Abstract
This paper addresses the high-frequency performance limitations of graphene field-effect transistors (GFETs) caused by material imperfections. To understand these limitations, we performed a comprehensive study of the relationship between the quality of graphene and surrounding materials and the high-frequency performance of GFETs fabricated on a silicon chip. We measured the transit frequency (fT) and the maximum frequency of oscillation (fmax) for a set of GFETs across the chip, and as a measure of the material quality, we chose low-field carrier mobility. The low-field mobility varied across the chip from 600 cm2/Vs to 2000 cm2/Vs, while the fT and fmax frequencies varied from 20 GHz to 37 GHz. The relationship between these frequencies and the low-field mobility was observed experimentally and explained using a methodology based on a small-signal equivalent circuit model with parameters extracted from the drain resistance model and the charge-carrier velocity saturation model. Sensitivity analysis clarified the effects of equivalent-circuit parameters on the fT and fmax frequencies. To improve the GFET high-frequency performance, the transconductance was the most critical parameter, which could be improved by increasing the charge-carrier saturation velocity by selecting adjacent dielectric materials with optical phonon energies higher than that of SiO2.
Highlights
Owing to an extremely high intrinsic carrier mobility of up to 105 cm2/Vs at room temperature [1], [2], graphene is considered a promising new channel material allowing for the development of new generation of field-effect transistors [3] for advanced mm-wave and sub-terahertz amplifiers
In conclusion, we have performed a comprehensive study of the relationship of the high-frequency performance of graphene field-effect transistors (GFETs) to the channel transport properties
An almost linear relationship between the high-frequency parameters of GFETs and low-field mobility was observed and is explained theoretically using a methodology based on the small-signal equivalent circuit model with parameters extracted from the low-field drain resistance model and the charge-carrier velocity saturation model
Summary
Owing to an extremely high intrinsic carrier mobility of up to 105 cm2/Vs at room temperature [1], [2], graphene is considered a promising new channel material allowing for the development of new generation of field-effect transistors [3] for advanced mm-wave and sub-terahertz amplifiers. We analyze the relationship between the graphene/dielectric material quality and the high-field highfrequency performance of GFETs, i.e., the extrinsic f T and f max at drain fields above 104 V/cm.
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