We have investigated shot noise and conductance of multiterminal graphene nanoribbon devices at temperatures down to 50 mK. Away from the charge neutrality point, we find a Fano factor $F\approx 0.4$, nearly independent of the charge density. Our shot noise results are consistent with theoretical models for disordered graphene ribbons with a dimensionless scattering strength $K_0\approx 10$ corresponding to rather strong disorder. Close to charge neutrality, an increase in $F$ up to $\sim$0.7 is found, which indicates the presence of a dominant Coulomb gap possibly due to a single quantum dot in the transport gap.

• Received 27 August 2013

DOI:https://doi.org/10.1103/PhysRevB.88.245415