Demonstration of 420GHz highly scaled InAlN/GaN HEMTs by Electron Beam Lithography

GaN-based high electron mobility transistors (HEMTs) are promising candidates for millimeter wave amplifiers above 100 GHz for 6G communications. To satisfy those requirements, a maximum oscillation frequency
$(\mathbf{f}_{\max})$
surpassing 400 GHz is essential, necessitating the deployment of advanced down-scaling and patterning technologies. Through the utilization of electron beam lithography, ultra-scaled InAlN/GaN HEMTs on sapphire with T-gates with gate length of~60 nm and source-drain distance of~300 nm were fabricated, reaching
$\mathrm{f}_{\max}$
over 420 GHz with a corresponding f
T
exceeding 150 GHz. To the best of the author's knowledge, these scaled HEMTs exhibit the highest fmax among reported HEMTs on sapphire.