Technology summary: A novel device structure that reduces light absorption inside the LED enables uniform light emission from the active layer and reduces light reflections occurring repeatedly inside the LED thus increasing the overall efficiency. Need: Current methods of improving efficiency in nitride LED systems such as the use of a thin nickel gold or zinc oxide layer growth to produce transparent electrodes lack the surface feature shaping capabilities needed to optimize light extraction. Detailed technology description: Researchers at the University of California Santa Barbara have developed a novel device structure which combines an (Al Ga In)N and ZnO direct wafer bonded LED with a shaped plastic optical element in which the directional light entering the optical element from a ZnO cone is extracted to air. In particular the LED structure is combined with a tapered lens in which most of the light entering the lens lies within the critical angle and is extracted. The device reduces reflection from the plastic encapsulant surface reduces reflections from the ZnO surface reduces light absorption inside the LED enables uniform light emission from the active layer and reduces light reflections occurring repeatedly inside the LED. As a result this combined structure extracts more light out of the LED and is thus more efficient than standard LEDs. In addition the fabrication method may require fewer process steps due to the ease of electrode formation. This LED is applicable to solid-state lighting and other optoelectronic applications. Technology Applications: Solid-State Lighting; Optoelectronic Applications
1) Optimized light extraction (about 500% increase in output power compared to that of a standard square gallium nitride chip at 460nm wavelength and 20mA drive current) 2) Highly efficient due to reduction of light absorption in the LED 3) Reduced number of fabrication steps due to ease of electrode formation