Evolution of the surface morphology of AlN epitaxial film by HVPE

The evolution of the surface morphologies of AlN films grown by hydride vapor phase epitaxy (HVPE) was studied using atomic force microscopy (AFM). Our results indicate that, after an initial growth time of 10 min, the surface is dominated by hexagonal-prism-shaped islands. Dislocation mediated surface structures of spiral hillocks are observed to cover the surface when the growth time extends to 1 h. Upon further extending the growth time to 3 h, the typical surface morphologies change and the density of dislocation decreases by one order. We also discuss the relationship between the diffusion behaviors of adatoms on the crystal surface with the shape of the terrace edges around dislocations. Explorations into the evolution of the surface morphology of AlN epitaxial films are crucial for understanding the origin and subsequent annihilation of dislocations, as well as to promote improved dislocation reduction techniques for III-nitride materials.