Thursday, October 26, 2006
ZnO the future of Lighting ?
ZnO is being touted as a viable alternative to GaN as the building block for Light Emitting Diodes. The prognosis appears promising with a startup MOXtronics having developed the first successful ZnO Arsenic doped LED's. The exciting part is that Zno shows great potential as a medium to produce full spectrum light as opposed to GaN devices that are phosphor activated. From what is clearly a PR note sent to Optics.org
The attractiveness of zinc oxide (ZnO) LEDs stems from the potential for phosphor-free spectral coverage from the deep ultraviolet (UV) to the red, coupled with a quantum efficiency that could approach 90% and a compatibility with high-yield low-cost volume production. One day these LEDs could even outperform their GaN-based cousins (which offer a narrower spectral range) thanks to three key characteristics – superior material quality, an effective dopant and the availability of better alloys.
ZnO also promises very high quantum efficiencies, and UV detectors based on this material have produced external quantum efficiencies (EQE) of 90%, three times that of equivalent GaN-based detectors. The physical processes associated with detection suggest that similarly high efficiency values should be possible for the conversion of electrical carriers to photons. So it is plausible that ZnO LEDs will have an EQE upper limit that is three times higher than that of GaN-based devices.
latest UV LEDs have a typical wall-plug efficiency of 0.1%, which would equate to an efficacy of 0.6 lm/W if the emission were in the visible spectrum. Although the efficiency is far lower than that of GaN LEDs, we are making rapid progress by addressing the various phenomena that degrade device performance. If progress continues at the same rate we will produce LEDs with a 1% wall-plug efficiency within one year, 1–5% within two years and about 10% or more within three years.