Current crowding mediated large contact noise in graphene field-effect transistors

Area of Science:

• Physics
• Materials Science
• Electrical Engineering

Background:

• Contact noise, intrinsic fluctuations at the graphene-metal interface, is a critical but understudied factor affecting graphene field-effect transistor (GFET) performance.
• Its impact can be as detrimental as contact resistance, yet its origins and prevalence are not well understood.

Purpose of the Study:

• To investigate the phenomenon of contact noise in GFETs across various device geometries and contact configurations.
• To determine the extent to which contact noise influences the overall measured resistance noise in GFETs.
• To explore the microscopic origins of contact noise in two-dimensional (2D) material-based devices.

Main Methods:

• Investigated contact noise in GFETs with carrier mobilities ranging from 5,000 to 80,000 cm²V^-1s^-1.
• Employed a phenomenological model for contact noise arising from current crowding in 2D conductors.
• Utilized two-probe, invasive four-probe, and nearly noninvasive four-probe (Hall bar) configurations.

Main Results:

• Contact noise was found to dominate the measured resistance noise in all GFET configurations studied (two-probe and invasive four-probe).
• Surprisingly, contact noise also dominated in the nearly noninvasive four-probe (Hall bar) configuration for high-mobility devices.
• The study confirms that contacts are a primary source of resistance noise in GFETs.

Conclusions:

• Contact noise is a significant contributor to the overall noise in GFETs, comparable to contact resistance.
• The fluctuating electrostatic environment at the metal-channel interface is identified as the microscopic origin of contact noise.
• This finding has implications for the design and performance optimization of electronic devices based on 2D materials.