors (Fe-FETs) with ferroelectric hafnium oxide (FE HfO
₂
) as the gate insulator are being extensively explored as a promising device candidate for non-volatile memory application. FE HfO
₂
exhibits long retention over ten years, high endurance over 10
¹²
cycles, high speed with subnanosecond polarization switching, and high remnant polarization of 10–
$30~\mu \text{C}$
/cm
²
. However, the performance of Fe-FETs is known to be much worse than FE HfO
₂
capacitors, which is not completely understood. In this work, we developed a comprehensive Fe-FET model based on a charge balance framework. The role of charge balance and the impact of leakage-assist-switching mechanism on the memory characteristics of Fe-FETs with Metal/Ferroelectric/Dielectric/Semiconductor (M/FE/DE/S) gate-stack is studied. It is found that the ferroelectric/dielectric (FE/DE) interface and DE layer instead of FE layer is critical to determine the memory characteristics of Fe-FETs, and experimental Fe-FETs can be well explained by this model, where the discrepancy between FE capacitors and Fe-FETs are successfully understood.