  Straightforward contact resistance extraction methods based on electrical
device characteristics are described and applied here to graphene field-effect
transistors from different technologies. The methods are an educated adaptation
of extraction procedures originally developed for conventional transistors by
exploiting the drift-diffusion-like transport in graphene devices under certain
bias conditions. In contrast to other available approaches for contact
resistance extraction of graphene transistors, the practical methods used here
do not require either the fabrication of dedicated test structures or internal
device phenomena characterization. The methodologies are evaluated with
simulation-based data and applied to fabricated devices. The extracted values
are close to the ones obtained with other more intricate methodologies.
Bias-dependent contact and channel resistances studies, bias-dependent
high-frequency performance studies and contact engineering studies are enhanced
and evaluated by the extracted contact resistance values.
