Molecular dynamics investigation of heteroepitaxial growth of quaternary AlInGaN on wurtzite-GaN surface along [0001] direction

We conducted molecular dynamics simulations of heteroepitaxial vapor deposition of the AlInGaN film on the polar [0001] GaN surface to investigate the influence of the substrate temperature and Al/In ratio on the epitaxial film. Time- and position-dependent boundary constraints were implemented to ensure appropriate growth conditions in the vapor phase region, the near-surface solid, and the bulklike solid region of the growing film. The simulation utilized an optimized Stillinger–Weber potential to describe the interactions among Al–In–Ga–N atoms. For the compositional study, the ratios of Al/In used are 1/9, 3/7, 1/1, 7/3, and 9/1. To investigate the temperature effect on the substrate, four different growth temperatures above half of the simulated melting temperature of the GaN substrate were employed. Following the growth of the AlInGaN film, surface roughness, domain structure, crystallinity, and dislocations were analyzed. Our findings indicate that surface roughness and crystallinity increase with higher Al/In ratios as well as elevated substrate temperatures. The domain size was also observed to increase with higher Al/In ratios and temperatures. At lower temperatures and low Al/In ratios, islands of different polytypes emerge with a high height-to-width ratio, resulting in a highly polytypic structure. The annealing process following growth significantly improves crystallinity and reduces surface roughness. From the dislocation study, it was observed that the maximum number of dislocation lines is of type 1/3[11¯00], which relieve the lattice mismatch strain along the x- and y-directions, and dislocations are minimized at 2500 K. The observed trends in the effects of temperature and the Al-to-In content ratio on dislocations, voids, surface roughness, and domain boundary structures closely resemble known experimental observations in AlInGaN/GaN.