Exalos demos 5000 hour GaN LEDs
Exalos, a Swiss company that develops semiconductor light sources, has successfully tested long-life GaN superluminescent light-emitting diodes (SLEDs) that deliver, under specific test conditions, an estimated lifetime of more than 5,000 hours.
Exalos says the results demonstrate that SLEDs can deliver much more reliable light sources for devices, suggesting that, for example, markets such as direct retina display, 3D printing, or pico projectors, might benefit from reliable, long-life semiconductors that generate extreme brightness.
Exalos will introduce the findings at the Photonic West conference in San Francisco, this week.
Exalos tested the reliability of GaN-based SLEDs emitting at a wavelength of 405nm demonstrating that optimised 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 doping levels in the p-type (positive) layers have an impact on both the device electro-optical characteristics and their reliability. SLED modules with standard and optimized p-type layers were tested in lifetime output.
Modules with standard and optimised 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 25degC. The modules with non-optimised p-type doping showed a fast and remarkable increase in the drive current during the first hundreds of hours together with an increase of the device series resistance.
No degradation of the electrical characteristics was observed after 2,000 hours on devices with optimised p-type layers. Under the specific test conditions, the estimated lifetime for those devices was higher than 5,000 hours. Furthermore, maximum output powers as high as 350mW (for an injection current of 500 mA) 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 commercialised in markets including medical and industrial applications, as well as laser projection and automotive head lamp design," said Christian Velez, CEO of Exalos. "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. This is what we believe new markets are seeking for light sources."
Exalos, which developed the industry's first blue SLED, has shipped since 2003 more than 300,000 SLEDs in the wavelength range from 405 nm to 1600nm.