title: Observation of "Ghost" islands and surfactant effect of surface gallium atoms during GaN growth by molecular beam epitaxy
abstract: We observe "ghost" islands formed on terraces during homoepitaxial nucleation of GaN. We attribute the ghost islands to intermediate nucleation states, which can be driven into "normal" islands by scanning tunneling microscopy. The formation of ghost islands is related to excess Ga atoms on the surface. The excess Ga also affect island number density: by increasing Ga coverage, the island density first decreases, reaching a minimum at about 1 monolayer (ML) Ga and then increases rapidly for coverages above 1 ML. This nonmonotonic behavior points to a surfactant effect of the Ga atoms.
authors.affiliation: Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong and State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China.
authors.initials: LX
authors.lastname: Zheng
authors.initials: MH
authors.lastname: Xie
authors.initials: SM
authors.lastname: Seutter
authors.initials: SH
authors.lastname: Cheung
authors.initials: SY
authors.lastname: Tong