Random variation of band bowing in pulsed laser deposited Mg doped (x=0.090, 0.147, 0.211, 0.268) ZnO thin films was observed. The X-ray diffraction and ultraviolet visible spectroscopy data reveal lattice relaxation and increase in band gap as well as disorclerness in the samples. The X-ray photoelectron spectroscopy data confirm the presence of magnesium and oxygen interstitials (Mg-i and O-i) as well as oxygen vacancies (V-o). The randomness of band bowing is attributed to the presence of these detects. (C) 2013 Elsevier B.V. All rights reserved.