Tuning transport across MoS2/graphene interfaces via as-grown lateral heterostructures

Shruti Subramanian,Yuanxi Wang,Donna Deng,Nicholas A Simonson,Vincent H Crespi,Joshua A Robinson,Ke Xu,Susan K Fullerton-Shirey,Simon Moser

doi:10.1038/s41699-020-0144-0

Abstract

An unexploited property of graphene-based heterojunctions is the tunable doping of the junction via electrostatic gating. This unique property may be key in advancing electronic transport across interfaces with semiconductors. Here, we engineer transport in semiconducting TMDs by constructing a lateral heterostructure with epitaxial graphene and tuning its intrinsic doping to form a p–n junction between the graphene and the semiconducting TMDs. Graphene grown on SiC (epitaxial graphene) is intrinsically doped via substrate polarization without the introduction of an external dopant, thus enabling a platform for pristine heterostructures with a target band alignment. We demonstrate an electrostatically tunable graphene/MoS2p–n junction with >20× reduction and >10× increased tunability in contact resistance (Rc) compared with metal/TMD junctions, attributed to band alignment engineering and the tunable density of states in graphene. This unique concept provides improved control over transport across 2D p–n junctions.

Highlights

Engineering p–n junctions in semiconductors requires choosing the right material combination for a target band alignment
Graphene grown on silicon carbide (SiC), dubbed epitaxial graphene (EG)[2], provides an additional chemical degree of freedom to control the potential for only the graphene component in the heterostructure
Building from our successful synthesis of lateral heterostructures between EG and MoS24, we demonstrate the formation of a low resistance lateral p–n junction between EG and molybdenum disulfide (MoS2), which allows for configurable electronic properties

Summary

INTRODUCTION

Engineering p–n junctions in semiconductors requires choosing the right material combination for a target band alignment. This challenge is only amplified for two-dimensional (2D) materials, semiconducting transition metal dichalcogenides (TMDs) owing to their ultra-thin nature, their layered structure, and the difficulties involved with achieving sufficiently high doping densities[1]. We demonstrate that the EG/MoS2 heterostructure has a pristine interface and allows for the EG to reduce the contact resistance by >20×. This is an improvement over utilizing chemical vapor deposited (CVD). With EG contacts, the challenges involved with controllable large-area transfer is eliminated making this a scalable, as-grown process

RESULTS AND DISCUSSION

Such lateral heterostructures exhibit a pristine interface with an overlap of

METHODS