We investigated the indium doping effects on ZnO thin film using radio frequency (rf) magnetron sputtering and rapid thermal annealing. The structural and electrical properties of indium doped ZnO thin films were measured by X-ray diffraction, atomic force microscopy, scanning electron microscopy, and Hall effect measurement. Thin films were deposited at a high temperature of 800 degrees C in order to improve the crystal quality and were annealed for a short time of only 3 min, sufficient time to activate the dopants. The structural properties of undoped and indium doped films were considerably improved with increasing oxygen gas in plasma. Indium doping also significantly increased the electron concentration, making the films heavily n-type. However, the crystallinity and surface roughness of the films degraded and the mobility decreased with increasing indium doping content, likely as a result of the formation of smaller grain size. From this study, on the basis of the structural and electrical properties of fabricated film, the best electrical properties have been obtained for 0.3 atom % indium doped ZnO thin film. This thin film, with a similar crystalline structure to undoped ZnO films, which presents the electron concentration of 1.296x10(19) cm(-3), resistivity of 0.0121 Omega cm and mobility of 39.71 cm(2)/V s, can be considered for application to light emitting diodes. (c) 2007 The Electrochemical Society.