Effects of Oxygen Vacancy on Ferroelectric Tunnel Junctions: An Ab initio Study

Oxygen vacancies (OVs) usually exist in hafnium-based oxides in ferroelectric tunnel junctions (FTJs), which significantly influence the electron transport properties of FTJ. Here, a TiN/HZO/Pt FTJ device structure was constructed. The electron transport properties of FTJ with fourfold oxygen vacancies are studied using density functional theory combined with nonequilibrium Green's function. The perfect FTJ device structure model has a TER of 12 in the equilibrium state. After introducing defects, the TER ratio is as high as 559, and the depolarization field of the device is reduced. At the same time, the effect of oxygen vacancy on transmission at low resistance is greater than that at high resistance. Our results are significant for the design of FTJs, as OVs are generally unavoidable in ferroelectric oxides, and suggest changing the location of OVs to enhance TER.