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 Al 2 O 3 /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. Al 2 O 3 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 Al 2 O 3 /GaN interface, which can be attributed to the interatomic diffusion between the Al 2 O 3 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.