GAAS C(4X4) SURFACE-STRUCTURE IN ORGANOMETALLIC VAPOR-PHASE EPITAXY

While GaAs(001) surface reconstructions have been studied extensively in the ultrahigh-vacuum environment associated with molecular-beam epi taxy (MBE), comparatively little is known of these structures in the c hemically rich environment associated with organometallic vapor-phase epitaxy (OMVPE). This work presents a structural study of the c (4 X 4 ) surface reconstruction stabilized in an arsenic-rich OMVPE environme nt. Measurements of the in-plane structure were performed in situ usin g grazing-incidence x-ray scattering with synchrotron radiation. Struc tural refinement confirms the presence of arsenic-arsenic dimers arran ged with the c(4 X 4) symmetry. In concurrence with similar studies pe rformed in the MBE environment, it is found that the surface is a mixt ure of structural domains composed of two- and three-dimer variants of the c (4 X 4) reconstruction. Atomic positions associated with these structures are presented. The size, aspect ratio, and orientation of t he reconstructed regions are shown to be closely related to the atomic step geometry on the crystal surface.