Inductive Source Degeneration in 40-nm GaN HEMTs for Operation Above 100 GHz

Source degeneration and neutralization techniques are investigated at millimeter-wave (mm-Wave) in gallium nitride (GaN) high-electron-mobility transistors (HEMTs). The role of thru-substrate vias for inductive source degeneration (ISD) is analyzed and modeled. A series of 40-nm GaN HEMTs with ISD are measured under small-signal, pulsed I–V and 94-GHz load pull. The ISD HEMTs demonstrate a 3-dB improvement in available gain at 83 GHz but also an unanticipated up to 75% increase in power density at 94 GHz with respect to the baseline devices. We discuss possible reasons for the performance enhancement. Device characterization to 200 GHz is presented.