Gate-Recessed InAlN/GaN HEMTs on SiC Substrate With $\hbox {Al}_{2}\hbox {O}_{3}$ Passivation

We studied submicrometer (L_G = 0.15-0.25 ??m) gate-recessed InAlN/AlN/GaN high-electron mobility transistors (HEMTs) on SiC substrates with 25-nm Al₂O₃ passivation. The combination of a low-damage gate-recess technology and the low sheet resistance of the InAlN/AlN/GaN structure resulted in HEMTs with a maximum dc output current density of I_DS,max = 1.5 A/mm and a record peak extrinsic transconductance of g_m,ext = 675 mS/mm. The thin Al₂O₃ passivation improved the sheet resistance and the transconductance of these devices by 15% and 25%, respectively, at the same time that it effectively suppressed current collapse.