Effect of halogen additives on the stability of a-Si:H films deposited at a high-growth rate

We deposited a-Si : H,F films at a high-growth rate (15 Å/s) using a SiH₄ and SiF₄ gas mixture to examine the effect of halogen additives on the film stability against light exposure. Fluorinated a-Si : H films show a high conductivity over 5×10⁻⁵ S/cm and the Schottky cells made with fluorinated films exhibit an improved fill factor after light-soaking. SIMS measurements show an increased oxygen incorporation into the film at a SiF₄ flow of 5 sccm or larger, while virtually no increase is seen when a small SiF₄ flow rate of 1 sccm is used. This is presumably an indication that a small amount of SiF₄ can actually help improve the stability of a-Si : H films against light exposure.