InGaN Channel High-Electron-Mobility Transistors with InAlGaN Barrier andfT/fmaxof 260/220 GHz

Depletion-mode high-electron-mobility transistors (HEMTs) with an 11 nm quaternary In 0.13 Al 0.83 Ga 0.04 N barrier and a 5 nm In 0.05 Ga 0.95 N channel on SiC substrates have been fabricated. The as-processed HEMT structure features a channel electron density of 2.08 × 10 13 cm -2 and a mobility of 1140 cm 2 V -1 s -1 . A device with a 50-nm-long T-shaped gate shows a maximum output current density of 2.0 A/mm, a peak extrinsic DC transconductance of 690 mS/mm, and cut-off frequencies f T / f max of 260/220 GHz at the same bias, representing a record high √ f T · f max of 239 GHz for InGaN channel HEMTs.