Theory of surface morphology of wurtzite GaN (0001) surfaces

The influence of growth conditions and surface polarity upon the morphology of (0001) GaN surfaces is studied from first principles. The charge transfer between the Ga and N atoms in GaN and the very large electronegativity of nitrogen are found to play decisive roles in determining the stable reconstructions. Further, hydrogen stabilizes the ideally cleaved surface irrespective of polarity. For both polarities, adsorption of 3/4 of a monolayer of hydrogen results in a very stable surface with a 2x2 symmetry.