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.