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23 November 2006


Nichia reports white LEDs producing 138lm/W at 20mA; over 90lm/W at 350mA

After Cree's June report of a white LED chip delivering 131lm/W at 20mA with a correlated color temperature of 6027K, Nichia Corp has reported a small-area (240µm x 420µm) white LED chip, operating at a forward-bias voltage of 3.11V and current of 20mA, with a record luminous efficacy of 138lm/W (a luminous flux of 8.6lm). The quantum efficiency is 63.3%, the wall-plug efficiency is 41.7%, and the correlated color temperature is 5450K.

A larger 1mm x1mm high-power chip operating at 3.29V and 350mA had a slightly lower color temperature (5200K) but delivers a luminous flux of 106lm (a luminous efficacy of 91.7lm/W, greater than the 90lm/W of a tri-phosphor fluorescent lamp). The wall-plug efficiency is 27.7%, greater
than the 25% of a fluorescent lamp in the visible region. Also, at 2A the luminous flux is 402lm (equivalent to the total flux of a 30W incandescent lamp).

In both LEDs, the InGaN/GaN chip, grown by MOCVD on a patterned sapphire substrate, emits blue light (with a wavelength of 450nm) that excites a yellow YAG phosphor, yielding white light. For a p-type electrode, the LEDs
use an indium tin oxide (ITO) contact with a higher transmittance than a conventional translucent Ni/Al contact.

* Presented in 'Recent Progress of High Efficiency White LEDs' at International Workshop on Nitride Semiconductors (IWN 2006) in Kyoto, Japan, 22-27 October. See Yukio Narukawa et al 'Ultra-High Efficiency White Light Emitting Diodes' 2006 Japanese Journal of Applied Physics 45 (41), L1084.