Significance of Multi and Few Domain Ferroelectric Switching Dynamics for Steep-Slope Non-Hysteretic Ferroelectric Field Effect Transistor

Ferroelectric materials, when introduced in the gate stack of conventional transistor, provide a pathway towards achieving sub-60 mV/dec sub-threshold slope (SS) through the emergence of negative capacitance (NC) [1]. In this work, we provide new insights into multi and few-domain ferroelectric switching dynamics that highlight the possibility of achieving steep-slope non-hysteretic ferroelectric field-effect transistor (FeFET) from internal voltage amplification and channel charge boost (Fig. 1) [2]. Our proposed modeling framework is built upon the interaction of the electric-dipoles with the local electric field, thereby accounting for the intrinsic positive feedback mechanism due to dipolar-interaction (Fig. 2) [3]. This approach, while equivalent to the previous free energy-landscape based analysis, gives new insights about the system's dynamic response by conceptually separating the switching dynamics dictated by the physics of the device from the effects added by the external circuital topology. To capture the intrinsic ferroelectric dynamics, we translate the Landau-Khalatnikov (LK) equations to an equivalent circuit model with a positive feedback loop and utilize a capacitor in series (CS) that provides a negative feedback loop. Analyzing the interplay of both feedbacks loops, we can explain our experimental data obtained from a stack of 10nm thick Hf_0.5Zr_0.5O ferroelectric capacitor and a varying linear dielectric capacitor in series and show how negative capacitance (NC) region is accessed and stabilized. Finally, we show how using this framework it is possible to tune the system parameters to generate a steep slope hysteresis free Ferroelectric Transistor (FeFET) due to the interval node voltage amplification and charge boost provided by the switching of the ferroelectric microscopic domains.