A high power density TaN/Au T-gate pHEMT with high humidity resistance for Ka-Band applications

A 0.8 W/mm high power pHEMT with high humidity resistance is reported. By using tantalum nitride as the refractory gate metal and a silicon nitride layer prepared by a catalytic chemical vapor deposition technique for passivation of this transistor, tough moisture resistance was obtained showing no Id degradation even after 500 hours at 130 degrees centigrade and 85% humidity. Moreover, the Schottky breakdown voltage of the TaN gate is higher than that of a WSiN gate. A one-stage prematched amplifier with the new pHEMT has achieved 0.83 W/mm output power at Vds = 8 V, with 8.5 dB gain and 40% power added efficiency in the Ka-band. These are some of the highest power figures ever reported.