Mobility extraction and quantum capacitance impact in high performance graphene field-effect transistor devices

The field-effect mobility of graphene devices is discussed. We argue that the graphene ballistic mean free path, L
_ball
can only be extracted by taking into account both, the electrical characteristics and the channel length dependent mobility. In doing so we find a ballistic mean free path of L
_ball
=300plusmn100 nm at room-temperature for a carrier concentration of ~10
¹²
cm
^-2
and that a substantial series resistance of around 300 Omega mum has to be taken into account. Furthermore, we demonstrate first quantum capacitance measurements on single-layer graphene devices.