InAlN/AlN/GaN HEMTs With Regrown Ohmic Contacts and fT of 370 GHz

We report 30-nm-gate-length InAlN/AlN/GaN/SiC high-electron-mobility transistors (HEMTs) with a record current gain cutoff frequency(fT)of 370 GHz. The HEMT without back barrier exhibits an extrinsic transconductance(gm.ext)of 650 mS/mm and an on/off current ratio of10⁶owing to the incorporation of dielectric-free passivation and regrown ohmic contacts with a contact resistance of 0.16Ω. Delay analysis suggests that the highfTis a result of low gate–drain parasitics associated with the rectangular gate. Although it appears possible to reach 500-GHzfTby further reducing the gate length, it is imperative to investigate alternative structures that offer higher mobility/velocity while keeping the best possible electrostatic control in ultrascaled geometry.