Nano Lett. 2016 Nov 09;16(11):6988-6993. doi: 10.1021/acs.nanolett.6b03078. Epub 2016 Oct 11.

Microwave Photodetection in an Ultraclean Suspended Bilayer Graphene p-n Junction.

Nano letters

Minkyung Jung, Peter Rickhaus, Simon Zihlmann, Peter Makk, Christian Schönenberger

PMID: 27704863 DOI: 10.1021/acs.nanolett.6b03078

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.

Keywords: Bilayer graphene; ballistic graphene; microwave; photocurrent; photodetector; photothermoelectric effect

Publication Types

• Journal Article
• Research Support, Non-U.S. Gov't