Hydrogenated amorphous silicon (a‐Si:H) films were prepared by remote plasma chemical vapor deposition (RPCVD) using SiH4/SiH2Cl2/He/H2mixtures. With increasing Cl content ina‐Si:H up to about 1019cm−3, the stablity of photoconductivity under light illumination was improved with keeping the defect density and Urbach energy constant. We deposited hydrogenated amorphous silicon films with hydrogen content of 6 at. %, Cl content of ∼1019cm−3, and defect density of 3×1015cm−3, which exhibited very small photoconductivity degradation under light illumination. The optimum Cl concentration ina‐Si:H for stablea‐Si:H appears to be ∼1019 cm−3. ©1995 American Institute of Physics.