Electrical activity of chalcogen-hydrogen defects in silicon

The interaction of hydrogen with substitutional chalcogen impurities (S, Se, or Te) is investigated by ab initio modeling. In Se-H-n and Te-H-n complexes (n=1,2), protons are located at sites antibonding to nearest-neighbor silicon atoms. For sulfur, two competitive sites for S-H are found, resulting in two nearly degenerate structures. All the singly hydrogenated complexes are predicted to be shallow donors with levels lying above those of the substitutional S, Se, and Te double donors. In contrast, doubly hydrogenated chalcogen impurities are predicted to be electrically inert. A comparison of our results with experimental data suggests that the NL60 and NL61 electron-paramagnetic-resonance centers can be identified with two Se-H defects, where H is antibonded to a Si neighbor of Se.