Lateral transport in InGaN/GaN quantum wells: time-of-flight experiments

The Indium Gallium Nitride material system is known to have very small lateral charge carrier diffusion constant. In case of quantum well structures this is most likely due to Indium fluctuations and defects. We present a method to directly observe travelling charge carriers in quantum wells by solely optical means. By combining a confocal setup with a pulsed laser, a streak camera and the possibility to perform so called pinhole scans we were able perform time-of flight experiments and observe lateral diffusion in a green emitting InGaN/GaN multiple quantum well. Our measurement results can be described quantitatively by continuity and rate equation. This quantitative description also provides us with a local charge carrier diffusion constant for this sample.