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.