GaN-on-Si HEMTs for Low-Voltage FR2 Applications Enabled by Reactive-Sputtered n ++ -GaN Ohmic Contacts

This letter reports GaN-on-Si high-electron-mobility-transistors (HEMTs) employing reactive-sputtered Ge-doped n++-GaN ohmic contacts for low-voltage FR2 applications. A low sputtered n++-GaN/2DEG interfacial resistance of 0.06 Ω·mm is achieved for the InAlN/GaN heterostructure. The transistor achieves a low on-resistance of 0.91 Ω·mm and a maximum drain current of 2.03 A/mm, resulting in excellent output power of 0.51, 1.25, and 2.44 W/mm atVDS= 3, 5, and 8 V at 28 GHz, respectively. These results demonstrate the strong potential of RF GaN HEMTs employing sputtered n⁺⁺-GaN ohmic contacts.