High f T and f MAX for 100 nm unpassivated rectangular gate AlGaN/GaN HEMT on high resistive silicon (111) substrate

A high current gain cutoff frequency ( f T ) of 90 GHz and a peak maximum oscillation frequency ( f MAX ) as high as 150 GHz are reported for a rectangular‐shaped gate AlGaN/GaN high‐electron mobility transistor (HEMT) on a high resistive silicon (HR‐Si) substrate. The combined high f T / f MAX values for 100 nm unpassivated gate device demonstrate the high‐quality heterostructure on silicon substrate. The reported high‐performance RF device characteristics are comparable and even superior to the existing passivated AlGaN/GaN HEMTs of similar gate length. In addition, good DC characteristics have been recorded with the drain current density and an extrinsic transconductance of 0.6 A/mm and 157 mS/mm, respectively.