雪崩增益效應是透過讓電晶體在逆向偏壓下產生雪崩崩潰，進而達到增加載子的一種效應，此效應被廣泛地運用在小訊號的偵測。本論文透過分析雪崩增益效應的物理機制來模擬出特定結構下的增益與雜訊，並藉由模擬結果推論該結構理論上可以達到的各種效能參數，包括電子電洞的解離比率、相對應的暗電流、靈敏度以及增益頻寬積。
在理論與模擬基礎上，本論文將分別分析矽鍺與鍺光偵測器之效能參數，並比較兩者之差異。結果顯示鍺光偵測器由於暗電流過大而無法降低其靈敏度；而矽鍺光偵測器則可以透過改變結構達到改進其靈敏度及降低操作電壓之結果。

Avalanche multiplication effect is to amplify small signal by operating the pn-junction at breakdown voltage. In this thesis, we analyze the physics of avalanche breakdown, and try to get mean gain and noise factor by simulation. With simulated mean gain and noise factor, we can extract the ionization ratio, dark current, sensitivity, and gain-bandwidth product for a certain structure.
Base on theory and simulation, we will analyze both silicon-germanium and germanium based avalanche photodetector, and give a summary for these avalanche photodetector. The result shows that, germanium based avalanche photodetector owns large dark current when we operate at breakdown voltage, which gives bad sensitivity. In contrast, silicon-germanium avalanche photodetector can be improved by changing injection type and splitting absorption and multiplication region.

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