Vacancy-type defects in GaN-based power device structure - defect characterization in ion implanted GaN and Al2O3/GaN -

Abstract

Vacancy-type defects in Mg-implanted GaN and an Al2O3/GaN structure were probed using monoenergetic positron beams. In Mg-implanted GaN, the major defect species was a complex of a Ga-vacancy and a nitrogen vacancy. After annealing above 1000°C, the major defect species was changed to vacancy clusters due to the agglomeration of vacancies. The carrier trapping/detrapping properties of the vacancy-type defects and their time dependences were also revealed. Al2O3 films with a thickness of 25 nm were deposited on GaN by atomic layer deposition. For the samples annealed at 800°C and 900°C, the vacancy-type defects were found to be introduced up to a depth of 40–50 nm from the Al2O3/GaN interface, which can be attributed to the interatomic diffusion between the Al2O3 film and the GaN substrate. The present research showed that positron annihilation technique can be applied for the study of annealing behaviors of vacancies in the GaN-based device structure. A knowledge obtained by this technique is useful for an optimization of the fabrication process of GaN power devices.