利用氫化非晶矽鍺/矽複層的選擇性氧化形成鍺量子點與鍺量子點金屬-半導體-金屬光偵測器之研製

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研究生：	吳培甄 Pei-Jen Wu
論文名稱：	利用氫化非晶矽鍺/矽複層的選擇性氧化形成鍺量子點與鍺量子點金屬-半導體-金屬光偵測器之研製 Ge Quantum-Dots Formed by Selective Oxidation of a-Si:H/a-SiGe:H Multilayer and Fabrication of Ge Quantum-Dots MSM Photodetectors
指導教授：	洪志旺 Jyh-Wong Hong
口試委員:
學位類別：	碩士 Master
系所名稱：	資訊電機學院 - 電機工程學系 Department of Electrical Engineering
畢業學年度：	94
語文別：	英文
論文頁數：	82
中文關鍵詞：	光偵測器、選擇性氧化、鍺量子點
外文關鍵詞：	Ge Quantum-Dots, Photodetectors, Selective Oxidation
相關次數：	點閱：6 下載：0
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本論文的主題是研製鍺量子點及其光偵測器。利用矽鍺合金中的矽與鍺在高溫氧化速率不同，鍺原子會自氧化物釋放出來並埋藏在氧化物與矽鍺合金介面的特性，可製造奈米尺寸的鍺量子點。我們先利用電漿助長化學氣相沉積系統沉積氫化非晶矽鍺薄膜或氫化非晶矽鍺/矽多層膜進行高溫氧化處理，形成鍺量子點並包埋在氧化層內，利用此法所形成的鍺量子點尺寸大小決定於鍺原子釋放與聚集的機制。實驗中，在室溫下量測樣品的陰極激發光頻譜可得到一紫光放射光譜，峰值波長在391 nm (3.1 eV)，其光譜峰值波長並不隨著鍺量子點的平均尺寸改變而位移，當量子點的平均尺寸變小時，可觀察到較強的CL強度。
我們亦將製備完成的鍺量子點應用於金屬-半導體-金屬光偵測器的研製，並探討不同指插間隙寬度與金屬電極材料對元件特性的影響。由實驗結果發現，較寬之指插間隙可得到較低之元件暗電流與較高之元件光電流與響應速度；與Ti金屬電極比較，使用Cr金屬電極可有效抑制所量測到的元件暗電流。

Ge-rich quantum-dots embedded in an oxide matrix have been fabricated by oxidizing the as-deposited hydrogenated amorphous Si0.91Ge0.09 layer or hydrogenated amorphous Si/Si0.91Ge0.09 multilayer. The formation of Ge-rich quantum-dots was realized by the Ge atoms’ segregation and agglomeration during thermal oxidation. The cthodoluminescence (CL) spectra for the obtained samples, measured at room-temperature, were within the violet-band and peaked approximately at 3.1 eV (391 nm), which was independent of the average size of Ge quantum-dots, and a higher CL intensity was observed when the average size of Ge quantum-dots decreased.
The metal-semiconductor-metal photodetectors based on Ge quantum-dots have also been fabricated. The effects of finger spacing and metal-electrode materials on characteristics of MSM-PDs with interdigitated electrodes have been studied. The device photo-current increased, dark-current decreased and response speed increased as finger spacing increased. The Cr-electrode could suppress the device dark-current more effectively, as compared with the Ti-electrode.

Chapter 1	 Introduction……………………………………………………1
Chapter 2	 Motivation and Device Operation Principles……………4
1 Motivation………………………………………………………4
1.1 Quantum confinement effect………………………………4
1.2 Comparison between Ge and Si quantum dots …………6
1.3 Formation of Ge quantum dots……………………………6
1.4 Effects of Ge concentration ……………………………8
2 Operation Principles of MSM-PD……………………………11
3	 Responsivity……………………………………………………16
4	 Response Speed…………………………………………………18
Chapter 3	 Device Fabrication and Measurement Techniques ………21
1	 Device Fabrication……………………………………………21
2 Measurement Techniques………………………………………29
2.1 Energy dispersive spectrometer (EDS)…………………29
2.2 Scanning electron microscope (SEM)……………………29
2.3 Cathodoluminescence (CL) spectroscopy ………………30
2.4 Responsivity…………………………………………………30
2.5 Response speed………………………………………………31
Chapter 4	Experimental Results and Discussion………………………34
1 Characterization of Ge quantum dots ……………………34
1.1 Transmission electron microscopy (TEM)………………34
1.2 Energy dispersive spectrometer (EDS)…………………37
1.3 Scanning electron microscope (SEM)……………………37
1.4 Cathodoluminescence (CL) spectroscopy ………………41
2 MSM-PDs based on Ge quantum dots…………………………51
2.1 Effects of finger spacing ………………………………51
2.2 Effects of metal-electrode materials…………………53
Chapter 5	 Conclusion………………………………………………………65
References……………………………………………………………………67

                                

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