MICROSCOPIC IDENTIFICATION OF THE COMPENSATION MECHANISMS IN SI-DOPEDGAAS

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 accepte rs, Si clusters, and Si-Ga-Ga-vacancy complexes. A microscopic model b ased on the screened Coulomb interaction between charged dopants, the amphoteric nature of Si, and the Fermi-level effect is proposed, It ex plains the observed defects, the critical Si concentrations of each id entified mechanism, and predicts the solubility limit of Si in GaAs.