Interstitial to antisite defect conversion during the molecular beam epitaxial deposition on c(4 3 4) GaAs(001) surfaces

In the model describing the origin of excess arsenic content in low‐temperature grown GaAs layers developed by the research group of professor Strunk during the last ten years, formation of an interstitial As atom was identified as precursor to excess arsenic formation. After an As2 molecule interacts with the GaAs surface, a metastable conformation can form, where one of the As atoms of the As2 molecule is located in an interstitial position. Starting from this geometry, during growth stable conformations can easily arise by the assistance of one or two arriving Ga atoms which stabilize the interstitial As atom in its position by forming a half or full cage‐like structure. Another model describes how the antisite excess As atoms form in GaAs layers by an incomplete exchange of As atoms in the surface reconstruction layer with arriving Ga atoms. The present article connects these two aspects of the excess As formation by analyzing the stability of the interstitial excess As atom, calculated in four different atomic arrangements according to experimentally observed surface structures. Energies of initial, final and transition states of interstitial to antisite reaction path were calculated by DFT/B3LYP/6‐31++G method. Results show that interstitial to antisite conversion happens preferably after a half‐cage formation, while after a full cage has been formed, the interstitial As atom remains fixed in its position. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)