Importance of gate-recess structure to the cutoff frequency of ultra-high-speed InGaAs/InAlAs HEMTs

Abstract

We have succeeded in developing 30-nm-gate lattice-matched InGaAs/InAlAs HEMTs with an extremely high cutoff frequency ft of 472 GHz, the highest value yet reported for any transistor. The superior high-speed characteristics of our HEMTs were mainly due to a much reduced lateral gate-recess length while maintaining a small gate-to-channel distance, which enhanced an average electron velocity under the gate. We fabricated asymmetically recessed-gate HEMTs to separately investigate the effect of source- and drain-side recess lengths on ft, and clarified that the drain-side recess is more critical to the superior ft, Monte Carlo simulation results were consistent with the experimental observations.