Research and Development of GaN-based HEMTs for Millimeter- and Terahertz-Wave Wireless Communications

GaN-based transistors and amplifiers are the most promising electron devices not only for high-power and high-voltage applications but also for millimeter-and terahertz-wave wireless communications in 5th generation (5G) and next-generation mobile communications systems. In this paper, we fabricated nanoscale-gate GaN-based high electron mobility transistors (HEMTs) on sapphire, SiC and GaN substrates, and investigated the effect on InAlN barrier thickness on DC and RF performances to improve the current-gain cutoff frequency (fT) and maximum oscillation frequency (fmax). As a result, we successfully obtained an fmax of 287 GHz and an fT of 228 GHz at a thinner 3-nm-thick In0.18Al0.82N barrier for a 45-nm-gate In0.18Al0.82N/AlN/GaN MES-HEMT on GaN substrates.