InAlN/AlN/GaN HEMTs With Regrown Ohmic Contacts and 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 (g_m.ext) of 650 mS/mm and an on/off current ratio of 10⁶ owing to the incorporation of dielectric-free passivation and regrown ohmic contacts with a contact resistance of 0.16 Ω·mm. Delay analysis suggests that the high fT is a result of low gate-drain parasitics associated with the rectangular gate. Although it appears possible to reach 500-GHz fT by 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.