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 frequenciesfTandfMAXsimultaneously exceeding 200 GHz at a given bias point. The current gain cutoff frequency does not vary significantly for 2.5VDSfMAXreaches a maximum value offMAX= 230 GHz atVDS= 6 V. This is the first realization of fully passivated AlInN/GaN HEMTs withfT/fMAX≥ 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.