The Importance of Defects in Energy Efficiency: Lighting and Power Electronics
presented by Dr. Mary Ellen Zvanut
Wednesday, October 31, 7:30 - 8:30pm, Woods Labs 216
One might assume that the only thing important about a defect is the method used to eliminate it. But one would be so wrong! A point defect is responsible for the electronic revolution of the last century and the lighting revolution of the present century. For example, GaN is the material that has given the world blue LEDs and and energy-efficient LED-lightbulbs. The material is composed of gallium and nitrogen atoms but at least two other elements must be added, in less than one part per ten thousand, G or N atoms, to make the LED operational: silicon and magnesium. Our work focuses on understanding the role of these elements and, in particular, a property referred to as the defect level.
This talk will tell the story of our quest to determine the defect energy level of a particular impurity atom in GaN by illuminating the sample while measuring the amount of the impurity. Electron paramagnetic resonance spectroscopy is used to detect the impurity and a series of laser diodes and LEDs is used for illumination. I will discuss how the research morphed from an investigation of the critically important impurity Mg to a lesser known impurity beryllium, finally concluding that the object of interest is really carbon. The work is aimed at convincing you that research does not have textbook answers, but is composed of a series of steps and missteps, advancing eventually to a realistic conclusion.
Mary Ellen Zvanut, Professor of Physics at the University of Alabama at Birmingham studied as an undergraduate and graduate student at Lehigh University in Bethlehem, PA. After receiving a PhDmin Physics at Lehigh, she studied the use of polymers for transistor applications at the University ofnNorth Carolina, Chapel Hill. She began a National Research Council Post Doctoral position at the Naval Research Laboratory where her work explored such materials as diamond and Si-Ge alloys for transistor based applications. Dr. Zvanut joined the University of Alabama at Birmingham Physics Department as an assistant professor, engaging in a research career based on defects in many different types of semiconductors including the ‘Nobel award winning GaN’, which has given us the white light LED. She is presently the Associate Chair and Graduate Program Director of the Physics Department at UAB. Dr. Zvanut works with colleagues throughout the world and recently brought them together as Chair of the 2018 Gordon Research Conference on Defects in Semiconductors.