Dynamic wavelength tunability has long been the holy grail of photodetectortechnology. Because of its atomic thickness and unique properties, grapheneopens up new paradigms to realize this concept, but so far this has beenelusive experimentally. Here we employ detailed quantum transport modeling ofphotocurrent in graphene field-effect transistors (including realisticelectromagnetic fields) to show that wavelength tunability is possible bydynamically changing the gate voltage. We reveal the phenomena that govern thebehavior of this type of device and show significant departure from the simpleexpectations based on vertical transitions. We find strong focusing of theelectromagnetic fields at the contact edges over the same length scale as theband-bending. Both of these spatially-varying potentials lead to an enhancementof non-vertical optical transitions, which dominate even the absence of phononor impurity scattering. We also show that the vanishing density of states nearthe Dirac point leads to contact blocking and a gate-dependent modulation ofthe photocurrent.
展开▼
