Raman谱研究不同缓冲层结构对Si_(1-x)Ge_x应力弛豫的影响

Influence of Buffer Structure on Relaxation of Stress in Si_(1-x) Ge_x by Raman Spectra

应用 Raman散射谱研究超高真空化学气相淀积 ( UHV/CVD)生长的不同结构缓冲层对恒定组分上表层 Si1- x Gex 层应力弛豫的影响 .Raman散射的峰位不仅与 Ge组分有关 ,而且与其中的应力状态有关 .在完全应变和完全弛豫的情况下 ,Si1- x Gex 层中的 Si- Si振动模式相对于衬底的偏移都与 Ge组分成线性关系 .根据实测的 Raman峰位 ,估算了应力弛豫 .结果表明 :对组分渐变缓冲层结构而言 ,超晶格缓冲层中界面间应力更大 ,把位错弯曲成一个封闭的环 ,既减少了表面位错密度 。

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.