Ambipolar device simulation based on the drift-diffusion model in ion-gated transition metal dichalcogenide transistors

Yoshihiro Iwasa,Nobuyuki Sano,Yijin Zhang,Akiko Ueda,Hiroshi Imamura

doi:10.1038/s41524-020-0293-x

Abstract

Ionic gating is known as a powerful tool for investigation of electronic functionalities stemming from low voltage transistor operation to gate-induced electronic phase control including superconductivity. Two-dimensional (2D) material is one of the archetypal channel materials which exhibit a variety of gate-induced phenomena. Nevertheless, the device simulations on such ion-gated transistor devices have never been reported, despite its importance for the future design of device structures. In this paper, we developed a drift-diffusion (DD) model on a 2D material, WSe2 monolayer, attached with an ionic liquid, and succeeded in simulating the transport properties, potential profile, carrier density distributions in the transistor configuration. 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. Such peculiar behavior becomes possible by the dramatic change of the potential profiles at the Schottky barrier by the ionic gating. The present result indicates that the DD model coupled to the Poisson equation is a fascinating platform to explain and predict further functionalities of ion-gated transistors through including the spin, valley, and optical degrees of freedom.

Highlights

In ion-gated transistors, the electric double layer works as a gate dielectric layer of about 1 nm in thickness, and such transistors are called electric double layer transistors (EDLTs) or electrolyte gated transistors
We developed a 2D layer transistor model including an ionic liquid (IL) as a gate dielectric, based on the DD method and succeeded in simulating the distribution of ions, and the dynamics of electron and holes passing through the metal contacts
We examined the characteristics of ion-gated transition metal dichalcogenides (TMDs)

Summary

Introduction

In ion-gated transistors, the electric double layer works as a gate dielectric layer of about 1 nm in thickness, and such transistors are called electric double layer transistors (EDLTs) or electrolyte gated transistors. We set the Fermi energy of the metal source old voltages of electron and hole currents is e(Vth−e − Vth−h) = 2.11 eV, which is 0.51 eV larger than the real band gap, Eg. Figure 2c shows the distribution of the net carrier concentration inside the channel.

Results

Conclusion