Scanning tunneling microscopy of the GaAs (311)A surface reconstruction

Reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM) are used to study the reconstruction of the GaAs (311)A surface. During and after molecular-beam epitaxy, in-situ RHEED of the surface shows a lateral periodicity of 3.2 nm perpendicular to the 33] direction. This periodicity is confirmed employing in-situ STM. The height of this periodic surface structure is two monolayers, i.e., 0.34 nm. We show how this reconstruction, characterized by a dimerization of the surface As atoms, can be formed using a simple electron counting model. The excellent agreement with the experimental results further support this model, that was already found to explain the reconstructions of the (100) and (111) surfaces.