LAUSR

This study investigated the formation of nitrogen-filled voids at the interface between a GaN layer grown on a sapphire substrate by metalorganic vapor phase epitaxy. These voids were formed in the sapphire substrate at the interface after annealing and previous research shows that they can induce an inversion domain in AlN, which affects the film quality and the device performance. We investigated the void formation using scanning electron microscopy, scanning transmission electron microscopy, energy-dispersive X-ray spectrometry, and electron energy loss spectroscopy. The voids are known to originate from the decomposition of sapphire in the presence of ammonia and hydrogen. Our analysis confirmed that the outgassing reaction between the decomposing sapphire and the low temperature GaN buffer layer resulted in the diffusion of aluminum and oxygen into the GaN buffer layer. During the annealing process, oxygen ions replaced nitrogen ions and created nitrogen-filled voids at the interface between the GaN buffer layer and the sapphire substrate. The presence of molecular nitrogen in the voids was confirmed by scanning transmission electron microscopy and electron energy loss spectroscopy.This study investigated the formation of nitrogen-filled voids at the interface between a GaN layer grown on a sapphire substrate by metalorganic vapor phase epitaxy. These voids were formed in the sapphire substrate at the interface after annealing and previous research shows that they can induce an inversion domain in AlN, which affects the film quality and the device performance. We investigated the void formation using scanning electron microscopy, scanning transmission electron microscopy, energy-dispersive X-ray spectrometry, and electron energy loss spectroscopy. The voids are known to originate from the decomposition of sapphire in the presence of ammonia and hydrogen. Our analysis confirmed that the outgassing reaction between the decomposing sapphire and the low temperature GaN buffer layer resulted in the diffusion of aluminum and oxygen into the GaN buffer layer. During the annealing process, oxygen ions replaced nitrogen ions and created nitrogen-filled voids at the interface between the GaN ...