Ultrafast graphene photodetector

Graphene research so far has focused on electronic1,2,3,4,5,6 rather than photonic applications, in spite of its impressive optical properties7,8. These include its ability to absorb ∼2% of incident light over a broad wavelength range despite being just one atom thick7. Here, we demonstrate ultrafast transistor-based photodetectors made from single- and few-layer graphene. The photoresponse does not degrade for optical intensity modulations up to 40 GHz, and further analysis suggests that the intrinsic bandwidth may exceed 500 GHz. The generation and transport of photocarriers in graphene differ fundamentally from those in photodetectors made from conventional semiconductors as a result of the unique photonic and electronic properties of the graphene. This leads to a remarkably high bandwidth, zero source–drain bias and dark current operation, and good internal quantum efficiency. Field-effect transistors made from graphene act as photodetectors at frequencies up to 40 GHz, demonstrating the advantage offered by graphene for photonic applications.