University of California Energy Institute

It is estimated that about 25% of all electrical energy is used for lighting purposes. Light-emitting diode (LED)-based lighting technologies can be a factor of nearly 10 times more efficient than incandescent lighting and a factor of about 2-3 times more efficient than fluorescent lighting technologies. It is predicted by Department of Energy (DOE) that by 2025 the use of solid-state lighting will reduce national energy consumption for lighting by 29%. The cumulative energy savings from 2006 to 2025 would result in more than 125 billion dollars of savings to consumer electricity bills. LEDs based on Gallium Nitride (GaN) materials are currently widely developed to conserve electrical energy in numerous lighting applications, such as headlights of vehicles, traffic lights, outdoor displays, and some indoor lighting. The trend towards higher brightness, lower operating current, and longer lifetime has increased the needs for developing alternative next-generation LEDs. Zinc Oxide (ZnO), as a wide bandgap semiconductor material, has long been believed to be a suitable candidate for high-efficient light emitting applications, due to its superior intrinsic properties over GaN. Our research on solving impurity-doping problems in ZnO offers an effective way towards the fabrication of useful LEDs for solid-state lighting applications.