The electrical properties, microcathodoluminescence spectra, and persistent photoconductivity observed for as-grown and annealed ZnO ( P ) and Zn0.93Mg0.07O (P) films grown by pulsed laser deposition on sapphire substrates are reported. As-grown ZnO (P) had n-type conductivity with the Fermi level pinned near E-c-0.035 eV. Annealing in Ar at progressively higher temperatures of 850, 900, and 950 S C shifted the Fermi level first to E-c-0.07 eV and then to E-v + ( 0.1-0.13 ) eV, the latter level being most likely the acceptor level of P. In ZnMgO (P) the residual donors and the P acceptors are slightly deeper than in ZnO, respectively, 0.08 and 0.19 eV. The persistent photoconductivity observed was due to centers located above E-v + 0.5 eV and having a barrier for capture of electrons of 0.45 eV. These centers are tentatively associated with off-center P atoms located on Zn sites. (c) 2007 The Electrochemical Society.