HEMTs with ultrahigh cutoff frequency

We succeeded in fabricating ultra-short 30-nm-gate InP-based high electron mobility transistors (HEMTs) with an extremely high current gain cutoff frequency (f_T) of 547 GHz. The superior high-speed performance of our InP-HEMTs was mainly due to their optimized gate-recess structures. We investigated the effect of lateral gate-recess length on f_T with the asymmetric gate-recess technique, and clarified the impact of source- and drain-side recess lengths on their high-speed performance from the viewpoint of electron velocity and source resistance. We also demonstrated the importance of parasitic resistances, which were no longer negligible in these ultra-high-speed InP-HEMTs.