Complementary-like semiconducting graphene logic inverters

The application of graphene as a post-silicon channel material is an interesting but challenging topic due to its metallic nature and low switching ratio. It is expected that the condition would change if a sizeable band gap is introduced. Here we report the electrical characteristics of the first semiconducting graphene-based logic inverters. Free of doping, the \textit{p}- and \textit{n}- branches in the bipolar graphene transistors are delicately used as the complementary components required in logic devices. Within perpendicular electric fields, large transport band gap ($>100$\,meV) and high switching ratio ($\sim200$ at 77\,K) are obtained in bilayer graphene channels. Besides, a simple and high capacitive-efficiency top gate with natural alumina dielectric ($\sim0.9$\,\textrm{$\mu$}F/cm$^2$) is adopted and the operating bias is lowered within 2\,V. For the first time, $>1$ voltage gain are extracted from graphene inverters. Voltage gain up to 8 and 2 are achieved at liquid-nitrogen and room temperatures, respectively. Importantly, a match between input and output voltage levels is realized, indicating the potential for direct cascading between multiple devices for future large-scale integration.