Calculations of electrical levels of deep centers:: Application to Au-H and Ag-H defects in silicon

First-principles local-density formalism cluster theory is used to determine the structure of Au- and Ag-hydrogen complexes in Si. The theory, with an empirical correction, is then applied to extract their donor and acceptor levels and these are compared with capacitance transient spectroscopic measurements. Assignments of these levels to specific H defects are then made. Models for the defects responsible for the neutralization of the electrical activity of the Au and Ag centers are proposed.