臺灣博碩士論文加值系統

本篇文章為利用低溫分子束磊晶技術，磊晶出一系列高品質之低維度結構之 鍺錫/鍺 超晶格結構並對其作特性分析。我們在矽晶圓上先成長高品質之鍺緩衝層作為虛擬基板以減少晶格不匹配效應，再成功地生長 鍺錫/鍺 週期性超晶格結構。從穿透式電子顯微鏡、原子力顯微鏡、反射式高能量電子繞射、高解析X射線繞射技術、拉曼光譜量測中得到樣品結構及應力特性，再接著利用傅立葉轉換紅外線光譜儀、光激發螢光光譜、光調制反射光譜得到其光學特性，最後在第一原理基礎下使用DFT原理計算出 鍺錫/鍺 超晶格之能隙與實驗結果比較，此外也利用光學上之實驗數據去擬合 鍺錫/鍺 異質接面之傳導帶偏移比例。本篇研究主要探討在鍺錫合金技術中之低維度結構特性，進而應用於矽光子學中之光電元件。

We report the characteristics of Ge1-xSnx/Ge strained layer superlattices ( ) pseudomorphically grown on Ge-buffered on Si(001) wafers by molecular beam epitaxy at low temperature. The crystal quality of the Ge1-xSnx/Ge superlattices was characterized by transmission electron microscopy, atomic force microscopy, and reflection high-energy electron diffraction. The composition and strain states were analyzed by x-ray diffraction and Raman microscopy. The optical spectra were measured by Fourier transform infrared spectroscopy, Photoluminescence, and Photoreflectance to determine the lowest direct-gap transition energies. The observed blue shifts of lowest direct-gap transition energies are attributed to the quantum confinement effect and strain effect, confirmed by our theoretical results using DFT theory. In addition, we also fit the conduction band offset ratio of GeSn/Ge heterostructure by the results of the optical experiments. In this thesis, low dimensional heterostructure of newly group IV material system is investigated. Ge1-xSnx/Ge superlattices are demonstrated by technique of low temperature growth using by Molecular Beam Epitaxy, and presenting characteristics of strained Ge1-xSnx/Ge superlattices (SLs) on Si substrates with x up to 6.96 %. Move a step forward toward the low dimensional Sn-based group IV photonic devices.

Contents
口試委員審定書...............................................#
誌謝 ............................................. .i
中文摘要 ...................................ii
Abstract ......................................iii
Contents .....................................iv
List of Figures ...........................vi
List of Tables ...........................viii

Chapter 1 Introduction
1.1 Motivation................................1
1.2 Germanium................................3
1.3 GeSn alloy techniques...............5


Chapter 2 Growth Equipments and Characterization Techniques
2.1 Molecular Beam Epitaxy............7
2.2 Transmission Electron Microscopy & Atomic Force Microscopy.......9
2.3 X-ray diffraction........................11
2.4 Raman scattering.......................12
2.5 Fourier Transform Infra-Red spectroscopy........................................14
2.6 Photoluminescence & Photoreflectance...................................16


Chapter 3 Structural Properties of GeSn/Ge superlattices
3.1 Crystal growth..........................17
3.2 Transmission Electron Microscopy & Atomic Force Microscopy.....20
3.3 Strain & Composition determination..........................................23
3.4 Raman effect...............................28


Chapter 4 Optical Properties of Ge1-xSnx/Ge superlattices
4.1 Fourier Transform Infra-Red spectroscopy.........................................32
4.2 Photoluminescence & Photoreflectance......................................36
4.3Band structures and conduction band offset ratio of Ge1-xSnx/Ge superlattices.....................................42

Chapter 5 Conclusion and Future Work
5.1 Conclusion...............................43
5.2 Future Work..............................46

Bibliography.................................47

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