Low Power Monolayer MoS2 Transistors for RF Applications

Abstract : High quality MoS2 monolayers have been formed by CVD and DC and RF transistors were fabricated using e-beam lithography and a gate last process. Initial DC characterizations of fabricated MoS2 FETs yielded current densities exceeding Ids = 200 A/ m at Vgs = 5 V and Vds = 3.5 V, and a transconductance gm = 38 S/ m at Vgs = -4.5 V and Vds = 3.5 V. Operating at a low-field Vds of 0.01 V, we extract a contact resistance corrected mobility of 55 cm2/Vs. To our knowledge these are the highest reported transconductance and mobility values for CVD MoS2. Radio frequency FETs were fabricated in the ground-signal-ground (GSG) layout and standard de-embedding structures were applied. Operating at the peak gm conditions, we measured short-circuit current-gain cutoff frequency, fT, of 6.7 GHz and a maximum oscillation frequency, fmax, of 5.3 GHz in 250 nm gate length Lg devices. A new process has been developed for wafer scale MoS2 fabrication using sulfurization of ultra thin deposited Mo films.