Doping of HfO 2 thin films is a powerful means for stabilizing ferroelectricity in this material. Yet, the amount of doping is critical to achieving the best ferroelectric response. This article investigates the impact of the Si doping content on the key performance metrics of ferroelectric field-effect transistors (FeFETs). We report on its considerable effect on the memory window, switching uniformity and steepness, number of intermediate conductance states, and data retention. Based on the experimental results, we introduce simple figures of merit for a rapid assessment of the FeFET performance. Finally, we identify an important tradeoff between the abovementioned properties as a function of the dopant content and discuss possibilities for specialized device design for nonvolatile memory applications and potential neuromorphic devices based on FeFETs.