W-Band Power Performance of SiN-Passivated N-Polar GaN Deep Recess HEMTs

This letter reports on the improvement of the large-signal W-band power performance of nitrogen-polar gallium nitride deep recess high electron mobility transistors with the addition of a 40-nm-thick ex-situ silicon nitride passivation layer deposited by plasma enhanced chemical vapor deposition. The additional passivation improves the dispersion control allowing the device to be operated at higher voltages. Continuous-wave load pull measurements performed at 94 GHz on a
$2\times 37.5\,\,\mu \text{m}$
transistor demonstrated an improvement in the peak power-added efficiency (PAE) to 30.2% with an associated output power density of 7.2 W/mm at 20 V drain bias. Furthermore, at 23 V, a new record-high W-band power density of 8.84 W/mm (663 mW) was achieved with an associated PAE of 27.0%.