Output power density of 5.1/mm at 18 GHz with an AlGaN/GaN HEMT on Si substrate

Microwave frequency capabilities of AlGaN/GaN high electron mobility transistors (HEMTs) on high resistive silicon (111) substrate for power applications are demonstrated in this letter. A maximum dc current density of 1 A/mm and an extrinsic current gain cutoff frequency (F
_T
) of 50 GHz are achieved for a 0.25 μm gate length device. Pulsed and large signal measurements show the good quality of the epilayer and the device processing. The trapping phenomena are minimized and consequently an output power density of 5.1 W/mm is reached at 18 GHz on a 2×50×0.25 μm
²
HEMT with a power gain of 9.1dB.