Advanced Gate Technologies for State-of-the-art f[subscript T] in AlGaN/GaN HEMTs

Abstract

In this paper, the lower-than-expected frequency performance observed in many AlGaN/GaN high electron mobility transistors (HEMTs) has been attributed to a significant drop of the intrinsic small-signal transconductance (g[subscript m]) with respect to the intrinsic DC g[subscript m]. To reduce this gm-collapse and improve high frequency performance, we have developed a new technology based on a combination of vertical gate-recess, oxygen plasma treatment, and lateral gate-etch which has allowed us to fabricate AlGaN/GaN HEMTs with a record current-gain cutoff frequency (f[subscript T]) of 225 GHz for a gate length (L[subscript g]) of 55 nm, and 162 GHz for an L[subscript g] of 110 nm.