W-band passive load pull system for on-wafer characterization of high power density N-polar GaN devices based on output match and drive power requirements vs. gate width

A W-band on-wafer passive load pull system constructed for the characterization of high power density N-polar GaN devices is presented. N-Polar GaN's large RF voltage swing enables high power densities but also increases the power match impedance which must be synthesized with the limited on-wafer tuning range. Increasing test cell gate width to decrease impedance increases the system's drive power requirement. The tradeoff between these is analyzed, showing that a passive load pull system can characterize a wide range of devices. This is demonstrated with measured data from an N-polar GaN device exhibiting 4.1 W/mm power density at 94 GHz.