Spectroscopic ellipsometry ofE1-like transitions in nanometer-thickness Ge layers

Spectroscopic ellipsometry of epitaxial Ge in bulk Si(100) has been used to study the effects of strain and layer thickness on the Ge-derived ${\mathrm{E}}_1$ transitions. Although a 4-Å-Ge layer exhibits no Ge-like ${\mathrm{E}}_1$ structure, localized ${\mathrm{E}}_1$-like transitions are observed for 7-Å-Ge layers showing the ${\mathrm{E}}_1$ transition is a robust probe of the Ge-like behavior in ultrathin layers.