Physical Mechanisms Behind the Annealing Temperature Effect on Ferroelectric Phase in HfAlO FTJs by First-Principles Calculations

To meet the needs of high speed and low power in the field of integrated circuits, hafnium-based ferroelectric tunnel junctions (FTJs) have been developed by doping different elements. In this study, we investigated the influence of annealing temperature on the ferroelectric properties of an Al-doped HfO2 device (HfAlO) using first-principle calculations and experimentally confirmed the simulation results. At annealing temperature >500 °C, TEM images showed that the HfAlO thin films had good crystallinity. At a critical annealing temperature of 600 °C, atomic force microscopy (AFM) images showed that the roughness reached a saturated state, which degraded HfAlO ferroelectricity. First-principle analyses verified that the orthogonal phase proportion in the film was the highest ( $\sim $ 30%) at 500 °C–550 °C due to decreased average bulk energy. The study paves way for HfAlO FTJs development for the next-generation in- memory computing applications.