  In this article, the bias-dependence of intrinsic channel thermal noise of
single-layer graphene field-effect transistors (GFETs) is thoroughly
investigated by experimental observations and compact modeling. The findings
indicate an increase of the specific noise as drain current increases whereas a
saturation trend is observed at very high carrier density regime. Besides,
short-channel effects like velocity saturation also result in an increment of
noise at higher electric fields. The main goal of this work is to propose a
physics-based compact model that accounts for and accurately predicts the above
experimental observations in short-channel GFETs. In contrast to long-channel
MOSFET based models adopted previously to describe thermal noise in graphene
devices without considering the degenerate nature of graphene, in this work a
model for short-channel GFETs embracing the 2D materials underlying physics and
including a bias dependency is presented. The implemented model is validated
with de-embedded high frequency data from two short-channel devices at
Quasi-Static region of operation. The model precisely describes the
experimental data for a wide range of low to high drain current values without
the need of any fitting parameter. Moreover, the consideration of the
degenerate nature of graphene reveals a significant decrease of noise in
comparison with the non degenerate case and the model accurately captures this
behavior. This work can also be of outmost significance from circuit designers
aspect, since noise excess factor, a very important figure of merit for RF
circuits implementation, is defined and characterized for the first time in
graphene transistors.
