Short channel AlGaN/GaN MODFET's with 50-GHz fT and 1.7-W/mm output-power at 10 GHz

A thin barrier-donor layer of 200 /spl Aring/ was used to increase the active input capacitance and improve the extrinsic current-gain cutoff frequency (f
_T
) of short-gate-length AlGaN/GaN MODFETs. 0.2-μm gate-length devices fabricated on such an epi-structure with sheet carrier density of /spl sim/8×10/sup 12/ cm/sup -2/ and mobility of 1200 cm
²
/Vs showed a record f
_T
of 50 GHz for GaN based FETs. High channel saturation current and transconductance of 800 mA/mm and 240 mS/mm respectively were also achieved along with breakdown voltages of 80 V per μm gate-drain spacing. These excellent characteristics translated into a CW output power density of 1.7 W/mm at 10 GHz, exceeding previous record for a solid-state HEMT.