Structure and stability of steps on the GaAs(110) surface

Abstract

The equilibrium structures and step energies of monolayer steps along [11\ifmmode\bar\else\textasciimacron\fi{}0], [11\ifmmode\bar\else\textasciimacron\fi{}1], and [11\ifmmode\bar\else\textasciimacron\fi{}2] on the GaAs(110) surface are examined theoretically using the autocompensation (electron-counting) principle. It is inferred that steps along [11\ifmmode\bar\else\textasciimacron\fi{}2] and [11\ifmmode\bar\else\textasciimacron\fi{}1] have significantly lower step energies than steps along [11\ifmmode\bar\else\textasciimacron\fi{}0]. The reason for this is that, unlike [11\ifmmode\bar\else\textasciimacron\fi{}0]-type steps, [11\ifmmode\bar\else\textasciimacron\fi{}2]- and [11\ifmmode\bar\else\textasciimacron\fi{}1]-type steps have topologies (connectivities) which permit a rehybridization of the step-edge atom dangling bond charge density by the creation of vacancies along the step line, perhaps accompanied by step-edge rebonding via the formation of dimers. This rehybridization results in stable, autocompensated steps. Step-edge atomic geometries are proposed for the step structures along [11\ifmmode\bar\else\textasciimacron\fi{}2] and [11\ifmmode\bar\else\textasciimacron\fi{}1]. Our results are then used to interpret reported scanning tunneling microscopy data for GaAs(110) surface steps, to discuss the behavior of steps resulting from cleavage, and to explain reported atomistic details of homoepitaxial growth on this surface. These results for steps on the GaAs(110) surface are also expected to be applicable to steps on other III-V (110) surfaces. \textcopyright{} 1996 The American Physical Society.