Electrical characterization of fully encapsulated ultra thin black phosphorus-based heterostructures with graphene contacts

摘要

The presence of finite bandgap and high mobility in semiconductor few-layerblack phosphorus offers an attractive prospect for using this material infuture two-dimensional electronic devices. Here we demonstrate for the firsttime fully encapsulated ultrathin (down to bilayer) black phosphorus fieldeffect transistors in Van der Waals heterostructures to preclude theirstability and degradation problems which have limited their potential forapplications. Introducing monolayer graphene in our device architecture forone-atom-thick conformal source-drain electrodes enables a chemically inertboron nitride dielectric to tightly seal the black phosphorus surface. Thisarchitecture, generally applicable for other sensitive two-dimensionalcrystals, results in stable transport characteristics which are hysteresis freeand identical both under high vacuum and ambient conditions. Remarkably, ourgraphene electrodes lead to contacts not dominated by thermionic emission,solving the issue of Schottky barrier limited transport in the technologicallyrelevant two-terminal field effect transistor geometry.