利用遠程電漿原子層摻雜技術製作摻雜氮之氧化鋅薄膜及發光二極體之研究

Nitrogen-doped ZnO Thin Films and Light-Emitting Diodes Prepared by Remote Plasma In-Situ Atomic Layer Doping Technique

簡瑞芬(Jui-Fen Chien)

指導教授 ： 陳敏璋

國立臺灣大學/工學院/材料科學與工程學研究所/博士(2013年)

https://doi.org/10.6342/NTU.2013.03110

摘要

本論文研究使用原子層沉積並搭配遠程電漿原位原子層摻雜(remote plasma in-situ atomic layer doping)技術所成長高品質之 n 型摻雜氮之氧化鋅(ZnO:N)和 p 型共摻雜氧化鋅(co-dooped ZnO)薄膜，並探討其局部電子結構和光電特性。
利用遠程電漿原位原子層摻雜技術成長 ZnO:N 薄膜，經由 X光-光電子光譜與X光吸收近邊緣結構光譜分析，觀測到鋅-氮鍵結以及氧原子 2p 軌域與鋅原子 4s 軌域所形成的混成軌域的能量下降；此外經由霍爾量測分析結果顯示， ZnO:N薄膜的載子濃度伴隨著氮摻雜濃度增加而下降，歸因於氮摻雜進入氧化鋅並置換氧原子形成受體能階；上述分析結果證實氮原子確實成功的摻雜進入氧化鋅中。此外， ZnO:N薄膜中的氮摻雜濃度與原子層摻雜百分比呈線性關係，說明原位的原子層摻雜技術可以精準的控制氧化鋅薄膜的電性和局部電子結構。
接著將此 n 型ZnO:N層成長於p-型氮化鎵(GaN)上，並製作成n-ZnO:N/ p-GaN異質接面之發光二極體。在室溫下操作順向偏壓時， n-ZnO:N /p-GaN LEDs 具有一個主要的紫外光(UV)發光波段，發光層為n-ZnO:N且發光波長為 370 nm。此紫外光發光波段可歸因於氮摻雜進入氧化鋅薄膜，使氧化鋅薄膜中的電子濃度下降，因此當元件操作在順向偏下時，可以減少大量的電子由n-ZnO:N直接注入至p-GaN ，使得電子電洞對在p-GaN 層結合，而在p-GaN層發光的情況。
基於原位原子層摻雜氮的技術為基礎的經驗，，進一步開發高品質的 p-型共摻雜氮、鎵與鎂的氧化鋅MgZnO:(N:Ga)薄膜。此MgZnO:(N:Ga)薄膜中電洞濃度為 6.44x1017 cm-3，佐證氮與鎵的共摻雜以及鎂的植入，造成氧化鋅薄膜的電性由 n 型轉變為 p 型；並由光激發螢光光譜(Photoluminescence)觀測到MgZnO:(N:Ga)薄膜波長藍移的現象。並利用此高品質的p-型共摻雜MgZnO:(N:Ga)薄膜製作出氧化鋅同質接面之發光二極體，此同質接面的結構為n-ZnO:Al/i-ZnO/p-MgZnO:(N:Ga)。在室溫操作時，此同質接面之發光二極體具有二極體特性；其電激發螢光(Electroluminescence)光譜包含對應於氧化鋅的近能隙發光的紫外光波段，以及來自於氧化鋅缺陷的可見光波段。由實驗結果證實原位原子層摻雜技術可以利用於氧化鋅異質和同質接面的發光二極體，並能精確的調制氧化鋅薄膜的電性。

關鍵字

原子層沉積 ； 遠程電漿 ； 原位原子層摻雜 ； 氧化鋅 ； 發光二極體 ； 異質結構 ； 同質結構

並列摘要

In this thesis, the well-controlled n-type nitrogen-doped and p-type co-doped ZnO were fabricated by remote plasma in-situ atomic layer doping technique base on the atomic layer deposition (ALD). The optical and electrical properties as well as the local electrical structure were investigated to clarify the effect of in-situ atomic layer doping on ZnO thin films.
The nitrogen-doped ZnO (ZnO:N) films were grown by remote plasma in-situ atomic layer doping. X-ray photoelectron and absorption near-edge spectroscopies manifest the presence of Zn-N bond and a decrease in strength of the O 2p hybridized with Zn 4s states, which are consistent with the decrease of electron concentration in ZnO:N films with increasing nitrogen content. The result indicates the formation of acceptor states by occupation of oxygen sites with nitrogen. Linear dependence between the nitrogen content and the atomic layer doping percentage indicates the electrical properties and local electronic structures can be precisely controlled using this atomic layer doping technique.
Afterwords, the remote plasma in situ atomic layer doping technique was uti-lized to prepare the n-type ZnO:N layer upon p-type GaN to fabricate n-ZnO:N/p-GaN:Mg heterojunction light-emitting diodes (LEDs). A dominant ultra-violet electroluminescence around 370 nm at room-temperature is ascribed to the band-edge emission from ZnO. The suppressed luminescence from GaN can be de-duced from the decrease of electron concentration in ZnO and reduction in electron injection from n-ZnO:N to p-GaN:Mg due to the precise nitrogen incorporation.
Remote plasma in-situ atomic layer doping technique was further used to tailor the p-type conductivity of nitrogen and gallium co-doped MgZnO thin films. The nitrogen doping into ZnO converts the conductivity from n-type to p-type, deduced from the formation of nitrogen-related acceptors. The hole concentration increases with the incorporation of gallium, ascribed to the stabilized substitution of nitrogen at appropriate lattice sites. The stability of p-type conductivity was further improved by incorporating Mg due to the increase in solubility of nitrogen-related acceptors.
Finally, the ZnO homojunction LEDs based on the n-ZnO:Al/i-ZnO/p-MgZnO:(N:Ga) structure were grown by remote plasma in-situ atomic layer doping technique. Electroluminescence (EL) of n-ZnO:Al/i-ZnO/p-MgZnO:(N:Ga) device at room temperature comprised a signifi-cation ultraviolet and a broad visible emission. As compared with the n-type ZnO:Al layer, the p-type MgZnO:(N:Ga) layer exhibited a small carrier concentration. Thus, the electron injection from n-ZnO:Al is dominant over the hole injection from p-MgZnO:(N:Ga) under the forward current, leading to the radiative recombination of electron and hole in p-MgZnO:(N:Ga) layer. The results indicate that the remote plasma in situ atomic layer doping technique is an effective approach to tailoring the electrical properties of materials in device applications.

並列關鍵字

atomic layer deposition (ALD) ； remote plasma ； in-situ atomic layer doping ； zinc oxide (ZnO) ； light emitting diode (LEDs) ； heterojunction structure ； homojunction structure

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