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18 September 2007


TDI demos prototype nonpolar GaN substrates

Nitride material manufacturer Technologies and Devices International Inc of Silver Spring, MD, USA says that it has demonstrated prototype 2-inch diameter nonpolar a-plane GaN-on-sapphire substrates. The new product will be featured at this week’s 7th International Conference on Nitride Semiconductors (ICNS 2007) in Las Vegas, NV (17-20 September).

Nonpolar gallium nitride substrates are needed to fabricate GaN light-emitting devices (LEDs and laser diodes) with improved efficiency and output power, especially for devices emitting in the green spectral region. Most commercial GaN-based devices are currently produced on crystalline substrates with polar surface crystallographic orientations parallel to the c-crystallographic plane which, in gallium nitride, is not optimal for optoelectronic applications due to piezoelectric polarization effects. In contrast, GaN devices fabricated on other crystallographic (nonpolar or semipolar) surfaces (such as the a-plane) have previously been demonstrated to show great promise for device improvement.

TDI says that it has developed a process to deposit a-plane GaN layers with improved surface and crystal quality on sapphire to produce commercial nonpolar GaN substrate materials. The product consists of a GaN layer several microns thick with a-plane orientation deposited on r-plane sapphire substrates. GaN deposition is performed using the firm’s proprietary hydride vapor phase epitaxial (HVPE) process and equipment.

“Governed by a strong demand from TDI customers for nonpolar GaN substrates, we have introduced a novel HVPE process to fabricate a-plane GaN materials with substantially improved properties while at the same time avoiding expensive technological steps to keep production cost low,” says president and CEO Vladimir Dmitriev. “This allows us to offer c-plane and a-plane GaN products in commercial quantities at similar price levels,” he adds. The product is now available in test quantities in two configurations: (i) with a GaN as-grown surface and (ii) with a GaN epi-ready polished surface. Full-scale production of a-plane GaN template substrates is scheduled for first-quarter 2008.

“Deposition of high-quality GaN materials with nonpolar crystallographic orientations is technically challenging,” adds R&D director Alexander Usikov. “Significant process improvements at TDI now allow us to provide our customers with a-plane GaN substrates, which will make development and commercialization work on nonpolar GaN light-emitting devices much easier,” he promises.

“We are working on the next generation of nonpolar substrates and device structures, and recently have succeeded in the fabrication of R&D samples of a-plane and m-plane InGaN materials on nonpolar GaN templates and bulk GaN substrates.” These results will be presented at ICNS, Usikov adds.

See related items:

Kyma partners with Caracal and EOC to improve nonpolar GaN substrates

TDI starts production of 100mm GaN and AlN epiwafers

TDI introduces InGaN substrates

UCSB achieves high-efficiency non-polar GaN LEDs at improved output power

Kyma's native GaN substrates merit defense contract