Low ohmic contact AlN/GaN HEMTs grown by MOCVD

AlN/GaN high-electron-mobility transistors (HEMTs) on SiC substrates were fabricated by metal-organic chemical vapor deposition (MOCVD) and then characterized. An Si/Ti/Al/Ni/Au stack was used to reduce ohmic contact resistance (0.33 Ω·mm) at a low annealing temperature. The fabricated devices exhibited a maximum drain current density of 1.07 A/mm ( V GS = 1 V) and a maximum peak extrinsic transconductance of 340 mS/mm. The off-state breakdown voltage of the device was 64 V with a gate—drain distance of 1.9 μm. The current gain extrinsic cutoff frequency f T and the maximum oscillation frequency f max were 36 and 80 GHz with a 0.25 μm gate length, respectively.