Amorphous Al2O3 doped Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron sputtering technique. Emission spectra exhibit a strong emission band around 410 nm and a series of emission band near 970, 980, 1018, 1042 and 1080nm. Ellipsometry measurements show that the refractive index of the ErAlO films in the region of 400～1000 nm is between 1.76-1.83. The reflectivity of the ErAlO on Si is much smaller than that of clean Si and pure Er2O3 films. All the results indicate that ErAlO could be a promising material for Si solar cells.