管傑雄臺灣大學：電機工程學研究所彭鈺華Peng, Yu HwaYu HwaPeng2007-11-262018-07-062007-11-262018-07-062004http://ntur.lib.ntu.edu.tw//handle/246246/53308在本論文中，我們分別使用CVD及MBE的系統來成長鍺量子點，利用S-K 的長晶方法我們可以在p 型矽(100)的基板上成長自我形成的鍺量子點，且已經在自我形成之鍺量子點結構中發現內部能階之間的躍遷。並討論鍺量子點在矽晶片上成長的方式以及各種參數對成長型態的影響，包括溫度，鍺原子層層數。應用多層的量子點結構來作為主動層，我們分別嘗試製作量子點紅外線光偵測器及量子點發光二極體。 在光偵測器的部分，分別以CVD及MBE的系統來生產製作元件的樣品。在MBE的系統中我們採用了delta doping及Si Blocking layer來製作量子點紅外線光偵測器。鍺量子點紅外線偵測器，具有增加載子補捉及鬆弛時間、正向入射等優點，並配合目前成熟的矽製程，很容易達到積體化的目的，我們藉由增加阻擋層的厚度減少暗電流，將背景操作溫度提升至50 K。並分析該元件的光激發與光譜響應的實驗結果，大致分析該元件的能帶結構。在CVD的系統中我們則採用modulation doped，另外在製程中使用Schottky barrier來降低暗電流的大小，進而提高操作的溫度。根據實驗的結果我們提出一個以蕭基位能障來減小暗電流的鍺量子點紅外線光偵測器，利用傅利葉轉換紅外線光譜儀可以得到在不同偏壓及不同溫度下紅外線吸收量對波長的函數。在2 到4.5 μm的波段中可以觀察到明顯的正向入射的紅外線吸收，這歸因於鍺量子點價帶裡的束縛能階與連續能階之間的躍遷，因為此吸收能量相當於矽之能隙與鍺量子點光激發能量的差。4.5到9μm的波段吸收也可以觀察到，這個吸收是來自於鍺溼層的響應，而這個波段的吸收在80K 時消失。在高效能聚焦平面陣列元件的製作上，正向入射紅外線的吸收特性是非常大有可為的。 在量子點發光二極體的部分，我們嘗試使用Background doping的多層量子點來製作，並改變層數條件為5層，10層，30層，我們在實驗中歸納出了層數對多層鍺量子點發光二極體特性所造成的影響，當此一發光二極體的鍺量子點層數增加，量子效率、頻譜半寬隨之增加，發光波長漸往短波長移動，發光頻譜中來自矽的發光之比例減少了。並且我們也提出一個物理的機制，此機制以少量載子電子擴散長度的溫度變化為基礎，來解釋造成其中一些影響的原因，特別是不同層數元件發光頻譜對溫度的變化。 我們已經成功的製作出奈米量子點的光電元件, 藉由使用蕭基位障來提高操作溫度的量子點紅外光偵測器將可以運用在熱影像的擷取. 在量子點的發光二極體部份, 在分析其頻譜及載子特性後, 提出增強發光效率的實驗方向, 1.55μm波長的發光頻譜也有機會應用於光纖的傳輸上, 總結我們的實驗成果, 奈米量子點的光電特性將可被用於發展光電元件, 藉由與矽製程的整合可以延伸半導體技術的應用層面.This thesis mainly focuses on Ge quantum dots (QDs) grown by ultra high vacuum chemical vapor deposition (UHVCVD). We have archived a density higher than 1011 cm-2 with informal QDs about 10%. We also have successfully fabricated optoelectronic devices by use of self-organized Ge QD nano structure. Different methods are designed to reduce the dark current for the devices grown with CVD and MBE respectively. In quantum dot infrared photodetector (QDIP) fabricated by MBE, we have demonstrated a QDIP in our preliminary work on Ge QDs devices. In IR responsivity, our QDIPs have a very broad and tunable spectrum in the range 1.6~20 μm under applied biases. The maximum single wavelength detectivity of our devices is about 2.1x1010 cm (Hz0.5)/W under 0.2 V for 6 μm wavelength radiation at 30K. According to the current-voltage characteristics, the background limited performance can reach 50 K. In QDIP grown by UHVCVD, we report the growth of a high quality 20-period perfectly vertically aligned Ge/Si multiple quantum dots with the structure of the metal-semiconductor Schottky barrier to reduce the dark current. In IR responsivity, our QDIPs show two groups of broad spectra in 2~4.5μm and 4.5~9μm at low temperature. They come from Ge QDs and wetting layers respectively. The response of wetting layers vanishes above 90K while the response of Ge QDs vanishes above 150K. For the samples we present in the thesis, the maximum detectivity at 30K under +0.5V is 7.3 × 109 cmHz0.5/W. The current-voltage characteristic shows that the dark current is reduced by the Schottky barrier so that the detector can be applied in higher temperature for the thermal image detection. In QD LEDs, we compared the experimental results of devices with different fold number of Ge quantum dots. By analyzing these results, we found the influence of stacking quantum-dot layers on electroluminescence spectra and other characteristics. A possible mechanism based on the temperature-dependent minority carrier electron diffusion length was also proposed to explain some of these influences, especially the temperature-dependence of EL spectra of the devices with various fold number. The optoelectronic devices based on nano Ge QDs have been demonstrated. According to our results, the Ge QDIPs with Schottky barrier as a dark current blocker show the thermal image capability for high working temperature. The carrier dynamic in the QD LEDs have been analyzed. Due to the property of Ge QD and p-i-n device structure, we found the intensity enhancement with temperature. This behavior may be the key for the light emission form Si based device. The 1.55μm operating wavelength also shows the possibility that nano Ge QDs can communicate with fiber. Summarizing our experimental results, the nano Ge QDs is a way leads to the OEICs with Si based technology.中文摘要 I Abstract II 博碩士論文授權書 IV Acknowledgements V Table of Contents VI List of Figures VIII List of Tables XI Chapter 1 Introduction to Ge Quantum Dots on Si (100) 1 1.1 Nano Technology 1 1.2 Stranski-Krastanov Ge Quantum Dots 3 1.3 Ge quantum dot for fiber optical communication 4 1.4 Reference 8 1.5 Figures 10 Chapter 2 Growth and Characterization of Ge Quantum-Dot Epilayer 14 2.1 Growth of Ge QDs 14 A. Growth Temperature, Growth Rate, and monolayer effect 16 B. Si capping, and Si Spacer 19 2.2 Multi-layers of Ge quantum dots 20 A. Lateral merging of small neighboring QDs [16] 23 B. Saturation of Surface Strain [11] 23 2.3 Band structure of Ge quantum dots 26 2.4 Reference 27 2.5 Figures 30 Chapter 3 Ge Quantum Dot Infrared Photodetector with Si Blocking Layer Using Molecular Beam Epitaxy 46 3.1 Introduction 47 3.2 Investigation of the Sample Structure 48 3.3 Characterization of Our Detector 51 3.4 Conclusion 54 3.5 Reference 56 3.6 Figures 62 Chapter 4 Ge Quantum Dot Infrared Photodetector with Schottky Barrier Using Ultra High Vacuum Chemical Vapor Deposition 70 4.1 Introduction 71 4.2 Experiment 72 4.3 Band Diagram and Operation Theory 76 4.4 Conclusions 77 4.5 Reference 79 4.6 Figures 81 Chapter 5 Ge Quantum Dots Light-emission Diode 88 5.1 Introduction 89 5.2 Experiment 90 5.3 Results and Discussions 92 5.4 Conclusion 95 5.5 Reference 96 5.6 Figures 98 Chapter 6 Conclusions 104 Publication List 107 Journal List 107 Conference List 1083868915 bytesapplication/pdfen-US量子點量子點紅外線光偵測器奈米元件光電元件QDsNano deviceQDIPOptoelectronic devicethesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/53308/1/ntu-93-D88921007-1.pdf