A series of N-type a-Si:H films were prepared by a plasma enhanced chemical vapor deposition method at different PH3/SiH4-doped flow ratios. The N-type a-Si:H film with the optimal PH3/SiH4 flow ratio was annealed in vacuum. The influence of PH3/SiH4 flow ratio on the microstructures and properties of a-Si:H films was investigated. The results indicate that the microstructure of N type a-Si:H films has no substantial change, but the electrical properties improves when PH3/SiH4 flow ratio increases. The a-Si...