Structure, kinetics, and passivation of hydrogen-acceptor complexes in gallium arsenide: A theoretical study

The structure, reorientation kinetics, and passivation mechanism of complexes formed by a H atom and As-site or Ga-site accepters, e.g., the Si-As-H-Ga and the Zn-Ga-H-As complexes in GaAs, have been investigated by first-principles local-density-functional methods. In both complexes, the stable configuration is found for the H atom located at a bond-centered site. The H atom is bound to the Si acceptor in the Si-As-H-Ga complex and to the As atom in the Zn-Ga-H-As complex. In spite of the different H bonds, similar vibrational properties and reorientation kinetics have been theoretically found for the two complexes. The present calculations well reproduce the experimental values of the vibrational frequencies and of the complex dissociation energies, as well as account for the acceptor passivation. A good agreement is also found with the reorientation energy of the Si-As-H-Ga complex, while the unusually high relaxation rates of the Zn-Ga-H-As complex measured by anelastic-relaxation investigations remains unexplained. In fact, neither the energy barrier estimated for the complex reorientation nor two different tunneling models account for those high relaxation rates.