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Optical and thermal properties of graphene field‐effect transistors

Graphene has attracted immense interest due to its unique electronic structure with conical bands and zero bandgap (Novoselov et al., Nature 438, 197 (2005) 1 ), and high carrier mobility (Du et al., Nature Nanotech. 3, 491 (2008) 2 , Bolotin et al., Solid State Commun. 146, 351 (2008) 3 ). While field‐effect transistors (FETs) using graphene as the channel material have been shown to perform well at high frequencies (Lin et al., Science 327, 662 (2010) 4 ), their use for logic applications requires opening of a bandgap to reduce the off‐state current. The thermal properties of graphene FETs also need to be better understood, since self‐heating and power management become important in high‐density, high‐performance electronics. The interaction of graphene with photons (visible and infrared) can shed new light onto all these issues. Here, we review various avenues of bandgap opening in graphene and bilayer graphene. Wherever available, optical experiments that corroborate the bandgap opening will be discussed. The thermal properties of graphene FETs, also measured by optical means, will be presented next. Finally, photocurrent experiments that can be used to determine band‐bending in active graphene channels will be discussed.