Graphene transistors for RF applications: Opportunities and challenges

Summary form only given: Graphene offers new opportunities for the optimization of high frequency FETs by virtue of high carrier velocity, excellent scaling properties, configurability as electron or hole channel devices, and limited scattering. The saturation velocity (v_sat) of graphene has not been determined clearly yet, but it is estimated to be ~5 times greater than that for Si MOSFETs. With large on-state current density and transconductance per gate capacitance compared to Si, graphene has the potential to offer excellent switching characteristics and short-circuit current gain cut-off frequency. With observed constant device transconductance over the gate voltages, graphene FETs could potentially offer low-noise amplifiers (LNAs) with higher dynamic range per given DC power (OIP3/Pdc) beyond the antimony-based low-bandgap devices. With graphene FETs biased near the ambipolar point, graphene FETs behave close to ideal “square-law” devices near the ambipolar point i.e., I(V_g) ∝ V_g², it would greatly suppress odd-order harmonics and/or third-order intermodulation products and improve dynamic range in communications. Graphene-on-Si FETs could potentially be further developed and processed in a manner compatible with Si CMOS with desirable integration density for system-on-chip applications. It also presents unique problems, such as limitations in voltage and poor pinchoff characteristics. The future success of the RF circuit applications depends on high-quality material growth on large-wafer scale, vertical and lateral scaling of graphene MOSFETs to minimize parasitics and improve gate modulation efficiency in the channel, a bandgap engineering of graphene channels in the MOSFETs, and innovative circuit concepts. In this talk, we will present recent progress in epitaxial graphene MOSFETs on both SiC and Si substrates for graphene-on-SiC and graphene-on-Si technologies, in high-speed graphene ba- ed RF transistors, and in circuit concept demonstration including mm-wave radiometers.