Analysis of Strain and Intermixing in Single-Layer Ge/Si Quantum Dots Using Polarized Raman Spectroscopy

The built-in strain and composition of as-grown and Si-capped single layers of Ge/Si dots grown at various temperatures 460–800 °C are studied by a comparative analysis of the Ge-Ge and Si-Ge modes in the polarized Raman spectra of the dots. A pronounced reduction of the strain and Ge content in the dots after deposition of the cap layer at low temperatures is observed, indicating that strain-induced Si diffusion from the cap layer is occurring. For large dots grown at 700–800 °C the observations are in agreement with a model of the Ge/Si dot consisting of a Si-rich boundary region and a Ge-rich core.