Surface electronic structure of GaN(0 0 0 1)-(1×1): comparison between theory and experiment

In a recent Surface Science paper [Surf. Sci. 467 (2000) L827], Ryan et al. have reported results of angle-resolved photoelectron spectroscopy measurements of GaN(0 0 0 1)-(1×1). The authors have clearly identified four discrete surface states. A quantitative analysis of the respective bands and an interpretation of some puzzling features in their dispersion is still lacking. We have recently calculated the surface electronic structure of clean relaxed and of Ga-terminated GaN(0 0 0 1)-(1×1). To resolve the above mentioned issues, we use the results of our calculations for a direct comparison between theory and experiment. A consistent interpretation, as it turns out from this comparison, is possible if we assume a two domain surface structure and a coexistence of clean and of Ga-covered regions at the surface. On the basis of these two assumptions, the experimental dispersions of the measured surface-state bands can be interpreted almost quantitatively.