Effect of flux rate on the growth of AlN films on sapphire by MNVPE

Aluminum nitride (AlN) is an ideal material for the preparation of devices such as deep ultraviolet light-emitting diodes (UV-LEDs) and vacuum detectors because of its wide forbidden bandwidth and excellent physical properties. The quality of AlN films determines the durability and reliability of these devices, and the gas flow rate is an important process parameter that determines the quality of the films. in this paper, metal nitride vapor phase epitaxy (MNVPE) was used to prepare AlN films on sapphire substrates. Firstly, based on the three-dimensional (3D) computational fluid dynamics (CFD) model, the film growth rate and uniformity were investigated at different V/III ratios, and the film quality was best at V/III = 4420. The flow field was analyzed by continuing to adjust the flow rates of Ar and N2 for different gas flow rates at the same V/III ratio, and the results showed that the appearance of vortices had a great influence on the subsequent surface morphology. The crystalline quality, surface morphology, root mean square roughness, and residual stress of the AlN films grown at different gas flow rates were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffractometer (XRD) and Raman spectroscopy. The results showed that the best surface roughness, crystalline quality, and the lowest residual stress were obtained when the Ar flow rate was 0.25 SLM and the N2 flow rate was 2.5 SLM. The best root-mean-square roughness and crystalline quality obtained under (0002) symmetric reflection conditions were 11 nm and 357 arcsec, respectively.