Hole trapping properties of germanium in α-quartz

Abstract

We present the first calculation of the self-trapping properties of germanium in α-quartz using the classic defect simulation technique. Our calculation suggests that it is easier for a hole to be self-trapped at oxygen ions next to a Ge3+ ion than a Ge4+ ion, which is in agreement with the experimental results. The hole self-trapping next to Ge3+ is accompanied by a large network distortion. Our results indicate that the most favourable hole trapping site is the next-nearest-neighbour oxygen to the Ge3+ ion, rather than the nearest-neighbour oxygens. Examining the most favourable hole trapping sites, we suggest that the distortion in the Si-O-Si bond angle plays a more important role in hole self-trapping than that in the Si-O bond length.