Approximately 2-mu m-thick Si-doped a-plane GaN films with different doping concentrations were grown on approximately 8-mu m-thick undoped a-plane GaN/r-sapphire by metal organic vapor phase epitaxy (MOVPE). The structural and electrical properties of the Si-doped a-plane GaN films were investigated by high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and temperature-dependent Hall measurement. The results showed that a small amount of Si doping can improve the surface morphology and decrease the density of pits. Upon increasing the CH3SiH3 flow rate, the crystalline quality of the (0 0 0 2) plane was slightly improved. The highest room-temperature mobility of 83.4 cm(2)/Vs was obtained at a carrier density of 6.2 x 10(18) with a CH3SiH3 flow rate of 10 sccm. (C) 2009 Published by Elsevier B.V.