850nm垂直共振腔面射型雷射之鈍化層改善及光電特性分析;Improvement of passivation layer and Characterization of 850 nm Vertically cavity surface-emitting lasers

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/79450

Title:	850nm垂直共振腔面射型雷射之鈍化層改善及光電特性分析;Improvement of passivation layer and Characterization of 850 nm Vertically cavity surface-emitting lasers
Authors:	吳國彰;Wu, Guo-Jhang
Contributors:	光電科學與工程學系
Keywords:	垂直共振腔面射型雷射;鈍化層;850nm VCSEL;passivation
Date:	2018-09-28
Issue Date:	2019-04-02 14:26:29 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文中，我們以AlGaAs磊晶片製做850nm VCSEL(垂直共振腔面射型雷射) 並透過下列兩種方法降低寄生電容值來改善VCSEL之頻寬特性。第一種方法:我們用濕蝕刻和乾蝕刻將元件結構蝕刻成高台型結構，此製程方法稱為Isolation。藉由此方法我們能降低元件表面之寄生電容。第二種方法:在晶片外部寄生電容上，我們分別以單層複合膜、BCB及雙層複合膜三種介質作為鈍化層(Passivation Layer)來降低電極產生的寄生電容值。首先，Isolation在高台型(mesa-type)結構中對元件的閥值條件、電阻影響不大，例如:在W/O Isolation下操作電阻分別為84.25Ω(雙層複合膜)和81.7Ω(BCB) ，在W/ Isolation下操作電阻分別為87.95Ω(雙層複合膜)和88.42Ω(BCB)，但電容值部分就有明顯的下降，如:在鈍化層為BCB，電容值由0.116 pF(W/O Isolation)降至0.069 pF(W/ Isolation)，由此可得Isolation能有效的降低元件的電容值。接著，鈍化層的材料方面，目前大部分是以BCB及Polymer兩種低介電係數(low-k)材料為主，原因為低介電係數材料能有效的降低元件外部的寄生電容值。Polymer的介電係數為 3.3，雖然元件的電容值能有效的下降，但Polymer的缺點為製程時材料表面容易產生龜裂，使元件的特性變差。BCB的介電係數為2.65，雖然BCB的優點為有效的降低元件的電容值，但BCB的缺點為金屬附著力差、製程複雜及成本高。為了解決BCB和Polymer 的缺點，我們選擇使用氮化矽(Si3N4)疊加氧化矽(SiO2)形成的複合膜 (Multilayer)改善製程中Polymer材料表面容易產生龜裂和BCB金屬附著力差、製程複雜及成本高的缺點。在W/ Isolation的元件結構中，分別以雙層複合膜、BCB作為鈍化層並比較其操作電阻、電容值及頻寬，雖然雙層複合膜的操作電阻、電容值略低於BCB的值，且操作頻寬也從9.6GHz(雙層複合膜)上升至9.9GHz(BCB)，但複合膜的優點為金屬附著力佳、製程流程簡單及成本較低。由於複合膜有相近於BCB的元件特性和改善BCB 的缺點，所以厚的複合膜能取代BCB成為較好的鈍化層材料。  ;In this thesis, we use AlGaAs epitaxial wafer to fabricate 10GHz 850nm Vertical Cavity Surface Emitting Laser and increase modulation bandwidth by reducing parasitic capacitance. Reducing parasitic capacitance by isolation and two kind of passivation layers. The passivation layer is Benzocyclobutene (BCB) and Multilayer. First of all, Isolation reduces capacitance value in the same passivation layer. The capacitance value is reduced from 0.116 pF (W/O Isolation) to 0.069 pF (W/Isolation) in the BCB. The capacitance value is reduced from 0.145 pF (W/O Isolation) to 0.121 pF (W/Isolation) in the Multilayer×2. On the other hand, the passivation layer reduce capacitance value in the W/ Isolation. The capacitance value is reduced from 0.161 pF (Multilayer×1) to 0.121 pF (Multilayer×2) in the W/ Isolation. The capacitance value is reduced from 0.121 pF (Multilayer×2) to 0.069 pF (BCB) in the W/ Isolation. In the W/ Isolation, the modulation bandwidth is increase from 9.6 GHz (Multilayer×2) to 9.9 GHz (BCB). Although the Multilayer×2 and BCB has the similar threshold condition and modulation bandwidth, the advantages of the Multilayer×2 are good metal adhesion, simple process flow and low cost. Since the Multilayer×2 has similar element characteristics to BCB and improves the disadvantage of BCB, a thick composite film can replace BCB as a better passivation layer material.
Appears in Collections:	[Graduate Institute of Optics and Photonics] Electronic Thesis & Dissertation

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