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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