Shot Noise in Ballistic Graphene

Abstract

We have investigated shot noise in graphene field effect devices in the temperature range of 4.2–30 K at low frequency ($f=600–850\mathrm{MHz}$). We find that for our graphene samples with a large width over length ratio $W/L$, the Fano factor $\mathfrak{F}$ reaches a maximum $\mathfrak{F}\sim 1/3$ at the Dirac point and that it decreases strongly with increasing charge density. For smaller $W/L$, the Fano factor at Dirac point is significantly lower. Our results are in good agreement with the theory describing that transport at the Dirac point in clean graphene arises from evanescent electronic states.