GaAs<i>c</i>(4×4) surface structure in organometallic vapor-phase epitaxy

Abstract

While GaAs(001) surface reconstructions have been studied extensively in the ultrahigh-vacuum environment associated with molecular-beam epitaxy (MBE), comparatively little is known of these structures in the chemically rich environment associated with organometallic vapor-phase epitaxy (OMVPE). This work presents a structural study of the c(4\ifmmode\times\else\texttimes\fi{}4) surface reconstruction stabilized in an arsenic-rich OMVPE environment. Measurements of the in-plane structure were performed in situ using grazing-incidence x-ray scattering with synchrotron radiation. Structural refinement confirms the presence of arsenic-arsenic dimers arranged with the c(4\ifmmode\times\else\texttimes\fi{}4) symmetry. In concurrence with similar studies performed in the MBE environment, it is found that the surface is a mixture of structural domains composed of two- and three-dimer variants of the c(4\ifmmode\times\else\texttimes\fi{}4) reconstruction. Atomic positions associated with these structures are presented. The size, aspect ratio, and orientation of the reconstructed regions are shown to be closely related to the atomic step geometry on the crystal surface.