All Nitride NbN/AlGaN/GaN Schottky Gate HEMT on (0001) 4H‐SiC: Improved DC Performance and Metallic Passivation

This article reports niobium nitride (NbN) as a Schottky gate for AlGaN/GaN high electron mobility transistors (HEMTs). Compared with conventional Ni/Au metal semiconductor HEMT used as control sample, NbN‐gated HEMT exhibit over three orders of magnitude reduction in gate leakage, improved ON/OFF ratio, lower subthreshold slope, and higher peak transconductance. Unlike insulating dielectric passivants, NbN is metallic in nature and therefore preserves the strong electrostatic coupling of a Schottky contact while simultaneously providing surface passivation. The article demonstrates a form of metallic passivation , wherein NbN suppresses both donor and acceptor type surface states at the GaN cap, thereby weakening Fermi‐level pinning and lowering the effective Schottky barrier. Bias–temperature stress and device‐to‐device variability studies further support this passivation mechanism. These results highlight NbN as a promising metallic nitride gate material for GaN‐based power devices, offering leakage suppression, threshold stability, and robust electrostatics.