Chlorine containing hydrogenated amorphous silicon films were deposited by adding HCl to SiH4 containing plasmas. Bulk and surface bonding features, film thickness and optical band gap were examined by in situ infrared spectroscopies and spectroscopic ellipsometry. The introduction of HCl does not affect the deposition rate significantly. In situ infrared spectra show that the HCl introduction eliminates unfavorable higher hydride bonding structures (SiH2 and/or SiH in voids) in the deposited bulk films, and increases the film density. The films deposited from mixtures of SiH4 and HCl do not show significant optical band gap widening in spite of containing over 1021cm-3 Cl atoms, a concentration that is comparable to that of hydrogen. In situ infrared spectra show that the growing top surface is changed drastically from higher silicon hydride to chlorinated lower hydride.