GaN-HEMT (high-electron-mobility-transistor) power electronic applications require threshold voltage (V_th) controlling for safe operation. Electrical aspects including OFF-state leakage current, V_th, and forward operating current, all rely greatly on the work function of the gate metal (ϕ_m). In this paper, we examined the influence of ϕ_m variation (the design factor that supports normally off operation) on the electrical properties of recessed T-gated AlN/ GaN HEMT with AlGaN (Fe-doped) buffer. The simulation results show that the highest gate metal (G_M) of 441.78 mS/mm, the peak ID of 1.002 A/mm, and high fT of 336.28 GHz is recorded for Mo-gate HEMT. As the values of ϕ_m are raised, then the V_th of the HEMT progressed in the right direction. This trend of V_th can be ascribed to the uplift of the conduction band (CB) in proportion to the increasing ϕ_m values. The findings imply that gate-engineering can be used to produce depletion-mode (D-mode) and enhancement-mode (E-mode) AlN/ GaN HEMTs at sub-100 nm regimes, enabling fail-safe future generation power electronics.

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