An Al0.3Ga0.7N/GaN undoped channel heterostructure field effect transistorwith F-max of 107 GHz

An Al0.3Ga0.7N/GaN heterostructure field effect transistor (HFET) grown on semi-insulating SiC with an 0.2-mu m gate length is reported. A source-drai n ohmic contact resistance of 0.15-Ohm-mm was achieved through the use of h igh Al content and high n-type doping (1E19 cm(-3)) in the AlGaN donor laye r and optimized metallization procedures. We obtained a maximum transconduc tance of 260 mS/mm, a saturated current density of 1.2 A/mm, and a maximum oscillation frequency in excess of 107 GHz in the devices, The results are one of the best achieved up to now, and they will open up the potential for the applications of AlGaN/GaN HFET's in high-power microwave radar, remote sensing, and communications.