Compact Virtual-Source Current–Voltage Model for Top- and Back-Gated Graphene Field-Effect Transistors

Abstract

This paper presents a compact model for the current-voltage characteristics of graphene field-effect transistors (GFETs), which is based on an extension of the “virtual-source” model previously proposed for Si MOSFETs and is valid for both saturation and nonsaturation regions of device operation. This GFET virtual-source model provides a simple and intuitive understanding of carrier transport in GFETs, allowing extraction of the virtual-source injection velocity <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">VS</sub> , which is a physical parameter with great technological significance for short-channel graphene transistors. The derived <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> characteristics account for the combined effects of the drain-source voltage <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">VDS</i> , the top-gate voltage <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">VTGS</i> , and the back-gate voltage <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">VBGS</i> . With only a small set of fitting parameters, the model shows excellent agreement with experimental data. It is also shown that the extracted virtual-source carrier injection velocity for graphene devices is much higher than in Si MOSFETs and state-of-the-art III-V heterostructure FETs with similar gate length, demonstrating the great potential of GFETs for high-frequency applications. Comparison with experimental data for chemical-vapor-deposited GFETs from our group and epitaxial GFETs in the literature confirms the validity and flexibility of the model for a wide range of existing GFET devices.