title: Microwave Photodetection in an Ultraclean Suspended Bilayer Graphene p-n Junction.
abstract: We explore the potential of bilayer graphene as a cryogenic microwave photodetector by studying the microwave absorption in fully suspended clean bilayer graphene p-n junctions in the frequency range of 1-5 GHz at a temperature of 8 K. We observe a distinct photocurrent signal if the device is gated into the p-n regime, while there is almost no signal for unipolar doping in either the n-n or p-p regimes. Most surprisingly, the photocurrent strongly peaks when one side of the junction is gated to the Dirac point (charge-neutrality point CNP), while the other remains in a highly doped state. This is different to previous results where optical radiation was used. We propose a new mechanism based on the phototermal effect explaining the large signal. It requires contact doping and a distinctly different transport mechanism on both sides: one side of graphene is ballistic and the other diffusive. By engineering partially diffusive and partially ballistic devices, the photocurrent can drastically be enhanced.
authors.affiliation: Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland.|Division of Nano-Energy, DGIST , 333 Techno Jungang-Daero, Hyeongpung, Daegu, Korea 42988.
authors.forename: Minkyung
authors.initials: M
authors.lastname: Jung
authors.forename: Peter
authors.initials: P
authors.lastname: Rickhaus
authors.affiliation: Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Simon
authors.initials: S
authors.lastname: Zihlmann
authors.affiliation: Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Makk
authors.affiliation: Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Schönenberger
keywords: Bilayer graphene; ballistic graphene; microwave; photocurrent; photodetector; photothermoelectric effect