Stability of Ge-related point defects and complexes in Ge-doped SiO2 -: art. no. 233201

We analyze Ge-related defects in Ge-doped SiO2 using first-principles density functional techniques. Ge is incorporated at the level of similar to1 mol % and above. The growth conditions of Ge:SiO2 naturally set up an oxygen deficiency relative to undoped SiO2, with vacancy concentrations increasing by a factor of 10(5) and O vacancies binding strongly to Ge impurities. All the centers considered exhibit potentially EPR-active states, candidates for identification as the Ge(n) centers. Substitutional Ge produces an apparent gap shrinking via its extrinsic levels.