Voids and vacancy-type defects in SiO₂/GaN structures probed by monoenergetic positron beams Available to Purchase

Voids in SiO₂ films deposited on GaN were probed by using monoenergetic positron beams. The films were fabricated on GaN substrates by using plasma-enhanced chemical vapor deposition. The size and density of the voids in the films increased up to an annealing temperature of 800 °C and then decreased at 1000 °C. The observed annealing behaviors of the voids were attributed to the desorption of impurities incorporated during the deposition process and the shrinkage of the Si–O matrix by high-temperature annealing. Vacancy-type defects were introduced into the GaN substrate after 1000 °C annealing in O₂ atmosphere due to the diffusion of Ga from the substrate to the SiO₂ film. No out-diffusion of Ga into the SiO₂ film was observed for the annealing in N₂ atmosphere. Thus, the observed out-diffusion of Ga was attributed to the enhanced oxidation of GaN during the annealing in O₂ atmosphere. The diffusion of positrons implanted into the GaN substrate toward the SiO₂ film was suppressed by annealing, suggesting a decrease in the negative charges in the SiO₂ film or near the SiO₂/GaN interface.