HexaTech Inc of Morrisville, NC, USA has reported the results of an ongoing collaboration with development partner Tokuyama Corp of Tokyo, Japan that has demonstrated UV-C LEDs with exceptional output power and improvements in internal quantum efficiency (IQE). HexaTech reckons that the results raise the bar to what is possible with the technology, and enable commercially available high-performance, high-reliability UV-C LEDs.

HexaTech was spun off from the Department of Materials Science of North Carolina State University in 2001 to produce single-crystal aluminium nitride (AlN) substrates for both electronic and optoelectronic devices. AlN substrate material can enable long-life UV-C LEDs for disinfection applications, as well as deep UV lasers for biological threat detection and high-voltage power semiconductors for smart grid and efficient power conversion. The firm’s existing product lines include single-crystal and polycrystalline AlN substrates (although long-life UV-C LEDs and high-voltage power devices based on AlN substrates are also in development).

HexaTech says that, since their inception, UV-C LEDs have held the promise of a compact, highly efficient, long-life light source for sterilization and purification applications. The rapidly accelerating interest in LEDs for disinfection applications operating at UV-C wavelengths requires a solution with high output power, high efficiency and long lifetimes, says the firm. However, most commercially available UV-C LED products currently struggle with limited output power, efficiency and device lifetimes. A key requirement for improving these limitations is to reduce the device defect density, for which IQE is a key measure and is critically related to the underlying bulk material quality.

“As HexaTech’s own device development has shown, using our high-quality, low-dislocation material, we are able to produce UV-C LEDs with record-setting reliability and lifetimes, exceeding more than 600 hours of accelerated testing, with virtually no degradation,” says HexaTech’s director of device development Dr Baxter Moody.

Now, by coupling HexaTech’s low-dislocation-density bulk aluminum nitride (AlN) substrates with Tokuyama’s hydride vapor phase epitaxy (HVPE) and device fabrication, Tokuyama was able to produce UV-C LEDs with over 25mW of output power at 265nm, and internal quantum efficiencies greater than 70%.

“This collaboration demonstrates that, when combining HexaTech’s market-leading bulk substrate quality, with Tokuyama’s high-quality HVPE and excellent device fabrication, breakthrough, record-setting results are possible,” says HexaTech’s CEO Joe Grzyb.

“Working together with HexaTech and their substrates, Tokuyama has made great improvements in the performance of our UV-C LEDs, accelerating the process for their commercial availability,” comments Tokuyama’s chief research engineer Toru Kinoshita