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15 February 2016

EXALOS unveils 5000hr-lifetime test results for 405nm GaN superluminescent LEDs

EXALOS of Zurich, Switzerland, which designs and manufactures light sources based on superluminescent light-emitting diodes (SLEDs) and external-cavity tunable lasers (Swept Sources), has successfully tested long-life gallium nitride (GaN) SLEDs that deliver, under specific test conditions, an estimated lifetime of more than 5000 hours. The results demonstrate that SLEDs can deliver much more reliable light sources for devices, claims the firm, suggesting that markets such as direct retina display, 3D printing or pico projectors might benefit from reliable, long-life semiconductors that generate extreme brightness.

EXALOS is unveiling the findings in a presentation at the SPIE Photonic West 2016 conference in San Francisco (16-18 February), where the firm is demonstrating its SLED products in booth #430.

EXALOS tested the reliability of GaN-based SLEDs emitting at a wavelength of 405nm, demonstrating that optimized doping levels provide decreased operating voltage on single-mode devices from more than 6V to less than 5V for an injection current of 100mA. The tests showed that magnesium (Mg) doping levels in the p-type (positive) layers have an impact on both the device's electro-optical characteristics and their reliability. SLED modules with standard and optimized p-type layers were tested in lifetime output. 

Modules with standard and optimized p-type layers were finally tested in terms of lifetime, at a constant output power of 10mW, in continuous wave (cw) operation and at a case temperature of 25°C. The modules with non-optimized p-type doping showed a fast and remarkable increase in drive current during the first hundreds of hours together with an increase in the device series resistance. No degradation in the electrical characteristics was observed after 2000 hours on devices with optimized p-type layers. Under the specific test conditions, the estimated lifetime for those devices was higher than 5000 hours. Furthermore, maximum output powers as high as 350mW (for an injection current of 500mA) have been achieved in continuous-wave operation (cw) at room temperature.

"We have seen, in recent years, tremendous improvement in the performance and reliability of GaN-based laser diodes in the 405nm wavelength, which have been successfully commercialized in markets including medical and industrial applications, as well as laser projection and automotive head-lamp design," says CEO Dr Christian Velez. "Our tests now show that the GaN-based SLEDs can deliver high output power with ideal directional beams with higher power levels for applications such as direct retina projection and pico projection," he adds. "This is what we believe new markets are seeking for light sources."

EXALOS, which developed the industry's first blue SLED, has shipped more than 300,000 SLEDs in the wavelength range 405-1600nm since 2003. The firm claims to be the leading supplier to the SLED-based current sensor market and to the fiber-optic gyroscope market for both space- and land-based applications. Since the commercialization of SLED technology, EXALOS has also supplied SLEDs to the optical coherence tomography (OCT) market.

Tags: SLED

Visit: http://spie.org/photonics-west.xml

Visit: www.exalos.com

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