Transferred-substrate HBTs with 254 GHz <i>f</i> _τ

Abstract

The authors report the simultaneous achievement of record current gain cutoff frequency f/sub /spl tau// and high power gain cutoff frequency f/sub max/ in a transferred-substrate HBT. The device parasitics are examined, and inferences made about the relative value of various approaches toward further improvements in f/sub /spl tau// and f/sub max/. Transferred-substrate HBTs with record f/sub /spl tau// of 254 GHz are reported.