矽晶圓表面奈米糙化結構去極化角反射譜特性研究

The Depolarization and Angular Spectral Properties of Nano-Roughened Structures on Si Wafer

孟繁舜(Fan-Shuen Meng)

指導教授 ： 林恭如

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.10054

摘要

在本論文中，錐狀和柱狀兩種不同型態之次波長半導體抗反射結構皆被證實具有超強的抗反射能力。在奈米錐狀結構相較於奈米柱狀結構在400-500 奈米波段展現了大約3%的超低反射率，此一結果與具有梯度漸變折射率之多層膜理論模型得出的結果相當一致。另一方陎，奈米柱狀結構在量測極限1700 nm之前，相對於奈米錐狀結構隨波長增加，反射率會趨近塊材之結果，依然保持著極低的反射率。更進一步，一系列具有不同尺寸之錐狀次波長半導體抗反射結構亦成功製備完成及加以研究。隨著奈米錐的高度增加至240 奈米，原先於TM模態入射下之角反射光譜的布魯斯特角現象會因極化率降低至52.9%而消失。此外，在具有梯度漸變折射率之多層膜理論模型取層數趨近於無窮的近似條件下，理論模擬的結果能與150奈米和210奈米厚之次波長半導體抗反射結構所展現之全波段反射光譜相吻合。雖然次波長半導體抗反射結構能有效壓制各波段之反射率，但實際將其製備於太陽能電池之半成品後所量測之I-V電性，並未隨抗反射能力的提升而優化，故我們直接將次波長半導體抗反射結構製備於石英基板上進行光學反射和穿透光譜分析，進而發現次波長半導體抗反射結構雖能有效降低表陎反射，但同時降低了穿透光的強度，導致太陽能光電轉換效率無法提升。

關鍵字

柱狀奈米柱 ； 錐狀奈米柱 ； 形態調控 ； 抗反射 ； 去極化 ； 梯度漸變折射係數

並列摘要

In this thesis, morphologically controlled Si nano-pillars/nano-rods based sub-wavelength semiconductor anti-reflective structure (SSAS) surface exhibits great anti-reflection (AR) ability are demonstrated. Extremely small reflectance dip of <3% at 400-500 nm for Si nano-pillars is extraordinary when comparing with Si nano-rods, in which the reflectance vs. L/lambda for Si nano-pillars coincides well with the graded-index multilayer based modeling spectrum. On the other hand, Si nano-rods preserve its flattened reflectance spectrum up to 1700 nm, whereas the Si nano-pillar surface reflectance monotonically increases to approach that of bulk Si. Furthermore, the SSAS surface with different geometrical factors are successfully fabricated and investigated. As the increasing the Si nano-pillar height to 240 nm, the Brewster angles phenomenon observed for the TM-mode reflectance completely diminishes due to the decreasing of polarization ratio to 52.9%. Besides, the simulation curves by employing graded refractive index model with infinite layers are in good agreement with the measured reflectance data of 150nm-thick and 210nm-thick SSAS surface. Although SSAS efficiently suppress the reflectance over a wide spectral bandwidth, the SSAS surface based solar cells with SSAS surface fabricated upon semi-manufactured cells directly still exhibit poor I-V characteristics with the improvement of AR ability. Then we fabricate SSAS surface directly upon quartz substrate to analyze the optical reflectance and transmittance. The reason that SSAS surface suppresses surface reflectance from 30% to 5% but the transmittance decreases from 15% to 3% simultaneously results in the energy conversion efficiency is still unimprovement.

並列關鍵字

Nano-rod ； Nano-pillar ； Morphological Control ； Anti-reflection ； Depolarization ； Graded Refractive Index

參考文獻

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