Surface energetics, pit formation, and chemical ordering in InGaN alloys

We present first-principle calculations of the structure and energetics of the $\mathrm{GaN}\text{(101\_1)}$ surface, and present models for the reconstructions. A strong preference for In surface segregation and occupation of specific surface sites is demonstrated. We argue that inverted pyramid defect formation is enhanced by segregation of In on $\text{(101\_1)}$ facets. We propose that the chemical ordering recently observed in InGaN alloys is driven by the preference for In incorporation at the sites of reduced N coordination present at step edges during growth on the (0001) and $\text{(0001\_)}$ surfaces.