Self-Align-Gated GaN Field Emitter Arrays Sharpened by a Digital Etching Process

Field emitters are attracting much attention recently because of their potential for high-frequency and harsh-environment applications. Although silicon is the most studied semiconductor for field emitters, III-Nitrides are also very promising thanks to their tunable electron affinities. Two main challenges exist for low turn-on-voltage III-Nitrides field emitters: lack of a self-aligned gate and tip-sharpening technologies. In this work, we demonstrate self-aligned-gated GaN field emitter arrays whose tips are sharpened by a wet-based digital etching technology. This technology allows to reduce the tip size from 40 nm down to 20 nm. Gated GaN field emitters with a turn-on voltage ( $\text{V}_{GE,ON}$ ) of 20 V and current density of 150 mA/cm2 at $\text{V}_{GE} =50$ V have been demonstrated.