氮化鎵由於其極佳之光電材料特性常被用於製作發光二極體、雷射二極體、太陽能電池、光感測元件、高功率電晶體以及高載子遷移率電晶體。一維奈米結構具有高深寬比及高比表面積幫助釋放晶格不匹配所形成之應力，且奈米柱結構能避免傳統薄膜型龜裂之問題，故本實驗室以自行開發之爐管型電漿輔助化學氣相沉積設備成長一維氮化鎵奈米柱作為製作發光二極體之用。而一維氮化鎵奈米柱也因高比表面積之特性，為表面缺陷及發光效率所苦，因此本研究以核殼式結構成長氮化鎵奈米柱希望能有效改善前述問題。
　　沿用先前本實驗室之經驗，於矽基板上成長高品質之氮化鎵奈米柱，並分別以矽、鎂作為摻雜雜質使氮化鎵具有n型及p型特性。針對p型氮化鎵之摻雜濃度作提升，調控鎂來源之蒸氣壓以增加或減少摻雜濃度，利用光致螢光光譜之訊號強度與摻雜濃度之正比關係判斷以取得相對最高摻雜濃度。第二階段成長殼層式n型氮化鎵時，為使晶體沿著預先成長之p型氮化鎵成長，需降低氮化鎵再成核之機會，透過提高反應區溫度、降低鎵來源蒸氣壓、減少反應區鎵金屬之過飽和度及降低反應壓力，我們能夠透過SEM觀察到第二階段成長情況，由原本大量的再成核現象逐漸轉為沿著預先成長之p型氮化鎵奈米柱成長。
　　將成長完成之氮化鎵奈米柱製作成為發光二極體元件，量測元件之電流-電壓曲線可以觀察到元件具整流特性。當電流密度上升高於80mA/mm2後逐漸能以肉眼觀察到發光現象，且隨著電壓及電流密度持續上升亮度也隨之提升。表示核殼式結構確實有助於改善效率問題，並幫助氮化鎵奈米柱元件達成電致發光。

Owing to the significant optoelectronic property, GaN is used for light emitting diodes, laser diodes, sensors and high mobility transistor. Since 1-D nano-structure has the advantage of high aspect ratio and high specific surface area which help releases the stress comparing to film structure, 1-D structure seems like the choice for light emitting diode devices. We combined the two elements mentioned above, GaN and 1-D nano-structure, and fabricated GaN nano-rods for light emitting diode devices with the self-developed PECVD reactor. However, 1-D nano-structure is having the disadvantage of high surface defect density and low recombination efficiency due to its high specific surface area. We hope to avoid the unwanted surface defect by fabricating the nano-rods into core-shell structure.
Due to the experience from our former team members, we are able to fabricate high quality GaN nano-rods on silicon substrates. We chose silane and Magnesium nitride as the doping source, dope silicon and magnesium in respect into n-type and p-type GaN. Focusing on the doping concentration in p-type GaN, we controlled the amount of magnesium by adjusting the Magnesium nitride vapor pressure so that we can achieve different concentrations of Magnesium being brought into the reacting area. Then we make use of the relationship between Photoluminescence intensity and doping concentration to get the relatively higher doping concentration for p-type GaN.
In second stage of growth, we want the n-type GaN to grow along the crystal of pre-grown p-type GaN. We lowered the opportunity of re-nucleation which usually took place on top of the pre-grown sample by rising the temperature of the reacting area, lowering the amount of Gallium source and lowering the reacting pressure. We observed through SEM image and found that the re-nucleation situation gradually disappeared, and the n-type from second stage of growth had started to grow along the pre-grown sample.
The samples with p-n junction were made into light emitting devices, and the rectifying I-V curves confirmed the existence of p-n junction. Once the current density reached 80mA/mm2, electroluminescence is observed. As the current density increase, the violet light became brighter. Core-shell structure did helped improved the efficiency in fabricating light emitting diodes, and led to electroluminescence.

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