Boltzmann Switching MoS<sub>2</sub> Metal–Semiconductor Field‐Effect Transistors Enabled by Monolithic‐Oxide‐Gapped Metal Gates at the Schottky–Mott Limit
Yeon Ho Kim, Wei Jiang, Donghun Lee, Donghoon Moon, H. M. Choi, June‐Chul Shin, Yeonsu Jeong, Jong Chan Kim, Jaeho Lee, Woong Huh, Chang Yong Han, Jae‐Pil So, Tae Soo Kim, Seong Been Kim, Hyun Cheol Koo, Gunuk Wang, Kibum Kang, Hong‐Gyu Park, Hu Young Jeong, Seongil Im, Gwan‐Hyoung Lee, Tony Low, Chul‐Ho Lee
Abstract
Abstract A gate stack that facilitates a high‐quality interface and tight electrostatic control is crucial for realizing high‐performance and low‐power field‐effect transistors (FETs). However, when constructing conventional metal‐oxide‐semiconductor structures with two‐dimensional (2D) transition metal dichalcogenide channels, achieving these requirements becomes challenging due to inherent difficulties in obtaining high‐quality gate dielectrics through native oxidation or film deposition. Here, a gate‐dielectric‐less device architecture of van der Waals Schottky gated metal–semiconductor FETs (vdW‐SG MESFETs) using a molybdenum disulfide (MoS 2 ) channel and surface‐oxidized metal gates such as nickel and copper is reported. Benefiting from the strong SG coupling, these MESFETs operate at remarkably low gate voltages, <0.5 V. Notably, they also exhibit Boltzmann‐limited switching behavior featured by a subthreshold swing of ≈60 mV dec −1 and negligible hysteresis. These ideal FET characteristics are attributed to the formation of a Fermi‐level ( E F ) pinning‐free gate stack at the Schottky–Mott limit. Furthermore, authors experimentally and theoretically confirm that E F depinning can be achieved by suppressing both metal‐induced and disorder‐induced gap states at the interface between the monolithic‐oxide‐gapped metal gate and the MoS 2 channel. This work paves a new route for designing high‐performance and energy‐efficient 2D electronics.