具侷限層之氮化鋁-氧化鋅/氧化鋅量子井結構應用於氧化鋅/氮化鎵發光二極體之研究

A Study of AlN-ZnO/ZnO Quantum Well Structure with barrier layer Applied to ZnO/GaN Light-Emitting Diode

林泓均(Hong-Jyun Lin)

指導教授 ： 劉代山

國立虎尾科技大學/電機資訊學院/光電工程系光電與材料科技碩士班/碩士(2017年)

摘要

本研究利用射頻磁控共濺鍍系統，使用氮化鋁、氧化鋅靶材製作氧化鋅薄膜與氮化鋁-氧化鋅共濺鍍薄膜，並製作氧化鋅/氮化鎵異質結構、氮化鋁-氧化鋅/氧化鋅量子井結構，再探討不同侷限層對於氧化鋅量子井結構之影響。以上侷限層固定為氮化鋁-氧化鋅共濺鍍薄膜(AlN-ZnO 40%)，下侷限層分別為氮化鋁-氧化鋅共濺鍍薄膜(AlN-ZnO 40%)與氮化鋁薄膜(AlN)，由此定義對稱(SQW)與非對稱(A-SQW)量子井結構。利用光激發螢光量測與霍爾量測系統套討其光電特性，對稱量子井結構由於鋁原子擴散而取代鋅的位置，除了抑制氧化鋅的本質缺陷-氧缺位，更提高了結構的載子濃度，改善了氧化鋅的結晶性；而非對稱結構受到下侷限層氮化鋁的鋁原子過量擴散，雖有抑制氧缺位的效果，卻產生過多絕緣的鋁-氧鍵結，導致結構電阻率提高，載子濃度較低，使得氧化鋅的結晶性較差。從電激發光量測可以發現對稱量子井元件主要發光波段位於410 nm，發光顏色接近藍紫光；而非對稱量子井元件發光強度較弱，但氮化鋁侷限層提供了良好的載子侷限能力，使氮化鎵發光與介面複合發光成分減少，屬於氧化鋅的本質發光開始出現，主要發光波段位於390 nm。為了進一步改善元件發光效能，又不破壞氧化鋅的結晶性，在p型氮化鎵基板預先沉積不同厚度的氮化鋁(AlN)10、20、35 nm，再沉積對稱量子井結構。從光激發螢光量測與X光繞射光譜中可以觀察到三個結構皆有鋁原子擴散而影響氧化鋅的結晶性，但整體結晶性還是較非對稱量子井結構佳。從電激發螢光量測可以發現隨著氮化鋁厚度增加，屬於p型氮化鎵發光成分逐漸遞減，氮化鋁侷限層厚度達20 nm以上時，氧化鋅的本質發光開始出現，發光峰值由410 nm逐漸藍移至390 nm。為了進一步提升元件單一發光效能，將最佳化厚度35 nm之氮化鋁侷限層預先沉積於p型氮化鎵基板，並進一步提高量子井對數至3、5、7、10對，由電激發螢光量測可得知隨著量子井對數增加使載子溢流的現象受到抑制，能有更多的電子電洞對在井區中產生有效輻射複合，元件發光強度隨著對數增加而上升，發光峰值位置由390 nm逐漸藍移至385 nm，表示元件發光皆由氧化鋅本質發光所主導。

關鍵字

射頻磁控共濺鍍 ； 氧化鋅 ； 氮化鋁 ； 量子井結構 ； 多重量子井 ； 發光二極體

並列摘要

In this study, we use RF magnetron co-sputtering system to deposit the ZnO thin film and AlN-ZnO co-sputtered thin film by Aluminum nitride (AlN), Zinc Oxide (ZnO) target, and Fabrication the ZnO/GaN heterostructure and AlN-ZnO/ZnO quantum well structure. The influence of different barrier layers on the Zinc Oxide quantum well is also discussed. The upper barrier layer was fixed with AlN-ZnO (40%) thin film，the lower barrier layer was divided into AlN-ZnO(40%) and AlN, and define both as “Single Quantum Well” and “Asymmetry Single Quantum Well”. For the different barrier layer of ZnO quantum well structure, The photoelectric characteristics of ZnO quantum well structures are discussed by using PL measurement and Hall measurement system.It shows the carrier concentration of Single Quantum Well (SQW) increased due to the diffusion of Al atoms, The ZnO intrinsic defect–oxygen vacancy (Vo) can be suppressed and improved the ZnO crystallinity.The Asymmetry Single Quantum Well (A-SQW) is subjected to excessive diffusion of Al atoms in the lower barrier layer AlN, the oxygen vacancy of ZnO can be suppressed, but it produces too many insulated Al-O bonds, which leads to higher structural resistivity and lower carrier concentration, which leads to poor crystallinity of ZnO. From the EL measurements, we can find that the dominant wavelength of the SQW/p-GaN LED is located at 410 nm, the emission color is close to blue-violet. The A-SQW/p-GaN has weak luminescence intensity, but the AlN barrier layer provides better carrier confinement capability, which makes the p-GaN-related emission and interfacial recombination decreased, and the dominant wavelength is located at 390 nm. In order to improve the luminous efficiency of LED devices, and keep the crystallinity of ZnO. The different thickness of AlN barrier, 10, 20, and 35 nm are deposited on p-GaN substrates, and deposited the single quantum well structure. From the PL measurements and XRD spectra, it is observed that the three structures have the diffusion of Al atoms to influence the crystallinity of ZnO, However, the overall crystallinity is better than the asymmetric quantum well structure. From the EL measurements, it can be found that the luminescence component of p-GaN decreases gradually with increase the thickness of AlN barrier layer. When the thickness of AlN barrier layer is limited to 20 nm or more, the intrinsic luminescence of ZnO begins to appear, the dominant wavelength is gradually blue-shifted from 410 nm to 390 nm.
In order to further enhance the single luminous efficiency of LED devices, AlN barrier layer 35 nm was deposited on p-GaN substrate. And further improve the quantum wells to 3, 5, 7, 10 periods. From the EL measurements, it is found that the overflow of the carriers is suppressed when the period of the quantum wells increases. There are more electron-holes that can produce effective radiation recombination in the well region, and the luminous intensity of the LED devices increases with the period of the quantum wells. The dominant wavelength of the LED is blue-shifted from 390 nm to 385 nm, indicating that the LED luminescence is dominated by ZnO intrinsic luminescence.

並列關鍵字

RF magnetron sputtering ； ZnO ； p-GaN ； AlN ； AlN-ZnO ； Single Quantum Well ； Multiple-Quantum Well ； Light Emitting Diode

參考文獻

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