Reducing LED Droop by Changing Crystal Orientation
Many people have high hopes for LEDs being a replacement for traditional incandescent light bulbs. This is because the power applied to LEDs is almost completely put to generating light, while the power for light bulbs goes to both light and waste heat. Unfortunately, LEDs droop in efficiency at the high currents needed for lighting homes. Researchers in California and Japan though appear to have found a solution and are reporting their results at the Optical Society of America’s Conference on Lasers and Electro-Optics (CLEO).
The exact reason for the efficiency droop is still debated but this did not deter the researchers from working on one theory. The semiconductors in LEDs are constructed by sandwiching together flat layers and it is possible that this orientation creates electric fields that inhibit the emission of light. The researchers tilted the crystal structure of the semiconducting layer to disrupt the electric fields. This resulted in LEDs with some of the lowest measured efficiency droops recorded.
Another benefit to this change in structure is a reduced size to the LED. This could lead to reduced manufacturing costs for the LEDs, which is important because the substrate used for these LEDs is fairly expensive. Researchers at the University of California, Santa Barbara are working on ways to bulk produce the substrate, which should help reduce costs.