2D material of graphene has inspired huge interest in fabricating of solid state gas sensors. In this work, epitaxial graphene, quasi-free-standing graphene, and CVD epitaxial graphene samples on SiC substrates are used to fabricate gas sensors. Defects are introduced into graphene using SF₆ plasma treatment to improve the performance of the gas sensors. The epitaxial graphene shows high sensitivity to NO₂ with response of 105.1% to 4 ppm NO₂ and detection limit of 1 ppb. The higher sensitivity of epitaxial graphene compared to quasi-free-standing graphene, and CVD epitaxial graphene was found to be related to the different doping types of the samples.