Microscopic Origin of Charged Impurity Scattering and Flicker Noise in MoS2 field-effect Transistors

TL;DR

This study reveals that localized trap states within MoS2 layers are the primary cause of charge carrier scattering and flicker noise in MoS2 field-effect transistors, advancing understanding of their microscopic origins.

Contribution

It demonstrates that internal trap states in MoS2 are responsible for both scattering and flicker noise, providing new insights into their microscopic mechanisms.

Findings

Trap states act as Coulomb scattering centers affecting transport.

Trap states exchange carriers, causing conductivity noise.

Internal trap states confirmed by experiments on different substrates.

Abstract

Scattering of charge carriers and flicker noise in electrical transport are the central performance limiting factors in electronic devices, but their microscopic origin in molybdenum disulphide~(MoS$_2$)-based field effect transistors remains poorly understood. Here, we show that both carrier scattering and low-frequency $1/f$ noise in mechanically exfoliated ultra-thin MoS$_2$ layers are determined by the localized trap states located within the MoS$_2$ channel itself. The trap states not only act as Coulomb scattering centers that determine transport in both equilibrium ($eV< k_BT$) and non-equilibrium ($eV>k_BT$) regimes, where $V$ and $T$ are the source drain bias and temperature respectively, but also exchange carriers with the channel to produce the conductivity noise. The internal origin of the trap states was further confirmed by studying noise in MoS$_2$ films deposited on crystalline boron nitride substrates. Possible origin and nature of the trap states is also discussed.