Tuesday, April 19, 2011

LED Droop Gets Quantum Viagra

Materials scientists at UC Santa Barbara have used quantum mechanical calculations to solve a riddle known as "LED droop," viz., the drop in efficiency that occurs when nitride-based LEDs are operating at the power sufficient to illuminate a room.

The droop phenomenon is associated with Auger recombination in semiconductors; a variant of the Auger effect, known to chemists and spectroscopists. The UCSB researchers discovered that indirect Auger effects, which involve scattering processes, account for the discrepancy between the observed droop and the predicted droop, Previous theoretical calculations only took into account direct Auger processes.
LED droop can't be eliminated because Auger effects are intrinsic, but it could be minimized, the researchers say, by using thicker quantum wells in LEDs or growing devices along non-polar or semi-polar growth directions in order to keep carrier density low. [Source: Science News]