Evolution of traps in TiN/O3-sourced Al2O3/GaN gate structures with thermal annealing temperature.

The interface between a GaN epitaxial layer and an Al₂O₃ gate dielectric, which was grown by atomic layer deposition using O₃ as the oxygen source on top of a 2-nm H₂O-sourced Al₂O₃ interfacial layer, was engineered by applying a high-temperature postmetal annealing (PMA) process. The O₃-sourced Al₂O₃ gate dielectric featured good thermal stability and breakdown behavior, even at a PMA temperature of 700 °C. Moreover, deep interface/bulk traps in the O₃-sourced Al₂O₃/GaN structures were effectively suppressed, as confirmed by characterization using deep-level transient spectroscopy. However, extended line defects and holelike traps were observed at higher PMA temperatures (750 °C), which were considered to originate from the interface reaction between partially crystallized O₃-sourced Al₂O₃ and the GaN epitaxial layer. [ABSTRACT FROM AUTHOR]