Kinetics of selective epitaxial growth of Si and relaxed Ge by ultrahigh vacuum chemical vapor deposition in Si(0Â 0Â 1) windows

Relaxed germanium was deposited following a low temperature-high temperature procedure by ultrahigh vacuum chemical vapor deposition in Si trenches opened through a SiO2 mask. The resulting growth is selective, the germanium fills the Si trenches and evolves towards a roof-shaped morphology limited by (0 0 1), {1 1 3} and {1 1 1} facets. The evolution in height of the Ge structure depends on the trench width, and can be understood by considering a growth rate in the 〈1 1 3〉 direction equal to 22% of that measured along the 〈0 0 1〉 axis. At last, a surprisingly strong Ge diffusion under the SiO2 mask was revealed by selective chemical etching. Such a phenomenon was unexpected because no diffusion through the Si/Ge interface was previously observed on plain wafer.