Quantification of Ge fraction using local vibrational modes in Raman spectra of silicon germanium by oil-immersion Raman spectroscopy

Abstract

We demonstrate that Raman spectra of the local vibrational mode (LVM) for Ge-rich SiGe are useful for the precise determination of Ge fraction. The relationship between Ge fraction and the Raman peak relative intensities of the Si–Si mode and LVM relating to the Si–Si mode was evaluated in detail. Clear negative correlation was found between the intensity ratio and the Ge fraction especially for Ge-rich SiGe thin films obtained by oil-immersion Raman spectroscopy. The present technique provides Ge composition independently from the strain states, therefore we can derive more reliable results than other techniques using peak position, especially for fine structures.