Sharp Switching by Field-Effect Bandgap Modulation in All-Graphene Side-Gate Transistors

Graphene is a 2-D electronic material that has drawn intensive interest due to its high carrier mobility, film flexibility, and tunable bandgap. The unique bandgap modulation by the transverse electrical field in the graphene nanoribbon (GNR) offers new opportunity to pursue switches with steep subthreshold not limited by thermal voltage. In this paper, we demonstrate a graphene routing process (GRP), which can implement the side-gate GNR transistor with field-effect bandgap modulation (FEBM). The GRP precisely aligns the side gates to the transistor channel, and provides scalable W/L without registry concerns. Besides, by controlling the pattern sizing, the metallic source/drain, side gates, and semiconducting channel are all defined on the large-area graphene thin-film by one-critical lithography step. The GRP process thus can be adapted to the backend process with thin-film transfer even on flexible substrates. The double side-gate GNR transistors exhibit FEBM and a negative temperature coefficient for the ON-state conductance which can stabilize thermal runaway. In addition, the single-layer routing for simple circuit topology can improve package density and reduce number of contact vias. Combining FEBM with the electrostatic control can bring forth higher ON current and sub-60 mV/decade switching. These device characteristics offer a potential power-gating technology in low-power applications.