Home > Press > Cleaning nanowires to get out more light
![]() |
Treating aluminum-gallium-nitride nanowires with a diluted potassium-hydroxide solution can enhance the ultraviolet light output power as compared to an untreated device. Reprinted with permission from Sun, H., Shakfa, M.K., Muhammed, M.M., Janjua, B., Li, K.-H., Lin, R., Ng, T.K., Roqan, I.S., Ooi, B.S. & Li, X. Surface-passivated AlGaN nanowires for enhanced luminescence of ultraviolet light emitting diodes. ACS Photonics advance online publication, 19 December 2017.© 2017 American Chemical Society; KAUST Heno Hwang |
Abstract:
A technique for reducing the loss of light at the surface of semiconductor nanostructures has been demonstrated by scientists at KAUST.
Some materials can efficiently convert the electrons in an electrical current into light. These so-called semiconductors are used to create light-emitting diodes or LEDs: small, light, energy-efficient, long-lasting devices that are increasingly prevalent in both lighting and display applications.
The color, or wavelength, of the emitted light can be determined by choosing the appropriate material. Gallium arsenide, for example, emits predominantly infrared light. For shorter wavelengths that move into the blue or ultraviolet region of the spectrum, scientists have turned to gallium nitride. Then, to tune down the emission wavelength, aluminum can be added, which alters the spacing between the atoms and increases the energy bandgap.
However, numerous factors prevent all the radiation created in the semiconductor escaping the device to act as an efficient light source. Firstly, most semiconducting materials have a high refractive index, which makes semiconductor-air interfaces highly reflected--at some angles all light bounces backwards in a process known as total internal reflectivity. A second limitation is that imperfections at the surface act as traps that reabsorb the light before it can escape.
Postdoc Haiding Sun and his KAUST colleagues, including his supervisor, Assistant Prof. Xiaohang Li, Prof. Boon Ooi and Assistant Prof. Iman Roqan, have developed LEDs that are made up of a tight array of dislocation-free nanometer-scale aluminum-gallium-nitride nanowires on a titanium-coated silicon substrate. More light can be efficiently extracted due to the presence of the air gaps between nanowires via scattering. The trade-off however is that arrays of nanowires have a larger surface area than a planar structure. "Because of the large surface-to-volume ratio of nanowires, their optical and electrical properties are highly sensitive to their surroundings," says Sun. "Surface states and defects will lead to low-efficiency light-emitting devices."
Sun and the team show that treating the nanowires in a diluted potassium-hydroxide solution can suppress the surface reabsorption by removing dangling chemical bonds and preventing oxidization. Their results showed that a 30 second treatment led to a 49.7 percent enhancement in the ultraviolet light output power as compared with an untreated device.
"We aim to improve our device's performance in several ways," says Sun. "For example, we will optimize the nanowire growth conditions, we will use quantum-well structures in the active region and we will use different metal substrates to improve the light-extraction efficiency."
####
For more information, please click here
Contacts:
Carolyn Unck
Copyright © King Abdullah University of Science and Technology
If you have a comment, please Contact us.Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Related Links |
Related News Press |
News and information
Stability of perovskite solar cells reaches next milestone January 27th, 2023
Qubits on strong stimulants: Researchers find ways to improve the storage time of quantum information in a spin rich material January 27th, 2023
Temperature-sensing building material changes color to save energy January 27th, 2023
Chemistry
Dual-site collaboration boosts electrochemical nitrogen reduction on Ru-S-C single-atom catalyst January 6th, 2023
Rapid fluorescent mapping of electrochemically induced local pH changes December 9th, 2022
New method of reducing carbon dioxide could be a golden solution to pollution December 9th, 2022
Display technology/LEDs/SS Lighting/OLEDs
3D-printed decoder, AI-enabled image compression could enable higher-res displays December 9th, 2022
Physicists from the University of Warsaw and the Military University of Technology have developed a new photonic system with electrically tuned topological features October 14th, 2022
Possible Futures
Stability of perovskite solar cells reaches next milestone January 27th, 2023
Danish quantum physicists make nanoscopic advance of colossal significance January 27th, 2023
UC Irvine researchers decipher atomic-scale imperfections in lithium-ion batteries: Team used super high-resolution microscopy enhanced by deep machine learning January 27th, 2023
Discoveries
Stability of perovskite solar cells reaches next milestone January 27th, 2023
Qubits on strong stimulants: Researchers find ways to improve the storage time of quantum information in a spin rich material January 27th, 2023
Temperature-sensing building material changes color to save energy January 27th, 2023
Materials/Metamaterials
Rice turns asphaltene into graphene for composites: ‘Flashed’ byproduct of crude oil could bolster materials, polymer inks November 18th, 2022
How “2D” materials expand: New technique that accurately measures how atom-thin materials expand when heated could help engineers develop faster, more powerful electronic devices November 18th, 2022
Semi-nonlinear etchless lithium niobate waveguide with bound states in the continuum November 4th, 2022
Announcements
Temperature-sensing building material changes color to save energy January 27th, 2023
Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters
Qubits on strong stimulants: Researchers find ways to improve the storage time of quantum information in a spin rich material January 27th, 2023
Temperature-sensing building material changes color to save energy January 27th, 2023
Danish quantum physicists make nanoscopic advance of colossal significance January 27th, 2023
Quantum nanoscience
Qubits on strong stimulants: Researchers find ways to improve the storage time of quantum information in a spin rich material January 27th, 2023
Danish quantum physicists make nanoscopic advance of colossal significance January 27th, 2023
![]() |
||
![]() |
||
The latest news from around the world, FREE | ||
![]() |
![]() |
||
Premium Products | ||
![]() |
||
Only the news you want to read!
Learn More |
||
![]() |
||
Full-service, expert consulting
Learn More |
||
![]() |