Low Contact Resistance on Monolayer MoS₂ Field-Effect Transistors Achieved by CMOS-Compatible Metal Contacts

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Contact engineering in monolayer (ML) semiconducting transition metal dichalcogenides (TMDs) is vital for advanced transistors.
• Fermi-level pinning and Schottky barriers limit the performance of ML TMD field-effect transistors (FETs).
• The impact of interface defects and reaction sites on ML TMD FET electrical performance is not well understood.

Purpose of the Study:

• To investigate the dependence of contact resistance on interface chemistry in ML TMD FETs.
• To correlate electrical measurements with surface analysis to understand contact formation.
• To explore the thermal stability and reliability of different contact metals.

Main Methods:

• Fabrication and electrical characterization of over 120 ML MoS2 FETs.
• Surface analysis using X-ray photoelectron spectroscopy (XPS).
• Deposition of Ni and Bi contacts under ultrahigh-vacuum (UHV) and high-vacuum (HV) conditions.

Main Results:

• Achieved a contact resistance of ~500 Ω·μm for ML MoS2 FETs with UHV-deposited Ni contacts, 5 times lower than HV-deposited contacts.
• XPS revealed significant Ni-MoS2 bonding under UHV, correlating with lower contact resistance.
• No significant difference in contact resistance or interface chemistry was observed for Bi contacts under UHV and HV conditions.

Conclusions:

• UHV deposition of Ni is critical for achieving low contact resistance in ML MoS2 FETs due to enhanced interface chemistry.
• The choice of contact metal significantly influences the interface properties and resulting device performance.
• Further research into contact engineering is essential for realizing high-performance ML TMD electronic devices.