Radio frequency performance projection and stability trade-off of h-BN encapsulated graphene field-effect transistors
Hexagonal boron nitride (h-BN) encapsulation significantly improves carrier transport in graphene. This work investigates the benefit of implementing the encapsulation technique in graphene field-effect transistors (GFET) in terms of their radio frequency (RF) performance. For such a purpose, a drift-diffusion self-consistent simulator is prepared to get the GFET electrical characteristics. Both the mobility and saturation velocity information are obtained by means of an ensemble Monte Carlo simulator upon considering the relevant scattering mechanisms that affect carrier transport. RF figures of merit are simulated using an accurate small-signal model that includes non-reciprocal capacitances. Results reveal that the cutoff frequency could scale up to the physical limit given by the inverse of the transit time. Projected maximum oscillation frequencies, in the order of few THz, are expected to exceed the values demonstrated by InP and Si based RF transistors. The existing trade-off between power gain and stability and the role played by the gate resistance are also studied. High power gain and stability are feasible even if the device is operated far away from current saturation. Finally, the benefits of device unilateralization and the exploitation of the negative differential resistance region to get negative-resistance gain are discussed.