Atomistic structure of Si atoms agglomerated nearby a stacking fault in a commercial GaAs:Si

Point defects nearby a Frank-type stacking fault in a commercial GaAs:Si wafer (with the Si concentration of about 10¹⁸ cm^-3) were examined by ultrahigh-vacuum cross-sectional scanning tunneling microscopy (UHV-XSTM). The defects were identified as pairs of a Si donor and a Ga vacancy. Even though the pairs were electrically neutral, the Si donors in the pairs might be active when they were in the bulk crystal, since the Ga vacancies in the pairs were considered to be introduced after the UHV-XSTM specimen preparation. The Si donors might be agglomerated towards the stacking fault, since the Si concentration nearby the stacking fault was rather high in comparison with the surrounding region.