Masahiro Totsuka

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.

A high reliability GaN HEMT with SiN passivation by Cat-CVD

This is the first report of catalytic vapor deposition (Cat-CVD) passivated AlGaN/GaN HEMT. We have found out that the Cat-CVD passivation film with NH3 treatment greatly enhances the reliability of the AlGaN/GaN HEMT. It is rationalized, through the low frequency capacitance-voltage measurement, that the NH3 treatment in the Cat-CVD reactor before the SiN film deposition minimizes the damage at the SiN/AlGaN interface, leading to reducing the surface trap density. The AlGaN/GaN HEMT passivated by the Cat-CVD SiN film suppresses the degradation of an output power to less than 0.4 dB under the RF operation of Vd = 30 V, f = 5 GHz after 200 h.