Raman spectroscopy study of amorphous SiGe films deposited by low pressure chemical vapor deposition and polycrystalline SiGe films obtained by solid-phase crystallization

Abstract

Amorphous Si 1− x Ge x layers with Ge fractions up to x=0.38 were deposited by low pressure chemical vapor deposition. Polycrystalline layers were obtained by solid-phase crystallization of the amorphous ones. Both types of layers were studied by Raman spectroscopy. The influence of the Ge fraction on the Raman spectrum of the amorphous and polycrystalline layers was analyzed. The possible contribution of residual stresses is also discussed. The Raman shift of the Si–Si and Si–Ge peaks with the Ge fraction in the spectra of the polycrystalline films was compared with the results reported for fully strained epitaxial layers and bulk strain-free material. The phonon lineshape of both Raman bands, Si–Si and Si–Ge, was studied in the polycrystalline layers in terms of the Ge fraction and the presence of crystallographic defects. Finally, the temperature dependence of the Raman spectrum between room temperature and 350°C was studied.