Crystallization Effects of Nanocrystalline GaN Films on Field Emission

Nanocrystalline GaN films are fabricated on Si substrates by pulsed laser deposition to achieve enhanced field emission (FE) based on microstructural engineering. In the process, the microstructure including crystallization and orientation can be conveniently and directly modulated by the temperature. XRD reveals that the fabrication temperature affects the crystallinity and grain size of the GaN films. A strong correlation between the microstructure and FE properties is also observed. The turn-on electric field decreases from 30.5 to 2.3 V/μm, and the FE current density increases by two to three orders of magnitude based on the microstructure of the GaN films. A qualitative grain boundary conduction model is proposed to explain the strong correlation between the microstructure and FE properties. The results demonstrate the importance of microstructural effects on FE, and they must be considered in the design and production of FE GaN devices.