Microscopic identification of the compensation mechanisms in Si-doped GaAs

The compensation mechanisms of Si-Ga donors in GaAs are determined by scanning tunneling microscopy. With increasing Si concentration the Si-Ga donors are consecutively electrically deactivated by Si-As accepters, Si clusters, and Si-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.