Gallium-nitride-on-silicon architecture inches closer to sapphire-based LED performance levels but a significant gap remains.
Plessey Semiconductors has announced the PLB010350 LED that it is manufactured on its gallium-nitride-on-silicon (GaN-on-Si) manufacturing platform. The 2×2-mm blue LEDs deliver 350 mW of radiometric power when driven at 420 mA — a significant jump from the company's previously announced Si-based LEDs and a product that can serve in some general solid-state lighting (SSL) applications.
Back in April, Plessey had announced availability of the PL111010 LEDs that were more of a proof of concept for the GaN-on-Si technology, delivering only a few lumens from very low drive currents and maxing out at 25 mA. These new LEDs can be driven at up to 1A continuously and 2A pulsed.
It's not clear why Plessey only announced a blue version of the new LED design. Certainly the LEDs could be used in remote phosphor applications. The 435–460-nm dominant wavelength range is similar to the royal blue LEDs from major LED manufacturers that are targeted at remote-phosphor SSL products. The company has not said if it will offer a white phosphor-converted version of the new LED.
In terms of efficiency, the new LEDs are markedly improved from the earlier product but still well behind sapphire-based LEDs. For example, Cree announced the 2.5×2.5mm XLamp XB-D LEDs in January 2012. The company offers a royal blue version of the LED that delivers 450–550 mW at 350 mA of drive current.
Plessey said that the new LEDs can be used in applications including entertainment and decorative lighting as well as in wall-washing and -grazing applications. Moreover, the company said the LEDs are especially suited to any SSL applications that require pulsed lighting.
The allure of GaN-on-Si remains lower-cost LEDs driven both by cheaper, widely-available Si wafers and the ability to use automated back-end manufacturing tools in depreciated Si fabs. Plessey is manufacturing its products on such a 6-in manufacturing line.
"This new 350mW product demonstrates the inherent flexibility we have for the manufacture of LEDs with a 6-inch GaN on silicon substrate in an integrated circuit manufacturing line," said Barry Dennington, Plessey COO. "We are seeing continual improvements in output efficiencies in the lab, which means we will continue to launch new products in line with our product release plan."
While there are a number of announced GaN-on-Si efforts that have been widely publicized (see links at right), there is still no evidence of such LEDs being used in mass-produced SSL products. But the industry will continue to pursue all avenues that could lead to lower manufacturing costs, so stay tuned for more news from Plessey and others.
