Carbon-doped beta-FeSi2 films synthesized by ion implantation are investigated with the aim to fabricate high-quality semiconducting beta-FeSi2 layer on silicon substrate. According to transmission electron microscopy (TEM) cross-section observations, carbon-doped films with homogeneous thickness and smooth beta-Si interface, have higher quality than binary Fe-Si films. In particular, annealing at 500 degreesC-700 degreesC leads to the formation of a flat and continuous beta-type silicide layer. Improved stability of the beta phase is also found. Optical emission spectroscopy measurements show that the carbon doping influences only slightly the band gap values. (C) 2004 American Vacuum Society.