Optical characterization of as-prepared and rapid thermal oxidized partially strain compensated Si1-x-yGexCy films

The optical properties of as-prepared and rapid thermal oxidized (RTO) heteroepitaxial Si1-x-yGexCy alloys grown on Si substrate have been characterized using spectroscopic ellipsometry. The critical points E-1, E'(0), E-2 band gaps were determined by line shape fitting in the second derivative spectra of the pseudo-dielectric functions. For as-prepared films, the E-1 gap increases with C concentration and a linear dependence on C content was observed. However, the E-2 gap decreases as the C concentration increases. For the RTO samples, the amplitude of E-2 transition reduces rapidly and the E-1 transition shifts to a lower energy. The reduction in the amplitude of E-2 transitions is due to the presence of oxide layer. A high Ge content layer and the low C content in the RTO films account for the E-1 shift to lower energy and the increase of the refractive indices. (C) 2002 Elsevier Science Ltd. All rights reserved.