Revisiting the theory of ferroelectric negative capacitance

TL;DR

This paper revisits the negative capacitance theory in ferroelectric systems, emphasizing the importance of considering the total Gibbs free energy for accurate modeling and exploring implications for steep slope transistors.

Contribution

It provides a comprehensive analytical and numerical analysis of negative capacitance in various ferroelectric configurations, highlighting the correct energy minimization approach and conditions for different operational regimes.

Findings

Corrected the theoretical framework by emphasizing total Gibbs free energy minimization.

Derived conditions for hysteresis and gain in ferroelectric-dielectric systems.

Analyzed ferroelectric-semiconductor combinations for hysteresis-free steep slope transistors.

Abstract

In this paper we revisit the theory of negative capacitance, in a (i) standalone ferroelectric, (ii) ferroelectric-dielectric, and (iii) ferroelectric-semiconductor series combination, and show that it is important to minimize the total Gibbs free energy of the combined system (and not just the free energy of the ferroelectric) to obtain the correct states. The theory is explained both analytically and using numerical simulation, for ferroelectric materials with first order and second order phase transitions. The exact conditions for different regimes of operation in terms of hysteresis and gain are derived for ferroelectric-dielectric combination. Finally the ferroelectric-semiconductor series combination is analyzed to gain insights into the possibility of realization of steep slope transistors in a hysteresis free manner.