Dipole-Engineering Strategy for Regulating the Electronic Contact of a Two-Dimensional Sb X /Graphene ( X = P ,

A Schottky barrier, formed in the contact of a two-dimensional (2D) semiconductor and metal electrode, seriously degrades device performance. Herein, we propose a dipole-engineering strategy to regulate the electronic contact properties of a 2D polar $\mathrm{Sb}$X (X = $\mathrm{P}$, $\mathrm{As}$, $\mathrm{Bi}$) and graphene ($\mathrm{Gr}$) van der Waals interface. Owing to the mirror asymmetry of $\mathrm{Sb}$X, we construct seven vertical heterostructures in the form of X$\mathrm{Sb}$-$\mathrm{Gr}$ and $\mathrm{Sb}$X$\text{\ensuremath{-}}\mathrm{Gr}$. Tunable Schottky barrier height and contact type can be obtained by using different atomic terminals to contact with $\mathrm{Gr}$. Based on the first-principles calculations, the dipole and its associated potential step are found to be responsible for the regulating effect. Moreover, owing to the remarkable properties of the $\mathrm{Sb}\mathrm{Bi}$-$\mathrm{Gr}$ heterostructure, such as Ohmic contact and low tunneling barrier, we design an optoelectronic field-effect transistor, which exhibits considerable responsivity (0.089 ${\mathrm{AW}}^{\ensuremath{-}1}$) and external quantum efficiency (28.57%). Our findings further confirm that regulating the electronic contact properties by the dipole in the heterostructure is a feasible strategy, which provides meaningful guidance for designing high-performance electronic and optoelectronic devices.