Strain relaxation in graded SiGe grown by ultra-high vacuum chemical vapor deposition (UHVCVD)

We have used ultra-high vacuum chemical vapor deposition (UHVCVD) system to grow step-graded SiGe/Si structures with relatively high growth temperature (780 degrees C). By using the phenomenon of Ge segregation to the growing surface during epitaxial growth we realized almost a linear Ge content variation in the buffer layer. X-ray diffraction and Raman spectroscopy measurements show that the upper layer is totally relaxed and the relaxation ratio is equal to 1. However, the measured results show that the density of dislocation in the compositionally graded structure is much lower than that in single-step buffer structures. (C) 1998 Elsevier Science B.V. All rights reserved.