Physics and modeling of multi-domain FeFET with domain wall induced Negative Capacitance

TL;DR

This paper models the complex multi-domain ferroelectric behavior in FeFETs, revealing how domain wall motion induces negative capacitance and affects device variability, validated through experiments and simulations.

Contribution

It introduces a comprehensive 2-D coupled electrostatic and energy-based model for multi-domain FeFETs, capturing domain dynamics and negative capacitance effects.

Findings

Domain wall motion induces local bound charge and negative capacitance.

Device variability is linked to domain period and wall transitions.

Model aligns well with experimental and phase-field simulation results.

Abstract

In this paper, we present the dynamics and modeling of multi-domains in the ferroelectric FET (FeFET). Due to the periodic texture of domains, the electrostatics of the FeFET exhibit an oscillatory conduction band profile. To capture such oscillations, we solve coupled 2-D Poisson's equation with the net ferroelectric energy density (gradient energy + free energy + depolarization energy) equation. Multi-domain dynamics are captured by minimizing the net ferroelectric energy leading to a thermodynamically stable state. Furthermore, we show that the motion of domain walls originates local bound charge density in the ferroelectric region, which induces the negative capacitance (NC) effect. The strength of domain wall-induced NC is determined by the gradient energy of the ferroelectric material. FeFET exhibits variability in the drain current with domain period due to the inherent NC effect. Additionally, the impact of domain wall transition (soft$\rightleftharpoons$hard) on the device's electrostatic/transport is also analyzed. The model also accurately captures both nucleations of a new domain and the motion of the domain wall. Furthermore, the model is thoroughly validated against experimental results and phase-field simulations.