Strain and composition in thin SiGe buffer layers with high Ge content studied by micro-Raman spectroscopy

Abstract

Virtual substrates with high Ge content x of 0.25<x<0.5 for nMOSFET structures are grown by MBE. Thin strain relaxed SiGe buffers are of special importance for this application, therefore, sub-100 nm layer growth procedures have been developed Micro-Raman spectroscopy has been extensively employed for measurements of Ge content (x) and the degree of relaxation (r) in obtained virtual substrates in order to determine optimum process conditions. The application of frequency and intensity methods, suggested earlier by Mooney et al. and Tsang et al., have been analysed for determination of x in thin SiGe layers with high Ge content. It has been shown that the frequency method and Mooney's intensity method give quite reasonable values of x which correlate with those obtained by X-ray diffraction method.