超净悬浮双层石墨烯PN结中的微波光电探测
Microwave Photodetection in an Ultraclean Suspended Bilayer Graphene pn Junction
摘要：
我们探索了双层石墨烯作为低温微波光电探测器的潜力，通过研究在8 K的温度下，在$1-5$ GHz的频率范围内，完全悬浮的清洁双层石墨烯PN结中的微波吸收。我们观察到一个独特的光电流信号，如果该设备被门控到pn制度，而几乎没有信号的单极掺杂的nn或pp制度。最令人惊讶的是，当结的一侧被选通到狄拉克点（电荷中性点CNP）时，光电流强烈地达到峰值，而另一侧保持在高掺杂状态。这与以前使用光辐射的结果不同。我们提出了一个新的机制的基础上的光热效应解释的大信号。它需要接触掺杂和两侧明显不同的传输机制：石墨烯的一侧是弹道的，另一侧是扩散的。通过设计部分扩散和部分弹道器件，光电流可以大大增强。
英文摘要：
We explore the potential of bilayer graphene as a cryogenic microwave photodetector by studying the microwave absorption in fully suspended clean bilayer graphene pn 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 pn regime, while there is almost no signal for unipolar doping in either the nn or pp 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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