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 Ω.mm is obtained. 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.