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

作者：Jung Minkyung^*; Rickhaus Peter; Zihlmann Simon; Makk Peter; Schonenberger Christian^*

来源：Nano Letters, 2016, 16(11): 6988-6993.

DOI：10.1021/acs.nanolett.6b03078

• Bilayer graphene
• photocurrent
• photodetector
• microwave
• photothermoelectric effect
• ballistic graphene

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.

• 出版日期2016-11