Implications of Dielectric Phases in Ferroelectric HfO$_{2}$ Films on the Performance of Negative Capacitance FETs

Abstract

Non-homogeneous orthorhombic phase in doped ferroelectric (FE) HfO$_{2}$ film presents challenges towards the optimization and performance predictability of negative capacitance (NC) field-effect transistor (FET) performance. We set out to understand the consequences of these dielectric (DE) phases in doped FE-HfO$_{2}$ on steep-switching device performance through self-consistent quantum transport simulations. Firstly, we consider a fixed DE phase study to understand how the position, percentage, and number of phase components alter the switching characteristics. Then, to predict device performance variation, we conduct a statistical analysis using a large number of randomly distributed DE phase profiles. We find that DE phases positioned near the center of the potential barrier exert the most significant impact on device performance by lowering the top-of-the-barrier, while those closer to the drain have minimal influence on carrier transport and current. While DE phases in the FE layer degrade the subthreshold swing, they also favorably narrow the hysteretic window, which presents opportunities for optimization in logic devices. Through dimensional scaling and statistical analysis, we demonstrate how optimized performance can be achieved even with large variations in device performance.