Role of Oxygen Vacancies in Electric Field Cycling Behaviors of Ferroelectric Hafnium Oxide

Based on the density functional theory (DFT) calculations, a new mechanism about the oxygen vacancies(Vo) in the HfO2-based ferroelectric devices is presented. In this mechanism, the Vo in m-phase HfO2 not only serve as the electron traps but also emerge ferroelectricity besides the known o-phase HfO2. And the increased remanent polarization during the “wake-up” process is mainly attributed to this part of Vo-m-phase HfO2 ferroelectric cells. Based on the new mechanism, a Kinetic Monte Carlo (KMC) simulator is developed to quantify the typical electric field cycling behaviors observed in the HfO2-based ferroelectric devices, including the wake-up, fatigue, split-up, and breakdown effects. This new understanding establishes relationship between the Vo and the cycling behaviors, and further shows the connection between the dopant and the wake-up characteristics of HfO2-based ferroelectric device.