Oxygen-rich GaN(1010) surfaces: first-principles total energy calculations
First-principles total energy calculations are employed to identify stable oxygen induced reconstructions of the GaN(10-10) surface. The calculations show that the surface energy is lowered by O segregation to N-sites at the surface. Under O-rich conditions, it is favorable for O to replace the N in the top two layers. In the resulting structure the surface Ga atoms act as acceptors, i.e. the Ga dangling-bond orbitals are occupied by two electrons. This is a new stabilization mechanism for GaN surfaces. The possibility that this reconstruction plays a role in the formation of nanopipes in O-rich GaN is discussed. The work was performed under an ONR contract to study nitride surfaces.
Northrup, J. E. Oxygen-rich GaN(1010) surfaces: first-principles total energy calculations. Physical Review B. 2006 March 15; 73 (11): 115304.