Department of Physics, University of California at Berkeley , Berkeley, California 94720, United States.
Nano Lett. 2014 Mar 12;14(3):1578-82. doi: 10.1021/nl404826r. Epub 2014 Feb 28.
We investigate the ultrafast terahertz response of electrostatically gated graphene upon optical excitation. We observe that the photoinduced terahertz absorption increases in charge neutral graphene but decreases in highly doped graphene. We show that this transition from semiconductor-like to metal-like response is unique for zero bandgap materials such as graphene. In charge neutral graphene photoexcited hot carriers effectively increase electron and hole densities and increase the conductivity. In highly doped graphene, however, photoexcitation does not change net conducting carrier concentration. Instead, it mainly increases electron scattering rate and reduce the conductivity.
我们研究了静电门控石墨烯在光激发下的超快太赫兹响应。我们观察到，在电中性石墨烯中，光诱导太赫兹吸收增加，但在高掺杂石墨烯中则减少。我们表明，这种从半导体样到金属样响应的转变对于零带隙材料如石墨烯是独特的。在电中性石墨烯中，光激发的热载流子有效地增加了电子和空穴密度，并增加了电导率。然而，在高掺杂石墨烯中，光激发不会改变净传导载流子浓度。相反，它主要增加了电子散射率并降低了电导率。
