245-GHz InAlN/GaN HEMTs With Oxygen Plasma Treatment

We report lattice-matched In 0.17 Al 0.83 N/GaN high-electron mobility transistors on a SiC substrate with a record current gain cutoff frequency ( fT ). The key to this performance is the use of an oxygen plasma treatment to form a thin oxide layer on the InAlN barrier and to reduce the gate leakage current by more than two orders of magnitude. In addition, the RF transconductance ( g m ) collapse is reduced in the O 2 -treated devices, which results in a significant improvement in the f T . In a transistor with a gate length of 30 nm, an f T of 245 GHz is achieved, the highest value ever reported in GaN-based field-effect transistors.