Small-signal model extraction of mm-wave N-polar GaN MISHEMT exhibiting record performance: Analysis of gain and validation by 94 GHz loadpull

In this paper we extract a small-signal model of a mm-wave deep-recess N-polar GaN MISHEMT exhibiting record 94 GHz power density. We show that certain existing methods for extrinsic parasitic extraction cannot be easily employed because of the device design but that an existing cold-bias method provides accurate extraction. The small-signal model with pad layout parasitics is then validated with the gain measured at low input powers by a 94 GHz loadpull system. The factors impacting the measured gain are analyzed to show their origins and relative impact, giving guidance and predictions for future improvement.