title: The role of the VZn-NO-H complex in the p-type conductivity in ZnO.
abstract: Past research efforts aiming at obtaining stable p-type ZnO have been based on complexes involving nitrogen doping. A recent experiment by (J. G. Reynolds et al., Appl. Phys. Lett., 2013, 102, 152114) demonstrated a significant (∼10(18) cm(-3)) p-type behavior in N-doped ZnO films after appropriate annealing. The p-type conductivity was attributed to a VZn-NO-H shallow acceptor complex, formed by a Zn vacancy (VZn), N substituting O (NO), and H interstitial (Hi). We present here a first-principles hybrid functional study of this complex compared to the one without hydrogen. Our results confirm that the VZn-NO-H complex acts as an acceptor in ZnO. We find that H plays an important role, because it lowers the formation energy of the complex with respect to VZn-NO, a complex known to exhibit (unstable) p-type behavior. However, this additional H atom also occupies the hole level at the origin of the shallow behavior of VZn-NO, leaving only two states empty higher in the band gap and making the VZn-NO-H complex a deep acceptor. Therefore, we conclude that the cause of the observed p-type conductivity in experiment is not the presence of the VZn-NO-H complex, but probably the formation of the VZn-NO complex during the annealing process.
authors.affiliation: CMT, Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium. mozhgan.amini@uantwerpen.be.
authors.forename: M N
authors.initials: MN
authors.lastname: Amini
authors.forename: R
authors.initials: R
authors.lastname: Saniz
authors.forename: D
authors.initials: D
authors.lastname: Lamoen
authors.forename: B
authors.initials: B
authors.lastname: Partoens