Radio Frequency Performance Projection and Stability Tradeoff of h-BN Encapsulated Graphene Field-Effect Transistors

Abstract

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 intrinsic radio frequency (RF) performance, adding the effect of the series resistances at the terminals. For such a purpose, a drift-diffusion self-consistent simulator is prepared to get the GFET electrical characteristics. Both the mobility and saturation velocity are obtained by 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. 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. Index Termsh-BN encapsulated graphene, graphene field-effect transistors, negative differential resistance, radio frequency, stability ACKNOWLEDGMENT Authors would like to thank Prof. Francisco García Ruiz for the helpful discussions.

Contact resistance extraction of graphene FET technologies based on individual device characterization

“…where V GS/DS is the extrinsic gate-to-source/drain-to-source voltage, V Dirac = V GS | min(I Dirac ) ∼ V GS0 + V DS /2 is the Dirac voltage with V GS0 as the flat-band voltage [26], β = µ 0 C ox w g /L g with a low-field mobility µ 0 , the oxide capacitance C ox , the gate width w g and length L g , and θ is the extrinsic mobility attenuation factor θ = θ 0 + R C β [30], [34] with the instrinsic attenuation factor due to vertical fields θ 0 . By considering Eq.…”

“…Scattering-affected DC transfer characteristics of top-gate GFETs with identical device architecture but with different gate lengths have been generated with numerical device simulations consisting on a self-consistent solution of the Poisson's equation and the current-continuity equation [26]. This set of different L g devices enables to imitate a TLM structure.…”

Multi-scale analysis of radio-frequency performance of 2D-material based field-effect transistors

“…In particular, three remarkable effects are considered: interface traps, electric field dependent mobility and access and contact resistances. The impact of the gate electric field on the mobility might be also of relevance as it has been studied in [19] and [20] but requires a detailed analysis of the scattering processes in MoS 2 . For the former, an arbitrary energetic profile for either donors or acceptors traps can be defined to evaluate the surface charge density associated with a certain interface as a function of the electrostatic potential and Fermi level (see S4 at SI).…”

Does carrier velocity saturation help to enhance fmax in graphene field-effect transistors?

“…A full description of the small-signal parameter calculation can be found in section S5 of the supplementary information. Finally, the RF figures of merit f T,x and f max are extracted from the current gain and unilateral power gain that result from the Y matrix [35].…”