摘要

RC頻寬效應決定了電致吸收光調變器的高速特性，為了降低元件的電容值，行波式波導為我們所採用。然而，若要進一步提昇元件的速度，如何有效降低元件的電容值是很重要的。本論文即著重於進一步降低元件電容以達到更高的調變效率。
全程使用濕蝕刻是本論文的主要特色，而其目地是為了得到很好的蝕刻表面以降低元件的光損耗。除此之外，利用濕蝕刻來執行內緣蝕刻不但可以得到較小的元件電容值，同時可以保有較小的電阻值，以利於元件在高速時的特性。
在這裡我們所採用的方法是利用濕蝕刻及內緣蝕刻來降低主動層的電容以達到高速的特性，再利用內緣蝕刻降低P型包覆層及N型包覆層中所產生的寄生電容以更進一步的提高調變效率。熱蒸鍍、電子束蒸鍍及平坦化亦是我們製程的重點。
最後元件之測試我們量測到：-15dB的光功率傳播、在40GHz的電傳輸只有衰減-6dB、而且在50Ω的輸出阻抗下，電光調變訊號已超過20GHz，如此之結果顯示此種元件有很大的潛力應用在光纖傳輸上。

Abstract

The high-speed performance of the lump-type electroabsorption modulator (EAM) is mainly limited by RC-effect. By taking advantage of the distributive effects, the traveling-wave structure can overcome the RC-lump effect. However, in order to enhance the limitation imposed by the conventional slow-waveguide type of traveling-wave structure, the speed of the device is still mainly restricted by the distributed capacitance of the waveguide. In this work, a novel type of traveling-wave-electroabsorption-modulator based on the undercut-etching the active region is successfully fabricated and measured.
The methods of the processing adopted here is to lower the capacitance by chemical-wet-etching and two-time subsequent undercut etching on active region to further decrease the parasitic capacitance between P-type and N-type cladding layer. Also, the optical scattering loss may be reduced due the smooth sidewall of the waveguide from the wet etching. The whole processing shown in this thesis includes the lift-off technique by lithography, the metalization for n-, p- contacts (by thermal evaporator) and CPW microwave transmission (by e-beam evaporator), and PMGI-planarization.
–15dB optical transmission, –6dB electrical transmission loss and >20GHz 3dB bandwidth of electrical-to-optical response at 50Ωtermination is measured on this kind of devices. It exhibits a high potential on the application of high-speed optical-fiber link in the future.

目錄

目錄………………………………………………………………………………Ⅰ
誌謝………………………………………………………………………………Ⅲ
中文摘要…………………………………………………………………………Ⅴ
英文摘要…………………………………………………………………………Ⅵ
圖表目錄…………………………………………………………………………Ⅶ
第一章 緒論…………………………………………………………………………1
1.1 前言…………………………………………………………………………1
1.2 研究動機……………………………………………………………………1
1.3 論文架構……………………………………………………………………3

第二章 電致吸收光調變器之工作原理……………………………………………4
2.1 載子躍遷……………………………………………………………………4
2.2 Franz-Keldysh Effect概述………………………………………………6
2.3 量子局限史塔克效應(Quantum Confined Stark Effect)………………6
2.3.1 量子局限史塔克位多(Quantum Confined Stark Shift)………………8
2.3.2 電子、電洞波函數的影響…………………………………………………10
2.4 飽合功率…………………………………………………………………．11
2.4.1 載子跳脫時間…………………………………………………………．．13
2.4.2 載子累積效應及電場屏蔽效應…………………………………………．14

第三章 材料結構與元件製程……………………………………………………．16
3.1 材料結構與特性…………………………………………………………．16
3.1.1 磊晶結構…………………………………………………………………．16
3.1.2 材料特性-光激銀光(PL)特性及光電流特性……………………………18
3.2 元件製程…………………………………………………………………．20
3.2.1 方向性測試………………………………………………………………．21
3.2.2 蝕刻液的選擇……………………………………………………………．23
3.2.3 製程步驟…………………………………………………………………．24

第四章 製程討論與量測結果……………………………………………………．59
4.1 電特性及相關製程討論…………………………………………………．59
4.2 光特性及相關製程討論…………………………………………………．63
4.3 電-光特性………………………………………………………………．66

第五章 結論………………………………………………………………………．68

參考文獻……………………………………………………………………………．69

參考文獻

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[20] 研究生:陳奕任；指導教授:朱安國博士 “平坦化InGaAsP半導體雷射之製作與應用”國立中山大學光電工程研究所碩士論文，中華民國92年6月