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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.