High fT and fMAX 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.