氮化銦鎵奈米碟在氮化鎵奈米柱上之光學性質研究; Optical properties of InGaN Nano Disk on GaN nanorods

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题名:	氮化銦鎵奈米碟在氮化鎵奈米柱上之光學性質研究;Optical properties of InGaN Nano Disk on GaN nanorods
作者:	楊名慧;Ming-Hui Yang
贡献者:	物理研究所
关键词:	氮化銦鎵;生命期;陰極電子束螢光光譜;光激發螢光光譜;時間鑑別光激發螢光光譜;奈米柱;氮化鎵;GaN nanorod;InGaN;time-resolved photoluminescence;photoluminescence;lifetime
日期:	2008-06-24
上传时间:	2009-09-22 11:00:08 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本篇論文探討成長於矽 (111) 方向上之氮化(銦)鎵奈米柱的光學特性分析，其中奈米柱結構之形貌係用掃描式電子顯微鏡及陰極電子束螢光光譜觀測，而奈米柱上之奈米碟的發光特性係用ㄧ系列之光激發螢光光譜及時間鑑別光激發螢光光譜來探討其發光特性以及載子的生命期。我們利用改變雷射波長之光激發螢光光譜證明氮化銦鎵奈米碟之發光波段約為500~750 nm，此發光層屬於紅光波段。同時我們觀測到多道光干涉現象所造成之多重峰值，利用正向收光、側向收光以及建設性干涉條件計算，這個干涉現象是由奈米柱與空氣以及基板的界面做反射而形成的。時間鑑別光激發螢光光譜實驗中，我們驗證氮化銦鎵奈米碟有兩個生命期。藉由估計發光強度，我們推測載子生命期較短者來自於為奈米碟外圍旁邊之載子生命期係由側向螢光量得，而載子生命期較長者來自於奈米碟中間內部之載子生命期係由正向螢光量得。最後我們驗證奈米柱結構可以造成應力釋放，使載子躍遷所需之時間縮短，螢光的生命期縮短，發光速率會較快。利用奈米柱結構可以有效降低其缺陷密度並釋放其應力，這些能有效改善發光層的發光效率，但是其受表面態的影響很大。如何抑制這些表面態的影響應是值得注意的。 This thesis investigates the optical properties of InGaN/GaN nanorods on Si(111) substrate grown by plasma-enhanced molecular beam epitaxy (PA-MBE). The structural properties of nanorods are explored by scanning electron microsope (SEM) and cathodoluminescence (CL). The optical emission properties of the InGaN/GaN nanorods are studied by photoluminescence (PL) as well as time-resolved photoluminescence (TRPL). The luminescence of InGaN layer can be proved emission at 500-750 nm by tuning the laser excitation energies above and below GaN band gap energy. The photoluminescence of InGaN layer also displays multiple peaks, we measure the luminescence at normal and 90o direction and confine with simple calculations to prove these peaks are originated from multi-beam interference, while the reflected planes are GaN/air and GaN/substrate interface. Two decay time constants are observed for InGaN layer in time-resolved photoluminescence measurements. After estimating their integrated intensity, we assume the shorter one is the lifetime of carriers near InGaN/air interface at lateral which can be measured at 90o direction and the longer one is the lifetime of carriers inside InGaN layer which can be measured at normal direction. Comparing with the lifetime of quantum wells, the reduced lifetime of InGaN layer on the nanorods is caused by effective suppressing the piezoelectric field due to strain relaxation. Growth of active layer on nanorods can effective reduces the density of defects and improves the spontaneous emission rate; the remained problem may be the nonradiative processes caused by the surface states.
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