Room-temperature larger-scale highly ordered nanorod imprints of ZnO film
Author
Kyaw, Z.
Wang J.
Dev, K.
Tiam Tan, S.
Ju, Z.
Zhang, Z.-H.
Ji, Y.
Hasanov, N.
Liu W.
Sun X.W.
Demir, Hilmi Volkan
Date
2013Source Title
Optics Express
Print ISSN
1094-4087
Publisher
Optical Society of American (OSA)
Volume
21
Issue
22
Pages
26846 - 26853
Language
English
Type
ArticleItem Usage Stats
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Abstract
Room-temperature large-scale highly ordered nanorod-patterned ZnO films directly integrated on III-nitride light-emitting diodes (LEDs) are proposed and demonstrated via low-cost modified nanoimprinting, avoiding a high-temperature process. with a 600 nm pitch on top of a critical 200 nm thick Imprinting ZnO nanorods of 200 nm in diameter and 200 nm in height continuous ZnO wetting layer, the light output power of the resulting integrated ZnO-nanorod-film/semi- transparent metal/GaN/InGaN LED shows a two-fold enhancement (100% light extraction efficiency improvement) at the injection current of 150 mA, in comparison with the conventional LED without the imprint film. The increased optical output is well explained by the enhanced light scattering and outcoupling of the ZnOrod structures along with the wetting film, as verified by the numerical simulations. The wetting layer is found to be essential for better impedance matching. The current-voltage characteristics and electroluminescence measurements confirm that there is no noticeable change in the electrical or spectral properties of the final LEDs after ZnO-nanorod film integration. These results suggest that the low-cost high-quality large-scale ZnOnanorod imprints hold great promise for superior LED light extraction. ©2013 Optical Society of America.
Keywords
Electric propertiesElectroluminescence
Metallic films
Nanoimprint lithography
Nanorods
Wetting
Zinc oxide
High temperature process
Injection currents
Light output power
Light-extraction efficiency
Nano-imprinting
Room temperature
Spectral properties
Transparent metals
Light emitting diodes