Negative-to-Positive Differential Resistance Transition in Ferroelectric FET: Physical Insight and Utilization in...

In this article, for the first time, we explained a detailed physical insight for negative differential resistance (NDR) to positive differential resistance (PDR) transition in a ferroelectric (FE)-based negative capacitance (NC) FET and also its dependence on the device terminal voltages. Using extensive well-calibrated TCAD simulations, we have investigated this phenomenon on fully depleted silicon on insulator (FDSOI)-NCFET. The NDR-to-PDR transition occurs due to FE layer capacitance changes from a negative to positive state during channel pinchoff. This, in turn, results in a valley point in the output characteristic ( I_DS - V_DS ) at which the output resistance is infinite. We also found that we could alter the valley point location by modulating the vertical electric field through the FE layer in the channel pinchoff region using body bias ( V_BB ). The interface oxide charges also impacted the NDR to PDR transition, and a positive interface charge results in faster NDR to PDR transition. Furthermore, we have utilized the modulation in the NDR-to-PDR transition due to V_BB for designing a current mirror. Results show that the output current ( I_OUT ) variation due to V_DS reduces from ~8% to ~2% with V_BB . We have also designed a single-stage common source (CS) amplifier and provided design guidelines to achieve a higher gain in the NDR region. The results obtained using a small-signal model of the FDSOI-NCFET demonstrate that ~25% higher gain can be achieved with the discussed design guidelines in the NDR region compared to the transition region of I_DS - V_DS . We have also explored the device scaling effect on the amplifier gain and found that ~ 2.23× gain can be increased with smaller channel length and higher device width.