title: Generation of photovoltage in graphene on a femtosecond timescale through efficient carrier heating.
abstract: Graphene is a promising material for ultrafast and broadband photodetection. Earlier studies have addressed the general operation of graphene-based photothermoelectric devices and the switching speed, which is limited by the charge carrier cooling time, on the order of picoseconds. However, the generation of the photovoltage could occur at a much faster timescale, as it is associated with the carrier heating time. Here, we measure the photovoltage generation time and find it to be faster than 50 fs. As a proof-of-principle application of this ultrafast photodetector, we use graphene to directly measure, electrically, the pulse duration of a sub-50 fs laser pulse. The observation that carrier heating is ultrafast suggests that energy from absorbed photons can be efficiently transferred to carrier heat. To study this, we examine the spectral response and find a constant spectral responsivity of between 500 and 1,500 nm. This is consistent with efficient electron heating. These results are promising for ultrafast femtosecond and broadband photodetector applications.
authors: ICFO - Institut de Ciències Fotòniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain.
authors: K J
authors: KJ
authors: Tielrooij
authors: ICFO - Institut de Ciències Fotòniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain.
authors: L
authors: L
authors: Piatkowski
authors: ICFO - Institut de Ciències Fotòniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain.
authors: M
authors: M
authors: Massicotte
authors: ICFO - Institut de Ciències Fotòniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain.
authors: A
authors: 0000000250244201
authors: A
authors: Woessner
authors: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors: Q
authors: Q
authors: Ma
authors: Department of Physics and Astronomy, University of California, Riverside, California 92521, USA.
authors: Y
authors: Y
authors: Lee
authors: Department of Physics and Astronomy, University of California, Riverside, California 92521, USA.
authors: K S
authors: KS
authors: Myhro
authors: Department of Physics and Astronomy, University of California, Riverside, California 92521, USA.
authors: C N
authors: CN
authors: Lau
authors: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors: P
authors: P
authors: Jarillo-Herrero
authors: 1] ICFO - Institut de Ciències Fotòniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain [2] ICREA - Institució Catalana de Recerca i Estudis Avançats, Barcelona 08010, Spain.
authors: N F
authors: NF
authors: van Hulst
authors: ICFO - Institut de Ciències Fotòniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain.
authors: F H L
authors: FH
authors: Koppens