期刊
NANO LETTERS
卷 16, 期 11, 页码 6988-6993出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.6b03078
关键词
Bilayer graphene; photocurrent; photodetector; microwave; photothermoelectric effect; ballistic graphene
类别
资金
- ERC project QUEST
- EC flagship Graphene
- Swiss National Science Foundation (SNF), project NCCR QSIT
- Swiss Nanoscience Institute
- DGIST [2016040006]
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.
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