Investigation of Traps Evolution in HfO 2 -Based FeFET During Cycling: Measurement and Analysis of Time Constant, Energy Level, and Trap Density

The trapping behaviors in the HfO2-based ferroelectric field effect transistor (FeFET) poses significant challenges to operation stability. In this study, we developed a comprehensive trap characterization method, using drain current transient and multi-frequency admittance measurements, to investigate the behavior of traps during the device’s program/erase (P/E) cycling process. The time constants and energy levels of different hole traps and electron traps were identified through current transient analysis and Bayesian deconvolution. Additionally, specific trap sites, including oxygen interstitials, oxygen vacancies, and interface traps, were characterized as contributors to hole and electron trapping. Furthermore, the energy-dependent interface trap density (Dit) and border trap density (Nbt) were extracted through the high-low frequency method and distributed trap model, utilizing the measured admittance dataset. As the number of P/E cycles increases, both the trapping amplitude and trap density were confirmed to increase, with the interface traps exhibiting a more substantial increase than those traps within the HZO layer. The methodologies used in this study provide valuable insights into the mechanisms underlying device degradation in endurance cycling and offer guidance for better control and optimization of FeFET devices.