  Graphene-based devices are planned to augment the functionality of Si and
III-V based technology in radio-frequency (RF) electronics. The expectations in
designing graphene {field-effect} transistors (GFETs) with enhanced RF
performance have attracted significant experimental efforts, mainly
concentrated on achieving high mobility samples. However, little attention has
been paid, so far, to the role of the access regions in these devices.
\mbox{Here, we analyse} in detail, via numerical simulations, how the GFET
transfer response is severely impacted by these regions, showing that they play
a significant role in the asymmetric saturated behaviour commonly observed in
GFETs. We also investigate how the modulation of the access region conductivity
(i.e., by the influence of a back gate) and the presence of imperfections in
the graphene layer (e.g., charge puddles) affects the transfer response. The
analysis is extended to assess the application of GFETs for RF applications,
by~evaluating their cut-off frequency.
