30-nm-gate AlGaN/GaN heterostructure field-effect transistors with a current-gain cutoff frequency of 181 GHz

We fabricated Al0.4Ga0.6N(8 nm)/GaN heterostructure field-effect transistors (HFETs) with a gate length (L-G) of 30 nm on a sapphire substrate. The AlGaN/GaN HFETs, which had a 2-nm-thick SiN passivation and gate-insulating layer formed by catalytic chemical vapor deposition, showed a maximum drain current density of 1.49 A/mm, a peak extrinsic transconductance of 402 mS/mm, a current-gain cutoff frequency (f(T)) of 181 GHz, and a maximum oscillation frequency of 186 GHz. From a delay time analysis of f(T) for the HFETs with L-G = 30-150 nm, the electron velocity overshoot was not observed even when L-G was decreased to 30 nm.