Infrared microscopy of Joule heating in graphene field effect transistors

We use infrared microscopy to image the temperature profile of graphene field-effect transistors operating at constant source to drain current bias. We find a peak in the temperature profile, i.e. a ¿hot spot¿ appears near the drain (anode) electrode of the graphene sheet at high current while operating in the hole-doped regime. We shift the hot spot position on the graphene sheet by tuning the gate voltage into an ambipolar transport regime. This shows a direct demonstration and manipulation of Joule heating in graphene transistors.