Atomistic simulation of graphene nanoribbon tunneling transistors

The recently discovered graphene nanoribbon (GNR) is ideal for tunneling FETs due to its symmetric bandstructure, light effective mass, and monolayer-thin body. In this work, we examine the device physics of p-i-n GNR tunneling FETs using atomistic quantum transport simulations. The important role of the edge bond relaxation in the device characteristics is identified. The device, however, has ambipolar I-V characteristics, which are not preferred for digital electronics applications. A properly designed gate underlap can effectively suppress the ambipolar I-V. A subthreshold slope of 14 mV/dec and a significantly improved on-off ratio can be obtained by the p-i-n GNR tunneling FETs. The on-current, which is low due to the tunneling barrier, can be improved by a lattice vacancy in the tunneling junction region due to the induced middle bandgap state.