具微奈米結構之發光二極體及太陽能電池光學特性研究The; Research on Optical Properties of Micro/Nano Structures in Light-emitting diodes and Photovoltaics

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/6951

Title:	具微奈米結構之發光二極體及太陽能電池光學特性研究The;Research on Optical Properties of Micro/Nano Structures in Light-emitting diodes and Photovoltaics
Authors:	李韻芝;Yun-chih Lee
Contributors:	光電科學研究所
Keywords:	波導模態共振;微奈米結構;發光二極體;太陽能電池;Guided-Mode Resonance;Photovoltaics;Light-emitting diodes;Micro/Nano Structures
Date:	2009-06-30
Issue Date:	2009-09-22 10:33:02 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本論文旨在研究具微奈米結構綠能光電元件之光學特性調控，尤其是氮化鎵發光二極體之光萃取效率提升與光型調變，以及矽薄膜太陽能電池之光捕捉效率改善。第一類研究是藉氮化鎵發光二極體之透明導電膜上進行淺層蝕刻產生微結構，以及進行穿透多重量子井至n型氮化鎵層之微型孔洞深蝕刻，探討兩種不同微陣列結構對氮化鎵發光二極體光萃取效率提升。第二類研究是於氮化鎵發光二極體上製作微透鏡陣列，利用微透鏡陣列調制光子行進方向，呈現空間均勻分佈之出光場型。第三類研究是藉由雙填充因子之非對稱型光柵，以導波模態共振效應，使入射至矽薄膜太陽能電池之光波在結構內產生共振，延長光波光程，來改善矽薄膜太陽能電池之光捕捉效率。本研究利用有限時域差分法，建立兩種不同光學模型，並用以預測具微奈米結構之發光二極體及太陽能電池的光子行為。在發光二極體的研究，於多重量子井中，以100 nm間距，均勻放置具TE/TM極化且非同時性多重點光源，模擬發光二極體內光子之時間及空間上不同調特性。在太陽能電池的研究，利用具有限空間寬度及時間間隔為10飛秒之平面波，正向入射至具導波模態共振結構之太陽能電池，為太陽能電池內之光子動態行提供一個良好的空間及時間解析度。本研究採用電子束顯影術，於發光二極體之p型氮化鎵層上製作週期為1.6 ?m微透鏡，以產生空間均勻分佈之出光場型。另外也於發光二極體之p型氮化鎵層製作週期為0.5 ?m之氮化矽微透鏡，以提升其光萃取效率。微奈米結構是以電子束曝寫定義於PMMA光阻上，顯影後，以電感耦合電漿乾蝕刻法，蝕刻微奈米結構於元件內。為了驗證光學模型對光子行為的預測，本研究也自行開發一套之具空間角度解析(解析度達4.4?)之自動化光激發螢光頻譜量測系統。在發光二極體之出光場型研究，實驗結果證實，在發光角度±50°內，微透鏡結構可使發光二極體的出光強度變化小於10%，產生空間均勻分佈之出光場型。在發光二極體光萃取效率提升研究，穿透多重量子井至n型氮化鎵層之微型孔洞深蝕刻，可提升光萃取效率達25.5%。在太陽能電池的光子補捉效率改善研究，由數值分析結果得知，具導波模態共振效應之雙填充因子非對稱型光柵，可於920 - 1040 nm頻譜範圍內，以及入射光角度在?40?內，提升太陽能電池的光子補捉效率達三倍。In this dissertation, the manipulation of optical performances using micro/nano structures on green photonic devices is investigated, especially for light-extraction enhancement and light-pattern modulation of III-nitride based light-emitting diodes (LEDs) as well as light-trapping improvement of thin-film silicon (TF-Si) solar cells. Two different micro-arrays are adopted to study the light-extraction enhancement, including the shallow etching of microstructures on the indium–tin-oxide (ITO) p-contact and the deep etching of microholes through the InGaN/GaN multiple-quantum-well (MQW) active structure and down to the n-type GaN layer. An azimuthally isotropic irradiance of GaN-based LEDs with GaN microlens arrays is proposed to demonstrate the concept of light-pattern modulation of LEDs. The spatial resonance of incident lightwave based on guided-mode resonance (GMR) effect is proposed to improve light trapping of TF-Si solar cells by adding a two-filling-factor asymmetric binary grating on cells. Two different numerical models are developed based on the finite-difference time domain (FDTD) method for predicting the photon behaviors within or outside LEDs and solar cells with micro/nano structures. The non-simultaneous multiple point sources with TE and TM polarizations in the MQW region with an interval of 100 nm are utilized to simulate the non-temporal/non-spatial coherent and unpolarized photons within or escaping from LEDs. For providing a good time and space resolutions in dynamic photon behaviors in solar cells, the normal-incidence and TE-polarized finite-width planar wave with a duration time of 10 femto-seconds is assumed to impinge upon the GMR structures on cells. To realize microlens arrays on the p-GaN layer of LED chip for azimuthally isotropic irradiance and to construct SiN microlens arrays on GaN-based green LEDs for light-extraction enhancement, intended microlens profiles with a period of 1.6 and 0.5 ?m are defined in PMMA by e-beam lithography. Then, the patterned PMMA is developed in a solution of methylisobutyl ketone and isopropyl alcohol. Finally, a following inductive-coupled plasma (ICP) dry etching process is used to transfer the patterned structure to the specific layers. In order to confirm the numerical prediction of photon behaviors, a home-made automatic angular-resolved photoluminescence (PL) measurement system with an angular resolution of 4.4? is developed. For spatial light pattern modulation of LEDs, an azimuthally isotropic irradiance with an intensity variation corresponding to the azimuth angles is as low as 10% within the angle region of ±50° is experimentally demonstrated. For light-extraction enhancement of LEDs, the deep etching of microholes through the InGaN/GaN multiple-quantum-well (MQW) active structure and down to the n-type GaN layer realize experimentally an improvement of 25.5%. For light-trapping enhancement of solar cells, simulation results reveal that it is 3-fold enhancement in the light absorption within a spectral range of 920-1040 nm. Moreover, such an enhancement can be maintained even the incident angle of near-IR broadband light wave varies up to ?40?.
Appears in Collections:	[Graduate Institute of Optics and Photonics] Electronic Thesis & Dissertation

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