Ballistic I-V Characteristics of Short-Channel Graphene Field-Effect Transistors: Analysis and Optimization for Analog and RF Applications

With the recent upsurge in experimental efforts toward fabrication of short-channel graphene field-effect transistors (GFETs) for analog and high-frequency RF applications-where the advantages of distinctive intrinsic properties of gapless graphene are expected to be leveraged-a critical understanding of the factors affecting both output and transfer characteristics is necessary for device optimization. Analyzing the device characteristics through ballistic electronic transport simulations within the nonequilibrium Green's function formalism, we show that a doping in the drain underlap region can significantly improve the quasi-saturation behavior in the GFET output characteristics and, hence, the output resistance and intrinsic gain. From this understanding, we provide a unified and coherent explanation for seemingly disparate phenomena-quasi-saturation and the recently reported three-terminal negative differential resistance in GFETs. We also investigate the scaling behavior of cutoff frequency and comment on some of the observed scaling trends in recent experiments.