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 <i>t</i> <sub>ins</sub> = 4 nm and <i>t</i> <sub>ch</sub> = 10 nm exhibits excellent <i>g</i> <sub>m</sub>, <sub>max</sub> of 1.62 S/mm, <i>f</i> <sub>T</sub> of 628 GHz, and <i>f</i> <sub>max</sub> of 331 GHz at <i>V</i> <sub>DS</sub> = 0.6 V . To the knowledge of the authors, the obtained <i>f</i> <sub>T</sub> is the highest ever reported in any FET on any material system. In addition, a 50-nm device shows the best combination of <i>f</i> <sub>T</sub>= 557 GHz and <i>f</i> <sub>max</sub> = 718 GHz of any transistor technology.

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