  We demonstrate graphene thickness-graded transistors with high electron
mobility and low 1/f noise (f is a frequency). The device channel is
implemented with few-layer graphene with the thickness varied from a single
layer in the middle to few-layers at the source and drain contacts. It was
found that such devices have electron mobility comparable to the reference
single-layer graphene devices while producing lower noise levels. The metal
doping of graphene and difference in the electron density of states between the
single-layer and few-layer graphene cause the observed noise reduction. The
results shed light on the noise origin in graphene.
