臺灣博碩士論文加值系統

本論文主要是研究650nm磷化鋁鎵銦雷射二極體中活性層的最佳化設計。磷化鋁鎵銦雷射二極體已發展超過二十年，因應許多戶外應用需求，其最大操作溫度由過去的70˚C已提升到現在的100˚C，但磷化鋁鎵銦雷射二極體由於導電帶能隙差較小、p型掺雜濃度不易提升且熱電阻較大，因而在高溫操作下易導致漏電流的產生，使得磷化鋁鎵銦雷射二極體的性能會隨著溫度的升高而急遽變差，因此如何減少漏電流對於磷化鋁鎵銦雷射二極體在高溫操作時的影響並提升操作溫度是許多研究團隊一直努力的目標。在本論文中的第一章與第二章中將會針對磷化鋁鎵銦雷射二極體的特性、發展歷程及具應力量子井的特性作介紹。
本篇論文將針對符合DVD規格之650 nm磷化鋁鎵銦雷射光源的活性層結構作設計與分析，目的在降低漏電流並提升雷射性能以符合光資訊儲存的戶外應用；本研究所探討的活性層結構參數包含量子井數目、量子位障(Quantum Barrier)和波導層的組成以及具應力補償結構之量子位障組成。
首先是分析量子井個數對於漏電流的影響。由於量子井的個數愈多，對電荷載子的侷限愈好，漏電流的現象愈不明顯，因而可提高操作溫度，但隨著量子井個數的增加，雷射的臨界電流也增加，因此應有一最佳化的量子井數目。根據模擬結果發現，當量子井的個數為5時，已經能有效地抑制大部分的漏電流，使得特性溫度大為提高，甚至在相同輸出功率下，高溫下的操作電流甚至比四個量子井的操作電流更低。
接著是調整量子位障和波導層的組成，以進一步提升雷射性能。主要改變的參數是(AlxGa1-x) 0.5In0.5P量子位障和波導層中的x分別為0.4、0.5及0.6；由理論分析結果得知，當x為0.5時有最佳的雷射性能，對此一結果，在第三章中會依據模擬結果作詳細地探討分析。
最後再引入與量子井具有相同應力但趨勢相反的0.5% 舒張應力量子位障結構，藉此來達到應力補償的效果。主要的研究方向是在 0.5% 舒張應力固定前提下，調整量子位障的鋁之組成比例，使得位障的能隙高低跟著調變。研究發現，當量子位障的能隙值小於波導層的能隙值時，會有較佳的雷射性能輸出；但當能隙值太小時，又會使得載子易累積在位障處產生自發輻射，因而降低量子井的受激放射率；因此，位障的成份設計會有一最佳值。對此我們將在第四章中做詳細討論。

AlGaInP laser diodes have been developed for more than two decades. The maximum operation temperature of the AlGaInP laser diodes (LD) has been increased from 70°C in the past to the more recent 100°C. However, some inherent disadvantages, such as small conduction band offset, low p-doping concentration and high thermal resistivity, inhibit AlGaInP LD from obtaining high operation temperature owing to more leakage currents over the p-cladding layer at elevated operation temperature. Therefore, how to reduce the leakage current and enhance the operation temperature have been the major study topics for AlGaInP LDs. In the beginning of this thesis, the material characteristics and laser diode development history of the AlGaInP will be reviewed.
The main purpose of this thesis is to optimize the active layer structure and improve the performance of the AlGaInP LD so that it is suitable for outdoor DVD application. The key parameters will be optimized including quantum well number, barrier and spacer compositions in the traditional strained active layer, and barrier compositions in the strain-compensated active layer. The theoretical analysis is done utilizing LASTIP simulation software by assuming the AlGaInP LD with a constant emission wavelength and a fixed far-field pattern.
First, different quantum well (QW) numbers and barrier compositions in the 0.5% compressive-strained QW active layer are used to analyze the leakage current. It is found that with an increase in quantum well number, the leakage current can be reduced. However, the threshold current is increased accordingly. The simulation results suggest that five quantum wells are good enough to inhibit the electron overflow. Moreover, a (AlxGa1-x)0.5In0.5P barrier with x=0.5 forms a deep well. More carriers and higher stimulated emission rates can be obtained. With a quantum well number of five and a (AlxGa1-x)0.5In0.5P barrier with x=0.5, the leakage current can be greatly reduced and the characteristic temperature is improved without significant increase in operation currents. This simulated result is in good agreement with the experimental result.
Furthermore, the effect of the barrier height for a strain-compensated MQW AlGaInP LDs is theoretically analyzed to improve the LD performance. The strain-compensation technique is used to prevent the formation of dislocations by alternating layers with compressive- and tensile-strain of equal amounts, resulting in zero-net strain. The simulation results suggest that there is a moderate range for the choice of the Al composition in the tensile-strained barrier layer. The performance of the LD is degraded if a higher Al composition is utilized due to the non-uniform carrier distribution inside wells. However, if the Al composition is too small, the LD characteristic is also degraded. It is found that the Al composition from 0.1 to 0.2 should be a better choice for this strain-compensated MQW AlGaInP LDs. The characteristic temperature for this strain-compensated LD is comparable with the traditional strained MQW LD. However, the reliability is expected to be greatly improved due to lower Al composition and strain-compensated structure.

目錄……………………………………………………………..………iv
中文摘要………………………………………………………………vii
英文摘要……………………………………………………………….ix
圖表索引………………………………………………………………..xi
第一章 磷化鋁鎵銦半導體雷射簡介 1
1.1 磷化鋁鎵銦材料簡介 2
1.1.1 晶格性質 2
1.1.2 能隙 4
1.1.3 載子有效質量 6
1.1.4 折射率 7
1.2磷化鋁鎵銦半導體雷射 8
1.2.1磷化鋁鎵銦半導體雷射的發展 9
1.2.2 晶格匹配基板 10
1.2.3 磊晶介紹 11
1.2.4 磷化鋁鎵銦雷射二極體的缺點 12
1.3 漏電流對磷化鋁鎵銦半導體雷射的影響 13
第二章 含應力之量子井雷射二極體 15
2.1 簡述應力和應變 15
2.1.1 應變大小的計算 15
2.1.2 應力(stress)和應變(strain)的關係 16
2.2 應力對半導體的影響 18
2.3 含應力之量子井 20
2.4含應力量子井雷射之偏振光 21
2.5 臨界厚度 23
2.6 含應力之量子井磷化鋁鎵銦雷射 24
第三章 使漏電流降低的最佳化DVD用650nm磷化鎵銦雷射二極體之活性層結構 29
3.1研究動機 29
3.2元件結構 32
3.3理論分析與實驗結果 33
3.3.1 固定鋁濃度的情況下討論不同量子井的情形 36
3.3.2 鋁濃度不同對能帶的影響 39
3.3.3 漏電流作圖分析 46
3.3.4 高溫下雷射性能分析 47
3.4 結論 49
3.5 實驗結果 50
第四章 含應力補償結構之最佳化磷化鋁鎵銦雷射二極體的位障設計與分析 51
4.1研究動機 51
4.2元件結構 52
4.3應變的計算與設計 53
4.4 模擬結果與分析 54
4.4.1 鋁濃度不同造成的能帶差異 55
4.4.2 隨鋁濃度降低(0.3-0.1): 雷射性能提升 56
4.4.3 隨鋁濃度降低(0.1-0.05): 雷射性能變差 61
4.5 結論 ……………………………………………………………64
參考資料………………………………………………………………..65
附錄A 論文發表清單…………………………………………………...I
附錄B Mash Ratio對模擬能帶圖的影響…………………………….II
附錄C 論文中所使用的模擬程式…………………………………….III
附錄D 模擬中所使用的材料參數……………..……………………XIII

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