GaAs(111)<i>A</i>-(2×2) reconstruction studied by scanning tunneling microscopy

Abstract

Atomic-resolution scanning tunneling microscope (STM) images have been obtained from the GaAs(111)A (gallium-terminated) surface. The STM images conclusively show that the (2\ifmmode\times\else\texttimes\fi{}2) periodicity arises from a regular array of gallium vacancies in agreement with a previously proposed model. It is shown that this reconstruction is explained by the reduction in energy that is achieved by the complete transfer of electrons from gallium dangling bonds into arsenic dangling bonds, which are then exactly filled.