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18 December 2006


Record efficiency nonpolar and semipolar GaN LEDs

Researchers at University of California, Santa Barbara’s Solid State Lighting & Display Center (SSLDC) and the Japan Science & Technology Agency’s Exploratory Research for Advanced Technology program (JST ERATO) have set new records for external quantum efficiency in LEDs based on non-polar and semi-polar orientations of gallium nitride.

For standard sizes (300µm x 300µm) and operating current (20mA), the new non-polar LEDs have an external quantum efficiency of 41% and radiant powers as high as 25mW; the semipolar LEDs exhibited external quantum efficiency of 30% and radiant powers as high as 18mW. The polarized light emission should enable a new class of light sources and will be useful in applications such as the backlights of liquid crystal displays, since the polarized light emission from non-polar and semi-polar LEDs does not necessitate a polarizing filter (unlike conventional LEDs). The commercial applications of non-polar LEDs also include projection televisions, medical imaging and general illumination.

The groups, led by professors Shuji Nakamura (formerly of Nichia), Steve DenBaars and James Speck, have also achieved conventional c-plane LEDs with external quantum efficiencies of 66%, which have been used to make white LED lamps with a luminous efficacy of 116lm/W (more than both incandescent bulbs and fluorescent lamps).

Funding for the research was jointly provided by JST ERATO and the member companies of the SSLDC.