AlGaN/GaN HEMTs versus InAlN/GaN HEMTs fabricated by150-nm Y-gate process

Y-gate process with short gate length (150 nm) and low parasitic gate capacitance (25%-reduction than conventional T-gate process) was successfully developed using an i-line stepper. This simple process is suitable for mass-production of high speed GaN high-electron mobility transistors (HEMTs). With this process technology, we fabricated AlGaN/GaN HEMTs and InAlN/GaN HEMTs, respectively. We confirmed InAlN/GaN HEMTs are superior to AlGaN/GaN HEMTs in terms of DC and RF characteristics. We could obtain high transconductance g
m
of 460 mS/mm and high current gain cutoff frequency f
T
of 70 GHz by combination of InAlN/GaN HEMTs and Y-gate process.