Assessing the Role of Dielectric Phase Defects in Doped Ferroelectric HfO2 Integrated in Negative Capacitance Field-Effect Transistors

The existence of cubic, tetragonal, and monoclinic phases and the resulting loss in ferroelectricity in doped ferroelectric (FE) HfO2 complicate the optimization and practical implementation of FE-HfO2-based negative capacitance (NC) field-effect transistors (FETs). We set out to understand the consequences of these dielectric phase defects in doped FE-HfO2 on steep-switching device performance through self-consistent quantum transport simulations. Our findings show that although DE defects worsen the subthreshold swing (SS) of the NC devices, it also favorably narrows the hysteretic window. Defects close to the middle of the potential barrier have the strongest influence on device performance by pushing the top of the barrier down while defects nearing the drain contribute the least to carrier transport and current. Through dimension scaling, we also demonstrate how the contributions from a fixed width of DE defect can be adopted to still generate favorable NC characteristics for logic devices.