The electronic structure around As antisite near (110) surface of GaAs

TL;DR

This study investigates the electronic structure of arsenic antisites in GaAs, revealing localized orbitals and surface effects, with implications for understanding defect states and surface defect imaging.

Contribution

It provides detailed analysis of the electronic states of As antisites in bulk and near the surface, including stable and metastable configurations, highlighting surface effects on defect states.

Findings

Localized p-orbitals extend from As antisite

Surface As antisite shows smeared midgap levels

Metastable As antisite exhibits p-orbital characteristics

Abstract

The electronic structure around a single As antisite in GaAs is investigated in bulk and near the surface both in the stable and the metastable atomic configurations. The most characteristic electronic structures of As antisite is the existence of the localized p-orbitals extending from the As antisite. The major component of the highest occupied state on As antisite in the stable configuration is s-orbital connecting with neighboring As atoms with nodes whereas that in the metastable configuration is p-orbital connecting without nodes. Localized p-orbitals on the surrounding As atoms around the As antisite exist in every configuration of As antisite. Such features are retained except the case of the As antisite located just in the surface layer in which the midgap level is smeared into the conduction band and no localized states exist near the top of the valence band. Scanning tunneling microscopic images of defects observed in low-temperature grown GaAs, possibly assigned as As antisite, the origin of the metastability, and the peculiarity of the defects in the surface layer are discussed.