Large peak-to-valley ratio of negative-differential-conductance in graphene p-n junctions

We investigate the transport characteristics of monolayer graphene p-n junctions by means of the nonequilibrium Green’s function technique. It is shown that due to the high interband tunneling of chiral fermions and a finite bandgap opening when the inversion symmetry of the graphene plane is broken, a strong negative-differential-conductance behavior with a peak-to-valley ratio as large as a few tens can be achieved even at room temperature. The dependence of this behavior on the device parameters such as the Fermi energy, the barrier height, and the transition length is then discussed.