現今消費市場對光電積體電路(OEICs)的需求日益增加，以及尺寸微縮和成本縮減考量下，高響應度(放大訊號能力)及高速性能的光檢測器製造技術是必需的。
並且現今多晶矽在物性以及製作技術上都有顯著的進步，例如低成本和在大面積的二氧化矽基板上都可以進行沉積，這些都是成為讓人注目的光電材料原因。
在此論文中，我們將使用MEDICI這套軟體對單晶與多晶矽的光二極體和光電晶體進行模擬研究。首先針對單晶矽基板上傳統型和增加p+延展區型光二極體進行討論。我們發現在低濃度約1014cm-3基板上擁有好的速度性能，但是在製程整合的過程卻是相當困難。並且我們發現在適度摻雜的基版上，有添加p+延展區的光二極體速度性能會優於尚未添加p+延展區的光二極體。也就是說我們可以使用增加p+延展區用以取得在低濃度製程整合較難完成的基板上光電二極體差不多的速度性能和增益。
緊接著針對薄膜二極體於1.2V下頻寬可達500GHz的單晶矽光二極體、1.2V頻寬達2.6GHz多晶矽的光二極體、單晶矽和多晶矽同質接面光電晶體進行討論。我們藉著減少總體厚度以及改變基極區面積以得到更好的速度性能和增益。並且發現到改變基極區面積大小對於單晶和多晶矽光偵測元件有著不同的結果
最後我們也討論了由矽與矽鍺組成的異質接面光電晶體。發現到摻雜越多的鍺可以得到越小的能帶，並且會有越低的電子注入效率。而越低的電子注入效率會有越差的頻寬。

In recent years, the commercial market for optoelectronic integrated circuits (OEICs) is expanding at rapid rate. It is necessary that a photodetector fabrication technique of high responsivity and high-speed performance is required for scale-down and cost-reduction concerns.
Hence there has been a remarkable advance in both the physics and processing technologies of polycrystalline silicon. Their significant properties, such as the low-cost and the mass-producability of large-area growth on glass substrate, have attracted much attention as a new optoelectronic material.
In this thesis, all the photodiodes and phototransistors are simulated by MEDICI. The single crystalline silicon photodiodes on bulk substrate and photodiode with extended-p- region are discussed first. We find that a lower concentration substrate (around 1014cm-3) has good frequency response, but the integrated process is too difficult. And we find that the bandwidth of extended-p- region photodiode is higher than that with no extended-p- region in the generally-used substrate doping concentration.
Subsequently, we have implemented the thin film single crystalline photodiode with bandwidth of 500 GHz at 1.2V, the polycrystalline silicon photodiode with bandwidth of 2.6 GHz at 1.2V, the single crystalline and polycrystalline homojunction phototransistors. We reduce the total depth or the n- collector region and adjust the area of p+ region, for improving frequency response and photo responsivity. And we find that adjusting the area of p+ region would lead to different results for single crystalline and polycrystalline.
Finally, we also consider heterojunction junction phototransistors that contain SiGe and Si. For a larger mole fraction germanium on silicon substrate, the SiGe bandgap becomes smaller, thus causing larger electron injection efficiency. However, larger electron injection efficiency shows more degradation of the bandwidth.

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