▎ 摘　　要

Graphene's unique symmetry between p- and n-branches has enabled several interesting device applications; however, short-channel devices often exhibit degraded symmetry. We examine how graphene nanoribbon geometries can improve transfer characteristics and p-n symmetry, as well as reduce Dirac point shift for highly scaled graphene devices. RF graphene transistors utilizing a multiribbon channel are fabricated with channel length down to 100 nm, achieving 4.5-fold improved transconductance, 3-fold improved cutoff frequency, and 2.4-fold improved symmetry compared with sheet devices. The improved performance is linked to reduced contact effects by modeling the extent of charge transfer into the channel as a function of graphene width. (C) 2014 The Japan Society of Applied Physics