Modelling and Performance Comparison of Graphene and Carbon Nanotube Based Fets

The era of nanoelectronics has emerged to overcome the effects of limits of physics due to technology scaling. Hence there is a need to explore the use of advanced nanomaterials namely, graphene and carbon nanotube that can overcome the limitations of short channel effects that arise in conventional silicon based field effect transistors (FET). The high carrier mobility of these materials on a substrate at room temperature and high electron velocity and thermal conductivity, are the motivation to explore the possibility to use FETs based on these materials. The focus in this work is the electronic characterization of such FET models. In this work, SPICE compactible models using closed form equations that are suitable for future circuit level simulations have been developed for single gate graphene FET (GFET), dual gate GFET (DG-GFET) and carbon nanotube field effect transistor (CNT-FET). This paper presents a modified single gate GFET model that is compatible with device length of 100nm and it is found to have better linear and saturation characteristics compared with the existing model. The modified GFET is found to have dirac point stability for lower values of drain to source voltage (Vds<0.4V) which is suitable for voltage scaling. A ballistic, non-linear piece-wise approximation approach in CNT-FET has been applied to achieve the saturation of drain current rather than using the computationally complex self-consistent field approach. This work also presents a detailed study of variation in transconductance and transit frequency for the modified GFET model and it is established to have a higher transit frequency at 100nm than the existing model. The simulation of models and comparison of various parameters are done using MATLAB.