Influence of the nucleation layer morphology on the structural property of AlN films grown on c-plane sapphire by MOCVD.

The influence of nucleation layer (NL) morphology on the structural property of AlN films grown by metal organic chemical vapor deposition (MOCVD) has been investigated using atomic force microscopy (AFM). It is found that the initial Ⅴ/Ⅲ ratio of the NL effectively controls the polarity, size, density, and coalescence rate of the islands, which is one of the most critical parameters determining the crystalline polarity and surface morphology. Due to difference adatom diffusion on the growth surfaces, it is observed that AlN films grown under high initial Ⅴ/Ⅲ ratios exhibit N polarity with rough surface, while that grown under low initial Ⅴ/Ⅲ ratios show Al polarity with smooth surface. And high quality crack-free AlN film with thickness about 1.4 μm has been obtained by optimizing initial Ⅴ/Ⅲ ratios during the NL deposition stage. [ABSTRACT FROM AUTHOR]