Influence of Buffer Structure on Relaxation of Stress in Si_(1-x) Ge_x by Raman Spectra
Raman谱研究不同缓冲层结构对Si_(1-x)Ge_x应力弛豫的影响

The influence of different types of the buffer structures on the extent of stress relaxation of the uniform composition Si 1- x Ge x layers grown by Ultrahigh Vacuum Chemical Vapor Deposition was studied by Raman spectra. There is a linear Ge composition dependence of the Si\|Si optical phonon mode shift,which is relative to the Si substrate for both fully relaxed and fully strained SiGe layers, as is used to calculate the extent of stress relaxation combined with the measured Raman shift. Because the stress on the interfaces of superlattice buffer is larger than that of the graded SiGe buffer, the threading arms of dislocations are bent to form the close loops, resulting in a lower surface dislocation density and a larger extent of stress relaxation.