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Direct Observation of Charge Carrier Diffusion and Localization in an InGaN Multi Quantum Well

The temperature dependence of the diffusion constant of an InGaN/GaN multi quantum well (MQW) emitting at 465 nm is studied by time of flight measurements. Utilizing a confocal microscopy setup and scanning the pinhole across the image plane allows us to observe charge carrier diffusion in real space with submicron resolution and to determine the diffusion constant by fitting the time delays of the spatially dependent photoluminescence signal using a simple diffusion model. We see direct evidence for a strong decrease of charge carrier mobility below 110 K and for localization of charge carriers at 10 K. The diffusion constant increases continuously with temperature up to about 0.27 cm2 s-1 at 293 K.