Optical properties of InSb and its electrochemically grown anodic oxide

Ellipsometrically determined complex dielectric-function data have been obtained for InSb and its electrochemically grown anodic oxide at room temperature from 1.5-6.0 eV. Our data for InSb are a clear improvement over the earlier data of Philipp and Ehrenreich. The critical-point energies of the $E_1$ and $E_1+{\Delta }_1$ transitions are determined to be 1.872±0.002 eV and 2.374±0.010 eV, respectively. The oxide has an intrinsic absorption threshold at 3.8 eV, near that of ${\mathrm{In}}_2$ ${\mathrm{O}}_3$. However, substantial absorption, probably due to the presence of elemental Sb, is found below this threshold in these films.