Phosphorous-doped SiNx:H thin films containing c-Si QDs were prepared by PECVD in H2-Ar mixed dilution under low temperature. QD density and QD size can be controlled by tuning H2/Ar flow ratio. The sample prepared at the H2/Ar flow ratio of 100/100 possesses both wide band gap and excellent conductivity. Detail discussion has been presented for illustrating the influence of H2/Ar mixed dilution on the crystallization process and P-doping.