We report on Li-doped p-type Zn0.9Mg0.1O thin films grown by pulsed laser deposition. An optimal p-type conductivity is achieved at the substrate temperature of 550 degrees C, namely a resistivity of 45.4 Omega cm, a Hall mobility of 0.302 cm(2) V-1 s(-1), and a hole concentration of 4.55 x 10(17)cm(-3). Additionally, the p-type conductivity is stable over 5 months. From temperature-dependent photoluminescence, the energy level of Li-Zn acceptor is determined to be 167 meV above the valence band maximum. (C) 2007 Elsevier B.V. All rights reserved.