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.
Highlights
Zinc oxide (ZnO) is a direct wide band gap (3.37 eV) semiconductor
The results showed that oxygen and nitrogen ambients are very effective on modifying the deep level defects, and that the red emission in ZnO was attributed to the superposition of emissions related to oxygen interstitial and oxygen vacancies in ZnO
Hexagonal, wellaligned, vertical ZnO nanotubes were obtained on the p-GaN substrate
Summary
Zinc oxide (ZnO) is a direct wide band gap (3.37 eV) semiconductor. In recent years, it has attracted the attention of the research community for a variety of practical applications due to its excellent properties combined with the facility of growing it in the nanostructure form.At present, ZnO is considered to be a very attractive material because it combines semiconducting and piezoelectric properties and in addition it is transparent, biocompatible, and bio-safe. The EL spectra of LEDs fabricated using the as-grown as well as the ZnO nanotubes annealed in argon, air, oxygen, and nitrogen ambients have been investigated. The results showed that oxygen and nitrogen ambients are very effective on modifying the deep level defects, and that the red emission in ZnO was attributed to the superposition of emissions related to oxygen interstitial and oxygen vacancies in ZnO.
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