Investigation of InSb critical-point energies at 25 K by using spectroscopic ellipsometry

Abstract

We report dielectric function data from 0.74 to 6.6 eV for InSb at 25 K obtained using spectroscopic ellipsometry. The values of the critical-point (CP) energies were determined from numerically calculated second energy derivatives of the data. The CP structures are blue shifted and significantly sharpened relative to those at room temperature (RT). The E1, E1 + Δ1, E′0, Δ5cu−Δ5vu, E′0 + Δ′0, and Δ5cl−Δ5vu CP structures are clearly observed at energies below 4 eV. We also report the E2, E′2, E2 + Δ2, E′2 + Δ2, E′1, E′1 + Δ′1, and E′1 + Δ′1 + Δ1 features in the E2−E′1 energy range of 4 to 6 eV. These cannot be resolved at RT, but are clearly separated at 25 K. In particular, several CPs in the E′2 and the E′1 + Δ′1 + Δ1 transitions have not previously been observed.