Fully Passivated AlInN/GaN HEMTs With fT/fMAX of 205/220 GHz

We report the fabrication and characterization of 30-nm-gate fully passivated AlInN/GaN high-electron mobility transistors (HEMTs) with cutoff frequencies f(T) and f(MAX) simultaneously exceeding 200 GHz at a given bias point. The current gain cutoff frequency does not vary significantly for 2.5 < V-DS < 10 V, while f(MAX) reaches a maximum value of f(MAX) = 230 GHz at V-DS = 6 V. This is the first realization of fully passivated AlInN/GaN HEMTs with f(T)/f(MAX) >= 205 GHz, a performance enabled by the careful shaping of the gate electrode profile and the use of a thin 60-nm SiN encapsulation film.