The stresses,structural and electrical properties of n-type Si-doped GaN films grown by metalorganic chemical vapor deposition (MOCVD) are systemically studied.It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples.But for higher doping samples,as the Si doping concentration increases,the inplane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities.Hall effect measurements reveal that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration.This phenomenon is attributed to the interaction between various scattering process.It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples. The stresses, structural and electrical properties of n-type Si-doped GaN films grown by metalorganic chemical vapor deposition (MOCVD) are systemically studied. It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples. But for higher doping samples, as the Si doping concentration increases, the inplane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities. Height effect measurements that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration .This phenomenon is attributed to the interaction between various scattering processes. It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples.