Development of Ka-Band GaAs pHEMTs with Output Power over 1 W/mm

We present GaAs pHEMTs demonstrating output power over 1 W/mm in Ka-band at an operating voltage of 8 V. DC, RF and reliability results are reported. Continuous wave load pull tests at 35 GHz show peak power added efficiency of 52% and associated gain of 8 dB. The saturated output power of 1.2 W/mm is achieved. Power performance improvement is attributed to a new dielectrically defined 0.15 μm gate process which allows successful operation of these devices at a drain voltage of 8 V. Devices also show excellent small signal performance with maximum cut-off frequency as high as 107 GHz at a drain voltage of 1 V. Using three-temperature accelerated DC life tests, activation energy of 1.45 eV and median life time over 1 million hours at a channel temperature of 150°C are estimated.