Biaxial stress evaluation in GeSn film epitaxially grown on Ge substrate by oil-immersion Raman spectroscopy

Abstract

Abstract GeSn is being paid much attention as a next-generation channel material. In this work, we performed the excitation of forbidden transverse optical (TO) phonons from strained GeSn, as well as longitudinal optical (LO) phonons, under the backscattering geometry from the (001) surface by oil-immersion Raman spectroscopy. Using the obtained LO/TO phonons, we derived the phonon deformation potentials (PDPs), which play an important role in the stress evaluation, of the strained Ge 1− x Sn x for the first time. The results suggest that PDPs are almost constant for the Ge 1− x Sn x ( x < 0.032). Biaxial stress calculated using the derived PDPs reasonably indicated the isotropic states.