Optical and electrical properties of b-FeSi2 particles embedded in silicon matrix were improved by growing an un-doped silicon buffer layer at high temperature. With silicon buffer layer, the formation defects were prevented in the silicon matrix during the growth of b-FeSi2 and the subsequent annealing, which results in the narrow photoluminescence spectra. The diodes with silicon buffer layer showed smaller leakage current than those samples without silicon buffer layer. The thermal quenching of electroluminescence from such samples with silicon buffer layer occurred at higher temperature and the intrinsic band gap energy shift between silicon and b-FeSi2 was measured at about 0.23 eV.