Variations of Contact Resistance in Dual-Gated Monolayer Molybdenum Disulfide Transistors Depending on Gate Bias Selection

Abstract

Monolayer molybdenum disulfide (MoS₂) is considered an alternative two-dimensional material for high performance ultra-thin field-effect transistors. MoS₂ is a triple atomic layer with a direct 1.8 eV bandgap. Bulk MoS₂ has an additional indirect bandgap of 1.2 eV, which leads to high current on/off ratio around 10⁸. Flakes of MoS₂ can be obtained by mechanical exfoliation or grown by chemical vapor deposition. Intrinsic cut-off frequency of multilayer MoS₂ transistor has reached 42 GHz. Chemical doping of MoS₂ is challenging and results in reduction of contact resistance. This paper focuses on modeling of dual-gated monolayer MoS₂ transistors with effective mobility of carriers varying from 0.6 cm²/V s to 750 cm²/V s. In agreement with experimental data, the model demonstrates that in back-gate bias devices, the contact resistance decreases almost exponentially with increasing gate bias, whereas in top-gate bias devices, the contact resistance stays invariant when varying gate bias.