High Current and Carrier Densities in 2D MoS<sub>2</sub>/AlScN Field-Effect Transistors via Ferroelectric Gating and Ohmic Contacts
Seunguk Song, Kwan‐Ho Kim, Rachael Keneipp, Myeongjin Jung, Nicholas Trainor, Chen Chen, Jeffrey Zheng, Joan M. Redwing, Joohoon Kang, Marija Drndić, Roy H. Olsson, Deep Jariwala
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 MoS 2 channel and a ferroelectric Al 0.68 Sc 0.32 N (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 × 10 7 ) in the FeFETs. In addition, the high carrier concentration in the MoS 2 channel during the on-state (>10 14 cm –2 ) owing to the large remnant polarization of AlScN facilitates the observation of a metal-to-insulator electronic phase transition in monolayer MoS 2 permitting observation of high field-effect mobility (>100 cm 2 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.