MgxZn1-xO films were successfully grown on a-plane sapphire (1 1 (2) over tilde 0) substrates by remote plasma enhanced metalorganic chemical vapor deposition (RPE-MOCVD). Diethyl zinc (DEZn), bis-ethylcyclopentadienyl magnesium (EtCp2Mg) and oxygen plasma were used as source materials. By increasing Mg content in the films, the crystal structure was shifted through a mixed state from wurtzite to rock-salt with no significant segregation. Both optical absorption edges and emission peaks of MgxZn1-xO films shifted to the higher energy by increasing the Mg content at room temperature, showing an alloy broadening. The Stokes' shift of wurtzite MgxZn1-xO alloy films was quantitatively evaluated, resulting in a linear dependence on the absorption edge energy. (c) 2004 Elsevier B.V. All rights reserved.