30-nm InAs pseudomorphic HEMTs on an InP substrate with a current-gain cutoff frequency of 628 GHz

We report on InAs pseudomorphic high-electron mobility transistors (PHEMTs) on an InP substrate with record cutoff frequency characteristics. This result was achieved by paying attention to minimizing resistive and capacitive parasitics and improving short-channel effects, which play a key role in high-frequency response. Toward this, the device design features a very thin channel and is fabricated through a three-step recess process that yields a scaled-down barrier thickness. A 30-nm InAs PHEMT with T-ins = 4 nm and t(ch) = 10 nm exhibits excellent g(m,max) of 1.62 S/mm, f(T) of 628 GHz, and f(max) of 331 GHz; at V-DS = 0.6 V. To the knowledge of the authors, the obtained f(T) is the highest ever reported in any FET on any material system. In addition, a 50-nm device shows the best combination of f(T) = 557 GHz and f(max) = 718 GHz of any transistor technology.