近周期超晶格中的声学声子及其光散射特性

利用转移矩阵方法计算了近周期超晶格体系（包括有限周期数的超晶格、耦合超晶格、层厚起伏和层厚渐变的超晶格）中声学声子的喇曼散射谱．结果表明上述近周期超晶格的光散射特性与理想严格周期的体系和完全无序的体系都不相同，呈现出许多独特的性质．对有限周期数的超晶格，由于边界的存在，喇曼谱中除了理想超晶格中存在的折叠声学声子峰（主峰）外，还会出现一系列等间距分布的卫星峰．对耦合超晶格体系，理想超晶格中存在的主峰将出现分裂．对层厚起伏变化的超晶格，主峰呈现非对称展宽，展宽主要出现在高波数端．计算结果和实验测得的谱线作了比 关键词：

RAMAN SPECTRA FROM ACOUSTIC PHONONS IN NEARLY PERIODIC SiGe/Si SUPERLATTICES

The transfer matrix method has been used to calculate the Raman spectra of acoustic phonons in nearly periodic SiGe/Si superlattices,including the supperlattices with finite number of periods,the coupled supperlattices,and those with layer-thickness fluctuations.The properties of the above nearly periodic systems are found to be very different from those of periodic or disordered systems.In stead of the folded acoustic phonons appearing in the Raman spectra from ideal superlattices (main peak),the other satellite peaks are also observable in the finite system due to the existence of boundaries.For the coupled superlattices,the main peaks split into two due to the interference of the acoustic waves in different superlattices.For the superlattices with layer-thickness fluctuation,the main Raman peaks show asymmetric broadening and a tail towards high wave number are observable.The calculated results are compared to the measured spectra and good agreement between them is obtained.