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Novel red LED lights show more stable temperatures than those made with conventional semiconductors, according to a new study published in the journal Applied Physics Letters.
This could be the basis for the next generation of televisions and monitors.
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Red LED lights show stable temperatures
With aims to optimize the performance of light-emitting diodes (LEDs), King Abdullah University of Science and Technology researchers seek to know every fabrication, design, and operation of these devices.
However, recently the team successfully created red LEDs based on the naturally blue-emitting semiconductor indium gallium nitride — inventing a new red LED with comparable stability to indium gallium phosphide, according to phys.org.
LEDs are optical sources created from semiconductors, and they improve conventional visible-light sources because they are smaller in size, support longer lifetimes, and save energy. LEDs emit light across the spectrum, including ultraviolet, blue (B), green (G), red (R), and onward into the infrared. Arrays of tiny RGB devices called micro-LEDs can accentuate vivid-color displays, which are expected to ground the next generation of monitors and televisions.
Challenges of microLED development
One of the major challenges in the way of creating micro-LEDs is to integrate green, red, and blue light into one LED chip. At present, RGB LEDs are developed via combining two kinds of materials: blue and green LEDs — which constitute indium gallium nitride (InGaN) semiconductors, and red-light LEDs — made from indium gallium phosphide (InGaP). "Creating RGB displays requires the mass transfer of the separate blue, green and red LEDs together," said KAUST researcher Zhe Zhuang. A simpler solution would involve developing different-colored LEDs on a singular semiconductor chip.
The thinking is since InGaP semiconductors can't emit blue or green light, the only way to make the monolithic RGB micro-LEDs is with the use of InGaN. This material could shift its emission from blue to green, red, and yellow via the introduction of more indium into the mix. InGaN red LEDs are believed to show better performance than InGaP ones, according to phys.org.
Varying LED size, electrical contact, current
In addition to growing high-quality indium-rich InGaN to develop red LEDs with nanofabrication facilities at the KAUST Core Labs, Zhuang and his colleagues also developed exceptional transparent electrical contacts with a thin film of indium-tin-oxide (ITO)1, which lets current pass through the team's new InGaN-based amber and red LEDs.
"We have optimized the fabrication of the ITO film to realize low electrical resistance and high transmittance," said Zhuang. The team found that these characteristics seriously improved the performance of InGaN red LEDs.
The team also studied InGaN red LEDs of varying sizes and temperatures. The latter affect the output light power and instigate different color impressions, which makes them critical for practical device performance.
"A critical disadvantage of InGaP red LEDs is that they are not stable when operated on high temperatures," explained Zhuang. "Therefore, we created InGaN red LEDs of different designs to realize very stable red-light InGaN sources at high temperatures." The team successfully developed an InGaN red LED structure, whose output power showed more stability than that of InGaP red LEDs.