臺灣博碩士論文加值系統

光通訊系統中，大致上可分為三個部分：發光源、光纖與接收器。發光源主要可分為雷射二極體(LD)與發光二極體(LED)；而光接收器主要分為三大類：光導體(MSM)、p-i-n感光二極體與雪崩型感光二極體【1】。p-i-n感光二極體與雪崩型感光二極體的主要差異在於後者具有內部的增益與較大的頻寬，適合用於長距離通訊與高速度的傳輸。
隨著半導體材料發展的進步，雷射二極體(LD)與發光二極體(LED)由短波長的AlGaAs/GaAs進展到長波長的InGaAsP/InP及InAlGaAs/InP結構。因此在光偵測器方面，隨著入射光波波長之不同，而採用不同的材料
砷化鋁銦鎵(InAlGaAs)是近來研發的另一種光電材料，由於它的晶格常數與磷化銦(InP)的基板匹配，適合光通訊光電元件的製作，且砷化鋁銦鎵的能隙變化可從0.75eV(In0.53Ga0.47As)調整到1.47eV(In0.52Al0.48As) ，由於能隙變化大，適合光電元件的設計與製作。
雪崩型感光二極體具有內部的增益，且靈敏度高，而影響其元件特性的因素中，倍增層材料的電子與電洞的撞擊游離係數比佔了極為重要的關鍵，對於矽而言，電子與電洞的撞擊游離係數比可達到20左右，對於雪崩型感光二極體是一個良好的材料；然而，矽只適合於短波長的光纖通訊傳輸。而III-V族化合物半導體材料的電子與電洞的撞擊游離能力差異均不大，因此，我們在倍增層採用超晶格( supperlattice )的結構，選擇了InAlAs/InAlGaAs作為量子井的材料，利用人工的方式來強化倍增層的電子與電洞撞擊游離能力的差異，藉由元件內部電場的控制來達到我們的要求。
在元件的結構上我們採用了SACM-APD(separate absorption , charge and multiplication avalanche photodiode)的設計。在倍增層的部分，我們採用超晶格(supperlattice)的結構，以MOCVD的磊晶方法成長28對InAlGaAs/InAlAs的量子井，以人工的方式去增加III-V族材料的電子、電洞之撞擊游離能力差異，以提高元件的特性。
根據理論的計算，推算出元件在工作時倍增層的電場>5 105V/cm，吸收層的電場<2 105V/cm；以化學溼蝕刻的方式成功製作出高台式的超晶格式雪崩型感光二極體。量測元件的崩潰電壓約為33.2伏特，0.95VB時的暗電流為1μA，增益約為13，電容值約為1.6pF

An avalanche photodiode has internal gain, so that it has high sensitivity and is suitable for long-haul fiber communication system.
The layer structure is a SACM (separate absorption, charge and multiplication) configuration. The multiplication layer is a 28 -pairs of InAlGaAs/InAlAs supperlattice structure, which was grown by MOCVD. And the supperlattice structure can enhance the difference between the ionization coefficient of electrons and holes further improves the performance.
According to the calculation, the minimum field of multiplication layer must be above 5 105V/cm, and the maximum field of absorption layer should below 2 105V/cm. The mesa SL-APD was successfully formed by wet etching, and the mesa diameter is 50um. The breakdown voltage is about 33.2 voltage; 0.95 VB, the dark current is anout 1uA, the gain is 13, and the capacitance is about 1.6 pF.

第一章 導論
1-1 簡介…………………………………..1
1-2 研究動機……………………………..2
第二章 雪崩型感光二極體之工作原理
2-1工作原理……………………………..6
2-2累增增益……………………………..7
2-3雪崩型感光二極體之材料結構……..9
2-4暗電流機制…………………………..13
2-5電場分布…………………………..…19
2-6頻率響應……………………………..20
第三章 元件之設計與製程
3-1元件設計……………………………32
3-2製作程序…………………………….34
第四章 元件特性量測與分析
4-1材料特性分析….……………………45
4-2電流電壓量測.….……………………45
4-3電容電壓量測.….……………………46
4-4雪崩倍增值.….………………………47
第五章 結論與未來工作
5-1結論…………………………………55
5-2未來工作……………………………55
參考文獻……………………….……60

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