Etch pit development and growth on GaAs(110)

Abstract

We used scanning tunneling microscopy to study etch pits that are formed at 650 K after exposure of GaAs(110) to ${\mathrm{Br}}_{2}$ at lower temperature. Dual bias imaging reveals that 80% of the pits that are one to two rows wide correspond to pairwise removal of Ga and As from surface lattice sites. These pits tend to grow along [11\ifmmode\bar\else\textasciimacron\fi{}0] and have ends that are equally likely to be bounded by either Ga or As atoms. In addition, there is etching across adjacent rows. The resulting pits cross several zigzag rows and have kinked [11\ifmmode\bar\else\textasciimacron\fi{}0] sides and irregular ends. When these pits grow larger, they increasingly exhibit kinked 〈11\ifmmode\bar\else\textasciimacron\fi{}2〉 boundaries and hexagonal appearances. Rebonding of As atoms at pit boundaries to exposed second-layer As atoms was observed, and an analysis of the pit boundaries indicates that there are equal numbers of As and Ga terminations. We suggest that etching along [11\ifmmode\bar\else\textasciimacron\fi{}0] involves removal of a Ga atom that was either a pit boundary atom or next to a rebonded As boundary atom and that such processes are equally accessible.