High-performance monolayer MoS2 field-effect transistor with large-scale nitrogen-doped graphene electrodes for Ohmic contact

Dongjea Seo,Gwan-Hyoung Lee,Keun Soo Kim,Dong Yun Lee,Heon-Jin Choi,Junyoung Kwon,Young Duck Kim,Jea Jung Lee,Kenji Watanabe,James Hone,Takashi Taniguchi

doi:10.1063/1.5094682

Abstract

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.

Highlights

Scitation.org/journal/apl pinning at the metal–MoS2 interface, most metals form the Schottky contact that interferes with efficient charge carrier injection and extraction, and this often limits the study of the intrinsic transport properties of MoS2
A finite Schottky barrier and large contact resistance between monolayer MoS2 and electrodes are the major bottlenecks in developing highperformance field-effect transistors (FETs) that hinder the study of intrinsic quantum behaviors such as valley-spin transport at low temperature
We demonstrate monolayer MoS2 FETs using nitrogen-doped graphene (NGr) with barrier-free Ohmic contact, instead of the pristine graphene contact platforms that were previously used

Summary

Introduction

Scitation.org/journal/apl pinning at the metal–MoS2 interface, most metals form the Schottky contact that interferes with efficient charge carrier injection and extraction, and this often limits the study of the intrinsic transport properties of MoS2. A gate-tunable graphene electrode platform has been developed to improve the performance of MoS2 FETs. 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 cmÀ2).

Results

Conclusion