Tri-Gate Graphene Nanoribbon Transistors With Transverse-Field Bandgap Modulation

The CMOS-compatible double-spacer lithography demonstrates a scalable approach to fabricate the tri-gate graphene nanoribbon (GNR) transistor with self-aligned side gates, controllable GNR width, and reduced variations in line-edge roughness and GNR width. The electrical characteristics show bandgap modulation with transverse fields and ambipolar conduction with perpendicular fields. Bandgap modulation parameters are extracted from various GNR devices, but the experimental results show lower critical fields than those in the theoretical calculation. By integrating the bandgap modulation effect into CMOS device designs, the device switching performance can be improved. The subthreshold region and ON-state characteristics are investigated by simulation with the extracted parameters to purge the parasitic effects in the present fabrication process. The extra side-gate dependence achieves drain current enhancement in both saturation and linear regions, and the decreasing bandgap by the increasing transverse field results in the sharp switching of 37 mV/decade close to the threshold voltage. This FET switching improvement can be directly used for low-power operation without sacrificing ON current. In addition, the low-linear-region resistance makes bandgap modulation a promising concept for power gating devices.