Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 7: Graphene: THz, NIR and Transport Properties (HL with O/TT)

O 7.6: Vortrag

Montag, 16. März 2015, 10:45–11:00, ER 270

Giant magnetophotoelectric effect in suspended graphene — •Jens Sonntag, Annika Kurzmann, Martin Geller, Ralf Schützhold, and Axel Lorke — Faculty of Physics and CeNIDE, University of Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany

Due to the broad absorption bandwidth and the possibility for carrier multiplication, graphene is a promising candidate for optoelectric applications.

In this context, we performed photocurrent measurements on a suspended graphene field-effect transistor structure in a magnetic field in the quantum Hall regime. Using an illumination power of only 3 µW, our device generates a current of up to 400 nA without an applied bias, which corresponds to a photoresponsivity of 0.14 A/W. To the best of our knowledge, this is one of the highest values ever measured for single layer graphene. Furthermore, the high current suggests that every absorbed photon creates more than 8 charge carriers, so that carrier multiplication is apparent.

We discuss these photocurrents in the framework of magnetothermoelectric effects and recent calculations of photocurrent generation in edge channels [1]. Taking into account the observed gate voltage, magnetic field and polarization dependence, we develop a quasi-ballistic model for the measured photocurrent. It includes edge channel transport and charge carrier multiplication and is in good agreement with the experimental results.

[1] Queisser et al. Phys. Rev. Let. 111, 046601 (2013)