Role of metal–semiconductor contacts on the performance of \(\hbox {MoS}_2\) field-effect transistor: an atomistic study

Abstract

Selecting the perfect contact for the two-dimensional (2D) material-based field-effect transistor (FET) is a big challenge. The Schottky barrier arises at the metal–semiconductor contact interface from Fermi-level pinning (FLP) near the semiconductor conduction or valence band, a bottleneck in designing the FET structure. Therefore, metal–semiconductor contact is of great interest in understanding electronic device performance. This paper performs atomistic device simulations for optimal contact performance using titanium (Ti), molybdenum (Mo), gold (Au), and palladium (Pd) as a metal with monolayer \(\hbox {MoS}_2\) as a channel region. The atomistic simulation includes density functional theory (DFT), maximally localized Wannier function (MLWF), and nonequilibrium Green’s function (NEGF) quantum transport for charge carriers. The FET device with Mo and Pd contact demonstrates n-type device characteristics, while Ti and Au show Schottky contact with p-type device behavior, respectively. In addition, the contact material with low work function demonstrates negative differential resistance (NDR) in the device output characteristics. Here, our study observed that the contact performance and device behavior can be completely predicted with the combination of FLP, orbital overlap, energy band diagram, and transmission spectrum. This study can be used to understand the contact performance for next technology nodes, which is still a critical issue in 2D material-based devices.