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 withtᵢₙₛ = 4\ nmandtch = 10\ nmexhibits excellentgm, maxof 1.62 S/mm,fTof 628 GHz, andfₘₐₓof 331 GHz atVDS = 0.6\ V. To the knowledge of the authors, the obtainedfTis the highest ever reported in any FET on any material system. In addition, a 50-nm device shows the best combination offT = 557\ GHzandfₘₐₓ = 718\ GHzof any transistor technology.