Atomic structure of the surface reconstructions of zincblende GaN(001)

Using scanning tunneling microscopy and reflection high energy electron diffraction, we study the surface reconstructions of zincblende GaN(001) prepared by molecular beam epitaxy on GaAs(001). We observe a (2 x 2) and a (root 10 x root 10)R18.4 degrees reconstruction at a Ga coverage of 0.5 and 0.8 monolayers, respectively. Local density map calculations of the highest occupied and lowest unoccupied molecular orbitals for the experimentally deduced structure models based on Ga dimer formation show excellent agreement with the filled and empty state STM images, respectively. (C) 1997 Elsevier Science B.V.