Unique Temperature Dependence on the Morphological Evolution of Ge on Si(100)

The Ge/Si system has been receiving much attention for both fundamental studies and device applications. It is a good model for understanding the basic physics for heteroepitaxy of lattice-mismatched semiconductors since Ge has a lattice constant of about 4.2% larger than that of Si. The presence of Ge in the Si lattice introduces stress, which has dramatic effects on the film growth. During the deposition of Ge on Si, small change in growth temperature will have big impact on the surface morphology and subsequently affect the optical properties of the system. The mechanism of this surface morphology evolution with respect to growth temperature is not well understood. In this study, we try to explain the surface morphology evolution of Ge on Si by intentionally introduce interdiffusion into the system by changing the growth temperatures in order to modify the total free energy that controls the energetics of surface morphology.