Impact of Ferroelectric Polarization Gradient and Viscosity Coefficient on Performance of Negative Capacitance FET Circuits

In this work, we discuss the impact of the ferroelectric polarization gradient (g) and viscosity coefficient (ρ) on the NCFET circuit. First, we examine the effect of g in the nmos and pmos transfer characteristics and VTC of the inverter circuit. Then, we examine low and high-frequency switching behavior by varying the ρ which is considered as the resistance of polarization switching. The operation of negative capacitance (NC) FET is examined at megahertz (MHz) and gigahertz (GHz) frequencies. We find that the dc and transient performance of NC-based circuits are strongly dependent on g and ρ respectively. We also show that at low ρ, the polarization state of the ferroelectric (FE) layer lies within the NC region while large ρ may bias the FE layer to positive capacitance (PC) region leading to performance degradation.