Approximately 2-μm-thick Si-doped a-plane GaN films with different doping concentrations were grown on approximately 8-μm-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 CH 3SiH 3 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 6.2×10 18 with a CH 3SiH 3 flow rate of 10 sccm.