Microscopic identification of the compensation mechanisms in Si-doped GaAs

The compensation mechanisms of ${\mathrm{Si}}_{\mathrm{Ga}}$ donors in GaAs are determined by scanning tunneling microscopy. With increasing Si concentration the ${\mathrm{Si}}_{\mathrm{Ga}}$ donors are consecutively electrically deactivated by ${\mathrm{Si}}_{\mathrm{As}}$ acceptors, Si clusters, and ${\mathrm{Si}}_{\mathrm{Ga}}$-Ga-vacancy complexes. A microscopic model based on the screened Coulomb interaction between charged dopants, the amphoteric nature of Si, and the Fermi-level effect is proposed. It explains the observed defects, the critical Si concentrations of each identified mechanism, and predicts the solubility limit of Si in GaAs. © 1996 The American Physical Society.