低溫水溶液法合成氧化鋅奈米柱之發光二極體

Abstract

本研究係以水溶液法於p型矽晶圓基材上，合成出高均向性一維氧化鋅奈米柱陣列，接著利用半導體相關製程技術完成發光二極體(LED)元件。本實驗以硝酸鋅(C4H6O4Zn･2H2O)與四氮六甲環(C6H12N4)濃度1:1之混和溶液，固定其反應時間與溫度分別為6小時及90ºC，並且以不同之溶液濃度、晶種、基材等為反應參數，合成出高品質之一維氧化鋅奈米柱陣列，用以探討氧化鋅奈米柱之表面形態與奈米柱陣列之發光特性。 以x光繞射儀(XRD)與場發射掃描式電子顯微鏡(FESEM)分別鑑定氧化鋅晶體結構與表面形態，於不同溶液濃度與成長時間下所製備出之氧化鋅奈米柱陣列具有不同之長寬比與成核成長密度。光激發光光譜(PL)顯示氧化鋅奈米柱具有紫外光與寬頻之可見光發光區域，紫外光區相對於綠光區之比值將隨著溶液濃度之增加而成正比之現象；進一步計算上述放射光譜數據之CIE色度座標，發現座標位於偏藍之白光區域。 於電性量測方面，首先使用半導體相關製程完成此p-n異質接合(hetrojunction)之氧化鋅奈米柱發光二極體，此元件經過電流-電壓特性曲線之量測，觀察其起始電壓(turn-on voltage)為3.4 V，符合發光二極體之特性曲線。 相較於傳統塊材(bulk)與量子井(quantum well)結構，奈米結構具有較高之內部量子效率(Internal quantum efficiency)與窄頻譜特性，對於提高元件效率、降低起始電流具有正面助益。在此能源議題受重視之際，高品質之氧化鋅奈米柱發光二極體乃為重要研究主題之一。

In this study, the aqueous solution method was employed to synthesize one-dimensional well-aligned ZnO nanorod array on p-type Si wafer, and the ZnO nanorod light emitting diode were fabricated by semiconductor technologies. The optimized quality and aspect ratio of ZnO nanorod array was obtained by the mixed aqueous solution (Zinc Nitrate Hexahydrate: Hexamethylenetetramine = 1:1), fixed the reaction time and temperature in 6 hours and 90ºC, respectively. We investigated the nanorods’ surface morphology and the characteristics of photoluminescence with some factors which including reactants concentration, different seeds and substrates. The crystal structure and growth orientation of the ZnO nanorods were characterized by x-ray diffraction and FESEM analysis, respectively. The various of aspect ratio and density of ZnO nanorods were obtained with different reactants concentration and growth time. Photoluminescence spectra of ZnO nanorods reveal UV and visible emission. The ratio of UV and visible light were increased as the reactants concentration increased and the bluish white region were observed on CIE Chromaticity Diagram. I-V curve measurements of the ZnO nanorods light emitting diode that conform to the typical current-voltage characteristics, the turn on voltage is 3.4 V. Compared with bulk and quantum well structure, nano-structures possesses higher internal quantum efficiency and narrow full width at half maximum (FWHM), therefore, it’s useful to enhance the device efficiency and reduce the threshold current. On the century of inadequate energy sources, high quality ZnO nanorods light emitting diode is one of important topics.