Stable and High Performance AlGaN Self-Aligned-Gate Field Emitter Arrays

AlGaN alloys are promising for field emission devices due to their low electron affinities. However, there have been limited demonstrations of AlGaN vacuum transistors so far. This letter combines a new self-aligned-gate (SAG) process and digital-etching tip sharpening to demonstrate three-terminal AlGaN SAG field emitter arrays (FEAs). These devices show a turn-on voltage of 19.5 V and an anode current density (J _A ) of 100 mA/cm ² at an overdrive voltage of 20 V, which are comparable with best Si devices. The AlGaN SAGFEAs can operate in DC mode at a fixed gate-emitter voltage ( $\text{V}_{\textit {GE}}$ ) with J _A of 3–5 mA/cm ² for at least 5 hours without a significant degradation. The gate leakage does not increase after the long DC operation, suggesting high-performance and stable AlGaN vacuum transistors.