Quantum mechanical simulation of graphene photodetectors

Graphene photodetectors promise ultrafast speed and wide bandwidth. Interplay of quantum transport effects, such as Klein tunneling, with electron-photon coupling can play an important role in device physics of graphene photodetectors. A quantum mechanical simulation approach, which solves quantum transport equation using the non-equilibrium Green's function formalism and treats electron-photon and electron-phonon coupling in the self-consistent Born approximation, is developed to model graphene photodetectors. A mode space approach utilizing parallel computing is implemented to achieve ultimate computational efficiency. It is found that using two metal contacts with distinctively different work function significantly improves the device performance. The photoresponse is strongest when the light spot is focused at the contact regions and is insensitive to the photon energy, which is in qualitative agreement with experiment. The effect of different device designs on the quantum efficiency and the effect of phonon scattering are examined. The simulation results also indicate wide band response of graphene photodetectors. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759369]