Optically active hydrogen dimers in silicon

First-principles calculations are used to explore the structure and propert ies of several defects which are prominent luminescent centers in Si. The t rigonal defects B-41 and B-1/71, which are known to contain two hydrogen at oms in equivalent and inequivalent sites, respectively, are attributed to a hexavacancy containing two H atoms in different configurations. It is sugg ested that the J luminescence centers arises from a stable hexavacancy with out hydrogen atoms. (C) 1999 Elsevier Science B.V. All rights reserved.