The two dimensional nature and chirality of the graphene charge carriers
have brought exciting opportunities for a new kind of electronics.
We are now able to realize devices exploiting the Dirac nature of graphene
electrons. They rely on i) the stacking of graphene on hexagonal boron
nitride (hBN) for the access to the ballistic regime and ii) a full
control of the doping profile using local back gate arrays. When graphene
goes ballistic electrons behave like light rays, where the optical index
is given by the doping and p-n junctions play the role of diopters.
Geometrical optic conditions can be satisfied at room temperature provided
that junctions are sharp at the scale of the Fermi wave length. I will
present the realization and characterization of such devices and
illustrate their potential for GHz electronics with two examples : the
gated-contact transistor and the Dirac fermion pinch-off transistor. The
first relies on the Klein tunneling at the contact junction ; the second on
the inhomogeneous doping profile in local gated graphene combined with the
velocity saturation by remote hBN surface phonons.