High-density plasma deposited silicon nitride films for coating InGaAlAs high-power lasers

Silicon nitride (SiN) films deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) technique have been used as optical coatings for the emitting facet of InGaAs/AlGaAs high-power lasers. The films were deposited at 90 deg C from a mixture of Ar, N2 and SiH4 as precursors. The most important properties of the films are low intrinsic stress and a negligible hysteresis in stress upon thermal cycling. Pre-cleaning of the surface to be coated, and the stable low stress in the film used for coating have been found to be highly valuable for the reliability of InGaAs/AlGaAs high-power lasers.