Analyzing the Carrier Mobility in Transition-metal Dichalcogenide MoS2 Field-effect Transistors

Abstract

Transition-metal dichalcogenides (TMDCs) are important class of two-dimensional (2D) layered materials for electronic and optoelectronic applications, due to their ultimate body thickness, sizable and tunable bandgap, and decent theoretical room-temperature mobility of hundreds to thousands cm2/Vs. So far, however, all TMDCs show much lower mobility experimentally because of the collective effects by foreign impurities, which has become one of the most important limitations for their device applications. Here, taking MoS2 as an example, we review the key factors that bring down the mobility in TMDC transistors, including phonons, charged impurities, defects, and charge traps. We introduce a theoretical model that quantitatively captures the scaling of mobility with temperature, carrier density and thickness. By fitting the available mobility data from literature over the past few years, we are able to obtain the density of impurities and traps for a wide range of transistor structures. We show that interface engineering such as oxide surface passivation, high-k dielectrics and BN encapsulation could effectively reduce the impurities, leading to improved device performances. For few-layer TMDCs, we analytically model the lopsided carrier distribution to elucidate the experimental increase of mobility with the number of layers. From our analysis, it is clear that the charge transport in TMDC samples is a very complex problem that must be handled carefully. We hope that this Review can provide new insights and serve as a starting point for further improving the performance of TMDC transistors.

arXiv comment61 pages, 9 figures, Advanced Functional Materials, in press

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• Dynamics and Spin-Valley Locking Effects in Monolayer Transition Metal Dichalcogenides
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• Tunable linearity of high-performance vertical dual-gate vdW phototransistor
• Accumulation-mode two-dimensional field-effect transistor: Operation mechanism and thickness scaling rule
• Optimal band gap for improved thermoelectric performance of two-dimensional Dirac materials
• The Role of Mobile Point Defects in Two-Dimensional Memristive Devices
• Possible charge-density-wave signatures in the anomalous resistivity of Li-intercalated multilayer MoS2
• Coulomb screening and scattering in atomically thin transistors across dimensional crossover
• Ultrafast photoconductivity and terahertz vibrational dynamics in double-helix SnIP nanowires
• Intricate modulation of interlayer coupling at GO/MoSe2 interface: application in time-dependent optics and device transport
• Approaching the Intrinsic Properties of Moiré Structures Using Atomic Force Microscopy Ironing
• Effectuating tunable valley selection via multi-terminal monolayer graphene devices
• Strong band-filling-dependence of the scattering lifetime in gated MoS2 nanolayers induced by the opening of intervalley scattering channels
• Transport anomalies in the layered compound BaPt4Se6
• Piezoelectric Strain FET (PeFET) based Non-Volatile Memories
• Direct observation of ultrafast defect-bound and free exciton dynamics in defect-engineered WS${}_2$ monolayers
• High-order harmonic generation in 2D Transition Metal Disulphides