75-nm-T-shaped-gate InAlN/AlN/GaN HEMT on sapphire with 100 GHz cutoff frequency

This paper reports on DC and RF performances of an In_0.15Al_0.85N/AlN/GaN high electron mobility transistor (HEMT) on sapphire substrate with a 75-nm-T-shaped-gate. A maximum DC current density of 1.27 A/mm and a peak extrinsic and intrinsic transconductances of 452 mS/mm and 680 mS/mm respectively are obtained. The device exhibits a current gain cutoff frequency (F_T) and a power gain cutoff frequency (F_MAX) of 100 and 140 GHz respectively. To the author knowledge, these cut-off frequencies are the highest reported values for InAlN/AlN/GaN HEMTs grown on sapphire substrate. Microwave power measurement at 18 GHz on a 2×50×0.225 μm² HEMT were also carried out. They revealed a maximum output power density (P_OUT) of 2.9 W/mm with an associated power-added efficiency (PAE) of 28%, showing the capabilities of these devices for microwave power applications at high frequency.