Relationship between Annealing and V/III Ratios during MNVPE of AlN Films

High-quality aluminum nitride (AlN) films are considered to be the key to the preparation of excellent UV optoelectronic devices. In this paper, metal nitride vapor phase epitaxy (MNVPE) and face-to-face annealing were combined to study the changes in crystal quality, internal stress, and optical properties of AlN films with different V/III ratios after high-temperature annealing with theoretical explanations. X-ray diffraction was used to characterize the film quality. The best quality of AlN films was found at V/III = 4420. After annealing at 1675 °C for 1 h, the quality of AlN films was significantly improved, with the AlN film at V/III = 4420 still having the best quality after annealing, and the full width at half-maximum of the (002) rocking curve was 521 arcsec. Combined with scanning electron microscopy tests, high-temperature annealing led to grain growth in the AlN films, promoting the reduction of grain boundaries. According to the Raman spectroscopy test results, the internal stresses of the annealed AlN films were released. The UV–visible spectroscopy results showed that annealing improved the transmittance and band gap of the films, thus optimizing the optical properties of the AlN films. This work enriches the mechanism of annealing to improve film quality and explores the relationship between the V/III ratio parameter of MNVPE and high-temperature annealing, which is of great significance for preparing high-quality AlN films.