Hafnia-based Phase-Change Ferroelectric Steep-Switching FETs on a 2-D MoS$_2$ platform

TL;DR

This paper introduces a novel Hafnia-based phase-change ferroelectric FET on a 2D MoS2 platform, achieving steep switching with subthreshold slopes below 25 mV/dec, promising for low-power electronics.

Contribution

It demonstrates a new ferroelectric FET design utilizing phase-change materials and 2D semiconductors, enabling steep switching and tunable operation at relevant temperatures.

Findings

Achieved subthreshold slope as steep as 25 mV/dec at 210 K.

Observed distinctive step-like channel current features during DC measurements.

Demonstrated reversible phase transition in the ferroelectric layer affecting device behavior.

Abstract

Ferroelectric field-effect transistors integrated on 2D semiconducting platforms are extremely relevant for low power electronics. Here, we propose and demonstrate a novel phase-change ferroelectric field effect transistor (PCFE-FET) for steep switching applications. Our gate stack is engineered as a ferroelectric Lanthanum doped hafnium oxide (LHO) proximity coupled with Mott insulator Ti$_x$O$_{2x-1}$(N$_y$) and is integrated onto a 2D MoS$_2$ channel. The interplay of partial polarization switching in the ferroelectric LHO layer and reversible field-tunable metal-insulator transition (MIT) in Ti$_x$O$_{2x-1}$(N$_y$) layer concomitantly triggers polar to non-polar phase transition in the LHO layer between 200 and 220 K. This results in distinctive step-like features in the channel current during DC measurements, and random current fluctuations in high-speed measurements with slim anticlockwise hysteresis. Our devices show subthreshold slopes as steep as 25 mV/dec at 210 K, breaking the Boltzmann limit. Our gate stack is also potentially tunable for operation at temperatures of interest, presenting innovative gate stack engineering approaches for low-power computing solutions.