High Current and Carrier Densities in 2D MoS₂/AlScN Field-Effect Transistors via Ferroelectric Gating and Ohmic Contacts.

Abstract

Ferroelectric field-effect transistors (FeFET) with two-dimensional (2D) semiconductor channels are promising low-power, embedded nonvolatile memory (NVM) candidates for next-generation in-memory computing. However, the performance of FeFETs can be limited by a charge imbalance between the ferroelectric layer and the channel and, for low-dimensional semiconductors, also by a high contact resistance between the metal electrodes and the channel. Here, we report a significant enhancement in performance of contact-engineered FeFETs with a 2D MoS₂ channel and a ferroelectric Al_0.68Sc_0.32N (AlScN) gate dielectric. Replacing Ti with In contact electrodes results in a 5-fold increase in on-state current (∼120 μA/μm at 1 V) and on-to-off ratio (∼2 × 10⁷) in the FeFETs. In addition, the high carrier concentration in the MoS₂ channel during the on-state (>10¹⁴ cm^-2) owing to the large remnant polarization of AlScN facilitates the observation of a metal-to-insulator electronic phase transition in monolayer MoS₂ permitting observation of high field-effect mobility (>100 cm² V^-1 s^-1) at cryogenic temperatures. Our work and devices broaden the potential of FeFETs and provide a platform to implement high-carrier-density transport in a 2D channel.