Graphene nanoribbon photodetectors based on an asymmetric potential barrier: a new concept and a new structure

In the last decade, graphene photodetectors have been introduced and investigated in many works. In any photodetector, the separation of the photo-excited electrons and holes is one of the most basic mechanisms. However, a few distinct methods have already been introduced for the separation and all of them are based on the usage of a longitudinal electric field. In this paper, a new method is proposed. Our method is based on applying a vertical electric field which induces an asymmetric potential barrier in front of one or both of the photo-excited carriers. First, a simple one-dimensional toy model consisting of a one-dimensional atomic chain is used to focus on the concept. Many aspects, including the effects of the potential barrier location, its height, and its width, are investigated by this model. Then, in order to extend to real applications, a new structure is introduced in this paper; it is based on graphene nanoribbons and an asymmetric metal gate. Our results show that this structure results in appropriate carrier separation. The nonequilibrium Green function method with a tight-binding model is employed for the simulation of the proposed devices, and the results are shown in the paper.