Electron-Hole Asymmetry in the Electron-phonon Coupling in Top-gated Phosphorene Transistor

Abstract

Using in-situ Raman scattering from phosphorene channel in an electrochemically top-gated field effect transistor, we show that its phonons with A${}_g$ symmetry depend much more strongly on concentration of electrons than that of holes, while the phonons with B${}_g$ symmetry are insensitive to doping. With first-principles theoretical analysis, we show that the observed electon-hole asymmetry arises from the radically different constitution of its conduction and valence bands involving $\ddot{I}€$ and $\ddot{I}ƒ$ bonding states respectively, whose symmetry permits coupling with only the phonons that preserve the lattice symmetry. Thus, Raman spectroscopy is a non-invasive tool for measuring electron concentration in phosphorene-based nanoelectronic devices.