Optical characteristic of Si/SiGe heterostructure with strain in Si

• Main Authors: Jia-Guei Xu, 許家桂
• Other Authors: Hung-Hsiang Cheng
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/80648370903690088097

碩士 === 國立臺灣大學 === 電子工程學研究所 === 94 === Abstract Silicon/silicon germanium (Si/SiGe) heterostructures with strain presented in the Si layer has attracted great attention in recent years due to its high mobility in the channel of Metal Oxide Semiconductor Field Effect Transistor (MOSFET). The structure has been employed in optoelectronic devices. Intensive research has been performed in concerning the transport properties of the heterostructure. Nevertheless, the band profile has been less investigated. In this thesis, we report photoluminescence on SiGe/Si with strained presented in the Si layer. Exciton in quantum wells is observed in our measurement. These features reflect the band profile of strained Si. From the analysis, the band alignment of the system is determined. This thesis is organized as four chapters described as followings: Chapter 1: the growth technique of Molecular Beam Epitaxy (MBE) is illustrated. The mechanism of high temperature buffer and low temperature buffer is described. The band structure of both silicon and germanium are introduced briefly. Silicon and germanium are both indirect bandgap materials, and are illustrated by dispersion relation figures and constant energy surface figures. States of electrons and holes in k space can be known easily. Chapter 2: the strain effect, band alignment of Si/SiGe heterostructures, Raman scattering, X-ray diffraction, Transfer Matrix method, and exciton are explained. The content of this chapter is helpful to analyze band structures and understand exciton transitions. Chapter 3: PL measurement is explained briefly, and PL experimental instrument setup is illustrated. In PL spectra, there are dislocation lines (D1, D2, D3, and D4) and phonon lines (no phonon line, TA phonon line, and TO phonon line). They can be measured in the PL experiments. Chapter 4: Exciton transition in the quantum wells are found in PL spectra. The band diagrams of the samples are plotted. The quantized energy levels in the quantum wells are solved by Transfer Matrix method. The experimental data and theoretical analysis are compared. Finally, the diamagnetic shift of exciton transition and which band transition (delta2-hh or delta4-hh) are discussed.