Short-period Si/Si_1−xGe_x multiple quantum wells: real-time spectro-ellipsometric characterization during growth by synchrotron-radiation-excited chemical-beam epitaxy

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• 作者：Akazawa ; Housei
• 关键词：Si/Si_1&minus ; xGe_x multiple quantum well ; Abrupt interface ; Spectroscopic ellipsometry ; Virtual-interface approximation ; Interference fringe
• 刊名：Applied Surface Science
• 出版年：2003
• 期刊代码：6_01694332
• 类别：ms
• 出版时间：June 30, 2003
• 卷：216
• 期：1-4
• 页码：554-559
• 文件大小：237 K

摘要

A short-period Si/Si_0.53Ge_0.47 multiple quantum wells (MQW) was grown at 250°C by synchrotron-radiation-excited chemical-beam epitaxy. Two-dimensional strained-layers with atomically abrupt interfaces were obtained. Atomic-scale roughness at the interfaces between the Si and Si_0.53Ge_0.47 layers is the main relaxation channel for misfit strain. The ellipsometric angles ψ and Δ exhibited short-period oscillations over time, which are the result of alternation of the top layer material. At transparent energy levels, long-period modulation caused by optical interference is superimposed on the shorter oscillations. Two different procedures for the real-time characterization of the MQW structure by fitting of simulation to the experimental data were investigated; one provided a wide-range fit to the long-period modulation where the whole MQW is approximated as a pseudo-dielectric film and the other was a local-fit, under virtual-interface approximation, to the short-period oscillation for the absorbent range of photon energy.