Ostendo Technologies Inc of Carlsbad, CA, USA (which develops solid-state lighting based display technologies and products for commercial and consumer markets) and Technologies and Devices International Inc (TDI, part of the UK’s Oxford Instruments Group) say that LED structures grown on their semi-polar (11-22) gallium nitride wafers have resulted in more than 2.5x the emission intensity of c-plane GaN-based LED structures (Strittmatter et al, ‘Semi-polar nitride surfaces and heterostructures’, Physica Status Solidi (b), October issue).

In 2008, Ostendo and TDI entered into an Information Exchange Agreement with Xerox Corp subsidiary Palo Alto Research Center (PARC) to make semi-polar GaN wafers available on which PARC could grow LED and laser diode structures, and to independently validate and report the results achieved.

As part of their validation, PARC has grown a multi-quantum-well (MQW) LED structure on the semi-polar GaN side-by-side with a reference c-plane LED structure in the same MOCVD run. Some of the key results verify that: the LED structure grown on the semi-polar GaN achieved more than 2.5x more emission intensity than the reference LED structure grown on c-plane GaN; and the semi-polar GaN allowed higher indium (In) incorporation, resulting in a longer peak wavelength of ~25nm for the structure grown.

“This is an excellent validation of our work in the semi-polar GaN area for the last two and a half years as it verified the main advantage of our semi-polar GaN and should help encourage LED makers to start considering it for future LED brightness improvements,” says Ostendo’s Dr Hussein S. El Ghoroury.

“We are delighted that the production-grade, semi-polar GaN wafers produced at TDI, which are as a result of research funded by Ostendo, has generated such encouraging results,” comments Frazer Anderson, business development director at Oxford Instruments. “This joint initiative with Ostendo and PARC meets our customers’ needs through the advanced technology our companies have available,” he adds.

In June, Ostendo and TDI announced the availability of a semi-polar (11-22) GaN layer on sapphire substrate wafers using Ostendo’s proprietary design and TDI’s proprietary hydride vapor phase epitaxy (HVPE) technology. The firms says that this joint development now provides the opportunity to high-brightness light-emitting diode (HB-LED) and laser diode developers to increase optical efficiency significantly compared with structures grown on c-plane GaN substrates.