Ge-Si intermixing at the Ge/Si(001) surface

Abstract

Ge-Si intermixing at the Ge/Si(001) surface is studied for 0.5-ML and 1-ML Ge coverages by using pseudopotential density-functional theory. We calculate the total energies of various Ge-Si intermixing configurations and estimate the possibility of Ge interdiffusion in the thermodynamic regime. We find that, while most of Ge atoms stay in the surface layer at room temperature, Ge interdiffusion tends to increase with temperature. Our results not only provide a quantitative understanding of recent experimental observations of high-temperature Ge interdiffusion at the Ge/Si(001) surface, but also demonstrate that there is a strong "site selectivity" of Ge arising from the dimerized surface reconstruction.