  The quality of graphene in nanodevices has increased hugely thanks to the use
of hexagonal boron nitride as a supporting layer. This paper studies to which
extent hBN together with channel length scaling can be exploited in graphene
field effect transistors (GFETs) to get a competitive radio frequency (RF)
performance. Carrier mobility and saturation velocity were obtained from an
ensemble Monte Carlo simulator that accounted for the relevant scattering
mechanisms (intrinsic phonons, scattering with impurities and defects, etc.).
This information is fed into a self consistent simulator, which solves the
drift diffusion equation coupled with the two dimensional Poisson's equation to
take full account of short channel effects. Simulated GFET characteristics were
benchmarked against experimental data from our fabricated devices. Our
simulations show that scalability is supposed to bring to RF performance an
improvement that is, however, highly limited by instability. Despite the
possibility of a lower performance, a careful choice of the bias point can
avoid instability. Nevertheless, maximum oscillation frequencies are still
achievable in the THz region for channel lengths of a few hundreds of
nanometers.
