Tests were conducted on Quanlight-designed epiwafers manufactured on production scale Veeco MOCVD equipment; color stability at increasing temperature was tested by measuring the peak wavelength emitted while externally heating the LED from 25 degrees to 125 degrees centigrade. The resulting shift of three nanometers over this temperature range was only one-fifth the shift of a conventional LED.
In a test of brightness stability, the light output from a Quanlight LED was measured as the external temperature was increased from 25 to 150 degrees centigrade. At the high end, the Quanlight unit emitted 48 percent of its original light output compared to 25 percent produced by a conventional LED.
Furthermore, Quanlight’s simplified manufacturing process employs direct growth on a transparent gallium phosphide (GaP) substrate. This eliminates the traditional step for AlGaInP LEDs of removing the epilayer from an opaque substrate (normally GaAs) and bonding it onto a new transparent substrate. This minimizes the process steps, reduces the amount of material required, and leads to lower production costs.
Quanlight’s CEO Neil Senturia says, “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. Benefits from the reduced wavelength shifts and improved high temperature efficiency will translate into simpler color-control mechanisms and enhanced lighting intensity.”
Quanlight plans to extend its range of epiwafers to include orange and yellow wavelengths between 585 and 660 nanometers. The patent pending technology for the San Diego-based company was originally developed at the University of California, San Diego (UCSD) by Charles Tu and Vladimir Odnoblyudov. Quanlight holds the exclusive license to commercialize the technology from UCSD, where co-founder Odnoblyudov worked on the technology for over three years before achieving this breakthrough.