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The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes.

Alvi NH, Ul Hasan K, Nur O, Willander M - Nanoscale Res Lett (2011)

Bottom Line: The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO.It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV).The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Science and Technology (ITN) Campus Norrköping, Linköping University, 60174 Norrköping, Sweden. nhalvi@gmail.com.

ABSTRACT
In this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600°C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96.

No MeSH data available.


SEM image of ZnO nanotubes on p-GaN substrate. (a) before annealing, (b) after annealing, (c) typical I-V characteristics for the fabricated LEDs, and (d) The schematic illustration of the fabricated LEDs.
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Figure 1: SEM image of ZnO nanotubes on p-GaN substrate. (a) before annealing, (b) after annealing, (c) typical I-V characteristics for the fabricated LEDs, and (d) The schematic illustration of the fabricated LEDs.

Mentions: Figure 1a,b shows the images of the top of the ZnO nanotubes before and after annealing, respectively. The figure shows clearly the morphology and size distribution of the as-grown ZnO nanotubes. Hexagonal, well-aligned, vertical ZnO nanotubes were obtained on the p-GaN substrate. The ZnO NTs grown had a uniaxial orientation of 〈0001〉 with an epitaxial orientation with respect to the p-GaN substrate, forming n-ZnO-(NTs)/p-GaN p-n heterojunctions. From the SEM images, the mean inner and outer diameters of the as-grown ZnO nanotubes in this study were found to be approximately 360 and 400 nm, respectively. Figure 1c shows the current-voltage, I-V, curves of the n-ZnO NTs/p-GaN LEDs developed in this study. All the LEDs have the same I-V curves. The I-V curves clearly show a rectifying behavior of the LED as expected with a turn on threshold voltage of about 4 V. This indicates clearly that both metal/GaN and metal/n-ZnO interfaces have formed good ohmic contacts. Figure 1d shows the schematic illustration of the fabricated LEDs.


The origin of the red emission in n-ZnO nanotubes/p-GaN white light emitting diodes.

Alvi NH, Ul Hasan K, Nur O, Willander M - Nanoscale Res Lett (2011)

SEM image of ZnO nanotubes on p-GaN substrate. (a) before annealing, (b) after annealing, (c) typical I-V characteristics for the fabricated LEDs, and (d) The schematic illustration of the fabricated LEDs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211177&req=5

Figure 1: SEM image of ZnO nanotubes on p-GaN substrate. (a) before annealing, (b) after annealing, (c) typical I-V characteristics for the fabricated LEDs, and (d) The schematic illustration of the fabricated LEDs.
Mentions: Figure 1a,b shows the images of the top of the ZnO nanotubes before and after annealing, respectively. The figure shows clearly the morphology and size distribution of the as-grown ZnO nanotubes. Hexagonal, well-aligned, vertical ZnO nanotubes were obtained on the p-GaN substrate. The ZnO NTs grown had a uniaxial orientation of 〈0001〉 with an epitaxial orientation with respect to the p-GaN substrate, forming n-ZnO-(NTs)/p-GaN p-n heterojunctions. From the SEM images, the mean inner and outer diameters of the as-grown ZnO nanotubes in this study were found to be approximately 360 and 400 nm, respectively. Figure 1c shows the current-voltage, I-V, curves of the n-ZnO NTs/p-GaN LEDs developed in this study. All the LEDs have the same I-V curves. The I-V curves clearly show a rectifying behavior of the LED as expected with a turn on threshold voltage of about 4 V. This indicates clearly that both metal/GaN and metal/n-ZnO interfaces have formed good ohmic contacts. Figure 1d shows the schematic illustration of the fabricated LEDs.

Bottom Line: The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO.It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV).The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Science and Technology (ITN) Campus Norrköping, Linköping University, 60174 Norrköping, Sweden. nhalvi@gmail.com.

ABSTRACT
In this article, the electroluminescence (EL) spectra of zinc oxide (ZnO) nanotubes/p-GaN light emitting diodes (LEDs) annealed in different ambients (argon, air, oxygen, and nitrogen) have been investigated. The ZnO nanotubes by aqueous chemical growth (ACG) technique on p-GaN substrates were obtained. The as-grown ZnO nanotubes were annealed in different ambients at 600°C for 30 min. The EL investigations showed that air, oxygen, and nitrogen annealing ambients have strongly affected the deep level emission bands in ZnO. It was concluded from the EL investigation that more than one deep level defect is involved in the red emission appearing between 620 and 750 nm and that the red emission in ZnO can be attributed to oxygen interstitials (Oi) appearing in the range from 620 nm (1.99 eV) to 690 nm (1.79 eV), and to oxygen vacancies (Vo) appearing in the range from 690 nm (1.79 eV) to 750 nm (1.65 eV). The annealing ambients, especially the nitrogen ambient, were also found to greatly influence the color-rendering properties and increase the CRI of the as - grown LEDs from 87 to 96.

No MeSH data available.