Phosphorus- and boron-doped hydrogenated amorphous silicon films were deposited by microwave electron-cyclotron-resonance plasma discharge. Electrical and optical properties of the films have been investigated. Low conductivity such as 10−8–10−7 (Ω cm)−1 was obtained for the as-grown films deposited without heating. The dark conductivity gradually increased by subsequent annealing steps up to 300 °C. After 300 °C annealing, conductivities of about 10−4 (Ω cm)−1 and optical gaps of 1.9 eV were obtained for both P-doped and B-doped films. Our doped a-Si:H films are expected to play the role of effective window layers of solar cells.