The formation of interstitial arsenic defects in low-temperature grown (LT) GaAs layers is examined by temperature dependent, direct trajectory molecular dynamics calculations at semiempirical level. In agreement with earlier ab initio calculations, a metastable interstitial position of an As2 molecule just below the As-rich c (4×4) β reconstructed GaAs(001) surface (characterized by As-As dimers) is obtained. We model this conformation as a precursor state for excess interstitial As in the LT-GaAs layers. Furthermore, a migration layer was found above the surface, where As2 molecules can move practically freely. We identify the hopping of As2 molecules from the interstitial position into this migration layer as the process that controls the experimentally observed dependencies of the excess arsenic content on substrate temperature and arsenic overpressure during growth of LT-GaAs layers.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Aug 15 2005|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics