A gate and recess fabrication technique for sub-millimeter-wave InP-based high electron mobility transistors (HEMTs) is presented. An ultra-short 30-nm T-shaped-gate is successfully fabricated by optimizing electron beam (EB) lithography and reactive ion etching (RIE) conditions, resulting in an extremely high cutoff frequency (f{sub}t) of 469 GHz in a pseudomorphic HEMT (PHEMT). A 60-nm-gate PHEMT with an asymmetric gate-recess structure that has a longer drain-side recess exhibits a much-improved maximum oscillation frequency (f{sub}(max)) of 503 GHz.
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