Performance improvement with non-alloyed ohmic contacts technology on AlGaN/GaN High Electron Mobility Transistors on 6H-SiC substrate

In this paper, non-alloyed ohmic contacts regrown by molecular beam epitaxy (MBE) are fabricated on AlGaN/ GaN high-electron-mobility transistors on 6H-SiC substrate. Low ohmic contact resistance of 0.13 omega.mm is ob-tained. This paper demonstrates the high frequency and high power performance improvements thanks to this technology regarding conventional technology based on alloyed ohmic contacts. The fabricated device with a 75-nm-T-shaped gate demonstrates a maximum drain current density of 1.1 A/mm at VGS = 1 V and a peak transconductance gm of 464 mS/mm. A current gain cut-off frequency fT of 110 GHz and a maximum oscillation frequency fMAX of 150 GHz are achieved. At VDS = 25 V, continuous-wave output power density of 3.8 W/mm is achieved at 40 GHz associated with 42.8% power-added efficiency and a linear power gain of 6 dB. A maximum power-added efficiency of 55% is also obtained at VDS = 20 V.