title: Tunable transport gap in phosphorene.
abstract: In this article, we experimentally demonstrate that the transport gap of phosphorene can be tuned monotonically from ∼0.3 to ∼1.0 eV when the flake thickness is scaled down from bulk to a single layer. As a consequence, the ON current, the OFF current, and the current ON/OFF ratios of phosphorene field effect transistors (FETs) were found to be significantly impacted by the layer thickness. The transport gap was determined from the transfer characteristics of phosphorene FETs using a robust technique that has not been reported before. The detailed mathematical model is also provided. By scaling the thickness of the gate oxide, we were also able to demonstrate enhanced ambipolar conduction in monolayer and few layer phosphorene FETs. The asymmetry of the electron and the hole current was found to be dependent on the layer thickness that can be explained by dynamic changes of the metal Fermi level with the energy band of phosphorene depending on the layer number. We also extracted the Schottky barrier heights for both the electron and the hole injection as a function of the layer thickness. Finally, we discuss the dependence of field effect hole mobility of phosphorene on temperature and carrier concentration.
authors.affiliation: Center for Nanoscale Material, ‡Materials Science Division, and §Division of High Energy Physics, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Saptarshi
authors.initials: S
authors.lastname: Das
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Marcel
authors.initials: M
authors.lastname: Demarteau
authors.forename: Axel
authors.initials: A
authors.lastname: Hoffmann
authors.forename: Madan
authors.initials: M
authors.lastname: Dubey
authors.forename: Andreas
authors.initials: A
authors.lastname: Roelofs
mesh_terms: D004583:Electrons; D004867:Equipment Design; D049329:Nanostructures / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry*; D014173:Transistors, Electronic
chemical_list: D010758:Phosphorus
keywords: Phosphorene; field effect transistor; mobility; transport gap