A group of researchers in China confirms the existence of localization states of charge carriers within indium gallium nitride materials and establishes a reference for their emission properties.
Light-emitting diodes made of indium gallium nitride provide better luminescence efficiency than many of the other materials used to create blue and green LEDs. But a big challenge of working with InGaN is its known dislocation density defects that make it difficult to understand its emission properties.
LEDs made of indium gallium nitride provide better luminescence efficiency than many of the other materials used to create blue and green LEDs, but a big challenge of working with InGaN is its known dislocation density defects that make it difficult to understand its emission properties. Researchers report an InGaN LED structure with high luminescence efficiency and what is believed to be the first direct observation of transition carriers between different localization states within InGaN. This figure shows the transition process of carriers between different localization states with increasing temperatures.
Credit: Yangfeng Li
Usage Restrictions: Journalists may use this image only with appropriate credit.
In the Journal of Applied Physics, from AIP Publishing, researchers in China report an InGaN LED structure with high luminescence efficiency and what is believed to be the first direct observation of transition carriers between different localization states within InGaN. The localization states were confirmed by temperature-dependent photoluminescence and excitation power-dependent photoluminescence.
Localization states theory is commonly used to explain the high luminescence efficiency gained via the large number of dislocations within InGaN materials. Localization states are the energy minima states believed to exist within the InGaN quantum well region (discrete energy values), but a direct observation of localization states was elusive until now.
"Based primarily on indium content fluctuations, we explored the 'energy minima' that remain within the InGaN quantum well region," said Yangfeng Li, the paper's lead author and a now postdoctoral fellow at the Hong Kong University of Science and Technology. "Such energy minima will capture the charge carriers -- electrons and holes -- and prevent them from being captured by defects (dislocations). This means that the emission efficiency is less affected by the large number of defects."
The group's direct observation of localization states is an important discovery for the future of LEDs, because it verifies their existence, which was a long-standing open scientific question.
"Segregation of indium may be one of the reasons causing localization states," said Li. "Due to the existence of localization states, the charge carriers will mainly be captured in the localization states rather than by nonradiative recombination defects. This improves the high luminescence efficiency of light-emitting devices."
Based on the group's electroluminescence spectra, "the InGaN sample with stronger localization states provides more than a twofold enhancement of the light-output at the same current-injection conditions as samples of weaker localization states," Li said.
The researchers' work can serve as a reference about the emission properties of InGaN materials for use in manufacturing LEDs and laser diodes.
They plan to continue to explore gallium nitride-related materials and devices "not only to gain a better understanding of their localizations but also the properties of InGaN quantum dots, which are semiconductor particles with potential applications in solar cells and electronics," Li said. "We hope that other researchers will also conduct in-depth theoretical studies of localization states."
The article, "Visualizing carrier transitions between localization states in a InGaN yellow-green light-emitting-diode structure," is authored by Yangfeng Li, Zhen Deng, Ziguang Ma, Lu Wang, Haiqiang Jia, Wenxin Wang, Yang Jiang and Hong Chen. The article appears in the Journal of Applied Physics (DOI: 10.1063/1.5100989) and can be accessed at http://aip.
ABOUT THE JOURNAL
The Journal of Applied Physics is an influential international journal publishing significant new experimental and theoretical results in all areas of applied physics. See https:/
Larry Frum | EurekAlert!
Quantum physics: On the way to quantum networks
27.01.2020 | Ludwig-Maximilians-Universität München
Physicists trap light in nanoresonators for record time
23.01.2020 | ITMO University
Researchers from Dresden and Osaka present the first fully integrated flexible electronics made of magnetic sensors and organic circuits which opens the path towards the development of electronic skin.
Human skin is a fascinating and multifunctional organ with unique properties originating from its flexible and compliant nature. It allows for interfacing with...
Researchers of the Carl Gustav Carus University Hospital Dresden at the National Center for Tumor Diseases Dresden (NCT/UCC), together with an international...
A Duke University research team has identified a new function of a gene called huntingtin, a mutation of which underlies the progressive neurodegenerative...
For years, a new synthesis method has been developed at TU Wien (Vienna) to unlock the secrets of "strange metals". Now a breakthrough has been achieved. The results have been published in "Science".
Superconductors allow electrical current to flow without any resistance - but only below a certain critical temperature. Many materials have to be cooled down...
KIT researchers develop novel composites of DNA, silica particles, and carbon nanotubes -- Properties can be tailored to various applications
Using DNA, smallest silica particles, and carbon nanotubes, researchers of Karlsruhe Institute of Technology (KIT) developed novel programmable materials....
16.01.2020 | Event News
15.01.2020 | Event News
07.01.2020 | Event News
27.01.2020 | Life Sciences
27.01.2020 | Life Sciences
27.01.2020 | Life Sciences