245-GHz InAlN/GaN HEMTs With Oxygen Plasma Treatment

We report lattice-matched In0.17Al0.83N/GaN high-electron mobility transistors on a SiC substrate with a record current gain cutoff frequency (f(T)). 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.