Energetically deep defect centers in vapor-phase grown zinc oxide

Frank, T.*; Pensl, G.*; Tana-Zaera, R.*; Ziga-Prez, J.*; Martnez-Toms, C.*; Muoz-Sanjos, V.*; Oshima, Takeshi; Ito, Hisayoshi; Hofmann, D.*; Pfisterer, D.*; Sann, J.*; Meyer, B.*

Deep Level Transient Spectroscopy (DLTS) measurements were carried out to investigate defects in vapor-phase grown ZnO crystals. The generation of defect center labeled E4 subsequent to annealing in different ambients was monitored. By conducting electron irradiations with energies, where either both the Zn- and O-sublattice are damaged or according to only the Zn-lattice, a chemical assignment to the defect centers E4 and E3 could be accomplished. DLTS investigations of ZnO samples under illumination give an evidence that E4 is a negative-U center.