Observation of Tunneling Current in Semiconducting Graphene p-n   Junctions
  We demonstrate a tunneling and rectification behavior in bilayer graphene. A stepped dielectric top gate creates a spatially modulated electric field, which opens the band gap in the graphene and produces an insulating region at the p-n interface. A current-voltage relationship exhibiting differential resistance peak at forward bias stems from the tunneling current through the insulating region at the p-n interface. The tunneling current reflects singularities in the density of states modified by the electric field. This work suggests that the effect of carrier charge tuning by external electric field in 2D semiconductors is analogously to that by impurity doping in 3D semiconductors. 
Hisao Miyazaki, Michael Lee, Song-Lin Li, Hidefumi Hiura, Kazuhito   Tsukagoshi, and Akinobu Kanda
cond-mat.mes-hall cond-mat.mtrl-sci