From state-of-the-art density-functional calculations using hybrid functionals we show that, persistent n-type conductivity in ZnO is due to defect complexes formed between H with intrinsic and extrinsic defects. H exhibits cationic, anionic, and electrically-inactive character on interacting with defects in ZnO. The electrically-inactive molecular hydrogen can contribute to n-type conductivity in ZnO by activating deep donor levels into shallow levels. By calculating local vibrational mode frequencies, we have identified origins of many H-related Raman and infra-red frequencies and thus confirmed the amphoteric behavior of H.
@article{arxiv.1309.5217,
title = {Understanding H-defect complexes in ZnO},
author = {R. Vidya and P. Ravindran and H. Fjellvåg},
journal= {arXiv preprint arXiv:1309.5217},
year = {2013}
}