Influence of anisotropic in-plane strain on critical point resonances in reflectance difference data

The sharp resonances in reflectance difference spectroscopy (RDS) data at the critical points of the dielectric function of bulk semiconductors have been assigned to surface-bulk transitions, photon localization, or optical transitions from bound dimer states to excited dimer states. For the case of ZnTe, CdTe, and ZnSe, we present experimental data indicating that a uniaxial in-plane stress component induces sharp resonances at these critical points by lifting the degeneracy of the optical transitions at the Λ and Γ points due to the resulting anisotropic strain. Even small stresses of about 1–5 MPa, or strains on the order of $1×10−5$ can be detected with RDS.