Electrical and thermal properties of structurally metastable iron-boron pairs in silicon

Structurally metastable iron-boron pairs in silicon have been detected using dark- or photocapacitance transient techniques combined with minority-carrier injection below 200 K. Five levels at EC-0.43, 0.46, 0.52, and 0.54 eV and EV+0.53 eV are observed as the metastable defects after the injection. The creation and annihilation behaviors of these defects by the injection are investigated in detail and discussed on the basis of the theory of recombination-enhanced defect reaction. The transmutations for respective defects are confirmed by isochronal anneals and the reaction kinetics are studied by isothermal anneals. These kinetic studies lead to a model for pair configurations responsible for these defect levels. The configuration-coordinate (CC) description for these metastable pairs is shown to account for all electrical and thermal properties. The CC model shows us why the metastability for the iron-boron pair cannot be observed in thermal equilibrium.