Determination of phonon deformation potentials and strain-shift coefficients in Ge-rich Si1−xGex using bulk Ge-rich Si1−xGex crystals and oil-immersion Raman spectroscopy

Abstract

The strain-free Raman shift of the Ge–Ge mode, , of Ge-rich Si1−xGex (x: Ge fraction) was determined accurately from the bulk Ge-rich Si1−xGex samples fabricated by the Czochralski (Cz) method. Using the obtained , the phonon deformation potentials (PDPs), p and q, and the strain-shift coefficient bLO of isotropic biaxial strained Ge-rich Si1−xGex thin films were extracted by oil-immersion Raman spectroscopy using Raman peak shifts of longitudinal and transverse optical (LO and TO) phonon modes. As a result, it was confirmed that these parameters are almost constant with small variations and that the strain-shift coefficient bLO is in good agreement with ab initio calculations. The parameters determined in this work are essential to realize accurate strain measurements using Raman spectroscopy for Ge-rich Si1−xGex devices.