Device simulation study of ion-gated ambipolar transition-metal dichalcogenide transistors

Ion gating is known as a powerful tool to access electronic functionalities with low voltage operation. Though many interesting experimental studies have been reported, the device simulation had never been performed before. In this work, we developed a two-dimensional layer transistor model based on the drift-diffusion method for an ionic liquid (IL) as a gate dielectric. We reproduced the transport characteristics of the ion-gated WSe₂ transistors reported in several experiments and explained the transport mechanism using the band profile and spatial distribution obtained by the calculation. In particular, the simulation explains the ambipolar behavior with the gate voltage comparable to the band gap energy, as well as the formation of p-n junctions in the channel reported in several experimental papers. The simulation clearly shows that the ambipolar behavior becomes possible by the dramatic change of the potential profile at the contacts. The developed model is highly advantageous for exploring the functionalities and design ideal devices for ion-gated transition-metal dichalcogenide transistors.