title: Hydrogen: a relevant shallow donor in zinc oxide.
abstract: Electron paramagnetic resonance and Hall measurements show consistently the presence of two donors ( D1 and D2) in state-of-the-art, nominally undoped ZnO single crystals. Using electron nuclear double resonance it is found that D1 shows hyperfine interaction with more than 50 shells of surrounding 67Zn nuclei, proving that it is a shallow, effective-mass-like donor. In addition D1 exhibits a single interaction with a H nucleus ( a(H) = 1.4 MHz), thus H is the defining element. It is in agreement with the prediction of Van de Walle [Phys. Rev. Lett. 85, 1012 (2000)] that H acts as a donor in ZnO. The concentration of D1 is 6x10(16) cm(-3) emphasizing its relevance for carrier statistics and applications.
authors.affiliation: I. Physikalisches Institut, Heinrich-Buff-Ring 16, Justus-Liebig-Universität Giessen, D-35392 Giessen, Germany.
authors.forename: Detlev M
authors.initials: DM
authors.lastname: Hofmann
authors.forename: Albrecht
authors.initials: A
authors.lastname: Hofstaetter
authors.forename: Frank
authors.initials: F
authors.lastname: Leiter
authors.forename: Huijuan
authors.initials: H
authors.lastname: Zhou
authors.forename: Frank
authors.initials: F
authors.lastname: Henecker
authors.forename: Bruno K
authors.initials: BK
authors.lastname: Meyer
authors.forename: Sergei B
authors.initials: SB
authors.lastname: Orlinskii
authors.forename: Jan
authors.initials: J
authors.lastname: Schmidt
authors.forename: Pavel G
authors.initials: PG
authors.lastname: Baranov