title: THz-circuits driven by photo-thermoelectric, gate-tunable graphene-junctions.
abstract: For future on-chip communication schemes, it is essential to integrate nanoscale materials with an ultrafast optoelectronic functionality into high-frequency circuits. The atomically thin graphene has been widely demonstrated to be suitable for photovoltaic and optoelectronic devices because of its broadband optical absorption and its high electron mobility. Moreover, the ultrafast relaxation of photogenerated charge carriers has been verified in graphene. Here, we show that dual-gated graphene junctions can be functional parts of THz-circuits. As the underlying optoelectronic process, we exploit ultrafast photo-thermoelectric currents. We describe an immediate photo-thermoelectric current of the unbiased device following a femtosecond laser excitation. For a picosecond time-scale after the optical excitation, an additional photo-thermoelectric contribution shows up, which exhibits the fingerprint of a spatially inverted temperature profile. The latter can be understood by the different time-constants and thermal coupling mechanisms of the electron and phonon baths within graphene to the substrate and the metal contacts. The interplay of the processes gives rise to ultrafast electromagnetic transients in high-frequency circuits, and it is equally important for a fundamental understanding of graphene-based ultrafast photodetectors and switches.
authors.affiliation: Walter Schottky Institut and Physics Department, Technical University Munich, Am Coulombwall 4a, 85748 Garching, Germany.|Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Brenneis
authors.affiliation: Walter Schottky Institut and Physics Department, Technical University Munich, Am Coulombwall 4a, 85748 Garching, Germany.|Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 Munich, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Schade
authors.affiliation: Walter Schottky Institut and Physics Department, Technical University Munich, Am Coulombwall 4a, 85748 Garching, Germany.|Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 Munich, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Drieschner
authors.affiliation: Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 Munich, Germany.|Lehrstuhl für Physik funktionaler Schichtsysteme, Physics Department, Technical University of Munich, D-85748 Garching, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Heimbach
authors.affiliation: Institute of Physics, University of Augsburg, 86135 Augsburg, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Karl
authors.affiliation: Walter Schottky Institut and Physics Department, Technical University Munich, Am Coulombwall 4a, 85748 Garching, Germany.|Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 Munich, Germany.
authors.forename: Jose A
authors.initials: JA
authors.lastname: Garrido
authors.affiliation: Walter Schottky Institut and Physics Department, Technical University Munich, Am Coulombwall 4a, 85748 Garching, Germany.|Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 Munich, Germany.
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Holleitner