30-nm-Gate InP-Based Lattice-Matched High Electron Mobility Transistors with 350 GHz Cutoff Frequency

The device characteristics and fabrication of 30-nm-gate InAlAs/InGaAs high electron mobility transistors (HEMTs) lattice-matched to InP substrates are reported. The gate length of 30 nm is achieved for a T-shaped gate geometry, which is necessary to minimize gate resistance for short-gate HEMTs, by using fullerene-incorporated nanocomposite resist in the electron beam direct writing of the bottom of the gate. In addition, the two-step-recess gate technology is used to minimize the extension of effective gate length. The devices provide excellent RF characteristics; a record cutoff frequency of 350 GHz is achieved.