Structures of As-Rich GaAs(001)-(2 × 4) Reconstructions

Abstract

Scanning tunneling microscope (STM) images together with reflection high-energy electron diffraction (RHEED) showed for the first time convincingly that the molecular-beam epitaxially grown GaAs(001)-(2 \ifmmode\times\else\texttimes\fi{} 4) $\ensuremath{\alpha}$, $\ensuremath{\beta}$, and $\ensuremath{\gamma}$ phases all have the same outermost surface layer of the unit cell, which consists of two As dimers and two dimer vacancies. Based on the STM and RHEED observations and dynamical RHEED calculation, a structure model consistent with various observations is proposed.