We deposited a-Si:H,F films at a high-growth rate (similar to 15 Angstrom /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 x 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 seem 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. (C) 2001 Elsevier Science B.V. All rights reserved.