Comparison of oxygen-chain models for late thermal double donors in silicon

Abstract

The electronic and atomic structures of the oxygen chains assigned to late thermal double donors (TDDs) in silicon are studied using accurate total-energy calculations. We find that the ring-type O-chain model is best suited for TDDs and better than the di-Y-lid-type O-chain model. The ring-type O chains have slightly alternating C2v–C1h symmetry consistent with the recent high-field electron paramagnetic resonance experiments. The spin densities of the double-donor states are located outside the region of the O atoms, which makes the hyperfine interaction of an unpaired donor electron with the O17 nuclear spins very weak.