2017 Graduate Fellows

Maria Viitaniemi

Despite the wide applicability of InGaN/GaN quantum wells (QWs) in blue light emitting diodes (LEDs), the mechanisms governing their internal quantum efficiency (IQE) are not fully understood. The large defect densities observed in InGaN QWs usually indicate high levels of non-radiative recombination; however GaN LEDs have been fabricated with IQEs of at least 90%. In order to better understand the nature of carrier localization and recombination, we are developing a stimulated emission depletion (STED) microscope tailored to InGaN QWs. STED microscopy is widely used in biological systems to achieve far-field spatial resolution below the diffraction limit. Currently, we have built and tested a confocal set up for our InGaN QW samples of interest. We have also shown promising preliminary results of excited state depletion in these samples. Over the next year, we will move forward by combining these results to build a STED microscope to further characterize InGaN QWs.

Advisor Kai-Mei Fu -Physics

“Providing clean energy to the inhabitants of our planet is a major challenge to future generations. The University of Washington is to be congratulated for establishing an Institute where faculty and students can work together to tackle the difficult global challenge of energy sustainability.”
– Mildred Dresselhaus, Professor of Physics and Electrical Engineering, Emerita and Institute Professor, Massachusetts Institute of Technology
“Energy competition is opening up in a variety of ways, the push for carbon control will continue, and the rate of technology advancement is exponential. All the things I’ve seen at the CEI are just perfect for the way we see things going in energy. You guys are at the cutting edge. We’re counting on you.”
– Ronald Litzinger, President, Edison Energy