Polarization-dependent Raman spectroscopic protocols for calibration of the alloy composition and strain in bulk and thin-film Si1-xGex

Polarization-dependent Raman spectroscopic methods are presented for extrac ting the integrated intensities of the first-order Si-Si, Si-Ge and Ge-Ge m odes in Si1-xGex. In unpolarized spectra, these modes are distorted by a br oad background causing anomalies in their apparent intensities, as derived by standard curve-fitting techniques, which can amount to 300%. The backgro und is strongly polarization dependent. However, the methods described here are successful in minimizing the background in the Raman spectrum and, as a result. the relative intensities measured in the parallel and crossed pol arizations differ by less than about 20%. Consequently, the protocols could be developed into process-control techniques for rapid determination of al loy composition (x) and strain in Si1-xGex. Additional weak features are re vealed when the Raman scattering geometry is altered from a configuration w here the first-order optical phonons are allowed to one in which they are f orbidden.