title: Bistability of hydrogen in ZnO: origin of doping limit and persistent photoconductivity.
abstract: Substitutional hydrogen at oxygen site (HO) is well-known to be a robust source of n-type conductivity in ZnO, but a puzzling aspect is that the doping limit by hydrogen is only about 10(18) cm(-3), even if solubility limit is much higher. Another puzzling aspect of ZnO is persistent photoconductivity, which prevents the wide applications of the ZnO-based thin film transistor. Up to now, there is no satisfactory theory about two puzzles. We report the bistability of HO in ZnO through first-principles electronic structure calculations. We find that as Fermi level is close to conduction bands, the HO can undergo a large lattice relaxation, through which a deep level can be induced, capturing electrons and the deep state can be transformed into shallow donor state by a photon absorption. We suggest that the bistability can give explanations to two puzzling aspects.
authors.affiliation: 1] Research Center for Dielectric and Advanced Matter Physics, Pusan National University, Pusan 609-735, Korea [2] Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea [3] Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea [4] Korea Research Institute of Standards and Science, Yuseong, Daejeon 305-340, Korea.
authors.forename: Ho-Hyun
authors.initials: HH
authors.lastname: Nahm
authors.affiliation: Research Center for Dielectric and Advanced Matter Physics, Pusan National University, Pusan 609-735, Korea.
authors.forename: C H
authors.initials: CH
authors.lastname: Park
authors.affiliation: 1] Korea Research Institute of Standards and Science, Yuseong, Daejeon 305-340, Korea [2] Department of Nano Science, University of Science and Technology, Daejeon 305-350, Korea.
authors.forename: Yong-Sung
authors.initials: YS
authors.lastname: Kim