547-GHz ft In0.7Ga0.3As-In0.52Al0.48AsHEMTs with reduced source and drain resistance

We fabricated 30-nm gate pseudomorphic channel In0.7Ga0.3As-In0.52Al0.48As high electron mobility transistors (HEMTs) with reduced source and drain parasitic resistances. A multilayer cap structure consisting of Si highly doped n(+)-InGaAs and n(+)-InP layers was used to reduce these resistances while enabling reproducible 30-nm gate process. The HEMTs also had a laterally scaled gate-recess that effectively enhanced electron velocity, and an adequately long gate-channel distance of 12 nm to suppress gate leakage current. The transconductance (g(m)) reached 1.5 S/mm, and the off-state breakdown voltage (BVgd) defined at a gate current of -1 mA/mm was -3.0 V. An extremely high current gain cutoff frequency (f(t)) of 547 GHz and a simultaneous maximum oscillation frequency (f(max)) of 400 GHz were achieved: the best performance yet reported for any transistor.