SiGe Epitaxy with Graded Buffer by Ultrahigh Vacuum Chemical Vapor Deposition

A SiGe/Si epilayer with a linear-step-graded buffer was grown by ultrahigh vacuum chemical vapor deposition technique at a relatively high growth temperature (780°C) and a relatively high growth rate. Almost linear Ge content variation was realized in the buffer layer due to the Ge segregation to the growing surface during epitaxial growth. Double crystal x-ray diffraction and Raman spectroscopy show that the upper layer is fully relaxed. However, the measured results show that the density of dislocation in the composition graded structure is much lower than that in single-step epilayer structures.