改善氮化鋁-氧化鋅/氧化鋅量子井結構應用於發光二極體之研究

A Study of the Improvement on AlN-ZnO/ZnO Quantum Well Structures Applied to Light-Emitting Diode

許凱強(Kai-Chiang Hsu)

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(2016年)

摘要

本研究利用射頻磁控共濺鍍系統，使用氮化鋁、氧化鋅靶材製作未摻雜氧化鋅薄膜與氮化鋁-氧化鋅共濺鍍薄膜，並製作出氧化鋅異質結構、氮化鋁-氧化鋅量子井結構，再藉由降低氮化鋁-氧化鋅阻障層厚度以改善結構特性。針對不同阻障層厚度量子井結構，利用霍爾量測系統與光激發螢光量測系統探討不同阻障層厚度結構光電特性，在霍爾電特性量測顯示量子井結構濃度隨著阻障層厚度降低而上升，光激發螢光量測結果由於鋁原子擴散影響，使得量子井結構能抑制氧化鋅本質缺陷-氧缺位。從電激發螢光量測發現由於阻障層厚度降低，使得整體元件串聯電阻下降，進而減少非輻射效應對元件的影響，因此發光強度上升，發光峰值為410 nm，元件發光為藍紫光，當阻障層厚度降低至20 nm時則會有610 nm峰值產生，且短波長有紅移的現象，元件發光為橘黃光，廣波段屬於Ga-O介面層缺陷發光，說明當阻障層厚度為35 nm時能夠有效提升短波長發光強度亦能抑制Ga-O介面層產生。
為進一步提升元件發光效能，以最佳化條件製作不同井區對數阻障層改善量子井結構，分別為1、5、7、10對之多重量子井結構發光二極體元件，從電激發螢光量測可得知相同井區對數阻障層厚度降低能使元件串聯電阻下降，短波長發光強度有些微上升的情況，隨著井區對數增加，於井區的載子侷限效應及復合效率上升，使元件發光效能提升，且由於阻障層厚度降低，非輻射效應亦隨之減少，進而提升元件短波長發光強度。發光峰值在井區對數增加後產生藍移現象，峰值從原先1對的410 nm藍移至10對的385 nm，元件發光由原本藍紫光轉為紫光，接近氧化鋅本質發光。說明當井區對數增加短波長發光強度有明顯增強的趨勢，並隨著阻障層厚度降低減少元件串聯電阻，短波長發光強度能更進一步增強。

關鍵字

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

並列摘要

In this study, we use RF magnetron co-sputtering system to deposit undoped ZnO thin film and AlN-ZnO co-sputtered thin film by AlN, ZnO target, and make ZnO heterostructure, AlN-ZnO quantum well structure, and then by decreasing AlN-ZnO barrier layer thickness to improve the structural properties. For different barrier layer thickness of the quantum well structure, using Hall measurement system and photoluminescence measurement system to study the structure of the different barrier layer thickness photoelectric properties. The structure properties are displayed in the Hall measurement; it shows the concentration of quantum well structure increasing by decreasing barrier layer thickness. Photoluminescence measurement results due to the diffusion of Al atoms, so single quantum well structure ZnO intrinsic defect – oxygen vacancy can be suppressed. And then from the electroluminescence measurement result, it shows by decreasing barrier layer thickness can reduce the device series resistance, thereby reducing the impact of the thermal radiation effects, thus the intensity of electroluminescence can be enhancing, the emission peak of electroluminescence located at 410 nm, the device light emitting is showed blue-violet. When the barrier layer thickness decrease to 20 nm, the emission of electroluminescence produced peak 610 nm, the short wavelength red-shift, the device light-emitting is showed orange, and the wide band emission at 610 nm emerging from the Ga-O interlayer. Thus when the barrier layer thickness is 35 nm, the structure can be effectively enhanced the intensity of short-wavelengths, and the Ga-O interlayer also be suppressed.
To further enhance the light emitting diode emitting performance, in optimal conditions to make different period with different barrier layer thickness quantum well structure, there are 1, 5, 7 and 10 period multiple-quantum well structure light emitting diode. From the electroluminescence measurement result, it shows the same period with decreasing barrier layer thickness device can reduce the series resistance, and the intensity of short wavelength enhance slightly. With increase in the number of the period, the carrier confinement effect and the carrier recombination efficiency are rose, it can enhance the device emitting performance. By decreasing barrier layer thickness the thermal radiation effects also be reduced, and thereby enhancing the device intensity of short wavelength. The emission peak of electroluminescence blue-shift after increasing the number of the period. From 1 period to 10 period multiple-quantum well structure, the emission peak was blue-shift from 410 nm to 385 nm, the device emitting from original blue-violet light turned to purple light, it close to intrinsic emitting of ZnO. Thus when the number of the well period increase, the intensity of short wavelength enhances obviously, and by decreasing barrier layer thickness can reduce the device series resistance, the intensity of short wavelength can be further enhanced.

並列關鍵字

RF magnetron sputtering ； ZnO ； quantum well structure ； multiple-quantum well structure ； light emitting diode

參考文獻

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