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19 October 2007


Quanlight reports dilute nitride LEDs with improved stability

Quanlight Inc of San Diego, CA, USA, which is developing high-brightness red LEDs based on the dilute nitride InGaNP (indium gallium nitride phosphide), has reported prototype devices fabricated in production-scale Veeco MOCVD reactors that deliver much improved color and brightness stability with changing temperatures compared to traditional LEDs.

While indium gallium nitride (InGaN) materials are used for blue and green LEDs, most commercial yellow, amber and red (YAR) LEDs are fabricated using aluminum gallium indium phosphide (AlGaInP). Chief finance officer Phil White says that current material systems used in YAR LED are nearly 20 years old, and it is no longer possible to cost-effectively increase the capabilities of such LEDs. Whereas current LEDs fall in efficiency as the drive current is increased, Quanlight says that InGaNP-based LEDs will remain very efficient at much higher current loads.

Also, the simplified manufacturing process employs direct growth pseudomorphically on a transparent gallium phosphide (GaP) substrate, eliminating the traditional wafer-bonding process step for an AlInGaP LED of removing the epilayer from an opaque substrate and bonding it onto a second, transparent substrate, in order to assist light extraction. This reduces material, process and labor costs, while increasing yield.

Color stability of the InGaNP-based LED was tested by measuring the peak wavelength emitted while externally heating the LED from 25 to 125 degrees centigrade. The resulting shift of 3nm is only one-fifth the 15nm shift of a conventional AlInGaP red LED.

In a test of brightness stability, light output was measured as the external temperature was increased from 25 to 150 degrees centigrade. At the high end, the Quanlight unit emitted 48% of its original light output compared to just 25% for a conventional LED.

“For applications requiring high power or stable color output, such as traffic signals, signage, theatrical lighting and backlighting units for LCD televisions, these differences are dramatic,” says CEO Neil Senturia. “Benefits from the reduced wavelength shifts and improved high-temperature efficiency will translate into simpler color control mechanisms and enhanced lighting intensity,” he adds.

The patent-pending technology was originally developed by Dr Charles Tu and co-founder and chief technology officer Dr Vladimir Odnoblyudov at the University of California, San Diego (UCSD). Quanlight holds the exclusive license to commercialize the technology.

In December 2006, Quanlight received $1m in Series A investment from San Diego-based Blackbird Ventures (whose principal Senturia joined as CEO). This May, to take the firm from R&D to wafer production, Quanlight raised $3m in a Series B round of funding led by Blackbird Ventures and (SHW) 2 Enterprises, together with a small group of private investors. (SHW) 2 Enterprises chairman Harvey White (a co-founder and former president and COO of Qualcomm) joined as chairman of the board. The firm is targeting an additional round in mid-2008.

Quanlight aims to sell epiwafers, enabling LED makers to use the technology. The firm adds that it plans to extend its range of epiwafers to include orange and yellow wavelengths of 585-660nm.

See related item:

Quanlight attracts $3m funding to commercialize dilute nitride material system for LEDs

Search: Veeco MOCVD Red LEDs AlGaInP