Effects of the growth parameters on the surface quality of InN films

On the basis of the improved Stillinger-Weber potential model, the growth process of an indium nitride (InN) film on a gallium nitride (GaN) substrate has been simulated by molecular dynamics. The effects of growth conditions, including the incident energy, polarity of the surface of the GaN substrate, substrate temperature, and deposited N:In atomic ratio, on the surface quality of the InN film have been investigated. We find that atoms with high incident energy have high mobility, which significantly improves the structures of the protrusions and pits on the surface of the film, thereby enhancing the surface quality. However, too high incident energy enhances the sputtering effect of the deposited particles on the surface atoms of the substrate and the destruction of the film, thereby reducing the density. On the basis of the optimal incident energy, the difference in the growth mode of InN films on the Ga-termination polarity surface and N-termination polarity surface is analyzed. At low temperatures, a three-dimensional island growth mode is present on the N-termination polarity surface and a two-dimensional layer growth mode is present on the Ga-termination polarity surface. It is easier to produce InN films with excellent surface quality on the Ga-termination polarity at low temperatures. Furthermore, according to the results obtained under different substrate temperatures and atomic deposition ratios, in an In-enriched environment, excessive In atoms are prone to form agglomerated island structures on the film surface, and the low-temperature substrate is more prone to produce an InN film with high surface quality. In an N-enriched environment, excessive N atoms combine with In atoms on the film surface to form a stepped island structure, and they are more prone to grow into an InN film with high surface quality on a high-temperature substrate.