Dielectric Function and Band Gaps of Si 1−x C x AND Si 0.924−x Ge 0.076 C x (0≤x≤0.014) Semiconductor Alloys Grown on Si

We have characterized the optical properties of heteroepitexial Si1−xCx and Si0.924−xGe0.076Cx (0≤x≤0.014) alloys grown on Si substrates by solid phase epitaxy using spectroscopic ellipsometry. The measured dielectric function confirms that the samples are of good crystalline quality. We determined the E1 and E2 band gaps by lineshape-fitting the features in the second derivative spectra of the dielectric functions. Also, we discuss the shift of the band gaps with C concentration arising from strain and chemical alloying.