Unpassivated AlGaN-GaN HEMTs with minimal RF dispersion grown by plasma-assisted MBE on semi-insulating 6H-SiC substrates

High Electron Mobility Transistors are fabricated from AlGaN/GaN heterostructures grown by plasma-assisted MBE on semi-insulating 6H-SiC substrates. Low-field electron mobilities of more than 1,300 cm sup 2/Vs at a sheet charge density of 1.2 x 10 sup 15 cm sup -2 have been obtained repeatedly. HEMT devices with a gate length of 2 mum, a gate width of 200 mum, and a source-drain spacing of 6 mum show a maximum drain current of 1.2 A/mm, and a peak transconductance of 130 mS/mm. We measured a saturated power output of 6.2 W/mm cw at 2 GHz using an on-wafer load-pull setup, with a power-added efficiency of 24% in class A operation. This is the first report of high-power AlGaN/GaN HEMTs grown by plasma-assisted MBE on semi-insulating 6H-SiC substrates.