Molybdenum Contacts to MoS2 Field‐Effect Transistors: Schottky Barrier Extraction, Electrical Transport, and Low‐Frequency Noise

• Published in: Physica status solidi. A, Applications and materials science Vol. 217; no. 17
• Main Authors: Kwon, Jiseok, Delker, Collin J., Janes, David B., Harris, Charles T., Das, Suprem R.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.09.2020
• Subjects: 2D field-effect transistors; Atomic properties; Contact resistance; Current injection; Electric contacts; Electrical junctions; Electronic devices; Field effect transistors; low work function; low-frequency noise; Molybdenum; Molybdenum disulfide; Scattering; Schottky barrier; Semiconductor devices; Semiconductor junctions; Thickness; Transistors
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.201900880

MoS2 has great interest for nanoscale electronic devices, including transistors and sensors. Defect‐free structure, clean interface with the gate dielectric, and metals with suitable metal–semiconductor junctions are key for reliable devices. Molybdenum is shown as an excellent electrode for MoS2 field‐effect transistors (FETs), but the correlation among device current, field‐effect mobility, and the low‐frequency noise (LFN) with number of atomic layers is not studied. Furthermore, the impact of Mo/MoS2 Schottky barrier on electronic injection and scattering in the device needs to be understood. Herein, by studying the FETs with channels of different numbers of atomic‐layer thicknesses, it is shown that a molybdenum metal contact to MoS2 provides reliable current injection with low Schottky barrier height, low contact resistance, low electron–phonon scattering, and negligible impurity scattering. The mobility and LFN are optimal at a channel thickness of ≈12 atomic layers, which is consistent with the “mobility maximum window” in MoS2 transistors with prior studies using other contact metals. Molybdenum contact to MoS2 field‐effect transistors offer low 1/f noise when the channel is 12 atomic layers, producing a channel Hooge constant of 5.5 × 10−3, low enough in emerging devices that can be considered for applications, such as reliable sensors. Molybdenum source/drain forms a low Schottky barrier of 130 meV, high switching, and a mobility limited by electron–phonon scattering.