A finite Schottky barrier and large contact resistance between monolayer MoS2 and electrodes are the major bottlenecks in developing high-performance field-effect transistors (FETs) that hinder the study of intrinsic quantum behaviors such as valley-spin transport at low temperature. A gate-tunable graphene electrode platform has been developed to improve the performance of MoS2 FETs. However, intrinsic misalignment between the work function of pristine graphene and the conduction band of MoS2 results in a large threshold voltage for the FETs, because of which Ohmic contact behaviors are observed only at very high gate voltages and carrier concentrations (∼1013 cm-2). Here, we present high-performance monolayer MoS2 FETs with Ohmic contact at a modest gate voltage by using a chemical-vapor-deposited (CVD) nitrogen-doped graphene with a high intrinsic electron carrier density. The CVD nitrogen-doped graphene and monolayer MoS2 hybrid FETs platform exhibited a large negative shifted threshold voltage of -54.2 V and barrier-free Ohmic contact under zero gate voltage. Transparent contact by nitrogen-doped graphene led to a 214% enhancement in the on-current and a fourfold improvement in the field-effect carrier mobility of monolayer MoS2 FETs compared with those of a pristine graphene electrode platform. The transport measurements, as well as Raman and X-ray photoelectron spectroscopy analyses before and after thermal annealing, reveal that the atomic C-N bonding in the CVD nitrogen-doped graphene is responsible for the dominant effects of electron doping. Large-scale nitrogen-doped graphene electrodes provide a promising device platform for the development of high-performance devices and the study of unique quantum behaviors.
Bibliographical noteFunding Information:
D.S. was supported by the Graduate School of YONSEI University’s research scholarship grants in 2017 (No. NRF-2018M3D1A1058924). D.S. and H.J.C. were supported by the Creative Materials Discovery Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT (No. 2018M3D1A1058536). K.S.K. was supported by the Priority Research Center Program (No. 2010-0020207) of the National Research Foundation (NRF) of Korea, funded by the Ministry of Education, and the Global Research & Development Center Program (No. 2018K1A4A3A01064272) of the NRF funded by the Ministry of Science and ICT. J.H. was supported by the NSF MRSEC program through Columbia in the center of Precision Assembly of Superstratic and Superatomic Solid (No. DMR-1420634). K.H.L was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (No. NRF-2017R1A2B2006568) and the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20173010013340). Y.D.K. and J.J.L. were supported by Samsung Research & Incubation Funding Center of Samsung Electronics under Project Number SRFC-TB1803-04. This work was supported by a grant from Kyung Hee University in 2017 (No. KHU-20171743).
© 2019 Author(s).
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)